Optimization of the enzymatic esterification of diglycerol and lauric acid

In recent years, a number of industrial applications for lipases in biotransformation of fatty acids and lipids have been developed. One of the main reasons for this growing interest is the reduced overall catalyst cost owing to the development of commercially available immobilized enzymes, using polymeric carriers that facilitate recovery and reuse of the catalyst. Additional benefits for industrial applications include the specificity of the enzyme and the mild processing conditions. Diglycerol resulting from the dimerization of glycerol may replace molecules such as propylene glycol as the hydrophilic moiety of surfactants. Also, diglycerol fatty acid esters are useful as biodegradable nonionic surfactants for food, cosmetics, and pharmaceuticals. In this study, the enzymatic esterification of diglycerol and lauric acid has been optimized in a solvent-free system. The reaction was carried out in a stirred batch reactor with a vacuum pump in order to shift the equilibrium toward the products. The commercial lipase Novozym-435 was chosen as the most suitable catalyst, and the initial acid/alcohol ratio was always 1∶1. The reaction of lauric acid and diglycerol leveled off at equilibrium conversion after approximately 1 h of reaction. Previous work indicated that only temperature and catalyst concentration had significant effects on the conversion, and a full two-factorial design has proved effective in the study of the influence of these two variables on the process. The temperature range studied was 63–77°C, and the range of the catalyst concentration was 0.2–5.8 wt%. Both catalyst concentration and temperature were found to be significant factors in the esterification process, and their influences are positive. The effect of the interaction between temperature and catalyst concentration was small. A first-order approach could not fit the data adequately, and a model that included quadratic effects was required. A second-order model was developed to predict the yield of ester as a function of the variables. Analysis of residuals showed that the model predicted accurately the acid conversion over the experimental range considered. This model is useful to determine the optimal operating conditions for the industrial process. Presented in part at the 91st Annual Meeting of the AOCS in San Diego, April 2000.     

Polymerization of dehydrated castor acids using an acid earth catalyst

The atmospheric pressure polymerization of a commercial dehydrated castor oil fatty acid mixture, by using as catalyst the acid clay Filtrol 13, has been studied under different conditions of temperature, catalyst concentration, reaction time, and concentration of conjugated linoleic acid in the starting material. At 180C or above, extremely rapid polymerization of the conjugated fatty acids occurred (50% complete in about 4 min at 66% concentration). This was accompanied bytrans isomerization and some hydrogen transfer to form oleic (oriso-oleic) acids. The ratio of dimer/polymer in the product was approximately 2 to 2.5 and was only slightly affected by variation in the reaction conditions.     

Kinetics of catalytic esterification of terephthalic acid with methanol vapour

This paper describes the investigations carried out on the kinetics of the solid-gas reaction between terephthalic acid and methyl alcohol in presence of phosphoric acid as the catalyst. As phosphoric acid itself reacts with the alcohol forming methyl phosphates, the kinetic data obtained have been analysed taking this reaction into account. The rate of formation of monomethyl phosphate has been found to be proportional to the square of the mole fraction of the acid present at any instant. The activation energy involved in this reaction is 11.3 kcal/g mole. The data obtained on terephthalic acid esterification show that; (i) the conversion sharply increases with an increase in the catalyst concentration between 30–35 per cent (w/w), (ii) the ‘shrinking particle’ model, proposed by Levenspiel for solid-gas reactions, can be conveniently adapted to represent the reaction, and (iii) the temperature dependency of the reaction follows the Arrhenius law, with activation energy being 11.5 kcal/g mole.     

Production of biodiesel from palm fatty acid distillate using sulfonated-glucose solid acid catalyst:Characterization and optimization

A palm fatty acid distillate (PFAD) has been used for biodiesel production. An efficient sulfonated-glucose acid catalyst (SGAC) was prepared by sulfonation to catalyze the esterification reaction. The effect of three variables i.e. methanol-to-PFAD molar ratio, catalyst amount and reaction time, on the yield of PFAD esters was studied by the response surface methodology (RSM). The optimum reaction conditions were:12.2:1 methanol-to-PFAD molar ratio, 2.9%catalyst concentration and 134 min of time as predicted by the RSM. The reaction under the optimum conditions resulted in 94.5%of the free fatty acid (FFA) conversion with 92.4%of the FAME yield. The properties of the PFAD esters were determined according to biodiesel standards.     

Kinetics of acetic acid esterification over ion exchange catalysts

Computer simulation showed that catalytic distillation is an attractive process for the removal of dilute acetic acid from wastewater. Selection of catalysts and kinetic data have been obtained for the design of the catalytic distillation column. Kinetic measurements were conducted in a batch reactor. Methanol was added to the dilute acetic acid solutions and reacted with the acid in water to form methyl acetate and water. The reaction can be catalyzed by solid acid catalysts. It was found that Amberlyst 15 was an effective catalyst for this reaction. The effects of stirrer speed, reaction temperature, reactant concentration and catalyst loading on reaction rate were investigated. A complete kinetic equation for describing the reaction catalyzed by Amberlyst 15 was developed. This equation can be used in the simulation and design of the catalytic distillation column for removing acetic acid from wastewater.     

