Monometallic Ni Catalysts Research Articles

Ni-Fe alloying enhances the efficiency of the maltose hydrogenation process: The role of surface species and kinetic study

Unlike the conversion of monosaccharides to the corresponding polyols, the production of maltitol by hydrogenation of maltose has been seldom investigated in the literature, despite its industrial importance. Monometallic Ni catalysts are known for their lack of stability, and the objective of the present paper is to determine through a kinetic study, to what extent a Ni-Fe/SiO2 bimetallic catalyst would outperform a Ni/SiO2 catalyst in the aqueous phase hydrogenation of maltose, as they have been reported to do for monosaccharides. The effect of reaction parameters (T = 80–150 °C, PH2 = 20–40 bar, maltose mass fraction in water = 4.4–17.5 wt%) on activity, selectivity, and stability was examined. In all cases, maltitol was the major product, with a carbon balance higher than 98%, but maltose hydrolysis to glucose occurred in the upper range of temperature. In order to preserve both the catalyst selectivity and stability, a temperature of 80 °C was selected for the kinetic study. A first order model including an inhibiting term based on maltose concentration could fit the evolution of the conversion of maltose as a function of time. The adsorption constant of maltose and the apparent hydrogenation rate constant for the Ni-Fe catalyst were both larger by a factor 2–3 compared with the Ni catalyst, indicating a stronger interaction of maltose with the Ni-Fe surface. Another major difference was a reaction order of 0.5 with respect to the hydrogen pressure on Ni-Fe/SiO2 compared with a near zero-order on Ni/SiO2, stressing significant differences in coverage of the bimetallic surface. The activity of the Ni-Fe catalyst remained constant for three runs of reaction without major structural changes, while the Ni catalyst deactivated by transforming to a phyllosilicate phase. As far as activity, selectivity and stability are concerned; Ni-Fe/SiO2 appeared as a better suited catalyst than Ni/SiO2 for the aqueous phase hydrogenation of maltose at 80 °C, with a more pronounced benefit than formerly reported for xylose on the same catalysts.

Hydrogen production from aqueous phase reforming of glycerol over attapulgite-supported nickel catalysts: Effect of acid/base treatment and Fe additive

In this paper, a series of nickel-based catalysts supported on modified attapulgite (ATP) by acid (citric acid and EDTA) and base (NaOH) were prepared and applied to the aqueous phase reforming of glycerol (APRG). The modified ATP (MA) and as-prepared catalysts were detected using N2 adsorption-desorption, ICP-OES, XRD, FT-IR, SEM-EDS, HRTEM, XPS, H2-TPR, NH3-TPD. The results manifested that the acid/base treatment of ATP significantly increased the surface area and pore volume, enhanced the metal-support interaction (MSI) and decreased the Ni particle size, resulting in the better glycerol conversion and H2 selectivity, especially for Ni/MA-E catalyst, where the ATP was pretreated using EDTA. In addition, the bimetallic NiFe/MA-E catalyst exhibited the highest conversion of glycerol to gas product (54.4%) and H2 selectivity (84.6%) at very low temperature (280 °C). These results were attributed to the strongest the interplay of active metal with support by the formation of Ni–Fe alloy, resulting in the highest active metal dispersion, smallest metal particle size, lowest the reducibility of active metal and most surface Ni0 content. According to the characterizations of spent catalysts, it demonstrated that monometallic Ni catalysts presented obvious sintering of Ni metal particle and larger accumulation of carbon deposition, which led to the deactivation of the catalyst. While NiFe/MA-E catalyst showed less particle agglomeration and coke formation attributed to the lower content of surface acid site. Apart from that, another cause of catalyst deactivation might be the destruction of ATP skeleton during APRG.

