Development Of Ni-based Catalysts Research Articles

Small interface with ample impact: Synergistic catalysis between Ni0 and Ni2+ during nitrobenzene hydrogenation

The development of Ni-based catalyst with simultaneous outstanding catalytic performance and low cost and the exploration of nitrobenzene hydrogenation mechanism are in urgent need but still remain a severe challenge. Herein, a nickel phyllosilicate (Ni@Si) catalyst in which Ni species are stabilized by SiOx ligands is successfully prepared and applied in nitrobenzene hydrogenation to obtain aniline, exhibiting excellent catalytic performance (∼97.6% yield). A combination study reveals that the Ni0 and Ni2+ species cooperatively catalyze the reaction and govern the catalytic performance of the rate-determining step, namely NO group reduction. Specifically, Ni0 species facilitates activation and dissociation of H2, while Ni2+ species accounts for the adsorption of NO group via the lone electron pairs in oxygen. This work would pave the way to the rational design of efficient Ni-based catalysts and deepen the fundamental understanding for nitrobenzene hydrogenation.

Insight into the anti-coking ability of NiM/SiO2 (M=ZrO2, Ru) catalyst for dry reforming of CH4 to syngas

The development of Ni-based catalysts with outstanding anti-coking ability is necessary for realizing the industrial application of dry reforming of CH4 (DRM) to syngas. Here, a facile combustion method with unique characteristic was employed to prepare the Ni/SiO2 catalyst with different promoters (ZrO2 or Ru). The effects of Ni particle size and promoter (ZrO2 or Ru) on the anti-coking ability of Ni/SiO2 catalyst were examined. The XRD and TEM results showed that improved Ni dispersion can be obtained via the facile combustion method, accompanying with enhanced metal-support interaction and CO2 adsorption capacity confirmed by H2-TPR and CO2-TPD, respectively. In comparison with Ni-IMP catalyst (prepared via the traditional impregnation method), the carbon deposition over Ni–C catalyst (prepared via the combustion method) decreased by 67% (from 2.7 to 0.9 mg carbon deposition·g−1CH4) as a result of the small Ni particles. The H2-TPR and XPS results revealed the interaction between promoter (ZrO2 and Ru) and Ni. The addition of ZrO2 can enhanced the CO2 activation ability of catalyst and the formed oxygen species can facilitate the elimination of carbon species, further decreasing the carbon deposition compared with Ni–C catalyst. The best catalytic performance with least carbon deposition (only 0.4 mg carbon deposition·g−1CH4) is achieved on the NiRu–C catalyst. The slower CH4 dissociation rate and the improved CO2 activation benefited from Ru can bring in the better balance between the carbon formation and elimination, leading to the best anti-coking ability of catalyst.

Development of Silicalite-1-encapsulated Ni nanoparticle catalyst from amorphous silica-coated Ni for dry reforming of methane: Achieving coke formation suppression and high thermal stability

Dry reforming of methane (DRM) is an important reaction for converting CO2 into synthesis gas (H2 + CO). Though Ni is one of the most promising catalysts, the agglomeration of Ni particles and the formation of coke on the catalyst proceed during DRM, resulting in rapid catalyst deactivation. Therefore, the development of Ni-based catalysts that exhibit high thermal stability and suppress coke formation is indispensable. The encapsulation structure of Ni nanoparticles in porous supports is reported to be effective for high DRM activities and the suppression of coke formation.Herein, we synthesized a Silicalite-1-encapsulated Ni catalyst (Ni@Silicalite-1) for DRM using amorphous silica-encapsulated Ni-oxide nanoparticles (NiOx@SiO2) as the Ni precursor, and the effect of physicochemical properties on DRM activities was investigated using Ni@Silicalite-1, Ni@SiO2 (NiOx@SiO2 after H2 reduction), and Ni/Silicalite-1 (impregnation). For Ni@Silicalite-1, Ni phyllosilicate was formed inside Silicalite-1 during the hydrothermal synthesis, and the encapsulation structure of 4.5-nm-sized Ni particles was realized by reducing Ni phyllosilicate to Ni particles inside the zeolite. Because the small Ni particles were stabilized in the porous supports, Ni@Silicalite-1 and Ni@SiO2 exhibited high and stable activity for DRM at 600 °C with negligible coke formation (6.6 and 8.2 mg-C/g-catalyst for Ni@Silicalite-1 and Ni@SiO2 respectively), whereas a large amount of coke was formed on Ni/Silicalite-1 (532 mg-C/g-catalyst). Ni@Silicalite-1 exhibited high and stable DRM activity throughout 24 h at 600 °C and GHSV = 108000 mL/(g-cat·h). Moreover, because Silicalite1 possessed high thermal stability, the high activity of Ni@Silicalite-1 was maintained throughout the 5 h of DRM at 850 °C, whereas the activity of Ni@SiO2 decreased because of the collapse of the pore structure of SiO2. Ni@Silicalite1 exhibited a higher conversion rate of methane (13.3 mol-CH4/(g-Ni·min) at 850 °C and GHSV = 1080000 mL/(g-cat·h)) than previously reported Ni-based catalysts.