Synthesis of plasticizing polyesters of dimer acid and propane–diol

The polyesterification of dimer acid with propane–diol under different experimental conditions has been studied to obtain the optimum conditions for synthesizing the poly(propane–diol) dimerate plasticizers. The effect of varying molar ratio, temperature, and catalyst concentration on the course of the reaction, acid number, intrinsic viscosity, and molecular weight of the resultant polyester has been investigated. p-Toluene sulfonic acid (PTSA) was found to be an effective catalyst for the polyesterification reaction. The kinetics of polyesterification in the presence and absence of a catalyst has been found to follow the second-order rate equation in equimolar concentrations of the reactants. © 1993 John Wiley & Sons, Inc.     

固体酸催化蔗糖制备乙酰丙酸的研究

以蔗糖为原料,焙烧后的硫酸钛为催化剂,水为溶剂制备乙酰丙酸。研究了催化剂焙烧温度对催化剂活性的影响,以及催化剂投加量、蔗糖浓度、反应温度和反应时间对乙酰丙酸收率的影响。在反应温度220 ℃、反应时间60 min、蔗糖浓度50 g·L^-1和催化剂加入量0.5 g条件下,乙酰丙酸收率可达57.9%。     

沙柳酸催化水解制备乙酰丙酸及分离提纯

以沙柳为原料,硫酸为催化剂,考察了催化剂浓度、反应时间、反应温度、液固比对沙柳水解制备乙酰丙酸得率的影响,通过正交实验方法得到最佳的水解反应条件为：反应温度200 ℃,反应时间90 min,催化剂质量分数9%,液固比（mL∶g）15∶1,乙酰丙酸的最高得率为18.80%;各因素对水解反应影响的大小顺序为：反应时间＞催化剂浓度＞反应温度＞液固比。在静态条件下,用335弱碱性阴离子交换树脂对水解液进行分离提纯,在附吸温度为35 ℃、树脂投料量为15 g、盐酸洗脱剂浓度为0.5 mol/L时,乙酰丙酸的回收率为95.35%。     

酸催化水解蔗糖制取乙酰丙酸

以蔗糖为原料,在H2SO4催化下制备乙酰丙酸,主要考察了反应时间、反应温度、蔗糖浓度、H2SO4浓度对乙酰丙酸产率的影响。实验结果表明,反应时间60min,反应温度110℃,蔗糖浓度0.4mol/L,H2SO4浓度3.5mol/L条件下乙酰丙酸的产率最高。     

以单体酸为原料制备生物柴油

研究了以单体酸为原料制备生物柴油的方法,反应以对甲苯磺酸为催化剂,单体酸与甲醇进行酯化反应获得脂肪酸甲酯。分别考察了酯化反应条件如甲醇与脂肪酸的摩尔比、反应时间、催化剂浓度以及反应温度对酯化率的影响。通过正交实验得到最佳酯化反应参数：醇酸摩尔比3∶1,反应时间3 h,对甲苯磺酸用量6%,反应温度60 ℃,该条件下单体酸酯化率达98.25%。实验制得的单体酸甲酯生物柴油的主要性能指标符合ASTM质量标准,并与0^#柴油性质接近。     

Vapour phase hydrogenation of olefins by formic acid over a Pd/C catalyst

It has been found that ethylene and propylene could be effectively hydrogenated by formic acid vapour over a Pd/carbon catalyst at low temperatures (<440 K). Surface hydrogen formation from formic acid is the rate-determining step for this hydrogenation reaction. Interaction of this hydrogen with the olefins is then fast. The conversion of formic acid in the presence of either of the olefins at any temperature is higher than in their absence. This has been explained by a much lower surface hydrogen concentration in the presence of the olefins. Direct experiments have confirmed that hydrogen inhibits the formic acid decomposition. Water vapour addition has a small positive effect on the decomposition of formic acid as well as on the hydrogenation of the olefins with formic acid. Catalysts consisting of gold supported on carbon or titania are both active in the production of hydrogen from formic acid. However, in contrast to the Pd/C catalyst, neither gives hydrogenation of the olefins with this acid.     

蔗糖脂肪酸酯的合成与性能研究

在酸催化作用下乙醇与硬脂酸反应合成了硬脂酸乙酯.以硬脂酸乙酯和蔗糖为原料,采用DMF溶剂法,在碱性条件下通过酯交换反应合成了硬脂酸蔗糖酯.采用正交实验设计对反应条件进行优化,在最佳工艺条件下产率可高达95.8%.测定了产品的表面化学性能.结果显示,产品的临界胶束浓度(cmc)为2.228×10-4 mol/L,此时的表面张力为39.88 mN/m,其钙皂分散、乳化、增溶等表面化学性能优良.     

