Feasibility study of a thermally coupled reactive distillation process for biodiesel production

Biodiesel fuel represents an interesting alternative as a clean and renewable substitute of fossil fuels. A typical biodiesel production process involves the use of a catalyst, which implies high energy consumptions for the separation of the catalyst and the by-products of the reaction, including those of undesirable side reactions (such as the saponification reaction). A recently proposed process involves the use of short-chain alcohols at supercritical conditions, avoiding the use of a catalyst and the occurrence of the saponification reaction. This process requires fewer pieces of equipment than the conventional one, but its high energy requirements and the need of special materials that support the reaction conditions makes the main product, biodiesel fuel, more expensive than petroleum diesel. In this work, a modification of the supercritical process for the production of biodiesel fuel is proposed. Two alternatives are proposed. The process involves the use of either reactive distillation or thermally coupled reactive distillation. Simulations have been carried out by using the Aspen One™ process simulator to demonstrate the feasibility of such alternatives to produce biodiesel with methanol at high pressure conditions. A design method for the thermally coupled system is also proposed. Both systems have been tested and the results indicate favorable energy performance when compared to the original scheme. Furthermore, the thermally coupled system shows lower energy consumptions than the reactive distillation column.     

Comparison of membrane extraction with traditional extraction methods for biodiesel production

Three traditional methods for the refining step in biodiesel production were compared: (i) washing with distilled water; (ii) washing with acid (HCl); and (3) dissolving and extracting in a solvent (hexane or petroleum ether) and then washing with distilled water. Biodiesel with a high purity (97.5%) could be obtained by all three methods, but serious emulsification occurred during the refining processes, which led to high refining losses. A novel refining method was developed by using hollow fiber membrane extraction, and polysulfone was selected as the most suitable membrane. This process effectively avoided emulsification during refining and decreased the refining loss. The purity of the biodiesel obtained was about 99%; and other properties, such as density, kinematic viscosity, water content, and acid value, conformed to the standards.     

Kalsilite based heterogeneous catalyst for biodiesel production

Kalsilite (KAlSiO₄) was used as a heterogeneous catalyst for transesterification of soybean oil with methanol to biodiesel. Kalsilite showed relatively low catalytic activity for transesterification reaction. The catalytic activity of this catalyst was significantly enhanced by introducing a small amount of lithium nitrate by the impregnation method. A biodiesel yield of 100% and a kinematic viscosity of 3.84 cSt were achieved at a mild temperature of only 120 °C over this lithium modified kalsilite catalyst (2.3 wt.% Li).     

Economic and ecological aspects of biodiesel production over homogeneous and heterogeneous catalysts

The objective of this paper is to highlight the economic and ecological differences of biodiesel production over homogeneous and heterogeneous catalysts in large-scale industrial plants. Comparative economic assessment of the two processes revealed the advantage of the heterogeneous process in terms of higher yield of biodiesel and higher purity of glycerine, lower cost of catalyst and maintenance, with an estimated cumulative impact on the reduction of the operating cost of US$59 per tonne of biodiesel, relative to the homogeneous process. The biggest challenge for its economic competitiveness is its higher energy consumption. The analysis showed that if the energy costs are below US$85 per tonne of biodiesel, the heterogeneous process can be economically viable. The environmental benefits of the heterogeneous process include absence of strong acids and of energy intensive and waste generating glycerine purification step. However, its application would contribute to depletion of fossil energy resources and higher emission of greenhouse gases due to higher energy and methanol consumption.     

Life cycle analysis of biodiesel production

Biodiesel has attracted considerable attention as a renewable, biodegradable, and nontoxic fuel and can contribute to solving the energy problems, significantly reducing the emission of gases which cause global warming.The first stage of this work was to simulate different alternative processes for producing biodiesel. The method used for the production of biodiesel is the transesterification of vegetable oils with an alcohol in the presence of a catalyst. The raw materials used were palm oils and waste cooking oil.The second stage was a life cycle analysis for all alternatives under study, followed by an economic analysis for the alternatives that present minor impacts and which are more promising from an economic point of view. Finally, we proceeded to compare the different alternatives from both the point of view of life cycle and economic analysis.The feasibility of all processes was proven and the biodiesel obtained had good specifications.From the standpoint of life cycle analysis, the best alternative was the process of alkaline catalysis with acid pre-treatment for waste cooking oil.The economic analysis was done to the previous mentioned process and to the process that uses raw virgin oils, methanol, and sodium hydroxide. This process has lower investment costs but the process of alkaline catalysis with acid pre-treatment, whose main raw material is waste oil, is much more profitable and has less environmental impacts.     

