The Catalytic Cracking Of C8on Acidic Zeolites

With the rapid growth of China’s national economy, China’s demand for crude oil is on the rise. With the expanding oil exploration, the proportion of heavy crude oil in oil resources is rising rapidly. Crude oil is becoming heavier and lower-quality worldwide and the demand for petrochemical feedstock and light oil is growing rap-idly. The contradictory relationship between crude oil resources supply and demand for petroleum products are continuous expanding. Therefore, how to convert crude oil, especially heavy residue conversion into high value-added light oil has become the most important focus of the development of the world’s oil refining industry.C8compounds, n-octane, cyclooctane, n-octene, cyclooctene, xylene and ethylbenzene were set as model compounds. Then the adsorption and desorption properties of C8compounds were investigated in different zeolites. Meanwhile pulse catalytic cracking reactions were used as technical ways, and a variety of catalytic cracking reactions of C8compounds on different zeolite were carried out. By review-ing the relationship between zeolite channels, acidity, acid strength of the zeolite and their cracking reactions, results obtained are as follows:In this paper, different models compounds’adsorption and desorption properties in BETA, HZSM-5, SAPO-34and RE-USY were examined. Results were found that the greater zeolite’s pore size the greater adsorption amount it had. The double bond in the model compounds could promote the adsorption of model compounds on zeo-lites. When the pore size of the zeolite was smaller than the model compounds, the moleculer can not enter into the pores of the catalyst, can only be adsorbed on the ze-olite surface. So the adsorption amount was very low. Model compounds with double bond can promote the adsorption capacity of the model compounds in BETA and HZSM-5zeolite. While, model compounds with double bond did not play a role in promoting in the RE-USY-1and RE-USY-2adsorption. The double bond in the model compound was not conducive to the SAPO-34zeolite adsorption of model com-pounds.By examining the desorption performance of different model compounds in the BETA, HZSM-5, RE-USY-1, RE-USY-2, and SAPO-34, results were found that the double bond of model compound can significantly improve the desorption amount of the zeolite and desorption temperature is generally about50℃higher. At the same time the double bond in the model compound can be connected to the zeolites, ad-sorption capacity between model compounds with and zeolite was significantly stronger than that model compounds without double bond. The adsorption capacity on strong acid sites is stronger than on the weak acid sites, the desorption temperature is higher.By examining the conversion rate and product selectivity in the pulse catalytic cracking reactions of different model compounds on different zeolites, it turned out that the double bonds in the reactant can greatly increase the activity of catalytic cracking reactions, but followed by an increase in byproducts and lower carbon num-ber hydrocarbons’selectivity. Due to the strong acidity, the coke deposition on RE-USY-1and RE-USY-2is serious and leaded to a significant reduction to the cata-lytic activity. SAPO-34channels were too small to absorb the model compounds, the catalytic cracking capacity of the zeolite had been severely restricted. BETA zeolite has larger pores, moderate acidity and acid density, catalytic cracking activity was higher, the products were well-distributed. Since the HZSM-5zeolite’s unique three-dimensional pore, the selectivity of the product was much better. The selectivity of olefin was higher in unsaturated model compounds catalytic cracking reaction.