Alcohol Selectivity Research Articles

Higher alcohols synthesis via Fischer–Tropsch reaction at hcp-Co@Co2C interface

The hcp-Co@Co2C catalysts were prepared by partial carbonization conversion of hcp-Co, which possessed rich Co-Co2C interface and strong synergy between hcp-Co and Co2C, compared with fcc-Co. The degree of carbonization conversion was easy to control, for ethyne was used as carbon source to dissociate on the surface of cobalt to form carbon species, and then carbonization conversion took place and hcp-Co@Co2C formed. The prepared hcp-Co@Co2C catalysts exhibited high selectivity of higher alcohols, compared with hcp-Co, owing to the rich interface and strong synergy between hcp-Co and Co2C.

A Simple Strategy Stabilizing for a CuFe/SiO2 Catalyst and Boosting Higher Alcohols’ Synthesis from Syngas

Stable F-T-based catalyst development in direct CO hydrogenation to higher alcohols is still a challenge at present. In this study, CuFe/SiO2 catalysts with a SiO2 support treated with a piranha solution were prepared and evaluated in a long-term reaction. The treated catalyst showed higher total alcohols’ selectivity and great stability during a reaction of more than 90 h. It was found that the treatment with the piranha solution enriched the surface hydroxyl groups on SiO2, so that the Cu–Fe active components could be firmly anchored and highly dispersed on the support, resulting in stable catalytic performance. Furthermore, the in situ DRIFTS revealed that the adsorption strength of CO on Cu+ on the treated catalyst surface was weakened, which made the C-O bond less likely to be cleaved and thus significantly inhibited the formation of hydrocarbon products. Meanwhile, the non-dissociated CO species were obviously enriched on the Cu0 surface, promoting the formation of alcohol products, and thus the selectivity of total alcohols was increased. This strategy will shed light on the design of supported catalysts with stabilized structures for a wide range of catalytic reactions.

Synthesis of C3+ alcohols through ethanol condensation and carbon-carbon coupling of ethanol with CO2

C3+ alcohols are widely used as organic solvents, raw chemicals and fuel additives. However, the self-condensation of alcohol can limit the distribution of products. Herein, the binary metal oxide ZnO-ZrO2 with solid solution structure was prepared and applied into the synthesis of higher alcohols through the ethanol condensation and the coupling of ethanol with the CO2 hydrogenation. The optimized 0.3ZnO-ZrO2 solid-solution catalyst shows that ethanol conversion can reach 29% with the C3+ alcohols (1-propanol, 1-butanol and 1-hexanol) selectivity of 67%. The high selectivity of C3+ alcohols can be attributed to the acid-base bifunction for performing the condensation of ethanol and the coupling of ethanol and the CHxO intermediates that are produced through CO2 hydrogenation. This work opens a new avenue for the synthesis of C3+ alcohols.

Selective Furfuryl Alcohol Production from Furfural via Bio-Electrocatalysis

The catalytic reduction of renewable furfural into furfuryl alcohol for various applications is in the ascendant. Nonetheless, the conventional chemo-catalysis hydrogenation of furfural always suffers from poor selectivity, harsh conditions, and expensive catalysts. Herein, to overcome the serious technical barriers of conventional furfuryl alcohol production, an alternative bio-electrocatalytic hydrogenation system was established under mild and neutral conditions, where the dissolved cofactor (NADH) and the alcohol dehydrogenase (ADH) participated in a tandem reaction driven by the electron from a novel Rh (III) complex fixed cathode. Under the optimized conditions, 81.5% of furfural alcohol selectivity can be realized at −0.43 V vs. RHE. This contribution presents a ‘green’ and promising route for the valorization of furfural and other biomass compounds.

A crystal growth kinetics guided Cu aerogel for highly efficient CO2 electrolysis to C2+ alcohols.

