Applied Catalysis A, General (v.309, #2)
Editorial Board (CO2).
Catalytic nanomotors—promising leads for new catalytic applications by Harold H. Kung; Mayfair C. Kung (159-161).
Keywords: Nanotechnology; Nanomotor; Catalysis; Catalytic actuator;
Chitosan supported phthalocyanine complexes: Bifunctional catalysts with basic and oxidation active sites by Alexander B. Sorokin; Françoise Quignard; Romain Valentin; Stéphane Mangematin (162-168).
The immobilisation of water-soluble metallophthalocyanine complexes on chitosan aerogel microspheres affords new bifunctional catalysts which have been used for the aerobic oxidation of β-isophorone. Chitosan is both the support of the metal complex and the organic base necessary for the reaction. These new materials have been characterized by nitrogen adsorption/desorption, scanning electron microscopy, diffuse reflectance UV–vis and 15N NMR spectroscopies. The influence of the reaction parameters on the efficiency of heterogeneous oxidation of β-isophorone, an important substrate for the preparation of flavour and fragrance fine chemicals has been studied. Combination of basic and oxidation sites in one solid material provided a more efficient heterogeneous clean oxidation of β-isophorone by O2 without any waste.
Keywords: Heterogeneous oxidation; Supported catalyst; Phthalocyanine; Aerobic oxidation; Chitosan; Isophorone;
Rhodium catalyzed hydroformylation of linalool by José G. da Silva; Humberto J.V. Barros; Eduardo N. dos Santos; Elena V. Gusevskaya (169-176).
The hydroformylation of linalool using [Rh(COD)(OAc)]2 as a catalyst precursor in the presence of triphenylphosphine or various diphosphines leads mainly to a mixture of cis and trans isomers of hemiacetal, which formally arise from the intramolecular cyclization of the primarily formed hydroxyl-aldehyde. An unexpected effect of the phosphorous ligands on the reaction rate was observed. With unmodified systems, linalool shows a very low reactivity under the hydroformylation conditions, probably due to the chelation of the substrate on rhodium. The introduction of (di)phosphine and the increase in its concentration exerts a great accelerating effect so that under optimized conditions at 40–50 °C and 20 atm of CO/H2, a virtually complete conversion of linalool has been achieved in 4–6 h. A good control of chemo and stereoselectivity was attained through the appropriate choice of reaction variables. Each of two isomers of hemiacetal can be obtained in ca. 95% chemo- and 85% stereoselectivity.
Keywords: Hydroformylation; Linalool; Rhodium catalysts;
Characterisation, acidity and catalytic activity of Ga–SBA-15 materials prepared following different synthesis procedures by B. Jarry; F. Launay; J.P. Nogier; V. Montouillout; L. Gengembre; J.L. Bonardet (177-186).
Incorporation or grafting of gallium atoms in/on mesoporous SBA-15 silicas was carried out using four different procedures. The structure and texture of the materials obtained were characterised by classical methods (X-ray diffraction, TEM, porosimetry measurements, XPS, 71Ga NMR spectroscopy). Acidity of the solids was evaluated by ammonia adsorption, TPD of this gas and FTIR spectroscopy of adsorbed probes (2,6-dimethylpyridine and deuterated acetonitrile). Catalytic activity was tested first in the isomerisation of α-pinene and second in the oxidative cleavage of cyclohexene oxide. In this latter case, the results are compared with those obtained in the presence of Al–SBA-15 catalysts prepared under similar conditions.
Keywords: Gallia–silica; Grafting; Co-hydrolysis; Acidity characterisation; α-Pinene isomerisation;
Active state of tungsten oxides on WO3/ZrO2 catalyst for steam reforming of dimethyl ether combined with CuO/CeO2 by Kengo Oka; Toshiya Nishiguchi; Hiroyoshi Kanai; Kazunori Utani; Seiichiro Imamura (187-191).
Steam reforming of dimethyl ether (DME) was carried out over WO3/ZrO2–CuO/CeO2 catalysts. The effect of the method of preparation of WO3/ZrO2 on its activity was investigated. Three kinds of WO3/ZrO2 were prepared by impregnating ammonium paratungstate (APT), ammonium metatungstate (AMT), and tungsten hexachloride (WCl). Although these WO3/ZrO2 catalysts had different activities, no difference was observed in their acidic property. The TG-DTA analysis clarified that the different kinds of W precursors affected the crystallization process of zirconia differently. The interaction with zirconia during calcination gave specific properties to the surface W species that are different from those of the single component WO3. The XPS study on the surface W species showed that H2 production rate depended on the surface WO3 amount and on the W(V)/[W(VI) + W(V)] ratio. Excess WO3 loading brought about the decrease in H2 production due to the formation of inactive bulk WO3. The active surface tungsten species were originated from W(V) components interacting with ZrO2. The APT gave the highest W(V)/[W(VI) + W(V)] ratio and, thus, was the best W precursor among the three.
