Catalysts for Fatty Alcohol Production from Renewable Resources

Fatty alcohols may be produced through the processing of fatty acids or their esters derived from palm or coconut oils. Fatty alcohol technology can be classified into two categories (a) a slurry‐phase process in which the fatty acid or its ester is converted into alcohol using a powdered catalyst and (b) fixed bed technology in which the fatty acid or its ester is processed over a formed catalyst, e.g. tablets or extrudates. Historically copper‐based catalysts are employed for achieving ester hydrogenolysis. In recent years, studies were also focused on precious metal catalysts for this process. This paper will critically review existing literature pertaining to the catalysts that operate at diverse conditions, handle different feedstocks, and are compatible with a variety of unit operations used by the fatty alcohol manufacturers. There is an effort to develop environmentally friendly non‐chrome copper catalyst in this process. Some recent progress on bimetallic Cu‐Fe catalyst and understanding Cu‐Fe interaction has been reported. Current development on homogenous catalysts in this process was carefully reviewed. The catalyst deactivation mechanism has been investigated and effect of different impurities, mainly phosphorous, sulfur, chloride, water, glycerine and free fatty acid was thoroughly reviewed.     

Fatty methyl ester hydrogenation to fatty alcohol part II: Process issues

Fatty alcohols are produced by hydrogenating fatty methyl esters in slurry phase in the presence of copper chromite catalyst at temperatures of 250–300°C and hydrogen pressures of 2000–3000 psi. The fatty methyl ester, catalyst, and hydrogen are fed to the reactor cocurrently. The product slurry is passed through gas-liquid separators and then through a continuous filtration system for removal of the catalyst. A portion of the used catalyst in crude alcohol is recycled to the hydrogenator. The overall efficiency of the process depends upon the intrinsic activity, life, and filterability of the catalyst. The fatty alcohol producer therefore requires a catalyst with high activity, long life, and good separation properties. The main goal of the present laboratory investigation was to develop a superior copper chromite catalyst for the slurry-phase process. Two copper chromite catalysts, prepared by different procedures, were tested for methyl ester hydrogenolysis activity, reusability, and filtration characteristics. The reaction was carried out in a batch autoclave at 280°C and 2000–3000 psi hydrogen pressure. The reaction rates were calculated by assuming a kinetic mechanism that was first-order in methyl ester concentration. The catalyst with the narrower particle size distribution was 30% more active, filtered faster, and maintained activity for several more uses than the catalyst with the broader particle size distribution. X-ray photoelectron spectroscopy data showed higher surface copper concentrations for the former catalyst.     

Fatty methyl ester hydrogenation to fatty alcohol: Reaction inhibition by glycerine and monoglyceride

The present work demonstrates the rate-limiting effect of varying levels of both glycerine and monoglyceride through a series of batch hydrogenations of fatty dodecyl methyl ester, using copper chromite as the catalyst. Reactions were carried out at 3000 psig H₂, 280°C with catalyst levels varying between 1.25 and 1.80%. With increasing contaminant levels of glycerine (0.0, 0.1, 0.5, 5 wt%), conversion of fatty methyl ester to alcohol is correspondingly reduced (95, 89, 80, 2 wt%). On a molar basis of contaminant, monoglyceride equally reduces the conversion of methyl ester to alcohol. In both cases the latent appearance of fatty-fatty ester results from the slower hydrogenation rate. Chemistry is proposed outlining the thermal decomposition of glycerine or glyceride to intermediate components (acetol and acrolein), leading to the generation of propanediols. Experimental studies indicate that diols effectively deactivate the copper chromite catalyst, limiting the rate of fatty methyl ester hydrogenation. Catalyst deactivation is not permanent, suggesting catalyst site blockage by physical adsorption of the polyhydroxyl components. The complete understanding of this interaction holds promise for the development of glycerine/monoglyceride-insensitive catalysts. In addition, a brief overview of methyl ester hydrogenation inhibition effects of some heteroelements, water, and soap is presented.     

