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The greenhouse gas CH4 is more potent than CO2, although both these gases are solely responsible for global warming. The efficient catalytic conversion of CH4 into hydrogen-rich syngas, which also demonstrates economic viability, can deplete the concentration of CH4. This study examines the partial oxidation of methane (POM) prepared by the wetness impregnation process using 5% Ni supported over DSZ95 (93.3% ZrO2 + 6.7% Sc2O3) and promoted with 1% Ga (gallium), 1% Sr (strontium), and 1% Ce (cerium). These catalysts are characterized by surface area porosity, X-ray diffraction, FT-Infrared spectroscopy, Raman infrared spectroscopy, temperature programmed reduction, CO2 temperature-programmed techniques, desorption techniques, thermogravimetry, and transmission electron microscopy. The characterization results demonstrate that Ni is appropriate for the POM because of its crystalline structure, improved metal support contact, and increased thermal stability with Sr, Ce, and Ga promoters. The synthesized catalyst 5Ni+1Ga-DSZ95 maintained stability for 240 min on stream during the POM at 700 °C. Adding a 1% Ga promoter and active metal Ni to the DSZ95 improved the CH4 conversion from 70.00% to 75.90% and raised the H2 yield from 69.21% to 74.80%, while maintaining the reactants' stoichiometric ratio of (CH4:O2 = 2:1). The 5Ni+1Ga-DSZ95 catalyst is superior to the other catalysts, given its rich catalyst surface, strong metal support interaction, high surface area and low amount of carbon deposit. The high H2/CO ratio (>2.6) and H2 yield close to 75% indicate that 5Ni+1Ga-DSZ95 is a potent industrial catalyst for hydrogen-rich syngas production through partial oxidation of methane. [ABSTRACT FROM AUTHOR]

Efficient production of H2 by combined (steam/CO2; steam/O2) reforming of CH4 was comparatively studied over perovskite-derived promoted Ni catalysts. The process performance was improved by regulating the redox and structural properties of the LaNi0.99M0.01O3 catalysts through promotion (M = Pt, Pd, Re, Mo, Sn). The catalysts were synthesized using the citrate sol–gel method, tested in combined reforming of methane and studied by X-ray fluorescence analysis, thermal analysis, N2 adsorption, X-ray diffraction, electron microscopy, temperature-programed hydrogen reduction to elucidate the impact of catalyst properties on their activity and resistance to re-oxidation and formation of carbon deposits under reaction conditions. It was shown that LaNi0.99M0.01O3 catalysts after calcination at 850 °C in air have a perovskite structure that was destroyed after reductive activation with formation of metal Nio particles with an average size of ~ 25 nm on the surface of lanthanum oxide/hydroxide. The resistance to re-oxidation of Nio particles depends on the type of promoter and is maximum in the case of M = Re. It was established that the type of promoter affects the conversion of reagents (CH4, CO2) and the H2 yield, which at 700 °C increases in the series of promoters Sn < Mo < Pt < Pd < Re in the case of steam/CO2 reforming and Pt < Sn < Mo < Pd < Re with steam/O2 reforming. The optimal composition of catalyst was identified: among the studied samples, LaNi0.99Re0.01O3 is characterized by a higher specific surface area, average reduction ability and high resistance to re-oxidation and coking. At 850 °C it provides the H2 yield of 95 and 50% at complete CH4 conversion in steam/CO2 and steam/O2 reforming, respectively. [ABSTRACT FROM AUTHOR]

In order to better understand the confinement effect of CNTs on the properties of Ni based catalysts, Ni/CNTs catalysts with different Ni locations via the modification of CNTs pretreatment and impregnation process were prepared, characterized and tested in glycerol steam reforming. The Ni-in/CNTs catalyst showed excellent low temperature reaction activity, with initial Ni time yield of 0.064 mol C3H8O3 ·g Ni −1·h−1 and H 2 yield of 50.1% at 275 °C, 0.1Mpa. The confinement of Ni particles inside CNTs nanotubes led to more active sites with weak H 2 absorption strength, which were more related to the activity for glycerol steam reforming reaction. All the catalysts exhibited a noticeable deactivation during the reaction, however, their main deactivation mechanisms were not the same. The confinement effect of CNTs nanotubes could limit the sintering degree of Ni particles, and thus the deactivation of Ni-in/CNTs catalyst was slow in the initial stage; nevertheless, its deactivation became faster in the subsequent stage, which was due to the severe carbon deposition. For the two catalysts with Ni particles on the outer surface of supports, their main deactivation reason was the significant sintering of Ni species, and therefore, their deactivation was faster first and then slow down. [Display omitted] • Ni-in/CNTs showed excellent activity at the temperature as low as 275 °C. • The confinement effect of CNTs nanotubes limits the sintering of Ni particles. • Weak H 2 adsorbed active sites were more related to the activity for GSR reaction. • Deactivation on Ni-in/CNTs was mainly due to carbon deposition. • Deactivation on Ni-out/CNTs and Ni/CNF was mainly due to sintering of Ni particles. [ABSTRACT FROM AUTHOR]

Abstract The catalytic partial oxidation of methane (POM) is aimed at the mitigation of CH4 (a highly potent greenhouse gas) from the environment and the synthesis of syngas with a high H2/CO ratio. Herein, to enhance the POM reaction, Ni‐supported phosphate‐modified‐zirconia were synthesized with promotor “Ce” to achieve high H2/CO ratio (2.4–3.2). The catalysts were characterized by surface area and porosity, X‐ray diffraction, RAMAN, temperature‐programmed experiments (TPR, CO2‐TPD, and TPO), and TEM. Increasing the ceria addition over 10Ni/PO4 + ZrO2 resulted in lower crystallinity, higher dispersion of active sites, and enhanced the surface area of catalyst. The unique and prominent reducibility and basicity of NiO‐species and surface oxide ions, respectively, are particularly notable at 4 wt.% ceria loading. At a reaction temperature of 600°C, the highest concentration of active sites and a unique concentration of moderate strength basic sites can be achieved with 4 wt.% ceria loading over 10Ni/PO4 + ZrO2. This leads to 44% conversion of CH4, 36% yield of H2, 35% yield of CO2, and H2/CO ratio of 3.16 for the POM reaction. The cyclic H2TPR‐O2TPO‐H2TPR experiment confirms the reorganization of the active site towards high temperature under oxidizing gas O2 and reducing gas H2 gas stream during the POM reaction.

