Hydrogenation Of Anthraquinone Research Articles

Ionic Liquids Boost Anthraquinone Hydrogenation over Pd‐based Bimetallic Pincer Catalysts

A series of bimetallic‐ionic liquid (IL) pincer catalysts Pd‐M@IL were synthesized using low Pd‐loading amount (0.3%) and adopting six kinds of ion liquids with the cation containing the imidazole ring, and then evaluated the catalytic activities toward 2‐ethylanthraquinone hydrogenation reaction with the purpose to produce H2O2. Under the reaction conditions of 60 ℃, 0.30 MPa and 15 min reaction time, over the catalysts Pd‐La@[BMIm]Ac/alu and Pd‐La@[VBIM]Br/alu achieved high hydrogenation efficiency(9.4 g/L and 8.5 g/L) but also high selectivity toward the active anthraquinone (98.9% and 99.6%). Through characterizations of STEM, TPD, in‐situ XPS, etc., it illustrates that the pincer catalysts Pd‐La@[BMIm]Ac/alu and Pd‐La@[VBIM]Br/alu have much better dispersity than the bimetallic Pd‐La/alu, these two ionic liquids of [BMIm]Ac and [VBIM]Br provide different local environment around Pd‐La sites, which in turn modulate the catalytic activity of the pincer‐catalysts toward anthraquinone hydrogenation. DFT calculations disclose the unique electron transfer between ILs ([BMIm]Ac and [VBIM]Br) and Pd‐La clusters and subsequent changes of energy barriers for anthraquinone hydrogenation. The work illuminates a facile strategy to design novel hydrogenation catalysts through combining the pincer microenvironment partially encapsulated by the cation and the anion of ionic liquids with the internal bimetallic sites.

Indirect H2O2 synthesis without H2

Industrial hydrogen peroxide (H2O2) is synthesized using carbon-intensive H2 gas production and purification, anthraquinone hydrogenation, and anthrahydroquinone oxidation. Electrochemical hydrogenation (ECH) of anthraquinones offers a carbon-neutral alternative for generating H2O2 using renewable electricity and water instead of H2 gas. However, the H2O2 formation rates associated with ECH are too low for commercialization. We report here that a membrane reactor enabled us to electrochemically hydrogenate anthraquinone (0.25 molar) with a current efficiency of 70% at current densities of 100 milliamperes per square centimeter. We also demonstrate continuous H2O2 synthesis from the hydrogenated anthraquinones over the course of 48 h. This study presents a fast rate of electrochemically-driven anthraquinone hydrogenation (1.32 ± 0.14 millimoles per hour normalized per centimeter squared of geometric surface of electrode), and provides a pathway toward carbon-neutral H2O2 synthesis.

AlCl3 modified Pd/Al2O3 catalyst for enhanced anthraquinone hydrogenation

Anthraquinone hydrogenation to produce H2O2 is an economically interesting reaction with great industrial importance. Here, we report a series of Pd/xAl catalysts with different AlCl3 contents by a conventional stepwise impregnation method. The optimal Pd/1.0Al catalyst exhibits a higher performance toward anthraquinone hydrogenation with 8.3 g·L−1 hydrogenation efficiency, 99.5% selectivity and good stability, obviously superior to that of Pd/Al2O3 catalyst (5.2 g·L−1 and 97.2%). Detailed characterization demonstrates that AlCl3 can be grafted on the γ-Al2O3 support to obtain a modified support with abundant surface weak acid and Lewis acid, which can adsorb and activate anthraquinone. Meanwhile, its steric hindrance could isolate and disperse active metals to form more active sites. The synergies between metal sites and acid sites promotes the anthraquinone hydrogenation. Furthermore, the good stability after grafting AlCl3 could attribute to the enhanced metal-support interaction inhibiting metal particles agglomeration and leaching.

