High CO Conversion Research Articles

Facile and continuous synthesis of highly dispersed α-MoC1-x nanoparticles via thermal plasma method for higher alcohols synthesis from syngas

The metastable phase molybdenum carbide-based (α-MoC1-x) catalysts stand out as a class of the most promising representatives among the non-sulfide catalysts for the synthesis of higher alcohols (HAS) from syngas (CO/H2) due to their noble metal-like characteristics, resistance to coking, sulfur tolerance and weak C–O bond dissociation. However, the synthesis of α-MoC1-x commonly involves temperature-programmed ammonification and carburization (TPAC) or the consumption of noble metals. The α-MoC1-x prepared by TPAC usually exhibited large particle size, low dispersion and poor catalytic performance. Herein, we developed a facile and continuous thermal plasma method for synthesizing nanosized α-MoC1-x, which was highly dispersed on amorphous carbon (α-MoC1-x/C-Pla). Compared with the α-MoC1-x prepared by TPAC method (α-MoC1-x-TPAC), the α-MoC1-x/C-Pla catalyst exhibited higher CO conversion and excellent stability. The high dispersion and reactant adsorption/desorption capacity of α-MoC1-x/C-Pla contributed to its high catalytic activity, while the anti-aggregation property of the nanosized α-MoC1-x in α-MoC1-x/C-Pla conferred the high stability for the α-MoC1-x/C-Pla catalyst.

Direct synthesis of liquid hydrocarbons from CO2 and H2 over bifunctional ZnCrOx-НZSM-5 combined and composite catalysts in a single reactor

A one-stage synthesis of gasoline fraction from CO2 and H2 was carried out on Zn-Cr–oxide-zeolite combined and composite catalysts. It was found that after oxidative and reduction treatment the catalysts contain ZnO and ZnCr2O4 phases. The one-step coprecipitation of zinc and chromium salts in the presence of zeolite allows obtaining an active bifunctional composite catalyst, each particle of which contains Zn-Cr oxide and zeolite components. A synergistic catalysis due to a closer distance of metal and acid sites increased the efficiency of such a catalyst in CO2 hydrogenation. It was found that the optimal temperature of oxidative activation of the composite catalyst is 400 ° C. With an increase in the temperature of oxidative treatment of the composite catalyst from 400 to 500°C, part of the zinc leaves the structure of the non-stoichiometric spinel and leads to a decrease in the basicity of the catalyst, which is responsible for the activation of CO2 on surface oxygen vacancies. Agglomerated ZnO particles blocked the pores and reduced their volume, as well as the specific surface of the catalyst. At the same time, the total acidity of the catalyst decreased. ZnO-species, which have hydrogenating activity, under the reaction conditions removed alkenes from the reaction cycle and thereby reduced the C5+–selectivity of the composite catalyst. Among the studied catalysts, the ZnCrOx-НZSM-5/Al2O3(400) composite catalyst in the tail-gas recirculation mode at 380°C and 10 MPa demonstrated high CO2 conversion of 25% and high selectivity for C5+–HCs of 53 wt% with a high content of isoalkanes 71 wt% for 60 hours. The methane content in the tail-gas did not exceed 3 vol%. The results obtained will be used to develop approaches to creating effective catalysts for the one-stage CO2 hydrogenation into valuable petrochemical products.

Highly stable Co/CeO2 catalyst for high-temperature water–gas shift reaction using a CeO2 support with an optimized precipitant ratio

We report hydrogen production from waste through waste gasification and the water–gas shift reaction using highly stable Co/CeO2 catalysts. Here, careful control of the KOH:K2CO3 precipitant ratio during CeO2 support synthesis yielded highly active and stable Co/CeO2 catalysts. Crucially, the precipitant ratio affects the Co dispersion, oxygen vacancies, crystallinity, and Co-CeO2 interactions, and the Co dispersion increases with increase in KOH content. Further, the oxygen storage capacity improves at the optimal KOH:K2CO3 ratio. In addition, the Co-CeO2 interaction is enhanced when catalysts are synthesized using CeO2 with a large amount of K2CO3. All prepared Co/CeO2 catalysts show high CO conversion, even at extremely high gas hourly space velocities: the Co/CeO2 (λ = 2:1 and 1:1.5) catalysts exhibit stable performance because of robust Co-CeO2 interactions, high oxygen storage capacities, and effective Co dispersions. These findings aid hydrogen production from waste and CeO2 support design for various catalytic reactions.

