Effect of Preparation Method on ZrO2-Based Catalysts Performance for Isobutanol Synthesis from Syngas

Yingquan Wu,Guohui Yang,Tao Zhang,Hongjuan Xie,Noritatsu Tsubaki,Jiangang Chen,Li Tan

doi:10.3390/catal9090752

Yingquan Wu, Guohui Yang + Show 5 more

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https://doi.org/10.3390/catal9090752

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Abstract

Two types of amorphous ZrO2 (am-ZrO2) catalysts were prepared by different co-precipitation/reflux digestion methods (with ethylenediamine and ammonia as the precipitant respectively). Then, copper and potassium were introduced for modifying ZrO2 via an impregnation method to enhance the catalytic performance. The obtained catalysts were further characterized by means of Brunauer-Emmett-Teller surface areas (BET), X-ray diffraction (XRD), H2-temperature-programmed reduction (H2-TPR), and In situ diffuse reflectance infrared spectroscopy (in situ DRIFTS). CO hydrogenation experiments were performed in a fixed-bed reactor for isobutanol synthesis. Great differences were observed on the distribution of alcohols over the two types of ZrO2 catalysts, which were promoted with the same content of Cu and K. The selectivity of isobutanol on K-CuZrO2 (ammonia as precipitant, A-KCZ) was three times higher than that on K-CuZrO2 (ethylenediamine as precipitant, E-KCZ). The characterization results indicated that the A-KCZ catalyst supplied more active hydroxyls (isolated hydroxyls) for anchoring and dispersing Cu. More importantly, it was found that bicarbonate species were formed, which were ascribed as important C1 species for isobutanol formation on the A-KCZ catalyst surface. These C1 intermediates had relatively stronger adsorption strength than those adsorbed on the E-KCZ catalyst, indicating that the bicarbonate species on the A-KCZ catalyst had a longer residence time for further carbon chain growth. Therefore, the selectivity of isobutanol was greatly enhanced. These findings would extend the horizontal of direct alcohols synthesis from syngas.

Highlights

Higher alcohols (C2+ alcohols) synthesized from syngas have been studied owing to their broad applications [1,2,3,4,5]
In a previous study [14], we found that amorphous ZrO2 promoted isobutanol synthesis
Adding potassium and copper significantly improved the activity of the ZrO2 catalysts for higher alcohols synthesis, with CO conversion over the E-KCZ

Summary

Introduction

Higher alcohols (C2+ alcohols) synthesized from syngas have been studied owing to their broad applications [1,2,3,4,5]. Higher alcohol isobutanol has been extensively used as an important organic chemical raw material to manufacture plasticizers (diisobutyl phthalate), adhesives, isobutylene isoprene rubber, and antioxidants, among others. Isobutanol is used in advanced solvents to purify special chemicals, such as salts of strontium, barium, and lithium. Isobutanol can be added to gasoline as a fuel additive, which increases the octane number, and reduces carbon monoxide, nitrogen oxides, and hydrocarbon emissions in exhaust gas. There is no industrialized method for the direct synthesis of isobutanol. The main source of isobutanol is as a by-product from the carbonylation of propylene to n-butanol. This low yield of isobutanol is far from meeting the increasing market demand.

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