Selective Hydrogenation Properties of Ni-Based Bimetallic Catalysts

Metallic Ni shows high activity for a variety of hydrogenation reactions due to its intrinsically high capability for H2 activation, but it suffers from low chemoselectivity for target products when two or more reactive functional groups are present on one molecule. Modification by other metals changes the geometric and electronic structures of the monometallic Ni catalyst, providing an opportunity to design Ni-based bimetallic catalysts with improved activity, chemoselectivity, and durability. In this review, the hydrogenation properties of these catalysts are described starting from the typical methods of preparing Ni-based bimetallic nanoparticles. In most cases, the reasons for the enhanced catalysis are discussed based on the geometric and electronic effects. This review provides new insights into the development of more efficient and well-structured non-noble metal-based bimetallic catalytic systems for chemoselective hydrogenation reactions.

Hydrogen production from steam reforming of acetic acid over Pt–Ni bimetallic catalysts supported on ZrO2

Acetic acid, a model compound of bio-oil, was chosen to investigate the H2 production from steam reforming reaction using Pt and Ni catalysts supported on ZrO2. Ni crystallite sizes decreased with addition of Pt (from 23 to 15 nm), increasing the metallic dispersion (from 4.4 to 6.5%). A spillover effect was identified in bimetallic catalysts and caused a significant decrease of Ni reduction temperature. Although the Ni crystallite size in 15Ni/ZrO2 is larger, it showed 100% of conversion and the highest H2 yield (about 30%) during 30 h of reaction at 500 °C. In contrast to what was expect, the performance of bimetallic catalysts was not so good when compared to the monometallic Ni catalyst. 5Pt15Ni/ZrO2 and 1Pt15Ni/ZrO2 showed about 20% of H2 yield at the end of reaction. 1Pt/ZrO2 presented the worst catalytic performance; it produced more acetone, which can be correlated to its higher acidity, and deactivated very fast, with the highest coke formation rate. Coke was predominantly amorphous for all catalysts.

The Effect of Modifiers on the Performance of Ni/CeO2 and Ni/La2O3 Catalysts in the Oxy-Steam Reforming of LNG.

This work interrogates for the first time the catalytic properties of various monometallic Ni catalysts in the oxy-steam reforming of LNG. Various research techniques, including X-ray diffraction (XRD), specific surface area and porosity analysis (BET method), scanning electron microscopy with X-ray microanalysis (SEM-EDS), temperature-programmed desorption of ammonia (TPD-NH3), temperature-programmed reduction (TPR-H2) and the FTIR method, were used to study their physicochemical properties. The mechanism of the oxy-steam reforming of LNG is also discussed in this paper. The high activity of monometallic catalysts supported on 5% La2O3–CeO2 and 5% ZrO2–CeO2 oxides in the studied process have been proven and explained on the basis of their acidity, specific surface area, sorption properties in relation to the reaction products, the crystallite size of the metallic nickel and their phase composition.

Ethanol condensation to butanol and higher alcohols over nickel and cobalt decorated Ce-Al mixed oxide catalysts

Anew series of bimetallic Ni-Co catalysts, prepared by step wise substitution of Ni by Co, in mono metallic Ni (8%)/ CeO2 -Al2O3,withthe compositions of 6%Ni-2%Co, 4%Ni-4%Co, 2.5%Ni-5.5% Co and 8% Co, have been evaluated for conversion of ethanol to butanol and higher alcohols according to Guerbet alcohol chemistry.XRD, TPR and XPS studies reveal the formation of Ni-Co alloys at specific bimetallic compositions. Maximum reducibility is observed for the composition 4%Ni-4%Co,which also displays maximum ethanol conversion (55.1%) with C4+ alcohols selectivity of 50.2%, which are higher than those realized for mono metallic Ni and Co catalysts. Ni-Co alloys in bimetallic catalysts promote the crucial ethanol dehydrogenation and C4 and C4+ aldehydes hydrogenation steps in the Guerbet process, there by increasing ethanol conversion and C4+ alcohol selectivity. Selection of bimetallic catalysts with specific compositions seems to be one of strategies to improve ethanol conversion and higher alcohols selectivity.

