摘要
以等体积浸渍法制备CuO-La2O3/SiO2催化剂,用于草酸二甲酯(DMO)加氢制乙二醇(EG)反应中,研究了不同氨(铵)源引起的溶液pH值变化对所制备催化剂结构和活性的影响,采用TEM,XRD和化学吸附等手段,表征了催化剂的结构,使用固定床反应器评价了催化剂的加氢活性。结果表明:氨源的添加除络合金属离子外,还可以调节溶液的酸碱性,从而改变Cu活性组分在催化剂中的分散度及抗烧结能力,影响催化剂的活性和稳定性;以氨水所制催化剂的加氢性能最优,DMO转化率和EG选择性分别可达98%(质量分数,下同)和97%,并且连续反应200 h后仍保持稳定;以四甲基氢氧化铵制备的催化剂虽然具有较高的Cu分散度和较小的粒径,但由于过高的pH值,使得载体发生晶型转变,导致Cu物种的还原度减小且在原位还原等热条件下迅速烧结,同时活性急剧降低。
The CuO-La2O3/SiO2-based catalyst was prepared by using the equal volume impregnation method and used in the hydrogenation-based conversion of dimethyl oxalate(DMO)to ethylene glycol(EG).The effects of the pH value changes in the solution caused by different ammonia sources on the structure and activity of the catalysts were extensively studied.Based on the results obtained through transmission electron microscope(TEM),X-ray diffraction(XRD),chemisorption characterization,and activity evaluation.The results that the addition of ammonia can not only complex metal ions,but also adjust the acidity and alkalinity of the solution,thereby changing the Cu dispersion and anti-sintering of Cu active sites.As a result,the addition of ammonia can affect the activity and stability of the obtained catalyst.Among these,the catalyst prepared by the aid of the ammonia water show the best hydrogenation performance,leading to the 98%conversion of DMO and the 97%selectivity of EG.Moreover,the prepared catalyst remained stable after the 200 h continuous reaction.Although the catalyst prepared by the aid of tetramethyl ammonium hydroxide have a higher Cu dispersion and smaller particle size,the crystal transformation of SiO2 happen due to the pH value of the solution,which lead to the decrease in the Cu reduction and rapid sintering of Cu species under the in-situ reduction and thermal conditions,resulting in a sharp decrease in the catalytic activity.
作者
刘慧敏
王美慧
于戈文
丁健
LIU Huimin;WANG Meihui;YU Gewen;DING Jian(Inner Mongolia Key Laboratory of Coal Chemical Engineering and Comprehensive Utilization, School of Chemistry and Chemical Engineering, Inner Mongolia University of Science and Technology, 014010 Baotou, China;Inner Mongolia Cooperative Innovation Center for Green Coal Mining and Green Utilization, 014010 Baotou, China)
出处
《煤炭转化》
CAS
CSCD
北大核心
2021年第1期81-88,共8页
Coal Conversion
基金
国家自然科学基金资助项目(22062018)
内蒙古自治区自然科学基金资助项目(2018BS02002).
