Given the high costs and stoichiometric amounts of reduced nicotinamide adenine dinucleotide (NADH) required by the many oxidoreductases used for organic synthesis and the pharmaceutical industry, ...there is a need for the efficient reductive regeneration of NADH from its oxidized form, NAD+. Bioelectrocatalytic methods for NADH regeneration involving diaphorase and a redox mediator have shown promise; however, strong reductive mediators needed for this system are scarce, generally unstable, and require downstream separation. The immobilization of diaphorase in cobaltocene-modified poly(allylamine) redox polymer is presented which is capable of producing bioactive 1,4-NADH with yields between 97% and 100%, faradaic efficiencies between 78% and 99%, and turnover frequencies between 2091 h–1 and 3680 h–1 over a range of temperatures spanning 20 to 60 °C. By using this system, methanol and propanol production by an NADH-dependent alcohol dehydrogenase were enhanced 7.1- and 5.2-fold, respectively, compared with a negative control. Finally, the efficiency of this approach coupled with its high operational stability (91% of the maximum activity after five experimental cycles) renders it among the most promising means of NADH regeneration yet developed.
Full text
Available for:
IJS, KILJ, NUK, PNG, UL, UM
Direct CO2 hydrogenation to higher alcohols (HAs) is a promising way to achieve the conversion of CO2 to high-value chemicals. Alkali metals as promoters are generally crucial for Cu–Fe-based ...catalysts, but their critical role in higher alcohol synthesis (HAS) is still far from clear. Here, we report the regulating effect of a potassium (K) promoter from a reactant activation perspective on Cu–Fe-based catalysts for HAS from CO2 hydrogenation using in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and chemisorption methods. The optimized catalyst denoted as 4.6K-CMZF with a moderate K content exhibits the highest HA space time yield (STY) in a fixed-bed reactor. It is found that the K can promote reverse water gas shift (RWGS) reaction and tailor the ratio of nondissociated CO to dissociated CO by strengthening linear CO adsorption and weakening bridging CO adsorption. A proper amount of K can balance the nondissociated and dissociated activation of CO, thus providing an adequate *CH x and *CO species to take part in *CH x –*CO coupling reaction. The K promoter can also suppress H2 activation, thereby inhibiting alkylation reaction. The promoting effect of K can be attributed to the balance of surface *CH x , *CO, and *H species by regulating CO activation and H2 activation, thus favoring HA synthesis via *CH x –*CO coupling and hydrogenation reactions.
Full text
Available for:
IJS, KILJ, NUK, PNG, UL, UM
Display omitted
•The catalysts were prepared by partial thermal decomposition of layered CoMn-MOF materials.•The optimal catalyst exhibited 57.5% alcohol selectivity with a high C2+OH distribution of ...82.4%.•The remaining Co2+ in MOF framework can provide additional CO non-dissociative adsorption sties.•The addition of manganese promotes the cobalt dispersion and Co2C formation.•The catalyst with remaining MOF framework showed an excellent stability during 250 h reaction.
Direct and selective conversion of syngas to higher alcohols (C2+OH, HA) is highly attractive but remains challenges in improving the high catalytic performance. Herein, a series of catalysts were prepared by thermal decomposing layered-structured CoMn-MOF materials and used in the HA synthesis.
Characterization results showed that the MOF framework could partially maintain after calcination at 350 °C under N2 flow, in which the Co2+ species can provide extra non-dissociative adsorption CO sties, leading to an improved alcohol selectivity. And the addition of manganese could promote the cobalt dispersion and Co2C formation. The synergistic catalysis of these active species allowed the optimal CoMn-350 catalyst to display a superior selectivity to HA, specifically the alcohol selectivity reached 57.5% and the distribution of C2+OH in total alcohols was up to 82.4 % when the CO conversion was 51.5%. The catalyst with remaining MOF framework also showed an excellent stability during 250 h reaction. This work highlights a feasible strategy for the design of highly efficient catalysts for HA synthesis via the partial decomposing MOF materials.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Converting the greenhouse gas CO2 into higher alcohols (HAs) via hydrogenation reaction requires more attention in C1 chemistry because the C2+ alcoholic products are value-added chemicals as fuel ...additives, reaction solvents, and intermediates. However, the chemical inertness of CO2, complexity in various reaction routes, and uncontrollability of C–C coupling from untamed surface moieties in higher alcohol synthesis (HAS) make this approach very challenging to achieve. In this review, we summarize and analyze the recent advances in catalytic HAS from direct CO2 hydrogenation. The first section highlights the potential promising catalyst families, including a noble-metal class of catalysts, modified Co-based catalysts, modified Cu-based catalysts, and Mo-based catalysts with the roles of promoters and supports specified in each case. The second section reviews the possible reaction mechanisms based on previous experimental results. The rational design of ideal catalyst systems for this reaction is discussed in the third section.
