An experimental and first principles DFT investigation on the effect of Cu addition to Ni/Al2O3 catalyst for the dry reforming of methane

Abstract

The influence of varying Cu atomic ratios in a bimetallic Ni-Cu catalytic system for the CO2 or Dry Reforming of Methane (DRM) is investigated experimentally, in conjunction with ab-initio Density Functional Theory (DFT) and Generalized Power Law Expression (GPLE)-based mathematical modeling approaches. Among the synthesized catalysts, an 8:1 Ni:Cu ratio shows highest activity with stable H2/CO selectivity compared to its monometallic counterpart. Detailed physico-chemical characterization of the catalysts indicate that copper addition minimizes deactivation by forming a Ni-Cu alloy that increases reducibility of the NiO and limits the tendency of the active site toward coke formation. DFT calculations reveal increased energy barrier for carbon adsorption, whilst promoting facile removal of deposited carbon. GPLE analysis of the deactivation profiles suggest coking as the primary deactivation route in monometallic Ni catalyst; although much lesser in extent, deactivation of Ni8Cu1/Al2O3 catalyst is induced by both sintering and coking regimes.