Higher Alcohol And Ketone Synthesis Study On ZrO₂-based Catalysts

The catalytic synthesis of higher alcohols from CO hydrogenation is one of thechallenging and attractive subjects in the field of C₁ chemistry. At present, thesynthesis of methanol from syngas is already industrialized. The research anddevelopment on the synthesis of C₂ oxygenates and diesel fuel in our group havemade very great progress. If higher alcohols with high content of isobutanol can besuccessfully synthesized from syngas, it will promote the development of C₁chemistry industry.In this dissertation, the synthesis of higher alcohol and ketone over ZrO₂-basedcatalyst was studied. It was found that M_nO-x-ZrO₂ (n(Mn):n(Zr)=1) catalystprepared by coprecipitation, showed higher activity and selectivity to isobutanol.Addition of K and Pd into M_nO_x-ZrO₂ catalyst enhanced the activity and selectivityto isobutanol obviously. The catalyst of 1.5%Pd-1%K/MnOx-ZrO2 shows betteractivity and selectivity to isobutanol at 673K, 8.0MPa and 10000h^-1. The STY ofisobutanol was up to 50.5g/kg.h. The effects of the reaction conditions wereinvestigated. Higher pressure is necessary to isobutanol synthesis from syngas.K-Pd/M_nO_x-ZrO₂-Z_nO is also an efficient catalyst for the synthesis of2-pentanonefrom ethanol. At 663K, 2.0MPa, GHSV 10000h^-1and LHSV 1h^-1, the ethanolconversion reached 100% and 2-pentanone based on carbon atomwas up to 41.9%.BET, XRD, UV Raman, CO₂-TPD and NH3-TPD were used to characterize theZrO₂-based catalysts. The results revealed that the surface properties of ZrO₂,especially the acidic and basic properties on the surface of ZrO₂ play an importantrole in isobutanol formation. The results of the chemisorption of H2 and CO and insitu FT-IR revealed that H₂ and CO uptakes on K-Pd/M_nO_x-ZrO₂ catalyst are higherthan those on K/M_nO_x-ZrO₂ catalyst. The higher H₂ and CO uptakes onPd-K/MnOx-ZrO2 catalyst are in favor of enhancement in the rate of isobutanolsynthesis. In order to understand the mechanism of isobutanoland the feasibility of raisingisobutanol yield by using methanol recycle over ZrO2-based catalyst. Addition ofmethanol, ethanol and 1-propanol into the syngas feed and the study of COhydrogenation by high pressure and high temperature infrared were carried out. Theresults indicated that the formate is the major intermediate in higher alcohol. Higheralcohols are produced by carbon chain growth, with COH ??→CCOH (α-addition) αas the slow initial step of chain growth and the rate-determining step of higheralcohol synthesis. β-addition(including aldolic condensation) is the main carbonchain growth reaction of higher alcohols from syngas. The mechanism of isobutanolformation can be depicted as COH??→CCOH??→CCCOH??→CC(CH3)COH. αββ Temperature-Programmed Surface Reaction (TPSR) and FT-IR of adsorbedethanol on Pd-K/MnOx-ZrO2-ZnO catalyst were carried out. The results ofcharacterization and methanol, ethanol and 1-propanol reaction on Pd-K/MnOx-ZrO2-ZnO showed that the catalyst is multifunctional: the dehydrogenation,aldol, dehydration and hydrogenation reactions can be simultaneously accomplishedon Pd-K/MnOx-ZrO2-ZnO catalyst.