Hydrogen Chemisorption Research Articles

Synthesis strategies of Zr- and Y-promoted mixed oxides derived from double-layered hydroxides for syngas production via dry reforming of methane

Ni-based Mg/Al double-layered hydroxides, also called hydrotalcites (HTs), were co-precipitated with Zr (5 wt%) and impregnated with Y (0.2, 0.4, 0.6 wt%), and compared to the catalyst co-precipitated with both Y (0.4 wt%) and Zr (5 wt%). Their performance in dry reforming of methane was determined in the temperature range of 850–600 °C and stability tests at 700 °C for 5 h. The materials were characterized by X-ray powder diffraction, X-ray fluorescence, nitrogen adsorption/desorption, H2-TPR, CO2-TPD, hydrogen chemisorption, thermogravimetric analysis, transmission electron microscopy, high-resolution transmission electron microscopy, and Raman spectroscopy. A decrease in reducibility and lower total number of basic sites were observed for the sample promoted only with zirconia compared to the unpromoted material. After promotion with yttrium, no formation of ZrO2–Y2O3 solid solution was evident from XRD. The Ni dispersion was decreased due to decoration of the surface with Y species, leading to blockage of available nickel sites. All Zr and Y promoted samples were, however, more active in DRM than unpromoted HTNi. The co-precipitated Zr and Y catalyst (HTNi-ZrY0.4-cop) exhibited increasing conversion over time, and a H2/CO close to 1 in the isothermal test at 700 °C. H2-TPSR on the spent catalysts revealed that the promotion with yttrium favored regeneration of the catalytic bed, consuming the majority of removable coke and decreasing the formation of unreactive coke.

"Lewis Base-Hungry" Amorphous-Crystalline Nickel Borate-Nickel Sulfide Heterostructures by In Situ Structural Engineering as Effective Bifunctional Electrocatalysts toward Overall Water Splitting.

The development of high-performance, low-cost, and long-lasting electrocatalysts for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is urgently needed for effective electrochemical water splitting. In the present study, an engineering process was employed to prepare "Lewis base-hungry" amorphous-crystalline nickel borate-nickel sulfide (Ni3(BO3)2-Ni3S2) heterostructures, which exhibited unprecedentedly high electrocatalytic activity toward both OER and HER in alkaline media. The optimal Ni3(BO3)2-Ni3S2/nickel foam (Ni3(BO3)2-Ni3S2/NF) electrode displayed an ultralow overpotential of only -92 and +217 mV to reach the current density of 10 mA cm-2 for HER and OER, respectively. When the Ni3(BO3)2-Ni3S2/NF electrode was used as both the anode and cathode for overall water splitting, a low cell voltage of 1.49 V was needed to achieve the current density of 10 mA cm-2, which was superior to the performance of most noble metal-free electrocatalysts. Results from density functional theory calculations showed that the Lewis base-hungry sites in the heterostructures effectively enhanced the chemisorption of hydrogen and oxygen intermediates, a critical step in HER and OER electrocatalysis. Results from this study highlight the significance of rational design and engineering of heterostructured materials for the development of high-efficiency electrocatalysts.

Effect of Precious Metals on NO Reduction by CO in Oxidative Conditions

Carbon dioxide has become an environmental challenge, where the emissions have reached higher level than can be handled. In this regard, conversion of CO2 to value-added chemicals and thus recycling of CO2 appear a viable option. Prior to valorization, CO2 must be purified. Among several opportunities, oxyfuel combustion is a process in rapid development. However, the gases resulting from this process contain some traces of impurities that can hinder the recovery of CO2 such as NO and CO. This work has, therefore, focused on the study of the NO-CO reaction in an oxidizing medium, using heterogeneous catalytic materials based on various supported noble metals. These materials were extensively characterized by a variety of methods including Brunauer–Emmett–Teller (BET) surface area measurements, hydrogen chemisorption, transmission electron microscopy (TEM) and H2 temperature programmed reduction (H2-TPR). The results obtained show that the catalytic behavior of M/Al2O3 catalysts in CO oxidation and NO reduction with CO in oxidative conditions depends mainly on the nature of the metal. The best result for both reactions is obtained with Pt/Al2O3 catalyst. The Pt nanoparticles in their metallic form (Pt°) as evidenced by TPR could explain the activity.

