Direct Hydrogenation Of CO2 Research Articles

CO2 hydrogenation to methanol over Cu catalysts supported on La-modified SBA-15: The crucial role of Cu–LaOx interfaces

The direct hydrogenation of CO2 to methanol has become a very active research field because CO2 can be prospectively recycled to mitigate greenhouse effect and store clean synthetic fuels. This reaction can be catalyzed by supported Cu catalysts and the catalysts display strong support or promoter effects. Sintering of Cu species accelerates the separation of Cu–oxide interfaces, reduces the active component, and diminishes the methanol selectivity. In this work, we report a Cu catalyst supported on La-modified SBA-15, where the Cu–LaOx interface is generated through the interaction of highly dispersed Cu nanoparticles with LaOx species bedded into the SBA-15 pore wall. The optimized Cu1La0.2/SBA-15 catalyst can achieve methanol selectivity up to 81.2% with no deterioration in activity over 100 h on stream compared with the La-free catalyst. A thorough study reveals that La species not only significantly improve the CO2 adsorption but also enhance Cu dispersion to produce well-dispersed active sites. The H/D exchange experiments show that the methanol synthesis displays a strong thermodynamic isotope effect and the Cu–LaOx interface plays a crucial role for the methanol synthesis rate in CO2/D2 feed. In situ DRIFTS studies reveal that *HCOO and *OCH3 species are the key intermediates formed during the activation of CO2 and methanol synthesis over the Cu1La0.2/SBA-15 catalyst.

Hydrogenation of Carbon Dioxide to Value-Added Chemicals by Heterogeneous Catalysis and Plasma Catalysis

Due to the increasing emission of carbon dioxide (CO2), greenhouse effects are becoming more and more severe, causing global climate change. The conversion and utilization of CO2 is one of the possible solutions to reduce CO2 concentrations. This can be accomplished, among other methods, by direct hydrogenation of CO2, producing value-added products. In this review, the progress of mainly the last five years in direct hydrogenation of CO2 to value-added chemicals (e.g., CO, CH4, CH3OH, DME, olefins, and higher hydrocarbons) by heterogeneous catalysis and plasma catalysis is summarized, and research priorities for CO2 hydrogenation are proposed.

Development of Tandem Catalysts for CO2 Hydrogenation to Olefins

The utilization of CO2 as a carbon source for synthesis of value-added chemicals and fuels, particularly light olefins, is one of the most attractive routes to convert CO2 as part of a large-scale process. Designing active, selective, and stable catalysts for olefin production is challenging because of the difficulty characterizing structure–property relationships for the highly complex CO2 hydrogenation reaction network. To understand the challenges and opportunities in converting CO2 directly to olefins over a single tandem catalyst, this Perspective reviews the following three routes: (1) direct hydrogenation of CO2 to olefins over promoted catalysts; (2) methanol synthesis followed by methanol-to-olefins (MeOH-mediated route); (3) CO production via the reverse-water–gas-shift reaction, followed by Fischer–Tropsch synthesis (CO-mediated route). Future research directions are proposed on the critical research areas of elucidating reaction mechanisms by combining in situ characterization techniques with ...

Modeling and optimization of hydrogenation of CO2: Estimation of kinetic parameters via Artificial Bee Colony (ABC) and Differential Evolution (DE) algorithms

Global warming, climate change, fossil fuel depletion and steep hikes in the price of environmentally friendly hydrocarbons motivate researchers to investigate CO2 hydrogenation for hydrocarbons production. However, due to the reaction complexities and varieties of produced species, the process mechanism and subsequently estimation of the kinetic parameters have been controversial yet. Therefore, estimating the kinetic parameters using Artificial Bee Colony (ABC) and Differential Evolution (DE) optimization algorithms based on Langmuir-Hinshelwood-Hougen-Watson (LHHW) mechanism is proposed as a possible remedy to fulfil the requirements. To this end, a one-dimensional heterogeneous model comprising detailed reaction rates of reverse water gas shift (RWGS), Fisher-Tropsch (FT) reactions and direct hydrogenation (DH) of CO2 is developed. It is observed that ABC exhibiting 6.3% error in predicting total hydrocarbons selectivity is superior to DE algorithm with 32.9% error. Therefore, the model employed the estimated kinetic parameters obtained via ABC algorithm, is exploited for products distribution analysis. Results reveal that maximum 73.21% hydrocarbons (C1C4) selectivity can be achieved at 573 K and 1 MPa with 0.85% error compared to the experimental value of 72.59%. Accordingly, the proposed model can be exploited as a powerful tool for evaluating and predicting the performance of CO2 hydrogenation to hydrocarbons process.

