Catalytic Carbon Dioxide Reforming of Methane to Synthesis Gas over Activated Carbon Catalyst

Ni-Co bimetallic catalysts on coconut shell activated carbon prepared using solid-phase method for highly efficient dry reforming of methane

Ni-Co bimetallic catalysts supported on coconut shell activated carbon are synthesized using solid-phase method and investigated for dry reforming of methane, to explore the impact of Ni:Co ratio on the catalyst activity and stability. The catalyst performances are evaluated under the temperature varying from 600 to 900 °C and gas hourly space velocity (GHSV) of 7200 mL/h·g-cat. The characterization results show that metal nanoparticles are produced on the support, and the bimetallic catalyst with an explicit Ni:Co ratio (2:1) is the most beneficial for metal particle dispersion and acquires the minimum particle size of 4.41 nm. The bimetallic catalysts with an explicit Ni:Co ratio of 1:2 and 1:1 exhibit a synergistic effect towards the conversions of CH₄ and CO₂, respectively. The experimental results reveal that the highest CH₄ and CO₂ conversions rise to 94.0% and 97.5% within 12 h at 900 °C on average, respectively, assisted with the two bimetallic catalysts. The intensity of disordered carbon and thermal stability are enhanced with the extension of reforming process, contributing to a long-term catalytic stability. Besides, no obvious carbon deposition is detected, leading to a highly catalytic stability for the bimetallic catalysts.

Valorization of Char From Biomass Gasification as Catalyst Support in Dry Reforming of Methane

This study responds to the need of finding innovative routes for valorizing char derived from biomass gasification. Char is currently treated as a waste representing an energetic and economic loss for plant owners. However, it displays many similarities to activated carbon (AC) and could replace it in several applications. In this regard, the current work investigates the use of gasification derived char as catalyst support in dry reforming of methane (DRM) reactions. Char collected from a commercial biomass gasifier currently in operation was characterized and employed for the synthesis of cobalt catalysts. The catalysts were characterized and tested in an atmospheric pressure fixed bed reactor operating at 850°C with CH₄:CO₂ = 1 and a weight hourly space velocity of 6,500 mL g⁻¹ h⁻¹. The effectiveness of the synthesized catalysts was defined based on CO₂ and CH₄ conversions, the corresponding H₂ and CO yields and their stability. Accordingly, catalysts were synthesized with cobalt loading of 10, 15 and 20 wt.% on untreated and HNO₃ treated char, and the catalyst with optimum comparative performance was promoted with 2 wt.%MgO. Catalysts prepared using untreated char showed low average conversions of 23 and 17% for CO₂ and CH₄, yields of 1 and 14% for H₂ and CO, and deactivated after few minutes of operation. Higher metal loadings corresponded to lower conversion and yields. Although HNO₃ treatment slightly increased conversions and yields and enhanced the stability of the catalyst, the catalyst deactivated again after few minutes. On the contrary, MgO addition boosted the catalyst performances leading to conversions (95 and 94% for CO₂ and CH₄) and yields (44 and 53% for H₂ and CO) similar to what obtained using conventional supports such as Al₂O₃. Moreover, MgO catalysts proved to be very stable during the whole duration of the test.

Fe-rich biomass derived char for microwave-assisted methane reforming with carbon dioxide

Microwave-assisted methane reforming with carbon dioxide was dealt with in this work, using a Fe-rich biomass-derived char by one-step preparation. The main factors on the reforming reaction and stability of this catalyst were evaluated, together with a series of characterization on the produced gas and the used char. The char obtained from biomass pyrolysis with Fe₂O₃ addition of 10% exhibited the best performance on dry reforming reaction. A target CH₄ conversion of 95% over this char was realized at 800 °C. Moreover, H₂/CO ratio achieved with this char was prone to approach the stoichiometric value. Compared to CO₂ conversion, CH₄ conversion was more promoted with the increase of CO₂/CH₄ ratio. The variation of CO₂/CH₄ ratio also leaded to a noticeable changes on H₂/CO ratio. More importantly, the selected char presented a satisfied stability, evidenced by the total decrease of 4.8% for CH₄ conversion and 3.1% for CO₂ conversion in the test of 160 min. This was contributed to a depressed in-situ carbon consumption and a moderate deterioration of porous structure. Gaseous products obtained with the appropriate char in a long run had a syngas content of 88.79% and H₂/CO ratio of 0.92 on average.

Combining Carbon Fibers with Ni/γ–Al2O3 Used for Syngas Production: Part A: Preparation and Evaluation of Complex Carrier Catalysts

To promote the adsorption and activation of carbon dioxide in the dry reforming of methane (DRM), Ni and Al2O3 were coprecipitated on activated carbon fibers (ACF). Various characterization methods were adopted in order to investigate the surface characteristics of different catalysts. Chemisorption characterization results, such as H2-temperature programmed reduction (H2-TPR), H2-temperature programmed desorption (H2-TPD), and CO2-temperature programmed desorption (CO2-TPD) illustrated that ACF in a nickel-based catalyst could enhance the basic sites and improve the metal dispersion on a catalyst surface, which is beneficial for the adsorption and activation of feed gas. The coprecipitated coating on ACF proved by scanning electron microscope (SEM) can prevent the carbon of ACF from participating in the reaction, while retain good surface properties of carbon fibers. X-ray diffraction (XRD) patterns illustrated that the ACF in a nickel-based catalyst could decrease the crystallite size of the spinel NiAl2O4, which is beneficial for methane reforming. In addition, the Fourier transform infrared spectroscopy (FTIR) of different catalysts revealed that the added ACF could provide abundant functional groups on the surface, which could be the intermediate product of DRM, and effectively promote the reaction. Different to the catalyst supported on single alumina, the performance evaluation and stability test proved that the catalyst added with ACF exhibited a better catalytic performance especially for CO2 conversion. Moreover, based on the characterization results as well as some related literature, the dry reforming mechanism over optimum catalyst was derived.

Progress in Synthesis of Highly Active and Stable Nickel-Based Catalysts for Carbon Dioxide Reforming of Methane

In recent decades, rising anthropogenic greenhouse gas emissions (mainly CO2 and CH4 ) have increased alarm due to escalating effects of global warming. The dry carbon dioxide reforming of methane (DRM) reaction is a sustainable way to utilize these notorious greenhouse gases. This paper presents a review of recent progress in the development of nickel-based catalysts for the DRM reaction. The enviable low cost and wide availability of nickel compared with noble metals is the main reason for persistent research efforts in optimizing the synthesis of nickel-based catalysts. Important catalyst features for the rational design of a coke-resistant nickel-based nanocatalyst for the DRM reaction are also discussed. In addition, several innovative developments based on salient features for the stabilization of nickel nanocatalysts through various means (which include functionalization with precursors, synthesis by plasma treatment, stabilization/confinement on mesoporous/microporous/carbon supports, and the formation of metal oxides) are highlighted. The final part of this review covers major issues and proposed improvement strategies pertaining to the rational design of nickel-based catalysts with high activity and stability for the DRM reaction.