Fig 1 - uploaded by Dr. Radheshyam R Pawar
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Selected portion of the 1 H NMR spectra of benzaldehyde-glycerol acetalization reaction products which clearly indicates the formation of the five-and sixmembered acetals.
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... cation exchanger, dry) were obtained from Sigma Aldrich. ZSM-5 and Na-Beta (Nab) zeolite were obtained from Zeochem L.L.C Uetikon, Switzerland. Other catalysts were synthesized by following the literature protocols. Detailed synthesis methodology and the PXRD profiles of synthesised catalyst are given in Supporting information (S1.1.-S1.5 and Fig. S1) ...
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... order to optimize the microwave conditions, the reaction of glycerol with benzaldehyde which yields two isomeric products namely, a five membered cyclic 1,3-dioxalane and six membered cyclic 1,3-dioxane was studied as a model reaction. The five-and six-membered products were characterized by 1 H-NMR and GC-MS spectroscopy, (Fig. 1 and Figs. S2-S9; Supplementary information). The progress of the reaction was monitored with respect to temperature, time, MW power and molar ratio of glycerol to benzaldehyde. The results of optimization studies are summarized in Fig. 2. An increase in reaction temperature from 40 °C to 140 °C showed significant increase in conversion ...
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... by-products formation was observed in the presence of catalysts such as K-10 MMT and SZr; however, formation of unknown by-product was observed in the case of PTSA catalysed reaction (Fig. S10, Supplementary information). We further investigated the possibility of reactants/products adsorption on the porous framework of heterogeneous catalysts by surface area measurements before and after the catalysis experiments. A significant drop in the surface area of K-10 MMT and SZr catalysts was observed after the acetalization reaction. The observed decrease ...
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... before and after the catalysis experiments. A significant drop in the surface area of K-10 MMT and SZr catalysts was observed after the acetalization reaction. The observed decrease in the catalysts surface area suggest the adsorption of reactants/ products on the catalyst surface which in turn reflects in the lower conversion (Table S1 and Fig. S11; Supplementary information) The PXRD profiles of the used catalyst (Fig. S12) suggest that the catalysts remain intact after the reaction and rule out any possibility of catalyst framework collapse and thus further improve the inferences derived from surface area measurements. Similar drop in conversion was noted when 4 Å molecular sieves were utilized as drying ...
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... surface area of K-10 MMT and SZr catalysts was observed after the acetalization reaction. The observed decrease in the catalysts surface area suggest the adsorption of reactants/ products on the catalyst surface which in turn reflects in the lower conversion (Table S1 and Fig. S11; Supplementary information) The PXRD profiles of the used catalyst (Fig. S12) suggest that the catalysts remain intact after the reaction and rule out any possibility of catalyst framework collapse and thus further improve the inferences derived from surface area measurements. Similar drop in conversion was noted when 4 Å molecular sieves were utilized as drying agent (attempt to shift the acetalization ...
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... the reaction between glycerol and cyclohexanone under the optimized reaction conditions gave 90% conversion of cyclohexanone to five-and six-membered cyclic ketal products with 98% selectivity towards five-membered cyclic ketal. Similar results have been reported by Corrado et al., by utilizing a dinuclear iridium complex as catalyst [12] (Figs. S13, S14; Supplementary information). The high selectivity of fivemembered ketals was also achieved for cyclopentanone (96% selectivity; 68% conversion) and cycloheptanone (99% selectivity; 77% conversion) where the decrease in conversion may be attributed to the geometrical hindrance posed by five-and seven-membered ring conformation. A ...
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The study of the production of glycerol ethyl acetal, through the acetalization of glycerol with acetaldehyde in a simulated moving bed reactor requires the selection of a suitable solvent/desorbent for the process. The methodology described in this paper, based on reaction, adsorption and environmental variables, lead to the identification of dime...
Citations
... 26,27 A protection strategy based on reversible acetalization reaction has been recently established to renewable biomass. 51,52 As a typical diol, ethylene glycol is a critical chemical with widespread industrial applications, 53 which can be directly obtained from cellulose over tungstenbased catalyst via cascade hydrolysis, retro-aldol condensation, and subsequent hydrogenation. [54][55][56] Another important biogenic polyol is glycerol. ...
