oalib
Search Results: 1 - 10 of 100 matches for " "
All listed articles are free for downloading (OA Articles)
Page 1 /100
Display every page Item
Kinetics of Modified Zirconia-catalyzed Heterogeneous Esterification Reaction for Biodiesel Production  [PDF]
M.I. Zubir,S.Y. Chin
Journal of Applied Sciences , 2010,
Abstract: Biodiesel is one of the new possible substitutes of regular fuel for engines and is produced from different vegetable oils or animal fats. The main reaction involved is the transesterification of triglycerides into esters. The employment of low quality or waste raw materials has been considered to strongly improve the economic competitiveness of this biofuel with respect to the petroleum-derived diesel. In the case of waste raw materials characterized by a high content of Free Fatty Acids (FFAs), direct esterification of the FFAs is the primary route for producing biodiesel. The novel sustainable esterification process based on catalytic Reactive Distillation Column (RDC) has been proposed to overcome the shortcomings in the conventional process. A reliable kinetic model which would be applicable in a wide range of operating conditions is an important data for the RDC design. In the present study, kinetics of heterogeneous catalyzed direct fatty acid esterification was studied with a tungstated zirconia catalyst in a stirred batch reactor to synthesis biodiesel. The waste cooking oil with high content of FFAs was simulated by mixing pure oleic acid with refined palm oil. Ethanol was used in the experiments instead of methanol because it is less toxic and safer to handle. The effects of the main variables involved in the process such as reaction temperature, amount of catalyst, amount of triglyceride and the molar ratio of alcohol/free fatty acid were analyzed. The experimental data were interpreted with a second order, pseudo homogeneous kinetic model and a good agreement between experimental data and the model is obtained.
Biodiesel production via esterification reactions catalyzed by lipase
Vieira,A. P. de A.; da Silva,M. A. P.; Langone,M. A. P.;
Latin American applied research , 2006,
Abstract: the synthesis of ethyl hexadecanoate was carried out by esterification of palmitic acid with ethanol in a solvent-free system. a commercial immobilized lipase (lipozyme rm-im) was mixed with the reagents, in a 15 ml closed batch reactor with constant stirring and coupled with a condenser. the effects of palmitic acid/ethanol molar ratio (0.16 to 1.84), reaction temperature (65 to 75oc) and enzyme concentration (0.48 to 5.52% w/w) on the initial reaction rate of ethyl hexadecanoate were determined using central composite design 23 with six central points. statistical analysis indicated that the enzyme concentration and palmitic acid/ethanol molar ratio had been found to be the most significant variables affecting the initial reaction rate. the best result was obtained under the following experimental conditions: palmitic acid/ethanol molar ratio of 0.50, temperature of 67oc, and enzyme concentration of 4.50% (w/w).
Biodiesel production via esterification reactions catalyzed by lipase
A. P. de A. Vieira,M. A. P. da Silva,M. A. P. Langone
Latin American applied research , 2006,
Abstract: The synthesis of ethyl hexadecanoate was carried out by esterification of palmitic acid with ethanol in a solvent-free system. A commercial immobilized lipase (Lipozyme RM-IM) was mixed with the reagents, in a 15 mL closed batch reactor with constant stirring and coupled with a condenser. The effects of palmitic acid/ethanol molar ratio (0.16 to 1.84), reaction temperature (65 to 75oC) and enzyme concentration (0.48 to 5.52% w/w) on the initial reaction rate of ethyl hexadecanoate were determined using central composite design 23 with six central points. Statistical analysis indicated that the enzyme concentration and palmitic acid/ethanol molar ratio had been found to be the most significant variables affecting the initial reaction rate. The best result was obtained under the following experimental conditions: palmitic acid/ethanol molar ratio of 0.50, temperature of 67oC, and enzyme concentration of 4.50% (w/w).
