Mini-Review on Char Catalysts for Tar Reforming during Biomass Gasification: The Importance of Char Structure

Abstract

With the depletion of fossil fuel reserves and the increasing concern about greenhouse gas emission, the need to develop technologies for using renewable and sustainable energy resources is becoming urgent. Solar, winds, geothermal, and hydro as well as nuclear energy are all considered as clean energy sources to (partially) substitute fossil fuels in energy generation. Biomass, however, remains the only renewable energy source consisting of hydrocarbon compounds, which is a necessity for making basic building blocks for chemical industries. The development of feasible gasification technologies to produce syngas (primarily H2 and CO) is considerably inhibited by the “tar issues”. The tar content in the product gas has to be extremely low in order to effectively use the gas downstream, such as for synthesizing liquid fuels and generating electricity. Although there are a wide range of options for removing, cracking, and catalyzing the tar, this review mainly discusses the catalytic reforming approach using char as catalysts, of which the importance of the carbon structure of chars will be underpinned because the char structure including matrix carbon structure and functional groups on the char surface not only affects the reactivity of nonmetal active sites but also largely dominates the role/fate of internally existing and externally added metal species.

Direct Conversion of Syngas Produced from Steam Reforming of Toluene into Methane over a Ni/Biochar Catalyst

“…18,19 As an emerging material, char (i.e., biochar and coal char) with a special structure and adsorption capacity could provide higher activity in H 2 -rich syngas production during tar reforming. 20,21 Ren et al 22 obtained Ni/lignite char by the ion-exchange method, and they found that the Ni/ lignite char can effectively crack biomass tar into H 2 -rich gas.…”

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

“…To the best of our knowledge, there are comprehensives reviews on these topics: (1) modification and development of Ni-based catalysts for biomass tar reforming, , (2) development of catalysts for steam reforming of a biomass tar model, (3) recent progress, challenges, and perspectives in catalytic tar elimination, − (4) coke formation and deactivation during tar reforming, and (5) design of anti-coking, anti-poisoning, and anti-sintering catalysts in biomass tar reforming . Most recently, char-derived catalysts with cheap prices and excellent activities have also attracted substantial attention in biomass tar reforming. , However, few works make the effort on the aspects of the deactivation mechanism and regeneration of the deactivated catalysts after tar reforming. Herein, in this perspective, the process and mechanism of catalyst deactivation and regeneration in the tar reforming process are deeply elucidated.…”

“…44 Most recently, char-derived catalysts with cheap prices and excellent activities have also attracted substantial attention in biomass tar reforming. 45,46 However, few works make the effort on the aspects of the deactivation mechanism and regeneration of the deactivated catalysts after tar reforming. Herein, in this perspective, the process and mechanism of catalyst deactivation and regeneration in the tar reforming process are deeply elucidated.…”

Enhanced Hydrogen Storage Properties of LiAlH4 by Excellent Catalytic Activity of XTiO3@h‐BN (X = Co, Ni)

“…Unfortunately, such sources are all intermittent. [ 6–8 ] Consequently, large scale deployment of renewables requires the implementation of more effective energy storage solutions as well as smart grids that can manage intermittent energy inputs. [ 9 ]…”