Novel Esterification of Glycerol Catalysed by Tin Chloride (II): A Recyclable and Less Corrosive Process for Production of Bio-Additives

Abstract  

In this work, a novel process based on use of a SnCl₂·2H₂O catalyst which is less corrosive, inexpensive, and a water tolerant Lewis acid was employed for synthesis of fuel bio-additives from glycerol. High yields and selectivities were achieved for glycerol esterification with acetic acid under mild reaction conditions. The SnCl₂ catalyst showed to be as active as p-toluene sulfonic and sulfuric acid, catalysts commonly used in acid-catalysed esterification reactions. However, its use has significant advantages in comparison to these Br?nsted acid catalysts, including lower reactor corrosion and unnecessary neutralization at the end reaction. The SnCl₂ catalyst can also be recovered and reused without loss of catalytic activity. Additionally, effects of reaction temperature, HOAc:glycerol molar ratio and catalyst concentration on both selectivity and yield of glycerol acetates were also investigated. The lower corrosiveness, facilitated handling, as well as potential for reuse without activity loss after simple recycle protocols are positive aspects of SnCl₂ catalysts.     

Esterification of high acidity vegetable oil catalyzed by tin-based catalysts with different sulfate contents: contribution of homogeneous catalysis

Biodiesel production costs can be significantly reduced by using nonrefined feedstock. Sulfated solid catalysts have been proposed for producing biodiesel from acid oils by esterification reactions. Nevertheless, leaching of sulfate species to the reaction medium may occur, but often it is not considered. In this article, a commercial tin sulfate (SnSO₄) was used as a catalyst for the esterification of a feedstock with high content of free fatty acid in order to assess the contribution of the homogeneous catalysis in different situations. SnSO₄ was calcined at different temperatures (300, 400, 500 and 700?°C) and converted into SnO₂ after calcination at temperatures higher than 300?°C. Homogeneous catalysis seems possible to occur with all of the catalysts, but it was clearly observed for the uncalcined catalyst (SnSO₄) and for that calcined at 300?°C (SnSO₄(300)). For these catalysts, an important leaching of the sulfate species was confirmed. Higher conversions were obtained with the uncalcined SnSO₄. Reactions at the same conditions using sulfuric acid as catalyst at concentrations of 0.1% were performed and confirmed conversions higher than 80%. Heterogeneous catalysis plays a significant role only with the catalyst that present the highest specific surface areas and acidity (SnSO₄(400)). As some small amount of sulfate species is retained in the structure or surface of the calcined catalysts (even after calcination at 700?°C), we cannot exclude the possibility that these species are also leached during reaction. Thus, a possible contamination of biodiesel through the use of sulfated catalysts cannot be ruled out.     

Producing Fatty Acid Methyl Esters from Free Fatty Acids with Ionic Liquids as Catalyst

Three Brønsted acidic imidazole dicationic ionic liquids (ILs) with different length of alkyl chains, [C_n(Mim)₂][HSO₄]₂ (n = 3, 6, 12), were prepared and used as catalyst for the esterification reaction of free fatty acids and methanol. Taking oleic acid as model acid, the catalytic performances of the synthesized ILs for the esterification were evaluated. The main physicochemical properties of the ILs, thermal stability, acidity, solubility in common solvents, and causticity on Austenitic stainless steel 316, were examined. [C₃(Mim)₂][HSO₄]₂ demonstrated the highest catalytic activity and enabled to assess the preliminary optimum esterification condition of oleic acid and methanol. Under optimized reaction conditions, the yield of oleic acid methyl ester was up to 95 %. The ILs have great potential as catalysts for producing fatty acid methyl esters from long‐chain free fatty acids.     

