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A new type of Ni/Al2O3 self‐supporting catalysts, with high specific surface area, was fabricated by blow‐spinning technology. These Ni/Al2O3 self‐supporting catalysts are hollow flexible fibers and were utilized for the dry reforming of methane. The Ni/Al2O3 catalysts exhibited exceptional catalytic performance, maintaining their activity for over 150‐h at a high temperature of 800°C. The Ni nanoparticles disputed on the hollow fibers demonstrated remarkable resistance to sintering and coking during high‐temperature catalysis. This was a noteworthy feature, as sintering and coking are common challenges faced by catalysts during high‐temperature reactions. Furthermore, the catalysts retained its activity even after a rigorous 150‐h test at 800°C, indicating its durability and stability. Importantly, the Ni/Al2O3 self‐supporting could be successfully reactivated after the test, further highlighting its reusable nature. This study offers promising new avenues for the development of high‐temperature, self‐supporting, and reactivatable catalysts. [ABSTRACT FROM AUTHOR]

The reductive amination of 1,6‐hexanediol with ammonia is one of the most promising green routes for synthesis of 1,6‐hexanediamine. Herein, we developed a phosphorous modified Ni catalyst of Ni−P/Al2O3. It presented satisfactory improved selectivity to 1,6‐hexanediamine in the reductive amination of 1,6‐hexanediol compared to the Ni/Al2O3 catalyst. The phosphorous tended to interact with Al2O3 to form AlPOx species, induced Ni nanoparticle to be flatter, and the decrease of strong acid sites, the new‐formed Ni−AlPOx−Al2O3 interface and the flatter Ni nanoparticle were the key to switch the dominating product from hexamethyleneimine to 1,6‐hexanediamine. This work develops an efficient catalyst for production of 1,6‐hexanediamine from the reductive amination of 1,6‐hexanediol, and provides a point of view about designing selective non‐noble metal catalysts for producing primary diamines via reductive amination of diols. [ABSTRACT FROM AUTHOR]

The sugarcane bagasse (SCB) is the most abundant residue of the sugar and alcohol industry and its use is predominantly in these same industries as a source of energy through burning. This work aims to diversify the proposals for the use of this residue; thus, the use of SCB in the alumina-supported nickel catalysts synthesis was investigated. Two routes were researched using SCB: one, the SCB was used in the alumina (catalytic support) synthesis to obtain the dimensionally predetermined materials and another to get powder materials. The materials were characterized by thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM), N2 physisorption at 77 K, energy-dispersive X-ray spectroscopy (EDX), and hydrogen temperature-programmed reduction (H2-TPR). The presence of SCB in the synthesis of powder materials facilitated the incorporation of nickel particles into the crystalline lattice of the support, decreasing active nickel content for catalytic. On the other hand, the pre-dimensioned catalytic materials exhibited higher crystallinity, lower nickel oxide reduction temperature and greater disposal of active nickel, resulting in higher production of ordered carbon (carbon nanotubes) and H2 COx-free under milder conditions in the methane decomposition reaction at 500 °C for 30 min. [ABSTRACT FROM AUTHOR]

This research investigates the catalytic performance of Ni/Al2O3 in the methanation of CO2 under both thermal and Gliding Arc Discharge (GAD) conditions. Utilizing in situ transmission infrared (TIR) absorption spectroscopy and quadrupole mass spectrometry (QMS), the study analyzes the transient behavior of the plasma-catalyst interaction of CO2 methanation. GAD significantly enhances CO2 conversion and methane production compared to thermal catalysis by CO2 activation, facilitating the rapid transformation of intermediate species on the catalyst surface. Additionally, the study provides a detailed analysis of the electrical characteristics of GAD, capturing voltage and current waveforms that illustrate the transient arc behavior under different phases of the discharge process. The results indicate that lower pressures, while reducing overall CO2 conversion, enhance methane production by suppressing the gas phase CO2 conversion to CO and promoting surface reactions. This comprehensive study not only advances the understanding of plasma-assisted catalysis for CO2 methanation but also highlights the potential of this technology for enhancing greenhouse gas utilization with renewable energy-driven plasma, paving the way for future optimization and industrial application. [ABSTRACT FROM AUTHOR]

Typically, the conversion of methane to value-added hydrocarbon (C2+) via the oxidative coupling of methane is accomplished using high energy due to the temperature of the operation (more than 700 °C). The conversion of methane to C2+ was investigated using a hybrid catalyst consisting of 15 wt% of Ni on Al2O3 (15Ni/Al2O3) and 10–25 wt% of Co supported on Al2O3 (Co/Al2O3) packed as a prioritized layer in a reactor. The effects of operating conditions—different Co loading in Co/Al2O3, reactor pressure and temperature, percentage of O2 in the feed, total feed flow rate, and different weights of Co/Al2O3—on the performance of the hybrid catalyst were studied for the reaction. The highest performance (3.6% C2+ yield with 7.9% C2+ selectivity and 46.3% CH4 conversion) of the hybrid catalyst was achieved at 6 bar, 490 °C, 37.5% of O2 in the feed, a total flow rate of 50 ml/min, and using 0.25 g of 15Ni/Al2O3 and 0.1 g of 15 wt% of Co/Al2O3 (15Co/Al2O3). The prepared catalysts were characterized using X-ray diffractometry, scanning electron microscopy, transmission electron microscopy, N2-sorption analysis, X-ray photoelectron spectroscopy, NH3- and CO2-temperature-programmed desorption, and thermogravimetric analysis to acquire the chemical and physical properties of the catalysts. A time-on-stream testing of the optimized hybrid catalyst for 24 h was performed to determine the stability of the catalyst and revealed that the formation of coke caused rapid deactivation of the catalyst. [ABSTRACT FROM AUTHOR]

This work presents a facile method to fabricate high‐white and robust superhydrophobic film on Al alloy surface. Ni/Al2O3 film with appropriate roughness and high‐white surface is constructed on the Al alloy by a simple chemical bath method via placing the Al alloy into the Ni2+ aqueous solution. Then the surface energy is reduced by spin‐coating the stearic acid (STA) to achieve excellent superhydrophobicity. As expected, the reflectivity, self‐cleaning, corrosion resistivity, and mechanical durability of Al alloy after modification have all displayed dramatic enhancements. The reflectance of the modified Al alloy is far above the pristine Al alloy at all wavelengths (200–2,000 nm). This high‐white film with remarkable reflectivity can effectively reduce its surface temperature and improve visibility in practical applications. Finally, a champion water contact angle of 161° and corrosion resistivity of 97.6% are attained by coating Ni/Al2O3‐STA composite film on Al alloy. The Leeb hardness of superhydrophobic film‐coated Al alloy is enhanced from 325 to 461 after coating superhydrophobic film on Al alloy. This work provides a framework for the development of superhydrophobic Al alloy with high‐whiteness and robustness. [ABSTRACT FROM AUTHOR]

