Two microporous carbon molecular sieve(CMS)samples with different surface properties were obtained from a commercial CMS through deashing treatment(C1)and then oxidation(C2)by 30%H2O2 solution.Both the two samples were characterized by acidic/basic titration,N2 adsorption isothermal(BET),point of zero charge(pHPZC).Decomposition of H2O2 in dilute unbuffered solution was carried and the evolved oxygen was measured volumetrically.After oxidation,the surface acidity and total surface oxygen-containing groups increased,while the special surface area and total pore volume slightly decreased.The experimental results showed that the H2O2 decomposition reaction on CMS obeyed the first-order kinetic.The activation energy(Ea)of the decomposition reaction on oxidized CMS increase from 33.3(C1)to 45.5(C2)kJ.mol-1,however the negative value of activation entropy of the reaction(ΔS≠)decreased from-197(C1)to-159(C2)J.mol-1.K-1 calculated by transition state theory.
Commercially available coal-based activated carbon was treated by nitric acid with different concentrations and the resultant samples were used as catalysts for the direct hydroxylation of benzene to phenol in acetonitrile. Boehm titration, X-ray photoelectron spectroscopy, scanning electron microscope coupled with an energy dispersive X-ray microanalyzer, and Brunauer-Emmett-Teller method were used to characterize the samples. The number of carboxyl groups on the surface was found to be the main factor affecting the catalytic activity. An optimum catalytic performance with a yield of 15.7% and a selectivity of 87.2% to phenol was obtained.
NiO nanoparticles were prepared by means of sol-gel method via varying the ratio of citric acid to nickel nitrate. The samples were characterized by powder X-ray diffraction（XRD）, Fourier transform infrared（FTIR） spectroscopy, transmission electron microscopy（TEM） and X-ray photoelectron spectroscopy（XPS）. It was found that the molar ratio of citric acid to nickel nitrate has a great effect on the crystal structure and particle size of NiO. The in- crease of the molar ratio of citric acid to nickel nitrate is favorable to the formation of NiO smaller particles within the range tested. Compared to bulk NiO obtained by thermal decomposition, NiO nanoparticles possess more surface oxygen species O- The activity test indicates that surface oxygen species O- plays a crucial role in the hydroxylation of benzene to phenol with hydrogen peroxide as oxidant. The active site may be originated from Ni2＋ on the surface of the samples, while Ni0 does not contribute to the hydroxylation reaction.
Fe/activated carbon was found to be catalytically effective for the one-step hydroxylation of several typical substituted aromatic compounds under milder reaction conditions(303 K,atmospheric pressure). It was found that the ring oxidation is predominant for all the substrates studied and the selectivity to ring oxidation was much greater than those reported previously.A comparison of the conversions with that of benzene revealed that electron-donating substituents increase the conversions of the substrates,while electron-withdrawing substituents decrease the conversions.The formation of o-and p-hydroxylated products for electron-donating substituted aromatic compounds and o-,m-,p-hydroxylated products for electron-withdrawing substituted aromatic compounds revealed an electrophilc mechanism.The predominant selectivity to o-hydroxylated products for the aromatic compounds with substituents which could coordianated with Fe also shows a new mechanism.This coordianation was affected by the steric hindrance of the substituents.The latter mechanism was also confirmed by DFT method.
One-step anodic acetoxylation of benzene to phenyl acetate was studied in acetic acid-water solution using a one-compartment electrochemical cell in galvanostatic mode. Compared to the anhydrous system, the addition of water improved the current efficiency for the electrosynthesis of phenyl acetate. The maximum efficiency reached 4.8% with the selectivity of 96% to phenyl acetate when the electrolysis was carried out under the optimal conditions. The investigation also indicated that the concentration of phenyl acetate increased linearly in 12 h and reached 1.07 g/L with the selectivity of 95%. Cyclic voltammetry experiments showed that the adsorption of benzene at Pt anode enhanced by the addition of water was critical to the formation of phenyl acetate. An activated benzene mechanism was proposed for the anodic acytoxylation, and the analysis of gas products demonstrated that Kolbe reaction was the main side reaction.
