Biodiesel reaction temperature

The transesterification reactions were conducted in a sealed 250 ml autoclave equipped with a stirrer. The molar ratio of methanol to oil was 12 1, reaction temperature was 200 C-230°C, and the ratio of catalyst to oil was about 2 wt%. Samples were taken out from the reaction mixture and biodiesel portions were separated by centrifuge. 

Fatty acid methyl esters (FAMEs) show large potential applications as diesel substitutes, also known as biodiesel fuel. Biodiesel fuel as renewable energy is an alternative that can reduce energy dependence on petroleum as well as air pollution. Several processes for the production of biodiesel fuel have been developed. Transesterification processes under alkali catalysis with short-chain alcohols give high yields of methyl esters in short reaction times. We investigated transesterification of rapeseed oil to produce the FAMEs. Experimental reaction conditions were molar ratio of oil to alcohol, concentration of catalyst, type of catalyst, reaction time, and temperature. The conversion ratio of rapeseed oil was enhanced by the alcohohoil mixing ratio and the reaction temperature. 

Generally, alkali-catalyzed transesterification is performed near the boiling point of the alcohol, but several researchers have reported high conversion yield at room temperature (8,14). Low reaction temperature was desirable, since reaction temperature was closely related to the energy cost of the biodiesel production process. 

Reaction temperature and time were significant operating parameters, which are closely related to the energy costs, of the biodiesel production process. Figure 7 shows the effect of reaction time on the transesterification of rapeseed oil at a catalyst concentration of 1%, molar ratio of 1 6, and 60°C. Within 5 min, the reaction was rapid. Rapeseed oil was converted to above 85% within 5 min and reached equilibrium state after about 10 min. Several researchers reported that the conversion of vegetable oils to FAME was achieved above 80% within 5 min with a sufficient molar ratio (8,11). For a reaction time of 60 min, linoleic acid methyl ester was produced at a low conversion rate, whereas oleic and linolenic methyl ester were rapidly produced. 

FAME production of rapeseed oil by alkali-catalyzed transesterification reaction was investigated. To obtain optimum conversion yield, anhydrous methanol and rapeseed oil with a free fatty acid content of <0.5% were used. The optimum conditions for alkali-catalyzed transesterification using KOH were determined as follows an oil to methanol molar ratio of 1 8 to 1 10 KOH, 1.0% (w/w) on the basis of oil weight, as catalyst a reaction temperature of 60°C and reaction time of 30 min. At these conditions, the FAME conversion yield was approx above 98%. From the refined FAME product (biodiesel), the FAME purity was obtained above 99% through posttreatment such as washing and centrifugation. 

From the results presented in Table 2 one can see that the greatest conversion was obtained at the upper limit of all process variables. Table 4 reveals that, as in the case of Lipozyme IM, the addition of water led to inhibition of the reaction. The enzyme concentration, the temperature, the oil ethanol molar ratio, and the interactions temperature-oil ethanol molar ratio and temperature-water addition had a positive effect on the production of biodiesel. Concerning temperature, the result obtained confirms the fact that the optimum temperature for this enzyme is about 70°C. As expected, the enzyme concentration, in the experimental range investigated, had a positive effect on the reaction conversion. Note also that for this system no alcohol inhibition was verified. The optimization for this system led to the following process variables values T = 65°C, [E] = 20 wt/wt%, [ W] = 0 wt/wt%, and R = 1 10, with a predicted maximum conversion of 82% in 6 h. The execution of the experiment resulted in an experimental value at these conditions of 81.4%, which agrees very well with the value predicted from the experimental model. 

Figure 9 shows a schematic process of biodiesel production by the two-step supercritical methanol method. Several advantages have been attributed to the two-step reaction method. At temperature of 270°C, a common type of 316 stainless steel can fulfill the requirements of good corrosion resistance and cover the reaction condition (5). Energy requirements may be less because mild reaction conditions for hydrolysis and methyl esterification are employed, whereas high-temperature treatment causes operational and equipment problems with, in some cases, the formation of undesirable degradation products. In addition, a reaction temperature of 270°C is commonly used in industries, so such a reaction condition is applicable for commercial applications. 

