Preparation Of Titanium Silicalite-1 With Large Particle And Its Application In Selective Oxidation Of Cyclohexane

The selective oxidation of cyclohexane is an important method of alkane conversion,which is of great significance to the national economy and social livelihood.The mixture of cyclohexanol and cyclohexanone is the oxidation products of cyclohexane,termed KA oil,which is a chemical intermediate to produce caprolactam and adipic acid,mainly used to produce nylon-6 and nylon-6.6.At present,the industrial production of KA oil mostly used the non-catalytic oxidation method or the cobalt salt oxidation method.Both methods are carried out under high temperature and high pressure,with air or nitrogen-oxygen mixed gas as the oxidant and soluble cobalt salt as the catalyst,with a KA oil selectivity of about 80%and a cyclohexane conversion of less than 5%.Although the reaction process has the disadvantages of poor economic efficiency and low atom utilization,due to the huge industrial demand for KA oil,it is also necessary to adopt such inefficient production methods.Based on the principle of cyclohexane selective oxidation,catalyst has become the key to solve the problem,and has received extensive attention from the scientific and industrial communities.Titanium-silicon molecular sieve?TS-1?is widely known as a green catalyst with excellent performance and usually used in combination with H₂O₂ to catalyze various oxidation reactions.TS-1/H₂O₂ system has extremely high industrial value.It has been successfully used in the large-scale production of propylene oxide,cyclohexanone oxime and other organic substances,and has exhibited excellent catalytic activity in cyclohexane oxidation.There are broad prospects for the industrial application of TS-1 catalytic cyclohexane oxidation process.However,the pores size?about 0.53 nm?of the traditional TS-1 molecular sieve are small,which makes it it difficult to catalyze bulky organic molecules.And the small particle size?about 500 nm?also prevent it to separate from the system by natural settlement.At the same time,the high cost of catalyst also limits its further application.Therefore,it is important to prepare a new low-cost large-particle TS-1 molecular sieve that can efficiently convert cyclohexane.On the basic of these studies,herein,this paper carried out a series of research work.Detailed research contents are as follows:?1?Based on the classic hydrothermal method,improving the original process,using the cheaper template agent,silicon source and titanium source,trying a new crystallization process,six TS-1 Molecular sieve have been synthesized by changing the alkalinity,aging temperature and crystallization temperature.The six TS-1 molecular sieves were characterized by Fourier-Infrared Spectroscopy?FT-IR?,Ultraviolet-Visible Spectroscopy?UV-vis?,X-ray Diffraction?XRD?,Scanning Electron Microscopy?SEM?and N2 adsorption and desorption,and the effects of different preparation conditions on the framework structure,crystal morphology and pore distribution of the catalyst were investigated.It provides a theoretical and practical basis for the large-scale preparation of TS-1 molecular sieve.?2?The relationship between the Ti content of the framework,particle size and pore volume and the catalytic activity of the TS-1 molecular sieve was explored,and the best synthesis process of the TS-1 molecular sieve was screened.Meanwhile,the effects of reaction temperature,reaction time,solvent dosage,oxidant dosage and catalyst dosage on cyclohexane oxidation reaction were studied,the optimal reaction conditions were determined,the catalytic stability of the catalyst was discussed,and the preliminary application of TS-1molecular sieve catalytic cyclohexane oxidation was achieved.?3?The separation conditions and recovery yields of products and raw materials in the reaction system were explored,and the differences of different catalyst regeneration methods were studied.Through the catalyst recovery test,the service life of TS-1 molecular sieve was discussed,and the stability of TS-1 molecular sieve pores and grains was proved.In addition,the sedimentation rate of such large particles TS-1 was discussed,and the problem of catalyst separation was solved.Finally,the pilot production of TS-1 molecular sieve was simulated.The structure and morphology of the catalyst were determined by XRD,FT-IR,UV-vis and SEM,and the catalytic performance of TS-1 in cyclohexane oxidation reaction was tested.The structure and morphology of the catalyst were determined by XRD,FT-IR,UV-vis and SEM,and its catalytic performance in cyclohexane oxidation reaction was tested,which suggests the data and theoretical support for the industrialization of TS-1 catalytic cyclohexane oxidation process.