Semi-carbonized fluorinated polyimide-assisted preparation of TiO2 with strikingly boosted photocatalytic CO2 reduction performance

In this study, oxygen vacancies (OVs)-enriched TiO2 photocatalysts were facilely obtained using a hydrothermal synthesis with the assistance of semi-carbonized fluorinated polyimide (FPI). Addition of FPI has influenced the crystal growth of TiO2, promoting the formation of abundant OVs in TiO2. OVs enhance separation of photogenerated charges and light absorption of TiO2. Moreover, photocatalytic CO2 reduction experiments demonstrate that CO conversion on the 6 % sample (mass ratio of FPI to TiO2 is 6 %) is 2.9 times higher than that on the reference TiO2 under a xenon lamp illumination for 4 h Even after 4 cycles of photocatalytic CO2 reduction, the 6 % sample still has a high CO conversion rate. This work provides a viable pathway for the development of highly performance TiO2-based photocatalysts to promote the conversion of CO2 into high-valent carbon-containing compounds.

Effectively regulating Ni distribution on CeO2 through formation of Ce1−xNixO2−y solid solution to enhance the selectivity in RWGS reaction

Nickel-based catalysts frequently encounter significant challenges in achieving both high CO2 conversion and superior CO selectivity during reverse water gas shift (RWGS) reactions. To address this issue, we developed a facile strategy to prepare highly dispersed Ni/CeO2 catalysts by forming Ce1−xNixO2−y solid solutions. Under conditions of 300–600 °C, 0.1 MPa, and a gas hourly space velocity (GHSV) of 40,000 mL gcat−1 h−1, the 5Ni/CeO2-A catalyst exhibited outstanding selectivity, approaching 100 %. The RWGS reaction rate reached 1332 μmolCO gNi−1 s−1 and maintained stable for 50 h almost without deactivation. The formation of Ce1−xNixO2−y solid solution uniformly disperses numerous Ni species in the CeO2 lattice, effectively inhibiting Ni aggregation. This highly dispersed Ni weakens CO adsorption and facilitates its direct desorption without excessive hydrogenation. Moreover, the catalyst remains well-dispersed state even after reduction. The formed Ce1−xNixO2−y solid solution generates abundant oxygen vacancies on the catalyst surface, enhancing H2 dissociation. The catalyst’s pore size distribution is also modified, creating stacked pores that favor reactant diffusion and expose more active centers. In-situ DRIFTS experiments demonstrate that Ce-OH plays a pivotal role in CO2 adsorption on the 5Ni/CeO2-A catalyst, while the stabilization of bicarbonate and formate intermediates by the highly dispersed Ni further promotes catalytic performance. This study introduces a novel preparation method and provides valuable insights for designing Ni-based catalysts with exceptional CO selectivity.

Coaxially Bi/ZnO@ZnSe Array Photocathode Enables Highly Efficient CO2 to C1 Conversion via Long-lived High-energy Photoelectrons.

The key aspect of the photoelectrochemical CO2 reduction reaction (PEC CO2 RR) lies in designing cathode materials that can generate high-energy photoelectrons, enabling the activation and conversion of CO2 into high-value products. In this study, a coaxially wrapped ZnO@ZnSe array heterostructure was synthesized using a simple anion exchange strategy and metallic Bi nanoparticles (NPs) were subsequently deposited on the surface to construct a Bi/ZnO@ZnSe photocathode with high CO2 conversion capability. This array photocathode possesses a large aspect ratio, which simultaneously satisfies a low charge carrier migration path and a large specific surface area that facilitates mass transfer. Additionally, the barrier formed at the n-n heterojunction interface hinders the transfer of high-energy photoelectrons from ZnSe to lower energy levels, resulting in their rapid capture by Bi while maintaining a relatively long lifetime. These captured electrons act as active sites, efficiently converting CO2 into CO with a Faradaic efficiency above 88.9 % at -0.9 V vs. RHE and demonstrating superior stability. This work provides a novel approach for synthesizing high-energy photoelectrode materials with long lifetimes.

