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Applied Catalysis A, General (v.399, #1-2)

Editorial Board (pp. co2).

Contents (pp. iii-xi).

Chlorination and dehydrochlorination reactions relevant to the manufacture of trichloroethene and tetrachloroethene by Iain W. Sutherland; Neil G. Hamilton; Christopher C. Dudman; Peter Jones; David Lennon; John M. Winfield (pp. 1-11).

.Display Omitted► The formation of trichloroethene and tetrachloroethene is investigated. ► A role for homogeneous and heterogeneous processes is established. ► Trichloroethene is identified as a kinetic product. ► The chemical foundations for the industrial process are established.Factors which affect the selectivity of the chlorination of 1,2-dichloroethane and the associated dehydrochlorination reactions have been examined using approximate thermodynamic calculations, equilibrium measurements, and a continuous flow micro-reactor. There is a balance between surface and gas-phase chemistry within the system. Heterogeneous catalysis is not necessary to effect dehydrochlorination of 1,1,2,2-tetrachloroethane to trichloroethene but an attapulgite-supported copper(II) chloride catalyst favours formation of pentachloroethane and its dehydrochlorination product, tetrachloroethene. The latter is the thermodynamic minimum of the system. Below 473K and with long reaction times (2h, batch reactor), radical chlorination to form pentachloroethane is dominant. Above 573K and under flow conditions, free radical dehydrochlorination to form trichloroethene becomes dominant. Heterogeneous chlorination under flow conditions provides a route to pentachloroethane and thence tetrachloroethene. High conversions favour the formation of oligomeric products.

Keywords: Chlorination; Dehydrochlorination; Attapulgite; Copper(II) chloride; Homogeneous catalysis; Heterogeneous catalysis

A kinetic study of the liquid-phase hydrogenation of citral on Au/TiO₂ and Pt–Sn/TiO₂ thin films in capillary microreactors by L.N. Protasova; E.V. Rebrov; H.E. Skelton; A.E.H. Wheatley; J.C. Schouten (pp. 12-21).

Display Omitted► The Pt–Sn/TiO₂ catalytic coating is more active and selective if to compare with Au/TiO₂ one. ► The yield of unsaturated alcohols of 79% was obtained on the Pt–Sn/TiO₂ thin film. ► The proposed kinetic model suitably describes the obtained experimental data. ► The reaction orders were found to be 1 for hydrogen and 0.07–0.08 for citral.The kinetics of the liquid-phase hydrogenation of citral (3,7-dimethyl-2,6-octadienal) on Au/TiO₂ and Pt–Sn/TiO₂ thin films was studied in the temperature range 313–353K and citral concentrations of 0.25–10.0molm⁻³. The thin films were deposited onto the inner walls of silica capillaries with internal diameter of 250μm. First-order dependence on hydrogen pressure and near zero order dependence on citral concentration were observed for the initial rate of citral hydrogenation over the Pt–Sn/TiO₂ and Au/TiO₂ thin films. The Au/TiO₂ catalyst prevents citronellal formation. The highest yield of unsaturated alcohols was obtained on the Pt–Sn/TiO₂ film at a reaction temperature of 343K, liquid residence time of 30min and a citral conversion of 99%.

Keywords: Nanoparticles; Mesoporous titania thin films; Citral hydrogenation; Kinetic modeling

Photocatalytic activity and its stacking order dependence of transparent 12 tungsto(VI) phosphoric acid-brookite hybrid films by Kunchaya Pruethiarenun; Toshihiro Isobe; Sachiko Matsushita; Akira Nakajima (pp. 22-27).

Display Omitted► Transparent hybrid films of brookite and PW₁₂ were prepared via layer-by-layer process. ► The combination of PW₁₂ to brookite increased the photocatalytic activity. ► The electron scavenger effect of PW₁₂ against brookite plays an important role. ► The degree of the improvement depends on the stacking order in the films. ► Photocatalytic activity was the highest when PW₁₂ was arranged on the topmost surface of the film.Transparent hybrid films of brookite (TiO₂) and 12 tungsto(VI) phosphoric acid (PW₁₂) were prepared via layer-by-layer (LBL) processes on a quartz substrate with various orders. Their photocatalytic activities were evaluated using gaseous 2-propanol (IPA) decomposition. Pure brookite film showed higher photocatalytic activity than the pure PW₁₂ one; the combination of PW₁₂ to brookite increased the photocatalytic activity. The electron scavenger effect of PW₁₂ against brookite under UV illumination is important for photocatalytic activity improvement. The degree of improvement depends on the film stacking order. Their photocatalytic activity was the highest when PW₁₂ was arranged on the film's topmost surface.

Keywords: Brookite; Photocatalyst; Layer-by-layer; KEGGIN; Stacking order

Structure of molybdenum oxide supported on silica SBA-15 studied by Raman, UV–Vis and X-ray absorption spectroscopy by Jörg P. Thielemann; Thorsten Ressler; Anke Walter; Genka Tzolova-Müller; Christian Hess (pp. 28-34).

Display Omitted► Dispersed molybdenum oxide consists of monomeric and connected species. ► For the loadings studied no dependence on preparation or loading is observed. ► Raman, UV–Vis and XA spectroscopy provide complementary structural information.The structure of molybdenum oxide supported by silica SBA-15 has been studied by visible Raman spectroscopy, diffuse reflectance UV–Vis spectroscopy and X-ray absorption spectroscopy in the dehydrated state obtained after thermal treatment at elevated temperatures (≥350°C). No dependence of the molybdenum oxide structure on preparation procedure or loading has been observed within the range of loadings studied in detail (0.2–0.8Mo/nm²). X-ray absorption spectroscopy (XAS) reveals that the dehydrated state consists of a mixture of monomeric and connected molybdenum oxide centres. While the presence of crystalline MoO₃ can be excluded by Raman spectroscopy, tetrahedrally and octahedrally coordinated MoO₄ and MoO₆ units are identified by XAS. The MoO₆ units possess connectivity similar to that of MoO₃ building blocks, whereas the MoO₄ units are isolated or connected to other Mo_xO_y units. These results are supported by UV–Vis spectra showing intensity at wavelengths (>300nm) typical for dimeric and/or oligomeric species.

Keywords: Molybdenum oxide; Structure; Supported; Silica; SBA-15; Raman; UV–Vis; XAS

Challenging the scope of continuous, gas-phase reactions with supported ionic liquid phase (SILP) catalysts—Asymmetric hydrogenation of methyl acetoacetate by Eva Öchsner; Martin J. Schneider; Carolin Meyer; Marco Haumann; Peter Wasserscheid (pp. 35-41).

