Click "read the original" to learn more
DOI：http://doi.org/10.1016/j.cjche.2019.01.027
Hydrophobic modification of SAPO-34 membranes for improvement of stability under wet condition
Rashid ur Rehman, song Qingnan, Peng Li, Chen Yang, Gu Xuehong
content validity
Membrane separation technology is a new type of separation technology, which has the advantages of low cost, high efficiency, small volume, low energy consumption, simple operation and small environmental pollution. It has attracted extensive and strong research interest of researchers all over the world. The pore structure of zeolite molecular sieve membrane is regular and has good thermochemical stability, which is suitable for the separation of small molecules. SAPO-34 molecular sieve, belonging to cha topological structure, has eight membered ring channels, and its effective pore diameter is 0.38 nm. It is one of the best framework structures for CO2 / CH4 gas separation. It can selectively allow CO2 (0.33 nm) molecules to pass through and block CH4 (0.38 nm) molecules. In recent years, the research work of SAPO-34 molecular sieve membrane has been widely concerned and made great progress. One of the main challenges of CO2 separation in natural gas is the presence of water vapor, which may reduce the separation performance of SAPO-34 membrane and even destroy the molecular sieve framework. Water vapor can be minimized or eliminated by optimizing operation conditions and pretreatment of feed gas, but these technologies often increase the total operating cost of membrane process. The modification of zeolite membrane surface, reduction of surface defects and improvement of membrane stability in water vapor environment have become the focus of research and industry. In this paper, based on SAPO-34 molecular sieve membrane, dodecyltrimethoxysilane (DTMs) was used to modify the surface of SAPO-34 molecular sieve membrane, in order to improve the membrane tolerance for CO2 / CH4 separation in water vapor environment. The results of FTIR, SEM and contact angle showed that dodecyltrimethoxysilane was successfully grafted on the surface of SAPO-34 molecular sieve membrane, which improved the hydrophobicity of the membrane surface. The effect of the concentration of dodecyltrimethoxysilane modified solution on the separation performance of SAPO-34 molecular sieve membrane was investigated. The results showed that compared with the unmodified SAPO-34 molecular sieve membrane, the modified SAPO-34 molecular sieve membrane had higher selectivity for the separation of equimolar CO2 / CH4 mixture, but the permeability of the gas decreased. With the increase of the concentration of the modified solution, the change is more obvious. The modified zeolite membrane has obvious advantages in the separation of CO2 / CH4 mixture in the presence of water vapor. Under 298K water vapor condition, due to the hydrophilicity of SAPO-34 molecular sieve membrane surface, the adsorption of water in the molecular sieve channel affects the permeation of CO2, and the selectivity of the original SAPO-34 molecular sieve membrane for the mixture of CO2 and CH4 is only 0.9. Dodecyltrimethoxysilane can significantly improve the hydrophobicity of the membrane surface, and with the increase of the concentration of the modified solution, the membrane surface is more hydrophobic, and the separation selectivity of CO2 / CH4 is also increased, up to 17. The further increase of the concentration of the modified solution will lead to the blockage of the pore, affect the permeation of CO2 and decrease the separation factor slightly. The effect of operating temperature and pressure on the separation performance of SAPO-34 zeolite membrane for CO2 / CH4 system was also discussed. Although increasing the separation temperature (e.g. 353K) can reduce the effect of water vapor, the high separation temperature (e.g. 373k) can also reduce the selectivity of CO2 / CH4 separation. The higher feed pressure will reduce the separation performance of CO2 / CH4 in water vapor environment. The modified SAPO-34 membrane is used for the separation of CO2 / CH4 dry gas, which shows lower CO2 permeability and higher separation selectivity. However, for the separation of CO2 / CH4 wet gas, the separation performance is significantly improved due to the improvement of surface hydrophobicity. When the separation temperature is 353K and the operating pressure drop is 0.4MPa, the selectivity of CO2 / CH4 is 65 and the permeability of CO2 is 4.73 × 10-8mol · m-2 · S-1 · PA-1. At 353K, the SAPO-34 molecular sieve membrane modified in this paper can be operated for 120h for CO2 / CH4 separation in water vapor environment. This study provides the basis for the practical gas separation and broadens the application field of SAPO-34 molecular sieve membrane.
