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Applied Catalysis A, General (v.357, #1)
Particle size effect in carbon supported Pt–Co alloy electrocatalysts prepared by the borohydride method: XRD characterization by I.N. Leontyev; D. Yu. Chernyshov; V.E. Guterman; E.V. Pakhomova; A.V. Guterman (pp. 1-4).
Pt3Co/C electrocatalysts prepared by wet synthesis method from water–ethylene glycol solutions of Pt and Co precursors were investigated by X-ray diffraction in conjunction with electrochemical measurements. It was shown that varying the binary solvent composition is an effective means of control over the average nanoparticle size and the grain size distribution. It was found that unit cell parameter of the Pt3Co/C electrocatalysts decreases nonlinearly with decreasing particle size. The activity of the prepared Pt3Co/C catalysts for the oxygen reduction reaction (ORR) in H2SO4 solution enhances with decrease in the particle size, the unit cell parameter, and the dispersion of the grain size distribution. All samples studied show higher catalytic activities in comparison with the commercial Pt/C materials.We report on combined X-ray diffraction and electrochemical investigation of Pt3Co/C electrocatalysts prepared by wet synthesis method from water–ethylene glycol solutions. X-ray diffraction analysis showed that variation of the binary solvent composition is an effective way to control microstructural characteristics of the catalysts nanoparticles. Nonlinear change in the variation of the unit cell parameter with decreasing particle size has been found.
Keywords: Pt–Co alloy; Size effects; Grain size distribution; Oxygen reduction; X-ray diffraction
Deactivation of iron oxide used in the steam-iron process to produce hydrogen by M.F. Bleeker; H.J. Veringa; S.R.A. Kersten (pp. 5-17).
The deactivation of iron oxide in the steam-iron process is caused by a decrease in surface area of the material. A sintering model is used to derive a relation for the loss in surface area, based on the conversion degree of the material. Furthermore a kinetic model is used to model the increase in grain size and increase in solids fraction in a particle.In the steam-iron process pure hydrogen can be produced from any hydrocarbon feedstock by using a redox cycle of iron oxide. One of the main problems connected to the use of the iron oxide is the inherent structural changes that take place during oxygen loading and unloading leading to severe deactivation. This deactivation reduces the capability of the material for uptake and release of oxygen, basically due to loss of specific surface area. In this paper a simplified (reactive) sintering model is used to derive a relation for the loss in surface area of the material in the first redox cycles. This model is based on the relative conversion and the resulting swelling of the material during oxidation. Furthermore the grainy pellet model is used to describe the increase in grain size and increase in solid fraction in a particle due to the subsequent cycling of the iron oxide in the redox process. Model predictions are compared with redox experiments of H2/H2O–Fe/Fe3O4 at 800°C. Grain growth over subsequent cycles could explain the observed deactivation over about 20 cycles satisfactorily.
Keywords: Steam-iron process; Deactivation; Hydrogen; Iron oxide; Structural changes
Synthesis of gasoline-range hydrocarbons over Mo/HZSM-5 catalysts by Shetian Liu; Amit C. Gujar; Peter Thomas; Hossein Toghiani; Mark G. White (pp. 18-25).
Mo/HZSM-5 has been found active for syngas conversion to gasoline-range hydrocarbons mainly composed of alkyl-substituted aromatics and lower branched and cyclized alkanes. Higher alcohols and carboxylic acids (C1–C6) were detected in the water phase liquids from the synthetic reaction. The formation of hydrocarbons on Mo/zeolite is through bifunctional-zeolite acidity and molybdenum metal catalysis via mixed alcohols as the intermediates.Mo/HZSM-5 has been found active in Fischer–Tropsch synthesis (FTS). The catalysts were evaluated under various reaction conditions with low H2/CO (molar ratio ∼1.0) syngas typical of a synthesis gas derived from biomass gasification. Liquid hydrocarbons formed on the Mo/HZSM-5 were composed mainly of alkyl-substituted aromatics and lower branched and cyclized alkanes. Aliphatic hydrocarbons were detected only in trace amounts. Lower hydrocarbons produced included mainly methane, ethane, propane and iso-butane. Higher alcohols and carboxylic acids (C1–C6) were detected in the water phase liquids from FTS. It is supposed that the formation of hydrocarbons on Mo/zeolite is through bifunctional-zeolite acidity and molybdenum metal catalysis via mixed alcohols as the intermediates. Investigation on the effects of zeolite structure indicated that zeolite Y is also an excellent support for Mo in the FTS.
