Continuous production of higher alcohols from synthesis gas and ethanol using Cs-modified CuO/ZnO/Al2O3 catalysts

CO Hydrogenation to Methanol over Cu/MgO Catalysts and Their Synthesis from Amorphous Magnesian Georgeite Precursors

“…Nevertheless, these amorphous samples require a special treatment in the subsequent preparation steps. After filtering the aged precipitate from the mother liquor, a washing step is necessary to remove Na + and NO 3 À ions that originate from the metal salt precursor solution and the basic precipitating agent and are detrimental for the catalytic performance of the finally obtained materials: Alkali metals are considered poisons for methanol synthesis -as they promote the formation of higher alcohols and can therefore decrease the methanol yield in CO and CO 2 hydrogenation; [35,36] and nitrate ions sticking to the surface are known to favor sintering during the calcination. [37] Usually, the washing step is considered complete when a conductivity criterion of σ < 100 μS • cm À 1 in the washing water is met -however, for the amorphous hydroxycarbonates we were not able to fulfill this criterion with reasonable effort: Even after 50 washing steps in 50 mL centrifuge tubes (using centrifugation and decantation to separate the solid from the washing water), the conductivity is still above 1 mS • cm À 1 and sodium is not fully eliminated from the solid, but magnesium is lost to the washing waters in significant amounts, causing the Cu : Mg ratio to decrease rapidly with increasing number of washing steps (Figure 12).…”

Effects of n‐Propanol Co‐feeding in Isobutanol Synthesis from Syngas over K‐CuMgCe Catalyst

“…Co‐feeding of ethanol or n‐propanol overcame the limitation of the rate‐determining step, increasing the higher alcohols yield. Furthermore, unlike the traditional fixed bed, while the effect in CO conversion was negative or not significant, [11a,b,22] the CO conversion increased from 46.6 % to 63.5 % after adding n‐propanol under the system conditions. It might be due to the back‐mixing in the slurry bed, which increased the residence time of C1 species and other intermediates on the catalyst surface.…”

“…It might be due to the strong alkalinity of K‐CuMgCe that facilitated the aldol condensation reaction. Two coupling paths had been confirmed for alkali metal‐doped catalysts [12,22] . One path involved the retention of the oxygen of the C1 intermediate (named aldol condensation with oxygen retention reversal β(R)), and another path the retention of the oxygen of the adsorbed alcohol species (named normal aldol condensation β(N)).…”

“…The 2‐methyl‐3‐pentanol mainly formed via self‐condensation (β(R)) of intermediates derived from n‐propanol. Aldehydes and ketones were both intermediates that form alcohols and esters, and the formation of esters and alcohols was a competitive reaction [22,27] . Cu provided hydrogenation/dehydrogenation sites and CO adsorption sites, while K and Mg−Ce provided basic sites for aldol condensation.…”

In Situ Encapsulated CuCo@M-SiO2 for Higher Alcohol Synthesis from Biomass-Derived Syngas

“…However, it is an enormous challenge to achieve a trade-off between the C–C coupling and the C–O retaining. Typically, four categories of catalysts including Rh-based, − Mo-based, − modified methanol-synthesized catalysts, − and modified Fischer–Tropsch (F–T)-synthesized catalysts have long been investigated for HAS. − Although Rh-based catalysts have high C 2+ OH selectivity with Rh 0 -/Rh n + -active centers, the industrialization was unrealistic because of limited reserves and exorbitant price. Harsh reaction conditions and strict H/C ratio with Mo-based catalysts is not conducive to the practical application in HAS.…”