Synthesis of Glycerol Triacetate Using a Brønsted–Lewis Acidic Ionic Liquid as the Catalyst

Brønsted–Lewis acidic ionic liquids (IL) were used in the esterification of glycerol and acetic acid to produce glycerol triacetate. The results show that the IL (3–sulfonic acid)–propyltriethylammonium chloroironinate [HO₃S–(CH₂)₃–NEt₃]Cl–[FeCl₃]_x (molar fraction of FeCl₃, x = 0.67) was an efficient catalyst for the esterification reaction. The yield of glycerol triacetate and its content were greater than 98 % when reacted under reflux for 4 h. It was observed that a synergistic effect of Brønsted and Lewis acid sites enhanced the catalytic performance of IL. The reusability of IL was good. After six reaction cycles, the glycerol triacetate yield and concentration were still greater than 98 %. Likewise, the Brønsted–Lewis acidic IL was an efficient catalyst for esterification reactions of high boiling points alcohols with acetic acid.     

Kinetics of the catalytic esterification of castor oil with lauric acid using <Emphasis Type="Italic">n</Emphasis>-butyl benzene as a water entrainer

The esterification of castor oil with lauric acid was investigated using tetra n-butyl titanate (TBT), SnCl₂·2H₂O (stannous chloride), CoCl₂·6H₂O (cobalt chloride), and (CH₃COO)₂Zn·2H₂O (zinc acetate dihydrate) as catalysts. Effects of catalyst concentration and reaction temperature on the progress of the reaction were investigated. TBT was the best catalyst for the esterification of castor oil with lauric acid at temperatures lower than 200°C. The reaction was first order with respect to each reactant. The activation energy for the esterification reaction of castor oil with lauric acid using TBT was 26.69 kcal/mol. The rate constants obtained for the esterification of castor oil with decanoic, lauric, palmitic, and stearic acids were nearly the same (15.80, 15.44, 15.06, and 14.67 mL mol⁻¹ min⁻¹), as were the rate constants obtained for the reaction of castor oil and hydrogenated castor oil.     

Microwave-Assisted Solution Combustion Synthesis of Spinel-Type Mixed Oxides for Esterification Reaction

Environmentally benign production of biodiesel using heterogeneous catalysts is an important issue that requires the preparation of catalysts with high activity and reusability by a simple procedure. In this study, pure alumina and zinc oxide- and copper oxide-modified alumina were tested for the esterification of oleic acid to its methyl ester. The microwave-assisted solution combustion (MSC) method was used to prepare the catalyst samples that were characterized by X-ray diffraction (XRD), Fourier transform infra-red (FTIR), Brunauer–Emmett–Teller (BET) surface area measurement, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The spinel-type zinc aluminate was successfully synthesized, but CuO-modified alumina particles were clearly observed. Whereas in the alumina, much lower activity was observed than the doped alumina, zinc aluminate showed higher activity than copper oxide-alumina due to its smaller particle size, higher BET surface area, larger average pore size, and higher acidity. Finally, after the reaction conditions for the conversion of oleic acid were optimized for the case of spinel ZnAl₂O₄ as nanocatalyst, a yield of higher than 94% was obtained at 180°C, 9 methanol/oleic acid molar ratio, 3?wt% of catalyst for 6?h. Furthermore, the catalyst deactivation was not observed after four reaction cycles at the optimal reaction conditions, indicating the feasibility of the proposed method for the preparation of industrial catalysts.     

固定化离子液体高效催化废弃食用油合成生物柴油

采用溶胶?凝胶技术和浸渍法制备了固定化1-(4-丁基磺酸)-3-甲基咪唑硫酸氢盐([(n-Bu-SO3H)MIm][HSO4])离子液体(IL),得到了一种适用于游离脂肪酸和甲醇酯化反应的不溶性IL催化体系,对合成的催化剂进行了表征,并对其活性进行了系统评价. 结果表明,离子液体成功负载于载体上,该固定化Br?nsted性离子液体在油酸和甲醇酯化反应中具有非常好的催化活性,在最佳反应条件下,油酸的转化率高达98.4%. 该催化剂用于催化高游离脂肪酸含量的废弃食用油酯化时,经后续碱催化酯交换反应,可获得收率高达94.7%的生物柴油.     

