Butyl acrylate production: A review on process intensification strategies

Chemical Engineering & Processing: Process Intensification 142 (2019) 107563

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Butyl acrylate production: A review on process intensification strategies Dânia S.M. Constantino , Rui P.V. Faria, Ana M. Ribeiro, Alírio. E. Rodrigues ⁎

T

Laboratory of Separation and Reaction Engineering, Laboratory of Catalysis and Materials (LSRE-LCM), Faculdade de Engenharia, Universidade do Porto, Rua Dr. Roberto Frias, 4200-465 Porto, Portugal

ARTICLE INFO

ABSTRACT

Keywords: Butyl acrylate Multifunctional reactors Heterogeneous catalysis Process intensification Process integration Key economic indicators

Butyl Acrylate is one of the most important acrylic monomers presenting great potential for several industrial applications mainly in surface coating field. Hence, the global butyl acrylate market has grown in the last years and, accordingly, the development of better alternatives to the conventional process, which involves a multistage procedure and homogeneous catalysis, is increasingly gaining the attention of the scientific community. This paper summarizes the state-of-the-art of butyl acrylate production and the main results achieved. Patented processes and process integration strategies studied so far are addressed as well as a brief review on the key economic indicators of each process scaled up at industrial scale suggested in the literature. Currently, process integration based strategies with focus on reactive distillation technology and chromatographic reactors (process intensification methods) have been pointed out as alternative routes for the continuous production of butyl acrylate. In summary, from the industrial point of view, Simulated Moving Bed Reactors based processes seem to be one of the most attractive due to its key economic indicators, presenting an economic potential of 30,500 €/y, which is approximately three times higher than the remaining studied processes.

1. Introduction Over the last decades, numerous global market researchers have predicted a considerable growth in the butyl acrylate (BAc) demand for long forecast periods mainly due to its resilient features which make it to be required for several industrial applications. BAc is usually obtained from an esterification reaction between acrylic acid (AAc) and nbutanol (n-BuOH) having water as by-product. However, its conventional production involves a complex multistage process with homogeneous catalysis [1] and the subsequent process (product purification) represents high operating and investment costs. Therefore, a Process Intensification (PI) study could lead to a more compact design towards a more energy efficient and profitable process. Process intensification methods are illustrated in Fig. 1, including: multifunctional reactors resulting from the integration of reaction and separation techniques, new hybrid separations and use of alternative energy sources [2]. Multifunctional reactors, where reaction and separation steps are integrated into a single equipment, are one of the most relevant examples of PI for reactive systems, allowing to reduce the energy demand and investment costs on the equipment required and, consequently, leading to more sustainable processes which is one of the biggest Process Engineering challenges. This way, reactive separation attracts the researchers attention because it leads to smaller,

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cleaner and more energy-efficient processes than the conventional multistage processes [2,3], since reaction and separation take place simultaneously allowing to overcome the equilibrium limitations by continuously removing one of the products and leading to reaction conversion improvement. Among the reactive separations, chromatographic reactors and reactive distillations are currently the most studied methods for systems that comprise equilibrium limited reactions as it is the case of BAc. Beyond several processes that were already patented for the BAc synthesis, process integration based strategies have been investigated along the last decades aiming to find the best solution in terms of industrial implementation that can be able to keep up with the market progress. In this work, an overview of the patented processes and process integration based strategies is presented showing the main achievements along the time that have contributed to improve BAc synthesis. 2. Market and applications BAc is a clear colorless liquid with a strong characteristic odor, which presents a low solubility in water (0.2% wt. at 20 °C) and a very similar boiling point to that of AAc (see Table 1). It is a very important acrylic monomer with a wide application field, due to its properties

Corresponding author. E-mail address: [email protected] (D.S.M. Constantino).

https://doi.org/10.1016/j.cep.2019.107563 Received 18 April 2019; Received in revised form 7 June 2019; Accepted 17 June 2019 Available online 28 June 2019 0255-2701/ © 2019 Elsevier B.V. All rights reserved.

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Nomenclature

MRP n-BuOH P PI Prod PTZ QDes QFeed QRec QX r R r(A/B) RD RR RSR S SMBR ΔS t T V X y

A15 Ion exchange resin Amberlyst-15 A46 Ion exchange resin Amberlyst-46 A131 Ion exchange resin Amberlyst-131 AAc Acrylic Acid Amort Amortization BAc Butyl Acrylate CAGR Compound Annual Growth Rate CAPEX Capital Expenditure CR Chromatographic Reactors CSpecProduct Specific Product Cost DC Distillation Column DesC. Desorbent Consumption Ea Reaction Activation Energy EP Economic Potential FBMR Fixed-Bed Membrane Reactor FBR Fixed-Bed Reactor HME Hydroquinone Monomethyl Ether ΔH Reaction Enthalpy kc,0 Arrhenius Pre-exponential Factor kc Kinetic Constant Keq Equilibrium Reaction Constant Adsorption Constant for Water Ks,water LHHW Langmuir-Hinshelwood-Hougen-Watson such as low temperature flexibility, adhesion, hardness, water and oil resistance, among others. Additional properties of all species involved in this system can be observed in Table 1. All these properties make this chemical compound an attractive feedstock for paint and coating formulations and for several other products like adhesives [4] (including pressure-sensitive adhesives (PSAs)) [5,6], varnishes, finishes of papers and textiles [7]. It has also been useful in the production of sealants, plastics, elastomers [8], and mostly to produce coatings and copolymers [9–13]. Cleaning products, antioxidant agents, amphoteric surfactants and aqueous resins are other uses of this chemical compound. Fig. 2 illustrates the main application areas of BAc with surface coatings representing the major one. Market research studies have reported a significant growth of the global demand of BAc during the last decade and this trend is expected to increase even further in the upcoming years. According to the market analysis [14], the global production capacity increased about 80% from 2005 to 2013 pointing out to 3.45 million t/y in 2013. A representation of the global production capacity

Market Reference Price n-Butanol Pressure Process Intensification Productivity Phenothiazine Desorbent Flowrate Feed Flowrate Recycle Flowrate Extract Flowrate Reaction Rate Ideal Gas Constant Molar Ratio (A = n-BuOH; B = AAc) Reactive Distillation Reflux Ratio Reactive-Separation-Recycle Membrane Area Simulated Moving Bed Reactor Reaction Entropy tonnes Temperature Reaction Volume Reaction Conversion year

can be observed in Fig. 3 in terms of the manufactures and respective geography. The data corresponds to the most recent information available in open literature (related to 2013) and shows that BAc has been mostly produced in China. Nevertheless, the largest manufacture, in that year, was Dow Chemical, located in the USA and Germany, with 14.7% of the global market followed by BASF with 12.6% and Arkema with 9.4 % [14]. The demand has increased mainly in Asia Pacific which is the largest consumer at about 1.44 million t/y, followed by the USA at 476 000 t/y and Western Europe at 446 000 t/y, respectively. The most recent publications [15] point out that the global BAc market will reach around $ 8.1 billion by 2026 expanding at a Compound Annual Growth Rate (CAGR) of 5.0% from 2018 to 2026 and expecting to reach 4.84 million tonnes by 2026. This market growth is due to the increase of the BAc usage in the manufacture of water-based coatings which are likely to replace solvent-based coatings. Moreover, the development of the automotive and construction industries boosts the global BAc market [15]. 3. Conventional synthesis process and challenges Although different routes can be followed to produce BAc, including acetylene-carbon monoxide mixtures in the presence of n-BuOH at high pressures [18,19], mass efficiency has been a general concern in the Table 1 Properties of all compounds involved in the butyl acrylate synthesis [16,17]. Properties −1

Molecular weight - M (g. mol ) Density- ρ (g. cm−3) Melting temperature - Tf (K) Normal boiling temperature - Tb (K) Critical temperature - Tc (K) Critical pressure - Pc (bar) Critical volume - Vc (cm3. mol−1) Acentric factor - w Radius of gyration- (Ắ) Dipole moment, in gas phase - (Debye)

Fig. 1. Process intensification methods [2].

a

2

in benzene.

AAc

n-BuOH

BAc

Water

72.06 1.05 286.15 414.15 615.00 56.60 208.00 0.540 2.978 1.460

74.12 0.81 183.85 391.90 563.10 44.14 273.00 0.590 3.251 1.661

128.17 0.90 208.55 420.55 598.00 29.10 428.00 0.480 4.765 1.931a

18.02 1.03 273.15 373.15 647.10 220.64 55.94 0.350 0.615 1.850

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and three distillation columns which are used for the recovery of the reactants as well as for product purification [1]. Usually, the alcohol is used in excess and the water resulted from esterification is removed by distillation as well as its azeotrope with BAc and n-BuOH to keep a high rate of AAc conversion. The separation of AAc from water, excess alcohol and BAc is not a simple task resulting in contamination of BAc containing, typically, 1–3% of AAc in a continuous process. Hence, there are reactant recovery problems leading to a significant energy use. In this manner, further improvements in the BAc production are required, namely, methods to make more efficient use of the water driving to an easier separation of BAc from AAc and recycling unreacted AAc energy efficiently [23]. Besides that, liquid catalysts such as sulfuric acid, hydrofluoric acid, and para-toluenesulfonic acid are toxic and corrosive while the solid acids are less toxic and facilitate the recovery and recycling of the catalysts. Therefore, many researchers have tried to improve this process with heterogeneous catalysts (reducing the system toxicity) and integrated processes aiming to attain a more efficient eco-friendly process either by increasing the process and/or the material use efficiencies.