To realize commercial CO2 electrochemical reduction to C2+ alcohols, the selectivity and production rate should be further improved. Establishing controllable surface sites with a favorable local environment is an interesting route to guide the C2+ pathway. Herein, we report a room-temperature one-step synthetic strategy to fabricate a highly stable Cu aerogel as an efficient CO2 reduction electrocatalyst. Controlling crystal growth kinetics using different reductants is an efficient strategy to modulate the nucleation and growth rate of Cu aerogels, enabling the creation of efficient surface sites for the C2+ pathway. Over the Cu aerogel obtained by reducing Cu2+ using a weak reductant (NH3·BH3), the faradaic efficiency of C2+ products could reach 85.8% with the current density of 800 mA cm-2 at the potential of -0.91 V vs. reversible hydrogen electrode, and the C2+ alcohol selectivity was 49.7% with a partial current density of 397.6 mA cm-2, while the Cu aerogel prepared using a strong reductant (NaBH4) was favorable to generating CO. Experimental and theoretical studies showed that the selectivity of the reaction depended strongly on the desorption and dimerization of *CO intermediates on the catalysts. The strong reductant induced a defective Cu surface that could facilitate the desorption of the *CO intermediate, subsequently producing CO, whereas the low defect Cu produced using a weak reductant could significantly enhance the selectivity for the C2+ product by improving *CO adsorption and the C-C coupling on the catalyst. This work opens a new way for constructing efficient electrocatalysts for CO2 electroreduction to C2+ alcohols.

Role of Er doping on isoamyl alcohol sensing performance of LaFeO3 microspheres and its prospects in wheat mildew detection

Er–LaFeO3 microspheres with high sensitivity and superior selectivity for isoamyl alcohol.

LaCo1-x-yCuxTiyO3/KIT-6 perovskites: synthesis and catalytic behavior in syngas conversion to higher alcohols.

Highly dispersed LaCo1-x-yCuxTiyO3/KIT-6 perovskites were synthesized by the citrate method with inert mesoporous KIT-6 addition. The KIT-6 matrix was removed by dissolution in 7% NaOH aqueous solution. The dispersity of perovskites probably varies depending on the largest cation and its content at the B position of the perovskite ABO3 structure. The CoS=23+/CoS=03+ ratio increases with the increase in copper content and in the presence of Ti4+. It may be explained by the compensation of the distortion of the perovskite structure. The maximum syngas conversion is achieved at nCo/nCu = 7/3. At a higher copper content, the activity of the samples decreases due to the formation of large copper particles (up to 40 nm) in the course of the reduction. The selectivity for alcohols increases with an increase in the proportion of copper and reaches maximum values at a ratio of nCo/nCu close to 1. The distribution of alcohols is the same for all samples, except for LaCo0.35Cu0.35Ti0.3O3/KIT-6. It can be assumed that the synthesis of alcohols proceeds on bimetallic CoCu particles 3 nm in size and cobalt particles 4-6 nm in size, most likely enriched with copper on the surface.

Alkali carbonate induced N-doped NiSn@NC for direct aqueous ethanol coupling to C6+ higher alcohols.

Synthesis of C6+ higher alcohols from readily-accessible aqueous ethanol is an alternative route of great potential for blending-fuel, plasticizer, surfactant and medicine precursors, but the direct coupling of aqueous ethanol to C6+ higher alcohols is still challenging. Herein, the alkali carbonate induced N-doping of a NiSn@NC catalyst was achieved by a facile gel-carbonization strategy, and the effect of alkali salt inductors was examined for the direct coupling of 50 wt% aqueous ethanol. Noteworthily, C6+ higher alcohol selectivity of 61.9% with 57.1% ethanol conversion was achieved for the first time over the NiSn@NC-Na2CO3-1/9 catalyst, which broke the step-growth carbon distribution of ethanol coupling to higher alcohols. The inductive effect of alkali carbonate for the N doped graphite structure from the NO3- precursor was revealed. Electron transfer from Ni to the pyridine N doped graphite layer is enhanced, thus elevating the Ni-4s band center, which lowers the dehydrogenation barrier of the alcohol substrate and further improves the C6+OH selectivity. The catalyst reusability was also examined. This work gained new insight into the selective synthesis of high-carbon value-added chemicals from C-C coupling of aqueous ethanol.

Controlling cobalt Fischer–Tropsch stability and selectivity through manganese titanate formation

Mn promotion in FT can direct products between oxygenates and paraffins. A simple in situ treatment forms MnTiO3 while an ex situ support is demonstrated with the benefits of Mn inclusion while controlling activity and inhibiting alcohol selectivity.