Keywords: WO3/ZrO2; Steam reforming; Dimethyl ether; Valence state of W; XPS; Hydrogen; TG-DTA;
Optimization of the reaction parameters of epoxidation of allyl alcohol with hydrogen peroxide over TS-2 catalyst by Agnieszka Wróblewska (192-200).
The influence of technological parameters on the epoxidation of allyl alcohol to glycidol with 30 wt.% hydrogen peroxide was presented. The reaction was performed in a autoclave at autogenic pressure and in methanol medium (protic solvent). The influence of the following parameters was investigated: temperature (15–90 °C), the molar ratio AA/H2O2 (0.5–5), methanol concentration in reaction mixture (5–90 wt.%), TS-2 concentration in reaction mixture (0.1–2.0 wt.%) and the reaction time (15–120 min). The optimum conditions were established by the mathematical method of design of experiments (rotatable-uniform design). The received results were described by the following mathematical functions: selectivity of transformation to glycidol in relation to consumed allyl alcohol and hydrogen peroxide and conversion of allyl alcohol and H2O2. The courses of functions for appropriate parameters were plotted in the system of two variable parameters. The optimum parameters of the epoxidation process were established based on the analyses of the layer drawings.
Keywords: TS-2; Titanium-silicalite catalyst; Glycidol; Allyl alcohol; Hydrogen peroxide; Liquid-phase epoxidation;
Synthesis and characterization of turbostratic carbons prepared by catalytic chemical vapour decomposition of acetylene by Li Li; Z.H. Zhu; G.Q. Lu; Z.F. Yan; R. De Marco (201-209).
The turbostratic mesoporous carbon blacks were prepared by catalytic chemical vapour decomposition (CCVD) of acetylene using Ni/MgO catalysts prepared by co-precipitation. The relationship between deposition conditions and the nanostructures of resultant carbon black materials was investigated. It was found that the turbostratic and textural structures of carbon blacks are dependent on the deposition temperature and nickel catalyst loading. Higher deposition temperature increases the carbon crystallite unit volume V nano and reduces the surface area of carbon samples. Moreover, a smaller V nano is produced by a higher Ni loading at the same deposition temperature. In addition of the pore structure and the active metal surface area of the catalyst, the graphitic degree or electronic conductivity of the carbon support is also a key issue to the activity of the supported catalyst. V nano is a very useful parameter to describe the effect of the crystalline structure of carbon blacks on the reactivity of carbon blacks in oxygen–carbon reaction and the catalytic activity of carbon-supported catalyst in ammonia decomposition semi-quantitatively.
Keywords: Carbon black; Catalytic depostion; Turbostratic structure; Catalytic chemical vapour desorption; Ammonia decomposition;
Generating hydrogen-rich fuel-cell feeds from dimethyl ether (DME) using Cu/Zn supported on various solid-acid substrates by Troy A. Semelsberger; Kevin C. Ott; Rodney L. Borup; Howard L. Greene (210-223).
Several incipient wetness prepared catalysts containing copper and zinc were prepared in-house and reactor tested for the production of hydrogen from dimethyl ether steam reforming (DME-SR). The incorporation of copper and zinc onto a solid acid substrate (viz., zeolites ZSM-5 and Y with Si/Al = 2.5–140, γ-Al2O3, and ZrO2) combined the catalytic components for DME hydrolysis to methanol (MeOH) and methanol steam reforming (MeOH-SR) into a single catalyst. Catalyst characterizations included BET surface areas, metal loading, acidity measurements using isopropyl amine, thermogravimetric uptakes of DME, and X-ray diffraction studies. One co-ion exchange sample was tested and was found to be inactive toward DME-SR because of its inactivity toward methanol steam reforming. The most active catalyst was copper–zinc supported on γ-Al2O3, reaching an equilibrium predicted hydrogen yield of 89% (steam-to-carbon ratio (S/C) = 1.5, space-time(τ) = 1.0 s, T = 400 °C, and P abs = 0.78 atm). Of the zeolite-supported Cu/Zn catalysts, copper–zinc supported on zeolite ZSM-5 with a Si–Al ratio of 25 was observed to be the most active with a hydrogen yield of 55% (S/C = 1.5, τ = 1.0 s, T = 275 °C, and P abs = 0.78 atm).
