Tuning the catalytic CO hydrogenation to straight- and long-chain aldehydes/alcohols and olefins/paraffins

Abstract

The catalytic CO hydrogenation is one of the most versatile large-scale chemical syntheses leading to variable chemical feedstock. While traditionally mainly methanol and long-chain hydrocarbons are produced by CO hydrogenation, here we show that the same reaction can be tuned to produce long-chain n-aldehydes, 1-alcohols and olefins, as well as n-paraffins over potassium-promoted CoMn catalysts. The sum selectivity of aldehydes and alcohols is usually >50 wt% whereof up to ∼97% can be n-aldehydes. While the product slate contains ∼60% n-aldehydes at /pCO=0.5, a 65/35% slate of paraffins/alcohols is obtained at a ratio of 9. A linear Anderson–Schulz–Flory behaviour, independent of the /pCO ratio, is found for the sum of C4+ products. We advocate a synergistic interaction between a Mn5O8 oxide and a bulk Co2C phase, promoted by the presence of potassium, to be responsible for the unique product spectra in our studies.

Superior Fischer-Tropsch performance of uniform cobalt nanoparticles deposited into mesoporous SiC

“…Unlike oriented Co single crystals, such Co bulk provides an appropriate texture with low yet sufficient specific surface area for high-pressure catalytic tests, as reported, for example, in Ref. [4].…”

“…Recent studies have also demonstrated the production of long chain terminal alcohols, aldehydes and/or short chain olefins with high selectivity from syngas as, for example, described in Ref. [4][5][6][7].…”

Metal organic framework-mediated synthesis of potassium-promoted cobalt-based catalysts for higher oxygenates synthesis

“…Higher oxygenate synthesis over cobalt based catalysts are generally carried out at low temperature ranging from 170°C to 280°C [5,19,34,51] since cobalt carbide decomposes above 300°C [52], so the oxygenate selectivity is lower at high temperatures. However, cobalt carbide on the MOF-mediated synthesized catalysts is maintained after reaction at 325°C, thus, the catalysts in this study showed high selectivity to C 2-C 6 oxygenates (36% at 325°C for 5K-Co 3 O 4 ).…”

“…Forming Co 2 C on the surface of a cobalt catalyst can provide both metallic cobalt and Co 2 C sites in close proximity, as is required for oxygenate formation. Although the role of Co 2 C in CO hydrogenation is not certain, there are several studies that detected the formation of cobalt carbide on catalysts with high oxygenate yields [20,[31][32][33][34].…”

Discovery of a Fischer‐Tropsch Hybrid Reaction: Hydrogenation of Methylformate to Long‐Chain Hydrocarbons with Anderson‐Schulz‐Flory Chain Length Distribution

“…While there is general agreement that a polymerization‐type reaction mechanism is in operation, the question for the chemical nature of the inserting monomer and the respective target chemical bonds have been a matter of debate for decades . This lack of established knowledge is particularly inhibiting in view of emerging FT process variants which aim at directing the synthesis to light olefins,, for example, or long‐chain alcohols and aldehydes through the use of advanced catalyst preparation techniques. Notwithstanding the deficits in molecular‐level understanding, the various opinions on the mechanistic pathways may be categorized by either claiming immediate or delayed carbon monoxide dissociation while composing hydrocarbon skeletons along with their functionalization.…”