Enhanced adsorption of bio-oil on activated biochar in slurry fuels and the adsorption selectivity

In this study, activated biochars were prepared by CO2 and KOH activations for enhanced bio-oil adsorption in the slurry system. The results showed that activated biochars show better adsorption capacities on bio-oil than unactivated biochars due to the improved pore structure, and the highest adsorption rate reached 5.49 g bio-oil/g biochar by CO2 activated biochar prepared at 900 °C. The biochars especially activated biochars showed the best selectivity over aromatic compounds in bio-oil, followed by the selectivity over acids and ketones, and relatively weak selectivity for alcohols, aldehydes and monosaccharides. The average molecular weights of adsorbed bio-oil samples were 476–578 g/mol, higher than the 436 g/mol of bio-oil, implying the selective adsorption over heavy components. Biochar with large specific surface area, high O content or highly aromatized structure can facilitate the adsorption of monophenols and fused rings through pore filling, hydrogen bonding, π-π interactions and hydrophobic effect. Biochars with high O content can also have better adsorption selectivity on the acids and ketones in bio-oil via hydrogen bonding and electrostatic force. In summary, the developed pore structure, abundant O-containing functional groups, and high graphitization degree of biochar are beneficial for bio-oil adsorption.

Boosting the selectivity of higher alcohols in upgrading of aqueous bioethanol over amphiphilic NiSn@C-MgO catalyst

Bio-ethanol produced from biomass has been regarded as a promising feedstock for producing higher alcohols (C4+ alcohols) through the Guerbet route. Nevertheless, the high-efficiency upgrading of bio-ethanol is driven by the current disadvantage of low selectivity to C6+ alcohols. Herein, we designed and synthesized an amphiphilic NiSn@C-MgO, which was composed of NiSn nanoparticles (NPs) coated with carbon shell and MgO nanoflakes support. Detailed experiments reveal that the amphiphilic NiSn@C-MgO catalyst can stabilize emulsions and facilitate the cross-coupling of ethanol and C4+ alcohols (generated by ethanol self-condensation) to generate C6+ alcohols in aqueous ethanol upgrading. Furthermore, the carbonization temperature has a great influence on the structure of NiSn@C-MgO, thus greatly affecting the catalyst performance. Consequently, the optimal NiSn@C-MgO-550 displays an excellent activity with ethanol conversion of 73.3 %, the selectivities of C6+ alcohols and C8+ alcohols in liquid products also reach up to 60.9 % and 32.5 %, respectively. This present strategy provides an efficient strategy for the direct upgrading of water-containing bio-ethanol to desired biofuel components, which may promote the fundamental researches on the production of biorefineries and green fuels.

Oxygen vacancy and facet engineering of cuprous oxide by doping transition metal oxides for boosting alcohols selectivity in electrochemical CO2 reduction

Nanostructured Cu-based catalysts have gained much attention for electrochemical CO2 reduction (ECR) to value-added alcohols, while they are facing the challenges of unsatisfactory catalytic activity and selectivity. Herein, oxygen vacancy and facet engineering strategies are employed to modulate the ECR performance of Cu2O by doping transition metal oxides (TMOs). TMOs doping improves CO2 conversion by suppressing hydrogen evolution reaction (HER). The catalyst doped with 0.001 mol% ZnO exhibits a high alcohols Faradaic efficiency of 63.67% at −0.3 V vs. RHE, which exceeds that of the bare Cu2O (35.4%). The enhanced activity and alcohols selectivity is ascribed to the enriched oxygen vacancy defects (57.26%) for enhanced CO2 adsorption and activation and the synergistic effect between Cu and Zn sites for facilitated CO* protonation and C–C coupling. Alcohols selectivity increases from 56.87% to 64.27% and then declines to 63.67% with the increasing ZnO molar ratio from 0.00025 to 0.001. The Cu2O–ZnO-0.0005 catalyst features the octahedral structure (enclosed by the (111) and (100) facets) exhibits favorable ECR performance with the highest alcohols selectivity of 64.27% at −0.3 V vs. RHE. The enhanced alcohols selectivity is associated with the facet-dependent effect, as the exposed (111) facet favors CO2 adsorption and activation in ECR.

Plant polyphenol-derived ordered mesoporous carbon materials via metal ion cross-linking

Critical assessment of plant polyphenols (ferulic acid, quercetin, caffeic acid, gallic acid, arbutin, proanthocyanide) that can be used for forming ordered mesoporous carbons (OMCs) via metal ion (Fe, Co, Ni, Zn, Zr, Mg, Ce, La) and bimetal ion (MgFe, CoNi) cross-linking chemistry is reported. In the methodology, coordination interactions between aromatic hydroxyl groups of polyphenol molecules and metal ion cross-linkers initiate OMC formation via ethanol evaporation induced self-assembly (EISA). Aromatic hydroxyl content, solubility in the evaporating solvent and low to moderate molecular mass are key factors in selecting plant polyphenols for OMC formation. The as-prepared metal-functionalized OMCs were applied to electrocatalytic reduction of nitrate to nitrogen (conversion 85.5%, nitrogen selectivity 99.8%), catalytic hydrogenation of furfural to tetrahydrofurfuryl alcohol (conversion 100%, tetrahydrofurfuryl alcohol selectivity 100%), and electrode materials for supercapacitors (specific capacitance, 222 F/g at 0.5 A/g). Using the proposed techniques, a wide range plant polyphenols can be used to form OMCs that are directly applicable to environmental applications after carbonization in a nitrogen atmosphere without further post-processing, doping or modification.

