Sol-derived AuNi/MgAl2O4 catalysts: Formation, structure and activity in dry reforming of methane

• Metal sol synthesis produces dispersed Ni–Au particles.
• Au enriched and Ni enriched alloyed particles are formed over MgAl2O4 after reduction.
• Au influences the dry reforming activity of the Ni catalyst and promotes the RWGS reaction.
• Less but more interacting carbon is formed during the reaction over the Au doped Ni catalysts.

Ni nanoparticles doped with different amount of gold were supported on MgAl2O4 by deposition from aqueous metal sol producing a series of catalysts with different Au content. The sol procedure was allowed to obtain dispersed metal particles with different composition. The particle size and the particle composition of the sol were maintained even after being deposited on the support. The catalysts, characterized by several techniques such as TPR, XPS, XRD, TEM, HRTEM and EELS at the different stages of their life exhibited significant structural modification. In particular, thermal treatments in reducing and oxidizing environment produced NiAu alloy phases and NiO surface segregation, respectively. When testing for methane dry reforming with CO2 in temperature ramped reaction, the monometallic nickel catalyst was more active at lower temperature whereas the bimetallic catalysts were more active at higher temperature. The presence of gold slightly affected the CO/H2 ratio due to the occurrence of parallel reactions such as the reverse water gas shift reaction (RWGS). Both types of catalysts, monometallic and bimetallic ones, deactivated a little with time but the degree of activity loss was not in straightforward relation with Au content due to the different effect of gold on the stability and on the amount of carbon formation.

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