γ-Al_2O_3负载磷钨酸催化合成乙二醇二甲醚

Catalytic synthesis of dimethoxyethane with γ-Al_2O_3 supported phosphotungstic acid

采用过量浸渍法制备γ-Al_2O_3负载磷钨酸(PW)系列催化剂,并在固定床反应器上考察了系列催化剂对二甲醚(DME)与环氧乙烷(EO)合成乙二醇二甲醚(DMEG)反应性能的影响;优化了PW负载量、反应温度、反应压力、原料配比以及气态空速等反应条件。采用XRD和NH_3-TPD方法表征了催化剂的分散性及酸性。表征结果显示,低PW负载量试样在γ-Al_2O_3表面高度分散,高PW负载量试样在γ-Al_2O_3表面聚集形成晶体;PW负载量为40%(w)的试样在γ-Al_2O_3表面呈现最大分散,40%PW/γ-Al_2O_3催化剂具有最大酸量。实验结果表明,40%PW/γ-Al_2O_3催化EO与DME合成DMEG反应,在n(DME)∶n(EO)=3、反应温度348 K、GHSV=1 500 h^(-1)、反应压力0.60 MPa的最优反应条件下,EO转化率为100%,DMEG选择性可达52.1%。

Theγ-Al2O3 supported phosphotungstic acid(PW)catalysts were prepared by excess impregnation method.The catalytic performance was tested during synthesis of dimethoxyethane(DMEG)with ethylene oxide(EO)and dimethyl ether(DME)in a fixed-bed reactor.The reaction conditions were optimized such as loading amount of PW,reaction temperature,reaction pressure,ratio of raw materials and gaseous hourly space velocity.Characterization of the catalyst’s dispersion and acidity were performed by XRD and NH3-TPD techniques respectively.The characterization results showed that high dispersion occurred on the surface ofγ-Al2O3 at low PW loading and crystals were formed at high PW loading.The sample with PW loading amount of 40%(w)showed maximum dispersion on the surface ofγ-Al2O3,and 40%PW/γ-Al2O3 showed the largest acid amount.Under optimal reaction conditions of 40%PW/γ-Al2O3,reaction temperature 348 K,reaction pressure 0.60 MPa,n(DME)∶n(EO)3 and GHSV 1 500 h-1,conversion of EO reached 100%and selectivity of DMEG reached 52.1%.