Biomass feedstocks contain inorganic compounds generally classified as ash. The ash consists of
compounds of potassium, calcium, magnesium, silicon, phosphorous and other elements. These
elements have been reported to influence both the pyrolysis reactions as well as destabilizing
the pyrolysis oils during storage. The inorganic elements have also been reported to deposit on
catalyst surfaces during in situ catalytic pyrolysis leading to the eventual deactivation of acidic
catalysts such as zeolites. The deposition of inorganic elements and their effect on formulated
red mud (FRM) catalyst during in situ catalytic pyrolysis of pinyon juniper wood was investigated.
The inorganic elements were measured for the fresh, coked, and regenerated catalysts. The BET
specific surface area of the FRM catalyst decreased from 76 m2/g for the fresh catalyst to 53 m2/g
for the stable regenerated catalyst. After three regenerations, the BET specific surface area
stabilized at 53 m2/g and remained constant after all other regenerations. Potassium, calcium,
magnesium, and phosphorous were deposited on the catalyst. Potassium deposition was linear
with the number of regenerations while magnesium and calcium depositions were initially rapid
but leveled off after three regenerations of the catalyst. Phosphorous deposition was almost
linear, but the data were more scattered compared to potassium. The potassium deposition was
attributed to physical phenomenon whereas calcium and magnesium depositions were more
akin to chemical reactions related to the loss of BET surface area of the catalyst. The deposition
of these elements on the surface of the catalyst did not deactivate it. After each catalyst
regeneration, the oil yield was not significantly affected and the oil oxygen content and viscosity
decreased slightly. This clearly showed that formulated red mud is a robust catalyst suitable for
in situ catalytic fast pyrolysis of biomass.
Revised: March 30, 2020 |
Published: March 19, 2020
Citation
Agblevor F., H. Wang, S. Beis, K. Christian, A. Slade, O. Hietsoi, and D.M. Santosa. 2020.Reformulated Red mud: a robust catalyst for in situ catalytic pyrolysis of biomass.Energy and Fuels 34, no. 3:3272-3283.PNNL-SA-150426.doi:10.1021/acs.energyfuels.9b04015