CO2 Hydrogenation Process Research Articles

Synergetic effect of Ce/Zr for ethanol synthesis from syngas over Rh-based catalyst

The direct synthesis of ethanol from syngas is a promising way in the field of clean and efficient use of fossil fuel, but it still suffers from insufficient ethanol selectivity and understanding of active sites. In this work, the Rh-based catalyst with Ce as promoter and ZrO2 as carrier exhibits excellent catalytic performance, showing the selectivity of ethanol toward 24.3 %. Moreover, the yield of methane decreases to 4.8 %, and the formation of CO2 is inhibited to a certain degree by tuning the active sites. The carrier is changed by doping Ce into the ZrO2 lattice, which assists to form the Rhδ+ active sites. The synergetic effect of Ce and Zr is important to influence the state of Rh species in the catalysts, leading to the differences in the CO hydrogenation process. On the other hand, the Rhδ+ active sites are also stabilized by promoted surface oxygen vacancies in the 2.0Rh5.0Ce-ZrO2 catalyst. The high-activity catalyst with Rhδ+ active sites will be helpful to understand the real active sites of Rh-based catalysts for ethanol synthesis from syngas, thereby guiding further design of the related catalyst with high performance to meet the industrial demand in syngas converting to ethanol.

Intensification of CO2 hydrogenation by in-situ water removal using hybrid catalyst-adsorbent materials: Effect of preparation method and operating conditions on the RWGS reaction as a case study

Intensifying CO2 hydrogenation reactions by in-situ water removal via hydrophilic adsorbents alongside the catalyst is an innovative approach that can drastically improve the performance of conventional processes whose yields are restricted by thermodynamics. Here, the sorption-enhanced (SE) reverse water–gas shift (RWGS) reaction was explored as a case study since it represents the starting point of all CO2 hydrogenation processes. Hybrid materials containing both catalyst (Cu/UGSO) and hydrophilic adsorbent (13X zeolite) were conceived to investigate for the first time (i) the effect of preparation method (with major impact on physicochemical properties and performance) and (ii) main operating parameters affecting greatly the yields (temperature and catalyst/adsorbent ratio). A comparison between mechanically mixed catalyst-adsorbent and bifunctional materials (containing active metal, catalytic support, and adsorbent within the same particle) revealed that Cu presence decreased the adsorptive ability of bifunctional materials, due to the decrease of specific surface area and zeolite acidity. In contrast, mechanical mixtures allowed to fully preserve the assets of both adsorbent and catalyst, to significantly intensify the reaction. The catalyst-adsorbent mixture obtained by wet mixing offered the best results by minimizing the average distance between catalytic and adsorption sites. 250 °C was found optimum for a significant reaction rate and a non-negligible water adsorption capacity of 13X zeolite. The reaction thermodynamic barrier was found to be crossed for catalyst/adsorbent mass ratio lower than 1, the intensification leading to a significant increase in CO2 conversion. The findings of this work are crucial for implementing this type of intensified process, which pushes the limits dictated by thermodynamic equilibrium, and provide information of high interest to guide future research on all SE processes of CO2 valorization via catalytic hydrogenation.

Metallurgical Residue-Derived Cu–ZnO-Based Catalyst for CO2 Hydrogenation to Methanol: An Insight on the Effect of the Preparation Method

Valorization of residual materials in the development of catalytic materials has an appealing potential from the perspective of a sustainable development. For the first time, Fe/Mg-containing metallurgical waste (UGSO) was utilized as a support for the development of innovative catalysts for CO2 hydrogenation into methanol. A series of different CuZn/UGSO catalysts were developed by conventional and modified deposition–coprecipitation methods. The addition of Cu/Zn into the structure of Fe3O4/MgxFeyO4 was found to improve Cu2+ and Zn2+ dispersion, while the presence of MgO favors methanol selectivity. Compared to 10Cu7.5Zn/UGSO (10 wt % Cu, 7.5 wt % Zn), the higher methanol yield obtained over 10Cu7.5Zn/UGSO–EtOH (10 wt % Cu, 7.5 wt % Zn, ethanol addition after coprecipitation) is a result of both higher CO2 conversion [attributed to (i) finer particle sizes of CuO and ZnO, (ii) a higher Cu0/Cu+ percentage, and (iii) higher oxygen vacancies and number of strong basic sites on the catalyst surface] and higher methanol selectivity [assigned to (i) the stronger interaction of Cu and ZnO and (ii) a higher number of medium basic sites] in comparison with its counterpart. This residue-based catalyst offers a 150% higher methanol yield than a commercial Cu-based methanol synthesis catalyst at 260 °C and 20 bar. These promising results can open a window to the utilization of this residue as a catalytic support in other CO2 hydrogenation processes.

