Porous Nickel‐Alumina Derived from Metal‐Organic Framework (MIL‐53): A New Approach to Achieve Active and Stable Catalysts in Methane Dry Reforming

Unbounding the Future: Designing NiAl-Based Catalysts for Dry Reforming of Methane

Dry reforming of methane (DRM), the catalytic conversion of CH4 and CO2 into syngas (H2+CO), is an important process closely correlated to the environment and chemical industry. NiAl-based catalysts have been reported to exhibit excellent activity, low cost, and environmental friendliness. At the same time, the rapid deactivation caused by carbon deposition, Ni sintering, and phase transformation exerts great challenges for its large-scale applications. This review summarizes the recent advances in NiAl-based catalysts for DRM, particularly focusing on the strategies to construct efficient and stable NiAl-based catalysts. Firstly, the thermodynamics and elementary steps of DRM, including the activation of reactants and coke formation and elimination, are summarized. The roles of Al2O3 and its mixed oxides as the support, and the influences of the promoters employed in NiAl-based catalysts over the DRM performance, are then illustrated. Finally, the design of anti-coking and anti-sintering NiAl-based catalysts for DRM is suggested as feasible and promising by tailoring the structure and states of Ni and the modification of Al-based supports including small Ni size, high Ni dispersion, proper basicity, strong metal-support interaction (SMSI), active oxygen species as well as high phase stability.

Stationary wavelet denoising of solid-state NMR spectra using multiple similar measurements

Accumulating several scans of free induction decays is always needed to improve the signal-to-noise ratio of NMR spectra, especially for the low gyromagnetic ratio solid-state NMR. In this study, we present a new denoising approach based on the correlations between multiple similar NMR spectra. Contrary to the simple averaging of multiple scans or denoising the final averaged spectrum, we propose a Wavelet-based Denoising technique for Multiple Similar scans(WDMS). Firstly, the stationary wavelet transform is applied to decompose every spectrum into approximation coefficients and detail coefficients. Then, the detail coefficients are multiplied by weights calculated based on Pearson's correlation coefficient and structural similarity index between approximation coefficients of different spectra. Finally, the average of these detailed components is used to denoise the spectra. The proposed method is carried on the assumption that noise between multiple spectra is uncorrelated while peak signal information is similar between different spectra, thus preserving the possibility of applying further processing to the data. As a demonstration, the standard wavelet denoise is applied to the WDMS-processed spectra, achieving a further increase in the S/N ratio. We confirm the reliability of the denoising approach based on multiple scans on 1D/2D solid-state MAS/static NMR spectra. In addition, we also show that this method can be used to deal with a single Car-Purcell-Meiboom-Gill (CPMG) echo train.

A Review on the Different Aspects and Challenges of the Dry Reforming of Methane (DRM) Reaction

The dry reforming of methane (DRM) reaction is among the most popular catalytic reactions for the production of syngas (H2/CO) with a H2:CO ratio favorable for the Fischer-Tropsch reaction; this makes the DRM reaction important from an industrial perspective, as unlimited possibilities for production of valuable products are presented by the FT process. At the same time, simultaneously tackling two major contributors to the greenhouse effect (CH4 and CO2) is an additional contribution of the DRM reaction. The main players in the DRM arena-Ni-supported catalysts-suffer from both coking and sintering, while the activation of the two reactants (CO2 and CH4) through different approaches merits further exploration, opening new pathways for innovation. In this review, different families of materials are explored and discussed, ranging from metal-supported catalysts, to layered materials, to organic frameworks. DRM catalyst design criteria-such as support basicity and surface area, bimetallic active sites and promoters, and metal-support interaction-are all discussed. To evaluate the reactivity of the surface and understand the energetics of the process, density-functional theory calculations are used as a unique tool.