Display omitted
New catalytic technologies to convert the greenhouse gas CO2 into useful products by renewable energy is becoming more important than ever due to recent alarming events attributable to climate change. Among various products from C1 chemistry, more attention should be paid to the hydrogenation of CO2 to higher alcohols since they are value-added chemicals as fuel additives, reaction solvents, and intermediates. However, higher alcohol synthesis is severely impeded by the difficulties in the chemical inertness of CO2 and complexity in various reaction routes and the uncontrollability of C–C coupling from untamed surface moieties. Development of highly effective and selective catalysts remains a great challenge to the production of higher alcohols. Moreover, further in-depth comprehension of the reaction mechanisms offers practical guidance to new design of catalyst systems. This review provides a new prospect for future research on catalytic CO2 hydrogenation to higher alcohols.
Higher alcohol synthesis from CO2 hydrogenation is a promising and challenging way to realize the efficient utilization of CO2 resources. Despite recent progress, there is still a lack of deeper understanding in this field. This review focuses on the recent advances in heterogeneous catalytic hydrogenation of CO2 to higher alcohols, in terms of catalyst families, reaction mechanisms, and the rational design of ideal catalysts. This will providea new prospect for future research on catalytic CO2 hydrogenation to higher alcohols.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Display omitted
•The structural evolution of a Co-rich Co-Cu catalyst in HAS was investigated.•Fast phase separation and sintering was observed in the first 2 h time on stream.•Carbidization of Co0 ...and its sintering occurred till steady state after 40 h TOS.•The final active structure consists of intergrown Cu0 and Co2C nanoparticles.•Multifunctional Co2C/Cu0 interface sites lead to the high selectivity to oxygenates.
Bimetallic Co-Cu catalysts are widely applied in higher alcohol synthesis (HAS), but the formation of the final active structure has not yet been fully clarified, especially for Co-rich catalysts. We investigated the structural evolution of a Co-Cu catalyst (Co:Cu = 2) from the hydrotalcite precursor containing additional Al3+ and Zn2+ to the final active state after 80 h under reaction conditions at 280 °C and 60 bar. The reconstruction of the bimetallic Co-Cu nanoparticles obtained by H2 reduction was induced by the feed gas consisting of an equimolar H2 and CO syngas mixture resulting in fast phase separation and sintering of metallic Cu0 and Co0 in the first 2 h time on stream (TOS) and a continuous carbidization of Co0 forming Co2C and its sintering until steady state was reached after 40 h TOS. An intergrowth of metallic Cu0 nanoparticles with Co2C nanoparticles was observed to occur under reaction conditions. The high selectivity to oxygenates amounting to 41% compared with 29% to hydrocarbons is ascribed to the multi-functional Co2C/Cu0 interface enabling dissociative CO adsorption, hydrogenation and CO insertion. The formation of hydrogenated carbon species (CxHy) originating from dissociative CO chemisorption is assumed to be favored by hydrogen spillover from Cu0 to Co2C. The adsorption sites for molecular CO provided by both Cu0 and Co2C facilitate its insertion into the CxHy intermediates thus leading to a higher selectivity to alcohols following the Anderson-Schulz-Flory distribution.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Synthesis gas (CO + H2) conversion is an important process in the transformation of coal, natural gas, or biomass into higher-value products. The explicit conversion into C2+ oxygenates on ...transition-metal-based catalysts suffers from a low selectivity, being a consequence of an imperative integration of C–O bond splitting and C–C coupling reactions. Recently, it has been demonstrated that a bimetallic CuCo catalyst has high higher alcohol selectivity under mild reaction conditions, but the details of the reaction mechanism on the surface are still elusive. In this work, we studied the formation of methane, methanol, and ethanol from syngas on a close-packed (111) and a stepped (211) CuCo surface combining density functional theory (DFT) and microkinetic modeling. We found the CuCo alloy to be a promising candidate catalyst, displaying the required coverage of CO and CH x on the surface to facilitate C–C coupling. In addition, we found the selectivity to be very structure sensitive: the CuCo (211) surface is selective toward ethanol under certain reaction conditions, while the (111) surface is selective toward methanol. We identified the much lower C–O dissociation barrier and the higher rate of CH x –CO coupling as the reason for the high activity and selectivity toward ethanol on the (211) surface.
