Preparation of imidazole modified MCM-22 molecular sieves and its catalytic performance in methane dehydroaromatization

doi:10.16085/j.issn.1000-6613.2018-0469

Abstract

Abstract:

Imidazole modified MCM-22 molecular sieves(MCM-22-I) were synthesized by hydrothermal synthesis method under dynamic conditions using imidazole as additives. The effect of imidazole on the synthesis of MCM-22 zeolites was investigated. The physicochemical properties of the molecular sieve samples were characterized by FTIR，XRD，SEM，ICP，BET，NH₃-TPD，H₂-TPR，and TG/DTG. The results showed that MCM-22-I displayed large specific surface area, abundant pore structure and enhanced acidity and the modification by imidazole can reduce the amount of the template agent HMI used. The 6Mo/MCM-22-I and 6Mo/MCM-22 catalysts were prepared by incipient-wetness impregnation method. The catalytic performance evaluation of the catalysts for methane dehydroaromatization were carried out in a fixed bed reactor under the reaction conditions of 700℃， P = 1atm and space velocity of 1500 mL/(g-cat·h). The results showed that methane conversion increased by 24.1%, the formation rate and the selectivity of benzene by using imidazole modified 6Mo/MCM-22-I catalyst increased by 24.3% and 10%，respectively, compared with conventional 6Mo/MCM-22 catalyst.

Key words: catalyst, MCM-22, molecular sieves, imidazole modified, synthesis, fixed-bed, methane dehydroaromatization

摘要：

以硅溶胶为硅源，环己亚胺为模板剂，在动态条件下利用水热合成法合成了MCM-22分子筛，并在该体系下以咪唑为添加剂合成了咪唑改性MCM-22-I分子筛，考察了咪唑对MCM-22-I分子筛合成的影响，利用FTIR、XRD、SEM、ICP、BET、NH₃-TPD、H₂-TPR和TG/DTG等手段分别对咪唑改性前后分子筛的物化性质进行了表征。结果表明，咪唑改性能够增大MCM-22的比表面积、孔容和酸性，同时可有效降低模板剂HMI的用量。采用等体积浸渍法制备了6Mo/MCM-22和6Mo/MCM-22-I双功能催化剂，在连续流动固定床反应器上，反应温度700℃、反应压力1.01×10⁵Pa（1atm）、空速1500mL/(g-cat·h)的反应条件下，考察了催化剂催化甲烷无氧芳构化合成苯的催化剂性能。结果表明，与6Mo/MCM-22催化剂相比，咪唑改性的6Mo/MCM-22-I催化剂具有更高的择形性能和催化活性，甲烷的平均转化率提高了24.1%，苯的平均生成速率和选择性分别提高了24.3%和10.0%。

关键词: 催化剂, MCM-22, 分子筛, 咪唑改性, 合成, 固定床, 甲烷无氧芳构化

CLC Number:

TE64

Jialiang GAO,Gen ZHANG,Xu CHENG,Chengyi DAI,Qingqing HAO,Xiaoxun MA. Preparation of imidazole modified MCM-22 molecular sieves and its catalytic performance in methane dehydroaromatization[J]. Chemical Industry and Engineering Progress, 2019, 38(03): 1387-1395.

高佳良,张根,程序,代成义,郝青青,马晓迅. 咪唑改性MCM-22分子筛的制备及甲烷无氧芳构化性能[J]. 化工进展, 2019, 38(03): 1387-1395.

Figures/Tables 10

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样品	n(HMI) /n(SiO₂)	n(咪唑) /n(SiO₂)	晶化时间 /天	晶化温度/℃	晶化产物	相对结晶度/%
A0	1 0.7	0	3	150	MCM-22	100
A1	1 0.7	0.3	3	150	MCM-22	97
A2	0.5	0.5	3	150	MCM-22	76
A3	0.1	0.9	3	150	MCM-22	43
A4	0.1	0	3	150	硅胶	0
A5	0.1	0	5	150	硅胶	0

样品	n(HMI) /n(SiO₂)	n(咪唑) /n(SiO₂)	晶化时间 /天	晶化温度/℃	晶化产物	相对结晶度/%
A0	1 0.7	0	3	150	MCM-22	100
A1	1 0.7	0.3	3	150	MCM-22	97
A2	0.5	0.5	3	150	MCM-22	76
A3	0.1	0.9	3	150	MCM-22	43
A4	0.1	0	3	150	硅胶	0
A5	0.1	0	5	150	硅胶	0

样品	BET比表面积/m²·g^-1			孔容/cm³·g^-1			平均孔径/nm
样品	介孔	微孔	总比表面积	介孔	微孔	总孔容	平均孔径/nm
MCM-22	70.073	390.998	461.071	0.276	0.153	0.429	3.043
6Mo/MCM-22	51.244	292.256	343.500	0.273	0.115	0.388	9.495
MCM-22-I	100.478	458.561	559.039	0.341	0.181	0.522	3.397
6Mo/MCM-22-I	65.159	292.794	357.953	0.298	0.116	0.414	7.709

样品	BET比表面积/m²·g^-1			孔容/cm³·g^-1			平均孔径/nm
样品	介孔	微孔	总比表面积	介孔	微孔	总孔容	平均孔径/nm
MCM-22	70.073	390.998	461.071	0.276	0.153	0.429	3.043
6Mo/MCM-22	51.244	292.256	343.500	0.273	0.115	0.388	9.495
MCM-22-I	100.478	458.561	559.039	0.341	0.181	0.522	3.397
6Mo/MCM-22-I	65.159	292.794	357.953	0.298	0.116	0.414	7.709

样品	弱酸		中强酸		强酸		总酸性
样品	相对面积	峰温/℃	相对面积	峰温/℃	相对面积	峰温/℃	相对面积	总酸量/mmol·g^-1
HMCM-22-I	599.8	156.4	1729.2	206.2	1744.5	326.3	4073.0	1.559
HMCM-22	507.5	156.9	1330.8	204.8	1534.1	355.5	3372.4	1.301
6Mo/MCM-22-I	780.9	169.5	1413.7	217.0	1670.3	311.8	3864.9	1.483
6Mo/MCM-22	829.2	165.3	1492.5	213.6	1473.7	310.7	3795.4	1.457