... 61- 63 An interesting destination for the valorization of biobased ethylene glycol/glycerol is to combine the simultaneous production of cyclic acetals fuel additives via the acetalization strategy (Fig. 2). 51,52 Specially, the synthesized cyclic acetals with octane-improving, antidetonant, and antifreezing properties can not only serve as pour point, cold filter plugging point, and cloud point improvers in biodiesel/ gasoline blends but can also be involved the improvement in vapor pressure (in gasoline blends) or flash point (in diesel/ biodiesel blends). [48][49][50][51][52] Moreover, the oxygenated additives based on cyclic acetals can be synthesized via the acetalization method under mild conditions, avoiding high reaction temperature and gaseous hydrogen, which are generally used in most other fuel additives/biofuels synthesis, thus endowing the merits of low cost and environmental friendliness. ...
... 51,52 Specially, the synthesized cyclic acetals with octane-improving, antidetonant, and antifreezing properties can not only serve as pour point, cold filter plugging point, and cloud point improvers in biodiesel/ gasoline blends but can also be involved the improvement in vapor pressure (in gasoline blends) or flash point (in diesel/ biodiesel blends). [48][49][50][51][52] Moreover, the oxygenated additives based on cyclic acetals can be synthesized via the acetalization method under mild conditions, avoiding high reaction temperature and gaseous hydrogen, which are generally used in most other fuel additives/biofuels synthesis, thus endowing the merits of low cost and environmental friendliness. ...
Acetalization represents an appealing approach for the valorization of biobased platform molecules into valuable chemicals and fuels. Typically, it serves as both a synthesis tool for renewable cyclic acetals and a protection strategy to improve selectivity in biomass conversion. This contribution provides an overview on the application of the acetalization strategy in biomass valorization including synthesis of cyclic acetal fuel additives from the acetalization of biobased furanic compounds with biogenic ethylene glycol/glycerol and acetalization as a protection approach to improve product selectivity in biomass valorization. The latest progresses in the development of catalytic systems for the acetalization of biobased furanic compounds and biogenic ethylene glycol/glycerol are systematically summarized and discussed, with an emphasis on the reaction pathway, relationship between catalyst structures and their performance, and relevant catalytic mechanism. Moreover, the application of the acetalization strategy for protecting carbonyl groups/diol structure functionalities to improve the target products' selectivity in lignin depolymerization, 5-hydroxymethylfurfural oxidation, sorbitol dehydration, and xylose hydrogenation is also highlighted. Eventually, the prospects and challenges in the synthesis of cyclic acetal fuel additives as well as applying acetalization as a protection strategy in biomass valorization are outlined.
Keywords: Oxygenated fuel additives; Furanic compounds; Bioalcohols; Acetalization; Chemocatalysis.
... ppm corresponds to the HC(OR)2 in the 1 H NMR spectra. In another research by Pawar et al. [39], the acetalization of glycerol with benzaldehyde produced 1,3-dioxolane. The proton shifts of this compound are shifted at 5.77 and 5.90 ppm in 1 H NMR spectra. ...
Perfumes and fragrances are seen as an essential part of life in many countries, and many men and women use perfumes regularly. Originally, the perfume ingredients were derived from natural sources such as essential oils. However, these natural ingredients encountered challenges, such as poor crop quality, a limited supply of supplies, or difficulties using plant or animal extracts. Hence, with the development of synthetic organic chemistry in the 19th century, many ingredients were produced synthetically, resulting from the creativity of laboratory chemists, and used in today’s perfumes. Acetal is one of the synthetic aromatic chemicals used as ingredients in perfume nowadays. This paper review focuses on synthesis and characterization techniques for analyzing acetal derivatives of 2-methyl-3- (4-R-phenyl)propanal and their perfumery application, such as odor characteristics.
... To the best of our knowledge, very few and recent studies were published involving in the use of microwave assisted synthesis of acetals (in particular solketal) starting from glycerol. Pawar et al. [29] investigated the MW-assisted acetalization of glycerol and carbonyl compounds in high yields under both catalyst-and solvent-free conditions. Different aromatic aldehyde reacted with glycerol at 140 • C, 600 W during 15 min achieving high glycerol conversion (90%) but low selectivity to five-(60%) and six-(40%) membered acetal. ...
... Moreover, considering the studied reaction conditions, the MWassisted production of solketal need to be still investigate and optimized. In fact, all the few already mentioned published papers still present some inconvenience, as the use of homogeneous [23] or metal-based catalysts [30], the low solketal selectivity with the formation of isomers [29], high temperature [29,30], high watt power [29,30] and/or long time [31]. ...