Keywords: Fischer–Tropsch synthesis; Branched alkanes; Aromatics; Mo/HZSM-5; Zeolite Y; Syngas; Biomass gasification
Visible light induced photoreduction of methyl orange by N-doped mesoporous titania by Meenal M. Joshi; Nitin K. Labhsetwar; Priti A. Mangrulkar; Saumitra N. Tijare; Sanjay P. Kamble; Sadhana S. Rayalu (pp. 26-33).
N-doped mesoporous titania was synthesized using templating method. Biopolymer chitosan was used as a template and also as a nitrogen source along with ammonium hydroxide. Three different types of N-doped mesoporous titania were synthesized by varying composition of chitosan and titania precursor. These photocatalysts were characterized using XRD, BET-SA, FTIR, UV-DRS, SEM–EDX and XPS analysis. The photocatalytic activity of mesoporous titania was studied by methyl orange (MO) photoreduction reaction. From the experimental results it was observed that the N-doped mesoporous titania (1:2) gives the highest photocatalytic reduction of MO as compared to N-doped mesoporous titania prepared with (1:1) and (1:3) stoichiometry. This could be due to the optimal level of ‘N’ incorporation in the N-doped mesoporous titania (1:2).Photocatalysts reduce the MO dye into derivative of hydrazine. Photoactivity of N-doped mesoporous titania (1:2) is 1.0721mg of MO reduced per g of TiO2 vis-à-vis 0.508mg of MO reduced per g of TiO2 for Degussa P25 photocatalyst. The effect of various operating parameters like photocatalyst loading, initial concentration and intensity of light also has been studied.N-doped mesoporous titania was synthesized using templating method. Biopolymer chitosan was used as a template and also as a nitrogen source along with ammonium hydroxide. Three different types of N-doped mesoporous titania were synthesized by varying composition of chitosan and titania precursor. These photocatalysts were characterized using XRD, BET-SA, FTIR, UV-DRS, SEM–EDX and XPS analysis. The photocatalytic activity of mesoporous titania was studied by methyl orange (MO) photoreduction reaction. From the experimental results it was observed that the N-doped mesoporous titania (1:2) gives the highest photocatalytic reduction of MO as compared to N-doped mesoporous titania prepared with (1:1) and (1:3) stoichiometry. This could be due to the optimal level of ‘N’ incorporation in the N-doped mesoporous titania (1:2).Photocatalysts reduce the MO dye into derivative of hydrazine. Photoactivity of N-doped mesoporous titania (1:2) is 1.0721mg of MO reduced per g of TiO2 vis-à-vis 0.508mg of MO reduced per g of TiO2 for Degussa P25 photocatalyst. The effect of various operating parameters like photocatalyst loading, initial concentration and intensity of light also has been studied.
Keywords: Biopolymer; Chitosan; N-doped mesoporous titania; Visible active photocatalyst; MO photoreduction
Investigations of reasons for the deactivation of rhenium oxide alumina catalyst in the metathesis of pentene-1 by A. Behr; U. Schüller; K. Bauer; D. Maschmeyer; K.-D. Wiese; F. Nierlich (pp. 34-41).
The metathesis of pentene-1 was studied with a heterogeneous rhenium alumina catalyst where the main focus stood on the catalyst deactivation.The purity of the pentene-1 has a main influence on deactivation and therefore trace impurities were identified and removed from the pentene-1. Afterwards the deactivation rate could be compared to not or partially purified pentene-1. Furthermore, the influence of temperature, solvents, vacuum and the alkene itself on the deactivation were investigated in detail.The metathesis of pentene-1 was studied with a heterogeneous rhenium alumina catalyst where the main focus stood on the catalyst deactivation. The reaction took place at 10barrel in liquid phase in a tubular reactor. The purity of the pentene-1 has a main influence on deactivation and therefore trace impurities were identified and removed from the pentene-1. Afterwards the deactivation rate could be compared to not or partially purified pentene-1. Furthermore, the influence of temperature was investigated where a strong dependence is recognisable. The experiments also showed that the addition of solvents cannot slower the deactivation rate. Therefore a metathesis in undiluted pentene is preferable. The deactivation of the rhenium catalyst is very likely caused by an intrinsic mechanism. The experiments showed that deactivation occurs when the catalyst has contact to the alkene. This deactivation is not depended on the flow rate of the alkene. Finally the by-products on the catalyst where analysed by stripping at high temperatures. There was no indication of an oligomerisation at reaction temperature. By-products have their origin in side reactions of pentene with double bond isomerisated 4-octene.
