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Hydrogenation catalyst is of major importance in the production of eco-friendly oxidant hydrogen peroxide. Herein, in this work co-precipitation and an incipient wetness-impregnation method are use...

In this study, Pd-Mg(Al)-LDH/γ-Al2O3 and Pd-Mg(Al)Zr-LDH/γ-Al2O3 precursors were synthesized by impregnating Na2PdCl4 on Mg(Al)-LDH/γ-Al2O3 and Mg(Al)Zr-LDH/γ-Al2O3, and then the precursors were calcinated and reduced to obtain Pd-Mg(Al)-MMO/γ-Al2O3 and Pd-Mg(Al)Zr-MMO/γ-Al2O3 catalysts. Compared with Pd/γ-Al2O3 catalyst, the hydrogenation efficiency of Pd-Mg(Al)-MMO/γ-Al2O3 and Pd-Mg(Al)Zr-MMO/γ-Al2O3 increased by 15.7% and 24.0%, respectively. Moreover, the stability of Pd-Mg(Al)Zr-MMO/γ-Al2O3 catalyst was also higher than that of Pd/γ-Al2O3. After four runs, the hydrogenation efficiency of Pd/γ-Al2O3 decreased from 12.1 to 10.0 g/L, while that of Pd-Mg(Al)Zr-MMO/γ-Al2O3 decreased from 15.0 to 14.3 g/L. The active aquinones selectivities of all catalysts were almost 99%. The structures of the catalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), N2 adsorption–desorption, inductively coupled plasma-atomic emission spectrometry (ICP-AES), CO chemisorption analysis, transmission electron microscopy (TEM), temperature-programmed reduction with hydrogen (H2-TPR), and X-ray photoelectron spectroscopy (XPS). The results indicate that the improved catalytic performance is attributed to the stronger interaction between Pd and Mg(Al)Zr-MMO/γ-Al2O3, smaller Pd particle size and higher Pd dispersion. This work develops an effective method to synthesize highly dispersed Pd nanoparticles based on the layered double hydroxides (LDHs) precursor.

Manipulating the surface acidic/basic property and pore structure of support are two effective approaches to increase catalytic performance of Pd-based catalyst in anthraquinone (eAQ) hydrogenation. Herein, to combine two promoting approaches, array-typed NiO/Al supported Pd catalyst were synthesized. By regulating preparation method, three Ni(OH)2/Al support precursors showed different morphologies of nest-like, face-to-face packed and dandelion-like structure, respectively. After loading Pd, three Pd/NiO/Al catalysts exhibited different catalytic performance in eAQ hydrogenation, among which the nest-like catalyst possessed the highest H2O2 space time yield of 107.5 g gPd−1 h−1 with > 99% selectivity to active anthraquinone. Detailed characterizations were performed to investigate the pore structure, basic property and electronic structure caused by different morphologies of catalysts, to explain the structure-performance relationship. Specifically, on the basis of ensuring effective collision of reactant molecules, the outer opening pores (20–100 nm) could decrease diffusion barriers of eAQ/eAQH2, which improves active site accessibility for eAQ and benefits desorption of eAQH2. In addition, suitable amount of weak basic sites Ni2+–OH with high electronic density appropriately improves surface electronic density of Pd NPs, which moderately enhances H2 activation/dissociation but could not lead to over hydrogenation to give deeply hydrogenated byproducts.

A series of Pd-La/SiO2/cordierite (cordierite = COR) and Pd-Zn/SiO2/COR bimetallic monolithic catalysts were prepared, characterized, and tested for the hydrogenation of 2-ethylanthraquinone (eAQ) as the key step of anthraquinone method for production of H2O2. It was found that the metal particle size is remarkably dependent on the Pd/M (M = La, and Zn) mass ratio of bimetallic monolithic catalysts. By virtue of its small metal particle size and the strong interaction, the 0.8% Pd-0.4% La/SiO2/COR monolithic catalyst presents the highest H2O2 yield (7.7 g L−1) and selectivity toward active quinones (95%), which is attributed to the addition of La leading to the synergistic effect between Pd and La. Moreover, the density functional theory (DFT) calculations for the adsorption of eAQ over the surface of Pd-La/SiO2/COR and Pd-Zn/SiO2/COR bimetallic monolithic catalysts have been conducted to further understand the mechanism of molecule–surface interactions between eAQ and the PdM(1 1 1) or Pd(1 1 1) surfaces. Detailed studies showed that the high catalytic activity of Pd-La/SiO2/COR bimetallic monolithic catalyst is attributed to the stronger adsorption between Pd3La1 (1 1 1) and the carbonyl group of eAQ.

