Hydrogen production from carbon dioxide reforming of methane over Ni–Co/MgO–ZrO 2 catalyst: Process optimization

Multiobjective optimization of synthesis gas production using non-dominated sorting genetic algorithm

Utilization of greenhouse gases through carbon dioxide reforming of methane over Ni–Co/MgO–ZrO2: Preparation, characterization and activity studies

The NiO-MgO solid solution has been proven to be an efficient catalyst for the carbon dioxide reforming of methane (CRM). However, the challenge is still there for the facilely controlled synthesis of the single-phase solid solution with the uniform composition, and the interactions between NiO and MgO are not consistently correlated with the CRM performance. To address these issues, in this work, the complex-decomposition method was applied to regulate the chemical and structural properties of NiO-MgO catalysts via simply changing the complexing agent, calcination temperature, and Ni/Mg molar ratio. The catalysts were comparatively evaluated for CRM under severe reaction conditions of 750 °C, 0.1 MPa, CH4/CO2 = 1, and a gas hourly space velocity of 60000 mL·g−1·h−1. Irrespective of the complexing agents investigated, NiO-MgO solid solution was exclusively formed. However, the structural and reductive properties of the NiO-MgO catalysts were strongly dependent on the complexing agent, which is reasonably explained as the varied coordinative capabilities of the complexing agent with the metal cations. Moreover, the highest CRM performance, i.e., the initial CH4 conversion of ~86% kept constant for a time-on-stream of 20 h, was achieved over the Ni0.1Mg0.9O catalyst by using glycine as the complexing agent and calcined at 800 °C. The characterization and CRM results vigorously confirmed that a good balance between the sintering and the in situ release of active metallic Ni under CRM reaction conditions was constructed over the NiO-MgO catalyst prepared using glycine as the complexing agent, leading to its highest stability. Considering the simple procedure of the complex-decomposition method and the convenient adjustment of the NiO and MgO interactions by simply changing the complexing agent and calcination temperature, the thus developed catalyst can be applied for extensive understanding the CRM mechanism, and extended for large-scale preparation.

Optimization of syngas production via methane bi-reforming using CeO2 promoted Cu/MnO2 catalyst

The catalytic activity and kinetic behavior of catalytic reforming of methane with carbon dioxide over activated carbon were investigated as a function of reaction temperature, gas hourly space velocity (GHSV), and partial pressures of CH4 and CO2. The CH4 and CO2 conversions were greatly influenced by the reaction temperature in the range of 850−1050 °C. The apparent activation energies for CH4 and CO2 consumption and CO and H2 production were 32.63 ± 1.06, 25.54 ± 1.79, 24.81 ± 3.06, and 32.99 ± 2.58 kcal/mol, respectively. The curves of reaction rates versus GHSV showed various trends at different temperatures and indicated 7500 mL/h·g-cat was sufficient for operation in the kinetic regime. The reaction rate of methane and carbon dioxide over activated carbon was affected significantly by the partial pressures. Under a higher CO2 pressure, the excess CO2 reacted with H2 through the reverse water−gas shift (RWGS) reaction. The predictions of the CH4 and CO2 reaction rates based on a semiexperimental formula fitted satisfactorily with the experiments data. The results of mass balance, BET, XRD, and SEM studies in the deactivation test indicated that the catalyst deactivation was mainly attributed to the carbon deposition and might be alleviated at high temperatures. On the basis of the experimental results and Langmuir−Hinshelwood mechanism in the literature, a reaction mechanism was proposed. The overall reaction pathway involves the adsorption and cracking of methane and CO2 adsorption and gasification with carbon cracked. The RWGS reaction occurs simultaneously. Overall, a derived semitheoretical kinetic equation satisfactorily predicted the experimental results.

The goal of this research was to synthesize two different catalysts, namely K-OMS-2 and MnOx. The K-OMS-2 was an octahedral manganese complex prepared by hydrothermal method, while manganese oxide (MnOx) was directly synthesized by precipitation method. Both catalysts were employed to decompose toluene, an organic solvent that is widely used in industries. The catalysts were characterized by means of X-ray diffraction (XRD) and N2-physorption. The surface areas of K-OMS-2 and MnOx were 83.50 and 20.04 m2/g, respectively. The precipitation route gave XRD patterns of γ-Mn2O3 structure, and a successful structure of an octahedral molecular sieve manganese oxide was obtained by the hydrothermal method. The toluene degradation was carried out in gas hourly space velocity (GHSV) range of 20,000-60,000 h-1 with toluene concentration of 7,700 ppmv. The higher GHSV over K-OMS-2 gave the lower contact time consequently resulting in the lower %toluene degradation, whereas the best GHSV over γ-Mn2O3 was suitable at 40,000 h-1. The complete oxidation temperature of toluene over K-OMS-2 occurred at 260 °C and was lower than the temperature by γ-Mn2O3 at 300 °C. The higher surface area of K-OMS-2 may not facilitate internal toluene diffusion to active K-OMS-2 sites because molecular toluene (5.6 Å) cannot migrate through its smaller pore diameter (4.6 Å); however, the fully oxidized K-OMS-2 can provide higher average oxidation state (AOS) and higher amount of lattice oxygen assisting toluene degradation compared to γ-Mn2O3. The full factorial design of experiment (DOE) exhibited a strong effect of temperature and catalyst types on toluene removal; in contrast gas hour space velocity (GHSV) exhibited no significant effect on %toluene removal even with increasing GHSV.

