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The removal of sodium from glycerol solutions by crystallization/precipitation of hydroxyapatite (HAP) through the co-addition of lime [Ca(OH) 2 ] and phosphoric acid was evaluated as a means to remove soluble catalyst from the glycerol byproduct of biodiesel production. Phosphate ions precipitated as hydroxyapatite upon reacting with calcium and hydroxide ions. Seed crystals and pH impacted crystallization. The yield decreased due to the polymerization of glycerol at high pH values (pH g 11). The continuous removal of phosphate by a lime packed column method was also evaluated for process scale-up considerations. Higher temperatures favored the phosphate removal efficiency with higher temperatures raising the pH and the supersaturation region of the respective effluents to the desired level for HAP crystallization/precipitation. The suitability of the resulting product was evaluated as a hydrogenolysis feedstock for producing propylene glycol. The yield of propylene glycol increased with increasing filtrate pH.

Reaction kinetics for the alcoholysis of soybean oil with methanol, ethanol, and isopropanol were evaluated in the absence of catalyst. Metal reactor surfaces catalyzed these reactions, so the reactions were conducted in glass capillary tubes at 120, 150, and 180°C. The reactivity of the alcohols increased with decreasing carbon number. Higher temperatures promoted faster reactions. Higher alcohol stoichiometries did not significantly increase reaction rates; this was attributed to the limited solubility of the alcohol in the soybean oil. At less than 20% conversion, the solubility of the alcohol in the oil phase continuously increased, resulting in increased reaction rates. At approximately 20% conversion, the reaction systems became homogeneous until a glycerine phase was formed at high conversions. In addition to their fundamental value, these data provided a basis on which catalytic reactions can be investigated between 100 and 200°C.Over the past few years, use of FAME derived from vegetable oils and animal fats as liquid fuel extenders (biodiesel) has received increased attention. Biodiesel cannot replace all the petroleum-based diesel fuels, but it can provide a near-zero sulfur content biodegradable additive that improves the quality of diesel fuel and creates new markets for fats and oils.Methanol reacts with TG to form methyl esters through mechanisms that include the formation of some DG and MG. Stoichiometry, reaction time, and removal of the glycerine byproduct can be used to promote yields of >98% methyl esters.The most common reaction schemes include the use of alkali catalysts to reduce reaction times to a few hours at atmospheric pressure and methanol reflux temperatures. Acid catalysts are also effective but typically require higher temperatures and/or longer reaction times. In the absence of solvent and with one to three times the stoichiometries of methanol, high conversions result in the formation of a glycerine phase that is immiscible in biodiesel. Although biodiesel can be decanted from the glycerine, removing the catalyst from glycerine is costly and generates a salt waste/by-product.Reaction schemes based on heterogeneous catalysts or no catalyst could reduce both operating costs and waste generation. A number of kinetic studies examine the transesterification of vegetable oil with alcohols using acid or basic catalysts (1-3). Few data are available on alcoholysis rates in the absence of catalysts (4,5). Diasakou et al. (4) evaluated the alcoholysis of methanol with soybean oil. At 220°C, 67% of methyl esters were obtained in 8 h; at 235°C, 10 h was required to achieve an 85% conversion. These studies were carried out in a 4560 Bench Top series minireactor (Parr Instrument Co., Moline, IL). Saka and Kusdiana (5) evaluated the alcoholysis of rapeseed oil using supercritical methanol. After 240 s, 95% conversion was obtained; however, high temperatures of 350-500°C and high pressures of 45-65 MPa were used. The studies were carried out in a batch-type reactor vessel made of Inconel-625. Da...