Ni-Al Hydrotalcite Research Articles

In-situ synthesis of Ni2P/Al2O3 catalyst with liquid-phase phosphidation for enhancing hydrogenation and desulfurization performance in C9 petroleum resin

The hydrogenation of unsaturated bonds and elimination of sulfur impurities in C9 petroleum resin (C9PR) are crucial for improving its quality and performance. In this study, we prepared a nanoflower-like Ni2P/Al2O3 catalyst using an in-situ synthesis combined with liquid-phase phosphidation strategy and applied for the production of value-added hydrogenated C9PR. In-situ synthesis of Ni-Al hydrotalcite anchors and disperses Ni nanoparticles, while liquid-phase phosphidation introduces high-content Niδ+ and Pδ− active sites and prevents the formation of inactive AlPO4, synergistically enhancing both hydrogenation and desulfurization activities. The synthesized Ni2P/Al2O3 catalyst achieves a 99.6 % hydrogenation degree and reduces sulfur content from 137 ppm to 0 ppm, much better than the catalysts prepared by conventional impregnation and metal phosphate reduction methods. These results give valuable insights for designing efficient catalysts and advancing single-step hydrorefining processes to generate high-quality, value-added hydrogenated petroleum resins.

Se vacancy-rich NiMoSe@NiAl-LDH hierarchical core-shell structure towards high-performance supercapacitors

As promising electrode materials, transition metal selenides show great potential applications in energy storage devices. Here self-supported Ni0.85Se nanowires with Se vacancies (denoted as NiMoSe) on NF were synthesized by a solvothermal route and post-selenization using NiMoO4 as the precursor, which electrochemical performance was optimized by adjusting the Se feeding during the selenization. Whereas, the supercapacitive properties of the optimal NiMoSe need to be further improved for achieving higher rate capability and electrochemical stability. So, an efficient strategy was proposed to improve the electrochemical performance through welding the NiAl hydrotalcite (NiAl-LDH) nanosheets on the NiMoSe surface to construct a novel 1D-2D-3D hierarchical core-shell material (NiMoSe@LDH), which provided more active sites and ensured a high rate-capability and long-term stability. Benefiting from the synergistic effect between NiMoSe nanowires core and NiAl-LDH shell, the NiMoSe@LDH delivered a favorable specific charge of 1381.1 C g−1 at 1 A g−1 with impressive rate capability and cyclic stability (85.2% retention after 5 000 cycles at 5 A g−1). Furthermore, the as-assembled NiMoSe@LDH//AC afforded a high energy density of 50.2 Wh kg–1 at a power density of 800 W kg–1 and good cycling stability (86.5% retention at 5 A g−1 after 10 000 cycles) compared to the NiMoSe//AC (36.3 Wh kg–1 at 800 W kg–1, 77.3% retention). This work provides a new strategy for the design of high-performance transition metal selenides in next-generation energy storage devices.

Gold and Ceria Modified NiAl Hydrotalcite Materials as Catalyst Precursors for Dry Reforming of Methane

Structured hydrotalcite NiAl-HT material with Ni/Al atomic ratio of 2.5 was prepared by co-precipitation of Ni and Al nitrate precursors and then modified by the addition of 1 wt% Ce and/or 3 wt% Au species. The obtained materials, after calcination at 600 °C, were characterized by XRD, XPS and TPR. Their catalytic performance was tested through dry reforming of methane (DRM) and by the temperature-programmed surface reaction of methane (TPSR-CH4). Thermal gravimetry analysis (TGA) of the spent catalysts was performed to determine the amount of carbon accumulated during the reaction. The effects of the addition of cerium as a support promoter and gold as nickel promoter and the sequential addition of cerium and gold on the structural properties and on the catalytic efficiency were investigated. Under the severe condition of high space velocity (600,000 mL g−1 h−1), all the catalysts were quite active, with values of CH4 conversion between 67% and 74% at 700 °C. In particular, the combination of cerium and gold enhanced the CH4 conversion up to 74%. Both additives, individually and simultaneously, enhanced the nickel dispersion with respect to the unpromoted NiAl and favored the reducibility of the nickel. During DRM all the catalysts formed graphitic carbon, contributing to their deactivation. The lower carbon gasification temperature of the promoted catalysts confirmed a positive effect played by Ce and Au in assisting the formation of an easier-to-remove carbon. The positive effect was testified by the better stability of the Ce/NiAl with respect to the other catalysts. In the gold-containing samples, this effect was neutralized by Au diffusing towards the catalyst surface during DRM, masking the nickel active sites. TPSR-CH4 test highlighted different CH4 activation capability of the catalysts. Furthermore, the comparison of the deposited carbon features (amount and removal temperature) of the DRM and TPSR spent catalysts indicated a superior activation of CO2 by the Au/Ce/NiAl, to be related to the close interaction of gold and ceria enhancing the oxygen mobility in the catalyst lattice.