Biogas to methanol: A comparison of conversion processes involving direct carbon dioxide hydrogenation and via reverse water gas shift reaction

Methanol is a clean fuel and an important intermediate in chemical synthesis. In this work, the synthesis of methanol from a large-scale biogas plant utilizing biomass in the form of animal, food and dairy wastes and wastewater sludge is studied. It considers upgrading the biogas into biomethane through a separation step to remove CO2 prior to steam reforming and produces syngas for methanol synthesis. Instead of rejecting to the atmosphere, the separated CO2 is mixed with the syngas from the reformer and fed to the methanol reactor. Three process schemes are simulated (using two different catalysts) and compared on the basis of maximum CH4 conversion and methanol productivity. While one of the catalysts is a conventional catalyst preferred for a CO-rich syngas feed, the second catalyst is designed for direct hydrogenation of a CO2-rich syngas feed. The process alternatives use reverse water gas shift reaction, direct CO2 hydrogenation and intermediate water removal. From the different cases considered, the maximum possible methanol production is 2100 tons per day from a biogas feed of 1.8 × 106 Nm3/year – this corresponds to a process of steam methane reforming followed by direct CO2 hydrogenation using Cu/Zn/Al/Zr catalyst (two methanol reactors in series with intermediate water removal between them.) It was also shown that all the three processes can be designed to be self-sufficient in meeting their electricity requirements without the use of any external fuel like natural gas, etc. Since we are converting waste to energy utilizing biomass and don't require any additional fossil fuels, this can be referred to as a clean and green production process.

Kinetic Model Discrimination for Methanol and DME Synthesis using Bayesian Estimation

Abstract Three parameter estimation methods are compared for the discrimination between two kinetic models of methanol and DME synthesis over Cu/ZnO/Al2O3 catalysts. Two methods apply Bayes’ rule and Monte Carlo sampling to approximate the posterior distribution, while the third one is the popular frequentist method of finding a maximum likelihood estimate and constructing ellipsoidal confidence regions. The credible regions obtained with either Bayesian methods are similar, and they are consistently smaller and more informative than the frequentist confidence regions. Both kinetic models suffer from some practical identifiability issues for the experimental data at hand, but the evidence derived from the Bayesian estimation strongly favors the kinetic model that accounts for direct CO hydrogenation.

CO2 hydrogenation by phosphorus-nitrogen PN3P-pincer iridium hydride complexes: elucidation of the deactivation pathway.

PN3P-Ir pincer hydride complexes were synthesized and characterized as catalysts and key intermediates in the direct hydrogenation of CO2 to formate under mild conditions. The formation of a dearomatized PN3P*-Ir(i)-CO species was identified as a plausible key process accountable for the loss of catalytic activity in the CO2 hydrogenation.

Roles of Structural Promoters for Direct CO2 Hydrogenation to Dimethyl Ether over Ordered Mesoporous Bifunctional Cu/M–Al2O3 (M = Ga or Zn)

The different behaviors of structural promoters such as gallium or zinc oxides on the acidic γ-Al2O3 surfaces were investigated for a direct CO2 hydrogenation to DME by using highly ordered mesopor...

Directly Converting Syngas to Linear α-Olefins over Core-Shell Fe3O4@MnO2 Catalysts.

