Effects of metal promotion on the performance, catalytic activity, selectivity and deactivation rates of Cu/ZnO/Al2O3 catalysts for methanol synthesis

Differences in Deterioration Behaviors of Cu/ZnO/Al2O3 Catalysts with Different Cu Contents toward Hydrogenation of CO and CO2

“…This can be explained by not only the agglomeration of metal and metal oxide particles but also the coke formation (carbon atom) that can cover the active site, showing the loss of active surface, resulting in the deactivation CZA catalysts during the CO and CO 2 hydrogenation. In fact, several authors have proven that carbon deposition on catalysts providing the active site is inactive and decreases the catalytic activity, 28 , 50 according to the catalytic activity results in our previous work. 3 In addition, the carbon deposition results as shown in Table 4 (from our previous report, 3 ) provide the content of metal elements including Cu, Zn, Al, and C in fresh and spent CZA catalysts.…”

“…From the results of ZnO crystallite size, the ZnO crystallite sizes of sCZA-L­(CO) and sCZA-H­(CO) were slightly larger those of sCZA-L­(CO 2 ) and sCZA-H­(CO 2 ), suggesting a decrease in the crystallite size of Cu, as shown in Table . A change in surface morphology occurred, which likely influenced the stabilization of Cu 0 species in partially different oxidation states according to several authors. , It is well known that the CO in the feed of hydrogenation results in the formation of inactive Cu sites; hence, the unstable Cu 0 site and smaller crystallite size of Cu 0 can be obtained from sCZA-L­(CO) and sCZA-H­(CO) …”

“…A change in surface morphology occurred, which likely influenced the stabilization of Cu 0 species in partially different oxidation states according to several authors. 28 , 29 It is well known that the CO in the feed of hydrogenation results in the formation of inactive Cu sites; hence, the unstable Cu 0 site and smaller crystallite size of Cu 0 can be obtained from sCZA-L(CO) and sCZA-H(CO). 28 …”

“… 28 , 29 It is well known that the CO in the feed of hydrogenation results in the formation of inactive Cu sites; hence, the unstable Cu 0 site and smaller crystallite size of Cu 0 can be obtained from sCZA-L(CO) and sCZA-H(CO). 28 …”

“…It revealed that the CZA-H catalyst exhibited high catalytic activity in both CO and CO 2 hydrogenation reactions due to the high Cu content and high Cu dispersion (as seen in Table 3 ), which retarded the carbon formation (anti-coking ability). 17 , 28 In addition, the deactivation of CZA catalysts under both CO and CO 2 hydrogenation reactions was observed, in which the spent catalysts after CO 2 hydrogenation [sCZA-L(CO 2 ) and sCZA-H(CO 2 )] presented large amounts of carbon deposition when compared to those after CO hydrogenation [sCZA-L(CO) and sCZA-H(CO)]. This is probably due to CO 2 hydrogenation producing more CO and H 2 O [reverse water-gas-shift (RWGS)], which deactivates the catalysts.…”