An efficient solid base catalyst from coal combustion fly ash for green synthesis of dibenzylideneacetone

Accepted Manuscript Title: An efficient solid base catalyst from coal combustion fly ash for green synthesis of dibenzylideneacetone Author: Nurul A. Mazumder Ruma Rano PII: DOI: Reference:

S1226-086X(15)00144-6 http://dx.doi.org/doi:10.1016/j.jiec.2015.04.015 JIEC 2490

To appear in: Received date: Revised date: Accepted date:

9-12-2014 9-4-2015 14-4-2015

Please cite this article as: N.A. Mazumder, An efficient solid base catalyst from coal combustion fly ash for green synthesis of dibenzylideneacetone, Journal of Industrial and Engineering Chemistry (2015), http://dx.doi.org/10.1016/j.jiec.2015.04.015 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

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Graphical Abstract (for review)

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Highlights  An efficient solid base catalyst (SBC) was produced from waste coal combustion fly ash.  The synthesized solid base catalyst exhibits excellent catalytic activity and stability for dibenzylideneacetone (DBA) synthesis.

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 DBA was synthesized by solvent free crossed aldol condensation of acetone with benzaldehyde.

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An efficient solid base catalyst from coal combustion fly ash for green synthesis of dibenzylideneacetone Nurul A. Mazumder, Ruma Rano*

*

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Department of Chemistry, National Institute of Technology, Silchar 788010, India

Technology Silchar, Silchar 788010, India. Tel.: +91 9864907775.

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Corresponding author. Postal address: Department of Chemistry, National Institute of

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E-mail addresses: [email protected] (N.A. Mazumder), [email protected] (R. Rano).

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Abstract

The objective of the investigation was to evaluate the catalytic efficiency of a solid base catalyst

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(SBC) derived from coal combustion fly ash to synthesize dibenzylideneacetone (DBA, 94%

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yield). The catalyst was produced using potassium hydroxide (30 wt.%) on thermally activated

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F-type fly ash. The physico-chemical, mineralogical and morphological characterization of the fly ash and catalyst were performed using XRF, FT-IR, BET surface area analyser, XRD and

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SEM-EDS. The results of such analysis revealed that the catalyst obtained was associated with strong basic hydroxyl (–OH) sites that were highly suited to produce DBA by crossed aldol condensation reaction. Keywords

Solid base catalyst; Dibenzylideneacetone; F-type fly ash; Crossed aldol condensation

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1. Introduction The growing dependence on coal-fired electricity generation has resulted accumulation of huge quantities of coal combustion by product - fly ash which is regarded as a problematic solid

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waste all over the world. It has become a threat to the environment [1]. Bulk utilization of fly ash is one of the acceptable solution to mitigate such problems. The annual generation of fly ash in

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India is more than 131 million metric tons, whereas only about 55% of total ash is being utilized

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in various applications [2]. As trace elements existing in fly ash can leach out and contaminate soil as well as surface and groundwater, their study has become important for environmental

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protection [3]. Fly ashes have been applied in production of glass-ceramics [4], in manufacture of bricks [5], in composite cements [6], in concrete [7], in recovery of highly valued metals [8-

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10], in extraction of alumina [11] and silica [12], in agriculture [13], in water and atmospheric

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pollution control [14], in dye removal [15] and in zeolite synthesis [16].