Screening Transition Metals (Mn, Fe, Co, and Cu) Promoted Ni-Based CO2 Methanation Bimetal Catalysts with Advanced Low-Temperature Activities

The Ni monometallic catalyst usually exhibits poor CO₂ methanation activity, although its low cost is beneficial for conducting large-scale application in industries. Herein, the transition metal (Mn, Fe, Co, and Cu)-doped Ni-based bimetallic catalysts loaded on mesoporous Ce₀.₈Zr₀.₂O₂ solid solution were prepared to address this challenge in CO₂ methanation. We found that the Co-doped catalysts exhibited much higher activity than the corresponding counterparts. Therefore, the relationship between the Co/Ni ratio and activity was further investigated to acquire the optimum ratio. The obtained catalysts were characterized by various measurements. The results demonstrated that doping the second transition metals could promote Ni dispersion and strengthen metal–support interaction. Resultantly, serious agglomeration of the metallic active sites was successfully inhibited. Besides, we also carried out the in situ diffuse reflectance infrared spectroscopy and online temperature-programmed surface reaction of CO₂ methanation to study the possible reaction intermediates and pathways over the Ni–Co bimetallic catalysts. A dynamic study was also conducted to further study the effect of the doped transition metals on the apparent activation energies. Besides, the present research also revealed that the Ni–Co synergistic effect significantly improved the low-temperature activity by regulating the reaction intermediates. As a result, the Ni–Co bimetallic catalysts supported by mesoporous Ce₀.₈Zr₀.₂O₂ solid solution were considered as a series of promising and efficient low-temperature CO₂ methanation catalysts.

Deoxygenations of palm oil-derived methyl esters over mono- and bimetallic NiCo catalysts

In this work, series of SAPO-11-supported monometallic Ni, Co and bimetallic NiCo catalysts were prepared and tested for their activities toward the deoxygenation of palm oil-derived fatty acid methyl esters (FAMEs). Effects of metal introduction methods, i.e., co-impregnation (NiCo/SAPO-11) and sequential-impregnation (Ni/Co/SAPO-11 and Co/Ni/SAPO-11) for bimetallic catalysts on their catalytic performance were also investigated. It was confirmed by X-ray diffraction and transmission electron microscopy with elemental mapping that bimetallic Ni–Co alloy phase was formed. X-ray photoelectron spectroscopy results revealed that different metal loading steps caused different Ni:Co ratios on catalyst surfaces. Those values corresponded to the sequence of metal loading from which the outer shell possessed higher concentration than the co-impregnated NiCo/SAPO-11 with a comparable Ni and Co atomic concentration. H2 temperature programmed reduction investigation showed that the incorporation of Co species could improve the reducibility of bimetallic catalysts. Among all synthesized catalysts, the deoxygenation of palm-oil derived FAMEs over Co/Ni/SAPO-11 catalyst, with Co surface enrichment, exhibited the highest yield of diesel range fuel (i.e., ~ 89% at 330 °C). It was revealed that Co active sites play an important role to promote the deoxygenation due to the strong Co–O interaction. The synergy through Ni–Co alloying would be an efficient approach to enhance the deoxygenation of palm-oil derived FAMEs to diesel-like hydrocarbon fuels.

Nano-rod like morphology of Ni@Fe3O4-NDCs on interaction of NDC-supported Fe3O4 with nickel NPs: An efficient catalyst for ligand free Chan-Lam coupling reaction in aqueous medium