Converting CO2 into methane is considered a promising and economically viable technology for global transportation and utilization of this greenhouse gas. This study involves the preparation of a Ni-CZ (CeO2-ZrO2)/ATP (attapulgite) catalyst through the co-precipitation and impregnation methods. XRD, SEM, TEM, N2 absorption-desorption isotherms, XPS, H2-TPR, CO2-TPD, TG/DSC, and Raman were adapted to characterize the obtained samples. Real-time GC was used to measure the catalytic performances and to intensively study the impact of Ni loading content and ATP to CZ ratio on the catalytic performance of the products. DRIFTs was used to monitor the interstitial radicals in the catalytic reactions and to deduce the catalytic mechanisms. The results indicate that the composite catalytic matrix composed of CZ assembled on ATP demonstrated higher CO2 methanation stability and better carbon deposition resistance ability than the single CZ or ATP as the carrier, which should be attributed to the improved specific surface area and pore volume of the ATP assembled matrix and the enhanced dispersibility of the CZ and Ni species. The adoption of CZ solid solutions improves the oxygen storage capability of the catalyst, thereby providing continued mobile O2− in the matrix and accelerating the molecular exchange rate in the catalytic reactions. The ideal loading quantity of nickel contents on the CZA matrix is 15%, as the CO2 conversion decreases at elevated temperatures when the Ni loading content reaches 20%. Among the tested samples, the 15Ni-0.8CZA sample showed the best catalytic performance of 75% CO2 conversion and 100% CH4 selectivity at 400 °C. After 50 h of stability tests, the CO2 conversion rate still remained 70.84%, and the CH4 selectivity obtained 97.46%. No obvious coke was detected according to the Raman spectra of the used catalyst. The in situ DRIFTS experiment showed that formate is the main intermediate of the CO2 hydrogenation reaction on the 15Ni-0.8CZA catalyst. [ABSTRACT FROM AUTHOR]

Transformation of maleic anhydride (MA) into succinic anhydride (SA) through the development of high‐performance catalysts is an appealing approach from a sustainable development perspective. Herein, a core‐shell catalyst with silicate‐1 supported and MCM‐41 encapsulated nickel was prepared, which exhibited extraordinarily high MA conversion (99.8 %) and SA selectivity (99.9 %). Detailed structural characterizations and catalytic evaluation demonstrated that the core‐shell catalyst derived from the liquid deposition method is a hierarchically porous material with tunable shell thicknesses, possessing strong interaction between Ni particles and the supports. Key to this success is the MCM‐41 shell that covered the defects such as silanol nests on the surface of the silicate‐1 zeolite, diminishing both the surface and intra‐particle diffusion barriers, thus the specially‐designed catalyst achieved high activity under rather mild conditions (100 °C, 3.0 MPa), which is 59 % higher than the conventional silicate‐1 supported Ni catalyst. Furthermore, the mesoporous MCM‐41 shell plays a crucial role in minimizing the leaching and sintering of Ni particles, thereby bolstering catalytic stability. Overall, the research provides a new approach for the rational design to optimize the performance of hydrogenation catalysts and introduces a novel idea to enhance the activity and stability of Ni‐supported catalysts. [ABSTRACT FROM AUTHOR]

A new sulfur and nitrogen dual-doped carbon nanotubes (SNCNTs) were synthesized by melamine and thiourea via a coordination and carbonization process. SNCNTs were characterized by N2 adsorption–desorption, Thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results demonstrated that this feasible synthetic route using melamine and thiourea was useful for synthesizing S- and N-dual-doped functional carbon nanotubes. The material is expected to be used in the fields of battery electrode and catalytic materials. [ABSTRACT FROM AUTHOR]

The catalytic partial oxidation of methane (POM) is aimed at the mitigation of CH4 (a highly potent greenhouse gas) from the environment and the synthesis of syngas with a high H2/CO ratio. Herein, to enhance the POM reaction, Ni‐supported phosphate‐modified‐zirconia were synthesized with promotor "Ce" to achieve high H2/CO ratio (2.4–3.2). The catalysts were characterized by surface area and porosity, X‐ray diffraction, RAMAN, temperature‐programmed experiments (TPR, CO2‐TPD, and TPO), and TEM. Increasing the ceria addition over 10Ni/PO4 + ZrO2 resulted in lower crystallinity, higher dispersion of active sites, and enhanced the surface area of catalyst. The unique and prominent reducibility and basicity of NiO‐species and surface oxide ions, respectively, are particularly notable at 4 wt.% ceria loading. At a reaction temperature of 600°C, the highest concentration of active sites and a unique concentration of moderate strength basic sites can be achieved with 4 wt.% ceria loading over 10Ni/PO4 + ZrO2. This leads to 44% conversion of CH4, 36% yield of H2, 35% yield of CO2, and H2/CO ratio of 3.16 for the POM reaction. The cyclic H2TPR‐O2TPO‐H2TPR experiment confirms the reorganization of the active site towards high temperature under oxidizing gas O2 and reducing gas H2 gas stream during the POM reaction. [ABSTRACT FROM AUTHOR]

The enhancement of carbon-supported components is a crucial factor in augmenting the interplay between carbon-supported and metal-active components in the utilization of catalysts for direct ethanol fuel cells (DEFCs). Here, we propose a strategy for designing a catalyst by modifying candle soot (CS) and loading nickel onto ordered carbon soot. The present study aimed to investigate the effect of the Ni nanoparticles content on the electrocatalytic performance of Ni–CS, ultimately leading to the identification of a maximum composition. The presence of an excessive quantity of nickel particles leads to a decrease in the number of active sites within the material, resulting in sluggishness of the electron transfer pathway. The electrocatalyst composed of nickel and carbon support, with a nickel content of 20 wt%, has demonstrated a noteworthy current activity of 18.43 mA/cm2, which is three times that of the electrocatalyst with a higher nickel content of 25 wt%. For example, the 20 wt% Ni–CS electrocatalytic activity was found to be good, and it was approximately four times higher than that of 20 wt% Ni–CB (nickel–carbon black). Moreover, the chronoamperometry (CA) test demonstrated a reduction in current activity of merely 65.80% for a 20 wt% Ni–CS electrocatalyst, indicating electrochemical stability. In addition, this demonstrates the great potential of candle soot with Ni nanoparticles to be used as a catalyst in practical applications. [ABSTRACT FROM AUTHOR]

A nickel catalyst on mesoporoussilica created through a direct synthesis and modified with a strontium promoter. After conducting dry and steam reforming tests, the prepared samples characterized using the XRD, XRF, BET, TPR and HR-TEM, and then considered to study the catalyst stability and activity. And, the CH 4 and CO 2 conversion and ratio of H 2 /CO with using the Sr–Ni/MCM-41 catalyst in the DRM and SRM processes at 700 °C, were determined about (73.3% and 80.6%), (55.81% and 60.25%), and (0.88 and 3.1), respectively. Furthermore, SEM, TPR, and TPD analysis were used to characterize the utilized catalyst. The finding demonstrated a good structural order and the specific surface area (SSA) of 889.5 m2/g. The presence of a strontium enhanced nickel oxide's reducibility and strengthened its interaction with the base. Furthermore, strontium enhanced the catalytic activity. [Display omitted] • Sr-promoted Ni/MCM-41 catalyst was synthesized by the direct method. • Catalysts were compared in two dry and steam methane reforming processes. • Sr–Ni/MCM-41 catalyst had better catalytic performance in dry reforming of methane. • Sr–Ni/MCM-41 catalyst shows the highest stability and resistance to deposition and coke formation. [ABSTRACT FROM AUTHOR]