壳聚糖生产的技术经济论证

介绍了壳聚糖的市场动态,生产方法、工艺特点和技术指标,对３００ｔ／ａ生产线进行了技术经济分析。     

Techno-economic analysis of a biodiesel production process from vegetable oils

Biodiesel, which is defined as the monoalkyl esters of long chain fatty acids derived from a renewable lipid feedstock, has received considerable attention worldwide as a medium-term alternative to diesel fuel obtained from petroleum. Biodiesel can be produced by the transesterification of vegetable oils or animal fats using short-chain alcohols in the presence of a suitable catalyst and glycerol is the only byproduct obtained in significant quantities. In this work a techno-economic analysis of a process that produces biodiesel from vegetable oils is presented with the aim to investigate the dependence of the critical profitability indicators on the production capacity.     

Optimization of the transesterification reaction in biodiesel production

In this paper response surface methodology (RSM) was used to study the transesterification reaction of rapeseed oil for biodiesel production. The three main factors that drive the conversion of triglycerides into fatty acid methyl esters (FAME) were studied according to a full factorial design at two levels. These factors were catalyst concentration (KOH), temperature and reaction time. The range investigated for each factor was selected taking into account the process of Fox Petroli S.p.A. Analysis of variance (ANOVA) was used to determine the significance of the factors and their interactions which primarily affect the first of the two transesterification stages. This analysis evidenced the best operating conditions of the first transesterification reaction performed at Fox’s plant: KOH concentration 0.6% w/w, temperature 50 °C and reaction time 90 min with a CH₃OH to KOH ratio equal to 60. Three empirical models were derived to correlate the experimental results, suitable to predict the behavior of triglyceride, diglyceride and monoglyceride concentration. These models showed a good agreement with the experimental results, demonstrating that this methodology may be useful for industrial process optimization.     

Calcined sodium silicate as solid base catalyst for biodiesel production

This paper examined the use of calcined sodium silicate as a novel solid base catalyst in the transesterification of soybean oil with methanol. The calcined sodium silicate was characterized by DTA-TG, Hammett indicator method, XRD, SEM, BET, IR and FT-IR. It catalyzed the transesterification of soybean oil to biodiesel with a yield of almost 100% under the following conditions: sodium silicate of 3.0 wt.%, a molar ratio of methanol/oil of 7.5:1, reaction time of 60 min, reaction temperature of 60 °C, and stirring rate of 250 rpm. The oil containing 4.0 wt.% water or 2.5 wt.% FFA could also be transesterified by using this catalyst. The catalyst can be reused for at least 5 cycles without loss of activity.     

Activity of solid catalysts for biodiesel production: A review

Heterogeneous catalysts are promising for the transesterification reaction of vegetable oils to produce biodiesel. Unlike homogeneous, heterogeneous catalysts are environmentally benign and could be operated in continuous processes. Moreover they can be reused and regenerated. However a high molar ratio of alcohol to oil, large amount of catalyst and high temperature and pressure are required when utilizing heterogeneous catalyst to produce biodiesel. In this paper, the catalytic activity of several solid base and acid catalysts, particularly metal oxides and supported metal oxides, was reviewed. Solid acid catalysts were able to do transesterification and esterification reactions simultaneously and convert oils with high amount of FFA (Free Fatty Acids). However, the reaction rate in the presence of solid base catalysts was faster. The catalyst efficiency depended on several factors such as specific surface area, pore size, pore volume and active site concentration.     

Tri-potassium phosphate as a solid catalyst for biodiesel production from waste cooking oil

Transesterification of waste cooking oil with methanol, using tri-potassium phosphate as a solid catalyst, was investigated. Tri-potassium phosphate shows high catalytic properties for the transesterification reaction, compared to CaO and tri-sodium phosphate. Transesterification of waste cooking oil required approximately two times more solid catalyst than transesterification of sunflower oil. The fatty acid methyl ester (FAME) yield reached 97.3% when the transesterification was performed with a catalyst concentration of 4 wt.% at 60 °C for 120 min. After regeneration of the used catalyst with aqueous KOH solution, the FAME yield recovered to 88%. Addition of a co-solvent changed the reaction state from three-phase to two-phase, but reduced the FAME yield, contrary to the results with homogeneous catalysts. The catalyst particles were easily agglomerated by the glycerol drops derived from the homogeneous liquid in the presence of co-solvents, reducing the catalytic activity.     

Technologies for production of biodiesel focusing on green catalytic techniques: A review

Biodiesel production is undergoing rapid technological reforms in industries and academia. This has become more obvious and relevant since the recent increase in the petroleum prices and the growing awareness relating to the environmental consequences of the fuel overdependency. In this paper, various technological methods to produce biodiesel being used in industries and academia are reviewed. Catalytic transesterification, the most common method in the production of biofuel, is emphasized in the review. The two most common types of catalysts; homogeneous liquids and heterogeneous solids, are discussed at length in the paper. Two types of processes; batch and continuous processes, are also presented. Although batch production of biodiesel is favored over continuous process in many laboratory and larger scale efforts, the latter is expected to gain wider acceptance in the near future, considering its added advantages associated with higher production capacity and lower operating costs to ensure long term supply of biodiesel.     