Display Omitted► SILP catalysis allows asymmetric ketone hydrogenation as gas phase reaction. ► ee's between 65% and 82% ee were obtained for more than 100h time-on-stream. ► Performance in tube reactor is superior to reaction in Berty reactor. ► Formation of heavy by-products is a main threat for catalyst stability.In the last years Supported Ionic Liquid Phase (SILP) catalysis has attracted growing interest for continuous gas phase reactions. The concept combines in a unique manner the advantages of traditional homogeneous and heterogeneous catalysis by making use of the extremely low vapor pressure of an ionic liquid film on support. In this way, continuous gas phase reactions with macroscopically solid but microscopically homogeneous catalyst materials have been successfully realized. However—so far—continuous gas-phase SILP catalysis has only been demonstrated for reactions with relatively simple selectivity problems (such as, regioselectivity, chemoselectivity). This study demonstrates the successful application of a SILP catalyst in continuous gas phase asymmetric hydrogenation. The hydrogenation of methyl acetoacetate (MAA) is presented using an immobilized dibromo[3-(2,5-(2R,5R)-dimethylphospholanyl-1)-4-di-o-tolylphosphino-2,5-dimethylthio-phene]-ruthenium (Ru1Br₂) catalyst.

Keywords: Asymmetric catalysis; Hydrogenation; Ionic liquids; Ketones; Supported catalysts; SILP

Solvent free liquid-phase alkylation of phenol over solid sulfanilic acid catalyst by Farook Adam; Kasim Mohammed Hello; Tammar Hussein Ali (pp. 42-49).

A solid sulfanilic acid catalyst was found to be active in the solution state alkylation reaction. Alkylation of phenol yielded 57% conversion of phenol and shows 52% selectivity towards 4- tert-butylphenol.Display Omitted► The immobilization of silica with sulfanilic acid has been done via a simple technique. ► The catalyst was active in the solvent free alkylation of phenol. ► The solvent free alkylation of phenol with tert-butyl alcohol at 120°C gave a 57% conversion with 52% selectivity towards 4- tert-butylphenol. ► The catalyst was regenerated easily and reused many times without loss of activity.Sulfanilic acid was immobilized onto rice husk ash via 3-(chloropropyl)triethoxy-silane to form an acidic solid catalyst denoted as RHAPhSO₃H. The BET surface area was found to be 308m²g⁻¹. Pyridine adsorption study revealed the presence of Brønsted acid sites. The EDX analysis showed the presence of S (10.88%) and N (10.37%). The²⁹Si MAS NMR showed the presence of T², T³, Q³ and Q⁴ silicon centres. The three carbon atoms of the propyl group were evident from the¹³C MAS NMR together with a series of chemical shifts consistent with the presence of the benzene ring. In the alkylation of phenol using RHAPhSO₃H as the catalyst resulted in 95% conversion of tert-butyl alcohol at 120°C with 52% selectivity towards 4- tert-butylphenol. The catalyst was reused several times without significant loss of catalytic activity.

Keywords: Surface modification; Sol–gel technique; Sulfanilic acid; Alkylation; 4-; tert; -Butylphenol

Nanocasted oxides for gas phase glycerol conversion by Cleanio L. Lima; Santiago J.S. Vasconcelos; Josué M. Filho; Bartolomeu C. Neto; Maria G.C. Rocha; Pascal Bargiela; Alcineia C. Oliveira (pp. 50-62).

Display Omitted► Binary nanostructured oxides evaluated in gas-phase dehydration of glycerol. ► Activity and stability of SnO₂–TiO₂. ► Cooperativity of Sn⁴⁺ and Ti⁴⁺.Catalytic performance of binary nanostructured oxides has been evaluated in the gas-phase dehydration of glycerol, an environmental friendly reaction. SnO₂–Mn₂O₃, SnO₂–ZrO₂, SnO₂–TiO₂, ZrO₂–Mn₂O₃ nanocasted oxides, and a reference, NiO–Co₃O₄, were characterised by XRD, Raman spectroscopy, acid–base measurements, SEM–EDX, TPR, HTEM and XPS. Correlations among the catalyst's activity and the surface, textural, and acid–base properties of the nanocasted oxides were tentatively conducted in attempts to justify the catalytic results. Influences of nanoparticle or nanostructure structural properties on the catalytic activity have been investigated. The better activity of SnO₂–TiO₂ at 250°C and a glycerol/water molar ratio of 0.25 was due to cooperativity of Sn⁴⁺ and Ti⁴⁺. The most important finding was that nanostructure features of the solid enhanced nanoparticle stability through the redox ability of the binary solid compared to conventional binary catalysts.

Keywords: Oxides; Dehydration; Nanocasting; Glycerol; Characterisations

Synergisms via hydrogen spillover between some transition metals during hydrodesulphurization: Increased activity towards conversion of refractory molecules by M. Villarroel; E. Camú; N. Escalona; P. Ávila; S.B. Rasmussen; P. Baeza; F. Gil-Llambías (pp. 63-68).

Display Omitted► We studied the synergism in stacked bed systems using two real feeds. ► We identified six refractory molecules present in the feed. ► A volcano curve was observed with both feed and with the six refractory molecules. ► We studied the activity on Co//Mo, Co//W and Co//Re systems of 4-MDBT and 4,6-DMDBT. ► Hso play an higher role in the HDS principally of refractory sulphur molecules.The synergism effects by hydrogen spillover on M_D//Re stacked bed systems and M_D (M_D=Mn/γ-Al₂O₃, Fe/γ-Al₂O₃, Co/γ-Al₂O₃, Ni/γ-Al₂O₃, Cu/γ-Al₂O₃ or Zn/γ-Al₂O₃) on two real diesel feeds with different sulphur contents, have been studied. The total sulphur content and the concentration of six refractory molecules present in the feeds were determinated. The dependence of the synergism with the position of the M_D in the periodic table describes a volcano curve with a maximum in Co//Re and Ni//Re pairs. This behavior was observed with both feed and with these six refractory molecules.Furthermore, the activity on Co//Mo, Co//W and Co//Re stacked bed systems of 4-MDBT and 4,6-DMDBT was studied. Results show that spillover factor is higher in 4,6-DMDBT than 4-MDBT, suggesting that Hso can play an important role in improving current state of the art catalysts with respect to the elimination of refractory sulphur molecules.

Keywords: Deep-hydrodesulphurization; Hydrogen spillover; Refractory molecules; Transition metals

Catalyst recycling in monophasic Pt-catalyzed hydrosilylation reactions using ionic liquids by Nicola Taccardi; Melinda Fekete; Markus E. Berger; Volker Stanjek; Peter S. Schulz; Peter Wasserscheid (pp. 69-74).

Display Omitted► Technically challenging hydrosilylation with trichlorosilane with ionic liquids. ► Ionic liquid tailoring to get homogeneous monophasic system. ► Catalyst full recyclability up to 10 times. ► Promising industrial implementation.The technical relevant Pt-catalyzed hydrosilylation of allyl chloride with trichlorosilane was investigated in a monophasic reaction system containing an ionic liquid (IL) additive. ILs screening allowed us to identify the liquid 1-decyl-3-methylimidazolium bis(trifloromethanesulfonyl)amide ([DMIM][NTf₂]) as the best additive for such process. This IL combined complete miscibility with reactants as long as chemical and thermal robustness. After the reaction, the hydrosilylation product (3-chloropropyl)trichlorosilane was distilled off and the residual IL/catalyst solution could be reused. In such a way, a final TON of 14,200 was achieved over 10 reaction/distillation cycles without any loss of catalytic activity. The ability of [DMIM][NTf₂] to prevent catalyst decomposition was deeper investigated and it was found that even with a Pt loading as high as 9500ppm, the IL acted as protective/stabilizing agent for the catalyst during the thermally stressing product distillation.

