Hydrogenation Route Research Articles

The crystallization dependent electron-proton synergistic doping for hydrogenation of WO3 film

Hydrogenation of metallic oxides was effective to modulate the chemical/physical properties and realize various functional applications. Normally, the traditional hydrogenating route always required high temperature annealing in hydrogen gas assisted by noble metal catalyst (Au or Pd et al.) or treatment by hydrogen plasma in vacuum condition. In the current study, we achieved a facile hydrogenation route for WO3 films at ambient conditions by contacting a Zn particle in a diluted acid solution and proposed a so-called electron-proton synergistic doping (EPSD) process. Due to the electrochromic property of WO3 film, the hydrogenation induced color change from transparent to deep-blue could be directly observed by eyesight. In addition, the higher H-doping concentrating in WO3 film would induce much deeper blue color. Results showed that the crystallinity and microstructures of WO3 film dominated the EPSD process, which not only effected the Fermi level difference between the Zn particle and WO3 film, but also changed the migrating barrier of proton at the interface. This macroscopic hydrogenation of WO3 films at ambience conditions showed some potential applications for tunable electrochromic devices.

Mechanism of CO2 hydrogenation to methanol on the W-doped Rh(111) surface unveiled by first-principles calculation

Understanding the mechanisms of CO2 hydrogenation on a specific catalyst is of profound significance for developing the high-efficient catalytic materials. Herein, first-principles calculation is performed to research the mechanisms of methanol synthesis from CO2 hydrogenation on tungsten (W)-doped Rh(111) catalyst. The optimal adsorption site, geometric parameters, and adsorption energy of each species are determined. The analysis of electronic structure reveals that CO2* is greatly activated on the W-doped Rh(111) surface due to the charge transfer and obvious orbital hybridization between them. Then, a descriptor is defined to preliminarily predict the reaction thermodynamics. Furthermore, the optimal reaction mechanism is determined by comparing the activation barriers and reaction energies of all elementary reactions. Compared with Rh(111), it can be found that the doping of W has a great hindrance to the elementary reactions in the RWGS and trans-COOH pathways, while the elementary reactions of the HCOO pathway are less affected. The optimal hydrogenation route on the W-doped Rh(111) surface is the HCOO pathway followed by CO2* → HCOO* → HCOOH* → H2COOH* → H2CO* → CH3O* → CH3OH*. The analysis of Mulliken charge shows that after the doping of W atoms, the modified electronic structure of Rh(111) is conducive to the conversion of CO2 and the generation of CH3OH.

Desulphurisation of dibenzothiophene and 4,6–dimethyl dibenzothiophene via enhanced hydrogenation reaction route using RePd–TiO2/SiO2 aerogel catalysts: kinetic parameters estimation and modelling

Re/Pd-TiO2/SiO2 aerogel catalysts were synthesized by using a sol-gel method and supercritical drying in excess solvent and investigated in the reaction of hydrodesulphurisation (HDS) of dibenzothiophene (DBT) and 4,6-dimethyl dibenzothiophene (4,6-DMDBT). Both Re/Pd catalysts, obtained with and without the use of mesitylene in the synthesis step, have shown increased conversions of up to 70 % in the desulphurization of 4,6-DMDBT, when compared to conventional Co/Mo hydroprocessing catalysts. This observation is of importance for conversion of highly refractory 4,6-DMDBT and hydroprocessing to produce ultra-low sulphur diesel fuels, ULSD. In order to quantify the extent of desulphurisation, which proceeds via a hydrogenation route, conversions of DBT and 4,6-DMDBT along with evolution of reaction products characteristic for the direct desulphurisation route and the hydrogenation route were monitored by using a gas chromatography?mass spectrometry (GC-MS) analytical technique. The reaction was performed at 630 K and 6 MPa in a batch catalytic reactor. The experimental results were used in the Hougen-Watson kinetic model describing DBT and 4,6-DMDBT desulphurisation on ? and ? active sites. Kinetic parameters of this complex catalytic kinetics were determined by using a Genetic Algorithm method and minimum deviation function. Values of calculated kinetic parameters and values of the ratio of 3-methylcyclohexyltoluene (MCHT and dimethyl biphenyl (DMBPH) expressed as the MCHT/(MCHT+DMBPH) ratio ranging between 0.66 and 0.94, have confirmed that the hydrogenation route is the dominant route for desulphurisation of 4,6-DMDBT.

