Methane steam reforming at low temperature: Effect of light alkanes’ presence on coke formation

The effects of Fe, Mg, and Pt-doping on the improvement of Ni stabilized on Al2O3-CeO3 catalysts for methane dry reforming

Herein, the promotional effects of Mg, Fe, and Pt on Ni-based catalysts supported on Al2O3-CeO2 (Ni/Al2O3-CeO2) were investigated in the dry reforming of methane (DRM) reaction. The interaction of a suitable amount of MgO and FeO with Ce2O3 stabilized in the catalysts was demonstrated by the temperature-programmed desorption of CO2 (CO2-TPD). Ce2O3 has a high basicity for adsorbing CO2, generating a monoclinic Ce2O2CO3 species in the DRM reaction. Surface oxygen ions were also produced by adding MgO and FeO, as demonstrated by the temperature-programmed reduction of H2 (H2-TPR). Monoclinic Ce2O2CO3 and surface oxygen may both be used to oxidize and remove the carbon that was deposited, maintaining the high activity and stability of the metal Ni and Pt catalysts. The high dispersion and synergistic interactions between the platinum and oxide phases, which are associated with the decrease in reduction temperature and the rise in the number of basic sites, are responsible for the increased activity of Pt with M-Ni/Al2O3-CeO2 catalysts. The co-doped Ni/Al2O3-CeO2 catalysts with Mg and Fe significantly enhanced the activity (more than 80% methane and 84% CO2 conversion), the selectivity toward syngas (∼90%), and maintained the H2/CO ratio at about 0.97 at 700 °C.

Progress on Catalyst Development for the Steam Reforming of Biomass and Waste Plastics Pyrolysis Volatiles: A Review

In recent decades, the production of H₂ from biomass, waste plastics, and their mixtures has attracted increasing attention in the literature in order to overcome the environmental problems associated with global warming and CO₂ emissions caused by conventional H₂ production processes. In this regard, the strategy based on pyrolysis and in-line catalytic reforming allows for obtaining high H₂ production from a wide variety of feedstocks. In addition, it provides several advantages compared to other thermochemical routes such as steam gasification, making it suitable for its further industrial implementation. This review analyzes the fundamental aspects involving the process of pyrolysis-reforming of biomass and waste plastics. However, the optimum design of transition metal based reforming catalysts is the bottleneck in the development of the process and final H₂ production. Accordingly, this review focuses especially on the influence the catalytic materials (support, promoters, and active phase), synthesis methods, and pyrolysis-reforming conditions have on the process performance. The results reported in the literature for the steam reforming of the volatiles derived from biomass, plastic wastes, and biomass/plastics mixtures on different metal based catalysts have been compared and analyzed in terms of H₂ production.

Non oxidative and oxidative dehydrogenation of n-octane using FePO4: effect of different FePO4 phases on the product selectivity

The activation of n-octane with O₂ has been investigated over different phases of FePO₄ which were formed under dehydrogenation and oxidative dehydrogenation (ODH) conditions.

Catalyst Performance in the HDPE Pyrolysis-Reforming under Reaction-Regeneration Cycles

The performance of a Ni commercial catalyst has been studied under reaction-regeneration cycles in a continuous process consisting of the flash pyrolysis (500 °C) of high-density polyethylene (HDPE) in a conical spouted bed reactor (CSBR), followed by catalytic steam reforming in-line (700 ºC) of the volatiles formed in a fluidized bed reactor. The catalyst is regenerated between reactions by coke combustion in situ in the reforming reactor, using a sequence of air concentrations and following a temperature ramp between 600 and 700 °C. Several analytical techniques (TPO, TEM, XRD, and TPR) have proven that the catalyst does not fully recover its initial activity by coke combustion due to the sintering of Ni0 active sites. This sintering process is steadily attenuated in the successive reaction-regeneration cycles and the catalyst approaches a steady state.