Keywords: Platinum; Hydrosilylation; Ionic liquid; Homogeneous; Monophasic

Highly efficient solvent free oxidation of ethylbenzene using some recyclable catalysts: The role of linker in competency of manganese nanocatalysts by Mohammad Arshadi; Mehran Ghiaci (pp. 75-86).

.Display Omitted► The Mn catalysts immobilized on functionalized nanosized SiO₂–Al₂O₃ used as catalysts. ► These catalysts were studied in the oxidation of ethylbenzene to acetophenone. ► Without the need of any solvent. ► The selectivity of acetophenone reached to 93% at TBHP/ethylbenzene molar ratio (1:1).SiO₂–Al₂O₃ mixed-oxide was functionalized with 3-aminopropyl-triethoxysilane (3-APTES) and 2-aminoethyl-3-aminopropyl-trimethoxysilane (2-AE-3-APTMS) groups. The resulting modified nanosized SiO₂–Al₂O₃ mixed-oxides were further functionalized with three different Schiff base groups followed by complexation with Mn(OAc)₂ to afford the corresponding immobilized Mn catalysts. The synthesized materials were characterized by FT-IR spectroscopy, UV–vis, CHN elemental analysis, ICP-MS, EPR, SEM, and TEM. The catalytic activities of the heterogenized Mn catalysts were studied in the oxidation of ethylbenzene without the need of any solvent, at 80°C, using tert-butyl hydroperoxide as oxygen source. Si/Al- pr-NH- et-Nmethyl-2-pyridylketone-Mn had high catalytic activity and selectivity to acetophenone (93%), and could be reused at least 4 times without significant loss in activity.

Keywords: Mn nanocatalyst; Ethylbenzene; Acetophenone; Oxidation; Nanosized SiO; ₂; –Al; ₂; O; ₃

Activated MgAl-layered double hydroxide as solid base catalysts for the conversion of fatty acid methyl esters to monoethanolamides by Xiaodong Lei; Wei Lu; Qing Peng; Haiyan Li; Tao Chen; Sailong Xu; Fazhi Zhang (pp. 87-92).

.Display Omitted► A green route was used to synthesize fatty acid monoethanolamides. ► Activated layered double hydroxides (LDHs) were used as the heterogeneous catalyst. ► The morphology of the catalysts plays an important role in the reaction. ► The catalysts with small size showed a higher activity at low temperature.Increasing concern about the environment demands that the chemical industry develop alternative greener routes to traditional processes. Two of the ways to achieve this aim are the replacement of homogeneous catalysts by heterogeneous analogs and the use of renewable raw materials. Fatty acid esters, in the form of biodiesel, have been suggested as raw materials for the sustainable production of high value chemicals. Here, we report a green route to the synthesis of fatty acid monoethanolamides using fatty acid methyl esters as the raw materials and activated layered double hydroxide (LDH) as a solid catalyst. Two kinds of MgAl-LDH precursors with different crystal morphologies were synthesized by the SNAS (separate nucleation and aging steps) method and the urea decomposition method. Activated LDH samples obtained from the LDH precursor synthesized by the SNAS method showed a higher catalytic activity in the amidation of methyl stearate than those prepared from the LDH precursor synthesized by the urea decomposition method, with about 87.0% methyl stearate conversion at 393K for 4h. The higher activity may be attributed to the smaller crystallite size and the larger surface area of the activated LDH obtained from the LDH precursor synthesized by the SNAS method. Moreover, activated LDH with an Mg/Al ratio of 4.0 exhibited a higher conversion of methyl stearate compared to those with Mg/Al ratios of 2.0 or 3.0 prepared by the same method.

Keywords: Layered double hydroxide; Hydrotalcite; Solid base catalysts; Fatty acid methyl esters; Monoethanolamides

On the acid–base properties of Zn–Mg–Al mixed oxides by Manuela C.I. Bezen; Cornelia Breitkopf; Johannes A. Lercher (pp. 93-99).

Display Omitted► Zn²⁺ cation substitution in Mg–Al mixed oxides induces a higher concentration of Lewis acid sites. ► High activity for dehydrogenation of propan-2-ol is related to the pronounced hydride abstraction ability of Zn²⁺ cations. ► Strength and concentration of basic sites decreases by substitution of Zn²⁺ cations in Mg–Al mixed oxides.The influence of Zn²⁺ cation substitution in Mg–Al mixed oxides is explored in the Zn²⁺ concentration range from 20 to 60mol%. The mixed oxides are derived by calcination of layered double hydroxide precursors. Structural analyses by XRD and²⁷Al MAS NMR show that Al³⁺, Mg²⁺ and Zn²⁺ cations are well dispersed among the oxide phases. The acid site concentration increases with increasing zinc content, while the concentration of basic sites decreases compared to Zn²⁺ free mixed oxides. Acetone is the primary reaction product of propan-2-ol elimination with all zinc containing oxides. This suggests that the high activity for dehydrogenation of propan-2-ol is related to the pronounced hydride abstraction ability of Zn²⁺ cations and not to an enhanced strength or concentration of basic sites.

Keywords: Zn–Mg–Al mixed metal oxides; XRD; ²⁷; Al MAS NMR; Propan-2-ol elimination reactions; Hydride transfer

Desilication of a TON zeolite with NaOH: Influence on porosity, acidity and catalytic properties by P. Matias; C. Sá Couto; I. Graça; J.M. Lopes; A.P. Carvalho; F. Ramôa Ribeiro; M. Guisnet (pp. 100-109).

Display Omitted► NaOH treatment conditions influence on the desilication of TON zeolite. ► Porosity modification of intermediate pore size zeolite TON. ► Influence of TON desilication on the 1-butene double bond shift reaction. ► Influence of TON desilication on the acidity. ► Active sites accessibility in desilicated TON zeolite.A TON zeolite (Si/Al=31) was treated at 353K with NaOH solutions of different concentrations C (0.05–0.4M) and for different times t (30–300min). The resulting samples were characterized by various techniques: SEM, XRD, nitrogen adsorption–desorption, pyridine chemisorption followed by FTIR and 1-butene isomerisation at 333K. The filtrate analysis shows a simultaneous dissolution of Si and Al with a large preference for Si (Si/Al from 35 to 150), especially at high t and low C values. The increase with t of the filtrate Si/Al ratio was related to the redeposition of Al on the zeolite under the form of extraframework species with Lewis acidity. The alkali treatment caused the creation of mesopores with ∼20nm diameter, a limited decrease in the Brønsted acidity and a significant increase in the Lewis acidity. With all samples, 1-butene double bond shift selectively occurred but with a fast deactivation due to carbonaceous deposits which can be eliminated from the zeolite through nitrogen sweeping. Desilication had no effect on the catalyst stability but increased the initial activity. The activity per protonic site (TOF) was shown to be correlated with the volume of created mesopores, which shows that these mesopores facilitate the access of 1-butene molecules to the active sites.