Palladium metal has been used extensively in the hydrogenation reactions due to their great affinity towards hydrogen atoms. In the present study, the catalyst preparation attempted with Pd supported Hollow Ceramic Microspheres using wet impregnation method and its use as catalysts is explored in the hydrogenation of 2-ethylanthraquinone studing the effect of the reaction time, temperature, volume of working solution and the catalyst dosages on the conversion of 2-ethylanthraquinone and yield of hydrogen peroxide. The hydrogenation reaction of 2-ethylanthraquinone is the key step in the anthraquinone method for the industrial production of the hydrogen peroxide. The Pd supported catalyst was characterized by XRF, FTIR, and BET to confirm the composition of the prepared catalyst, Pd deposition, and the surface area. The highest catalyst activity was found to be 9.42 ​g/L with the maximum conversion of 96% at 70°C, 0.3 ​MPa. The kinetics of the heterogeneous hydrogenation reaction of 2-ethylanthraquinone with Pd supported on Hollow Ceramic Microspheres as catalyst was also investigated. This paper is in contribution of our earlier publication.

A series of Pd/zeolite/cordierite (zeolite = MCM-41, SBA-15, Beta, or MCM-22; cordierite = COR) monolithic catalysts, as well as Pd/ZIF-8/COR, Pd/Al2O3/COR, and Pd/SiO2/COR, were prepared, characterized, and evaluated for the hydrogenation of 2-ethylanthraquinone (eAQ) to 2-ethyl-9,10-anthrahydroquinone (eAQH2). We found that a 0.8% Pd/MCM-41/COR catalyst exhibited the highest H2O2 yield (7.54 g L−1) and selectivity (85.3%) toward active quinones for hydrogen peroxide (H2O2) production using the anthraquinone method. Notably, the Pd efficiency (1573 gH2O2 g−1Pd h−1) for the 0.8% Pd/MCM-41/COR monolithic catalyst was much higher than that of a commercial pellet catalyst (500 gH2O2 g−1 Pd h−1). The intrinsic kinetics of hydrogenation of eAQ over 0.8% Pd/MCM-41/COR was measured, and the kinetic equation parameters were incorporated into a computational fluid dynamics (CFD) model. The mass transfer coefficients for the monolithic catalysts are 5–20 times higher than the pelleted catalyst. In addition, we found that the gas-liquid mass transfer is the controlling step, showing the unique advantages of monolithic catalysts for process intensification.

Pd–Ir mesocrystals with rough surface and highly branched structure were synthesized through a facile co-reduction method. The morphology evolution shows the mesocrystals were formed by oriented attachment of nanoparticles, and abundant defects sites as well as synergetic effect between building units were formed during mesocrystals oriented attachment process. Therefore, the supported Pd–Ir mesocrystals show a significant enhancement in catalytic performance in hydrogenation of 2-ethylanthraquinone compared with conventional Pd–Ir nanoparticles. The high activity can be ascribed to high densities of defect sites in Pd–Ir MCs catalyst, which facilitated H2 activation. In addition, the geometric effect of Pd–Ir MCs catalyst was responsible for inhibiting further hydrogenation of eAQH2 to undesired consecutive byproducts.