Nitrogen doped carbons were synthesized and fabricated with magnetite nanoparticles leading to a new magnetic and nitrogen functionalities rich carbon material. This material has dual characteristics as the magnetization of carbons makes it easily separable and the nitrogen moieties act as a binder for both magnetite and metal nanoparticles. This excludes the need for extra binding sites. Nickel and/or iron supported five different catalysts were synthesized and their catalytic activity was tested for Chan-Lam coupling and satisfactory results were obtained with two catalysts- Ni@Fe–Fe3O4–NDCs and Ni@Fe3O4–NDCs, wherein the monometallic counterpart having an upper edge. The characterization of these catalysts provides sufficient evidence for the unexpected enhanced catalytic activity of the monometallic Ni catalyst as compared to its bimetallic counterpart. The most eye-catching thing observed was the difference in morphology of the two synthesized catalysts, which clearly indicated some major changes in the interaction of the metal nanoparticles with the support material in the two catalysts since same method was adopted for the preparation of both. Additional lattice fringes of NiFe2O4 in the HRTEM images along with their corresponding peaks in the XRD spectrum, and the presence of pure Ni2+ species in the XPS spectrum of the monometallic catalyst provides a clear vision of the reason behind the enhanced catalytic activity of the monometallic catalyst. The formation of nano-rod like supported NiFe2O4 particles with increased surface area, mean pore volume and large number of active sites increases the activity of monometallic-Ni for Chan-Lam cross-coupling.

Synthesis, Characterisation, and Performance Evaluation of Promoted Ni‐Based Catalysts for Thermocatalytic Decomposition of Methane

AbstractThermocatalyatic decomposition (TCD) of methane to COX free hydrogen and carbon nanofibre (CNF) was investigated over a series of self‐designed monometallic Ni catalyst and bimetallic Ni−Cu and Ni−Pd catalysts. The catalysts were synthesised from the wet impregnation method and characterised using a series of complementary techniques include TGA, XRD, BET, TPR, FESEM, TEM, and Raman Spectroscopy. Despite a substantial reduction of surface area in the promoted catalysts, the catalytic activity of the promoted catalyst was enhanced due to the nature of the process which is a metal‐catalysed reaction. As a whole, bimetallic Pd−Ni catalyst with a surface area of 2.76 m2 g−1 possesed the highest conversion of 77 % after 6 h reaction. The overall TCD reaction was found to be first‐order with the calculated activation energy, Ea of 38 kJ mol−1. The methane consumption rates at 1023 K and 1073 K were 0.5 mol s−1gcat−1 and 0.58×104 mol s−1gcat−1 respectively. Meanwhile, the methane consumption rates improved considerably from 0.58 mol s−1gcat−1 to 0.67×104 mol s−1gcat−1 under the methane partial pressure of 41 kPa. The XRD profile of the fresh catalysts revealed that mixed oxides were formed over the surface of the support upon the addition of Cu and Pd to 50 %Ni/Al2O3. Moreover, the formation of carbon nanofibers followed both tip and base growth mechanisms as evident from the TEM images. Larger and wider carbon fibres were found in the Pd promoted catalyst.

Atomically-ordered active sites in NiMo intermetallic compound toward low-pressure hydrodeoxygenation of furfural

Activation of oxygen-containing functional groups plays a key role in sustainable biomass upgrading and conversion. In this work, a NiMo intermetallic compound (IMC) catalyst was prepared based on layered double hydroxides (LDHs) precursors, which displayed prominent catalytic performance for furfural hydrodeoxygenation (HDO) to 2-methylfuran (2-MF) (yield: 99 %) at a rather low hydrogen pressure (0.1 MPa), significantly superior to NiMo alloy, monometallic Ni and other Ni-based catalysts ever reported. CO-IR, STEM, EXAFS and XANES give direct evidences that the atomically-ordered Ni/Mo sites in NiMo IMC determine the uniform bridging-type adsorption mode of CO bond in furfural whilst adsorption of furan ring is extremely suppressed. In situ FT-IR and DFT calculation further substantiate that ordered Ni-Mo bimetallic sites of IMC, in contrast to the random atomic sequence in NiMo alloy, facilitate the activation and cleavage of COH bond in the intermediate (furfuryl alcohol, FOL), accounting for the production of 2-MF. This work demonstrates the decisive effect of atomically-ordered active sites in IMC catalyst on activation of oxygen-containing functional groups and product selectivity, which can be extended to catalytic upgrading of biomass-derived platform molecules.