Keywords: Desilication; TON zeolite; Mesopore; Acidity; 1-Butene isomerisation

Low temperature CO adsorption and oxidation over Au/rare earth-TiO₂ nanocatalysts by Nruparaj Sahu; K.M. Parida; A.K. Tripathi; V.S. Kamble (pp. 110-116).

Display Omitted► Au promoted rare earth (RE) doped TiO₂ shows excellent activity for CO oxidation. ► RE doping affects the structural properties of Au/TiO₂. ► RE helps in stabilization of gold nanoparticles during high temperature reaction. ► Au/RE-TiO₂ provides additional adsorption/reaction sites for O₂ adsorption.Titania supported nanogold (3–4nm) catalyst exhibits remarkable activity for low temperature CO oxidation. Low melting point of gold nanoparticles may cause sintering of gold catalysts during their application at elevated temperatures which limit their use. It is reported that doping of the oxide support with rare earth (RE) ion helps in stabilization of gold metal particles due to change in the structural properties of the support. RE doped TiO₂ supported Au catalysts have been investigated for CO adsorption by in situ Fourier transforms infrared spectroscopy and oxidation in a fixed bed reactor. It has been observed that RE doping significantly improves the catalytic activity of Au/TiO₂ under ambient condition. Europium doping showed the highest effect on CO oxidation activity among different RE used in this study. It is suggested that doping of TiO₂ with RE helps in stabilization of gold nanoparticles in Au/TiO₂ during high temperature reaction. It provides additional adsorption/reaction sites for oxygen adsorption and interaction with adsorbed CO.

Keywords: Rare earth; Gold/titania; CO oxidation/adsorption

Selective hydrogenation of chloronitrobenzenes with an MCM-41 supported platinum allyl complex derived catalyst by Arindam Indra; Pattuparambil R. Rajamohanan; Chinnakonda S. Gopinath; Sumit Bhaduri; Goutam Kumar Lahiri (pp. 117-125).

Platinum derived functionalized MCM-41 supported catalyst (1) exhibits excellent catalytic activities towards the selective hydrogenations of o-, m-, p-chloronitrobenzenes to corresponding chloroanilines whereas no such high selectivity exists either with the analogous Pd-derived catalyst or commercial catalysts (5%) Pt/C and (5%) Pt/Al₂O₃.Display Omitted► Organometallic derived Pt(II) precatalyst supported on functionalized MCM-41. ► Selective hydrogenation of chloronitrobenzenes with low dehydrohalogenation. ► High selectivity towards the hydrogenation of meta- and para-chloronitrobenzenes. ► Unlike its Pd-analogue, in the used catalyst Pt is mainly in +2 oxidation state. ► Much better performance than commercially available 5% Pt/C and Pt/alumina.A platinum precatalyst (1) has been prepared by reacting [( η³-C₃H₅)₄Pt₄Cl₄] with surface functionalized MCM-41 with pendant –(CH₂)₃NH(CH₂)₂NH₂ groups. For the hydrogenation of o-, m- and p-chloronitrobenzenes to the corresponding chloroanilines,1 is found to be a highly active catalyst with good selectivities for the m- and p-isomers. Its performance is superior to that of its palladium analogue and far superior to that of commercial (5%) Pt/C or (5%) Pt/Al₂O₃. Comparison of solid state and solution NMR data and other evidences indicate that on treatment with the functionalized MCM-41 support; [( η³-C₃H₅)₄Pt₄Cl₄] loses the allyl ligand. XPS data show that in the fresh catalyst Pt is present in the 2+ oxidation state. Based on these and analytical data, co-ordination by surface diamine and hydroxo groups to Pt²⁺ in1 is suggested. In the used catalyst both Pt²⁺ and Pt⁰ are present but the amount of metallic platinum is ∼16% of the total.

Keywords: Heterogeneous catalyst; Selective hydrogenation; Dehydrohalogenation; Chloronitrobenzenes; MCM-41

Silica grafted polyethylenimine as heterogeneous catalyst for condensation reactions by Sonia M. Ribeiro; Arménio. C. Serra; A.M. d’A. Rocha Gonsalves (pp. 126-133).

Display Omitted► A heterenogeneous material with poliethylenimine grafted in a silica matrix (ASCPEI) can be easily synthesized. ► ASCPEI catalyzes nitroaldol condensations. ► ASCPEI is an efficient catalyst for Knoevenagel condensation reactions with ethyl cyanoacetate.Primary amine groups were attached to a silica surface by using α,ω-diamines derivatives and (3-glycidyloxypropyl)-trimethoxysilane activation. The same activation was used to graft polyethylenimine, which also contains secondary and tertiary amine groups. These silica aminated structures were tested as heterogeneous catalysts in nitroaldol condensation with nitromethane, the derivative with the polyethylenimine moiety being the more active catalyst. This catalyst also showed efficiency in the Knoevenagel condensation of benzaldehydes with ethyl cyanoacetate under very mild reaction conditions and showed much the same efficiency when used in consecutive reaction runs. A reaction mechanism with participation of the several amine groups of the catalysts is discussed.

Keywords: Polyethylenimine; Silica; Heterogeneous catalysts; Knoevenagel condensation

Study of Sm₂O₃-doped CeO₂–Al₂O₃-supported Pt catalysts for partial CH₄ oxidation by R.B. Duarte; S. Damyanova; D.C. de Oliveira; C.M.P. Marques; J.M.C. Bueno (pp. 134-145).

Display Omitted► Sm-doped CeO₂ over alumina has bifunctional effect on supported Pt catalysts. ► Addition of Sm increases the reducibility and dispersion of Pt. ► Pt/SmCeAl catalysts show the best catalytic performance in partial oxidation of methane.The effect of xSm₂O₃ addition to yCeO₂–Al₂O₃-supported Pt catalysts (where x and y are the Sm₂O₃ and CeO₂ content, respectively, giving x+ y=12wt.%) on the surface, structure and catalytic properties of the catalysts was studied. The samples were characterized using various techniques, such as N₂ adsorption–desorption isotherms, XRD, XPS, FTIR and TPR. The catalytic properties of the catalysts were evaluated in the reaction of partial oxidation of methane. The relationship between the catalytic performance and physichochemical properties of Pt/ xSm₂O₃– yCeO₂–Al₂O₃ catalysts was evaluated. The improvement of the catalytic activity and stability observed for Sm₂O₃-doped CeO₂–Al₂O₃-supported Pt catalysts was attributed to the increase of the platinum metallic dispersion, reducibility and oxygen storage capacity. An optimum interaction between the platinum oxide species and the total surface oxygen vacancies was observed at Sm₂O₃ content of 3wt.% revealed by TPR.