Enhanced demethylation of aromatic ether to phenol over NiAl hydrotalcite-derived nickel sulfide catalyst

The production of phenol from lignin or its model compounds, instead of cumene oxidation is very interesting from the viewpoint of sustainability and economics. The selective demethylation of anisole was an efficient but challenging route to produce phenol. In this work, we demonstrated the fabrication of nickel sulfide (Ni9S8+NixS6) nanoparticles on Al2O3 matrix by a facile in situ sulfidation of NiAl hydrotalcite and announced that nickel sulfide can serve as efficient active site for the demethylation of anisole for the first time. The as-designed 4Ni1Al-S catalyst exhibited a hierarchical morphology with a high particle density and high dispersion, affording a 95.6% yield of phenol in the demethylation of anisole under relative milder reaction temperature (270 °C) when compared to the reported state-of-the-art results. By comprehensive characterizations and experiments, we inferred that the nickel sulfide exsolved from the LDH structure exhibited stronger metal-support interaction than that obtained from the impregnation method, which not only benefits the uniform dispersion of active nickel sulfide but also results in the electronic transfer from Ni center to Al2O3 support. As a consequence, enhanced demethylation activity was achieved on 4Ni1Al-S in comparison to Ni-S/Al2O3-IM.

Ni-based catalysts derived from Ni-Zr-Al ternary hydrotalcites show outstanding catalytic properties for low-temperature CO2 methanation

Developing Ni-based catalysts with high activity and stability in low-temperature methanation is necessary due to their sintering and coking at high temperatures. Here, we report our developed novel Ni-Zr-Al catalysts derived from Ni-Zr-Al ternary hydrotalcites synthesized by a hydrothermal process, followed by a reduction in hydrogen. Comparing with the Ni-Al catalyst derived from Ni-Al hydrotalcite and the commercial Ni-based catalyst, the Ni-Zr-Al catalysts show a remarkably higher low-temperature activity (210−270 °C) in CO2 methanation. Both the experimental and theoretical calculations confirmed the introduction of Zr into the Ni-Al binary hydrotalcite could generate synergetic effects between Ni and ZrO2, resulting in more surface oxygen vacancies, basic sites, and abundant mesopores. In-situ DRIFTS analysis showed the CO2 methanation to CH4 follows the intermediate formate route. This work provides a new theoretical understanding of CO2 activation and methanation, and a practical way to address the existing problem for Ni-based catalysts.

Beyond flower-like structure – The synergy within Pd/Ni-Al hydrotalcite for base-free oxidation of benzyl alcohols

A highly efficient supported metal catalyst, Pd/Ni-Al hydrotalcite with flower-like structure was synthesized and applied for catalytic oxidation of benzyl alcohols; affording >99 % conversion and 94–100 % selectivity in a base-free solution. The surface basicity and cation-oxygen mode in the layer of hydrotalcite were found to be pronouncedly associated with the changes of morphologies of the Ni-Al hydrotalcites. Compared to negligible activity by Ni-Al hydrotalcite itself, low efficiency by Pd nanoparticles or its simple mixture with Ni-Al hydrotalcite, a significant enhancement in the catalytic activity by the Pd deposited on flower-like Ni-Al hydrotalcites suggested a synergistic effect occurred between Pd and well-structured Ni-Al hydrotalcite. A plausible mechanism for the catalytic reaction involving the formation of metal-alkoxide and metal-hydroperoxide intermediates was postulated based on the control reactions, FTIR and XPS analysis and Hammett experiment.