Ammonia borane (AB) is a promising candidate as a hydrogen reservoir in terms of both dihydrogen storage and hydrogen source for transfer hydrogenation (TH) to unsaturated organic substrates. Ultrasmall Ni nanoparticles (NPs) have been synthesized by metal vapor synthesis (MVS) and supported on a selected covalent triazine framework (CTFPh). The physical and chemical properties of the Ni/CTFPh nanocomposite have been thoroughly investigated. Despite the high Ni loading (10 wt %), the material exhibits well-dispersed ultrasmall Ni nanoparticles (2.2 nm), unveiling the non-innocent role of the N-doped templating carrier toward NPs dispersion and stabilization. The Ni/CTFPh has shown excellent catalytic performance in the AB hydrolysis and AB transfer hydrogenation (AB-TH) for the conversion of a variety of nitroarenes, including halogen-substituted ones, into the corresponding anilines. As for the latter process, Ni/CTFPh has unveiled a remarkable catalytic efficiency, durability, and reusability under both batch and continuous-flow operative conditions. Noteworthily, whatever the catalytic process at work, Ni/CTFPh certainly ranks or even outperforms most Ni-based systems of the state-of-the-art, including its Ni/VXC analogue (Ni 10 wt % prepared by MVS technique) synthesized using a plain and undoped carbon support (i.e., Vulcan XC-72R). [ABSTRACT FROM AUTHOR]

Cheap Ni catalysts are highly active for the catalytic conversion of biomass, but it is challenging to prepare Ni-based catalysts with high selectivity and stability under mild conditions. Adjusting the adsorption strength of Ni catalysts to reaction substrates and intermediates by metal introduction is an effective strategy to achieve high yields of products. In this paper, a series of xNi-Al2O3/CN catalysts were prepared by introducing Al content as a variable and were used for hydrogenation of furfural (FAL) to tetrahydrofurfuryl alcohol (THFOL). Under the mild condition of 90 °C, the yield of the 3Ni–Al2O3/CN catalyst with the optimal Ni/Al ratio of 3:1 reached 99.9%, which was 8.3 times that of Ni/CN without Al. The improvement in the catalytic performance was mainly attributed to the enhanced interaction of Ni and Al2O3 by Al introduction, which increased the content of active Ni0 and Lewis acid. This not only promoted the adsorption and activation of H2 and FAL but also increased the adsorption strength of 3Ni–Al2O3/CN on the intermediate FOL to improve THFOL selectivity. The correlation between the modulation of Al content and catalytic performance was explored in detail through relevant characterization and theoretical calculations. In addition, Al-introduced 3Ni–Al2O3/CN maintained high stability over 10 cycles relative to the rapid deactivation of Ni/CN, which was attributed to the strong interaction of Ni–Al2O3. This strategy to modulate the activation ability of the catalyst provides a reference for the logical design of efficient bifunctional metal catalysts. [ABSTRACT FROM AUTHOR]

Catalytic ammonia borane (AB) hydrolysis using supported Ni catalysts is a cost-effective way for H 2 production. However, constructing highly active Ni catalysts is still challenging due to the low intrinsic activity and easy aggregation of Ni particles at high Ni content. In this study, Ni particles in SBA-15 (mi -Ni@SBA-15) were prepared using the template-assisted melt infiltration method. For comparison, Ni catalysts supported on SBA-15 were also prepared using conventional impregnation (imp -Ni/SBA-15-NT) and melt infiltration method (mi - Ni/SBA-15-NT). The catalysts were fully characterized and catalytic AB hydrolysis was carried out on the catalysts. The results showed that for imp - Ni/SBA-15-NT and mi -Ni/SBA-15-NT large Ni agglomerates were obviously observed and the mesopores of SBA-15 were partially blocked due to the formation of rodlike Ni particles. In contrast, for mi -Ni@SBA-15 the combination of the steric effect of template and tunable mesopore size of SBA-15 enables SBA-15 to effectively confine the Ni particles in its mesopores and regulate the particle size of Ni respectively. Increasing Ni content from 7.7 to 24.5 wt% only led to denser Ni particles in SBA-15 without marked growth of Ni particles for mi -Ni@SBA-15. The well-dispersed Ni particles on mi -Ni@SBA-15 with Ni content of 24.5 wt% enriched the active sites on the catalyst surface, thus leading to high catalytic activity for AB hydrolysis with a TOF of 37.8 mol H2 mol Ni −1 min−1, which was at least 3.9 times higher than those of other tested catalysts. A comparison of the normalized catalytic activities by exposed Ni sites of catalysts with varied Ni particle sizes suggested that Ni sites on small Ni particles are more active than those on large ones. This work highlighted that mi -Ni@SBA-15 prepared using the template-assisted melt infiltration method are highly active catalysts for H 2 production from AB hydrolysis. [Display omitted] • Ni@SBA-15 were prepared using the template-assisted melt infiltration method. • The tunable mesopore size of SBA-15 enables effectively confine and regulate sizes of Ni particles. • Ni@SBA-15 exhibited a high TOF value for catalytic ammonia borane hydrolysis. [ABSTRACT FROM AUTHOR]

Abstract The potential dry reforming of methane technology allows for the synthesis of syngas from methane and carbon dioxide. Numerous investigations have been conducted on developing catalysts with exceptional activity and stability. Carbon deposition causes severe deactivation in typical nickel‐based catalysts, which is one of the most prevalent and important problems. In this study, methane was dry‐reformed over 5 wt.% Ni+xSr‐9La+Zr (x = 0–4 wt.%) catalysts for 7.5 h at 700°C and ambient pressure in a tubular fixed‐bed reactor. According to the weight percent of Sr loading, the features of the material's texture, morphology, and catalysis were investigated. N2‐physisorption, H2‐temperature programmed reduction, X‐ray diffraction, Raman, and TEM were used to evaluate the physicochemical characteristics of the catalysts. N2‐physisorption research revealed that changing the weight percentage loading of the Sr promoter had little effect on the textural qualities. The overall number of reducible NiO‐interacting species over the catalyst surface increased with increasing Sr loading. The 5Ni+2Sr‐9La+Zr catalyst exhibited the optimum CH4 and CO2 conversions of 62.9%–65.9% and 69.1%–70.3%, respectively, and the lowest deactivation factor of 4.7.

This study presents the results of comparative hydrogenation of sunflower oil over a platinum catalyst supported on activated diatomite and an industrial nickel catalyst (Pricat-9910). Catalysts are characterized using physical methods, such as transmission electron microscopic, temperature programmed hydrogen desorption, Brunauer–Emmett–Teller and inductively coupled plasma atomic emission spectrometry, enabling the determination of the size of catalyst particles, forms of adsorbed hydrogen, and specific surface area. Depending on the process conditions, hydrogenation reaction rates on platinum catalysts have been found to be 2–5 times higher than cis-trans isomerization reaction rates. Using a nickel catalyst, the hydrogenation and isomerization rates at low temperatures (110°C-130 °C) and 0.5 MPa pressure are almost similar, while, the hydrogenation rate is 1.4–1.8 times lower than the isomerization rate at high temperatures and pressures, leading to the formation of a large number of trans isomers. The difference in catalysts selectivity may be attributed the speciation and different adsorption energies of surface hydrogen, leading to the possibility of simultaneous hydrogenation of linoleic and oleic acids on the nickel catalyst.

