Catalysis Letters

article

Suppressed hydrogen chemisorption of zeolite encaged metal clusters: discrimination between theoretical models on the basis of Ru/NaY

T.J. McCarthy, C.M.P. Marques, H. Treviño, W.M.H. Sachtler

Catalysis Letters > 1997 > 43 > 1-2 > 11-18

The effects of thermal treatment and zeolite proton concentration on the chemical state and metal particle size of zeolite Y supported ruthenium (3.0 wt%) have been investigated using H₂-TPR, H₂-TPD, TPMS, FTIR, TEM, and EXAFS. Heating in Ar of the precursor after ion exchange, [Ru(NH₃)₆]³⁺/NaY, up to 400°C leads to nearly 100% autoreduction of the ruthenium, as evidenced by H₂-TPR and TPMS. Heating...

article

Influence of cocation on catalytic activity of CuMOR catalysts for NO SCR by propene. Effect of water presence

C. Torre-Abreu, M.F. Ribeiro, C. Henriques, F.R. Ribeiro

Catalysis Letters > 1997 > 43 > 1-2 > 25-29

Catalytic activity of CuMOR catalysts for NO selective catalytic reduction by propene was investigated as a function of the cocation (H, Na, Cs, Mg and Ba) present in the zeolite. It was verified that the cocation plays an important role in the CuMOR activity, its effect being more pronounced at low temperatures. Moreover, the results suggest that we can prevent the catalyst deactivation by choosing...

article

Characterisation of the active phase in caesium-doped iron-vanadium-oxide catalysts for the selective oxidation of polyaromatics

A.P.E. York, A. Brückner, P.-M. Wilde, H. Mehner, more

Catalysis Letters > 1997 > 43 > 1-2 > 107-115

The addition of caesium sulphate to unsupported vanadium-iron-oxide materials leads to the formation of an amorphous non-stoichiometric phase, as well as the crystalline phases, FeVO₄, Fe₂V₄O₁₃, and Fe_1-XS (pyrrhotite). Caesium was only present in the amorphous parts of the sample, and the amount of the new phase formed was found to vary depending on the vanadium:iron ratio and the amount of caesium...

article

The characterization of a highly effective NiO/MgO solid solution catalyst in the CO₂ reforming of CH₄

Y.H. Hu, E. Ruckenstein

Catalysis Letters > 1997 > 43 > 1-2 > 71-77

A NiO/MgO catalyst prepared by impregnation, which reduced in H₂ had very high CO yield and stability in CO₂ reforming of methane, was investigated by XPS, XRD, BET and pulse-MS response. This catalyst was compared to that obtained by mechanical mixing of powders of the two oxides. It was found that the entire NiO formed a solid solution with MgO in the former catalyst, while only a fraction of NiO...

article

Characterization of vanadia-silica and titania-silica aero- and xerogels by acid-base probe reactions

Á. Molnár, M. Bartók, M. Schneider, A. Baiker

Catalysis Letters > 1997 > 43 > 1-2 > 123-126

The acid-base properties of 10 wt% V₂O₅-SiO₂ and 10 wt% TiO₂-SiO₂ binary mixed oxide aero- and xerogels were determined by studying the transformation of methyloxirane and 1-butane. The transformations (the isomerization of methyloxirane to propanal and the double-bond migration of 1-butene to form isomeric 2-butenes) indicate that all samples contain mainly acidic sites. Correlations are shown to...

article

Partial oxidation of methane to synthesis gas over Rh/α-Al₂O₃ at high temperatures

J.C. Slaa, R.J. Berger, G.B. Marin

Catalysis Letters > 1997 > 43 > 1-2 > 63-70

The partial oxidation of methane to synthesis gas has been studied in a continuous flow reactor using a Rh/α-Al₂O₃ catalyst under conditions as close as possible to those industrially relevant: pressures up to 800 kPa and temperatures higher than 1274 K in order to avoid the formation of carbon and to obtain high equilibrium selectivities to CO and H₂. Intrinsic kinetic data were obtained when the...

