(530a) Acid Catalyzed Production of 1,3-Butadiene from Biomass Derived Tetrahydrofuran

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). 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.

Figure
1. 
Dehydra-decyclization in a catalytic packed-bed flow reactor. Reaction of
tetrahydrofuran to butadiene at 250−350 °C, WHSV = 1.0 h⁻¹
and 5 Torr with catalysts: P-SPP (red), Sn-BEA (blue), amorphous
silica−alumina (SiAl, yellow), and ZSM-5 (Si:Al = 140, green). Conversion
for each experiment noted numerically within each bar.

[1] Abdelrahman,
O. A.; Park, D. S.; Vinter, K. P.; Spanjers, C. S.; Ren, L.; Cho, H. J.;
Vlachos, D. G.; Fan, W.; Tsapatsis, M.; Dauenhauer, P. J. ACS
Sustainable Chem. Eng. 2017, In Press.