Sorption-enhanced steam methane reforming (SESMR) can produce high-purity H 2 in one step, while removing CO 2 to reduce carbon emissions. The sorbents, catalysts or bifunctional composite used in this system typically exist in powder form, which is difficult to use in industrialized fluidized bed reactors. Granulation can effectively avoid reactor clogging, increase practicality and operability of the system. In this work, Al-modified CaO-based sorbents were granulated using the graphite-casting method and test its sorption-enhanced hydrogen production effects during methane steam reforming. The effects of granulation on the microstructure, carbonation reactivity and mechanical properties were characterized. The reaction conditions (temperature and water-gas ratio) and the combination method of catalyst and sorbent (powder mixing, pellets mixing, layered placement and bifunctional materials mixed evenly at the molecular level) on hydrogen yield were investigated. Results showed that CaO-based pellets after granulation had a fluffy and porous structure, exhibited excellent adsorption performance under low CO 2 partial pressure. The average crushing load of 75Ca25Al and 15Ni70Ca15Al pellets exceeded 6 N, showing good mechanical strength. The optimal reaction temperature range was found to be 550–600 °C. Increasing the water-gas ratio and reducing the flow rate were effective ways of improving CH 4 conversion and H 2 purity. The bifunctional 15Ni70Ca15Al powder prepared by sol-gel method had no catalytic effect on CH 4 –H 2 O reforming at 600 °C. After granulation, the catalytic performance was improved and the purity of H 2 reached 95%, but it declined rapidly during multiple SESMR cycles. In the case of mixed of two pellets (catalyst and sorbent), the outlet H 2 reached almost 100% with no decay observed over 15 cycles. When the switching time of feed gas was set to 60 min, high-purity (>96%) hydrogen can be produced continuously for 600 min on the parallel two fixed-bed reactors. • The graphite-casting method is used for granulation. • CaO-based pellets have good mechanical strength and efficient CO 2 capture capacity. • Granulation and heating can improve the catalytic activity of Ca–Ni–Al bifunctional powder. • H 2 can reach 100% when two pellets (catalyst and sorbent) are evenly blended. • High-purity (>96%) H 2 can be produced continuously for 600 min. [ABSTRACT FROM AUTHOR]

Ni-containing SiOC bulk ceramics have been prepared by spark plasma sintering at 1300 °C from polysiloxane at Ar atmosphere in the present work. The microstructure and properties of SiOC ceramics with different Ni content were studied. The resultant Ni-containing SiOC ceramics consists of in situ formed turbostractic layer carbon, CNTs (C nanotubes) and SiC crystals which dispersed in the SiOC matrix. With increasing content of Ni, the Ni-containing SiOC ceramics displayed less porosity. And the increasing Ni improved the mechanical, thermal and friction properties of SiOC ceramics. Ni-containing SiOC ceramics developed a carbon friction layer, which enhanced abrasion resistance to provide friction materials with stable friction coefficients and low abrasion values. A decrease in wear mass, from 2.06 to 0.18 mg was observed as the Ni content increasing from 0 to 2 wt%. The primary wear mechanisms of SiOC ceramics were recognized as abrasive wear, fatigue wear, and adhesion wear. [ABSTRACT FROM AUTHOR]

The renewable resource such as rice husk has been utilized to synthesize Hβ zeolite as a support for Ni catalysts for the production of clean hydrogen and carbon nanofibers (CNFs) by CH4 cracking at 550°C without any CO or CO2 formation. Hydrogen production rates and area of surface Ni are in good correlation, implying the optimum Ni loading of 25 wt % that demonstrated better hydrogen yields and CNFs. The electrochemical properties of the deactivated catalysts indicated that they were near semiconducting in nature, showing future prospects as carbon electrode materials. The physicochemical characteristics of the fresh, reduced, and used catalysts were rationalized by BET surface area, p‐X‐ray diffraction, temperature programmed reduction using H2, SEM, TEM, H2‐pulse chemisorption, and Raman spectroscopic analyses in conjunction with hydrogen rates. [ABSTRACT FROM AUTHOR]

5Ni/MgO and 5Ni/γAl2O3 are pronounced in the line of cheap catalyst systems for the dry reforming of methane. However, the lower reducibility of 5Ni/MgO and the significant coke deposition over 5Ni/γAl2O3 limit their applicability as potential DRM catalysts. The mixing capacity of MgO and Al2O3 may overcome these limitations without increasing the catalyst cost. Herein, a 5Ni/xMg(100 − x)Al (x = 0, 20, 30, 60, 70, and 100 wt. %) catalyst system is prepared, investigated, and characterized with X-ray diffraction, surface area and porosity measurements, H2-temperature programmed reduction, UV-Vis-IR spectroscopy, Raman spectroscopy, thermogravimetry, and transmission electron microscopy. Upon the addition of 20 wt. % MgO into the Al2O3 support, 5Ni/20Mg80Al is expanded and carries both stable Ni sites (derived through the reduction of NiAl2O4) and a variety of CO2-interacting species. CH4 decomposition at Ni sites and the potential oxidation of carbon deposits by CO2-interacting species over 5Ni/20Mg80Al results in a higher 61% H2-yield (against ~55% H2-yield over 5Ni/γAl2O3) with an excellent carbon-resistant property. In the major magnesia support system, the 5Ni/60Mg40Al catalyst carries stable Ni sites derived from MgNiO2 and "strongly interacted NiO-species". The H2-yield over the 5Ni/60Mg40Al catalyst moves to 71%, even against a high coke deposition, indicating fine tuning between the carbon formation and diffusion rates. Ni dispersed over magnesia-alumina with weight ratios of 7/3 and 3/7 exhibit good resistance to coke. Weight ratios of 2/8 and 7/3 contain an adequate amount of reducible and CO2-interactive species responsible for producing over 60% of H2-yield. Weight ratio 6/4 has a proper coke diffusion mechanism in addition to achieving a maximum of 71% H2-yield. [ABSTRACT FROM AUTHOR]

The potential dry reforming of methane technology allows for the synthesis of syngas from methane and carbon dioxide. Numerous investigations have been conducted on developing catalysts with exceptional activity and stability. Carbon deposition causes severe deactivation in typical nickel‐based catalysts, which is one of the most prevalent and important problems. In this study, methane was dry‐reformed over 5 wt.% Ni+xSr‐9La+Zr (x = 0–4 wt.%) catalysts for 7.5 h at 700°C and ambient pressure in a tubular fixed‐bed reactor. According to the weight percent of Sr loading, the features of the material's texture, morphology, and catalysis were investigated. N2‐physisorption, H2‐temperature programmed reduction, X‐ray diffraction, Raman, and TEM were used to evaluate the physicochemical characteristics of the catalysts. N2‐physisorption research revealed that changing the weight percentage loading of the Sr promoter had little effect on the textural qualities. The overall number of reducible NiO‐interacting species over the catalyst surface increased with increasing Sr loading. The 5Ni+2Sr‐9La+Zr catalyst exhibited the optimum CH4 and CO2 conversions of 62.9%–65.9% and 69.1%–70.3%, respectively, and the lowest deactivation factor of 4.7. [ABSTRACT FROM AUTHOR]

