| The separation of hydrocarbons is extremely important in the petrol chemical industry, and it has caused extensive concern of international academia and industry. Metal-organic frameworks(MOFs) show great promises for the adsorption and separation of hydrocarbons. However, although MOFs have high specific area and excellent adsorption capacity, they show low separation selectivity of alkanes/alkenes. What’s more, significant high energy consumption is required for the desorption process. To resolve these issues, novel flexible metal-organic frameworks were synthesized and characterised. Then their adsorption performance toward hydrocarbons were also examined. Furthermore, the traditional hydrothermal method is dependent on large amount of organic solvents, which is environmentally unfriendly. Therefore a solvent-free mechanochemical method was developed for the synthesis of MOF-5 and GO@MOF-5 composites. And the adsorption performance of MOF-5 and GO@MOF-5 composites for a series of n-alkanes and alkanes/alkenes were investigated. This work has great scientific research value and practical significance.A flexible and thermosensitive porous CPL-1 material was synthesized by hydrothermal method. And the influence of solvents on the structure and C3H6/ C3H8 separation were systematically investigated. Results showed that the solvents molecular were the templates during the synthesis of CPL-1. Thus, CPL-1 synthesized in the solvent of CH2Cl2, which molecular size is slightly larger than propylene, performanced the lowest C3H6 gate pressure about P =37 kPa. Furthermore, the structure of thermosensitive CPL-1 can expand in response to propylene molecular at 273 K, but shrink at 298 K. And the removel of propylene was over 90% at 298 K, P=90 kPa.CPL-2 was synthesized by hydrothermal method., and the influence of solvents on the structure and alkanes/alkenes separation were systematically investigated. Results showed that the crystal morphology of samples synthesized in the solvent of H2 O and CH2Cl2 were regular flakiness, and they presented higher thermal stability. CPL-2 expanded only in response to propylene molecular at 273 K, so it showed excellent separation ability of C3H6/ C3H8, which was up to 26.A solvent-free mechanochemical method was developed for the synthesis of MOF-5. Results showed that when Zn(OA)2·H2O and terephthalic acid in the ratio of 3:1 were ground at 1100 r/min for 60 min, the as-synthesized MOF-5 showed the highest BET surface area of 3465.9 m2/g and pore volume of 1.097 cm3/g. The interaction between n-alkanes and MOF-5 were mainly dependent on the molecular size. Thus, the analogous gate pressure of n-alkanes decreased with the increasing of absorbates molecular size. And the adsorption capacities of C5-C7 on MOF-5 were 8.0~10.2 mmol/g, which was about 1.2~8.2 times of activited carbon and zeolites.The adsorption performance of GO@MOF-5 composites for alkanes/alkenes was investigated. Results showed that GO@MOF-5 presented higher alkanes/alkenes selectivity than parent MOF-5 due to the introduction of GO, which was offered more –COOH and –OH to interact with alkenes. Among them, 5%GO@MOF-5 showed the highest C2H6/C2H4 selectivity(about 3.6), 8%GO@MOF-5 showed the highest C3H6/C3H8 selectivity(about 3.3). In addition, GO@MOF-5 had stronger interaction with C3 molecular than C2 because 8%GO@MOF-5 composite created a large number of new micropores about 8 ? with the introduction of GO, therefore 8%GO@MOF-5 exhibited the highest selectivity of C3H8/C2H6 and C3H6/C2H4, which were up to 33 and 78 separately. |
PDF Full Text Request