Highly efficient iron(III) molecular catalysts for solketal production

Fuel Processing Technology 167 (2017) 670–673

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Short communication

Highly efficient iron(III) molecular catalysts for solketal production a,b

Roberto Esposito , Maria Elena Cucciolito Fabio Montagnaroa, Francesco Ruffoa,b,⁎ a b

a,b

, Angela D'Amora

a,b

a,b

, Rossella Di Guida

MARK

,

Dipartimento di Scienze Chimiche, Università di Napoli Federico II, Complesso Universitario di Monte S. Angelo, via Cintia 21, 80126 Napoli, Italy Consorzio Interuniversitario di Reattività Chimica e Catalisi, via Celso Ulpiani 27, 70126 Bari, Italy

A R T I C L E I N F O

A B S T R A C T

Keywords: Iron Solketal Glycerol Acetone

This communication describes extremely efficient homogeneous iron(III) catalysts for the synthesis of solketal from glycerol and acetone. The activities are the highest ever reported so far for this type of reaction, with TOFs up to 105 h− 1 at negligible catalyst loading.

1. Introduction It is well acknowledged that the choice of the auxiliary substances is strategic to reduce the impact of a chemical manufacture [1]. Within this context, the selection of the solvent is of crucial importance because the traditional VOCs are source of concern and main cause of pollution, due to their volatility, toxicity and flammability. Recently, the processing of renewable biomass has made available a wide range of alternative solvents, whose evaluation is the subject of important discussion and intensive research [2]. Among them, solketal (Scheme 1) attracts increasing interest, especially due to the valorization of glycerol, the by-product of biodiesel manufacture [3], and its applicability as fuel additive. Not surprisingly, new catalytic systems for the sustainable conversion of glycerol into solketal are constantly proposed [4–24]. Most of them are heterogeneous, and generally imply the use of solid acid catalysts such as Amberlyst [4–6,12,13], heteropolyacids supported on silica [8], Zr- and Sn-mesoporous substituted silicates [10], carbon functionalized with Brønsted acid groups [14,18], zeolites [15,24], metal aluminum phosphates M-AlPO4/xAlPO4 (x = Zn, Cu, Ni, or Co) [16], mixed Al/Nb oxides [19], and montmorillonite [22]. In these cases, complete conversion of glycerol is rarely achieved [20], and a substantial amount of solid catalyst is generally required (5–40%). By far less investigated are homogeneous catalysts, despite they commonly warrant mild reaction conditions, high efficiency, better control of the reactive sites, and an easier understanding of the reaction mechanism. In the face of these advantages, the difficult separation from the product often limits their application. The homogenous catalysts so far described for the production of solketal are both Brønsted

⁎

Corresponding author. E-mail address: francesco.ruff[email protected] (F. Ruffo).

http://dx.doi.org/10.1016/j.fuproc.2017.08.018 Received 4 May 2017; Received in revised form 14 August 2017; Accepted 14 August 2017 0378-3820/ © 2017 Elsevier B.V. All rights reserved.

[9,20] and Lewis acids, such as SnCl2 [11] and iridium complexes [7], either used at considerable concentrations (1%) and in the presence of additional solvents, or based on an extremely expensive metal. Very recently, a catalyst based on a Brønsted acid ionic liquid has been proposed [21], which combines the benefits of homogenous and heterogeneous catalysis, thanks to its possible reuse. In this case, the obstacle to a large scale application seems to be the high cost of the reaction medium. Therefore, it seems that a fully convincing catalytic system for the production of solketal has not yet been optimized. Recently, our research group became interested towards the application of Lewis acids in the convenient conversion of vegetable oils. In this context, it was successfully developed a family of zinc-based catalysts for the production of biodiesel [25–27], along with a process based on tungsten(VI) for the oxidative cleavage of oleic acid [28]. With the aim of further contributing to this flourishing field of research, our attention has been directed towards the production of solketal. This activity has resulted in the screening of simple iron(III) salts along with a class of new complexes containing pyridin-2-imine ligands (Fig. 1). The latter ones were selected aiming to discover any beneficial effect arising from the presence of the modular ancillary ligands 1-R. Furthermore, unlike many simple salts of iron(III), they are not hygroscopic and can be easily handled in air, which greatly facilitates the experimental manipulations. Herein, we communicate preliminary results of our study, that introduce unique novelties in this field of research thanks to the use of simple catalysts based on an economical and non-toxic metal, which promote the formation of solketal with unprecedented TOFs values (up to 105 h− 1). Their extraordinary efficiency ensures expedient reaction

Fuel Processing Technology 167 (2017) 670–673

R. Esposito et al.

Scheme 1. Manufacture of biodiesel and solketal production.

