Effect of thermal treatment on the nickel state and CO hydrogenation activity of titania-supported nickel catalysts

Journal Article · Sat Aug 15 04:00:00 EDT 1998 · Journal of Catalysis

DOI:https://doi.org/10.1006/jcat.1998.2102· OSTI ID:659070

Ho, S W; Chu, C Y; Chen, S G ^[1]

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1. National Cheng Kung Univ., Tainan (Taiwan, Province of China). Dept. of Chemistry

A series of 6 wt% Ni/TiO{sub 2} catalysts were prepared by pore volume impregnation under various calcination conditions (225--600 C, 1--16 h), and were characterized by XRD, XPS, TG-MS, and chemisorption (H{sub 2} and O{sub 2}). The results of XRD, XPS, and TG-MS show the presence of incompletely decomposed nickel nitrates and NiO for catalysts calcined at 225--250 C, and the presence of NiO for catalysts calcined at 300--500 C. NiTiO{sub 3} becomes the dominant nickel species in the catalyst calcined at 600 C. Reducibility of nickel to nickel metal depends on the chemical states of nickel in the calcined catalysts. For catalysts calcined below 600 C, where NiO is the main nickel species, 100% reducibility can be obtained at a reduction temperature of 400 C. However, for catalysts calcined at 600 C, where NiTiO{sub 3} is the dominant nickel species, complete reduction of nickel species can be achieved at 600 C. Lower turnover frequencies (TOF(H{sub 2})) for CO hydrogenation were observed for the catalysts with unreduced nickel phase. When nickel is completely reduced, TOF(H{sub 2}) is independent of the chemical states of nickel in the calcined catalysts or reduction temperature. The TOF(H{sub 2})`s are an order of magnitude higher than that reported for unsupported nickel indicating the promotion effect of titania on CO hydrogenation even after high reduction temperature. However, an increase in ethene formation rate, methane and C2-C4 percentages, and the olefin to paraffin ratio (C2-C4) was observed, along with a significant decrease in the H/O adsorption ratio as reduction temperature was increased to 600 C for all catalysts. This suggests further interaction of TiO{sub x} moieties with nickel surface in addition to blocking.

• OSTI ID: 659070
• Journal Information: Journal of Catalysis, Journal Name: Journal of Catalysis Journal Issue: 1 Vol. 178; ISSN 0021-9517; ISSN JCTLA5
• Country of Publication: United States
• Language: English

Related Subjects

01 COAL, LIGNITE, AND PEAT
10 SYNTHETIC FUELS
CALCINATION
CARBON MONOXIDE
CATALYTIC EFFECTS
HYDROGENATION
METHANATION
NICKEL
NICKEL OXIDES
REDUCTION
TITANIUM OXIDES