Catalytic upgrading of coal pyrolysis volatiles by Ga-substituted mesoporous ZSM-5. (1st May 2020)

• Record Type: Journal Article
• Authors: Bi, Chenyao; Wang, Xu; You, Qing; Liu, Baoyu; Li, Zhuo; Zhang, Jianbo; Hao, Qingqing; Sun, Ming; Chen, Huiyong; Ma, Xiaoxun
• Is Part Of: Fuel. Volume 267(2020)
• Publication Date: 2020-05-01
• Subjects: Coal volatiles -- Catalytic upgrading -- Mesoporous zeolite -- MFI -- Gallium substitution; Fuel -- Periodicals; Coal -- Periodicals; Coal; Fuel; Periodicals; 662.6
• DOI: 10.1016/j.fuel.2020.117217
• Languages: English
• ISSNs: 0016-2361

Abstract

Graphical abstract: Highlights: Dual-templating synthesis of gallium-substituted mesoporous ZSM-5 (Ga-MZ5). Ga-MZ5 exhibited superior performances with high aromatic-yield and effective phenol-reduction in CFP. Dehydrogenation/cracking ratio decided by zeolite acidity. Deoxygenation of phenols dominated by non-framework Gax Oy species. Diffusion superiority contributed by hierarchical meso-/microporosity. Abstract: Five MFI-type zeolite catalysts, which were aluminosilicate ZSM-5 (Z5), gallium-substituted silicalite-1 (Ga-S1), mesoporous ZSM-5 (MZ5), gallium-substituted mesoporous silicalite-1 (Ga-MS1) and gallium-substituted mesoporous ZSM-5 (Ga-MZ5), were hydrothermally synthesized with combined using of TPAOH and TPOAC as micropore and mesopore structure-directing agents respectively, followed by the application in the catalytic upgrading of volatiles from low-rank coal fast pyrolysis. The obtained results indicated that significant improvements with the yield of high value-added products of BTEXN (benzene, toluene, ethylbenzene, xylene and naphthalene) increased from 5.4 mg.g −1 to 11.9–26.4 mg.g −1, as well as the content of light fractions (<300 °C) in coal tars increased from 51% to 65–88% were realized by using the representative MFI-type zeolite catalysts in contrast to non-catalyst pyrolysis. Moreover, the possible mechanism for catalytic upgrading over the best-performing catalyst of gallium-substituted mesoporous ZSM-5 (Ga-MZ5) with the highest yield of aromatics and effective reduction of phenols was proposed on the basis of systematic comparison of structural features and catalytic performances of various MFI-type zeolite catalysts and fundamental study of the synergetic effects dominated by acidity, ratio of Brønsted/Lewis acid sites, intra-/extra-framework gallium species and hierarchical meso-/microporosity.