Carbon Dioxide Reforming of Methane over Nickel-Supported Zeolites: A Screening Study

As the utilization of zeolites has become more frequent in the dry reforming of methane (DRM) reaction, more systematic studies are required to evaluate properly the influence of zeolites’ composition and framework type on the performance. Therefore, in this work, a step-by-step study was performed with the aim of analyzing the effects of Ni loading (5, 10 or 15 wt.% over USY(3) zeolite), Si/Al ratio (3, 15 or 38 on USY zeolites with 15 wt.% Ni) and framework type (USY, BEA, ZSM-5 or MOR for 15 wt.% Ni and Si/Al ratios of ≈40) on catalysts’ properties and performances. Increasing Ni loadings enhanced CH4 and CO2 conversions even though the catalysts’ stability was decreasing over the time. The variation of the Si/Al ratio on USY and the use of different zeolites had also a remarkable impact on the catalytic performance. For instance, at 500–600 °C reaction temperatures, the catalysts with higher basicity and reducibility exhibited the best results. However, when the temperature was further increased, catalysts presenting stronger metal–support interactions (nickel nanoparticles located in mesoporous cavities) displayed the highest conversions and stability over time. In brief, the use of 15 wt.% Ni and a USY zeolite, with both micro- and mesopores and high surface area, led to the best performances, mainly attributed to a favorable number of Ni0 active sites and the establishment of stronger metal–support interactions (due to nanoparticles confinement inside the mesopores).

Future Paradigm of 3D Printed Ni-Based Metal Organic Framework Catalysts for Dry Methane Reforming: Techno-economic and Environmental Analyses

Dry reforming of biogas is referred as an attractive path for sustainable H₂ production over decades. Meanwhile, in the Malaysian context, the abundance of palm oil mill effluent (POME) produced annually is deemed as a potential renewable source for renewable energy generation. Conventionally, nickel (Ni) is the most common catalyst used in the industrial-scale dry reforming of methane (DRM) to yield H₂, but it is subject to the drawbacks of sintering and deactivation after a long reaction time at high temperatures (>500 °C). Therefore, this work aims to provide an insight on the feasibility of the application of modified Ni-based catalysts in DRM, specifically in the economic and environmental aspects. From the benchmarking study of various Ni-based catalysts (e.g., bimetallic (Ni-Ce/Al₂O₃), alumina support (Ni/Al₂O₃), protonated titanate nanotube (Ni-HTNT), and unsupported), the Ni-MOF catalyst, notably, had proven its prominence in both economic and environmental aspects on the same basis of 10 tonnes of H₂ production. The MOF-based catalyst not only possessed a better economic performance (net present value 61.86%, 140%, and 563.08% higher than that of Ni-Ce/Al₂O_3, Ni/Al₂O₃, and Ni-HTNT) but also had relatively lower carbon emissions (13.18%, 20.09%, and 75.72% lower than that of Ni/Al₂O₃, Ni-HTNT, and unsupported Ni). This work also accounted for 3D printing technology for the mass production of Ni-MOF catalysts, where the net present value was 2 to 3% higher than that of the conventional production method. Additionally, sensitivity analysis showed that the H₂ price has the greatest impact on the feasibility of DRM as compared to other cost factors.

Tuning parameters for the synthesis of MIL-53(Al): Mn doped MIL-53(Al) as a high potential catalyst for methanol dehydration

Recently, many studies are dealing with developments of Metal-Organic Frameworks (MOFs), especially MIL-53(Al), which shows high thermal and mechanical stability. Among these, optimizing the synthesis condition of MIL-53(Al) to obtain appropriate characteristics has attracted much attention in academia and the industry. Here, the effect of synthesis time and ligand to metal molar ratio on the hydrothermal synthesis of MIL-53(Al) are pursued. The synthesized MIL-53(Al) samples are characterized by X-ray diffraction (XRD), the Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), energy dispersive X-ray analysis (EDX), thermal gravimetric analysis (TGA), and nitrogen adsorption-desorption technique (BET). The present study shows that MIL-53(Al) can be conventionally synthesized with a high yield within a shorter reaction time than the previous studies. Furthermore, the catalytic activity of the optimized MIL-53(Al) in the pure and Mn-doped form is studied in a methanol dehydration reaction. It is thus inferred that this popular MOF in the Mn/MIL-53(Al) form has a high activity and DME selectivity during methanol conversion. Our present results confirm the merits of employing the MIL-53(Al) as a catalyst in methanol to DME conversion, which can be an avenue for the practical application of acidic catalyst.

