| As a key field of new materials industry,unsaturated polyester resin industry will get great development,which will bring the problem of excessive emission of typical organic pollutants such as styrene,ethylene glycol and diethylene glycol,in which Among them,styrene is the most used and the most harmful.If there is not an economic and efficient solution,it will seriously restrict the development of China's unsaturated polyester resin industry and even the new material industry.The adsorption method is widely used in the treatment of organic waste gas and has a good effect.The key to the method is the selection of adsorbent materials.Although activated carbon has good adsorption effect on VOCs,the ignition problem of regeneration process has not been solved well.Therefore,this paper selects 13X molecular sieve with high temperature resistance and large pore diameter as the adsorption material of organic waste gas.In this paper,the 13X molecular sieves were modified by impregnation method and roasting method.The effects of four chemical reagents?NaOH,NH3,CH3COOH,HCl?,immersion time,calcination temperature and calcination time on the adsorption of styrene on modified molecular sieves were investigated.The best modification conditions were determined by factor experiment and orthogonal experiment.The13X molecular sieves before and after modification were characterized by SEM-EDS,FTIR and BET.Through the adsorption experiment of the adsorption column packing layer,determination of between the penetration time of the styrene vapor and the height of the adsorption layer was investigated,and the saturated molecular sieve was regenerated by heating desorption and vacuum desorption.The main conclusions of the experiment are as follows:?1?The optimal modification conditions were obtained by single factor experiment:HCl concentration is 6.0 mol·L-1,immersion time is 24 h,calcination temperature is 450?,calcination time is 8 h.The molecular sieve adsorbed by the optimal conditions reached the saturation time of 6 h,and the dynamic saturated adsorption amount was 90.4 mg·g-1,which was shortened by 6 h compared with the unmodified molecular sieve,and the dynamic saturated adsorption increased by 83.4mg·g-1.The optimum modification conditions obtained by orthogonal experiment were:HCl concentration is 8.0 mol·L-1,immersion time is 24 h,calcination temperature is 450?calcination time is 7 h?under the optimal orthogonal conditions,the modified molecular sieve is represented by H8-450°C.?.Under the optimal conditions,the modified zeolite adsorbed styrene to a saturation time of about8h,and the saturated adsorption amount was 104.2 mg·g-1.?2?Three kinds of molecular sieves?the original sample,hydrochloric acid modification,orthogonal modification?were used to carry out dynamic adsorption experiments of two other organic substances?ethylene glycol,diethylene glycol?.The order of dynamic saturated adsorption amount was:orthogonal modification>hydrochloric acid Modified>the original sample,the dynamic saturated adsorption capacities of three kinds of molecular sieves for ethylene glycol were 63.6 mg·g-1,143.6 mg·g-1,153 mg·g-1,respectively;the dynamic saturated adsorption amount of diethylene glycol was 13.2 mg·g-1,23.5 mg·g-1,49.9 mg·g-1.?3?By SEM electron microscopy and BET specific surface area analysis,it was found that the surface of the molecular sieve became rough and porous after the modification of hydrochloric acid,and the porosity increased obviously.The surface modification was not obvious under the condition of high temperature modification on the basis of hydrochloric acid;the molecular sieve was analyzed by FTIR,the modified molecular sieve skeleton is basically the same as before the modification;through the BET specific surface area analysis,it is considered that the hydrochloric acid modification is beneficial to increase the distribution of various pores,and the high temperature modification can expand the micropores into the mesopores.The correlation analysis between the pore area and the adsorption amount shows that the adsorption amount has a good positive correlation with the pore area in the molecular sieve,indicating that the adsorption performance of the molecular sieve on styrene is improved,and the pore area in the molecular sieve should be improved.?4?The optimum regeneration conditions determined by the heating desorption experiment were heating at 105?for 4 h,and the dynamic saturated adsorption amount of styrene after 4 cycles was 42.3 mg·g-1.At room temperature?about 8.9??vacuum desorption for 4 h,cyclic adsorption desorption for 3 times,the fourth dynamic adsorption of styrene to the amount of 65.7 mg·g-1,indicating that the vacuum desorption effect is better than the heating regenerated molecular sieve adsorption effect.The modified 13X molecular sieves under vacuum regeneration were subjected to dynamic adsorption experiments of ethylene glycol and diethylene glycol,and the adsorption and desorption were repeated three times.The dynamic saturated adsorption amount of ethylene glycol for the fourth time was 108.2 mg·g-1;The dynamic saturated adsorption amount is 42.1 mg·g-1,which indicates that the effect of vacuum regeneration molecular sieve is better than heating regenerated molecular sieve. |
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