Keywords: Alkene metathesis; Heterogeneous catalysis; Rhenium; Deactivation
Influence of the cobalt salt precursors on the cobalt speciation and catalytic properties of H-ZSM-5 modified with cobalt by solid-state ion exchange reaction by Mourad Mhamdi; Sihem Khaddar-Zine; Abdelhamid Ghorbel (pp. 42-50).
Ammoxidation of light hydrocarbons was tested over Co-ZSM-5 catalysts. The cobalt salt precursors had an important influence on the physico–chemical and catalytic properties. The preparation procedure results in the disappearance of Brönsted acid sites and the creation of new Lewis acid sites. Furthermore, TEM/EDX, H2-TPR and XRD indicated the presence of cobalt oxide when cobalt chloride, formate or nitrate was used. In fact, a cobalt phyllosilicate phase is present at the outer surface of the zeolite for the sample issued from cobalt acetate as precursor.Co-ZSM-5 catalysts prepared by either aqueous or solid-state ion exchange using different cobalt precursors (acetate, chloride, nitrate or formate) were studied in the selective ammoxidation of ethylene and ethane to acetonitrile. Co2+ supported catalysts were characterized by chemical analysis, X-ray powder diffraction, N2 adsorption (BET), TEM/EDX, FTIR, XANES and EXAFS spectroscopy, H2 TPR and TPD of ammonia. It was found that all the preparations led to cobalt exchanged metal ion at the bridging oxygen of Si–OH–Al groups or to Co oxide or phyllosilicate. XRD, TEM and H2 TPR indicated the presence of cobalt oxide when cobalt chloride, formate or nitrate was used. TPD of ammonia and FTIR of pyridine, used respectively as probe molecules showed that solid-state exchange catalysts exhibited new Lewis acid sites. The catalyst resulting from cobalt acetate, which contained mostly isolated Co2+ ions in cationic exchange position and cobalt phyllosilicate, showed high activity and selectivity toward acetonitrile.
Keywords: Co-ZSM-5; Solid-state reactions; Precursor; Speciation; Ammoxidation; Spectroscopy; XANES/EXAFS; TEM/EDX
Reaction kinetics of oxychlorination of carbon monoxide to phosgene based on copper(II) chloride by Tianzhu Zhang; Carsten Troll; Bernhard Rieger; Juergen Kintrup; Oliver F.-K. Schlüter; Rainer Weber (pp. 51-57).
The characteristics of reaction kinetics of oxychlorination of carbon monoxide to phosgene were systematically investigated. The maximum cumulative yield of phosgene, 86.5%, was obtained when the reaction conditions are 5bar CO, 300°C and 6min.The reaction parameters of oxychlorination of carbon monoxide to phosgene, reaction temperature, reaction time and CO pressure were optimized. The online FT-IR technique is successfully employed for the first time to determine the composition of the product effluent. The formation rate of phosgene increases with the reaction temperature. The maximum formation rate of phosgene is 1.2×10−3mmolmL−1min−1 at 375°C. At the same time, the decomposition rate of phosgene increases with the reaction temperature, too. A higher pressure of CO can lead to a faster formation rate and a higher yield of phosgene. The catalyst is more stable at 300°C than at 345 or 375°C. At 415°C the catalyst is nearly completely deactivated. The optimized reaction conditions are 300°C, 6min and 5bar CO, where the cumulative yield of phosgene can reach up to 86.5%. The by-product HCl comes from the hydrolysis of phosgene or the surface reaction of CuCl2 and the residual water or the hydroxyl groups on the silica surface. CO2 is formed from the hydrolysis of phosgene.
Keywords: Reaction kinetics; Oxychlorination; IR; Phosgene; Hydrogen chloride; Carbon monoxide
Catalytic decomposition of natural gas for CO x-free hydrogen production in a structured multilayer reactor by G. Italiano; C. Espro; F. Arena; F. Frusteri; A. Parmaliana (pp. 58-65).