We report a physical mixture of 1 wt% Ru/Al 2 O 3 with 10 wt% Ni/Al 2 O 3 obtained from the NiAl 2 O 4 phase as a highly active, durable, and cost-effective catalyst for the dry reforming of methane (DRM). Since the presence of Ru facilitates the reduction of Ni oxides, resulting in not only enhanced CH 4 conversion but also increased carbon deposits, the optimal formation of metallic Ni sites is a key factor for the mixed Ru-Ni catalyst. Here, we used a NiAl 2 O 4 /Al 2 O 3 catalyst and reduced it with CH 4 under reaction conditions for the limited formation of metallic Ni sites, depending on the reaction temperatures. As a result, this mixed catalyst showed higher performance for DRM than a Ru single catalyst with mild carbon deposits at both low (650 ℃) and high (800 ℃) temperatures taking advantage of improved cost-effectiveness, on top of that, the existence of a Ni catalyst compensated for the loss of activity of a Ru catalyst due to sintering. We also suggest different mechanisms for DRM over the Ru catalyst and Ni catalyst respectively from the results of temperature-programmed surface reaction and CH 4 /CO 2 cycling experiments. [Display omitted] • The presence of Ru facilitates the reduction of Ni oxides. • The optimal formation of metallic Ni sites is a key factor for the Ru-Ni catalyst. • A physical mixture of RuO 2 /Al 2 O 3 with NiAl 2 O 4 /Al 2 O 3 shows the best activity for DRM. [ABSTRACT FROM AUTHOR]

In the present work, the individual or synergistic effect of Ni-based catalysts (Ni/CeO2, Ni/Al2O3) and an eutectic carbonate salt mixture (MS) on the CO2 gasification performance of olive kernels was investigated. It was found that the Ni/CeO2 catalyst presented a relatively superior instant gasification reaction rate (Rco) compared to Ni/Al2O3, in line with the significant redox capability of CeO2. On the other hand, the use of the binary eutectic carbonate salt mixture (MS) lowered the onset and maximum CO2 gasification temperatures, resulting in a notably higher carbon conversion efficiency (81%) compared to the individual Ni-based catalysts and non-catalytic gasification tests (60%). Interestingly, a synergetic catalyst-carbonate salt mixture effect was revealed in the low and intermediate CO2 gasification temperature regimes, boosting the instant gasification reaction rate (Rco). In fact, in the temperature range of 300 to 550 °C, the maximum Rco value for both MS-Ni/Al2O3 and MS-Ni/CeO2 systems were four times higher (4 × 10−3 min−1 at 460 °C) compared to the individual counterparts. The present results demonstrated for the first time the combined effect of two different Ni-based catalysts and an eutectic carbonate salt mixture towards enhancing the CO production rate during CO2 gasification of olive kernel biomass fuel, especially in the devolatilization and tar cracking/reforming zones. On the basis of a systematic characterization study and lab-scale gasification experiments, the beneficial role of catalysts and molten carbonate salts on the gasification process was revealed, which can be ascribed to the catalytic activity as well as the improved mass and heat transport properties offered by the molten carbonate salts. [ABSTRACT FROM AUTHOR]

We developed a rapid aging method for Ni/Al2O3 methanation catalysts mimicking the real aging in the actual application. The method is based on hydrothermal deactivation of the catalyst at 600 or 700 °C, which leads to a catalyst with nearly constant conversion after a much shorter time period compared to normal aging. The hydrothermally aged catalysts are characterized by N2 adsorption, X-ray powder diffraction, temperature-programmed reduction and H2 chemisorption. The catalytic performance of the aged catalysts is comparable to the one of a catalyst deactivated in a long-term measurement with up to 720 h on stream. The time needed for reaching a stable conversion can be diminished by rapid aging by a factor of 10. The investigations also showed that the long-term deactivation is caused by Ni particle sintering and that the support pores limit the Ni particle size. [ABSTRACT FROM AUTHOR]

Alumina oxide supported nickel (Ni/Al2O3) catalysts generally suffer from fast deactivation caused by coking and formation of nickel aluminate (NiAl2O4) in dry reforming of methane (DRM). Herein, for the first time, a self-stabilization mechanism of the Ni/Al2O3 catalyst (with 0.1 wt% Ni loading) was revealed and effectively applied for DRM. Namely, the conversion of catalytically active Ni species into catalytically inert NiAl2O4 spinel in DRM over the Ni/γ-Al2O3 catalyst could be mitigated by repeated reduction-reaction treatments owing to the increasing amount of Ni located on the NiAl2O4 isolation layer rather than the reactive γ-Al2O3. The self-stabilization could be achieved over Ni/α-Al2O3 as well, even with a faster rate, since the NiAl2O4 isolation layer can be directly formed in the first reduction-reaction cycle due to its small surface area and weak metal-support interaction. These observations not only highlight the importance of an isolation layer for protecting the catalyst from deactivation, but also provide a novel and efficient self-stabilization approach for catalytic DRM. [ABSTRACT FROM AUTHOR]

[Display omitted] • Lower pressure favors deoxygenation, which occurs only at higher temperatures. • Benzene is formed by dehydrogenation of cyclohexane, not by direct deoxygenation. • Demethylation of anisole occurs due to its reactive adsorption on Al 2 O 3. • Methylation of the aromatic ring accompanies demethylation at lower pressure. Anisole is a model molecule for studying hydrodeoxygenation (HDO) of lignin-derived oxygenates. Here we elucidate its HDO pathway over 10 % Ni/Al 2 O 3 catalyst. Adsorption experiments showed that anisole is adsorbed on the acidic sites of the Al 2 O 3. Anisole adsorption at 200–300 °C is reactive in nature, and results in its demethylation. The catalyst was tested at 100–300 °C, 5–40 bar H 2 pressure. Conversion of 78 % was obtained at 5 bar and 300 °C, restricted by hydrogenation-dehydrogenation equilibrium. HDO mainly starts through the ring-hydrogenation pathway. This is followed by demethoxylation beyond 180 °C. At 5–12 bar, cyclohexane dehydrogenates to benzene. This was confirmed by conducting an HDO experiment with methoxycyclohexane. At lower pressure deoxygenation is favored; and demethylation is accompanied with methylation of the aromatic ring, for temperature >260 °C. Investigation of the initial reaction stages showed that anisole HDO on Ni/Al 2 O 3 catalyst proceeds via two independent pathways i.e., reactive adsorption/(de)methylation and aromatic ring hydrogenation. [ABSTRACT FROM AUTHOR]