Encapsulation, Release, and Cytotoxicity of Doxorubicin Loaded in Liposomes, Micelles, and Metal-Organic Frameworks: A Review

Doxorubicin (DOX) is one of the most widely used anthracycline anticancer drugs due to its high efficacy and evident antitumoral activity on several cancer types. However, its effective utilization is hindered by the adverse side effects associated with its administration, the detriment to the patients’ quality of life, and general toxicity to healthy fast-dividing cells. Thus, delivering DOX to the tumor site encapsulated inside nanocarrier-based systems is an area of research that has garnered colossal interest in targeted medicine. Nanoparticles can be used as vehicles for the localized delivery and release of DOX, decreasing the effects on neighboring healthy cells and providing more control over the drug’s release and distribution. This review presents an overview of DOX-based nanocarrier delivery systems, covering loading methods, release rate, and the cytotoxicity of liposomal, micellar, and metal organic frameworks (MOFs) platforms.

Catalytic Upgrading of Clean Biogas to Synthesis Gas

Clean biogas, produced by anaerobic digestion of biomasses or organic wastes, is one of the most promising substitutes for natural gas. After its purification, it can be valorized through different reforming processes that convert CH4 and CO2 into synthesis gas (a mixture of CO and H2). However, these processes have many issues related to the harsh conditions of reaction used, the high carbon formation rate and the remarkable endothermicity of the reforming reactions. In this context, the use of the appropriate catalyst is of paramount importance to avoid deactivation, to deal with heat issues and mild reaction conditions and to attain an exploitable syngas composition. The development of a catalyst with high activity and stability can be achieved using different active phases, catalytic supports, promoters, preparation methods and catalyst configurations. In this paper, a review of the recent findings in biogas reforming is presented. The different elements that compose the catalytic system are systematically reviewed with particular attention on the new findings that allow to obtain catalysts with high activity, stability, and resistance towards carbon formation.

Understanding the opportunities of metal–organic frameworks (MOFs) for CO2 capture and gas-phase CO2 conversion processes: a comprehensive overview

The rapid increase in the concentration of atmospheric carbon dioxide is one of the most pressing problems facing our planet.

Catalytic Performance of Metal Oxides Promoted Nickel Catalysts Supported on Mesoporous γ-Alumina in Dry Reforming of Methane

Dry reforming of CH4 was conducted over promoted Ni catalysts, supported on mesoporous gamma-alumina. The Ni catalysts were promoted by various metal oxides (CuO, ZnO, Ga2O3, or Gd2O3) and were synthesized by the incipient wetness impregnation method. The influence of the promoters on the catalyst stability, coke deposition, and H2/CO mole ratio was investigated. Stability tests were carried out for 460 min. The H2 yield was 87% over 5Ni+1Gd/Al, while the CH4 and CO2 conversions were found to decrease in the following order: 5Ni+1Gd/Al > 5Ni+1Ga/Al > 5Ni+1Zn/Al > 5Ni/Al > 5Ni+1Cu/Al. The high catalytic performance of 5Ni+1Gd/Al, 5Ni+1Ga/Al, and 5Ni+1Zn/Al was found to be closely related to their contents of NiO species, which interacted moderately and strongly with the support, whereas free NiO in 5Ni+1Cu/Al made it catalytically inactive, even than 5Ni/Al. The 5Ni+1Gd/Al catalyst showed the highest CH4 conversion of 83% with H2/CO mole ratio of ~1.0.

Investigation of new routes for the preparation of mesoporous calcium oxide supported nickel materials used as catalysts for the methane dry reforming reaction

Calcium oxide mesoporous supports were successfully synthetized and used to disperse nickel nanoparticles for the dry reforming of methane catalytic reaction.

Nanostructured Nickel Aluminate as a Key Intermediate for the Production of Highly Dispersed and Stable Nickel Nanoparticles Supported within Mesoporous Alumina for Dry Reforming of Methane

Two routes of preparation of mesoporous Ni-alumina materials favoring the intermediate formation of nanostructured nickel-aluminate are presented. The first one involves an aluminum containing MOF precursor used as sacrificial template to deposit nickel while the second is based on a one-pot synthesis combined to an EISA method. As shown by a set of complementary techniques, the nickel-aluminate nanospecies formed after calcination are homogeneously distributed within the developed mesoporous alumina matrices whose porous characteristics vary depending on the preparation method. A special attention is paid to electron-microscopy observations using especially STEM imaging with high chemical sensitivity and EDS elemental mapping modes that help visualizing the extremely high nickel dispersion and highlight the strong metal anchoring to the support that persists after reduction. This leads to active nickel nanoparticles particularly stable in the reaction of dry reforming of methane.