Keywords: Pt catalysts; Sm; ₂; O; ₃; –CeO; ₂; –Al; ₂; O; ₃; oxides; Partial oxidation of methane; Sol–gel method; Characterization

MgO-based catalysts for monoglyceride synthesis from methyl oleate and glycerol: Effect of Li promotion by C.A. Ferretti; C.R. Apesteguía; J.I. Di Cosimo (pp. 146-153).

Display Omitted► Solid base catalysts for fatty acid methyl ester glycerolysis toward monoglycerides. ► Li-promoted MgO catalysts give 70–73% selectivity to monoglycerides. ► Li promotion enhances catalyst base site density and strength. ► Linear increase of the initial activity with Li content.The synthesis of monoglycerides (glyceryl monooleates) by heterogeneously catalyzed glycerolysis of an unsaturated fatty acid methyl ester (methyl oleate) was studied on MgO and Li-promoted MgO catalysts.Several MgO-based catalysts with different Li loadings were prepared by incipient wetness impregnation and characterized by XRD, N₂ physisorption, and FTIR and TPD of CO₂ among other techniques. Promotion of MgO with lithium, a basic promoter, affected the textural and structural properties of the resulting oxides so that more crystalline MgO phases with decreased surface area were obtained at increasing Li contents. Furthermore, the addition of Li generated new strong base sites because of formation of dispersed surface Li₂O species, and thereby increased the total base site density of parent MgO.Li-containing MgO catalysts efficiently promoted the glycerolysis reaction, achieving high monoglyceride yields (70–73%) at 493K. The initial monoglyceride formation rate increased linearly with the Li content on the sample following the enhanced overall catalyst base strength. Although conversions at the end of the run were ≈100% for all the catalysts, the monoglyceride selectivity slightly decreased with the Li loading, probably as a consequence of the less surface affinity for glycerol adsorption that facilitates competing monoglyceride re-adsorption and transformation to diglycerides by consecutive glycerolysis or disproportionation reactions.

Keywords: Glycerolysis; Monoglyceride; Glycerol; Fatty acid methyl ester; Base catalysis

Pd nanoparticles deposited on poly(lactic acid) grafted carbon nanotubes: Synthesis, characterization and application in Heck C–C coupling reaction by Gururaj M. Neelgund; Aderemi Oki (pp. 154-160).

Display Omitted► High catalytic activity of f-CNTs-Pd was demonstrated through Heck reaction. ► CNTs were effectively functionalized by covalent grafting of poly(lactic acid). ► Functionalized CNTs were utilized as platform for deposition of Pd nanoparticles. ► Covalently grafted poly(lactic acid) on CNTs was observed by TEM. ► f-CNTs-Pd is easily recoverable and maintains its activity over a number of cycles.Herein we described the synthesis of a novel f-CNTs-Pd nanocatalyst by covalent grafting of poly(lactic acid) (PLA) onto carbon nanotubes (CNTs) and subsequent deposition of Pd nanoparticles. Prior to grafting of PLA, CNTs were oxidized with a mixture of HNO₃/H₂SO₄ and successively activated with thionyl chloride. The PLA grafted CNTs ( f-CNTs) were then used as platform for in situ deposition of Pd nanoparticles. The formation of f-CNTs-Pd nanocatalyst was analyzed by UV–vis, FTIR and Raman spectroscopy, powder XRD, energy dispersive spectroscopy and thermogravimetric analysis. The morphologies of the nanocatalyst were characterized using scanning and transmission electron microscopes. The f-CNTs stabilized Pd nanoparticles are found to be more effective in the promotion of Heck cross-coupling reaction between aryl halides and n-butyl acrylate. The f-CNTs-Pd nanocatalyst was regenerated for three cycles of reaction without any significant loss in its activity.

Keywords: Carbon nanotubes; Poly(lactic acid); Palladium; Catalytic activity; Heck reaction

Diesel soot and NO_x abatement on K/La₂O₃ catalyst: Influence of K precursor on soot combustion by María A. Peralta; María S. Zanuttini; María A. Ulla; Carlos A. Querini (pp. 161-171).

Display Omitted► The effect of the surface composition of K/La₂O₃ catalysts on the soot combustion rate is addressed. ► The basicity of the surface is affected by the chemical state of K. ► The basicity of the surface decreases in the order: KOH>KNO₃>K₂CO₃. ► The interaction between the catalyst and the CO₂ is stronger at higher basicity, and this leads to an irreversible CO₂ adsorption.Soot particles and NO_x are the main pollutants emitted by diesel engines. The K/La₂O₃ catalyst is active for soot combustion and it is able to adsorb NO_x; therefore, it could work as NO_x trap. In this work, the effect of the chemical state of K on the catalytic activity is addressed. Both, the influence of the precursor used in the preparation and the effect of NO in the gas phase, are studied. Potassium nitrate, carbonate, and hydroxide were used to prepare the K/La₂O₃ catalysts. The catalytic activity for soot combustion was studied by TPO. XRD and FTIR were used to characterize the different crystalline phases found in the catalyst. Pulses of CO₂ and CO₂-TPD were useful to understand the effect of each precursor on the catalytic activity. The analysis of CO₂ adsorption–desorption dynamics made it possible to determine that the strength of the interaction between this molecule and the catalyst depends on the K precursor, and follows the order: KOH>KNO₃>K₂CO₃. The presence of La(OH)₃ leads to a strong and irreversible interaction between the catalyst and the CO₂, while the interaction is reversible with the dehydroxilated catalyst. The shape of the TPO profiles is related to the basicity of the surface, which according to the dynamics of the CO₂ adsorption–desorption is significantly affected by the potassium precursor used during the preparation, the thermal treatment, and the treatment with gases normally found in the diesel exhaust, such as the NO.

Keywords: Diesel soot; Potassium precursor; Lanthanum

Solvent-free chromium catalyzed aerobic oxidation of biomass-based alkenes as a route to valuable fragrance compounds by Patricia A. Robles-Dutenhefner; Bruno B.N.S. Brandão; Líniker F. de Sousa; Elena V. Gusevskaya (pp. 172-178).

Display Omitted► Cr-MCM-41 was prepared by a direct hydrothermal method using a surfactant. ► Cr–SiO₂/sol–gel was prepared by a conventional sol–gel method. ► The oxidation of limonene and α-pinene gives epoxides and allylic oxidation products. ► β-Pinene gives allylic mono-oxygenated derivatives in up to 92% combined selectivity. ► Cr-MCM-41 showed much higher selectivity than Cr–SiO₂/sol–gel in these reactions.Chromium containing mesoporous molecular sieves MCM-41 were shown to be an efficient heterogeneous catalyst for the liquid-phase aerobic oxidation of various monoterpenic alkenes under mild solvent-free conditions. The material was prepared through a direct hydrothermal method and characterized by ICP-AES, N₂ adsorption–desorption, TEM, XRD, SAXS, and H₂-TPR techniques. Characterizations suggest that chromium introduced in MCM-41 is essentially incorporated in the silica framework, with no extraframework chromium oxides being detected. Various oxygenated monoterpenoids important for the flavor and fragrance industry were obtained with high combined selectivities (75–92%) at 30–40% substrate conversions. The oxidation of β-pinene led almost exclusively to allylic mono-oxygenated derivatives, whereas limonene and α-pinene gave both epoxides and allylic oxidation products. The catalyst undergoes no metal leaching and can be easily recovered and re-used. A silica-included chromium catalyst prepared through a conventional sol–gel method showed activity comparable with that of Cr-MCM-41; however, selectivity was much lower.