Simplistic transesterification approach for the synthesis of benzyl salicylate over honeycomb monoliths coated with modified forms of zirconia as catalysts: Kinetics

The catalysts such as Al₂O₃/ZrO₂ with 2–10?wt% of Al₂O₃ were coated on honeycomb monoliths by dip-and-dry technique. These catalysts were also prepared in their powder form. All the catalysts (honeycomb and powder form) were characterized for their surface acidity, crystallinity, functionality, elemental analysis, and morphology. The catalytic activity of all the catalysts was performed in the transesterification of methyl salicylate with benzyl alcohol to synthesize benzyl salicylate. Reaction conditions like reaction time, reaction temperature, and the molar ratio of the reactants were varied to obtain the highest yield of benzyl salicylate. The 6% Al₂O₃/ZrO₂ coated on honeycomb exhibited the highest conversion of methyl salicylate at 383?K in 60?min. Kinetic studies were conducted to determine the energy of activation and temperature coefficient. The rate constants in the case of 6AZ (HCM) was found to be 5.0?×?10^?3?min^?1 (373?K); 6.4?×?10^?3?min^?1 (383?K) and 2.2?×?10^?3?min^?1 (373?K); 3.2?×?10^?3?min^?1 (383?K) in the case of 6AZ (PF) catalyst, while the energy of activation (E_a) values were found to be 35.12 and 39.93 kJ mol^?1 for 6AZ (HCM) and 6AZ (PF), respectively. The reactant preadsorption study discloses that the transesterification follows the Eley–Rideal mechanism. Reactivation and recyclability of the catalysts were also examined and the results clearly indicate that Al₂O₃/ZrO₂ coated on the honeycomb is efficient and green catalytic system.     

Effects of functionalization conditions of sulfonic acid grafted SBA-15 on catalytic activity in the esterification of glycerol to monoglyceride: a factorial design approach

A series of propyl sulfonic acid-modified SBA-15 catalysts (SBA-15SO₃H) was prepared under various conditions using post-functionalization approach. A factorial design coupled with response surface analysis were employed to evaluate the effects of the preparation conditions on the catalyst activity. Optimization of the conditions to find the most active SBA-15SO₃H catalyst with the highest activity in glycerol esterification with lauric acid at 160?°C for 6?h was also made. Amount of 3-(mercaptopropyl)trimethoxysilane (MPTMS) and reflux time were chosen as parameters of the preparation conditions. The presence of propyl sulfonic acid groups in SBA-15SO₃H catalysts was confirmed by FT-TIR method. The catalysts were also characterized by means of surface analysis, XRD, TEM and TGA. The results obtained from the statistical models suggested that the amount of MPTMS was more important parameter to influence the activity compared to the reflux time. The optimum preparation condition was achieved at a reflux time of 20?h and an MPTMS amount of 1?mL/gram SBA-15 to obtain the SBA-15SO₃H(1) with the highest monoglyceride selectivity (70.2%) and corresponding lauric acid conversion (95%) in the esterification process.     

Investigation on the Esterification of Fatty Acids Catalyzed by the H<Subscript>3</Subscript>PW<Subscript>12</Subscript>O<Subscript>40</Subscript> heteropolyacid

In this work, the H₃PW₁₂O₄₀ heteropolyacid (HPW) was employed as a homogeneous catalyst to promote the efficient esterification (ethanolysis) of a number of saturated and unsaturated fatty acids (myristic, palmitic, stearic, oleic, and linoleic) under mild reaction conditions. HPW showed a similar activity to those observed for p-toluene sulfonic acid (PTSA) and sulfuric acid (H₂SO₄), the other acidic catalysts we compared them with in this study. In the HPW-catalyzed esterification of stearic acid, the addition of water caused a remarkable decrease in the ethyl stearate yields. On the other hand, the increase in the HPW concentration (up to a maximum value) promoted a proportional improvement in the oleic acid to ethyl oleate conversion. Kinetic measurements using oleic acid as a prototype substrate revealed that the esterification reactions catalyzed by HPW, H₂SO₄, and PTSA are of first-order in relation to the fatty acid concentration. Finally, the catalytic activity of HPW remained unaltered even after several recovery/reutilization cycles whereas the tungsten content in the final product (biodiesel produced by the HPW-catalyzed esterification of oleic acid) was found to be at an acceptably low level (0.0095 mg of W per g of biodiesel).     