A series of χ wt % Pd-(1-χ) wt % Ir (χ = 0.75, 0.50, and 0.25) catalysts supported on γ-Al2O3 have been prepared by co-impregnation and calcination-reduction, and subsequently employed in the hydrogenation of 2-ethylanthraquinone—a key step in the manufacture of hydrogen peroxide. Detailed studies showed that the size and structure of the bimetallic Pd–Ir particles vary as a function of Pd/Ir ratio. By virtue of its small metal particle size and the strong interaction between Pd and Ir, the 0.75 wt % Pd–0.25 wt % Ir/Al2O3 catalyst afforded the highest yield of H2O2, some 25.4% higher than that obtained with the monometallic 1 wt % Pd catalyst. Moreover, the concentration of the undesired byproduct 2-ethyl-5,6,7,8-tetrahydroanthraquinone (H4eAQ) formed using the Pd–Ir bimetallic catalysts was much lower than that observed with the pure Pd catalyst, which can be assigned to the geometric and electronic effects caused by the introduction of Ir. © 2017 American Institute of Chemical Engineers AIChE J, 63: 3955–3965, 2017

The catalytic performance of Pd-N/Silicon Dioxide/Cordierite (Pd-N/SD/C) (N = Ga and Ag) bimetallic monolithic catalysts for 2-ethylanthraquinone (eAQ) hydrogenation was investigated. Catalyst characterization by HRTEM, XPS, and TPR reveal that Pd-Ga/SD/C can form an alloy structure to produce significant synergetic effects. Moreover, the use of different Pd/Ga mass ratio in catalysts reveals that when the mass ratio of Pd and Ga/Ag = 2:1, Pd-Ga/SD/C obtains the highest yield of H2O2 and selectivity toward active quinones, which can reach 7.4 g L−1 and 90%. Moreover, to have a deep understanding of the eAQ-PdN(1 1 1) or eAQ-Pd(1 1 1) interaction mechanism, the calculation of eAQ adsorption on Pd-N/SD/C catalysts surface was performed by density functional theory (DFT). It is shown that the higher catalytic activity over Pd-Ga/SD/C is due to the stronger carbonyl group of eAQ adsorption on Pd3Ga1 (1 1 1).

The hydrogenation of 2-ethylanthraquinone (eAQ), 2-tert-amylanthraquinone (taAQ) and their mixtures with molar ratios of 1:1 and 1:2 to the corresponding hydroquinones (eAQH2 and taAQH2) were studied over a Pd/Al2O3 catalyst in a semi-batch slurry reactor at 60 °C and at 0.3 MPa. Compared to eAQ, TaAQ exhibited a significantly slower hydrogenation rate (about half) but had a higher maximum yield of H2O2 and a smaller amount of degradation products. This can be ascribed to the longer and branched side chain in taAQ, which limits its accessibility to the Pd surface and its diffusion through the pores of the catalyst. Density functional theory calculations showed that it is more difficult for taAQ to adsorb onto a Pd (111) surface than for eAQ. The hydrogenation of the eAQ/taAQ mixtures had the slowest rates, lowest H2O2 yields and the highest amounts of degradation products.

A series of bimetallic PdRu catalysts supported on γ-Al2O3 were prepared by incipient wetness impregnation method and were assessed in the 2-ethylanthraquinone hydrogenation process. It is found that the addition of Ru to Pd can improve the catalyst's activity and maintain high selectivity at the same time for 2-ethylanthraquinone hydrogenation. Several analysis techniques including N2 adsorption–desorption, ICP-AES, XRD, TEM, H2-TPR, H2-TPD and XPS were adopted for characterizing the structural and electronic properties of the samples. It is revealed that PdRu bimetallic system shows stronger hydrogen desorption behavior in contrast to the monometallic catalysts. In addition, the higher fraction of Pd2+ and the presence of Ru4+ in the PdRu system may act as the electrophilic sites for the adsorption and activation of the CO of the 2-ethylanthraquinone molecule through the lone electron pair of the oxygen atom. These factors may be attributed to the superior performance of PdRu bimetallic samples for 2-ethylanthraquinone hydrogenation.