Fig. 2. Global butyl acrylate applications (data from 2013) [14].

selection of the employed synthesis reaction. In this process, BAc is, usually, obtained from an equilibrium limited esterification reaction between AAc and n-BuOH, in acidic medium, having water as by-product, as can be seen in Fig. 4. The reaction enthalpy value of 13.4 kJ mol−1, which can be obtained from the enthalpy of formation of the respective products (ΔHf,BAc = −375.3 kJ mol−1, ΔHf,water = −241.81 kJ mol−1) [16,20] and reactants (ΔHf,n-BuOH = −274.6 kJ mol−1, ΔHf,AAc = −355.91 kJ mol−1) [20], indicates this is an endothermic reaction. This system has several drawbacks which has been identified in the literature, namely, it presents very slow reaction kinetic [16], a complex thermodynamic behavior with several azeotropes (see Table 2) and high risk of polymerization of AAc and BAc when they are exposed to high temperatures [21]. The polymerization reaction should be avoided during the esterification and separation processes, since it is highly exothermic which can lead to an uncontrolled self-accelerating reaction when high temperatures are used. Moreover, the equilibrium reaction conversion is low, according to the literature is about 60% at 363 K [16]. So, all these limitations make the BAc synthesis and its purification a very challenging process, since commercially a high purity is required (≥ 99.5 wt. %). Conventionally, the BAc production is conducted in a homogeneously catalyzed multistage process, like it is shown in Fig. 5, using two reactors with a total residence time of approximately three hours

4. Patented processes overview There are numerous patented processes in the literature related with the BAc synthesis and most of them focus a first stage involving a reactor, where the esterification reaction between AAc and n-BuOH in an acidic medium is carried out, followed by several distillation processes with recycling in order to extract the BAc from the organic phases. The invention that belongs to Hoechst Aktiengesellschaft, from Germany [24], claims the production of BAc by reacting AAc with n-BuOH in liquid phase over an acid cation exchanger catalyst (Amberlyst 15 (A15), for instance). The authors report a continuous feed in the reaction zone, which is filled with the catalyst, using a molar ratio (AAc/ nBuOH) from 1:1 to 1:2.5, at 353 K to 403 K, under a pressure from 3 to 15 atm with reaction periods within the range of 20–90 minutes. The esterification reaction is performed in a single reaction zone and, after that, the final mixture comprising a ternary mixture of BAc/ n-BuOH /water is led through a three zones distillation sequence from which the respective organic phases are recovered. After the second distillation, a

Fig. 3. Global butyl acrylate production capacity (data from 2013) [14]. 3

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Fig. 4. Esterification reaction for the synthesis of butyl acrylate. Table 2 Azeotropic data of the butyl acrylate system (P = 0.267 bar) [21]. Reference

Type

Compounds

Tb (K)

xAAc

xBAc

xn-BuOH

xWater

Calculated (UNIQUAC_HOC) [21] Gmehling, 2004 [22] Gmehling, 2004 [22] Gmehling, 2004 [22] Gmehling, 2004 [22]

Homogeneous Heterogeneous Homogeneous Heterogeneous Heterogeneous

AAc and BAc BAc and Water n-BuOH and BAc n-BuOH and Water n-BuOH, BAc and Water

379 335 356 335 333

0.37 – – – –

0.63 0.18 0.12 – 0.09

– – 0.88 0.19 0.15

– 0.82 – 0.81 0.76

temperature between 293 K and 423 K under a pressure range of about 6.7 to 53.3 kPa. The finished product (BAc) is withdrawn as a vapor side stream from the finishing tower presenting a purity between 99.0 and 99.99 wt. %. Aichinger’s et al. invention [26] comprises at least two reactors for producing BAc over sulphuric acid or a mono-C4—C12alkyl sulphate as catalyst. The first reactor operates, preferably, between 353 and 383 K, with the water content of the feed mixture being below 3 wt. % (based on the total amount of starting materials) and the respective optimum conversion is reached after a residence time of about 1 h, being at least 40%, where the reaction is carried out while a single phase is observed. After that, at least one more reactor is used between 363 and 403 K. The water formed is removed by distillation in a stream containing a maximum residual amount of alcohol of 5%. One year later, BASF Aktiengesellschaft [27] published another patent in which the reaction mixture from the esterification zone is first fed to a three-stage pre-purification and then worked up by rectification for BAc isolation. The reaction occurs, preferably, between 353 K and 403 K and between 0.1 and 0.8 bar (according to the authors, reduced pressures facilitates the removal of water by rectification). In the first pre-purification stage the catalyst is separated by extraction and washing with water. Then, the strongly acidic components are neutralized and extracted by reactive extraction using an aqueous alkali solution. After passing the remaining organic reaction mixture in an additional separation zone, the resulting alkyl ester is isolated. In the third stage, residual salts and aqueous foreign-phase fractions are removed by extraction with water from the organic reaction mixture that remained after the second pre-purification stage, before it is passed on into the separation zone comprising further rectification units. A new process was patented by Union Carbide Chemicals & Plastics Technology Corporation in 2003 [28], which claims a process for refining BAc after the esterification reaction. The esterification reaction is performed between 363 K and 413 K under a pressure range between 0.1 and 1.5 bar and using a feed molar ratio of 0.8-1.2 to 1 (n-BuOH/AAc). A splitter distillation column (DC) is used to perform a separation between lights, which include dibutylether, butyl acetate, n-BuOH and lower boiling components (overhead fraction) and acrylate and heavier components (bottom fraction). The bottom fraction is removed from the splitter DC and the heavier compounds are separated by introducing that fraction into a DC to provide an overhead product containing BAc and a bottom product containing heavier components. In 2005, Arkema released a new invention [29] disclosing a process that encompasses a reactor charged with AAc, phenothiazine (PTZ) stabilizer, 96% of sulphuric acid and the BAc/ n-BuOH mixture from the top column wherein the water formed is entrained by distillation in the form of a heteroazeotropic mixture with n-BuOH being then separated in a decanter after condensation. The esterification reaction is conducted preferably with an initial n-BuOH /AAc molar ratio of 0.92, which rises to 1.12

Fig. 5. Conventional process for butyl acrylate synthesis [1].

n-BuOH/ BAc azeotrope is obtained, which is then condensed and recycled to the reaction zone. At the end, pure BAc is obtained at the bottom of the third distillation zone, with yield between 94% and 97%. In 2001, Bauer, Jr. et al [23] presented a new invention with two new process components, one being related with the hydrolytic recovery of valuable reactants from their higher boiling adducts, and a second component related with an improved distillation of a crude product yielding BAc substantially free of AAc. A reaction conversion of 60%, at least, is obtained in the esterification reaction using a feed molar ratio of 1 to 1.1–1.7 (AAc/ n-BuOH). The hydrolysis reactor is kept between 363 K and 413 K with a residence time of 0.5 to 20 h in a continuous acid-catalyzed process under 6.7 to 133.3 kPa while the cracking reactor is maintained at the same temperature with the same residence time under 2.7 to 26.7 kPa. In summary, the authors report a highly efficient continuous process for BAc synthesis comprising one esterification reactor, one hydrolytic reactor, one cracking reactor and a separation column to extract AAc providing an n-BuOH/BAc mixture which returns to the first reactor after subsequent conventional processing and final BAc isolation. Jawaid and Schepp’s invention [25] focuses on a process where a feed molar ratio of 0.85 to 1.3 mol (nBuOH /AAc) is used and a polymerization inhibitor is considered to be mixed with the AAc in the feed zone. The reaction vessel operates at a 4

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following completion of the deferred introduction of n-BuOH. Initially, it is conducted with a temperature of 353 K for 30 min by varying pressure from 0.293 bar to 0.227 bar and, then, maintaining this pressure the temperature is allowed to increase up to 373 K. The final product obtained contains at least 99.8 wt. % of BAc. The Rohm and Hass’s invention [30] includes two process units running in parallel with interconnections designed to maximize yield and purity of the products from both units. A method for combining parts of the two units into a single process unit for improved yield and purity is also detailed. Both processes encompass an esterification reactor and a dehydration distillation column. The first process unit involves a

hydrolysis reactor, a cracking reactor and an AAc separation column and the second process unit contains a bleed stripper, a recycle tank and a neutralization and acidification system. The feed molar ratio of AAc and n-BuOH for esterification reactor is preferably from 1:1.25 to 1:1.45 over an acid catalyst. The AAc conversion is at least 60%. The cracking reactor is kept preferably from 383 to 398 K under a pressure of 2.7 to 26.7 kPa and a residence time of 0.5 to 20 h, based on the feed reactor bleed stream, is employed. The final product (BAc) presents reduced levels of AAc and n-butyl acetate.

Table 3 Summary of heterogeneous catalyzed BAc synthesis and PI strategies. Source

Processes and Materials

Conditions

Remarks/Results

Pascale Dupont et al., 1995 [32]

Batch Heteropolyacids supported on activated carbon: H3PW12O40 (HPW); Inhibitor: PTZ (0.16 wt. %). Three neck flask with water-cooler condenser; Screening of catalysts including: A15, Amberlite 200C, Nafion-H, Nafion-SiO2, Solid oxides and Liquids.

T = 353 K; P = 0.2 bar; rA/B = 0.75.

Schwarzer, S. and Hoffman U., 2002 [36]

Batch Tube Reactor + RD; Kinetic: Lewatit K 2621; Equilibrium: Toluene sulfonic acid.

Kinetic: T = 393 K; P = 0.2 MPa ; rA/B = 1.3 - 2.1; Equilibrium: T = 293 - 373 K; P = . 1 bar.

Zeng, K. et al., 2006 [7]

RD with decanter Kinetic parameters from Schwarzer, S. and Hoffman U., 2002 [36]. Batch; Heterolpolyacids: H3PW12O40 (catalyst A) and H3PMo12O40 (catalyst B); Inhibitor: HME.

T = 363 - 428 K; TDecanter = ;313 K; P = 1.1 bar. T = 343 - 373 K; rA/B = 3.0, 5.0 and 10.0; Catalysts (wt. %) = 1.23 - 9.84 (Cat. A) and 3.12 - 12.48 (Cat. B).

