Preparation of PtReAl2O3 catalysts by surface redox reactions II. Influence of the acid medium on Re deposition and PtRe interaction Original Research Article

Bimetallic PtReAl2O3 catalysts are prepared under hydrogen atmosphere by a surface redox reaction between hydrogen adsorbed on a parent platinum/alumina catalyst and the perrhenate ion ReO4−. This reaction, called catalytic reduction, occurs only in an acidic medium, a maximum rhenium deposition appearing as a function of the concentration of the acid solution. The preparation of bimetallic PtReAl2O3 catalysts by catalytic reduction of the rhenium salt on a highly dispersed platinum catalyst leads to bimetallic particles after activation by direct reduction under hydrogen. The calcination at 450°C partially destroys the interaction between the two metals, the effect being more obvious on chloride containing samples. The activation procedure produces the reverse effect at high rhenium loading deposited on a parent catalyst of low dispersion.