Isomorphously substituted cerium induced oxygen vacancy and medium basicity in Ni/fibrous silica catalyst for superior low-temperature CO2 methanation

A series of promoters (Ce, La, Mo, and Zr) was introduced into the Ni/CHE-SM catalyst by using the impregnation method and tested for CO2 methanation. Among these, Ni-Ce/CHE-SM possessed a high CO2 conversion of 80 % at 250 °C, signifying its potential at low temperature. The superior performance of Ni-Ce/CHE-SM was attributed to the formation of Si-O-Ni and Si-O-Ce species, as confirmed by FTIR-KBr analysis. XPS and CO2-TPD analyses revealed an abundance of oxygen vacancies existed within Ni-Ce/CHE-SM, resulting in enhancement of basicity amount and strength. In addition, Raman analysis showed the existence of three and four silica member rings which was believed that the Si atom be substituted with the Ce atom, thus contributing to create more oxygen vacancies. Hence, additional active sites were provided which enhance the adsorption of reactant molecules and improve the production of CH4, thus emphasizing the greater potential of Ni-Ce/CHE-SM in CO2 methanation application.

Pt-supported on N-doped carbon/TiO2 nanomaterials derived from NH2-MIL-125 for efficient photo-thermal RWGS reaction

To mitigate carbon dioxide (CO2) emissions and advance carbon neutrality, the conversion of CO2 into value-added fuels and chemicals via the reverse water–gas shift (RWGS) reaction is recognized as a promising approach. In this study, we designed platinum (Pt)-loaded nitrogen-doped carbon composite dual-phase titanium dioxide (TiO2) nanomaterials to achieve efficient photo-thermal performance in the RWGS reaction. The incorporation of Pt, nitrogen doping, and the selection of an appropriate calcination temperature enhance light responsiveness and reduce the recombination of photo-generated carriers, thereby improving the efficiency of the photo-thermal RWGS reaction. The optimized catalysts exhibited a high CO2 conversion (42.79 %), a carbon monoxide (CO) production rate (81.46 mmol gcat−1 h−1) and over 99.9 % selectivity under conditions of 400 °C and 1.2 W cm−2 light illumination. In addition, electron paramagnetic resonance (EPR) and X-ray photoelectron spectroscopy (XPS) analyses revealed that Pt/TiO2@CN-525 was enriched with more oxygen defects, which was facilitate the adsorption and activation of CO2. CO temperature-programmed desorption (CO-TPD) showed that Pt/TiO2@CN-525 possesses a strong desorption capacity for CO. In addition, in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) pointed to COOH* as a key intermediate in the reaction process. The photo-thermal co-catalyzed CO2 reduction by CO-TPD as well as in-situ DRIFTS indicated that Pt/TiO2@CN-525 follows the RWGS reaction. This work provides a potential strategy for the synthesis of catalysts for enhancing photo-thermal co-catalyzed RWGS reactions.

Model-based optimization strategies for direct hydrogenation of carbon dioxide to dimethyl ether

This study discusses model-based optimization strategies for CO2 hydrogenation to dimethyl ether (DME) over a CuZnZr (CZZ) and ferrite (FER) mixed catalyst system in a packed-bed reactor configuration. A two-dimensional axisymmetric, nonisothermal packed-bed reactor model was developed using COMSOL Multiphysics 6.2 software. The model solves two-dimensional (radial and axial) heat and mass transport equations in the packed-bed and integrates intraparticle diffusion and heat transfer in a 1D approach. This powerful feature differs from a traditional porous media approach and takes into account any heat and mass transfer limitations that may exist. Analysis shows that the heat transfer limitations are negligible, but strong internal mass transfer limitations were observed at 10 ≤ WHSV ≤ 90 h−1 on the FER catalyst and at 240 °C. The optimum catalyst composition (i.e., mixing ratio) varies depending on the operating regime. The FER catalyst weight in the mixture can be as low as 5 wt.%, but the ideal composition depends on the internal mass transfer limitation and its relationship with the operating regime (i.e., weight hourly space velocity, temperature). A catalyst composition of 80 wt.% CZZ and 20 wt.% FER was suggested; this composition can provide high CO2 conversion and DME production rates at a wide range of temperatures and flow rates.