WOx‐Modified Ni Catalyst Supported on Mesoporous Silica with Extra‐Large Mesopores for CO Methanation

A group of Ni–WOx/FDU‐12 (x < 3; FDU‐12: Fudan University ordered mesoporous materials) catalysts is prepared via a polyhydroxy compound–assisted impregnation method for carbon monoxide (CO) methanation. Ethylene glycol is used as the solvent, and citric acid is added as the second polyhydroxy compound to enhance the dispersion of Ni2+ ions. These polyhydroxy compounds are carbonized as sacrificial carbon via calcination in an inert atmosphere. Meanwhile, H2O is used as the reference solvent. These catalysts are systematically characterized by various techniques. The results show that the utilization of ethylene glycol and citric acid significantly reduces the size of Ni, and the addition of the WOx promoter further improves Ni dispersion. The optimal catalyst shows a high low‐temperature activity, which reaches thermodynamic equilibrium at only 360 °C and obtains the maximum CH4 yield of 86.2% at 400 °C due to the fine Ni particle size and enhanced hydrogen chemisorption capacity. In addition, this catalyst shows high stability in a 100 h‐lifetime test at 400 °C, 0.1 MPa, and a high weight hourly space velocity of 60 000 mL g−1 h−1. This is attributed to the synergistic effect of the WO3 promoter and the physical barrier of carbon residue, as well as the confinement effect of FDU‐12 support.

Nanoscale probing of broken-symmetry states in graphene induced by individual atomic impurities

Inherent symmetries of a system lead to multiple degeneracies of its energy spectra. Introducing individual atomic impurities can locally break these symmetries, which is expected to lift the degenerate degrees of freedom around the impurities. Although central to our understanding of the fundamental properties of solids, the broken-symmetry states induced by individual atomic impurities have so far eluded observation. Here, we report nanoscale probing of the broken-symmetry states in graphene induced by two types of individual atomic impurities, i.e., isolated nitrogen dopants and isolated hydrogen atoms chemisorbed on graphene. Our experiments demonstrate that both types of atomic impurities can locally break sublattice symmetry of graphene and generate valley-polarized states, which extends several nanometers around the impurities. For the isolated hydrogen atom chemisorbed on graphene, the enhanced spin-orbit coupling, which arises from the sp3 distortion of graphene due to the hydrogen chemisorption, further lifts the spin degeneracy, resulting in a fully spin and valley polarized states within about 1 nm around the hydrogen atom. Our result paves the way to control various broken-symmetry states at the nanoscale by various atomic impurities.

Amino-Modified Silica as Effective Support of the Palladium Catalyst for 4-Nitroaniline Hydrogenation

The article describes the synthesis of aminoorgano-functionalized silica as a prospective material for catalysis application. The amino groups have electron donor properties which are valuable for the metal chemical state of palladium. Therefore, the presence of electron donor groups is important for increasing catalysts’ stability. The research is devoted to the investigation of silica amino-modified support influence on the activity and stability of palladium species in 4-nitroaniline hydrogenation process. A series of catalysts with different supports such as SiO2, SiO2-C3H6-NH2 (amino-functionalized silica), γ-Al2O3 and activated carbon were studied. The catalytic activity was studied in the hydrogenation of 4-nitroaniline to 1,4-phenylenediamine. The catalysts were characterized by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and chemisorption of hydrogen by the pulse technique. The 5 wt.% Pd/SiO2-C3H6-NH2 catalyst exhibited the highest catalytic activity for 4-nitroaniline hydrogenation with 100% conversion and 99% selectivity with respect to 1,4-phenylenediamine.

