Catalytic Performance Of Sulphates For Oligomerization Of Low Carbon Olefins

In China,the National-ⅣStage Vehicle Exhaust Emission Standard was excuted in 2014, and the National-Ⅴ Stage was carried out in some developed regions recently. The lower octane numbers of gasoline is an important problem facing many chemical enterprises. Because of the use limitation of MTBE, development of the gasoline with both high octane number and low aromatics based on low carbon olefins oligomerization is one of the effective ways to solve this problem. Nonene and octane, formed from propylene trimer and butene dimer respectively, are the good additive components for gasoline with high octane numbers. So the effective catalyst for oligomerization of low carbon olifins is required.In this thesis, a series of catalysts of MSO4/γ-Al2O3 (M for the Fe, Ni, Co or Al) were prepared by equal volume impregnation method, and tested in the oligomerization reaction of low carbon olefins in fixd-bed reactor. The physico-chemical properties of the catalysts were characterized by XRD and NH3-TPD. The influences of active components, preparation conditions and catalytic reaction conditions were investigated. And the catalytic stability of the catalyst was tested. The main results are shown as follows:(1)For propylene oligomerization:A series of NiSO4/γ-Al2O3 catalysts with different of NiSO4 loadings was prepared by impregnation method. The best catalytic performance for oligamerization of propene was obtained over 9wt% NiSO4/γ-Al2O3 catalyst under the reaction conditions of P=3.0 MPa, LHSV=1.0 h-1, T=70 ℃, with 27.2% C9= selectivity and 96% propene conversion. XRD results showed that the monolayer despersionof the active component was found on the catalyst surface when the NiSO4 loadings was 9wt%. Addition of promoter and/or cosolvent into the supported sulfate catalysts is benefited to enhance C9-selectivity. The highest of C9-selectivity of 49.7% was found over the catalyst of NiSO4-FeSO4/y-Al2O3 with additions of (NH4)2HPO4 and FeSO4. And this catalyst exhibit good stability during the reaction.(2)For mixed butene oligomerization:The catalyst of Al2(SO4)3/γ-Al2O3 was prepared by impregnation method, and tested in the selective oligomerization reaction of butene. The influences of aluminum sulfate loadings, the reaction conditions and the surface acidity of the catalyst were investigated. The results noted that the activation energy of Z (E)-2-butene oligomerization is higher than that of 1-butene (isobutene) oligomerization reactions, and Z (E)-2-butene Oligomerization occurs at a higher reaction temperature. The weak acid sites of catalyst are the active centers for oligomerization of all kind of butenes, but the weak acid center for Z (E)-2-butene oligomerization is easy to inactivate. The best catalytic performance for selective oligamerization of butane was obtained over 2wt% Al2(SO4)3/γ-Al2O3 catalyst under the reaction conditions of P=4.0 MPa, LHSV=2.0 h"1, T=80 ℃, with no reaction of Z (E)-2-butene oligomerization and 96% 1-butene(isobutene) conversion.