Low-Temperature Steam Reforming of Natural Gas after LPG-Enrichment with MFI Membranes

Low-temperature hydrogen production from natural gas via steam reforming requires novel processing concepts as well as stable catalysts. A process using zeolite membranes of the type MFI (Mobile FIve) was used to enrich natural gas with liquefied petroleum gas (LPG) alkanes (in particular, propane and n-butane), in order to improve the hydrogen production from this mixture at a reduced temperature. For this purpose, a catalyst precursor based on Rh single-sites (1 mol% Rh) on alumina was transformed in situ to a Rh1/Al2O3 catalyst possessing better performance capabilities compared with commercial catalysts. A wet raw natural gas (57.6 vol% CH4) was fully reformed at 650 °C, with 1 bar absolute pressure over the Rh1/Al2O3 at a steam to carbon ratio S/C = 4, yielding 74.7% H2. However, at 350 °C only 21 vol% H2 was obtained under these conditions. The second mixture, enriched with LPG, was obtained from the raw gas after the membrane process and contained only 25.2 vol% CH4. From this second mixture, 47 vol% H2 was generated at 350 °C after steam reforming over the Rh1/Al2O3 catalyst at S/C = 4. At S/C = 1 conversion was suppressed for both gas mixtures. Single alkane reforming of C2–C4 showed different sensitivity for side reactions, e.g., methanation between 350 and 650 °C. These results contribute to ongoing research in the field of low-temperature hydrogen release from natural gas alkanes for fuel cell applications as well as for pre-reforming processes.

Understanding the performance and mechanism of Mg-containing oxides as support catalysts in the thermal dry reforming of methane

Dry reforming of methane (DRM) is one of the more promising methods for syngas (synthetic gas) production and co-utilization of methane and carbon dioxide, which are the main greenhouse gases. Magnesium is commonly applied in a Ni-based catalyst in DRM to improve catalyst performance and inhibit carbon deposition. The aim of this review is to gain better insight into recent developments on the use of Mg as a support or promoter for DRM catalysts. Its high basicity and high thermal stability make Mg suitable for introduction into the highly endothermic reaction of DRM. The introduction of Mg as a support or promoter for Ni-based catalysts allows for good metal dispersion on the catalyst surface, which consequently facilitates high catalytic activity and low catalyst deactivation. The mechanism of DRM and carbon formation and reduction are reviewed. This work further explores how different constraints, such as the synthesis method, metal loading, pretreatment, and operating conditions, influence the dry reforming reactions and product yields. In this review, different strategies for enhancing catalytic activity and the effect of metal dispersion on Mg-containing oxide catalysts are highlighted.

Kinetic analysis of the steam reforming of ethanol over Ni/SiO2 for the elucidation of metal-dominated reaction pathways

Reaction mechanism strongly affected by temperature with two steam-independent pathways being active, involving acetaldehyde and an ethanol decomposition-derived surface intermediate.

Enhanced methane steam reforming activity and electrochemical performance of Ni0.9Fe0.1-supported solid oxide fuel cells with infiltrated Ni-TiO2 particles

Ni_0.9Fe_0.1 alloy-supported solid oxide fuel cells with NiTiO₃ (NTO) infiltrated into the cell support from 0 to 4 wt.% are prepared and investigated for CH₄ steam reforming activity and electrochemical performance. The infiltrated NiTiO₃ is reduced to TiO₂-supported Ni particles in H₂ at 650 °C. The reforming activity of the Ni_0.9Fe_0.1-support is increased by the presence of the TiO₂-supported Ni particles; 3 wt.% is the optimal value of the added NTO, corresponding to the highest reforming activity, resistance to carbon deposition and electrochemical performance of the cell. Fueled wet CH₄ at 100 mL min^-1, the cell with 3 wt.% of NTO demonstrates a peak power density of 1.20 W cm^-2 and a high limiting current density of 2.83 A cm^-2 at 650 °C. It performs steadily for 96 h at 0.4 A cm^-2 without the presence of deposited carbon in the Ni_0.9Fe_0.1-support and functional anode. Five polarization processes are identified by deconvoluting and data-fitting the electrochemical impedance spectra of the cells under the testing conditions; and the addition of TiO₂-supported Ni particles into the Ni_0.9Fe_0.1-support reduces the polarization resistance of the processes ascribed to CH₄ steam reforming and gas diffusion in the Ni_0.9Fe_0.1-support and functional anode.