Performance For CO2 Hydrogenation Research Articles

Reduction treatment of nickel phyllosilicate supported Pt nanocatalysts determining product selectivity in CO2 hydrogenation

Catalyst design is one of the most critical factors in selectively converting CO2 and renewable H2 to value-added chemicals. In this work, Pt nanoparticles with an average size of 2.9 nm were uniformly loaded on hollow mesoporous nickel phyllosilicate which then underwent various reduction treatments to partial extraction of Ni atoms and formation of Ni-Pt bimetallic catalysts for the selective CO2 hydrogenation in a fixed bed reactor. Experimental results reveal that Pt nanoparticles supported on SiO2 are highly selective to CO via reversed water gas shift (RWGS) reaction with 100% CO selectivity, while Pt nanoparticles supported on nickel phyllosilicate show high selectivity for CH4, particularly, under high reduction temperature. By simply changing the reduction temperature or reaction pressure, the production selectivity can be facilely tuned, and the maximum CH4 selectivity achieved in the bimetallic Pt/Ni@phyllosilicate catalyst is 100%. The metallic Ni0 reduced from nickel phyllosilicate owns a high concentration of Lewis basic sites, which could enhance the adsorption strength of CO2 but prevent the dissociated adsorption. The diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) in different transient states were applied to study the mechanistic insights into how Ni-Pt dual sites tune the product selectivity. The results suggest that CO* over Pt site is the key species for CO2 conversion to CO, whereas the produced CO* could be further hydrogenated to CHxO* intermediate over Ni site, leading to the formation of CH4. The present work offers a new method to prepare Ni-Pt bimetallic catalysts with excellent CO2 hydrogenation performance towards CH4.

Promotion effect of iron addition on the structure and CO2 hydrogenation performance of Attapulgite/Ce0.75Zr0.25O2 nanocomposite supported Cu-ZnO based catalyst

• Fe introduction improves the surface dispersion of metallic Cu on CZF x K/ATP-CZO catalysts. • Medium Fe addition enhances the formation of surface adsorbed and lattcie oxygen species and ZnO-CZO interfaces. • In-situ DRIFT is adopted to explore the CO 2 adsorption mode and reaction intermediate species. • Methanol is synthesized over CZF 0.5 K/ATP-CZO catalyst with the highest CO 2 conversion and space time yield. A series of CZF x K/ATP-CZO catalysts (x= 0, 0.3, 0.5, 1.0, 1.5 and 2.0) are applied to clarify the effects of the iron addition on the catalytic performance of CO 2 hydrogenation to CH 3 OH. The physicochemical properties and catalytic mechanism were investigated by N 2 adsorption/desorption, XRD, TEM, N 2 O chemisorption, XPS, H 2 -TPR, CO 2 -TPD and in-situ DRIFT techniques. The best catalytic performance is achieved over CZF 0.5 K/ATP-CZO catalyst, exhibiting X CO2 = 17.5%, STY CH3OH = 0.108 g/g cat. ∙h and STY CO = 0.146 g/g cat. ∙h (T = 320°C, P = 6 MPa). The formation of dispersed surface metallic Cu species and larger number of surface adsorbed and lattcie oxygen species and ZnO-CZO interfaces are detected over CZF 0.5 K/ATP-CZO due to stronger interaction between dispersed metallic Cu particles on ZnO-Fe nano-cluster and ATP-CZO composite, resulting in the superior activation ability for H 2 and CO 2 respectively. Additionally, the evidence is provided by in-situ DRIFTS under the activity test temperature (320°C) that HCOO∗ and CO* species are preferable for accumulating over CZK/ATP-CZO catalyst without Fe addition while medium Fe-modified CZF x K/ATP-CZO catalysts (CZF 0.3 K/ATP-CZO, CZF 0.5 K/ATP-CZO) catalysts are benefitial to promote the transformation of HCOO∗ species to CH 3 OH. These excessive Fe-modified CZF x K/ATP-CZO catalysts (CZF 1.0 K/ATP-CZO, CZF 2.0 K/ATP-CZO) are more easily to produce CH 4 via formate pathway (CO 2 * → HCOO* → HCO* → CH* → CH 4 *). The abundant population and high transformation activity of formate intermediate species over CZF 0.5 K/ATP-CZO give a strong positive effect on the CO 2 hydrogenation to methanol performance. The strong interactions between dispersed metallic Cu species and larger number of surface adsorbed and lattcie oxygen species and ZnO-CZO interfaces give rise to favorable methanol synthesis performances over CZF0.5K/ATP-CZO catalyst.