Influence of structures and functional groups of carbon on working potentials of supercapacitors in neutral aqueous electrolyte: In situ differential electrochemical mass spectrometry

Abstract Achieving high cell potential supercapacitors in aqueous-based electrolytes is an essential step to the development of safe energy storage devices with high energy density. It is well known that the extension of cell potentials is due to the chemisorption of hydrogen in the micropores of activated carbon electrodes in neutral aqueous electrolytes. In this work, we have found that the structural feature, electronic property, and functional group of carbon electrodes do also play important roles to the cell potentials and performances of carbon-based supercapacitors. We employed four different carbons i.e., carbon fiber paper (CFP), functionalized carbon fiber paper (f-CFP), semiconducting macroporous reduced graphene oxide (rGO), and microporous activated carbon (AC) having different morphologies, structures, and functional groups. The symmetrical supercapacitors of AC and rGO show the maximum cell potential of 1.6 V by floating up to 200 h. This indicates that not only does the chemisorption of hydrogen within micropores play a key role on the wide working cell potentials (> 1.23 V) but others also play an important role confirmed by in situ mass spectrometry. This work may be useful for further development of carbon-based supercapacitors.

A Highly Stable and Efficient Co–Mg–Sr Mixed Oxide Catalysts for Hydrogen Production from Glycerol Steam Reforming

The production of hydrogen from glycerol steam reforming (GSR) was studied over a series of Co–Mg–Sr (CMS) mixed oxide catalysts. Co-precipitation method was adopted to prepare catalysts by varying the molar ratios of MgO–SrO and keeping Co3O4 content constant. The physico-chemical properties of the samples were investigated by BET surface area, X-ray diffraction, hydrogen chemisorption, temperature programmed reduction, temperature programmed desorption of CO2, Raman spectroscopy and CHNS analysis. The reforming activity depended on the composition of the metal oxides. The catalyst with Co–Mg–Sr molar ratio of 3:1:1 exhibited the highest catalytic activity at 700 °C. Glycerol was completely converted to gaseous products and showed 72% hydrogen yield. Catalytic activity of the catalysts was explained on the basis of cobalt particle size, basicity and metal oxides interaction. The catalysts basicity originating from MgO–SrO is also playing an important role in GSR. The present catalyst activity was unaltered even after 100 h of time on stream analysis.

Rectifying the chemisorption – XRD discrepancy of carbon supported Pd: Residual chloride and/or carbon decoration

A conspicuous discrepancy is prevalent in the characterization of carbon supported palladium catalysts: particle size estimated by XRD and electron microscopy agree, while the chemisorption of hydrogen is substantially suppressed with respect to the small size measured by XRD/STEM. In this work, a systematic study of carbon materials, pretreatments, and characterization has isolated the contributions of carbon decoration and residual chloride, both of which can cause a chemisorption shortfall. The degree of decoration decreases with graphitization of the carbon supports due to stronger CC interaction, whereas increased density of oxygen functional groups on the surface increases decoration, due to enhanced Pd-C interactions. The discrepancy can be rectified by employing a low temperature burnoff of the decorating carbon layers prior to chemisorption, and by using metal precursors without chloride ligands or counterions.

Reactivity of Defective Hexagonal Boron Nitride Monolayers

The results are presented from quantum-chemical modeling of the chemisorption of atomic hydrogen and fluorine on the surface of a hexagonal boron nitride monosheet containing a number of stable intrinsic, impurity, and complex defects in different charge states. The objects of study are antisite defects, interstitial atoms, vacancy defects, carbon and oxygen impurities, and complex “impurity + vacancy” defects. The configurations of molecular orbitals (MOs) for the studied defects are analyzed. It is found that hydrogen is more actively with nitrogen atoms in most of the considered cases, while fluorine exhibits higher activity toward boron atoms.

