Effect of copper surface area and acidic sites to intrinsic catalytic activity for dimethyl ether synthesis from biomass-derived syngas

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.…”

“…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. Therefore, the fast methanol dehydration rate to DME on the acid sites and the suppression of copper aggregation by forming a strong metal-support interaction can significantly change the net production rate of DME and catalyst stability [3,23]. with a value of 11.7 mmol H 2 /g cat .…”

The role of external acid sites of ZSM-5 in deactivation of hybrid CuZnAl/ZSM-5 catalyst for direct dimethyl ether synthesis from syngas

“…Several possible reasons of the DME synthesis catalyst deactivation have been reported in the literature: coke deposition [26,27], Cu sintering [28] or copper and zinc ion exchange with protons of zeolite [15,29]. García-Trenco et al [29] showed the presence of isolated Cu 2+ cations occupying exchange positions in the HZSM-5 zeolite by EPR spectroscopy.…”