Catalytic Pyrolysis of Pinyon–Juniper Using
Red Mud and HZSM‑5
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Abstract
Pinyon and juniper are invasive woody
species in the western United
States that occupy over 30 million hectares of land. The U.S. Bureau
of Land Management (BLM) has embarked on harvesting these woody species
to make room for range grasses for grazing. The major application
of harvested pinyon–juniper (PJ) is low-value firewood. Thus,
there is a need to develop new high value products from this woody
biomass to reduce the cost of harvesting. We investigated the fractional
catalytic pyrolysis of PJ using both HZSM-5 catalyst and red mud at
475 °C in a fluidized bed reactor at atmospheric pressure. Both
the HZSM-5 and the red mud were effective catalysts for producing
low-viscosity pyrolysis oils. Oils that were catalyzed with red mud
had a lower viscosity (96 cP @40 °C) than oils that were catalyzed
with HZSM-5 (213 cP @40 °C). In both cases, the yields of liquids
ranged from 42 wt % to 49 wt %. The mechanisms of catalysis
by the two catalysts were quite different. The HZSM-5 rejected oxygen
mostly as carbon monoxide (CO) and produced lower amounts of carbon
dioxide (CO<sub>2</sub>); in contrast, the red mud produced more CO<sub>2</sub> and less CO. However, both catalysts produced similar amounts
of water. The char/coke yields from both catalysts were similar but
the total gas yields were slightly different. The higher heating value
of the red mud catalyzed oil (HHV = 29.46 MJ/kg) was slightly higher
than that catalyzed by HZSM-5 (HHV = 28.55 MJ/kg). Thus, red mud can
be used to achieve similar catalytic pyrolysis results as HZSM-5 catalysts