Reactivity and deactivation mechanisms of pyrolysis chars from bio-waste during catalytic cracking of tar

Hervy, Maxime; Weiss-Hortala, Elsa; Minh, Doan Pham; Dib, Hadi; Villot, Audrey; Gérente, Claire; Berhanu, Sarah; Chesnaud, Anthony; Thorel, Alain; Coq, Laurence Le; Nzihou, Ange

doi:10.1016/j.apenergy.2019.01.021

Cited by 56 publications

(18 citation statements)

References 69 publications

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“…Proper activation temperature was selected as 750 °C, based on facts that higher temperatures lead to pore sintering, while lower temperatures lead to slower micropore development [28][29][30]. Additionally, 750 °C is a temperature low enough to ensure that the inorganic species in the char matrix will not migrate to the surface and block the char pores [11]. On the other hand, the activation time was chosen as 2 hours to ensure sufficient micropore area, because the activation reaction rate with CO2 is known as lower than that with steam [24,31,32].…”

Section: Catalyst Preparation and Characterizationmentioning

confidence: 99%

“…Table 2 presents the BET surface areas, average pore diameter, micropore area and micropore volume of the chars before and after 3 hours of use. The surface characteristics of the chars from references [11,14,20] are also included for comparison purposes (see section 4). Expectedly, the activated char exhibited a higher initial micropore area, specific surface area and average micropore diameter than the regular char.…”

Section: Surface Functional Groupsmentioning

confidence: 99%

“…The char-catalytic tar reforming performance is affected by various factors, including: (1) the physicochemical characteristics of char, e.g. particle size [10], surface area [11][12][13][14][15][16][17] , (2) the presence of ashes (i.e. inorganic species) on its surface [11,12]; and (3) operation parameters, e.g.…”

Section: Introductionmentioning

confidence: 99%

“…particle size [10], surface area [11][12][13][14][15][16][17] , (2) the presence of ashes (i.e. inorganic species) on its surface [11,12]; and (3) operation parameters, e.g. the tar concentration, steam concentration [10,14], or temperature [9,10,14].…”

Section: Introductionmentioning

confidence: 99%

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Performance of biochar as a catalyst for tar steam reforming: Effect of the porous structure

Buentello-Montoya

Zhang

et al. 2020

Applied Energy

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The application of gasification to thermally treat biomass as carbon neutral resources has been constrained by the technical challenges associated with tar formations, which cause operational problems in downstream equipment for syngas processing. Catalysts, such as transition metals, calcined rocks and char, can be used to catalyse tar reforming. Biochars, which are naturally produced during biomass gasification, are particularly attractive as an alternative catalyst due to their catalytic functions, low cost and long endurance. Despite these promising characteristics, adequate knowledge on the relationship between the porous structure of biochar and its deactivation by coking during the steam reforming of tars is not available. In this work, the influence of the porous structure of biochar on its performance across time for reforming tar was investigated in a fixed-bed reactor, over a temperature range from 650 to 850 °C. Regular biochar and physically activated biochar from the same precursor biomass were employed as bed material. The tar samples were the composed mixture of benzene, toluene and naphthalene. Both fresh and spent catalysts were analysed with Brunauer-Emmet-Teller, tplot, Fourier Transform Infrared and Scanning Electron Microscopy/Energy Dispersive Spectroscopy. Results showed that, while at moderate temperatures of 650 and 750 °C, the activated biochar offered a higher tar conversion but more severe deactivation than that of the regular biochar. At the high temperature of 850 °C, the difference in the catalytic performance between the two chars was negligible, and over 90% of the initial tar species were removed throughout the 3-hour long experiments. At 850 °C, the coke deposited in the meso-and macro-pores of both chars was gasified, leading to a stable catalytic performance of both chars. The results indicated that meso-and macro-porous biochars are resilient and active enough to become a viable option for tar steam reforming.

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Section: Catalyst Preparation and Characterizationmentioning

confidence: 99%

Section: Surface Functional Groupsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Performance of biochar as a catalyst for tar steam reforming: Effect of the porous structure

Buentello-Montoya

Zhang

et al. 2020

Applied Energy

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“…Additionally, there is a relationship between the pore sizes and the catalyst resilience. It has been found that while mesopores do not contribute as much as micropores to provide a high initial tar conversion, they are more resilient to coke and increase the lifespan of the catalyst [131].…”

Section: Use Of Regular Char As a Catalystmentioning

confidence: 99%

The use of gasification solid products as catalysts for tar reforming

Buentello-Montoya

Zhang

2019

Renewable and Sustainable Energy Reviews

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The presence of tars in syngas is a major technological constraint for upscaling biomass gasification to produce heat, power, and other value-added chemicals such as biofuels. At the same time, the solid remains from biomass gasification i.e. char and ashes, have capabilities to catalyse the reforming of gasification tars. This work presents a comprehensive analysis of the relevance of gasification chars and ashes as catalysts for tar reforming. A description of the solid products from biomass gasification, their formation, chemical characteristics and potential applications is given. Additionally, a review of the state of the art of the uses of regular char, activated carbon and ashes as a catalyst for tar reforming is presented. Further, kinetics reported in literature, and the homogeneous and heterogeneous mechanisms for tar reforming over char are discussed and explained. From reviewing literature it was found that activated chars exhibit the best reforming capabilities, followed by regular char and ashes. Knowing the role of the interactions between the char and the tars is a key factor for optimization of char catalysts. Ultimately, this work provides guidance for understanding the uses of biomass solids as catalysts for tar reforming, and aid in future research to increase the economic feasibility of biomass gasification.

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