Chemical News

Tuesday, January 29, 2008

Use of byproduct Glycerol from Biodiesel manufacturing

Here’s a way to prevent glycerol oversupply from biodiesel fuel production. Most biodiesel fuels comprise fatty acid methyl esters (FAMEs) obtained from rapeseed oil (primarily in Europe) or soybean oil (primarily in the United States). The production technology is not new or particularly complicated. It is based on the technology used for many years to produce oleochemicals:

The natural oil is treated with MeOH in the presence of base, usually NaOH or KOH, to yield the methyl esters of the fatty acids contained in the starting triglycerides, along with coproduct glycerol. A guideline in the industry is that every 100 lb of oil requires 10 lb of MeOH and produces 100 lb of biodiesel fuel and 10 lb of glycerol.

As for any coproduct process, the economics of the overall biodiesel process depend on the credit obtained for glycerol. The relatively rapid buildup of biodiesel fuels, especially in Europe, has caused havoc in the glycerol market. Prices have fallen dramatically; low glycerol prices hurt the conventional glycerol suppliers and the biodiesel producers alike.

Inventors G. Hillion, B. Delfort, and I. Durand suggest a solution to this problem. They propose treating the glycerol coproduct from biodiesel fuel production with isobutylene to make a mixture of mono-, di-, and tri-tert-butyl ethers of glycerol. When this ether mixture is combined with the methyl ester from rapeseed oil, a novel biodiesel product is obtained that is ~82 wt% FAME and ~18% glycerol tert-butyl ethers. As a result, no coproducts are produced, and all of the natural oil is consumed in the fuel application.

In one example, glycerol tert-butyl ethers were made by combining crude glycerol with isobutylene in an autoclave with Amberlyst 15 ion-exchange resin at 50–90 °C. After the unreacted isobutylene was vented and the catalyst was filtered out, a colorless liquid was obtained. The composition of the tert-butyl glycerol ether was ~26% mono-, ~59% di-, and ~14% triether. This is a particularly intriguing idea for the U.S. market because isobutylene feedstock and methyl tert-butyl ether (MTBE) production equipment are available as a result of the phase-out of MTBE

Source: CAS site