One-Step Synthesis of Highly Active and Stable Ni–ZrOx for Dry Reforming of Methane

Highly Efficient Conversion of Greenhouse Gases Using a Quadruple Mixed Oxide-Supported Nickel Catalyst in Reforming Process

The greenhouse gas reduction as well as the utilization of more renewable and clean energy via a dry reforming reaction is of interest. The impact of a CeMgZnAl oxide quad-blend-supported Ni catalyst on performance and anticoking during dry reforming reactions at 700 °C was studied. A high Ce-Mg/Zn ratio, as seen in the CeMg0.5ZnAl-supported nickel catalyst, enhances lattice oxygen, and the presence of strong basic sites, along with the creation of the carbonate intermediate species, is accompanied by the production of gaseous CO through a gasification reaction between the carbon species and Ni-COads-lin site. The phenomena caused the outstanding performance of the Ni/CeMg0.5ZnAl catalyst-CH4 (84%),CO2 (83%) conversions, and the H2/CO (0.80) ratio; moreover, its activity was also stable throughout 30 h.

Surface basicity controls C-C coupling rates during carbon dioxide-assisted methane coupling over bifunctional Ca/ZnO catalysts

Carbon dioxide-assisted coupling of methane offers an approach to chemically upgrade two greenhouse gases and components of natural gas to produce ethylene and syngas. Prior research on this reaction has concentrated efforts on catalyst discovery, which has indicated that composites comprised of both reducible and basic oxides are especially promising. There is a need for detailed characterization of these bifunctional oxide systems to provide a more fundamental understanding of the active sites and their roles in the reaction. We studied the dependence of physical and electronic properties of Ca-modified ZnO materials on Ca content via X-ray photoelectron and absorption spectroscopies, electron microscopy, and infrared spectroscopic temperature-programmed desorption (IR-TPD). It was found that introduction of only 0.6 mol% Ca onto a ZnO surface is necessary to induce significant improvement in the catalytic production of C₂ species: C₂ selectivity increases from 5% on un-modified ZnO to 58%, at similar conversions. Evidence presented shows that this selectivity increase results from the formation of an interface between the basic CaO and reducible ZnO phases. The basicity of these interface sites correlates directly with catalytic activity over a wide composition range, and this relationship indicates that moderate CO₂ adsorption strength is optimal for CH₄ coupling. These results demonstrate, for the first time to our knowledge, a volcano-type relationship between CO₂-assisted CH₄ coupling activity and catalyst surface basicity, which can inform further catalyst development.

Barium-Promoted Yttria-Zirconia-Supported Ni Catalyst for Hydrogen Production via the Dry Reforming of Methane: Role of Barium in the Phase Stabilization of Cubic ZrO2

Developing cost-effective nonprecious active metal-based catalysts for syngas (H₂/CO) production via the dry reforming of methane (DRM) for industrial applications has remained a challenge. Herein, we utilized a facile and scalable mechanochemical method to develop Ba-promoted (1-5 wt %) zirconia and yttria-zirconia-supported Ni-based DRM catalysts. BET surface area and porosity measurements, infrared, ultraviolet-visible, and Raman spectroscopy, transmission electron microscopy, and temperature-programmed cyclic (reduction-oxidation-reduction) experiments were performed to characterize and elucidate the catalytic performance of the synthesized materials. Among different catalysts tested, the inferior catalytic performance of 5Ni/Zr was attributed to the unstable monoclinic ZrO₂ support and weakly interacting NiO species whereas the 5Ni/YZr system performed better because of the stable cubic ZrO₂ phase and stronger metal-support interaction. It is established that the addition of Ba to the catalysts improves the oxygen-endowing capacity and stabilization of the cubic ZrO₂ and BaZrO₃ phases. Among the Ba-promoted catalysts, owing to the optimal active metal particle size and excess ionic CO₃ ^2- species, the 5Ni4Ba/YZr catalyst demonstrated a high, stable H₂ yield (i.e., 79% with a 0.94 H₂/CO ratio) for up to 7 h of time on stream. The 5Ni4Ba/YZr catalyst had the highest H₂ formation rate, 1.14 mol g^-1 h^-1 and lowest apparent activation energy, 20.07 kJ/mol, among all zirconia-supported Ni catalyst systems.

