A Novel Method For The Synthesis Of Nickel-modified Sulfated Zirconia Core-shell Catalyst And Its Performance For Isomerization

The catalytic hydroconversion of n-paraffins is an important reaction to improve the quality of gasoline in the oil-refining industry.Environmentally friendly solid superacid catalysts,especially sulfated zirconia?SZ?,are promising candidates to replace conventional chlorinated alumina catalyst due to their high activity at low temperatures.In this paper,we report a novel route to prepare non-noble-nickel-modified persulfated Al₂O₃@Zr O₂ core–shell catalyst?Ni–SA@Z?.And the preparation method was investigated by the selection of core materials,the content of Al and the citric acid modification.The prepared catalysts were characterized by XRD?BET?FTIR?Py-IR?TG?XPS?TEM?C-S Analysis to illustrate their physical and chemical properties.The isomerization catalytic performance of catalysts was evaluated via using n-pentane isomerization as probe reaction.The results were as follow:?1?The catalyst prepared by Al₂O₃ core material possesse smaller Zr O₂ paricle size,higher surface area and the pore volume,stronger acidity and the highest acitivity.The isopentane yield of isopentane reaches 64% under the temperature of 180 ?.?2?The addition of Al can inhibit the transformation of Zr O₂ from the metastable tetragonal phase to the monoclinic phase,improve the surface area?pore volume?pore size and stabilize S species.When the Al content is 30 wt.%,the acidity of the catalyst is stongest and the isopentane yield reaches 64%.?3?The surface area and pore size for core-shell catalyst are significantly increased.The strong B acid sites and strong L acid sites are both improved.The core-shell catalyst performed excellent stability.In the optimum reaction condition: temperature is 180 ?,pressure is 2.0 MPa,H2/n-pentane is 4:1,WHSV is 1.0 h-1,the Ni–SA@Z–x?x = 30 wt.%?catalyst showed a sustained high isopentane yield?64%?with little or no deactivation within 5000 min.?4?With the increase of citric acid content,the surface area,pore size and the acid sites are all increase.The optimum reaction temperatures of catalysts decrease first and then increase.When the citric acid content is 2 %,the reaction temperature is lowest.The isopentane yield is 60% at 140 ?.Compared with the catalyst without citric acid,the best reaction temperature was reduced by 40 ?.