Understandings of Catalyst Deactivation and Regeneration during Biomass Tar Reforming: A Crucial Review

Abstract

Value-added chemicals originating from biomass gasification in the presence of advanced catalysts have proved to be promising for valuable chemical generation via deep processing. In the issues of biomass gasification, the deactivation of heterogeneous catalysts is a common problem during the reforming of biomass tar and derived model compounds. Herein, deactivation pathways and regeneration methods are crucial to understand the production of value-added chemicals and guide the design of heterogeneous catalysts during biomass gasification. Unfortunately, to the best of our knowledge, there still has been no review to conclude the recent advances in catalyst deactivation and regeneration. To address the issues mentioned above, in this perspective, common catalysts for biomass tar reforming are first discussed. Then, key features and considerations of catalyst deactivation especially catalyst poisoning and carbon deposition are comprehensively reviewed based on the latest literature reports. Finally, the possible methods of tar elimination, metallic site recovery, and catalyst optimization are reviewed. Meanwhile, the future perspectives toward catalyst design, deactivation, and regeneration in tar reforming are shared. Through this perspective, the existing challenges, solutions, and future strategies in tar reforming or other gas−solid reactions are expected to be made clearer for following research on practical applications on an industrial scale.

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 “amorphous” carbon usually known as encapsulating coke over metallic Ni particles, together with “turbostratic” carbon (formed from the self-condensation reactions of volatiles), is preferable to be combusted at a low temperature or in the presence of steam. Furthermore, that for a combustion temperature above 700 °C should be “graphitic” carbon (like filamentous coke), which is not directly adsorbed on active sites but has continuous precipitation to separate the metallic Ni from the support . As shown in Figure , reforming temperature exhibited a decisive influence on the coke type and amount.…”

“…Furthermore, that for a combustion temperature above 700 °C should be "graphitic" carbon (like filamentous coke), which is not directly adsorbed on active sites but has continuous precipitation to separate the metallic Ni from the support. 44 As shown in Figure 6, reforming temperature exhibited a decisive influence on the coke type and amount. In particular, the introduction of steam could further promote the gasification of carbon deposition, especially the graphenic coke, over Ni/Z80 at 650 °C.…”

Plasma-Catalytic Reforming of Naphthalene and Toluene as Biomass Tar over Honeycomb Catalysts in a Gliding Arc Reactor

“… 13 However, the conventional catalytic reforming process faces major limitations such as rapid catalyst deactivation induced by coke deposition and sintering at high temperatures. 14 …”

“…13 However, the conventional catalytic reforming process faces major limitations such as rapid catalyst deactivation induced by coke deposition and sintering at high temperatures. 14 Nonthermal plasmas (NTPs) offer an effective and sustainable alternative approach for converting tars to syngas and other valuable chemicals at lower temperatures. 15,16 Compared to conventional thermal cracking and catalytic processes, NTP shows unique characteristics of high activity and fast reaction rate, which overcomes the limitation of high reaction temperature and reduces the overall energy cost.…”

“…A variety of catalysts have been investigated for catalytic tar reforming, including transition-metal catalysts (Ni, Mn, Fe, and Co), noble-metal catalysts (Pt, Ru, and Rh), and natural catalysts. − Among them, Ni-based catalysts have been extensively investigated for tar reforming due to their high reactivity and dehydrogenation capacity . However, the conventional catalytic reforming process faces major limitations such as rapid catalyst deactivation induced by coke deposition and sintering at high temperatures …”