Development and application of slurry–bed production technology of hydrogen peroxide by anthraquinone auto-oxidation process

This article analyzes the problems existing in the domestic hydrogen peroxide production plant, and introduces slurry-bed production technology developed by SINOPEC from various aspects, including anthraquinone hydrogenation catalysts, slurry-bed hydrogenation reactor, high-throughput filtering, oxidation process intensification, efficient extraction, safe and environmentally friendly working solution regeneration technique. The operation of the pilot plant and industrial production plant shows that the technical indicators of the developed technology are significantly better than those of the traditional technology, with high intrinsic safety and easy to large-scale production. The slurry-bed production technology developed by SINOPEC greatly improves the level of hydrogen peroxide production technology in China and provides raw material guarantee for the development of downstream green chemical industry.

Photoelectrochemical Production of Hydrogen Peroxide with TiO2 and 1,5-Di(thien-2-yl)-9,10-anthraquinone via a Selective Two-Electron Oxygen Reduction Reaction in the Two-Compartment Cell

The industrial process of hydrogen peroxide (H2O2) synthesis proceeds through the hydrogenation of anthraquinone followed by successive oxidation in an organic solvent. This process is a multistep synthesis that is far away from green synthesis. An alternative photoelectrochemical (PEC) H2O2 production method requires only sunlight and water. Herein, we established the direct production of H2O2 by using a two-compartment PEC cell composed of TiO2 nanorods hydrothermally grown on fluorine-doped tin oxide as a photoanode for water oxidation and 1,5-di(thien-2-yl)-9,10-anthraquinone (AQTh) anchored carbon cloth as a cathode for the selective two-electron (2e–) reduction of oxygen. This photoanode and cathode are positioned in an anodic compartment and a cathodic compartment of a two-compartment cell, respectively. The Nafion membrane (N-117) separates these two compartments. This PEC cell continuously produces H2O2 at −0.1 VRHE applied voltage, which reaches 60 μM after 3 h. The density functional theory study is carried out to better understand the H2O2 production mechanism and the role of thiophene substituents on anthraquinone.

The Metal-Based Catalysts for Selective Hydrogenation of Anthraquinone to Produce Hydrogen Peroxide

The Metal-Based Catalysts for Selective Hydrogenation of Anthraquinone to Produce Hydrogen Peroxide

The Effects of AlPO-n Additives as Catalytic Support on Pd-Catalytic Hydrogenation of 2-Amylanthraquinone Process

The Pd-catalyzed hydrogenation of anthraquinone to synthesize hydrogen peroxide is an important process in the chemical industry. A Pd catalyst with high dispersion is the key to hydrogenation activity and selectivity. For the first time, this team introduced the AlPO-5 zeolite to SiO2 powder to prepare a finely dispersed Pd catalyst with higher efficiency than the conventional Pd/SiO2 catalyst. Based on previous research, other aluminophosphate molecular sieves (AlPO-n) with different properties from AlPO-5 were introduced to the SiO2 support, and then the synthesized hydrogenation catalysts were characterized by the BET, XRD, H2-TPR, NH3-TPD, H2-TPD, XPS and HRTEM methods and then tested for the hydrogenation of 2-amylanthraquinone in a continuous stirred tank reactor (CSTR). It was demonstrated that the Pd-AlPO-31/SiO2 catalyst exhibits superior H2O2 yield (8.4 g·L−1) and selectivity (96%) among all prepared Pd-AlPO-n/SiO2 and Pd/SiO2 catalysts. The characterization results suggest that the dimensions and structure of AlPO-31 micropore channels are responsible for highly dispersing Pd particles, preventing the accumulation of Pd particles, and intensifying H2 adsorption in its micropore channels, which is significant for the catalytic activity.

