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Supported and unsupported (with or without Co and Ni promotors) MoS2-based catalysts were prepared using conventional incipient wetness impregnation method on pure and carbonized alumina with an appropriate aqueous solution of a 12-molybdophosphoric heteropolyacid and cobalt or nickel citrate. Unsupported MoS2 catalysts were synthesized by leaching away the supports from MoS2/Al2O3, MoS2/C/Al2O3 and using industrial CoMo/Al2O3 catalyst (named as Et-MoS2-Ind) with HF acid. Catalysts were investigated by low-temperature nitrogen adsorption and transmission electron microscopy techniques to characterize their structure and morphology. Catalysts were tested in hydrodeoxygenation (HDO) of oleic acid (OA) in an autoclave under hydrogen pressure. CoMoS2/Al2O3, NiMoS2/Al2O3, and Et-MoS2-Ind catalysts were also investigated as single and dual catalytic systems, using a bench-scale flow reactor in co-hydroprocessing of mixed feed, containing straight-run gas oil and 15 wt. % of waste sunflower oil. The results of the catalyst tests show that hydrogenation/decarbonylation (HYD/DEC) selectivity in oleic acid HDO strongly depends on catalyst type. The CoMoS2/C/Al2O3 and CoMoS2/Al2O3 catalysts show low HYD/(HYD + DEC) selectivity, equal to 0.55. Unpromoted MoS2/C/Al2O3, MoS2/Al2O3, Et-MoS2-Ind and Ref-MoS2 samples have quite similar HYD/(HYD + DEC) selectivity around 0.85. The highest HYD/(HYD + DEC) selectivity (0.95) was reached over Et-MoS2/C and Et-MoS2 samples, which indicated that HDO had gone through HYD route without any formation of CO and CO2. A double-bed catalyst reactor comprising of the upper-layer bulk Et-MoS2-Ind and the under-layer Co(Ni)–MoS2/Al2O3 catalysts are proposed for the effective co-hydroprocessing of diesel and vegetable oil.

Bimetallic catalysts MoW/СОK-12 are synthesized on the basis of mesostructured silicate COK‑12 prepared from sodium silicate aqueous solution using the Keggin structure hetero polyacid H4Si-Mo3W9O40 as an oxide precursor of the sulfide active phase and with the use of the mechanical mixture of two monometallic hetero polyacids (H4SiMo12O40 and H4SiW12O40) at a molar ratio of Mo/W = 3/9. Alumina-based analogs with the same surface metal content are used as reference samples. The test samples are analyzed by low-temperature nitrogen adsorption and high-resolution transmission electron microscopy. The catalytic activity is studied in the combined hydrotreatment of dibenzothiophene and naphthalene and in the hydrodesulfurization of 4,6-dimethyldibenzothiophene in a flow unit. It is shown that the use of mesostructured silicate COK-12 as a support leads to an increase in catalytic activity in target hydrotreating reactions.

A bulk MoWS2 catalyst has been synthesized by acid etching of the carrier from the supported MoWS2/Al2O3 catalyst obtained on the basis of the mixed bimetallic heteropoly acid (HPA) H4[SiMo3W9O40]. As reference samples, monometallic MoS2 and WS2 catalysts have been prepared from the corresponding supported analogues, as well as a Mo + WS2 sample based on a mechanical mixture of monometallic HPA in the atomic ratio of Mo/W = 1/3. The catalytic properties of the synthesized catalysts have been studied in model reactions of hydrodesulfurization (HDS) of dibenzthiophene (DBT) and hydrogenation (HYD) of naphthalene in a flow unit. It has been shown that the catalytic activity of the samples in both the DBT HDS and naphthalene HYD reactions increases in the following order: MoS2 < WS2 < Mo + WS2$$ \ll $$ MoWS2. It has been found that the bulk tungsten-containing catalysts exhibit higher specific catalytic activity than the supported counterparts. Increased values of hydrogen uptake according to the results of hydrogen temperature-programmed reduction for the bulk catalysts indicate an increase in the number of active sites and the formation of a more effective active phase compared to supported catalysts.

Trimetallic NiCoMo catalysts supported on γ-alumina (γ-Al2O3), amorphous silicon dioxide (SiO2), and mesostructured silicate (SBA-15) with equal surface concentration of active components were synthesized, and their physicochemical characteristics, including the morphology of the active phase particles, were studied. The performance of the synthesized catalysts in target hydrotreating reactions at different concentrations of an organic nitrogen-containing inhibitor, quinoline (0–1000 ppmw nitrogen), was determined. The inhibiting effect of quinoline on the hydrodesulfurization and hydrogenation reactions occurring on the synthesized catalysts and the influence of the kind and properties of the support on this effect were evaluated.

Mo(W)/SBA-15 catalysts are prepared using heteropoly acids H4SiMo12O40, H4SiW12O40, and H4SiMo3W9O40. The catalysts in the sulfide form are studied by low-temperature nitrogen adsorption, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy. Catalytic properties are tested in the hydrodesulfurization of 4,6-dimethyldibenzothiophene. It is shown that the gas-phase sulfiding of Mo(W)/SBA-15 catalysts leads to increase in the average length of particles and the number of Mo(W)S2 layers in active phase particles compared with liquid-phase sulfiding with the use of dimethyl sulfide. The replacement of a quarter of tungsten atoms with molybdenum ones makes it possible to considerably improve the catalytic activity of the mixed catalyst Mo + W/SBA-15 compared with the monometallic counterparts. This effect can be enhanced due to the use of mixed heteropoly acid H4SiMo3W9O40 as a precursor of the active phase of the MoW/SBA-15 catalyst, which is apparently associated with the formation of MoWS2 active sites.

Demetallization of a mixture of vacuum gas oil with heavy coker gas oil on CoMo/γ-Al2O3 catalysts with different pore structures was studied, and the influence of the catalyst pore structure on the process results was demonstrated. For the demetallization catalysts to be effective, their pore size should be restricted not only from below but also from above. When using samples with broad pores, effects of the hydrodesulfurization and hydrodemetallization inhibition can arise owing to adsorption of supramolecular structures of heavy residues, in particular, of asphaltenes.

A series of alumina supported CoMo catalysts with different molybdenum surface density was prepared using incipient wet impregnation method and applying H6[Co2Mo10O38H4] (Co2Mo10HPA) as a single oxidic precursor. Dried and sulfided catalysts were characterized by a variety of techniques, such as N2 adsorption, micro-Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and high-resolution transmission electron microscopy (HRTEM). Catalytic properties have been examined in co-hydrotreating of dibenzothiophene and naphthalene using a fixed bed high-pressure flow reactor. It was found that using Co2Mo10HPA as a single precursor enables more than the double increase of maximum metal loading compared to conventional compounds. This also contributed to a significant increase in catalytic activity in hydrotreating.