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Coal generated fly ash, a mixture of various inorganic oxides viz. silica, alumina, ferric oxide, calcium oxide and other metal oxides (Mn2O3 and TiO2) along with inert crystalline

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phases such as mullite, quartz and magnetite [17,18] has been used as a catalytic support in many catalytic reactions [19-21]. Previously, as a catalyst itself, fly ash has been used for H2 production, deSOx, deNOx, hydrocarbon oxidation, hydrocracking, gas-phase oxidation of volatile organic compounds, aqueous-phase oxidation of organics, solid plastic pyrolysis and solvent-free organic synthesis [19]. Catalysts derived from magnetic enriched component of fly ash (ferrosphere) have been used for oxidative conversion of methane [22,23]. Fly ash supported various catalysts were also used for catalytic decomposition of ammonia [24,25], for benzylation of benzene and toluene [26] and for catalytic removal of p-nitrophenol in water [27]. Recently, fly ash supported various catalysts were utilized for synthesis of aryl chalcones [28], for

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biodiesel production by transesterification of sunflower oil with methanol [29], for production of glycerol carbonate by transesterification of glycerol with dimethyl carbonate [30,31] and for vapor phase dehydration of methanol [32].

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Heterogeneous catalytic aldol and crossed-aldol condensation is a powerful tool for formation of carbon-carbon bond in many kinds of carbonyl compounds [33]. Previously, Self-

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and crossed-aldol condensations of ketones and aldehydes have been reported over solid base

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catalysts [34-37]. Recently, modified calcium oxide has been used as stable solid base catalyst for aldol condensation reaction [38].

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Commercially, the base catalyzed reactions are largely performed by using homogeneous bases like NaOH, Ca(OH)2, KOH etc. [39,40]. But these bases are harmful, required in excess

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stoichiometric amount and difficult to recover from reaction mixture. Hence, high operating

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costs and severe environmental issues regarding base neutralization, product separation and

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purification, corrosion and waste generation motivated substantial efforts toward the development of processes mediated by heterogeneous catalysts [40]. The solid bases were found

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best alternative for solving the above said problems of homogeneous bases to make the reactions more selective [40], as the type of basicity (Brǿnsted or Lewis basic sites) and basic strength of the solid base can be designed according to the requirement of the reactions [41]. The solid bases are also of industrial interest because of their low temperature operation, environment friendly nature and higher selectivity of required product with ease of product separation. Utilization of solid base catalysts such as hydrotalcite, MgO and KF/Al2O3 are well documented in literature [39]. Base catalyzed Claisen-Schmidt condensation over NaOH modified fly ash as solid base catalyst has been reported earlier [21]. Such reaction was promoted by metal oxides constituting

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the fly ash, although, the percentage conversion and selectivity of reaction product were quite low. In the present investigation, the authors wish to report a new type of solid base catalyst

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(SBC), developed from fly ash, having catalytic efficiency comparable to other solid bases. SBC was synthesized using potassium hydroxide (30 wt.%) over thermally activated F-type fly ash.

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The catalyst was utilized for crossed aldol condensation of acetone with benzaldehyde to

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produce dibenzylideneacetone (DBA), an important compound used as a potential sunscreen component, as a medicine in treatment of oral cancer cells [42], as a ligand in organometallic

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chemistry [43] and as a reactant in various organic transformations [44,45]. So far the use of fly ash as a solid base catalyst to synthesize DBA is unprecedented in the literature. In this study, the

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effect of various reaction parameters such as catalyst-substrate weight ratio (w/w), reaction time

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(hours) and reaction temperature (°C) were also investigated. The catalyst was found effectively

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recyclable up to four cycles of synthesis, indicating its extraordinary stability, outstanding capability and that the active sites are not lixiviated in the reaction mixture. Thus the work

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reports an alternative pathway for utilization of solid waste fly ash by using it for developing novel, low-cost, recyclable and effective catalyst system and gives a solution to overcome the use of harmful liquid bases and other costly commercial heterogeneous catalysts for industrially important crossed aldol condensation reactions. 2. Experimental 2.1. Materials Fly ash was collected from Farakka Super Thermal Power Plant, West Bengal, India. Potassium hydroxide and acetone (99.5%) were purchased from Nice Chemicals Pvt. Ltd., India.

