Investigation On Alkylation Of Isobutane With Butene Over Heteropolyacid Catalyst Supported On Carbonized Resin

Alkylation of isobutane with butene to produce clean-burning gasoline component is an important reaction in petrochemical industry. The development of new solid catalysts to substitute traditionally used liquid acids has became one of the world-widely attracted subjects, in order to overcome the shortcomings of liquid acid catalysis. Although there exist still some problems about catalyst longlife and regeneration of catalyst to be solved, some achievements in this field have been obtained. Exploration of the new type of solid acid catalyst for the alkylation is theoretically and practically valuable. This thesis deals with the study on the alkylation of isobutane with butene over heteropolyacid HPW12 catalyst supported on carbonized resin in details. Globular carbonized resin carrier is prepared by the calcination and vapor activation of DKC large pore cation exchange resin. It has proper specific surface area,pore structure and better mechanical strength. Its preparation conditions are determined as follows: carbonization temperature 873K, carbonization time 3h, vapor activation time 1.5h, N2 flow rate 30ml/min, and its specific surface area 638.9m2.g-1 and average pore diameter 33.5?. The prepared resin is used to prepare the supported HPA catalyst, in which HPW12 is selected as active component for its stronger acidity. The balance time and isotherm equation for the adsorption of HPW12 on the carrier are determined. Pretreatment of the carrier has an effect on the supportation of HPW12 on it. Suitable conditions for preparation of the catalyst are: reflux impregnation with 30% HPW12 methanol solution; impregnation time 12h; activation temperature 473K. After 40h forced dissolution experiments of the catalyst, it is showed that the HPW12 is tightly binded on the carrier, and it demonstrates better activity for the alkylation than that of other similar supported catalysts. Characterization of the catalyst was carried out by means of IR,TPD-NH3,XRD,SEM and N2 adsorption. Results show that supportation doesn't damage the structure of HPW12 microstructure and the acidic amount of catalyst increases with the increasing of supported HPA amount. But the acidic strength remains constant. It is concluded that a proper supported amount is enough for the alkylation. SEM analysis shows that HPW12 is uniformly distributed on the carrier. The discontinuously operated autoclave under pressure and the atmospheric continuous flow tubular reactor are employed for the evaluation of alkylation activity. Effects of alkylation temperature, pressure, paraffin/olefin molar ratio, butene WHSV and reactant input ways on the activity of catalyst are investigated and the suitable alkylation conditions have been determined. The corresponding results are as follows: butene conversion 100%, TMP selectivity 90.8% for the alkylation under pressure, and butene conversion 50%, TMP selectivity 65.8% for the atmospheric alkylation. Characterization results for the used catalyst by means of IR, N2-adsorption and SEM show that the deactivation of catalyst is mainly caused by the covery of coke precursor formed from the side-reactions during alkylation. The coke precursor could be mainly the long-chain paraffins with more than ten carbons. Regeneration of the used catalyst is carried out, using the extraction by organic solvent and the H2O2 oxidation at lower temperature. Proper conditions of regeneration of catalyst are determined for the two methods respectively. For solvent extraction, the mixture of dichloromethane with petroether as the solvent, and extraction time is 10h; and as for H2O2 oxidation, oxidation time is 20h, oxidation temperature is 353~363K. After regeneration by these two methods, the activity of the used catalyst can be recovered to above 85% of its initial value. Process flow sheet of alkylation catalyzed by the heteropolyacid HPW12 supported on carbonized resin catalyst is subjected, which employs the riser-type reactor and combination of the alkylation and regeneration of catalyst.