ZnO逆修饰小尺寸Cu/SiO2催化剂及其在CO2加氢制甲醇中的应用  

Inverse Decoration of ZnO on Small-Sized Cu/Sio2 with Controllable Cu-ZnO Interaction for CO2 Hydrogenation to Produce Methanol

作　　者：吕翰林 胡兵[2] 刘国亮[2] 洪昕林[2] 庄林 Hanlin Lyu;Bing Hu;Guoliang Liu;Xinlin Hong;Lin Zhuang(Institute for Advanced Studies,Wuhan University,Wuhan 430072,P.R.China;College of Chemistry and Molecular Sciences,Wuhan University,Wuhan 430072,P.R.China)

机构地区：[1]武汉大学高等研究院,武汉430072 [2]武汉大学化学与分子科学学院,武汉430072

出　　处：《物理化学学报》2020年第11期142-150,共9页Acta Physico-Chimica Sinica

基　　金：financially supported by the National Natural Science Foundation of China(21872106,21603244);the Fundamental Research Funds for the Central Universities,China(2042019kf0019)。

摘　　要：Cu-ZnO催化剂广泛应用于CO2还原制甲醇,但是如何构建具备强金属-载体相互作用、粒径可控的Cu-ZnO催化剂仍然富有挑战性。本文发展了一种利用高比表面硅酸铜前驱物合成小粒径且组分相互作用可控的Cu-ZnO/SiO2催化剂的方法,制备得到一系列ZnO含量不同的Cu-ZnO/SiO2催化剂,并对其CO2加氢制甲醇的催化活性进行系统考察。发现在523 K的条件下,甲醇选择性由未加入ZnO的20%提高至ZnO含量为14%时的67%。催化剂活性与ZnO含量之间呈现火山型关系,在ZnO含量为7%,温度为543 K,H2/CO2压力为4.5 MPa时,甲醇时空产率(STY)最优,为244 g·kg^-1·h^-1。此外,本文探究了催化剂中Cu与ZnO的协同效应,发现ZnO可以显著增强Cu的催化活性,但过量ZnO的引入会使Cu颗粒粒径增长,降低催化剂中的总反应位点数,进而影响催化剂催化活性。Cu-ZnO is broadly used as a catalyst in CO2 reduction to produce methanol, but fabricating small-sized CuZnO catalysts with strong Cu-ZnO interactions remains a challenge. In this work, a simple, low-cost method is proposed to synthesize small-sized Cu-ZnO/SiO2 with high activity and controllable Cu-ZnO interactions derived from copper silicate nanotubes. A series of Cu-ZnO/SiO2 samples with different amounts of ZnO were prepared. The activities of the as-prepared catalysts for methanol synthesis were tested, and the results revealed a volcano relationship with the weight fraction of ZnO. At 523 K, the methanol selectivity increased from 20% to 67% when 14% ZnO was added to the Cu/Si O2 catalyst, while the conversion of CO2 increased first and then decreased with the addition of ZnO. The optimum space time yield(STY) of 244 g·kg-1·h-1 was obtained on C-Si O2-7%ZnO at 543 K under 4.5 MPa H2/CO2. Furthermore, the synergistic effect of Cu and ZnO was studied by high resolution transmission electron microscopy(HRTEM), powder X-ray diffraction(XRD), Xray photoelectron spectroscopy(XPS), in situ diffuse-reflectance infrared Fourier transform spectroscopy(DRIFTS), and temperature-programmed reduction(TPR) analyses. The HRTEM images showed that the Cu particles come in contact with ZnO more frequently with increased addition of ZnO, indicating that the catalysts with higher ZnO contents have a greater probability of formation of the Cu-ZnO interface, which promotes the catalytical activity of Cu-ZnO/Si O2. Meanwhile, the HRTEM images, XRD patterns, and TPR results showed that the addition of excess ZnO leads to an increase in the size of the Cu particles, which in turn decreases the total number of active sites and further degrades the activity of the catalysts. The activation energy(Ea) for methanol synthesis and reverse water gas shift(RWGS) was calculated based on the results of the catalytical test. With the addition of ZnO, Ea for methanol synthesis decreased from 72.5 to 34.8 k J·mol-1, while that for RWGS incre

关 键 词：CO2还原制甲醇 Cu-ZnO催化剂 硅酸铜 Cu-ZnO协同效应 

分 类 号：O643[理学—物理化学]