Promotional Effects of Cesium Promoter on Higher Alcohol Synthesis from Syngas over Cesium-Promoted Cu/ZnO/Al₂O₃ Catalysts

Abstract

The promotional effects of a cesium promoter on higher alcohol (C2+OH) synthesis from syngas over Cs2O-Cu/ZnO/Al2O3 catalysts were investigated using a combined experimental and density functional theory (DFT) calculation method. In the presence of a cesium promoter, the C2+OH productivity increases from 77.1 to 157.3 g kgcat –1 h–1 at 583 K due to the enhancement of the initial C–C bond formation. A detailed analysis of chain growth probabilities (CGPs) confirms that initial C–C bond formation is the rate-determining step in the temperature range of 543–583 K. Addition of a cesium promoter significantly increases the productivities of 2-methyl-1-propanol, while the CGP values (C3* to 2-methyl-C3*) are almost unaffected. With the assistance of a cesium promoter, the CGPs of the initial C–C bond formation step (C1* to C2*) increase from 0.13 to 0.25 at 583 K. DFT calculations indicate that the initial C–C bond formation during syngas synthesis over the ZnCu(211) model surface is mainly due to the HCO + HCO coupling. In the presence of Cs2O, the stabilities of key intermediates such as HCO and H2CO are enhanced, which facilitates both HCO + HCO and HCO + H2CO coupling steps with lower activation barriers. In addition, Bader charge analysis suggests that the presence of cesium ions could facilitate nucleophilic coupling between HCO and H2CO for the initial C–C bond formation.

Oriented Isomorphous Substitution: An Efficient and Alternative Route to Fabricate the Zn Rich Phase Pure (Cu1−x,Znx)2(OH)2CO3 Precursor Catalyst for Methanol Synthesis

“…The Cu/ZnO based catalysts are widely applied on various catalytic reactions involving synthesis of alcohols . Studies on the phases of Cu‐containing hydroxycarbonates revealed that some precursor phases play important role for the catalytic performance .…”

“…The Cu/ZnO based catalysts are widely applied on various catalytic reactions involving synthesis of alcohols. [1][2][3][4][5][6][7][8] Studies on the phases of Cu-containing hydroxycarbonates revealed that some precursor phases play important role for the catalytic performance. [9][10][11][12][13] The Zn-doped malachite, (Cu 1À x ,Zn x ) 2 (OH) 2 CO 3 , possess homogeneous microstructure, well dispersion of Cu 2 + and Zn 2 + at an atomic level, enhanced metal-oxide interaction after calcination, stability against sintering and high specific surface area and is considered as an effective precursor for industrial Cu/ZnO catalyst.…”

New Theoretical Insights into the Origin of Highly‐Effective Dispersion of Cu‐Based Catalysts As‐Synthesized Using Mg/Zn Doped Malachite as Precursors

“…The copper‐based catalysts with attractive properties have been extensively utilized for the synthesis of methanol and ethanol, for water‐gas shift reaction and for reduction of NO x . Among them, the Cu/ZnO based catalysts have received great attentions due to their remarkable activities for methanol synthesis and reverse water‐gas shift (rWGS) reactions.…”

Influence of alkali metal (Li and Cs) addition to Mo2N catalyst for CO hydrogenation to hydrocarbons and oxygenates

“…A syngas to higher alcohol reaction was reported on Cs promoted Cu‐Zn‐Al catalysts. The authors explained the C‐C bond formation and subsequent chain growth on active sites of Cs . Li promoted Cu‐Zn‐Al catalysts were studied for the CO hydrogenation reaction and the improved alcohol selectivity was attributed to the increased overall basicity of Li‐Cu‐Zn‐Al…”