In the present work, the individual or synergistic effect of Ni-based catalysts (Ni/CeO2, Ni/Al2O3) and an eutectic carbonate salt mixture (MS) on the CO2 gasification performance of olive kernels was investigated. It was found that the Ni/CeO2 catalyst presented a relatively superior instant gasification reaction rate (Rco) compared to Ni/Al2O3, in line with the significant redox capability of CeO2. On the other hand, the use of the binary eutectic carbonate salt mixture (MS) lowered the onset and maximum CO2 gasification temperatures, resulting in a notably higher carbon conversion efficiency (81%) compared to the individual Ni-based catalysts and non-catalytic gasification tests (60%). Interestingly, a synergetic catalyst-carbonate salt mixture effect was revealed in the low and intermediate CO2 gasification temperature regimes, boosting the instant gasification reaction rate (Rco). In fact, in the temperature range of 300 to 550 °C, the maximum Rco value for both MS-Ni/Al2O3 and MS-Ni/CeO2 systems were four times higher (4 × 10−3 min−1 at 460 °C) compared to the individual counterparts. The present results demonstrated for the first time the combined effect of two different Ni-based catalysts and an eutectic carbonate salt mixture towards enhancing the CO production rate during CO2 gasification of olive kernel biomass fuel, especially in the devolatilization and tar cracking/reforming zones. On the basis of a systematic characterization study and lab-scale gasification experiments, the beneficial role of catalysts and molten carbonate salts on the gasification process was revealed, which can be ascribed to the catalytic activity as well as the improved mass and heat transport properties offered by the molten carbonate salts.

The conversion of 5-hydroxymethylfurfural (HMF) to 1-hydroxy-2,5-hexanedione (HHD) represented a typical route for high-value utilization of biomass. However, this reaction was often catalyzed by the noble metal catalyst. In this manuscript, W promoted Ni/Al2O3 was prepared as a noble-metal-free catalyst for this transformation. The catalysts were characterized by XRD, XPS, NH3-TPD, TEM, and EDS-mapping to study the influence of the introduction of W. There was an interaction between Ni and W, and strong acid sites were introduced by the addition of W. The W promoted Ni/Al2O3 showed good selectivity to HHD when used as a catalyst for the hydrogenation of HMF in water. The influences of the content of W, temperature, H2 pressure, reaction time, and acetic acid (AcOH) were studied. NiWOx/Al2O3-0.5 (mole ratio of W:Ni = 0.5) was found to be the most suitable catalyst. The high selectivity to HHD was ascribed to the acid sites introduced by W. This was proved by the fact that the selectivity to HHD was increased a lot when AcOH was added just using Ni/Al2O3 as catalysts. 59% yield of HHD was achieved on NiWOx/Al2O3-0.5 at 393 K, 4 MPa H2 reacting for 6 h, which was comparable to the noble metal catalyst, showing the potential application in the production of HHD from HMF.

[Display omitted] • 1. Proposed the "Ni-NiO synergistic effect" to achieve optimal activity and stability in CO methanation reaction. • 2. Synergistic effect of Ni and NiO reduces the overall reaction system energy barrier. • 3. Hydrogen reduction regulates the dimensions and valence states of Ni species in Ni/Al catalysts. The synthesis of methane from syngas represents a pivotal technology in the artificial synthesis of natural gas, with the study of methanation catalysts being a fundamental aspect of this process. Extensive research has focused on CO methanation using Ni/Al 2 O 3 catalysts; however, enhancements in catalyst stability and low-temperature activity are still required. This research investigated the structure of Ni/Al 2 O 3 under H 2 reduction at varying temperatures and the catalytic performance in natural gas synthesis (SNG) through CO methanation. It was observed that a higher reduction temperature resulted in nickel species agglomeration. Notably, Ni catalysts reduced at 600 °C demonstrated optimal CO conversion and CH 4 selectivity under the tested conditions. Characterization studies uncovered a synergistic effect between Ni and NiO species, which was most effective for catalytic activity under hydrogen reduction at 600 °C but only at an appropriate reduction temperature. These insights are significant for the advancement of Ni/Al 2 O 3 methanation catalysts in natural gas production. [ABSTRACT FROM AUTHOR]

[Display omitted] • A mechanism for sulfur poisoning the Ni/Al 2 O 3 catalyst was proposed. • The main factor accelerating catalyst poisoning is the migration of elemental S. • The catalyst adding 1.0% SiO 2 exhibits improved sulfur tolerance. • Smaller Ni particles are more sulfur-tolerant than larger ones. Dry reforming of methane (DRM) is the method to convert two greenhouse gases to synthesis gas. The nickel-based catalysts used in the DRM are extremely easily poisoned by H 2 S in the feed gas, however, the associated poisoning process is not clear. In this work, a mechanism for poisoning the Ni/Al 2 O 3 catalyst by elemental sulfur migration was proposed, and silica was added to the catalyst to prolong the sulfur tolerance of the catalyst. From the characterizations of the catalyst with different methods, it was noted that the main factor accelerating catalyst poisoning was the formation and migration of elemental sulfur. The catalyst Ni/Al 2 O 3 with 1.0 % SiO 2 exhibited improved sulfur tolerance. The addition of SiO 2 inhibits the growth of Ni particles during the reduction process, and the smaller Ni particles lead to less coke and a longer period of sulfur tolerance. [ABSTRACT FROM AUTHOR]

In this work, the performance of a series of nickel catalysts supported on alumina containing the promoters Mg, Mn, Ce and P was evaluated against the dry reforming of methane (DRM). Alumina support was obtained quickly and simply through the microwave-assisted combustion method using low levels of urea. The catalysts were characterized by XRD, TPR, FTIR and XRD in situ , proving that successive hydration and heat treatment steps during synthesis can generate modifications in the alumina phases, in addition to the formation of aluminate species that are reduced during the catalytic activation step and modify the level of interaction between active and support phases. The catalytic activity test was performed with GHSV = 100 L g−1 h−1 and the formed carbon was quantified by thermogravimetric analysis. The Mn promoter exhibited the highest methane conversion rate during the initial stages of the reaction, in which the presence of MnO 2 favored parallel reactions of methane decomposition. The phosphorus and cerium produced smaller amounts of coke, reducing the carbon generated due to the interaction of promoters with carbon on the surface of the catalytic sites. The Mg increases the interaction of the active phase with the support. [Display omitted] • Microwave-assisted selfcombustion with low fuel content was efficient in synthesis of alumina in a quick one-step method. • Sequential wet-impregnation steps and thermal treatment change the crystalline structure of support Al 2 O 3. • Phosphorus presence as promoter decrease the reduction temperature of active phase and produced H 2 /CO ratio nearly one. • The manganese promoter increase the conversion rate of CH 4 and CO 2 in catalytic test. • Cerium insertion improved catalytic stability over 20h in GHSV = 100 L/g.h. [ABSTRACT FROM AUTHOR]