XAAc = 98.0%; The activity per proton of the HPW/carbon is higher than conventional resins but smaller than pure HPW; Occurs deactivation. The highest conversion was obtained with Nafion-H, XAAc = 61.1%; The highest selectivity to BAc was obtained with Amberlite 200C; Selectivity to BAc = 95.6%. Keq = exp (- 8.805 + 0.05743 × (T/K) – 6.429 × 10–5 × (T/ K)2 + 3.821 × 10−9 × (T/K)); ΔH = 14.27 kJ mol-1; XAAc = 62%; Maximum of BAc fraction = 93%; LHHW model was considered. BAc ≥ 99.83 mol. %; Water ≥ 95.90 mol. %.

Batch; Zirconia supported by tungstophoric acid. Batch; Catalyst: A15, A131 and Dowex 50Wx-400

T = 358 K; r(A/B) = 1 T = 338 K, 348 K and 358 K; rA/B = 1, 2 and 3.

Niesbach, A. et al., 2012 [21]

RD; Catalyst A46; Inhibitors: PTZ and HME.

Sert E. and Atalay F., 2014 [40]

Pervaporation-esterification hybrid process; Pervap 2201; Ctalyst A131.

T = 380 - 393 K; P = 0.30 - 0.40 bar; rA/B = 1.10 - 3.26; mcat,dry = 0.205 kg m−1; 2 wt. % PTZ and 2 wt. % HME (top feed); 1000 ppm PTZ (AAc feed). T = 358 K; r(A/B) = 8; catalyst loading of 10 g/L S/V ratio = 70 m−1

Ostaniewicz-C. et al., 2014 [16]

Batch; Catalyst A15.

T = 323 - 363 K; r(A/B) = 2 to 3; Catalyst (wt. %) = 1-3.5.

Constantino, D. S. M. et al., 2015 [37]

Fixed-Bed Reactor (FBR); Catalyst A15.

T = 363 K; r(A/B) = 1.3.

Constantino, D. S. M. et al., 2015 [41]

SMBR; Catalyst A15.

Constantino, D. S. M. et al., 2017 [38]

Fixed-Bed Membrane Reactor (FBMR); Hybrid Silica AR membrane (Pervatech BV); Catalyst A15.

T = 323 K and 363 K; Configuration 2-4-4-2 columns per section (4 sections); Switching time =3.1 min; r(A/B) = 1.0. T = 363 K; r(A/B) = 1.0-3.0; PFBMR = 0.045 bar.

Xin Xen et al., 1999 [39]

Skrzypek, J. et al., 2009 [33]

Sert E., et al., 2012 [34] Sert E., et al., 2013 [35]

T = 353 K; rA/B = 1.

5

Cat. A: Ea = 66.00 ± 0.4 kJ mol−1; kc,0 = 1.12 × 104 (m4·5 mol−1·5 min−1); Cat. B: Ea = 72.30 ± 0.8 kJ mol-1; kc,0 = 9.82 × 104 (m4·5 mol−1·5 min−1); Keq = 9.603 × 105 × exp (-31400/(RT)); ΔH = 31.40 kJ mol−1 ΔH = 15.20 kJ mol−1; XAAc = 33%. Ea = 57.40 kJ mol−1; Keq= exp (2134/T-1.799); XAAc = 88.8% (over A131 at 338 K). Ea = 81.26 kJ mol−1; ΔH = 15.70 kJ mol−1; Keq = exp (-1888.66/T(K) + 8.17); XAAc = 38.69%; LHHW model was considered. XAAc = 96.3%; High selectivity to water in the n-BuOH/AAc/BAc/water system; Pervaporation and reaction rate increase with the operating temperature. kc = 1.52 × 107 × exp (– 66 988/(RT)) (mol·gcat−1·min−1); Ks,water = 1.589; Keq = exp (-1490/T(K) + 7.21); ΔH = 12.39 ± 4.80 kJ mol-1; ΔS = 59.98 ± 13.87 J.mol−1·K-1; LHHW model was considered. Multicomponent adsorption data were determined at 323 and 363 K (Table 4); BAc was produced with conversions significantly above the equilibrium; XAAc_FBR = 59.4%. XAAc = 99.7%; BAc ≥ 99.9 mol. % (in solvent free basis); Prod. = 6.0 kgBAc.(Lads−1.day−1); DesC. = 33.3 Ln-BuOH.kgBAc−1 Multicomponent pervaporation data were measured at 323 K, 353 K and 363 K (Table 5); BAc was produced with conversion 66% higher than in FBR with r(A/B) = 1.3; XAAc_FBMR = 98.7%.

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5. Towards process intensification

hydroquinone monomethyl ether (HME) and phenothiazine (PTZ). In that study, they also reported that the required amount of PTZ to avoid the polymerization reaction is defined by the AAc, because the polyacrylic acid formation is faster than the poly-butyl acrylate one and PTZ was found to be a more effective inhibitor than HME, as it does not depend on the presence of oxygen. Meanwhile, Niesbach and his coworkers [21], investigated experimentally, for the first time, the BAc synthesis using a pilot-scale RD column. This research team changed the key operating parameters considering the high risk of polymerization of BAc and AAc assessed in their previous work [52]. Several experiments were performed aiming to analyze different parameters, such as reflux ratio, distillate-to-feed mass ratio, feed molar ratio, top pressure and total liquid load. According to the results, the authors concluded that among the studied process parameters, the reflux ratio is the one with more influence in the RD process leading to the reduction of the conversion and product purity by increasing the reflux ratio and keeping the remaining parameters constant. A concentration profile can be observed in Fig. 7, which was obtained in a RD pilot scale unit for a set of operating parameters. In this case, the distillate-to-feed mass ratio was investigated concluding that decreasing this parameter (from 0.5 to 0.4), which is represented by the grey lines, leads to lower n-BuOH concentrations in the reactive section and, consequently, higher concentrations of AAc and BAc are achieved. This way, the reaction conversion increases due to the faster reaction rate leading to an higher BAc overall concentration. Regarding the feed molar ratio (n-BuOH/ AAc) parameter, when it decreases the AAc concentration increases in the reactive section. However, the reaction rate remains nearly constant since it depends on the concentration of all components. On the other hand, the BAc purity in the bottom product is improved with the decreasing of the feed molar ratio due to the lower n-BuOH concentration in that section. The pressure was also evaluated which directly influences the reactants conversion, increasing it due to a change in pressure from 0.3 to 0.4 bar, leading to a higher BAc purity in bottom product. Moreover, this is a sensitive parameter since it involves operating temperature changes. Therefore, the pressure value should be limited to avoid the system polymerization and taking into account the catalyst

Nowadays, it is possible to find different descriptions for PI in the open literature, which is one of the latest trends in Chemical Engineering and Process Technology. Gerven and Stankiewicz [31] gathered some of them in their recent review about fundamentals of PI and, in summary, most of them are related with strategies that allow to drastically reduce the energy consumption and to improve the process efficiency by compacting the respective plant design or/and reducing wastes. For that, innovation and creativity are a constant challenge in this field with process integration being one of the most relevant strategies for the PI. Different studies have been conducted aiming to find more sustainable alternative processes for the BAc synthesis. The first studies about heterogeneous catalysis were made about two decades ago where, equilibrium and kinetic constants, activation energy and vaporization enthalpy for the BAc system were reported as fundamental data [16,32–35]. Meanwhile, studies involving multifunctional reactors started to emerge, which are units where the reaction and separation occur simultaneously allowing to reduce operating and investment costs, such as: reactive distillation (RD) [7,36], fixed-bed reactor (FBR) [37] and fixed-bed membrane reactor (FBMR) [38], among others. The most relevant strategies and operating conditions are summarized in Table 3 as well as the principal results obtained. 5.1. Multifunctional reactors 5.1.1. Reactive distillation There are numerous studies concerning reactive distillation (RD) process for different equilibrium limited reactions with particular emphasis on esterifications [1,42–44]. Besides esterification cases, other successful commercial applications of RD include etherifications [45–47], cumene [48] and ethylene glycol [49] production and olefin metathesis [50]. Generally, this is the first option for an industrial application due to its practical implementation and to the deep knowledge about the industrial application of distillation processes available in the literature [51]. A RD process comprises reaction and separation in the same operation unit and its operating principle is based on the continuous separation of the products through the differences in the species volatilities while reaction occurs. Commonly, a solid catalyst like an ion exchange resin, for instance, is used as packing material in the reaction zone as represented in Fig. 6. Depending on the volatilities, the products can be separated either from the top or the bottom of the column enabling to shift the equilibrium towards the forward reaction. However, high temperatures are required in systems that present low volatilities as the BAc system case, which is harmful for this system since some of the present species tend to polymerize at high temperatures. For this reason, the use of inhibitors is crucial for the process. Schwarzer and Hoffman [36] studied experimentally the reaction equilibrium and measured kinetic data using a macroporous acid ion exchange resin, Lewatit K 2621, and those data were then used to simulate a process involving a catalytic tubular reactor and a RD column at 393 K. The maximum molar ester fraction reached was 93% after optimization. Zeng K. et al. [7], investigated theoretically the design and control of a RD column with an overhead decanter providing for the first time a control strategy for an industrial application to produce high purity BAc (99.83 mol. %) using the kinetic data from Schwarzer’s and Hoffman’s work [36]. However, these publications were only concerned about the production of BAc in an RD column on a theoretical basis. Moreover, the polymerization risk of the heat-sensitive compounds (BAc and AAc) was not considered in the simulation study. Niesbach et al. [52] were pioneers in the study of the inhibition period of AAc and BAc polymerization, which is the time taken for a significant extent of polymerization to occur. They concluded that this process is dependent on the amount of inhibitor added, the temperature and the gas phase composition. The conventional chemicals, commonly called inhibitors, that are used to stabilize AAc and other acrylates are

Fig. 6. Schematic representation of a reactive distillation unit for the butyl acrylate synthesis. 6

