Page 115 - Advances in bioenergy (2016)

has long-range order, large monodispersed mesopores (up to 50 nm), and thicker walls
(typically between 3 and 9 nm), which make them more thermally and hydrothermally stable
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than MCM-41-type materials. Samolada et al. evaluated a mesoporous Al-MCM-41
material for the catalytic pyrolysis of biomass and found that it exhibited poor hydrothermal
stability, suggesting that further optimization of this material is needed for the pyrolysis
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process. Iliopoulou et al. studied the steam stability and the effect of acidity of Al-MCM-41
catalysts. They found that lower numbers of acid sites had a beneficial effect for the production
of liquid organic product, whereas higher number of acid sites favored the conversion of the
pyrolysis vapors toward gas and coke. Moderate steaming of the materials resulted in
reduction of their surface area and number of acid sites by 40–60%. However, steamed
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samples were still active for the upgrading of biomass pyrolysis vapors. Adam et al. studied
the pyrolysis of spruce wood biomass in a Py-GC–MS system in the presence of four different
Al-MCM-41-type catalysts (Si–Al ratio of 20) and modified Al-MCM-41 catalysts (by pore
enlargement and introduction of copper (Cu) cations into the material structure). They found
that after catalysis, the yield of acetic acid and furans increased and the yield of high molecular
mass phenols decreased. The overall yield of phenols increased and there was also a slight
increase of the hydrocarbon yield. The enlargement of the catalyst's pores reduced the yield of

acetic acid and H O and in general, pore enlargement and Cu cation introduction to the catalyst
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led to higher molecular mass products. In another study, Adam et al. investigated the effect of
four Al-MCM-41 catalysts with Si–Al ratio of 20, a pure siliceous SBA-15 and an aluminum
SBA-15 on the upgrading of biomass pyrolysis vapors in a fixed bed reactor. They also studied
Al-MCM-41 materials modified by pore enlargement and Cu cation introduction into their

structure. They found that gas and H O yields increased after catalysis with all materials.
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Hydrocarbon, phenol, and PAHs yields increased as well, whereas carbonyl and acid yields
decreased. They observed that all catalysts reduced the amount of undesirable compounds
present in the bio-oil. The pore enlargement of the Al-MCM-41 seemed to have a deteriorating
effect on the quality of the bio-oil. Cu cation introduction on the other hand had a beneficial
effect and increased the amount of desirable products. The incorporation of aluminum into the
SBA-15 framework resulted in very high content of desirable products in the bio-oil. 37
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Antonakou et al. evaluated three Al-MCM-41 materials with different Si–Al ratios and three
metal containing (Cu, Fe, and Zn) Al-MCM-41 materials for the biomass pyrolysis in a fixed
bed reactor. The production of bio-oil and its organic fraction decreased in comparison to the
noncatalytic runs and the production of coke increased. All catalysts were found to increase the
amount of phenolic compounds. Fe-Al-MCM-41, Cu-Al-MCM-41, and the lowest Si/Al Al-
MCM-41 were the best catalysts for phenols production. They also observed a decrease in the
undesirable fractions of acids, carbonyls, and heavy compounds with almost all tested
materials. They found that lower Si–Al ratios positively affect the product yields and
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composition. Nilsen et al. also studied metal modified and their parent Al-MCM-41
materials with Si–Al ratio of 20 for the catalytic pyrolysis of biomass. They observed a better
bio-oil quality with respect to phenols yield with all materials. The Zn-Al-MCM-41 catalyst
led to the lower yield of phenols but gave the best results with respect to coke produced.

MSU materials for the catalytic pyrolysis of biomass have also been tested. Triantafyllidis