Synthesis of renewable hydrocarbons from vegetable oil feedstock by hydrotreatment over selective sulfur-free SiO2-Al2O3 supported monometallic Pd, Pt, Ru, Ni, Mo and bimetallic NiMo catalysts

Screening tests of commercial and prepared monometallic Ni, Mo, Pd, Pt, Ru and bimetallic NiMo catalysts synthesized by four different impregnation methods were performed to evaluate their selectivity and performance on hydrocarbon production from vegetable oil feedstock with high free fatty acid (FFA) content (~50%) by solvent-free hydrotreatment (HT). Catalysts were characterized by N2 sorption analysis, XRF, XRD, FE-SEM and TEM. Composition of feedstock and liquid, gaseous products were analyzed by C, H, N, S elemental analysis, FT-IR, GC-FID, GC–MS and GC-TCD. Mo promoted Ni17Mo3DP synthesized using developed one-pot deposition–precipitation procedure exhibits great performance, selectivity to n-C18 and 6–7% higher hydrocarbon yield (~87%) than elevated metal loading (≥65%) commercial Ni65C and Ni66C catalysts achieved at relatively mild reaction temperature 320–340 °C and initial H2 pressure 6–10 MPa. Completely different selectivity of highly active Ru, Ni and NiMo catalysts can be beneficial for wide molecular weight marketable renewable hydrocarbon production from fatty acid containing raw materials.

Effect of Ag-Addition on the Catalytic and Physicochemical Properties of Ni/ZrO2 Catalyst in Oxy-Steam Reforming of CH4 and LNG Processes

This work presents, for the first time, the catalytic studies of bimetallic Ag-Ni catalysts in the oxy-steam reforming (OSR) of liquefied natural gas (LNG) to hydrogen generation. The physicochemical properties of monometallic Ni and bimetallic catalysts were investigated using various techniques, such as: BET, TPR-H2, TPD-NH3, XRD, TG and SEM-EDS. The catalytic studies showed that the promotion of 20% Ni/ZrO2 catalyst by silver (by 1 or 2 wt.%) improves the efficiency of the produced hydrogen in the oxy-steam reforming of LNG at high temperature. The promotional effect of silver on the reducibility of a Ni/ZrO2 catalyst has been proven. The interactions between Ag and Ni have been proven, and explain the catalytic activity of the catalysts in the investigated processes. TG-DTA-MS results obtained for the spent catalysts proved that the small addition of silver to monometallic nickel catalyst reduces the amount of the carbon deposit formed on the catalyst surface during the oxy-steam reforming of LNG process. Obtained results in this work confirmed that liquid natural gas processing may become an alternative to fossil fuels and confirmed the validity of the hydrogen production via oxy-steam reforming of LNG.

Characterization of none and yttrium-modified Ni-based catalysts for dry reforming of methane

Monometallic and bimetallic RhNi catalysts supported on γ-alumina and yttria-modified alumina were developed. The relation between the support kind, the structure and catalytic properties of the catalysts in dry reforming of methane was studied by using different techniques such as: N2 isotherms, UV–vis DRS, XRD, TPD-NH3, TPR-H2, XPS and HRTEM. Variation in the electronic environment of the nickel, rhodium and yttrium atoms as a function of the catalyst pretreatment and support kind was observed. It was shown that the couple pairs of Nio/Nin+ and/or Rho/Rhn+ act as active sites. The difference in the catalytic behaviors of catalysts was connected with the distribution of metal particles. Y-loaded monometallic Ni catalyst showed higher activity and stability than alumina supported Ni due to the proximity of nickel to yttrium oxide species expressed by the increase of metal dispersity. The close contact between Rh and Ni leaded to better catalytic behavior of bimetallic RhNi/Al catalyst due to the better reducibility of nickel oxide species and homogeneous distribution of the particles with average diameter size of ∼ 5 nm.