Kinetics of esterification of palmitic acid with isopropanol using p‐toluene sulfonic acid and zinc ethanoate supported over silica gel as catalysts

Kinetic data on the esterification of palmitic acid with isopropanol were obtained using homogeneous (para‐toluene sulfonic acid, p‐TSA) and heterogeneous (zinc ethanoate coated on silica gel, ZnA/SG) catalysts in a batch reactor. The ZnA/SG catalyst was prepared using a sol–gel technique. The esterification reaction was studied at different reaction temperatures (373–443 K), initial reactants molar ratio (1–5), catalyst loading (1–5 gcat dm^?3) and water concentration in feed (0–15 vol%). A power law rate equation was used for homogeneous kinetics analysis. The Langmuir Hinshelwood Hougen Watson (LHHW) model was used for heterogeneous kinetics. The kinetic parameters of both models were obtained using Polymath software. The reaction parameters were used to obtain simulated values of conversion for both catalytic systems. The simulated values were compared with the experimental values and were in good agreement. Copyright © 2004 Society of Chemical Industry     

Conversion of Synthesis Gas to Dimethylether Over Gold-based Catalysts

It is shown that Au?Czinc oxide?Calumina catalysts are suitable for the water?Cgas shift reaction and for methanol (MeOH) and DME synthesis, indicating their use in a direct single-stage process for converting syngas to a DME?+?methanol mixture. Temperatures above 340?°C were required in order to obtain reasonable catalytic activity. A 67?% DME selectivity was achieved at 380?°C with a low space velocity 0.75?dm³?h^?1?g^?1 and 50?bar. The lower CO conversions at the higher temperature of 460?°C was probably due to the MeOH equilibrium limitation in the range of temperatures 340 to 460?°C, but deactivation is observed as well, above 460?°C. Au/ZnO/??-Al₂O₃ is more stable than traditional copper-based catalysts, which are stable below about 300?°C, and then only in the absence of water. The gold composite catalyst was mainly selective toward DME, MeOH and CH₄, and to C₂ to C₅ hydrocarbons. An analysis of the main reactions involved indicates that only the methanol synthesis reaction reaches a near-equilibrium situation, with the other reactions being under kinetic control.     

Esterification of stearic acid with p-cresol over modified Indian bentonite clay catalysts

The esterification of stearic acid with p-cresol using modified Indian bentonite clay catalysts has been reported. The reaction was studied over exchanged clays, acid activated clays, exchanged acid activated clays, aluminium pillared clay, aluminium pillared acid activated clay, molecular sieve Al-MCM-41, zeolite Hβ, ZrO₂, S-ZrO₂, p-TSA, montmorillonite K10, and montmorillonite KSF in o-xylene for 6 h. The catalysts were characterized by X-ray diffraction and surface area measurements. The acidity was determined by n-butylamine back-titration method and DRIFTS after pyridine adsorption. Acid activated Indian bentonite (AAIB) was found to be a better catalyst compared to other catalysts in the esterification of stearic acid with p-cresol.     

Synthesis of Phytosteryl Esters by Using Alumina-Supported Zinc Oxide (ZnO/Al<Subscript>2</Subscript>O<Subscript>3</Subscript>) from Esterification Production of Phytosterol with Fatty Acid

The feasibility of zinc oxide-catalyzed esterification of natural phytosterols with oleic acid was investigated well by a chemical process. The influences of various reaction parameters were evaluated. Basic solid zinc oxide is the most desirable catalyst due to its high selectivity (more than 90%), reusability, activity and less corrosivity, whereas sterol selectivity with other catalysts, such as H₂SO₄, NaHSO₄ and NaOMe, did not exceed 80%. Further results showed that during zinc oxide-catalyzed synthesis, the nature of the acyl donor was of paramount importance with direct esterification with fatty acids, which gives better results with higher conversion rate selectivity and more mild reaction conditions than transesterification with methyl esters. The substrate molar ratio of 2:1 (oleic acid/phytosterol) was optimal. Other parameters such as optimal catalyst load (0.5%) and temperature (170 °C) showed a maximum production of steryl esters close to 98% after 8 h. It was also found that the amount of trans fatty acid formed in esterification was low, and the trans fatty acid content (%) in the phytosterol oleate ester fraction (3.26%) was much lower than that in free oleic oil (7.35%), which suggested that fatty acids in esters were more stable than free fatty acids regarding the combination with sterol. Immobilized ZnO could be a promising catalyst for replacing homogeneous and corrosive catalysts for esterification reactions of sterol.     

