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利用吡啶吸附红外光谱(Py-IR)和X-射线衍射法表征了磷钨酸(PW)、氢氧化铌改性分子筛的表面酸性和结构,用催化法脱除芳烃中微量烯烃的烷基化反应研究其酸催化性质。结果表明,催化剂的结构、表面酸含量和磷钨酸、氢氧化铌在催化剂中所占的比例,都显著地影响烷基化反应;Dawson结构的磷钨酸比Kiggen结构的磷钨酸具有较好的催化烷基化反应活性;随着磷钨酸含量的增加,催化剂B酸量先增加后减少,L酸量减少;随着氢氧化铌含量的增加,总B酸量和L酸量都减少,催化剂的活性随总B酸量与总L酸量比值的增加而提高;用磷酸或草酸处理氢氧化铌,总B酸量与总L酸量的比值增大,可进一步提高分子筛的活性和寿命。研究结果还表明,强B酸不利于脱烯烃反应。
The surface acidity and structure of phosphotungstic acid (PW) and niobium hydroxide-modified molecular sieves were characterized by Pyridine-IR and X-ray diffraction. The alkylation of trace olefins in aromatic hydrocarbons was removed by catalytic method The reaction studies its acid catalytic properties. The results show that the structure of the catalyst, the surface acid content and the proportion of phosphotungstic acid and niobium hydroxide in the catalyst all significantly affect the alkylation reaction. The Dawson-structured phosphotungstic acid has a better performance than the Kiggen-structured phosphotungstic acid With the increase of phosphotungstic acid content, the amount of acid of catalyst B firstly increases and then decreases, while the amount of L acid decreases. With the increase of niobium hydroxide content, the amount of total acid B and acid L are The activity of the catalyst increases with the increase of the ratio of the total acid B to the total L acid. The ratio of the total acid B to the total L acid increases with the treatment of niobium hydroxide with phosphoric acid or oxalic acid to further increase the activity of the molecular sieve And life expectancy. The results also show that strong B acid is not conducive to de-olefin reaction.