Polyol-Derived Alkoxide/Hydroxide Base Catalysts II: Transesterification Reactions

Biodiesel, fatty acid methyl ester (FAME), was produced by transesterification of canola oil with methanol in the presence of a series of alkoxide/hydroxide base catalysts produced from glycerol, 1,2-propanediol, 1,3-propanediol, xylitol, or sorbitol produced by dehydration reaction of sodium hydroxide in the presence of polyols. Transesterification reactions proceeded efficiently in the presence of sodium alkoxide catalysts prepared at three different mole ratios of sodium hydroxide to glycerol (1:1, 2:1, and 3:1). The production of methyl ester during the course of the reaction was determined repeatedly and the reaction progress was compared with that achieved in a reaction catalyzed by freshly prepared anhydrous sodium methoxide as a standard catalyst. Sodium alkoxide/hydroxide catalysts activity during the first 2 min of the reaction was in the order of: sorbitol < xylitol < sodium methoxide < 1,2-propanediol < 1,3-propanediol < glycerol regardless of the mole ratio of sodium hydroxide to glycerol. All catalysts showed a higher methyl ester accumulation at higher ratios of sodium hydroxide to polyol and had the following order 1:1 < 2:1 < 3:1 (sodium hydroxide:glycerol). Several of these catalysts were as powerful as sodium methoxide in catalyzing the transesterification reaction at the same mole concentration. All alkoxide/hydroxide catalysts resulted in a high FAME accumulation (>95 wt%) in a single transesterification batch reaction.     

Optimization of transesterification for methyl ester production from chicken fat

In this study, low cost feedstock chicken fat was used to produce methyl ester. After reducing the free fatty acid level of the chicken fat less than 1%, the transesterification reaction was completed with alkaline catalyst. Potassium hydroxide, sodium hydroxide, potassium methoxide and sodium methoxide were used as catalyst and methanol was used as alcohol for transesterification reactions. The effects of catalyst type, reaction temperature and reaction time on the fuel properties of methyl esters were investigated. The produced chicken fat methyl esters were characterized by determining their viscosity, density, pour point, flash point, acid value, methanol content, heat of combustion value, total-free glycerin, mono-di-tri glycerides, copper strip corrosion and ester yield values. The measured fuel properties of the chicken fat methyl ester met EN 14214 and ASTM D6751 biodiesel specifications when using potassium hydroxide and sodium hydroxide catalysts with high ester yield.     

Evaluation of biodiesel obtained from cottonseed oil

Esters from vegetable oils have attracted a great deal of interest as substitutes for petrodiesel to reduce dependence on imported petroleum and provide a fuel with more benign environmental properties. In this work biodiesel was prepared from cottonseed oil by transesterification with methanol, using sodium hydroxide, potassium hydroxide, sodium methoxide and potassium methoxide as catalysts. A series of experiments were conducted in order to evaluate the effects of reaction variables such as methanol/oil molar ratio (3:1–15:1), catalyst concentration (0.25–1.50%), temperature (25–65 °C), and stirring intensity (180–600 rpm) to achieve the maximum yield and quality. The optimized variables of 6:1 methanol/oil molar ratio (mol/mol), 0.75% sodium methoxide concentration (wt.%), 65 °C reaction temperature, 600 rpm agitation speed and 90 min reaction time offered the maximum methyl ester yield (96.9%). The obtained fatty acid methyl esters (FAME) were analyzed by gas chromatography (GC) and ¹H NMR spectroscopy. The fuel properties of cottonseed oil methyl esters (COME), cetane number, kinematic viscosity, oxidative stability, lubricity, cloud point, pour point, cold filter plugging point, flash point, ash content, sulfur content, acid value, copper strip corrosion value, density, higher heating value, methanol content, free and bound glycerol were determined and are discussed in the light of biodiesel standards such as ASTM D6751 and EN 14214.     

