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[Display omitted] • Mixed Na-Fe 3 O 4 and Fe 5 C 2 can enhance the performance of CO 2 hydrogenation to C 5+. • An optimal oxide/carbide ratio is crucial for achieving high yields of C 2 -C 4 olefins and C 5+ hydrocarbons. • Closer proximity of oxide and carbide hindered CH 4 formation and olefin hydrogenation. • Oxide/carbide reduction can enhance carbon shell graphitization and C 5+ formation. CO 2 hydrogenation into sustainable chemical feedstocks and fuels is a pivotal focus of energy research. Fe-based catalysts have emerged as promising candidates due to their high efficiency in the CO 2 hydrogenation toward C 2 –C 4 olefins and C 5+ hydrocarbons. Fe 5 C 2 is known as the active phase of the CO 2 hydrogenation. Therefore, it is imperative to discern the roles of active phases in product distribution. Accordingly, in the present study, Fe 5 C 2 is synthesized separately and physically mixed with Na-Fe 3 O 4. The effects of oxide/carbide ratio, the proximity of active phases, and reduction treatment are investigated. The results show that adding carbide to oxide in an appropriate ratio significantly increases CO 2 conversion due to the controlled reduction of the oxide phase and enhanced CO 2 adsorption. Additionally, a closer distance (mixed-powder pellets) between Na-Fe 3 O 4 and Fe 5 C 2 results in higher selectivity for C 2 -C 4 olefins and C 5+ hydrocarbons and less CH 4. Furthermore, the graphitized layers of reduced catalyst (R-Na-Fe 3 O 4 /Fe 5 C 2 (70/30 wt%)) enhance the selectivity to C 2 -C 4 olefins (40 %) and C 5+ hydrocarbons (35 %) at around 40 % CO 2 conversion. In contrast, amorphous carbon in the non-reduced catalyst (NR-Na-Fe 3 O 4 /Fe 5 C 2 (70/30 wt%)) favors more C 2 -C 4 paraffins and CH 4. Therefore, the interplay between the influential factors, i.e., oxide/carbide ratio, spatial distance, and reduction treatment, can result in tailoring an efficient CO 2 hydrogenation catalyst toward the formation of valuable hydrocarbons. [ABSTRACT FROM AUTHOR]

Ethene is a commodity chemical of great importance for manufacturing diverse consumer products, whose synthesis via crude oil steam cracking is one of the most energy-intensive processes in the petrochemical industry. Oxidative dehydrogenation (ODH) of ethane is an attractive, low energy, alternative route to ethene which could reduce the carbon footprint for its production, however, the commercial implementation of ODH requires catalysts with improved selectivity. This review critically assesses recent developments in catalytic technologies for ethane ODH, and discusses how insight into proposed mechanisms from computational studies, and CO2 assisted ethane dehydrogenation (CO2-DHE), provide opportunities for economically viable processes to meet growing demands for ethene while reducing carbon emissions. Future trends and emerging technologies for ethane ODH are also discussed. [ABSTRACT FROM AUTHOR]

The separation and purification of light hydrocarbons are significant challenges in the petrochemical and chemical industries. Because of the growing demand for light hydrocarbons and the environmental and economic issues of traditional separation technologies, much effort has been devoted to developing highly efficient separation techniques. Accordingly, polymeric membranes have gained increasing attention because of their low costs and energy requirements compared with other technologies; however, their industrial exploitation is often hampered because of the trade-off between selectivity and permeability. In this regard, high-performance mixed matrix membranes (MMMs) are prepared by embedding various organic and/or inorganic fillers into polymeric materials. MMMs exhibit the advantageous and disadvantageous properties of both polymer and filler materials. In this review, the influence of filler on polymer chain packing and membrane sieving properties are discussed. Furthermore, the influential parameters affecting MMMs affinity toward hydrocarbons separation are addressed. Selection criteria for a suitable combination of polymer and filler are discussed. Moreover, the challenges arising from polymer/filler interactions are analyzed to allow for the successful implementation of this promising class of membranes. [ABSTRACT FROM AUTHOR]

The development of an efficient reactor for hydrocarbons (C 2 –C 4) production through hydrogenation of CO 2 , requires a deep understanding of the operating conditions effects. Subsequently, a model is proposed to analyze the reaction rates and investigate the sensitivity of hydrocarbons yield and products distribution to the variations of temperature, pressure and space velocity (SV). Besides, Thiele modulus and effectiveness factor are calculated for all of the reactions considered in the model. Results reveal that simultaneous occurrence of both endothermic reverse water gas shift (RWGS) and exothermic Fischer-Tropsch (FT) reactions, may be the main reason of temperature and rate fluctuations at the fixed-bed reactor inlet. In addition, increasing temperature and pressure, and decreasing SV can shift the process to produce more light olefins. Finally, sensitivity analysis demonstrates that reactor behavior is independent of the changes in pressure and SV at high temperature, which is an indication of high temperature dependency of this process. These findings can be effectively employed to achieve a better insight about appropriate operating conditions of hydrocarbons production via hydrogenation of CO 2. Image 1 • Effectiveness factor and Thiele modulus for all reactions are calculated. • Sensitivity analysis are performed via the mathematical modeling of reactor. • Variations of reaction rates and reactor temperature are analyzed. • Effect of temperature, pressure and space velocity on products are studied. [ABSTRACT FROM AUTHOR]