Effect of calcination temperature (350 °C – 850 °C) on the physicochemical properties as well as catalytic performance of Ni-based catalyst for the hydrogen production via steam methane reforming (SMR) and sorption enhanced reforming (SER) has been investigated. Catalyst calcined at highest temperature (850 °C) shows formation of NiAl2O4 confirmed by XRD. Consequently, a much higher reduction temperature (875 °C) is required to reduce this Ni aluminate spinel to an active Ni catalyst. Catalyst calcined at highest temperature (850 °C) showed much higher CH4 conversion and H2 production in SMR compared to the catalysts calcined at lower temperatures. In addition, higher CH4 conversion and H2 production was observed for the 15%Ni/alumina_850 catalyst after aging (long exposure to steam and high temperature) compared to commercial reforming catalyst. Finally, a much better stability is observed for the 15%Ni/alumina_850 catalyst compared to the commercial reforming catalyst after 100 SER/regeneration cycles under relevant reaction conditions. The formation of NiAl2O4 during high temperature calcination plays a vital role in the robustness and stability of the Ni-based catalysts and can be useful synthesis procedure for increasing the catalyst lifetime.

Carbonate hydrogenation to formate is a promising route to convert captured carbon dioxide into valuable chemicals, thus reducing carbon emissions and creating a revenue return. Developing inexpensive catalysts with high activity, selectivity, and stability remains challenging. We report a supported non‐noble metal catalyst, Ni/TiO2, with great selectivity over 96 % and excellent stability in catalyzing the conversion of carbonate into formate in aqueous solution. Ni0 and Ni2+ species are both observed in Ni/TiO2 catalysts, and the synergistic effect of these two Ni components leads to high activity and high selectivity of carbonate hydrogenation to formate. [ABSTRACT FROM AUTHOR]

Lanthanum hexaaluminate (LHA) supported NiO catalysts (xNi/LHA) with varied mass loading of Ni (x = 15, 20, 25, 30 wt%) were prepared by impregnating NiO nanoparticles (NPs) on LHA support that synthesized through urea combustion method. The catalysts were characterized by high-resolution transmission electron microscope (HRTEM), temperature programmed reduction (TPR), temperature programmed desorption (TPD), etc. The results showed that NiO NPs were dispersed densely on the LHA surface. The 25Ni/LHA catalyst provided the optimal ammonia conversion of 85.75% with a space velocity of 30,000 ml gcat−1 h−1 at 600 °C, corresponding to the hydrogen production rate of 28.73 mmol H2 gcat−1 min−1. The strong alkalinity of LHA could modify the interaction between the active sites and the nitrogen of ammonia, which was conducive to the ammonia decomposition reaction. The high performance of the catalyst represented a feasible approach towards the application of ammonia as hydrogen carrier to produce hydrogen. [ABSTRACT FROM AUTHOR]

Ni catalysts are commonly used for important transformations in organic chemistry. However, they frequently attend the employment as Ni complexes. Herein, we design an efficient and environmentally compatible nanoscale Ni catalyst for debenzylation reactions via hydrogenative C–N bond cleavage. The Ni nanoparticles (NPs) can be in situ generated by pure H2 reduction based on the precursor Ni–Al hydrotalcite-like compound. The Ni nanocatalysts were systematically characterized with various technique approaches including physical adsorption, XRD, Raman, H2-TPR, TEM, and SEM. Two types of Ni species can be detected, i.e., NiO and Ni0. The latter was supposed to be the active sites. The ultra-small and highly dispersed active Ni0 NPs with average diameters of 5 nm can be formed on the surface of the Ni–Al2O3–H2–78 catalyst. Then the complete conversion and high yield (> 90%) for hydrogenative C–N bond cleavage of some substrates (6 examples) can be achieved. [ABSTRACT FROM AUTHOR]

Hydrogenation of biomass-derived furfuryl alcohol to widely used tetrahydrofurfuryl alcohol is an important industrial route, which however calls for a more efficient catalyst. In this work, a highly selective and stable Ni-C-Al2O3 catalyst for furfuryl alcohol hydrogenation to tetrahydrofurfuryl alcohol is reported. The catalyst precursor is prepared by in-situ growth of Ni-based metal organic frameworks (Ni-BTC) on Al2O3 and then the precursor undergoes thermal decomposition to obtain the catalyst directly. For comparison, Ni-C/Al2O3 acquired from pyrolysis of physically mixed Ni-MOFs with Al2O3 and Ni/Al2O3 prepared by impregnation method are also tested as the hydrogenation catalysts. The prepared catalysts are characterized by a series of techniques, including XRD, FT-IR, TG, TEM, SEM, XPS and BET to reveal the relationship between the catalysts structure and their performance. The results show that small metal Ni particle size and appropriate interaction between Ni and the support, which benefit from the in-situ preparation method are key factors that ensure the high furfuryl alcohol conversion (99.8%) and high selectivity to tetrahydrofurfuryl alcohol (98.2%) at moderate reaction conditions (120 °C, 30 min, 4 MPa H2). [ABSTRACT FROM AUTHOR]

In this artcile, methane catalytic oxidation was studied over the Ni/MgAl2O4 catalysts with different weight percentages of nickel oxide synthesized by a simple solid-state mechanochemical preparation method. The Mesoporous nanocrystalline Ni/MgAl2O4 catalysts with high specific surface area displayed high catalytic activity in methane catalytic oxidation. The obtained results demonstrated that the increment in Ni loading improved the CH4 conversion and CO2 selectivity. The influence of O2:CH4 molar ratio and gas hourly space velocity (GHSV) was investigated and the obtained results indicated that the increase in feed ratio and GHSV enhanced the CH4 conversion. Moreover, the incarease in calcination temperature from 500 to 700°C had a negative influence on the catalytic activity because of the formation of agglomerated particles on the calcined catalysts at higher temperatures. [ABSTRACT FROM AUTHOR]

At present, the selective hydrogenation of α, β-unsaturated aldehydes remains a challenge due to competition between unsaturated functional groups (C=C and C=O). In this study, N-doped carbon deposited on silica-supported nickel Mott–Schottky type catalysts (Ni/SiO2@NxC) was prepared for the selective hydrogenation of cinnamaldehyde (CAL) by using the respective hydrothermal method and high-temperature carbonization method. The prepared optimal Ni/SiO2@N7C catalyst achieved 98.9% conversion and 83.1% selectivity for 3-phenylpropionaldehyde (HCAL) in the selective hydrogenation reaction of CAL. By constructing the Mott–Schottky effect, the electron transfer from metallic Ni to N-doped carbon at their contact interface was promoted, and the electron transfer was demonstrated by XPS and UPS. Experimental results indicated that by modulating the electron density of metallic Ni, the catalytic hydrogenation of C=C bonds was preferentially performed to obtain higher HCAL selectivity. Meanwhile, this work also provides an effective way to design electronically adjustable type catalysts for more selective hydrogenation reactions. [ABSTRACT FROM AUTHOR]