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Benzaldehyde (98.5%) and chloroform (99.5%) were obtained from Fischer Scientific Ltd., UK . Methanol (99.0%) was supplied from Hi-media Chem. Ltd., India. 2.2. Methods

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In order to obtain representative sample of fly ash, a systematic sampling procedure was followed. Homogenized fly ash was placed into a pan and oven-dried at 105 °C ± 0.5 °C for 24

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hours. Subsequently dried sample was sieved and less than 75 µm sized fraction was taken for

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further process. Thorough physico-chemical, mineralogical and morphological characterization were carried out using XRF (Phillips PW 2404), XRD (Windmax), FT-IR (Bruker), BET surface

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area analyser (ASAP 2010) and SEM-EDS (JSM-7600F). 2.2.1. Catalyst synthesis

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The solid base catalyst (SBC) was synthesized by chemical activation of thermally

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activated fly ash with potassium hydroxide for which 8 g of sieved fly ash (particle size ˂ 75

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µm) was washed with distilled water several times to remove dirt and impurities. It was dried and preheated for 4 hours at 900 °C to remove C, S and other impurities [46], cooled down to

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room temperature and then transferred into a 100 ml conical flask. 66.6 ml of KOH (30 wt.%) was transferred into the conical flask and kept in a stirred reactor and refluxed at 70 °C and 1000 rpm for 10 h under constant stirring. The solid thus obtained was separated by filtration, washed several times with distilled water and finally dried at 105 °C for 4 h, followed by calcinations at 250 °C for 2.5 h.

2.2.2. Catalyst characterization Fourier transform infrared (FTIR) spectrophotometer (Bruker) was used to identify the surface functional groups of the solid base catalyst (SBC) and the spectra were recorded over the range of 4000–400 cm-1.

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The crystalline nature and crystallite size of the samples were analyzed by X-ray diffraction study from X-ray powder diffractometer (Windmax) using Cu-Kα radiation (λ = 1.5406 Å) at 30 kV and 15 mA and the samples were scanned in 2θ range of 0-80°. Average

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crystallite size was estimated from the peak broadening according to the Debye-Scherrer equation [47]:

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B = 0.9 λ / β cos θ

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Where β is the broadening of the peak (measured as the full-width at half maximum intensity, FWHM), λ is the X-ray wavelength (1.5406 Å for Cu-Kα), B is the average crystallite

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size and θ is the angular location of the peak.

BET surface area analyser (ASAP 2010) was used to study the surface area of the

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synthesized catalyst by using nitrogen adsorption-desorption at 77 K by the Brunauer-Emmett-

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Teller (BET) method.

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Field emission gun-scanning electron microscopy (JSM-7600F) was used to study surface morphology of the solid base catalyst (SBC). The elemental composition was analyzed by using

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an energy dispersive X-ray detector (EDS) mounted on the microscope. 2.3. Catalytic activity of synthesized catalyst 2.3.1. Crossed aldol condensation of acetone with benzaldehyde Scheme 1.

The condensation of acetone with benzaldehyde (Scheme 1) was performed in liquid phase batch reactor consisting of 50 ml round bottom flask with condenser in a constant temperature oil bath with continuous magnetic stirring. A mixture of acetone (5 mmol) and benzaldehyde (10 mmol) was taken in the round bottom flask. The catalyst (catalyst to substrate ratio = 1 : 3), activated at 250 °C for 4 h was added in the reaction mixture. The reaction was

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carried out at different temperatures in the range of 50–90 °C for time ranging from 1 h to 3 h. After completion of the reaction, the reaction mixture was cooled and filtered to separate the catalyst. The filtrate was then collected in a petri dish and kept overnight at room temperature.