Pd/oxide/cordierite monolithic catalysts (oxide = Al 2 O 3 , SiO 2 and SiO 2 Al 2 O 3 ) were prepared by the impregnation method. The results of ICP, XRD, SEM–EDX, XPS and N 2 adsorption–desorption measurements revealed that the Pd penetration depth increased with increasing the thickness of oxide layer, and the catalysts with Al 2 O 3 layers had the larger pore size than those with SiO 2 and SiO 2 Al 2 O 3 layers. Catalytic hydrogenation of 2-ethyl-anthraquinone (eAQ), a key step of the H 2 O 2 production by the anthraquinone process, over the various monolithic catalysts (60 °C, atmosphere pressure) showed that the monolithic catalyst with the moderate thickness of Al 2 O 3 layer (about 6 μm) exhibited the highest conversion of eAQ (99.1%) and hydrogenation efficiency (10.0 g·L − 1 ). This could be ascribed to the suitable Pd penetration depth and the larger pore size, which provides a balance between the distribution of Pd and accessibility of active sites by the reactants.

Highly dispersed Pd/AlPO-5 catalyst was prepared and tested in the hydrogenation of 2-ethylanthraquinone. Characterization results suggested that the abundant surface P-OH groups of AlPO-5 zeolite substituted NH3 ligands of [Pd(NH3)4]2+ precursor to form [Pd(NH3)3(POH)]2+. After calcination, the latter formed Pd-O-P interfacial linkage between Pd nanoparticles and AlPO-5, benefiting the suppression of Pd sintering. SiO2 and SiO2-AlPO-5 composite were used as supports for comparison. Catalyst supported on SiO2-AlPO-5 composite (25 wt% AlPO-5) exhibited improved catalytic activity and stability in consideration of reactant activation as well as the mass transfer of reactant molecules, which is expected to decrease precious metal loading in industrial application.

An in situ synthesized Pd catalyst with an egg–shell structure was employed to catalyze the hydrogenation of 2-ethylanthraquinone in a fixed bed. The effects of residence time, gas to liquid phase ratio, reaction temperature and Pd loading amounts on the yield and hydrogenation efficiency were investigated specifically. The yield and hydrogenation efficiency attained values of 35.5% and 6.6 g L−1 using the optimum Pd loading amount of 0.32%, respectively, with a residence time of less than 4 seconds and exhibiting excellent catalytic activity. Meanwhile, within the temperature range of 50 °C to 70 °C, the Thiele modulus and effective internal diffusion factors were calculated to be about 0.008 to 0.033 and 0.9996 to 0.9999, respectively, which indicates that the prepared catalyst with an egg–shell structure weakened the internal diffusion resistance effectively and is suitable for fast reactions. The maximum space time yield value reached 567.5 gH2O2 gPd−1 h−1 and was much higher than the reported results from other literature.

Anthraquinones have been the subject of numerous photochemical studies and their photopolymerization activities have been examined under various conditions to improve more efficient photochemical systems. This article involves further detailed investigations into the photophysical, photochemistry and photopolymerisation properties of 4 commercial derivatives of 2-substituted anthraquinone, namely, 2-Bromomethylanthraquinone (2BA), 2 Chloromethylanthraquinone (2CA), 2 Ethylanthraquinone (2EA), 2 Hydroxymethylanthraquinone (2HA) and one novel synthesized anthraquinone, 2 Acryloxymethylanthraquinone (2AA). 2AA is synthesized from 2HA. The results from both spectroscopic and analysis studies proved the 2AA to having the ester link. Absorption spectroscopy and solvent shift data are used to characterise their spectral activity. Luminescence studies involving fluorescence and phosphorescence analysis indicates efficient intersystem crossing to triplet state and n-π* nature of the lowest excited triplet state. The polymerisation activity was studied using methyl methacrylate (MMA) and analysis of the cure rate was measured using the gravimetric method. All the compounds are shown to be highly dependent on the structure. However, the rate of polymerisation (Rp) was reduced in the presence of amine. This is consistent with other results, proving the behaviour of derivatives with n-π* configuration. Hardness tests for all compounds took place using a different formula of acrylated resin/monomer systems. The excited state characteristics of the methyl derivatives have also been examined using micro and nanosecond flash photolysis. Triplet absorption spectra of all the anthraquinone derivatives show a significant red shift in the region of 340–370 nm with increasing solvent polarity due to stabilisation of the lowest triplet state by solvent reorganization. Hydrogen atom abstraction takes place in 2 propanol, forming a semiquinone radical. In the presence of the tertiary amine, triethylamine, all anthraquinone derivatives show the formation of intermediary species related to either the exciplex or the radical ion pair. Under aerobic conditions, the first decay rate for all anthraquinone derivatives increases and showed oxygen to be a good quencher with a bimolecular rate constant of around 2 × 10 mol. dm s. Relative to benzophenone, the molar absorption coefficient, ε, and quantum yield of intersystem crossing, Φisc were calculated, and it is summarised that the value for Φisc for all compound is less than 1.00 and controls to a major extent their photochemical activities., The authors thank the University of Sains Malaysia for funding Hazira Mazah.