Synergistic Effect of Alkali Na and K Promoter on Fe-Co-Cu-Al Catalysts for CO2 Hydrogenation to Light Hydrocarbons

Alkali metal K- and/or Na-promoted FeCoCuAl catalysts were synthesized by precipitation and impregnation, and their physicochemical and catalytic performance for CO2 hydrogenation to light hydrocarbons was also investigated in the present work. The results indicate that Na and/or K introduction leads to the formation of active phase metallic Fe and Fe-Co crystals in the order Na < K < K-Na. The simultaneous introduction of Na and K causes a synergistic effect on increasing the basicity and electron-rich property, promoting the formation of active sites Fe@Cu and Fe-Co@Cu with Cu0 as a crystal core. These effects are advantageous to H2 dissociative adsorption and CO2 activation, giving a high CO2 conversion with hydrogenation. Moreover, electron-rich Fe@Cu (110) and Fe-Co@Cu (200) provide active centers for further H2 dissociative adsorption and O-C-Fe intermediate formation after adsorption of CO produced by RWGS. It is beneficial for carbon chain growth in C2+ hydrocarbons, including olefins and alkanes. FeCoCuAl simultaneously modified by K-Na exhibits the highest CO2 conversion and C2+ selectivity of 52.87 mol% and 89.70 mol%, respectively.

In situ XPS studies of MoS2-based CO2 hydrogenation catalysts

Various formulations of Co, Ni and K modified MoS2-based catalysts were synthesized hydrothermally and compared in their catalytic performance in CO2 hydrogenation at 21 bar and 220 °C–330 °C. The products were CO, CH4 and methanol. The addition of K reduced the selectivity to CH4 and moved the maximum of the methanol formation rate to a higher temperature. The materials were characterized by N2 physisorption, temperature programmed oxidation, temperature programmed reduction, and x-ray diffraction spectra (XRD). Under reducing conditions the catalysts were stable until 700 °C and under oxidizing conditions until 300 °C. XRD had shown mainly a MoS2 phase, as well as metal sulfide in the cobalt and nickel promoted catalysts. Different species of Mo and O were observed under reaction conditions by in situ x-ray photoelectron spectroscopy (XPS). When switching from H2 to CO2 + H2 an increase in the amount of oxygen, both lattice oxygen and surface adsorbates, was observed as a consequence of CO2 addition and H2O formation in the reaction. The amount of lattice oxygen correlates with the minor amount of Mo(VI) detected. Increasing reaction temperature and thus conversion led to an increase of the O 1s signals at 533 eV assigned to surface OH, formate and adsorbed H2O. XPS measurements in CO2 + H2 feed showed an effect of K addition on the adsorbate-related O 1s peak, which appeared at lower binding energy (532 eV) and was assigned to carbonates. This may indicate a different reaction mechanism in the presence of the promoter.

Yttria-doped Cu/ZnO catalyst with excellent performance for CO2 hydrogenation to methanol

Revealing the origin of the enhanced performance on yttria (Y2O3) promoted Cu/ZnO based catalyst for methanol synthesis via CO2 hydrogenation is still challenging. To shed light upon the promotion effect of Y2O3 modifier on binary Cu/ZnO catalyst for CO2 hydrogenation reaction, a ternary Cu/ZnO/Y2O3 catalyst was synthesized via a citric acid coordination-assisted strategy. The developed Cu/ZnO/Y2O3 catalyst exhibited a remarkably higher Weight-time yeild of methanol (236.8 gMeOH gcat−1∙h − 1) and methanol selectivity (81.1%) in comparison to Cu/ZnO catalyst (159.6 gMeOH gcat−1∙h − 1 and 73.9%, respectively). Various characterizations results have uncovered the enhanced catalytic activity of Cu/ZnO/Y2O3 catalyst for methanol synthesis was associated with small size and highly dispersed Cu species and abundant surface adsorption sites as well as more Cu-ZnO interfaces with strong interaction. Moreover, the Cu/ZnO/Y2O3 catalyst displayed a superior weight-time yield of methanol with a time-on-stream of 100 h in comparison with classic Cu/ZnO catalyst. We anticipate that this basic design strategy will provide a novel alternative to expand opportunities to explore scalable, cost-effective catalysts for industrial methanol synthesis.