Fatty methyl ester hydrogenation to fatty alcohol part I: Correlation between catalyst properties and activity/selectivity

Fatty alcohols, derived from natural sources, are commercially produced by hydrogenation of fatty acids or methyl esters in slurry-phase or fixed-bed reactors. One slurry-phase hydrogenation of methyl ester process flows methyl esters and powdered copper chromite catalyst into tubular reactors under high hydrogen pressure and elevated temperature. In the present investigation, slurry-phase hydrogenations of C₁₂ methyl ester were carried out in semi-batch reactions at nonoptimal conditions (i.e., low hydrogen pressure and elevated temperature). These conditions were used to accentuate the host of side reactions that occur during the hydrogenation. Some 14 side reaction routes are outlined. As an extension of this study, copper chromite catalyst was produced under a number of varying calcination temperatures. Differences in catalytic activity and selectivity were determined by closely following side reaction products. Both activity and selectivity correlate well with the crystallinity of the copper chromite surface; they increase with decreasing crystallinity. The ability to follow the wide variety of side reactions may well provide an additional tool for the optimized design of hydrogenation catalysts.     

New resin systems for high performance top coats

Maleic anhydride copolymer was synthesized and reacted with mono functional alcohols. The reaction was slower than that between monomeric anhydride and alcohol because of the polymer effect. Under heating, recyclization of the half ester to anhydride occurred. This was examined with reference to the structure of alcohols as well as types of catalysts. The maximum recyclization ratio obtained was as high as 84%, while that of copolymers produced with maleic anhydride monoalkyl ester was very low. A trans structure is formed through free rotation at the terminal of the propagating polymer radical in the latter polymer and this is hardly recyclized. A clearcoat obtained by combination of a half ester copolymer and a copolymer containing both hydroxyl and oxirane groups showed excellent acidic water resistance. These findings have been fully developed for the formulation of a 1-package acid rain resistance finish.     

硫酸氢钠催化合成十六烷二酸二乙酯的研究

以十六烷二元酸与乙醇为原料,采用硫酸氢钠做催化剂合成十六烷二元酸二乙酯。考察了原料的摩尔比、反应时间、催化剂量和带水剂对酯化收率的影响。通过分析实验结果,得出反应的最佳条件:醇酸摩尔比7∶1,催化剂量为二元酸质量的5%,带水剂环己烷为酸醇总质量的15%,回流反应时间5h,酯化的最高收率可达94.5%。硫酸氢钠重复使用4次后酯化收率为80.7%。     

Studies on electrosynthesis of organic compounds. I. Electrolytic esterification in aqueous solutions

The anodic oxidation of methyl alcohol in the presence of different carboxylic acids was found to give the methyl ester of these acids as the main product. Neither Kolbe products nor formaldehyde were formed. These results are interpreted in terms of a free radical mechanism which involves attack of the carboxylic acids by methoxyl radicals to give the ester.     

油酸异丙酯的合成及其对生物柴油低温流动性研究

油酸与异丙醇在对甲苯黄酸催化剂的作用下发生酯化反应制备油酸异丙酯。单因素研究催化剂用量、醇酸配比、反应时间、反应温度等对酯化反应得率的影响规律,并通过测定凝固点、冷滤点、粘度来考察脂肪酸异丙脂对生物柴油的降凝效果。结果表明,催化剂的量3%,醇酸体积比2∶1（摩尔比8.2∶1）,反应温度80℃,反应时间4 h,酯化率达到90.5%。降凝实验结果表明把一定量的脂肪酸异丙酯添加到生物柴油中可有效地降低生物柴油的凝固点、冷滤点,改善其低温流动性能。     

Chemistry and technology of some drying oil fatty acid esters of polyvinyl alcohol

