Intensification of Dry Reforming of Methane on Membrane Catalyst: Confirmation and Development of the Hypothesis.

Maria Myachina,Valentin Sapunov,Natalia Gavrilova,Valery Skudin,Sergey Gubin

doi:10.3390/membranes12020136

Maria Myachina, Valentin Sapunov + Show 3 more

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https://doi.org/10.3390/membranes12020136

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Abstract

This article presents an analysis of kinetic studies of dry methane reforming (DRM) in a reactor with a membrane catalyst (RMC) in the modes of a contactor with “diffusion” and “forced” mass transfer. Comparison of the specific rate constants of the methane dissociation reaction in membrane and traditional reactors confirmed the phenomenon of intensification of dry methane reforming in a membrane catalyst (MC). It has been experimentally established that during DRM, a temperature gradient arises in the channels of the pore structure of the membrane catalyst, characterized by a decrease in temperature towards the inner volume of the MC, and initiates the phenomenon of thermal slip. The features of this phenomenon are highlighted and must be considered in the analysis of kinetic data. The main provisions of the hypothesis explaining the effect of intensification by the occurrence of thermal slip in the channels of the pore structure of the MC are formulated. The proposed hypothesis, based on thermal slip, explains the difference in rate constants of traditional and membrane catalysts, and substantiates the phenomenological scheme of DRM stages in a reactor with a membrane catalyst.

Highlights

The use of membranes and membrane catalysts, which is always accompanied by the division of the reactor volume into two parts, creates conditions for controlling the transport of substances in the pore structure of such partitions by changing the differences of pressures, concentrations, or temperatures in these adjacent parts
This paper presents the results of kinetic studies of dry methane reforming (DRM) in a reactor with a membrane catalyst in which the active substance is molybdenum carbide (Mo2C)
The transport of gases in porous materials in the modern theory of mass transfer is characterized by the Knudsen number (Kn), the numerical values of which determine the modes of gas flow in micro- and nanochannels of the pore structure of various materials

Summary

Introduction

The use of membranes and membrane catalysts (or catalytic membranes), which is always accompanied by the division of the reactor volume into two parts, creates conditions for controlling the transport of substances in the pore structure of such partitions (diaphragms) by changing the differences of pressures, concentrations, or temperatures in these adjacent parts. The use of the temperature difference as a driving force for the transport of gases in the pore structure of the membrane is still extremely rare in the membrane apparatus [5]. The modern theory, explaining the advantages of membrane catalysis over the traditional one, suggests that the main mechanism of membrane influence in a reversible reaction is the selective transport from the reaction zone of one or several products of the mixture through the pore structure [6,7,8]. In membrane gas separation processes, the transport characteristics of membranes (ideal or real separation factors) are usually determined under isothermal conditions

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