MoW alumina supported hydrotreating (HDT) catalysts were synthesized by using mixed SiMonW12-n heteropolyacids (HPAs) and also from a mixture of SiMo12 and SiW12 HPAs with the same Mo/W ratios for reference. Gas phase sulfidation of the catalysts prepared from mixed MoW HPAs led to the formation of a mixed phase evidenced by high-angle annular dark-field (HAADF) images, where a core of Mo atoms was surrounded by W atoms. Contrariwise, most of MoS2 or WS2 slabs were observed in the solids prepared from a mixture of the HPAs. This mixed phase induced higher hydrodesulfurization (HDS) of DBT, as well as hydrogenation (HYD) of naphthalene, than it was observed in the case of the reference catalysts. Comparison of activation procedures (gas phase versus liquid phase) confirmed that sulfidation in gas phase led to more efficient catalysts, even in the case of the formation of the mixed slabs. Beneficial effect of the mixed MoWS phase was even more pronounced in the case of the HDS of a more refractory molecule, 4,6-dimethyldibenzothiophene (4,6-DMDBT), which was attributed to the more hydrogenating properties of this mixed phase.

Supports based on pseudoboehmite, ultrastable zeolite Y, and ZSM-5 with different silica ratio and concentration of acid sites are prepared. NiMoS catalysts are synthesized by the incipient wetness impregnation of the prepared supports by the joint solution of H3PMo12O40 and nickel citrate. The composition and properties of the supports and catalysts are studied by low-temperature nitrogen adsorption, ammonia temperature-programmed desorption, IR spectroscopy of pyridine adsorption, and high-resolution transmission electron microscopy. Catalytic properties are investigated in dibenzothiophene hydrodesulfurization (HDS), naphthalene hydrogenation (HYD), and hexadecane hydrocracking (HC) concurrent reactions in a flow unit equipped with a microreactor. It is shown that the HDS activity of the synthesized samples declines as the dispersity of active-phase particles decreases in correlation with a change in the surface area of support mesopores. It is shown that the NiMo/ZSM-5/23 catalyst exhibits a high activity in naphthalene HYD and subsequent reactions of tetralin and decalin naphthene ring opening and hexadecane HC. It is found that the activity of zeolite-containing catalysts in naphthalene HYD grows with the proportion of Bronsted acid sites.

The catalytic properties of trimetallic NiMoWS catalysts supported on alumina are studied in the process of straight-run diesel fraction hydrotreating. It is shown that the nature of the oxide precursor of the mixed NiMoWS active phase strongly affects catalyst activity in the hydrodesulfurization (HDS), hydrodenitrogenation (HDN), and hydrogenation (HYD) of polycyclic aromatic hydrocarbons (PAH). The NiMoWS/Al2O3 catalyst synthesized from the mixed H4SiMo3W9O40 heteropoly acid is more efficient than the sample prepared from a mixture of individual H4SiMo12O40 and H4SiW12O40 heteropoly acids in both HDS and HDN transformations at the same metal content. The highest activity in PAH hydrogenation is exhibited by the NiMoWS/Al2O3 catalyst prepared using H4SiMo3W9O40.

CoMoS/Cx/Sup Catalysts were prepared using 12-molybdophosphoric heteropolyacid and cobalt citrate. The supports were Al2O3, SiO2, nos, ZrO2, and carbonized Cr/Sup derived substrates (2 and 6 mass % carbon). The catalytic properties of these samples in the hydrodeoxygenation of guaiacol in a microflow apparatus were studied. With increasing carbon content in the supports, the length and number of MoS2 layers in the package increase in all the samples, apparently due to a decrease in the strength of the particle interaction with the more inert carbonized surface. Furthermore, the dispersion of the molybdenum particles on the catalyst surface, the content of promoter in the CoMoS active phase, and the extent of promotion of the crystallite edges differ significantly. The reasons were examined for the observed behavior and possible activity interrelationship during the hydrodeoxygenation of guaiacol with the parameters of the catalyst and active phase nanoparticles.

The effect of quinoline on the hydrodesulfurization and hydrogenation activities of bi- and trimetallic NiMo(W)/Al2O3 hydrotreating catalysts obtained using Keggin heteropoly acids H4SiMo3W9O40, H4SiMo12O40, and H4SiW12O40 (denoted as SiMo3W9, SiMo12, and SiW12, respectively) and a mixture of two monometallic heteropoly acids (SiMo12 and SiW12) was studied. The catalytic properties were determined in a fixed-bed microreactor in hydrotreating of model feedstock containing dibenzothiophene and naphthalene and of the same feedstock with the addition of quinoline. The trimetallic NiMoW/Al2O3 sample based on the mixed SiMo3W9 heteropoly acid exhibited 1.5 times higher catalytic activity in all the reactions studied compared to its analog prepared from a mixture of SiMo12 and SiW12 heteropoly acids with the same metal ratio. The trimetallic NiMoW/Al2O3 catalyst based on the mixed SiMo3W9 heteropoly acid surpassed in the activity the NiMo/Al2O3 sample and was more resistant to the inhibiting effect of quinoline than its analog prepared from a mixture of the two heteropoly acids. The correlations of the inhibiting effect of quinoline with the morphology of the active phase particles and the content of promoted active sites Ni(Mo)WS in the bi- and trimetallic NiMo(W)/Al2O3 catalysts were found.

Unsupported molybdenum disulfide catalysts were synthesized from ammonium tetrathiomolybdate with chitosan, hexadecylammonium and Triton X100 as structural agents by leaching of MoS2/Al2O3 and MoS2/C/Al2O3 catalyst supports with HF acid and covering of “FeS” seeds by the MoS2 shell. Activation of the solids was performed under the H2S/H2 flow or by the decomposition of precursors in the presence of a hydrocarbon solvent in an autoclave reactor with varied H2 pressure. X-ray diffraction, N2 adsorption, temperature-programmed reduction, X-ray photoelectron spectroscopy and transmission electron microscopy techniques were used to characterize their structure and morphology. The nature of organic additives and activation conditions affect the surface area, pore size distribution, and morphological characteristics of MoS2 particles. Hydrodesulfurization of dibenzothiophene was performed in an autoclave reactor over unsupported MoS2based catalysts. The catalytic behavior of bulk MoS2 catalysts showed that the hydrogenation pathway prevailed over the direct desulfurization pathway. Higher HYD/DDS selectivity for dibenzothiophene hydrogenation was observed with the bulk molybdenum disulfide catalyst formed by etching of the MoS2/Al2O3 catalyst support. Unsupported Mo sulfide catalysts exhibited high hydrogenation activity in dibenzothiophene hydrodesulfurization and, therefore, might find wide applications in hydroprocessing of heavy feed and co-hydrotreating of petroleum fractions and plant oils.

