Coke formation on the surface of Ni/HZSM-5 and Ni-Cu/HZSM-5 catalysts during bio-oil hydrodeoxygenation. (1st February 2017)

• Record Type: Journal Article
• Authors: Li, Yu; Zhang, Changsen; Liu, Yonggang; Tang, Songshan; Chen, Guanghui; Zhang, Ruiqin; Tang, Xiaoyan
• Is Part Of: Fuel. Volume 189(2017)
• Page Start: 23
• Page End: 31
• Publication Date: 2017-02-01
• Subjects: Bio-oil -- Hydrodeoxygenation -- Catalyst deactivation -- Deposition of coke; Fuel -- Periodicals; Coal -- Periodicals; Coal; Fuel; Periodicals; 662.6
• DOI: 10.1016/j.fuel.2016.10.047
• Languages: English
• ISSNs: 0016-2361

Abstract

Highlights: Coke formation is the main cause of catalyst deactivation in bio-oil hydrodeoxygenation. Quantity and species of coke on spent catalysts determine possibility of catalyst regeneration. Oxygenated compounds and graphitic carbon contained in coke deactivate catalysts. Cu reduces coke formation for Ni/HZSM-5 catalyst. Abstract: Deactivation of zeolite catalysts due to coke deposition is a pronounced challenge in the hydrodeoxygenation (HDO) of bio-oil. This paper reports on the mechanism of coke formation and catalyst regeneration for two catalysts (Ni/HZSM-5, Ni-Cu/HZSM-5). FT-IR, XPS and Raman spectroscopy characterizations indicate that catalyst deactivation can be divided into three main stages: (1) Lewis acid sites in HZSM-5 support are rapidly covered by oxygenated hydrocarbons. The Brønsted acid sites of HZSM-5 donate protons to oxygenates, leading to the formation of carbocations - precursors of soluble coke on the catalyst surfaces. (2) Soluble coke is then stacked to form disordered filament-like carbon strands that are similar to carbon nanotubes or graphite-like structures. (3) Filament-like carbon evolves into graphite carbon. At the same HDO temperature, more graphite particles are found on the Ni/HZSM-5 catalyst than on the Ni-Cu/HZSM-5 catalyst, indicating higher resistance for the coke formation for Ni-Cu/HZSM-5 catalyst.