Keywords: Monoterpenes; Oxidation; Oxygen; Chromium catalysts; Mesoporous molecular sieves

Deactivation of Pt/F-KL zeolite-type naphtha reforming catalysts: In-situ IR and on-line mass spectrometry studies of fluorine loss by Yu Xing; Gyanesh P. Khare; Steven L. Suib (pp. 179-183).

Display Omitted► Deactivation mechanism of fluorine-promoted Pt/KL reforming catalysts was revealed. ► In-situ IR, on-line mass spectrometry, and isotope exchange were employed. ► Comparative (moisture-free vs moisture-containing) experiments were conducted. ► Fluorine leaves the catalyst in the forms of COF₂ and HF as hexane and H₂O coexist.This paper presents the employment of a method, which combines in-situ IR spectrometry, on-line mass spectrometry, comparative (moisture-free vs moisture-containing) experiments, and isotope exchange, to reveal the deactivation mechanism of fluorine-promoted Pt/KL zeolite-type naphtha reforming catalysts. Fluorine leaves the catalyst in the forms of COF₂ and HF as hydrocarbon feedstock and trace amount of H₂O coexist.

Keywords: Catalyst deactivation; Fluorine loss; Zeolite L; Infrared spectrometry; Mass spectrometry; Naphtha reforming

A high performance multi-walled carbon nanotube-supported palladium catalyst in selective hydrogenation of acetylene-ethylene mixtures by H. Bazzazzadegan; M. Kazemeini; A.M. Rashidi (pp. 184-190).

Display Omitted► 0.5% pd/MWCNT displayed 93% ethylene yield in selective hydrogenation of acetylene. ► By temperature rising, ethylene selectivity and acetylene conversion were enhanced. ► At elevated temperatures, hydrogenation in tail-end process occurs in a single reactor. ► Suppressing of oligomers and displaying high stability are features of this catalyst. ► Hydrogen transfer mechanism plays an essential role over Pd/MWCNT catalyst.In this research, a palladium nanocatalyst was synthesised over a multi-walled carbon nanotube (MWCNT) support and then applied for selective hydrogenation of acetylene in an ethylene-richflow stream. This material displayed a very promising selectivity toward ethylene production with increasing temperature, and also suppressed oligomer formation during acetylene hydrogenation. New operating conditions for selective hydrogenation of acetylene in an ethylene-richflow were introduced. This nanocatalyst gave a considerably higher yield, as high as 93%, than that previously obtained for ethylene production. It was postulated that the governing mechanism for acetylene hydrogenation over 0.5wt.% Pd/MWCNT was hydrogen transfer.

Keywords: Selective hydrogenation; Ethylene yield; Nanocatalyst; Multi-walled carbon nanotube

New homogeneously doped Fe(III)–TiO₂ photocatalyst for gaseous pollutant degradation by Siteng Tieng; Andrei Kanaev; Khay Chhor (pp. 191-197).

Display Omitted► Fe–TiO₂ photocatalyst made in micromixing reactor has higher activity than pure TiO₂. ► Fe–TiO₂ photocatalyst has best activity at 0.005at.% doping. ► By-products formation causes slow transient regime of ethylene conversion. ► First order kinetics are obtained with a continuous flow reactor. ► CB electron localisation model allows defining an optimal particle size of ≈8nm.We report on photocatalytic activity of new homogeneously Fe(III)-doped TiO₂ nanocoatings. The material is prepared in a two-stage process including (1) oxo-TiO₂ nanoparticles nucleation, doping by iron(acetylacetonate)₃ and reactive deposition on glass substrates in a sol–gel micromixing reactor and (2) thermal treatment. The photocatalytic test of the nanocoatings is conducted on ethylene degradation in a continuous-flow fixed bead reactor. The catalyst shows the best performance at Fe/Ti molar ratio of 0.005at.%, which is explained by a competition between VB-hole localisation on Fe³⁺ and its annihilation on Fe²⁺. The proposed model permits an estimation of the localisation distance of the CB-electron in anatase TiO₂ after a photoexcitation and defines the optimal size for the nanoparticulate TiO₂ photocatalyst to be ∼8nm.

Keywords: TiO; ₂; nanoparticles; Fe(III) doping; Photocatalysis; Ethylene decomposition; Effect of doping; Charges recombination

Catalytic deoxygenation of oleic acid in continuous gas flow for the production of diesel-like hydrocarbons by Matthias Arend; Thomas Nonnen; Wolfgang F. Hoelderich; Jürgen Fischer; Jeremie Groos (pp. 198-204).

Display Omitted► Diesel-like hydrocarbons from renewable feedstock. ► Decarboxylation and decarbonylation reactions took place. ► Continuous gas phase reactions under solvent-free conditions. ► Up to 28.5% selectivity to C17 hydrocarbons.Continuous gas phase deoxygenation of oleic acid in the presence of hydrogen employing a granular 2wt% Pd/C catalyst was investigated under solvent free conditions. Conversion of oleic acid and selectivity to the desired diesel-like C17 hydrocarbons heptadecane and heptadecenes was studied at different reaction conditions such as temperature, gas flow and catalyst amount. The best hydrocarbon yield was achieved with low reaction temperatures, high catalyst amounts and high hydrogen flows. To further decrease the reaction temperature but yet maintain a pure gas phase reaction, reactions were conducted in vacuum. Furthermore, water was added in varying amounts to support desorption and to determine if catalyst deactivation could be overcome. The deoxygenation catalyst was characterized by nitrogen adsorption isotherms (BET; Brunauer–Emmet–Teller method), X-ray powder diffraction (XRD), thermogravimetric analysis (TGA) and field emission scanning electron microscopy (FESEM).

Keywords: Biofuels; Continuous gas phase reactor; Deoxygenation; Palladium-on-carbon (Pd/C); Oleic acid

Simple and efficient water soluble thioligands for rhodium and iridium catalyzed biphasic hydrogenation by Sabrina Di Dio; Mauro Marchetti; Stefano Paganelli; Oreste Piccolo (pp. 205-210).

