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Organosilane-functionalized mesoporous silica SBA-15 was prepared by the co-condensation method and then applied as a support of Pd catalysts for hydrogenation of 2-alkyl-anthraquinone (AQ, alkyl = ethyl, tert-butyl and amyl). The as-prepared Pd catalysts were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, N2 adsorption-desorption, zeta potential, water contact angles measurement and transmission electron microscopy. By extending the pre-hydrolysis time of the silica source, the content of functional groups in the catalysts slightly increases. However, there is an initial increase in zeta potential and water contact angles up to a maximum at 2 h, followed by a decrease as the pre-hydrolysis time was further prolonged. The hydrophobicity created by organic functionalization has positive effects on AQ hydrogenation. The catalyst with the highest hydrophobicity exhibits the highest catalytic activity, with increments of 33.3%, 60.0% and 150.0% for hydrogenation of ethyl-, tert-butyl- and amyl-anthraquinone compared with the unfunctionalized one.

The effect of the composition of the catalytic system and the size of particles on the properties of palladium catalysts in 2-ethyl-9,10-anthraquinone hydrogenation was studied. It was shown that, depending on the nature of a reducing agent (H2, AlEt3), palladium species formed in the absence of a modifying agent catalyze various side processes to a substantial extent together with 2-ethyl-9,10-anthraquinone hydrogenation: mostly hydrogenolysis (in the case of H2 as a reducing agent) and hydrogenation of aromatic rings in 2-ethyl-9,10-anthrahydroquinone (in the case of AlEt3 as a reducing agent). Elementary phosphorus was found to have a promoting effect on the selectivity of palladium catalysts in the synthesis of hydrogen peroxide by the anthraquinone method. The main factors that make it possible to control the selectivity of palladium catalysts were discussed.

Polymer, namely poly(4-vinylpyridyne) (PVP) was used as a support for palladium catalysts acting in liquid phase hydrogenation of 2-ethylanthraquinone (eAQ), a key step in industrial production of hydrogen peroxide. The catalytic hydrogenation was carried out in a slurry reactor at atmospheric pressure of H2 and temperature 43°C. The progress of eAQ hydrogenation over Pd/PVP catalyst was the same as observed earlier in the presence of Pd/SiO2. In initial stage of reaction eAQ was reduced with high selectivity to eAQH2 (2-ethylanthrahydroquinone). In the further process termed "deep hydrogenation" hydrogenation of aromatic rings (formation of tetrahydroanthrahydroquinone H4eAQH2) and hydrogenolysis of carbon-oxygen bonds (formation of degradation products) in eAQH2 proceeded. It was stated that in the presence of mass transport limitations the progress of reactions leading to the formation of "degradation products" was intensive.

Hydrogenation of 2-ethylanthraquinone (eAQ) was carried out over 4percent Pd/SiO2 catalyst under the stirred batch reactor conditions at atmospheric pressure of hydrogen and temp. 62 deg C.Catalysts containing the hydrated palladium oxide were reduced with hydrogen in situ or outside of the reactor using formaldehyde, hydrazine or hydrogen (at temp. 50-300 deg C).It was stated that the method of catalyst pretreatment influences both the course of >C=O to C-OH reduction and the "deep hydrogenation"comprising hydrogenation of aromatic rings as well as hydrogenolysis of carbon-oxygen bond.The highest rate of >C=O reduction and the high selectivity of this reaction was observed over catalyst reduced in situ.At the presence of such a catalyst also the selectivity of 2-ethyl-5,6,7,8-tetrahydroantraquinone (H4eAQ) formation in "deep hydrogenation" was relatively high (50percent).Key words: anthraquinone method, deep hydrogenation, activity and selectivity of catalysts.

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