Amberlyst-15 supported zirconium sulfonate as an efficient catalyst for Meerwein-Ponndorf-Verley reductions.

The Meerwein-Ponndorf-Verley (MPV) reaction is an important chemoselective route for carbonyl group hydrogenation, and thus designing new and effective catalysts for this transformation remains important and challenging. In this work, a new sulfonate coordinated Zr(IV) catalyst was prepared by the coordination of Zr(IV) onto the sulfonate groups of Amberlyst-15, which can effectively catalyze the MPV reaction and quantitatively convert carbonyl compounds to the corresponding alcohols with high reactivity and stability. Detailed mechanistic investigations reveal that the catalytic performance of Zr-AIER can be attributed to the synergetic effect between Zr4+ and the sulfonate group, and the porous structure with high surface area.

Ligand-assisted nickel catalysis enabling sp3 C–H alkylation of 9H-fluorene with alcohols

A nickel catalysed chemoselective sp3 C–H alkylation of 9H-fluorene with alcohols is reported which follows a radical pathway employing the borrowing hydrogen route.

Low-carbon biomass-fueled integrated system for power, methane and methanol production

A novel near zero-CO2 emission system based on gasification of municipal solid waste (MSW) is proposed and analyzed for waste-to-power and power-to-fuel purposes. The integrated system includes an externally fired gas turbine (EFGT), a molten carbonate fuel cell (MCFC), a Rankine cycle and an organic Rankine cycle (ORC), methane and methanol synthesis units and proton exchange membrane electrolyzer (PEME). Three different scenarios for synthetic fuel production (methane-only, methanol-only and dual-production) are investigated considering different operating loads of PEME, as green hydrogen route. For the case that 10% of produced power is consumed by PEME to generate the required hydrogen for methane and methanol synthesis, overall energy and exergy efficiencies are obtained 41 and 36%, respectively. In this case, the system consumes 1012 ton/yr of CO2 to produce 179 ton/yr methane and 393 ton/yr methanol with sustainability index of 1.57. The exergy analysis revealed that the employed EFGT unit is the main source of irreversibility with gasifier as the most exergy destructive component. In addition, the results of sensitivity analysis showed that increasing gas turbine inlet temperature improves both thermodynamic performance of the system and rate of synthetic fuel.

Water-mediated hydrogen spillover accelerates hydrogenative ring-rearrangement of furfurals to cyclic compounds

Upgrading bioderived furfurals (furfural, 5-hydroxymethylfurfural) to cyclopentanones (cyclopentanone, 3-hydroxymethylcyclopentanone) and cyclopentanols (cyclopentanol, 3-hydroxymethylcyclopentanol) is a representative bifunctional catalytic process in biomass conversion. Here, a class of Pd/NiMoO4 catalysts (Pd/NiMoO4-Cl, Pd/NiMoO4-AC) with low Pd loading (1.0 wt%) and different Pd dispersion are synthesized. The hydrogenation active sites and acidic sites of catalysts were adjusted by a water-mediated hydrogen spillover process. 56.3–85.3% yields of cyclopentanones and 65.4–85.2% yields of cyclopentanols were obtained by hydrogenative ring-rearrangement route of furfurals over Pd/NiMoO4-Cl and Pd/NiMoO4-AC, respectively. Over-hydrogenated byproducts (tetrahydrofurfuryl alcohol, 2,5-bis(hydroxymethyl)tetrahydrofuran) with a yield above 54% were generated by a full hydrogenation route over Pd/C. The difference in catalytic performance is results from alteration of the adsorption configurations of reactants and the transformation of Lewis acid sites to Brønsted acid sites by hydrogen spillover. This work presents an effective strategy for governing reaction routes and enhancing bifunctional catalysis with a hydrogen spillover mechanism.

