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In this work, the reaction mechanism of 2-ethylanthraquinone (eAQ) and Tetrahydro-2-ethyl anthraquinone (H4eAQ) hydrogenation over Pd and Pd-M bimetallic catalysts (M = Ni and Cu) was first investigated by density functional theory (DFT) using VASP software. The simulation results showed that the reaction mechanism of eAQ and H4eAQ over different catalysts is similar. The three benzene rings of eAQ or H4eAQ are on bridge sites over the surface of Pd(111) or PdM(111). Dihydrogen is preferentially adsorbed on the top site of a Pd atom in Pd-eAQ or Pd-H4eAQ model, and then the hydrogen atoms dissociated from dihydrogen are located at two neighboring threefold hollow fcc positions. The two carbonyl oxygen atoms of eAQ and H4eAQ successively react with the hydrogen atoms on the surface of Pd(111) or PdM to produce anthrahydroquinone (eAQ) and tetrahydroanthrahydroquinone (H4eAQ), respectively. Moreover, the simulation results showed that the reaction activation energy for the hydrogenation of H4eAQ and eAQ over Pd-Ni bimetallic catalyst is lower than those over other catalysts, which is attributed to the better synergy of Pd and Ni on the surface of Pd-Ni bimetallic catalyst. The reaction activation energy of the hydrogenation of H4eAQ is lower than that of the hydrogenation of eAQ. [ABSTRACT FROM AUTHOR]

We report a photocatalytic process for H 2 O 2 synthesis by using 2-ethylanthraquinone (EAQ) as photocatalyst. H 2 EAQ (or HEAQ ) was in-situ produced by photocatalytic hydrogenation of EAQ with various solvents as hydrogen-donors (H-donors), and thus the pre-production of power-intensive H 2 was circumvented. The industrial hydrogenation of EAQ and the oxidation of H 2 EAQ with O 2 here were combined into one pot for H 2 O 2 photocatalytic production. EAQ molecule can be repeatedly used with high TON under both UV and visible light irradiation. When dual-phase reaction was adopted, the maximal H 2 O 2 concentration of 574.0 mM in aqueous phase was achieved with mesitylene as H-donor. As the produced H 2 O 2 concentration in the industrial AO process is estimated as ca. 400 mM in one cycle, our method with the dual-phase reaction greatly promotes the possibility for the practical production of H 2 O 2 with photocatalytic method. [ABSTRACT FROM AUTHOR]

Abstract: Present research concentrates on the role of alkali modifiers (Li, Na, K, Cs) in activity of 2%Pd/Al2O3 catalyst for 2-ethyl-9,10-anthraquinone (eAQ) hydrogenation. The catalysts with various content of alkali modifier (Me/Pd molar ratio ranges from 0.5 up to 4, Me-alkali metal) were prepared by impregnation of pre-reduced 2%Pd/Al2O3 catalyst with appropriate alkali metal carbonates. The XPS, EDS and TEM measurements show that alkali promoters are introduced into alumina matrix. The microcalorimertic experiments of CO adsorption prove the interaction of CO with catalysts leading to stronger bonding of carbon monoxide by alkali doped catalysts. The presence of alkali promoters in Pd/Al2O3 catalyst plays an essential role in the whole eAQ hydrogenation process. The nature of alkali promoter and its content (Me/Pd atomic ratio) in catalyst are of importance. As the alkalinity of promoter increases going from Li to Cs all the effects caused by their presence become stronger. In the presence of alkali doped catalysts the content of 2-ethyloxoanthrone (OXO, isomer of 2-ethyl-9,10-anthrahydroquinone) formed is higher than that on un-doped 2%Pd/Al2O3. On the other hand, reactions in the “deep hydrogenation” stage comprising the formation of 2-ethyl-5,6,7,8-tetrahydro-9,10-anthraquinone (H4eAQ) and the transformation of OXO to 2-ethylanthrone and other degradation products are remarkably inhibited. In particular, the formation of 2-ethylanthrone via hydrogenolysis of OXO isomer is strongly suppressed. The Cs-doped catalyst exhibits the highest activity to OXO among all the catalysts tested whereas the ability of Cs-doped catalysts to the formation of anthrone is most effectively inhibited. The role of alkali modifiers is considered to be associated with stronger interactions between the catalyst and quinone reagents, and in particular OXO isomer. Moreover, in the reagent adsorption the centres of support nearby the palladium particles may also participate by affecting the mode of reagents adsorption. [Copyright &y& Elsevier]