... Moreover, considering the studied reaction conditions, the MWassisted production of solketal need to be still investigate and optimized. In fact, all the few already mentioned published papers still present some inconvenience, as the use of homogeneous [23] or metal-based catalysts [30], the low solketal selectivity with the formation of isomers [29], high temperature [29,30], high watt power [29,30] and/or long time [31]. ...
Sulfonic and propylsulfonic silica-based catalysts were synthesized, characterized and tested in the acetalization of glycerol (G) by a sustainable, solvent-free and fast procedure, under microwave irradiation, to produce solketal (S). The catalysts were prepared by different grafting procedures and their surface and structural properties were investigated by means of N2 adsorption isotherms, Thermogravimetric Analysis (TGA), X-ray Photoelectron Spectroscopy (XPS) and X-Ray Fluorescence Spectroscopy (XRF). Under the optimized reaction conditions (Temperature 40 °C, microwave power ˂100W, time 2 min and 1:12 glycerol/acetone molar ratio) the sulfonic materials, produced by the hydrothermal grafting, showed excellent performance in terms of activity, selectivity and stability, with no leaching of sulfonic groups after several cycles. By the correlation of the structure properties of the materials and their activity, the performance of the catalysts was shown strictly correlated both to the acidity and the surface density of the active sites.
... As pointed out above, when conventional heating is employed, a crucial issue in the ketalization reaction is the long reaction time, from half of an hour to 12 h, observed for a high solketal yield (82-99%), independently of the catalyst used. In this sense microwave irradiation has been an alternative heating system over the past few years and is known as to have a high synthetic potential (Leadbeater 2010); some works can be found in the literature concerning microwave-assisted chemical transformations of glycerol (Xie et al. 2019;Pawar et al. 2014;Priya et al. 2017). Pawar et al (2014) performed microwave assisted acetalization of glycerol with benzaldehyde using a 1:2 molar ratio in the presence of solid catalysts reaching conversions of 80% in 15 min with reaction temperature of 140 °C. ...
... In this sense microwave irradiation has been an alternative heating system over the past few years and is known as to have a high synthetic potential (Leadbeater 2010); some works can be found in the literature concerning microwave-assisted chemical transformations of glycerol (Xie et al. 2019;Pawar et al. 2014;Priya et al. 2017). Pawar et al (2014) performed microwave assisted acetalization of glycerol with benzaldehyde using a 1:2 molar ratio in the presence of solid catalysts reaching conversions of 80% in 15 min with reaction temperature of 140 °C. In particular, the use of a continuous microwave reactor for the synthesis of solketal was reported earlier (Cablewski et al. 1994) where a maximum 84% solketal yield was achieved with a high 1:13.5 glycerol/acetone molar ratio using p-TSA as catalyst. ...
The knowledge concerning the behavior of the dielectric properties of reaction mixtures, as the reaction proceeds, is essential for a deep understanding of the process involving microwave-heating technology. In this study it is investigated the dielectric properties of solketal/water/acetone/H2SO4 mixtures varying acid concentration and of the reaction mixtures during the glycerol ketalization with acetone under conventional heating. The reaction mixtures exhibits high loss tangent (0.2 < tan δ < 0.4 at 2.45 GHz) during reaction, reflecting a high absorption of microwave energy and its use allow to overcome long conventional-heating reactions times. Microwave-induced reactions are performed in a batch monomode pilot reactor to solketal production using various glycerol/acetone molar ratios and H2SO4, FeCl3·6H2O, and p-toluenesulfonic acid (p-TSA) as catalysts at various concentrations. Water formation during the reaction is a limiting factor to achieve complete conversion since the reaction quickly reaches equilibrium with the reverse reaction inhibiting the formation of more solketal. Hence water removal is vital in order to shift equilibrium towards the products. Due to the strong interaction of acetone and water with microwave irradiation a change in the vapor–liquid equilibrium occurs increasing the concentration of acetone/water in the vapor phase. Microwave experiments done without water removing do not intensify the solketal production and water removal of the reaction using molecular sieve provide reasonable conversions in shorter times. Process intensification with microwave irradiation is achieved by distillation of hydrated acetone and simultaneous addition of anhydrous acetone. Employing this novel approach the best experiments show 99.90% conversions to solketal in reaction times of 15 and 20 min using 0.22% (w/wt) of FeCl3·6H2O and H2SO4 respectively and employing 1:6 glycerol/acetone molar ratio.