A Multi‐Parametric Catalyst Screening for CO2 Hydrogenation to Ethanol

AbstractThe direct hydrogenation of CO2 to higher alcohols has the potential to turn the main contributor of global warming into a valuable feedstock. However, for this technology to become attractive, more efficient and, especially, selective catalysts are required. Here we present a high throughput study on the influence of different promoters on the CO2 hydrogenation performance of Rh−SiO2 catalysts. Fe and K promoters were found to improve ethanol selectivity at the expense of undesired CH4. The best‐performing catalyst, with a composition 2 wt.% K, 20 wt.% Fe, and 5 wt.% Rh, displays an EtOH selectivity of 16 % at CO2 conversion level of 18.4 % and CH4 selectivity of 46 %. The combination of different characterization techniques and catalyst screening allowed us to unravel the role of each catalyst component in this complex reaction mechanism.

Solvothermal preparation of CuO-ZnO-ZrO2 catalysts for methanol synthesis via CO2 hydrogenation

Solvothermal preparation of CuO-ZnO-ZrO2 (CZZ) was realized using ethylene glycol as a solvent. The effects of solvothermal temperature (140–200 °C) on the properties of catalysts and catalytic performance in CO2 hydrogenation were studied. ICP-OES, N2 sorption, XRD, SEM-EDX, reactive N2O adsorption, XPS, H2-TPR, H2-TPD, and CO2-TPD were used as characterization tools. The data indicate that the CZZ-180 catalyst prepared at a solvothermal temperature of 180 °C has the smallest Cu crystallites and the largest surface area of Cu0, thus exhibiting the highest methanol yield. The effects of reaction temperature, pressure, and space velocity were also investigated.

CO2 hydrogenation to C5+ hydrocarbons over K‐promoted Fe/CNT catalyst: Effect of potassium on structure–activity relationship

Developing efficient catalysts for direct CO2 hydrogenation to fuel hydrocarbons is of great significance for the effective utilization of CO2, and C5+ selectivity is one critical indicator for the process economics. In this work, a series of K‐promoted Fe/CNT catalysts were prepared by the co‐impregnation method, and their catalytic performance for CO2 hydrogenation was studied in a slurry‐bed reactor. As a result, CO2 conversion and C5+ selectivity showed positive correlation with the increase of K/Fe ratio from 0 to 0.3, but further increase of K/Fe ratio above 0.3 slightly affected its. The catalyst with a K/Fe molar ratio of 0.3 achieved the best performance with CO2 conversion of 23.7% and C5+ selectivity of 56%. In addition, the structure–activity relationship of the catalyst was discussed based on various characterization results. K‐modified catalysts presented a higher specific surface area and stronger CO2 chemisorption, which helped to improve CO2 conversion and C5+ selectivity. However, excessive potassium loading caused a loss of specific surface area, reduction degree, and graphitization degree of the catalyst, which inhibited the CO2 chemisorption and the formation of C5+ hydrocarbons.

Catalytic consequences of the decoration of sodium and zinc atoms during CO2 hydrogenation to olefins over iron-based catalyst

This study unravels the effects of Na decoration and/or ZnO addition on the structures of Fe based catalysts, and the reaction pathways and the rate dependencies on both the composition of reactants and reaction temperature for CO2 hydrogenation to olefins, using kinetics and structure characterization by Raman spectroscopy, X-ray diffraction, and temperature-programmed CO reduction techniques. CO2 hydrogenation over Fe based catalysts occurs as a combination of the primary reverse water-gas-shift reaction to form CO and the subsequent CO hydrogenations to produce olefins and paraffins. Adding ZnO into Fe catalysts enhanced the rates of CO2 hydrogenation to all carbon containing products because ZnO facilitated the generation of iron carbide, as an active phase in Fe based catalysts, however, the relative rates among primary RWGS reactions, secondary CO hydrogenation to olefins and to paraffins were insensitive to the addition of Zn. Decoration of Na into Fe catalysts altered significantly the rate dependencies on both reactants and reaction temperature for olefins formation, which might be the results of the modification of the reducibility and surface identities of Fe catalysts by Na atoms, thus changed the rate ratios of paraffins and olefins. As results of decoration of Na and addition of Zn, the modified Fe based catalyst exhibits optimal performance for CO2 hydrogenation to olefins, which shows a CO2 conversion of 43 % with a selectivity of 54.1 % to high olefins, and a high olefins-to-paraffins ratio of 7.3.

