Preparation And Aromatic Ring Opening Performance Of MeAPO-5 Zeolite Catalysts

The use of clean energy is the main trend of energy development in the future,and higher requirements are put forward for sulfur,nitrogen content and cetane number of diesel oil.Unsupported catalysts have high hydrogenation activity but poor ring opening selectivity.Bifunctional catalysts prepared by solid-state reaction without water are promising because of the combination of sieves and unsupported catalysts.APO-5 zeolite was prepared by solid-state reaction,doped with Ni and Mo.The optimum hydrogenation activity and selectivity of ring opening were obtained at 200?and 36 h crystallization time.The structure of the catalyst is affected by the amount of metal doping,and the structure of the zeolite is destroyed when the content of metal doping exceeds 30%.The specific surface area and pore volume of bimetallic doped MeAPO-5 zeolite first increase and then decrease with the increase of doping amount,and the average pore size increases continuously.Both Ni and Mo can enter the framework of zeolite to produce acidity.The hydrogenation activity and ring opening selectivity of the reduced catalyst are better than those of the sulfided catalyst.The conversion of naphthalene and the ring opening selectivity of the reduced catalyst are 61.2%and 9.9%respectively at 200 C and 30%metal doping.A small amount of Co doping will increase the crystallinity of the zeolite,and the color of the zeolite will change from white to blue.The doping of Co can decrease the acid strength and increase the acid content of the catalyst.Co10Mo10 has the lowest specific surface area and pore volume,99 m²/g and 0.16 cm³/g,respectively.The average pore size is 6.84 nm.The pore volume decreases with the increase of Co content,and the surface of the catalyst becomes denser with the increase of Co content.Ni10Mo10 catalyst has the best sulfide activity and lower ring opening activity.Ni8Co2Mo10 has a high reduction hydrogenation activity,and its ring opening activity reaches 12.8%at 380?.The combination of zeolite and unsupported catalyst can improve the catalytic activity for high temperature hydrogenation,and the ring opening selectivity has no obvious change.The cracking activity and selectivity have been greatly improved.The selectivity of individual cracking products is the best when the doping amount of Ni10Mo10 zeolite is 10%.The selectivity of toluene is 40%,and xylene is 26.2%.Reduced catalyst has better ring opening selectivity and cracking rate than first sulfeded then reduced catalyst.This may be related to the fact that R-Ni Mo catalyst has more Mo⁴⁺and Mo⁵⁺and that sulfided MoS₂ may have no effect or inhibition on pyrolysis reaction.Nickel may promote the pyrolysis reaction.The ring-opening reaction of the reduced catalyst follows the hydrogenolysis mechanism of C-C bond cleavage in the exocyclic ring to form methane and monocyclic C9 compounds,and then to produce C8 and C7 products by continuous hydrogenolysis.