Ultra-durable Ni-Ir/MgAl2O4 catalysts for dry reforming of methane enabled by dynamic balance between carbon deposition and elimination

Abstract

Carbon deposition is the main cause for the catalyst deactivation of methane dry reforming, and researchers are committed to exploring effective catalyst systems with zero carbon deposition in order to achieve a practically long lifetime. In this work, we propose an equilibrium theory with matched rates of CH 4 dissociation and CO 2 activation to establish a balance between carbon deposition and carbon elimination and construct highly dispersed Ni-Ir/MgAl 2 O 4 alloy catalysts accordingly, where Ni activated CH 4 , MgAl 2 O 4 adsorbed CO 2 to form surface carbonates, and Ir effectively used the carbonates to eliminate carbon species generated by CH 4 dissociation. Theoretical assessment further unveiled that the preferred CO 2 activation on Ir over Ni is derived from its stronger oxophilicity. With an optimal Ni/Ir atomic ratio of 1/2, high activity and long-period stability (600 h) with zero carbon deposition were obtained concurrently for dry reforming of methane at industrially relevant temperature (650°C). • Ultra-durable highly dispersed Ni-Ir/MgAl 2 O 4 alloy catalysts • Zero carbon deposition for dry reforming of methane for 600 h • A balance mechanism between the active sites and the carbon deposits-eliminations Dry reforming of methane (DRM) can effectively use the greenhouse gas CO 2 and CH 4 to produce syngas (a mixture of CO and H 2 ), which acts as a key platform for the industrial production of fuels and chemicals. Carbon deposition is the main cause for the catalyst deactivation of DRM, so core of the stable DRM reaction is the equilibrium between efficient CH 4 dissociation and CO 2 activation. Here, we design an ultra-stable Ni-Ir/MgAl 2 O 4 alloy system for DRM, which has high activity and long-period stability (600 h) with zero carbon deposition obtained concurrently for DRM. In this system, Ni plays the role of activating CH 4 , and MgAl 2 O 4 adsorbs CO 2 to form carbonate species that can be effectively used by Ir to eliminate carbon species generated from CH 4 activation on Ni. We proposed a balance mechanism between the active sites and the carbon deposits-eliminations. Our results would inspire new ideas on the development of novel catalysts for activation of inert C 1 molecules. The highly dispersed Ni-Ir/MgAl 2 O 4 alloy catalyst has high activity and long-period stability (600 h) with zero carbon deposition for dry reforming of methane at industrially relevant temperature (650°C). This special catalytic system follows a balance mechanism between the active sites and the carbon deposits-eliminations, where Ni played the role of activating CH 4 and MgAl 2 O 4 adsorbed CO 2 to form carbonate species that can be effectively used by Ir to eliminate carbon species generated from CH 4 activation on Ni.