(592b) Effects of Reactor Configurations and Catalyst Properties for Vapor Upgrading in HZSM5 Catalyzed Pyrolysis Vapor Upgrading

Effects
of Reactor Configurations and Catalyst Properties on HZSM5
Catalyzed Upgrading of Biomass Pyrolysis Vapors

Shaolong
Wan, Christopher Waters, Abhishek Gumidyala, Rolf Jentoft, Lance Lobban, Steven
Crossley, Daniel Resasco, and Richard Mallinson

Since
the mid 1980s, HZSM-5 has been shown to be a superior catalyst for upgrading
the vapors from biomass pyrolysis to produce aromatic hydrocarbons.  However,
this comes with relatively low liquid yields, significant coke and gas
formation and rapid deactivation.  We have studied HZSM-5 catalysis of biomass
pyrolysis vapors in a custom CDS pyroprobe with a separate reactor in order to
understand how to increase liquid yield and improve catalyst stability. 
Compared with pyrolyzing the catalyst mixed with the biomass, different product
selectivities are observed with the separate reactor due primarily to
differences in residence time.  The pyroprobe pyrolysis of a biomass-catalyst mixture
lasts for seconds and results in high conversion of a primary cellulose
decomposition product, levoglucosan, as well as light oxygenates including
acetic acid.  When configured in a separate reactor with much shorter residence
time, high conversion of the light oxygenates is obtained, but low conversion
of levoglucosan is observed.  In this separate configuration, multiple pulses
of pyrolysis vapors may be passed over the catalyst, thus allowing the
deactivation characteristics to be studied.  For example, at a constant number
of acid sites in the catalyst bed, the deactivation rate was found to be much
faster with a catalyst containing a higher acid site density.  Different HZSM-5
materials have been tested, with different separate reactor temperatures.  These
have included variation in the Si/Al ratio from 40 to 11.5 and the use of
core-shell materials with a core of silicalite, an outer layer of HZSM-5, and
also a material with a further outer layer of silicalite.  Additionally, the
effect of the passivation of surface acidity has been examined.