Biodiesel catalyst concentration

In general, acid catalyzed reactions are performed at high alcohol-to-oil molar ratios, low-to-moderate temperatures and pressures, and high acid catalyst concentrations. Table 9 summarizes reactions conditions proposed by Zhang et al. to prepare biodiesel from waste cooking oil using sulfuric acid as the catalyst. A simplified BFD of the acid process is shown in Figure 9. 

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. 

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. 

Tremblay, A. Y., Cao, P., Dube, M. A. (2008). Biodiesel production using ultralow catalyst concentrations. Energy Fuels, 22, 2748—2755. 

Biodiesel yield High, usually around 90% High, usually >96% High yields (>90%) only for high alcohol to oil molar ratio, high catalyst concentration, and high temperature... 

The main unit is the catalytic primaiy process reactor for gross production, based on the ATR of biodiesel. After the primary step, secondary units for both the CO clean-up process and the simultaneous increase of the concentration are employed the content from the reformated gas can be increased through the water-gas shift (WGS) reaction by converting the CO with steam to CO and H. The high thermal shift (HTS) reactor is operating at 575-625 K followed by a low thermal shift (LTS) reactor operating at 475-535 K (Ruettinger et al., 2003). A preferential oxidation (PROX) step is required to completely remove the CO by oxidation to COj on a noble metal catalyst. The PROX reaction is assumed to take place in an isothermal bed reactor at 425 K after the last shift step (Rosso et al., 2004). 

Even though the base-catalyzed process seems operator friendly and economically possible, it suffers from a key limitation only refined oils and pretreated fats with low concentrations of FFAs be used to produce biodiesel using homogeneous base catalysts. FFAs can react with the base catalyst giving... 

In homogeneous catalysis, the catalyst is in the same phase as the reactants and products. Here we will concentrate on homogeneous catalysis in the liquid phase. In the classic case, the reactant (also called the substrate) molecules and the catalyst are reacted in a solvent. For example, the transesterification of fatty acid triglycerides with methanol (Figure 1.10) is catalyzed by hydroxide (OH-) ions. This is an important process for making fatty acid methyl esters which are then used as biodiesel. 

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. 

The formation of soap consumes catalyst and may cause problans downstream during the separation of the biodiesel from the glycerin phase. If the oil contains free fatty acids with concentrations above 1%, then the oil is usually first reacted with methanol and an acid catalyst to esterify the free fatty acids and form fatty acid methyl esters. The possibility that the saponification reaction may occur also necessitates that the oil be dry, thus requiring the dewatering steps described earlier in this chapter. Oil drying is another significant contributor to the energy consumption of the overall process. 

Despite research on heterogeneous catalysts having taken place for the last three decades, to date several disadvantages make them less cost competitive and not as environmentally friendly as traditionally used homogeneous catalysts. As an example, the excellence of CaO-based catalysts are numerous and well proven, but they still remain distant from the industry due to their low resistance to water and CO2, low attrition endurance, and solubility in biodiesel and alcoholic phases, which results in ion concentrations exceeding the limits imposed by the European Norm EN14214 (Micic et al., 2015). 

Soapstock acid oil, a concentrated by-product of the soybean oil rehning process based on fatty acid salts, was proposed by Soares et al. as a raw material for the production of biodiesel via acid heterogeneous catalysts using ethanol. The esterihcation reaction was conducted in a packed-bed bioreactor containing a lipase-rich fermented solid (sugarcane bagasse and sunflower seed meal fermented by Burkholderia cepacia) with a configuration that avoided inhibition of the catalyst by the presence of ethanol (Soares et al., 2015). 

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