Highly Efficient SiC-Supported Ni-Based Catalysts with Enhanced Recycle Stability for One-Pot Cellobiose Hydrolytic Hydrogenation to Hexitols

In this contribution, SiC material was applied as the catalyst support in the aqueous-phase reaction of one-pot cellobiose hydrolytic hydrogenation to hexitols, with the less costly transition metal Ni. Even with its neutral nature, more than 50% hexitol yield was achieved with Ni contents as low as 3 wt % supporting on SiC, and further improved to near 70% hexitol yield with Ni loadings increased to 5 wt %. The catalytic performances were superior to the others supported with different carriers (Al2O3, carbon nanotube (CNT), and AC). DFT simulation results indicate that the H2 dissociation energy on the Ni4/SiC(111) slab is at −26.9 kcal/mol, which is substantially lower than those on the Ni4/Al2O3(100) slab (−34.1 kcal/mol) and Ni4/graphene slab (−32.5 kcal/mol, taken graphene as a local structure of CNT). The hexitol yield on SiC-supported Ni catalyst was further improved to 75.7% with Ir promoter, more importantly, with a much enhanced recycle stability. Hexitol yield could be maintained around 60% even after five cycles on Ir-promoted catalyst, compared to 12% after only three cycles on Ni monometallic catalyst. ICP-OES results revealed that the leaching of Ni was greatly inhibited with the assistance of Ir. The results of the H2-TPR analysis suggest an easier H2 activation ability observed on the surface of Ir-promoted catalyst due to the synergetic effects between Ni and Ir. The findings would shed light on SiC for further applications in biomass conversion.

An experimental and first principles DFT investigation on the effect of Cu addition to Ni/Al2O3 catalyst for the dry reforming of methane

The influence of varying Cu atomic ratios in a bimetallic Ni-Cu catalytic system for the CO2 or Dry Reforming of Methane (DRM) is investigated experimentally, in conjunction with ab-initio Density Functional Theory (DFT) and Generalized Power Law Expression (GPLE)-based mathematical modeling approaches. Among the synthesized catalysts, an 8:1 Ni:Cu ratio shows highest activity with stable H2/CO selectivity compared to its monometallic counterpart. Detailed physico-chemical characterization of the catalysts indicate that copper addition minimizes deactivation by forming a Ni-Cu alloy that increases reducibility of the NiO and limits the tendency of the active site toward coke formation. DFT calculations reveal increased energy barrier for carbon adsorption, whilst promoting facile removal of deposited carbon. GPLE analysis of the deactivation profiles suggest coking as the primary deactivation route in monometallic Ni catalyst; although much lesser in extent, deactivation of Ni8Cu1/Al2O3 catalyst is induced by both sintering and coking regimes.

COx co-methanation over coal combustion fly ash supported Ni-Re bimetallic catalyst: Transformation from hazardous to high value-added products

The hazardous industrial waste, coal combustion fly ash (CCFA), was creatively applied as Ni-Re bimetallic catalyst support. The expected catalyst was facilely prepared by co-impregnation method and further tested for COx co-methanation in a continuous fixed-bed reactor. The physico-chemical properties of the catalyst were examined by a series of techniques including XRF, ICP, XRD, N2 isothermal adsorption, H2-TPR, SEM and TEM. The results showed that compared to non-promoted monometallic Ni catalyst, the addition of Re promoter forming Ni-Re bimetallic catalyst was able to facilitate NiO reduction and increase Ni dispersion as well as inhibit carbon deposition and Ni sintering during reaction. The performance tests revealed that Ni15Re1.0 presented superior COx co-methanation activity over Ni15Re0, Ni15Re0.5 and Ni15Re1.5 due to its better anti-coking and anti-sintering ability. Based on in-situ DRIFTS analysis, a possible cycle reaction mechanism of COx co-methanation was reasonably proposed in the end. The reaction pathway for CO and CO2 methanation differed from each other, where CO was linearly adsorbed on Ni metals followed by stepwise hydrogenation while CO2 was first immobilized by the surface hydroxyl group and then gradually reacted with H2 to form CH4.

