Lower olefins-generally referring to ethylene, propylene and butylene-are basic carbon-based building blocks that are widely used in the chemical industry, and are traditionally produced through ...thermal or catalytic cracking of a range of hydrocarbon feedstocks, such as naphtha, gas oil, condensates and light alkanes. With the rapid depletion of the limited petroleum reserves that serve as the source of these hydrocarbons, there is an urgent need for processes that can produce lower olefins from alternative feedstocks. The 'Fischer-Tropsch to olefins' (FTO) process has long offered a way of producing lower olefins directly from syngas-a mixture of hydrogen and carbon monoxide that is readily derived from coal, biomass and natural gas. But the hydrocarbons obtained with the FTO process typically follow the so-called Anderson-Schulz-Flory distribution, which is characterized by a maximum C
-C
hydrocarbon fraction of about 56.7 per cent and an undesired methane fraction of about 29.2 per cent (refs 1, 10, 11, 12). Here we show that, under mild reaction conditions, cobalt carbide quadrangular nanoprisms catalyse the FTO conversion of syngas with high selectivity for the production of lower olefins (constituting around 60.8 per cent of the carbon products), while generating little methane (about 5.0 per cent), with the ratio of desired unsaturated hydrocarbons to less valuable saturated hydrocarbons amongst the C
-C
products being as high as 30. Detailed catalyst characterization during the initial reaction stage and theoretical calculations indicate that preferentially exposed {101} and {020} facets play a pivotal role during syngas conversion, in that they favour olefin production and inhibit methane formation, and thereby render cobalt carbide nanoprisms a promising new catalyst system for directly converting syngas into lower olefins.
Selective synthesis of higher oxygenates (linear α‐alcohols and α‐aldehydes, C2+
OH) from syngas is highly attractive but remains challenging owing to the low C2+
OH selectivity and low catalytic ...stability. Herein we introduce a multifunctional catalyst composed of CoMn and CuZnAlZr oxides that dramatically increased the oxygenates selectivity to 58.1 wt %, where more than 92.0 wt % of the produced oxygenates are C2+
OH. Notably, the total selectivity to value‐added chemicals including oxygenates and olefins reached 80.6 wt % at CO conversion of 29.0 % with high stability. The appropriate component proximity can effectively suppress the formation of the undesired C1 products, and the selectively propulsion of reaction network by synergetic effect of different components contributes to the enhanced selectivity to higher oxygenates. This work provides an alternative strategy for the rational design of new catalysts for direct conversion of syngas into higher oxygenates with co‐production of olefins.
A stable multifunctional catalyst composed of CoMn oxides and CuZnAlZr oxides was developed for direct conversion of syngas to higher oxygenates and olefins with a total selectivity of 80.6 wt % at a CO conversion of 29.0 %. The interaction manner of the two components plays a crucial role in suppressing C1 products formation and enhancing the selectivity to higher oxygenates.
Na-promoted CoMn catalyst is able to produce higher alcohols via syngas with C2+ and C6+ fractions account for >90wt% and ∼50wt%, respectively.
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•Na-promoted CoMn catalyst is able to ...produce higher alcohols with high C2+ and C6+ fractions.•Significant structural evolution occurs during reaction with formation of bulk Co2C and MnCO3.•Na plays a significant role in promotion of Co2C formation.•Co2C/Co and synergistic effect of certain facets of Co2C are suggested to be active sites for higher alcohol synthesis.
CoMn model catalysts were prepared by co-precipitation and evaluated for higher alcohol synthesis (HAS) via syngas. The selectivity to oxygenates (mainly alcohols and aldehydes) was found to be higher than 20C% for the Na-promoted CoMn catalyst. Among the oxygenates, C2+ and C6+ fractions accounted for >90wt% and ∼50wt%, respectively. Metallic Co0 particles and MnCO3 were found in both Na-promoted and unpromoted CoMn catalysts after the reaction, whereas Co2C nanoparticles could only be observed in the spent Na-promoted catalyst. The addition of Na benefited the carbonization of cobalt and increased the selectivity to oxygenates and CO2. Our studies thus suggested that Co/Co2C were the bifunctional dual-sites for the oxygenates formation over the Na-promoted CoMn catalyst, where Co catalyzed CO dissociation and chain propagation, while Co2C was responsible for CO non-dissociative activation and subsequent insertion. In addition, the sole Co2C nanoparticles with certain exposed facets may also act as another kind of active dual-sites for oxygenates formation.