Converting syngas to value-added chemicals via Fischer-Tropsch synthesis has attracted much attention, whereas the direct hydrogenation of CO to heavy olefins, especially linear α-olefins (LAOs), remains a challenge. In this study, we designed a core-shell Fe3O4@MnO2 catalyst to realize the direct conversion of syngas to LAOs with high efficiency. This catalyst exhibited a high selectivity of 79.60% for total alkenes and 64.95% for C4+ alkenes, 91% of which are LAOs, at a CO conversion of approximately 75%. Promotion of the electron transfer from MnO2 to Fe3O4 inside the core-shell Fe3O4@MnO2 catalyst facilitated the dissociative adsorption of CO molecules on Fe3O4 and the spillover of H atoms onto the MnO2, which enhanced C-C coupling, weakened the hydrogenation activity of the catalyst, and improved the production of LAOs. A superior stability over 100 h was observed, demonstrating the promising potential of this catalyst for industrial applications.

Highly Selective Conversion of Carbon Dioxide to Aromatics over Tandem Catalysts

Summary Conversion of CO2 to aromatics is a promising route to realize the proposal on carbon capture and utilization based on strategic CO2 carbon resource. In this work, CO2 is converted to aromatics with aromatics selectivity up to 73% at CO2 conversion of 14%, and the selectivity of CO was suppressed down to 44% over a tandem catalyst ZnZrO/ZSM-5, which was constructed by using ZnZrO solid solution and H-ZSM-5 zeolite. The selectivity of aromatics can reach to 78% at the space velocity of 1,800 mL/gcat/h. Tandem catalysis enables the direct hydrogenation of CO2 to aromatics favorable in thermodynamics through the coupling of CO2 hydrogenation over ZnZrO and aromatics formation over H-ZSM-5. The H2O generated through CO2 hydrogenation over ZnZrO can obviously increase the selectivity of aromatics and the CO2 in the reaction system promotes the formation of aromatics. Interestingly, it is found that the presence of H2O and CO2 significantly suppresses the generation of polycyclic aromatics and consequently enhances the stability of the tandem catalyst; therefore, no obvious deactivation of tandem catalysts was observed for at least 100 hr in the reaction stream.

Catalytic application of ferrierite nanocrystals in vapour-phase dehydration of methanol to dimethyl ether

The FER-type zeolite was found to be a reliable catalyst for DME synthesis via both direct CO2 hydrogenation or gas phase methanol dehydration. In this work, the effect of the crystal size of FER-type zeolites on the catalytic behavior during methanol-to-DME conversion is studied. A series of FER-type crystals ranging from 0.1 μm to 10 μm in size were synthesized and their physicochemical properties (e.g. crystal morphology, acidity, textural characteristics) analyzed. The catalytic performance of FER-type catalysts was studied in a wide range of reaction temperatures (120–280 °C). The set experimental data show that the catalytic effectiveness of FER-type catalysts in terms of methanol conversion, DME selectivity and coke resistance, can strongly be improved by reducing the zeolite crystal size.

Enhanced low-temperature performance of CO2 methanation over mesoporous Ni/Al2O3-ZrO2 catalysts

Converting carbon dioxide to value-added chemicals has been attracted much attention, whereas direct hydrogenation of CO2 to synthetic natural gas (SNG) at a lower temperature remains a big challenge. Mesoporous Al2O3-ZrO2 modified Ni catalysts were prepared via a single-step epoxide-driven sol-gel method for CO2 methanation. Almost 100% selectivity of CH4 with 77% CO2 conversion were obtained at a lower temperature of 300 °C, and no catalyst deactivation was observed in 100 h. Different characterization methods including N2 adsorption-desorption, H2-TPR, H2-TPD, XRD, XPS, and TEM were combined together to explore the interaction of Ni-ZrO2 and Al2O3-ZrO2. Incorporation of ZrO2 into Ni/Al2O3 weakened the Ni-Al2O3 interaction via the combination of Al2O3-ZrO2 solid solution, promoting the reduction and dispersion of NiO phase. The adding of higher Zr loading increased the amount of active metallic nickel sites and oxygen vacancies on the composite support, improving obviously the lower temperature catalytic activity and CH4 selectivity. Higher Ni species loading further resulted in the formation of active Ni sites and improved the low-temperature CO2 methanation performance. Moreover, the enhanced stability of the Al2O3-ZrO2 support and oxygen vacancies provided by the ZrO2 promoter could help to promote the catalytic stability.

