NaBH4处理LaCuZnX(X=Zr、Al、Zr+Al)(类)钙钛矿型催化剂及其CO2加氢合成甲醇性能的研究

LaCuZnX (X=Al, Zr, Al+Zr) perovskite-like catalysts treated by NaBH4 and their catalytic performance for CO2 hydrogenation to methanol

    摘要
  • 摘要: 通过并流沉淀法制备出La：Cu：Zn：X（X=Zr、Al、Zr+Al）（类）钙钛矿型催化剂，并使用NaBH4作为还原剂进行液相还原。将催化剂装填在固定床反应器中并用于CO2加氢制甲醇的性能评价，并通过一系列表征方法对催化剂的物化性能进行了测试。结果表明，所制备的催化剂主要具有La2CuO4（类）钙钛矿结构，并且在该结构中掺入元素后将导致（类）钙钛矿结构的空间扭曲。经NaBH4还原后，结构中存在金属铜物种和部分未还原的高价态铜物种，在反应过程中会发生高价态铜物种的还原。相比于LaCuZn催化剂，Al元素的引入提高了CO2的转化率，Zr元素的引入，降低了催化剂的催化活性，Al和Zr元素同时引入提高了CO2转化率和甲醇的收率。LCZA催化剂CO2转化率最高，LCZ催化剂甲醇选择性最高，LCZZA催化剂甲醇时空收率最高。CO2转化率和催化剂的Cu的比表面积、Cu的分散度、（Cuα++Cu0）/Cutotal呈正相关；催化剂Cuα+的结合能越远离Cu+，相应催化剂的甲醇选择性越高。

     

    Abstract: La:Cu:Zn:X (X=Zr, Al, Al+Zr) perovskite-like catalysts were prepared by coprecipitation method followed by liquid phase reduction by NaBH4. The physicochemical properties of the catalysts were tested by a series of characterization methods, and the catalysts were tested for methanol synthesis from CO2 hydrogenation in a fixed-bed reactor. The results showed that the as-prepared catalysts were mainly composed of La2CuO4 perovskite-like crystal structure and doping of elements led to the spatial distortion of the perovskite-like structure. After reduction by NaBH4, metal copper species and some high-valence copper species were found, which could be further reduced during the reaction. The CO2 conversion was positively correlated with the Cu surface area, the dispersion of Cu, and the (Cuα++Cu0)/Cutotal of the catalyst. The higher methanol selectivity was obtained when Cuα+ binding energy was farther away from Cu+ binding energy. LCZA had the highest CO2 conversion, LCZ catalyst possessed the highest methanol selectivity, and LCZZA catalyst presented the optimal methanol space time yield.

     

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