Continuous Catalyst-Free Esterification of Oleic Acid in Compressed Ethanol  [PDF]
Ana Carolina de Araujo Abdala,Vitor Augusto dos Santos Garcia,Caroline Portilho Trentini,Lúcio Cardozo Filho,Edson Antonio da Silva,Camila da Silva
International Journal of Chemical Engineering , 2014, DOI: 10.1155/2014/803783
Abstract: The esterification of oleic acid in a continuous catalyst-free process using compressed ethanol was investigated in the present study. Experiments were performed in a tubular reactor and variables investigated were temperature, pressure, and oleic acid to ethanol molar ratio for different residence time. Results demonstrated that temperature, in the range of 473?K to 573?K, and pressure had a positive effect on fatty acid ethyl esters (FAEE) production. In the experimental range investigated, high conversions can be obtained at low ethanol concentrations in the reaction medium and it was observed that oleic acid to ethanol molar ratios greater than 1?:?6 show no significant increase in conversion. Nonnegligible reaction conversions (>90%) were achieved at 573?K, 20?MPa, oleic acid to ethanol molar ratio of 1?:?6, and 20 minutes of residence time. 1. Introduction Fatty acid, methyl or ethyl, esters can be usually obtained from free fatty acid (FFA) esterification reaction, through vegetable oils hydrolysis followed by the fatty acid esterification or from direct vegetable oils transesterification [1]. The importance of examining the esterification reaction in a more detailed manner is justified by the huge amount and variety of vegetable oils worldwide available for biodiesel production which may have a high percentage of FFA making the conventional alkali-catalyzed transesterification impracticable, since for this process the percentage of FFA needs to be less than 0.5% [2]. Recent studies propose to obtain esters in two reaction steps of substrates with high acidity, consisting of two approaches: (a) esterification of FFA and subsequent transesterification of triglycerides [3–5] or (b) hydrolysis of triglycerides, followed by esterification of fatty acids obtained [6–8]. In these approaches are commonly used chemical catalysts (homogeneous or heterogeneous) or enzymatic catalysts. More recently, the noncatalytic process where is proposed the hydrolysis occurs primarily in subcritical water and subsequent esterification using a solvent in sub- or supercritical [9, 10]. According to the current literature, catalyst-free reactions at high temperature and pressure conditions provide improved phase solubility and decreased mass-transfer limitations; the reaction rate increases significantly in the supercritical state and, thus, the reaction is complete in shorter periods and simpler separation and purification steps [11, 12]. Some studies available in the literature reported the biodiesel production from free fatty acids (FFA) by noncatalytic method at sub-
Determination of Free Fatty Acid by FT-NIR Spectroscopy in Esterification Reaction for Biodiesel Production  [PDF]
Djéssica Tatiana Raspe,Camila da Silva
Journal of Energy , 2013, DOI: 10.1155/2013/301647
Abstract: This work reports the use of FT-NIR spectroscopy coupled with multivariate calibration to determine the percentage of free fatty acids (FFA) in samples obtained by the esterification of FFA in vegetable oils. The analytical method used as calibration matrix samples of the reaction medium of esterification of oleic acid in soybean oil in proportions of 0.3 to 40 wt% (by weight) of oleic acid obtained under different experimental conditions and utilized the partial least squares (PLS) regression. The efficiency of the method was tested to predict the content of FFA in reactions of esterification of oleic acid in soybean oil catalysed by KSF clay and Amberlyst 15 commercial resin, both in a batch mode. Good Correlations were observed between the FT-NIR/PLS method and the reference method (AOCS). The results confirm that FT-NIR spectroscopy, in combination with multivariate calibration, is a promising technique for monitoring esterification reaction for biodiesel production. 