HYDROGENOLYSIS OF FORMIC ESTERS WITH HOMOGENEOUS AND HETEROGENEOUS RHENIUM CATALYSTS

The hydrogenolysis of formic esters to methanol, as the second step of the low temperature methanol synthesis from syngas, has been studied using rhenium catalysts, 'Rhenium blacks' containing reduced Re(O) species produced 'in situ' starting from soluble rhenium precursors like Re2O7 or Re-2(CO)(10) are active and generally very selective (99%) in the hydrogenation of the formyl group to methanol. Unfortunately this catalyst suffers from CO poisoning: however, the poisoning is reversible and the catalytic activity can be restored by treatment with pure hydrogen, Rhenium catalysts supported on oxides generally are less active and selective: the acid or basic centres of the support, which strongly interact with the oxophilic rhenium cations, make difficult the generation of the active Re(O) species and on other hand promote the decarboxylation of the formic ester