| Solid super acid catalyst is a new type of catalyst which has been developed in recent years. It can overcome many problems presented in the traditional industrial catalyst (i.e. liquid inorganic acid sulfuric acid and phosphate; metal halide AlC13, SnCl4, TiCl4), such as the corrosion, environmental pollution, separation, vice-reactions, low selectivity, low catalytic activity, etc. Composite metal oxides solid acid catalysts have the strong acid, thermal stability, environment friendly and excellent catalytic performances, therefore, it can be applied in the petrochemical industry. In recent years, solid super acid catalysts, e.g., WO3/ZrO2, have attracted much attention of the researchers.Catalytic activity of the solid super acid catalyst is closely related to its BET surface area, which providing a lot of surface acid sites, hierarchically porous structure can effectively increases BET surface area and catalytic activity of the catalyst. WO3/ZrO2 solid acid catalyst with hierarchically porous structure was prepared by the one-pot hydrothermal method involving templating from a composite surfactant. The prepared samples were characterized by X-ray diffraction, N2 adsorption, Raman spectroscopy and NH3 temperature-programmed desorption analysis. The results indicated that W doping in ZrO2 by solid solution, and the catalysts showed much higher BET surface areas,which provided more surface acid centers. The esterification of acetic acid and butanol over the prepared samples showed that the hierarchically porous WO3/ZrO2 solid acid catalyst has excellent catalytic activity and reusability. The catalyst sample with 20% WO3 loading calcined at 550 ℃ for 5 h has highest catalytic activity. The effect of calcination temperatures of the prepared catalysts on the acid strength is studied as well as the total amount of acidity. The reaction of benzene alkylation with 1-dodecene was chosen as model acid catalysis. The results indicated that the acid strength and the total amount of acidity of the prepared catalysts increased with increasing of surface area and crystallization of t-ZrO2. Such catalyst shows a strong catalytic activity of the alkylation, and both the alkylation conversion and selectivity increase with acid strength. Thereinto, the catalyst sample calcined at 450 ℃ for 5 h has the highest catalytic activity and selectivity.In order to increasing lattice defects and the surface acid sites of the catalyst, it can doped the different valence metal active component into the catalyst, the atomic radius of Co is similar to Zr catalyst that more Co3+ can be dopped into ZrO2 by solid solution, which can enhanced catalytic activity according to more lattice defects caused by the O coordinatively unsaturated.A novel Co2O3-WO3/ZrO2 solid acid catalyst with hierarchically porous structure was prepared by a one-pot hydrothermal approach involving templating from a composite surfactant. The prepared catalyst loaded with 20wt.% WO3 and 25wt.% CO2O3 (in the composite WO3/ZrO2) calcined at 500℃ (named as 25CWZ) was found to be the highest activity in the catalysis reaction. The effect of temperature, molar ratio and hierarchically porous structure on dodecene conversion and product selectivity were studied in detail. Typically, when the optimized reaction conditions were chosen, such as the reaction temperature of 70℃ and the 4 molar ratio of phenol to 1-dodecene,92% dodecene conversion and as high as 76% dodecylphenol selectivity without by-product could be obtained in 2h for the prepared sample 25CWZ. This prepared catalyst was also found to have the outstanding reusability of more than 5 times in the etherification process, indicating excellent anti-poisonous performance owing to the hierarchically porous structure.Rare earth elements material has many special physical and chemical properties. Doping Nd3+ which has larger radius than Zr4+ into WO3/ZrO2 solid acid catalyst can produce a greater lattice distortion, as a result, it can effectively improve catalytic activity. A novel Nd2O3-WO3/ZrO2 solid acid catalyst with hierarchically porous structure was prepared after further loading with Nd2O3.The introduction of Nd2O3 has many advantages:1) the increased BET surface area can improve the effective contact area between reactants and catalyst; 2) the increase of the surface acid sites and the total acid amount can enhance the acid catalytic activity; 3) the change of the chemical state of the surface atoms and the reinforcement of electron-withdrawing ability of metal ions can reduce the loss of acidity in the process of catalytic reaction and improve the reusability of the catalyst.Based on the synergetic effect, TiO2-ZrO2 composite matrix can be obtained by introduction of TiO2, and ternary system WO3/TiOZrO2 and the quaternary system WO3-Co2O3/TiO2-ZrO2 can be synthesized after loading with the WO3 and WO3-Co2O3. The results indicate that there is a synergetic effect between TiO2 and ZrO2, and the introduction of TiO2 can improve the distribution of the strong acid sites, improving the selectivity toward target product in alkylation reaction. The catalyst has the strongest acid catalytic activity when titanium zirconium mass ratio is 1:1. Both the introduction of C02O3 and TiO2 in matrix ZrO2, and the synergetic effect among the active components of catalyst make the catalyst produce more acid sites, which can increase the acid strength, further improving the catalytic activity. |
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