Preparation And Desulfurization Performance Of Transition Metal Single-atom Catalysts

The combustion of sulfurcompound in fuel will produce sulfur oxides and cause environmental problems including acid rain and photochemical smog,which seriously affect people's physical and mental health.Therefore,fuel desulfurization has become one of the urgent problems to be solved.Governments impose strict restrictions on the sulfur content of fuel oil,limiting the sulfur content to less than 10 or 15 ppm.This requires that the macromolecular sulfur compounds such as dibenzothiophene and phenylpropenyl in the fuel must be removed.At present,the main desulfurization method is hydrodesulfurization,but the conditions of hydrodesulfurization is relatively harsh,and it is difficult to remove heterocyclic sulfur compounds.Oxidative desulfurization and adsorption desulfurization are typical non-hydrodesulfurization technologies.Due to low cost,low energy consumption and mild process conditions,they are considered to have good application potential in the field of deep desulfurization,which has attracted wide attention of researchers.In recent years,non-precious metal single-atom catalysts have developed rapidly and have good effects in various fields.In this paper,non-precious metal single-atom catalysts are used as research objects,and XRD,SEM,TEM and other technologies are used to characterize the catalyst samples.The adsorptive desulfurization and catalytic oxidative desulfurization performance of the catalyst were studied by using dibenzothiophene(DBT)and benzothiphene(BT)as targets in the model fuel.The main results are as follows:(1)The rod-shaped FeOOH and the slice Co(OH)2,Ni(OH)2 were synthesized by hydrothermal synthesis.And then dopamine polymerization on the surface of the prepared sample.The characterization results show that the synthesized sample is a core-shell mechanism.And then the prepared sample is subjected to high temperature treatment under Ar conditions to obtain a metal(hydrogen)oxide@nitrogen doped carbon(CN).Further,the metal on the(hydrogen)oxide@CN which does not form a ligand with N on the carbon support is washed away with HCl.And then the above sample was centrifuged,filtered,and dried,to obtain a non-precious metal monoatomic catalyst.By characterization,it was found that the single atom is dense and uniform on the carbon carrier.(2)The Single atom catalyst was applied to the adsorption desulfurization.The performance of the single atom catalyst for desulfurization was investigated,and the reaction conditions were optimized to further improve the desulfurization performance.The results show that temperature and time have a significant effect on the adsorption desulfurization reaction.Under the conditions of 0.01g catalyst and 120min reaction time,the desulfurization rate of SA-Fe/CN(20?),SA-Co/CN(20?)and SA-Ni/CN(40?)were 58.02%,59.2%and 70%for DBT.Through the fits of the adsorption data to the adsorption isotherm model,it was found that the catalyst DBT and BT adsorption processes belong to Langmuir type and were monolayer adsorption.(3)In the adsorption desulfurization process,since the desulfurization effect is not very good,the deep desulfurization by catalytic oxidation was carried out,and the effects of reaction temperature and oxygen-sulfur ratio on the performance of oxidative desulfurization were investigated.The results showed that under the conditions of oxygen-sulfur ratio of 7,reaction temperature of 60?,catalyst dosage of 0.010 g and reaction time of 60 min,the catalyst had the best effect on DBT and BT,and the oxidative desulfurization rate of SA-Ni/CN for DBT and BT were 95.1%and 87%.The kinetics of oxidative desulfurization reaction found that the oxidation of the catalyst for DBT and BT was a first-order reaction,and the activation energy of the reaction was low.