Pd nanoparticles anchored and stabilized on N-doped boehmite@C with enhanced catalytic performance in 2-ethyl-9,10 anthraquinone hydrogenation

Pd nanoparticles (NP) immobilized on nitrogen (N)-doped boehmite@C composites (CCB) with enhanced catalytic performance for 2-ethyl-9,10 anthraquinone hydrogenation were successfully prepared by a mild vapor-phase hydrothermal method. The characterization results showed that the phase structures, morphologies and texture properties of CCB are analogous to the corresponding boehmite. The dosages of sucrose and urea determined the contents of C and N in CCB, which controlled the loading capacities of 0.64–1.50%, particle sizes of 3.75–5.48 nm and dispersity of 18.6–33.8% of the Pd NP. The C, N atoms and -OH groups on the surface of CCB are beneficial to anchor and stabilize Pd NP in situ reduction. Compared with the hydrogenation efficiency of Pd/boehmite (8.68 g/L), the corresponding value of Pd/CCB (11.18 g/L) increased by 28.8%. Furthermore, compared with the traditional preparation methods of catalyst in the field of anthraquinone hydrogenation, this effective and mild vapor-phase hydrothermal method does not use any excess reductant and capping reagent, and thus provides an alternative approach for preparing high-performance catalyst.

Highly dispersed and stabilized Pd species on H2 pre-treated Al2O3 for anthraquinone hydrogenation and H2O2 production

Anthraquinone hydrogenation is the core reaction in H2O2 production process. In this work, γ-Al2O3 samples with different H2 treatment temperatures (denoted as R-Al-T) were prepared to be the catalytic supports, and a series of Pd/R-Al-T catalysts were obtained by a simple impregnation method. Among the catalysts, Pd/R-Al-500 exhibits the best catalytic performance for anthraquinone hydrogenation of 10.63 g⋅L−1 hydrogenation efficiency and 885.83 gH2O2⋅gPd−1⋅h−1 H2O2 productivity, which increases by 37.7% compared with Pd/γ-Al. The stability of Pd/R-Al-500 is also significantly higher than that of Pd/γ-Al. Characterization results show the pre-treatment can construct more coordinatively unsaturated pentacoordinate Al3+ (denoted as Al3+penta) and forms more Pd-O-Al structures, which improve the Pd dispersion and synergistic effect between Pd0 and Pd2+, so as to improve the catalytic activity. Al3+penta sites also enhance the anchoring effect on Pd species and lessen the Pd leaching and agglomeration, which lead to the high stability of Pd/R-Al-500 catalyst. This work provides a simple strategy to disperse and stabilize active Pd species on γ-Al2O3 for anthraquinone hydrogenation.

Intensifying strategy of ionic liquids for Pd-based catalysts in anthraquinone hydrogenation

Pd–IL complex catalyst was first employed in anthraquinone hydrogenation. ILs are uniformly dispersed around Pd species, which adjust acidic sites, accomplish charge transfers, stretch CO bond lengths and promote occurrence of desirable reactions.

Reaction Mechanism of Anthraquinone Hydrogenation over Pd Based Monometallic and Bimetallic Catalyst

Reaction Mechanism of Anthraquinone Hydrogenation over Pd Based Monometallic and Bimetallic Catalyst

Fast, Large-Scale, and Stable Preparation of η-Al2O3 Microspheres by Fully Utilizing N,N-Dimethylformamide at Room Temperature

A fast, large-scale, and stable preparation method was successfully developed to obtain η-Al₂O₃ microspheres with particle sizes of 3–10 μm from cheap and widely sourced NaAlO₂ solution using N,N-dimethylformamide (DMF) as a morphological modifier and a precipitant simultaneously at room temperature. The yield of alumina increases from 33.3 to 77.3% by increasing the dose of DMF from 100 to 400 mL. The utilization efficiency of DMF significantly increased by adding fresh NaAlO₂ into the reused filtrate after separating the bayerite precipitate (precursor of η-Al₂O₃). Importantly, the η-Al₂O₃ microspheres obtained from the filtrate-reuse experiments show the stable phase structures, morphologies, and pore structure properties. Furthermore, the typical η-Al₂O₃ microspheres supported Pd catalyst presents a higher catalytic activity of 10.6 g/L for the hydrogenation of anthraquinone than that of the commercial γ-Al₂O₃-supported Pd catalyst (8.5 g/L), suggesting that the as-prepared η-Al₂O₃ microspheres have good application prospects for catalytic hydrogenation and related fields.

