Biodiesel synthesis

Biodiesel can be produced by a sustainable continuous process based on catalytic reactive distillation. The integrated design ensures the removal of water byproduct that shifts the chemical equilibrium to completion and preserves the catalyst activity. The novel alternative proposed here replaces the liquid catalysts with solid acids, thus dramatically improving the economics of current biodiesel synthesis and reducing the number of downstream steps. The key benefits of this approach are ... 

In biodiesel preparation, vegetable oils and animal fats are typically employed as biomass feedstocks, but waste greases such as yellow grease and brown grease can also be used. Thus, biodiesel synthesis provides a means for... 

Table 8 Typical reaction conditions for biodiesel synthesis using homogeneous base catalysis ...

Existing Problems with Homogeneous Catalysts. - The use of homogeneous catalysts involved in biodiesel synthesis currently presents separation and catalyst recovery issues. For instance, process methodologies using homogeneous... 

The reader should also be aware that some information provided in this section and in the sections below does not directly address the subject of biodiesel synthesis. Some discussions, for instance, are about the transesterification of simple esters or the production of monoglycerides by transesterification of vegetable oils nevertheless, the information provided is relevant to the topic of biodiesel synthesis since knowledge of catalyst reactivity in these systems is directly applicable to reactions involving TGs and FFAs. 

An important issue concerning the use of heterogeneous catalysts for biodiesel synthesis is the lack of systematic research exploring the principles of solid catalyst activity for transesterification of TGs and esterification of FFAs with alcohols. For instance, the question about the true catalytic nature of some solid bases, called heterogeneous, remains unanswered. For example, the most active heterogeneous catalysts reported to date is Ba(OH)2. However, due to its... 

Current biodiesel technologies are in many aspects simple, operator friendly and, within their boundaries, efficient. Homogeneous base catalysts, such as NaOH and MeONa (most commonly used in biodiesel synthesis), are fast and produce high biodiesel yields in relatively short reaction times. However, only... 

Bucholtz, E. (2007) Biodiesel synthesis and evaluation An organic chemistry experiment. /. Chem. Educ. 84,296-298. 

A five-level-five-factor CCRD was employed in this study, requiring 32 experiments (Cochran and Cox, 1992). The fractional factorial design consisted of 16 factorial points, 10 axial points (two axial points on the axis of each design variable at a distance of 2 from the design center), and 6 center points. The variables and their levels selected for the study of biodiesel synthesis were reaction time (4-20 h) temperature (25-65 °C) enzyme amount (10%-50% weight of canola oil, 0.1-0.5g) substrate molar ratio (2 1—5 1 methanol canola oil) and amount of added water (0-20%, by weight of canola oil). Table 9.5 shows the independent factors (X,), levels and experimental design coded and uncoded. Thirty-two runs were performed in a totally random order. 

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.

Most biodiesel synthesis processes produce a fuel that has a slight contamination with acylglycerols, and this fact is recognized in most current biodiesel standards (Table 1). In spite of their low concentrations, these acylglycerols may contribute disproportionately to fuel lubricity. 

The powdered sample was soaked in n-hexane for three days and the oil-hexane miscella was then filtered by suction through a Buchner funnel. Most of the -hexane in the mixture was removed using a rotary evaporator with the temperature of the bath set at 40 °C, and the resulting oil sample was left in a fume hood for 72 hours to allow the remaining solvent to evaporate. The oil was then treated with anhydrous Na2S04 to remove all moisture. The resulting dry oil was used for biodiesel synthesis by reaction of the oil with anhydrous methanol in presence of NaOH catalyst. 

Cantrell, D.G. L.J. Gillie A.F. Lee K. Wilson. Structure-reactivity correlations in mgal hydrotal-cite catalysts for biodiesel synthesis. Appl Catal. A 2005, 287, 183—190. 

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