Table 1 Screening of catalystsa.

Fig. 1. Catalysts of type [FeCl3(1)]. UV (in acetone, λmax): [FeCl3(1-H)], 360 nm; [FeCl3(1-OMe)], 360 nm; [FeCl3(1-CF3)], 360 nm; [FeCl3(1-NO2)], 363 nm. Imine IR stretching (in nujol): [FeCl3(1-H)], 1626 cm− 1; [FeCl3(1-OMe)], 1623 cm− 1; [FeCl3(1CF3)], 1635 cm− 1; [FeCl3(1-NO2)], 1634 cm− 1. Anal. Calcd (found): [FeCl3(1-H)] (C12H10Cl3N2Fe): C, 41.85 (41.61); H, 2.93 (2.99); N, 8.13 (8.24). [FeCl3(1-OMe)] (C13H12Cl3N2OFe): C, 41.70 (41.52); H, 3.23 (3.35); N, 7.48 (7.32). [FeCl3(1-CF3)] (C13H9Cl3F3N2Fe): C, 37.86 (37.93); H, 2.20 (2.09); N, 6.79 (6.67). [FeCl3(1-NO2)] (C12H9Cl3N3O2Fe): C, 37.01 (37.26); H, 2.33 (2.40); N, 10.79 (10.61).

Entry

Catalyst

Catalyst, % (mol/mol)b

Conversion, %c

1 2 3 4 5 6 7 8 9 10 11 12 13 14

– FeCl3 FeCl3 FeCl3 FeCl3 [FeCl3(1-NO2)] [FeCl3(1-NO2)] [FeCl3(1-NO2)] [FeCl3(1-NO2)] FeCl3·6H2O Fe(ClO4)3 [FeCl3(1-H)] [FeCl3(1-OMe)] [FeCl3(1-CF3)]

– 0.050 0.0050 0.0010 0.00050 0.050 0.0050 0.0010 0.00050 0.00050 0.00050 0.00050 0.00050 0.00050

< 20 > 99 > 99 93 ± 92 ± > 99 > 99 94 ± 78 ± 84 ± 87 ± 45 ± 46 ± 74 ±

1 1

1 1 1 1 1 1 1

a Under reflux, 1.5 h, acetone purity grade 99.8% (2.3 g, 40 mmol), glycerol purity grade 99.5% (0.92 g, 10 mmol). b With respect to glycerol. c Selectivity ≥ 98%.

conditions, very low catalyst loading (up to only 10 ppm), and easy isolation of the product. This set of conditions meets the constraints imposed by green chemistry, that imply use of economical and safe solvents, the absence of auxiliaries, the application of efficient and cheap catalysts that do not require a demanding work-up for their separation.

mol), the same catalysts showed significant activities (entry 5 vs 9). Noteworthy the average TOFs were meaningful (up to 105 h− 1 for entry 5 case), and much higher than those ever reported for this reaction in similar experimental conditions: ca. 500 h− 1 for expensive iridium catalysts [7], and ca. 50 h− 1 for SnCl2 and common Brønsted acids, such as sulfuric or p-toluenesulfonic acid [11]. This evidence also demonstrates that the iron complexes act as true Lewis acids, plausibly through the mechanism described in literature [20]: the key-step is the attack of the alcoholic –CH2OH function of glycerol to the carbonyl group, activated via coordination to the metal center. This step is followed by cyclization and dehydration with formation of the product. The same loading (0.00050%) was adopted for comparing the other selected iron(III) compounds (entries 10–14). The screening of the entire panel revealed that the simple salts along with [FeCl3(1–CF3)] and [FeCl3(1–NO2)] are considerably active. These results also point out that the likely mitigation of acidity due to the presence of the nitrogen donors is largely compensated by the electron-withdrawing substituents. Therefore, successive experiments (Table 2) were carried out using [FeCl3(1–NO2)] because of its excellent activity even at low concentrations and its insensitivity to air and moisture. These further experiments were carried out varying the acetone/glycerol ratio while keeping the catalyst loading between 0.0010 and 0.0020% mol/mol. It is clear that the ratio acetone/glycerol plays a fundamental role. In fact a high value (6/1, entries 1 and 5) depresses the conversion, probably due to the consequent dilution of the catalyst. Instead a low ratio (2/1, entries 4 and 8) does not give satisfactory results, perhaps given the lower availability of the reagent. Therefore, the best outcomes

