Heterologous Butane - Butene Alkylation Reaction Of Solid Acid Catalyst

In this dissertation, toward the subject of solid acid catalyzed alkylation of isobutane with butenes, prevenient research work has been summarized and novel mesoporous solid acid catalysts MoO₃/ZrO₂ and WO₃/ZrO₂ were synthesized employing template method with S I route. The physicochemical features and acidity properties of the catalysts were investigated by several analysis techniques. Their catalytic capability to alkylation of isobutane with butenes also has been studied. In addition, another solid acid catalyst SO₃/γ-Al₂O₃ was prepared by adsorption of SO₃ gas onto the surfaces of activated γ-Al₂O₃. The structure and acidity of SO₃/γ-Al₂O₃ were studied and its catalytic performance for alkylation of isobutane with 1-butene was investigated. The detailed results of the research work are presented as follows:The mesoporous solid acid catalysts MoO₃/ZrO₂ and WO₃/ZrO₂ were synthesized employing co-precipitation of ammonium heptamolybdate and zirconium oxychloride in aqueous solution by using polyethylene glycol as template. The samples possess large surface area and pore volume, and the pore size distribution is concentrative. Highly dispersed MoO₃ (WO₃) on the surface of ZrO₂ prevented the zirconia phase transition and particulates condensation at high temperature which induced the shrinkage of the surface and the collapse of the porosity, so the majority of the pores remained when the samples were calcined at high temperature to remove the templates, the catalysts possess large surface area and pore volume after the templates removed. The NH3-TPD results showed that three different strength acid sites existed on the surface of both two samples. The acid scales of mesoporous WO₃/ZrO₂ are larger than that of MoO₃/ZrO₂, and the acid strength of mesoporous WO₃/ZrO₂ are also stronger than that of MoO₃/ZrO₂. According the ¹3C chemical shift changes after adsorbed acetone-2-¹3C, the acid strengths of the MoO₃/ZrO₂ and WO₃/ZrO₂ catalysts are stronger than that of zeolite HZSM-5, but still weaker than that of 100% H₂SO₄.Isobutane / 1-butene alkylation experiments were carried out to test the catalytic activityof mesoporous MoO3/ZrC>2 and WCh/ZrOa. The reaction parameters of time, temperature, and P/O ratio were studied, and the optimum reaction conditions were obtained. When the TOS = 60 minutes, and T = 60°C, the Cg content of the products achieved the maximum. Since many factors affected the products distribution, such as oligomerization, hydride transfer reaction, cracking, diffusion rate of products et al, the alkylation has an optimum TOS and a favorable reaction temperature. The Cs fraction increased with the increase of P/O ratio. When the mesoporous WOs/ZrO2 as catalyst, the conversion of butane and the Cs fraction is more than that of mesoporous Mo03/Zr02 as catalyst. This probably attribute to the larger surface area and stronger acid sites of mesoporous WO3/ZrO2 than those of mesoporous MoO3/ZrO2, these properties contribute to the alkylation and decrease the oligomerization of olefins. The deactivated catalyst was characterized by TG-DTA, FT-IR et al, and the alkylation reaction and deactivation mechanism on solid acid catalysts is proposed.A solid acid catalyst SO3/Y-AI2O3 was prepared by adsorption of SO3 gas onto the surfaces of activated Y-AI2O3, and its catalytic performance for alkylation of isobutane with 1-butene was investigated. XRD and 27A1 MAS NMR results indicated that SO3 reacting with activated Y-AI2O3 to form a small quantity of Al2(SO4)3, and at the same time, the adsorption of SO3 on the surface of y-Al2O3 introduced two different kinds of Bronsted acid sites, which can be attributed to two different acid hydroxyl groups, including the bridging hydroxyl groups and the terminal hydroxyl groups attached to S atoms. The NH3-TPD results indicated that two different strength acid sites existed on the surface of SO3/Y-AI2O3. The acid strength of SO3/Y-AI2O3 is stronger than that of zeolite HZSM-5, but still weaker than that of SO42"/y-Al2O3, which is a conventional solid superacid catalyst. The structure of Bronsted acid sites on the surface of catalyst SO3/Y-AI2O3 has been proposed based on lYU21A\ TRAPDOR and FT-IR results. Since the acid strength of S0427y-Al203 is stronger than that of SO3/Y-AI2O3, the the conversion of butane is higher when SO427y-Al2O3 as catalyst, but the contents of the C5--C7 fraction which produced by craking reaction are very high when SO427y-Al2O3 as catalyst.