The performance of Ni/SiO2/silica cloth thin layer catalysts (Ni-TLCs) to study the catalytic decomposition of natural gas (CDNG) for making “CO x-free” hydrogen using a novel structured multilayer reactor (MLR) has evaluated. The influence of Ni loading (5–50wt%), particle size, TR (773–873K) and GHSV (1900–9600h−1) on the reaction pattern has assessed. The features of the MLR in the CDNG irrespectively of operating conditions and the extent of carbon formation are discussed.Using a new structured multilayer reactor (MLR) that houses Ni based thin layer catalysts, catalytic decomposition of natural gas (CDNG) for making “CO x-free” hydrogen in a TR range of 773–873K was investigated. The influence of Ni loading (5–50wt%), Ni particle size, TR, and GHSV (h−1) on the reaction pattern was evaluated. A volcano shape relationship between H2 space time yield(STYH2,stp dmH23/kgNi/h) and Ni loading with a maximum range of 20–25wt% was found. H2 productivity and catalyst lifetime are controlled by the nature of the coke formed on Ni active species. As such, TR and GHSV significantly affect both the kinetics and the mechanism of coking. At TR<873K and low GHSV (<2000h−1), the prevailing formation of filamentous carbon (whisker-like) prolongs the catalyst lifetime, while at TR=873K and high GHSV (>2000h−1) encapsulating carbon is formed, causing a sudden decline in catalytic activity. A preliminary attempt to find optimal operating conditions ensuring the highest values of H2 productivity is presented. The features of the MLR that allowed CDNG reaction under a quasi-isothermal regime without any pressure drop, irrespective of operating conditions and the extent of carbon formation, are discussed.
Keywords: Methane decomposition; Hydrogen “CO; x; -free”; Thin layer catalysts; Multilayer reactor; Silica cloth; Carbon forms
Effect of Cu loading on the catalytic performance of Fe–Al–Cu for water-gas shift reaction by Lingzhi Zhang; Jean-Marc M. Millet; Umit S. Ozkan (pp. 66-72).
We have previously reported Fe–Al–Cu catalysts prepared by the sol–gel method to exhibit superior water-gas shift performance compared to catalysts of similar composition prepared by precipitation/impregnation techniques. The difference in performance was ascribed to the formation of the γ-Fe2O3 structure and a better incorporation and distribution of Cu in the iron oxide matrix. In the current study, the effect of the Cu loading level was examined for its influence on surface and structural properties, and in turn, catalytic performance. Catalysts with various Cu loading levels were evaluated at steady state at different reaction temperatures. In situ X-ray diffraction was used to monitor crystalline phases present in catalysts with different Cu loadings and phase evolution during reduction. The role of Cu loading in γ-Fe2O3 structure formation was studied using X-ray diffraction and Mössbauer spectroscopy techniques.Fe–Al–Cu catalysts prepared by a sol–gel technique show low-temperature activity as well as high-temperature stability. Cu loading as well as synthesis technique appear to determine the crystalline phase of the iron oxide phase.
Keywords: Water-gas shift; Fe–Al–Cu; Cu loading; Cr-free; Sol–gel; α-Fe; 2; O; 3; γ-Fe; 2; O; 3; Magnetite; Mössbauer
Photocatalytic splitting of water on NiO/InTaO4 catalysts prepared by an innovative sol–gel method by Yi-Ching Chiou; Umesh Kumar; Jeffrey C.S. Wu (pp. 73-78).
InTaO4 is a photocatalyst with visible-light response that is used to split water and produce hydrogen. InTaO4 is traditionally prepared by solid-state fusion of In2O3 and Ta2O5 at ≥1100°C. A sol–gel procedure was developed to synthesize InTaO4 from In(NO3)3 and Ta(OC4H9)5 precursors. A uniform crystalline InTaO4 phase was easily obtained on calcination at 1100°C because the sol–gel method allows homogeneous liquid-phase mixing. The method yields small InTaO4 particles with a high specific surface area. InTaO4 catalysts with different Ni loading were prepared by incipient wetness impregnation. Ni loading greatly enhanced the initial rate of H2 production during photocatalytic splitting of water. Ni metal within Ni–NiO core/shell nanoparticles can efficiently transfer photoelectrons on the InTaO4 surface and thus reduce H+ to hydrogen. NiO x/InTaO4 was deactivated due to the formation of Ni(OH)2. Overall, NiO x/InTaO4 prepared by the sol–gel method had higher activity than catalysts prepared by solid-state fusion. Among all the photocatalysts, 3.0wt.% NiO x/InTaO4 exhibited the highest photoactivity, with an initial rate of H2 production of 2.10μmol/gh.Visible-light-responsive InTaO4 was used to split water and produce hydrogen. A uniform crystalline InTaO4 phase was obtained because the sol–gel method allowed homogeneous liquid-phase mixing. NiO x/InTaO4 prepared by the sol–gel method had higher activity than catalysts prepared by solid-state fusion. 3.0wt.% NiO x/InTaO4 exhibited the highest photoactivity, with an initial rate of H2 production of 2.10μmol/gh.