2. Results and discussion The catalysts [FeCl3(1-R)] [29] were prepared in diethyl ether through a simple template procedure [30], which involved the reaction in situ between pyridine-2-carboxaldehyde and the appropriate aniline in the presence of FeCl3. Immediate precipitation of the yellow-orange complexes was observed. UV [31] and IR [32] spectroscopy confirmed the presence of the C]N bonds. A first screening of catalysts was carried out using FeCl3 and [FeCl3(1-NO2)] in the range 0.050–0.0010% by moles with respect to the alcohol (entries 2–4 vs 6–8 of Table 1). The catalytic runs were performed under reflux with a acetone/ glycerol ratio 4/1 for 90 min. The vapors passed through a short column of 3A molecular sieves before reaching the condenser. In general, the initial reaction mixture is biphasic due to the poor miscibility of glycerol in acetone. As the reaction proceeds, the system becomes homogeneous because the presence of solketal improves the mutual miscibility of the components. The mixture was directly analyzed through 1H NMR spectroscopy, and conversion and selectivity were assessed by integrating proper regions (see example of Fig. 2). Without any catalyst (entry 1 of Table 1) the conversion was poor and, in fact, the biphasic mixture disclosed the presence of substantial amounts of unreacted glycerol. Even upon further reduction of their concentration (0.00050% mol/ 671

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R. Esposito et al.

4.4

4.3

4.2

4.1

4.0

3.9

3.8

3.7

3.6

3.5

3.4

3.3

3.2

3.1

3.0

2.9

2.8

2.7

2.6

2.5

2.4

2.3

2.2

2.1

2.0

1.9

1.8

1.7

1.6

1.5

1.4

1.3

Fig. 2. 1H NMR spectrum of an exemplificative reaction mixture at high conversion (in D2O).

with unprecedented TOFs values. The easy procedure allows the production of pure solketal with low iron content. The possibility to use complexes with modular nitrogen ligands is particularly attractive for their stability and handling, and also because their tunability makes the methodology transferable to other carbonyl compounds wherein simple iron salts may not be soluble. Furthermore, the introduction of chiral ligands opens towards the enantioselective synthesis of chiral acetals, which are important synthons for high value-added compounds. All of these possibilities will be studied in the near future.

Table 2 Optimization of the catalysis with [FeCl3(1-NO2)]a. Entry

[FeCl3(1-NO2)], % (mol/ mol)b

Acetone (mmol)/glycerol (mmol)

Conversion, %c

1 2 3 4 5 6 7 8

0.0010 0.0010 0.0010 0.0010 0.0020 0.0020 0.0020 0.0020

6:1 4:1 3:1 2:1 6:1 4:1 3:1 2:1

78 94 88 72 79 95 97 65

± ± ± ± ± ± ± ±

1 1 1 1 1 1 1 1

Acknowledgment Angela D'Amora thanks MIUR for a scholarship (Finanziamento Progetti Competitivi).

a Under reflux, 1.5 h, acetone purity grade 99.8% (2.3 g, 40 mmol), glycerol purity grade 99.5%. b With respect to glycerol. c Selectivity ≥ 98%.

References

were observed with intermediate ratios of 3/1 and 4/1. On this basis, the reaction mixture of entry 7 was treated aiming at isolating solketal. After the catalytic run, excess acetone was recovered by flash distillation. This simple work-up, which did not require any additional solvents or severe conditions, returned solketal with an iron content below 10 ppm, i.e. a purity grade compatible with bulk applications. As final remark, it is interesting to know that a preliminary test also successfully verified the compatibility of the catalysts with crude glycerol from biodiesel production through our catalytic systems [27]. Complete conversion of glycerol was obtained in the conditions of entry 6 of Table 1, and this result strongly encourages further studies aimed at bulky applications.