Near ambient-pressure X-ray photoelectron spectroscopy study of CO2 activation and hydrogenation on indium/copper surface

Indium-based catalysts exhibit excellent performance for CO2 hydrogenation to methanol, yet their nature and chemical evolution under reaction conditions are still elusive, thus hindering an understanding of their reaction mechanism. In this work, near ambient-pressure X-ray photoelectron spectroscopy (NAP-XPS) is employed to investigate the chemical properties and the catalytic role of indium/copper model catalysts under CO2 hydrogenation conditions. We found that the deposition of In on the surface of a Cu foil led to the formation of Cu-In alloy, whereas upon CO2 exposure, In was partially oxidized to In2O3-x and Cu remains metallic. Due to the presence of In2O3-x, CO2 was activated on the surface of In/Cu samples mainly in the form of carbonate. In addition, compared with the pure In foil reference, both the fraction of oxygen vacancies and the coverage density of carbonate were higher on the In/Cu samples, indicating the promotion effect of Cu-In alloy in the activation of CO2. These results reveal the evolution of the active sites of indium/copper catalysts and inspire the design of advanced In-based bimetallic catalysts for CO2 hydrogenation.

Fe-Co-K/ZrO2 Catalytic Performance of CO2 Hydrogenation to Light Olefins

Fe-Co-K/ZrO₂ Catalytic Performance of CO₂ Hydrogenation to Light Olefins

Effect of alkali (Cs) doping on the surface chemistry and CO2 hydrogenation performance of CuO/CeO2 catalysts

The reaction of captured carbon dioxide with renewable hydrogen towards the eventual indirect production of liquid hydrocarbons via CO2 reduction to CO (reverse water-gas shift reaction, rWGS) is a promising pathway in the general scheme of worldwide CO2 valorization. Copper-ceria oxides have been largely employed as rWGS catalysts owing to their unique properties linked to copper-ceria interactions. Here, we report on the fine-tuning of CuO/CeO2 composites by means of alkali promotion. In particular, this work aims at exploring the effect of cesium doping (0–4 atoms Cs per nm2) on co-precipitated CuO/CeO2 catalysts under CO2 hydrogenation conditions. The as-prepared samples were characterized by N2 physisorption, X-ray diffraction (XRD), H2-temperature programmed reduction (H2-TPR), X-ray photoelectron spectroscopy (XPS), CO2-temperature programmed desorption (CO2-TPD), Fourier-transform infrared spectroscopy (FTIR) of pyridine adsorption and CO-diffuse reflectance Fourier-transform infrared spectroscopy (CO-DRIFTS). The results demonstrated that a low amount of Cs exerted a beneficial effect on CO selectivity, inhibiting, however, CO2 conversion. Specifically, a doping of 2 atoms Cs per nm2 offers > 96 % CO selectivity and equilibrium CO2 conversion at temperatures as low as 430 °C, whereas further increase in cesium loading had no additional impact. The present findings can be mainly interpreted on a basis of the alkali effect on the textural and acid/base properties; Cs doping results in a significant reduction of the surface area and thus to a lower population of active sites for CO2 conversion, whereas it enhances the formation of basic sites and the stabilization of partially reduced Cu+ species, favoring CO selectivity.

