CaTiO3催化正戊醛羟醛自缩合反应性能

CaTiO3 Catalyzed Self-Condensation of n-Valeraldehyde

摘要:

为克服液体碱催化剂难以回收再利用、腐蚀设备、污染环境等问题，选择酸碱活性位点丰富的钙钛矿氧化物，用于催化正戊醛羟醛自缩合反应。采用XRD、SEM、NH3-TPD、CO2-TPD等方法对催化剂进行表征，结合活性评价研究了催化剂制备条件和反应条件的影响，明晰了催化剂酸碱活性位点之间的作用关系。结果表明，采用溶胶-凝胶法，在分散剂聚乙二醇（PEG-1000）加入量为2.5%（以硝酸钙的质量为基准，下同）、500 ℃焙烧1 h条件下，可以得到纯相CaTiO3，此时其分散性和催化性能也较优。CaTiO3催化正戊醛羟醛自缩合反应的适宜反应条件为：反应温度190 ℃，反应时间8 h，催化剂加入量15%（以正戊醛的质量为基准，下同）。在该反应条件下，正戊醛的转化率可达97.0%，产物2-丙基-2-庚烯醛的选择性可达99.1%。CaTiO3催化剂使用4次，其催化活性无明显下降。分别以NH3和CO2为探针分子选择性中毒CaTiO3催化剂的活性位点，结果表明，酸碱活性位点之间存在明显的协同催化作用。

Abstract:

In order to overcome the disadvantages of difficult recycling, equipment corrosion and environmental pollution, perovskite oxides with abundant acid-base active sites were selected to catalyze n-valeraldehyde self-condensation. The catalysts were characterized by XRD, SEM, NH3-TPD and CO2-TPD. Combined with the activity evaluation, the influences of catalyst preparation conditions and reaction conditions were investigated, and the interaction between acid and base active sites was clarified. The results show that pure phase CaTiO3 with better dispersion and catalytic performance can be obtained by sol-gel method under the optimal condition: a dosage of dispersant polyethylene glycol (PEG-1000) = 2.5%(benchmarked against the quality of calcium nitrate, the following is the same), calcined at 500 ℃ for 1 h. The suitable n-valeraldehyde self-condensation conditions catalyzed by CaTiO3 were determined as follows: a reaction temperature of 190 ℃, a reaction time of 8 h and a weight percentage of catalyst = 15% (benchmarked against the quality of n-valeraldehyde, the following is the same). Under the above conditions, the conversion of n-valeraldehyde and the selectivity of 2-propyl-2-heptenal reached 97.0% and 99.1% separately. After being reused for four times, the catalytic performance of CaTiO3 had no significant decrease. NH3 and CO2 were used as probe molecules to selectively poison the active sites of CaTiO3 catalysts, respectively, and the results indicate that there is an obvious synergistic catalysis between the acid and base active sites.