Direcdirect Synthesis Of Hydrogen Peroxide From H₂/o₂ And Integration Thereof Into Ammoximation Of Cyclohexanone

The direct synthesis of hydrogen peroxide from H2/O2 conforms to atomic economy idea,and it is also the most desirable manufacturing method of hydrogen peroxide; Titanium silicalitezeolite TS-1 has exhibited the unique catalytic performance and selectivity at low temperature forammoximation of cyclohexanone with H2O2 as the oxidant. Theoretically speaking, the integratedprocess of the two reactions related above is feasible; and it has great attraction in the reducingcomplexity of technological process, enhancing utilization of the raw materials, decreasingenergy consumption. Based on this, direct synthesis of hydrogen peroxide from H2/O2 andintegration thereof into ammoximation of cyclohexanone were studied in the paper.M-Pd/TS-1(M=Ce, La, Pt, Fe, Co, Ni, Cr, Mn, Zn, Cd, Cu) catalysts were prepared byincipient wetness impregnation and their performance was evaluated for the direct synthesis ofhydrogen peroxide from hydrogen and oxygen at atmospheric pressure. The evaluation resultsshow that the highest yield of the key product was obtained over the M-Pd/TS-1 catalyst dopedwith cerium. The influence of factors on H2 conversion and H2O2 selectivity/yield were examinedsuch as nO2/nH2 molar ratio, gas flow rate and reaction time. The yield of H2O2, the masspercentage of H2O2 and TOF are up to 25.7 %, 0.8 % and 18.7 mol·mol-1·h-1, respectively, after 3h reaction at nO2/nH2 of 3 with 25 mL·min-1 gas flow rate. The experimental results are superiorto those reported at the atmospheric pressure.The technological conditions of ammoximation of cyclohexanone were examined such asn(NH3)/n(cyclohexanone), reaction temperature and catalyst amount. The influences of H2O2concentration and methyl alcohol on ammoximation of cyclohexanone were also investigated. Ina certain range, results show that the yield of cyclohexanone oxime is decreased by reducingconcentration of H2O2 dropped. Moreover, the yield of cyclohexanone oxime is significantlydecreased when methyl alcohol was used as solvent.One step and two steps were used in integrated process of H2O2 from H2/O2 and theammoximation of cyclohexanone respectively. In one step integrated process, the materials ofammoximation of cyclohexanone were added to the reactor at n(cyclohexanone)/n(NH3) molar ratio of 2.5:2 after H2/O2 3 h reaction in methyl alcohol/water, then after 3 h reaction, the yield ofcyclohexanone oxime is 4.8 %. In two steps integrated process, hydrogen peroxide, which wassynthesized from H2/O2 in methyl alcohol/water, used in the ammoximation of cyclohexanone,the yield of hydrogen peroxide is 14.1 % in the first step, the utilization of hydrogen peroxide is9.6 % at n(cyclohexanone)/n(NH3) molar ratio of 2.5:2 in the second step, the yield ofcyclohexanone oxime is 5.5 %, overall, the yield of hydrogen is 1.3 %; Hydrogen peroxide, whichwas synthesized from H2/O2 in water, used in the ammoximation of cyclohexanone, the yield ofhydrogen peroxide is 7.2 % in the first step, the utilization of hydrogen peroxide is 24.9 % in thesecond step, the yield of cyclohexanone oxime is 14.9 %, overall, the yield of hydrogen is 1.8 %.