•CuFe bimetallic NPs as model catalyst for HAS.•Alcohol selectivity decreased with time on stream.•Phase separation of Cu and Fe components occurred during HAS.•Phase separation caused the decrease ...of alcohol selectivity with TOS.•Correlation between catalytic performance and structural evolution
CuFe bimetallic nanoparticles were prepared and used as model catalyst for deactivation study in higher alcohol synthesis. The structural evolution of CuFe bimetallic nanoparticles during reaction was investigated. Phase separation of Cu and Fe components was observed directly by STEM-EDS and HRTEM. It was found that CuFe bimetallic nanoparticles with homogeneous dispersion of Cu and Fe components separated into monometallic Cu nanoparticles, Fe3O4 nanoparticles, Fe3O4 nanorods and χ-Fe5C2 in the form of very small crystallites or amorphous layer on Fe3O4 containing nanoparticles and nanorods. The phase separation weakened the synergism between Cu and Fe and led to decreased selectivity to alcohols with time on stream. The correlation between the change of catalytic performance and the structural evolution was also discussed.
Higher alcohol synthesis (HAS) from syngas has attracted much attention and Cu-modified FischerTropsch (FT) catalysts exhibited promising catalytic performance for HAS. In this paper, three model ...modified FT catalysts, CuFe, CuCo and CuNi nanoparticles, were synthesized by co-reduction method for the comparison of their performance in HAS. XRD, TEM and EDS characterizations for spent samples indicate that severe phase separation of Cu and Fe took place for CuFe, and Cu@Co coreshell structure formed with co-existence of CuCo alloy nanoparticles for CuCo, but only CuNi alloys were observed for CuNi. Such structural change led to different performance in higher alcohol synthesis. As a result, CuFe mainly kept the original FT property of Fe, CuCo showed different performance from Co, and CuNi performed as methanol catalyst.
CuFe, CuCo and CuNi went through different structural changes during HAS, making CuFe resembled Fe, CuCo differed from Co and CuNi performed as methanol catalyst.
Bifunctional catalysis on dual sites plays an important role in higher alcohol synthesis from syngas. It makes use of two types of active sites of which one type dissociates CO and forms surface ...alkyl species and the other type catalyzes non-dissociative CO adsorption for CO insertion and alcohol formation. To improve catalytic activity for higher alcohol synthesis, it is necessary to design dual sites on the atomic scale to give them high stability. The recent advances in higher alcohol synthesis using bifunctional catalysts are reviewed. The design of the dual sites, the structure of the dual sites on several typical catalyst systems, and the structural evolution of the dual sites during reaction are discussed using our latest research results.
混合醇合成要求催化剂具备至少两类活性中心, 一类用于解离吸附CO以生成烷基链, 另一类用于非解离吸附CO以使烷基链含氧化生成醇. 两类中心通过协同作用共同构成混合醇合成所需的双活性中心. 简要综述了近年来合成气制混合醇过程中涉及的双功能催化研究进展, 并以几类典型的催化剂体系为例, 从双活性中心的构筑、典型的双活性中心结构、反应过程中双活中心结构的演变等方面进行了阐述. 混合醇催化剂的研发应从纳米尺度上对催化剂进行设计, 使催化剂表面具有足够多的双活性中心, 并设法稳定催化剂的双活性中心结构.
Higher alcohol synthesis is a bifunctional catalytic process occurring on a dual site. There is a need to design the dual site on the atomic scale to give high stability in order to improve catalytic performance.
Syngas conversion is a useful technology for converting nonpetroleum carbon resources into chemicals such as olefins. Iron- and cobalt-based catalysts, as two major categories, have been extensively ...studied in Fischer–Tropsch synthesis to olefins (FTO) reactions. Although both iron and cobalt catalysts have shown distinct merits and shortcomings, they are also complementary in their properties and catalytic performances when combined with each other. Herein, Na-modified CoFe bimetallic catalysts were fabricated using a co-precipitation method. It was found that there was a synergistic effect between Co and Fe that promoted a CO dissociation rate and carburization, and an appropriate Co/Fe ratio was conducive to improvements in their catalytic performances. The desired olefins selectivity reached 66.1 C% at a CO conversion of 37.5% for a Co2Fe1 catalyst, while the methane selectivity was only 4.3 C%. In addition, no obvious deactivation was found after nearly 160 h, indicating their potential industrial application.