No substitute for phenol as the mutual solvent was found. Other solvents which were tried produced deleterious side effects such as bad color and product recovery difficulties. Furthermore, the yields of ester were not as good as those in the phenol process. At the present time, the yield of ester using the standard procedure cannot be improved. The final product analyses seem to indicate polyethers are formed simultaneously with the fatty acid esters, and that polyvinyl alcohol undergoes chain cleavage with the formation of non-hydroxyl groups, or a deacylation of one of two 1舑2 hydroxyl groups which results in a ketone group. Esters of high and low mol wt polyvinyl alcohol based on 0.5/1 (fatty acid/polyol) equivalents as the optimum can be successfully prepared with and without basic catalysts. An ester as low as 0.1/1 fatty acid/LMPVA can be prepared without a gel. This ester is barely soluble in aromatic solvents. The evaluation data on several coatings indicates that improved clear varnishes and house paints are possible and that further evaluation of these esters as can coatings or industrial bakes should be considered. Linseed esters showed better properties than the soya and tall oil esters. No particular advantages were seen in the other pigmented coatings.     

乙烯与极性单体共聚的研究进展

综述了采用齐格勒-纳塔催化剂、茂金属催化剂和后过渡金属催化剂等通过乙烯与极性单体共聚合反应制备功能性聚乙烯的研究进展,简述了催化剂类型与结构对催化活性以及产物结构的影响。研究包括超支化功能性聚乙烯合成、乙烯与醇、酯类极性单体共聚合、乙烯与降冰片烯共聚合、乙烯与硅烷单体共聚合及乙烯与甲基丙烯酸甲酯共聚合等。     

Environment-friendly synthesis of nitrogen-containing heterocyclic compounds

A novel environment-friendly vapour phase synthesis of different classes of nitrogen-containing heterocyclic compounds was developed using non-hazardous, commercially available and low cost feeds. 2-Methyl-8-ethylquinoline (MEQUI) was obtained from 2-ethylaniline (2-ETAN) and ethylene glycol (EG) or chloroethanol (CE), operating at high temperature in the presence of acid-treated K10 montmorillonite or ZnCl₂/K10 montmorillonite. At lower temperatures and using copper chromite catalysts, 7-ethylindole (7-ETI) or 5-ethylindole (5-ETI) were obtained from 2-ETAN or 4-ethylaniline (4-ETAN), respectively, and EG; excess of alkylaniline was required to avoid the formation of polyalkylated by-products. Mixing SiO₂ with the best copper chromite, made it possible to operate with higher LHSV values, thus improving the yield in alkylindoles. Finally, N-(2-ethylphenyl)pyrrole (EPP) and N-(2-ethylphenyl)pyrrolidine (EPD) were synthesised using a commercial copper chromite catalyst and feeding 2-ETAN and 2,3-dihydrofuran (DHF), EPP being favoured by high temperatures and absence of water in the feed. The possible reaction pathway for each synthesis is proposed, to evidence the key features of the best catalysts identified.     

Selective hydrogenation with copper catalysts: II. Kinetics

To explain the unusually high selectivity of copper catalysts toward linolenate, model compounds were hydrogenated (150 C and atmospheric pressure) and the reaction products analyzed. Products varied depending upon location of the double bonds. Monoenes were not reduced by copper chromite except when the double bond was next to a carboxyl group. Dienes with isolated double bonds also were not reduced. Binary mixtures of model compounds were hydrogenated with copper chromite. From the composition of the initial and final products, a competitive rate ratio of the two compounds was determined. Esters with conjugated double bonds reacted faster than esters containing methylene interrupted double bonds. Kinetic data on the hydrogenation of linolenate indicated conjugation of the double bonds. Simulation of the kinetic data gave competitive reaction rates for the different isomers formed. Presented at the AOCS Meeting, New York, October 1968. No. Utiliz. Res. Dev. Div., ARS, USDA.     