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observe an example of the concentration histories for the BAc synthesis in a FBR operating at 363 K. It is clear that, close to 100 min, the BAc maximum concentration at the column outlet significantly surpassed (38%) the BAc concentration attained in the equilibrium conditions (Ceq) due to the strong solid affinity for water removing it from the reaction medium by adsorption. Afterwards, the same authors investigated a cyclic process comprising several FBR, commonly designated by Simulated Moving Bed Reactor (SMBR), allowing a continuous production of BAc [41] with high-purity even if low-selectivity adsorbents are available [64], unlike batch chromatography. A series of fixed-bed columns are interconnected in a closed system, as represented in Fig. 9, which are usually packed with one solid material able to work as catalyst and adsorbent or packed with an adsorbent/catalyst homogeneous mixture, or other heterogeneous packing strategies [65]. It is a versatile equipment comprising four sections with different purposes: regeneration of the solid (section I), desorption of the less adsorbed compound (section II), adsorption of the most adsorbed compound (section III) and regeneration of the eluent/desorbent by the adsorption of the less adsorbed compound (section IV). At the same time, the reaction occurs in sections II and III. Different configurations (number of columns per section) can be used, which means that it is possible to increase or decrease the number of fixed-bed columns in the reaction/separation sections (section II and section III) as required, depending on the system, for the respective process optimization simultaneously optimizing the respective section flow rates. This kind of reactors makes use of Simulating Moving Bed Technology allowing the products separation by transporting them in opposite directions. At regular time intervals (commonly designated by switching time), all inlet and outlet streams move one fixed-bed column ahead in the fluid flow direction. In this way, the countercurrent mode between the fluid and the stationary phases is performed by simulating the stationary solid phase movement. Hence, the same column is in different sections during a cycle (Nct*, where Nc is the number of total columns in the equipment) passing through the different stages of the process. Indeed, SMBR has been successfully investigated for the production of different acetals and esters [66–72] showing to be an effective process for systems involving equilibrium limited reactions [73]. Nevertheless, this kind of reactors requires a substantial consumption of desorbent in order to ensure the complete regeneration of the solid mainly when it presents a large affinity towards one of the products, which is water in BAc synthesis, when compared with the affinity to the desorbent, as the A15 case. The desorbent consumption is directly related with the affinity that can be reduced by decreasing the resin sulfonic groups. Though, for reaction-separation systems a compromise should be considered once that decreasing the resin sulfonic groups implies a reduction on the catalytic activity [74]. Constantino and her co-workers [41] studied the influence of different operating parameters such as, switching time, configuration of the columns (number per section), the operating temperature and the feed molar ratio. For that, a complex mathematical model was developed based on the mathematical model for one FBR that was validated in their previous work taking into account the kinetic and adsorption data measured over the A15. Moreover, they considered internal and external mass transfer resistance,

Fig. 7. Concentration profile of a RD unit using a feed molar ratio of 3.1 (nBuOH/AAc), a reflux ratio of 1.99 and a distillate-to-feed ratio of 0.5 at 0.3 bar. The grey lines represent the same simulation but with a distillate-to-feed ratio of 0.4. Adapted with permission from Niesbach et al., 2012 [21].

specifications in terms of the maximum operating temperature. Additionally, the authors increased the total feed flow (about 21%) and they observed no significant effect except on BAc profile that resulted from the conversion reduction, which shows that the RD column is a kinetically controlled process for the synthesis of BAc. In that work, a non-equilibrium-stage model was considered to predict all experimental results and the model was validated using their own experimental data. Nevertheless, experimentally, the maximum AAc conversion obtained over Amberlyst 46 was about of 39% using a reflux ratio of 1.014, a distillate-to-feed ratio of 0.494 and a feed molar ratio of 3.18 at 0.4 bar. 5.1.2. Sorption enhanced reaction processes New alternative processes for BAc synthesis have arisen focusing on different technologies, namely chromatographic reactors. Similarly to the RD process, chromatographic reactors (CR) also comprise reaction and separation in the same equipment enabling to shift the equilibrium conversion in the forward direction and, consequently, achieving higher conversions by continuously removing one of the products. However, in CR a different separation technique is used, the chromatography separation, which is based on the selective adsorption of specific species in a solid stationary phase inducing different composition fronts along the reactor at different propagation velocities [53]. It means that, the compounds for which the solid/adsorbent has less affinity move faster along the reactor than the compounds for which the solid/adsorbent has more affinity, which are more retained. Commonly, the CR are packed with one solid material able to work as catalyst and adsorbent [54–59]. Some commercial ion exchange resins (as A15 for instance) have shown to be a very effective material mainly for esterification reactions by playing this dual role in the process [37,60–63]. Constantino et al. [37] performed a dynamic study of a FBR for the BAc synthesis starting by measuring multicomponent adsorption parameters over A15 considering non-reactive binary mixtures (n-BuOH/Water, nBuOH/BAc, AAc/Water and AAc/BAc) at two different temperatures (323 K and 363 K). The results are presented in Table 4, which evidence that A15 is very selective for water comparing with the remaining species. The solid affinity follows the descending order: water, n-BuOH, AAc and BAc. In the same work, the authors developed a mathematical model able to predict the concentration histories obtained in a FBR where adsorption and reaction occur simultaneously. For that, the kinetic data available in the literature [16] and the multicomponent adsorption parameters measured over A15 in that work were considered. According to the authors, the mathematical model was validated at different experimental conditions. In Fig. 8, it is possible to

Table 4 Multicomponent adsorption parameters for BAc system over A15 at 323 K and 363 K. [37]. Component

n-Butanol Acrylic Acid Butyl Acrylate Water

7

Qi (mol.L−1 wet

solid)

Ki (L. mol−1)

323 K

363 K

323 K

363 K

4.88 6.52 3.13 25.33

4.55 6.09 2.91 24.19

6.90 3.51 2.67 48.74

7.07 1.90 1.94 22.74

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recommended for esterification reactions mainly when heat-sensitive compounds are involved since it enables operating at milder temperatures than RD processes. Moreover, pervaporation has been recognized as a very efficient technique for azeotropic mixtures separation with low energy requirements and no additional species into the feed streams is needed [75]. Sert and Atalay [40] investigated a pervaporation-esterification hybrid process to carry out simultaneously the esterification reaction of AAc and n-BuOH and the separation of the BAc from water in order to increase the limiting reactant conversion. For that, the authors used a configuration that consists in a batch reactor (2 L) where a Pervap 2201 polymeric membrane was placed with an effective area of 179 cm2 and the Amberlyst 131 ion exchange resin was used as catalyst using a pressure of 4 mbar at the permeate side for sampling collection. The pervaporation assisted esterification process was evaluated by changing different operating parameters including temperature, molar ratio of n-BuOH to AAc, catalyst loading and membrane area to reactor volume ratio (S/V), with temperature being pointed out as the principal parameter since it showed a dual effect increasing both the pervaporation and the reaction rate. In addition, the authors reported that the used membrane presented high selectivity to water in that system and they concluded that coupling pervaporation with esterification reaction showed to be an efficient strategy for the equilibrium shifting towards BAc production by continuous water removal from the reaction medium. The maximum conversion of AAc achieved was 96.3% at 358 K. However, that work was not complemented with a model able to predict the experimental results that would be interesting for future work in the design of different processes with integration of Pervap 2201 membrane for BAc production. Constantino et al. [38] accomplished a study involving integration of chromatographic reactors with membrane technology evaluating the effect of membranes integration in the BAc synthesis. The authors compared the performance of a fixed-bed membrane reactor (FBMR), which consists of a commercial membrane packed with a catalyst/adsorbent material, with the performance obtained in a FBR. The same stationary phase was used in both reactors, A15, which works as catalyst and adsorbent simultaneously and identical operating temperature (363 K) was considered. Aiming a fair comparison, a mathematical model was developed based on the mathematical model previously determined and experimentally validated in the FBR study [37] using fundamental kinetic data [16] and multicomponent adsorption data [37] available in the literature. Additionally, multicomponent pervaporation data were measured by the authors using a commercial microporous silica membrane from Pervatech, which showed high selectivity for water in that system. The respective multicomponent pervaporation data are shown in Table 5. After simulating a FBR and a FBMR at the same operating conditions, it is possible to compare both concentrations profiles that can be obtained in different reactors, which can be observed in Fig. 11. According to the results, the reaction conversion in FBMR at steady state and isothermal conditions (363 K) increased about 66% in relation to

Fig. 8. Concentration histories of a FBR at steady state, using a feed equimolar ratio at 1 ml.min−1 and 363 K. Adapted with permission from Constantino et al., 2015 [37]. Ceq corresponds to the concentration of Butyl Acrylate at the equilibrium in batch conditions.

axial dispersion, velocity variations due to changes in the bulk composition and isothermal operation in order to predict the dynamic behavior of a SMBR for the BAc synthesis. Afterwards, important design parameters were determined through the Equilibrium theory enabling to achieve reactive separation regions for two different temperatures (323 K and 363 K). The best performance achieved is represented in Fig. 10, where it is possible to observe the different concentration profiles obtained for the reactants and products in the SMBR. For that, a 2-4-4-2 (columns per section) configuration operating at 363 K with an equimolar feed ratio and a switching time of 3.1 min were used. A higher amount of BAc is visible when compared with water since the last one is the most retained compound by the solid being dragged with it (to the left) in the opposite direction of the fluid (to the right) which is more concentrated in BAc leading, in this way to the products separation. According to the configuration used, the raffinate is collected at the outlet of column 10 and the extract at the outlet of column 2. Indeed, in those ports BAc and water are, respectively, the most concentrated compounds in solvent-free basis. Although an equimolar ratio is used as feed solution, the AAc is the limiting reactant since n-BuOH is also used as desorbent being in excess along all of the unit resulting in very diluted products. Therefore, downstream units are required for the extract and raffinate treatment in order to have the products with the desired purity, which was also investigated by the authors, who proposed a new process design, having SMBR as the process core unit, at industrial scale that will be discussed in section 6. 5.1.3. Pervaporation based hybrid processes Similarly to the chromatographic separation technique, membrane technology, where pervaporation process occurs, is strongly

