Effect of preparation procedures on the activity of supported palladium/lanthanum methanol decomposition catalysts

A series of palladium catalysts promoted with lanthanum were prepared on a silica support and the activities of these catalysts examined for the decom position of methanol into CO and H-2. The preparation procedure and the La2 O3/Pd weight ratio of these Pd/La2O3/SiO2 catalysts (5 wt.% Pd) was found t o be important for high catalytic activities. If Pd is deposited after La2O 3 using a precipitation procedure, the methanol decomposition activity incr eases up to a La2O3/Pd weight ratio of 1.0. The optimized weight ratio for the methods of co-precipitation and co-impregnation were found to be 0.8 an d 0.5, respectively. Relatively low activities are obtained if a sequential procedure with La2O3 deposition in the final step is applied. The effect o f the preparation procedure and La2O3/Pd weight ratio on activity of the re sulting catalysts can be explained by: (i) the amount of Pd particles in co ntact with La2O3 moieties, positively affecting the activity, and (ii) the extent of coverage of Pd particles by La2O3 patches, negatively affecting t he activity. (C) 2001 Elsevier Science B.V. All rights reserved.