Research On Cyclohexane Oxidation Process Catalyzed By NHPI/ SMA-Co Multiple Active Site

In the industry,cyclohexane liquid-phase air oxidation is the main technology route for the preparation of cyclohexanone and cyclohexanol(KA oil).KA oil is the raw material for the production of caprolactam(nylon-6),and its further oxidized product adipic acid is used in the synthesis of polyamides(monomer of nylon-66).At present,the main synthesis method of KA oil is cyclohexane oxidation catalyzed by cobalt salt,which yield can reach millions of tons per year.However,this process has many deficiencies,such as poor selectivity of KA oil(< 80%),low conversion rate of cyclohexane(<5%),high energy consumption and serious pollution,limiting the development of nylon fiber industry.Therefore,the development of new catalysts is of great significance.Firstly,low molecular weight Styrene-maleic anhydride copolymer(SMA)was synthesized.Then,the transition metal cobalt was introduced into the ligand carboxyl group in the molecular chain of the hydrolysis product.In selected experimental conditions,changing the molar ratio between SMA and Co to synthesize a series of metal complexes of Styrene-maleic acid Cobalt(SMA-Co).The highest content of Co in the SMA-Co was 4.57%,and the coordination ratio was 17.81%.The complexes was characterized by elemental analysis,FT-IR,XRD,TG-DTA and SEM.The analysis showed that the carboxyl groups in the copolymer SMA might be coordinated to the transition metal cobalt ions as the bidentate ligand.The catalytic activity of cyclohexane was confirmed by the reaction of cyclohexane with hydrogen peroxide.The results showed that the prepared SMA-Co exhibited good catalytic activity on the oxidation of cyclohexane with the synergistic effect of the NHPI catalyst.The reaction of molecular oxygen oxidation of cyclohexane catalyzed by NHPI/ SMA-Co multiple active site was studied in this paper.The optimum reaction conditions were as follows: cyclohexane of 5mL,acetonitrile of 10 mL,the molar ratio of NHPI/SMA-Co is 10:3,HHPI/SMA-Co composite catalyst dosage is 0.04 g,reaction temperature is 120?,initial oxygen pressure is 1.0MPa.React for 6h under these conditions,the conversion of cyclohexane was 19.84%,the selectivity of cyclohexanol was 22.23%,the selectivity of cyclohexanone was 38.65%,and the selectivity of KA was 60.88%.Repeated use experiments showed that the catalyst could be recycled.The reaction of hydrogen peroxide oxidation of cyclohexane catalyzed by NHPI/ SMA-Co multiple active site was studied in this paper.The optimum reaction conditions were: 0.6mL cyclohexane,10 mL acetonitrile,NHPI/SMA-Co molar ratio of 2:1,HHPI/SMA-Co composite catalyst dosage of 0.04 g,reaction temperature is 70?,30% hydrogen peroxide dosage is 3mL.React for 5h under these conditions,the conversion of cyclohexane was 13.32%,the selectivity of cyclohexanol was 19.48%,the selectivity of cyclohexanone was 45.73%,and the selectivity of KA was 65.21%.