酸催化合成生物柴油的研究现状

生物柴油生产过程中的催化剂是一个关键问题.目前,在生物柴油的规模化生产中碱催化和酸催化应用最为广泛.与碱催化相比,酸催化由于反应速度慢、所需反应条件苛刻而使其应用受到了限制,然而酸催化制备生物柴油的优点也是显而易见的.简述了在酸催化作用下将高酸值原料油转化为生物柴油的原理、酸催化工艺,主要介绍了国外从机理方面对酸催化剂的研究,涉及酯交换和酯化两个方面.最后对酸催化反应的影响因素以及仍存在的问题也稍加叙述.     

固体酸催化酯交换制备生物柴油的研究进展

制备生物柴油最常用的方法是植物油和动物脂肪的均相碱或酸催化酯交换.与石油基柴油相比,从植物油和动物脂肪生产生物柴油的主要瓶颈是生产价格,特别是原料价格.为降低生物柴油成本,应利用廉价原料(如废油脂)、采用连续酯交换工艺并从生物柴油副产品(甘油)中回收高纯度甘油.均相酸催化剂虽反应产率高,但废催化剂会带来环境问题,故固体酸催化剂已成为目前研究热点.简述了固体酸催化酯交换制备生物柴油的研究进展和发展趋势,最后提出了一些建议.     

固体酸催化制备生物柴油的研究进展

生物柴油是一种清洁可再生能源.固体酸催化制备生物柴油具有受原料影响小和产物易分离等优点.简要综述了几种主要固体酸催化剂在制备生物柴油中的应用,并对当前油脂酯交换反应中固体酸催化剂存在的问题提出了一些建议.     

固体酸催化制备生物柴油研究进展

生物柴油是一种绿色的可再生能源,主要通过酯交换反应生产。催化剂在酯交换反应中起重要作用,固体酸催化剂因污染少、效率高、易分离而成为研究热点。本文介绍了固体酸催化制备生物柴油的反应机理,综述了国内外近几年生物柴油制备中所用固体酸催化剂的研究进展,分为固体杂多酸、无机酸盐、金属氧化物及其复合物、沸石分子筛及阳离子交换树脂等,分析了催化剂的制备流程、反应操作条件和反应结果等,得出固体酸在催化含有大量水分和游离酸的油脂酯交换反应方面具有独特的优势,且符合生物柴油绿色生产的要求,是需要进一步研究和开发的方向。     

固体酸催化制备生物柴油研究进展

生物柴油是一种具有优良燃烧性能的石化替代燃料,开发可用于通过酯交换反应制备生物柴油的固体酸催化剂已成为国内外研究热点。本文综述了固体酸在催化合成生物柴油方面的研究进展,介绍了以纳米材料、磁性材料作为载体以及掺杂稀土元素等固体酸改性方法,并对固体酸催化制备生物柴油的发展前景进行了展望。     

制备生物柴油的固体酸催化剂研究进展

生物柴油是一种绿色可再生能源。目前,大多采用高活性的固体酸催化酯化、酯交换反应进行制备,该工艺具有产品与催化剂易分离、催化剂可回收再生且环保等优点。本文综述了固体超强酸、负载型固体酸、金属氧化物及复合物、沸石分子筛、阳离子交换树脂、离子液体及杂多酸等不同类型固体酸催化剂催化制备生物柴油的最新研究进展,包括催化剂的制备、活性、催化行为。最后,对制备生物柴油的固体酸在物理化学性质、成本等方面的研究进行展望。     

几种固体酸催化剂在生物柴油反应中的应用

固体酸作为催化剂,具有重复利用及分离方便等优点。对生物柴油的研发和利用,有利于缓解我国的能源危机,因此很有必要对其进行研究。而催化剂的使用对其产品的性能和工业化生产也有着很重要的影响。简要讲述了生物柴油的组成成分及其制备方法,主要介绍了几种固体酸催化剂在生物柴油制备中的应用,并对固体酸催化剂在催化过程中的问题,提出了几点建议。     

固体酸催化剂制备生物柴油研究进展

生物柴油是一种可再生的生物能源,近年来得到广泛关注.固体酸催化剂可同时催化油脂和脂肪酸制备生物柴油,同时还具有环境友好、易于和产物分离等优点.本文综述了沸石分子筛、杂多酸、离子交换树脂、固体超强酸等同体酸在催化合成生物柴油方面的研究进展.     