Enzymatic esterification of dihydroxystearic acid

Dihydroxystearic acid (DHSA) ester was synthesized enzymatically to overcome the problems associated with chemical processes. Immobilized enzyme, Lipozyme IM and Novozym 435, were employed as catalysts in the esterification reaction between DHSA and monohydric alcohol. Various factors that may affect the esterification reaction were studied, such as initial water content (a _w ), organic solvent, substrate concentration and the influence of alcohol chain length. It was found that the percent conversion was higher in organic solvents with log P (the logarithm of the partition coefficient of solvent in octanol/water system) from 2.0 to 4.0. The reaction was not affected by a _w from 0.09 to 0.96. Increasing the mole ratio of alcohol to acid above 2.0 did not increase the percent converions of ester. The ester was identified by Fourier transform infrared and ¹³C nuclear magnetic resonance spectroscopy.     

醋酸酯的酯化水相是否参与回流的确定

从理论上阐述以冰醋酸和醇为原料,浓H2SO4为催化剂合成醋酸酯的生产工艺,为提高酯的产率,通过比较酯化反应生成的水含量与产品酯、水形成的二元共沸混合物中的水含量的大小来确定酯化塔顶的水相是否参与回流。实际生产中验证这一确定方法是可行的,并得出结论：对于酯化合成法生产醋酸酯系列产品,分子量低于醋酸乙酯（包括醋酸乙醋）的酯,即分子量较小的酯,其酯化塔顶水相不参与回流;分子量大于或等于醋酸丙酯的酯,即分子量较大的酯,其酯化塔顶水相需要部分参与回流。     

Kinetics of hydrogenation of conjugated triene and diene with nickel,palladium, platinum and copper-chromite catalysts

A mixture of methyl linoleate and alkali-conjugated methyl linoleate was reduced with nickel, palladium, platinum and copper-chromite catalysts. The course of hydrogenation was followed by gas liquid chromatography of samples withdrawn at intervals. Relative rate constants of reactants and inermediates were calculated by a computer. Conjugated linoleate was 10–18 times more reactive than methyl linoleate with all catalysts except platinum, which showed no selectivity at 60 C. At 150 C conjugated diene reacted four times faster than methyl linoleate with platinum catalyst. A conjugated diene-to-stearate shunt was observed with palladium and platinum catalysts. When β-eleostearate was hydrogenated with the same catalysts, 50–97% of the triene was reduced directly to monoene with all catalysts except copper chromite, which selectively reduced conjugated triene to conjugated diene. On the basis of present kinetic data and previous knowledge about the mode of hydrogen addition to conjugated systems, a scheme has been proposed to account for the products formed during hydrogenation of methyl linolenate. ARS, USDA.     

Transesterification reactions in molten polymers

The transesterification reaction of molten ethylene and vinyl alcohol copolymers (EVA), in presence of paraffinic alcohols and basic catalysts, leads to high conversion of the ester groups to secondary alcohol in both discontinuous and continuous processing equipment. Various kinds of alcohols and two different catalysts were used. Sodium methoxide is a powerful catalyst for the equilibrated transesterification reaction, but we also observed side reactions, such as cross-linking with low-molecular-weight alcohols and hydrolysis of the catalyst followed by partial saponification of the EVA. Kinetic studies were performed in the presence of dibutyltin dilaurate, an efficient catalyst without any side reactions. The solubility of the main alcohol reagents was verified by diffusion measurements. The general reaction scheme and the related kinetics, corresponding to a homogeneous system, lead to a fair evaluation of the rate constants.     

钴次卟啉衍生物催化空气氧化环己烷

用合成的4种钴次卟啉衍生物作催化剂,在未加入辅助还原剂和其他溶剂的条件下催化空气氧化环己烷。反应温度150℃,釜压0.80 MPa,n(催化剂)∶n(底物)≈1∶4.63×105时,钴次卟啉衍生物表现出良好的催化性能。4种钴次卟啉衍生物催化的底物转化率在4 h内都达到了14%以上,目标产物环己酮和环己醇的选择性(简称酮醇选择性)在82%以上。其中,钴3,8-二硝基次卟啉二甲酯催化活性最好:环己烷转化率在3.5 h升至19.34%,环己烷氧化目标产物酮醇的选择性为82.30%,催化剂转化数达8.86×104。     

Solvent-free Oxidation of Primary Alcohols to Aldehydes using Supported Gold Catalysts