On the basis of alumina synthesized via addition of mesostructured aluminum hydroxide gel, which is prepared by the hydrolysis of secondary aluminum butoxide in the presence of triblock copolymer Pluronic P123 to the AlOOH commercial powder, and the commercial reference sample, NiWS/Al2O3 catalysts are prepared using H3PW12O40 heteropolyacid and nickel citrate. The physicochemical properties of the supports and catalysts are studied by low-temperature nitrogen adsorption, temperature-programmed desorption of ammonia, and high-resolution transmission electron microscopy. The catalytic properties are investigated in the process of straight-run diesel fraction hydrotreating in a flow unit. It is shown that the use of the synthesized alumina as a catalyst support leads to an increase in the dispersity of nanosized particles of the NiWS active phase. The catalytic activity in targeted reactions also grows appreciably. The causes of these phenomena are discussed.

Alumina supports were synthesized from aluminum hydroxide produced by the hydrolysis of secondary aluminum butoxide in the presence of the triblock copolymer Pluronic P123 (m-AlOOH) and from the commercial AlOOH pseudoboehmite powder (TH-AlOOH), as well as by mixing of m-AlOOH and TH-AlOOH gel in a ratio of 5:95 (m-TH-AlOOH sample). NiW/Al2O3 catalysts were prepared by impregnation of the synthesized supports with H3PW12O40 heteropolyacid and nickel citrate. Physicochemical properties of the supports and catalysts were investigated by low-temperature nitrogen adsorption, X-ray diffraction, NH3 thermo-programmed desorption, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy. Catalytic properties were tested in hydrotreatment of straight-run gas oil and vacuum gasoil on a flow unit. The resulting hybrid support had a non-additively higher average pore radius (75 A) and surface area (307 m2/g) than a conventional alumina support and hence preferred morphology of NiWS active phase (3.8 nm against 6.6 nm with the same stacking number) and an increase in the W sulfidation degree (68% against 54%) and Ni content in NiWS phase (44% against 26%). Therefore, the catalyst on the hybrid support exhibits higher activity in hydrodesulfurization, hydrodenitrogenation and hydrogenation of petroleum feeds, and a lower degree of deactivation and coke formation.

CoMo hydrotreating catalysts with varied metal loading (1–4 Mo at nm− 2) based on Co2Mo10 heteropolyacid (HPA) and different supports (γ-Al2O3, SBA-15, SiO2) were prepared by incipient wetness impregnation. The catalysts were characterized by N2 physisorption, high resolution transmission electron microscopy (HRTEM), Raman and X-ray photoelectron spectroscopy (XPS). Catalytic activity was evaluated in co-hydrotreating (HDT) of the model feed containing dibenzothiophene (DBT) and naphthalene. The catalytic properties of CoMo catalysts were shown to depend on the morphological characteristics of CoMoS species, its promotion degree, and metal loading. The sulfidation degree of the initial precursor and effective cobalt amount in the CoMoS species increased with the Mo loading increase from 1 to 4 at nm− 2 in all studied catalysts. The DBT conversion maximum was achieved over CoMo/Al2O3 and CoMo/SBA-15 with 4 Mo at nm− 2. CoMo/SBA-15 catalysts had higher TOF numbers both in DBT HDS and in naphthalene hydrogenation (HYD) at the surface concentration of Mo same as in the other samples. These results can be attributed to optimal morphology of sulfide particles and the Co/Mo promotion degree due to a more suitable interaction between the active phase and support in mesoporous silica channels.

Reactivation of industrial CoMo/Al2O3 hydrotreating (HDT) catalysts was studied. A spent catalyst was used in the ULSD production for about 2.5 years. It was oxidatively regenerated and rejuvenated by organic acids (citric and thioglycolic), glycols (ethylene and triethylene), and dimethylsulfoxide solutions. All solids were characterized by the elemental analysis, N2 physisorption, X-ray powder diffraction, thermogravimetric analysis, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy. Changes in the active phase composition and morphology during the CoMo/Al2O3 HDT catalyst operation, regeneration and rejuvenation were shown. The rejuvenated catalysts were tested in hydrodesulfurization (HDS) of dibenzothiophene and hydrogenation (HYD) of naphthalene. It was found that oxidative regeneration allowed restoring about 70–85% rel. of initial activity. Rejuvenation with organic chemicals resulted in the complete restoration of HDS and HYD activities. Resulting catalytic activity of the reactivated catalysts depended on the properties of the formed active phase species. These correlations are discussed in the study.

СоМоS/Sup catalysts were prepared from 12-molybdophosphoric heteropoly acid and cobalt citrate, with Al2O3, SiO2, TiO2, and ZrO2 used as supports (Sup). The synthesized catalysts were studied by low-temperature nitrogen adsorption, X-ray diffraction, temperature-programmed ammonia desorption, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy. The catalytic properties of the catalysts were studied in a flow-through installation at 260 and 340°С, pressure of 3.0 MPa, feed space velocity of 80 h–1, and Н2/feed ratio of 500 Ln.c. L–1. The guaiacol hydrodeoxygenation rate increases with a decrease in the mean length of the active phase particles, irrespective of the kind of the oxide support. As for the support effect, the catalyst activity decreases in the order SiO2 > Al2O3 > ZrO2 ~ TiO2. On the other hand, the catalysts supported on ZrO2 and Al2O3 exhibit the highest stability. The causes of the observed trends and the possible relationships between the characteristics of the catalysts and active phase nanoparticles are discussed.

International audience; H4[SiMonW12−nO40] heteropolyacids (HPAs) are interesting precursors for the preparation of alumina-supported hydrotreatment catalysts to introduce both metals simultaneously while maintaining a Mo–W nanoscale proximity. Two heteropolyacids (n = 1 and 3) have been synthesized and used for the first time to prepare hydrotreatment catalysts. Crystal structure refinement has been performed and evidenced the formation of β-H4[SiMo3W9O40] with three ordered Mo sites forming a face. The purity of the samples in aqueous solution has been determined by Raman spectroscopy and polarographic characterization. These heteropolyacids were then impregnated on alumina to prepare supported MoW-based catalysts. As references, catalysts with the same Mo/W ratios have been prepared using monometallic H4SiMo12O40 and H4SiW12O40 HPAs (mixture of these 2 HPAs in the impregnating solution). EXAFS characterization after drying performed simultaneously at the Mo K and W LIII edges indicates preservation of the mixed heteropolyanion SiMonW12−nO404− at the alumina surface even if partial decomposition to Keggin lacunary species could not be excluded and evidences the mixed MoW–S2 slab formation after sulfidation. Better catalytic hydrogenation properties for dibenzothiophene hydrodesulfurization and naphthalene hydrogenation have been obtained when using β-H4[SiMo3W9O40], which is explained by the formation of the mixed MoW–S2 active phase.