Full text
Available for:
IJS, KILJ, NUK, PNG, UL, UM
Display omitted
•The number of oxygen vacancies could be adjusted by the feeding ratio of Cu and Zn.•The higher oxygen vacancy contents significantly promote the formation of CHxO*.•The carbon chain ...growth proceeds by CC coupling of CHx* with CHxO*/CO* on Znδ+ defect sites.•The selectivity of ethanol and C2+OH exhibit a positive correlation with the oxygen vacancy content.
The catalytic conversion of syngas to higher alcohols (C2+OH) has drawn widespread attention because it can alleviate the oil crisis and realize the clean and efficient use of coal. Nevertheless, the seesaw problem between C2+OH and total alcohol selectivity has not been solved. In recent years, catalytic processes involving oxygen vacancies have been widely investigated. However, the existing literature on this topic is fragmentary and unsystematic. Herein, we report a significant improvement in C2+OH synthesis by varying the oxygen vacancies on CuZn catalysts and systematically elaborate the structural and catalytic effects of the oxygen vacancies. Oxygen vacancy content shows almost linear positive correlations with many of the physical and chemical properties of the catalysts, such as SBET, Vp, Dp, Cu0 size, H2 consumption, and Cu0/(Cu0 + Cu+) ratio. The presence of oxygen vacancies drives catalysis in two ways. One, the dissociation of water adsorbed on oxygen vacancies causes the formation of hydroxyl groups, which interact with activated CO* to form surface formate (HCOO*) groups. This is followed by successive hydrogenation to form surface CHxO* intermediates. The CHxO* or CO* species are then coupled with surface CHx* to form ethanol on Znδ+ defect sites, realizing the growth of carbon chains. Two, oxygen vacancies drive electron transfer from ZnO to Cu, generating more Znδ+ defects and regulating the Cu0/(Cu0 + Cu+) ratio. The presence of electron-rich Cu is conducive to CO dissociation and adsorption, which promotes the formation of the critical surface intermediate CHx*. Consequently, the optimized CZ-0.80 catalyst exhibits exceptional catalytic performance, achieving 9.98 % CO conversion as well as ethanol and C2+OH proportions of up to 54.27 % and 59.95 %, respectively. Thus, by developing a new catalyst system that avoids the use of F-T elements such as Co or Fe for C2+OH synthesis from syngas, this work provides a new understanding of the growth of carbon chains.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Display omitted
•The hierarchical KNiMoS|ZnCrAl-based multifunctional catalyst was designed for HAS.•The hierarchical structure can regulate crystal size and low stacking degree of MoS2.•Synergistic ...reaction played important role on CO activation and C–C coupling.•KNiMoS|ZnCrAlS-O(E) enabled CO conversion of 20.2 % and ROH selectivity of 63.8 %.•KNiMoS|ZnCrAlS-O(E) afforded C2 + OH/ROH fraction of 68.5% with enhanced STY and stability.