CO2 methanation with Ru@MIL-101 nanoparticles fixated on silica nanofibrous veils as stand-alone structured catalytic carrier

An important challenge in the valorization of CO2 and H2 into fuels is the development of a stable, reusable and easy to handle heterogeneous catalyst. Here, a silica nanofibrous membrane is investigated as carrier for Ru nanoparticles, themselves encapsulated inside the metal organic framework (MOF) Cr-MIL-101. The catalytic membrane is investigated for the Sabatier methanation reaction. The direct electrospinning of a tetraorthosilicate (TEOS) sol results in a highly thermal resistant silica nanofibrous structure (up to 1100 °C) with pores between the fibers in the µm-range, allowing a high gas throughput with low pressure requirements. A straightforward dip-coating procedure of the carrier was used to obtain a Ru@MIL-101 functionalized silica nanofibrous veil, avoiding Ru clustering. The obtained catalytic membrane exhibited an apparent turnover frequency of 3257 h-1 at 250 °C. This system therefore paves the way towards structured reactors for efficient CO2 hydrogenation processes.

CO2 Hydrogenation to Hydrocarbons over Fe/BZY Catalysts

AbstractThis manuscript reports a CO2 hydrogenation process in a catalytic laboratory‐scale packed‐bed reactor using an Fe/BZY15 (BaZr0.85Y0.15O3‐δ) catalyst to form hydrocarbons (e. g., CH4, C2+) at elevated pressure of 30 bar and temperatures in the range °C. The effects of temperature, feed composition (i. e., CO2/H2 ratio, and residence time (i. e., Weight Hourly Space Velocity (WHSV) are studied to understand the relationship between CO2 conversion and carbon selectivity. Catalyst characterization elucidates the relationships between the catalyst structure, surface adsorbates, and reaction pathways. Thermodynamic analyses guide the experimental conditions and assist in interpreting results. While the feed composition and temperature influence the product distribution, the results suggest that the higher‐carbon (C2+) selectivity and yield depend strongly on residence time. The results suggest that the CO2 hydrogenation reaction pathway is similar to Fischer–Tropsch (FT) synthesis. The reaction begins with CO2 activation to form CO, followed by chain‐growth reactions similar to the FT process. The CO2 activation depends on the redox activity of the catalyst. However, the carbon chain growth depends primarily on the residence time. as is the case for the FT synthesis, high residence time (on the orders of hours) is required to achieve high C2+ yield.

Low-temperature methanol synthesis via (CO2 + CO) combined hydrogenation using Cu-ZnO/Al2O3 hybrid nanoparticle cluster

Conversion of CO2 into valuable fuel or chemical feedstock is important to sustainable technological development. Hydrogenation of CO2 to methanol, preferably under a relatively low temperature and moderate pressure, is attractive. In this study, a combined (CO2 + CO) hydrogenation process is proposed as an alternative two-stage route for methanol production. Cu-based hybrid catalysts supported on alumina nanoparticle clusters were developed for promoting methanol production. The results show an increase of ≈ 3.2 times in methanol space-time yield (STYMeOH) at 220 °C by incorporating CO to the CO2 hydrogenation process, and the maximum STYMeOH, 6.1 mmolgcat-1h-1, was achievable under a low-temperature (220 °C), moderate high-pressure operation (30 bar). The work demonstrates a rational design of hybrid nanostructured material to achieve superior catalytic performance in the combined (CO2 + CO) hydrogenation. The mechanistic understanding gives insights into the interfacial catalysis by Cu-ZnO hybrid nanostructured materials for methanol production.

Insights into the one-step ethanol synthesis through CO hydrogenation over surfactant-assisted preparation of CuCo/SiO2 catalyst

We explored herein the feasibility of using surfactant-assisted CuCo catalysts for the synthesis of ethanol by CO hydrogenation. Combined characterization results demonstrated that surfactant CTAB can significantly inhibited the aggregation and retarded the deep reduction of Cu and Co species, which was crucial to obtaining highly dispersed metal particles and the optimal electronic environment of Cu and Co species. A strong synergistic effect occurred at the interface of Cu+-Co0 species in intimate contact on bimetallic CuCo-0.10C/(Si) catalyst, have evidenced to be responsible for efficiently conversion of CO to ethanol by integrating the CO* and CHx* intermediates depend on the classical insertion mechanism. The optimal bimetallic CuCo-0.10C/(Si) catalyst with an enhanced ethanol selectivity of 33.4 wt% at a superior CO conversion of 32.0%, achieving the highest space-time-yield toward total alcohols of 52.0 mg/mLcat·h and ROH selectivity (21.5%), thus presenting a critic step to guide the rational design of CuCo-based catalysts for ethanol synthesis in CO hydrogenation process.

