Catalytic mechanism of ion-exchanging alkali and alkaline earth metallic species on biochar reactivity during CO2/H2O gasification. (15th January 2018)

• Record Type: Journal Article
• Authors: Feng, Dongdong; Zhao, Yijun; Zhang, Yu; Xu, Huanhuan; Zhang, Linyao; Sun, Shaozeng
• Is Part Of: Fuel. Volume 212(2018)
• Page Start: 523
• Page End: 532
• Publication Date: 2018-01-15
• Subjects: AAEM -- CO2/H2O -- Gasification -- Biochar structure -- Specific reactivity; Fuel -- Periodicals; Coal -- Periodicals; Coal; Fuel; Periodicals; 662.6
• DOI: 10.1016/j.fuel.2017.10.045
• Languages: English
• ISSNs: 0016-2361

Abstract

Graphical abstract: Highlights: K promotes the formation of O-containing functional groups. K and Ca increase the proportion of large aromatic ring structures. Biochar-CO2 reaction occurred at gas-solid interface, while biochar-H2 O one existed in whole particle. A better availability of active sites is obtained on AAEM pre-loaded biochar surface. Abstract: To understand the detailed catalytic mechanism of ion-exchanging AAEM species on biochar structure and its specific reactivity during CO2 /H2 O gasification, the experiments were carried out in a laboratory fixed-bed reactor at 800 °C, with two kinds of AAEM-loading methods. The migration and precipitation characteristics of AAEM species was evaluated by ICP-AES, while the transformation of biochar structures were analyzed by FTIR and Raman. The specific reactivity of H2 O/CO2 gasification biochar was determined by TGA analysis in Air at 370 °C. The results show that the stronger catalytic properties of K and Ca species in H2 O atmosphere are obtained than that in CO2 . The effect of K is mainly on the formation of O-containing functional groups (e.g. alcohol/phenolic-OH, aldehyde/ester CO and carboxylic COO groups) and the transformation from small ring systems to larger ones, while the catalytic effect of Ca is only to increase the proportion of large aromatic ring structures (≥6 fused benzene rings). The biochar-CO2 reaction took place mainly at the gas-solid interface of biochar, while biochar-H2 O one existed throughout the biochar particle. A better distribution of active sites (i.e. surface K/Ca species and O-containing groups) on biochar surface would result in the high specific reactivity of biochar during gasification.