The trend of chemisorption of hydrogen and oxygen atoms on pure transition metals: Magnetism justifies unexpected behaviour of Mn and Cr

The spin of the electron is decisive to understand electronic interactions in heterogeneous catalysis, mainly because the stabilizing Quantum Spin Exchange Interactions (QSEI) are always a significant contribution to the energy of magnetic catalysts and absorbates during reaction events. Cooperative QSEI in compositions with multi-atomic open-shell configurations (QSEI-OS) maximize the influence of the spin dependent potentials, determining the electronic properties of magnetic materials and shaping their reactivity. In this paper, we explain that because of the intra- and inter- atomic QSEI-OS, high-spin (3d5) antiferromagnetic (AFM) metals like Cr and Mn can be more inert (or “noble”) than Au itself towards the formation of covalent bonds with hydrogen atoms. AFM QSEI-OS lead to a relative higher destabilization of the unoccupied (spin-)orbitals (Mott upper band) in Cr and Mn compared with other metals. In oxygen adsorption, QSEI-OS lead to the reduction of the electronic repulsions in occupied 3d5 orbitals with a concomitant decrease of the chemisorption enthalpy of the oxygen atoms. Since hydrogen and oxygen atoms are the most important intermediates in relevant catalytic processes like oxygen reduction reaction and water splitting, we observe how the effect of QSEI-OS needs to be properly incorporated as a critical factor to understand the activity of catalysts based on magnetic metals.

Cooperative physisorption and chemisorption of hydrogen on vanadium-decorated benzene.

3d TM-decorated carbon composites have been proved to be a new generation of hydrogen storage materials. However, detailed hydrogen storage mechanisms are still unclear. Investigation of the H2 dissociation and H migration on the 3d TM-decorated six-membered carbocycles is very critical for better understanding the hydrogen storage mechanism. In this paper, the processes of chemisorption and physisorption of multiple H2 molecules on synthesized VC6H6 were simultaneously investigated for the first time. The Gibbs free energy calculations show that the optimal chemisorption pathway with the hydrogen storage capacity of 5.97 wt% is exothermic by 2.83 kcal mol−1. Both the continuous hydrogenation giving the product of VC6H11–3H and reverse dehydrogenation could run smoothly at room temperature. The physisorption with a hydrogen storage capacity of 4.48 wt% will be exothermic by 13.49 kcal mol−1. The H2 molecules can be physisorbed at any temperature under 416 K and readily desorbed above 480 K at 1 atm. In summary, physisorption and chemisorption synergistically boost the hydrogen storage property of complex VC6H6. Our study provides a comprehensive picture of the interaction between hydrogen and VC6H6 and opens a new window for optimizing the future hydrogen storage materials.

Ni particles generated in situ from spinel structures used in ethanol steam reforming reaction

The in situ generation of Ni particles from a spinel structure used in the ethanol steam reforming reaction was studied. A series of Ni1-xCuxAl2O4 (x=0, 0.01, 0.05, 0.1) catalysts precursors were synthesized by the citrate method. Samples were characterized by SBET, X-ray diffraction, neutron powder diffraction, temperature-programmed reduction, X-ray photoelectron spectroscopy, thermogravimetric-mass spectrometry, scanning electron microscopy, and hydrogen chemisorption. The inclusion of Cu into the spinel structure was beneficial to facilitate the exsolution of Ni particles to the surface at lower reduction temperatures, and thus it was essential to generate highly dispersed particles on the spinel surface. Ni0.9Cu0.1Al2O4 catalyst presented the highest H2 selectivity and low mean values of CO selectivity, around 15% with zero formation of methane.