The need for speed - optimal CO[formula omitted] hydrogenation processes selection via mixed integer linear programming

The race towards mitigating carbon emissions led to the development of countless processes, product chemicals, and catalysts for carbon capture, storage, and utilization. The abundance of data and potential pathways for decarbonization thus require the development of models that could easily adapt to the increasing boundaries of evaluation. The model presented herein offers a rapid evaluation tool to find the optimal choice(s) amongst reported thermocatalytic CO2 hydrogenation processes. Using mixed-integer linear programming (MILP), the model sizes and costs 4 major types of chemical units (compressor, heat exchanger, reactor, and distillation column) in a network optimization of 29 literature processes. The model results show excellent agreement with results of its nonlinear program (NLP) equivalent (max 2% objective function deviations), with a two order of magnitude reduction in CPU solving time. The findings highlight the potential to enhance decision making via the evaluation of myriad carbon utilization processes at low computational times.

CO2 Hydrogenation Catalyzed by Graphene-Based Materials.

In the context of an increased interest in the abatement of CO2 emissions generated by industrial activities, CO2 hydrogenation processes show an important potential to be used for the production of valuable compounds (methane, methanol, formic acid, light olefins, aromatics, syngas and/or synthetic fuels), with important benefits for the decarbonization of the energy sector. However, in order to increase the efficiency of the CO2 hydrogenation processes, the selection of active and selective catalysts is of utmost importance. In this context, the interest in graphene-based materials as catalysts for CO2 hydrogenation has significantly increased in the last years. The aim of the present paper is to review and discuss the results published until now on graphene-based materials (graphene oxide, reduced graphene oxide, or N-dopped graphenes) used as metal-free catalysts or as catalytic support for the thermocatalytic hydrogenation of CO2. The reactions discussed in this paper are CO2 methanation, CO2 hydrogenation to methanol, CO2 transformation into formic acid, CO2 hydrogenation to high hydrocarbons, and syngas production from CO2. The discussions will focus on the effect of the support on the catalytic process, the involvement of the graphene-based support in the reaction mechanism, or the explanation of the graphene intervention in the hydrogenation process. Most of the papers emphasized the graphene’s role in dispersing and stabilizing the metal and/or oxide nanoparticles or in preventing the metal oxidation, but further investigations are needed to elucidate the actual role of graphenes and to propose reaction mechanisms.

Sputtering FeCu nanoalloys as active sites for alkane formation in CO2 hydrogenation

Catalytic conversion of CO2 to high-value products is a crucial method to achieve targets of carbon dioxide emissions peak and carbon neutralization. However, realizing a controllable product distribution in a single CO2 hydrogenation process is of great challenge. Herein, we prepared the CuFe nanoalloy catalyst that directly transforms CO2 to alkanes using physical sputtering method in mild condition. The characteristic results show that the proximity between Cu and Fe is the crucial factor to tunable products among the different catalysts. The formation of unique coordination of FeCu4 nanoalloys from high-energy sputtering process provides close interaction between Cu and Fe, which is favorable to formation of low carbon paraffin, however, a distant proximity and weak interaction will increase the selectivity of olefins and alcohols. This work provides a general strategy for tuning target chemicals and enriches the viewpoints in CO2 hydrogenation.

Promotion effects of oxygen vacancies on activity of Na-doped CeO2 catalysts for reverse water gas shift reaction

CeO2-based catalysts have been widely used in the CO2 hydrogenation process. The oxygen vacancies on CeO2 resulted from Na ion incorporation play a vital role in CO2 conversion activity, the effect of Na+ ion-doped in CeO2 during CO2 hydrogenation was rarely studied. In this work, the LN-CeO2 catalysts with different nNaOH:nCe ratios were prepared with liquid nitrogen(Liquid Nitrogen-CeO2, LN-CeO2), and the effect of the nNaOH:nCe ratio on the microstructure of the LN-CeO2 catalysts were evaluated. The best CO2 hydrogenation performance was achieved by LN-CeO2-100 with a CO production rate of 3.90 mol/gcat·h at 800 °C (100% CO selectivity). The kinetic results indicated that the CO2 hydrogenation performance difference among these LN-CeO2 catalysts resulted from the CO2 activation process. Oxygen vacancies could enhance CO2 activation on the surface of LN-CeO2, and oxygen vacancies displayed a linear correlation relationship with the Na content doped in LN-CeO2. The highest concentration of oxygen vacancies resulted from Na ion incorporated and lower CO2 reaction order was closely related to CO2 hydrogenation performance of LN-CeO2-100. These results will give insight into the Na effect on the CO2 hydrogenation mechanism over CeO2.