Present research concentrates on the process of anthraquinone degradation in the course of hydrogenation carried out in the presence of palladium catalyst. Hydrogenation experiments were carried out using agitated glass laboratory batch type reactor at atmospheric pressure of hydrogen and temperature of 55 °C. Catalytic tests were performed using solutions composed of 2-ethyl-9,10-anthraquinone (eAQ) and a mixture of eAQ and 2-ethyloxanthrone (OXO) with various proportions. Degradation of anthraquinone was studied and in particular, the role of reduced forms of quinone namely hydroquinone and its tautomer OXO is discussed. A difference in the course of reactions pathways: hydrogenation of aromatic rings to give 2-ethyl-5,6,7,8-tetrahydro-9,10-anthraquinone (active quinone) and hydrogenolysis reactions yielding degradation products was observed. Graphical Abstract: Present research concentrates on the process of 2-ethyl-9,10-anthraquinone degradation on palladium catalyst. The role of reduced forms, hydroquinone-enol form and its keto-tautomer is discussed. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

[Display omitted] • One-pot synthesis of 2-EAQ from phthalic anhydride and ethylbenzene was developed. • Sc modification was used to create new strong Lewis acid and increases acid amount of Hβ. • An appropriate synergistic effect of Lewis/Bronsted acids and acid strength are obtained by adjusting loading amount of Sc on Hβ. • Sc-Hβ is firstly used in the synthesis of 2-EAQ using phthalic anhydride and ethylbenzene as feedstock. 2-Ethylanthraquinone is frequently used for producing bulk consuming chemicals. However, the synthesis of 2-ethylanthraquinone is still restricted by expensive raw materials, complex preparation process and poor-cycling catalyst. Herein, a one-pot method is developed to synthesize 2-ethylanthraquinone using phthalic anhydride and ethylbenzene as feedstock by combination of acylation and dehydration over a Sc-modified Hβ catalyst. Sc-modified Hβ was prepared via impregnation and catalyzed conversion of phthalic anhydride about 58.8% and 2-ethylanthraquinone selectivity up to 78.5% which is better than the results by other metals-modified Hβ zeolites. By adjusting Sc loading amount in Hβ, more acids are created especially strong Lewis acid and an appropriate synergistic effect of Lewis/Bronsted acids is obtained for cascade reactions of acylation and dehydration. Then, the reaction conditions were investigated and the catalyst can be reused in 4 runs. This work provides a green and simple way for 2-ethylanthraquinone synthesis. [ABSTRACT FROM AUTHOR]

Anthraquinone [1, 2-C] methylisoxazole is synthesized from 2-ethylanthraquinone through nitration and treating with oleum. The different methods of 2-ethylanthraquinone nitrated were discussed. The optimum conditions were determined. The structure of the product was confirmed by MS and 1H NMR. [ABSTRACT FROM AUTHOR]

Abstract: This paper reports an investigation on the performance of a catalyzed H2O2 electrogeneration process using a modified oxygen-fed graphite/PTFE electrodes in which the redox catalyst was incorporated into the graphitic mass. The organic redox catalyst chosen for the modification was 2-ethylanthraquinone (EAQ). The H2O2 electrogeneration rate was optimized relative to potential and catalyst concentration. Hydrogen peroxide formation rate on oxygen-fed graphite/PTFE was greatly improved by the presence of the organic redox catalyst and the overpotential for oxygen reduction was shifted more positive. During electrolysis, hydrogen peroxide electrogeneration reaction showed a pseudo-zero-order kinetics and apparent rate constants increased with EAQ concentration. For the electrodes containing 10% of EAQ, apparent rate constants were 30% higher at a potential 400mV more positive when compared to the performance of a non catalyzed electrode. [Copyright &y& Elsevier]