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The yellow crystalline products were then washed with methanol-water system (1:20) and recovered by recrystallizing with chloroform. The product obtained was confirmed by melting

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point measurement, FT-IR and 1H NMR Spectroscopy. The conversion of acetone and yield of

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dibenzylideneacetone (DBA) was calculated as follows:

Conversion of acetone (%) = 100 x (Initial wt.% – Final wt.%) / Initial wt.%

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Yield of DBA (%) = 100 x (Grams of DBA obtained / Grams of DBA obtained theoretically) 2.4. Regeneration of catalyst

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In order to make the process economic for further application, the used catalyst was

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washed with acetone and dried in oven at 105 °C for 4 h followed by activation at 250 °C for 2 h

3. Results and discussion

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before reuse in next reaction cycle under similar reaction conditions as earlier.

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3.1. Catalyst Characterization

3.1.1. Physico-chemical characterization The chemical composition (Table 1) of the fly ash from Farakka Super Thermal Power Plant for the synthesis of solid base catalyst (SBC) primarily contained SiO2, Al2O3, Fe2O3, TiO2, K2O, CaO, MgO along with other trace elements and mainly belongs to class F fly ash (SiO2 + Al2O3 + Fe2O3 ˃ 70%). The presence of Fe2O3 in the fly ash is attributable to the existence of hematite mineral in the feed coal [48]. BET surface area of the synthesized solid base catalyst (SBC) calculated from N2 adsorption-desorption isotherm was found as 12.62 m2/g and that of

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fly ash was 0.08 m2/g. The higher surface area of the catalyst provided more basic sites for the reaction. Table 1

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The FT-IR spectroscopic studies (Fig. 1) reveal that there is marked difference in the spectrum of fly ash and solid base catalyst (SBC). The broad intense band at around 3438 cm-1 is

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assigned to stretching mode of hydroxyl groups of silanols (–Si–OH) and adsorbed water

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molecules on the surface of SBC [49]. The broadness of the band is due to the strong hydrogen bonding. The hydroxyl groups do not exist in isolation and a high degree of association is

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experienced as a result of extensive hydrogen bonding with other hydroxyl groups. Fly ash exhibited characteristic peaks of silica at 1091, 784, 569 and 467 cm-1. The intense peak at 1091

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cm-1 is attributed to the asymmetric stretching vibrations of Si–O–Si bond and the band at about 784 cm-1 is associated with the symmetric stretching vibrations of Si–O–Si bridges, the band at

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569 cm-1 is due to asymmetric stretching vibration of Si–O–Al present in aluminosilicate structures and band at about 467 cm-1 is connected with bending vibrations O–Si–O present in

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silicate tetrahedra [50]. For SBC, the band at 1091 cm-1 was shifted to 1017 cm-1. The shifting of Si–O–Si band was due to the change on Si/Al ratio which is confirmed by the EDS (Fig. 4b and 5b). The slight reduction on Si–O–Si band owes to the substitution of a Si4+ for an Al3+ which thought to be tetrahedrally positioned on structure of the catalyst [51,52]. Fig. 1.

3.1.2. Mineralogical characterization The XRD pattern of fly ash (Fig. 2) and solid base catalyst (SBC) (Fig. 3) shows the presence of hexagonal quartz (JCPDS Card No. 85-1780) and orthorhombic mullite (JCPDS Card No. 88-2049) both in fly ash and solid base catalyst (SBC). In addition, small amount of

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hematite (JCPDS Card No. 88-2359) remains in the catalyst even after the chemical activation. The average crystallite size of solid base catalyst (SBC) was 45 nm showing the presence of nano-crystalline phases in the sample.

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Fig. 2. Fig. 3.

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3.1.3. Morphological characterization

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SEM micrograph of fly ash (Fig. 4a) shows that most of the fly ash particles are of spherical shape with smooth surface. Presence of some irregularly shaped amorphous particles

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was also confirmed from the SEM image. The SEM image of synthesized solid base catalyst

hydroxyl groups on the fly ash surface.