3-甲氧基丙酸甲酯合成工艺研究

以甲醇和丙烯酸甲酯(MA)为原料,甲醇钠为催化剂,合成了3-甲氧基丙酸甲酯(MMP)。用正交实验法优化了反应条件,结果表明,当n(甲醇)∶n(丙烯酸甲酯)=1.2∶1,n(甲醇钠)∶n(丙烯酸甲酯)=0.02∶1,反应温度50℃,反应时间3.5 h时,MMP的产率可达97%以上。将分馏时所得前馏分进行套用后,MMP的产率可达98.9%。气相色谱分析表明,产品纯度在99.6%以上。     

生物质多元醇选择性催化氢解制小分子二元醇研究进展

乙二醇、1,2-/1,3-丙二醇等小分子二元醇在精细和有机化工、生物医药等领域应用广泛。与石化路径相比,以可再生的生物质多元醇（丙三醇、山梨醇/木糖醇）为原料选择性催化氢解制取上述小分子二元醇具有过程简单、绿色高效等显著优势,已成为生物质催化转化的研究热点。本文综述了典型生物质多元醇山梨醇/木糖醇和丙三醇选择性催化氢解为乙二醇、1,2-/1,3-丙二醇等小分子二元醇,重点阐述了丙三醇选择性氢解制1,2-丙二醇、1,3-丙二醇和山梨醇/木糖醇选择性氢解制小分子二元醇的催化剂体系和反应机理,并对该领域的发展前景作了展望,提出开发高效稳定的催化剂体系和工艺是未来的研究重点。     

Stabilisation of trypsin-like enzymes from antarctic krill: Effect of polyols,polysaccharides and proteins

The stabilisation of trypsin-like enzymes purified from krill processing wastewater was studied using different proteins, polyols and polysaccharides. The effect of the different stabilisers was evaluated both in solution and in dry samples of the enzymes. In 40% (w/v) stabiliser solutions, the increase in half-life of enzyme activity followed the pattern: sorbitol > xylitol > glycerol > sucrose > maltodextrins, when polyols and polysaccharides were used. In 3% (w/v) protein solutions, the stabilising effect followed the order: hydrolysed collagen > bovine serum albumin > casein. The best result was obtained in a 50% (w/v) sorbitol solution where a 12-fold half-life increase was achieved. Different mechanisms of stabilisation were observed for these two groups of substances. In 50% (w/w) dry enzyme/stabiliser mixtures, the increase in half-life of krill trypsin-like enzymes was: maltodextrins > sucrose > sorbitol > mannitol > xylitol. Dry samples were also prepared by coprecipitation of the enzyme/stabiliser mixture with 95% ethanol, followed by oven drying of the coprecipitates. Under these conditions, the modified maltodextrin PSM 10 (Reppe-Glykos AB, Sweden) gave the best result with a 25-fold half-life increase. The relevance of this result for the industrial application of krill trypsin-like enzymes is discussed.     

Standard biodiesel from soybean oil by a single chemical reaction

Laboratory methods are described for producing standard biodiesel from low-acid-number vegetable oils in single-step reactions without distillation of the products. Either sodium hydroxide or methoxide is used as the catalyst. Biodiesel fuel is currently made from vegetable oils using basic catalysts. With this methodology, the oils must be reacted two or three times with methanol, in the presence of sodium methoxide, to make a product that meets the standard for the total chemically bound and unbound glycerol content. Previously it was thought that sodium hydroxide could never be used as the catalyst because it forms soap with the ester, which lowers the yield and makes product isolation difficult. Two of the described methods use sodium hydroxide as the catalyst and the other uses sodium methoxide. These methods rely on the use of oxolane as co-solvent to manipulate phase behavior during the reaction. Reactant molar ratios and base concentrations are also optimized to drive the reactions to the necessary degree of completion.     

The pseudo-single-phase,base-catalyzed transmethylation of soybean oil

The base-catalyzed transmethylation of soybean oil has been studied under conditions whereby the reaction starts as a single phase, but later becomes two phases as glycerol separates. Methanol/oil molar ratios of 6∶1 were used at 23°C. The catalysts were sodium hydroxide (0.5, 1.0, and 2.0 wt%), potassium hydroxide (1.0 and 1.4 wt%), and sodium methoxide (0.5, 1.0, and 1.35 wt%), all concentrations being with respect to the oil. Oxolane (tetrahydrofuran) was used to form a single reaction phase. The reactions deviated from homogeneous kinetics as glycerol separated, taking with it most of the catalyst. When 1.0 wt% sodium hydroxide was used, the methyl ester content reached 97.5 wt% after 4 h, compared with 85–90 wt% in the two-phase reaction. Sodium hydroxide (1.0 wt%), sodium methoxide (1.35 wt%), and potassium hydroxide (1.4 wt%) gave similar results, presumably because the same number of moles was used. The ASTM biodiesel specification for chemically bound glycerol was achieved after only 3 min when 2.0 wt% sodium hydroxide was used. However, the standard was not achieved after 4 h when 1.0 wt% sodium hydroxide was used, the MG content being 1.1–1.6 wt%. The use of 2.0 wt% catalyst is commercially impractical.     