Mono- and bimetallic Mo(W)S2 catalysts supported on γ-Al2O3 and SBA-15 have been prepared using the Keggin heteropoly acids (HPAs) H4SiMo12O40 and H4SiW12O40. The catalyst samples have been analyzed by temperature-programmed reduction with hydrogen, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy. Catalytic properties have been examined in the joint hydrotreating of dibenzothiophene and naphthalene on a flow-through unit. It has been shown that the use of mesoporous silica SBA-15 as a support can reduce the average length of Mo(W)S2 particles from 4.9 to 3.7 nm and increase the average number of layers and the particle size of the active phase, changes that lead to an increase in catalytic activity by a factor of ~3 relative to the alumina-supported counterparts. The use of a mixture of SiMo12HPA and SiW12HPA for preparing MoW catalysts leads to a significant enhancement of catalytic activity, which is apparently due to the formation of mixed active sites.

The bimetallic MoWS2/Al2O3 catalyst was synthesized using the Keggin-type mixed heteropolyacid H4SiMo3W9O40. The monometallic catalysts SiMo12/Al2O3 and SiW12/Al2O3 based on the H4SiMo12O40 and H4SiW12O40 acids are prepared as reference samples. The sulfidized catalysts are analyzed by temperature-programmed reduction with hydrogen, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy. Their catalytic properties are studied in the cohydrotreatment of dibenzothiophene (DBT) and naphthalene on a flow-type setup. The introduction of three molybdenum atoms into the structure of an oxide precursor is shown to increase the degree of sulfidation of the tungsten particles by 20% in comparison with SiW12/Al2O3. The DBT turnover frequency in the hydrodesulfurization (HDS) on the sites on the edges of the active phase of the SiMo3W9/Al2O3 catalyst is shown to be 5.5 times higher than in the presence of SiW12/Al2O3. The bimetallic sample demonstrated the highest selectivity in the preliminary DBT hydrogenation route and activity in the prehydrogenation of naphthalene. The high level of activity of the SiMo3W9/Al2O3 catalyst was due to the formation of a mixed Mo x W(1–x)S2 active phase with a MoW oxide precursor, whose structure contained both metals bonded at the molecular level.

Trimetallic NiMoW/Al2O3 catalyst was prepared using mixed H4SiMo3W9O40 heteropoly acid of Keggin structure and nickel citrate. Bimetallic NiMo/Al2O3 and NiW/Al2O3 catalysts based on H4SiMo12O40 and H4SiW12O40, respectively, were synthesized as reference samples. The use of mixed H4SiMo3W9O40 heteropoly acid as an oxide precursor allows the tungsten sulfidation degree and the degree of promotion of active phase particles to be increased. The hydrodesulfurization activity is enhanced as compared to NiW/Al2O3 catalyst. The synergistic enhancement of the activity of the NiMo3W9/Al2O3 catalyst relative to the bimetallic analogs is probably caused by formation of new mixed promoted active sites for direct desulfurization.

The promoter nature effect on the sensitivity of Mo/Al2O3, Ni–Mo/Al2O3, Co–Mo/Al2O3, and Ni‒Co–Mo/Al2O3 catalysts to dodecanoic acid in the hydrotreating of a mixture containing dibenzothiophene and naphthalene has been investigated. The experiments have been carried out using a flow-through setup. The catalysts have been prepared using the PMo12 heteropoly acid, Сo(Ni) citrates, and Co2Mo10 heteropoly acid and have been characterized by high-resolution transmission electron microscopy. The highest hydrodesulfurization activity in the presence of dodecanoic acid is shown by the trimetallic catalyst Ni–Co–Mo/Al2O3. The introduction of Ni is favorable for dodecanoic acid conversion via the hydrogenation route, thus increasing the С11: С12 ratio in the conversion products. Effective dodecanoic acid adsorption constants under the hydrotreating conditions have been calculated using the Langmuir–Hinshelwood model.

CoPMo/Al2O3 catalysts were prepared using H3PMo12O40 and Co complexes with citric acid (CA) or non-complexing organic additives such as ethylene glycol (EG), diethylene glycol, triethylene glycol (TEG), glycerol, and a mixture of EG and CA. The catalysts were characterized by low-temperature N2 adsorption, Raman spectroscopy, thermogravimetric analysis, temperature-programmed reduction, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy. The prepared samples were tested in hydrodesulfurization (HDS) of dibenzothiophene (DBT). The addition of either CA or glycols led to several beneficial effects such as weakening of the slab-support interaction at enhancing the promotion degree, dispersion and stacking number of the CoMoS species. It has been shown that the promotion degree of CoMoS edges increased with a pore volume gain by the additive-impregnated catalysts after their sulfidation. Catalysts with CA, TEG or the EG-CA mixture demonstrated higher activity in DBT HDS. Probable reasons for the found relationships are discussed.

Ni(Co)-PW/Al2O3 catalysts both unmodified and modified with potassium were synthesized with the use of H3PW12O40, CoCO3 or NiCO3, KOH and citric acid. The catalysts were characterized by the techniques such as low-temperature N2 adsorption, temperature-programmed reduction, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy. The prepared samples were tested in hydrotreating of model FCC gasoline that contained 1000 ppm of sulfur from thiophene and 36 wt.% of n-hexene-1 as a representative olefinic compound. The modification with an alkali metal influenced both the characteristics of the catalyst active phase and catalytic properties of (K)-Ni(Co)-PW/Al2O3 samples. The incorporation of potassium led to some l growth of the linear size of active phase crystallites, to a decrease of reactivity and of the number of active sites, to a strong decrease of CoWS and NiWS particle amounts with a simultaneous rise of separate CoSx and NiSx. The potassium addition also induced a drastic drop of hydrodesulfurization (HDS) and hydrogenation (HYDO) activity with a HDS/HYDO selectivity decrease for Ni- and Co-promoted systems and with a significant increase of the selectivity factor for unpromoted PW/Al2O3. The Ni-promoted catalyst proved to be more sensitive to the potassium modification than the Co-promoted one. So, the modified catalysts can be ranged by activity as follows: KWS

Co x -Co 2 Mo 10 /SiO 2 and Co 2 Mo 10 /Co x /SiO 2 catalysts with various Co/Mo ratios and active species compositions are prepared using H 6 [Co 2 Mo 10 O 38 H 4 ] heteropolyacid, CoCO 3 and citric acid. Catalysts are characterized using the following techniques: low-temperature N 2 adsorption, temperature-programmed reduction, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy. Catalytic activities of the synthesized catalysts are examined in hydrotreating of model fluid catalytic cracking (FCC) gasoline that contains 1000 ppm of sulphur from thiophene and 36 wt.% of n-hexene-1. As the Co/Mo ratio increases, hydrodesulphurization (HDS) and hydrogenation (HYD) activities of the prepared catalysts significantly builds up. The changes of catalytic properties and specifically of the HDS/HYDO selectivity factor of the synthesized CoMo catalysts arise from two effects: an alteration of the promotion degree of CoMoS active phase particles and a hydrogen spillover from CoS x species to active sites. The developed silica-supported CoMo catalysts may be a prospect for selective HDS and hydro-upgrading of FCC gasoline.