Display Omitted►Rh/Cap andRh/Cy were efficient hydrogenation catalysts in aqueous biphasic medium. ►Ir/Cy andIr/Cap were less active than the related rhodium catalysts. ► All the catalysts were easily recycled without significant loss of activity.The activity of catalytic systems derived from the interaction between Rh(CO)₂acac and [Ir(COD)Cl]₂, respectively, with the water soluble thioligands (L)-Cysteine (1) and (S)-Captopril (2), was tested in the aqueous biphasic hydrogenation of some representative α,β-unsaturated compounds as 2-cyclohexen-1-one (I), trans-cinnamaldehyde (V) and [3-(1,3-benzodioxol-5-yl)-2-methylpropenal] (X), precursor of the fragrance Helional^® (XI). The precatalystRh/Cap was able to hydrogenate cyclohexenone even at low pressure at 60°C in a neutral medium whileRh/Cy required either higher pressure and temperature or an alkaline medium. The iridium based catalysts,Ir/Cy andIr/Cap, showed an analogous trend though their activities were lower than those of the related rhodium catalysts. All the catalysts were easily recycled without significant loss of activity. The rhodium catalysts were also used in the hydrogenation of the above aldehydesV andX and their activity was strongly enhanced when ethylene glycol was used as organic solvent or co-solvent.

Keywords: Key words; Rhodium; Iridium; Biphasic hydrogenation; Catalyst; Water soluble ligand

Hydrodesulfurization catalyst bodies with various Co and Mo profiles by John Vakros; Christina Papadopoulou; Alexis Lycourghiotis; Christos Kordulis (pp. 211-220).

Display Omitted► Five HDS catalysts with various Co and Mo radial profiles and industrial loading have been developed. ► The catalytic behavior of these catalysts depends on their micro/macro-characteristics. ► The CoMo/γ-Al₂O₃ extrudates with uniform Co and Mo profiles are proved to be the most active for thiophene hydrodesulfurization. ► Egg-shell Co profiles favour the hydrogenation ability of these catalysts.We have achieved the preparation of five catalysts with various Co and Mo radial profiles in γ-Al₂O₃ extrudates and loadings similar to the industrial hydrotreatment catalysts. EDS microanalysis was used for determining the profiles achieved. The catalyst bodies prepared were powdered and characterized using N₂ adsorption–desorption, temperature programmed reduction, X-ray powder diffraction, UV–vis diffuse reflectance spectroscopy and NO adsorption. The hydrodesulfurization of thiophene under atmospheric pressure was used as a probe reaction. The selectivity for the butane produced was taken as a measure of the hydrogenation ability of the catalysts.The different procedures inevitably used for the preparation of the different profiles affect somewhat the microscopic characteristics of the catalysts (Co and Mo dispersion, concentration of the coordinatively unsaturated sites, cobalt species formed) and to some extent their intrinsic catalytic behavior (determined in the powdered samples). The catalytic activity of the catalyst bodies depends on the aforementioned microscopic characteristics and the internal mass transfer resistance associated with the location of active phases and pores blocking. The combination of these factors becomes the sample with uniform Co and Mo profiles the most active one. DRS, TPR and XRD results indicated high Co dispersion in this sample.The hydrogenation ability of the CoMo/γ-Al₂O₃ catalysts is higher over the catalyst bodies than over the powdered samples and enhanced on the catalysts with egg-shell Co profiles.

Keywords: Key words; CoMo/γ-Al; ₂; O; ₃; catalysts; HDS catalysts; Profiles; Macro-distribution; Hydrodesulfurization; DRS; XRD; TPR; Effectiveness factor; Hydrogenation; Hydrotreatment; Thiophene

Fischer–Tropsch synthesis over alumina-supported molybdenum carbide catalyst by Dai-Viet N. Vo; Adesoji A. Adesina (pp. 221-232).

Display Omitted► Alumina-supported Mo carbide has decent FT activity under usual conditions. ► H₂ gas phase attack of molecularly chemisorbed CO gave a fitting kinetic model. ► Active site appeared to be an oxycarbide centre. ► Kinetic model and an ROP model permitted general hydrocarbon rate prediction. ► E_a for termination to olefin and paraffin are 71 and 104kJmol⁻¹ respectively.Alumina-supported molybdenum carbide catalyst prepared by temperature-programmed carburization has been evaluated for Fischer–Tropsch synthesis between 473K and 515K with feed gas containing H₂/CO=1:5–5:1. Optimum CO consumption rate was found at H₂ mole fraction of 0.67 for all temperatures suggesting that similar FT mechanism was operative over the temperature range studied. Associated Arrhenius parameters revealed that activation energy values varied between 51kJmol⁻¹ and 158kJmol⁻¹. Olefin-to-paraffin ratio (ROP) initially rose with carbon number, n, to a maximum value followed by a tailing drop. A mechanism involving molecular CO chemisorption with gas phase H₂ attack to yield enolic species was used to develop a kinetic model that adequately captured individual hydrocarbon species as well as the behaviour of the ROP with composition. Combination of the kinetic model with the nonlinear ROP model permitted, for the first time, estimation of the separate intrinsic activation energy values for termination to olefin and paraffin on the catalyst surface.

Keywords: Fischer–Tropsch synthesis; Molybdenum carbide; Temperature-programmed carburization

Effect of hexamethylenetetramine on the visible-light photocatalytic activity of C–N codoped TiO₂ for bisphenol A degradation: evaluation of photocatalytic mechanism and solution toxicity by Xiaoping Wang; Teik-Thye Lim (pp. 233-241).

Display Omitted► Effect of hexamethylenetetramine on the physicochemical properties and photoactivity of C–N codoped TiO₂ synthesized via solvothermal method. ► Evolution of solution toxicity during photocatalytic mineralization of BPA. ► Mechanism of photocatalytic reaction upon C–N codoped TiO₂ under visible light irradiation. ► O₂⁻ was the predominant oxidative species to oxidize BPA.Our previous work showed that highly visible-light photoactive C–N codoped TiO₂ (CN-TiO₂) was synthesized by a solvothermal method. The CN-TiO₂ prepared using hexamethylenetetramine (HMT) as the dopant source exhibited excellent photoactivity on bisphenol A (BPA) degradation under visible light irradiation. The influences of pH and inorganic anions on BPA degradation were evaluated. Three main studies were elucidated in this work. (1) Effect of HMT dosage on the physicochemical properties and photoactivity of CN-TiO₂ was investigated. After 2h of irradiation with white LED, 95% of BPA was removed by Ti-0.375HMT, which exhibited large surface area (157.7m²g⁻¹) and low band gap (2.46eV). (2) Mineralization and evolution of solution toxicity upon BPA degradation under white LED, simulated solar light and UV irradiation were systematically studied. After 4h of reaction, BPA was almost completely mineralized under simulated solar light and UV irradiation by the CN-TiO₂, and generally the BPA solution became almost non-toxic irrespective of the light source used. (3) Photocatalytic mechanism of BPA degradation by the CN-TiO₂ under visible light irradiation was proposed. The carbon and nitrogen codoping could create the intragap localized states located above the valence band of TiO₂, and carbonate species formed on the TiO₂ surface could serve as photosensitizer. As a result, O₂⁻,¹O₂ and h⁺ could be generated on the surface of CN-TiO₂ under visible light irradiation; they together contributed to the BPA degradation. Particularly, O₂⁻ was the predominant oxidative species to oxidize BPA. Trace OH was produced but its role in BPA degradation was insignificant.