Different pragmatic approaches have recently been adopted in Paris Agreement of 2015 on the reduction of greenhouse gases, especially carbon dioxide (CO2). A viable option toward reduction of CO2 emission is to couple an exhaust gas fuel reforming reactor to an oxy-combustion power plant for in situ recycling and utilization of unwanted CO2 emission for fuel upgrade. In such a system, steam and dry fuel reforming take place simultaneously with the exhaust gases that are mainly water vapor and carbon dioxide. This study was carried out to explore the advantage of using the gas turbine high exhaust temperature and utilize the unwanted CO2 for fuel upgrade via methane-exhaust gas reforming. A numerical model was developed to study the effect of reforming temperature, gas hourly space velocity (GHSV) and reformer gas ratio (CO2/H2O) on the following performance metrics: methane conversion, fuel upgrade, and hydrogen yield in an exhaust gas-reforming reactor. Results show that the methane conversion increases ...

Enhancement effect of heat recovery on hydrogen production from catalytic partial oxidation of methane

In this study, a Pd catalyst was prepared with promoters such as CeO2, BaO and SrO in a washcoated form on a metallic monolith for autothermal reforming of methane to syngas for the Fischer-Tropsch synthesis. A reactor was installed with an electric heater in the form of the metallic monolith as a start-up device instead of a burner with which stable and fast start-ups (within 4 min) were achieved. Gas hourly space velocity and O2/CH4 governed, methane conversion, while H2O/CH4 controlled H2/CO ratio. A methane conversion of approx. 96%, H2+CO selectivity of approx. 85%, and H2/CO of approx. 2.6 were obtained under the conditions of gas hourly space velocity (GHSV) at 103000 h−1, O2/CH4=0.7 and H2O/CH4=0.35.

The autothermal reforming of methane to syngas for use in the Fischer-Tropsch synthesis was studied in this work over PdO containing various combinations of CeO2, BaO or SrO in a washcoated form on a metallic monolith at atmospheric pressure. This study focused on the autothermal operation of the system, in which an electric heater inside the reactor was used only to reach the ignition temperature, and thereafter the autothermal reaction successfully sustained itself without any external heat source. It was concluded from the experiments that the PdO/Al2O3 catalyst was better than the others, except for PdO-CeO2-BaO-SrO/Al2O3, which showed similar performance in terms of the CH4 conversion and H2+CO selectivity, while affording a higher H2/CO ratio (close to ca. 3) than the PdO/Al2O3 catalyst did (close to ca. 2). The gas hourly space velocity and O2/CH4 ratio governed the methane conversion, while the H2O/CH4 ratio controlled the H2/CO ratio. A methane conversion of ∼87%, H2+CO selectivity of ∼94%, H2/CO ratio of ∼2.9, and M factor ∼2.15 were obtained under the conditions of a gas hourly space velocity (GHSV) of 120,000 h−1, O2/CH4=0.6 and H2O/CH4=0.5.

Catalytic combustion of gasified biomass over hexaaluminate catalysts: influence of palladium loading and ageing

The influence of Ni load and support material on catalysts for the selective catalytic oxidation of ammonia in gasified biomass

Vanadium magnesium oxide (VMgO) catalysts with different vanadium loadings were synthesized and tested for catalytic activity in the oxidative dehydrogenation of n-hexane. High surface area catalysts were obtained by the wet impregnation technique. Magnesium oxide (MgO) and magnesium orthovanadate [Mg3(VO4)2] were the only phases observed in each catalyst. All the catalysts were tested at 0.6–7.8 % of n-hexane in air within a temperature range of 350–550 °C, varying the gas hourly space velocities. Catalytic testing conducted below the lower flammability limit (0.6 % n-hexane in air) showed only benzene and carbon oxides in the product stream, whereas for experiments done above the upper flammability limit (7.8 % n-hexane in air), hexenes, in addition to benzene and carbon oxides were observed. Decreasing the feed composition from 7.8 to 5.5 % resulted in higher yields towards benzene and total dehydrogenated products. The effect of variations in the gas hourly space velocity investigated using the 19 wt% vanadium catalyst and a feed concentration of 7.8 % showed that the selectivity to benzene increased slightly with an increase in the gas hourly space velocity.

Comparative Techno-economic analysis of methanol production via carbon dioxide reforming of landfill gas using a highly active and stable Nickel-based catalyst

Synthesis gas production from carbon dioxide reforming of methane over Ni-MgO catalyst: Combined effects of titration rate during co-precipitation and CeO2 addition