Copper Salts As Co-catalyst Boosting Efficiency On The Cumene Oxidation Catalyzed By Carbon Nanotubes

The oxidation of hydrocarbons to yield high value-added intermediates is the important reactions in the chemical manufacture.The development of low-cost,high-activity catalytic systems is of great significance.In this study,the aerobic oxdiation of cumene using carbon nanotubes as catalyst with copper salts to improve the cumene conversion and the selectivity of high value-added products such as 2-phenyl-propan-2-ol?PP?.The interaction between carbon nanotubes?CNTs?and copper salts has been well investigated,which greatly affects the activity of CNTs in the cumene oxidation.The main research contents of this study are as follows:?1?CuO/CNTs prepared with Cu?OAc?₂ as copper source in the presentce of the mechanically mixed CNTs?mass ratio with 1:10000?were used as catalysts for cumene oxidation with oxygen as terminal oxidant at 80?for 8 h.The conversion rates of cumene are49.5%and 54.5%respectively and the corresponding target product PP selectivity are 32.5%and 44.7.Compared with CNTs?38.5%conversion and 25.1%PP selectivity?,the catalytic performance has been greatly improved.The catalytic system with mechanically mixed Cu?OAc?₂ and CNT displays the best catalytic performance.The increase in the amount of copper-based cocatalyst did not significantly improve the catalytic activity,indicating that trace amount of Cu?OAc?₂?about 1 ppm relative to the reactant?can effectively promote the reaction.Through peroxide decomposition experiments under different catalytic systems,it was found that the Cu?OAc?₂-CNTs system is conducive to the decomposition of CHP,thereby promoting the oxidation of cumene.This study proposes a new method of trace amount of Cu?OAc?₂adding to CNTs to promote cumene oxidation at high conversion rate to generate PP and this has application prospects.?2?Using prestine CNTs,acid-washed CNTs and the recycled CNTs as catalysts for cumene oxidation were carried out.The performance of different catalysts and the interaction between the surface properties of CNTs and trace copper promoter were fully investigated.Results demonstrated that the catalytic perfromance of HCl-washed CNTs could be greatly improved by adding trace amount of Cu?OAc?₂.Further study found that there is no apparent influence on the surface chemistry/physicaal property of CNTs after the HCl washing,but the adsorption or doping of Cl would occur in this process.The adsorbed or doped Cl can promote the tranformation of Cu²⁺to Cu⁺ions,which might be involved into the free radical chain reaction of cumene oxidtion and imporve the catalytic efficiency.We speculate that Cu and Cl on CNTs surface would form a Cu-Cl component.DFT calculations prove that there is an interaction between C-Cl-Cu,which makes the positive charge of Cu in a lower state and is favorable to the formation of peroxy radicals and thus promotes the reaction.Furthermore,Cu Cl₂ as a model additive was added to co-catalyze the oxidation of cumene in the presence of p CNTs without HCl washing.As expected,the reaction activity was greatly improved,evidencing that the key of the catalytic promotion of Cu?OAc?₂ is to form a C-Cu-Cl group on CNTs surface.In addition,the addition of other transition-metal chlorides in this catalytic system displayed no promoting effect on cumene conversion,indicating that Cu element is one of the most important components for this study.The study believes that the acid-washing process of carbon materials may introduce an unexpected adsorption or doping of heteroatom,which has an unexpected effect on the catalytic performance.This study could provide an significant guidance for the carbon-catalysis research.