Assessing C3–C4 alcohol synthesis pathways over a MgAl oxide supported K/MoS2 catalyst via 13C2-ethanol and 13C2-ethylene co-feeds

Abstract

Mechanisms of C 3-C 4 alcohol synthesis from syngas are elucidated over a Mg/Al mixed metal oxide (MMO) supported K/MoS 2 catalyst via 13 C 2-ethanol and 13 C 2-ethylene co-feeds. K/bulk-MoS 2 is used as a control catalyst to provide insight into the role of K/MoS 2 and K/MoS 2-MMO sites on higher alcohol formation pathways. Analysis of the products via 13 C-NMR show preferential enrichment of terminal carbons in C 3-C 4 alcohols with both co-feeds, suggesting that CO insertion is the primary higher alcohol synthesis pathway, and that olefin carbonylation proceeds through the same pathway as alcohol formation. The observation of 13 C 4-1-butanol species during the CO hydrogenation reactions with 13 C 2-ethanol co-feeds provides conclusive evidence of ethanol self-coupling to 1-butanol as a secondary pathway. Additionally, acetate species are shown to be formed via an acyl precursor reacting with an alkoxy anion. Hydrogenation of an acetyl species (CH 3 CO*) to an ethoxy intermediate (C 2 H 5 O*) is shown to be largely irreversible under the reaction conditions employed, as no preferential enrichment is observed for the acetyl group in acetate species. Propionate species are shown to be formed via esterification of propionate with the corresponding alcohol, while isobutyl alcohol formation observed over both the K/bulk-MoS 2 and the MMO supported catalysts occurs via methanol coupling with 1-propanol or 1-propanol derived species.

Manganese-Catalyzed Upgrading of Ethanol into 1-Butanol

“…Therefore, only a handful of catalysts that realize the catalytic Guerbet reaction of ethanol have been developed. Heterogeneous catalytic systems generally require harsh reaction conditions and/or suffer from low selectivity . In contrast, well-defined homogeneous catalysts based on precious metals (Ru and Ir) show higher reactivity and selectivity for this transformation under milder conditions (Figure ).…”

A Study of the Effects of K-Modification and (Co, Ni, Fe)-Promotion on a Supported MoS2-Based Catalyst for Ethanol Conversion

“…This implies that the direct coupling of C 2 fragments is a probable source of additional C 4+ alcohols and hydrocarbons. Previous studies 13,35 on ethanol conversion using 13 C have shown that the coupling of C 2 fragments is involved in the formation of butanol (see in Table 3).…”

“…Only small amounts of DEE were observed, which is a major product of ethanol conversion on a Bronsted acid catalyst. 35 This suggests that even in the absence of potassium, ethanol conversion, including dehydrations, proceeds on the Lewis acid sites of the sulfide catalyst, which are likely associated with CUS.…”

The Complex Way to Sustainability: Petroleum-Based Processes versus Biosynthetic Pathways in the Formation of C4 Chemicals from Syngas

“…Two chemical ways are worthy of note: a selective two-step approach coupling the formation of propylene via a standard MTO technology with hydroformylation/hydrogenation steps according to the alcohols OXO synthesis − and a more challenging, rather unselective, route with the direct use of syngas to generate either methanol selectively or a broader range of so-called “higher” alcohols (HAS route). Among the numerous catalytic systems developed over the years, four main classes are noteworthy, being the focus of many valuable reviews: − Rhodium-based catalysts producing mainly ethanol, − modified FT catalysts based on cobalt and, to a lesser extent, iron, , MoS 2 /MoC-based catalysts, − and optimized high- and low temperatures methanol catalysts based either on ZnO/Cr 2 O 3 or on the Cu/ZnO/Al 2 O 3 system often modified with alkali promoters (e.g., Cs and K). − Although many of these four catalytic approaches have been further developed, some tested in pilot plants and/or patented, no large-scale industrial implementation has been so far reported. This might be explained by enduring problems associated with the stability of the catalysts, the exothermic character of the synthesis, and the moderate selectivity of the synthesis resulting in a broader product range (e.g., linear vs branched alcohol issue, oligomerization, etc.).…”