In the context of using renewable energies and recycling climate‐changing gases, methanation of CO2 provides one possibility. However, volatile availability of renewable energies for hydrogen production and fluctuating CO2 streams from different sources lead to enhanced demand in investigating the influence of dynamic process operation on the catalyst performance, including detailed kinetic characterization. Reliable kinetic measurements require isothermal temperature control and absence of macrokinetic diffusion limitations. Both were investigated in this work while the determination of steady‐state kinetic parameters is part of ongoing studies. Furthermore, a detailed analysis with respect to the long‐term‐stability of the nickel‐based catalyst was performed. [ABSTRACT FROM AUTHOR]

Hydrogen production from biogas over alumina-supported Ce1−xNixO2−x catalysts was studied in a temperature range of 600–850 °C with an initial gas composition of CH4/CO2/H2O of 1/0.8/0.4. To achieve a high and stable hydrogen yield, highly dispersed Ni catalysts were prepared through the exsolution approach. A solid solution of Ce1−xNixO2−x was firstly formed on the surface of Al2O3 and then activated in H2/Ar at 800 °C. The genesis and properties of the Ce1−xNixO2−x/Al2O3 catalysts were established using X-ray fluorescence analysis, thermal analysis, N2 adsorption, ex situ and in situ X-ray diffraction, Raman spectroscopy, electron microscopy, EDX analysis, and temperature-programmed hydrogen reduction. The performance of Ce1−xNixO2−x/Al2O3 catalysts in biogas conversion was tuned by regulation of the dispersion and reducibility of the active component through variation of content (5–20 wt.%) and composition (x = 0.2, 0.5, 0.8) of Ce1−xNixO2−x as well as the mode of its loading (co-impregnation (CI), citrate sol–gel method (SG)). For the 20 wt.% Ce1−xNixO2−x/Al2O3 catalyst, the rate of the coke formation decreased by a factor of 10 as x increased from 0.2 to 0.8. The optimal catalyst composition (20 wt.% Ce0.2Ni0.8O1.8/80 wt.% Al2O3) and preparation mode (citrate sol–gel method) were determined. At 850 °C, the 20 wt.% Ce0.2Ni0.8O1.8/Al2O3-SG catalyst provides 100% hydrogen yield at full CH4 conversion and 85% CO2 utilization. [ABSTRACT FROM AUTHOR]

For the creation of new highly active and stable catalysts for the complete processing of coal methane, different methods for designing catalytic systems are being applied, including the use of the effects of mutual strengthening of the action of metals and modifying the composition of the supports. Different chemical synthesis approaches were considered for obtaining supported Ni nanoparticles with controllable compositions and sizes. For the citrate sol-gel method, it was found that with an increase in the citric acid/metals molar ratio from 0 to 1, the textural characteristics (specific surface area: 76-100 m2/g) of Ce0.2Ni0.8O12/Al2O3 catalysts, dispersion (average particle size: 10-5 nm) and reducibility (temperature of maximum H2 consumption: 580-530 °C) of the Ni-containing species improved. For calcined in air at 500 °C catalysts it was shown that Ni2+ cations stabilized in NiO or in the Ce-Ni-O solid solution. The proportion of the latter was maximum at a citric acid/metal molar ratio equal to 0.25, which was chosen as the optimal value in the investigated range of 0.25-1.0. An increase in the calcination temperature from 500 to 900 °C contributes to the stabilization of Ni2+ in the Al-Ni-O solid solution, which leads to a slight deterioration in the textural properties of the samples and a significant difficulty in their reducibility. After reductive activation at 800 °C of Ce0.2Ni0.8O12/Al2O3 samples, catalytically active metal Nio nanoparticles of -7 nm in size were formed for effective reforming of coal industry methane into synthesis gas. [ABSTRACT FROM AUTHOR]

Sustained increase in plastic use has placed a significant burden on waste disposal infrastructure. Pyrolysis is the process of decomposing high-molecular-weight compounds by heating waste plastics at 500–1000 °C without oxygen. This process considerably reduces greenhouse gas emissions and has a high alternative energy effect (0.57 TOE ton−1). After a separation process, the oil produced by pyrolysis (C5–C20) can yield naphtha oil (C6–C7). Subsequently, hydrogen can be produced through a reforming reaction of this naphtha oil. Here, we produced hydrogen from waste plastic pyrolysis oil over a Ni/Ce-Zr-Mg/Al2O3 catalyst using a steam reforming process. A model oil combining the major substances of C6 and C7 (hexane, hexene, heptane, heptene, and toluene) was formed. From the reaction products, the hydrogen yield was obtained based on analysis of H2, CO, and CO2 concentrations using gas chromatography. The effect of N2 and O2 addition on hydrogen yield was analyzed within a temperature range of 750–850 °C, steam/carbon (S/C) ratio of 0.6–4, and space velocity of 7600–19,100 h−1. In addition, a durability test was performed using 3 wt.% Ni/Ce-Zr-Mg/Al2O3 catalysts for 100 h; a hydrogen yield of 91.3% was maintained from the refined waste plastic oil. [ABSTRACT FROM AUTHOR]

Ammonia decomposition is a promising method to produce high-purity hydrogen. However, this process typically requires precious metals (such as Ru, Pt, etc.) as catalysts to ensure high efficiency at relatively low temperatures. In this study, we propose using several Ni/GdxCe1-xO2-δ catalysts to improve ammonia decomposition performance by adjusting the support properties. We also investigate the underlying mechanism for this enhanced performance. Our results show that Ni/Ce0.8Gd0.2O2-δ at 600 °C can achieve nearly complete ammonia decomposition, resulting in a hydrogen production rate of 2008.9 mmol.g−1.h−1 with minimal decrease over 150 h. Density functional theory calculations reveal that the recombinative desorption of nitrogen is the rate-limiting step of ammonia decomposition over Ni. Our characterizations indicate that Ni/Ce0.8Gd0.2O2-δ exhibits a high concentration of oxygen vacancies, highly dispersed Ni on the surface, and abundant strong basic sites. These properties significantly enhance the associative desorption of N and strengthen the metal support interactions, resulting in high catalytic activity and stability. We anticipate that the mechanism could be applied to designing additional catalysts with high ammonia decomposition performance at relatively low temperatures. [ABSTRACT FROM AUTHOR]

Although supported Ni is generally considered the most active non-noble metal catalyst for decomposing NH 3 to produce CO x -free H 2 , its activity is not sufficient. Herein, supporting high-loading Ni on SBA-15 is explored to alleviate the low intrinsic activity issue of Ni. SBA-15 supports with tunable textual properties are synthesized to support Ni catalyst for NH 3 decomposition. Characterization shows that Ni catalyst with a loading close to 40 wt% supported on SBA-15 with the largest specific surface area (Ni/SBA-15-80) exhibits a NH 3 decomposition performance much better than those reported on other Ni-based NH 3 decomposition catalysts, resulting from its favorable textural properties and high Ni loading. In addition, Ni/SBA-15-80 shows excellent catalytic stability, with no activity degradation over an 80-h NH 3 decomposition test. This work reveals the importance of textural properties of support and Ni loading to NH 3 decomposition performance and can provide a new idea for synthesizing high-performance NH 3 decomposition catalysts. [Display omitted] • SBA-15 supports with tunable textual properties are synthesized. • Ni particles are supported both on the exterior and interior surfaces of SBA-15. • Ni particles supported on exterior are more efficient for NH 3 decomposition. • Ni/SBA-15 with 40 wt% Ni loading shows excellent NH 3 decomposition performance. [ABSTRACT FROM AUTHOR]