Enhanced catalytic activity and stability over P-modified alumina supported Pd for anthraquinone hydrogenation

Pd catalysts loaded on P-doped alumina (Pd/Al2O3-xP) were prepared and applied to H2O2 production by means of anthraquinone hydrogenation. The catalytic performance over Pd/Al2O3-xP catalysts showed a volcano-shape trend with phosphorus content. Pd/Al2O3-1P catalyst containing 1 wt% phosphorus exhibited the most excellent catalytic performance and reusability. The physicochemical properties of phosphorus-doped supports and Pd-loaded catalysts were investigated by several characterization methods. Doping phosphorus into Al2O3 increased thermal stability and adjusted surface acid intensity of the supports. Introducing suitable amount of phosphorus improved the Pd dispersion, regulated the reducibility of the catalysts. These factors contributed to the superior performance of Pd/Al2O3-1P for the anthraquinone hydrogenation reaction. Furthermore, Pd/Al2O3 catalyst gradually deactivated during the recycle test, which was mainly attributed to Pd loss and byproduct deposition on the catalyst. Incorporation of phosphorus could enhance the anchoring effect between Pd nanoparticle and support, which could also inhibit the generation of byproducts.

Computational Exploration of the Mechanism of the Hydrogenation Step of the Anthraquinone Process for Hydrogen Peroxide Production

Hydrogen peroxide is produced commercially by the sequential hydrogenation and oxidation of anthraquinone (AQ) and tetrahydroanthraquinone (THAQ). The hydrogenation of AQ and THAQ on the Pd(111) surface is investigated with periodic density functional theory (DFT) calculations in this work. Dihydrogen is preferentially adsorbed on the top of a Pd atom, and the produced hydrogen atoms are on two neighboring 3-fold hollow fcc positions. The three benzene rings of AQ are located at bridge sites on the Pd(111) surface. The two carbonyl oxygen atoms of AQ and THAQ successively abstract the surface hydrogen atoms to produce anthrahydroquinone (AHQ) and tetrahydroanthrahydroquinone (THAHQ), respectively. The formation of unwanted byproducts, anthrone (AN), tetrahydroanthrone (THAN), oxanthrone (OAN), and tetrahydro-oxanthrone (THOAN), in the hydrogenation step of the AQ process is also studied to consider the suppression of these byproducts.

Controllable preparation and catalytic performance of Pd/anodic alumina oxide@Al catalyst for hydrogenation of ethylanthraquinone

Anodic alumina oxide (AAO) supports with different pore sizes and depths were controllable prepared by a two-step low-potential anodizing process. The prepared AAO supports with θ-ring shape were utilized to prepare supported Pd catalysts by impregnation method for the first time. The catalytic performance of the Pd/AAO@Al catalysts were investigated in the catalytic hydrogenation of 2-ethylanthraquinone (eAQ) to 2-ethylanthrahydroquinone, a key step in the anthraquinone process for the manufacture of hydrogen peroxide. Compared with Pd supported on spherical Al2O3 catalyst, Pd/AAO@Al catalysts showed much higher anthraquinone hydrogenation activity and preferable selectivity due to the highly ordered array of cylindrical shaped pores, short diffusion distance and confinement effect of the AAO supports. Furthermore, the effect of pore size and depth to the catalytic performance towards hydrogenation of eAQ has also been studied. Pd nanoparticles supported on AAO support with 24.5nm pore size and 18μm depth exhibited the best catalytic performance towards hydrogenation of eAQ.

A highly stable Pd/SiO2/cordierite monolith catalyst for 2-ethyl-anthraquinone hydrogenation

Pd/SiO2/cordierite monolith catalysts show superior stability in a 1000 h test for anthraquinone hydrogenation.