酸催化蓖麻油甲醇醇解反应制生物柴油

以固体酸—一水硫酸氢纳、硫酸铝,液体酸—浓硫酸、磷酸为催化剂,分别对其催化蓖麻油甲醇解反应制备生物柴油进行了研究。采用单因素试验法,考察了醇油物质的量比、催化剂用量、反应温度及反应时间对蓖麻油转化率的影响。得到了上述四种酸催化蓖麻油甲醇解制备生物柴油的优化工艺条件。其中,一水硫酸氢钠和浓硫酸,因其酸性强,催化活性好,常压反应就可取得好的效果。硫酸铝和磷酸,因其酸性弱,催化活性差,反应必须在高压下进行才能取得好的效果。对四种酸催化蓖麻油甲醇解反应的优缺点进行了比较。     

废餐饮油制备生物柴油研究现状与应用前景

介绍了利用废餐饮油制备生物柴油的研究现状与应用前景;叙述了酸催化、碱催化和酶催化的酯交换制备生物柴油工艺,以及每种工艺的优缺点.阐述了我国利用餐饮废油制取生物柴油的意义和利用餐饮废油制取生物柴油的商业化生产的可行性.     

生物柴油的合成和使用研究进展

总结了近年来生物柴油的合成方法和使用方法。催化方法上,生物柴油的合成方法有酸催化、碱催化、酶催化和超临界催化等;工艺路线上,生物柴油可由高温热裂解和酯交换两种路线合成。目前一般采用混合和微乳液两种方法来使用生物柴油。     

超临界流体制备生物柴油研究进展

生物柴油是一种环境友好的绿色能源。目前国内外的制备方法主要有酸催化法、碱催化法、生物酶催化法以及超临界流体法。文章主要阐述了各种超临界法制备生物柴油的国内外研究最新进展,介绍了其反应机理及反应动力学,并与传统的方法做了比较,指出其优点在于无需使用催化剂、反应速度快、提纯分离过程简单、对环境友好、无污染等。     

A Novel Method for the Production of Biodiesel from the Whole Stillage-Extracted Corn Oil

The extraction of corn oil from whole stillage and condensed distillers’ solubles (CDS) with hexane and its conversion to biodiesel were investigated. The analysis of the extracted oil showed 6–8 wt.% free fatty acid (FFA) in this oil. Acid, base, acid–base, and acid–base catalyzed transesterifications with intermediate neutralization with anion exchange resin were investigated. Experiments were performed with model corn oil substrates which contained 1.0–6.0 wt.% FFA. The effect of catalyst at 0.50–1.25 wt.% was studied at a 1:8 oil/methanol molar ratio. At 6.0 wt.% FFA concentration, the acid-catalyzed scheme was slow and resulted in less than 20% yield after 4 h, while the base-catalyzed was mostly consumed by the FFA and very little conversion was achieved. The acid–base catalyzed scheme succeeded in reducing the FFA content of the oil through the acid-catalyzed stage, and yields in excess of 85% were achieved after the second stage of the reaction with a base catalyst. However, formation of water and soap prevented the separation of product phases. An alternative acid–base catalyzed scheme was examined which made use of a strong anion exchange resin to neutralize the substrate after the initial acid-catalyzed stage. This scheme resulted in the effective removal of the acid catalyst as well as the residual FFA prior to the base-catalyzed stage. The subsequent base-catalyzed stage resulted in yields in excess of 98% for a 7.0 wt.% FFA corn oil and for the corn oil extracted from CDS.     

Structure of Polymeric PbTiO3 Gels

The structural features of PbTiO₃ gels were found to be highly dependent on hydrolysis conditions. Gels formed from acid-catalyzed solutions were clear and rubbery, whereas base-catalyzed gels were translucent or cloudy with phase separation. Direct TEM observations determined that acid-catalyzed gels were fibrous in character and physically homogeneous, whereas base-catalyzed gels had a coarse texture. Analyses by EDX and SAD indicated that acidic gels were chemically homogeneous and microcrystalline, whereas basic gels were heterogeneous and amorphous.     