Biodiesel production using tetramethyl- and benzyltrimethyl ammonium hydroxides as strong base catalysts

In recent years, the acceptance of fatty acid methyl esters (biodiesel) as an alternative fuel has rapidly grown in EU. The most common method for biodiesel production is based on triglyceride transesterification to methyl esters with dissolved sodium hydroxide in methanol as catalyst. In this study, cottonseed oil and used frying oil were subjected to the transesterification reaction with tetramethyl ammonium hydroxide and benzyltrimethyl ammonium hydroxide as strong base catalysts. This work investigates the optimum conditions for biodiesel production using amine-based liquid catalysts. Biodiesel ester content was strongly related with the type of feedstock and the reaction variables, such as those of the catalyst concentration, methanol to oil molar ratio, and reaction time. The overall results suggested that the transesterification of cottonseed oil achieved high conversion rates with both catalysts, while the use of waste oil resulted in lower yields of methyl esters due to the possible formation of amides.     

Variables Affecting the Production of Standard Biodiesel

Biodiesel is composed of fatty acid methyl esters, currently made from vegetable oils using basic catalysts. The oils must be reacted two or three times with methanol, in the presence of sodium methoxide to make products which meet the ASTM and European biodiesel standards. It is also believed that sodium hydroxide can never be used as the catalyst because it causes soap formation, which either lowers the yield or raises the acid number and makes product isolation difficult. Methods for producing standard biodiesel from low-acid-number soybean oil, in one chemical reaction using sodium hydroxide and a cosolvent, were recently reported. This study reports the effects of variables on the acid numbers and chemically bound glycerol contents of the products which led to the methods. These variables were the molar ratio of alcohol to oil, catalyst concentration, cosolvent volume, and reaction time. The alcohol-to-oil molar ratio must be at least 14, and the sodium hydroxide concentration should be at least 1.2 wt% (based on oil), to meet the necessary acid number and glycerol contents of the biodiesel. The volume of tetrahydrofuran cosolvent used must be 90–130% of that required to just create complete miscibility at the beginning of the reactions.     

Synthesis and Characterization of the Different Soy-Based Polyols by Ring Opening of Epoxidized Soybean Oil with Methanol, 1,2-Ethanediol and 1,2-Propanediol

Three soy-based polyols intended for application in polyurethanes were prepared by ring opening the epoxy groups in epoxidized soybean oil (ESO, 0.385 mol/100 g epoxy rings) with methanol, 1,2-ethanediol and 1,2-propanediol in the presence of tetrafluoroboric acid catalyst. The effect of the different opening reaction reagents, different low molecular weight alcohols, on the polyols was investigated by spectroscopic, chemical and physical methods. The viscosities, viscous-flow activation energies, molecular weight and melting point of the samples increased in the following order: polyol (3) > polyol (2) > polyol (1) > ESO [polyol (1); polyol (2) and polyol (3) represented the samples synthesized from the same epoxidized soybean oil generated by opening reactions with methanol, 1,2-ethanediol and 1,2-propanediol, respectively]. All the samples were crystalline solids below their melting temperature, displaying multiple melting point peaks. Compared with polyol (1), polyol (2) had a primary hydroxyl group, promoting the reactive activity of the polyol with isocyanates; polyol (3) contained large numbers of hydroxy groups, improving the properties of polyurethanes.     