Mechanism and sites requirement for CO hydrogenation to CH3OH over Cu/CeO2 catalysts

This study investigated the Cu-CeO2 interactions for CO hydrogenation to methanol by applying rate measurements, chemical titration/desorption, together with in-situ/operando spectroscopy techniques under realistic reaction conditions. Ce components were enriched in the surface region of Cu/CeO2 catalysts while Ce3+ and Ce4+ atoms co-existed during CO hydrogenation. The ratio of Ce3+ to Cu0 in the surface region of catalysts increased linearly with the Ce content. The turnover rates of CH3OH formation increased as a single-valued function of the ratio, irrespective to the individual contact extent between Cu and CeO2 clusters or Ce content in the Cu/CeO2 catalysts, indicating that the Cu0-Ce3+ sites pair acts as active sites for CO hydrogenation to methanol over Ce-CeO2 samples. This study also unraveled that formyl and formate species, as reactive surface intermediates, were co-adsorbed on the Cu0-Ce3+ sites, and their hydrogenation routes occurred concurrently for CH3OH formation during CO-H2 reactions.

An insight of CO 2 hydrogenation to methanol synthesis: Thermodynamics, catalysts, operating parameters, and reaction mechanism

Catalytic hydrogenation of CO2 to methanol is an exciting avenue to curb the rising CO2 emissions and generate renewable energy or value-added products. Methanol synthesis via the thermal catalysis route gets increasing emphasis due to its fast kinetics and flexible combination of active components. In the last decade, many studies on CO2 hydrogenation to methanol have been reported with different kinds of catalysts that have been synthesized and characterized using state-of-the-art surface science tools and techniques. In situ analysis techniques as well as theoretical (eg, density functional theory, Monte Carlo simulations, and Micro-Kinetics modeling) studies have been performed to understand the insights of morphology changes, the interaction of active sites, and the formation of intermediate species under the reaction conditions. In the present review, the advancements on CO2 to methanol via hydrogenation route have been presented taking into consideration different perspectives spanning across thermodynamic aspects, the influence of reaction temperature, pressure, feed composition, space-velocity, and morphologically tuned novel catalyst on CO2 conversion and methanol selectivity. Among the reported catalysts, the Al2O3-supported Cu-Zn catalyst showed better performance with 25% CO2 conversion and 73% methanol selectivity at 170°C and 50 bar pressure. The CeO2-supported Pd-Zn catalyst showed 14% CO2 conversion and 97% methanol selectivity at 220°C under 20 bar pressure. Also, CeO2-nanorods supported Cu-Ni catalyst showed good performance at 260°C and 30 bars, with around 18% CO2 conversion and 73% methanol selectivity. Additionally, the mechanistic insights of the process are emphasized with necessary figures and diagrams. The rate-determining steps for each mechanism are also highlighted with chemical structures for further clarity. This review also summarizes potential catalysts and their optimum operating conditions to achieve maximum CO2 conversion and methanol selectivity. We believe, the review is unique and not found in any article which addressed the above aspects altogether in a compact form.

Explaining the Advantageous Impact of Tertiary versus Secondary Nitrogen Center on the Activity of PNP-Pincer Co(I)-Complexes for Catalytic Hydrogenation of CO2.

Pincer ligated coordination complexes of base metals have shown remarkable catalytic activity for hydrogenation/dehydrogenation of CO2 . The recently reported MeN[CH2 CH2 (i Pr2 )]2 Co(I)PNP-pincer complex was shown to exhibit substantially higher catalytic activity in comparison to the corresponding catalyst, HN[CH2 CH2 (i Pr2 )]2 Co(I)PNP, bearing a secondary nitrogen center on the pincer ligand. Here, we computationally investigate the mechanisms for hydrogenation of CO2 to formate catalyzed by these two Co-PNP complexes to explain how such a small structural difference could have a sizable impact on their catalytic activity. Plausible hydrogenation routes were examined in details and our findings provide solid support for the experimental observations. Our results reveal that such trends in catalytic activity could be explained from the lower activation barrier for the hydride transfer step upon changing the pincer nitrogen center from secondary to tertiary.