Catalytic conversion of syngas into high value-added chemicals such as higher alcohols (C2+OH) are vitally crucial in chemical industry but still remains a challenge due to the low conversion and C2+OH selectivity. Herein, the combination of powerful CO activation on ZnCr-based sites and strong C–C coupling for chain propagation on KNiMoS is highly desirable to achieve high C2+OH yield on hierarchical KNiMoS|ZnCrAlS-based multifunctional catalysts. The hierarchical structure can facilitate the dispersion of MoS2 slabs with dominant double-layer stacking to enable the high sulfuration degree of Mo and high proportion of NiMoS active phases due to the appropriate metal-support interaction. As a result, KNiMoS|ZnCrAlS-O(E) showed the highest CO conversion (20.2 %), total alcohols selectivity (63.8 %) with high C2+OH/ROH fraction of 68.5 %, TOF (176.8 h−1), STY (116.4 mg g-1h−1) and excellent stability. A plausible reaction path was also proposed on hierarchical KNiMoS|ZnCrAlS-O(E) multifunctional catalyst that the alkoxy intermediates species formed on ZnCr active species can partially transform to MoS2-based active phase to form CHyCHxO* species for the favourable C2+OH synthesis. This work offers a promising strategy through the integration of multifunctional catalyst with hierarchical pore to strengthen CO activation and C–C coupling for selective conversion of syngas to C2+OH.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
CO hydrogenation to isobutyl alcohol is a promising route for CO transformation to high value-added products. However, the formation mechanism of isobutyl alcohol is complex, and its synthesis ...requires complex catalysts and harsh reaction conditions, which hinders the identification of active sites. Herein, we efficiently synthesized isobutyl alcohol under mild conditions over a simple Cu–ZrO2 catalyst by decreasing the Cu loading. The space–time yield (STY) of isobutyl alcohol using an optimal CZ-0.11 catalyst was as high as 61.3 g·Lcat –1·h–1 with a CO conversion of 19.2%, far surpassing the STY of the state-of-the-art isobutyl alcohol synthesis (44.6 g·Lcat –1·h–1) under harsh conditions. Decreasing the Cu loading increased the distribution of smaller Cu particles and clarified the structure–activity relationship of Cu–Zr interactions for isobutyl alcohol synthesis. The enhanced Cu–Zr interaction led to the formation of more electron-deficient Cu species on the CZ-0.11 catalyst, which enriched the linearly adsorbed CO on Cu, as demonstrated by in situ diffuse reflectance infrared Fourier-transform spectroscopy. Experimental and theoretical results revealed that coupling of the bicarbonate species on ZrO2 with the linearly adsorbed CO species on electron-deficient Cu clusters promoted the formation of C2 intermediates and finally produced isobutyl alcohol through rapid β-addition. These insights into the active sites for CO hydrogenation to isobutyl alcohol may guide further catalyst designs.
Full text
Available for:
IJS, KILJ, NUK, PNG, UL, UM
Direct conversion of readily available alkenes into high-value-added alcohols is important yet challenging in both organic synthesis and industry. One-pot reductive hydroformylation of alkenes offers ...a straightforward and atom-economical method for the synthesis of one-carbon homologated alcohols. However, the reaction catalyzed by a stable and efficient heterogeneous catalyst has been underexplored. Herein, we report a bench-stable porous organic polymer (POP) with incorporation of a specific monophosphine ligand into the scaffold, which serves as both a solid ligand and a support to prepare a heterogeneous Ru catalyst for one-pot reductive hydroformylation. The monophosphine ligand helps to stabilize atomically dispersed trinuclear Ru sites on POP, resulting in a heterogeneous Ru catalyst with a catalytic performance comparable to its homogeneous counterpart under the same conditions. The catalyst could be easily separated for successive reuses without a significant loss in both activity and selectivity. Remarkably, the catalyst exhibited outstanding chemo- and regioselectivity, allowing for the efficient conversion of a wide range of terminal, internal, and functional alkenes to their respective alcohols in good to high yields. This work demonstrates the use of atomically dispersed metal sites for the reductive hydroformylation of alkenes for the direct synthesis of alcohols.
Full text
Available for:
IJS, KILJ, NUK, PNG, UL, UM
PDF
