Acidity And Activity Of The Catalytic Cracking Catalyst

Fluid catalytic cracking(FCC) is the primary conversion of crude oil to lighter products. Though the FCC process, conversion of crude oil to lighter products can be converted into highly valueable products, such as diesel and gas, which provide numbers of benefits for factories as well. Catalytic cracking reaction is an acid catalytic reaction, catalyst is the core of the catalytic cracking reaction and offer acidity the reaction need. By understanding the nature of the product, we can change the amount of acid, acid strength and acid availability to meet the products we need and control the generation of dry gas and coke.Catalytic cracking catalyst has three major components: Zeolite, Mtrix and Binder. Zeolite commonly as active component, basically have Y zeolite, ZSM-5 zeolite, and so on. Matrix is a component of the catalyst, aside from the zeolite, basically have kaolin, alumina and so on. Due to the crude oil is heavier and poorer in the world, the large aperture and highly active matrix become the research hot spot. The binder serves as a glue to hold the zeolite and matrix together. Binder may or may not have catalytic activity, basically have aluminum silicon sol, silicon sol and alumina sol. This article mainly Y zeolite as the active component, kaolin as the matrix, acidification of pseudoboehmite and alumina sol as the binder to study the cracking catalyst acidity and activity.The unit cell size(UCS), rare erath level and sodium content is the most basic parameters affecting its acid respectively in Y zeolite. UCS is a measure of aluminum sites or the total potential acidity per unit cell. The negatively charged aluminum atoms are sources of actives sites in the zeolite. Silicon atoms do not possess any activity. Quantitative relation exists between the UCS with aluminum atoms, so the UCS and Y zeolite also have a certain relationship between acidity. Rare earth elements are very important components of the commercial catalysts for the process of catalytic cracking. Indeed, it is well-established that the presence of the rare earth(RE) cations on Y zeolites is responsible for improving acidity, cracking activity, and thermal and hydrothermal stability. As the aluminum in the aluminum oxygen tetrahedron is +3 valence band a negative charge, generally to be neutralized by sodium ion. Sodium decrease the hydrothermal stability of zeolite and sodium ions at high temperatures is free mobile easiliy to neutralize the acid sites to decrease the acidity. So must control the sodium content is below 0.2% in Y zeolite.Kaolin not have cracking activity, after high temperature roasting kaolinite of alumina octahedral structure was damaged, the farmework aluminum was activation, and then after acid treatment, kaolin has undergone a dehydroxylation, hydroxylation and secondary dehydroxylation process, hydroxylation change the coordination of framework aluminum in Kaolin, the part of the six ligand Al(?) under the action of acid into four ligand Al(?), which can make the kaolin produces large holes and have higher activity.Acidification of pseudoboehmite and alumina sol as the binder in catalyst after roasting become ?-alumina increased mechanical strength of catalysts, has the very good pore structure, made the catalytic cracking catalyst has a good cracking ability for heavy oil, residual oil and reduce the coke and dry gas.In this study, different cell size of Y zeolite and different content of rare earth Y zeolite, different amount of hydrochloric acid treatment of kaolin, different amount of hydrochloric acid treatment of pseudoboehmite, aluminum alumina sol and different amount of hydrochloric acid treatment of pseudoboehmite model catalytic cracking catalyst and different content of Y zeolite model catalytic cracking catalyst are made. These samples be characterized by a variety of chemical and physical measurement methods: X-ray diffraction(XRD), X-ray fluorescence(XRF), N2 isothermal absorption-desorption, ammonia temperature programmed adsorption instrument(NH3-TPD), pyridine adsorption IR spectrometer, Microactivity Test(MAT). By controlling the variable to explore the acidity and activity of the sample we got a lot of valuable conclusions. Further understanding the different catalyst acidity and activity, and its effect on the activity and acidity of catalyst, these research is important in the industrial development of catalytic cracking catalyst.