(47f) Contaminants Present in Ethanol and the Impact on Bio-Based Ethylene Production

Due to market interest in sustainability and decarbonization initiatives, ethylene producers have a growing interest in shifting from conventional fossil feedstocks such as naphtha to bio-based feedstock such as ethanol. The EtE EverGreen™ technology, Lummus Technology’s process producing ethylene from ethanol dehydration, is commercially producing ethylene from alcohol since 2010, with Braskem’s 260 KTA Plant in Brazil.

Due to ethanol’s hygroscopic properties and production process, the primary impurity found in ethanol is water. Ethanol is typically produced as either hydrous, including 7.5 wt% water, or anhydrous, including less than 1 wt% water. In the EtE EverGreen™ process, since steam is used as a thermal fluid in the reaction medium, water is not considered an impurity.

Ethanol contaminants are typically compounds present in sugar cane or formed during its fermentation. The main contaminants are described in table below.

Class of contaminants	Contaminants
Alcohols present in fusel oil	Methanol 1-propanol 2-methyl-1-propanol 3-methyl-1-butanol
Other alcohols	2-propanol 1-butanol
Acetaldehyde and derivatives	Acetaldehyde Ethyl acetate 1,1-diethoxy-ethane (acetal)
Others	Diethyl ether Heavy hydrocarbons Ethyl tertiary butyl ether Salts

Other route of contamination for the ethanol can be related to the transportation matrix (pipelines, road, railway, and waterway) and storage. In Brazil, one of the possible problems in ethanol logistics is the potential for contamination with diesel or biodiesel during railway transport. Sharing of tanks and cars to transport these fuels without appropriate cleaning between loadings, increases the chance of contamination.

Additionally, to prevent high taxes on sale of ethanol, various jurisdictions have requirements of adding denaturants to ethanol to make it undrinkable. There are a wide variety of potential denaturants, which are contaminants to the ethanol-to-ethylene process.

These various contaminants can inhibit the ethanol dehydration reaction, and they may also react to by-products which impact the recovery section design, operation, and product quality.

The paper will discuss in more details the EtE EverGreen™ process, major ethanol markets, key contaminants found in ethanol, and some of the impacts that can be expected from such contaminants.