Hβ沸石催化剂酸性及晶粒尺寸对2-(4′-乙基苯甲酰基)苯甲酸脱水闭环反应的影响

EFFECTS OF ACIDITY AND CRYSTAL SIZE OF Hβ CATALYSTS ON THE DEHYDRATION AND RING-CLOSURE REACTION OF 2-(4′-ETHYLBENZOYL) BENZOIC ACID

采用4种不同硅/铝比(n(SiO2)/n(Al2O3))β沸石经柠檬酸改性制备了4种催化剂。采用XRF、XRD、NH3-TPD和SEM等方法对催化剂进行了表征。并将它们用于2-(4′-乙基苯甲酰基)苯甲酸(BEA)脱水闭环合成2-乙基蒽醌(2-EAQ)反应,考察其催化性能。结果表明,在较低反应温度(230℃)下,4种催化剂样品的活性差别很大,n(SiO2)/n(Al2O3)=25的催化剂样品上反应物BEA的转化率为82.2%,而n(SiO2)/n(Al2O3)=38的催化剂样品上BEA的转化率仅为30.3%;在较高反应温度(258℃)下,4种催化剂样品的活性差别较小。结果还表明,β沸石的酸性质对催化剂的催化性能有一定影响,而催化剂晶粒尺寸对其催化性能影响较大,晶粒小,扩散容易,反应活性高;反之,活性较低。

Four catalysts were prepared by using four β zeolites with different n （SiO2）/n （Al2O3） and modified by citric acid, and characterized by means of XRF, XRD, NH3-TPD and SEM. The dehydration and closure ring reaction of 2-（4′-ethylbenzoyl） benzoic acid（BEA） for the synthesis of 2-ethylanthraquinone（2-EAQ） over the four catalysts were carried out to investigate their catalytic performance. The results showed that there was great difference in catalytic activity among the four samples at lower temperature（230℃）, at which the conversion of BEA on the catalyst sample with n（SiO2）/n（Al2O3） of 25 was 82.2%,while on the catalyst sample with n（SiO2）/n（Al2O3） of 38, the conversion of BEA was only 30.3%. When the reaction temperature was 258℃, there was no obvious difference in catalytic activity among the four samples. The acidity of Hβ zeolite had some influence on the catalytic performance in the dehydration of BEA into 2-EAQ, while the crystal size of the catalysts had great influence on their performance. The smaller the crystal size of the catalyst, the easier the diffusion of the reactant and the product, which led to high catalytic performance in the dehydration of BEA.