Biodiesel production from tobacco (Nicotiana tabacum L.) seed oil with a high content of free fatty acids

The production of fatty acid methyl esters (FAME) from crude tobacco seed oil (TSO) having high free fatty acids (FFA) was investigated. Due to its high FFA, the TSO was processed in two steps: the acid-catalyzed esterification (ACE) followed by the base-catalyzed methanolysis (BCM). The first step reduced the FFA level to less than 2% in 25 min for the molar ratio of 18:1. The second step converted the product of the first step into FAME and glycerol. The maximum yield of FAME was about 91% in about 30 min. The tobacco biodiesel obtained had the fuel properties within the limits prescribed by the latest American (ASTM D 6751-02) and European (DIN EN 14214) standards, except a somewhat higher acid value than that prescribed by the latter standard (<0.5). Thus, tobacco seeds (TS), as agricultural wastes, might be a valuable renewable raw material for the biodiesel production.     

An enzymatic/acid-catalyzed hybrid process for biodiesel production from soybean oil

The present study is aimed at developing an enzymatic/acid-catalyzed hybrid process for biodiesel production using soybean oil as feedstock. In the enzymatic hydrolysis, 88% of the oil taken initially was hydrolyzed by binary immobilized lipase after 5 h under optimal conditions. The hydrolysate was further used in acid-catalyzed esterification for biodiesel production and the effects of temperature, catalyst concentration, feedstock to methanol molar ratio, and reaction time on biodiesel conversion were investigated. By using a feedstock to methanol molar ratio of 1:15 and a sulfuric acid concentration of 2.5%, a biodiesel conversion of 99% was obtained after 12 h of reaction at 50 °C. The biodiesel produced by this process met the American Society for Testing and Materials (ASTM) standard. This hybrid process may open a way for biodiesel production using unrefined and used oil as feedstock.     

Improving the economics of biodiesel production through the use of low value lipids as feedstocks: vegetable oil soapstock

Semirefined and refined vegetable oils are the predominant feedstocks for the production of biodiesel. However, their relatively high costs render the resulting fuels unable to compete with petroleum-derived fuel. We have investigated the production of fatty acid methyl esters (FAME; biodiesel) from soapstock (SS), a byproduct of edible oil refining that is substantially less expensive than edible-grade refined oils. Multiple approaches were taken in search of a route to the production of fatty acid methyl esters from soybean soapstock. The most effective method involved the complete saponification of the soapstock followed by acidulation using methods similar to those presently employed in industry. This resulted in an acid oil with a free fatty acid (FFA) content greater than 90%. These fatty acids were efficiently converted to methyl esters by acid-catalyzed esterification. The fatty acid composition of the resulting ester product reflected that of soy soapstock and was largely similar to that of soybean oil. Following a simple washing protocol, this preparation met the established specifications for biodiesel of the American Society for Testing and Materials. Engine emissions and performance during operation on soy soapstock biodiesel were comparable to those on biodiesel from soy oil. An economic analysis suggested that the production cost of soapstock biodiesel would be approximately US$ 0.41/l, a 25% reduction relative to the estimated cost of biodiesel produced from soy oil.     

Transesterification of Jatropha curcas oil glycerides: Theoretical and experimental studies of biodiesel reaction

Vegetal oil, also known as triglycerides, is a mixture of fatty acid triesters of glycerol. In the triglycerides alkyl chains of Jatropha curcas oil, predominate the palmitic, oleic and linoleic fatty acids. The process usually used to convert these triglycerides to biodiesel is called transesterification. The overall process is a sequence of three equivalent, consecutive and reversible reactions, in which di- and monoglycerides are formed as intermediates. Semi-empirical AM1 molecular orbital calculations were used to investigate the reaction pathways of base-catalyzed transesterification of glycerides of palmitic, oleic and linoleic acid. The most probable pathway and the rate determining-step of the reactions were estimated from the molecular orbital calculations. Our results suggest the formation of only one tetrahedral intermediate, which in a subsequent step rearranges to form the products. The rate determining-step is the break of this tetrahedral intermediate.     

Calcium Containing Silicate Mixed Oxide-Based Heterogeneous Catalysts for Biodiesel Production

A series of calcium containing silicate mixed oxide materials has been developed for biodiesel production. It has been shown that these materials can catalyze transesterification reactions from feedstocks with various fatty acid contents. However, their reaction kinetics for biodiesel synthesis was very slow compared to that of homogeneous-catalyst-catalyzed reactions. Herein, we report fast-reacting solid catalysts for biodiesel production. Two types of materials have been developed: a non-porous and an anionic-surfactant-templated catalysts. Compared to previously reported transesterification reaction by mesoporous calcium containing silicate catalysts, the reaction rates from both families were much faster. In addition, both the preparation time of catalysts and the cost of preparation were significantly reduced. Details in material synthesis and its effect on catalysis are discussed.