International audience; Trimetallic CoMo3W9/Al2O3 catalyst is prepared using the Keggin structure mixed heteropolyacid H4SiMo3W9O40 and cobalt citrate. CoMo12/Al2O3 and CoW12/Al2O3 catalysts based on H4SiMo12O40 and H4SiW12O40, respectively, are synthesized as reference samples. Sulfided catalysts are analyzed by high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy. Catalytic properties are investigated in the co-hydrotreatment of dibenzothiophene (DBT) and naphthalene in a flow unit. It is shown that the catalytic activity in both DBT hydrodesulfurization and naphthalene hydrogenation (HYD) decreases in the following sequence: CoMo12/Al2O3 > CoMo3W9/Al2O3 > CoW12/Al2O3, and it correlates with the degree of promotion of active-phase particles by cobalt atoms. A comparison with the published data available for Ni-promoted catalysts makes it possible to reveal the general regularity for bi- and trimetallic Со(Ni)-Mo(W)S catalysts: the use of mixed Mo-W H4SiMo3W9O40 heteropolyacid instead of monometallic H4SiW12O40 causes an increase in the degree of promotion of MoWS2 crystallite edges for the series of catalysts promoted by both cobalt and nickel. The use of nickel as a promoter leads to a higher degree of promotion of edges of active-phase particles in comparison with cobalt; as a result, the NiMo3W9/Al2O3 catalyst is much more active than the CoMo3W9/Al2O3 counterpart. Possible reasons behind the found features are discussed.

Hydroprocessing catalysts based on transition metal sulfides have been extensively used worldwide in refineries for upgrading heavy fractions to better quality fuels. The present work reviews the studies dealing with Anderson heteropolyanions (HPAs) and the derived dimeric structure for synthesizing hydrotreating catalysts. The development of new preparation methods based on HPA catalysts led to efficient catalytic systems due to better sulfidation allowed by a better dispersion of the oxidic precursor even at high metallic loadings. The increase of the Co/Mo ratio in the heteropolycompounds up to 0.5 was possible due to the formation of dimer cobalt salt. The association of Co and Mo at the molecular level in the same heteropolycompound preserved after the drying step during the catalyst preparation ensured the efficiency of the promoting effect with a higher quantity of the CoMoS active phase. This HPA-based system was further improved by the simultaneous use of HPAs and chelating agents.

XMo6/Al2O3 catalysts were synthesized using XMo6-heteropolycompounds with Anderson’s structure (where X = Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Al). The sulfided catalysts were characterized by N2 adsorption, temperature-programmed reduction, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy. The catalysts were tested in hydrotreating of model FCC gasoline contained thiophene (1000 ppm of sulfur) and 1-hexene (36 wt%). The correlations between HDS/HYDO selectivity and characteristics of XMoS species depending on the nature of the heteroatom X in XMo6-heteropolycompound indicated the predominance of the electronic effect under the geometrical impact in the catalytic properties. It was found that to create a catalyst with high HDS/HYDO selectivity, reaching the mixed CoMoS active phase is the key requirement.

Ni(Co)x-Co2Mo10/Al2O3 catalysts with various (Co+Ni)/(Co + Ni + Mo) atomic ratio (from 0.17 to 0.45) and constant Mo loading (10 wt.%) were synthesised using decamolybdodicobaltate heteropolyacid (Co2Mo10HPA) and cobalt or nickel citrate. The catalysts were characterised using N2 physisorption, high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy and tested in the hydrodesulphurisation (HDS) of dibenzothiophene (DBT). It was found that adding the Co(Ni) citrate to Co2Mo10/Al2O3 catalyst significantly altered the active phase morphology. The average slab length increased from 3.0 to 4.1 nm in Cox-Co2Mo10/Al2O3 catalysts and to 3.6 nm in Nix-Co2Mo10/Al2O3 counterparts. The average stacking number of the MoS2 crystallites grew from 1.4 to 2.0 with loading the Co or Ni. Increasing the Co content in the Cox-Co2Mo10/Al2O3 catalysts decreased the Co percentage in the CoMoS phase and led to the growth of Co fraction in cobalt sulphide. With the increase of Ni content in Nix-Co2Mo10/Al2O3 catalysts the Ni percentage in the NiCoMoS phase decreased from 47 to 25 rel.% and the Co percentage in the NiCoMoS phase was constant and equal to ∼62 rel.%. For both series of the catalysts, activity in DBT HDS passed through maximum at 0.33 of the atomic ratio (Co + Ni)/(Co + Ni + Mo). Nix-Co2Mo10S/Al2O3 catalysts indicated higher rate constants in DBT HDS than Cox-Co2Mo10S/Al2O3 counterparts at the same metal content. It was concluded that Ni1-Co2Mo10/Al2O3 sample with minimal Ni/Mo ratio had mixed Ni-Co-Mo sites with high turnover frequencies values.