Construction of CuCoCe ternary catalyst via a porous organic polymer template approach for efficient CO-PROX with wide operating temperature window

Preferential CO oxidation (CO-PROX) is a promising approach for removing trace CO from hydrogen-rich streams, effectively preventing Pt anode poisoning in proton-exchange membrane fuel cells (PEMFCs). To effectively eliminate CO within the PEMFC operating temperature range, catalysts must exhibit high CO conversion and O2 selectivity. Expanding the operating temperature window of these catalysts is crucial. This study presents the synthesis of a CuCoCe ternary catalyst (CuCo/Ce-P) using an imidazole-functionalized porous organic polymer as a sacrificial template. Compared to the CuCoCe ternary catalyst prepared without a template (CuCo/Ce), CuCo/Ce-P exhibits significantly enhanced catalytic activity, with a T50 reduction from 85 °C to 55 °C and an expanded operating temperature window of approximately 40 ℃. Characterization results indicate that the imidazole-functionalized porous organic polymer facilitates improved dispersion of active species by anchoring metal ions through electron-rich groups, enhances intermetallic interactions, promotes electron transfer, and significantly improves the oxygen-deficient capacity of the CuCoCe ternary catalyst. Consequently, the catalyst exhibits a greater number of active interfaces, leading to enhanced catalytic activity and a wider operating temperature window.

Enhanced microwave-catalytic performance for CO2 oxidative propane dehydrogenation by acidified and Bi-doped ZnO-based microwave catalysts

The oxidative dehydrogenation of propane by carbon dioxide (CO2-ODHP) has great potential in producing propylene. Resource utilization of CO2 will be the dominant trend in the future to mitigate environmental problems and cope with the growth in energy demand. However, simultaneously achieving high propane conversion, high propylene selectivity, and high CO2 conversion at low temperatures remains challenging. Herein, we report a novel efficient microwave catalyst (1.0-Zn4Bi1/Silicalite-1+SiC) by doping Bi on ZnO/Silicalite-1 and then acid treatment. The (1.0)-Zn4Bi1/Silicalite-1+SiC microwave catalyst exhibited 92 % C3H8 conversion, 84 % C3H6 selectivity, and 45 % CO2 conversion under microwave mode, significantly better than under the thermocatalysis (without microwave: 27 % C3H8 conversion, 92 % C3H6 selectivity, and 14 % CO2 conversion). The CO2 capture capacity was improved by adding Bi to ZnO/Silicalite-1. In addition, acid modification increased the propane and CO2 conversion by 1.9 and 1.3 times, respectively. Notably, acid treatment enriched the pore structure of the catalysts, altered surface acidity and alkalinity, and promoted C3H8 and CO2 activation and C3H6 desorption. In particular, the acid treatment enriches the state of the presence of Zn species in the catalyst. Microwave irradiation reduces the apparent activation energy of the catalytic system and accelerates the removal of coke from the catalyst surface. Microwave catalysis can activate CO2 and propane at lower temperatures than thermocatalysis.

Modulating the electronic interaction of ZnFemCrOx/SAPO-34 to boost CO2 hydrogenation to light olefins

Hydrogenation of CO2 into light olefins presents a promising strategy to realize carbon neutrality. Efficient adsorption and activation of CO2 are critical steps in CO2 hydrogenation into light olefins. Nevertheless, the development of a promotional catalyst that obtains high CO2 conversion and C2=-C4= selectivity is challenging, constrained by the chemical inertness of CO2. In this paper, we have synthesized a highly stable catalyst consisting of ZnFe0.38CrOx oxides and SAPO-34 zeolite, which achieves 11.4 % C2=-C4= yield at CO2 conversion up to 35.4 %. Comprehensive characterization results substantiate the existence of electronic interaction among Fe, Zn, and Cr, which facilitates the adsorption and activation of CO2. More significantly, the CO2 adsorption capacity is linearly related to the degree of electron transfer. In situ DRIFTS results further reveal that electronic interaction promotes the production of carbonate species and subsequent transformation into formate species, contributing to high CO2 conversion. These findings uncover an intrinsic connection between electronic interaction and catalytic activity, offering theoretical guidance for designing bifunctional catalysts.

