| In the contemporary petrochemical industry,more than 90%are catalytic reactions,most of which are based on metal/metal oxide catalysts,especially 60%of the processes use precious metal catalysts represented by precious metals such as platinum,rhodium,and palladium.However,due to the limited reserves of precious metal catalysts,susceptibility to poisoning and deactivation,and high prices,they have been restricted from their widespread use in the petrochemical industry.Therefore,there is an urgent need to develop green,efficient and sustainable metal-free catalysts to replace metal-based catalysts.Graphene-based carbon materials represented by graphene and biomass-based carbon materials represented by cellulose have received many favored by scholars,it is prepared as a carbon-based metal-free catalyst due to their advantages such as morphology,easily doping,tunable electronic state,excellent thermal stability,renewable and low cost.High gravity technology is a breakthrough technology to achieve an enhanced transfer and multi-phase reaction process by dispersing,cuting and breaking the liquid through a high-speed rotating rotor and a porous packing to form a highly atomized continuously updated liquid film or droplets and other micro-units.Thus,this thesis starting from the structure of metal-free carbon materials,explored the catalytic effect and catalytic mechanism of doped metal-free carbon-based materials.The effect of RPB reactor on the enhanced mass-catalysis of carbon-based metal-free catalysis was investigated.The main results are as follows:(1)Using ?-cellulose crystallites widely presented in nature as the carbon source,and inexpensive diammonium hydrogen phosphate crystals as the nitrogen and phosphorus sources,the doping content of nitrogen and phosphorus atoms of the metal-free carbon materials prepared by high-temperature pyrolysis activation method were 4.3%and 10.6%,respectively.The NPC catalyst showed good catalytic performance in the reduction of p-nitrophenol to p-aminophenol.The kapp is 0.0394 min-1 and the turnover frequency is 2 × 10-5 mmol mg-1 min-1,the Ea is 21.55 kJ mol-1.After 4 cycle tests,the reaction rate performance can still maintain more than 90%of the first time,presenting significant durability.In addition,through DFT and PDOS,the optimal catalytic active sites of NPC metal-free carbon materials were explored and verified.It was found that among the seven configurations of nitrogen-phosphorus co-doped metal-free catalytic materials,the absolute value of Eads of the C3PO+N2.0 model is the largest,which is 0.9254 eV,and the adsorption of p-NP is the strongest,that is,the catalytic performance of C3PO+N2.0 doping configuration is the best.(2)Sulfur-modified graphene nanosheets(S-GNPs)metal-free catalysts were prepared by ball-milling method,and it can efficiently catalyze the hydroxylation of phenol to produce dihydroxybenzene(hydroquinone,catechol,resorcinol).The optimal reaction conditions for phenol hydroxylation were explored in STR.When the temperature was 60? and the concentration of S-GNPs was 0.2 mg/mL,the conversion of phenol was 38.2%,and the selectivity of dihydroxybenzene was as high as 88.5%.(3)S-GNPs catalyzed the phenol hydroxylation reaction in the STR and RPB reactors.It was found that the phenol conversion rate of RPB was 2.5 times of that of STR in 2 h.The selectivity of dihydroxybenzene is not much different,both are about 86%,but the selectivity of hydroquinone(33%)of the RPB reactor is much higher than that of STR(21%).A new way to control the selectivity of catalytic reaction products through RPB reactor. |
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