Liquid-phase Catalytic Oxidation Of P-tert-Butyltoluene

The main products of p-tert-butyltoluene(PTBT) oxidation reaction are P-tert-butyl benzaldehyde(PTBD) and p-tert-butyl benzoic acid(PTBA), they are important intermediates, which are widely and extensively used in organic synthetic industry and fine chemical products industry. This paper is dedicated to investigating the catalysis of the liquid-phase oxidation of PTBT by using Co(Ⅱ) complex compound, Co(Ⅲ) complex compound, Co(Ⅱ) and Mn(Ⅲ) complex compound with different proportions and CoSBA-15as catalysts separately.Firstly, the liquid-phase oxidation of PTBT by air with Co(Ⅱ) complex compound was studied under atmospheric pressure without solvent. We optimized the operation parameters, such as air flow rate, reaction temperature and Co concentration. It was found that when the air flow rate reached150mL/min, it could supply the oxygen adequately and eliminate the effect of the mass transfer. The reaction temperature had a strong impact on the reaction rate. Raising the temperature could accelerate the rate and high temperature was advantageous to the synthesis of PTBA. The conversion of PTBT increased firstly and reduced afterward with the increase of Co concentration. The yield of PTBA changed little when Co concentration was greater than30ppm. Under the optimum process conditions in which air flow rate was150mL/min, reaction temperature was150℃and Co concentration was30ppm, PTBT was oxidized at54.9%conversion to form PTBA in94.8%yield after8hours. Additionally, based on the reaction scheme, a kinetic model was proposed, and the kinetic parameters were determined from the concentration of reactant and products at different temperatures.Secondly, we compared the catalytic effect of Co(Ⅱ) complex compound with Co(Ⅲ) complex compound under the optimum process conditions, with the experimental results showing that they were similar on the catalysis of oxidation of PTBT. In addition, the synergistic catalytic effect between Co(II) and Mn(III) complex compound in PTBT liquid-phase oxidation was studied. The results showed that the synergistic catalytic effect was closely related to the proportion of cobalt and manganese, for the proportion affected the reaction rate and distribution of oxidation products. When the mass ratio of Co/Mn was1:1, the reaction pre-rate was faster than other conditions. And the yield of PTBD was significantly higher with the1:3Co/Mn ratio than that with Co(II) complex compound catalyst. Thus, PTBT selective oxidation could be achieved by adjusting the proportion of cobalt and manganese.Finally, Mesoporous CoSBA-15molecular sieves were directly synthesized and characterized by XRD, N2adsorption and TG. CoSBA-15materials were used as catalyst for liquid-phase oxidation of PTBT for selective synthesis of PTBD using O2, H2O2and tert-butyl peroxide(TBHP) as oxidant respectively. The experimental results showed that CoSBA-15with NHPI had a good catalytic activity, for PTBT could be oxidized to PTBD with32.9%conversion and73.6%yield at70℃after5hours.