The effect of Ce and P loading on catalytic performance of HZSM-5 in thermal catalytic cracking of naphtha to light olefins

In order to increase catalyst stability and light olefins yield in catalytic cracking of naphtha, a series of HZSM-5 catalysts with various Phosphorous (0.2, 1.1 and 10 wt. %) Loadings were prepared by co Phosphorous on the structure and acidity of HZSM adsorption/desorption and NH3 analysis was done. The characterization results demonstrated that the structure of catalysts rarely changed by modification while the amount of acid sites increased. The results of cracking tests showed that the yield of propylene was to parent catalyst while the ethylene yield did not change. Also increasing P loading the catalyst stability increased while increasing Ce loading resulted in higher propylene yield. At 680 maximum Yield of ethylene and propylene were obtained about 16% and 36% respectively, for 6%Ce-1.1%P/HZSM-5, while these yields showed no lost through 20 hours of reaction tests. These results revealed that there might be an optimum for acid density to maxi olefins yield. In addition The TGA analysis indicates that the coke deposition is not a major factor for catalysts deactivation. So, catalyst deactivation might be attributed to the structural change.