[1] P.G. Jessop, The use of auxiliary substances (e.g. solvents, separation agents) should be made unnecessary wherever possible and innocuous when used, Green Chem. 18 (2016) 2577–2578. [2] C.M. Alder, J.D. Hayler, R.K. Henderson, A.M. Redman, L. Shukla, L.E. Shuster, H.F. Sneddon, Updating and further expanding GSK's solvent sustainability guide, Green Chem. 18 (2016) 3879–3890. [3] C.-H. Zhou, J.N. Beltramini, Y.-X. Fan, G.Q. Lu, Chemoselective catalytic conversion of glycerol as a biorenewable source to valuable commodity chemicals, Chem. Soc. Rev. 37 (2008) 527–549. [4] J. Deutsch, A. Martin, H. Lieske, Investigations on heterogeneously catalysed condensations of glycerol to cyclic acetals, J. Catal. 245 (2007) 428–435. [5] C.X.A. da Silva, V.L.C. Gonçalves, C.J.A. Mota, Water-tolerant zeolite catalyst for the acetalisation of glycerol, Green Chem. 11 (2009) 38–41. [6] G. Vicente, J.A. Melero, G. Morales, M. Paniagua, E. Martín, Acetalisation of bioglycerol with acetone to produce solketal over sulfonic mesostructured silicas, Green Chem. 12 (2010) 899–907. [7] C. Crotti, E. Farnetti, N. Guidolin, Alternative intermediates for glycerol valorization: iridium-catalyzed formation of acetals and ketals, Green Chem. 12 (2010) 2225–2231. [8] P. Ferreira, I.M. Fonseca, A.M. Ramos, J. Vital, J.E. Castanheiro, Valorisation of glycerol by condensation with acetone over silica-included heteropolyacids, Appl. Catal. B Environ. 98 (2010) 94–99. [9] N. Suriyaprapadilok, B. Kitiyanan, Synthesis of solketal from glycerol and its

3. Conclusion These preliminary results demonstrate that simple iron(III) compounds promote the formation of solketal from acetone and glycerol 672

Fuel Processing Technology 167 (2017) 670–673

R. Esposito et al. reaction with benzyl alcohol, Energy Procedia 9 (2011) 63–69. [10] L. Li, T.I. Korányi, B.F. Sels, P.P. Pescarmona, Highly-efficient conversion of glycerol to solketal over heterogeneous Lewis acid catalysts, Green Chem. 14 (2012) 1611–1619. [11] F.D.L. Menezes, M.D.O. Guimaraes, M.J. da Silva, Highly selective SnCl2-catalyzed solketal synthesis at room temperature, Ind. Eng. Chem. Res. 52 (2013) 16709–16713. [12] M.R. Nanda, Z. Yuan, W. Qin, H.S. Ghaziaska, M.-A. Poirier, C.C. Xu, Thermodynamic and kinetic studies of a catalytic process to convert glycerol into solketal as an oxygenated fuel additive, Fuel 117 (2014) 470–477. [13] M.R. Nanda, Z. Yuan, W. Qin, H.S. Ghaziaskar, M.-A. Poirier, C.C. Xu, Catalytic conversion of glycerol to oxygenated fuel additive in a continuous flow reactor: process optimization, Fuel 128 (2014) 113–119. [14] R. Rodrigues, M. Gonçalves, D. Mandelli, P.P. Pescarmona, W.A. Carvalho, Solventfree conversion of glycerol to solketal catalysed by activated carbons functionalised with acid groups, Cat. Sci. Technol. 4 (2014) 2293–2301. [15] P. Manjunathan, S.P. Maradur, A.B. Halgeri, G.V. Shanbhag, Room temperature synthesis of solketal from acetalization of glycerol with acetone: effect of crystallite size and the role of acidity of beta zeolite, J. Mol. Catal. A Chem. 396 (2015) 47–54. [16] S. Zhang, Z. Zhao, Y. Ao, Design of highly efficient Zn-, Cu-, Ni- and Co-promoted M-AlPO4 solid acids: the acetalization of glycerol with acetone, Appl. Catal. A Gen. 496 (2015) 32–39. [17] S. Gadamsetti, N.P. Rajan, G.S. Rao, K.V.R. Chary, Acetalization of glycerol with acetone to bio fuel additives over supported molybdenum phosphate catalysts, J. Mol. Catal. A Chem. 410 (2015) 49–57. [18] M. Gonçalves, R. Rodrigues, T.S. Galhardo, W.A. Carvalho, Highly selective acetalization of glycerol with acetone to solketal over acidic carbon-based catalysts from biodiesel waste, Fuel 181 (2016) 46–54. [19] R. Rodrigues, D. Mandelli, N.S. Gonçalves, P.P. Pescarmona, W.A. Carvalho, Acetalization of acetone with glycerol catalyzed by niobium-aluminum mixed oxides synthesized by a sol–gel process, J. Mol. Catal. A Chem. 422 (2016) 122–130. [20] M.R. Nanda, Y. Zhang, Z. Yuan, W. Qin, H.S. Ghaziaskar, C.C. Xu, Catalytic conversion of glycerol for sustainable production of solketal as a fuel additive: a review, Renew. Sust. Energ. Rev. 56 (2016) 1022–1031. [21] Z. Gui, N. Zahrtmann, S. Saravanamurugan, I. Reyero, Z. Qi, M.A. Bañares,