Esterification over rare earth oxide and alumina promoted SO4/ZrO2

Solid superacid catalysts including SO₄²⁻/ZrO₂ (SZ), rare earth (RE) oxide-promoted SZ and RE oxides together with alumina-promoted SZ were prepared. Their catalytic performances in the esterification reaction of ethanol and acetic acid were investigated. The textural property, crystalline phase and surface acidity of the prepared catalysts were characterized by using nitrogen adsorption–desorption isotherms, X-ray diffraction (XRD) and Fourier-transform infrared (FTIR) spectroscopy of pyridine adsorption techniques, respectively. Effects of the reaction time and catalyst reuse cycle as well as catalyst regeneration on the catalytic behaviors were studied. Experimental results showed that Yb₂O₃–Al₂O₃ promoted SZ (designated as SZAY) catalyst exhibited an optimal esterification performance; the Lewis acid sites with moderate and super strong strength could mainly be responsible for the esterification reaction; and doping both Yb₂O₃ and Al₂O₃ on SZ not only boosted the esterification activity but also alleviated catalyst deactivation resulted from the surface sulfur loss by solvation.     

Catalytic performance of sulfate-grafted graphene oxide for esterification of acetic acid with methanol

Graphene oxide possesses tremendous mechanical and electronic properties in combination with large surface area and accessible active sites leading to the development of novel innovative heterogeneous catalysts. The present study elaborates the catalytic activity of graphene oxide, enhanced by grafting active sulfate groups on its surface to result as a superior catalyst. The catalyst was evaluated in the model acetic acid esterification reaction with methanol in terms of acid conversion. Catalysts consisting of varied sulfate concentrations and calcination time were synthesized and optimized for its best catalytic activity. The prepared catalysts (GO-SO₄) were characterized using XRD, FT-IR, SEM-EDS, XPS, and BET. A 44% enhancement in catalyst activity was observed using sulfate-grafted graphene oxide (GO-SO₄) catalyst over bare GO due to the synergistic effect of sulfate ions. The catalyst can be separated out by simple filtration. Further, the influence of operating process parameters including catalyst loading, and the reaction temperature was evaluated toward the maximum acid conversion. In addition, the detailed kinetic study was also done in this system using Pseudo-homogeneous model.     

Study of various catalysts in the synthesis of poly(propylene terephthalate) and mathematical modeling of the esterification reaction

Pure terephthalic acid (TPA) was esterified with 1,3-propanediol (1,3-PDO) in the presence of various catalysts, in order to find the most effective one for this esterification reaction. The prepared oligomers were polycondensated in a second step under high vacuum and using the same catalyst (Sb(OCOCH₃)₃, Ti(OC₄H₉)₄, GeO₂₎ as before, or the well known catalyst for poly(ethylene terephthalate) (PET) production technology Sb₂O₃. The esterification reaction was monitored by measuring the distilled water as a function of time and from these data the modeling of this process was carried out. The received poly(propylene terephthalate) (PPT) samples were characterized by viscometry, carboxyl end-group content and color measurement. From this study, tetrabutoxytitanium was proved to be the most effective catalyst for the esterification reaction. When this catalyst was used in the second step a PPT polymer with the highest molecular weight was received.     

Effects of zirconia loading in sulfated zirconia/SBA-15 on esterification of palmitic acid with glycerol

Sulfated zirconia supported on SBA-15 (SZSBA-15) catalysts with different zirconia loadings (5–20 wt%) were synthesized using urea hydrolysis method. Effects on the physicochemical properties of the catalysts and activity in selective glycerol esterification with palmitic acid were particularly investigated. Various characterization techniques such as N₂ adsorption-desorption analysis, SEM, TEM, TGA, FTIR, NH₃-TPD and acidity measurement by titration were used. Increasing zirconia loading decreased the surface area, pore size and pore volume of the catalysts, but increased the sulfate content and improved the catalyst acidity. Larger surface area was not the major factor in determining the catalyst activity especially in the reaction involving bulky molecules. The reaction was found to be influenced by the amount of active sites presence on the catalyst and also by the dimension of the pores which slightly promoted the shape selective reaction. Among all catalyst, 15SZSBA-15 demonstrated the highest activity with 88% conversion and 44% monopalmitin yield.     