Production of benzylamine by tandem dehydrogenation/amination/reduction over Cu and Au catalysts

The feasibility of continuous synthesis of benzylamine from benzyl alcohol by tandem dehydrogenation/amination/reduction has been demonstrated over Cu/SiO2 and Au/TiO2. Both catalysts exhibited an equivalent metal particle size range (1−6 nm) and mean (3.1–3.2 nm, from STEM). Hydrogen chemisorption measurements revealed (five-fold) higher uptake on Au/TiO2 than Cu/SiO2 under reaction conditions. Reductive amination of benzaldehyde over Cu/SiO2 generated a 99 % yield of dibenzylamine with no detectable benzylamine. Reaction of benzyl alcohol with NH3 (in N2) over Cu/SiO2 established utilisation of reactive hydrogen from alcohol dehydrogenation to convert intermediate imines to amines. Benzonitrile was the principal product due to the limited hydrogenation capacity of Cu. Inclusion of Au/TiO2 with Cu/SiO2 as a physical mixture promoted benzylamine formation and inhibited condensation-hydrogenation of benzylamine with benzaldehyde. Incorporation of H2 at low partial pressure (PH2= 0.04 atm) in the feed and a lower reaction temperature (498 K → 448 K) enhanced benzylamine production.

Redox bifunctional activities with optical gain of Ni3S2 nanosheets edged with MoS2 for overall water splitting

Exploring cost-efficient catalysts with bifunctional activities of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) holds practical significance for overall water splitting. Herein, for the first time, we report a unique lateral heterostructure of ultrathin Ni3S2 nanosheets (NSs) edged with MoS2 as an efficient and durable bifunctional catalyst for overall water splitting in alkaline media. Benefiting from maximizing functional Mo-S-Ni interfaces that favor the chemisorption of hydrogen and oxygen-containing intermediates, the resultant Ni3S2/MoS2 (NiMoS) catalyst exhibits respectively low overpotentials of 78 and 260 mV at 10 mA cm−2 for HER and OER, superior to the commercial benchmarks (IrO2 and Pt/C), ranking among the best records reported to date. In particular, the NiMoS catalyst renders an attractive light-enhanced effect on both HER and OER activities due to photogenerated charge transfer at Mo-S-Ni interface towards redox kinetic acceleration. An assembled two-electrode alkaline electrolyzer using NiMoS as bifunctional catalysts can deliver a current density of 10 mA cm−2 at low cell voltage of 1.53 V (1.50 V under 1 sun irradiation) with remarkable stability for over 100 h, demonstrating the robust overall water splitting with accessible solar integration.

Highly dispersive bimetallic sulfides afforded by crystalline polyoxometalate-based coordination polymer precursors for efficient hydrogen evolution reaction

Molybdenum disulfide (MoS2) is viewed as one of the most promising hydrogen evolution reaction (HER) electrocatalyst thanking to its graphene-like layered structure and suitable hydrogen chemisorption free energy. However, its application is still hindered by some obstacles, such as less exposed active sites and poor inherent conductivity. Herein, two new crystalline polyoxometalate-based metal-organic polymers with Co/Ni and Mo, {(C2H2N3)3Co2·6H2O}[H3SiMo12O40]·9H2O (1) and {(C2H2N3)3Ni2·6H2O}[H3SiMo12O40]·5H2O (2) (1,2,4-triazole = C2H2N3) are firstly designed and fabricated, and characterized by sufficient technologies including single-crystal X-ray diffraction and so on. And they are directly utilized as ‘preassembly platform’ reacting with thiourea to synthesize highly dispersive CoS2–MoS2 and Ni3S2–MoS2 bimetallic sulfides with mesoporous structure. In virtue of the synergistic effects, and high dispersiveness and porosity of CoS2/Ni3S2 and MoS2 in carbon cloth (CC), 50%CoS2–MoS2@CC and 50%Ni3S2–MoS2@CC composites display a low overpotential of 222 and 224 mV at 10 mA cm−2, and a small Tafel slope of 64.2 and 65.7 mV·dec−1 in H2SO4 solution, respectively. Such superior electrocatalytic HER performances outperform most of both POM-based and MoS2-based non-noble metal catalysts. Hence, this work presents a facile tactic for engineering highly dispersive bimetallic sulfides with excellent electrocatalytic HER performance.