Keywords: C–N codoped TiO; ₂; Solvothermal; Visible light; Photosensitization; Oxidative species

Effect of Co-content on the structure and activity of Co–Al hydrotalcite-like materials as catalyst precursors for CO oxidation by Margarita Gabrovska; Rumeana Edreva-Kardjieva; Krasimir Tenchev; Peter Tzvetkov; Alla Spojakina; Lachezar Petrov (pp. 242-251).

▪.► Coprecipitated Co–Al hydrotalcites as catalyst precursors in CO oxidation. ► Comparison of the results with unsupported Co₃O₄. ► Complete and prolonged CO oxidation at room temperature on Co–Al sample with the highest cobalt content. ► Oxygen ion-radicals O₂ x^– stabilization by Al³⁺ cation. ► Hypothetic scheme about the active ensemble.The present investigation was undertaken in an endeavor to study the effect of the cobalt content on the structure and activity of Co–Al hydrotalcite-like materials as catalyst precursors for CO oxidation by varying the Co²⁺/Al³⁺ atomic ratio, thermal treatment of the samples and the reaction temperature. The samples (Co²⁺/Al³⁺=0.5, 1.5, 3.0) have been synthesized by the co-precipitation method. The unsupported Co₃O₄ has been prepared according to the same procedure as the reference compound in order to reveal the role of Al³⁺ ions presence.The physicochemical characterization of the uncalcined, hydrothermally treated, calcined and tested samples has been accomplished appropriately by ICP-AES, N₂ adsorption, Powder X-ray diffraction technique and Diffuse Reflectance Spectroscopy and H₂-TPR measurements.The samples were examined by a number of heating–cooling cycles during the activity tests as a procedure to screen the most active catalyst precursor. It was established that the hydrotalcite-like structure of all uncalcined samples had been completely destroyed during the CO oxidation reaction. A concomitant phase transformation into poorly crystallized spinel-type Co²⁺(Co³⁺,Al³⁺)₂O₄ mixed oxide occurred. This spinel-like mixed oxide phase is better organized in all samples after their calcination at 500°C. The TPR examinations reveal concomitant presence of high-temperature reduced non-stoichiometric CoAl₂O₄.It was found out that the Co–Al mixed oxide, derived from the sample with the highest cobalt loading (Co²⁺/Al³⁺=3.0) preserves a complete and prolonged CO oxidation ability even after cooling down to ambient temperature. On the contrary, the samples with ratios Co²⁺/Al³⁺=0.5 and 1.5 as well as the Co₃O₄ oxide deactivate more rapidly during the cycles. A hypothetic scheme is proposed for activation/deactivation of the catalysts. It is related to the oxygen ion-radicals O₂ x^– stabilization by Al³⁺ cation association with the Co²⁺/Co³⁺ redox couple via anionic vacancy.

Keywords: Co–Al hydrotalcite-like materials; Co–Al mixed oxide; Co; ₃; O; ₄; Low temperature CO oxidation

C–N–S tridoped TiO₂ for photocatalytic degradation of tetracycline under visible-light irradiation by Penghua Wang; Pow-Seng Yap; Teik-Thye Lim (pp. 252-261).

Display Omitted► Visible-light responsive C–N–S tridoped TiO₂ was synthesized using a sol–gel method. ► The photocatalytic degradation and mineralization of tetracycline were more efficient under solar irradiation. ► The extended solar photocatalysis was efficient in the detoxification of tetracycline solution according to the Microtox assay.C–N–S tridoped TiO₂ was synthesized using a facile, cost-effective and easily scaled-up sol–gel method with titanium butoxide (Ti(OC₄H₉)₄) as titanium precursor and thiourea as the dopant source. It was found that thiourea could suppress the crystal growth of the anatase TiO₂ and inhibit its transformation from anatase to rutile phase. X-ray photoelectron spectroscopy (XPS) analysis revealed that carbon substituted some of the oxygen to form Ti–C bonds, nitrogen was interstitially and substitutionally doped into the TiO₂ lattices to form Ti–N–O, Ti–O–N and O–Ti–N, and S⁶⁺ substituted for the lattice Ti⁴⁺ to result in cationic sulfur doping. The photocatalyst with the thiourea-to-Ti molar ratio of 0.05:1 and calcined at 450°C ( T0.05–450) possessed the optimum surface elemental contents of C (12.56at.%, excluded adventitious carbon at 284.8eV), N (0.54at.%) and S (1.60at.%) based on the XPS analysis, and exhibited the highest photocatalytic degradation efficiency of tetracycline (TC) under visible-light irradiation. This was attributed to the synergistic effects of TC adsorption on T0.05–450 due to its high specific surface area, band gap narrowing resulting from C–N–S tridoping, presence of carbonaceous species serving as photosensitizer, and well-formed anatase phase. The slightly alkaline pH condition and solar irradiation were more favorable for both the photocatalytic degradation and mineralization of TC. Microtox assay indicated that the extended solar photocatalysis was efficient in the detoxification of TC solution.

Keywords: C–N–S tridoped TiO2; Visible light; Solar; Tetracycline; Acute toxicity

Effect of acidity of ZSM-5 zeolite on conversion of ethanol to propylene by Yoshiyasu Furumoto; Yasumitsu Harada; Nao Tsunoji; Atsushi Takahashi; Tadahiro Fujitani; Yusuke Ide; Masahiro Sadakane; Tsuneji Sano (pp. 262-267).

Display Omitted► HZSM-5(M) (M=Al, Ga, and Fe) zeolites having different acid strengths were prepared. ► High propylene yields were obtained over HZSM-5(Ga) and HZSM-5(Al). ► P-modification was effective for improving the catalytic performance of HZSM-5(Ga).Protonated ZSM-5 zeolites (HZSM-5(M), M=Al, Ga, and Fe) having different acid strengths were prepared under various synthesis conditions, and the effect of acidity of the ZSM-5 zeolite on the conversion of ethanol to propylene was investigated in detail. HZSM-5(Ga) and HZSM-5(Al) showed high propylene yields. However, HZSM-5(Fe) yielded ethylene instead of propylene, i.e., only dehydration of ethanol occurred on HZSM-5(Fe). These results indicate that the acid strength is a crucial factor for the selective production of propylene. In other words, for successful selective conversion of ethanol to propylene, HZSM-5(M) zeolites must contain acid sites with an acid strength that is more than that of HZSM-5(Ga). It was also found that phosphorous-modified HZSM-5(Ga) zeolite exhibited an improved propylene yield relative to the unmodified zeolite and that the modification considerably enhanced the catalytic stability because of the suppression of both elimination of framework gallium and coke deposition.

Keywords: Ethanol; ZSM-5; Propylene; Acidity; Phosphorous

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Applied Catalysis A, General (v.399, #1-2)

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Applied Catalysis A, General (v.399, #1-2)