Hydroxylated TiO2-induced high-density Ni clusters for breaking the activity-selectivity trade-off of CO2 hydrogenation

The reverse water gas shift reaction can be considered as a promising route to mitigate global warming by converting CO2 into syngas in a large scale, while it is still challenging for non-Cu-based catalysts to break the trade-off between activity and selectivity. Here, the relatively high loading of Ni species is highly dispersed on hydroxylated TiO2 through the strong Ni and −OH interactions, thereby inducing the formation of rich and stable Ni clusters (~1 nm) on anatase TiO2 during the reverse water gas shift reaction. This Ni cluster/TiO2 catalyst shows a simultaneous high CO2 conversion and high CO selectivity. Comprehensive characterizations and theoretical calculations demonstrate Ni cluster/TiO2 interfacial sites with strong CO2 activation capacity and weak CO adsorption are responsible for its unique catalytic performances. This work disentangles the activity-selectivity trade-off of the reverse water gas shift reaction, and emphasizes the importance of metal−OH interactions on surface.

CO2 hydrogenation to light olefins over highly active and selective Ga-Zr/SAPO-34 bifunctional catalyst

The production of light olefins from the hydrogenation of CO2 is an efficient way to utilize CO2, where the surface oxygen vacancy in metal oxide plays an important role in CO2 adsorption and activation. Here, the Ga-Zr metal oxides were prepared by hydrolysis of urea at different temperatures and combined with SAPO-34 to prepare the bifunctional catalyst for CO2 hydrogenation to light olefins. The surface oxygen vacancy content of Ga-Zr oxide increases with increasing urea hydrolysis temperature, and a high CO2 conversion of 26.4% and C2=–C4= hydrocarbon selectivity of 87.2% were obtained by a well-matched amount of desorbed CO2 and H2. Using the CO2 and H2/HCOOH/CH3OH as probe molecules, the in-situ DRIFT spectra reveal that the CO2 could be activated on surface oxygen vacancy and converted to CO3* and HCO3* species, which were further hydrogenated to HCOO* and CH3O* species. While the by-product CO mainly originates from the decomposition of HCOO* and the presence of SAPO-34 converts CH3O* to C2=–C4=. The current study illustrates that boosting the surface oxygen vacancy in defected surfaces of metal oxide and providing a matching H2 dissociation ability is the key to improve the performance of CO2 hydrogenation to light olefins.

Fine regulation of Cu-ZnO interfaces for enhanced CO2 hydrogenation to methanol by atomic layer depositing thin ZnO films on copper phyllosilicates

Regulation of abundant Cu-ZnO interfaces in Cu/ZnO catalysts is critical to the thermal hydrogenation of CO2 to methanol. Herein, Cu-ZnO interfaces were precisely regulated by depositing thin ZnO films on copper phyllosilicates (CuSiO3) through atomic layer deposition (ALD) to prepare Cu/ZnO/SiO2 composite catalysts (denoted as xZnO/CuSiO3, x is the number of ALD cycles) for CO2 hydrogenation to methanol. Interestingly, 5ZnO/CuSiO3 exhibited much higher methanol selectivity of 68.1 % and methanol space-time yield (STYMeOH) of 0.39 gMeOH h−1gcat−1 toward CO2 hydrogenation at 275 ℃ and 3 MPa, as compared to the pristine CuSiO3 (38.1 % and 0.24 gMeOH h−1gcat−1), suggesting the significant role of Cu-ZnO interfaces. Compared to ZnO/CuSiO3(IM) prepared by the conventional impregnation method, 5ZnO/CuSiO3 possessed much higher CO2 conversion (13.8 % vs. 10.1 %) and methanol selectivity (68.1 % vs. 56.2 %). Furthermore, the catalytic activities of the prepared Cu/ZnO catalysts can be effectively regulated by changing the thickness of ZnO-ALD films, in which 5ZnO/CuSiO3 showed the best catalytic activity. Various characterization methods were applied to demonstrate that ALD-ZnO was evenly laid flat on the surface of CuSiO3 to construct abundant Cu-ZnO interfaces during the H2 reduction treatment, which facilitated the dissociated activation of CO2 and formation of CH3O* reaction intermediate and simultaneously inhibited the generation of CO byproduct. In addition, the density functional theory (DFT) calculations revealed the stronger interaction between Cu and ZnO over 5ZnO/CuSiO3, which implied more Cu-ZnO interfaces were generated for methanol production. Accordingly, this study verifies the significance of Cu-ZnO interfaces for CO2 hydrogenation to methanol and provides a facile method to regulate Cu-ZnO interfaces by depositing ALD-ZnO films on the copper phyllosilicate precursor.