A comprehensive review on improving the production of rich-hydrogen via combined steam and CO2 reforming of methane over Ni-based catalysts

During the last few decades, the global energy requirement is soaring significantly due to the rise of global population and economic development. This resulted in colossal release of CO2 and CH4, emissions into the atmosphere referred as greenhouse gases (GHGs), which poses a detrimental effects for the environment. One of the sustainable solutions to curb emissions of GHGs into the atmosphere is efficient utilization of syngas in order to produce useful chemicals and fuels. A comprehensive review is presented to highlight the capability of Ni-based catalysts in methane reforming through the application of both steam and dry routes referred to as bi-reforming of methane (BRM). Ni-based catalysts were found to support favorable reaction activity as they are cheaper than many exorbitant catalysts. The metal used for catalyst support exhibits higher stability and thermal resistance with improved resistance to coke formation. This review entails recent progresses in the development of Ni-based catalysts along with physical and kinetic aspects of the BRM process.

Co-Promoted Ni Nanocatalysts Derived from NiCoAl-LDHs for Low Temperature CO2 Methanation

Ni-based catalysts are prone to agglomeration and carbon deposition at high temperatures. Therefore, the development of Ni-based catalysts with high activities at low temperatures is a very urgent and challenging research topic. Herein, Ni-based nanocatalysts containing Co promoter with mosaic structure were prepared by reduction of NiCoAl-LDHs, and used for CO2 methanation. When the reaction temperature is 250 °C (0.1 MPa, GHSV = 30,000 mL·g−1·h−1), the conversion of CO2 on the NiCo0.5Al-R catalyst reaches 81%. However, under the same test conditions, the conversion of CO2 on the NiAl-R catalyst is only 26%. The low-temperature activity is significantly improved due to Co which can effectively control the size of the Ni particles, so that the catalyst contains more active sites. The CO2-TPD results show that the Co can also regulate the number of moderately basic sites in the catalyst, which is beneficial to increase the amount of CO2 adsorbed. More importantly, the NiCo0.5Al-R catalyst still maintains high catalytic performance after 92 h of continuous reaction. This is due to the confinement effect of the AlOx substrate inhibiting the agglomeration of Ni nanoparticles. The Ni-based catalysts with high performance at low temperature and high stability prepared by the method used have broad industrial application prospects.

Ni-based structured catalyst for selective 3-phase hydrogenation of nitroaromatics

We report herein on the development of Ni-based catalyst using activated carbon fibres (ACFs) as a structured support and its application for the three‐phase hydrogenation of nitroarenes (T=353K; P=10bar). It was shown that metallic Ni0 nanoparticles (NPs) with a mean diameter of ∼2.0nm stabilized by the ACF microporous network were responsible for the catalytic transformation. To obtain optimum catalytic activity, the Ni/ACF catalyst must be freshly prepared and activated in situ by H2 at T>353K. Pre-treatment of the ACFs by nitric acid boosted the activity of the Ni/ACF catalyst, which exhibits high performance in hydrogenation of nitrobenzene to aniline (yield, Y ∼100%). The catalyst was tested for the reuse attaining a quasi-steady-state after the sixth reaction thereafter remaining relatively stable over seven consecutive runs. Near-quantitative transformation (Y>99%) of p-chloronitrobenzene to p‐chloroaniline was achieved under mild conditions over the Ni/ACF catalyst with a ca. 20-fold higher activity than conventional Raney Ni. Thus, new catalyst reported here represents a significant step forward towards a simple, heterogeneous catalytic selective hydrogenation of nitroarenes that employs H2 as the hydrogen source.