Keywords: Dimethyl ether; Hydrolysis; Zeolites; Methanol; Alumina; Zirconia; Acidity; ZSM-5; Y; Steam reforming; Hydrogen; Fuel cells;
Hydroconversion of n-hexadecane over Pt/WO x –ZrO2 catalysts prepared by a PVA-template coprecipitation route by A. Martínez; G. Prieto; M.A. Arribas; P. Concepción (224-236).
A series of high surface area tungstated zirconia catalysts (WZ) with tungsten densities in the range of 4.8–9.9 W/nm2 were prepared by a coprecipitation route in the presence of polyvinyl alcohol (PVA) at a constant pH of 10 and final oxidation at 800 °C. Bifunctional catalysts were obtained by impregnating Pt (1 wt.%) on the calcined WZ samples. The materials were characterized by XRD, N2 adsorption, Raman spectroscopy, DRIFTS of adsorbed CD3CN, and H2 chemisorption, and then evaluated for the hydroconversion of n-hexadecane taken as representative molecule of the long-chain n-alkanes produced in Fischer–Tropsch processes. Raman spectroscopy clearly revealed that saturation of the zirconia surface was attained at a tungsten density of 6.9 W/nm2, which practically matched the theoretical monolayer coverage. IR of adsorbed CD3CN on pre-reduced Pt/WZ samples showed the presence of Brönsted acid sites of lower strength at W surface coverages below the monolayer. The n-C16 conversion rate sharply increased with tungsten density and reached its maximum at the monolayer coverage. Interestingly, we found that the product selectivity significantly varied with the tungsten surface coverage. Thus, the highest hydroisomerization selectivity was obtained for Pt/WZ with a tungsten density below the monolayer capacity. The trends in activity and selectivity have been rationalized on the basis of differences in acid properties of the Pt promoted tungstated zirconias. The activity and product selectivity of Pt/WZ materials were compared with that of bifunctional catalysts based on USY zeolite and amorphous silica–alumina.
Keywords: Tungstated zirconia; Platinum; Bifunctional catalyst; n-Hexadecane; Fischer–Tropsch; Hydroisomerization; Hydrocracking; Raman spectroscopy; DRIFTS of adsorbed acetonitrile;
Sintering of nickel catalysts: Effects of time, atmosphere, temperature, nickel-carrier interactions, and dopants by Jens Sehested; Johannes A.P. Gelten; Stig Helveg (237-246).
Supported nickel catalysts are widely used in the steam-reforming process for industrial scale production of hydrogen and synthesis gas. This paper provides a study of sintering in nickel-based catalysts (Ni/Al2O3 and Ni/MgAl2O4). Specifically the influence of time, temperature, atmosphere, nickel-carrier interactions and dopants on the rate of sintering is considered. To probe the sintering kinetics, all catalysts were analyzed by sulfur chemisorption to determine the Ni surface area. Furthermore selected samples were further analyzed using X-ray diffraction (XRD), mercury porosimetry, BET area measurements, and electron microscopy (EM). The observed sintering rates as a function of time, temperature, and P H 2 O / P H 2 ratio were consistent with recent model predictions [J. Sehested, J.A.P. Gelten, I.N. Remediakis, H. Bengaard, J.K. Nørskov, J. Catal. 223 (2004) 432] over a broad range of environmental conditions. However, exposing the catalysts to severe sintering conditions the loss of nickel surface area is faster than model predictions and the deviation is attributed to a change in the sintering mechanism and nickel removal by nickel-carrier interactions. Surprisingly, alumina-supported Ni particles grow to sizes larger than the particle size of the carrier indicating that the pore diameter does not represent an upper limit for Ni particle growth. The effects of potassium promotion and sulfur poisoning on the rates of sintering were also investigated. No significant effects of the dopants were observed after ageing at ambient pressure. However, at high pressures of steam and hydrogen (31 bar and H2O:H2 = 10:1) potassium promotion increased the sintering rate relative to that of the unpromoted catalyst. Sulfur also enhances the rate of sintering at high pressures, but the effect of sulfur is less than for potassium.
Keywords: Sintering; Nickel; Steam-reforming; Sulfur; Potassium;
Studies on bulk metal phosphate catalysts for the ammoxidation of 2-methylpyrazine by Ch. Srilakshmi; N. Lingaiah; P. Nagaraju; P.S. Sai Prasad; Kalevaru V. Narayana; A. Martin; B. Lücke (247-253).