Superhydrophobic Surface Modification of a Co-Ru/SiO2 Catalyst for Enhanced Fischer-Tropsch Synthesis

Commercial silica support pellets were impregnated and calcined to contain cobalt oxide and ruthenium oxide for Fischer-Tropsch synthesis (FTS). The precatalyst pellets were split evenly into two groups, the control precatalyst (c-precat) and silylated precatalyst (s-precat), which were treated with 1H,1H, 2H, 2H-perfluorooctyltriethoxysilane (PFOS) in toluene. The samples of powderized s-precat were superhydrophobic, as determined by the water droplet contact angle (>150°) and sliding angle (<1°). Thermal analysis revealed the PFOS groups to be thermally stable up to 400 °C and temperature programmed reduction (TPR) studies showed that H2 reduction of the cobalt oxide to cobalt was enhanced at lower temperatures relative to the untreated c-precat. The two active catalysts were examined for their FTS performance in a tubular fixed-bed reactor after in situ reduction at 400 °C for 16 h in flowing H2 to give the active catalysts c-cat and s-cat. The FTS runs were performed under identical conditions (255 °C, 2.1 MPa, H2/CO = 2.0, gas hourly space velocity (GHSV) 510 h–1) for 5 days. Each catalyst was examined in three runs (n = 3) and the mean values with error data are reported. S-cat showed a higher selectivity for C5+ products (64 vs. 54%) and lower selectivity for CH4 (11 vs. 17%), CO2 (2 % vs. 4 %), and olefins (8% vs. 15%) than c-cat. S-cat also showed higher CO conversion, at 37% compared to 26%, leading to a 64% increase in the C5+ productivity measured as g C5+ products per g catalyst per hour. An analysis of the temperature differential between the catalyst bed and external furnace temperature showed that s-cat was substantially more active (DTinitial = 29 °C) and stable over the 5-day run (DTfinal = 22 °C), whereas the attenuated activity of c-cat (DTinitial = 16 °C) decayed steadily over 3 days until it was barely active (DTfinal < 5 °C). A post-run surface analysis of s-cat revealed no change in the water contact angle or sliding angle, indicating that the FTS operation did not degrade the PFOS surface treatment.

Construction of An Artificial Photosynthesis System with A Single CdS QDs-Ferritin Hybrid Molecule.

Establishing artificial photosynthesis systems in a simple but effective manner to mitigate the greenhouse effect and address the energy crisis remains challenging. The combination of photocatalysis technology with bioengineering is an emerging field with great potential to construct such artificial photosynthesis systems, but so far, it has barely been explored in this area. Herein, an artificial photocatalysis platform is constructed with high CO2 conversion and H2O splitting capability by integration of CdS QDs into the intra-subunit interface of H-type ferritin (Marsupenaeus japonicus), a natural ferroxidase through protein interface redesign. The crystal structure of the synthesized CdS QDs with engineered ferritin molecules as bio-templates confirmed the design at an atomic level. Notably, upon absorbing desirable visible light (≈420nm), such a single CdS-ferritin hybrid molecule is able to selectively catalyze the reduction of CO2 into HCOOH (≈90%), meanwhile catalyzing the oxidation of H2O into O2 in an aqueous environment. The O2 production rate reached to 180µmolg-1h-1, and the HCOOH output hit almost 800µmolg-1h-1. This work advances the utilization of the four-helix bundle structure for crafting artificial photosynthesis systems, facilitating the seamless integration of bioengineering and photocatalysis technology.

