Production of drop-in biodiesel blendstocks via competitive acid-catalyzed dehydration reactions using ethanol oligomerization products

Abstract

Ethanol can be converted into diesel fuel ethers using a three-step catalytic approach that involves ethanol oligomerization to larger alcohols, hydrogenolysis of the esters followed by dehydration of the C₄ to C₈ alcohols into ethers. In this paper we report results for the dehydration of a mixture of C₄–C₈ alcohols using a zeolite Y catalyst in a continuous flow reactor. Mono-molecular dehydration of the alcohols produces olefins while bi-molecular dehydration of the alcohol produces ethers. Increasing the pressure increases the ether selectivity while decreasing the pressure produces more olefins. Linear alcohol feeds produce more C₈₊ ethers, while branched and secondary alcohols lead to more olefins. Olefin and coke selectivities increase with increasing carbon chain length of alcohols. Secondary alcohols lead to higher coke selectivities. Ethanol/butanol oligomerization experiments showed that the incoming dehydration feedstock can be grown to larger C₆₊ alcohol fractions, leading to higher yields of C₁₀₊ diesel-range ethers.