The effect of preparation route of commercial Co/γ-Al2O3 catalyst on important Fischer-Tropsch kinetic parameters studied by SSITKA and CO-DRIFTS transient hydrogenation techniques

Two commercial Co-based catalysts supported on carbon-coated and uncoated γ-Al2O3 (during Co deposition) of different Co particle size (∼7 and 10 nm) and surface structure were investigated to address the effect of preparation route on important kinetic parameters of the methanation reaction (5 vol% CO, H2/CO = 2, P = 1.1 bar) by advanced transient isotopic and operando DRIFTS experiments. 13CO-SSITKA-Mass Spectrometry experiments performed at 230 °C and after 32 h on TOS, showed that the surface coverage (θCO) and mean residence time (τCO, s) of reversibly adsorbed CO-s are not influenced by the different preparation route, while θCHx, TOFCH4 (s−1) and the τCHx (s) related to the active carbonaceous species were slightly increased with increasing Co particle size (in the 7–10 nm range). On the other hand, the kinetic rates of CO conversion and CH4 production (μmol g−1 s−1) were found to increase with decreasing Co particle size. The TOFCH4,ITK (s−1) estimated on the basis of the measured active CHx-s and CO-s species was found very similar for the two Co particle sizes. The effective rate constant of hydrogenation of CHx-s (keff, s−1) after short time on stream (1 h) was found to increase with increasing Co particle size as the result of the different preparation route applied. Transient isothermal hydrogenation (TIH) experiments following the 13CO-SSITKA-MS gas switch measured the concentration of inactive CHx (Cβ) species formed after 32 h of reaction and which were found to be readily hydrogenated at 230 °C. Temperature-programmed hydrogenation (TPH) experiments estimated the concentration of other types of inactive carbonaceous species (Cγ), which were hydrogenated at elevated temperatures (250–600 °C). The amounts of Cβ and Cγ species were found to significantly increase with increasing Co particle size, and their kinetics of hydrogenation was dependent of Co particle size. These results provided evidence for the lower deactivation rate observed under industrial FTS conditions over the Co/γ-Al2O3 (carbon-coated) catalyst. Operando SSITKA-MS-DRIFTS studies followed by transient isothermal hydrogenation coupled with kinetic modeling highlighted the influence of Co particle size on the relative reactivity (keff) of two different types of adsorbed CO-s towards hydrogen. Catalyst characterization was performed by HAADF-STEM, H2-TPR and transient hydrogen chemisorption at 100 °C followed by TPD.

Nitrate anion reduction in aqueous perchloric acid as an electrochemical probe of Pt{1 1 0}-(1 × 1) terrace sites

The electrochemical reduction of nitrate anions in aqueous 0.1 M perchloric acid has been studied using Pt(S)-[n{1 1 0} × {1 1 1}] and Pt(S)-[n{1 1 0} × {1 0 0}] single crystal electrodes. It is demonstrated that the presence of Pt{1 1 0} adsorption sites is associated with a single, broad nitrate reduction peak centred at 0.18 V (RHE). Moreover, depending on the cooling environment used after flame-annealing (CO, H2, Ar, air, nitrogen), the surface concentration of such sites varies which in turn regulates the nitrate reduction current density achievable for a given stepped Pt{h k l} electrode. The origin of this phenomenon is the propensity of the clean Pt{1 1 0} basal plane (and vicinal surfaces containing this plane) to reconstruct towards a stable (1 × 2) phase with strong CO chemisorption favouring formation of larger Pt{1 1 0}-(1 × 1) domains. In contrast, argon/air-cooling appears to promote the development of a largely (1 × 2) reconstructed surface which is much less active for nitrate reduction since the surface density of Pt{1 1 0}-(1 × 1) terrace sites is significantly diminished. Interestingly, hydrogen-cooling affords nitrate reduction activity intermediate between these two extremes. We suggest that under this particular preparation condition, a partially deconstructed (1 × 1) phase forms containing the “excess” 50% of surface atoms (originating from the (1 × 2) phase) sitting proud of the surface in the form of small (1 × 1) islands, together with residual (1 × 2) missing row regions. Hence, after hydrogen cooling, the nominal Pt{1 1 0} surface plane is speculated to exhibit a wider distribution of smaller terrace widths than found with CO cooling together with residual areas of (1 × 2). The weaker chemisorption of hydrogen apparently limits the size of the Pt{1 1 0}-(1 × 1) domains achievable and consequently, nitrate reduction activity is diminished. Based on these findings, it is proposed that nitrate reduction may be used as a quantitative electrochemical probe of Pt{1 1 0}-(1 × 1) sites at Pt nanoparticles in an analogous fashion to the method of ammonia electrooxidation presently used to quantify the surface abundance of Pt{1 0 0} sites.