Comparative Study on Ethanol-Based Oxygenate Synthesis via Syngas over Monometallic Rh Catalysts Supported on Different Zr-MOFs

Three types of Zr-based metal–organic frameworks (Zr-MOFs) were employed as supports to prepare monometallic Rh catalysts by the impregnation method. The effects of the structural properties of Zr-MOFs on their supported monometallic Rh catalysts for syngas conversion were investigated. The results showed that, compared to catalysts with Rh@MOF-808 and Rh@UiO-66, Rh@UiO-67 had higher CO conversion and C2+ oxygenate selectivity. The state of the Rh site is affected by the different structure of the Zr-MOFs, which is responsible for the difference in catalytic performance. The relatively higher Rh dispersion on the UiO-67 support boosted its CO adsorption ability, and Rh@UiO-67 having the best C2+ oxygenate selectivity was mainly attributed to it having the highest Rh+/Rh0 ratio.

Performance and mechanism investigation of Cu loading and S vacancy synergistic promotion of MoS2 catalyzed low-temperature water gas shift reaction: Experimental and theoretical calculations

In this paper, MoS2 with S vacancies and Cu loading (Cu/VS-MoS2) was synthesized and used for low-temperature water gas shift reactions (WGSR); the intrinsic reasons and reaction mechanisms for the high catalytic activity of Cu/VS-MoS2 were studied through DFT calculation. The material characterization fully confirms the successful construction of Cu loading and S vacancies on spherical cluster structures of Cu/VS-MoS2. The experimental results show that Cu/VS-MoS2 exhibits the highest CO conversion, up to 40.41%, which is 3.9 times, 1.8 times, and 1.5 times higher than MoS2, VS-MoS2, and Cu/MoS2, respectively. DFT calculations indicate that Cu/VS-MoS2 has high WGSR activity due to the superior electron transfer ability of the dual active sites, and the S vacancy is used to activate CO to generate CO2, while the Cu site activates H2O to produce hydrogen. The synergistic effect of S vacancies and Cu sites, while satisfying hydrogen production and carbon dioxide enrichment, greatly enhances the activity of MoS2. In addition, Cu/VS-MoS2 can more effectively break down the transfer barriers between surface electrons and CO, H2O molecules, allowing electrons to continuously transfer to CO and H2O using S vacancies and Cu atoms as mediators, reducing the energy barrier of the rate-determining step in association mechanism.

LaCoO3 is a promising catalyst for the dry reforming of benzene used as a surrogate of biomass tar.

Tar build-up is one of the bottlenecks of biomass gasification processes. Dry reforming of tar is an alternative solution if the oxygen chemical potential on the catalyst surface is at a sufficient level. For this purpose, an oxygen-donor perovskite, LaCoO3, was used as a catalyst for the dry reforming of tar. To circumvent the complexity of the tar and its constituents, the benzene molecule was chosen as a model compound. Dry reforming of benzene vapor on the LaCoO3 catalyst was investigated at temperatures of 600, 700, and 800 °C; at CO2/C6H6 ratios of 3, 6, and 12; and at space velocities of 14,000 and 28,000 h-1. The conventional Ni(15 wt.%)/Al2O3 catalyst was also used as a reference material to determine the relative activity of the LaCoO3 catalyst. Different characterization techniques such as X-ray diffraction, N2 adsorption-desorption, temperature-programmed reduction, and oxidation were used to determine the physicochemical characteristics of the catalysts. The findings demonstrated that the LaCoO3 catalyst has higher CO2 conversion, higher H2 and CO yields, and better stability than the Ni(15 wt.%)/γ-Al2O3 catalyst. The improvement in activity was attributed to the strong capacity of LaCoO3 for oxygen exchange. The transfer of lattice oxygen from the surface of the LaCoO3 catalyst facilitates the oxidation of carbon and other surface species and leads to higher conversion and yields.