The effect of varying reaction temperature and substrate molar ratio at constant reaction time (12h), enzyme amount (30%), and added water content (10%) is shown in Figure 9.1. In general, an increase in substrate molar ratio led to lower yields at any temperature. It was concluded that a great deal of methanol inactivated Novozym 435 to synthesize the biodiesel. Similar results, that an excess of methanol decreased the enzymatic biodiesel catalyzed by Lipozyme IM77, was reported by our previous study (Shieh et al., 2003). 

Figure 9.1. Response surface plot showing the effect of substrate molar ratio, reaction temperature, and their mutual interaction on biodiesel synthesis. Other synthesis parameters (reaction time, enzyme concentration, and added water amount) are constant at 0 levels.

Abstract Biodiesel is a fatly acid alkyl ester that can be derived fiom any v etable oil or animal fat via the process of transesterification. It is a renewable, biodegradable, and nontoxic fuel. In this paper, we have evaluated the efficacy of a transesterification process for rapeseed oil with methanol in the presence of an enzyme and tert-butanol, which is added to ameliorate the negative effects associated with excess methanol. The application of Novozym 435 was determined to catalyze the tiansesterification process, and a conversion of 76.1% was achieved under selected conditions (reaction temperature 40 °C, methanol/oil molar ratio 3 1, 5% (w/w) Novozym 435 based on the oil weight, water content 1% (w/w), and reaction time of 24h). It has also been determined that rapeseed oil can be converted to fatty acid methyl ester using this system, and the results of this study contribute to the body of basic data relevant to the development of continuous enzymatic processes. 

In the enzymatic process utilized for the production of fatty acid methyl ester (biodiesel) from rapeseed oil, several factors can influence both the yield and rate. These factors include the reaction solvent, reaction temperature, reaction time, methanol/oil molar ratio, enzyme amount, and water content [7, 9, 12-14]. The initial step of this study involved the identification of factors likely to influence the conversion. 

In the process of biodiesel production, reaction temperature, methanol quantity, and reaction time were found to be significant operating parameters, which are closely associated with energy costs from an economic perspective [3]. Figure 6 shows the effects of reaction time on enzyme-catalyzed rapeseed oil methanolysis at the following conditions 5% (w/w) Novozym, 3 1 methanol/oil molar ratio, and 40 °C. Within lOh, the reaction proceeded very fast and in a linear fashion. Rapeseed oil was converted at a rate greater than 67.7% within 12h and achieved an equilibrium state after approximately 24h. 

In this study, we have attempted to evaluate the efficacy of a technique for the production of the methyl ester of rapeseed oil via enzyme-catalyzed transesterifications using tert-butanol, a moderately polar organic solvent. We conducted experiments involving the alteration of several reaction conditions, including reaction temperature, methanol/oil molar ratio, enzyme amount, water content, and reaction time. The selected conditions for biodiesel production were as follows reaction temperature 40 °C, Novozym 435 5% (w/w), methanol/oil molar ratio 3 1, water content 1% (w/w), and 24h of reaction time. Under these reaction conditions, a conversion of approximately 76.1% was achieved. Further studies are currently underway to determine a method by which the cost of fatty acid methyl ester production might be lowered, via the development of enzyme-catalyzed methanolysis protocols involving a continuous bioprocess. 

Schwarz et al. [85] studied the efficiency of different microstructured mixers followed by microchannels and their influence on the space time for obtaining high product yields. With increasing mass transfer performance of the micromixer and decreasing channel diameter of the microchannel reactors, shorter reaction times of several minutes at lower reaction temperatures compared to conventional batch reactor were obtained. Similar observations are reported for the synthesis of biodiesel in capillary microreactors [86] and in zigzag microchannels [87]. 

Although the importance of the methanol-to-oil ratio was briefly mentioned. The yield of biodiesel is affected by other parameters, including reaction temperature, catalyst concentration, feed flow rate, transmembrane pressure (TMP), and membrane thickness and pore size (Hoong Shuit et al., 2012). Some of these factors are briefly discussed. 