Highly Active Mn3–xFexO4 Spinel with Defects for Toluene Mineralization: Insights into Regulation of the Oxygen Vacancy and Active Metals

A series of highly defected Mn3-xFexO4 spinels with different amounts of oxygen vacancies and active metals were successfully synthesized by regulating the insertion of Fe ions into the crystal structure of Mn3O4 via self-polymerizable monomer adjustment of the molten Mn-Fe salt dispersion. The characterization of X-ray diffraction, Raman, scanning electron microscopy, X-ray photoelectron spectroscopy, and N2 adsorption-desorption showed that the doping of Fe increased the lattice defects, oxygen vacancy concentration, specific surface area, mesoporosity, and catalytic properties compared to Cu ions doping. Temperature-programmed reduction with hydrogen and oxygen pulse chemisorption tests determined that the doping level of Fe ions had an important influence on the oxygen vacancy content and the dispersion of active metals on the catalysts' surfaces. For the best Mn-dispersed and most active Mn2.4Fe0.6O4 catalyst, a long-term toluene oxidation measurement running for 120 h of uninterrupted reaction, at the low temperature of 240 °C, high humidity (relative humidity = 100%), and high weight hourly space velocity of 60000 mL·g-1·h-1, was also carried out, which indicated that the catalyst possessed high stability and endurability. Moreover, the continuous oxidation route and internal principle for toluene oxidation were also revealed by the in situ diffuse-reflectance infrared Fourier transform spectroscopy and gas chromatography-mass spectrometry techniques and deep dynamics study.

Hydrogenation of toluene over nickel nanoparticles supported on SBA-3 and AlSBA-3 materials

Pure siliceous and aluminosilicate mesoporous molecular sieves of SBA-3 type were used as supports for nickel catalysts obtained via wet impregnation (1 wt.%). Characterization of obtained materials was performed by means of X-ray diffraction (XRD), X-ray fluorescence (XRF), low-temperature nitrogen adsorption/desorption (BET), temperature-programmed desorption of ammonia (TPD-NH3), hydrogen chemisorption measurements and temperature-programmed reduction with hydrogen (TPR-H2). The effect of nickel precursor (nickel nitrate or nickel acetate) and chemical composition of support (SBA-3 and AlSBA-3) on catalytic activity of prepared materials in toluene hydrogenation was studied. It was found that the catalysts obtained using nickel nitrate showed better preserved mesoporous structure with higher dispersion of Ni particles than catalysts obtained from nickel acetate. The use of AlSBA-3 as a support causes the formation of Ni particles with lower dispersion in comparison to the catalysts supported on SBA-3. The activity of nickel catalysts supported on the AlSBA-3 (especially the catalyst obtained using nickel nitrate) for toluene hydrogenation was higher than that of the catalyst supported on SBA-3 despite the lower Ni dispersion. The obtained results bring to conclusion that catalytic activity for toluene hydrogenation is significantly influenced by textural and chemical properties of the support.