Fig. 9. Schematic representation of a Simulated Moving Bed Reactor with a configuration of 2-4-4-2. Dashed lines represent the preceding position of the streams in the previous period (step) of that cycle. A = n-Butanol, B = Acrylic Acid, C = Butyl Acrylate and D = Water. 8

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Fig. 10. Concentration profile of a SMBR at steady state, using a feed equimolar ratio at 363 K, switching time of 3.1 min and configuration of 2-4-4-2 (columns per section) with the following flow rates: QFeed =5 ml.min−1, QDes =122 ml.min−1, QRec =24 ml.min−1, QX = 118 ml.min−1. Adapted from Constantino et al., 2015 [41]. Table 5 Multicomponent pervaporation data for Butyl Acrylate system over a commercial hydrophilic silica membrane from Pervatech BV: pre-exponential factors and overall activation energies. Adapted with permission from Constantino et al., 2017 [38]. Component n-Butanol Acrylic Acid Butyl Acrylate Water

Q0, i (mol/(s. m2.Pa) −13

5.66 × 10 5.17 × 10−10 1.72 × 10−12 3.90 × 10−11

Eperm, i (kJ/mol) −26.62 −9.37 −20.85 −30.53

FBR, which directly resulted from the integration of membranes with FBR allowing a more efficient continuous water removal from the reaction media through adsorption and pervaporation processes. The optimal feed molar ratio in FBMR was considered to be 1.3 (n-BuOH/ AAc) for which a maximum conversion of AAc of 98.7% was attained with a final product purity (BAc) of 97.8 mol. %.

Fig. 11. Concentration profiles at steady state of: a) a Fixed-Bed Reactor and b) a Fixed-Bed Membrane Reactor at isothermal conditions (363 K) and using a feed molar ratio of 1.3 (n-BuOH /AAc) at 1.0 ml.min−1. Adapted with permission from Constantino et al., 2017 [38].

6. Process integration strategies at industrial scale and economical evaluation

processes, which involve the presence of impurities that can considerably affect the performance of the previously studied RD process. Aiming to understand the impact of those impurities in the global process, Niesbach et al. developed a four-step methodology, which comprises the design of the base-case process (step 1), the identification and clustering of impurities (step 2), process simulation and process analysis (step 3) and, finally, the detailed design of bio-based process (step 4). Thereby, they started by analysing the biosynthetic routes for the synthesis of n-BuOH and AAc as well as possible side-reactions of the main components and impurities in the RD column in order to identify which of the impurities present in each bio-reactant and the key components would have the biggest impact on the product purity. For that, the Acetone-Butanol-Ethanol (ABE) fermentation process using clostridium species to ferment sugars from biomass was considered for the synthesis of bio-BuOH [82]. Regarding AAc, the most promising feedstock for its bio-based production is lactic acid either by a chemically catalysed dehydration reaction or by a fermentation process [83]. Nevertheless, according to the literature there are other alternative routes to get bio-AAc [84–87]. The similarity of the boiling points of the impurities and the boiling point of the final product, possible azeotropes and the reliability of thermodynamic and physical properties were taken into account for the identification of the representative component in each cluster. Thus, in summary, among the several impurities that can be present in these bio-based raw materials, the four key components for the reactive distillation process towards

Alternative process designs at industrial scale for the BAc synthesis have emerged along the last years aiming to find a more feasible and competitive solution to answer to the fast market growth. A summary of all these strategies and the respective main output data can be found in Table 6. Niesbach and his co-workers performed a scale up of the RD process previously studied at pilot scale, which was optimized by coupling a decanter at the top of a RD column to allow the recycling of unused reactants. That new configuration and respective optimized operating parameters lead to a reduction on the actual product (BAc) cost of 37% when compared with the conventional process (1350 €/tBAc) [1]. Moraru and Bildea [80] also investigated the design and control of a RD process with a decanter and a flash vessel at industrial scale allowing the recovery of 99 wt. % purity of waste water and leading to unreacted alcohol recovery. An economic evaluation was also performed and similar economic parameters to the values reported by Niesbach et al. [1] were reported, just reducing about 4 % of the product cost since a very similar process configuration is presented. Afterwards, Niesbach et al. [76,77] investigated a RD process making use of sustainable bio-based resources aiming to produce bioBAc driven by the fossil fuels reserves decline as well as by the urge of achieving eco-friendly and sustainable processes through the implementation and design of “greener” processes. In this way, the authors suggested the use of n-BuOH and AAc derived from biological 9

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Table 6 Review of the process integration strategies for butyl acrylate synthesis at industrial scale: processes, conditions and main results. Source

Processes and Materials

Conditions

Remarks/Results

Niesbach, A. et al., 2013 [1]

Single RD and RD coupled with Decanter (20,000 t/y); Catalyst A46; Inhibitors: PTZ and HME.

XAAc = 73.5%; 99.9% (with decanter) Reduction on the actual BAc market price (1350 €/t) = 12 %; 37 % (with decanter)

Niesbach, A. et al., 2013 and 2015 [76,77]

Semicontinuous Distillation coupled with a RD column and Decanter; Catalyst A46; Inhibitors: PTZ and HME; Bio-n-BuOH and bio-AAc as feed stream (containing impurities).

Constantino D. S. M. et al., 2015 [41]

SMBR followed by a DC (raffinate stream) and a Pervaporation unit (extract stream) (51,500 t/y); Catalyst A15 .

T = 380 to 403 K; r(A/B) = 0.81; r(A/B) = 1.08 (with decanter); P = 0.58 - 0.59 bar; RR = 1.67; RR = 6.96 (with decanter). RD column: No change is required in the operating parameters in relation to the previous study [1]; Semicontinuous Distillation: Top P = 0.2, 0.4 and 0.576 bar; RR = 200, 300 and 600; Top/bottom mass flow = 5, 7.5 and 10; Initial AAc, n-BuOH purity = 99.20, 9.44, 99.60 and 99.72 wt. %; Final AAc, n-BuOH purity = 99.70, 99.80, 99.90 and 99.95 wt. %. T =363 K; Configuration 2-4-4-2 columns per section (4 sections); Switching time =3.1 min.

Constantino D. S. M. et al., 2016 [78]

FBR coupled with SMBR followed by a DC (raffinate stream) and a Pervaporation unit (extract stream) (67,000 t/y); Catalyst A15.

T =363 K; Configuration 2-3-5-2 columns per section (4 sections); Switching time =3.1 min.

Moraru M. D. et al., 2016 [79]

Two conventional reactive-separation-recycle processes (20,000 t/y): FBR + 2 DC (one recycle); FBR + 4 DC (two recycles); Catalyst A131 (2000 kg). Design and control of a RD with Decanter and Flash Vessel (20,600 t/y); Catalyst A131 (2000 kg).

TReactor 1 = 355.7 - 358.2 K; TReactor 2 = 353.2 - 358.2 K; TDC_RSR 1 = 373.2 - 493.2 K; TDC_RSR 2 = 338.2 - 428.2 K.

Design and plantwide control of two conventional reactive-separation-recycle processes (20,500 t/y): FBR + 2 DC (one recycle); FBR + 4 DC (two recycles); Catalyst A131 (2000 kg).

T =356.2 K; r(A/B) = 3.

Moraru M. D. and Bildea C. S., 2017 [80]

Moraru M. D. and Bildea C. S., 2017 [81]

T = 338.2 - 403.2 K; P = 0.05 - 3.65 bar; Kinetic data from literature [35].

bio-BAc production that were identified through the four-step methodology developed by the authors are: isobutanol, butyric acid, propionic acid and butyl butyrate. Afterwards, their impact on the RD process for the BAC synthesis was studied considering concentrations up to 3000 ppm according to the n-BuOH and AAc suppliers material data sheets. The authors observed that additional purification steps are required since the critical impurities could not be removed just by changing the operating parameters of the RD process. So, they considered a semicontinuous distillation process to get the final product (BAc) with the desired commercial purity (≥ 99.5 wt.%), either by purifying the bio-reactants upstream before they enter the RD column or by purifying the final product after its production. According to the authors, the semicontinuous distillation is advantageous over batch distillation due to its flexibility to handle batch-to-batch variations in the initial concentrations of impurities (depending on the bio-sources) and in the final purity setpoint of the primary product. Moreover, the distillate and bottom products can be removed continuously at near steady-state, which is a significant advantage over the continuous and batch distillation. A detailed study of ternary semicontinuous distillation process is available in open literature for the BAc production from bio raw materials [76], where the purification of the final product and the bio-based reactants are considered, separately. The results obtained for the first approach showed that this separation strategy allows

All impurities of bio-based sources were identified as well as the impurities that resulted from side reactions in a RD column; Semicontinuous distillation process is suggested for the purification of the final product and/or biobased reactants; Cycle time is the critical parameter to reach the minimal purity desired.

