Study On The Additive Effect And Carrier Effect Of Ferric Chloride-based Ethane Oxychlorination Catalysts

PVC is one of the world's top five general-purpose plastics and is widely used in many fields.Vinyl chloride as a monomer of polyvinylchloride can be produced by acetylene hydrochlorination,ethylene oxychlorination and ethane oxychlorination.The most obvious shortcomings of acetylene hydrochlorination are high energy consumption and severe pollution.In developed countries,acetylene hydrochlorination has been replaced by ethylene oxychlorination.Ethylene oxychlorination may have some advantages in oil-rich countries,but the cost of ethylene oxychlorination has been going up with the shortage of oil resources around the world.Ethane oxychlorination is the most economic and environment-friendly process using ethane as raw material but constrained by the lack of high performance catalyst for industrial application.Therefore,the study of ethane oxychlorination is of great importance.In this paper,a series of ferric chloride-based ethane oxychlorination catalysts were prepared by impregnation with ferric chloride as the active component.We conducted a screening of common alkali and alkaline earth metals to find out the best alkali/alkaline earth metal additives.The additive effect of potassium chloride and the carrier effect of different mixed carriers on the ferric chloride-based ethane oxychlorination catalysts were studied in detail.The effect of different reaction conditions on the performance of the catalysts were investigated by orthogonal test.The catalysts were characterized by XRD,nitrogen adsorption,XPS,H2-TPR,Mossbauer spectrum,Raman spectrum,etc.We have obtained the following results:1.Screening of common alkali and alkaline earth metals to find out the best alkali/alkaline earth metal additives.It is found that alkali/alkaline earth salt additives have a significant effect on the ferric chloride-based ethane oxychlorination catalysts.The ethane conversion and vinyl chloride selectivity are obviously improved by the additives.Moreover,potassium chloride shows the most impressive additive effect.2.The additive effect of potassium chloride on the ferric chloride-based ethane oxychlorination catalysts were studied in detail.It is found that the ethane conversion and vinyl chloride selectivity of the catalysts increase with the increase of the molar ratio of K/Fe(x,0?x?2).The significantly improved performance of the catalyst and the results of various characterization methods demonstrated the change in the active component of the catalyst(FeCl3?KFeCl4).On this basis,this paper trys to put forward the reaction mechanism,that KFeCl4 than FeCl3 has a higher chlorine release capacity,and ultimately lead to improved catalytic performance.3.The carrier effect of different mixed carriers on the ferric chloride-based ethane oxychlorination catalysts were studied in detail.It is found that in the ceria/zirconia-alumina mixed carrier catalyst,the zirconia-alumina mixed carrier catalyst exhibited better performance.The results of XRD,XPS,Raman spectroscopy proved the interaction between zirconia and alumina.Some Al3+ get into the zirconia lattice,resulting in the zirconia lattice shrinkage.This interaction favors the improvement of ethane oxychlorination activity.4.The effect of different reaction conditions on the performance of the catalysts were investigated by orthogonal test.It is found that different ethane flow rate,different feed ratio and different temperature have an effect on ethane conversion and vinyl chloride selectivity,and finally the space-time yield of vinyl chloride.Among them,the ratio of ethane flow to HCl flow has a significant effect on the ethane conversion,vinyl chloride selectivity and space-time yield.Whether the hydrogen chloride is excessive or not,and how much it excesses are of significance to ethane oxychlorination.