The Clean Synthesis Of Multi-functional Zeolite And Active Matrix In FCC Catalyst

Fluid catalytic cracking?FCC?is one of the most important conversion processes used in petroleum refineries.Zeolite and matrix are two major components of modern FCC catalyst.Due to the depletion of high quality crude oil resources,it is desirable to develop FCC catalyst which provides high accessibility for the heavy feed molecules to the zeolite and the matrix for maximum bottoms cracking.To this end,this thesis reported a simple yet efficient method for the dealumination of Y zeolite and also detailed the synthesis of porous matrix.In the first part?Chapter three?,a versatile dealumination strategy has been proposed to stabilize low-silica zeolites through a cannibalistic interaction between host framework A1?FAL?and guest aluminum salt.It is possible to capture selectively the FAL and Na ions in NaY zeolite by employing a special external Al source like aluminum sulphate as dealuminating agent.The host framework Al?FAL?cannibalistic interacted with guest aluminum salt to generate mineral natroalunite which was converted readily into ?-alumina?the matrix of FCC catalyst?by washing with aqueous alkali solution,such as sodium hydroxide,sodium carbonate,ammonia.The intracrystal mesopores was introduced accompanied by the dealumination,and resultant dealuminated Y zeolite has the BET surface area of 681 m² g^-1,external surface area of 142 m² g^-1.After hydrothermally treated with 100%steam at 800 ?for 17 h,the dealuminated Y zeolite possessed relative crystallinity of 46%,and maintained a higher external surface area of 127 m² g^-1.Possessing greatly enhanced hydrothermal stability,newly generated intracrystal mesopores,the resultant dealuminated Y zeolite catalysts have high activity in the cracking of bulky 1,3,5-triisopropylbenzene?TIPB?than the traditional hydrothermally dealuminated Y?USY?zeolite.We further revealed the mechanism of the dealumination and the results suggested that the formation of ultra-thermodynamics stable natroalunite via reaction between FAL and Na ions in NaY zeolite and aluminum sulfate is responsible to the dealumination.In the second part?Chapter four?,the binary SiO₂/Al₂O₃ composite with fibrous y-alumina coating on the external surface of SBA-15 has been synthesized by simply mixing SBA-15 with fibrous boehmite sol,followed by aging and calcination step.The binary SiO₂/Al₂O₃ composite with hierarchical porous had the surface area of 425 m² g^-1 and pore volume of 0.97 m³ g^-1,and no obvious blocked mesoporous was found.The crystalline ?-alumina phase in the mixture was proposed to stabilize the surface area.It was found that both Bronsted acid sites and Lewis acid sites were presented in the binary SiO₂/Al₂O₃ composite resulted by the migration of Si and Al in the matrix.Moreover,steaming treatment under critical condition further improved the migration of these atoms leading to strengthened acidity,though with some loss in surface area.The binary SiO₂/Al₂O₃ composite prepared by this facile means displayed much higher activity than the SiO₂/Al₂O₃ material prepared by conventional impregnation method in the cracking of TIPB,and the catalytic activity was well retained after 100%steam treatment at 800 ? for 4 h.In the third part?Chapter five?,the flower-like boehmite was synthesized from a bayerite precursor via phase transformation in a template-free way.The resultant boehmite composed of the nanosheets with 1-5 nm thickness with bimodal porosities.The bayerite precursor gradually dehydrated and transformed to boehmite from the crystal outside to the inside,with no changes of the primary crystallite size and the coordination state of aluminum.In contrast,the surface area of the material increased from 28 to 221 m² g^-1.The ?-alumina derived from boehmite via calcination exhibited a high surface area of 281 m² g^-1.Possessing open pore structure and larger pore size,the conversion of TIPB on flower-like y-alumina was about 2 times as high as that on comparison commercial alumina.Last but not the least?Chapter six?we further investigated the practical application of thus obtained zeolite and matrix as a FCC catalyst under reaction conditions close to the industrial process in a micro fluid catalytic cracking testing unit.The cannibalism dealuminated Y zeolite containing sprayed catalyst exhibited higher conversion and higher gasoline yield than the USY containing sprayed catalyst in the cracking of heavy oil.The cannibalism dealuminated Y zeolite and binary SiO₂/Al₂O₃ matrix containing sprayed catalyst showed higher conversion,higher gasoline and liquefied petroleum gas?LPG?yield than the USY and SiO₂ matrix containing sprayed catalyst in the cracking of heave oil.