Preliminary investigations on the catalytic hydrogenation of polycyclic aromatic hydrocarbons via WGSR

The water-gas shift reaction (WGSR) is a crucial reaction in the direct liquefaction of lignite in a syngas (CO + H2) system. In this study, anthracene was utilized as a polycyclic model compound of lignite, to which hydrogen is donated by the H2/D2 produced from CO and H2O/D2O via the WGSR. The results show that the model compound of the polycyclic aromatic hydrocarbon in coal (anthracene) undergoes partial cracking and polycondensation under non-hydrogen-donor conditions at 400 °C. In addition, WGSR catalyzed by NiO can generate hydrogen for the hydrogenation of anthracene. Comparing the mass spectra of deuterated products with those of conventional hydrogenation products by isotope labeling, the alkyl side chain positions of toluene, 1,4-xylene, methylnaphthalene, 1,1-diphenylethylene, methylanthracene and other compounds are prone to deuteration, enabling speculation of the main hydrogenation route of anthracene, which provides theoretical support for the catalytic hydrogenation in direct liquefaction of lignite in a syngas (CO + H2) system.

Highly Controllable Hydrogenative Ring Rearrangement and Complete Hydrogenation Of Biobased Furfurals over Pd/La2B2O7 (B=Ti, Zr, Ce)

AbstractDeveloping a highly selective catalyst to upgrade furfurals (5‐hydroxymethyl furfural and furfural) to cyclopentanones (3‐hydroxymethyl cyclopentanone and cyclopentanone) and tetrahydrofuran alcohols (2,5‐bishydroxymethyl tetrahydrofuran and tetrahydrofuran alcohol) is highly significant for biobased fine chemical synthesis. Here, a series of La2B2O7 (B=Ti, Zr, Ce) metal oxides, featuring the same chemical formula but different topological structures are fabricated. After Pd loading, the Lewis acidity and metal‐support interaction are well governed by the support type, which further affects the hydrogenation and acid‐catalyzed ability. A greater than 82 % yield of cyclopentanones is obtained via a hydrogenative ring rearrangement route over Pd/La2Ti2O7. However, Pd/La2Ce2O7 shows high catalytic efficiency for tetrahydrofuran alcohols with an approximately 80 % yield via a complete hydrogenation route. Additionally, the catalyst exhibits outstanding recycling performance and structural stability. This study presents an interesting design strategy for the selective preparation of cyclopentanones and tetrahydrofuran alcohols through the regulation of the adsorption mechanism.

Production of Negative-Emissions Steel Using a Reducing Gas Derived from DFB Gasification

A dual fluidized bed (DFB) gasification process is proposed to produce sustainable reducing gas for the direct reduction (DR) of iron ore. This novel steelmaking route is compared with the established process for DR, which is based on natural gas, and with the emerging DR technology using electrolysis-generated hydrogen as the reducing gas. The DFB-DR route is found to produce reducing gas that meets the requirement of the DR reactor, based on existing MIDREX plants, and which is produced with an energetic efficiency comparable with the natural gas route. The DFB-DR path is the only route considered that allows negative CO2 emissions, enabling a 145% decrease in emissions relative to the traditional blast furnace–basic oxygen furnace (BF–BOF) route. A reducing gas cost between 45–60 EUR/MWh is obtained, which makes it competitive with the hydrogen route, but not the natural gas route. The cost estimation for liquid steel production shows that, in Sweden, the DFB-DR route cannot compete with the natural gas and BF–BOF routes without a cost associated with carbon emissions and a revenue attributed to negative emissions. When the cost and revenue are set as equal, the DFB-DR route becomes the most competitive for a carbon price >60 EUR/tCO2.

A First-Principles-Based Microkinetic Study of CO2 Reduction to CH3OH over In2O3(110)

Methanol synthesis from catalytic recycling of CO2 is one viable route to produce fuel and a stock chemical from a greenhouse gas. Herein, hydrogenation of CO2 to CH3OH is investigated with density functional theory calculations combined with mean-field microkinetic modeling. The model explores the direct route for CO2 hydrogenation (HCOOH route) and the competing reverse water-gas shift (RWGS) reaction. The predicted temperature dependence of turnover frequencies, selectivities, and reaction orders are in good agreement with previous experimental results. The formation of methanol at relevant reaction temperatures (470–670 K) is found to be kinetically controlled by H2COOH dissociation to H2CO + OH, whereas the RWGS reaction is solely controlled by CO2 hydrogenation to COOH. An analysis of the kinetic behavior reveals that the stabilization of hydrogen adsorption should be one way to improve the catalyst performance.

