Mahmoud Eyas
Department of Chemical and Petroleum Engineering, United Arab Emirates University, Al-Ain, UAE.
Department of Chemical and Biomolecular Engineering, University of Delaware, Newark, DE, USA.
R Soc Open Sci. 2018 May 23;5(5):172471. doi: 10.1098/rsos.172471. eCollection 2018 May.
p-Xylene is a commodity chemical used for the manufacture of plastic bottles and textiles. For the biomass-based route from 2,5-dimethylfuran (DMF) and ethylene, the properties of the catalyst such as acidity affect product selectivity and catalyst activity. To determine the effect of acidity and extraframework position in faujasite zeolite on p-xylene selectivity, type Y (Si/Al = 40 and Si/Al = 2.55) and X (Si/Al = 1.25) zeolites containing the extraframework Lewis acids Na+, K+, Li+, Ag+ and Cu+, and a Brønsted acid-containing zeolite, HY (Si/Al = 40), were prepared by ion exchange and tested for p-xylene production under solvent-free conditions and low conversions (less than 35%). Here, it is reported that NaX zeolite catalyses DMF and ethylene conversion to p-xylene with 91% selectivity at 30% conversion, which is better than the 25% p-xylene selectivity obtained when using HY at similar conversion. A statistical model and estimation technique, ANOVA, was used to show that there is a synergistic effect between acidity and extraframework position on the rate of p-xylene production. At 7% DMF conversion, Lewis acids were more selective than the Brønsted acid tested (50 versus 30% p-xylene selectivity). p-Xylene selectivity is optimal when using Lewis acids with moderate acidity and extraframework positions located in the faujasite supercage (sites II and III) [corrected].
对二甲苯是一种用于制造塑料瓶和纺织品的商品化学品。对于由2,5-二甲基呋喃（DMF）和乙烯制备对二甲苯的生物质基路线，催化剂的性质（如酸度）会影响产物选择性和催化剂活性。为了确定八面沸石中酸度和骨架外位置对对二甲苯选择性的影响，通过离子交换制备了含有骨架外路易斯酸Na⁺、K⁺、Li⁺、Ag⁺和Cu⁺的Y型（Si/Al = 40和Si/Al = 2.55）和X型（Si/Al = 1.25）沸石以及含布朗斯特酸的沸石HY（Si/Al = 40），并在无溶剂条件和低转化率（小于35%）下测试了它们对对二甲苯生产的性能。在此报道，NaX沸石在30%转化率下催化DMF和乙烯转化为对二甲苯，选择性为91%，这优于在类似转化率下使用HY时获得的25%的对二甲苯选择性。使用统计模型和估计技术方差分析（ANOVA）表明，酸度和骨架外位置对对二甲苯生成速率存在协同效应。在7%的DMF转化率下，路易斯酸比测试的布朗斯特酸更具选择性（对二甲苯选择性分别为50%和30%）。当使用酸度适中且骨架外位置位于八面沸石超笼（位点II和III）[已校正]的路易斯酸时，对二甲苯选择性最佳。
