Effects on Tetralin Catalytic Hydrocracking over Mordenite Zeolites Treated by Framework Atoms Extraction
State Key Laboratory of Green Chemical Engineering and Industrial Catalysis, Shanghai Research Institute of Petrochemical Technology, SINOPEC, Shanghai 201208, China
Abstract A series of modified mordenite zeolite catalysts were prepared Framework Atoms Extraction by desilication and dealumination, and systematically characterized by X-ray diffraction(XRD), Fourier transform infrared spectroscopy(FT-IR), Inductively coupled plasma atomic emission spectrometry(ICP), 27Al nuclear magnetic resonance(27Al NMR), 29Si nuclear magnetic resonance(29Si NMR), scanning electron microscope(SEM), transmission electron microscope(TEM) and nitrogen adsorption-desorption, etc. The results demonstrated that the controllable desilication and dealumination could efficiently extract the Si atoms and Al atoms from framework to introduce mesoporisity and adjust acidity, respectively. In tetralin catalytic cracking, the introduction of mesoporisity and acid density increase of alkali treated samples can effectively improve the diffusivity of polycyclic aromatic hydrocarbons and the accessibility of active sites, thus promoting the initial conversion. Attributed to the extraction of framework aluminum atoms, the acid density decrease of acid treated sample leaded to effective inhibition of bimolecular reactions and the formation of coke precursor, thus improving the catalysis stability. Combined the advantages of the mesoporisity introduced by Si atoms extraction and the optimization of acid density by the subsequent Al atoms extraction, the initial conversion of tetralin catalytic cracking over the desilicated-dealuminated samples increased by nearly 20% and the selectivity of target products especially mononuclear aromatics enhanced by 9% compared with the parent one, and a significantly improvement was obtained on catalytic stability.