Prospects and Technical Challenges in Hydrogen Production through Dry Reforming of Methane

Environmental issues related to greenhouse gases (GHG) emissions have pushed the development of new technologies that will allow the economic production of low-carbon energy vectors, such as hydrogen (H2), methane (CH4) and liquid fuels. Dry reforming of methane (DRM) has gained increased attention since it uses CH4 and carbon dioxide (CO2), which are two main greenhouse gases (GHG), as feedstock for the production of syngas, which is a mixture of H2 and carbon monoxide (CO) and can be used as a building block for the production of fuels. Since H2 has been identified as a key enabler of the energy transition, a lot of studies have aimed to benefit from the environmental advantages of DRM and to use it as a pathway for a sustainable H2 production. However, there are several challenges related to this process and to its use for H2 production, such as catalyst deactivation and the low H2/CO ratio of the syngas produced, which is usually below 1.0. This paper presents the recent advances in the catalyst development for H2 production via DRM, the processes that could be combined with DRM to overcome these challenges and the current industrial processes using DRM. The objective is to assess in which conditions DRM could be used for H2 production and the gaps in literature data preventing better evaluation of the environmental and economic potential of this process.

Simple mechanisms of CH4 reforming with CO2 and H2O on a supported Ni/ZrO2 catalyst

To understand the metal-support interaction of oxide supported transition metal catalysts, we computed the reaction mechanisms of dry and steam reforming of methane on a tetragonal ZrO₂(101) supported Ni catalyst. Based on the limited number of active sites on the surface, an irregular and non-ideal Ni₁₃ cluster on ZrO₂(101) is identified as a catalyst. A simple reaction mechanism is proposed, and the first direct dissociation step of CO₂, CH₄ and H₂O is the most difficult based on the computed Gibbs free energies and no surface CH_XO and CH_XOH intermediates are involved, different from that on the flat Ni(111) surface. Analysis of other supported nickel catalysts shows that not only the support but also the size and shape of the metal clusters play an important role in the reaction mechanisms and kinetics.

Costa P, Hu C. Syngas Production via CO2 Reforming of Methane over Aluminum-Promoted NiO-10Al2O3-ZrO2 Catalyst

CO2 reforming of methane was studied at medium temperature (700 °C) using a GSHV of 48,000 h-1 over nickel catalysts supported on ZrO2 promoted by alumina. The catalysts were prepared by a one-step synthesis method and characterized by BET, H2-TPR, XRD, XPS, TEM, Raman spectroscopy, and TGA. The NiO-10Al2O3-ZrO2 catalyst exhibited higher catalytic performance in comparison with the NiO-ZrO2 catalyst. The enhancement of catalytic activity in dry reforming could be associated with the alterations in surface properties due to Al promotion. First, the Al promoter could modify the structure of ZrO2, leading to an increase of its pore volume and pore diameter. Second, the NiO-10Al2O3-ZrO2 catalyst exhibited high resistance to sintering. Third, the NiO-10Al2O3-ZrO2 catalyst showed high suppression to the loss of nickel during a long-term catalytic test. Finally, the addition of Al could inhibit the reduction of ZrO2 during the reduction and reaction, endowing further the stability.

Ni@ZrO2 yolk-shell catalyst for CO2 methane reforming: Effect of Ni@SiO2 size as the hard-template

This paper reports the usage ratio of TEOS and Zr(OBu)₄ on the formation of Ni@ZrO₂ yolk-shell for dry reforming of methane. From XPS analysis, the ZrO₂ hollow shell texture is demonstrated to be [TEOS]/[Zr(OBu)₄] dependent due to different sizes of SiO₂ produced. It found that an adequate ratio of [TEOS]/[Zr(OBu)₄] improves the catalytic conversion of dry reforming of methane. It (Ni@ZrO₂-SiZr-7.7) shows 90% conversion for CH₄ and 93% for CO₂ at a WHSV of 72,000 mLg_cat^-1h^-1 for 50 h at 800 °C with TOF_CH4 of 8.7 s^-1. It proposed that the changes in surface Si/Zr and gradual interconnecting pores contributed to its activity and stability. These finding's potential to be utilized in other high-temperature reactions.