Nickel–alumina cryogel was prepared from aluminium sec-butoxide and nickel acetate by one-pot sol–gel processing and subsequent freeze drying. Catalysis for CO2 reforming of CH4 and carbon formation during the reforming were examined on the cryogel by comparison to those on the corresponding xerogel catalyst prepared by employing normal drying in order to evaluate the utility of the freeze drying. While the catalytic activity was not different significantly between the two sol–gel catalysts, carbon formation was suppressed more markedly on the cryogel than on the xerogel. The surface area and pore volume of the catalyst after the calcination and after the subsequent high-temperature reduction were larger for the cryogel than for the xerogel. XRD, UV-visible, FT-IR, and Raman spectra suggested the principal formation of NiAl2O4 after the calcination for both catalysts, whereas the presence of NiO, leading finally to large nickel particle, was suggested for the xerogel although it may be a small portion. Mean diameter of nickel particles estimated from TEM and XRD showed smaller size for the cryogel than for the xerogel. These results suggested that role of the freeze drying was to improve structural and textual properties of alumina gel as well as to give finer nickel particles throughout the gel. Highlights: Ni/Al2O3 cryogel was synthesized by one-pot sol-gel processing and subsequent freeze drying. Large surface area and pore volume were obtained after calcination and subsequent reduction. Fine nickel particles were formed on alumina after the reduction. Carbon formation during CO2 reforming of CH4 was suppressed. [ABSTRACT FROM AUTHOR]

• Ni/Al 2 O 3 is superior in activity to unsupported Ni for NO 3 – reduction. • Selectivity to undesirable ammonia is around 45 % for Ni/Al 2 O 3. • NO 3 – reduction over Ni/Al 2 O 3 does not proceed through NO 2 – as an intermediate. • Ni/Al 2 O 3 has at least two active sites formed by low and high temperature reduction. • The two active sites show different catalytic natures for NO 3 – reduction. Pollution of groundwater with NO 3 – is a serious problem in the world. While catalytic reduction of NO 3 – over Pd-bimetallic catalysts including Cu-Pd and Sn-Pd is a promising method for purification of the groundwater, the use of precious metal is a major obstacle for practical applications. In the present study, we applied Ni/Al 2 O 3 for the catalytic reduction of NO 3 – and compared the catalytic performance with that of unsupported Ni catalyst. The reaction rate over 5 wt.% Ni/Al 2 O 3 was about 5 times higher than that of the unsupported Ni catalyst, based on unit weight of catalyst. While the unsupported Ni catalyst was completely deactivated in low partial pressure of H 2 (=0.75 atm) and high concentration of NO 3 – (=800 ppm), Ni/Al 2 O 3 was still active even under less reductive conditions ([NO 3 – 0 = 800 ppm and P(H 2) =0.5 atm). The unsupported Ni catalyst had the Ni0 particles formed by the reduction of NiO with H 2 at 310–420 °C. On the other hand, 5 wt.% Ni/Al 2 O 3 possessed the Ni0 particles formed from NiAl 2 O 4 on Al 2 O 3 by the reduction with H 2 above 450 °C. It is plausible that those Ni0 particles had different properties, giving different catalytic properties. The Ni loadings for Ni/Al 2 O 3 had a significant impact on the catalytic properties. The reaction orders with respect to both NO 3 – and H 2 were 0.8 for 5 wt.% Ni/Al 2 O 3 , while those were 0 and –0.2, respectively, for 10 wt.% Ni/Al 2 O 3. On 10 wt.% Ni/Al 2 O 3 , there were two kinds of the Ni° particles, which were formed by low (310-420 °C) and high (above 450 °C) temperature H 2 reductions. Unlike the Pd-bimetallic catalysts, the reduction of NO 3 – over Ni/Al 2 O 3 did not proceed through NO 2 –. [ABSTRACT FROM AUTHOR]

The precursors of Ni/Al2O3 catalysts with different metal contents (2–10 wt % Ni) and calcination temperatures were obtained by wet impregnation. Their composition and physicochemical properties were determined by low-temperature nitrogen adsorption, atomic absorption spectroscopy, scanning electron microscopy, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy (XPS), and temperature-programmed reduction (TPR) with hydrogen. The formation of free and chemically bound forms of nickel was studied by TPR-H2. Calcination above 400°C leads to complete binding of nickel with Al2O3, forming nickel–aluminum spinel. According to TPR-H2, free NiO appears in the samples calcinated at 550°C only at 10% Ni. The stability of the reduced catalysts to oxidation in air and the effect of the temperature of treatment with hydrogen on the reduction of the nickel forms bonded with the support were determined. The XPS and TPR studies showed that the oxidation of reduced nickel in air led to a transition from Ni2+ forms tightly bound with support to weakly bound forms that are more easily reduced. The catalytic action in hydrodechlorination of chlorobenzene (CB HDC) of the samples that differed in the ratio of weakly and tightly bound Ni forms was considered. The spinel forms that are nearly inactive in chlorobenzene hydrodechlorination can be reduced with hydrogen to form more active Ni0 sites under the reaction conditions. The active sites obtained by the reduction of Ni2+ forms weakly bound to the support are stable under chlorobenzene hydrodechlorination conditions. [ABSTRACT FROM AUTHOR]

The effects of hydrogen addition on the formation of hydrogen and carbon from methane decomposition over Ni/Al2O3 were studied. The results show that the added hydrogen in methane greatly affects the methane conversion, hydrogen output rate, and the properties of the carbon deposits on the surface of the Ni/Al2O3. The methane conversion and hydrogen output rate are significantly improved by the addition of hydrogen. As the flowrate of hydrogen increases from 0 to 25 mL/min, the initial activity of Ni/Al2O3 decreases sharply, while the stability increases first and then decreases due to the suppression of hydrogen to CH4 decomposition in the thermodynamics equilibrium. When the addition flowrate of the hydrogen is 15 mL/min, that is, 37.5% of the methane flowrate, a much higher methane conversion and the best stability of Ni/Al2O3 are obtained. The addition of a specific amount of hydrogen benefits the methane decomposition; however, the excessive hydrogen will suppress the decomposition. Most of the carbon that deposits on the surface of Ni/Al2O3 is filamentous carbon when hydrogen is added to the methane, however, encapsulated carbon is mainly produced when no hydrogen is added. In addition, the formation of encapsulated carbon, which deactivates the catalyst, is inhibited by the added hydrogen. [ABSTRACT FROM AUTHOR]

