P对Cu/Al2O3催化剂结构及其催化甘油氢解反应性能的影响

采用分步浸渍法制备了P改性的Cu/Al2O3催化剂,利用N2吸附-脱附、X射线衍射、红外光谱、紫外-可见光谱、H2程序升温还原、NH3程序升温脱附和N2O解离吸附等方法对催化剂进行了表征,考察了P含量及浸渍次序对催化剂结构及其催化甘油氢解反应性能的影响.结果表明,先浸渍P再浸渍Cu时,所制Cu/Al2O3催化剂酸性较高,同时还促进了Cu的分散.随P含量的增加,催化剂的酸量及Cu分散度提高,并且Cu与P物种的相互作用增强;然而,P含量较高时会覆盖Cu,使暴露的Cu表面降低.先浸渍Cu后浸渍P时,尽管也提高了相应催化剂的酸性,但对Cu分散的影响不大,并且还会覆盖Cu使暴露的Cu表面明显降低.先浸渍P明显提高了Cu/Al2O3上甘油氢解反应性能.在220oC,3MPa,质量空速2h?1以及H2/甘油摩尔比20的条件下,当P含量由0增加至6%时,甘油转化率从17.1%升至95.0%,1,2-丙二醇选择性从83.7%升至97.2%.这可归因于催化剂酸性的提高及Cu与P间的相互作用.

Effect of Phosphorus on Structure and Performance of Cu/Al2O3 Catalysts for Hydrogenolysis of Glycerol

Phosphorus(P) modified Cu/Al2O3 catalyst was prepared by the successive impregnation method.The physicochemical properties of the catalyst were studied by means of N2 adsorption-desorption,X-ray diffraction,infrared spectroscopy,UV-visible diffuse reflectance spectroscopy,H2 temperature-programmed reduction,NH3 temperature-programmed desorption,and dissociative N2O adsorption.The effects of the P content and the impregnation sequence on the structure and the performance of the catalyst for the hydrogenolysis of glycerol to 1,2-propanediol(1,2-PDO) were discussed.The addition of P to Cu/Al2O3 enhanced the acidity and Cu dispersion,especially when P species was impregnated prior to Cu.Also,there was a strong interaction between P and Cu species.However,the strong interaction leads to the coverage of Cu atoms with the P species at high P content.The coverage may be more serious when the P species was added after Cu to the catalyst.In the hydrogenolysis of glycerol,the addition of P prior to Cu remarkably promoted the catalytic performance of Cu/Al2O3.Under the conditions of 220 oC,3.0 MPa,space velocity of 2.0 h?1,and the H2/glycerol molar ratio of 20,as the P content increased from 0 to 6%,the glycerol conversion and the 1,2-PDO selectivity increased from 17.1% to 95.0% and from 83.7% to 97.2%,respectively.The promotion effect of P on the performance of Cu/Al2O3 is attributed to the increase of catalyst acidity as well as the strong interaction between Cu and P species.