金属氢氧化物对室温硫化硅橡胶陶瓷化性能的影响

以α,ω-二羟基聚二甲基硅氧烷(107硅橡胶)为基体,金属氢氧化物(氢氧化铝和氢氧化镁)为陶瓷化助剂,制备可陶瓷化室温硫化(RTV)硅橡胶,研究金属氢氧化物对硅橡胶性能的影响。结果表明:与未添加金属氢氧化物的硅橡胶相比,添加氢氧化镁的硅橡胶的力学性能明显降低,而添加氢氧化铝的硅橡胶的力学性能变化不明显;与添加氢氧化镁的硅橡胶相比,添加氢氧化铝的硅橡胶在1 000℃烧蚀后所得陶瓷体的外观更加稳定,形状保持更好,陶瓷体断面更致密;添加氢氧化铝的硅橡胶陶瓷体的三点弯曲强度比未添加金属氢氧化物的硅橡胶陶瓷体显著增大。     

Prediction of Water Activity in Aqueous Polyol Solutions

In intermediate moisture foods polyols are added to decrease the water activity. However, an easily readable diagram for industrial use describing combined effects of different polyols on the final water activity of the food product is, to our knowledge, missing. Therefore, in this study the influence of sorbitol and glycerol on the water activity in the range of 0.6 – 0.8 in monomeric and binary polyol solutions was examined and predicted using combinations of the Raoult, Norrish and Ross equations. A ternary diagram describing the combined effects for the use in confectionery was developed.     

Hydrogenolysis of sorbitol to glycols over carbon nanofiber supported ruthenium catalyst

Sorbitol hydrogenolysis was carried out over a carbon nanofiber supported ruthenium catalyst prepared by incipient wetness impregnation. The carbon nanofiber supported ruthenium catalyst was shown to have an attracting behavior when compared with a commercial activated carbon supported ruthenium catalyst, especially in terms of selectivity to glycols. The preferable hydrogen partial pressure for sorbitol hydrogenolysis was ca. 8.0 MPa, lower than that usually reported in previous works. Slightly soluble calcium hydroxide, which was used as a basic promoter, remarkably increased the selectivity to glycols, as compared with the soluble sodium hydroxide. The variation of product selectivity with catalyst amount indicated that glycerol was the initial C3 polyol product while propylene glycol was derived from glycerol. The parametric investigation was further focused on the intrinsic features of sorbitol hydrogenolysis.     

Über die Produkte der Reaktion von Methylbromid und Ethylbromid mit Kaliumhydroxid in wäßrig–methanolischen Lösungen und den Verlauf dieser SN2-Reaktion

Concerning the Products of the Reaction of Methyl Bromide and Ethyl Bromide with Potassium Hydroxide in Aqueous Methanolic Solutions and the Progress of this S_N2-Reaction Investigations of the reaction of methyl bromide and ethyl bromide with potassium hydroxide in methanolic and aqueous methanolic solutions show that the main products of these reactions are dimethyl ether and ethylmethyl ether. The reaction rates measured in methanolic or aqueous methanolic solutions are the same whether potassium hydroxide or potassium methoxide are used. These results are caused by an equilibrium between hydroxide and methoxide ions with which we could establish the equilibrium constant near 0.6. This means that a solution of sodium hydroxide c = 0.1 moll⁻¹ in methanol contains roughly 99.8% of methoxide ions. The reaction rates in methanolic as well as in aqueous methanolic solutions are strict second order. The reaction rate measured at several temperatures permitted the calculation of E_A^≠, ΔH^≠, ΔS^≠ and ΔG^≠. Furthermore the kinetic investigations show that the nucleophilicity of methoxide ions is lower compared to hydroxide ions. The calculation of the Swain–Scott-parameter n results in a nucleophilicity scale in order to methoxide, hydroxide, ethoxide ions. The kinetic investigations of the reaction of ethyl bromide with methoxide and hydroxide ions in methanolic solutions demonstrate that at high temperatures the rate constant of methoxide ions is higher than that of hydroxide ions. The opposite case can be observed at lower temperatures. At the temperature of 20 °C the rate constants of both reactions are equal. This is to do with the isokinetic effect which one is rarely able to observe at room temperatures.     

