Porosity and Structure of Hierarchically Porous Ni/Al2O3 Catalysts for CO2 Methanation (original) (raw)
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Effect of a Swelling Agent on the Performance of Ni/Porous Silica Catalyst for CH4–CO2 Reforming
Langmuir, 2017
Hierarchical porous materials are of great interest in various industrial applications because of their potential to overcome the mass transport limitations typically encountered for single-mode porous materials. This report describes the synthesis of a hierarchical tri-modal porous silica-based material using a 7.5 molar ratio of a relatively inexpensive non-ionic surfactant template, tri-block copolymer P123, EO 20 PO 70 EO 20. The pore size distribution curve shows the presence of three types of pores with average diameters of ~8, 25 and 89 nm. Electron microscope images confirm the existence of smaller ordered mesopores (1 st mode), larger ordered mesopores (2 nd mode), and macropores (3 rd mode). Ni nanoparticles dispersed on this tri-modal porous silica produce a material that exhibited excellent catalytic performance for the CO 2 reforming of CH 4. This research provides new insights that will facilitate the development of tri-modal porous silica (TMS) materials for a variety of applications. The results demonstrated that the presence of large pores (2 nd and 3 rd mode pores) in TMS material increased the number of accessible active Ni sites, which led to the high activity observed for Ni/TMS catalyst.
Ni/Al2O3 nanocatalyst for CO2 methanation
In this work, we investigate the application of catalysis using nanostructured material in methanation reaction. For this purpose, a group of Ni/Al 2 O 3 anancatalysts with different Ni contents from 10 to 25 wt% was synthesized by wet impregnation method for carbon dioxide methanation. The lA/iN 2 O 3 nanocatalysts were characterized by N 2 adsorption-desorption and X-ray diffraction (XRD) techniques. The results show that pore size and crystalline size of catalysts are in nanometer scale. Also appropriate loading of Ni to produce methane from carbon dioxide and hydrogen is investigated at a reaction temperature ranging from 200 to 500 ºC. It was shown that 20Ni/Al 2 O 3 nanocatalyst has high activity and stability for CO 2 methanation. Moreover, the optimal condition for CO 2 methanation was achieved by investigating the effect of reaction temperature and H 2 /CO 2 molar ratio over 20 lA/i N 2 O 3 nanocatalyst.
Low-Rank Coal Supported Ni Catalysts for CO2 Methanation
Energies
As renewable energy source integration increases, P2G technology that can store surplus renewable power as methane is expected to expand. The development of a CO2 methanation catalyst, one of the core processes of the P2G concept, is being actively conducted. In this work, low-rank coal (LRC) was used as a catalyst support for CO2 methanation, as it can potentially enhance the diffusion and adsorption behavior by easily controlling the pore structure and composition. It can also improve the process efficiency owing to its simplicity (no pre-reduction step) and high thermal conductivity, compared to conventional metal oxide-supported catalysts. A screening of single metals (Ni, Co, Ru, Rh, and Pd) on LRC was performed, which showed that Ni was the most active. When Ni on the LRC catalyst was doped with a promoter (Ce and Mg), the CO2 conversion percentage increased by >10% compared to that of the single Ni catalyst. When the CO2 methanation activity was compared at 250–500 °C, the...
The Journal of Physical Chemistry C, 2019
The hierarchical pore systems of Pt/Al2O3 exhaust gas aftertreatment catalysts were analyzed with a collection of correlative imaging techniques to monitor changes induced by hydrothermal aging. Synergistic imaging with laboratory X-ray microtomography, synchrotron radiation ptychographic X-ray computed nanotomography and electron tomography allowed quantitative observation of the catalyst pore architecture from cm to nm scale. Thermal aging at 750 °C in air and hydrothermal aging at 1050 °C in 10% H2O/air caused increasing structural degradation, which manifested as widespread sintering of Pt particles, increased volume and quantity of macropores (>20 nm), and reduction in effective surface area coupled to decreasing volume and frequency of mesopores (2-20 nm) and micropores (<2 nm). Electron tomography unraveled the 3D structure with high resolution allowing visualization of meso-and macropores, but with samples of maximum 300 nm thickness. To complement this, hard X-ray ptychographic tomography produced quantitative 3D electron density maps of 5 µm diameter samples with spatial resolution <50 nm, effectively filling the resolution gap between electron tomography and hard X-ray microtomography. The obtained 3D volumes are an essential input for future computational modelling of fluid dynamics, mass transport or diffusion properties and may readily complement bulk 1D porosimetry measurements or simulated porosity.
Spray-Dried Ni Catalysts with Tailored Properties for CO2 Methanation
Catalysts
A catalyst production method that enables the independent tailoring of the structural properties of the catalyst, such as pore size, metal particle size, metal loading or surface area, allows to increase the efficiency of a catalytic process. Such tailoring can help to make the valorization of CO2 into synthetic fuels on Ni catalysts competitive to conventional fossil fuel production. In this work, a new spray-drying method was used to produce Ni catalysts supported on SiO2 and Al2O3 nanoparticles with tunable properties. The influence of the primary particle size of the support, different metal loadings, and heat treatments were applied to investigate the potential to tailor the properties of catalysts. The catalysts were examined with physical and chemical characterization methods, including X-ray diffraction, temperature-programmed reduction, and chemisorption. A temperature-scanning technique was applied to screen the catalysts for CO2 methanation. With the spray-drying method p...
