Polyol‐Derived Alkoxide/Hydroxide Base Catalysts I. Production

Abstract

AbstractA metal methoxide is more expensive than a metal hydroxide and dissolves in methanol releasing a methoxide ion without producing water. The methoxide ion has a higher reaction rate making it more preferred for industrial biodiesel production. This study describes the preparation of alkoxide catalysts from metal hydroxides and non‐volatile, non‐toxic polyols. Heating aqueous solutions of metal hydroxides and different polyols (1,2‐propanediol, 1,3‐propanediol, glycerol, xylitol and sorbitol) under vacuum yielded polyol‐derived alkoxide base catalysts (PDABC). Comparison of the drying process for respective sodium hydroxide‐polyol combinations at two mole ratios of sodium hydroxide to polyol showed that drying at 2:1 mole ratio (metal hydroxide to polyol) was more efficient than that of 3:1. Dehydration of alkaline solutions containing three or more hydroxyl groups (glycerol, sorbitol and xylitol) was faster than drying similar solutions of diols. The empirical formula determined confirmed that the resulting powders contained mono‐sodium substituted alkoxides at 1:1, 2:1 and 3:1 (sodium hydroxide: polyol) mole ratio. Fatty acid methyl esters were prepared from canola oil and methanol using glycerol sodium alkylate as a catalyst. The conversion yield of oil to methyl ester was greater than 99 %.