1. Introduction The merits of biodiesel (fatty acid ethyl or methyl esters) obtained from vegetable oils or animal fats as an alternative to mineral diesel comprise a nontoxic, biodegradable, and a domestically produced and renewable source which is well documented in the literature [1, 2]. Because of the well-known environmental and economical benefits, biodiesel fuel may be expected to be a good alternative to petroleum-based fuel [3]. The biodiesel production is generally accomplished in homogeneous [4–6] and heterogeneous [7–9] reaction systems at low pressures. Recently, the noncatalytic reaction, using alcohol under supercritical conditions at high temperatures and pressures, has also been investigated as an alternative method for fatty acid esters production [10–12]. Fatty acid, methyl or ethyl, esters can be usually obtained from free fatty acid (FFA) esterification reaction, through vegetable oils hydrolysis followed by the fatty acid esterification or from direct vegetable oils transesterification [13]. The importance of examining the esterification reaction in a more detailed manner is justified by the huge amount and variety of vegetable oils worldwide available for biodiesel production [14–16], which may have a high percentage of FFA making the conventional alkali-catalyzed transesterification impracticable, since for this process, the percentage of FFA is to be less than 0.5% [1, 17, 18]. Recent studies propose to obtain esters in two reaction steps of substrates with high acidity, consisting of two approaches: (1) esterification of FFA and subsequent transesterification
H3PW12O40 (HPA), an efficient and reusable catalyst for biodiesel production related reactions: esterification of oleic acid and etherification of glycerol
Sepúlveda, Jorge H.;Vera, Carlos R.;Yori, Juan C.;Badano, Juan M.;Santarosa, Daniel;Mandelli, Dalmo;
Química Nova , 2011, DOI: 10.1590/S0100-40422011000400009
Abstract: in esterification of oleic acid with methanol at 25 °c hpa displayed the highest activity. moreover the hpa could be reused after being transformed into its cesium salt. in the reaction of etherification of glycerol hpa and amberlyst 35w showed similar initial activity levels. the results of acid properties demonstrate that hpa is a strong protonic acid and that both surface and bulk protons contribute to the acidity. because of its strong affinity for polar compounds, hpa is also seemingly dissolved in both oleic acid and methanol. the reaction in this case proceeds with the catalyst in the homogenous phase.
Production of Biodiesel from Oleic Acid and Methanol by Reactive Distillation  [cached]
Kusmiyati Kusmiyati,Agung Sugiharto
Bulletin of Chemical Reaction Engineering & Catalysis , 2010, DOI: 10.9767/bcrec.5.1.37.1-6
Abstract: Biodiesel is an alternative diesel fuel that is produced from vegetable oils and animal fats. Generally, it is formed by transesterification reaction of triglycerides in the vegetable oil or animal fat with an alcohol. In this work, esterification reaction was carried out using oleic acid, methanol and sulphuric acid as a catalyst by reactive distillation method. In order to determine the best conditions for biodiesel production by reactive distillation, the experiments were carried out at different temperature (100 oC, 120 oC, 150 oC and 180 oC) using methanol/oleic acid molar ratios (1:1, 5:1, 6:1, 7:1, 8:1), catalyst/ oleic acid molar ratios (0.5%wt, 1%wt, 1.5%wt and 2%wt) and reaction times (15, 30, 45, 60, 75 and 90 minutes). Results at temperature 180 oC, methanol/ oleic acid molar ratio of 8:1, amount of catalyst 1% for 90 minute reaction time gives the highest conversion of oleic acid above 0.9571. Biodiesel product from oleic acid was analysed by ASTM (American Standard for Testing Material). The results show that the biodiesel produced has the quality required to be a diesel substitute. 2010 BCREC UNDIP. All rights reserved (Received: 1st January 2010, Revised: 18th March 2010; Accepted: 18th March 2010) [How to Cite: K. Kusmiyati, A. Sugiharto. (2010). Production of Biodiesel from Oleic Acid and Methanol by Reactive Distillation. Bulletin of Chemical Reaction Engineering and Catalysis, 5(1): 1-6. doi:10.9767/bcrec.5.1.37.1-6] [How to Link/DOI: http://dx.doi.org/10.9767/bcrec.5.1.37.1-6 ]
Synthesis of High-Stability Acidic β/Al-MCM-41 and the Catalytic Performance for the Esterification of Oleic Acid  [PDF]
Zhiping Wang, Shitao Yu
Advances in Chemical Engineering and Science (ACES) , 2016, DOI: 10.4236/aces.2016.64031
Abstract: β/Al-MCM-41 molecular sieve was synthesized and used to catalyze the esterification of oleic acid with short chain alcohols such as methanol, ethanol, isopropanol and isobutanol to obtain biodiesel. The results indicated that β/Al-MCM-41 exhibited the excellent catalytic activity and stability, which was obviously superior to traditional Al-MCM-41. The relationship between acidity and catalytic activity was in detail examined by NH3-TPD and Py-FTIR. Moreover, the kinetics of esterification of oleic acid with methanol showed that the average reaction order n was 1.97 and that activation energy was 50.01 kJ/mol.
