Nanowire-Based Materials as Coke-Resistant Catalyst Supports for Dry Methane Reforming

Apolo Nambo,Jacek B Jasinski,Mahendra Sunkara,Veerendra Atla,Vivekanand Kumar,Sivakumar Vasireddy,Sreedevi Upadhyayula

doi:10.3390/catal11020175

Abstract

In this paper, nanowire-supported catalysts loaded with nickel are shown to be coke resistant compared to nanoparticle-supported catalysts. Specifically, Ni-loaded titania-based nanowire catalysts were tested with the dry methane reforming process in a laboratory-scale continuous packed-bed atmospheric reactor. The CO2 conversion rate stayed above 90% for over 30 h on stream under coke-promoting conditions, such as high flow rates, low temperatures, and a high ratio of CH4 to CO2. The coke (CxHy, x>>y) on the spent catalyst surface for both nanowire- and nanoparticle-supported catalysts was characterized by TGA, temperature-programmed reduction (TPR), and electron microscopy (SEM/TEM/EDS), and it was revealed that the types of carbon species present and their distribution over the morphology-enhanced materials played a major role in the deactivation. The CO2 conversion activity of Ni supported on titania nanoparticles was reduced from ~80% to less than 72% in 30 h due to the formation of a graphitic coke formation. On the other hand, Ni particles supported on nanowires exhibited cube-octahedral morphologies, with a high density of non- (111) surface sites responsible for the increased activity and reduced graphitic coke deposition, giving a sustained and stable catalytic activity during a long time-on-stream experiment.

Highlights

Published: 28 January 2021Global warming is one of the greatest problems facing humanity and it threatens society’s well-being, challenges the process of economic development, and alters the natural environment [1]
Catalysts are made by decorating potassium titanate nanowires with nickel and are tested for CO2 conversion in the dry methane reforming reaction
The nickel supported on titania nanowires maintained a stable activity of >90% CO2 conversion with the dry methane reforming reaction for more than 30 h at 750 ◦ C, with a GHSV of 60,000 mlgr−1 h−1 and a feed ratio of methane to carbon dioxide of 3

Summary

Introduction

Global warming is one of the greatest problems facing humanity and it threatens society’s well-being, challenges the process of economic development, and alters the natural environment [1]. The syngas produced is considered a building block that can be used as a reactant for other applications, such as Fischer–Tropsch fuel, methanol, and other valuable liquid fuels and chemicals [7] This technology allows the mitigation of the most important environmental issue at present and provides a new generation of fuels [8]. Mo infused with nickel nanoparticles on a highly crystalline-fumed MgO support exhibited a high activity and stability.This catalyst [22] stability is attributed to the migration of the nanoparticles; to heating; and to the step edges of the support forming larger and highly stable nanoparticles, passivating the coking sites on the oxide support. Nanowire morphologies are investigated as supports for Ni in the DMR process in terms of the type of coke formation and level of stability achieved compared to that achieved with nanoparticle-supported catalysts

Results and Discussion

Experimental Section

Conclusions