In this study, single-crystal Pd nanocrystals with exposed (100) and (111) facets were prepared and their catalytic performance were compared in 2-ethylanthraquinone hydrogenation reaction through immobilization on γ-Al2O3 as catalyst. Our experimental results combined with density functional theory calculations showed that the Pd (100) facet was more active than Pd (111) in CO hydrogenation but less active in saturation of aromatic rings. Directed by this result, a high-performance Pd/γ-Al2O3 nanocatalyst was successfully prepared using a one-step synthesis method, which could not only control the exposure of the Pd (100) facet but also increase the stability of Pd components. This catalyst exhibited superior catalytic performance with a hydrogenation efficiency of up to 15.0 g L−1 and a selectivity of 99.1% under mild reaction conditions (0.2 MPa, 50 °C, 15 min), which was superior to that of the catalyst prepared by an impregnation method.

Alkylated anthraquinone is widely used as promising redox-active materials for both redox flow batteries technology and hydrogen peroxide production via anthraquinone oxidation (AO) process, yet its inadequate solubility in solvents has been the one of the main limitations resulting to insufficient energy density of working solution. In present study, solubility of 2-ethylanthraquinone was specifically investigated by the synthetic method at the temperature range from 304.15 to 344.15 K under the pressure of 101.325 kPa. In support for decent working solution exploit, various types of solvents were specifically selected as the working solution constituent in this work. Solubility data and activity coefficient of 2-ethylanthraquinone were correlated by modified Apelblat and λ-h models. Furthermore, thermodynamic analysis was subsequently performed based on the thermodynamic fitting results. As a result, dissolution process of 2-ethylanthraquinone is endothermic and entropy-driven in these neat solvents, higher dissolution temperature leads to smaller value of partial molar excess Gibbs free energy and therefore results to a greater solubility.

The main process for industrial synthesis of hydrogen peroxide is to subject 2-ethylanthraquinone to cyclic hydrogenation and oxidation. Hydrogenation catalyst is one of the key techniques of anthraquinone route. A new egg-shell palladium catalyst with racshig-ring alumina supported was developed for meeting the mechanism and improving mass transformation based on the kinetics and mass transfer theory, the effects of materials feeding methods together with operating conditions on the hydrogenation efficiency were detailed. It was concluded that the egg-shell palladium catalyst developed by this research has higher hydrogenation efficiency than the commercial contrast catalysts.

This paper reports an investigation on the degradation of cellulose via electro-Fenton method. The electrodes chosen were graphite/PTFE electrodes modified by 2-ethylanthraquinone (EAQ). The presence of EAQ greatly improved the rate of hydrogen peroxide formation on air-fed graphite/PTFE electrodes, which was determined by a UV spectroscopic method using molybdate as the color agent. Hydrogen peroxide can react with Fe 2+ to form hydroxyl radicals in an acidic medium, which accelerates cellulose degradation by cleaving the glycosidic bonds between glucose units. The degradation products of the cellulose contain soluble sugar and 5-HMF, which were fully characterized by 1 H NMR and 13 C NMR.

