Biomass Catalytic Pyrolysis over Zeolite Catalysts with an Emphasis on Porosity and Acidity: A State-of-the-Art Review

Abstract

The massive consumption of petroleum and the increasingly deteriorating environment has triggered the attention and development of sustainable chemistry recently. Biomass source is the only renewable carbon source on Earth, which is regarded as the potential alternative to the current fossil fuels that cannot be regenerated in a short time. Past decades have witnessed great advances in the utilization of biomass with developed technologies. However, the quality of bio-oils obtained from pyrolysis at the various temperature is poor, which cannot be directly used as valuable chemicals and fuels. Molecular sieve catalyst (zeolite) have successfully applied in the catalytic conversion of different products after biomass pyrolysis, because of their uniform pore structure, strong acidity, and stable framework. This review emphasizes the traditional and the modification of the zeolite acidic active sites and pore structure and their roles in biomass catalytic pyrolysis. First, we compared the catalytic effects of biomass and its derivatives on traditional zeolites. The results show that ZSM-5 has the best catalytic effect (more high-value products), because of its shape selectivity. Different from the previous articles about the effect of modification on one side, this Review mainly introduces the combination of different methods to modify and optimize acidic sites and pores to improve the catalytic effect of rapid biomass pyrolysis. The zeolite was modified to improve the selectivity and yield of the target product, and a certain optimization effect was achieved. From different methods of mesopore formation to metal doping, the ways of adjusting zeolite catalysts and discussions of changes in acidity after metals being doped into zeolites are reviewed. Simultaneously, a hydrogen source was introduced to deal with the problem of insufficient hydrogen content, to improve the quality of bio-oils. Finally, the advantages and disadvantages of catalytic conversion over the modified zeolite (ZSM-5) are analyzed, and the prospects in this field are also discussed.

Thermochemical Conversion of Plastic Waste into Fuels, Chemicals, and Value‐Added Materials: A Critical Review and Outlooks

“…In general, catalysts with higher acidic properties, surface area, and porosity are favored for depolymerization of plastics. [79,186] The acidic nature could initiate the cracking of hydrocarbons. The pore size of catalyst can also influence the composition of oil products.…”

“…Catalysts can also dictate the product selectivity. In general, catalysts with higher acidic properties, surface area, and porosity are favored for depolymerization of plastics [79,186] . The acidic nature could initiate the cracking of hydrocarbons.…”

Catalytic Fast Pyrolysis of Lignocellulosic Biomass to Benzene, Toluene, and Xylenes

“…The pyrolysis vapor must condense quickly to avoid unwanted secondary reactions such as cracking. Alkali and alkaline earth metal ions in biomass feed pose substantial challenges to the process (addressed in Pretreatment) [17,[19][20][21][22][23][24][25][26][27][28][29][30][31][32][33].…”

Recent Advances in Catalysis Based on Transition Metals Supported on Zeolites

“…Several zeolites (Y, β , ZSM-5, SAPO-34, MCM-22, ITQ-2, etc.) were applied for CFP and the best performance was demonstrated by ZSM-5 with high yield of aromatics rather than aliphatic hydrocarbon and significant percentages of deoxygenation ( Zheng et al, 2017 ; Naqvi and Naqvi, 2018 ; Li J. et al, 2019 ; Cai et al, 2020 ). CFP on ZSM-5 is currently the most studied and is already employed in refineries ( Jae et al, 2011 ; Taarning et al, 2011 ; Kubička et al, 2013 ).…”