Pd改性K/MnO_x-ZrO_2催化剂上CO加氢制甲醇和异丁醇

Synthesis of Methanol and Isobutanol by CO Hydrogenation over Pd-Modified K/MnO_x-ZrO_2 Catalysts

采用H2和CO吸附、FT-IR和TPR等表征手段对不同Pd含量的Pd-K/MnOx-ZrO2催化剂进行了研究,并考察了其对CO加氢制甲醇和异丁醇反应的催化性能.结果表明,Pd的加入促进了锰的还原和氧空位的生成,有利于异丁醇的生成;Pd的加入改变了催化剂表面的吸附行为.Pd-K/MnOx-ZrO2催化剂表面有较高的H2和CO吸附量,有利于甲醇与异丁醇合成速率的提高.当Pd的添加量超过1.5%时,Pd的分散度降低,粒径变大,致使甲醇与异丁醇的合成速率降低.

The influence of Pd on the catalytic performance of K/MnOx-ZrO2 catalyst for synthesis of methanol and isobutanol from syngas （CO ＋ H2） was studied. Pd shows excellent promoting effects on K/MnOx-ZrO2 and remarkably improves the activity of K/MnOx-ZrO2. Under the reaction conditions of SV = 10 000 h 1, p = 8.0 MPa and T= 673 K, the space time yield of alcohols increased greatly from 122.8 to 232.6 g/（kg·h） when 1.5 % Pd （Pd（NO3）2 as precursor） was added into the K/MnOx-ZrO2 catalyst, and the selectivity for isobutanol increased from 15.5 % to 21.7 %. However, the catalytic activity and selectivity for isobutanol greatly decreased when the Pd loading exceeded 1.5 %. The results of H2 and CO chemisorption, FT-IR and TPR indicated that the addition of Pd promoted the reduction of MnOx in the K/MnOx-ZrO2 catalyst and the formation of oxygen vacancy, which might play a role in isobutanol formation. Moreover, the addition of Pd changed the adsorption behavior of K/MnOx-ZrO2. The H2 and CO uptakes on the Pd-modified K/MnOx-ZrO2 catalyst surface were higher than those on K/MnOx-ZrO2. The higher H2 and CO uptakes would be in favor of enhancement in the synthesis rate of methanol and isobutanol. The uptakes of H2 and CO decreased with Pd loading in excess of 1.5 %, so that the space time yield to methanol and isobutanol decreased.