Influence of surface Lewis acid sites for the selective hydrogenation of levulinic acid to γ-valerolactone over Ni–Cu–Al mixed oxide catalyst

Al2O3 interacted Cu–Ni bimetallic catalysts derived from incorporation of Cu into Ni–Al hydrotalcite were found to be efficient in the selective transformation of levulinic acid (LA) to γ-valerolactone (GVL). The promotional effect of Cu on Ni hydrogenation activity was explained due to an increased ease of NiO reduction and also enhanced surface Lewis acid sites measured by DRIFT spectroscopy. An optimum composition of Ni–Cu–Al catalyst with a mole ratio of 44:22:33 (NCA-423) exhibited a higher Ni metal surface area which demonstrated superior performance in the hydrogenation of LA to GVL with a productivity of 1.68 kgGVL kg cat −1 h−1. The physicochemical properties of Ni–Cu–Al catalysts were rationalized by XRD, H2-TPR, XPS, EPR, BET surface area, H2 chemisorption and pyridine adsorbed IR spectroscopy.

Production of green biofuel by using a goat manure supported Ni-Al hydrotalcite catalysed deoxygenation process.

The high oxygen content in natural biomass resources, such as vegetable oil or biomass-pyrolysed bio oil, is the main constraint in their implementation as a full-scale biofuel for the automotive industry. In the present study, renewable fuel with petrodiesel-like properties was produced via catalytic deoxygenation of oleic acid in the absence of hydrogen (H2). The deoxygenation pathway of oleic acid to bio-hydrocarbon involves decarboxylation/decarbonylation of the oxygen content from the fatty acid structure in the form of carbon dioxide (CO2)/carbon monoxide (CO), with the presence of a goat manure supported Ni–Al hydrotalcite (Gm/Ni–Al) catalyst. Goat manure is an abundant bio-waste, containing a high mineral content, urea as well as cellulosic fiber of plants, which is potentially converted into activated carbon. Synthesis of Gm/Ni–Al was carried out by incorporation of pre-activated goat manure (GmA) during co-precipitation of Ni–Al catalyst with 1 : 3, 1 : 1 and 3 : 1 ratios. The physico-chemical properties of the catalysts were characterized by X-ray diffractometry (XRD), Brunauer–Emmet–Teller (BET) surface area, field emission surface electron microscopy (FESEM) and temperature program desorption ammonia (TPD-NH3) analysers. The catalytic deoxygenation reaction was performed in a batch reactor and the product obtained was characterized by using gas chromatography-mass spectroscopy (GCMS) for compound composition identification as well as gas chromatography-flame ionisation detector (GC-FID) for yield and selectivity determination. The optimization and evaluation were executed using response surface methodology (RSM) in conjunction with central composite design (CCD) with 5-level-3-factors. From the RSM reaction model, it was found that the Gm/Ni–Al 1 : 1 catalysed deoxygenation reaction gives the optimum product yield of 97.9% of hydrocarbon in the range of C8–C20, with diesel selectivity (C17: heptadecane and heptadecene compounds) of 63.7% at the optimal reaction conditions of: (1) reaction temperature: 327.14 °C, (2) reaction time: 1 h, and (3) catalyst amount: 5 wt%.

Highly Active Ni-Based Catalyst Derived from Double Hydroxides Precursor for Low Temperature CO2 Methanation

The Ni nanoparticles supported on Al2O3 metal oxides with different Ni2+/Al3+ molar ratios from 1/1 to 6/1 (denoted as NixAL-MO) derived from Ni–Al hydrotalcite precursors (NixAl-LDHs) were prepared and applied to CO2 methanation at a low temperature. By adjusting the Ni2+/Al3+ ratios, the alkaline and reducibility of the catalysts were designed, and the catalysts showed efficient catalytic performance at a low temperature. The Ni5AL-MO catalyst demonstrated the highest CO2 conversion of 89.4% at 250 °C. The superior catalytic property was related to the basic property, readily reducible NiO species, and the cooperation of metal nanoparticles and basic sites. The reaction intermediate species formed on the catalyst surface were identified by in situ FTIR analysis, and the reduction mechanism of CO2 was revealed. Moreover, the Ni5Al-MO catalyst had excellent resistance to carbon deposition and metal sintering after a long reaction duration. The NixAl-LDHs as the catalyst precursor show a promising potentia...