Transesterification of neat and used frying oil: Optimization for biodiesel production

In this study, the characteristics and performance of three commonly used catalysts used for alkaline-catalyzed transesterification i.e. sodium hydroxide, potassium hydroxide and sodium methoxide, were evaluated using edible Canola oil and used frying oil. The fuel properties of biodiesel produced from these catalysts, such as ester content, kinematic viscosity and acid value, were measured and compared. With intermediate catalytic activity and a much lower cost sodium hydroxide was found to be more superior than the other two catalysts. The process variables that influence the transesterification of triglycerides, such as catalyst concentration, molar ratio of methanol to raw oil, reaction time, reaction temperature, and free fatty acids content of raw oil in the reaction system, were investigated and optimized. This paper also studied the influence of the physical and chemical properties of the feedstock oils on the alkaline-catalyzed transesterification process and determined the optimal transesterification reaction conditions that produce the maximum ester content and yield.     

Stability of Pt/γ-Al2O3 Catalysts in Model Biomass Solutions

The stability of a Pt/??-Al₂O₃ catalyst in liquid water and aqueous solutions of 5?wt% glycerol or sorbitol at 225?°C is examined using a variety of physicochemical methods. It is demonstrated that the presence of glycerol and sorbitol significantly reduces the hydration of ??-Al₂O₃ to form boehmite as compared to treatment in pure water. The stability against hydration increases with increasing carbon chain length. Treatment with polyol solutions also results in reduced agglomeration of supported metal particles. The prevention of boehmite formation and agglomeration of metal particles are attributed to the formation of carbonaceous species on the surface. In addition to these effects, the deposits block a considerable portion of active metal surface area. IR spectroscopic analysis indicates that dehydration reactions play an important role in the formation of the carbonaceous deposits. The present results illustrate that water and dissolved biomass compounds can strongly affect the stability of heterogeneous catalysts under reaction conditions.     

Kinetics of hydroxide‐catalyzed methanolysis of crude sunflower oil for the production of fuel‐grade methyl esters

Methyl esters from crude sunflower oil were produced via methanolysis reaction using sodium hydroxide catalyst. Methanolysis was carried out at different agitation speeds (200–600 rpm), temperatures (25–60 °C), catalyst loadings (0.25–1.00% by weight of oil), and methanol:oil mole ratios (6:1–20:1). Mass‐transfer limitation was effectively minimized at agitation speeds of 400–600 rpm with no apparent lag period. Lowering the temperature resulted in a fall in the rate of reaction prolonging the reaction time necessary to achieve maximum production of methyl ester. Using 0.50% hydroxide catalyst was found to be adequate, resulting in 97–98% conversion without compromising recovery due to soap formation. Increasing the methanol:oil mole ratio beyond the usual amount of 6:1 tended to speed up the initial rate of methanolysis and was found to lower the bonded glycerol content, especially the amount of diglyceride in the sample. Kinetic rate constants were derived from experimental results using second‐order rate expressions, and values of activation energy for glyceride methanolysis have been established. Copyright © 2007 Society of Chemical Industry     

响应面法优化羊毛脂甲酯化工艺研究

以羊毛脂为原料,采用甲醇钠、氢氧化钠2种催化剂,考察了反应温度、时间、催化剂用量、醇用量等因素对甲酯化的影响。结果表明:甲醇钠为催化剂时,在反应温度60℃、甲醇与羊毛脂质量比1.6、反应时间60 min、催化剂质量分数4%的条件下,酯转化率达到94.3%。用响应面法优化氢氧化钠为催化剂的羊毛脂甲酯化工艺,得到最佳工艺条件为:反应温度65.3℃、甲醇与羊毛脂质量比1.85、催化剂质量分数6%、反应时间90 min,在此条件下酯转化率可达94.2%。     

膜分离法精制低不饱和度聚醚多元醇

采用聚醚砜超滤膜对ZSN-330低不饱和度聚醚多元醇进行精制,粗聚醚多元醇由正己烷1∶1体积比稀释,精制效果很好,大部分检测时间下锌、钴离子截留率高达90%以上,含量低于1 mg/g。采用红外分析并验证了截留物中含有双金属氰化络合物催化剂（DMC）成分。考察了膜截留分子量、料液黏度、操作压力、料液流速等对膜通量的影响,确定了较佳的超滤条件为膜截留分子量为150 kDa、由正己烷1∶1稀释、操作压力0.5 MPa、料液流速40 L/h。分别采用去离子水、2‰氢氧化钠溶液、正己烷溶剂超声清洗污染的膜,2‰氢氧化钠溶液的清洗效果较好,膜通量恢复率达66.4%。