International audience; MoW catalysts supported on Al2O3 with equal surface content of metals (Mo + W = 3.9 at/nm2) were synthesized by using mixed Keggin type heteropolyacids (HPAs) H4[SiMo1W11O40] and H4[SiMo3W9O40] and corresponding mixture of monometallic H4[SiMo12O40] and H4[SiW12O40] HPAs. After liquid phase sulfidation, catalysts were characterized by high-resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS). For the first time, High Angle Annular Dark Field microscopy (HAADF) was used to evidence the morphology and composition of the active sulfide phase. The catalysts were tested in hydrotreating of model feed that contained dibenzothiophene (DBT) and naphthalene. Using mixed SiMonW12-nHPAs as starting precursors had a beneficial effect on the catalytic activity. Incorporation of molybdenum in the structure of SiW Keggin-type HPA led to a decrease of the size of active phase crystallites, to an increase of the metal sulfidation degree and of the number of active sites. Substitution of a quarter of tungsten atoms by molybdenum allowed to achieve DBT conversion comparable to value obtained on pure SiMo12HPA based catalyst and higher conversion of naphthalene. Both SiMonW12-nHPAs based catalysts had higher rate constants in studied reactions compared to their corresponding references prepared from two separate monometallic HPAs. Moreover, MonW12-n/Al2O3 catalysts had the highest selectivity in respect of hydrogenation (HYD) pathway of DBT hydrodesulfurization (HDS). The presence of mixed MoxW1-xS2 slabs was evidenced by HAADF analysis. On Mo3W9/Al2O3, small randomly distributed islands of Mo were present in the WS2 slabs, while on Mo3 + W9/Al2O3, Mo islands appeared larger and in the core of the WS2 slabs. Moreover, on this last sample, some monometallic slabs were also present. It was concluded that using mixed HPA precursors resulted in the formation of mixed MoxW1-xS2 active phase possessing higher synergetic effect between the two metals and consequently higher catalytic activity.

Effects of activated carbon in a carbon-coated alumina (CCA) support, active phase morphology and its composition of Ni 6 -PW 12 S/C x /Al 2 O 3 catalysts in hydrotreating of model compounds were studied. The catalysts were synthesized using 12-tungstophosphoric heteropolyacid, nickel citrate and CCA and characterized with multiple methods: N 2 physisorption, X-ray powder diffraction, H 2 temperature programmed reduction, temperature-programmed desorption of ammonia, high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy. The catalytic properties were determined using a fixed-bed microreactor in hydrotreating of dibenzothiophene, naphthalene and quinoline. It was found that with the increase of carbon content in the CCA up to 5 wt.%, reducible reactivity, sulphidation degree, average length and stacking number of WS 2 crystallites in the catalysts increased. Observed changes can be explained by weakening interaction between metal oxide species and carbon-coated support. Full promotion of the NiWS edges by nickel was achieved in the catalysts supported on the CCA with carbon content equal 0.3 wt.% and more. Activities of the catalysts in dibenzothiophene hydrodesulphurization, naphthalene hydrogenation and quinoline hydrodenitrogenation were essentially depended on the carbon content in the CCA-support. Ni 6 -PW 12 S/C 1 /Al 2 O 3 catalyst showed maximal conversions of the substrates in studied reactions. This result was achieved due to an optimal balance between turnover frequency value of the active sites and their content.

Co 2 Mo 10 /Co x /Al 2 O 3 catalysts were synthesized from the ammonium salt of [Co 2 Mo 10 O 38 H 4 ] 6− anion supported on alumina modified with various amount of cobalt sulphide. The catalysts were analyzed using X-ray powder diffraction, N 2 physisorption, high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy. The catalysts were tested in the hydrodesulphurization (HDS) of dibenzothiophene and 4,6-dimethyldibenzothiophene and the hydrodenitrogenation (HDN) of quinoline. The presence of cobalt sulphide particles on the catalysts surface affects catalytic properties significantly, whereas the structure of the active phase remains constant. The catalytic activity, selectivity and turnover frequency during the HDS and HDN reactions depend on the amount of modifier (cobalt sulphide) in the Co x /Al 2 O 3 supports and can be explained by hydrogen spillover effect. The model of HDS reaction over Co 2 Mo 10 /Co x /Al 2 O 3 catalyst involving hydrogen spillover was established. The obtained results allow us to focus attention on the role of the cobalt sulphide particles on the surface of hydrotreating catalysts.

A concept on the dynamic nature of active centers (AC) of the catalysts based on transition metal sulfides is described. The concept formed the basis of a “dynamic” model, according to which AC formed and functioning under the reaction conditions can oscillate between layers of promoted molybdenum sulfide. The model assumes the existence of “rapid” and “slow” AC and the possibility of their intertransformation due to the reversible migration of sulfur and promoter between the crystallite layers in a hydrogen atmosphere. The frequency of these migrations (oscillations) determines the catalyst activity. An assumption is substantiated that the hydrogenation sites are localized at the rims of Co(Ni)MoS2 crystallites and desulfurization (hydrodesulfurization) sites are localized on the edges. The proposed model makes it possible to develop criteria for the evaluation of the efficiency of catalytic performance for hydrodesulfurization of hydrocarbon raw materials of various types and for synthesis of higher alcohols from syngas.

Effects of activated carbon of a carbon-coated alumina support and active phase morphology of transition metal sulfide (TMS) catalysts in hydrotreatment (HDT) of S-containing compounds were studied. The catalysts were synthesized from Anderson-type heteropoly compounds and characterized with multiple methods: X-ray powder diffraction, N2 physisorption, temperature-programmed desorption of ammonia, pyridine-adsorbed Fourier transform infrared spectroscopy, H2 temperature-programmed reduction, and high-resolution transmission electron microscopy. The catalysts were tested in hydrodesulfurization (HDS) of thiophene, dibenzothiophene and HDT of diesel. The results suggest that the catalytic activity in HDS and hydrogenation reactions depends on the shape of crystallites of the active phase. The results are interpreted using recently proposed concept of interlayer dynamics. This concept is helpful in establishing structure–activity relations for TMS.

CoMo/MeOx(Sy)/Al2O3 catalysts have been synthesized on supports modified with oxides (sulfides) of transition metals (Co, Ni, Mn, and Zn) using decamolybdodicobaltic heteropoly acid H6[Co2Mo10O38H4]. A correlation between the activity of the catalysts and the ability of transition metal sulfides to accumulate molecular hydrogen has been found in the hydrodesulfurization (HDS) of dibenzothiophene (DBT) and in the hydrotreating of the diesel fraction. It has been shown that the presence on the surface of Al2O3 of sulfides (NiSx, CoSx) capable of activating hydrogen has a positive effect on the activity of the supported catalysts. It has been found that the hydrogen spillover effect, which was studied in a range of 300–350°C, contributes to an increase in the hydrogenating function of the catalyst systems.

The structures of the two predominant metabolites ( M4 and M5 ) of RVX-208, observed both in in vitro human and animal liver microsomal incubations, as well as in plasma from animal in vivo studies, were determined. A panel of biocatalytic systems was tested to identify biocatalysts suitable for milligram scale production of metabolite M4 from RVX-208. Rabbit liver S9 fraction was selected as the most suitable system, primarily based on pragmatic metrics such as catalyst cost and estimated yield of M4 (∼55%). Glucuronidation of RVX-208 catalyzed by rabbit liver S9 fraction was optimized to produce M4 in amounts sufficient for structural characterization. Structural studies using LC/MS/MS analysis and 1 H NMR spectroscopy showed the formation of a glycosidic bond between the primary hydroxyl group of RVX-208 and glucuronic acid. NMR results suggested that the glycosidic bond has the β-anomeric configuration. A synthetic sample of M4 confirmed the proposed structure. Metabolite M5 , hypothesized to be the carboxylate of RVX-208, was prepared using human liver microsomes, purified by HPLC, and characterized by LC/MS/MS and 1 H NMR. The structure was confirmed by comparison to a synthetic sample. Both samples confirmed M5 as a product of oxidation of primary hydroxyl group of RVX-208 to carboxylic acid.

