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作为聚对苯二甲酸丙二醇酯(PTT)的不可替代原料,1,3-丙二醇(1,3-PDO)广泛应用于聚酯、树脂、化妆品、润滑剂和制冷剂等领域.采用丙二酸二乙酯(DEM)一步加氢合成1,3-PDO可避免传统化学工艺中醛类副产物的生成和生物法中产品纯度不高的问题,进而满足下游PTT的品质要求.Cu/SiO_2催化剂因铜与载体间的强相互作用以及硅胶的弱酸性有利于催化活性中心的建立而被广泛应用于气相加氢反应,可以选择性地活化C.O键而不活化C.C键.因此,本文将Cu/SiO_2催化剂应用于DEM加氢反应,重点考察了焙烧温度对催化剂结构与性能影响的本质原因.采用蒸氨法制备Cu/SiO_2催化剂,将一定量氨水滴加到硝酸铜水溶液中形成铜氨溶液后滴加JN-30硅溶胶,经老化、过滤、洗涤、烘干、焙烧、压片成型后得到40.60目的催化剂.将不同温度(623.1023 K)焙烧的Cu/SiO_2催化剂装填入自制连续高压固定床反应器中进行DEM加氢反应,并采用N_2物理吸脱附、电感耦合等离子体发射光谱、N_2O化学吸附、X射线衍射、傅里叶红外光谱、H_2程序升温还原(TPR)、透射电镜及X射线光电子能谱等手段对不同温度焙烧催化剂进行表征.结果表明,在723 K焙烧的催化剂具有最大的比表面积和最均一的孔径分布,其铜组分分散均匀,活性铜表面积最大,焙烧后可以形成最多的页硅酸铜,导致还原后Cu~+/Cu~0比例较高.在该催化剂作用下,于473 K、2.0 MPa、氢酯摩尔比330和液体空速1.8 h–1条件下,DEM转化率为90.7%,1,3-PDO选择性为32.3%.焙烧温度对Cu/SiO_2催化剂组成、织构、结构、形貌及还原后的价态有较大影响.在焙烧温度为623.1023 K时,低温焙烧有利于生成页硅酸铜,而高温焙烧则有利于形成CuO.在焙烧温度升高的过程中,铜组分形态会发生较大变化,在623.723 K焙烧的催化剂中页硅酸铜含量不断增加;继续升高温度至823 K,页硅酸铜含量减少,但是分散变差,导致铜的比表面积、孔体积和孔径最小;进一步升高温度至923 K,页硅酸铜消失,CuO分散均匀,H_2-TPR的还原峰窄且对称;当温度升高到1023 K时,铜晶体迅速长大而较难被还原
As an irreplaceable raw material of polytrimethylene terephthalate (PTT), 1,3-propanediol (1,3-PDO) is widely used in the fields of polyester, resin, cosmetics, lubricant and refrigerant. The one-step hydrogenation of diethyl ester (DEM) to 1,3-PDO can avoid the formation of aldehyde by-products in traditional chemical processes and the low purity of products in biological processes, thus meeting the quality requirements of downstream PTTs.Cu / SiO 2 catalyst Due to the strong interaction between copper and support and the weak acidity of silica gel, it is widely used in the gas-phase hydrogenation reaction and can selectively activate CO bond without activating CC bond.Therefore, Cu / SiO 2 catalyst was applied to the hydrogenation reaction of DEM, focusing on the nature of the influence of calcination temperature on the structure and properties of the catalyst. The Cu / SiO 2 catalyst was prepared by the steam ammonia method and a certain amount of ammonia was added dropwise to the aqueous copper nitrate solution to form the copper ammonia solution 40.60 mesh catalyst was obtained after aging, filtering, washing, drying and calcining.The Cu / SiO 2 catalyst calcined at different temperature (623.1023 K) was loaded into self-made continuous high pressure fixed bed reaction (Superscript TM), and the hydrogenation of DEM was carried out. The results of N 2 physisorption, inductively coupled plasma atomic emission spectroscopy, N 2 O chemisorption, X - ray diffraction, Fourier transform infrared spectroscopy, TPR, TEM and X - The results show that the catalyst calcined at 723 K has the largest specific surface area and the most uniform pore size distribution, the copper component is dispersed uniformly, the surface area of the active copper is the largest, and the maximum can be formed after the calcination Of copper silicate, resulting in a higher Cu ~ + / Cu ~ 0 ratio after reduction.Under this catalyst, under the conditions of 473 K, 2.0 MPa, hydrogenate molar ratio 330 and liquid space velocity 1.8 h-1, The conversion rate was 90.7% and the selectivity of 1,3-PDO was 32.3%. The calcination temperature had a great influence on the composition, texture, structure, morphology and the valence state of Cu / SiO 2 catalyst. At the calcination temperature of 623.1023 K , Calcination at low temperature is beneficial to the formation of Cu-Cu sheet, while calcination at high temperature is conducive to the formation of CuO.When the calcination temperature increases, the morphology of Cu component changes greatly. In the calcined 623.723 K catalyst, Copper content continues to increase; continue to rise When the temperature is up to 823 K, the content of copper silicate decreases, but the dispersion deteriorates, resulting in the smallest specific surface area, pore volume and pore size. When the temperature is further increased to 923 K, the copper silicate disappears and the CuO disperses evenly. Of the reduction peak is narrow and symmetrical; when the temperature rises to 1023 K, the copper crystals grow rapidly and are more difficult to be reduced