Insight into MgO promoter with low concentration for the carbon-deposition resistance of Ni-based catalysts in the CO2 reforming of CH4

The CO2 reforming of CH4 is studied over MgO-promoted Ni catalysts, which were supported on alumina prepared from hydrotalcite. This presents an improved stability compared with non-promoted catalysts. The introduction of the MgO promoter was achieved through the ‘‘memory effect’’ of the Ni-Al hydrotalcite structure, and ICP-MS confirmed that only 0.42 wt.% of Mg2+ ions were added into the Ni-Mg/Al catalyst. Although no differences in the Ni particle size and basicity strength were observed, the Ni-Mg/Al catalyst showed a higher catalytic stability than the Ni/Al catalyst. A series of surface reaction experiments were used and showed that the addition of a MgO promoter with low concentration can promote CO2 dissociation to form active surface oxygen arising from the formation of the Ni-MgO interface sites. Therefore, the carbon-resistance promotion by nature was suggested to contribute to an oxidative environment around Ni particles, which would increase the conversion of carbon residues from CH4 cracking to yield CO on the Ni metal surface.

Removal of volatile odorous organic compounds over NiAl mixed oxides at low temperature

In this paper, a series of NiAl hydrotalcite–like compounds (HTLCs) were prepared by the urea–decomposition method. Removal of carbonyl sulfide (COS) and methyl mercaptan (CH4S) over the hydrotalcite–derived oxides (HTO) at low temperature was studied. The Ni3Al-HTO exhibited higher catalytic activities than Ni3Al mixed oxides prepared by physical mixing method (Ni3Al-PM) or impregnation/calcination method (Ni3Al-IC). Based on the characterization, it was found that desulfurization activities are closely tied to the surface acid-base properties of catalysts. CO2-TPD indicates that the basic characteristic of the Ni3Al-HTO is prominent. XPS results showed that there was a strong interaction between Ni and Al element on Ni3Al-HTO. The first principle calculation based on density function theory was applied with the aim to study the change of basic sites. The results showed that Ni3Al-HTO presents a half-metallic characteristic. Electron transfer from the Al and O atom to the Ni atom was observed, which is helpful for the transfer of electrons from the surface and improves the catalytic activity. Analysis of the DRIFT spectra suggests that sulfate species was formed by the action of surface basic sites, resulting in the formation of H2O on the surface.

A Short Review on the Catalytic Activity of Hydrotalcite-Derived Materials for Dry Reforming of Methane

Nickel-containing hydrotalcite-derived materials have been recently proposed as promising materials for methane dry reforming (DRM). Based on a literature review and on the experience of the authors, this review focuses on presenting past and recent achievements on increasing activity and stability of hydrotalcite-based materials for DRM. The use of different NiMgAl and NiAl hydrotalcite (HT) precursors, various methods for nickel introduction into HT structure, calcination conditions and promoters are discussed. HT-derived materials containing nickel generally exhibit high activity in DRM; however, the problem of preventing catalyst deactivation by coking, especially below 700 °C, is still an open question. The proposed solutions in the literature include: catalyst regeneration either in oxygen atmosphere or via hydrogasification; or application of various promoters, such as Zr, Ce or La, which was proven to enhance catalytic stability.

(MnO/Mn3O4)-NiAl nanoparticles as smart carbon resistant catalysts for the production of syngas by means of CO2 reforming of methane: Advocating the role of concurrent carbothermic redox looping in the elimination of coke