Keywords: Photocatalysis; Water splitting; NiO; x; /InTaO; 4; Sol–gel; Hydrogen
Nb-containing hematites Fe2− xNb xO3: The role of Nb5+ on the reactivity in presence of the H2O2 or ultraviolet light by Adilson C. Silva; Diana Q.L. Oliveira; Luiz C.A. Oliveira; Alexandre S. Anastácio; Teodorico C. Ramalho; João H. Lopes; Hudson W.P. Carvalho; Claudia E. Rodriguez Torres (pp. 79-84).
Niobium was introduced in the hematite structure to produce an active heterogeneous Fenton system and also to improve the photocatalytic activity. The reactions in the presence of H2O2 or ultraviolet light were carried out using the organic dye methylene blue. Niobium shows interesting features for this system such as, ionic ray compatible with the Fe structural and the high reactivity.A series of Nb-containing hematites, Fe2− xNb xO3 (%Nb=0.00, 1.49, 5.00 and 9.24) was prepared using the conventional co-precipitation method. Mössbauer and temperature-programmed reduction (TPR) measurements suggested the formation of the crystalline phase with partial substitution of Fe3+ by Nb5+ in the structure. N2 adsorption/desorption revealed that the presence of Nb has a remarkable effect on the textural properties of the material with an increase in the BET surface area. The reactivity of Fe2− xNb xO3 was investigated using the oxidation of the methylene blue dye used as a model pollutant. The obtained results showed that the presence of Nb seems not to act directly promoting the H2O2 decomposition, but improving the dye oxidation. The analysis using the ESI-MS technique showed partial oxidation observed through different intermediates before the mineralization. This suggests the use of Nb-doped hematite as an efficient catalyst in degradation reactions in the presence of H2O2 or ultraviolet light.
Keywords: Hematite; Niobium; Organic oxidation; ESI-MS
Ceramic foams as structured catalyst inserts in gas–particle filters for gas reactions—Effect of backmixing by Sebastian Zuercher; Kyra Pabst; Georg Schaub (pp. 85-92).
Kinetic studies of open-cell foams as catalyst structure address combined effects of reaction and backmixing for low velocity conditions. Simulating the foam as insert in gas–particle filter elements the catalytic conversion of NO x and organic compounds (VOC) is investigated experimentally and by mathematical methods. As a conclusion, the effect of backmixing is quantified in comparison with a fixed bed configuration.Ceramic open cell foams have recently been proposed as a new catalyst structure to benefit from its characteristic properties like low pressure drop at relatively high specific surface and enhancement of heat and mass transfer. This study focuses on the application of an impregnated ceramic foam inside a gas–particle filter element to create a multifunctional reactor configuration. Selective catalytic NO reduction (SCR) and C3H6 oxidation over a V2O5–WO3–TiO2 catalyst are used as model reactions. Experiments were performed in two different reactor configurations (axial flow in cylindrical foam, radial flow in foam ring) and at typical conditions of filtration in flue gas cleaning (low gas velocity, low concentrations) and compared with data from a particle fixed bed as reference structure. Experiments at various temperatures (150–340°C) and modified residence times (0.02–0.07gs/cm3) in foams show no deviation from particles in the axial configuration. Conversion in the radial flow configuration, however, is significantly lower for both reactions. Given the low gas velocities due to a higher cross-sectional area and a shorter length of the catalyst in flow direction, backmixing is presumed to be the cause. For closer examination, experiments were performed to quantify the foam backmixing behaviour by measuring the residence time distribution (RTD). Combining the results, it was possible to establish mixed flow models in agreement with the data, thus suggesting backmixing to be the cause of decreasing conversion. The results of the kinetic study show no effect on the performance comparing fixed bed configurations of particles and foams. Ceramic foams appear well suited as structured catalyst inserts in gas–particle filters, given their low pressure drop and permeability in all flow directions.
Keywords: Open cell foam; Catalytic gas cleaning; SCR; VOC oxidation; Multifunctional filter reactor; Residence time distribution; Dispersion; Mathematical modelling
The complete conversion of cyclohexane into cyclohexanol and cyclohexanone by a simple silica-chromium heterogeneous catalyst by Farook Adam; Premalatha Retnam; Anwar Iqbal (pp. 93-99).