One-Step Preparation of Pd-SiO2 Composite Microspheres by the Sol–Gel Process in a Microchannel

This paper presents a novel one-step method for the preparation of palladium (Pd) nanoparticles loaded on SiO2 with a core–shell structure using the sol–gel process and microfluidic methods. The reduction of Pd2+ ions at high temperatures was achieved with ethanol molecules hydrolyzed from tetraethyl orthosilicate (TEOS) instead of the more commonly used hydrogen. The prepared microspheres possessed a highly uniform diameter near 420 μm and a mesoporous structure, with specific surface areas above 600 m2/g and average pore diameters ranging from 4.23 to 5.02 nm. Pd nanoparticles with mean particle diameters of 3–5 nm were dispersed uniformly on the outer surface of the spheres and catalyst loading ranged from 0.83 to 4.91 mg/g. The prepared catalyst was used for the hydrogenation of anthraquinone. In addition, Au-SiO2 composite microspheres were successfully synthesized to demonstrate the versatility of this method.

Highly dispersed Pd catalyst for anthraquinone hydrogenation supported on alumina derived from a pseudoboehmite precursor

Pseudoboehmite was synthesized using the separate nucleation and aging steps (SNAS) method for the first time. An alumina support (Al2O3(PB)) was then prepared by extrusion method using the synthesized pseudoboehmite as precursor. Compared with spherical alumina (Al2O3(OD)) prepared by the conventional oil-drop method, Al2O3(PB) exhibits higher surface area, more regular pore structure and narrower pore size distribution. Al2O3(PB) and Al2O3(OD) were used as supports to prepare Pd catalysts. The catalytic performance of the two Pd catalysts was investigated in the catalytic hydrogenation of 2-ethylanthraquinone (EAQ) to 2-ethylanthrahydroquinone, a key step in the anthraquinone process for the manufacture of hydrogen peroxide. Compared with Pd/Al2O3(OD) catalyst, Pd/Al2O3(PB) catalyst showed higher Pd dispersion and thinner Pd penetration depth which resulted in more catalytically active site and easier diffusion of the reactants, and consequently Pd/Al2O3(PB) catalyst exhibited higher anthraquinone hydrogenation activity and better selectivity.

Characteristics of anthraquinone hydrogenation catalysts in a liquid‐solid fluidized bed

AbstractThe fluidization characteristics of anthraquinone hydrogenation catalysts were investigated in a liquid–solid fluidized bed. The effects of the initial bed conditions such as particle size, bed depth‐to‐column diameter ratio and liquid density and viscosity on the fluidization behaviour, bed expansion and applicability of the Richardson–Zaki equation were studied. The results reveal a strong particle size effect on the Richardson–Zaki (R‐Z) expansion index which in general decreased as the particle diameter increased. One type of particles exhibited two distinct bed expansion behaviours, depending mainly on the bed depth‐to‐column diameter ratio, with an experimentally established boundary at $h_{\rm b}0/D \approx 1.75$. This behaviour could be attributed to increasing wall friction and a tendency to exhibit slugging. The dependence of the Richardson–Zaki exponent on the liquid dynamic viscosity confirms the classic result $n_{\rm a} = f(1/Re_{t})$.

The effect of solvents on the rate of catalytic hydrogenation of 6‐ethyl‐1,2,3,4‐tetrahydroanthracene‐9,10‐dione

AbstractThe rate of hydrogenation of 6‐ethyl‐1,2,3,4‐tetrahydroanthracene‐9,10‐dione was investigated at 313 K and 0.1 MPa in 20 solvents. A multiple linear regression was used to describe the solvent effect. The regression of the reaction rates was carried out using two five‐parameter linear regression models: the Abraham–Kamlet–Taft (AKT) and the Koppel–Palm (KP) model. After the elimination of the insignificant terms from the regression models, it was found that the basic character of the solvent and its Hildebrand cohesion energy density were the most important attributes influencing the hydrogenation rate. The analysis of both models led to the same conclusion. The resultant simplified AKT model gave closer fitting in comparison to the KP model. The results could facilitate the solvent selection for the industrial process of hydrogen peroxide production by the anthraquinone method with respect to the kinetics of anthraquinone hydrogenation. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 40: 240–252, 2008