[Display omitted] • Crystal plane regulative hydrogen spillover strategy was developed on Al 2 O 3. • Ni/Al 2 O 3 (1 1 1) exhibited a high turnover number in reductive amination. • Hydrogen migration prevented Ni sites from hydrogen poisoning. • Adsorption and activation of NH 3 for reductive amination was enhanced. • Ammonolysis of intermediate Schiff-base to primary amine was accelerated. Hydrogen spillover had played a significant role in catalytic processes involving reducible oxide supported metal catalyst and hydrogen molecule. Herein, crystal plane regulative hydrogen spillover strategy for the effective reductive amination on Ni/Al 2 O 3 was developed. A rod-like alumina supported Ni catalyst with primarily external (1 1 1) facets was prepared. In the presence of NH 3 and H 2 , Ni/Al 2 O 3 (1 1 1) exhibited a turnover number of 30.4 h−1, which was 136-fold higher than that of Ni/Al 2 O 3 (1 1 0) in the reductive amination of furfural to furfuryl amine. For the Ni/Al 2 O 3 (1 1 1) catalyst, Al 2 O 3 (1 1 1) facets exhibited strong Lewis acidity, resulting in an enhanced H affinity of Al 2 O 3 (1 1 1) and a positively charged of Ni through electronic interaction. It was revealed that strong H affinity of Al 2 O 3 (1 1 1) and positively charged Ni sites significantly promoted hydrogen migration from Ni surface to Al 2 O 3 (1 1 1) facets, which effectively prevented the Ni sites from hydrogen poisoning and enhanced the adsorption and activation of NH 3 and intermediates for reductive amination. Consequently, the activation energy of Schiff base reductive ammonolysis was obviously reduced, resulting in high inherent activity for furfural reductive amination to furfuryl amine. This work developed a new strategy for high efficiency reductive amination catalyst in terms of hydrogen spillover effect. [ABSTRACT FROM AUTHOR]

Abstract The hydrogenation of acetylenic contaminates into valuable chemicals is a clean and promising process for minimizing the waste and improving economic benefits. In this work, the enhancement of Ag on Ni/Al 2 O 3 catalyst for acetylenic stream hydrogenation was studied by multiple characterization techniques and DFT calculations. The addition of Ag shows negligible effect on the particle size of Ni nanoparticles, but modifies the electronic and geometric structures of Ni active sites by electron transfer and site isolation, respectively, which weaken the adsorption strength of Ni sites for reactants and intermediates and thus suppress their polymerization. Due to the enhancement of Ag, Ni-Ag/Al 2 O 3 catalyst exhibited excellent performance for the hydrogenation of acetylenic contaminates for a 700-h evaluation: ∼99.8% of total conversion and ∼98% of butane selectivity. Moreover, besides the high-quality products of butane, the results of simulation by Aspen Plus simulator indicates that 98% of benzene in acetylenic contaminates can be recovered as a chemical product with 99% of purity. This Ni-Ag/Al 2 O 3 catalyzed hydrogenation process for acetylenic contaminates exhibits a potential of substantial economic and green benefits for the industrial production. Highlights • Ni-Ag/Al 2 O 3 catalytic conversion of acetylenic contaminants into valuable product was explored. • The performance of Ni-Ag/Al 2 O 3 catalyst was greatly enhanced compared to Ni/Al 2 O 3. • The enhancement of Ag was elucidated by multiple characterization techniques and DFT calculations. • In the proposed process, the yield of target products was simulated and investigated by Aspen Plus simulator. [ABSTRACT FROM AUTHOR]

The most important products that can be produced from syngas are methanol, dimethyl ether and light olefins (ethylene and propylene). The light olefins are the most important syngas products, because many of the chemicals are produced from them. The aim of this work was to study the olefins production from syngas over Al2O3-supported Ni-Cu nano-catalysts. In addition, the effect of various factors such as catalyst on olefin production and CO conversion has been investigated. The concentration of heavier olefins (C5) was greater than the remaining olefins, since the rate of reactions must be increased to form C1 to C4. In the case of a Ni/Al2O3 catalyst, C1 and C4 was initially increased and then decreased with an increase in Ni loading from 0% to 15%. [ABSTRACT FROM AUTHOR]

Abstract The composite Ni/Al 2 O 3 -SiC catalyst was designed and synthesized for hydrogen production from propane partial oxidation. Through the composite of high thermal conductivity SiC and porous solid acid Al 2 O 3 , it improved the shortcoming of sintering and inactivation of high-temperature reaction for Ni-based catalysts. The samples were characterized by X-ray diffraction, N 2 physical adsorption, scanning electron microscopy, transmission electron microscopy, and thermogravimetric analysis etc. From the results, the SiC doped catalyst exhibited superior catalytic properties for hydrogen production by propane partial oxidation. By doping SiC with high thermal conductivity to Al 2 O 3 support, the catalyst was improved for sintering and carbon deposition resistance and reducing the aggregation of Ni active sites reflected by improving the stability of hydrogen production. [ABSTRACT FROM AUTHOR]

Performance of Ni/Al2O3 catalysts (10 wt.% Ni) in steam reforming of n-butane was investigated in terms of n-butane conversion, selectivity to hydrogen and hydrogen yield. The process was carried out in a fixed-bed tubular reactor at 650 °C and atmospheric pressure. The volumetric flow rates of n-butane and steam were 0.1 mL/min and 0.6 mL/min, respectively. The catalysts were prepared by precipitation-sedimentation method at different precipitation, drying and calcination temperatures as well as precursor types. Synthesized catalysts were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and BET analyses. It was found that Ni- Nitrate as the precursor was more favorable than the other. Mathematical predictive formulas were generated for responses by Design Expert software. Also, the optimum condition of the catalyst preparation was obtained by using the response surface methodology (RSM). Ultimately, it was concluded that the overall optimum condition were: Tprecipitation= 30°C, Tdrying= 115°C, Tcalcination= 700°C .

Ni-based catalysts as replacement for noble metal catalysts are of particular interest in the catalytic conversion of biomass due to their cheap and satisfactory catalytic activity. The Ni/SiO2 catalyst has been studied for the hydrogenolysis of glycerol, and doping with phosphorus (P) found to improve the catalytic performance significantly because of the formation of Ni2P alloys. However, in the present work we disclose a different catalytic phenomenon for the P-doped Ni/Al2O3 catalyst. We found that doping with P has a significant effect on the state of the active Ni species, and thus improves the selectivity to 1,2-propanediol (1,2-PDO) significantly in the hydrogenolysis of glycerol, although Ni-P alloys were not observed in our catalytic system. The structure and selectivity correlations were determined from the experimental data, combining the results of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), hydrogen temperature-programmed reduction (H2-TPR) and ammonia temperature-programmed desorption (NH3-TPD). The presence of NiO species, formed from P-doped Ni/Al2O3 catalyst, was shown to benefit the formation of 1,2-PDO. This was supported by the results of the Ni/Al2O3 catalyst containing NiO species with incomplete reduction. Furthermore, the role the NiO species played in the reaction and the potential reaction mechanism over the P-doped Ni/Al2O3 catalyst is discussed. The new findings in the present work open a new vision for Ni catalysis and will benefit researchers in designing Ni-based catalysts.