Modulation of the Effective Metal‐Support Interactions for the Selectivity of Ceria Supported Noble Metal Nanoclusters in Atmospheric CO2 Hydrogenation

AbstractEver‐increasing attention is paid to the sustainable utilization of CO2 in the atmosphere out of environmental and economic considerations. The deep‐going clarification of the effective and ineffective metal‐support interactions (MSI) in the supported catalysts for the catalytic performance of CO2 hydrogenation is particularly needed to design highly active nanocatalysts. How to tune the MSI to be effective for the selectivity of goal hydrogenation products is a significant but rather challenging subject. In this work, we demonstrate that the selectivity in CO2 hydrogenation can be regulated from preferential CH4 production to preferential CO production by varying the nature of the electronic MSI for ceria supported noble metal nanoclusters, and the effective MSI play a pivotal role for the catalytic systems with opposite hydrogenation selectivity. The modulation of the effective MSI for the selectivity in CO2 hydrogenation sheds new light on the comprehensive understanding of the MSI and interfacial effects in terms of tailoring and controlling the performance of supported heterogeneous catalysts.

HI-Light: A Glass-Waveguide-Based "Shell-and-Tube" Photothermal Reactor Platform for Converting CO2 to Fuels.

SummaryIn this work, we introduce HI-Light, a surface-engineered glass-waveguide-based “shell-and-tube” type photothermal reactor which is both scalable in diameter and length. We examine the effect of temperature, light irradiation, and residence time on its photo-thermocatalytic performance for CO2 hydrogenation to form CO, with a cubic phase defect-laden indium oxide, In2O3-x(OH)y, catalyst. We demonstrate the light enhancement effect under a variety of reaction conditions. Notably, the light-on performance for the cubic nanocrystal photocatalyst exhibits a CO evolution rate at 15.40 mmol gcat−1 hr−1 at 300°C and atmospheric pressure. This is 20 times higher conversion rate per unit catalyst mass per unit time beyond previously reported In2O3-x(OH)y catalyst in the cubic form under comparable operation conditions and more than 5 times higher than that of its rhombohedral polymorph. This result underscores that improvement in photo-thermocatalytic reactor design enables uniform light distribution and better reactant/catalyst mixing, thus significantly improving catalyst utilization.

Inverse ZrO2/Cu as a highly efficient methanol synthesis catalyst from CO2 hydrogenation

Enhancing the intrinsic activity and space time yield of Cu based heterogeneous methanol synthesis catalysts through CO2 hydrogenation is one of the major topics in CO2 conversion into value-added liquid fuels and chemicals. Here we report inverse ZrO2/Cu catalysts with a tunable Zr/Cu ratio have been prepared via an oxalate co-precipitation method, showing excellent performance for CO2 hydrogenation to methanol. Under optimal condition, the catalyst composed by 10% of ZrO2 supported over 90% of Cu exhibits the highest mass-specific methanol formation rate of 524 gMeOHkgcat−1h−1 at 220 °C, 3.3 times higher than the activity of traditional Cu/ZrO2 catalysts (159 gMeOHkgcat−1h−1). In situ XRD-PDF, XAFS and AP-XPS structural studies reveal that the inverse ZrO2/Cu catalysts are composed of islands of partially reduced 1–2 nm amorphous ZrO2 supported over metallic Cu particles. The ZrO2 islands are highly active for the CO2 activation. Meanwhile, an intermediate of formate adsorbed on the Cu at 1350 cm−1 is discovered by the in situ DRIFTS. This formate intermediate exhibits fast hydrogenation conversion to methoxy. The activation of CO2 and hydrogenation of all the surface oxygenate intermediates are significantly accelerated over the inverse ZrO2/Cu configuration, accounting for the excellent methanol formation activity observed.

Iron catalysts supported on nitrogen functionalized carbon for improved CO2 hydrogenation performance

Preparation of highly efficient Fe-based catalysts is a reliable and achievable goal for catalyzing CO2 hydrogenation. Herein, ethylene diamine as a benign modifier well regulates the surface properties of carbon support, achieving a good dispersion of active small-size iron carbide sites. With the further incorporation of alkaline K promoter, heavy hydrocarbon selectivity (C5+) is increased from 14.8% to 39.8%. Combining several catalyst characterization (XRD, CO2-TPD, H2-TPR, TEM, and XPS) and reaction data, discloses that good dispersion, enhanced reduction/carburization behavior, and small-size carbides formation are essential for improving CO2 performance. Simultaneous doping of nitrogen atoms and alkali metal provides a promising means for CO2 fixation and rational design of functionalized metal-supported carbon catalysts.

