Study On The Selective Oxidation Of Cyclohexane Based On Phthalocyanines

In the chemical industry,the oxidation of cyclohexane is a reaction of oxidizing C-H bonds,especially the oxidation process using O₂,and its oxidation products KA oil（That’s the industrial collective name for the mixture of cyclohexanol and cyclohexanone）and adipic acid.Is a very important substance,cyclohexanol and cyclohexanone are used in the production of complex and diverse caprolactam,nylon-6 and nylon-66.The traditional selective oxidation of cyclohexane to prepare KA oil generally uses a homogeneous catalyst.This process is carried out at about 150°C and under the pressure of 1～2 MPa,the conversion rate of cyclohexane is 4%and KA oil selectivity is 70～85%at this time.Both the conversion rate of cyclohexane and the selectivity of KA oil are very low,which is not conducive to the development of cyclohexane commercial value.The development of an emerging technology that utilizes air or oxygen as an oxidant and has the advantages of environmental protection,greenness,energy saving,and high efficiency,and its application to the oxidation of cyclohexane is a current research hotspot.As an important class of topological materials,metal phthalocyanines（Pc M）have the characteristics of low toxicity,no pollution,stable chemical properties,excellent photosensitivity,good thermal stability,low price,and prominent metal active sites.Therefore,Pc M has good applications in catalytic reactions,semiconductor industry,optical and electrical devices.In view of this,metal phthalocyanine containing carboxyl group was selected as the research material,and a series of heterogeneous catalysts were designed and synthesized to study the selective oxidation of cyclohexane in O₂atmosphere.The carboxyl-containing metal phthalocyanine（HPc M）can promote the generation of active radicals and activate the C-H bond in the O₂ atmosphere,thereby improving the reaction speed and efficiency.The catalysts were characterized by Fourier transform infrared spectroscopy（FT-IR）,Ultraviolet-visible absorption spectroscopy（UV-vis）,Powder X-ray diffraction（PXRD）,Scanning electron microscopy（SEM）and other characterization methods,and the catalytic conditions were investigated.Optimization to explore the effect of different conditions on the response.In this paper,two phthalocyanine catalysts have been effectively developed,both of which have good catalytic activity and have good industrial prospects in the oxidation of C-H bonds of cycloalkanes,which provide an effective reference for the future research and development of metal phthalocyanine catalyzed cyclohexane to prepare KA oil.The research is as follows:1.Using 4-nitrophthalonitrile and p-hydroxybenzoic acid as raw materials,amorphous and network-like tetra-β-（4-carboxyphenoxy）phthalocyanine iron（HPcFe）was synthesized by DBU method.As the catalytic site,metallic Fe has efficient catalytic performance for the oxidation of cyclohexane,the conversion rate of cyclohexane can reach 6.2%,and the selectivity of KA oil is 95.65%.It far exceeds the existing industrial catalyst standards.After 5 cycles of use,the catalyst performance remains unchanged and has good cycle stability.2.γ-Al₂O₃/M-TNPc（M=Fe,Zn,Co）supported nanocatalysts were prepared by sol-gel method,and it was proved that metal Co had the best catalytic effect among the three metals,andγ-Al₂O₃/Co-Based on TNPc,the reaction conditions were optimized.Under these conditions,the conversion rate of cyclohexane was 11.35%,and the selectivity of KA oil was 93.3%,which was nearly 3 times higher than the industrial conversion rate of 4%.In addition,the catalyst can be recycled without deactivation.The catalyst was characterized by FT-IR,UV-vis,SEM,N₂ adsorption and other characterization methods,which proved that the catalyst has a mesoporous structure and presents a network lamellae.In addition,the catalytic process of both catalysts was proved to be a radical reaction mechanism,and the cyclohexane oxidation products were qualitatively and quantitatively analyzed by various methods..