Preparation Of La-ni-s2o82-/zro2-al2o3 Solid Superacid Catalyst And Its Performance For Isomerization

Isomerized gasoline is the cleanest high-octane gasoline component,which is free of sulfur,olefins and aromatics.Solid superacids have several advantages as catalysts,including strong acidity,stability,and environmental friendliness.SO₄^2-/ZrO₂ and S₂O₈^2-/ZrO₂ solid super acid catalyst is considered to be the most development potential of catalytic materials.In this paper,La-Ni-S₂O₈^2-/ZrO₂-Al₂O₃ catalysts were prepared.The prepared catalysts were characterized by XRD?BET?FTIR?PyIR?XPS?XRF?TEM?TG/DTA to illustrate their physical and chemical properties.The isomerization catalytic performance of catalysts was evaluated via using n-pentane isomerization as probe reaction.This paper mainly contains three parts:In this paper,the ZrO₂-Al₂O₃ composite supports are prepared by co-precipitation method,constant pH method and hydrothermal method.The influence of preparation method of supports on the La-Ni-S₂O₈^2-/ZrO₂-Al₂O₃?La-Ni-SZA?catalyst properties was studied.The results showed that preparation method of supports has a great influence on surface area and pore structure.The catalysts prepared by co-precipitation method and hydrothermal method showed a better activity and selectivity,while the preparation process of co-precipitation method is simple and convenient.Secondly,the catalysts were prepared by two kinds of acid leaching methods,that is equal volume impregnation method and traditional acid leaching method.The influence of acid leaching method on the La-Ni-SZA catalyst properties was studied.The results show that the catalyst of B acid and L acid were significantly higher than that of the traditional acid preparation method.The yield and selectivity of isopentane of traditional acid preparation method are 66.5 % and 98.5 %,respectively.The initial activity of the La-Ni-S-ZA catalyst was 55%,the yield of isopentane can be stabilized at more than 50%,and the selectivity was kept higher than 85%,when the La-Ni-S-ZA catalyst was employed at the following reaction conditions;temperature 280 oC,space velocity 1.0 h-1,H2/n-pentane molar ratio 4.0 and reaction pressure 2.0 MPa.It showed that the catalyst prepared by leaching acid had with equal volume has the best stability.Thirdly,the stability of La-Ni-SZA catalyst was investigated.The spent La-Ni-SZA catalysts were regenerated by calcined spent La-Ni-SZA catalyst and resulfated the calcined catalyst.The results revealed that?1?the yield of isopentane using fresh La-Ni-SZA was maintained above 65% in the first 1000 minutes.However,the yield fell sharply from 65% to 25% during the subsequent 2000 minutes.?2?The deactivation of the La-Ni-SZA catalyst may be due to a combination of carbon deposition,loss of Br?nsted acidity,removal of sulfur entities.?3?The spent catalyst,calcined 3 h under 500 °C,can basically eliminate carbon deposit on the surface,and the early activity can be recovered to 58% of the fresh catalyst.However,it also showed a sustained decline in activity for pentane isomerization.?4?The spent catalyst was resulfated after calcined not only eliminates the surface area of carbon,the total acid amount and S content is also higher than that of fresh catalyst.The isopentane yield using the resulfated La-Ni-SZA was maintained at about 58%,with isopentane selectivity above 90%,during the tested 3000 minutes.Compared with fresh catalyst,the resulfated catalyst showed sustained excellent stability,although the initial activity was slightly lower.The improved stability of the resulfated catalyst can be explained by:?1?formation of improved acidic nature by resulfation,suppression of carbon deposition to some extent;?2?the combination of S and Zr was firmer,and S species loss was inhibited;?3?restructuring of the acid and metal sites via the calcination-resulfation procedure,the isomerization reaction was promoted.