Study Of Solid Catalysts And Process For Alkylation Of Isobutane With Butene

Alkylation of isobutane with butene is an effective method to producehigh-octane gasoline. Developing new solid catalysts without pollution is a topicconcerned by many petrochemical corporations. This thesis studied the alkylationperformances of supported heteropoly acid and zeolite catalysts as well as correlativeprocesses, which is significant for theory and practical application.The acidity and alkylation performances of supported heteropoly acid had beenstudied. Unfortunately, the results showed that this type of catalyst had lowselectivity of trimethylpentane(TMP), and was unsuitable for the alkylation ofisobutane with butene. The relation between acidity and reactivity of supportedheteropoly acid was examined by skeletal isomerization of n-butane. The resultexhibited that activity and stability of the catalyst was improved by adding 1.6% ofsteam into the feed, which was ascribed to that suitable crystal water of heteropolyacid was maintained, and the strong acid sites, especially super-strong acid sites,needed for skeletal isomerization of n-butane were kept for a long time by addingsuitable amount of steam.Alkylation performances of Beta zeolite catalyst under low temperature andliquid-phase conditions were studied. Higher ratio of paraffin/olefin and suitablepressure could increase stability of the catalyst. In addition, the Beta zeolite catalysthad higher selectivity of TMP and better stability in a slurry-bed reactor than in afixed-bed reactor.The stability of Beta zeolite catalyst was obvious improved by treating it withcitric acid solution. The results from N2 adsorption-desorption isotherms, X-raydiffraction (XRD), NH₃ temperature programmed desorption (NH₃-TPD) andpyridine-adsorbed infrared spectrum (Py-IR) exhibited that this kind of treatmentcould keep the crystal structure of Beta zeolite, and increase the specific area andtotal pore volume. Both a large specific surface area and a large total pore volumewere obtained by treating the catalyst with 0.25 mol/l of citric acid solution for 2h.Furthermore, proper treatment of citric acid solution could modify acidity of thecatalyst, increase the ratio of Br?sted to Lewis acid sites, and especially increase theproportion of medium strength Br?sted acid sites in the total Br?sted acid sites. The reason for deactivation over Beta zeolite catalyst was studied from aspectsof carbon deposition, pore structure and acidity. It is concluded that the deactivationresults from both blocking of Beta zeolite channel and decrease of medium strengthacid sites, which is all ascribed to the formation of long-chain iso-paraffin andalkyl-aromatics. Calcination in air stream is one of the efficient methods for theregeneration of reacted Beta zeolite catalyst. In summary, the alkylation performances of isobutane with butene over bothheteropoly acid and zeolite catalysts have been investigated in this thesis, and theresults are helpful for further development of the solid acid catalysts for this process.