Formation of Light Aromatics and Coke during Catalytic Reforming of Biopolymer-Derived Volatiles over HZSM-5

Abstract

In this study, the formation mechanism of light aromatics including benzene, toluene, ethylbenzene, xylene, and naphthalene (BTEXN) and the coke growth during catalytic reforming of thermally derived volatiles of cellulose, glucose, and lignin over HZSM-5 under a H 2 atmosphere were investigated rigorously. The shape selectivity of HZSM-5 coupled with H 2 as the promoted agent was found to be highly efficient in trapping volatiles to promote the production of BTEXN. The reactivity of the three biopolymers from biomass structures was compared over HZSM-5 to reveal the hydrocarbon pool and the phenolic pool mechanisms, which are the key mechanistic steps for the BTEXN products and the undesired coke. The results of the present work indicated that there are competing adsorption between the reactions of the aromatics formation and the reactions responsible for the catalytic coke. The formation of both the "soft" and the "hard" coke species strongly depends on biomass structures. The main coke species on spent HZSM-5 are polyaromatics formed via ring growth and the heavy aliphatic species with longer chain (C 10 −C 30 ) formed via chain growth of the C 6 −C 10 oligomers. By analyzing the coke location and the coke nature, we proposed the coke growth mechanism in terms of the aliphatic-based cycle and the aromatic-based cycle.

Low-Temperature Reforming of Biomass Tar over Ni/ZSM-5 Catalysts: Unraveling the H2-Rich Gas Production Pathways Using In Situ and Ex Situ Techniques

“…The gas yield and C dep were 22.3 mmol/g and 22.3%, which can be explained as the serious carbon deposition. As reported in the literature, tar can be easily adsorbed over the acidic support and then generated coke especially the Ni/Z catalyst with a high Si/Al ratio . Carbon deposition over spent Ni/Z catalysts was analyzed by TPO-MS (Figure d).…”

“…As reported in the literature, tar can be easily adsorbed over the acidic support and then generated coke especially the Ni/Z catalyst with a high Si/Al ratio. 48 Carbon deposition over spent Ni/Z catalysts was analyzed by TPO-MS (Figure 7d). On the basis of the results, it was found that Ni/Z5 with worse activity exhibited the worst coke resistance in CTR, and 44.7 mg coke /g cat.…”

Catalytic Upgrading of Cellulose Pyrolysis Volatiles over Ce Modified Hierarchical ZSM-5 Zeolite: Insight into the Effect of Acid Properties on Light Aromatics and Catalyst Stability

“…However, its rapid deactivation caused by coke deposition is still a big challenge for application . The diffusional limitation of micropores for macromolecular oxygenates and the excessive acid sites on the surface are the main reasons for deactivation. − Hierarchical Z5 zeolite has shown great potential to improve the mass transfer efficiency during the CFP of biomass, while it inevitably suffers from heavy coke formation caused by the on-surface strong acid sites. − Thus, it is necessary to improve the catalytic performance by regulating the surface acid sites of the hierarchical Z5 catalyst through metal modification.…”

Anchoring Effect of Organosilanes on Hierarchical ZSM-5 Zeolite for Catalytic Fast Pyrolysis of Cellulose to Aromatics

“…Aromatization is the main pathway for small-molecule oxygenates and olefins to form aromatics through the “hydrocarbon pool mechanism,” activated by the shape-selective effect of ZSM-5 zeolite channels. 16 …”

“…With the shortage of fossil resources and increasing carbon emissions, biomass energy, as the only renewable carbon source, has gradually attracted attention to replace traditional fossil resources. − Catalytic fast pyrolysis (CFP) is a promising technology for producing aromatics directly from biomass that integrates fast pyrolysis and catalytic cracking technology. , In recent years, extensive research into the reaction mechanism − and catalysts − for CFP has been reported. Aromatization is the main pathway for small-molecule oxygenates and olefins to form aromatics through the “hydrocarbon pool mechanism,” activated by the shape-selective effect of ZSM-5 zeolite channels …”