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(SBC) (Fig. 5a) shows agglomerated nanocrystalline particles (18.4 nm - 42.7 nm) with loaded

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EDS analysis of fly ash (Fig. 4b) reveals that there is high enrichment of Al, Si, O with

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traces of K, Mg etc. This shows that the finer particles (below 75 µm size) are essentially alumino-siliceous particles of spheroidal nature. EDS of solid base catalyst (SBC) (Fig. 5b)

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shows the increase in alumina content due to which Al/Si ratio increases. This increase in Al/Si ratio is due to the dissociation of silica during the activation process and the substitution of silica with aluminium on the structure of synthesized solid base catalyst (SBC) [53]. The high extent of basicity of solid base catalyst (SBC) was also supported by the presence of appreciable amount of potassium (7%).

Fig. 4. Fig. 5. 3.2. Catalytic activity of solid base catalyst (SBC)

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In order to demonstrate the catalytic activity of solid base catalyst (SBC) for maximum conversion of acetone producing highest yield of DBA, the effect of various reaction conditions such as catalyst-substrate weight ratio (w/w), reaction time (hours) and reaction temperature (°C)

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have been investigated.

To determine the optimum catalyst-substrate weight ratio (w/w), the reaction was

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performed taking various catalyst-substrate weight ratios ranging from 1 : 3 to 1 : 15 (Fig. 6). It

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was observed that the maximum yield of DBA has been attained upon the weight ratio 1 : 3 (catalyst : substrate) due to the maximum availability of the surface hydroxyl groups of solid

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base catalyst (SBC). The reactant (acetone) easily lost its proton to solid base catalyst (SBC) and transformed into nucleophile for initiating the condensation reaction.

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To find out the optimum reaction time (hours) in acetone conversion and DBA yield with

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solid base catalyst (SBC), the reaction was performed at 80 °C for different reaction times

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ranging from one hour to three hours (Fig. 7). The results revealed that the optimized reaction time is 2.5 hours in which solid base catalyst (SBC) provide maximum conversion (95%) of

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acetone to DBA with 94% yield.

To evaluate the effect of reaction temperature (°C) giving maximum yield of DBA, the reaction was allowed to attain various temperatures ranging from 50 to 90 °C (Fig. 8). It was observed that there occurred a uniform increase in percentage conversion of acetone from 50 to 80 °C producing maximum yield of DBA (94%) at 80 °C. Percentage conversion of acetone was not so much affected upon the increase in temperature beyond 80 °C. For fly ash, most of the chemical compounds are Al2O3 and SiO2, which have been treated at much higher combustion temperature, exhibiting good quality as catalyst support [19]. Modification of the fly ash with KOH exhibit active surface hydroxyl groups (–Si–OH and Al–

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OH) which are responsible for catalyzing the reaction. Similar catalytic performance was obtained upon repetition of the process with solid base catalyst (SBC) developed from waste fly ash collected at three different times from the thermal power plant. Due to the absence of active

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surface hydroxyl groups in original fly ash, without modification, it showed no such catalytic performance in DBA synthesis.

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Fig. 6.

Fig. 8.

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3.3. DBA characterization

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Fig. 7.

Melting point of yellow shiny crystalline solid (DBA) was obtained as 105 °C. FT-IR

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spectra (Fig. 9) of synthesized DBA reveals that the compound exhibits –C–H bending mode at 1418 cm-1, –C=O and –C=C stretching frequency at 1665 cm-1 and 1573 cm-1, asymmetric and

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symmetric aromatic –C–H stretching frequency at 3069 cm-1 and 2822 cm-1 respectively. H NMR (300 MHz, CDCl3): δ 8.14 (d, J=8.1 Hz, 2H), δ 7.64-7.59 (m, 6H), δ 7.50-7.45

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(m, 6H) (Fig. 10). Doublets at chemical shift position, δ 8.14 ppm appear due to hydrogen atoms of ethylene moiety of DBA. Multiplets appear in the range δ (7.64-7.59) ppm and δ (7.50-7.45) ppm due to aromatic as well as olefinic hydrogen atoms of the compound DBA. Fig. 9. Fig. 10.