A chromium-silica catalyst (RH-Cr) and the chromium and 4-(methylamino)benzoic acid incorporated catalyst (RH-Cr-A) was synthesized from rice husk. The specific surface area of RH-Cr and RH-Cr-A was determined to be 3.95 and 71.3m2g−1, respectively. Complete conversion of cyclohexane was achieved in 6h with H2O2 as the oxidant and acetonitrile as the solvent for both catalysts at 70°C, yielding only cyclohexanone and cyclohexanol as products.Chromium and 4-(methylamino)benzoic acid (MBA) were incorporated into silica extracted from rice husk (RH). The chromium incorporated silica was labeled as RH-Cr and the chromium and MBA incorporated catalyst was labeled as RH-Cr-A. The specific surface area of RH-Cr and RH-Cr-A was determined to be 3.95 and 71.3m2g−1, respectively. The RH-Cr showed a wide pore distribution, while RH-Cr-A showed a very narrow pore structure. Both catalysts were shown to be amorphous by XRD. FTIR and EDX analysis showed that the amino benzoic acid and chromium had been incorporated into the silica matrix which resulted in nano-sized pores in RH-Cr-A. Complete conversion of cyclohexane was achieved in 6h with H2O2 as the oxidant and acetonitrile as the solvent for both catalysts at 70°C, yielding only cyclohexanone and cyclohexanol as products. The catalyst was reusable over many cycles.
Keywords: Oxidation of cyclohexane; Chromium-silica catalyst; Rice husk silica; Nano-porous catalyst; Amino benzoic acid template
Zr(HSO4)4 and Mg(HSO4)2 as mild and efficient catalysts for the one-pot multicomponent synthesis of β-acetamido carbonyl compounds by Ahmad Reza Momeni; Maryam Sadeghi (pp. 100-105).
An efficient one-pot three-component coupling process for the synthesis of β-acetamido ketones or esters catalyzed by Zr(HSO4)4 and Mg(HSO4)2 at room temperature has been described. The mechanism of this reaction was also studied. The present methodology offers several advantages such as excellent yield, simple procedure, short reaction time and milder conditions.Synthesis of β-acetamido carbonyl compounds by the one-pot multicomponent coupling of an aromatic aldehyde, an enolisable ketone or keto ester, acetonitrile, and acetyl chloride using Zr(HSO4)4 and Mg(HSO4)2 as mild, inexpensive, and highly efficient catalysts is studied in the present article.
Keywords: β-Acetamido carbonyl compounds; Enolisable ketone; Multicomponent coupling; Efficient catalysts; One-pot reactions
Selective conversion of cis-2-butene-1,4-diol to 2-hydroxytetrahydrofuran over K, Ca and Ba metals-promoted Ru/SiO2 catalysts: Role of the promoter by Maria Grazia Musolino; Cinzia V. Caia; Concetta Busacca; Francesco Mauriello; Rosario Pietropaolo (pp. 106-113).
The effect of alkali and alkali earth promoters addition on the catalytic properties of 5% Ru/SiO2 catalyst in the selective conversion of cis-2-butene-1,4-diol to 2-hydroxytetrahydrofuran was investigated. The performance of the promoted catalysts is strongly affected by the metal nature and loading. The role of the promoters is discussed on the basis of the characterization data.The effect of K, Ca and Ba metals addition on the catalytic properties of SiO2 supported ruthenium catalysts in the selective liquid phase conversion of cis-2-butene-1,4-diol affording, when hydrogenated, 2-hydroxytetrahydrofuran has been investigated. Catalysts containing 5wt% Ru and promoted with a different amount of selected first and second group metals salts have been prepared and characterized by TPR, XRD, TEM, FT-IR of adsorbed pyridine and CO. It has been found that promoters modify the microstructural and electronic properties of Ru particles compared with those of the undoped Ru/SiO2 sample, depending on the metal nature and loading. Consequently, the catalytic activity and selectivity towards reaction products, in cis-2-butene-1,4-diol hydrogenation, is strongly affected by the presence of promoters.In particular, K-promoted systems give an excellent selectivity to 2-hydroxytetrahydrofuran but a poor activity; whereas group IIA metals salts addition leads to an enhancement of activity and a slight increase of selectivity to the desired product with respect to the bare Ru sample. The promoted Ru catalysts behaviour is discussed in terms of charge/ionic radius ratio effect of doping cations. Finally, the salient result is the maximum yield to 2-hydroxytetrahydrofuran of 80%, so far obtained, over the sample promoted with the highest potassium loading and mainly attributed to kinetic factors.
Keywords: Silica supported ruthenium catalysts; Alkali and alkali earth promoters; cis; -2-Butene-1,4-diol hydrogenation; 2-Hydroxytetrahydrofuran