The dehydration of 2-(4′-ethylbenzoyl) benzoic acid (BE acid) for the synthesis of 2-ethylanthraquinone (2-EAQ) has been studied over solid acid catalysts. Among the catalysts tested, a H-Beta zeolite, which was modified by dilute HNO3 solution, exhibited high catalytic performances. A 96.7% yield of 2-EAQ was achieved in our study in a batch reactor. The influences of various parameters, such as reaction temperature and time, the weight ratio of BE acid to H-Beta zeolite were investigated in detail. [ABSTRACT FROM AUTHOR]

Abstract: The hydrogenation of 2-ethylanthraquinone (eAQ) was performed over alumina, silica and carbon supported palladium catalysts. Present research is concentrated on the process of eAQ degradation and especially a role of the type of catalyst is examined. Degradation of eAQ in the catalytic experiments has been discussed on the basis of reaction pattern reported for the reduction of carbonyl groups in anthraquinone by standard procedures (Zn, Sn, NaBH4). Various by-products formed by degradation of hydroquinone (eAQH2) have been identified by GC–MS. They are the product of Cnolysis such as 2-ethylanthrone (eAN, two isomers), 2-ethylanthracene (eANT) and the products of eAN hydrogenation (H4eAN, two isomers). Tautomerization of partially and fully saturated hydroquinones produces OXO-isomers [two isomers OXO-H4(1,2) and OXO-H8(1,2)]. Reduction of eAQ with NaBH4 gives 2-ethyl-9,10-dihydroxy-9,10-dihydroanthraquinone, intermediate product in the consecutive reactions occurring during the hydrogenolysis of Culting in eAN. A difference in performance of 0.5% Pd/C, 0.5% Pd/SiO2 and 0.5% Pd/Al2O3 catalysts is related with their reactivity in degradation of eAQH2. Much higher reactivity in the whole degradation process and especially in the formation of intermediate product exhibits alumina-supported catalyst. [Copyright &y& Elsevier]

Abstract: A novel palladium catalyst supported on silica grains coated with polyaniline (PANI) (24.4wt% of polymer) was used for the hydrogenation of 2-ethylanthraquinone (eAQ). This 2%Pd/PANI(SiO2) catalyst exhibited much better selectivity in the hydrogenation of eAQ to active quinones than that of 2%Pd/SiO2 prepared by a conventional precipitation method. It is suggested that the modification of properties of Pd centres by PANI matrix, has an effect on their reactivity. The weakening of the strength of hydrogen bonding and hydrophobic character of polymer both can be considered as factors remarkably improving performance of Pd/PANI(SiO2) catalyst. [Copyright &y& Elsevier]

Abstract: The effect of water and NaOH was studied on the hydrogenation of 2-ethylanthraquinone (eAQ) over alumina supported 2% Pd/Al2O3-A and 1.2% Pd/Al2O3-B catalysts. The hydrogenation was performed in a fixed-bed reactor by circulating the eAQ solution (the concentration of eAQ was 60g/dm3) at 50°C and 5 bar hydrogen pressure. The egg-shell catalysts were prepared by the precipitation of palladium hydroxide onto the support A (activated alumina, preimpregnated with NaH2PO4) or support B (alumina containing 10% SiO2, and preimpregnated with Na2SiO3). Prior to the hydrogenation, the catalysts were dried and pre-treated with water vapour or NaOH solution. The effect of water and NaOH on the amount of active quinones (eAQ and 2-ethyl-5,6,7,8-tetrahydroanthraquinone, H4eAQ) and in particular the role of such reagents in the consumption of aromatic hydroquinone eAQH2, the primary product of the quinone system of eAQ reduction was examined. The saturation of the phenyl rings in eAQH2 produces H4eAQH2, which is a reactive compound and the hydrogenolysis of the C-O bond in the tautomerized eAQH2 leads to other degradation products. Water and NaOH influence the hydrogenation of C hydrogenolysis of C-O bond but have no effect on the hydrogenation of the aromatic rings. The increase in activity in the former C reduction did not depend of alumina A and B as well as the type of reagent (NaH2PO4 or Na2SiO3) introduced to alumina during the catalyst preparation. These reagents however, influenced the course of degradation processes. Water when introduced to the catalyst exhibited unprofitable effect on maintenance the activity of catalyst during the hydrogenation run. Such an unprofitable role is related to influence of water on the course of reactions yielding degradation products. [Copyright &y& Elsevier]