Mixed oxide MnO/Mn3O4 was successfully incorporated into NiAl hydrotalcite derived systems following an ionic exchange protocol via initial introduction of [MnY]2− (Y = ethylenediaminetetraacetic acid (EDTA)) into the interlayer space of NiAl hydrotalcite structure. Upon calcination and subsequent reduction, the resulting material (NiAl-MnYcal.) was successfully screened for its catalytic activity and carbon resistance in the reaction of CO2 reforming of methane; NiAl-MnYcal exhibited conversion values of CH4 and CO2 more than 93% while the ratio H2/CO was close to 1 at 700 °C, an excellent combination to gain access to other long chained hydrocarbons following the Fischer-Tropsch approach. Most importantly, NiAl-MnYcal. showed 0.40 wt.% carbon deposition towards the end of the process of CO2 reforming of methane, potentially owing to the presence of an integrated carbothermic redox cycle based on Mn3O4/C/MnO/CO2 within the nickel rich catalyst as well as the large surface area of Ni particles obtained. All precursors and mixed oxides were characterized by Thermogravimetric analysis (TG), inductively coupled plasma atomic emission spectroscopy (ICP–AES), X-ray diffraction (XRD), Brunauer–Emmett–Teller method (BET), Fourier transform infrared spectroscopy (FTIR), temperature programmed reduction (TPR) and scanning electron microscopy (SEM). Analyses of the material demonstrated the formation of nano-sized particles containing mixed crystalline phases of Ni, NiO, MnO, Mn3O4 and NiAl2O4. The catalytic results were also valorized against other catalysts (NiAlcal and MnAlcal) synthesized via co-precipitation method. At 700 °C, NiAl-MnYcal displayed ca. 10% more conversion of CH4 and CO2 than that of NiAlcal.; the ratio H2/CO was 0.99, 6.4% higher than that of NiAlcal.. No reaction of CO2 reforming of methane took place in the absence of Ni.

Synthesis, Characterization, and Activity Pattern of Ni–Al Hydrotalcite Catalysts in CO2 Methanation

Two nickel–aluminum hydrotalcite samples (HTLCs) were prepared by a coprecipitation method at different pH values and investigated as catalysts for the hydrogenation of carbon dioxide. The newly synthesized samples have been compared with a reference alumina supported nickel-based commercial catalyst, with equal nickel content. The as-prepared and commercial samples were characterized by BET analysis, atomic adsorption spectroscopy (AAS), X-ray diffraction (XRD), and temperature-programmed techniques (H2-TPR and CO-TPD). Catalytic activity of the analyzed samples was investigated toward hydrogenation of CO2 at atmospheric pressure by varying reaction temperature between 250 and 400 °C. The maximum CO2-to-CH4 conversion value achieved by hydrotalcyte was ≈86% at 300 °C. The superior performance of HTLCs has been put in relationship with the major catalysts reducibility nature and with the higher metal surface area and metal dispersion. The stability of the HTLCs was investigated through long-term tests, re...

Enhancement effects of ultrasound assisted in the synthesis of NiAl hydrotalcite for carbonyl sulfide removal

Ultrasonic effect in the synthesis of catalysts of NiAl oxides prepared starting from the coprecipitation method of a hydrotalcite structure was evaluated in this work. Removal of carbonyl sulfide (COS) at low temperature over the hydrotalcite-derived oxides was studied. The samples were characterized by X-ray Diffraction (XRD), scanning electron microscope (SEM), N2 adsorption/desorption techniques, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and CO2 temperature-programmed desorption (TPD). It is found that hydrotalcite treated with ultrasonic has smaller average crystallite size and higher particle dispersion compared to hydrotalcite without ultrasonic treatment. As a result, mixed oxides derived from hydrotalcite treated with ultrasonic show more developed pore structure which is good for the physical adsorption of gaseous pollutant. The result of desulfuration test showed that removal efficiency of COS on the NiAl mixed oxides prepared by ultrasonic method (30min) is greater than that on the catalyst prepared without the ultrasonic irradiation assistance with the same aging time. One important reason for the high activity is that when the ultrasonic is used the number of weak basic sites (OH− groups) and moderate basic sites (M–O) was increased, whereas the number of strong basic sites (O2−) was decreased. Therefore, ultrasonic treatment promoted the COS hydrolysis and suppress the poisoning of the catalyst.

Environment-Friendly Reduction of Aromatics to Alicyclic Compounds at Room Temperature Using Superactive Calcined Ni-Al Hydrotalcite Catalysts