Summary of charts and tables
Preparation process of SAPO-34 zeolite membrane modified by dodecyltrimethoxysilane (DTMs)
Communication author and Team Introduction
Gu Xuehong, Ph.D., Professor, doctoral supervisor, deputy director of national special separation membrane engineering technology research center, winner of National Excellent Youth Fund and Jiangsu Outstanding Youth Science Fund. In June 2002, he received his doctor's degree in engineering from Nanjing University of technology. From April 2003 to January 2007, he worked as a postdoctoral researcher at the Institute of mining technology of New Mexico and the University of Cincinnati, returned to teach in February 2007, and paid a senior visit to Imperial College of technology from January to June 2014. At present, the preparation and application of molecular sieve membranes are mainly focused on the energy and environmental needs, and the industrialization technology of molecular sieve membranes is focused on. It is the winner of 2013-1014 "top ten young technological stars of Jiangsu Province" and 2017 Jiangsu Province's first innovation competition certificate, the six talent peaks of Jiangsu Province, the second level of "333 high level talent training project" of Jiangsu Province and the training object of Nanjing Science and technology entrepreneurs. In the past decade, it has undertaken more than 20 scientific research projects of national 973 Plan, 863 plan, National Natural Science Foundation, etc. He has published more than 50 SCI papers, authorized more than 20 Chinese invention patents, 2 Japanese invention patents, and applied for 4 international PCT invention patents. Won 5 provincial and ministerial awards including the first prize of technical invention award of China Petrochemical Federation. Breakthroughs have been made in the preparation of molecular sieve membrane and the design of complete set of equipment. The research results hatch out of Jiangsu Jiutian High Tech Co., Ltd., which has been listed on the new third board (Stock Name: Jiutian high tech, stock code: 832440). The success of molecular sieve membrane dehydration technology has been applied to solvent production and recovery in more than 80 enterprises such as Harbin Pharmaceutical Group and Zhejiang Haizheng Pharmaceutical Co., Ltd., and promoted More than 100 sets of industrial devices have produced remarkable economic and social benefits.
Full text link: http://doi.org/10.1016/j.cjche.2019.01.027
About CJChE
Chinese Journal of Chemical Engineering (cjche), a sister Journal of chemical engineering, is a comprehensive international academic journal jointly published by China Association of science and technology, China Chemical Society and chemical industry press Co., Ltd. and Elsevier. Founded in 1982, it was renamed in 1993 and then re filed. At that time, Chen Jiayong, the pioneer of hydrometallurgy, and Yu guocong, the internationally famous rectification expert, were two academicians, and the Journal of China Chemical Society. Since its inception, it has gone through the development process from semi annual to quarterly, bimonthly and even monthly. At present, it is a monthly magazine, with 16 open pages, and is publicly distributed at home and abroad. Currently, he is the chief editor of academician Fei Weiyang of Tsinghua University and executive editor of Professor Luo Guangsheng.
The purpose of this journal is to promote the academic development and exchange of chemical engineering at home and abroad. Based on the development frontier of chemical engineering in China and even in the world and the major needs of national economy, it mainly publishes original research papers on chemical basic theories, new technologies, new methods, new equipment and new materials, reports basic data with important value and plays a guiding role in discipline development and technological progress Summary and monograph of. The scope of content includes chemical engineering, chemical process, chemical equipment, process development, chemical metallurgy and related high-tech fields such as biology, information, energy, materials, environmental engineering and safety engineering.
Since 1996, the journal has been included by SCI search, EI, Scopus, CA, statistics and analysis of China's scientific papers, China Science Citation Database and other famous retrieval systems and databases at home and abroad, with readers covering more than 100 countries and regions. According to the latest data released by Kerui Wei'an, the impact factor of cjche in 2018 is 1.911, a 12% increase over the previous year. The total cited frequency is 3775, with a 22% increase. The chemical minor disciplines rank 71 / 138, the top 51%, and the sci3 area. According to Scopus database, cjche's three-year impact factor citescore is 2.12, ranking 79 / 272 in the international chemical industry comprehensive field, top 30%, Q2 area. In 2019, the Chinese Academy of Sciences released the latest journal zoning table, and cjche entered zone 3 of Engineering Technology / chemical industry.
In 2019, Chinese Journal of chemical engineering won the title of "China's most internationally influential academic journal" (top 5%) for the eighth consecutive year since it first participated in the evaluation, and was selected into the echelon journal project of China's science and technology journal excellent action plan (only one journal of chemical industry was selected in the National English journal of chemistry, chemical industry and materials).
Click "read original"