A New Generation of Renewable Fuels Is on the Horizon

by Wayne Seames (American Oil Chemists Society/Inform Magazine) A new generation of technologies to generate renewable fuels is nearing commercialization. Some of these are focused on producing ethanol and other alcohols from cellulosic biomass using fermentation technologies. These alcohol-based fuels can be used as a substitute for gasoline.

Another group of technologies is focused on producing fuels that replace kerosene and diesel fuels. These technologies take advantage of the chemical composition of crop oils, such as camelina, to generate organic chemical mixtures that are more similar to existing kerosene (jet fuel) and diesel products than current biofuels such as biodiesel. Crop oils contain a group of chemicals known as triacylglycerides (TG).

A TG molecule consists of three carbon chains ending in a carboxylic acid group, with each carbon chain (known as a fatty acid) connected to a glycerol backbone.

...Two process schemes are nearing commercialization for the production of fuels to replace kerosene and diesel: hydrotreating and noncatalytic cracking. Both process schemes manipulate TG oils to generate renewable fuels and by-products.

As the name implies, hydrotreating involves the reaction of TG oils with hydrogen. The TG oil and hydrogen are fed into a reactor where a combination of heat, pressure, and time induce chemical reactions that will (i) remove the fatty acids from the glycerol backbone and (ii) replace the carboxylic acid group on the fatty acids with a hydrogen atom, producing hydrocarbons.

...This carbon bond cleavage process is known as cracking. Hydrotreating processes typically produce diesel, kerosene, propane, and syngas products.

...The other process that is nearing commercialization is the University of North Dakota’s noncatalytic cracking process (patents pending). In this process, TG oil is fed into a reactor where heat, pressure, and time are used to induce cracking reactions in the TG molecules.

This generates a complicated mixture—we’ve identified more than 250 separate chemical compounds in the reactor products—that is dominated by short-chain fatty acids, paraffins (hydrocarbons with all single-bond carbon-pair connections), and aromatics (compounds containing a six-carbon ring with three double-bond carbon-pair connections). The reactor product stream is then separated into intermediate product fractions and further processed into a final suite of fuels and by-products. READ MORE (subsciption required for full article)