• Energy Research

This article examines opportunities of enzyme application during the production of biodiesel from microalgae oil by its transesterification in the mixture with mineral diesel fuel. The oil and mineral diesel fuel ratio in the reaction mixture enabled a yield of 7% ester content in the mixture. Effectiveness tests were conducted on seven industrial lipases, and Lipozyme TL IM was selected as the most effective lipase for further optimization. The process of algae oil transesterification with ethanol was optimized by applying response surface methodology. The interactions and impacts of the following independent variables on the transesterification yield were evaluated: ethanol and oil molar ratio, process duration, lipase content, and temperature. Optimum conditions were determined: a temperature of 30 °C, 13.26% biocatalyst (from the oil content), an ethanol and oil molar ratio of 4.54:1, and a process duration of 13 h. The transesterification yield of the product under the above conditions reached 98%.

Dolomite as a heterogeneous catalyst can be used in biodiesel synthesis. Process material costs can be reduced by regenerating and reusing the catalyst. Two methods of regeneration of dolomite were studied: (1) washing for 30 min with methanol, filtration, and washing for 30 min with hexane and (2) calcination at high temperature. Catalytic efficiency and catalyst changes after 1–6 cycles were evaluated. X-ray, FTIR, and SEM studies were performed. Calcination has been found to be a more effective method of catalyst regeneration than washing with solvents. The catalytic effectiveness of dolomite only slightly decreased over six application cycles. The results of the instrumental analysis showed that the structure and composition of the dolomite do not change during calcination after three cycles, while obvious changes in the structure of dolomite during catalyst washing were observed.

The constant increase in greenhouse gases in the environment is forcing people to look for different ways to reduce such pollution. One of these ways is the use of biodiesel for road transport. Conventional biodiesel production involves the catalytic triglyceride transesterification process. When using homogeneous two-stage catalysis, it is difficult to purify the resulting product from the by-products formed, and the catalysts cannot be reused. In the case of heterogeneous catalysis, the process costs are increased due to separation and regeneration of the catalysts. To solve these problems of catalytic synthesis, a noncatalytic process has been recently studied that which takes place under supercritical conditions for an alcohol or other acyl receptor. In such biodiesel production, fatty feedstocks and alcohols are used as raw materials, with the synthesis taking place at supercritical conditions for alcohol, i.e., high temperature and pressure, thus making the process quite simple. This paper reviews the results obtained from biodiesel synthesis using a noncatalytic supercritical process for transesterification using both alcohols and carboxylate esters of low molecular weight, evaluating the optimal conditions for these processes and biofuel stability at high temperatures.

Increasing concentrations of greenhouse gases in the atmosphere are leading to increased production and use of biofuels. The industrial development of biodiesel production and the use of biodiesel in the EU transport sector have been ongoing for almost two decades. Compared to mineral diesel production, the process of producing biodiesel is quite complex and expensive, and the search for new raw materials and advanced technologies is needed to maintain production value and expand the industrial production of biodiesel. The purpose of this article is to review the application possibilities of one of the new technologies—simultaneous extraction of oil from oily feedstock and transesterification (in situ)—and to evaluate the effectiveness of the abovementioned process under various conditions.

Solubility of biodiesel fuel components in fossil diesel fuel-methanol-rapeseed oil methyl ester, fossil diesel fuel-ethanol-rapeseed oil methyl ester and fossil diesel fuel-ethanol-rapeseed oil ethyl ester systems was investigated. The solubility of components in the fossil diesel fuel-ethanol-rapeseed oil methyl ester system at 20 degrees C was substantially higher than in the fossil diesel fuel-methanol-rapeseed oil methyl ester system. The solubility of components in the fossil diesel fuel-ethanol-rapeseed oil ethyl ester system was slightly lower than in the fossil diesel fuel-ethanol-rapeseed oil methyl ester mixture. The moisture content of ethanol had a great influence on mixture solubility. With decrease of temperature, the solubility of components in the fossil diesel fuel-ethanol-rapeseed oil methyl ester system decreased.

Abstract This paper discusses the determination of the optimal conditions for enzymatic transesterification of model waste oil (with 4% acid value) with butanol. It was found that biodiesel synthesis by the enzymatic transesterification of waste rapeseed oil rich in free fatty acid with butanol can be very effective if the catalysis is carried out in two steps. Both transesterification steps were catalysed by Lipozyme RM IM. The optimal conditions for the first step were determined: temperature of 39 °C, butanol and oil molar ratio of 4.5, lipase concentration of 6%, and reaction time of 9.8 h, with an expected yield of 60.1%. The removal of glycerol, enzyme renewal and subsequent addition of 7.8% lipase, with a 1.5 butanol and oil molar ratio and 8-h incubation at 39 °C predicted a 96.7% yield and resulted in a 96.6% butyl ester yield.

In the conventional synthesis of biodiesel, not only fatty acid esters (biodiesel) are formed, but also the by-product is the glycerol phase, which amounts to about 10 wt.%. Recently, the studies on the interesterification of oil using carboxylate esters have been launched. In this case, no glycerol is formed, and esters of glycerol and short-chain organic acids soluble in biodiesel are produced. The biodiesel yield is increased, and the biodiesel production process is more economically viable. The process of interesterification with methyl formate yields a mixture of biodiesel and triformylglycerol, which is not inferior in quality to biodiesel, but also has better low-temperature properties. The paper analyzes the application of chemical and enzymatic catalysis methods for the interesterification of triglycerides with methyl formate. The influence of catalyst amount, reagent molar ratio, temperature, and process time on the product yield is presented. The quality indicators of the obtained fuel and their compliance with the requirements of the biodiesel fuel standard are discussed.

During the production of biodiesel, a by-product - the glycerol phase is formed (about 10% of the obtained biodiesel). The interesterification of vegetable oil using carboxylate esters of low molecular weight does not produce glycerol, instead its compounds (mono-, di- and triformyl glycerides) are obtained in a mixture with fatty acid alkyl esters (conventional biodiesel). Such a product can be used as fuel for diesel engines. The aim of the work was to investigate the possibilities of application of methyl formate in the biotechnological production of biodiesel. The industrial enzyme preparation Lipozyme TL IM was used as a catalyst for interesterification. The influence of the amount of catalyst, the molar ratio of methyl formate to oil and the duration of the process on the yield of biodiesel was evaluated. The highest yield of rapeseed oil methyl esters was obtained under the following conditions: 14-15% of the enzyme preparation Lipozyme TL IM (based on the weight of the oil), molar ratio of methyl formate to oil - 40:1, duration - 60 h. Under these conditions, an 81.6% yield of rapeseed oil methyl esters was obtained.