Cu-based catalysts play pivotal role in many industrial processes, however, its application under high temperature is restricted due to the low Tammann temperature of Cu. Improving the stability and activity of Cu-based catalysts at high temperature is a challenge. In this work, a stable Cu/ZnO@SiO 2 catalyst was prepared, in which silicon was introduced into CuZn-BTC precursor via a steam-assisted hydrolysis method before calcination and reduction. Characterizations found that Cu/ZnO@SiO 2 catalyst prepared via above strategy possesses increased surface area, more exposed active sites and excellent stability for ethanol dehydrogenation than Cu/ZnO (prepared from CuZn-BTC without SiO 2 ). It was confirmed that the space-time yield of acetaldehyde reached 9.0 g-acetaldehyde/g-cat/h, and Cu/ZnO@SiO 2 could maintain its activity within 200 h at 350 °C due to the ZnO decorated Cu particles (Cu/ZnO) were encapsulated in the octahedral shaped SiO 2 hollow.
CO 2 hydrogenation is one of the reactions to realize effective utilization of CO 2 , while Cu-Zn based catalyst is widely adopted for CO 2 hydrogenation to value-added chemicals like methanol. However, this process is less efficient since the poor performance of catalyst due to its poor dispersion or sintering issue. In this study, three kinds of SiO 2 supports (SBA-15, MCM-41 and Nano-SiO 2 ) with different porous structure were conducted to load same amount of 5.0 wt% Cu-ZnO active component (the molar ratio of Cu/Zn is 2.0), which were further applied for CO 2 hydrogenation. All catalysts were characterized chemically, morphologically and structurally by different techniques such as XRD , BET, TEM , H 2 -TPR and CO 2 -TPD. The results showed that the structure of three catalysts was basically preserved and the surface aera kept stable after loading active component, while the active component had the best dispersion when SBA-15 was used as the support and space-time yield of methanol is about 705.6 g MeOH •kg Cu −1 •h −1 ,which is higher than that of Nano-SiO 2 -5% (532.9 g MeOH •kg Cu −1 •h −1 ) and MCM-41–5% (213.2 g MeOH •kg Cu −1 •h −1 ). Due to the confined effect of mesoporous channel structure provided by SBA-15 support, the Cu-Zn interaction could be significantly enhanced with increasement of medium and strong alkaline sites, further improving CO 2 activation ability. This work provides a useful strategy to improve the catalytic efficiency of classical Cu-Zn catalyst for the CO 2 hydrogenation process.
Xinlei Wang,Kui Ma,Lihong Guo,Ye Tian,Qingpeng Cheng,Xueqin Bai,Jingjing Huang,Tong Ding,Xingang Li
Herein, we reduced the ZnO-modified copper phyllosilicate to synthesize a series of Cu/ZnO/SiO 2 catalysts ( x CuZn/SiO 2 ) which were mixed with γ-Al 2 O 3 for dimethyl ether steam reforming (DME SR). The structure and the formation of copper phyllosilicate were systematically characterized by nitrogen adsorption, XRD and IR. The novel synthetic route led to the remarkably high dispersion of copper species and adjustable Cu 0 /Cu + ratio on the catalyst surface, resulting in the superior catalytic performance for DME SR. The amount of Cu 0 and Cu + sites on the catalyst surface was dramatically affected by ZnO loading, and the turnover frequency results indicated that the 4CuZn/SiO 2 catalyst (Cu/Zn = 4) with the Cu 0 /Cu + ratio of 1 showed the highest catalytic performance. The XPS, H 2 -TPR and TEM results revealed the existence of strong interaction between Cu species and ZnO on the reduced 4CuZn/SiO 2 catalyst, which suppressed the reverse water-gas reaction and prevented the sintering of copper.
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