Abstract: Liquid-phase hydrogenation of 2-ethylanthraquinone to 2-ethylanthrahydroquinone has been investigated over Raney Ni, nanosized amorphous Ni–B, and chromium-modified Ni–B catalysts. It has been found that the amorphous Ni–B and chromium-modified Ni–B catalysts exhibited superior selectivity, whereas the chromium-modified Ni–B catalysts had better activity and selectivity than unmodified Ni–B catalyst. Based on the characterizations, the higher selectivity of the amorphous catalysts is ascribed to the dominant population of the strongly bound hydrogen, which is not reactive for the hydrogenation of the aromatic ring, along with the repulsive interaction between the aromatic ring and the electron-rich Ni due to electron donation from alloying B. The addition of chromium decreased the particle size of the amorphous catalysts, which is beneficial for the improvement of activity. Moreover, surface chromium oxide can function as a Lewis acid, which lowers the orbital of the reactant, favoring a carbonyl group-bonded configuration. The best selectivity was achieved over the Ni–Cr–B2 catalyst, where the hydrogenation of the aromatic ring was thoroughly blocked before the saturation of the carbonyl groups. [Copyright &y& Elsevier]

The effects of pore structure on the reaction rates and selectivities in the liquid-phase hydrogenation of 2-ethylanthraquinone over NiB amorphous alloy catalysts prepared by the reductant-impregnation method were studied using regular (HMS, MCM-41, and SBA-15) and commercial mesoporous silicas as supports. The composition, particle size, and location of the NiB particles were profoundly influenced by the pore structure of the supports. It is found that the location of the NiB particles depended on the pore size of the supports, whereas the uniformity of particle size was related to the interaction between the NiB particles and the supports. The hydrogenation rate was much faster on NiB catalysts with pore diameters exceeding 5 nm than on the narrow-pore catalysts, whereas the selectivity to 2-ethyldihydroanthraquinone, the carbonyl group hydrogenation product, was higher on NiB catalysts supported on regular mesoporous silicas. The best activity and selectivity were achieved when using SBA-15 as the support, which is attributable to the formation of more uniform active sites due to the unique pore structure of SBA-15. [Copyright &y& Elsevier]

Hydrogenation of 2-ethylanthraquinone (eAQ) in the fixed-bed reactor was studied in the “Anthra” (AQ) and “All-Tetra” systems on egg-shell palladium profile catalysts (0.7–2 wt.% Pd). Alumina modified with Na2SiO3 solution was used as a support. Solution of active quinones (eAQ and 2-ethyltetrahydroanthraquinone H4eAQ) was saturated with hydrogen and circulated through the catalyst bed at the temperature 50 °C and the pressure 5 bar. The concentrations of eAQ, H4eAQ and degradation product were analysed by the GC method. Modification of the starting support with Na2SiO3 was performed with three Sh, Lg and Vc procedures differing in the method of support drying and the time of support contacting with the Na2SiO3 solution. Efficiency of modification was studied by specific surface area, porosity and Pd concentration profile. Procedure of support modification did not influence appreciably the rate of the main reaction eAQ to eAQH2 reduction, while evidently affected the course of side reactions consuming desirable eAQH2 and producing H4eAQ and degradation products. Performance of the catalysts in terms of their ability towards hydrogenolytic reactions producing degradation products and decrease in the activity during the hydrogenation run have been correlated with the efficiency of support modification with Si species. The better this efficiency, as in Vc procedure, the better maintenance of catalysts activity during the hydrogenation experiment. [Copyright &y& Elsevier]