Calcined Ni-Al hydrotalcite (HT) 2: 1, Cat. A, is a superactive catalyst for reduction of substituted aromatics, i. e. toluene, benzene, nitrobenzene, chloro-, bromo-, and iodobenzene to their respective alicyclic products at room temperature in the presence of molecular hydrogen. Cat. A attained higher conversions compared to calcined Ni-Al hydrotalcites with ratios of 2.5: 1, and 3: 1. Calcined Ni-Al HT is a superactive catalyst whereas catalysts Niγ-Al₂O₃ or Ni-SiO₂ with Ni contents of 2%, 5%, and 10% resulted in poor conversions. In these cases, Ni in association with the respective oxide is the active precursor for molecular hydrogen initiation in the reduction of aromatics to alicyclic compounds. The objective is to evalua4e Ni as the best catalyst for aromatic ring reduction to alicylic molecule. Quantitative yield were obtained for all the substrates toluene, benzene, nitrobenzene, chloro-, bromo-, and iodobenzene to their respective cyclohexanes. These results indicate that hydrogenation with reusable Ni-Al HT catalysts is a green sustainable process and atom economy efficient for the production of various alicyclic compounds.

Influence of Rare Earth (La, Pr, Nd, Gd, and Sm) Metals on the Methane Decomposition Activity of Ni–Al Catalysts

Rare earth (RE = La, Pr, Nd, Gd and Sm) metal-doped Ni-Al (Ni-RE-Al) hydrotalcite precursors were obtained by coprecipitation and calcined to form mixed oxide catalysts. The physicochemical characteristics of calcined and reduced Ni-RE-Al samples were determined by X-ray powder diffraction, Brunauer–Emmett–Teller surface area, H2 temperature-programmed reduction, O2 pulse chemisorption, UV-diffuse reflectance spectroscopy, electron spin resonance spectrometry, and Fourier transform infrared spectroscopy. The catalysts were evaluated for CH4 decomposition at 550 °C until their complete deactivation. The deactivated catalysts were examined by transmission electron, scanning electron, and Raman spectroscopy and elemental analysis. The Raman spectra indicated the presence of both ordered and disordered carbon in deactivated catalysts. A correlation is drawn between H2 production rates and the Ni metal surface area of catalysts. The addition of La to Ni-Al dramatically changed the Ni behavior, leading to highe...

Montmorillonite-supported Ni nanoparticles for efficient hydrogen production from ethanol steam reforming

Alkaline-promoted of NiAl–montmorillonite (NiAl–Mt) catalysts were prepared by ion-exchange method, tested in ethanol steam reforming (ESR) for hydrogen production, and characterized by a combination analysis of XRD, TPR, SEM, HR–TEM, EDS and N2 adsorption–desorption. Characterization results indicated that the textural properties of the as-prepared catalysts are strongly dependent on the alkaline treatment. More importantly, a clear improvement on stability and catalytic activity, especially for the high selectivity to hydrogen, was observed in ESR. For NiAl–Mt/NaOH catalyst, ∼74.7% selectivity of hydrogen was kept at 773K during 10-h test, while that of NiAl–hydrotalcite (NiAl) catalyst decreased from 20.4% to 5.3% within 10h, and the selectivity of hydrogen on NiAl–Mt was ∼55.1%, accompanying with byproducts of acetaldehyde and ethylene. The improved activity and stability were attributed to the neutralization of acid sites by alkaline treatment, which accelerated the dehydrogenation and suppressed the dehydration of ethanol.

Unique catalysis of Ni-Al hydrotalcite derived catalyst in CO2 methanation: cooperative effect between Ni nanoparticles and a basic support

Ni-Al hydrotalcite derived catalyst (Ni-Al2O3-HT) exhibited a narrow Ni particle-size distribution with an average particle size of 4.0 nm. Methanation of CO2 over this catalyst initiated at 225 °C and reached 82.5% CO2 conversion with 99.5% CH4 selectivity at 350 °C, which was much better than its impregnated counterpart. Characterizations by means of CO2 microcalorimetry and 27Al NMR indicated that large amount of strong basic sites existed on Ni-Al2O3-HT, originated from the formation of Ni-O-Al structure. The existence of strong basic sites facilitated the activation of CO2 and consequently promoted the activity. The combination of highly dispersed Ni with strong basic support led to its unique and high efficiency for this reaction.

Heterogeneous acylation of phenol with acetic anhydride over hydrotalcite-like compounds

Liquid phase acylation of phenol with acetic anhydride was studied over the mixed oxides obtained from Mg-Al, Ni-Al, and Cu-Al hydrotalcites (HTs). The mixed oxides were characterized by XRD and SEM. The main acylation products of phenol over these oxide catalysts are phenylacetate and o-hydroxyacetophenone.