Methanol production via direct carbon dioxide hydrogenation using hydrogen from photocatalytic water splitting: Process development and techno-economic analysis

In this work, we demonstrate the process and economic viability of a new production route for methanol utilizing captured CO2 and H2 produced from renewable, photocatalytic water splitting. Initial assessments of H2 production from this approach revealed a low-cost potential through inexpensive feedstock, but with one major drawback. Simultaneous production of H2 and O2 increases the risk of forming an explosive mixture. In our previous work, we identified membrane-based processes to safely recover the H2 product. To reduce the H2 capture costs, we developed a conceptual process comprised of integrated facilities to produce methanol while solving the flammability constraints. The first unit supplies captured CO2, which is used as a raw material and a diluent to recover H2 from the photocatalytic reactors. The tertiary mixture (H2/O2/CO2) is safely processed in an optimized membrane-based separation plant to produce a 3:1 H2 and CO2 mixture. This binary mixture is then used as feedstock for methanol production via direct CO2 hydrogenation. Based on a detailed economic analysis, the break-even value of the methanol produced is higher than the current market price. The main drivers for the high cost are the separation plant and the feedstock costs of CO2. The best-case scenario (for the selected parameters), where the plant lifetime is 30 years with 0.060 $/kWh electricity price and 0.020 $/kg CO2 cost, has a break-even value for methanol at 0.96 $/kg. Based on a target solar-to-hydrogen efficiency of 10% in the photocatalytic reactor, the gross energy efficiency of the process was 6.25%. As a final element, we compared our process with alternative renewable methanol synthesis route from the literature to highlight the differences in electrochemical and thermochemical approaches.

An Efficient Ruthenium Catalyst Bearing Tetradentate Ligand for Hydrogenations of Carbon Dioxide

AbstractA ruthenium complex with a tetradentate bipyridine ligand was proved to be a highly efficient catalyst for the conversions of CO2. Turnover numbers up to 300 000, 9800, and 2100 were achieved for the hydrogenations of CO2 to formamides, formamides to methanol and amines, and the direct hydrogenation of CO2 to methanol, respectively.

Metal Organic Framework-Derived Iron Catalysts for the Direct Hydrogenation of CO2 to Short Chain Olefins

We report the synthesis of a highly active, selective, and stable catalyst for the hydrogenation of CO2 to short chain olefins in one single step by using a metal organic framework as catalyst precursor. By studying the promotion of the resulting Fe(41 wt %)-carbon composites with different elements (Cu, Mo, Li, Na, K, Mg, Ca, Zn, Ni, Co, Mn, Fe, Pt, and Rh), we have found that only K is able to enhance olefin selectivity. Further catalyst optimization in terms of promoter loading results in catalysts displaying unprecedented C2–C4 olefin space time yields of 33.6 mmol·gcat–1·h–1 at XCO2 = 40%, 320 °C, 30 bar, H2/CO2 = 3, and 24 000 mL·g–1·h–1. Extensive characterization demonstrates that K promotion affects catalytic performance by (i) promoting a good balance between the different Fe active phases playing a role in CO2 hydrogenation, namely, iron oxide and iron carbides and by (ii) increasing CO2 and CO uptake while decreasing H2 affinity, interactions responsible for boosting olefin selectivity.

Ternary copper-cerium-zirconium mixed metal oxide catalyst for direct CO2 hydrogenation to methanol

CuCe, CuZr and CuCeZr mixed metal oxide catalysts were prepared by one step co-precipitation method and used for direct CO2 hydrogenation to methanol. It is found that the maximum CO2 conversion of 14.3% and the highest CH3OH space time yield of 5.15 mmolCH3OH·h−1·gcat−1 can be obtained over the ternary catalyst synthesized at the ratio of CeO2/ZrO2 = 1 with the CuO content kept at 30 wt%. The combination of Cu, Ce and Zr oxides increases the amounts of easily reducible CuO species and oxygen vacancies, thereby resulting in high activity for CO2 conversion. Furthermore, the ternary catalyst has a higher CO2 adsorption capability at both weak and moderate basic sites, which can further enhance CO2 reduction. The physiochemical properties-activity correlation study suggests that the ternary catalyst exhibits excellent structural properties, reducibility and surface chemical characteristics, which determines catalytic performance of CO2 hydrogenation. Moreover, the proposed reaction mechanism shows that formaldehyde is a common intermediate for the formation of CH3OH and CO.