Supported Au catalysts are investigated for the oxidation of primary alcohols under solvent-free conditions in the absence of base. Three representative primary alcohols have been investigated: benzyl alcohol, octan-1-ol and geraniol using a range of supports for gold nanocrystals prepared using coprecipitation, deposition precipitation and impregnation. For benzyl alcohol and octan-1-ol selective oxidation to the corresponding aldehydes is observed, particularly with Au/CeO₂, whereas for more acidic supports, e.g. Fe₂O₃, subsequent oxidation of the aldehydes to the corresponding acids, forming an ester (benzyl benzoate, octyl octanoate, respectively) by reaction with the alcohol, by a standard acid-catalysed mechanism. Alternatively, the mechanism of ester generation could involve hemiacetal formation between the aldehyde and residual alcohol, followed by direct oxidation to the observed ester. The reaction of geraniol is much more complex and the reaction is carried out in the presence and absence of acids to gain a full understanding of the interplay between oxidation and isomerisation reactions. Comparison with other active catalysts reveals that using Au catalysts in solvent free conditions gives very high turnover frequencies for the synthesis of the aldehydes with 100% selectivity (150 h⁻¹ and 26 h⁻¹ for benzyl alcohol and octan-1-ol, respectively), which are comparable to the best reported to date for these reactions.     

Lipase made active in hydrophobic media

Enzymes are distinguished from other catalysts by their high substrate specificity. This is a great asset when one wants to apply them for syntheses of various compounds. Their usage, however, generally is limited to hydrophilic reaction media, because they usually are not soluble and active in hydrophobic media. Recently, we have been able to make various enzymes soluble and active in highly hydrophobic organic solvents. The key to this success is the chemical modification of enzymes with an amphipathic synthetic polymer, polyethylene glycol. The activated polymers can be attached to enzymes in aqueous buffer solutions, and once enzymes are modified they become soluble and active in various organic solvents such as benzene, toluene and cholorinated hydrocarbons and exhibit high enzymic activities in these organic solvents. Modified hydrolytic enzymes catalyzed the reverse reaction of hydrolysis in organic solvents. The modified lipase catalyzed various ester synthesis reactions. Because the reactions were conducted in the pure solvent system, it also was possible to study the kinetics and the substrate specificity for ester synthesis reaction. It also catalyzed the polymerization of a hydroxy group containing carboxylic acid due to the bifunctional nature. The modified lipase catalyzed ester exchange between an ester and an alcohol, between an ester and a carboxylic acid and between two esters in organic solvents. When the two substrates for ester exchange were liquid, the reaction could take place without organic solvents. The modified lipase catalyzed an ester exchange reaction between trilaurin and triolein when dissolved in these substrates. Dilauroyl-monooleoylglycerol and monolauroyl-dioleoyl-glycerol were formed from these two substrates in the presence of the modified lipase. The modified enzyme was extremely thermostable in its substrates. In the ester synthesis and ester exchange reactions, a trace amount of water was necessary for expression of the enzymic activity. It is suggested that the amphipathic polymer molecules retained water in close proximity to the enzyme. Presented at the symposium “The Biology, Biochemistry and Technology of Lipase” at the 78th annual meeting of the American Oil Chemists’ Society held May 17–21, 1987, in New Orleans, Louisiana.     

杂多酸催化合成顺丁烯二酸二丁酯研究

以杂多酸为催化剂、顺丁烯二酸酐和正丁醇为原料合成了顺丁烯二酸二丁酯。研究了杂多酸种类和用量、醇酐物质的量比、反应时间对酯收率的影响。结果表明 :此法催化剂用量少、催化活性高、反应时间短、酯收率高、反应工艺简单。用正交实验确定了合成该酯的最佳工艺条件为 :m(催化剂 )∶m(酐 ) =1 6∶1 0 0 0 ,n(醇 )∶n(酐 ) =3∶1 ,反应温度 1 1 5～ 1 2 5℃ ,反应时间 2 5～ 3 0h。在此条件下 ,酯收率超过 96%。