Tin-Catalyzed Esterification and Transesterification Reactions: A Review  [PDF]
Arthur Batista Ferreira,Abiney Lemos Cardoso,Márcio José da Silva
ISRN Renewable Energy , 2012, DOI: 10.5402/2012/142857
Abstract: The recent increase in the world biofuels demand, along with the need to reduce costs while improving the environmental sustainability of the biodiesel production, have led to the search for catalysts that should be economically viable, efficient, and environmentally friendly. This paper reviews recent research and development of organic and inorganic tin catalysts; focusing on kinetic properties and catalytic activity in two key reactions for biodiesel production: free fatty acids (FFA) esterification and triglycerides (TG) transesterification. First the basic knowledge of homogeneous tin catalysts in esterification reactions of different carboxylic acids is provided. Second, main advances obtained in the study of FFA esterification reactions catalyzed by tin chloride are covered. The effect of the principal parameters of reaction on the yield and rate of alkyl esters production is described. Kinetic measurements allowed the determination of the activation energy (46.79?kJ?mol?1) and a first-order dependence in relation to both FFA and tin chloride catalyst concentration. Aspects related to recycling of the tin chloride catalyst in phase homogeneous are discussed. Third the advances obtained in the development of homogeneous catalysts based on tin complexes in transesterification reactions are summarized. Finally, results obtained from the use of tin organometallics compounds in reactions of vegetable oils transesterification reactions are concisely presented. The optimization of processes catalytic homogeneous utilized in the transesterification reactions can contribute to the improvement of the technology biodiesel production. 1. Introduction The demand for renewable energy sources has made biofuels an attractive alternative that can reduce the consumption of the traditional fossil fuels [1]. Biofuels have a closed loop for the CO2, that is, the main greenhouse gas and besides that they can contribute to the reduction in the emissions of toxic gases such as SO2, SO3, and CO [2]. Among the biofuels currently explored, biodiesel deserves highlights because it can be used pure or in blends with the diesel fuel. Biodiesel is a renewable fuel, biodegradable, and less polluting than diesel, obtained from the triglycerides transesterification (Figure 1) or esterification of free fatty acids (FFA) with short chain alcohol (methyl or ethyl alcohol) (Figure 2) [3]. Figure 1: Transesterification reaction of triglycerides (TG) for biodiesel production. Figure 2: Esterification reaction of fatty acids for biodiesel production. Biodiesel has been considered as a
Esterification of By-products of Biodiesel Fuel Production with Methanol and Technical Glycerol Using Biocatalysts  [cached]
Milda Gumbyt?,Violeta Makareviciene,Egl? Send?ikien?
Environmental Research, Engineering and Management , 2011, DOI: 10.5755/j01.erem.56.2.334
Abstract: In production of biodiesel fuel several by-products, such as glycerol and free fatty acids, are formed. The options for applying biochemical methods to process these by-products have been studied. The process of free fatty acid esterification with methanol using Lipozyme RM IM is to be performed in steps, with gradual addition of methanol into the reaction media. In 4 hours of a multi-step process it is possible to esterify up to 60% of free fatty acids. Novozym 435 is not inactivated by methanol, therefore, esterification with methanol of free fatty acids can be performed in one step. Free fatty acid esterification with glycerol is slowed down by admixtures present in by-products of biodiesel fuel production. After 7 hours of reaction, only 82.2% of free fatty acids react when using Novozym 435, and only 41.7% do in a case of Lipozyme RM IM, whereas in the case of esterification of pure oleic acid with pure glycerol the amounts reach 97.7% and 84.8%, respectively. Efficiency of ferment preparation Novozym 435is almost twice higher compared to Lipozyme RM IM. However, taking into account the prices of ferment preparations, it is possible to conclude that Lipozyme RM IM has future prospects in industrial synthesis.
Page 1 /100
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.