Mesoporous MO/ZrO₂-La₂O₃Solid Base Catalyst And Catalytic Activity Of Transesterification

In this thesis, mesoporous zirconia （ZrO₂） were synthesized by hydrothermal andimmersion process with a cationic surfactant C16H33（CH3）3NBr （CTAB） as template.After that, the mesoporous solid base catalysts of MgO/ZrO₂and MgO/ZrO₂-La₂O₃-xwere prepared with ZrO₂, MgO and La₂O₃as the carrier, active component andadditives, respectively. On this basis, by immersing those catalysts respectively in theKNO₃or KOH solution,the mesoporous catalysts K₂O-x/ZrO₂-MgO andK₂O-x/ZrO₂-MgO-La₂O₃were prepared. The catalytic activities were evaluated in thesynthesis of di-2-ethylhexyl carbonate （DEHC） from dimethyl carbonate （DMC） and2-ethylhexanol （EHOH）. The physical and chemical properties of the catalysts werecharacterized by XRD, Raman spectra, CO₂-TPD, BET method, SEM and TEM. Andthe influence of the potassium content, the calcination temperature, and the additionof magnesium or lanthanum on the crystal structure and basicity of the catalyst werecomparatively investigated.The mesoporous MgO/ZrO₂and MgO/ZrO₂-La₂O₃-x characterization resultsindicated that there is main tetragonal phase for the catalysts with typical mesoporousstructure, which implies that MgO is highly dispersed on tetragonal phase ZrO₂forming a stable MgO/ZrO₂solid solution. When the Mg/Zr molar ratio is0.45, MgOcan steady simultaneously the surface phase and bulk phase of t-ZrO₂. La₂O₃is able topromote the dispersion of MgO covered on ZrO₂surface, which leads to the exposureof the alkalescence of partial ZrO₂. Additionally, the grain refinement, the specificsurface area are increased. When the content of La₂O₃is0.7%, there is the largestcatalytic activity.For mesoporous K₂O-x/ZrO₂-MgO and K₂O-x/ZrO₂-MgO-La₂O₃catalysts, whenthe load of KNO₃or KOH is0.2, the resulting sample exhibits a typical mesoporousstructure. With the increasing of the content of potassium, the partial channels areblocked, which caused the changes of the specific surface area, pore diameter andchannels. With the increasing of the content of KNO₃, the structures of the catalystsare gradually changed from surface single dispersion to K₂O sandwich, thus the weakbasic site and medium strong basic site of ZrO₂are covered. As the content of KOHincreases, CO₂-TPD corresponding to medium strong basic site is weakened with the increasing of MgO desorption peak. La₂O₃is able to promote the dispersion of MgOcovered on ZrO₂surface and the grain refinement.The catalytic performances were evaluated in the synthesis of di-2-ethylhexylcarbonate （DEHC） from dimethyl carbonate （DMC） and2-ethylhexanol （EHOH）. Inorder to characterize the synthetic product, FT-IR and gas chromatography was used.