Preparation Of Different Acid - Base Palladium - Based Catalysts And Their Application In Methyl Isobutyl Ketone Synthesis

Methyl isobutyl ketone(MIBK) is one of the most important chemical products, which is widely used in the field of chemical engineering. The advanced process for producing MIBK is one-step synthesis from acetone. In this process, the key technology is to develop the multi-fuctional catalyst, which has both the ability of hydrogenation and condensation, as well as suitable acid-base sites. In this study the balance of condensation and hydrogenation was explored by adjusting the acidity and alkalinity of the carrier at a fixed amount of Pd. Metal oxides have the rich pore structure, good thermal stability, large specific surface area, and suitable acidity-basicity properties, which were widely used as the carrier of this reaction. In this paper, basic MgO, acid Al2O3, as well as MgAl mixed oxide derived from HTLc are synthesized by coprecipitation. In order to find the most suitable metal-carrier combination, these three oxides with different acidity-basicity properties impregnated Pd or/and Ni, and evaluated by a batch reactor. The catalyst samples are characterized by XRD、BET、CO2-TPD、H2-TPR and TEM. Some effects such as the load of mental content on the structure of oxides, base strength of the derived oxides, metal dispersion, and the reducibility of catalysts are discussed. Then the catalytic acitivities of acetone liquid-phase condensation and hydrogenation over these catalysts are tested. Different features were shown on the carriers of different acid and alkali with the addition of Ni. It plays a promote role on Mg(Al)O, whereas it shows inhibition effect on MgO and Al2O3. The hydrogenation activity of PdNi/MgO is insufficient and the conversion of acetone declined significantly. That is mainly because the interaction between Ni and MgO makes Ni2+ blend in the unit lattice of MgO in the process of preparation of catalyst. Consequently, the catalytic active site for hydrogenation is passivated. Even though, one may identify a significant increase of hydrogenated compound(IPA) on the PdNi/Al2O3 samples in comparison with Pd/Al2O3. For Mg(Al)O samples, the association of Ni to Pd have positive effect on the yield of MIBK, the influence of the preparation method and metal contents on catalytic properties was also investigated. The optimum catalyst PdNi/Mg(Al)O prepared with coimpregnation method, was evaluated under the reduction temperature 300℃ and reaction temperature 160℃. The conversion of acetone and the selectivity of MIBK reached to 48.8% and 80.6% respectively.In order to adjust a proper acid or base support to catalyzes the one-pot synthesis MIBK from acetone, Pd catalysts supported on sulfonic/amine-functionalized SBA-15(SBA-15-SO3 H, SBA-15-NH2) were prepared and characterized. A comparable series of 1wt% Pd supported on SBA-15-NH2, SBA-15-SO3 H, SBA-15 catalysts were performed in a liquid-phase at 160℃ and 2.0MPa. Experimental results indicate that after immobilized Pd, both sulfonic/amine-functionalized SBA-15 were effective for the formation of MIBK. The acid-functionalized catalyst was more active than base-functionalized one, it gives the maximum MIBK yield at 200℃, with 61.7% conversion and 85.8% selectivity to MIBK. The lower conversion of acetone over Pd/SBA-15-NH2 catalysts may be due to the inaction of acetone condensation step. Pd/SBA-15 with free silanol groups displays lowest activity with no MIBK detected. The 1.0 wt% Pd/SBA-15-SO3 H catalyst was thermally stable and reused for six times without significant loss of activity, it could effectively regenerated by adding acid sites.