Two nickel alumina catalysts containing 60 wt. % Ni were synthesized by wet impregnation and co-precipitation in order to study the effect of preparation methods on the catalytic efficiency concerning the transformation of sunflower oil into green diesel. The effect of activation temperature on the catalytic efficiency of the most active catalyst was also studied. The catalysts were characterized using various techniques and which were evaluated in the aforementioned reaction using a semi-batch reactor. The catalyst prepared by co-precipitation exhibited a higher specific surface area and smaller mean crystal size of the nickel nanoparticle (higher nickel metallic surface). These justify its higher efficiency with respect to the corresponding catalyst synthesized by wet impregnation. The increase in the activation temperature from 400 to 600 °C increased the size of the nickel nanoparticles through sintering, thus destroying the small pores. These led to a decrease in the nickel surface and specific surface area and, thus, to a decrease in the catalytic efficiency. The optimization of the reaction conditions over the most active catalyst (prepared by co-precipitation and activated at 400 °C) leads to the complete transformation not only of the sunflower oil (edible oil) but also of waste cooking oil (non-edible oil) into green diesel. The liquid produced after the hydrotreatment for these two feedstocks for 7 h, at H2 pressure 40 bar and temperature 350 °C using 100 mL of oil and 1 g of catalyst was composed of 97 and 96 wt. % of green diesel, respectively. [ABSTRACT FROM AUTHOR]

Greenhouse gases, the main cause of global warming, are generated largely in the energy sector. As the need for technology that has reduced greenhouse gas emissions while producing energy is on an increase, CCU technology, which uses CO2 to produce CH4 (SNG energy, synthetic natural gas), is drawing attention. Thus, the reaction for converting CO2 to CH4 at a specific temperature using a catalyst is CO2 methanation. The field of CO2 methanation has been actively studied, and many studies have been conducted to enhance the activity of the catalysts. However, there is a lack of research on the variables that may appear when CO2 methanation is attempted using emissions containing CO2 generated from industrial fields and bio-plants. According to previous studies, it is reported that realistic feed gases from gasification or biomass plants contain a significant amount of CO. this study is a follow-up study focused on the application of CO2 methanation in various real processes. In the CO2 methanation reaction, a study was conducted on the catalyst efficiency and durability of CO gas that can coexist in the inlet gas rather than CO2 and H2 gas. The CO2 methanation activity was observed at 200–350 °C when 0–15% CO coexisted using the Ni-Ce-Zr catalyst, and the operating variables were set for optimal SNG production. As a result of adjusting the ratio of inlet gas to increase the yield of CH4 in the produced gas, the final CO2 conversion of 83% and CO conversion of 97% (with 15% CO gas at 280 °C) were obtained. In addition, catalytic efficiency and catalyst surface analysis were performed by exposing CO gas during the CO2 methanation reaction for 24 h. It showed high activity and excellent stability. The results of this study can be used as the basic data when applying an actual process. [ABSTRACT FROM AUTHOR]

CO 2 and CH 4 are converted to syngas by dry reforming of methane (DRM) reaction. This research investigated the effects of the Mg promoter on Al 2 O 3 -supported Ni catalysts and Mg calcination temperature on the DRM performance in a parallel plate dielectric barrier discharge reactor. The Mg promoter played a crucial role in the DRM performance, as increasing the Mg calcination temperature from 700 °C to 800 °C significantly improved the DRM performance and catalyst properties, including increased specific surface area, decreased total acidity, reduced crystallite and particle sizes, and more uniform dispersion of the Ni nanoparticles. Under these conditions, the H 2 and CO selectivity were 77.0 % and 70.7 %, the CH 4 and CO 2 conversion were 25.1 % and 20.6 %, and the energy efficiency was 8.4 %. In addition, the catalyst was associated with a lower coking rate (0.5 mg C/g cat h), a relatively low carbon deposit of 1.5 %, and a carbon loss of 2.8 %, possibly because the weak acidity hindered the Boudouard reaction and CH 4 decomposition. However, increasing the Mg calcination temperature to 900 °C increased the total acidity and Ni particle size, decreasing H 2 and CO selectivities and increasing carbon deposits on the catalyst surface. • CO 2 reforming of CH 4 (DRM) is a promising way to convert greenhouse gases into syngas. • The Ni/Mg–Al 2 O 3 enhances the DRM efficiency and diminishes the carbon formation in the DBD. • Higher Mg calcination temperature of 800 °C improves the catalyst property and DRM efficiency. • DRM performance is considerably enhanced in the DBD by the Ni/Mg–Al 2 O 3 with reduced acidity. • Coking rate, deposited carbon, and carbon loss are all reduced in the DBD by the Ni/Mg–Al 2 O 3. [ABSTRACT FROM AUTHOR]

A rational design of transition metal catalysts to achieve selective hydrogenation of furfural (FFR) to tetrahydrofurfuryl alcohol (THFA) under facile conditions is a promising option. In this work, a series of Ni catalysts were synthesized by controlled thermal treatment of Ni-based metal-organic frameworks (MOFs), with the purpose of modulating the interface of nickel nanoparticles by the reticular coordination in MOF precursors. The catalytic performance indicates that Ni/C catalyst obtained at 400 °C exhibits efficient conversion of FFR (>99%) and high selectivity to THFA (96.1%), under facile conditions (80 °C, 3 MPa H2, 4.0 h). The decomposition of MOF at low temperatures results in highly dispersed Ni0 particles and interfacial charge transfer from metal to interstitial carbon atoms induced by coordination in MOF. The electron-deficient Ni species on the Ni surface results in an electropositive surface of Ni nanoparticles in Ni/C-400, which ameliorates furfural adsorption and enhances the hydrogen heterolysis process, finally achieving facile hydrogenation of FFR to THFA. [ABSTRACT FROM AUTHOR]

Hydrogen production through the bi-reforming of methane over exsolution-derived Ni catalysts has been studied. Nickel-based catalysts were prepared through the activation of (CeM)1−xNixOy (M = Al, La, Mg) solid solutions in a reducing gaseous medium. Their performance and resistance to coking under the reaction conditions were controlled by regulating their textural, structural, morphological, and redox properties through adjustments to the composition of the oxide matrix (M/Ce = 0–4; x = 0.2–0.8; y = 1.0–2.0). The role of the M-dopant type in the genesis and properties of the catalysts was established. The efficiency of the catalysts in the bi-reforming of methane increased in the following series of M: M-free < La < Al < Mg, correlating with the structural behavior of the nickel active component and the anti-coking properties of the support matrix. The preferred M-type and M/Ce ratio determined the best performance of (CeM)1−xNixOy catalysts. At 800 °C the optimum Ce0.6Mg0.2Ni0.2O1.6 catalyst provided a stable H2 yield of 90% at a high level of CO2 and CH4 conversions (>85%). [ABSTRACT FROM AUTHOR]