The Abraham model is used to calculate the numerical values of the solute descriptors for 2-ethylanthraquinone from experimental solubilities. The correlations are log ( / ) = c + e · E + s · S + a · A + b · B + v · V, log ( /C G) = c + e · E + s · S + a · A + b · B + l · L, where and refer to the solute solubility in the organic solvent and water, respectively, C G is a gas phase concentration and E, V, A, B, S and L denote the solute descriptors. The remaining symbols in the above expressions are known solvent coefficients, which have been determined previously for a large number of gas/solvent and water/solvent systems. The Abraham solvation parameter model was found to describe the measured solubility data to within an overall standard deviation of 0.123 log units.

A new synthesis method of hydrogen peroxide was investigated by the photoreduction of 2-ethylanthraquinone (AQ) in water-insoluble organic solvents. Through optimizing the photoreduction condition including solvent, atmosphere and irradiated time, the photolysis system of 1,3,5-trimethylbenzene/trioctyl phosphate (3:1) solvent mixture under oxygen atmosphere was found to give a high yield of hydrogen peroxide. Furthermore, the formation mechanism of hydrogen peroxide was proposed, i.e. photoreduction and subsequent oxidation of AQ. The photoreduction of 2-ethylanthraquinone undergoes the hydrogen abstraction from solvent to form the anthrahydroquinone, which is subsequently oxidized by oxygen to give hydrogen peroxide.

Spherical Al2O3 and SiO2–Al2O3 supports with different silica contents have been synthesized by the oil column method. After impregnation with Na2PdCl4 solution and subsequent calcination, PdO/Al2O3 and PdO/SiO2–Al2O3 catalyst precursors were obtained. X-ray powder diffraction and low temperature N2 adsorption–desorption measurements showed that the addition of silica increased the thermal stability, surface acidity, specific surface area and total pore volume of the spherical alumina. Temperature programmed reduction and H2–O2 titration indicated that Pd supported on the SiO2–Al2O3 spheres possessed higher dispersion and smaller particle size than that supported on pristine spherical Al2O3. Catalytic hydrogenation of ethylanthraquinone using molecular hydrogen was studied over the reduced Pd/Al2O3 and Pd/SiO2–Al2O3 catalysts with different silica contents. Under identical reaction conditions, the reaction activity and stability increased with increasing silica content.

The hydrogenation of 2-ethylanthraquinone (eaq) to 2-ethylanthrahydroquinone (eahq) was carried out under taylor flow in single square channel monolith reactors. the two opening ends of opaque reaction channel were connected with two circular transparent quartz-glass capillaries, where taylor flow hydrodynamics parameters were measured and further used to obtain practical flow state of reactants in square reaction channels. a carefully designed gas-liquid inlet mixer was used to supply steady gas bubbles and liquid slugs with desired length. the effects of various operating parameters, involving superficial gas velocity, superficial liquid velocity, gas bubble length, liquid slug length, two-phase velocity and temperature, on eaq conversion were systematically researched. based on eaq conversion, experimental overall volumetric mass transfer coefficients were calculated, and also studied as functions of various parameters as mentioned earlier. the film model, penetration model, and existing semi-empirical formula were used to predict gas-solid, gas-liquid, and liquid-solid volumetric mass transfer coefficients in taylor flow, respectively. the predicted overall volumetric mass transfer coefficients agreed well with the experimental ones. (c) 2009 american institute of chemical engineers aiche j, 55: 726-736, 2009

A novel Pd/Al2O3/cordierite monolithic catalyst was prepared and investigated in hydrogenation of 2-ethylanthraquinone (eAQ) for H2O2 production. It was found that there was an optimal penetrating depth on the monolithic catalyst. By adjusting the loading on the Al2O3, the penetrating depth of Pd could be efficiently confined in the Al2O3 washcoat. When Pd distribution matched well with Pd content, the higher yields of H2O2 could be obtained. As a result, the average yield on monolithic catalyst was 1.3 times of that on pellet catalyst, and the products distribution confirmed the monolithic catalyst was the optimal for H2O2 production. (C) 2008 Elsevier B.V. All rights reserved.