CuFe bimetallic nanoparticles were synthesized by co-reduction method as model catalysts for HAS. Cu contacted with Fe component in the form of Cu–Fe alloy, CuFe2O4 and Cu(Fe)–CuFe2O4 interface in ...the fresh CuFe sample. However, Cu/Fe3O4 and Cu/FeCx composites formed after activation. Cu–FeCx center benefited alcohol formation which led to higher selectivity to total alcohol for CuFe than that for Fe and physical mixture of Fe and Cu nanoparticles. In addition, CuFe showed very high C6+OH selectivity in alcohol distribution and 33wt.%–74wt.% was achieved, demonstrating the potential for direct synthesis of C6+OH from syngas.
•CuFe bimetallic nanoparticles were synthesized by co-reduction.•Cu contacts Fe components in the form of Cu–Fe3O4 and Cu–FeCx after activation.•Cu–FeCx benefited alcohol selectivity in HAS.•CuFe bimetallic nanoparticles showed very high C6+OH selectivity in HAS.
Colon cancer is one of the typical malignant tumors, and its prevalence has increased yearly. The ketogenic diet (KD) is a low-carbohydrate and high-fat dietary regimen that inhibits tumor growth. ...Donkey oil (DO) is a product with a high nutrient content and a high bioavailability of unsaturated fatty acids. Current research investigated the impact of the DO-based KD (DOKD) on CT26 colon cancer in vivo. Our findings revealed that DOKD administration significantly lowered CT26
tumor cell growth in mice, and the blood
-hydroxybutyrate levels in the DOKD group was significantly higher than those in the natural diet group. Western blot results showed that DOKD significantly down-regulated Src, hypoxia inducible factor-1
(HIF-1
), extracellular signal-related kinases 1 and 2 (Erk1/2), snail, neural cadherin (N-cadherin), vimentin, matrix metallopeptidase 9 (MMP9), signal transducer and activator of transcription 3 (STAT3), and vascular endothelial growth factor A (VEGFA), and it significantly up-regulated the expressions of Sirt3, S100a9, interleukin (IL)-17, nuclear factor-kappaB (NF-
B) p65, Toll-like receptor 4 (TLR4), MyD88, and tumor necrosis factor-α. Meanwhile, in vitro validation results showed that LW6 (a HIF-1
inhibitor) significantly down-regulated the expressions of HIF-1
, N-cadherin, vimentin, MMP9, and VEGFA, which supported those of the in vivo findings. Furthermore, we found that DOKD inhibited CT26
tumor cell growth by regulating inflammation, metastasis, and angiogenesis by activating the IL-17/TLR4/NF-
B p65 pathway and inhibiting the activation of the Src/HIF-1
/Erk1/2/Snail/N-cadherin/Vimentin/MMP9 and Erk1/2/HIF-1
/STAT3/VEGFA pathways. Our findings suggest that DOKD may suppress colon cancer progression and help prevent colon cancer cachexia.
In this study, effects on the growth performance, nutrient digestibility, volatile fatty acids (VFA) production, and fecal microbiota of weaned donkeys were observed using different concentrate ...feeding sequences. Fifteen healthy 6-month-old weaned male donkeys with a body weight of 117.13 ± 10.60 kg were randomly divided into three treatment groups, including group C1 (roughage-then-concentrate), group C2 (concentrate-then-roughage), and group C3 (total mixed ration, TMR). The experiment lasted 35 d. We measured nutrient digestion by the acid-insoluble ash method and analyzed the fecal microbiota of the weaned donkeys by high-throughput sequencing of 16s rRNA genes in the V3-V4 region. The results show that group C3 obtained the best growth performance, and the digestibility of crude protein (CP) and crude extract (EE) was significantly higher than that of group C1 (p < 0.05). Acetic acid, isobutyric acid, valeric acid, isovaleric acid, and caproic acid were notably different among all groups (p < 0.05). In addition, we observed that Firmicutes and Bacteroidetes were dominant in the fecal microbes of each group, and Firmicutes was significantly higher in group C3 (p < 0.05). At the genus level, the different genera were Treponema, Rikenellaceae-RC9-gut-group, Unidentified-F082, and Bacteroidales-RF16-group (p < 0.05). The prediction of fecal microbiota function by PICRUSt indicated that different feeding sequences had minimal impact on the function of the fecal microbiota, particularly on the high-abundance pathway. In summary, the concentrate feeding sequence changed the composition of the fecal microbe of weaned donkeys.
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