The Catalytic Oxidation Of Cyclohexane To Adipic Acid Catalyzed By TM-HTS

TS-1 is a hetero-atom molecular sieve composed of tetrahedral titanium oxygen bonds and tetrahedral silicon oxygen bond. It is a kind of novel mesoporous materials that enwrapped tetrahedral titanium into the framework of silicon molecular sieve. It has attracted much attention of many researchers due to it’s stable structure and excellent catalytic performance. Using H2O2 as oxidant, the catalytic epoxidation of olefins has been a hot field of catalytic synthesis. Many synthetic methods of TS-1 have been reported, the current methods is based on butylsilicate(TEOS) as silicon source, tetrabutylorthotitanate(TBOT) as titanium source and Tetrapropylammoniumoxide(TPAOH) as the template, through a one-step hydrothermal method to synthetise TS-1. However, due to the limitation of mesoporous pore size in TS-1 and hydrogen peroxide as a more expensive oxidant, which greatly limits its application in industry. In order to expand the application of TS-1 and increase the catalytic activity of TS-1, modifying the TS-1 to obtain the HTS is necessary. Then used transition metal doped it, getted the TM-HTS catalyst. At last, tested the catalytic performance of prepared catalysts which through the catalytic oxidation reactions of cyclohexane.Then, under Mn-HTS as the catalyst and oxygen as the oxidant, cyclohexane was oxidated directly to adipic acid without any initiator and solvent. Under the optimum conditions(140 ℃, 1.0 MPa), the cyclohexane of conversion can reach 13.43% and the selectivity of adipic acid is 57.5%. The advantages of the catalyst is easily separated from the reaction system, the catalytic performance is not reduced in repeated use, which indicate the stability of the catalyst is good. Through the FT-TR, UV-Vis, N2 adsorption–desorption, XRD, XPS, TEM and other characterization methods to analyze the structure of the prepared catalysts.Cyclohexanone is an intermediate product in the oxidation of cyclohexane, nitric acid was used oxidated cyclohexanone to adipic acid in industry usually. Although high conversion rate(90%) of cyclohexane and high selectivity(70%) of adipic acid could be obtained, releasing a large number of nitrogen oxides and other toxic gases at the same time, which causing serious environmental pollution. In addition, concentrated nitric acid is highly corrosive, the corrosion of equipment is very serious. This paper developed a new method to oxidate cyclohexanone to adipic acid, which using oxygen as oxidant and Mn-HTS as catalyst. In this reaction, for the oxidant is cheap and not any solvent wasted, improving economic benefit largely. Under the condition of 100 ℃ and 0.6 MPa oxygen pressure, the conversion of cyclohexanone can reach 68.4% and the selectivity of adipic acid up to 93.1% after 9 h.