In general, it can be said that if the reaction temperature increases, the conversion of the reactant to the biodiesel increases without considering the type of the membrane and with no methanol evaporation. This is because of endothermic transesterification and Chaterlier s principle (Dube et al., 2007 Samart, Sreetongkittikul, Sookman, 2009). Thus, the total reaction time will be decreased (Cheng, Yen, Su, Chen,... 

Taher et al. (2011,2014b) studied the effect of reaction temperature (35 C-60 C), methanol-to-lipids molar ratios (3 1-15 1), and enzyme loading (10%-50%) on biodiesel production yields from animal fats and microalgae lipids. Process conditions were optimized via response surface methodology. Transesterilication yield of only 40% was obtained when animal fats were used, at 50°C, 200 bar, a 4 1 molar ratio, and a 30% loading of the enzyme (Taher et al., 2011), whereas a conversion above... 

Mendes (2011) produced biodiesel from com oil with using ethanol as an alcohol reactant and NaOH as a catalyst. He pointed out that 0.4% NaOH in weight, 40°C reaction temperature and 90 minutes transesterification time is enough to obtain a higher biodiesel yield. One step alkali transesterification is sufficient to obtain higher biodiesel yield when com oil contains lower amount of free fatty acid (Patil Deng 2009). 

Alkali earth oxides such as CaO, BaO, MgO and K CO supported on alumina catalysts were used for the transesterification of canola oil with methanol. Among the oxides, BaO was found to be effective yielding 85% of biodiesel but due to poisonous nature, it was not considered for further studies. It was found that K COj/Al Oj was the best catalyst in terms of both ester yields and being environmentally friendly in nature. Based on response surface methodology, it was found that 1 11.5 ratio of oil to methanol with 3.16% catalyst at a reaction temperature of 60° C were found to be optimum conditions for obtaining 96.3% biodiesel in 2 h. [57]. 

In another study, shrimp shell eatalyst was developed by incomplete carbonization and loading of KF (30%) and subsequent activation of the material. The reaction conditions of oil to methanol ration of 1 9, with catalyst amount of 2.5% and reaction temperature of 65° C for 3 h gave 89% conversion for the transesterification of rapeseed oil with methanol. The study showed that the catalyst had a porous framework structure and has environmentally friendly properties and can be used as a heterogeneous base eatalyst for biodiesel production [94]. 

In our first experiment we decided to test the conversion of sunflower oil into biodiesel (16). Treatment of sunflower oil (1) with NaOMe in MeOH results in formation of a mixtme of fatty acid methyl esters (FAME), also known as biodiesel, and glycerol (2) (Figme 4.3). The reaction was performed with a six-fold molar excess of methanol with respect to sunflower oil at elevated temperatures (60°C) using a basic catalyst (NaOMe, 1% w/w with respect to sunflower oil). The CCS was equipped with a heating jacket to ensure isothermal conditions. The sunflower oil was preheated to 60°C and was pumped at 12.6 ml/min into one entrance of the CCS. Subsequently, a solution of NaOMe in MeOH was introduced through the other entrance at a flow rate of 3.1 ml per minute. After about 40 minutes, the system reaches steady state and the FAME containing some residual sunflower oil is coming... 

Very poor biodiesel and biodiesel blends do not shed water as effectively as conventional diesel fuel fuel haze, gelling, and low-temperature handling problems can develop if biodiesel is contaminated with water in storage and transport. Poor double bonds present in the methyl ester compounds are active sites for oxidation and condensation reactions peroxide values can increase fuel darkening and deposit formation in storage systems can occur the addition of oxidation inhibitors to biodiesel helps improve storage stability. 

Esterification. The esterification reaction (Figure 3) involves the reaction of a FFA with an alcohol (usually a low molecular weight alcohol, such as MeOH, EtOH, PrOH, and ButOH) to produce an alkyl ester (biodiesel) and water. Either base or acid catalysts can be used for the reaction. However, base catalysts can only be used at high temperatures (or catalyst deactivation takes place by soap formation). More commonly, acid catalysts such as sulfuric acid are employed to carry out the esterification reaction under mild conditions. 

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