PH-Induced selective electrocatalytic hydrogenation of furfural on Cu electrodes

AbstractThe efficient and selective electrocatalytic hydrogenation (ECH) of furfural is considered a green strategy for achieving biomass-derived high-value chemicals. Regulating an aqueous electrolytic environment, a green hydrogen energy source of water, is significant for improving the selectivity of products and reducing energy consumption. In this study, we systematically investigated the mechanism of pH dependence of product selectivity in the ECH of furfural on Cu electrodes. Under acidic conditions, the oxygen atom dissociated directly from hydrogenated furfural-derived alkoxyl intermediates, followed by stepwise hydrogenation until H2O formation via a thermodynamically favorable proton-coupled electron transfer process, thereby inducing a high proportion of the hydrogenolysis product (2-methylfuran). However, under partial alkaline conditions, furfural could be directly hydrogenated to furfuryl alcohol (selectivity ~98%) due to the high-energy barrier of the deoxidation process via a surface hydride (Had) transfer. Our results highlight the vital role of the electrolytic environment in furfural selective conversion and broaden our fundamental understanding of hydrodeoxygenation reactions in ECH.

A multi-functional Ru Mo bimetallic catalyst for ultra-efficient C3 alcohols production from liquid phase hydrogenolysis of glycerol

Ru and Mo bimetallic catalysts supported on active carbon modified by phosphotungstic acid (PW) were designed and applied in glycerol hydrogenolysis reaction. The physicochemical properties of the catalysts were characterized and the presence of active sites was investigated from the perspective of the glycerol hydrogenolysis performance. The MoO x is highly selective for the C—O bond cleavage of glycerol molecules, which can reasonably regulate the strong C—C bond cleavage activity of Ru nanoparticles. By using sequential deposition of Ru and Mo supported on mesoporous PW-C, the characterization results show that the combination of isolated low-valence MoO x with metal Ru particles can form “MoO x -Ru-PW”, which provides highly catalytic activity toward C—O bond cleavage, selectively producing more C3 alcohols (mainly 1,2(3)-propanediol). The glycerol conversion of 1% Mo/Ru/PW-C catalyst was 59.6%, the selectivity of C3 alcohol was 96.1%, and the selectivity of propanediol (1,2(3)-propanediol) was 94.9%. It is noteworthy that the selectivity of 1,3-propanediol reached 20.7% when the PW was 21.07% (mass). This study provides experimental evidence for the tandem dehydration and hydrogenation mechanism of the multifunctional Mo/Ru/PW-C catalyst.

Parametric investigations on plasma‐activated conversion of CH4–CH3OH to C2–C4 alcohols by nanosecond pulsed discharge

AbstractThe single‐step conversion of CH4 to higher alcohols without catalyst or complex processing is the dream solution both in C1 chemistry and the chemical industry. Here, an innovative synthesis of higher alcohols from CH4–CH3OH was driven by a highly flexible nanosecond pulsed plasma. Experimental results showed that the products distribution was strongly correlated with the electric field variation and reactants composition, and the maximum conversion of CH4 (35.9%) and CH3OH (77.4%) were obtained at the CH4/Ar ratio of 1:2. Interestingly, the addition of H2O and H2O2 effectively promoted the C2–C4 alcohols selectivity up to 19.4%. In addition, optical diagnostics were used to obtain active species distribution and integrated insights into the C–C coupling of higher alcohols generation. A possible reaction mechanism of CH4–CH3OH plasma was also discussed.

