Catalytic steam reforming of biomass tar: Prospects and challenges

Abstract

Tar is unavoidable by-product during biomass gasification process. Catalytic steam reforming of tar to syngas is a promising way for the removal of tar from the gas products. However, the key issue for this way is catalyst development. To date, the developed catalysts always have advantages and disadvantages: nickel-based catalysts have high activity, but they are easily deactivated by coking; noble metal based catalysts have high catalytic activity, long-term stability and high carbon deposition resistance, but they are expensive; other transition metal catalysts such as Fe, Co and Cu exhibit a good performance, but they are also deactivated easily by carbon deposition in the case of high heavy-tar content in the tar; alkali metal catalysts also have high catalytic activity for tar reforming, but they are easy to be evaporated with the generated gases; natural catalysts have been widely applied for the steam reforming of tar due to its inexpensive, abundant and disposable, but their catalytic activities are lower than those man-made ones, and especially have low mechanical strength, making them not suitable to be used in fluidized bed reactor; zeolite is suggested to be a good catalyst support due to its high thermal/hydrothermal stability, high resistance to sulfur compounds, and easy to be regenerated; biomass char has been used as the catalyst or catalyst support in the steam reforming of tar due to its low cost and its natural production inside the biomass gasifier; even biomass ash now is considered to be a good catalyst for tar removal. In this review, to get better understanding of the mechanism of catalytic steam reforming of tar derived from biomass, tar formation, tar properties and catalytic reaction mechanism are also introduced, and prospects and challenges are summarized.

Recent advances on the utilization of layered double hydroxides (LDHs) and related heterogeneous catalysts in a lignocellulosic-feedstock biorefinery scheme

“…In addition, tar is often responsible for serious coke deposition on the downstream catalysts provoking a rapid deactivation if the synthesis gas is utilized for production of methanol and Fischer-Tropsch liquids. 245 Among the different methods proposed (including physical separation and thermal cracking), the catalytic steam reforming of tar (CSRT) has been described as the most promising route to remove tar from the gas product, since it can convert tar into syngas at temperatures equal to if not lower than the gasification temperature and without the production of waste water. 245,246 Thus, the implementation of this process has pushed the development of highly active and stable heterogeneous catalysts for this reaction.…”

“…245 Among the different methods proposed (including physical separation and thermal cracking), the catalytic steam reforming of tar (CSRT) has been described as the most promising route to remove tar from the gas product, since it can convert tar into syngas at temperatures equal to if not lower than the gasification temperature and without the production of waste water. 245,246 Thus, the implementation of this process has pushed the development of highly active and stable heterogeneous catalysts for this reaction. In particular Ni-based catalysts have been widely investigated for the steam reforming of tar, due to their low cost and high activity.…”

“…In particular Ni-based catalysts have been widely investigated for the steam reforming of tar, due to their low cost and high activity. 245,247,248 In many cases, Al 2 O 3 is used as the support; however, the main problem with Al 2 O 3 supported Ni catalysts is the deactivation caused by coke deposition and aggregation of metal particles. In order to decrease the coke deposition on the catalyst and increase the interaction of the metal species with support surfaces and modifiers (e.g.…”

Catalisadores de Ni suportados em Al₂O₃ modificados com V, Nb e Zn aplicados na reforma à vapor do ácido butírico para produção de H₂

“…Na reforma a vapor do metano, por exemplo, processo responsável pela maior parte da produção industrial de hidrogênio, é empregado catalisador do tipo Ni/Al2O3. Vários estudos avaliaram as propriedades catalíticas do níquel metálico e mostraram a alta atividade desse metal na ruptura de ligações C-C, C-H, C-O e O-H, o tornando especialmente adequado às reações de reforma a vapor (NICHELE et al, 2014;GUAN et al, 2016;TRIBALIS et al, 2016).…”

“…A principal matéria-prima para a produção da alumina é o mineral bauxita e quando calcinada ou sinterizada, a alumina pode apresentar diversas fases cristalográficas, dentre elas temos: a γ-alumina e outras aluminas de transição (γ, δ, θ, η, ρ, κ, χ). A gama-alumina (γ-Al2O3) é uma das formas comercialmente mais utilizadas e apresenta propriedades ácidas na forma de sítios de Lewis (CAO; RAMBO;SIEBER, 2004;AUROUX;SHEN, 2006;BIZKARRA et al, 2015;GUAN et al, 2016).…”