article

Characterization of supported Pd-Cu bimetallic catalysts by SEM, EDXS, AES and catalytic selectivity measurements

J. Batista, A. Pintar, M. Ceh

Catalysis Letters > 1997 > 43 > 1-2 > 79-84

Pd-Cu/γ-Al₂O₃ bimetallic catalysts were prepared according to different impregnation sequences of γ-Al₂O₃ and characterized by XRD, SEM, EDXS and AES. The catalysts were tested for the selective hydrogenation of aqueous nitrate solutions to nitrogen. The reaction selectivity was found to be dependent on the catalyst preparation procedures, which affect the spatial distribution of metallic copper and...

article

CO bonding and hydrogenation activity of promoted noble metal catalysts during restructuring in high-pressure CO hydrogenation: FeIr/SiO₂

L.M.P. van Gruijthuijsen, S.P.A. Louwers, R.A. van Santen, J.W. Niemantsverdriet

Catalysis Letters > 1997 > 43 > 1-2 > 45-49

Bimetallic FeIr/SiO₂ catalysts that are active for methanol production from synthesis gas (CO+H₂) bind CO less strongly, and exhibit higher activity for the hydrogenation of ethylene in the presence of CO, than catalysts that produce mainly methane. It is argued that promotion of the noble metal serves to weaken the adsorption of CO, thereby lowering its tendency to dissociate, and, most importantly,...

article

Catalytic oxidation of styrene by manganese(II) bipyridine complex cations immobilized in mesoporous Al-MCM-41

S.-S. Kim, W. Zhang, T.J. Pinnavaia

Catalysis Letters > 1997 > 43 > 1-2 > 149-154

Manganese 2,2'-bipyridine (bpy) complex cations, [Mn(bpy)₂]²⁺, have been immobilized in mesoporous Al-MCM-41 (Si/Al=9) and used as a catalyst for the oxidation of styrene by iodosylbenzene, H₂O₂ and tert-butyl hydroperoxide (TBHP). The oxidation products included epoxide, diol and aldehyde. Al-MCM-41-immobilized [Mn(bpy)₂]²⁺ exhibited a higher catalytic activity for styrene oxidation than the corresponding...

article

The role of methyl radicals in the reduction of NO by CH₄ over a Ba/MgO catalyst

S. Xie, M.P. Rosynek, J.H. Lunsford

Catalysis Letters > 1997 > 43 > 1-2 > 1-5

Under conventional flow conditions at 760 Torr, 4 mol% Ba/MgO is an effective catalyst for the reduction of NO by CH₄. The conversion of NO at 700°C is increased ca. threefold when O² is added to the system. When reactions are carried out at 500 mTorr, CH₃· radicals are detected in the gas phase over the catalyst with O₂ as the oxidant, but not with NO as the oxidant. Moreover, CH₃· radicals appear...

article

Adsorption of C₈-hydrocarbons, potential intermediates of skeletal isomerisation of n-butene, in the 10-membered ring zeolite

J. Houzvicka, R. Klik, L. Kubelková, V. Ponec

Catalysis Letters > 1997 > 43 > 1-2 > 7-10

Adsorption of various octenes and octanes was studied with a 10-membered ring molecular sieve, H-[B]ZSM-5. Adsorption of octane was very fast, the double-branched octane diffused slowly, and the triple-branched molecules could not enter the channels of the sample. Since the 10-membered ring molecular sieves are the best catalysts for skeletal isomerisation of n-butene, trimethylpentenes or other larger...

article

Selective oxidation of o-xylene to phthalic anhydride on V₂O₅ supported on TiO₂-coated SiO₂

C.R. Dias, M.F. Portela, M. Galán-Fereres, M.A. Bañares, more

Catalysis Letters > 1997 > 43 > 1-2 > 117-121

A ternary V-Ti-Si catalyst was prepared by depositing the vanadium oxide precursor on a SiO₂ previously coated by TiO₂. The ternary V-Ti-Si catalyst and the corresponding binary V-Ti and V-Si counterparts were tested for the selective oxidation of o-xylene to phthalic anhydride. Silica-supported vanadium oxide shows lowest activity and selectivity, meanwhile selectivity to phthalic anhydride is higher...

