Effects of Cu–ZnO Content on Reaction Rate for Direct Synthesis of DME from Syngas with Bifunctional Cu–ZnO/γ-Al2O3 Catalyst

K-promoted NiMo catalysts supported on activated carbon for the hydrogenation reaction of CO to higher alcohols: Effect of support and active metal

“…Wu et al [20] reported correlation between acid site concentration and conversion for Cu Ni catalysts supported on different supports with varying acidity. Also Jeong et al [58] proved a direct correlation between the catalyst acid sites and CO conversion, in agreement with Das et al [59] who claim that CO absorbs on weak acid sites in order to carry out the Fischer-Tropsch reaction, thus increased activity with acidity is observed. However, to the best of our knowledge, such correlations have not been identified for CO activation on Mo-based catalysts.…”

The role of the acidity of alumina prepared by aluminum-carbon black composite for CO hydrogenation to dimethyl ether on hybrid Cu–ZnO–Al2O3/alumina

“…The direct relationships of the total amount of acid sites and the surface area of metallic copper to the catalytic activity for a direct synthesis of DME from syngas have been well reported in our previous works [7,12,14,23]. In general, a larger surface area of metallic copper and a proper amount of acid sites are known to be responsible for a higher CO conversion, and the stability of hybrid catalysts has been generally known to be related with a stability of metallic copper species on the acid sites [3,7,18,19,23,24]. The NH 3 -TPD patterns on the mesoporous c-Al 2 O 3 supports and the hybrid CZA/Al 2 O 3 catalysts are respectively displayed in the supplementary Figs.…”

“…S5 and S6, and the results are summarized in Table 2. Generally, the hybrid catalysts show three characteristic NH 3 desorption peaks assigned T 1 (T \ 300°C), T 2 (300°C \ T \ 500°C), T 3 (T [ 500°C), and they can be assigned to weak acid sites, strong acid sites and water desorption from the main frameworks of metal oxides, respectively [3,7,8,22,23]. The observed two characteristic desorption peaks on the c-Al 2 O 3 supports at around 200 and 350°C can be assigned to the weak and strong acid sites.…”

“…3 and summarized in Table 2. The reducibility of copper oxide on the fresh hybrid catalysts can largely alter catalytic activities of a first step CO hydrogenation to methanol, which is a favorable reaction on the metallic copper sites by dissociative adsorption of CO molecules, and the second step of the subsequent dehydration of methanol to DME through a favorable route of the simultaneous two molecule adsorptions on the acid sites compared with the activation of one methanol molecule adsorption [3,18,23]. Although the possible coke formation by the strong adsorption of the methoxy intermediate on the metallic copper can also enhance the catalyst deactivation [19], an aggregation of metallic copper crystallites can be more important factor for the deactivation by decreasing the surface area of active metallic copper.…”

“…DME can be commercially synthesized through a two-step process: syngas hydrogenation to methanol on the copper-based catalyst and the subsequent dehydration of methanol to DME on the solid acid Al 2 O 3 or zeolites [1,2]. However, a one-step direct synthesis of DME from syngas by using hybrid (or bifunctional) catalysts has also been largely investigated due to its higher equilibrium conversion of CO by the concomitant water-gas shift reaction activity and an efficient utilization of syngas having a lower H 2 /CO ratio below one, especially for the biomass-derived syngas [1][2][3][4]. Generally, the reaction rate of the dehydration of methanol has been known to be faster than that of the hydrogenation of CO to methanol through the following reactions [3] with lower exothermicity.…”