Hydrogenation of CO 2 to hydrocarbons in fixed-bed and annular reactors (AR) can be limited via problems associated with high water production as the main by-product. Selective in-situ water removal using a hydrophilic membrane can be a promising solution for enhancing reactor performance. To this aim, a one-dimensional heterogeneous model comprising mass and heat transfers in the shell and tube of a membrane reactor (MR) is proposed. Firstly, the performance of different rector configurations exhibiting similar cross sectional areas and volumes are compared. Afterwards, influential factors affecting the MR performance such as shell/tube temperature, sweep ratio (θ) and pressure ratio (φ) are investigated thoroughly. Results show that increasing initial tube/shell temperature has positive effect on total hydrocarbons yield. However, sharp and sudden temperature elevation (hot spot) due to large extent of water removal, may have detrimental effects on catalyst performance. Moreover, it is observed that increasing θ and φ alter products distribution due to the equilibrium displacement and results in the lack of H 2 for further reactions. In addition, kinetic parameters corresponding to the inhibiting effect of water are indicated to have significant roles in hydrocarbons distribution. Therefore, water removal impose various changes, which cannot be considered independently in analyzing the MR performance. Image 1 • Modeling of CO 2 hydrogenation in membrane reactor is presented. • Effect of in-situ water removal on the reactor performance is analyzed. • Hydrocarbons distribution and reactor temperature are assessed in AR and MR. • Effect of sweep ratio and sweep pressure on products yield are studied. [ABSTRACT FROM AUTHOR]

Abstract Global warming, climate change, fossil fuel depletion and steep hikes in the price of environmentally friendly hydrocarbons motivate researchers to investigate CO 2 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 CO 2 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 (C 1 C 4) 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 CO 2 hydrogenation to hydrocarbons process. Graphical abstract Image 1 Highlights • Studying kinetic parameters of CO 2 hydrogenation has remained controversial. • One-dimensional heterogeneous model including detailed reaction rates is developed. • Kinetic parameters are estimated via ABC and DE algorithms using experimental data. • Components distribution along reactor length are presented based on ABC algorithm. • Performance of the theoretical reactor is compared with available experimental data. [ABSTRACT FROM AUTHOR]

Global warming, fossil fuel depletion and energy security are driving scientists to investigate the mechanism of hydrocarbons production from CO 2 hydrogenation. The need for more comprehensive understanding on mechanism of CO 2 hydrogenation to hydrocarbons remains controversial because of the complex reaction mechanism and a large number of involved species. The micro mechanism of CO 2 hydrogenation to hydrocarbons has been considered as a possible remedy to fulfill the requirements. This review comprehensively discusses two processes: reverse water gas shift (RWGS) and CO 2 hydrogenation to hydrocarbons. The review includes reaction mechanisms and catalyst effects on yields and rates. In addition, the review outlines each of the Fischer-Tropsch (FT) micro mechanisms. The review infers some mechanisms from existing work and proposes a new mechanism that improves several predictions. These mechanisms form the design basis for optimal reactor design. [ABSTRACT FROM AUTHOR]

Climate change, global warming, fossil fuel depletion and rising fuel prices have created great incentives to seek alternative fuel production technologies. CO 2 transformation to value-added products using renewable H 2 has proven to be an emerging solution to enable this goal. In this regard, three different promising processes, namely methane, methanol and hydrocarbon synthesis via CO 2 hydrogenation are thoroughly discussed. In addition, the influential factors affecting process efficiencies such as catalyst design and mechanistic insight, operating conditions as well as reactor types are investigated, with key pathways that dictate catalyst activity and selectivity of the most promising materials described. Furthermore, a brief overview of the reactor configuration and its crucial role in the improving process viability is analyzed. Accordingly, fixed-bed, fluidized-bed, annular and spherical reactors along with H 2 O/H 2 perm-selective membrane reactors are disscussed for hydrocarbon production. In addition, different reactor configurations are compared to assess the best one that is adjustable depending on the reaction mechanism. Consequently, a corrugated-wall dual-type membrane reactor is proposed as an emerging alternative for CO 2 hydrogenation to value-added products. [Display omitted] [ABSTRACT FROM AUTHOR]

