Deactivation of Cu/ZnO/Al2O3 methanol synthesis catalyst by sintering

The loss of Cu/ZnO/Al2O3 activity for methanol synthesis has been studied o ver 50 h under a range of synthesis gas compositions. Experiments have been carried out at differential and finite conversions in order to compare dea ctivation under the pure feed to that in the presence of products. Under di fferential conversion, it was found that the degree of deactivation was rel ated to the CO concentration, being particularly acute under CO/H-2. Under CO/H-2, there was a close correlation beta een activity loss and loss of Cu surface area, suggesting that an important cause of deactivation is sinter ing, which may be promoted by over-reduction of Cu. At finite conversion wi th CO/H-2 feed the deactivation was less severe. This lower rate of deactiv ation is most likely due to exposure of the catalyst to products that can s tabilize oxidized Cu species. Interestingly, under CO2/H-2, the deactivatio n was negligible at differential conversion. However some deactivation was apparent at finite conversion. The exposure of the catalyst to the products , CO and water, at finite conversion can explain these results.