New insights on CO and CO2 hydrogenation for methanol synthesis: The key role of adsorbate-adsorbate interactions on Cu and the highly active MgO-Cu interface

By coupling density functional theory calculations (DFT) with microkinetic modeling, we address two controversial problems pertaining to methanol synthesis: i) Which of the CO or CO2 hydrogenation routes dominates the synthesis rate, and ii) what makes irreducible, inert oxides like MgO an efficient promoter for the CO hydrogenation process? We determine that the inconsistency between the experimental activity trend and the previous theoretical results in the literature is attributed to the absence of interactions between adsorbed formate and intermediates, which would underestimate the rate of CO2 route by having a too high formate coverage. We show that when adsorbate-adsorbate interactions, especially the derived H bond, are included, the CO2 hydrogenation dominates for pure Cu catalysts, which is consistent with experiments. In addition, a new transition state for hydrogenation of adsorbed HCOOH* is discovered, which is further stabilized by hydrogen bonding. We also identify the MgO/Cu interface as a highly active site and propose a novel lattice-oxygen involved reaction mechanism at the interface for methanol formation. The CO hydrogenation reactivity can then be enhanced by stabilizing HCO* in the formate-type species, while the CO2 hydrogenation is inhibited by the poisoning of CO2* and HCOO*.

A comparative life cycle assessment of clean aviation fuels

In this study, life cycle assessments and comparative evaluations are performed for different types of renewable and alternative fuels for aircrafts. The life cycle impacts of both hydrogen and ammonia fuels are primarily investigated considering conventional and renewable energy-based routes. The overall life cycle impacts of several hydrocarbon fuels including kerosene, ethanol, methanol, dimethyl ether, and biodiesel are also studied. The steam methane reforming-based route for hydrogen and ammonia fuels is found to have higher global warming potentials as compared to alternative production routes. High phosphate emissions result in a higher freshwater eutrophication potential for the solar-based route for ammonia fuel. Fossil fuel-based dimethyl ether is found to have a comparatively higher global warming potential of 1.3 kgCO2 equivalent per tonne-km amongst the considered hydrocarbon fuels that include ethanol (1.1 kgCO2 equivalent per tonne-km), kerosene (1.04 kgCO2 equivalent per tonne-km), methanol (1.01 kgCO2 equivalent per tonne-km), and biodiesel (1.07 kgCO2 equivalent per tonne-km). Dimethyl ether is found to entail high toxicity potentials and the reduction of life cycle arsenic, barium, cadmium, chromium, cobalt, and lead emissions is recommended. However, higher photochemical ozone formation potentials of 0.0055 and 0.0046 kgNOx equivalent per tonne-km are associated with biodiesel and kerosene fuels respectively.

The feasibility study of the indium oxide supported silver catalyst for selective hydrogenation of CO2 to methanol

Silver catalyst has been extensively investigated for photocatalytic and electrochemical CO2 reduction. However, its high activity for selective hydrogenation of CO2 to methanol has not been confirmed. Here, the feasibility of the indium oxide supported silver catalyst was investigated for CO2 hydrogenation to methanol by the density functional theoretical (DFT) study and then by the experimental investigation. The DFT study shows there exists an intense Ag–In2O3 interaction, which causes silver to be positively charged. The positively charged Ag species changes the electronic structure of the metal, facilitates the formation of the Ag–In2O3 interfacial site for activation and dissociation of carbon dioxide. The promoted CO2 dissociation leads to the enhanced methanol synthesis via the CO hydrogenation route as CO2∗→CO∗→HCO∗→H2CO∗→H3CO∗→H3COH∗. The Ag/In2O3 catalyst was then prepared using the deposition-precipitation method. The experimental study confirms the theoretical prediction. The methanol selectivity of CO2 hydrogenation on Ag/In2O3 reaches 100.0% at reaction temperature of 200 °C. It remains more than 70.0% between 200 and 275 °C. At 300 °C and 5 MPa, the methanol selectivity still keeps 58.2% with a CO2 conversion of 13.6% and a space-time yield (STY) of methanol of 0.453 gmethanol gcat−1 h−1, which is the highest methanol STY ever reported for silver catalyst. The catalyst characterization confirms the intense Ag–In2O3 interaction as well, which causes high Ag dispersion, increases and stabilizes the oxygen vacancies and creates the active Ag–In2O3 interfacial site for the enhanced CO2 hydrogenation to methanol.