The effects of the type of support and Pd concentration profile in alumina and silica supported egg-shell catalysts and their performance in the hydrogenation of 2-ethylanthraquinone (eAQ) were studied in ‘Anthra’ (AQ) and ‘All-Tetra’ systems. The activity and deactivation of catalysts were determined in the fixed-bed reactor. Solution saturated with hydrogen, (concentration of active quinones 60g/dm3, eAQ in the AQ system, 30% of eAQ and 70% of H4eAQ–2-ethlytetrahydroanthraquinone, in the All-Tetra system) was circulated through the catalyst bed at temperature 50°C and pressure 5bar. The contents of eAQ, active quinones, H4eAQ and degradation products were determined in the course of hydrogenation by GC method. The egg-shell palladium catalysts (1–2wt% Pd) prepared by the precipitation of palladium hydroxide onto alumina and silica supports pre-impregnated with various alkaline (NaHCO3, NaH2PO4, Na2SiO3) solutions were used in the hydrogenation experiments. Pd concentration profile inside the grains of catalysts was characterized by scanning electron microscopy. A difference between alumina and silica carriers with respect to the course of side reactions producing degradation products was found. Degradation of quinones in the hydrogenolytic reactions predominated on alumina supported catalysts, while the catalysts with silica favoured the hydrogenation of aromatic rings resulting in H4eAQ-active quinone. As a crucial factor for the decrease in the activity during the hydrogenation run, the reactivity of catalyst in the hydrogenolytic reactions was established. Alumina supported catalysts exhibited much higher deactivation than those of silica supported ones. Silica carrier as well as silica species introduced onto alumina under pre-impregnation with Na2SiO3 exhibited an advantageous role in the catalyst performance, in terms of activity and deactivation. [ABSTRACT FROM AUTHOR]

The chemical incorporation of palladium into polyaniline (PANI) deposited onto the silica gel microparticles (15-μm in diameter) was studied. The as-prepared silica particles coated with PANI–hydrochloride (AC) were treated with aqueous ammonia solution (0.1 M) to transform polyaniline to its base (BA) form. Both AC and BA samples were reacted with PdCl2 solutions (2.3×10−3 M) strongly differing in the concentration of HCl (0.1 M HCl, series K; 6.6×10−4 M HCl, series Z). Two series of samples with 0.43–2.14 wt.% Pd were obtained. Fourier-transform infra red (FTIR), UV-Vis, X-ray photoelectron spectroscopies (XPS) and scanning electron microscopy have been used to examine the nature of processes involved upon insertion of Pd and to characterize palladium species in the final samples. Very similar palladium species were found in the polymer matrix independently of the acidity of PdCl2 solutions and the extent of PANI protonation (AC and BA samples). Pd2+ was the only form if no more than 0.86% Pd was introduced. Incorporation of higher content of palladium resulted in the partial reduction (14.6–28.7%) of Pd2+ to Pd0. The presence of Pd2+ species in the form of complexes in which besides Cl− ligands also nitrogen groups of PANI participated has been postulated. The catalytic properties of Pd/PANI-SiO2 have been studied in the liquid-phase hydrogenation of 2-ethylanthraquinone (EAQ) at 60 °C under 1 atm of hydrogen. Very low activity of the as-prepared catalysts significantly increased due to reduction of the samples with NaH2PO2 and subsequently with dihydrogen. The specific activities of reduced series K and Z samples were comparable and the maximum activity exhibited catalysts with 1–1.5% Pd. [Copyright &y& Elsevier]