Kinetic parameters estimation via dragonfly algorithm (DA) and comparison of cylindrical and spherical reactors performance for CO2 hydrogenation to hydrocarbons

Climate change and global warming, as well as growing global demand for hydrocarbons in industrial sectors, make great incentives to investigate the utilization of CO2 for hydrocarbons production. Therefore, finding an in-depth understanding of the CO2 hydrogenation reactors along with simulating reactor responses to different operating conditions are of paramount importance. However, the reaction mechanisms for CO2 hydrogenation and their corresponding kinetic parameters have been disputable yet. In this regard, considering the previously proposed Langmuir-Hinshelwood-Hougen-Watson (LHHW) mechanism, which considered CO2 hydrogenation as a combination of reverse water gas shift (RWGS) and Fischer-Tropsch (FT) reactions, and using a one-dimensional pseudo-homogeneous non-isothermal model, kinetic parameters of the rate expressions are estimated via fitting experimental and modelling data through a novel swarm intelligence optimization technique called dragonfly algorithm (DA). The predicted reactants conversion using DA algorithm are closer to the experimental data (with about 4% error) comparing to those obtained by the artificial bee colony (ABC) algorithm, and are in significant agreement with available literature data. The proposed model is used to assess the effect of reactor configuration on the performance and temperature fluctuations. Results show that axial flow spherical reactor (AFSR) and radial flow spherical reactor (RFSR) exhibiting the same surface area with that of the cylindrical reactor (CR), i.e., AFSR-2 and RFSR-2-i are the most efficient exhibiting hydrocarbons selectivity of 40.330% and 40.286% at CO2 conversion of 53.763% and 53.891%. In addition, it is revealed that the location of the jacket has an essential role in controlling the reactor temperature.

Tuning interaction of surface-adsorbed species over Fe/K-Al2O3 modified with transition metals (Cu, Mn, V, Zn or Co) on light olefins production from CO2 hydrogenation

The presence of transition metals (Cu, Co, Zn, Mn or V) in Fe/K-Al2O3, modifying the adsorption-desorption properties of CO2 and H2 with the catalyst surface remarkably influences the catalytic performance for CO2 hydrogenation to light olefins. The addition of either Cu or Zn to Fe/K-Al2O3 significantly increases the number of weakly adsorbed H atom, yielding the high CO2 conversion and shifting the product distribution towards longer chain hydrocarbon with a higher content of paraffins. The addition of Co to Fe/K-Al2O3 also enhances the CO2 conversion but it provides the short chain hydrocarbon (C1-C4) and thus achieving the highest light olefins yield of 16.2%. The presence of either Mn or V inhibits the CO hydrogenation to hydrocarbon, leading to the low CO2 conversion. The Mn promoter reduces the number of weakly adsorbed H atom, lowering the hydrogenation ability of the catalyst, resulting in the highest olefin to paraffin ratio of 7.4.

CO2 hydrogenation on Co/CeO2-δ catalyst: Morphology effect from CeO2 support

The Co/CeO2-δ catalysts with different morphology structure were prepared for CO2 catalytic hydrogenation reaction. The physical and chemical properties of these catalysts were characterized by H2-TPR, XRD, TEM, ICP and H2-TPD. The characterization results indicated that the different morphology structure of CeO2 support obviously influence the exposed crystal plane, and then affect the concentration of oxygen vacancies, the metal-support interaction and the dispersion of Co0 active species on the CeO2 support. In addition, the Co ions can be dissolved into the CeO2 lattice to form Ce–O–Co solid solution, which promotes the formation of Co0 active species, oxygen vacancies, and the Ce3+-□-Co0 structure, thus significantly affects the CO2 hydrogenation performance of Co/CeO2-δ catalysts. The exposed {110} and {100} crystal plane of CoCe140 catalyst with nano-rods structure ensure the excellent CO2 hydrogenation performance, including CO2 conversion is 48.7%, the CH4 and CO selectivity are 91.7% and 8.3%, respectively.

Cu2In Nanoalloy Enhanced Performance of Cu/ZrO2 Catalysts for the CO2 Hydrogenation to Methanol

In this work, compared with non-Cu2In nanoalloy counterpart Cu-In/ZrO2 catalysts, Cu1In2Zr4-O catalyst with the structure of Cu2In alloy exhibited an excellent performance for CO2 hydrogenation to ...