摘要
研究了催化剂制备方法、Ｍｏ含量、预处理条件和反应条件对在无氧条件下ＨＺＳＭ－５负载的Ｍｏ基催化剂上甲烷直接芳构化反应的影响，及积炭和烧炭再生对催化剂性能的影响．发现Ｍｏ含量为３．５～４％时催化剂活性最高，生成苯的速率高达１．２×１０－３ｍｏｌ·ｇ－１·ｓ－１．降低空速和提高反应温度均有利于甲烷的直接芳构化．随着反应的进行，乙烯的选择性不断提高，苯的选择性则不断降低．ＸＰＳ结果表明，反应后催化剂表面积炭，且研磨法制备的催化剂中Ｍｏ６＋被还原成不具活性的金属态Ｍｏ０．卡宾中间体（Ｍｏ＝ＣＨ２）可能是甲烷芳构化反应的起始物．
The effect of preparation method, Mo content, pretreatment conditions, space velocity, reaction temperature on the preformance of methane aromatization under oxygen free conditions over HZSM 5 supported Mo catalyst has been studied, the effect of carbon deposition on catalyst after reaction and regeneration by carbon burning with O 2 was investigated. It was found that the initial activity of catalysts prepared by grinding technique was higher than that of catalysts prepared by impregnating technique, but the activity of the former decreased quickly with reaction time increased, and decreased obviously after regeneration, while the activity of the latter was similar to that of fresh catalysts. The catalyst with Mo content of 3 5%￣4 0% showed the best aromatization activity. Decreasing space velocity and increasing reaction temperature improved the aromatization activity. With reaction time increased, the selectivity for ethylene enhanced while selectivity for benzene decreased. Furthermore, XPS results suggested that the most of Mo 6+ in the catalysts prepared by impregnating method dispersed in the framework of HZSM 5 zeolite and those of grinding method dispersed on the surface of HZSM 5 zeolite, the carbon content on the catalyst surface increased rapidly, and Mo 6+ in the ground catalysts was reduced to Mo 0 after reaction for 4 h. On the basis of these results, it is proposed that molybdena carbene with configuration of MoO 3=CH 2 is an initial product of methane aromatization reaction.
出处
《催化学报》
SCIE
CAS
CSCD
北大核心
1996年第3期232-236,共5页
基金
浙江省自然科学基金
关键词
甲烷
芳构化
催化剂
分子筛
苯
钼
Methane, Aromatization, Mo based catalyst, HZSM 5 zeolite, Oxygen free condition, Benzene