Liquid phase hydrodearomatization (HDA) of monoaromatic model molecules (toluene, indane, tetralin, cyclohexylbenzene, nonylbenzene) from naphtha and middle distillate was conducted at a temperature of 170 °C and a pressure of 100 bar over Ni/Al2O3 in order to compare their reactivity separately and in mixture. A reactivity scale was established where toluene is more reactive than tetralin, indane, cyclohexylbenzene and nonylbenzene. The difference of reactivity is due to steric hindrance of the substituent and its electronic effect. In all cases, the fully hydrogenated product is the main product. Toluene hydrodearomatization is inhibited by the presence of another monoaromatics. This inhibition effect is more significant with indane than with cyclohexylbenzene and nonylbenzene and tetralin corresponding to competitive adsorptions and highlighted by kinetic modeling.Graphical Abstract: [ABSTRACT FROM AUTHOR]

Modelling and optimization of chemical reactors require a good understanding of the reactions mechanism with the corresponding kinetic description. Therefore, high quality kinetic data are needed, which can be challenging to obtain, especially for fast and highly exothermic reactions such as the CO2 methanation. Traditionally, kinetic studies rely on measuring the exit gas composition (1 data point per species and experiment) using differential reactors with diluted catalyst beds and reactants to avoid temperature change. Therefore, an optically accessible catalytic channel reactor was designed, which allowed for the chance to gather spatially-resolved information on axial gas composition and catalyst surface temperature, specifically by means of a movable sampling capillary and shortwave infrared-thermography (SWIR), respectively. A catalyst coated plate was placed at the bottom of the channel, while a set of two quartz glass plates covers the top. In the current study 35 data points per gas species were collect for 1 experiment conducted under laminar flow conditions at 425 °C. Catalyst surface temperature determined via a SWIR camera was not influenced by polyatomic molecules partaking in the reaction and thus did not falsify the kinetic data. The catalyst mass distribution along the reactor axis was determined, enabling the development of a correct reactor model for kinetic parameter estimation and model discrimination. [ABSTRACT FROM AUTHOR]

The synergy between plasma and catalysis has been long noticed, but how to further improve the synergy remains challenging. Herein, a series of Ni/Al 2 O 3 catalysts with different Al 2 O 3 morphologies (nanorod-NR, nanosheet-NS and spherical flower-SF) were investigated for plasma-assisted dry reforming of methane (DRM). Surface properties, metal dispersion, and discharge properties were modulated, and thereby affected catalytic performance and plasma-catalysis synergistic efficiency. Sufficient surface hydroxyls on NS-Al 2 O 3 dispersed and anchored Ni centers via forming Ni-O-Al linkages, and the specific two–dimensional structure facilitated charge deposition and generated a stronger local electric field. Accordingly, the Ni/NS-Al 2 O 3 catalyst showed the best catalytic activity & stability and energy efficiency in the reaction. The present study provides a promising strategy to enhance the synergy and energy efficiency of plasma-catalysis by coupling highly dispersed Ni active centers and specific structures of Al 2 O 3 substrate to obtain an efficient catalyst motivating the DRM reaction under mild conditions. [Display omitted] • Ni/Al 2 O 3 catalysts with different Al 2 O 3 morphologies were investigated for plasma-assisted DRM. • The dispersion mechanism of Ni species on different Al 2 O 3 nanostructures were revealed. • Sufficient surface hydroxyls on NS-Al 2 O 3 facilitated Ni dispersion via forming Ni-O-Al linkages. • Coupling highly dispersed Ni and nanosheet structure boosted charge deposition and higher energy efficiency was obtained. • Superior stability performance was exhibited over the Ni/NS-Al 2 O 3 catalyst in plasma-catalytic DRM reaction. [ABSTRACT FROM AUTHOR]

Ce-modified Ni/Al2O3 catalysts for methanation of glycerol reforming gases were prepared by impregnation, and characterized by BET, XRD, H2-TPR and CO2-TPD respectively. And the effects of Ce amount, methanation temperature and time-on-stream on the catalytic properties of Ce-modified Ni /AI2O3 in the glycerol reforming gases to methane were also investigated. The results indicated that the introduced Ce species preferentially occupied on the surface of micro-pores of Ni/Al2Os catalysts, inhibited the strong interaction between active Ni species and support AI2O3 to spinel NiAl2O4, and promoted the formation of highly-dispersed active Ni species. Therefore, the Ce-modified Ni/Al2O3 catalysts exhibited a higher catalytic property in methanation. For example, Ni/Al2 CO3 modified by 3 wt % of Ce exhibited an excellent catalytic stability at 275 — 300 °C , received ratios of conversion towards CO and CO2 with above 99% and 75% respectively. It was estimated that 1 kg biomass glycerol could produce 570 L of methane through the steam reforming and methanation according to the results in present work. [ABSTRACT FROM AUTHOR]

Due to the ongoing change of energy supply, the availability of a reliable high-capacity storage technology becomes increasingly important. While conventional large-scale facilities are either limited in capacity respective supply time or their extension potential is little (e.g., pumped storage power stations), decentralized units could contribute to energy transition. The concepts of PtX (power-to-X) storage technologies and in particular PtG (power-to-gas) aim at fixation of electric power in chemical compounds. CO2 hydrogenation (methanation) is the foundation of the PtG idea as H2 (via electrolysis) and CO2 are easily accessible. Methane produced in this way, often called substitute natural gas (SNG), is a promising solution since it can be stored in the existing gas grid, tanks or underground cavern storages. Methanation is characterized by a strong exothermic heat of reaction which has to be handled safely. This work aims at getting rid of extreme temperature hot-spots in a tube reactor by configuring the catalyst bed structure. Proof of concept studies began with a small tube reactor (V = 12.5 cm³3) with a commercial 18 wt % Ni/Al2O3 catalyst. Later, a double-jacket tube reactor was built (V = 452 cm³), reaching a production rate of 50 L/h SNG. The proposed approach not only improves the heat management and process safety, but also increases the specific productivity and stability of the catalyst remarkably. [ABSTRACT FROM AUTHOR]

Steam reforming of commercially available LPG using Ru/Al2O3and Ni/Al2O3catalysts has been studied at temperatures between 573 and 773 K. Ru/Al2O3catalyst showed higher rates of reaction and lower activation energies of the three main components of LPG, compared with Ni/Al2O3. However, Ni/Al2O3catalyst showed a better H2:CH4selectivity. The activation energy of n-butane was the lowest over Ru/Al2O3, whereas over Ni/Al2O3, propane had the lowest activation energy. The activation energy of i-butane was always the highest over both catalysts, which suggests that both catalysts performed better with unbranched molecules. A slight increase in activation energy was observed, when each component of the LPG mixture was studied separately as a pure gas, compared with being mixed in LPG. At a constant temperature of 773 K, hydrogen production yield and H2:CH4selectivity were determined using Ru/Al2O3at different steam:carbon (S:C) ratios and LPG flow rates. It was found that the yield and selectivity increased with the increase in S:C ratio and the decrease in the flow rate. The highest yield of 0.64 was achieved using S:C ratio of 6.5 and a LPG flow rate of 50 mL min−1. The work provides valuable information on steam reforming of pure components of LPG, compared with when they are in the mixture. The comparison is done using conventional steam reforming catalyst, Ni/Al2O3, and compared with Ru/Al2O3. The observed trends and variations in reaction rates, in pure and mixed gases, indicated that the mechanism of steam reforming of a hydrocarbon mixture depends on its composition. [ABSTRACT FROM AUTHOR]

