Study On Adsorption Separation Of M-cresol And P-cresol With HZSM-5 Molecular Sieve

O-cresol,m-cresol and p-cresol are important chemical intermediates.but their production capacity is insufficient in China,they need to rely on foreign imports?the import of cresol is as high as 2855.96 tons from January to March2018?.Although coal-based liquids contain a large amount of cresol,the separation product is a mixture of o-cresol,m-cresol and p-cresol.Among them,o-cresol can be obtained by distillation by boiling point difference,but the boiling point difference between m-cresol and p-cresol is only 0.4?,which is difficult to separate.In order to achieve the simple and efficient separation of the m-cresol and p-cresol,adsorption separation method was selected in this paper.The key of this method is adsorbent.the molecular sieves are widely used in the separation of isomers because of their excellent shape selection,In this paper,HZSM-5molecular sieves are selected as the precursor of adsorbents by comparing the minimum molecular dynamic diameter of cresol?m-cresol,p-cresol?.?1?the adsorption properties and adsorption behavior of m-cresol and p-cresol on HZSM-5 molecular sieves were investigated by using m-cresol and p-cresol as model compounds.;?2?the effect of chemical liquid deposition on the adsorption properties of HZSM-5 molecular sieves and its mechanism were studied.?3?The cyclic utilization of the adsorbent and its adsorption to the mixed phenol were studied.The main contents and results of the paper include:1.Through the comparison of the adsorption properties of p-cresol and m-cresol on HZSM-5?Si/Al ratio:25³00?,it can be seen that the adsorption site of p-cresol on HZSM-5 molecular sieves and the acid content of molecular sieves is independent.From change of the adsorption properties over time,it can be seen that HZSM-5 molecular sieves have no separation ability for them.The adsorption rate of p-cresol(0.60754 g/?mg/min?on HZSM-5 molecular sieves was higher than that of m-cresol(0.23509 g/?mg/min?,but the saturated adsorption capacity of p-cresol was basically same,which indicated that diffusion alone could not separate them.2.HZSM-5 molecular sieves modified chemical liquid phase deposition?CLD,chemical liquid deposition?can realize the separation of p-cresol and m-cresol.The optimum modification conditions were as follows:TEOS?ethyl orthosilicate?was as deposition agent,n-hexane was as diluent,pre-treatment temperature was 0? and TEOS addition was 0.2 mL/g.It is proved by characterization that the excellent separation performance of the modified adsorbents is due to the modification of the pore size of the molecular sieves.3.The 0.2SiO₂-HZSM-5 molecular sieves obtained under the optimal modification conditions can reduce the difficulty of operation and waste during the use of powdered molecular sieves.The results show that Y-HZSM-5?0.2 SiO₂-2?adsorbent is a suitable granular molecular sieve with a selectivity of 90%.On the other hand,the 0.2SiO₂-HZSM-5 adsorbent can realize the recycling of the adsorbent through the elution regeneration,so it is an efficient adsorbent.4.In order to investigate the application of adsorbents in coal-based crude oil,0.2SiO₂-HZSM-5 was applied to coal direct liquefied oil mixed phenols.0.2SiO₂-HZSM-5 adsorbed only phenol and p-cresol,other phenols will be not adsorbed.The shape selectivity of 0.2SiO₂-HZSM-5 adsorbents is not affected by the environment,but only related to the molecular size.It can be used to obtain phenol and p-cresol in liquefied petroleum phenol products.