The Deoxygenation of Jatropha Oil to High Quality Fuel via the Synergistic Catalytic Effect of Ni, W2C and WC Species

Tungsten carbide-based materials have good deoxygenation activity in the conversion of biomass. In this paper, catalysts with different nickel–tungsten carbide species were prepared by tuning the reduction temperature and Ni loading, and the effects of these different tungsten carbide species in the conversion of jatropha oil were studied. XRD, XPS, TEM, HRTEM, Raman, H2-TPR, ICP-AES were used to characterize the catalysts. The results suggested that metallic W was gradually carburized to W2C species, and W2C species was further carburized to WC species with the increase in reduction temperature and Ni loading. The obtained 10Ni10W/AC-700 catalyst exhibited outstanding catalytic performance with 99.7% deoxygenation rate and 94.5% C15-18 selectivity, which were attributed to the smallest particle size, the best dispersion, the most exposed active sites, and the synergistic effect of Ni, W2C and WC species.

The Effect of Si on CO2 Methanation over Ni-xSi/ZrO2 Catalysts at Low Temperature

A series of Ni-xSi/ZrO2 (x = 0, 0.1, 0.5, 1 wt%, the controlled contents of Si) catalysts with a controlled nickel content of 10 wt% were prepared by the co-impregnation method with ZrO2 as support and Si as a promoter. The effect of different amounts of Si on the catalytic performance was investigated for CO2 methanation with the stoichiometric H2/CO2 molar ratio (4/1). The catalysts were characterized by BET, XRF, H2-TPR, H2-TPD, H2-chemisorption, CO2-TPD, XRD, TEM, XPS, and TG-DSC. It was found that adding the appropriate amount of Si could improve the catalytic performance of Ni/ZrO2 catalyst at a low reaction temperature (250 °C). Among all the catalysts studied, the Ni-0.1Si/ZrO2 catalyst showed the highest catalytic activity, with H2 and CO2 conversion of 73.4% and 72.5%, respectively and the yield of CH4 was 72.2%. Meanwhile, the catalyst showed high stability and no deactivation within a 10 h test. Adding the appropriate amount of Si could enhance the interaction between Ni and ZrO2, and increase the Ni dispersion, the amounts of active sites including surface Ni0, oxygen vacancies, and strong basic sites on the catalyst surface. These might be the reasons for the high activity and selectivity of the Ni-0.1Si/ZrO2 catalyst.

Novel Preparation of Cu and Fe Zirconia Supported Catalysts for Selective Catalytic Reduction of NO with NH3

Copper and iron promoted ZrO2 catalysts were prepared by one-pot synthesis using urea. The studied catalysts were characterized by XRD, N2 physisorption, XPS, NH3-TPD, and tested in the selective catalytic reduction of NO with NH3 (NH3-SCR) in the absence and presence of water vapor under the experimental conditions representative of exhaust gases from stationary sources. The influence of SO2 on catalytic performance was also investigated. Among the studied catalysts, the Fe-Zr sample showed the most promising results in NH3-SCR, being active and highly selective to N2. The addition of SO2 markedly improved NO and NH3 conversions during NH3-SCR in the presence of H2O. The improvement in acidic surface properties is believed to be the cause.

CeZrOx Promoted Water-Gas Shift Reaction under Steam–Methane Reforming Conditions on Ni-HTASO5

Ni-based catalysts (Ni-γ-Al2O3, Ni-HTASO5 and Ni-CeZrOx) were prepared by impregnation method and characterized by BET, AAS, XRD, H2-TPR, CO-TPD, NH3-TPD, XPS, TG-DSC-MS and Raman spectroscopies. Using CeZrOx-modified Al2O3 (HTASO5) as support, the catalyst exhibited good catalytic performance (TOFCH4 = 8.0 × 10−2 s−1, TOFH2 = 10.5 × 10−2 s−1) and carbon resistance for steam-methane reforming (SMR) reaction. Moreover, CeZrOx was able to enhance water-gas shift (WGS) reaction for more hydrogen production. It was found that the addition of CeZrOx could increase the content of active nickel precursor on the surface of the catalyst, which was beneficial to the decomposition of water and methane on Ni-HTASO5. Furthermore, Ni-HTASO5 could decrease the strong acid sites of the catalyst, which would not only contribute to the formation of low graphited carbon, but also decrease the amount of carbon deposition.