Reducible oxide and allotropic transition induced by hydrogen annealing: synthesis routes of TiO2 thin films to tailor optical response

Optical properties of hydrogenated TiO2 thin films deposited by the ion beam sputtering method are reported. By reducing the oxide by hydrogenation in situ (during deposition) and ex situ (by means of posterior thermal annealing) a controlled phase modification allows to manipulate optical properties to improve photoactivity for solar energy conversion and catalytic applications. The hydrogenation procedure prompts remarkable structural changes and optical properties of the TiO2 hierarchical thin films. Photoemission electron spectroscopy (XPS) results show the presence of titanium in Ti4+ into Ti3+ state of oxidation, i.e., compatible with oxygen vacancies and titanium interstitials. Vibrational properties inspected by IR absorption and Raman spectroscopy allowed identifying potentially catalytic sites and vibration modes associated with hydrogen. The vibrational spectra show that both in situ and ex situ hydrogenation routes contribute to prompt (dis)order in the films, involving the presence of anatase crystalline phase embedded in an amorphous matrix or mixed-phase (anatase + rutile) crystalline TiO2. To avoid debate about the TiO2 theoretical (indirect) and expected and measured (direct, normally reported) optical gap (Egap), the absorption coefficient spectra were analyzed by a recently developed method based on the Boltzmann sigmoidal function. From these analyses, conclusions about defects states prompted by the hydrogenation processes are presented.

Impact of proximity between NiMoS and zeolitic HY sites on cyclohexene hydroconversion: An infrared operando study of sulfide catalysts

This work evaluates the effects of sulfide phase location on zeolite-containing catalysts in cyclohexene hydroconversion using the infrared operando technique. Parallels between activity, product yield, and surface species changes with time on stream and under pyridine poisoning were assessed on pure HY zeolite, sulfided NiMo/HY, NiMo/Al2O3, and NiMo/Al2O3 + HY. Isomerization activity could be related to zeolitic acidic OH groups and hydrogenation activity to sulfide phase sites. From the changes due to pyridine pulse injection, intrinsic activities could be calculated for isomerization (1-methyl-1-cyclopentene) and hydrogenation (cyclohexane) routes. The turnover frequency value for isomerization is greater than that for hydrogenation by one order of magnitude. Hence, the poisoning effect of one N-molecule on isomerization will be 10 times higher than that on the hydrogenation route. Whatever the location of the sulfide phase, the coke is mostly formed on the zeolite. As a consequence, on NiMo/HY, the close proximity between acidic and sulfide sites results in lower formation of hydrogenated products, due to blockage of some sulfide sites by coke. In contrast, the hydrogenation activity of NiMo/Al2O3 + HY is less affected by coke, NiMoS being mostly located on alumina. However, the results show that the close proximity between acid and sulfide sites allows a higher degree of hydrogenation of the isomerization product (1-methyl-1-cyclopentene). Thus, the higher proximity has a beneficial effect on methylcyclopentane formation.

Design of an intercalated Nano-MoS2 hydrophobic catalyst with high rim sites to improve the hydrogenation selectivity in hydrodesulfurization reaction

The preparation of the intercalated lamellar hydrophobic nano-MoS2 (size: 60−100 nm, interlayer spacing: 0.7–1.2 nm) through the substitution of organic amine for inorganic ammonium salt and the subsequent catalytic reaction as a hydrodesulfurization catalyst is presented. The intercalated amine groups broadened the interspacing of the lamellar nano-MoS2 and promoted the formation of hydrophobic stacking structure consisting of stable monolayers. The high hydrophobicity of the nano-MoS2 monolayer catalyst was confirmed. The as-synthesized intercalated hydrophobic nano-MoS2 catalyst with lower steric hindrance and higher number of rim sites showed better hydrodesulfurization performance and higher hydrogenation route selectivity than the traditional MoS2 catalyst. The conversion of dibenzothiophene using the intercalated hydrophobic nano-MoS2 catalyst was 86 % in comparison to 23 % for the traditional MoS2 catalyst. The intercalated hydrophobic nano-MoS2 catalyst was stable in five subsequent catalytic cycles.