article

Homogeneous and supported titanates as catalysts for transesterification of acrylic esters

C. Blandy, J.-L. Pellegatta, P. Cassoux

Catalysis Letters > 1997 > 43 > 1-2 > 139-142

The transesterification of methylmethacrylate with 1-dodecanol has been studied by using Brønsted acid and Lewis acid type catalysts either for homogeneous or heterogeneous systems. Initial rates studies in a batch reactor lead to a greater efficiency for the Lewis acid catalysts (soluble or supported titanates). The activity of the supported catalyst can be linked to the molecular association of...

article

Hydrolytic cleavage of epoxy ring during the epoxidation of alkenes over boron modified titanium silicalites of MFI topology

M.P. Kapoor, D. Trong On, J.E. Gallot, S. Kaliaguine

Catalysis Letters > 1997 > 43 > 1-2 > 127-131

Boron incorporated bifunctional microporous titanium silicalites of MFI topology, which contained both oxidizing and acidic sites, can effectively catalyse the selective epoxidation of α-olefins, followed by ring opening of the epoxide through hydrolysis reactions. Data are presented that correlate the oxidative and acidic functions of these catalysts. The rate of hydrolysis is seen to depend on the...

article

Deactivation of CuMFI catalysts under NO selective catalytic reduction by propene: influence of zeolite form, Si/Al ratio and copper content

C. Torre-Abreu, M.F. Ribeiro, C. Henriques, F.R. Ribeiro, more

Catalysis Letters > 1997 > 43 > 1-2 > 31-36

Deactivation of CuMFI catalysts under NO selective catalytic reduction (SCR) by propene in both the absence and the presence of water was investigated as a function of zeolite form, Si/Al ratio and copper content. It was verified that the CuMFI deactivation extent is higher on H-form zeolite compared to Na-form and decreases when the copper exchange level increases, which can be achieved either by...

article

Interaction between CD₃OH and a H-mordenite studied by ¹H NMR, broad-line at 4 K and MAS at 300 K

L. Heeribout, C. Dorémieux-Morin, L. Kubelkova, R. Vincent, more

Catalysis Letters > 1997 > 43 > 1-2 > 143-147

The simulation of 4 K ¹H broad-line NMR spectra of CD₃OH interacting with the acidic OH groups of H-mordenite zeolite shows no CD₃OH₂ ⁺ ions but hydrogen-bonded complexes. For high CD₃OH concentrations, clusters of hydrogen-bonded methanol molecules are formed, also hydrogen-bonded to Brønsted acid sites of the zeolite. The 300 K ¹H MAS spectra prove that the desorbed H-mordenite sample contains also...

article

CoMo bimetallic nitride catalysts for thiophene HDS

D.-W. Kim, D.-K. Lee, S.-K Ihm

Catalysis Letters > 1997 > 43 > 1-2 > 91-95

CoMo bimetallic nitride catalysts were prepared by temperature-programmed reduction of CoMo oxides with flowing ammonia, and the effects of cobalt addition on the thiophene hydrodesulfurization (HDS) reaction were investigated. MoO₃ transformed into Mo₂N, while cobalt oxide was just reduced to Co metal rather than Co nitride. When Co was added to Mo, the surface area decreased significantly but the...

article

The influence of alkali metals on the activity of supported ruthenium catalysts for the water-gas shift reaction

A. Basinska, F. Domka

Catalysis Letters > 1997 > 43 > 1-2 > 59-61

This paper presents the results of the studies on the influence of alkali metals on the activity of ruthenium catalysts, which were supported on the products of α- and δ-iron oxide-hydroxide calcination. Modification of these supports with alkali metals, in particular potassium, rubidium and cesium, prior to deposition of ruthenium was found to increase the activity of Ru/Fe₂O₃ catalysts in the water-gas...