3.4. Proposed mechanism The chemical activation of the fly ash with higher concentration of KOH at high temperature and longer duration resulted in breaking of Si–O–Si, Si–O–Al and Al–O–Al bonds. Release of Si and Al ions into the solution imparted reactive –Si–OH and Al–OH species.

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Increase in surface hydroxyl groups due to higher surface area and percentage of alumina prompted eminent basicity and catalytic activity of solid base catalyst (SBC) [21]. The plausible mechanism (Scheme 2) shows that the basic hydroxyl groups (surface –OH groups of Al–OH

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and –Si–OH) of solid base catalyst (SBC) abstracts proton from acetone resulting in the formation of nucleophile, which then attacks the electron deficient carbon of carbonyl group of

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benzaldehyde and finally produces DBA. The conversion proceeds via the intermediacy of

Scheme 2.

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3.5. Catalyst recyclability

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benzylideneacetone.

The used solid base catalyst (SBC) was filtered, washed with acetone and regenerated by

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heating in oven at 105 °C for 4 h followed by activation at 250 °C for 2 h. The excellent stability

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of the catalyst was confirmed from the fact that the catalyst could be recyclable up to four

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reaction cycles giving approximate yield of DBA in the range 94-81% and conversion of acetone in the range 95-84% (Table 2). Percentage yield of DBA was significantly decreased after 4th

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reaction cycle, which is attributed due to the deposition of carbonaceous material on the external surface of the used catalyst, which may block the active sites present on the catalyst [20,54]. This catalytic process for condensation reaction may lower the cost of production of the product in fine chemical industries, as commercial catalyst (zeolites, KF etc.) can be replaced by environment-friendly and cost-effective solid base catalyst (SBC) developed from waste fly ash. The catalyst synthesized in this study showed superior stability and catalytic activity in crossed aldol condensation reaction compared to the solid base catalyst reported by Jain et al. [21].

Table 2

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4. Conclusions From the foregoing discussions, it is apparent that an efficient catalytic method has been established for synthesis of DBA (94% yield) by crossed aldol condensation reaction between

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acetone and benzaldehyde using a solvent free environmentally greener solid base catalyst (SBC). The enhanced increase in surface area and percentage of alumina are the important

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factors for the increase in surface hydroxyl groups responsible for basicity and higher catalytic

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activity of solid base catalyst (SBC). Recyclability up to four reaction cycles indicates the extraordinary stability and capability of the catalyst. This investigation results in the production

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of a low-cost, effective, environment friendly and stable solid base catalyst. Acknowledgements

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The authors are grateful to Sophisticated Analytical Instrument Facility, IIT Bombay for

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providing XRF, FT-IR, 1H NMR and SEM-EDS analysis; CSIR-CSMCRI, Bhavnagar, Gujarat

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for BET surface area analysis and also would like to thank Ministry of Human Resource Development, Government of India for financial support.

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d

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te

[48] N. Koukouzas, C. Ketikidis, G. Itskos, Fuel Process. Technol. 92 (2011) 441-446. [49] N.M. Musyoka, L.F. Petrik, E. Hums, H. Baser, W. Schwieger, Catal. Today 190 (2012)

Ac ce p

38-46.

[50] W. Mozgawa, M. Król, J. Dyczek, J. Deja, Spectrochim. Acta A 132 (2014) 889-894. [51] N. Sapawe, A.A. Jalil, S. Triwahyono, M.I.A. Shah, R. Jusoh, N.F.M. Salleh, B.H. Hameed, A.H. Karim, Chem. Eng. J. 229 (2013) 388-398. [52] M. Criado, A. Fernández-Jiménez, A. Palomo, Micropor. Mesopor. Mat. 106 (2007) 180191. [53] N. Murayama, T. Takahashi, K. Shuku, H. Lee, J. Shibata, Int. J. Miner. Process. 87 (2008) 129-133. [54] B. Tyagi, M.K. Mishra, R.V. Jasra, Catal. Commun. 7 (2006) 52-57.