3D printed Ni/Al2O3 based catalysts for CO2 methanation - a comparative and operando XRD-CT study
Journal of CO2 Utilization, 2019
Ni-alumina-based catalysts were directly 3D printed into highly adaptable monolithic/multichannel systems and evaluated for CO2 methanation. By employing emerging 3D printing technologies for catalytic reactor design such as 3D fibre deposition (also referred to as direct write or microextrusion), we developed optimised techniques for tailoring both the support's macroand microstructure, as well as its active particle precursor distribution. A comparison was made between 3D printed commercial catalysts, Ni-alumina based catalysts and their conventional counterpart, packed beds of beads and pellet. Excellent CO2 conversions and selectivity to methane were achieved for the 3D printed commercial catalyst (95,75 and 95,63 % respectively) with stability of over 100 h. The structure-activity relationship of both the commercial and in-house 3D printed catalysts was explored under typical conditions for CO2 hydrogenation to CH4, using operando 'chemical imaging', namely X-Ray Diffraction Computed Tomography (XRD-CT). The 3D printed commercial catalyst showed a more homogenous distribution of the active Ni species compared to the in-house prepared catalyst. For the first time, the results from these comparative characterisation studies gave detailed insight into the fidelity of the direct printing method, revealing the spatial variation in physico-chemical properties (such as phase and size) under operating conditions.
CO2 methanation over Co-Ni/Al2O3 and Co-Ni/SiC catalysts
Bulgarian Chemical Communications, 2020
In this study, highly loaded 20 wt% (СоxNi100–x)/Al2O3 and (СоxNi100–x)/SiC catalysts, where x = 0, 20, 60, 80, and 100 wt%, were prepared by a three-stage method, which includes wet impregnation of Al2O3 and SiC with the metal nitrates, thermal decomposition of the loaded nitrates, and obtaining of the loaded metals by reducing their oxides with hydrogen at 350 °C. The prepared catalysts were examined by different methods and tested in the CO2 methanation. Scanning electron microscopy and X-ray powder diffraction studies showed a difference in the loaded particle dispersion and the phase composition of catalysts. The highly loaded 20 wt% Co–Ni/Al2O3 catalysts showed the highest catalytic activity. In the presence of 20 wt% Co60Ni40/Al2O3, 20 wt% Co80Ni20/Al2O3, and 20 wt% Co100/Al2O3 catalysts, 100% CO2 can be converted into CH4 at 300 °C. This temperature is lower by 100 °C than the temperature at the total conversion over 20 wt% (Co–Ni)/SiC catalysts. Thermal desorption mass spectroscopy revealed that the methanation of CO2 passed through the formation of CHO* intermediate over the most active 20 wt% Co80Ni20/Al2O3 and 20 wt% Co80Ni20/SiC catalysts.
In the up-and-coming power-to-gas scenario (PtG), surplus of renewable electricity is stored in the form of methane, by reacting green hydrogen with waste CO2 through the Sabatier reaction (CO2 methanation). While the catalytic hydrogenation of CO2 to methane has already attracted much attention, the development of catalysts that feature a high specific activity at low temperature and a reasonable cost remains challenging but is needed in the perspective of industrial deployment. Concomitantly, the mechanism of CO2 methanation remains debated, and its elucidation would drive further progress. Herein, we disclose the preparation of a series of high-loading Ni/SiO2 catalysts via sol-gel method. Through (HR)-TEM, XRD, N2 physisorption, and H2 chemisorption, we show that small Ni particles (<5 nm, high Ni dispersion) could be obtained in a highly porous silica matrix, even at loading up to 50 wt%. The most active catalyst reached a high specific activity of 10.2 µmolCH4.g-1.s-1 at 30...
Solid Nanoporosity Governs Catalytic CO2 and N2 Reduction
ACS Nano, 2020
Global demand of green and clean energy is increasing day by day owing to the ongoing developments by human race that are changing the face of the earth at a rate faster than ever. Exploring the alternative sources of energy to replace fossil fuel consumption has become even more vital to control the growing concentration of CO 2 , and reduction of CO 2 into CO or other useful hydrocarbons (e.g. C 1 and C ≥2 products) as well as reduction of N 2 into ammonia can greatly help in this regard. Various materials are developed for the reduction of CO 2 and N 2. The introduction of pores in these materials by porosity engineering is demonstrated highly effective in increasing the efficiency of the involved redox reactions, over 40% increment for CO 2 reduction up to date, by providing increased number of exposed facets, kinks, edges, and catalytic active sites of catalysts. By shaping the surface porous structure, selectivity of redox reaction can also be enhanced. In order to better understand this area benefiting rational design for future solutions, this review systematically summarized and constructively discussed the porosity engineering in catalytic materials, including various synthesis methods, characterization on porous materials and the effects of porosity on performance of CO 2 reduction and N 2 reduction.
Applied Catalysis A: General, 1996
A series of coprecipitated Ni/A1203 catalysts containing 0-25 wt.-% Ni were examined for total surface area, total pore volume, metal surface area, CO 2 adsorption and CO 2 methanation activity in order to study the relation between metal content, structure and catalyst activity. Coprecipitated Ni/A1203 catalysts are found to be efficient promoters for methanation. Methanation activity is dependent on the nickel content and the degree of CO 2 adsorption at the reaction considered. Although A1203 does not exhibit methanation activity, it is found to be active for CO 2 adsorption. Reverse spillover increases methane production per unit nickel surface particularly for catalysts with low Ni loadings.