Techno-economic analysis of integrated hydrogen and methanol production process by CO2 hydrogenation

Global climate change is one of the major concerns of today's world. Indeed, the carbon capture and sequestration (CCS) has a great potential to abate global climate changes but the economic infeasibility of this process has motivated the researchers to develop methods for direct utilization of captured carbon dioxide (CO2) to value-added end products. For instance, the methanol production by hydrogenation of CO2 is extensively investigated for over two decades but the high operating cost of this process, especially for hydrogen production, has discouraged its commercial implementation. In this work, a high temperature solid oxide electrolyzer (SOE) as a source of hydrogen production (12.16 ton/hr) from steam is integrated with the CO2 hydrogenation process to reduce the cost of methanol production. Integration of SOE with methanol production process resulted into 22.3% reduction in the cost of hydrogen as compared to the alkaline water electrolyzer. Consequently, the cost of 63.5 ton/hr methanol production was reduced, from 1063 $/ton to 701.5 $/ton, by employing SOE and optimizing the process flowsheet (by considering seven different configurations of the flowsheet, along with heat and process integrations). It is anticipated that a further reduction in the cost of methanol production by aforementioned process is possible by the advancement of hydrogen production technology, especially the high performance materials development and commercialization of electrolyzers.

Outside Front Cover: Plasma Process. Polym. 2/2022

Outside Front Cover: The schematic diagram of possible synergistic effects in the plasma-catalytic CO2 hydrogenation processes by a nanosecond pulsed discharge with Ni and Cu catalysts. From the electron-collision reactions in gas phase, vibrational excited species (i.e., CO2(v)) may reduce the energy barrier of CO2 dissociation while the reactive species may be capable of promoting ER and LH reactions. The synergistic effect will produce more intermediates and the selectivity of CH4 and CH3OH. Further details can be found in the article by Jun Du, Lijun Zong, Shuai Zhang, Yuan Gao, Liguang Dou, Jie Pan, and Tao Shao (e2100111).

Гидрирование монооксида углерода на композитных каталитических системах на основе никеля и поливинилового спирта

The article considers the catalytic and physico-chemical properties of composite materials obtained by heat treatment of nickel nitrate immobilized on polyvinyl alcohol. The influence of the composite formation temperature on the phase composition of metal-containing and the particle size is studied. It is shown that the resulting composite material is an active catalyst for the hydrogenation of carbon monoxide without a pre-activation stage. The following synthesis parameters were achieved: the degree of carbon monoxide conversion under the conditions of CO catalytic hydrogenation process: CO conversion — 29%, CH4 yield — 28 g/m3 . Assumptions about the particle size effect on the activity of the synthesized composite and the effect of volume velocity on the parameters of the CO hydrogenation process are made.

Design of CO2 hydrogenation catalysts based on phosphane/borane frustrated Lewis pairs and xanthene-derived scaffolds

New naphtho[2,1,8,7-klmn]xanthene and benzo[kl]xanthene-based intramolecular phosphane–borane frustrated Lewis pairs (FLPs) were investigated in catalyzed H2 activation and CO2 hydrogenation processes. According to DFT predictions at the B3LYP-D3 level, the presence of rigid scaffolds and increased P···B distances in the investigated FLPs lead to a remarkable drop in the energy barrier for CO2 hydrogenation (by up to 19.2 kcal mol−1, compared to the parent dimethylxanthene-based FLP). Furthermore, the energy differences between the transition states for H2 activation and CO2 hydrogenation are significantly reduced, making both processes feasible under relatively mild experimental conditions.

Single Ni supported on Ti3C2O2 for uninterrupted CO2 catalytic hydrogenation to formic acid: A DFT study

Catalytic hydrogenation of carbon dioxide to formic acid (CO2 + H2 → HCOOH) is considered as promising strategy for CO2 fixation and recycling utilization. Supported single metal atom exhibits exceptional activity resulted from its unique local chemical environment. In this work, single Ni atom immobilized on O-vacancy defected Ti3C2O2 ([email protected]3C2O2) is investigated for CO2 hydrogenation to HCOOH by first principles calculations. Results show that Ni atom can be steadily immobilized on Ti3C2O2, while CO2 catalytic hydrogenation to HCOOH is favorable with a small energy barrier of 0.54 eV via ER mechanism through HCOO intermediate. Importantly, the hydrogenation process could be occurred uninterruptedly. The as-generated HCOOH will be rapidly released during the subsequent CO2 hydrogenation process owning to the lowest desorption barrier of 0.12 eV, which will not restrict the overall catalytic hydrogenation efficiency. Moreover, the large barrier of side reactions, such as C-C coupling, dehydroxylation and further hydrogenation suggests the high selectivity of CO2 hydrogenation to HCOOH. These findings improve our understanding of CO2 hydrogenation mechanism over supported single atom catalysts, and provide a potential platform for CO2 fixation.

