Biodiesel reaction kinetics

Index Entries Alcoholysis vegetable oils lipases reaction kinetics biodiesel. 

The kinetic model based on the mechanism of transesterification for biodiesel reaction shown in Figure 3.8 presented below. 

Reports have shown solid catalysts for esterification of FFA have one or more problems such as high cost, severe reaction conditions, slow kinetics, low or incomplete conversions, and limited lifetime. We will present research describing our newly developed polymeric catalyst technology which enables the production of biodiesel from feedstock containing high levels (> 1 wt %) of FFAs. The novel catalyst, named AmberlysH BD20, overcomes the traditional drawbacks such as limited catalyst life time, slow reaction rates, and low conversions. 

Compared to the base-catalyzed synthesis of biodiesel, fewer studies have dealt with the subject of acid-catalyzed transesterification of lipid feedstocks. Among acid catalysts, sulfuric acid has been the most widely studied. In the previously mentioned work of Freedman et al., the authors examined the transesterification kinetics of soybean oil with butanol using sulfuric acid. The three reaction regimes observed (in accordance with reaction rate) for base-catalyzed reactions were also observed here. A large molar ratio of alcohol-to-oil, 30 1, was required in this system in order to carry out the reaction in a reasonable time. As expected, transesterification followed pseudo-first-order kinetics for the forward reactions (Figure 2), while reverse reactions showed second-order kinetics. 

As a simulation example we treat the production of biodiesel from rapeseed in a plant capacity of 200 ktonne per year. The feedstock has a high content of oleic acid triglyceride, around 65%, such that the kinetic data from Section 14.6 can be used for sketching the design of the reaction section. For simplification, we consider that the oil was pretreated for removing impurities and gums, as well as FFA by esterification over solid catalyst. The free fatty acids and water content in oil feed should be less than 0.5%w. NaOH and KOH in 0.5 to 1.5% w/w are used as catalysts. 

Many advances have been made in development of P-DSC and other thermal analysis techniques in the study of oxidation reactions in fatty derivatives such as biodiesel. Kinetic parameters and phase transitions associated with oxidative degradation may be rapidly and accurately determined. However, the applicability of P-DSC may be limited in analysis of fuel formu-... 

You performed a test reaction in your kitchen to study the kinetics of this process. You were able to monitor the concentration of the oil and found that the concentration dropped from 0.500 M to 0.250 M in 20.0 minutes. It took an additional 40.0 minutes for the concentration of the oil to further drop to 0.125 M. How long will it take for you to convert 97.0% of the oil to biodiesel ... 

Ping-pong mechanisms are more complex and require of certain assumptions to arrive to compact kinetic expressions amenable for evaluation by conventional experimental methods. There are several reactions of technological relevance that correspond to this type of mechanism, like the production of biodiesel with lipases (see section 6.3) and the synthesis of pharmaceuticals and fine-chemicals with oxidore-ductases (see section 6.4). 

Zubir, M. I. S. Y. Chin (2010) Kinetics of Modified Zirconia-catalyzed Heterogeneous Esterification Reaction for Biodiesel Production. Journal of Applied Sciences, 10, 2584-2589,ISSN 1812-5654. 

The two common modes of reactor operations are batch and continuous modes. Batch reactors are commonly nsed for kinetics studies, which are important for process optimization and scale-np. System design in this mode is simple, controllable, and cheap. Typically, reaction snbstrates are first added to the reactor, followed by the immobilized lipase. CO2 is then introduced to the reactor and pressurized to the desired level. Figure 6.3 shows a schematic diagram of a setup used for enzymatic transesteriflcation of lamb fats and microalgae lipids to biodiesel using Novozym 435 under SC-CO2 (Taher, 2009, 2014). 

Harper, M.R., Van Geem, K.M., Pyl, S.P., Marin, G.B., Green, W.H. Comprehensive reaction mechanism for -butanol p5rrolysis and combustion. Combust. Flame 158,16-41 (2011) Herbinet, O., Pitz, W.J., Westbrook, C.K. Detailed chemical kinetic oxidation mechanism for a biodiesel surrogate. Combust. Flame 154, 507—528 (2008)... 

Rapeseed-based biodiesel production has been widely studied in terms of optimization and kinetics of alkali catalyzed transesterihcation reaction (Luque et al., 2011). Recaitly, production of solid base catalysts, such as Ca/Zr mixed oxide catalysts (Liu et al., 2015), CaO-based catalysts or4-sulfophenyl activated carbon-based solid acid catalyst, has been reported with a performance similar to commacial heterogeneous catalyst Amberly st-15 (Malins et al., 2015). Present researches are also focusing on the use of supercritical ethanol and methanol as reagents to avoid drawbacks due to the use of homogeneous catalysts (Farobie and Matsumura, 2015a,b). Technoeconomic and performance studies on the use of supercritical methanol concluded that lower direct costs and environmental impacts are achieved at highest biodiesel yields, where oil consumption per unit of biodiesel... 

Westbrook CK, Naik CV, Herbinet O, et al. Detailed chemical kinetic reaction mechanisms for soy and rapeseed biodiesel fuels. Combust Flame. April 2011 158 742-755. 

Naik CV, Westbrook CK, Herbinet O, Pitz Mehl M. Detailed chemical kinetic reaction mechanism for biodiesel components methyl stearate and methyl oleate. Proc Combust Inst. 2011 33 383-389. 

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