This paper reports a comparative study of the electrochemical performance of in situ hydrogen peroxide electrogeneration on gas diffusion electrodes modified by organic redox catalysts 2-ethylanthraquinone, 2-terc-butylanthraquinone and azobenzene in medium of 0.1 mol L-1 H2SO4 plus 0.1 mol L-1 K2SO4, pH = 1. Hydrogen peroxide generation proved strongly dependent on the applied potential and on the concentration of added catalysts. Electrode modifications led to a significant increase in H2O2 yield (30%) reaching 850 mg L-1, and the overpotential for oxygen reduction shifted to less negative values (400 mV vs Ag/AgCl for electrodes modified by quinones and 300 mV vs Ag/AgCl for electrodes modified by azobenzene) compared to noncatalyzed gas diffusion electrodes, resulting in reduced energy consumption of 596.5 to 232.4 kWh kg-1. The results indicated that the best electrode for H2O2 electrogeneration is the gas diffusion electrode modified with 10% of 2-ethylanthraquinone, offering the best cost to benefit ratio.

A ZrO2-γ-Al2O3 supported Pd catalyst was prepared and characterized by XRD, XPS, H2-TPR and TEM techniques. The catalytic activity was evaluated in the liquid-phase hydrogenation of 2-ethylanthraquinone. Comparing with Pd/γ-Al2O3, it showed high catalytic activity.

Skeletal Ni catalysts (RQ Ni) prepared by alkali leaching of rapidly quenched Ni–Al alloys have been systematically characterized, focusing on the effect of the cooling rate during alloy preparation. It is found that the residual Al content, texture, structure, surface hydrogen species, and active sites of the RQ Ni catalysts can be controlled by the cooling rate of the Ni–Al alloys. In liquid-phase hydrogenation of 2-ethylanthraquinone (eAQ), the RQ Ni catalyst with higher cooling rate favors hydrogenation of the carbonyl group and retards the saturation of the aromatic ring and the formation of the degradation products, thus leading to a higher yield of H 2 O 2 . Based on the characterizations, the improved selectivity is ascribed to the dominant population of strongly chemisorbed hydrogen, which is inactive for the hydrogenation of the aromatic ring, along with the electronic interaction between residual metallic Al and Ni, favoring a carbonyl group-bonded configuration of eAQ on the catalyst.

A series of La-doped Ni–B amorphous alloy catalysts were prepared by a KBH4 reduction method. Ni powders were prepared by hydrazine reduction. These samples were characterized by inductively coupled plasma (ICP), BET, XRD, X-ray photoelectron spectroscopy (XPS), H2-chemisorption, H2-TPD, etc., and studied in the hydrogenation of 2-ethylanthraquinone (EAQ). The Ni–B amorphous alloy catalysts showed higher specific surface area, higher extents of H2-chemisorption and higher H2-TPD areas than Ni powders. In Ni–B amorphous alloys, with the addition of La, the extents of H2-chemisorption and H2-TPD areas first increased markedly and then decreased, with the maximum appeared at the atomic ratio of La to Ni of 0.034. The hydrogenation activity also showed the same trend. The effects of La were attributed to its dispersion of Ni particles, resulting in the formation of more surface Ni centers. However, much higher La contents may result the coverage of surface Ni centers. After heat treatment at higher temperatures, the amorphous structure of Ni–B was destroyed.

An environmentally benign SBA-15-supported amorphous nickel boride alloy catalyst, prepared by a novel reductant–impregnation method, exhibits superior activity, selectivity, and stability in the selective hydrogenation of 2-ethylanthraquinone (eAQ) to 2-ethylanthrahydroquinone (H 2 eAQ), which is the dominating process for the production of hydrogen peroxide in industrial scale. The unique characters of the amorphous alloy as well as the pore structure of the mesoporous SBA-15 molecular sieve are crucial for the excellent catalytic behavior of the title catalyst.

A novel skeletal Ni catalyst, prepared by alkali leaching of a Ni–Al alloy obtained by the rapid quenching technique, exhibited higher selectivity in hydrogenation of 2-ethylanthraquinone to “active quinones” than that of the Raney Ni catalyst originating from a conventional alloy. It is suggested that the structural defects of the rapidly quenched alloy lead to a high population of the strongly bound hydrogen, which is essential for selective hydrogenation of the carbonyl group.