Using the Anderson-type heteropoly compounds (HPCs) [X(OH)6Mo6O18]n− (X = Co, Ni, Mn, Zn) and [Co2Mo10O38H4]6− and cobalt (or nickel) nitrate, XMo/Al2O3 and Co(Ni)-XMo/Al2O3 catalysts were prepared. The catalysts were studied by low-temperature nitrogen adsorption, X-ray diffraction, and high-resolution transmission electron microscopy. The average length of the active-phase particles of the catalysts was 3.5 to 3.9 nm, and the average number of MoS2 layers in a packet was 1.4 to 2.1. The catalytic properties of the samples, which were estimated in dibenzothiophene (DBT) hydrodesulfurization and in the hydrotreating of the diesel fraction, are considerably dependent upon both the type and composition of the HPC, and the nature of the applied promoter (Ni or Co). As compared to the Ni-promoted catalysts, the Co-promoted samples exhibit a higher desulfurization activity, whereas the hydrogenation ability of the Ni-XMo/Al2O3 catalysts surpasses that of the Co-XMo/Al2O3 ones. The catalytic properties depend on the morphology of the nanostructured active phase. With a growing number of MoS2 layers in the packet of the catalysts’ active phase, the DBT hydrodesulfurization rate constants for both the direct desulfurization route and the preliminary hydrogenation rote rise linearly and the selectivity falls linearly for the hydrogenation route. The selectivity of Ni-XMo/Al2O3 decreases to a greater extent than that of Co-XMo/Al2O3. The dependences of the catalytic properties on the morphology of the catalysts’ active phase are consistent with the “dynamic” model of the functioning of the active sites of transition metal sulfides.

Co(Ni)MoS/Al2O3 catalysts have been prepared from ammonium 10-dodecamolybdodicobaltate (NH4)6[Co2Mo10O38H4] (further, Co2Mo10HPC) and cobalt(nickel) salts of 10-dodecamolybdodicobaltic acid H6[Co2Mo10O38H4] (hereinafter, Co2Mo10HPA). It has been found that a high activity of the Co(Ni)3-Co2Mo10HPA/Al2O3 catalysts in the hydrodesulfurization and hydrogenation reactions is due to the formation of a nanostructured type II CoMoS phase via the contact of the metals (Mo and Co(Ni)) at the molecular level. The use of Ni as a copromoter in the Ni3-Co2Mo10HPA/Al2O3 catalyst leads to a simultaneous increase, compared with Co3-Co2Mo10HPA/Al2O3, in the linear size of nanoparticles and the number of MoS2 layers in the packing of active phase. The nature of the promoter X has a substantial effect on the properties of X3Co2Mo10HPC/Al2O3 catalysts. It has been found that the catalysts with X = Co exhibit the highest activity in the hydrodesulfurization reactions and those with X = Ni, in hydrogenation reactions.

Catalysts have been synthesized using the Anderson polyoxometalates (POMs) (NH4)4[Ni(OH)6Mo6O18] (NiMo6POM), (NH4)6[Co2Mo10O38H4] · 7H2O (Co2Mo10POM), and H6[Co2Mo10O38H4] (Co2Mo10HPA) as the precursors and hydrogen peroxide as the solvent. The catalysts have been characterized by low-temperature nitrogen adsorption, XPS, and HRTEM. Their catalytic properties have been tested in thiophene hydrodesulfurization and in the hydrodesulfurization and hydrogenation of components of diesel oil. The active phase of the catalysts synthesized using the POMs is the type II CoMoS phase in which the mean plate length is 3.6–3.9 nm and the mean number of MoS2 plate per plate packet is 1.8–2.0. Use of hydrogen peroxide provides an efficient means to reduce the proportion of Co2+ promoter atoms surrounded by oxygen in the case of an impregnating solution containing both an ammonium salt of a heteropoly acid and a Co2+ salt. In the catalysts synthesized using cobalt salts of Co2Mo10HPA, the support surface contains the multilayer type II CoMoS phase and cobalt sulfides. These catalyst show high catalytic properties in thiophene hydrogenolysis and diesel oil hydrorefining. Models are suggested for the catalysts synthesized using Anderson POMs.

Combinatorial biocatalysis was applied to generate a diverse set of dihydroxymethylzearalenone analogs with modified ring structure. In one representative chemoenzymatic reaction sequence, dihydroxymethylzearalenone was first subjected to a unique enzyme-catalyzed oxidative ring opening reaction that creates two new carboxylic groups on the molecule. These groups served as reaction sites for further derivatization involving biocatalytic ring closure reactions with structurally diverse bifunctional reagents, including different diols and diamines. As a result, a library of cyclic bislactones and bislactams was created, with modified ring structures covering chemical space and structure activity relationships unattainable by conventional synthetic means.

2-Hydroxybiphenyl 3-monooxygenase (HbpA, E.C. 1.14.13.44) was partially purified on a gram scale from recombinant E. coli JM101 by expanded bed adsorption (EBA) chromatography. In order to develop an effective in vitro biotransformation system using isolated HbpA as catalyst, its stability and activity in the presence of different apolar and polar organic solvents was investigated. HbpA showed good stability in 80% (v/v) decanol and 10% (v/v) methanol. Since the reaction catalyzed by HbpA is cofactor dependent, enzymatic NADH cofactor regeneration by yeast alcohol dehydrogenase (YADH) was tested in the presence of 10% (v/v) methanol used both as a cosolvent and substrate for YADH. In an in vitro biotransformation on a 25 ml scale 5.4 mM of 2,2′-dihydroxybiphenyl was hydroxylated to 2,2′,3-trihydroxybiphenyl in 2.5 h and 2,2′,3,3′-tetrahydroxybiphenyl in 23 h at a mean volumetric productivity of 0.43 g/(l h) and 0.05 g/(l h), respectively. Additionally, HbpA and formate dehydrogenase (FDH) were applied in 80% (v/v) decanol to hydroxylate 2-hydroxybiphenyl with a productivity of 0.46 g/(l h) and a total turnover number of 503. In 10% (v/v) aqueous methanol the total turnover number of 30 and enzyme stability for at least 60 h were shown. This demonstrated the feasibility of using isolated HbpA for syntheses in the presence of polar as well as apolar solvents with enzymatic regeneration of reduced cofactors.