XAAc = 99.5% BAc ≥ 99.9 mol. % Prod. = 7.20 kgBAc.Lads−1. day-1 Des.C = 27.6 Ln-BuOH.kgBAc-1 Reduction on the actual BAc market price (1350 €/t) = 44 % XAAc = 99.3% BAc ≥ 99.7 mol. % Prod. = 11.1 kgBAc.Lads−1. day-1 Des.C = 16.7 Ln-BuOH.kgBAc-1 Reduction on the actual BAc market price (1350 €/t) = 33 % XAAc = 50% (one recycle) XAAc = 55% (two recycles) Reduction on the actual BAc market price (1350 €/t) = 38 % X = 99.9% (both reactants) Water ≥ 99 wt. % Recovery of unreacted alcohol Reduction on the actual BAc market price (1350 €/t) = 44% Extractive distillation showed to be a better choice than conventional distillation BAc ≥ 99.5 wt. % Water ≤ 0.05 wt. % AAc ≤ 0.01 wt. %

keeping the final product purity just by changing the cycle times, and higher purities were attained with longer cycle times and without any change in the operating parameters (reflux ratio or column pressure). Concluding, it is an effective technology for the purification of the final product, as long as only small amounts of propionic acid are found in the bio-based feed streams leading to BAc with no significant concentrations of butyl propionate. Otherwise, butyl propionate is formed in the presence of propionic acid in the RD column, which is difficult to separate from BAc by semicontinuous distillation process due to its similar vapor pressure of the BAc. Regarding the upstream purification of the two bio reactants of the RD column, the semicontinuous process demonstrated that it should only be feasible for n-BuOH since in the AAc case, although all propionic acid is removed, a slight separation of AAc from acetic acid is observed. Moreover, it was concluded that this separation process is an attractive technology for other bio-based separations due to its high flexibility in respect to the chemical system treated and due to the fact that it is possible to perform different purification tasks using the same semicontinuous distillation apparatus. Nevertheless, no economic evaluation study about this process is available to determine its economic viability for an industrial application. Meanwhile, Moraru et al. [79] disclosed two alternative reactiveseparation-recycle processes based on a fixed-bed reactor coupled with 10

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Fig. 12. Process integration based on a conventional Simulated Moving Bed Reactor process for the continuous production of butyl acrylate. A, B, C and D correspond to n-Butanol, Acrylic Acid, Butyl Acrylate and Water, respectively [41].

Fig. 13. Process integration based on an Enhanced Simulated Moving Bed Reactor process for the continuous production of butyl acrylate. A, B, C and D correspond to n-Butanol, Acrylic Acid, Butyl Acrylate and Water, respectively [78].

different distillation columns (DC) to split AAc and BAc. The first configuration encloses a conventional distillation and another one comprises an extractive distillation process using ethylene glycol. Later, the same authors provided a plantwide control study considering the previous configurations [81] According to the authors, the control at the unit level was able to keep the mass inventory in the plant in dynamic simulations performed and achieve the required product purity when changes in throughput and reactor inlet temperature were made. The multiple possibilities to change the capacity, the ability for larger fresh feeds of AAc processing and the presence of only one steady state were factors pointed out as advantageous of the process. They also concluded that employing extractive distillation is to some extent better, overcoming important drawbacks of the conventional distillation: the unit is smaller, less BAc is recycled, and the risk of polymerization is lower due to lower temperatures. Though, slightly higher

production cost comparing with the values presented by Niesbach et al. [1] were reported. Constantino et al. [41] extended their study about SMBR for the BAc synthesis at industrial scale for which two different downstream units were proposed aiming to reach a competitive production of BAc (51,500 t/y). The authors pointed out a DC and a pervaporation unit as the most suitable options for the raffinate and extract streams treatment, respectively, as shown in Fig. 12. Several scenarios for eluent recovery were considered, by recycling n-BuOH to the SMBR unit to achieve the best performance. Hereafter, the global process was simulated taking into account all operating units and the optimal operating conditions were determined showing that the SMBR is an interesting alternative process for the BAc synthesis involving high reaction conversion (99.8%) with a high product purity (≥ 99.5 mol. %) after the respective raffinate treatment in a conventional single distillation 11

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743 714 707 725 866 238 – 191 69.6 57.6

76.6 15.0 101 26.9 37.4

34.4 33.0 27.3 9.94 8.23

855 762 836 762 911

36.7 43.6 38.1 43.6 32.5

11.2 12.1 9.69 30.5 30.4

column. Later, the same authors suggested a new process design based on the SMB technology by coupling a FBR with a SMBR [78] aiming to get higher productivity and lower desorbent consumption than in the previous study (conventional SMBR) for the same BAc purity (BAc ≥ 99.5 mol. %). Thus, the main difference between this configuration and the previous one (conventional SMBR unit), is the feed stream, which is composed by a reaction mixture in equilibrium, obtained from the FBR as is shown in Fig. 13. The optimal operating parameters were found showing a better performance than that obtained in the conventional SMBR, namely, the productivity was enhanced by about 54% and the eluent consumption decreased approximately 39.0%. Afterwards, similar downstream units considered in the conventional SMBR study were used for the extract and raffinate treatment and different scenarios for the eluent recovery were also taken into account in the global process integration. According to the simulation results, the best configuration comprises the recycling of 48.5% of the top stream of the DC to the feed of the FBR which leads to approximately 93.0% of eluent saving. A brief economic analysis for each process integration strategy investigated at industrial scale is summarized in Table 7 allowing to evaluate the feasibility and the competitiveness in relation to the conventional process described in the literature, from which the market reference price (MRP) for BAc is 1350 €/tBAc. [1]. According to the key economic indicators, all process integration strategies using heterogeneous catalysis present very competitive specific product cost, all of them below the MRP, allowing reducing its value from 32.5 to 43.6% as can be observed in Table 7. Moreover, it is possible to conclude that the SMBR based processes require lower capital expenditure (CAPEX) to reach more than twice of the production capacity when compared with RD based processes. Looking at the economic potential indicator, the conventional SMBR process seems to be the most economically attractive solution for the BAc synthesis at industrial scale. According to Table 7, it presents the highest economic potential (EP) value (30,500 €/y) with one of the lowest specific product cost (762 €/tBAc) and similar energy demand when compared with the remaining process integration strategies presented in the literature (1.8 MJ/kgBAc). 7. Conclusions Several studies have been developed to find the most feasible and eco-friendly process for butyl acrylate production. Hence, different process integration strategies have emerged and have been proposed as alternative processes for the butyl acrylate synthesis with significant economic and environmental progresses in relation to the conventional process. After a literature survey, the principal operating parameters used in the alternative studied processes, goals and respective results were summarized and gathered along this review allowing a direct analysis of future challenges and further developments towards the butyl acrylate production improvement in order to keep up with the global market evolution. Even though most of them focus on reactive distillation technology, more recently, other separation processes, namely, adsorption and/or pervaporation processes integrated with reaction, have demonstrated to be very promising strategies to overcome the drawbacks associated with esterification reactions involving heat-sensitive compounds as the butyl acrylate case. Although the pervaporation membrane technology integrated with chromatographic reactors lead to a more efficient separation process, as far as our knowledge goes, there is no available economic study assessing its viability. Therefore, the Simulated Moving Bed Reactor based process seems to be one of the most effective processes from the industrial point of view, comparing the key economic indicators of the different processes studied so far.

1.69 – – 1.80 1.87 RD with Decanter [1] RD with Decanter and Flash [80] RSR (one recycle) [79] Conventional SMBR [41] FBR plus SMBR [78]

20.0 20.6 20.5 51.5 67.0

CReactants (€/tBAc) CAPEX (€/tBAc/y) Production Capacity (x 103) (tBAc/y) Energy (x 103) (kJ/kgBAc) Key Indicators/ Processes

Table 7 Summary of key economic indicators for the different alternative industrial processes studied for the synthesis of butyl acrylate.

CUtilities (€/tBAc)

CAmort. (€/tBAc)

CSpecProduct (€/tBAc)

MRP Reduction (%)

EP (x 103) (€/y)

D.S.M. Constantino, et al.

Acknowledgments Financial support for this work was provided by Project 12

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“AIProcMat@N2020 - Advanced Industrial Processes and Materials for a Sustainable Northern Region of Portugal 2020”, with the reference NORTE-01-0145-FEDER-000006, supported by Norte Portugal Regional Operational Programme (NORTE 2020), under the Portugal 2020 Partnership Agreement, through the European Regional Development Fund (ERDF); Associate Laboratory LSRE-LCM - UID/EQU/50020/2019 - funded by national funds through FCT/MCTES (PIDDAC).