Methylation of wood fatty and resin acids for production of biodiesel

The purpose of the present paper is to evaluate the potentiality of the wood oil of Oriental spruce (Spruce orientalis) for biodiesel production. Two methods have been applied for obtained wood oil with and without solvent such as separation of crude tall oil from sulfate soaps by Kraft pulping process. Production of biodiesel from wood oil follows two steps, first extraction of oil using a solvent (acetone) and then base catalyzed (KOH) or non-catalytic supercritical methanol transesterification. This paper studied the effect of temperature on transesterification of wood oil to find the optimum temperature of maximum biodiesel yield. Transesterification of the wood oils were performed in a 100-mL cylindrical autoclave using supercritical methanol. In a typical run, the autoclave was charged with a given amount of the wood oil (20-25 g) and alcohol (20-50 g) with changed molar ratios at 500, 525, 550 and 575 K. The yield of the biodiesel produced under optimal condition is 96-98%.     

Rubber seed oil as a potential source for biodiesel production in Bangladesh

In the present paper, rubber seed oil (RSO) has been investigated as a potential source for biodiesel production in Bangladesh. Rubber seed oil has been extracted from the rubber seeds collected from the local garden. Different methods have been applied for the oil extraction, such as mechanical press with and without solvent and cold percolation. Maximum oil content of 49% has been found by mechanical press with periodic addition of solvent. The physico-chemical properties of the oil have been investigated. Effect of seed storage time on free fatty acid (FFA) content of the oil is studied an it is found that the FFA content increases from 2 wt.% (fresh seed) to 45 wt.% after 2 months of storage at room temperature. Biodiesel has been prepared using a three-step method comprises with saponification of oil, acidification of the soap and esterification of FFA. Overall yield of FFA from RSO is found to be around 86%. The final step is esterification that produces fatty acid methyl ester (FAME). The effect of methanol to oil ratio and catalyst content has been investigated for esterification reaction. ¹H NMR spectrum of the RSO and biodiesel samples are analyzed which confirms the conversion of RSO to biodiesel. The biodiesel properties have been investigated and are found to be comparable with diesel.     

Heterogeneous catalyzed biodiesel production from Moringa oleifera oil

In this study, biodiesel was produced from Moringa oleifera oil using sulfated tin oxide enhanced with SiO₂ (SO₄²⁻/SnO₂-SiO₂) as super acid solid catalyst. The experimental design was done using design of experiment (DoE), specifically, response surface methodology based on three-variable central composite design (CCD) with alpha (α) = 2. The reaction parameters studied were reaction temperature (60 °C to 180 °C), reaction period (1 h to 3 h) and methanol to oil ratio (1:6 to 1:24). It was observed that the yield up to 84 wt.% of Moringa oleifera methyl esters can be obtained with reaction conditions of 150 °C temperature, 150 min reaction time and 1:19.5 methanol to oil ratio, while catalyst concentration and agitation speed are kept at 3 wt.% and 350-360 rpm respectively. Therefore this study presents the possibility of converting a relatively new oil feedstock, Moringa oleifera oil to biodiesel and thus reducing the world's dependency on existing edible oil as biodiesel feedstock.     

Solvent assisted decomposition of the tetrahedral intermediate of the transesterification reaction to biodiesel production. A density functional study

B3LYP/6-31 + G(d) calculations were employed to investigate the mechanism of the transesterification reaction between a model monoglyceride and the methoxide and ethoxide anions. The gas-phase results reveal that both reactions have essentially the same activation energy (5.9 kcal mol⁻¹) for decomposition of the key tetrahedral intermediate. Solvent effects were included by means of both microsolvation and the polarizable continuum solvation model CPCM. Both solvent approaches reduce the activation energy, however, only the microsolvation model is able to introduce some differentiation between methanol and ethanol, yielding a lower activation energy for decomposition of the tetrahedral intermediate in the reaction with methanol (1.1 kcal mol⁻¹) than for the corresponding reaction with ethanol (2.8 kcal mol⁻¹), in line with experimental evidences. Analysis of the individual energy components within the CPCM approach reveals that electrostatic interactions are the main contribution to stabilization of the transition state.     

Kinetics of hydrolysis and methyl esterification for biodiesel production in two-step supercritical methanol process

For high-quality biodiesel fuel production from oils/fats, the catalyst-free two-step supercritical methanol process has been developed in a previous work, which consists of hydrolysis of triglycerides to fatty acids in subcritical water and subsequent methyl esterification of fatty acids to their methyl esters in supercritical methanol. In this paper, therefore, kinetics in hydrolysis and subsequent methyl esterification was studied to elucidate reaction mechanism. As a result, fatty acid was found to act as acid catalyst, and simple mathematical models were proposed in which regression curves can fit well with experimental results. Fatty acid was, thus, concluded to play an important role in the two-step supercritical methanol process.