CO hydrogenation to ethanol and higher alcohols over ultrathin CuCoAl nanosheets derived from LDH precursor

Ultrathin CuCoAl nanosheets derived from layered double hydroxide (LDH) precursor (1–3 cationic-layers) were successfully synthesized by aqueous miscible organic solvent treatment (AMOST) strategy and performed for ethanol and higher alcohols production via CO hydrogenation. The ultrathin CuCoAl nanosheets (CuCo-LDH-aw) demonstrated a comparatively higher total alcohols (ROH) selectivity of 47.6 %, and the molar fraction of ethanol reached up to 37.5 % among the total alcohols. As revealed by XRD, TEM, SEM, BET and AFM characterizations, the uniform dispersion of CuCo NPs was observed over the ultrathin CuCoAl nanosheets. Moreover, the optimum ultrathin CuCoAl nanosheets exhibited a higher ratio of Cu+/(Cu0 + Cu+), which exerted a positive role on non-dissociative CO* insertion CHx intermediates. More significantly, XPS and in situ CO-DRIFT techniques uncovered the formation of CHx intermediates derived from bridge CO dissociation on the metallic Co species and the formate hydrodeoxygenation route, which involved CO* and surface hydroxyl groups (–OH) reaction. Consequently, it was concluded that the triply synergistic effect of Cu+, Co and surface hydroxyl groups (–OH) species contributed to the improvement in ethanol selectivity via CO hydrogenation.

Oxidation of benzyl alcohol catalyzed by ligand-stabilized Au nanoparticles in the presence of weak bases

Ligand-stabilized gold nanoparticles (tetrakis(hydroxymethyl)phosphonium chloride-Au, citrate-Au, cetrimonium bromide-Au) were synthesized and mixed with several weak-base solids (barium carbonate, Amberlite IRA-900) and acidic solid (Dowex 50WX2 resin). Those catalysts were applied for the oxidation of benzyl alcohol in water at 80 oC. Almost ligand-stabilized Au nanoparticles/weak-base solids showed good conversion of benzyl alcohol and high selectivity of benzoic acid, whereas ligand-stabilized Au nanoparticles/acidic solid were catalytically inactive. Nanoparticles were characterized by transmission electron microscopy, zetapotential measurement, and dynamic light scattering. The catalytic activity and product selectivity were determined by using a gas chromatography coupled with a mass selective detector. Our study suggests that the oxidation reaction in water could be catalyzed by gold with the presence of weak-base solids.

Effects of Fatty Alcohols with Different Chain Lengths on the Performance of Low pH Biomass-Based Foams for Radioactive Decontamination.

Compared with polymers and nanoparticles, fatty alcohols can not only increase the stability of foam, but also maintain better foamability at pH < 2, which is beneficial to reduce waste liquid and increase decontamination efficiency for radioactive surface pollution. However, different fatty alcohols have different hydrophobic chain lengths. The effects of fatty alcohols with different chain lengths on the performance of decontamination foam were studied at pH < 2, to assist in the selection of suitable fatty alcohols as foam stabilizers. Combined with betaine surfactant and phytic acid, biomass-based foams were synthesized using fatty alcohols with different chain lengths. When the hydrophobic tail groups of the fatty alcohol and the surfactant were the same, the foam showed the best performance, including the lowest surface tension, the highest liquid film strength, the greatest sag-resistance and the best stability. However, when the hydrophobic tail groups were different, the space between adjacent surface active molecules was increased by thermal motion of the excess terminal tail segments (a tail-wagging effect), and the adsorption density reduced on the gas-liquid interface, leading to increased surface tension and decreased liquid film strength, sag-resistance and stability. The use of decontamination foam stabilized by fatty alcohols with the same hydrophobic group as the surfactant was found to increase the decontamination rate of radioactive uranium pollution from 64 to over 90% on a vertical surface.

Engineering Sn doping Ni/chitosan to boost higher alcohols synthesis from direct coupling of aqueous ethanol: Modifying adsorption of aldehyde intermediates for C-C bond cleavage suppressing

The direct aqueous ethanol coupling to higher alcohols is an essential bridge between abundant bio-ethanol and the outstanding application of higher alcohols as alternative jet-fuel or plasticizer precursors. In this work, the Sn-Ni/CS catalysts were developed, and the synergy between Ni and doped Sn species promoted the selective upgrading of ethanol to higher alcohols. Experimental and theoretical evidence revealed that the enhanced selectivity of higher alcohols was attributed to the weakened adsorption of midbody aldehydes over the catalyst and the suppression of the gas by-products, which was due to the change of the electron density around the Ni active site by Sn doping causing a rich electron set around Ni specie. Benefiting from the Sn doping, the Sn-Ni/CS-500–1/1 catalyst achieved > 85% selectivity for higher alcohols with 60% ethanol conversion at 230 °C.