17 Page 18 of 33

Figure captions Fig. 1. FT-IR spectra of (a) fly ash and (b) solid base catalyst (SBC).

Fig. 3. XRD pattern of solid base catalyst (SBC). Fig. 4. (a) Scanning electron micrograph and (b) EDS spectra of fly ash.

ip t

Fig. 2. XRD pattern of fly ash.

cr

Fig. 5. (a) Scanning electron micrograph and (b) EDS spectra of solid base catalyst (SBC).

us

Fig. 6. Effect of catalyst : substrate weight ratio (w/w) on crossed aldol condensation of acetone with benzaldehyde. Reaction conditions: Reaction time 2.5 h, Reaction temperature 80 °C.

an

Fig. 7. Effect of reaction duration (hours) on crossed aldol condensation of acetone with benzaldehyde. Reaction conditions: catalyst : substrate weight ratio 1:3 (w/w), Reaction

M

temperature 80 °C.

d

Fig. 8. Effect of reaction temperature (°C) on crossed aldol condensation of acetone with

h.

te

benzaldehyde. Reaction conditions: catalyst : substrate weight ratio 1:3 (w/w), Reaction time 2.5

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Fig. 9. FT-IR spectra of dibenzylideneacetone (DBA). Fig. 10. 1H NMR spectra of dibenzylideneacetone (DBA). Scheme 1. Crossed Aldol condensation of acetone with benzaldehyde over solid base catalyst (SBC).

Scheme 2. Mechanistic pathway for crossed aldol condensation of acetone and benzaldehyde over solid base catalyst (SBC).

18 Page 19 of 33

O

ip t

CHO O SBC H3C Benzaldehyde

CH3

cr

+ 800C, 2.5 h

Acetone

Dibenzylideneacetone

Ac ce p

te

d

M

an

Scheme 1.

us

2

19 Page 20 of 33

e hyd e d zal CHO Be n

O

O

CH3

O M O

O

O O

+

CH3 M OH

M OH2

O +

CH3

OH2

ip t

Ac

et o

ne

H2C

cr

H2O O

CROSSED ALDOL

M OH O SBC

CONDENSATION

an

O

en ea ce to ne

M OH2

O

M OH2

O

M OH

O

O

d

yl id

O

te

be nz

+

O

Ac ce p

Di

CHO

CH3

Benzylideneacetone

M

O

us

O

CH2

( M = -Si / Al )

Scheme 2.

20 Page 21 of 33

Table 1 Chemical composition of fly ash (XRF analysis) Al2O3 Fe2O3 27.719 6.736

TiO2 1.792

K2O 1.002

CaO 0.378

P2O5 0.278

MgO 0.144

Na2O 0.102

MnO 0.046

SrO SO3 0.031 0.011

te

d

M

an

us

cr

ip t

SiO2 55.842

Ac ce p

Composition Weight (%)

21 Page 22 of 33

Table 2 Condensation of acetone with benzaldehyde over fresh and regenerated solid base catalyst (SBC).

Ac ce p

te

d

M

an

us

cr

ip t

Reaction cycle Conversion of acetone (%) Yield of DBA (%) st 1 95 94 2nd 94 92 rd 3 91 87 4th 84 81 Reaction conditions: catalyst : substrate weight ratio 1 : 3, Reaction temperature 80 0C, Reaction time 2.5 h.

22 Page 23 of 33

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M

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cr

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Figure

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M

an

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cr

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Figure

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ed

M

an

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cr

i

Figure

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ed

M

an

us

cr

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Figure

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ed

M

an

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cr

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Figure

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ed

M

an

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cr

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Figure

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M

an

us

cr

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Figure

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ce

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ed

M

an

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cr

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Figure

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ed

M

an

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cr

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Figure

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M

an

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cr

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Figure

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