• Modeling of CO 2 hydrogenation to hydrocarbons in CR, AFSR and RFSR are accomplished. • Kinetic parameters are estimated via heuristic DA optimization algorithm. • Performance of the theoretical CR is compared with available experimental data. • Effect of reactor configuration is investigated in terms of conversion and selectivity. Climate change and global warming, as well as growing global demand for hydrocarbons in industrial sectors, make great incentives to investigate the utilization of CO 2 for hydrocarbons production. Therefore, finding an in-depth understanding of the CO 2 hydrogenation reactors along with simulating reactor responses to different operating conditions are of paramount importance. However, the reaction mechanisms for CO 2 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 CO 2 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 CO 2 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. [ABSTRACT FROM AUTHOR]

• Modeling of CO 2 hydrogenation to hydrocarbons in a three-side reactor is developed. • Tr, Ts, Tt, θ and φ are considered as main effects in determining product yields. • Statistical analysis is performed to study the effects of variables on the yields. • Optimized operating conditions are determined to maximize olefin yields. Direct CO 2 hydrogenation to hydrocarbons is a promising method of reducing CO 2 emissions along with producing value-added products. However, reactor design and performance have remained a challenging issue because of low olefin efficiency and high water production as a by-product. Accordingly, a one-dimensional non-isothermal mathematical model is proposed to predict the membrane reactor performance and statistical analysis is used to assess the effects of important variables such as temperatures of reactor (Tr:A), shell (Ts:B) and tube (Tt:C) as well as sweep ratio (θ:D) and pressure ratio (φ:E) and their interactions on the products yields. In addition, the optimized operating conditions are also obtained to achieve maximum olefin yields. Results reveal that interacting effects comprising AB (TrTs), AC (TrTt), AE (Trφ), BC (TsTt), CE (Ttφ), CD (Ttθ) and DE (θφ) play important roles on the product yields. It is concluded that higher temperatures at low sweep and pressure ratios can maximize the yields of olefins, while simultaneously the yields of paraffins are minimized. In this regard, optimized values for Tr, Ts, Tt, θ and φ are determined as 325 °C, 306.96 °C, 325 °C, 1 and 1, respectively. [ABSTRACT FROM AUTHOR]

Auto-thermal reforming (ATR), a combination of exothermic partial oxidation and endothermic steam reforming of methane, is an important process to produce syngas for petrochemical industries. In a commercial ATR unit, tubular fixed bed reactors are typically used. Pressure drop across the tube, high manufacturing costs, and low production capacity are some disadvantages of these reactors. The main propose of this study is to offer an optimized radial flow, spherical packed bed reactor as a promising alternative for overcoming the drawbacks of conventional tubular reactors. In the current research, a one dimensional pseudo-homogeneous model based on mass, energy, and momentum balances is applied to simulate the performance of packed-bed reactors for the production of syngas in both tubular and spherical reactors. In the optimization section, the proposed work explores optimal values of various decision variables that simultaneously maximize outlet molar flow rate of H 2 , CO and minimize molar flow rate of CO 2 from novel spherical reactor. The multi-objective model is transformed to a single objective optimization problem by weighted sum method and the single optimum point is found by using genetic algorithm. The optimization results show that the pressure drop in the spherical reactor is negligible in comparison to that of the conventional tubular reactor. Therefore, it is inferred that the spherical reactor can operate with much higher feed flow rate, more catalyst loading, and smaller catalyst particles. [ABSTRACT FROM AUTHOR]

Fossil fuel depletion, global warming, climate change, and steep hikes in the price of fuel are driving scientists to investigate commercial and environmentally friendly energy carriers like hydrogen. Steam methane reforming (SMR), a current commercial route for H 2 production, has been considered the best remedy to fulfill the requirements. Despite the remarkable quantity of H 2 produced by the SMR, this technology still faces major challenges such as catalyst deactivation due to the sintering of metal nanoparticles, coking, and generation of a large quantity of CO 2. Firstly, the effects of catalyst types, kinetic models, and operating conditions on high-yield H 2 production, the evolution path from gray to blue, via the conventional SMR are comprehensively reviewed. Secondly, exploiting intensified techniques such as membrane technology, sorption, fluidization, and chemical looping for SMR to blue H 2 are discussed in detail. Further, a novel and sustainable path for the SMR process, hybridizing the use of novel materials and emerging technologies to produce turquoise H 2 , is proposed. Finally, the critical points for steam reforming process technology that can help leverage environmental, social, and governance (ESG) profiling have been discussed. [Display omitted] • Evolution path from gray to turquoise H 2 via catalytic SMR is discussed. • Recent advances in catalysis, kinetic models, and operating conditions are reviewed. • The importance of SMR process intensification for blue H 2 production is highlighted. • A novel and sustainable path for the SMR process to efficiently produce turquoise H 2 is proposed. • Key points for SMR technology that can help leverage ESG profiling are listed. [ABSTRACT FROM AUTHOR]