Butadiene is an industrially relevant precursor in the production of polymers, where it is typically polymerized with itself or other monomers to produce synthetic rubber. Polymerizing butadiene with styrene and acrylonitrile produces the plastic acrylonitrile butadiene styrene (ABS), while polymers of butadiene and styrene are also used in the production of automobile tires. Here we present a renewable pathway to produce butadiene from biomass based tetrahydrofuran (THF), proceeding via a dehydrative ring opening of THF (Dehydra-Decyclization) [1]. A screening of various solid acid catalysts reveals that an all silica phosphorous containing zeolite (Phosphrous-self pillared pentasil, P-SPP) provides the highgest selectivity to butadiene of ~ 95%.1 The most significant undesired reaction pathway is the conversion of THF to propene and formaldehyde, which proceeds via a retro-prins condensation reaction. Increased methyl substitution at the 2 and 5 carbon positions of THF leads to significant increase in the rate, without change in selectivity to dienes, while substitution at the 3 carbon position leads to no change in rate. This suggests that a carbenium ion formed at the 2 and 5 carbon positions, is a kinetically relevant surface intermediate. A combination of in-situ titrations of pyridine and a sterically hindered base, 2,6-ditertbutyl pyridine, suggest that the surface chemistry is pre-dominantly Brønsted acid catalyzed.

Acid catalyzed production of 1,3-butadiene from biomass derived tetrahydrofuran

256th National Meeting (2018)

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