Carbon Nanotube Formation on Cr-Doped Ferrite Catalyst during Water Gas Shift Membrane Reaction: Mechanistic Implications and Extended Studies on Dry Gas Conversions

Catalysts

Noe T. Alvarez¹  Xinhui Sun¹  Panagiotis G. Smirniotis¹  Devaiah Damma¹  Antonios Arvanitis¹  Vesselin Shanov¹  Junhang Dong¹ 

[1] Department of Chemical and Environmental Engineering, University of Cincinnati, Cincinnati, OH 45221, USA;

关键词: Cr-doped ferrite;    membrane reactor;    water gas shift;    carbon nanotubes;    sulfur resistance;   

DOI  :  10.3390/catal10080927

来源: DOAJ

【 摘 要 】

A nanocrystalline chromium-doped ferrite (FeCr) catalyst was shown to coproduce H₂ and multiwalled carbon nanotubes (MWCNTs) during water gas shift (WGS) reaction in a H₂-permselective zeolite membrane reactor (MR) at reaction pressures of ~20 bar. The FeCr catalyst was further demonstrated in the synthesis of highly crystalline and dimensionally uniform MWCNTs from a dry gas mixture of CO and CH₄, which were the apparent sources for MWCNT growth in the WGS MR. In both the WGS MR and dry gas reactions, the operating temperature was 500 °C, which is significantly lower than those commonly used in MWCNT production by chemical vapor deposition (CVD) method from CO, CH₄, or any other precursor gases. Extensive ex situ characterizations of the reaction products revealed that the FeCr catalyst remained in partially reduced states of Fe³⁺/Fe²⁺ and Cr⁶⁺/Cr³⁺ in WGS membrane reaction while further reduction of Fe²⁺ to Fe⁰ occurred in the CO/CH₄ dry gas environments. The formation of the metallic Fe nanoparticles or catalyst surface dramatically improved the crystallinity and dimensional uniformity of the MWCNTs from dry gas reaction as compared to that from WGS reaction in the MR. Reaction of the CO/CH₄ mixture containing 500 ppmv H₂S also resulted in high-quality MWCNTs similar to those from the H₂S-free feed gas, demonstrating excellent sulfur tolerance of the FeCr catalyst that is practically meaningful for utilization of biogas and cheap coal-derived syngas.

【 授权许可】

Unknown