Influence of supported vanadium catalyst on ethylene polymerization reactions

BACKGROUND: In the research area of homogeneous Ziegler–Natta olefin polymerization, classic vanadium catalyst systems have shown a number of favourable performances. These catalysts are useful for (i) the preparation of high molecular weight polymers with narrow molecular weight distributions, (ii) the preparation of ethylene/R‐olefin copolymers with high R‐olefin incorporation and (iii) the preparation of syndiotactic polypropylenes. In view of the above merits of vanadium‐based catalysts for polymerization reactions, the development of well‐defined single‐site vanadium catalysts for polymerization reactions is presently an extremely important industrial goal. The main aim of this work was the synthesis and characterization of a heterogeneous low‐coordinate non‐metallocene (phenyl)imido vanadium catalyst, V(NAr)Cl₃, and its utility for ethylene polymerization. RESULTS: Imido vanadium complex V(NAr)Cl₃ was synthesized and immobilized onto a series of inorganic supports: SiO₂, methylaluminoxane (MAO)‐modified SiO₂ (4.5 and 23 wt% Al/SiO₂), SiO₂? Al₂O₃, MgCl₂, MCM‐41 and MgO. Metal contents on the supported catalysts determined by X‐ray fluorescence spectroscopy remained between 0.050 and 0.100 mmol V g^?1 support. Thermal stability of the catalysts was determined by differential scanning calorimetry (DSC). Characterization of polyethylene was done by gel permeation chromatography and DSC. All catalyst systems were found to be active in ethylene polymerization in the presence of MAO or triisobutylaluminium/MAO mixture (Al/V = 1000). Catalyst activity was found to depend on the support nature, being between 7.5 and 80.0 kg PE (mol V)^?1 h^?1. Finally, all catalyst systems were found to be reusable for up to three cycles. CONCLUSION: Best results were observed in the case of silica as support. Acid or basic supports afforded less active systems. In situ immobilization led to higher catalyst activity. The resulting polyethylenes in all experiments had ultrahigh molecular weight. Finally, this work explains the synthesis and characterization of reusable supported novel vanadium catalysts, which are useful in the synthesis of very high molecular weight ethylene polymers. Copyright © 2007 Society of Chemical Industry     

Synthesis of high‐molecular weight poly(trimethylene terephthalate) catalyzed by MoO3 supported Al2O3‐TiO2 catalysts

Poly(trimethylene terephthalate) (PTT) is an excellent fiber materials. Although it was synthesized as early as 1940s, obtaining high‐molecular weight PTT suitable for spinning is not easy due to no evident breakthrough in the catalysts for PTT synthesis. Patents and literatures disclosed a lot of the catalysts of preparing PTT, but which are more or less disadvantageous. Based on acid catalytic mechanism of PTT preparation, a series of solid acid as x% MoO₃/(50% Al₂O₃ ? 50% TiO₂) (briefly written as xM/(A ? T), x = 0, 10, 15, 20 by weight) were prepared by sol–gel coprecipitation and wetting impregnation methods, and first used for PTT synthesis in this work. When 50% Al₂O₃ ? 50% TiO₂ (briefly written as A ? T) was supported by MoO₃ using wetting impregnation technique of (NH₄)₆Mo₇O₂₄.4H₂O aqueous solution, a lot of Brφnsted acid and Lewis acid sites were formed on xM/(A ? T) catalyst surfaces, which was confirmed by the characteristics of their NH₃‐TPD (temperature programmed desorption). All the prepared catalysts were highly active ones toward synthesis of PTT. PTT with high‐intrinsic viscosity (IV) was obtained in the presence of trace amount of the catalysts. IV ranging of the PTT synthesized from 0.66 to 0.95 dL g^?1 corresponds to weight average molecular weight from 49,197 to 73,004. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010