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合成了一种具有优良择形催化性能的有机胺型分子筛(DG型)。其x光衍射图虽然具有ZSM-5的特征峰,但其吸附性能却不同于ZSM-5。它不仅是憎水的,吸附正己烷量比吸附水量高,而且吸附二甲苯三种异构体的能力悬殊很大(吸附对二甲苯能力很强,少量吸附间二甲苯,而几乎不吸附邻二甲苯)。与此相反,ZSM-5对三种异构体都有很好的吸附能力。DG型分子筛晶粒大小为17～18μ,经用NH_4NO_3交换和在540℃下焙烧成为HDG甲苯歧化催化剂。它具有很高的选择生成对二甲苯的能力,在空速为8小时~(-1)、550℃时,甲苯转化率为17.47%,产物二甲苯中对二甲苯浓度高达61%,活性稳定。HDG催化剂经磷,镁浸渍后用甲醇-水处理能显著提高选择生成对二甲苯的能力,但活性有不同程度的下降。焙烧脱除正丁胺的气氛对催化剂的活性和选择性有影响,在氮气气氛中焙烧比在空气中焙烧效果好。外表面中毒试验表明,在HDG催化剂上的甲苯歧化反应发生在晶体内表面。
An organic amine molecular sieve (DG type) with excellent shape selectivity was synthesized. Although its x-ray diffraction pattern has the characteristic peak of ZSM-5, its adsorption performance is different from that of ZSM-5. Not only is it hydrophobic, the amount of n-hexane adsorbed is much higher than the amount of water adsorbed, and the ability to adsorb three isomers of xylene is disproportionately high (p-xylene is strongly adsorbed, adsorbed m-xylene slightly, and scarcely adsorbs xylene Xylene). In contrast, ZSM-5 has good adsorption capacity for all three isomers. The molecular size of DG zeolite is 17-18μ, which is exchanged with NH_4NO_3 and calcined to HDG toluene disproportionation catalyst at 540 ℃. It has a high ability to generate p-xylene. At a space velocity of 8 h -1, the conversion of toluene is 17.47% at 550 ℃. The concentration of p-xylene in xylene is as high as 61% and its activity is stable . The HDG catalyst treated with methanol and water after phosphorus and magnesium impregnation could significantly improve the ability to select p-xylene, but the activity of HDG catalyst decreased to some extent. The atmosphere in which n-butylamine is removed by calcination has an influence on the activity and selectivity of the catalyst. The calcination in a nitrogen atmosphere is more effective than the calcination in air. External surface poisoning tests showed that the toluene disproportionation reaction on the HDG catalyst occurred on the inner surface of the crystal.