CO2 hydrogenation on CeO2@Cu catalyst synthesized via a solution auto-combustion method

Cu-based catalysts had been widely used in CO2 hydrogenation process for their excellent performance and high selectivity. Micron-sized Cu powder obtained by ball milling exhibited poor CO2 activity for its large particle size and small specific surface area, limited its catalytic application. In this work, micron Cu powder was modified with CeO2 species synthesized from different cerium precursor salts via a solution auto-combustion method to investigate CO2 hydrogenation activity. This work revealed that CeO2 species formed from cerium acetate precursor salt achieved excellent CO2 performance (1.64 mol/gcat.h at 400 °C), which was 3.8 times and 6000 times higher than that from cerium nitrate salt or cerium chloride salt, respectively. Interestingly, a thick dense CeO2 shell would be formed on micron Cu generated from cerium(III) chloride precursor salt, which inhibited CuOx reduction and had the opposite effect for RWGS reaction. In addition, the CuOx species in CeO2@Cu synthesized from cerium chloride salt resulted in the CH4 selectivity. The enhancement performance of the CeO2@Cu prepared from cerium acetate salt and cerium nitrate salt could be attributed to the oxygen defects formed around the Cu-Ox-Ce interface area and metallic Cu in the RWGS reaction. Cerium precursor salts enhanced the structural integrity of CeO2@Cu and played a vital role in RWGS reaction. These results will support a new direction for exploring micron Cu powder in Cu-based catalysts for CO2 utilization.

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*.

Heterogeneous catalysts for the hydrogenation of amine/alkali hydroxide solvent captured CO2 to formate: A review

AbstractCarbon capture and utilization technology is one of the medium‐term technology options to reduce CO2 emissions while producing value‐added fuels and chemical products. The integrated CO2 capture and hydrogenation process is an encouraging replacement to the conventional decoupled CO2 capture and hydrogenation process, which allows direct utilization of captured CO2 thus eliminating the energy‐intensive CO2 desorption and compression steps in the typical carbon capture and storage (CCS) process. The hydrogenation of captured CO2 in amine/alkali hydroxide solvents is the key step to attain the integrated CO2 capture and hydrogenation process. Considering the lack of timely review on the topic of hydrogenation of amine/alkali hydroxide solvent captured CO2 to formate in the presence of heterogeneous catalysts, a summary of such process with different capturing solvents and heterogeneous catalyst were critically summarized and briefly reviewed in the current paper. The main goal of this review is to provide fundamental insights and guidance for the future design of heterogeneous catalysts for the hydrogenation of captured CO2 in amine/alkali metal hydroxide‐based solvents. Future research directions to advance the process of hydrogenation of captured CO2 were also recommended. © 2021 Society of Chemical Industry and John Wiley & Sons, Ltd.

CO2 utilization for methanol production; Part I: Process design and life cycle GHG assessment of different pathways

The process design and life cycle assessment (LCA) of various methanol production processes, including the conventional natural gas reforming process and alternative CO2 utilization-based pathways, are performed in this work. Three main technologies are considered for the CO2 conversion to methanol: direct CO2 hydrogenation, dry reforming and tri-reforming of methane. For each pathway, a process simulation that includes the CO2 capture from typical flue gas of a cement kiln, the methanol synthesis and purification steps, is performed using the Aspen engineering suite. In addition, for each process, several heat integration measures are considered to maximize thermal efficiency. According to the simulation results, the thermal efficiency of the direct CO2 hydrogenation process (47.8 % LHV) is higher than the dry reforming (40.6 % LHV) while it is lower than the conventional (68.4 % LHV) and tri-reforming (57.9 % LHV) processes. The LCA results showed that the direct CO2 hydrogenation pathway is an environmentally friendly option, only when the electricity GHG intensity is lower than 0.17 kg CO2 equivalent per kWh of electricity. As a result, in the context of Canada, the CO2 hydrogenation options can be recommended only for the provinces where low-carbon electricity is available, such as Quebec, British Columbia, Manitoba and Ontario.