Preparation And Application Of Coconut Shell Activated Carbon Mmobilized Metal Palladium Ion Organic Complexes Catalyst

Coconut shell activated carbon (cAC) was used as carrier to covalently immobilize palladium complexes, HNO3solution was used as oxidation agent, an orthogonal test was designed to optimize the oxidation conditions. When the concentration of HNO3solution was20%, reaction temperature was85℃and reaction time was4h, boehm titration showed that hydroxyl content of the cAC surface reached0.376mmol/g. The product was characterized by FT-IR and XPS.The different types of solvents were used to investigate silanization reaction medium impact on grafting reaction of the oxidized cAC with (MeO)3Si(CH2)3NH2. The results of FT-IR, XPS and N2adsorption-desorption show that when toluene was used as silanization reaction medium, the suface of cAC grafted maximum and homogeneous-dispersed silane, at the same time, cAC maintained maximum BET surface area and average pore diameter. And then the oxidized cAC was silylated by grafting with (MeO)3Si(CH2)3NH(CH2)2NH2,(MeO)3Si(CH2)3Cl and Cl3Si(C6H4)CH2Cl, respectively.Subsequently, the different types of nitrogen-containing bidentate ligands were synthesized, followed by Pd(PhCN)2Cl2complexation. The product was characterized by FT-IR and XPS. The ICP results show that the Pd2+loading capacity of the cycloheptyl diamine ligand-complexed palladium catalyst, ethylenediamine ligand-complexed palladium catalyst, propyl malononitrile ligand-complexed palladium catalyst, benzyl malononitrile ligand-complexed palladium catalyst and hexamethylene diamine ligand-complexed palladium catalyst reached1.53%,1.79%,0.82%,1.22%and0.72%, respectively. The N2adsorption-desorption results show that the BET surface area and average pore diameter of above catalysts were479.9m2/g,2.03nm;490.1m2/g,2.17nm;437.9m2/g,1.99nm;505.2m2/g,2.07nm and553.9m2/g,2.11nm, respectively.Oxidative carbonylation of phenol was investigated in a high pressure reaction vessel over the ethylenediamine ligand-complexed palladium catalyst, benzyl malononitrile ligand-complexed palladium catalyst, cycloheptyl diamine ligand-complexed palladium catalyst, hexamethylene diamine ligand-complexed palladium catalyst and propyl malononitrile ligand-complexed palladium catalyst. The reaction conditions were as follows:m(catalyst)=1.0g; n(Pd2+)/n(TBAB)/n(BQ)/n(Ce(OAc)3)=1/10/20/2; V(CH2C12)=30mL; n(phenol)=0.32mol; m(3A moleculai sieve)=2.5g; p=1.0MPa;p(CO)/p(O2)=10/1; T=100℃; t=4h and r=600r/min. The results show that the conversion rate of phenol and the diphenyl carbonate (DPC) selectivity were12.06%,91.03%;12.00%,90.65%;11.91%,86.82%;7.38%,85.36%and6.22%,81.02%, respectively. At the same time, the above series of catalysts showed good catalytic stability.Last, oxidative carbonylation of phenol was investigated in a fixed-bed reactor over the ethylenediamine ligand-complexed palladium catalyst and benzyl malononitrile ligand-complexed palladium catalyst, which were screened out based on the catalytic performance results of catalysts were investigated in the high pressure reaction vessel. The reaction conditions were as follows:m(catalyst)=20.0g; m(3A moleculai sieve)=5.0g; w(phenol)=15%; w(TBAB)=1%; w(BQ)=1%; w(CH2Cl2)=83%; qV,L=5mL/min; qv,G=200mL/min;p=2.5MPa; p(CO)/p(O2)=19/1and T=100℃. The results show that the conversion rate of phenol and the DPC selectivity were12.03%,93.05%and9.36%,90.97%for the ethylenediamine ligand-complexed palladium catalyst and benzyl malononitrile ligand-complexed palladium catalyst, respectively. The application of such catalysts in the fixed-bed reactor laid the foundation for the continuous and large-scale production of the DPC in industry in the future.