Arylsulfotransferase (AST, EC 2.8.2.22), an enzyme capable of sulfating a wide range of phenol-containing compounds was purified from a Clostridium innocuum isolate (strain 554). The enzyme has a molecular weight of 320 kDa and is composed of four subunits. Unlike many mammalian and plant arylsulfotransferases, AST from Clostridium utilizes arylsulfates, including p-nitrophenyl sulfate, as sulfate donors, and is not reactive with 3-phosphoadenosine-5'-phosphosulfate (PAPS). The enzyme possesses broad substrate specificity and is active with a variety of phenols, quinones and flavonoids, but does not utilize primary and secondary alcohols and sugars as substrates. Arylsulfotransferase tolerates the presence of 10 vol% of polar cosolvents (dimethyl formamide, acetonitrile, methanol), but loses significant activity at higher solvent concentrations of 30-40 vol%. The enzyme retains high arylsulfotransferase activity in biphasic systems composed of water and nonpolar solvents, such as cyclohexane, toluene and chloroform, while in biphasic systems with more polar solvents (ethyl acetate, 2-pentanone, methyl tert-butyl ether, and butyl acetate) the enzyme activity is completely lost. High yields of AST-catalyzed sulfation were achieved in reactions with several phenols and tyrosine-containing peptides. Overall, AST studied in this work is a promising biocatalyst in organic synthesis to afford efficient sulfation of phenolic compounds under mild reaction conditions.

Amino groups in alpha-chymotrypsin were reacted with pyromellitic anhydride, introducing 17 to 32 additional carboxyl groups. This modification causes a major change in the water adsorption isotherm of the lyophilized protein powder. Little water is bound by the modified enzyme at water activity (aw) below 0.35, but it shows increased water binding at aw over 0.5. This correlates with a similar change in the aw dependence of the catalytic activity of the enzyme powder suspended in hexane, with a much steeper increase in activity of the modified chymotrypsin.

Oxidative enzymes, laccase C from Trametes sp. and horseradish and soybean peroxidases, catalyzed oxidation reactions in systems with ionic liquids whose content varied from several volume percent to almost total non-aqueous ionic liquids. Similar to the effects produced by standard organic solvents used in non-aqueous enzymology, catalytic activity of the enzymes was decreased by adding a water-miscible ionic liquid, 4-methyl-N-butylpyridinium tetrafluoroborate, or by suspending the enzyme in a water-immiscible ionic liquid, 1-butyl-3-methylimdizaolium hexafluorophosphate. For the oxidation of anthracene, catalyzed by laccase C and assisted by a number of mediators, addition of 4-methyl-N-butylpyridinium tetrafluoroborate, instead of tert-butanol, increased the yield of the oxidation product several-fold.

Elevated hydrostatic pressure has been used to increase catalytic activity and thermal stability of alpha-chymotrypsin (CT). For an anilide substrate, characterized by a negative value of the reaction activation volume (DeltaV( not equal)), an increase in pressure at 20 degrees C results in an exponential acceleration of the hydrolysis rate catalyzed by CT reaching a 6.5-fold increase in activity at 4700 atm (4.7 kbar). Due to a strong temperature dependence of DeltaV( not equal), the acceleration effect of high pressure becomes more pronounced at high temperatures. For example, at 50 degrees C, under a pressure of 3.6 kbar, CT shows activity which is more than 30 times higher than the activity at normal conditions (20 degrees C, 1 atm). At pressures of higher than 3.6 kbar, the enzymatic activity is decreased due to a pressure-induced denaturation.Elevated hydrostatic pressure is also efficient for increasing stability of CT against thermal denaturation. For example, at 55 degrees C, CT is almost instantaneously inactivated at atmospheric pressure, whereas under a pressure of 1.8 kbar CT retains its anilide-hydrolyzing activity during several dozen minutes. Additional stabilization can be achieved in the presence of glycerol, which is most effective for protection of CT at an intermediate concentration of 40% (v/v). There has been observed an additivity in stabilization effects of high pressure and glycerol: thermal inactivation of pressure-stabilized CT can be decelerated in a supplementary manner by addition of 40% (v/v) glycerol. The protection effect of glycerol on the catalytic activity and stability of CT becomes especially pronounced when both extreme factors of temperature and pressure reach critical values. For example, at approximately 55 degrees C and 4.7 kbar, enzymatic activity of CT in the presence of 40% (v/v) glycerol is severalfold higher than in aqueous buffer.The results of this study are discussed in terms of the hypotheses which explain the action of external and medium effects on protein structure, such as preferential hydration and osmotic pressure.

A novel biocatalytic reaction of transamidation of non-activated amides with amines is reported. Among 45 different lipolytic and proteolytic enzymes tested, only the lipase from Candida antarcticawas able to catalyze this reaction. The reaction proceeded with up to ca. 80% conversion in anhydrous methyl tert-butyl ether and worked with both N-substituted and unsubstituted amides. The biocatalytic transamidation is an equilibrium process and, therefore, higher conversions to the desired amide were achieved by using increased concentrations of the amine nucleophile.

Chymotrypsin-catalysed kinetically-controlled peptide synthesis was studied in mixtures of dimethylformamide (DMF) and acetonitrile containing 6% water. The free enzyme showed no detectable activity with 60% or more DMF. However, by pre-forming a complex with poly-acrylate (optimum 50 carboxyl groups to 1 enzyme molecule), activity and stability were good at 60% DMF, and reasonable at 70% DMF. In 60% DMF, the peptide Ac-Tyr-Lys-NH2 could be made in 95% yield using this catalyst.

A simple combinatorial strategy for sequential regioselective enzymatic acylation of multifunctional lead compounds has been developed and demonstrated using a polyhydroxylated flavonoid, bergenin, as a model. The approach is based on the ability of different enzymes to regioselectively acylate different sites on a lead molecule without affecting other similar functional groups. In sharp contrast to enzymatic acylation, conventional chemical acylation methods showed almost complete lack of regioselectivity. The enzymatic strategy was applied successfully to produce a solution phase combinatorial library of 167 distinct selectively acylated derivatives of bergenin on a robotic workstation in a 96-well plate format. General applicability of the automated combinatorial biocatalysis strategy is discussed.

α-Chymotrypsin has been modified with poly(ethylene glycols) and proxanols, block-copolymers of poly(propylene oxide) and poly(ethylene oxide). These conjugates were several-fold more thermostable and showed high catalytic activity at elevated concentrations of water-miscible organic cosolvents (alcohols and dimethyl sulfoxide) which caused inactivation of free (non-modified) α-chymotrypsin.