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Characterization of potassium-modified FAU zeolites and their performance in aldol condensation of furfural and acetone
Applied Catalysis A: General ( IF 5.5 ) Pub Date : 2017-09-18 , DOI: 10.1016/j.apcata.2017.09.017
Oleg Kikhtyanin , Yadolah Ganjkhanlou , David Kubička , Roman Bulánek , Jiří Čejka

The effects of both Si/Al ratio and preparation method (ion exchange vs. impregnation) on the physico-chemical properties of potassium modified Y zeolites were studied in detail. The samples were used as basic catalysts for aldol condensation of furfural and acetone. A relationship between physico-chemical properties and catalytic performance of potassium-containing Y zeolites was established using XRD, N2 physisorption, IR spectroscopy of adsorbed CO2‎ and CO2-TPD. Neither ion-exchange nor impregnation with KNO3 removed completely all acid sites in Y (Si/Al = 2.5). Moreover, K2O clusters were not formed under thermal activation of the samples prepared from the parent H-Y(2.5). As a consequence, both ion-exchanged and impregnated K-Y(2.5) possessed low activity in aldol condensation, but they had high ability to dehydrate reaction products. In contrast, thermal activation of USY zeolites (Si/Al = 15 and 40) impregnated with potassium resulted in the formation of K2O species which, according to CO2-IR spectroscopy and CO2-TPD, were strong basic sites. It was concluded that the lower amount of proton sites available for an ion-exchange together with the ‎larger mesopore volume and more defective crystalline framework promoted the accumulation of KNO3 in the USY zeolites during the impregnation step. Subsequently, K2O species were formed by thermal treatment. Impregnated and calcined USY zeolites possessed a superior catalytic activity in comparison with HY (Si/Al = 2.5). The presence of K2O species as strong basic sites in K-impregnated USY zeolites was favorable for both the high activity of the catalysts in aldol condensation and the occurrence of the second condensation step.



中文翻译:

钾改性的FAU沸石的表征及其在糠醛和丙酮的醛醇缩合中的性能

详细研究了硅铝比和制备方法(离子交换与浸渍)对钾改性Y型沸石理化性质的影响。样品用作糠醛和丙酮的醛醇缩合的碱性催化剂。利用XRD,N 2物理吸附,吸附的CO 2和CO 2 -TPD的IR光谱,建立了含钾Y沸石的理化性质与催化性能之间的关系。离子交换或用KNO 3浸渍都不能完全消除Y中所有的酸位(Si / Al = 2.5)。而且,K 2在由母体HY(2.5)制备的样品热活化下未形成O团簇。结果,离子交换和浸渍的KY(2.5)在醛醇缩合中均具有较低的活性,但它们具有使反应产物脱水的高能力。相比之下,浸渍有钾的USY沸石(Si / Al = 15和40)的热活化导致形成K 2 O物种,根据CO 2 -IR光谱和CO 2 -TPD,它们是强碱性位点。得出的结论是,可用于离子交换的质子位点越少,中孔体积越大,晶体框架越有缺陷,就会促进KNO 3的积累。在浸渍步骤中的USY沸石中。随后,通过热处理形成K 2 O物质。与HY(Si / Al = 2.5)相比,浸渍和煅烧的USY沸石具有优异的催化活性。K 2浸渍的USY沸石中存在强碱位的K 2 O物种,既有利于醛醇缩合催化剂的高活性,又有利于第二步缩合步骤的发生。

更新日期:2017-09-18
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