A porous lithium aluminate carrier for catalyst has a spinel structure which has a mean pore diameter in the range of 40 to 1,000 angstroms and a total pore volume in the range of 0.2 to 1.5 mL/g. The porous lithium aluminate carrier can be used for supporting a catalyst compound containing a platinum group metal. The catalyst on the carrier can be favorably employed for promoting catalytic reaction of a nitrite ester and carbon monoxide to prepare a carbonate diester such as dimethyl carbonate.