[Display omitted] • Zr-Modified Ni-La 2 O 2 CO 3 catalyst efficiently catalyze CO 2 methanation reaction. • Zr4+ incorporated in La 2 O 2 CO 3 lattice enhances Ni dispersion and H 2 activation ability. • Zr modification tunes the surface basic property for promoting CO 2 chemisorption. • Hydrogenation pathways of CO and formate intermediates are co-existed with relatively high activity. • Surface carbonate species are in dynamic reconstruction and interconversion during reaction. A Ni/Zr-La 2 O 2 CO 3 catalyst with interfaces between Ni metal and Zr-modified carbonate support was used for atmospheric CO 2 methanation reaction, exhibiting 81% conversion and 99.6% CH 4 selectivity at 300 °C. The Zr4+ ions incorporated in La 2 O 2 CO 3 lattices properly strengthened the Ni-carbonate interaction for enhancing the Ni dispersion and hydrogen activation ability of the catalyst. The Zr-modification could also tune the surface basic property for promoting the adsorptive dissociation of CO 2. In-situ DRIFT spectra demonstrated that only the hydrogenation reaction pathway of formate intermediates was proceeded in Ni/La 2 O 2 CO 3 -catalyzed CO 2 methanation. As a contrast, the hydrogenation pathways of CO and formate intermediates with relatively high activity were co-existed at the modified Ni-Zr-La 2 O 2 CO 3 interfaces. Furthermore, the isotopic data evidenced that dynamic reconstruction and interconversion of the surface carbonate species occurred in the reaction, which might contribute to the key steps of CO 2 dissociation and intermediates transformation. [ABSTRACT FROM AUTHOR]

Biogas is mainly composed of CH4 and CO2, so it is used as an alternative energy to CH4 with high energy density by separating and removing CO2 from biogas. In addition, it can be utilized by producing synthesis gas (CO and H2) through thermal decomposition of biogas or by synthesizing CH4 by methanation of CO2. The technique of CO2 methanation is a method that can improve the CH4 concentration without CO2 separation. This study aims to produce more efficient methane through CO2 methanation of biogas over Ni-Mg-Al catalyst. So, the effect of Ni contents in catalyst, catalyst reduction temperature, CO2 concentration in biogas, and the initial concentration of CH4 on CO2 conversion rate and CH4 selectivity was investigated. In addition, the effect of increasing CO2 concentration, H2/CO2 ratio, and GHSV (gas space velocity per hour) on H2 conversion, CH4 productivity, and product was investigated. In particular, the durability and stability of CO2 methanation was tested over 60 wt% Ni-Mg-Al catalyst at 350 °C and 30,000/h for 130 h. From the long-term test results, the catalyst shows stability by maintaining a constant CO2 conversion rate of 72% and a CH4 selectivity of 95%. [ABSTRACT FROM AUTHOR]

Ni-based catalysts have been widely studied in reforming methane with carbon dioxide. However, Ni-based catalysts tends to form carbon deposition at low temperatures (≤600 °C), compared with high temperatures. In this paper, a series of Ni/SiO 2 -XG catalysts were prepared by the glycine-assisted incipient wetness impregnation method, in which X means the molar ratio of glycine to nitrate. XRD, H 2 -TPR, TEM and XPS results confirmed that the addition of glycine can increase Ni dispersion and enhance the metal-support interaction. When X ≥ 0.3, these catalysts have strong metal-support interaction and small Ni particle size. The Ni/SiO 2 -0.7G catalyst has the best catalytic performance in dry reforming of methane (DRM) test at 600 °C, and its CH 4 conversion is 3.7 times that of Ni/SiO 2 -0G catalyst. After 20 h reaction under high GHSV (6 × 105 ml/g cat /h), the carbon deposition of Ni/SiO 2 -0.7G catalyst is obviously lower than that of Ni/SiO 2 -0G catalyst. Glycine-assisted impregnation method can enhance the metal-support interaction and decrease the metal particle size，which is a method to prepare highly dispersed and stable Ni-based catalyst. [Display omitted] • Highly dispersed Ni/SiO 2 -XG catalysts were prepared by glycine-assisted impregnation. • The Ni/SiO 2 -0.7G shows high activity and coke resistance during low-temperature DRM. • Excellent activity and coke resistance is due to the high Ni dispersion. • Highly dispersed Ni was stable due to the strong metal-support interaction. [ABSTRACT FROM AUTHOR]

Syngas generated from the catalytic dry reforming of methane (DRM) enables the downstream production of H2 fuel and value-added chemicals. Ni-based catalysts with metal oxides, as both supports and promoters, are widely applied in the DRM reaction. In this review, four types of metal oxides with support confinement effect, metal-support interaction, oxygen defects, and surface acidity/basicity are introduced based on their impacts on the activity, selectivity, and stability of the Ni-based catalyst. Moreover, the structure–performance relationships are discussed in-depth. Finally, conclusive remarks and prospects are proposed. [ABSTRACT FROM AUTHOR]

This review presents well‐defined copper and nickel complexes that have been used in the formation of C−S bonds. The use of Cu or Ni catalysts represent an advantage in comparison with those based on precious metals such as Pd, by being two of the most abundant metals in the earth's crust and thus cheaper. As can be expected the catalytic activity of the different Cu and Ni complexes is strongly dependent on the nature of the ligands used. Thus, multidentate and strong electron‐donating ligands are of common use to design highly active species since such ligands are capable to stabilize species in high oxidation states which are key intermediates in the reaction mechanisms of these processes. This being particular true in the case of copper, where Cu(III) produces unstable and reactive species that require an "extra stabilization" during the reaction mechanism. Hence, the reaction mechanisms using copper and nickel complexes as catalysts are also discussed in this paper, including the role of the different ligands during the catalytic processes. Although there is an increasing number of reports on C−S cross coupling reactions, due to the relevance of this transformation, they are often difficult to reproduce and not of general use since the actual catalytic species are not identified. Thus, we hope that this report will help to promote the search and synthesis of new ligands for the design of more active well‐defined complexes that can be used as catalysts in a more rational manner in the formation of valuable C−S bond‐containing species. [ABSTRACT FROM AUTHOR]

Due to their outstanding physicochemical features, azulene derivatives have been proposed for a wide range of prospective technical applications, including molecular switching, sensors, solar cells, and beneficial biological activities. Transition metal‐catalyzed cross‐coupling reactions are catalytic processes that create carbon–carbon bonds in one of the most straightforward and practical ways possible. These techniques have proven to be a very practical way to functionalize azulene. This study summarizes the progress made in this field by employing Rh, Ir, Ru, Au, Fe, Ni, and Cu catalysts over the last two decades. [ABSTRACT FROM AUTHOR]