Highly Selective Conversion of Syngas to Higher Oxygenates over Tandem Catalysts

Abstract

Selective synthesis of higher oxygenates from syngas is an important but challenging research target, and the present methods for converting syngas into oxygenates suffer from low selectivity and high energy consumption in multiple processes. Herein, we report a tandem catalyst composed of carbon-supported CoMn and Rh-metalated 3v-PPh3-based porous organic polymers (POPs), which can convert syngas to oxygenates with a selectivity of up to 62.7% and where the percentages of C2+ and C6+ oxygenates exceed 96.6 and 70.7%, respectively. The CoMn/modified activated carbon (MAC) works as a Fischer–Tropsch synthesis (FTS) catalyst to produce paraffins, olefins, and alcohols, and the Rh–P active site embedded on Rh/3v-PPh3@POPs serves as a heterogeneous hydroformylation catalyst to convert the obtained olefins into aldehydes. The present work puts forward an alternative strategy for the design of relay catalysts for the direct synthesis of higher oxygenates.

Distance for Communication between Metal and Acid Sites for Syngas Conversion

“…The CO conversion levels over ZnZrO x with different Zn/Zr ratios were lower than 2.0% because of thermodynamic restriction (Figure c–e and Tables S3–S5). The typical millimeter-scale fixed-bed reactor is often considered a plug-flow reactor with little or no back-mixing of the flowing gas stream . However, an unconventional integration manner with the zeolite in the upstream bed and ZnZrO x in the downstream bed (the second manner in Figure a) showed that the conversion of syngas over ZnZrO x was significantly disturbed by zeolite (the second catalyst in Figure c–e); even the thickness of the quartz wool in-between was 3 mm.…”

Recent advances in the routes and catalysts for ethanol synthesis from syngas

“…Due to the strong ability This journal is © The Royal Society of Chemistry 2022 of carbon chain growth, these catalysts presented higher selectivity to higher alcohols, but lower selectivity to ethanol. 222 For these multifunctional catalysts, the distances between the active sites (appropriate component proximity) are always the research focus. Lin et al reported that CO* or CH x O* insertion is the rate-determining step for C 2+ oxygenates.…”

“…Due to the strong ability of carbon chain growth, these catalysts presented higher selectivity to higher alcohols, but lower selectivity to ethanol. 222…”

Direct Conversion of Syngas to Higher Alcohols via Tandem Integration of Fischer–Tropsch Synthesis and Reductive Hydroformylation

“…Owing to the above limitations of direct conversion approaches, at present, the production of higher alcohols from syngas would inevitably rely on multi‐step processes comprising firstly the FTS of synthetic hydrocarbons enriched in linear olefins, followed by hydroformylation of the latter to the corresponding aldehyde derivatives with additional syngas, and finally aldehyde hydrogenation to alcohols, or reductive olefin hydroformylation (RHF) directly to alcohol end‐products [14] . While attractive as a process intensification strategy, the tandem integration of the FTS and olefin (R)HF conversion steps into a one‐pot transformation has long been impeded by incompatibility in process parameters such as operating temperatures [15] . Olefin‐producing FeC x ‐based FTS catalysts operate at temperatures >513 K, at which the molecular HF catalysts are not stable [5a, 16] .…”