[22]

[23]

[24]

[25]

[26]

[27]

[28]

[29]

[30] [31]

[32]

673

A. Riisager, E.J. Garcia-Suarez, Brønsted acid ionic liquids (BAILs) as efficient and recyclable catalysts in the conversion of glycerol to solketal at room temperature, ChemistrySelect 1 (2016) 5869–5873. M.N. Timofeeva, V.N. Panchenko, V.V. Krupskaya, A. Gil, M.A. Vicente, Effect of nitric acid modification of montmorillonite clay on synthesis of solketal from glycerol and acetone, Catal. Commun. 90 (2017) 65–69. M.J. da Silva, M.J. de Ávila, A.A. Júlio, SnF2-catalyzed glycerol ketalization: a friendly environmentally process to synthesize solketal at room temperature over on solid and reusable Lewis acid, Chem. Eng. J. 307 (2017) 828–835. V. Rossa, Y.S.P. Pessanha, G.C. Díaz, L. Diógenes Tavares Câmara, S.B.C. Pergher, D.A.G. Aranda, Reaction kinetic study of solketal production from glycerol ketalization with acetone, Ind. Eng. Chem. Res. 56 (2017) 479–488. M. Di Serio, G. Carotenuto, M.E. Cucciolito, M. Lega, F. Ruffo, R. Tesser, M. Trifuoggi, Shiff base complexes of zinc(II) as catalysts for biodiesel production, J. Mol. Catal. A 353–354 (2012) 106–110. V. Benessere, M.E. Cucciolito, G. Dal Poggetto, M. Di Serio, M. López Granados, F. Ruffo, A. Vitagliano, R. Vitiello, Strategies for immobilizing homogeneous zinc catalysts in biodiesel production, Catal. Commun. 56 (2014) 81–85. V. Benessere, M.E. Cucciolito, R. Esposito, M. Lega, R. Turco, F. Ruffo, M. Di Serio, A novel and robust homogeneous supported catalyst for biodiesel production, Fuel 171 (2016) 1–4. V. Benessere, M.E. Cucciolito, A. De Santis, M. Di Serio, R. Esposito, F. Ruffo, R. Turco, Sustainable process for production of azelaic acid through oxidative cleavage of oleic acid, J. Am. Oil Chem. Soc. 92 (2015) 1701–1707. K. Marjani, M. Mousavi, D.L. Hughes, Synthesis and crystal structure determination of copper(II) and iron(III) complexes of 2-(2-pyridyl)benzothiazole, Transit. Met. Chem. 34 (2009) 85–89. G. Olivo, O. Lanzalunga, S. Di Stefano, Non-heme imine-based iron complexes as catalysts for oxidative processes, Adv. Synth. Catal. 358 (2016) 843–863. G. Olivo, M. Nardi, D. Vìdal, A. Barbieri, A. Lapi, L. Gómez, O. Lanzalunga, M. Costas, S. Di Stefano, CeH bond oxidation catalyzed by an imine-based iron complex: a mechanistic insight, Inorg. Chem. 54 (2015) 10141–10152. M. Taghi Goldani, A. Mohammadi, R.J. Sandaroos, Green oxidation of alkenes in ionic liquid solvent by hydrogen peroxide over high performance Fe(III) Schiff base complexes immobilized on MCM-41, J. Chem. Sci. 126 (2014) 801–805.