固体超强酸SO4^2-/ZrO2-CeO2催化油酸酯化反应的研究

以固体超强酸SO4^2-/ZrO2-CeO2为催化剂,以油酸和甲醇为原料,在高温高压反应釜中进行酯化反应。对反应条件的研究表明,当甲醇与油酸的体积比为2：1（摩尔比为15：1）,反应温度为160℃,反应时间4h,催化剂用量8％（与油酸的质量百分比）时,反应的酯化率达到97．34％。动力学计算表明,该酯化反应的反应级数为1．42,反应活化能为25．25kJ／mol。     

二氯乙酸选择性加氢脱氯制备高纯氯乙酸

以Pd/C为催化剂,通过固定床反应器对含氯乙酸、二氯乙酸以及乙酸的氯化液进行选择性催化加氢脱氯研究,使氯化液中的大部分或全部二氯乙酸转化为一氯乙酸或乙酸。考察催化剂制备条件对催化性能的影响,结果表明,在Pd负载质量分数0.9%、浸渍液浓度4.5 g·L-1和浸渍温度20℃条件下制备的催化剂,催化活性和产物选择性最佳,运行时间超过1 500 h活性未出现明显衰减。     

催化剂对4-乙酰氧基苯甲酸的合成影响研究

以对羟基苯甲酸(PHB)和乙酸酐(Ac2O)为原料,醋酸(HAc)为溶剂,考察浓硫酸和杂环化合物催化合成4-乙酰氧基苯甲酸(PABA),反应物配比为羟基苯甲酸∶乙酸酐∶醋酸=1∶1.05∶0.5,确定最佳催化剂加入量、反应时间和反应温度。结果表明,浓硫酸为催化剂时,最佳反应时间2 h,反应温度100℃,催化剂加入量为PHB质量的4%,产率67%;杂环化合物P为催化剂时,最佳反应温度80℃,反应时间2 h,催化剂加入量为PHB质量的0.3%,产率99.8%。杂环化合物比浓硫酸对PABA合成有更好的催化活性,反应条件温和,具有较好的工业化应用前景。     

Liquid phase oxidation of p-xylene to terephthalic acid by air in the absence of a promoter

Liquid phase oxidation of p-xylene to terephthalic acid by air in the presence of solvent acetic acid and a relatively large amount of cobalt acetate as catalyst has been investigated in the absence of any promoter at 100–130°C and a pressure of 2.5–10 kg cm^?2. The effect of temperature, catalyst concentration, p-xylene concentration, air flow rate, pressure, reaction period and addition of small amounts of zirconium salts, etc., on the conversion to terephthalic acid has been studied. p-Toluic acid, which is an intermediate in the process, was the only major by-product. The possibility of recycling the mother liquor after the separation of the product was ascertained.     

磁性固体超强酸的制备及催化酯化反应的研究

制备了钴基磁性固体超强酸催化剂，代替硫酸用于酯化反应，对反应的工艺条件进行了优化，结果表明磁性物种的引入对催化剂的催化活性有一定影响，随着磁性物种含量的增加，催化剂的催化活性有所提高，当磁性物种含量为2．44％时催化转化率达最高值97．31％，磁性物种继续增加，转化率反而下降，磁性固体超强酸催化剂的回收率达85％，回收性较好。     

蒙脱石负载铝基固体酸的制备及其催化性能

采用浸渍法制备了蒙脱石负载铝基固体酸(SO_4~(2-)/Al-O-MMT),用FTIR、XRD、TG/DSC、SEM、BET和PyFTIR对其结构进行表征与分析。以乙酸-正丁醇、柠檬酸-正丁醇的酯化反应为探针,研究了焙烧温度、浸渍液浓度对SO_4~(2-)/Al-O-MMT固体酸催化性能的影响,并测定SO_4~(2-)/Al-O-MMT固体酸的重复使用性。结果表明:蒙脱石负载铝基固体酸大大地提高了其催化活性。当焙烧温度为400℃,浸渍液浓度为0.75 mol/L时,SO_4~(2-)/Al-OMMT固体酸表现出最佳的催化活性,其催化合成乙酸正丁酯和柠檬酸三丁酯的酯化率分别可达到99.7%和96.1%。同时,SO_4~(2-)/Al-O-MMT固体酸表现出较好的重复使用稳定性,重复使用6次后,对于上述两个反应的酯化率分别保持在89.0%和84.6%。     

柠檬酸改性原位晶化催化剂的性能及传质扩散行为研究

采用不同浓度的柠檬酸溶液对原位晶化催化剂进行了改性脱铝研究,利用XRD、荧光衍射、氮气吸附、吡啶红外吸附等表征手段对脱铝后的催化剂进行了分析表征,分析表征结果表明柠檬酸能显著调变催化剂孔结构,有效改变中强酸和总酸量。ACE的反应评价结果表明,采用柠檬酸改性后催化剂的裂化能力显著增强,转化率提高3.23%（质量分数）以上、油浆收率降低1.13%（质量分数）以上、液化气质量分数增加2.7%以上、柴油质量分数降低1.94%以上、焦炭选择性变好。说明柠檬酸改性可显著提高原位晶化催化剂酸性位可接近性,从而改善反应选择性,柠檬酸质量分数为0.5%时具有最佳的反应结果。以菲为探针分子测试的催化剂穿透曲线验证了这一点。