Chemoselective nitroarene hydrogenation over Ni-Pd alloy supported on TiO2 prepared from ilmenite-type PdxNi1−xTiO3

Herein, we prepared TiO2 (rutile)-supported monometallic Ni and bimetallic Pd-Ni catalysts by thermal reduction of PdxNi1−xTiO3 (x = 0 and 0.045) and evaluated their performance for the chemoselective hydrogenation of nitrobenzene under optimized conditions. In contrast to Ni/TiO2, Pd-Ni/TiO2 featured a negligible loss of both conversion and aniline yield over five consecutive catalytic cycles, and instrumental analysis and catalytic activity evaluation revealed that this enhanced stability is due to Pd-Ni-alloy formation. Furthermore, Pd-Ni/TiO2 was used to prepare aromatic-amines used as building blocks for the production of important drugs precursors, achieving conversions of >98 % and a chemoselectivity of 99 % in the absence of undesired side-reactions.

Hydrogen Production via the Oxy-Steam Reforming of LNG or Methane on Ni Catalysts

Ni catalysts supported on ZrO2, 5%CeO2-ZrO2, and 5%La2O3-ZrO2 were prepared via the impregnation method and tested in the oxy-steam reforming of methane and liquified natural gas (LNG). All tested catalysts exhibited high catalytic activity in the studied process at 700 and 900 °C. The improvement of the stability of Ni catalysts after the addition of CeO2 oxide in the studied oxy-steam reforming of LNG process was confirmed. In addition, high activity and selectivity towards hydrogen was proven in the oxy-steam reforming process at 900 °C over a 20%Ni/5%CeO2-ZrO2 catalyst. It was also proved that the addition of CeO2 onto a ZrO2 carrier leads to a decrease in the NiO and metallic Ni crystallite sizes that were detected by the X-Ray diffraction (XRD) technique. The solid solution formation between NiO and ZrO2 and/or NiO and CeO2 was proved. Superior reactivity in the oxy-steam reforming of CH4 and the LNG process exhibited a 20%Ni/ZrO2 catalyst, which showed the highest methane conversions at 500 and 600 °C, equal to 63% and 89%, respectively. In addition, also in the case of the LNG reforming reaction, the most active catalyst was the 20%Ni/ZrO2 system, which demonstrated 46.3% and 76.9% of the methane conversion value at 500 and 600 °C and the total conversion of others hydrocarbons (ethane, propane and butane). In addition, this catalytic system exhibited the highest selectivity towards hydrogen formation in the oxy-steam reforming of the LNG reaction equal to 71.2% and 71.3% at 500 and 600 °C, respectively. The highest activity of this system can be explained by the uniform distributions of Ni species and their highest concentration compared to the rest of the monometallic Ni catalysts. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) results also confirmed a strong interaction of NiO with ZrO2 in the case of the 20%Ni/ZrO2 catalysts. The presence of selected NiZrO+ ions emitted from the investigated surface of the 20%Ni/ZrO2 system was detected.

Supported Ni–Au Colloid Precursors for Active, Selective, and Stable Alkyne Partial Hydrogenation Catalysts

Bimetallic NiAu catalysts have garnered broad interest for a variety of reactions including automotive emissions, selective hydrogenation, selective oxidation, hydrodechlorination, and biomass conversion. However, the bulk immiscibility of the two metals, complicating catalyst synthesis, has limited studies of this bimetallic system. We report a solution-phase synthesis for Ni and bimetallic NiAu heterogeneous catalysts. Using oleylamine as a capping agent, an optimized synthesis for Ni catalysts led to supported particles with a narrow size distribution (4.7 ± 0.4 nm). Gold was added to the Ni nanoparticles via galvanic displacement of Ni in organic solution, the particles were deposited onto commercial alumina, and oleylamine capping agent was removed. The catalytic activity of the bimetallic materials in 1-octyne partial hydrogenation was in between the activity of monometallic Ni and Au catalysts. At high space velocity, the bimetallic catalysts largely maintained the high alkene selectivity associate...