Arkema. US 6846948 B2, 2005. [30] C. Cooper, R. Zamarripa, Method for producing butyl acrylate, Rohm and Haas. US 20050059837 A1, 2005. [31] T. Van Gerven, A. Stankiewicz, Structure, Energy, Synergy, Time—The Fundamentals of Process Intensification, Ind. Eng. Chem. Res. 48 (2009) 2465–2474, https://doi.org/10.1021/ie801501y. [32] P. Dupont, J.C. Védrine, E. Paumard, G. Hecquet, F. Lefebvre, Heteropolyacids supported on activated carbon as catalysts for the esterification of acrylic acid by butanol, Appl. Catal. A Gen. 129 (1995) 217–227, https://doi.org/10.1016/0926860X(95)00099-2. [33] S. Jerzy, W. Teresa, G. Mirosław, W. Mariusz, Kinetics of the synthesis of propyl and butyl acrylates in the presence of some heteropolyacids as catalysts, Int. J. Chem. Kinet. 41 (2009) 12–17, https://doi.org/10.1002/kin.20358. [34] E. Sert, F.S. Atalay, Esterification of acrylic acid with different alcohols catalyzed by zirconia supported tungstophosphoric acid, Ind. Eng. Chem. Res. 51 (2012) 6666–6671, https://doi.org/10.1021/ie202609f. [35] E. Sert, A.D. Buluklu, S. Karakuş, F.S. Atalay, Kinetic study of catalytic esterification of acrylic acid with butanol catalyzed by different ion exchange resins, Chem. Eng. Process. (2013), https://doi.org/10.1016/j.cep.2013.06.004. [36] S. Schwarzer, U. Hoffmann, Experimental reaction equilibrium and kinetics of the liquid-phase butyl acrylate synthesis applied to reactive distillation simulations, Chem. Eng. Technol. 25 (2002) 975–980, https://doi.org/10.1002/15214125(20021008)25:10<975::AID-CEAT975>3.0.CO;2-3. [37] D.S.M. Constantino, C.S.M. Pereira, R.P.V. Faria, A.F.P. Ferreira, J.M. Loureiro, A.E. Rodrigues, Synthesis of butyl acrylate in a fixed-bed adsorptive reactor over Amberlyst 15, AlChE J. 61 (2015) 1263–1274, https://doi.org/10.1002/aic.14701. [38] D.S.M. Constantino, R.P.V. Faria, A.M. Ribeiro, J.M. Loureiro, A.E. Rodrigues, Performance evaluation of pervaporation technology for process intensification of butyl acrylate synthesis, Ind. Eng. Chem. Res. (2017), https://doi.org/10.1021/acs. iecr.7b01328. [39] X. Chen, Z. Xu, T. Okuhara, Liquid phase esterification of acrylic acid with 1-butanol catalyzed by solid acid catalysts, Appl. Catal. A Gen. 180 (1999) 261–269, https://doi.org/10.1016/S0926-860X(98)00337-8. [40] E. Sert, F.S. Atalay, n-Butyl acrylate production by esterification of acrylic acid with n-butanol combined with pervaporation, Chem. Eng. Process. 81 (2014) 41–47, https://doi.org/10.1016/j.cep.2014.04.010. [41] D.S.M. Constantino, C.S.M. Pereira, R.P.V. Faria, J.M. Loureiro, A.E. Rodrigues, Simulated moving bed reactor for butyl acrylate synthesis: from pilot to industrial scale, Chem. Eng. Process. 97 (2015) 153–168, https://doi.org/10.1016/j.cep. 2015.08.003. [42] I.K. Lai, Y.-C. Liu, C.-C. Yu, M.-J. Lee, H.-P. Huang, Production of high-purity ethyl acetate using reactive distillation: experimental and start-up procedure, Chem. Eng. Process. 47 (2008) 1831–1843, https://doi.org/10.1016/j.cep.2007.10.008. [43] V.H. Agreda, L.R. Partin, Reactive distillation process for the production of methyl acetate, Eastman Chemical US 4435595 A, 1984. [44] W.L. Luyben, K.M. Pszalgowski, M.R. Schaefer, C. Siddons, Design and control of conventional and reactive distillation processes for the production of butyl acetate, Ind. Eng. Chem. Res. 43 (2004) 8014–8025, https://doi.org/10.1021/ie040167r. [45] A. Bakshi, E.M. JonesJr, B.A. Strain, Process for the preparation of ETBE, Catalytic Distillation Technologies. US 5248836 A, 1993. [46] J.R. Adams, L.A. Smith Jr, D. Hearn, E.M. Jones Jr, R.P. Arganbright, Integrated Process for the Production of TAME, Catalytic Distillation Technologies US 5792891 A, 1998. [47] L.A. Smith Jr, Process for the Preparation of MTBE, Chemical Research & Licensing. US 5118873 A, 1992. [48] A.S. Pathak, S. Agarwal, V. Gera, N. Kaistha, Design and control of a vapor-phase conventional process and reactive distillation process for cumene production, Ind. Eng. Chem. Res. 50 (2011) 3312–3326, https://doi.org/10.1021/ie100779k. [49] A. Kumar, P. Daoutidis, Modeling, analysis and control of ethylene glycol reactive distillation column, AlChE J. 45 (1999) 51–68, https://doi.org/10.1002/aic. 690450106. [50] M.A. Al-Arfaj, W.L. Luyben, Design and control of an olefin metathesis reactive distillation column, Chem. Eng. Sci. 57 (2002) 715–733, https://doi.org/10.1016/ S0009-2509(01)00442-0. [51] S.R. Hiwale, V.N. Bhate, S.Y. Mahajan, M.S. Mahajani, Industrial applications of reactive distillation: recent trends, Int. J. Chem. React. Eng. (2004). [52] A. Niesbach, J. Daniels, B. Schröter, P. Lutze, A. Górak, The inhibition of acrylic acid and acrylate ester polymerisation in a heterogeneously catalysed pilot-scale reactive distillation column, Chem. Eng. Sci. 88 (2013) 95–107, https://doi.org/10. 1016/j.ces.2012.10.029. [53] M. Mazzotti, B. Neri, D. Gelosa, M. Morbidelli, Dynamics of a chromatographic reactor: esterification catalyzed by acidic resins, Ind. Eng. Chem. Res. 36 (1997) 3163–3172, https://doi.org/10.1021/ie9606348. [54] V.M.T.M. Silva, A.E. Rodrigues, Dynamics of a fixed-bed adsorptive reactor for synthesis of diethylacetal, AlChE J. 48 (2002) 625–634, https://doi.org/10.1002/ aic.690480319. [55] G.K. Gandi, V.M. Silva, A.E. Rodrigues, Synthesis of 1, 1-dimethoxyethane in a fixed bed adsorptive reactor, Ind. Eng. Chem. Res. 45 (2006) 2032–2039, https://doi. org/10.1021/ie051096e. [56] N.S. Graça, L.S. Pais, V.M. Silva, A.E. Rodrigues, Dynamic study of the synthesis of 1, 1-dibutoxyethane in a fixed-bed adsorptive reactor, Sep. Sci. Technol. 46 (2011) 631–640, https://doi.org/10.1080/01496395.2010.534121. [57] M.J. Regufe, R.P.V. Faria, A.M. Ribeiro, J.M. Loureiro, A.E. Rodrigues, Synthesis of the Biofuel Additive 1,1-Diethoxybutane in a Fixed-Bed Column with Amberlyst-15 Wet, Chem. Eng. Technol. 39 (2016) 1509–1518, https://doi.org/10.1002/ceat. 201500696.

References [1] A. Niesbach, H. Kuhlmann, T. Keller, P. Lutze, A. Górak, Optimisation of industrialscale n-butyl acrylate production using reactive distillation, Chem. Eng. Sci. 100 (2013) 360–372, https://doi.org/10.1016/j.ces.2013.01.035. [2] A.I. Stankiewicz, J.A. Moulijn, Process intensification: transforming chemical engineering, Chem. Eng. Prog. 96 (2000) 22–33. [3] A. Stankiewicz, Reactive separations for process intensification: an industrial perspective, Chem. Eng. Process. 42 (2003) 137–144, https://doi.org/10.1016/S02552701(02)00084-3. [4] F.X. Brady, Thomas F. Kauffman, Hot melt adhesives based on ethylene-n-butyl acrylate, National Starch and Chemical Corporation. US 4874804, 1989. [5] M.D. Gower, R.A. Shanks, Acrylic acid level and adhesive performance and peel master-curves of acrylic pressure-sensitive adhesives, J. Polym. Sci. Part B: Polym. Phys. 44 (2006) 1237–1252, https://doi.org/10.1002/polb.20779. [6] M.M. Gerst, G.B.D. Auchter, C.P.A. Beyers, PSA polymer of n-butyl acrylate, ethyl acrylate, vinyl acrylate, and acid monomer, BASF SE, Ludwigshafen (DE). US 0213992 A1, 2012. [7] K.-L. Zeng, C.-L. Kuo, I.L. Chien, Design and control of butyl acrylate reactive distillation column system, Chem. Eng. Sci. 61 (2006) 4417–4431, https://doi.org/10. 1016/j.ces.2006.01.041. [8] O. SIDS, N-Butyl Acrylate (Accessed on May 2013), http://www.inchem.org/ documents/sids/sids/141322.pdf. [9] W. Klaus Pfleger, W. Wieland Zacher, W. Klaus Boettcher, C. Ronald Skorczyk, D. Oskar Buechner, L. Franz Georg Mietzner, Manufacture of ethylene/n-butyl acrylate copolymers, US 4087601, 1978. [10] E.V. Chernikova, V.V. Yulusov, E.S. Garina, Y.V. Kostina, G.N. Bondarenko, A.Y. Nikolaev, Controlled synthesis of styrene-n-butyl acrylate copolymers with various chain microstructures mediated by dibenzyl trithiocarbonate, Polym. Sci. Ser. B 55 (2013) 176–186, https://doi.org/10.1134/S1560090413040027. [11] E.V. Chernikova, V.V. Yulusov, K.O. Mineeva, E.S. Garina, E.V. Sivtsov, Controlled synthesis of copolymers of vinyl acetate and n-butyl acrylate mediated by trithiocarbonates as reversible addition-fragmentation chain-transfer agents, Polym. Sci. Ser. B 54 (2012) 349–360, https://doi.org/10.1134/S1560090412070020. [12] G. Cooper, F. Grieser, S. Biggs, Butyl Acrylate/Vinyl acetate copolymer latex synthesis using ultrasound As an initiator, J. Colloid Interface Sci. 184 (1996) 52–63, https://doi.org/10.1006/jcis.1996.0596. [13] B.L. Funt, E.A. Ogryzlo, Copolymerization of butyl acrylate and vinylpyridine, J. Polym. Sci. 25 (1957) 279–284, https://doi.org/10.1002/pol.1957.1202511003. [14] Chemical Profile: Butyl Acrylate, TranTech Consultant, 2016 (Accessed on November, http://www.chemplan.ir/chemplan_demo/sample_reports/BA_ PROFILE.pdf. [15] T.M. Research, Global Butyl Acrylate Market, Transparency Market Researc h, 2018 (Accessed on September, https://globenewswire.com/news-release/2018/09/03/ 1564510/0/en/Global-Butyl-Acrylate-Market.html. [16] A.M. Ostaniewicz-Cydzik, C.S.M. Pereira, E. Molga, A.E. Rodrigues, Reaction kinetics and thermodynamic equilibrium for butyl acrylate synthesis from n-Butanol and acrylic acid, Ind. Eng. Chem. Res. 53 (2014) 6647–6654, https://doi.org/10. 1021/ie5002247. [17] C.L. Yaws, Thermophysical Properties of Chemicals and Hydrocarbons (Electronic Edition), Knovel, 2010. [18] S.K. Bhattacharyya, D.P. Bhattacharyya, Catalytic synthesis of n-butyl acrylate from acetylene, carbon monoxide and n-butanol under high pressure, J. Appl. Chem. 16 (1966) 202–205, https://doi.org/10.1002/jctb.5010160702. [19] R. Walter, S. Robert, Acrylic acid ester production, BASF SE. US 2883418A, 1959. [20] DIPPR, Thermophysical Properties Database, American Institute of Chemical Engineers, New York, 1998. [21] A. Niesbach, R. Fuhrmeister, T. Keller, P. Lutze, A. Górak, Esterification of acrylic acid and n-Butanol in a pilot-scale reactive distillation column—experimental investigation, model validation, and process analysis, Ind. Eng. Chem. Res. 51 (2012) 16444–16456, https://doi.org/10.1021/ie301934w. [22] J. Gmehling, Azeotropic Data, Wiley-VCH, Weinheim, 2004. [23] J. W. Bauer, J.T. Chapman, M.G.L. Mirabelli, J.J. Venter, Process for producing butyl acrylate, Rohm and Haas Company. US 6180819 B1, 2001. [24] H. Erpenbach, K. Gehrmann, H.t. Joest, P. Zerres, Continuous production of n-butylacrylate free from dibutylether, Hoechst Aktiengesellschaft. US 4012439 A, 1977. [25] M.N.A. Jawaid, D.E. Schepp, Process for the production and purification of n-butyl acrylate, Celanese International Corporation. US 6172258 B1, 2001. [26] H. Aichinger, M. Fried, G. Nestler, Method for producing (meth) acrylic acid esters, BASF Aktiengesellschaft. US 6320070 B1, 2001. [27] P. Deckert, H. Herbst, Continuous preparation of alkyl esters of (meth) acrylic acid, BASF SE. US 6472554 B1, 2002. [28] F. Ho, V. Julka, Processes for refining butyl acrylate, US 6605738 B1, 2003. [29] A. Riondel, J. Bessalem, Process for preparing butyl acrylate by direct esterification,

