Study On The Layered Titanium Niobate And Its Catalytic Effect On The Esterification Reaction

Recently, sulfuric acid using as the catalyst of esterification reaction of acetate and n-butanol is very widely, which have higher esterification rate. But there are many shortcomings such as corrosion of equipment, serious pollution and so on. The environmentally friendly layered solid acid is an important class of esterification catalyst because of its surface strongly acidic, highly selectivity and non-pollution. As mentioned above, the layered solid acid H3Ti5NbO14was prepared by the proton exchange of layered K3Ti5NbO14, which was synthesized by high temperature solid-state reaction (SSR). TiO2-H3Ti5NbO14composite materials were synthesized by pillared TiO2of the layered H3Ti5NbO14. And the super acid materials SO42-/TiO2-H3Ti5NbO14were obtained by sulphuric acid dipping. The phase structure, morphology and acidic characteristic of the samples were characterized by means of XRD, SEM, TEM, BET, TG-DTG, FT-IR and NH3-TPD. The catalytic performance was evaluated through the esterification reaction of acetate and n-butanol.The results show that:the layered K3Ti5NbO14after proton exchanging becomes H3Ti5NbO14solid acid. Because its ionic radius of H+becomes smaller than that of K+the layer spacing becomes smaller and the BET specific surface area decreases by nearly six times, but the layered structure remains well. The layer spacing, BET specific surface area and pore volume of the composition of TiO2-H3Ti5NbO14become larger, but do not have significant impact on the layered structure of the host layer and skeleton vibration. The structural characteristics of TiO2-H3Ti5NbO14samples dipped by sulfuric acid and roasted at500℃change significantly. During the heat treatment in a high temperature, the adsorbed water and crystallized water removal make the main crystal surface (001) plane move significantly to the high angle, the layer spacing become smaller, and its morphology become fluffy, the pore volume and the specific surface area of the samples increase significantly. The study of acid characteristics find out that the order of acid strength and acid quantity of the samples is as follows:TiO2-H3Ti5NbO14-500℃> H3Ti5NbO14>> TiO2-H3Ti5NbO14.The four factors of molar radio of n-butanol and acetic acid, the reaction temperature, the reaction time, and the amount of catalyst were chosen as the test index. At the same time orthogonal experiments were designed with each factor three levels to test the catalytic activity of each catalyst to esterification of acetic acid and n-butanol.The results showed that:the optimal solutions of esterification reaction catalyzed by H3TisNbO14of TiO2-H3Ti5NbOi4and SO42-/TiO2-H3Ti5NbOi4-500℃were different. The yield of esterification catalyzed by H3TisNbO14in the optimal solution reached55.61%. While, the catalyst of Tio2-H3TisNbO14play a role in promoting the reverse reaction of the esterification reaction of n-butanol and acetic acid for its lower amount of acid, the acid strength and a larger surface area. But the samples dipped by sulfuric acid has the best catalysis of the esterification and the yield of the reaction reached up to72.5%under the optimization schemes due to its higher amount of acid and acid strength,. SO42-/TiO2-H3Ti5NbO14-500℃which has the highest catalytic efficiency was selected as the catalyst for single-factor optimization test to gain the optimum reaction conditions The researchs show that the prepared catalyst has a high activity to esterification reaction of acetic acid and n-butyl and esterification rate is closely related to the amount of acid catalyst and acid strength.