[Display omitted] • Temperature-sensitivity effect of H 2 on catalytic performance was evidenced. • The rapid deactivation of Ni/Al 2 O 3 in N 2 atmosphere was investigated. • The highest graphite selectivity of 84.5 % were obtained at 500 °C in 5 %H 2 atmosphere. This work investigates the conversion of tar model compounds (toluene) to hydrogen and coke at different reaction medium (5 %H 2 or 100 %N 2), aiming at the prolonged catalytic lifetime and high-purity CNTs (carbon nanotubes) production. Temperature-sensitivity effect of H 2 on prolonging catalytic endurance of Ni/Al 2 O 3 and increasing graphite selectivity was intuitively evidenced, in which the minimum dehydrogenation damage of 17.6 % and the highest graphite selectivity of 84.5 % were obtained at 500 °C in 5 %H 2 atmosphere. It is demonstrated that the formation of NiC x crystallite phase is the main reason for the rapid deactivation of the dehydrogenation performance in 100 % N 2 atmosphere, and the prolonged catalytic endurance in 5 %H 2 atmosphere is due to the etching effect of H 2 on reducing NiC x to metallic Ni phase. Based on the decrease of the outer diameter of CNTs and dehydrogenation reaction rate with the increase of reforming temperature, it is established that the mismatch between the optimum consumption of carbon atoms required for CNTs growth and the actual carbon supply at the metal/CNTs interface is the reason for the CNTs growth termination, which exhibits the highest match degree at 500 °C. [ABSTRACT FROM AUTHOR]

Ni- and Cu/alumina powders were prepared and characterized by X-ray diffraction (XRD), scanning electronic microscope (SEM), and N2 physisorption isotherms were also determined. The Ni/Al2O3 sample reveled agglomerated (1 μm) of nanoparticles of Ni (30–80 nm) however, NiO particles were also identified, probably for the low temperature during the H2 reduction treatment (350 °C), the Cu/Al2O3 sample presented agglomerates (1–1.5 μm) of nanoparticles (70–150 nm), but only of pure copper. Both surface morphologies were different, but resulted in mesoporous material, with a higher specificity for the Ni sample. The surfaces were used in a new proposal for producing copper and nickel phthalocyanines using a parallel-plate reactor. Phthalonitrile was used and metallic particles were deposited on alumina in ethanol solution with CH3ONa at low temperatures; ≤60 °C. The mass-transfer was evaluated in reaction testing with a recent three-resistance model. The kinetics were studied with a Langmuir-Hinshelwood model. The activation energy and Thiele modulus revealed a slow surface reaction. The nickel sample was the most active, influenced by the NiO morphology and phthalonitrile adsorption.

This paper investigates the oxidative dehydrogenation of ethane to produce ethylene at low temperatures (500 °C) in metallic structured substrates. To check this point, the FeCrAlloy® monoliths with different channel sizes (289–2360 cpsi) were prepared. The monoliths were coated with a Ni/Al2O3 catalyst (by washcoating of alumina and the latter nickel impregnation) and characterized by Scanning Electron Microscopy and Energy-Dispersive X-ray analysis (SEM-EDX), Temperature-Programmed Reduction (TPR), X-ray Diffraction (XRD) and X-ray Photoelectron Spectroscopy (XPS). The catalytic results showed that all monoliths coated with ~300 mg of catalyst presented similar ethane conversion (15%) at 450 °C. However, the lowest selectivity to ethylene was found for the monolith with the lower channel size and the higher geometric surface area, where a heterogeneous catalyst layer with Ni enriched islands was generated. Therefore, it can be said that the selectivity to ethylene is linked to the distribution of Ni species on the support (alumina). Nevertheless, in all cases the selectivity was high (above 70%). On the other hand, the stability in reaction tests of one of the coated monoliths was done. This structured catalyst proved to be more stable under reaction conditions than the powder catalyst, with an initial slight drop in the first 8 h but after that, constant activity for the 152 h left.

• The performance of Y promoted Ni/Al 2 O 3 catalysts was investigated in SRM process. • Ni loading, Y loading, and support structure in SRM reaction were assessed. • 20Ni-3.0Y/HAl exhibited the best activity and stability in the SRM process. • 20Ni-3.0Y/HAl showed the minimum decreased conversion over 12 h SRM reaction. • Y improved the BET surface area of Ni/Al 2 O 3 catalysts. This work deals with the application of Y-promoted Ni-based catalysts supported on both bulk and hollow Al 2 O 3 supports with spherical shape in the steam reforming of methane (SRM) process. For evaluating the influence of Ni and Y loadings, 15, 20, and 25 wt% Ni and 1.5, 3.0, and 4.5 wt% Y were loaded on both alumina supports. Furthermore, for enhancing the stability and activity of SRM Ni-based catalysts, reaction temperature (600, 650, and 700 °C) and steam to methane (S/M) molar ratio (1.5 to 3.0) are also adjusted in this research. Various characterizing techniques listed as X-ray powder diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), transmission electron microscope (TEM), N 2 adsorption/desorption, energy dispersive X-ray spectroscopy (EDX), field emission scanning electron microscopy (FESEM), H 2 temperature programmed reduction (H 2 -TPR), and temperature programmed oxidation (TPO) were employed on the fresh and used catalyst. Improvements in metal dispersion, catalytic performance, and long-time stability in SRM were achieved with the aim of a hollow Ni-Y-Al catalyst. As a result, 20Ni-3.0Y/HAl depicted the highest methane conversion of 95.77 %, hydrogen yield of 97.74 %, and H 2 /CO molar ratio of 6.61 at 700 °C, which is probably due to the higher surface area of hollow alumina support in comparison with bulk one. [ABSTRACT FROM AUTHOR]

Energy from woody biomass could supplement renewable energy production towards the replacement of fossil fuels. A multi-stage process involving gasification of wood and then catalytic transformation of the producer gas to synthetic natural gas (SNG) represents progress in this direction. SNG can be transported and distributed through the existing pipeline grid, which is advantageous from an economical point of view. Therefore, CO methanation is attracting a great deal of attention and much research effort is focusing on the understanding of the process steps and its further development. This short review summarizes recent efforts at Paul Scherrer Institute on the understanding of the reaction mechanism, the catalyst deactivation, and the development of catalytic materials with benign properties for CO methanation.

