Preparation And Characterization Of Functionalized Nano-gold Complex Catalyst And Its Application In Selective Oxidation

Selective oxidation of organics involves many aspects of chemical production,it plays an important role in chemical industry.However,due to the existence of many parallel reactions and series reactions,especially under high temperature without good catalyst,there are many side reactions which leads to low selectivity of main products.Therefore the highly active and highly selective oxidation under mild conditions has been paid much attention,while it is a great challenge too.So,in this thesis,preparation and characterization of functionalized nano-gold complex catalyst and its application in selective oxidation are studied.This thesis is divided into seven chapters.It investigates preparation and characterization of nano gold supported on manganese porphyrin metal-organic frameworks Au/MnPS catalyst for selective oxidation of cyclohexene,preparation and characterization of gold center metal organic frameworks AuBTC catalyst for selective oxidation of benzyl alcohol,and preparation of microchannel reactor coating with Au/Al₂O₃ catalyst on the inner wall for cyclohexane oxidation.The conclusions are as follows:Firstly,Au/MnPS was successfully prepared by hydrothermal synthesis method and impregnation method.TEM characterization of the catalyst showed that MnPS owed the cubic crystal structure in dark color,and part of that owed amorphous floc structure in light color,where Au NPs with particle size less than 10 nm and larger Au NPs are present,which indicated that Au NPs were successfully loaded.XRD characterization of the catalyst showed that structure of MnPS might be similar to that of manganese carbonate,which provided a possibility to make a further decision of its real structure.The catalytic performance of selective oxidation of cyclohexene over Au/MnPS catalyst showed that all process conditions,such as solvents,oxidants,reaction temperature,reaction pressure,reaction time,catalyst dosage and gold loading,had effect on reaction performance.For the oxidation of cyclohexene under atmospheric pressure,the process conditions of reactant cyclohexene amount 10 mmol,a gold loading of 2 wt%in Au/MnPS,catalyst dosage 0.2 g,acetonitrile as a solvent,tert-butyl hydroperoxide with a little water as an oxidant,reaction temperature of 35?,reaction time of 15 h,were appropriate,while the conversion of cyclohexene reached the highest 76.7%and the selectivity of epoxy cyclohexane reached 75.1%.For the oxidation of cyclohexene under high pressure in autoclave,the process conditions of reactant cyclohexene amount 10 mmol,a gold loading of 0.25 wt%in Au/MnPS,catalyst dosage 0.1 g,acetonitrile as a solvent,4-5 drops of tert-butyl hydroperoxide as an initiator,reaction temperature of 120?,reaction pressure of 1.2MPa,reaction time of 10 h were appropriate,while the conversion of cyclohexene reached the highest 88.4%and the selectivity of epoxy cyclohexane reached 83.0%.The catalyst was recycled four times with no noticeable loss of activity,which demonstrated its good recyclability.Secondly,AuBTC was prepared successfully by hydrothermal synthesis method.XRD characterization of the catalyst showed that structure of AuBTC might be similar to that of HKUST-1?CuBTC?,where Au was in the centre of the crystal structure.SEM characterization of the catalyst showed gold and trimesic acid were combined to form a new crystal after hydrothermal synthesis with a columnar stuctre consisting of layers.The catalytic performance of selective oxidation of benzyl alcohol over AuBTC catalyst showed that all process conditions,such as reaction temperature,reaction pressure,reaction time and catalyst dosage,had effect on reaction performance.The process conditions of reactant benzyl alcohol amount 10 mmol,catalyst dosage 0.1 g,acetonitrile as a solvent,4-5 drops of tert-butyl hydroperoxide as an initiator,reaction temperature of 80?,reaction pressure of 1.0 MPa,reaction time of 15 h,were appropriate,while the conversion of benzyl alcohol reached 11.8%and the selectivity of benzaldehyde reached 90.3%.The research about the cyclic properties of the catalyst showed that the selectivity of benzaldehyde decreased rapidly after the catalyst was reused.Thirdly,microchannel reactor coating with Au/Al₂O₃ catalyst on the inner wall was prepared successfully by our independently innovated coating method.TEM and XRD characterization of Au/Al₂O₃ showed that the Au NPs in the catalyst were uniformly dispersed in the ultra-fine alumina support.SEM characterization of the microchannel before and after coating showed that the acid treatment had a certain effect on enhancing the bond between the catalyst and the inner wall of the microchannel reactor.The process conditions of reaction temperature of 180?,residence time of 4 min,reaction pressure of 3 MPa and molar ratio of oxygen to cyclohexane of 0.3:1 were appropriate,while the conversion of cyclohexane reached 2.09%,with the selectivity of cyclohexanol 29.4%,cyclohexanone 39.9%,cyclohexyl hydroperoxide 2.46%,and adipic acid 18.9%,respectively.Experiments showed that stainless steel microchannel coated with a supported nano gold catalyst in cyclohexane oxidation was feasible,the reaction time was shortened and the process operation security was improved significantly.In summary,functionalized nano-gold complex catalysts have not only excellent catalytic performance and great industrial application potential for the selective oxidation process of organics,but also a great research value in academics,which is worth further study.