Thermochemical CO2 Hydrogenation to Single Carbon Products: Scientific and Technological Challenges

Catalytic conversion of CO2 to chemicals and fuels is a “two birds, one stone” approach toward solving the climate change problem and energy demand–supply deficit in the modern world. Recent advances in mechanistic insights and design of suitable catalysts for direct thermocatalytic hydrogenation of CO2 to C1 products are thoroughly discussed in this Review. The role of catalyst composition and process conditions in determining the selective pathways to various products like carbon monoxide, methanol, methane, and dimethyl ether has been overviewed in light of thermodynamic and kinetic considerations. After extensive elaboration of the main motivation of the reaction pathways, catalytic roles, and reaction thermodynamics, we summarize the most important macroscopic aspects of CO2 hydrogenation technology development, which include reactor innovations, industrial status of the technology, life cycle assessment and technoeconomic analysis. Finally, a critical perspective on the future challenges and opportu...

Photochemically Driven Reverse Water-Gas Shift at Ambient Conditions mediated by a Nickel Pincer Complex.

The endothermic reverse water-gas shift reaction (rWGS) for direct CO2 hydrogenation to CO is an attractive approach to carbon utilization. However, direct CO2 hydrogenation with molecular catalysts generally gives formic acid instead of CO as a result of the selectivity of CO2 insertion into M-H bonds. Based on the photochemical inversion of this selectivity, several synthetic pathways are presented for CO selective CO2 reduction with a nickel pincer platform including the first example of a photodriven rWGS cycle at ambient conditions.

Photochemically Driven Reverse Water‐Gas Shift at Ambient Conditions mediated by a Nickel Pincer Complex

AbstractThe endothermic reverse water‐gas shift reaction (rWGS) for direct CO2 hydrogenation to CO is an attractive approach to carbon utilization. However, direct CO2 hydrogenation with molecular catalysts generally gives formic acid instead of CO as a result of the selectivity of CO2 insertion into M−H bonds. Based on the photochemical inversion of this selectivity, several synthetic pathways are presented for CO selective CO2 reduction with a nickel pincer platform including the first example of a photodriven rWGS cycle at ambient conditions.

Role of zirconium in direct CO2 hydrogenation to lower olefins on oxide/zeolite bifunctional catalysts

Direct production of lower olefins (C2=−C4=: ethylene, propylene and butylene), basic carbon-based building blocks, from carbon dioxide (CO2) hydrogenation is highly attractive, although the selectivity towards olefins has been too low. Here we present a series of bifunctional catalysts contained indium-zirconium composite oxides with different In:Zr atomic ratios and SAPO-34 zeolite, which can achieve a selectivity for C2=–C4= as high as 65–80% and that for C2–C4 of 96% with only about 2.5% methane among the hydrocarbon products at CO2 conversion of 15–27%. The selectivity of CO via the reverse water gas shift reaction is lower than 70%. The product distribution is completely different from that obtained via CO2-based Fischer-Tropsch synthesis and deviates greatly from the classical Anderson-Schulz-Flory distribution. The zirconium component plays a critical role in determining the physicochemical properties and catalytic performance of bifunctional catalysts. Catalyst characterization and density functional theory calculations demonstrate that the incorporation of a certain amount of zirconium can create more oxygen vacancy sites, stabilize the intermediates in CO2 hydrogenation and prevent the sintering of the active nanoparticles, thus leading to significantly enhanced catalytic activity, selectivity of hydrocarbons and stability for direct CO2 hydrogenation to lower olefins at the relatively high reaction temperature of 380 °C.