... Homogeneous and heterogeneous catalysis 24 and microwaveassisted solvent-and catalyst free-reactions 25 have been reported to improve the selectivity and conversions of these glycerol ketals. Our interest was drawn to glycerol ketals due to their increased potential for commercialization from the availability of ketones derived directly from biomass. ...
... The samples before and the end of the reaction were then analyzed by Gas Chromatography-Mass Spectrometer (Agilent Technologies 7809 GC System with Agilent 19091-433 HP-5 MS 5% phenyl-methyl-polysiloxane). The conversion of 3,4-dimethoxybenzaldehyde to acetal was calculated with Eq. 1 [19]. ...
Synthesis strategy of hierarchical aluminosilicates was carried out by varying the starting material, type of a basic solution, and the hydrothermal condition. Aluminosilicate was synthesized using pre-treated low-quality kaolin by three kinds of basic solution, such as sodium hydroxide, sodium fluoride, and tetrapropyl ammonium hydroxide. The hydrothermal condition was carried out by gradual temperature and constant temperature. The desired mole ratio of Si/Al achieved by dealumination or by addition of silica. Products were characterized by X-ray diffraction, FTIR spectrometry, and nitrogen physisorption. Cation exchange was carried out on the product to obtain an acid catalyst. The acidity test of the catalyst was carried out by FTIR-pyridine spectrometry. The catalyst activity test was carried out to the acetalization reaction of 3,4-dimethoxybenzaldehyde with propylene glycol. The results showed that the catalyst synthesized with the basic solution of tetrapropyl ammonium hydroxide had the highest acid site number and the highest conversion of 3,4-dimethoxybenzaldehyde to acetal.
... Radheshyam R. Pawar et al. [78] performed acetylation of glycerol with carbonyl compounds using a microwave-assisted processing. The main feature is that the reaction is catalyst-and solventfree and high yields of cyclic acetals/ketals, including commercially-valuable compounds and precursors of the fuel additive, were observed. ...
... The yield of acetals under the above conditions was about 50% in the case of water and 55% in the presence of DMSO. p-Toluenesulfonic acid was also used in the reaction of acetalization of glycerol with benzaldehyde (Scheme 6) by Radheshyam et al. [78]. The process was carried out using SINEO M-II microwaves with variable frequency and temperature. ...
... Under these conditions, the benzaldehyde conversion was 67%, while the selectivity for dioxolane and dioxane was 47% and 53%, respectively. p-Toluenesulfonic acid was also used in the reaction of acetalization of glycerol with benzaldehyde (Scheme 6) by Radheshyam et al. [78]. The process was carried out using SINEO M-II microwaves with variable frequency and temperature. ...
Biodiesel is one of the most attractive sources of clean energy. It is produced by the transformation of vegetable oils with up to 10% formation of glycerol as a by-product. Therefore, development of new approaches for processing bio-glycerol into such value-added chemical compounds as solketals is necessary. Thus, various six- and five-membered cyclic compounds can be prepared by acetalization of glycerol with aldehyde or ketone. The resulting glycerol oxygenates are excellent fuel additives that increase viscosity, octane or cetane number, and stability to oxidation. In addition, these products significantly reduce carbon monoxide emissions from standard diesel fuel. In this review, we highlight recent advances in the glycerol valorization for the sustainable production of bio-additives. The review includes a discussion of the innovative and potential catalysts to produce solketals.
... Essa nova rota potencializa a sustentação de produção e comercialização da acroleína(CHAI et al., 2016;GINJUPALLI et al., 2014).Processos como fermentação, hidrogenólise ou desidroxilação do glicerol, produzem o composto 1,3-propanodiol, matéria-prima muito utilizada para produção de lubrificantes, polímeros, bem como na fabricação de solventes e adesivos(GONG et al., 2009;GONG et al., 2010;DURGAPAL et al., 2014).Vários sistemas catalíticos viáveis tem sido desenvolvidos para realizar a acetalização do glicerol para obtenção de acetais. É feita através da reação de álcoois com aldeídos ou cetonas, sob ação de catalisadores ácidos(PAWAR et al., 2014). Quando esta mesma reação é realizada com acetona forma-se como único produto o solketal, que adicionado à gasolina é capaz de diminuir a formação de goma e aumentar a octanagem(TORRES et al., 2012).A esterificação, reação da glicerina com ácido acético em presença de catalisadores ácidos, é uma das mais promissoras abordagens para utilização do glicerol e resulta na produção de mono, di e triacetatos de glicerol. ...
