Characterization And Preparation Of Supported Metal Oxide Catalysts For Di-2-ethylhexyl Carbonate Synthesis

ZrO₂ was prepared by the coprecipitation,Na₂O/ZrO₂,K₂O/ZrO₂,CaO/ZrO₂ solid base catalyst were prepared by impregnation method with NaNO₃,KNO₃, Ca(NO₃)₂ and calcined at different temperature.γ-alumina as the supporter, Na₂O/Al₂O₃,K₂O/Al₂O₃,CaO/Al₂O₃ solid base catalyst were prepared by impregnation method with the same precursors and calcined at different temperature.The catalytic performances were evaluated in the synthesis of di-2-ethylhexyl carbonate from dimethyl carbonate and 2-ethyl-hexanol.Accord to the literature,the operation conditions for the reaction were obtained as follows: atmospheric conditions,reaction temperature 130℃(first step),reaction time 4 h, n(DMC):n(EHOH)=1:2,catalyst loadings 1.5%of mass of the feed.The characterization by XPD of Na₂O/ZrO₂,K₂O/ZrO₂,CaO/ZrO₂ solid base catalyst showed there were tetragonal ZrO₂ phases calcined at low temperature, tetragonal ZrO₂ phases is beneficial for activity.With the calcination temperature increasing,there monoclinic ZrO₂ phases were appeared,the specific surface area and activity decreased at the same time.With the calcination temperature increasing,the nitrate decomposed thoroughly on zirconia surface,but the specific surface area decreased with the increase of calcination temperature.Na₂O/ZrO₂, K₂O/ZrO₂,CaO/ZrO₂ reached their highest activity at 600℃,500℃,700℃, respectively.The characterization by CO₂-TPD showed strengths of basicity of catalysts. There were strong basic sites appeared on Na₂O/ZrO₂ calcined at 600℃.K₂O/ZrO₂ had strong basic centres and also moderate basic centres,only moderate basic centres appeared on CaO/ZrO₂,there were no strong basic centres. The more basicity,the higher activity.It was proved that the rare earth cerium added should enhance the basic of zirconia-supporter.The activity of Na₂O/ZrO₂-CeO₂(0.92%)was good,it reached 66.1%。Energy spectrum show that cerium content of Na₂O/ZrO₂-CeO₂(0.92%) is 0.65%.The characterization by XRD of Na₂O/Al₂O₃,K₂O/Al₂O₃,CaO/Al₂O₃ solid base catalyst showed no impact on alumina phase calcined at different temperature.There were added rare earth cerium alumina-supporter solid base,it was diffraction peaks of aluminate and aluminate cerium.The decomposition of nitrate and the specific surface area decreased.The decomposition of nitrate on zirconia were more completely than it on alumina.Na₂O/Al₂O₃,K₂O/Al₂O₃, CaO/Al₂O₃ both reached their highest activity at 700℃.But,the activity of alumina-supporter was lower than zirconia-supporter.CO₂-TPD test of alumina-supporter proved alumina-supporter solid base only had weak basic centres and moderate basic centres.As a whole,the addition of rare earth cerium enhance the basic of Na₂O/Al₂O₃,K₂O/Al₂O₃,but had little impact on CaO/Al₂O₃. Energy spectrum show that cerium content of Na₂O/Al₂O₃-CeO₂(3%) is 1.14%.The synthesized samples were analysed by FT-IR,¹H-NMR,gas chromatography,MS,which proved the structure of the synthesized samples conformed to di-2-ethyl-hexyl carbonate.The analysis gas chromatography online tracking reaction showed that there appeared di-2-ethylhexyl at 2 h,intermediate product disappeared at 4 h.lt also showed catalysts had high catalytic activity.