article

Characterization and catalytic activity of Al₂O₃-supported Pt-Co catalysts

B. Moraweck, R. Fréty, G. Pecchi, M. Morales, more

Catalysis Letters > 1997 > 43 > 1-2 > 85-89

A series of Pt-Co supported on γ-alumina have been prepared from acetylacetonate precursors with 2 wt% as total metal loading and different atomic contents. The catalysts were characterized by hydrogen chemisorption, TPR, TEM, XPS and they were tested in two different reactions: methylcyclohexane dehydrogenation and n-butane hydrogenolysis. The results have shown that platinum is in reduced state...

article

The difference between alkanes and alkenes in the reduction of NO by hydrocarbons over Pt catalysts under lean-burn conditions

R. Burch, T.C. Watling

Catalysis Letters > 1997 > 43 > 1-2 > 19-23

The activities of Pt/SiO₂ and Pt/Al₂O₃ samples with comparable Pt dispersions for the reduction of NO_X under lean-burn conditions using C₃H₈ and C₃H₆ as the reductant is reported. C₃H₆ is more effective than C₃H₈ at reducing NO_X with both catalysts. With C₃H₆, Pt/SiO₂ exhibits greater deNO_X activity than Pt/Al₂O₃, while with C₃H₈ the opposite was observed. Kinetics measurements show that at steady...

INFONA - science communication portal

Catalysis Letters

Suppressed hydrogen chemisorption of zeolite encaged metal clusters: discrimination between theoretical models on the basis of Ru/NaY

Influence of cocation on catalytic activity of CuMOR catalysts for NO SCR by propene. Effect of water presence

Characterisation of the active phase in caesium-doped iron-vanadium-oxide catalysts for the selective oxidation of polyaromatics

The characterization of a highly effective NiO/MgO solid solution catalyst in the CO₂ reforming of CH₄

Characterization of vanadia-silica and titania-silica aero- and xerogels by acid-base probe reactions

Partial oxidation of methane to synthesis gas over Rh/α-Al₂O₃ at high temperatures

Characterization of supported Pd-Cu bimetallic catalysts by SEM, EDXS, AES and catalytic selectivity measurements

CO bonding and hydrogenation activity of promoted noble metal catalysts during restructuring in high-pressure CO hydrogenation: FeIr/SiO₂

Catalytic oxidation of styrene by manganese(II) bipyridine complex cations immobilized in mesoporous Al-MCM-41

The role of methyl radicals in the reduction of NO by CH₄ over a Ba/MgO catalyst

Adsorption of C₈-hydrocarbons, potential intermediates of skeletal isomerisation of n-butene, in the 10-membered ring zeolite

Selective oxidation of o-xylene to phthalic anhydride on V₂O₅ supported on TiO₂-coated SiO₂

Homogeneous and supported titanates as catalysts for transesterification of acrylic esters

Hydrolytic cleavage of epoxy ring during the epoxidation of alkenes over boron modified titanium silicalites of MFI topology

Deactivation of CuMFI catalysts under NO selective catalytic reduction by propene: influence of zeolite form, Si/Al ratio and copper content

Interaction between CD₃OH and a H-mordenite studied by ¹H NMR, broad-line at 4 K and MAS at 300 K

CoMo bimetallic nitride catalysts for thiophene HDS

The influence of alkali metals on the activity of supported ruthenium catalysts for the water-gas shift reaction

Characterization and catalytic activity of Al₂O₃-supported Pt-Co catalysts

The difference between alkanes and alkenes in the reduction of NO by hydrocarbons over Pt catalysts under lean-burn conditions

Filter options

Publication date

Year

Content availability

Keywords

INFONA - science communication portal

Catalysis Letters

Add recipient

Sending message cancelled

Are you sure you want to cancel sending this message?

Send message

Filter options

Publication date

Date range setting

Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.

Year

Content availability

Keywords

Reporting an error / abuse

Sending the report failed

Accessibility options