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Chemical Engineering & Processing: Process Intensification 142 (2019) 107563

D.S.M. Constantino, et al. [58] R.P.V. Faria, C.S.M. Pereira, V.M.T.M. Silva, J.M. Loureiro, A.E. Rodrigues, Sorption enhanced reactive process for the synthesis of glycerol ethyl acetal, Chem. Eng. J. 258 (2014) 229–239, https://doi.org/10.1016/j.cej.2014.07.073. [59] N.S. Graça, A.E. Delgado, D.S.M. Constantino, C.S.M. Pereira, A.E. Rodrigues, Synthesis of a renewable oxygenated diesel additive in an adsorptive reactor, Energy Technol. 2 (2014) 839–850, https://doi.org/10.1002/ente.201402079. [60] M. Kawase, T.B. Suzuki, K. Inoue, K. Yoshimoto, K. Hashimoto, Increased esterification conversion by application of the simulated moving-bed reactor, Chem. Eng. Sci. 51 (1996) 2971–2976, https://doi.org/10.1016/0009-2509(96)00183-2. [61] M. Mazzotti, A. Kruglov, B. Neri, D. Gelosa, M. Morbidelli, A continuous chromatographic reactor: SMBR, Chem. Eng. Sci. 51 (1996) 1827–1836, https://doi.org/ 10.1016/0009-2509(96)00041-3. [62] C.S.M. Pereira, A.E. Rodrigues, New sorption enhanced reaction technologies (SMBR and PermSMBR) for the production of diesel blends and green solvents, Chim. Oggi 31 (2013) 64–67. [63] C.S.M. Pereira, V.M.T.M. Silva, A.E. Rodrigues, Fixed bed adsorptive reactor for ethyl lactate synthesis: experiments, modelling, and simulation, Sep. Sci. Technol. 44 (2009) 2721–2749, https://doi.org/10.1080/01496390903135865. [64] A. Rodrigues, C. Pereira, M. Minceva, L.S. Pais, A. Ribeiro, A.M. Ribeiro, M. Silva, N. Graça, J.C. Santos, Simulated Moving Bed Technology: Principles, Design and Process Applications, Elsevier Science, 2015. [65] J.C. Gonçalves, A.E. Rodrigues, Simulated moving bed reactor for p-xylene production: dual-bed column, Chem. Eng. Process. 104 (2016) 75–83, https://doi.org/ 10.1016/j.cep.2016.01.010. [66] C.S.M. Pereira, M. Zabka, V.M.T.M. Silva, A.E. Rodrigues, A novel process for the ethyl lactate synthesis in a simulated moving bed reactor (SMBR), Chem. Eng. Sci. 64 (2009) 3301–3310, https://doi.org/10.1016/j.ces.2009.04.003. [67] C.S.M. Pereira, P.S. Gomes, G.K. Gandi, V.M.T.M. Silva, A.E. Rodrigues, Multifunctional reactor for the synthesis of dimethylacetal, Ind. Eng. Chem. Res. 47 (2007) 3515–3524, https://doi.org/10.1021/ie070889t. [68] N.S. Graça, L.S. Pais, V.M.T.M. Silva, A.E. Rodrigues, Analysis of the synthesis of 1,1-dibutoxyethane in a simulated moving-bed adsorptive reactor, Chem. Eng. Process. 50 (2011) 1214–1225, https://doi.org/10.1016/j.cep.2011.08.004. [69] V.M.T.M. Silva, A.E. Rodrigues, Novel process for diethylacetal synthesis, AlChE J. 51 (2005) 2752–2768, https://doi.org/10.1002/aic.10531. [70] M. Minceva, P.S. Gomes, V. Meshko, A.E. Rodrigues, Simulated moving bed reactor for isomerization and separation of p-xylene, Chem. Eng. J. 140 (2008) 305–323, https://doi.org/10.1016/j.cej.2007.09.033. [71] M. Kawase, Y. Inoue, T. Araki, K. Hashimoto, The simulated moving-bed reactor for production of bisphenol A, Catal. Today 48 (1999) 199–209, https://doi.org/10. 1016/S0920-5861(98)00374-5. [72] G. Ströhlein, Y. Assunção, N. Dube, A. Bardow, M. Mazzotti, M. Morbidelli, Esterification of acrylic acid with methanol by reactive chromatography: experiments and simulations, Chem. Eng. Sci. 61 (2006) 5296–5306, https://doi.org/10.

1016/j.ces.2006.04.004. [73] D.S.M. Constantino, R.P.V. Faria, A.E. Rodrigues, Chapter Four - sorption-enhanced reaction with simulated moving bed reactor and PermSMBR technologies, in: A.A. Lemonidou (Ed.), Advances in Chemical Engineering, Academic Press, 2017, pp. 261–330. [74] C.S. Pereira, A.E. Rodrigues, Process intensification: new technologies (SMBR and PermSMBR) for the synthesis of acetals, Catal. Today 218 (2013) 148–152, https:// doi.org/10.1016/j.cattod.2013.04.014. [75] P. Shao, R.Y.M. Huang, Polymeric membrane pervaporation, J. Membr. Sci. 287 (2007) 162–179, https://doi.org/10.1016/j.memsci.2006.10.043. [76] A. Niesbach, T.A. Adams, P. Lutze, Semicontinuous distillation of impurities for the production of butyl acrylate from bio-butanol and bio-acrylic acid, Chem. Eng. Process. 74 (2013) 165–177, https://doi.org/10.1016/j.cep.2013.09.008. [77] A. Niesbach, N. Fink, P. Lutze, A. Górak, Design of reactive distillation processes for the production of butyl acrylate: impact of bio-based raw materials, Chin. J. Chem. Eng. 23 (2015) 1840–1850, https://doi.org/10.1016/j.cjche.2015.08.019. [78] D.S.M. Constantino, R.P.V. Faria, C.S.M. Pereira, J.M. Loureiro, A.E. Rodrigues, Enhanced simulated moving bed reactor process for butyl acrylate synthesis: process analysis and optimization, Ind. Eng. Chem. Res. 55 (2016) 10735–10743, https://doi.org/10.1021/acs.iecr.6b02474. [79] M.D. Moraru, C.S. Bildea, A. Milea, Design and economic evaluation of a process for n-Butyl acrylate production, U.P.B. Sci. Bull, Series B 78 (2016) 113. [80] M.D. Moraru, C.S. Bîldea, Process for n-butyl acrylate production using reactive distillation: design, control and economic evaluation, Chem. Eng. Res. Des. 125 (2017) 130–145, https://doi.org/10.1016/j.cherd.2017.06.038. [81] M.D. Moraru, C.S. Bildea, Design and plantwide control of n-butyl acrylate production process, J. Process Control 58 (2017) 46–62, https://doi.org/10.1016/j. jprocont.2017.08.008. [82] V. García, J. Päkkilä, H. Ojamo, E. Muurinen, R.L. Keiski, Challenges in biobutanol production: How to improve the efficiency? Renew. Sustain. Energy Rev. 15 (2011) 964–980, https://doi.org/10.1016/j.rser.2010.11.008. [83] J.V. Haveren, E.L. Scott, J. Sanders, Bulk chemicals from biomass, Biofuels, Bioproducts and Biorefining 2 (2008) 41–57, https://doi.org/10.1002/bbb.43. [84] J.-L. Dubois, C. Duquenne, W. Hölderich, Method for producing acrylic acid from glycerol Arkema US 7910771 B2, 2011. [85] J. Ding, W. Hua, Game changers of the C3 value chain: gas, coal, and biotechnologies, Chem. Eng. Technol. 36 (2013) 83–90, https://doi.org/10.1002/ceat. 201200297. [86] E. Jong, A. Higson, P. Walsh, M. Wellisch, Bio-based Chemicals: Value Added Products from Biorefineries, IEA Bioenergy Task 42 Biorefinery, 2012. [87] J. Deleplanque, J.L. Dubois, J.F. Devaux, W. Ueda, Production of acrolein and acrylic acid through dehydration and oxydehydration of glycerol with mixed oxide catalysts, Catal. Today 157 (2010) 351–358, https://doi.org/10.1016/j.cattod. 2010.04.012.

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