Various bulk metal (Nb, Zr, Al, Fe, Sb) phosphates were prepared, characterized and evaluated for the vapour phase selective synthesis of 2-cyanopyrazine by the ammoxidation of 2-methylpyrazine. Furthermore, well-known vanadium phosphates like α- and β-VOPO4 were also prepared, tested and compared their performance with that of bulk metal phosphates as described above. Catalysts containing the M＝O bond seemed to be highly active compared to those not containing it. The ease of transformation of the catalysts into their ammonium compounds facilitates high selectivity. FePO4 exhibited extremely high selectivity (ca. 100%) at ca. 20% conversion of 2-methylpyrazine compared to all other metal phosphates. Acidity characteristics of the different metal phosphates are found to show strong influence on the catalytic performance of the catalysts. Among all the metal phosphates investigated in the present study, α-VOPO4 displayed the highest acidity.
Keywords: Ammoxidation; 2-Methylpyrazine; Acidity measurements–potentiometric titration; Various metal phosphates; XRD; FT-IR studies;
Characterization and catalytic investigation of NO + CO reaction on perovskites of the general formula La x M1 − x FeO3 (M = Sr and/or Ce) prepared via a reverse micelles microemulsion route by A.E. Giannakas; A.A. Leontiou; A.K. Ladavos; P.J. Pomonis (254-262).
Four different perovskite type solids with nominal composition LaFeO3 (LFOr), La0.85Sr0.15FeO3 (LSFOr), La0.8Sr0.1Ce0.1FeO3 (LSCFOr) and La0.8Ce0.2FeO3 (LCFOr) were prepared via a reverse micelles microemulsion route. The aim of this work was to investigate the effect of doping with Sr and Ce in the structural properties, surface area and catalytic properties of final solids in comparison with the undoped reference solid LaFeO3. The microemulsion system which was used is composed of cetyl-trimethyl-ammonium-bromide (CTAB), 1-butanol, n-octane and nitrate salts of the metals. XRD measurements combined with Rietveld analysis helped us to identify the % quantity of structural phases which were formed. Scanning electron microscopy (SEM) images showed that the obtained solids consist of nanoparticles in the range of 20–80 nm. BET experiments showed that the final solids achieve much higher specific surface area (ssa) (30–61 m2/g) than similar solids which have been prepared by other methods. Catalytic tests in NO + CO reaction were made with the use of gases He/NO/CO in the ratio 96/2/2 with a total flow rate of 100 cm3/min. The full sequence of catalytic activity of tested solids is LCFOr > LSCFOr > LSFOr ≥ LFOr and this sequence is in full agreement with the sequence of increment of ssa of the solids.
Keywords: Perovskites; Ce; Sr; NO + CO; Reverse microemulsion;
Autothermal reforming of methanol using paper-like Cu/ZnO catalyst composites prepared by a papermaking technique by Hirotaka Koga; Shuji Fukahori; Takuya Kitaoka; Akihiko Tomoda; Ryo Suzuki; Hiroyuki Wariishi (263-269).
Copper-zinc oxide catalyst/ceramic fiber composites were successfully prepared using a papermaking technique. As-prepared catalyst materials, called catalyst paper, were used in autothermal reforming (ATR) of methanol to produce hydrogen for fuel cell applications. The performance of the catalyst paper for hydrogen production in the ATR process at 250 °C was twice as high as that of commercially available catalyst pellets. The concentration of carbon monoxide, which acts as a catalytic poison for the Pt anode electrocatalyst of fuel cells, decreased remarkably. Furthermore, the gas generation with catalyst paper was much more stable than with catalyst powder or with pellets, resulting in constant hydrogen production. Such interesting features may be caused by the unique porous structure of paper composites that allows heat and reactants to be supplied effectively onto the catalyst surfaces. In addition, the ATR stability with catalyst paper improved considerably when ZSM-5 zeolite was mixed within the catalyst paper. Therefore, the porous, flexible and easy-to-handle catalyst paper is expected to be a promising catalytic material for enhancing practical performance in the catalytic reforming process.
Keywords: Catalyst paper; Paper fabrication; Autothermal reforming; Hydrogen production; Reforming stability;
Chromium-exchanged zeolite (CrE-ZSM-5) as catalyst for alcohol oxidation and benzylic oxidation with t-BuOOH by Zoubida Lounis; Abdelkhalek Riahi; Fatiha Djafri; Jacques Muzart (270-272).
The oxidative properties of chromium-exchanged zeolite (CrE-ZSM-5) towards the oxidation of alcohols and benzylic methylene groups with t-butyl hydroperoxide have been evaluated. In most cases, high yields of ketones have been obtained. Experimental evidence is presented that these reactions were, at least in part, homogeneously catalyzed by leached chromium.
Keywords: Chromium-exchanged zeolite; CrE-ZSM-5; t-Butyl hydroperoxide; Alcohol oxidation; Benzylic oxidation; Leaching;
Calendar of Forthcoming Events (273-274).