Course: BFM 202 Biodiesel Production

Lecture

Catalysis
Credits
BFM 202 Biodiesel Production Unit 5 Lecture has been adapted from "ENGY 131 Unit 5 Commentary Catalysis" by Southeastern Illinois College.

ENGY 131 Biodiesel Production course content by Southeastern Illinois College is licensed under a Creative Commons Attribution 3.0 Unported License. Except where indicated otherwise.

Unit 5 Catalysis

A catalyst is defined as: A substance that increases the rate of a chemical reaction
without being consumed in the process. (in Wiktionary, CC BY-SA 3.0)

The Impact of the Feedstock when Choosing a Catalyst

The feedstock used in biodiesel manufacturing represents 80-90% of the
final cost of biodiesel fuel. Producers continually review feedstock,
searching for cheaper alternatives. A less expensive feedstock contains
greater amounts of impurities and higher levels of free fatty acids
which produces soap and uses additional catalyst. The soap creates an
emulsion layer between the biodiesel and glycerol during the separation
phase of production. In order to separate the emulsion, long storage
periods or expensive processing becomes necessary and adds cost. If
low-cost feedstock is to be used, then cost effective FFA removal is needed.

High-quality feedstock are most often edible oils, such as soybean oil,
rapeseed oil, and palm oil. In developing countries, these oils are not allowed
to be used as feedstock due to limited supply, food shortages, and high cost.
Therefore low-cost, non-edible oils, like Jatropha, animal fat, and
waste oils are used. These oils usually contain water and free fatty
acids (FFAs) that form soap when homogeneous base catalysts are used.

Solid heterogeneous catalysts eliminate these problems and are
noncorrosive, non-toxic, and easily-separated for recycling back into
the process. Reusability of heterogeneous catalysts makes continuous,
fixed-bed resin operations possible and is accomplished via Ion Exchange.

Washing biodiesel to remove impurities and suspended catalytic material

FFA is removed by water washing biodiesel with a diluted base during the
degumming phase. However, this creates liquid waste and lowers biodiesel
yield. By reacting suspended  FFAs with methanol, these FFAs can be converted
to methyl esters and increase yield.