Due to the ongoing change of energy supply, the availability of a reliable high-capacity storage technology becomes increasingly important. While conventional large-scale facilities are either limited in capacity respective supply time or their extension potential is little (e.g., pumped storage power stations), decentralized units could contribute to energy transition. The concepts of PtX (power-to-X) storage technologies and in particular PtG (power-to-gas) aim at fixation of electric power in chemical compounds. CO2 hydrogenation (methanation) is the foundation of the PtG idea as H2 (via electrolysis) and CO2 are easily accessible. Methane produced in this way, often called substitute natural gas (SNG), is a promising solution since it can be stored in the existing gas grid, tanks or underground cavern storages. Methanation is characterized by a strong exothermic heat of reaction which has to be handled safely. This work aims at getting rid of extreme temperature hot-spots in a tube reactor by configuring the catalyst bed structure. Proof of concept studies began with a small tube reactor (V = 12.5 cm3) with a commercial 18 wt % Ni/Al2O3 catalyst. Later, a double-jacket tube reactor was built (V = 452 cm3), reaching a production rate of 50 L/h SNG. The proposed approach not only improves the heat management and process safety, but also increases the specific productivity and stability of the catalyst remarkably.

Autothermal reforming (ATR) of methane was carried out over nanocrystalline Al2O3-supported Ni catalysts with various Ni loadings. Mesoporous nanocrystalline γ-Al2O3 powder with high specific surface area was prepared by the sol-gel method and employed as support for the nickel catalysts. The prepared samples were characterized by X-ray diffraction, Brunauer-Emmett-Teller, temperature-programmed reduction, temperature-programmed hydrogenation, and scanning electron microscopy techniques. It is demonstrated that the methane conversion increased with increasing in Ni content and that the catalyst with 25 wt % Ni exhibited the highest activity and a stable catalytic performance in the ATR process, with a low degree of carbon formation. Furthermore, the effects of the reaction temperature, the calcination temperature, the steam/CH4 and O2/CH4 ratios, and the gas hourly space velocity on the catalytic performance of the 25 % Ni/Al2O3 catalyst were investigated. [ABSTRACT FROM AUTHOR]

The thermal residual stress in the fabrication of functionally graded material (FGM) systems can give rise to various mechanical failures. For a FGM system under a given fabrication environment, the thermal residual stresses are determined by the spatial distribution of its constituent components. In this study, we optimize a Ni/Al2O3 FGM plate aiming at minimizing the thermal residual stresses through controlling its compositional distribution. Material properties are graded in the thickness direction following a power law distribution in terms of the volume fractions of constituents (P-FGM). An analytical model and a hybrid genetic algorithm with the pattern search are employed to predict and to minimize the thermal residual stresses, respectively. Simulation results show that an optimal design of the FGM plate could help fulfill its potential in reducing the thermal residual stresses. [ABSTRACT FROM AUTHOR]

Ni-based catalysts as replacement for noble metal catalysts are of particular interest in the catalytic conversion of biomass due to their cheap and satisfactory catalytic activity. The Ni/SiO2 catalyst has been studied for the hydrogenolysis of glycerol, and doping with phosphorus (P) found to improve the catalytic performance significantly because of the formation of Ni2P alloys. However, in the present work we disclose a different catalytic phenomenon for the P-doped Ni/Al2O3 catalyst. We found that doping with P has a significant effect on the state of the active Ni species, and thus improves the selectivity to 1,2-propanediol (1,2-PDO) significantly in the hydrogenolysis of glycerol, although Ni-P alloys were not observed in our catalytic system. The structure and selectivity correlations were determined from the experimental data, combining the results of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), hydrogen temperature-programmed reduction (H2-TPR) and ammonia temperature-programmed desorption (NH3-TPD). The presence of NiO species, formed from P-doped Ni/Al2O3 catalyst, was shown to benefit the formation of 1,2-PDO. This was supported by the results of the Ni/Al2O3 catalyst containing NiO species with incomplete reduction. Furthermore, the role the NiO species played in the reaction and the potential reaction mechanism over the P-doped Ni/Al2O3 catalyst is discussed. The new findings in the present work open a new vision for Ni catalysis and will benefit researchers in designing Ni-based catalysts. [ABSTRACT FROM AUTHOR]

The magnetically separable Ni/NiO nanocatalyst was synthesized for hydrogenation of substituted aromatics in renewable biokerosene fuel. The catalyst showed acidity of 0.21 mmol/g and ferromagnetic character. The catalytic activity was compared with the traditional noble metal-based catalysts (Pd/NiO, Ni/Al 2 O 3 , Pd/Al 2 O 3 , and Pt/Al 2 O 3). Among all the catalysts, the non-noble metal catalysts (Ni/NiO, Ni/Al 2 O 3) showed complete conversion (100%) of aromatics to cycloalkanes at the optimal reaction conditions of temperature = 150 °C, Pressure = 100 bar, catalyst mass = 0.6 g, and reaction time = 14 hr. The activation energy for the Ni/NiO catalyst was 51 kjmol−1, similar to Ni/Al 2 O 3 (53 kjmol−1). The coke deposition was much lower for Ni/NiO (<1 wt%) which was lower than Ni/Al 2 O 3 catalyst. Furthermore, FTIR analysis also confirmed the absence of any observable carbon deposition in the used Ni/NiO catalyst while spent Ni/Al 2 O 3 showed prominent peaks due to deposited carbonaceous compounds. [Display omitted] • Non-noble metal-based support free catalyst; Ni/NiO was used to convert aromatics to cycloalkanes. • Magnetically separable and cost-effective Ni/NiO catalyst exhibited high stability and negligible coke deposition. • A reaction pathway for transforming aromatics present in bio-kerosene fuel to cycloalkane was proposed. • Complete conversion of aromatics into cycloalkanes at moderate temperature and high pressure was achieved. [ABSTRACT FROM AUTHOR]

An impregnation-reduction method has been developed in this study to prepare the Ni/Al2O3 catalyst for steam reforming of bio-oil model compounds for hydrogen production. This method can alleviate the interactions between nickel species and an alumina carrier and promote metal dispersion and utilization of the nickel species, achieving a highly active, selective and stable reforming catalyst. Moreover, this method is very simple and fast. Only the impregnation and reduction steps are involved and the catalyst can be prepared in situ. In addition, coke formation in steam reforming is not uniform on a catalyst bed. Coking in the topmost catalyst layer is much more serious. [ABSTRACT FROM AUTHOR]

A series of ZrO2/Al2O3 composite oxides with different ZrO2 contents were prepared by impregnation method. The NiO/ZrO2/Al2O3 catalysts for CO methanation were prepared and tested in a tubular microreactor under the condition of T=300–650°C, P=1.5MPa, GHSV (gas hourly space velocity)=10,000h−1, and H2/CO=3. The results revealed that adding ZrO2 restrains the formation of NiAl2O4, weakens the Ni–Al2O3 interaction, and makes the catalyst more easily reduced, enhancing significantly the activity of catalyst. Especially, among these catalysts, 20Ni/40ZA catalyst with ZrO2 content of 40wt.% exhibits high CO conversion and CH4 selectivity in a broad temperature region of 300–550°C. Moreover, 20Ni/40ZA performs superior stability than 20Ni/Al2O3. The added ZrO2 also improves the anti-carbon deposition and anti-sintering performance of Ni/Al2O3 catalyst. [ABSTRACT FROM AUTHOR]