O excedente de glicerol produzido nas últimas décadas, devido ao aumento global na produção de biodiesel, vem criando uma demanda por novas tecnologias de purificação ou transformação do glicerol bruto em produtos de alto valor agregado, levando à viabilização do custo final do biodiesel. A glicerina bruta obtida como subproduto no processo de transesterificação contém, além de glicerol (45-85%), álcool, água, sais inorgânicos, ácidos graxos livres, mono-, di-, triglicerídeos, outras matérias orgânicas e resíduos em diferentes quantidades. É de extrema importância a purificação do glicerol para sua reutilização, a fim de reduzir problemas ambientais devido ao seu acúmulo e tornar o biodiesel mais rentável. O glicerol oferece uma ampla gama de oportunidades em muitas aplicações devido às suas propriedades únicas e disponibilidade no mercado. Este artigo analisa os avanços recentes nas tecnologias de purificação da glicerina bruta para utilização em produtos alimentícios, cosméticos e farmacêuticos, como purificação por membranas, troca iônica, destilação e adsorção; transformações biológicas e químicas para o processamento do glicerol em produtos químicos de alto valor agregado, como produção de gás hidrogênio, acroleína, éster, acetais, entre outros; e fornece estratégias para enfrentar os desafios de produção. Diante disso, alguns exemplos são dados para sustentar o objetivo do estudo.
... Pawar et al. [65] obtained high yields of cyclic acetals and ketals by microwave assisted acetalization under catalyst and solvent free conditions. ...
With the rapid development of the biodiesel industry all over the world, a large surplus of glycerol has been created, so economic uses of glycerol for value-added products are critical for the sustainability of the biodiesel industry. One of the main interests in recent years for glycerin utilization is its conversion in acetals and ketals, with the potential to be used as fuel additives. Glycerol acetals and ketals can be synthesized through the acid-catalyzed reaction of glycerol with aldehydes and ketones, respectively. This paper reviews different approaches and techniques used to obtain glycerol acetals and ketals, regarding the reactor design, catalyst design and the effect of different parameters in the reaction system.
... These two isomers are formed by reacting glycerol with formaldehyde and since these products are similar to those obtained in the reaction between glycerol and phenylacetaldehyde, the order of magnitude of the response factors was assumed to be similar. Typically, the most appropriate technique to identify the reaction products is 1 H NMR. Pawar et al. (2014) have recently demonstrated the feasibility of use of this technique, which was also used in the present study in addition to the identification. The identification can also be confirmed by 13 C NMR, as presented by Amrute et al. (2009), Bulanov et al. (2016, and Thota et al. (2015), among others. ...
... Even in the presence of a reduced amount of catalyst, 5 wt%, it was possible to achieve a glycerol conversion above 95 %. The addition of glycerol in a quantity greater than PA:glycerol equimolar ratio results in high PA conversion, as expected, and already observed by other authors (Pawar et al. 2014). On the other hand, the product selectivity is not significantly changed. ...
Oxidized and sulfonated-activated carbons (AC) were tested in the catalytic conversion of glycerol by acetalization reactions. The solids were treated with concentrated nitric acid and/or fuming sulfuric acid (AC, AC-N, AC-S, and AC-NS). The presence of sulfur and an increase in the acidity of the solids demonstrate the suitability of the oxidation as well as the sulfonation process, especially in the sample treated with concentrated nitric acid and fuming sulfuric acid (AC-NS). The best catalyst for the reaction of glycerol acetalization with phenylacetaldehyde was AC-NS, with a phenylacetaldehyde conversion of 95 % after 90 min at 383 K and selectivity of 88 and 12 %, respectively, to dioxolane and dioxane. These products can be used as hyacinth fragrance flavoring compounds. Furthermore, a contribution of homogeneous catalysis in these systems was not identified. Thus, we identified a possibility of glycerol conversion, a biodiesel by-product, into value-added products by suitable catalysts produced from activated carbons.
