Gérard Delahay

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Dimas Firmanda Al Riza

University of Brawijaya

David Seamon

Kansas State University

Sadhan Mahapatra

Tezpur University

Leigh Aldous

King's College London

Yasna L Schifferli

Alireza Keyhani

University of Tehran

Hakeem Niyas

Rajiv Gandhi Institute Of Petroleum Technology

Mohamed Radid

Université Hassan II-Mohammedia

Jong R Kim

Nazarbayev University

C. Masquelier

Université de Picardie Jules Verne

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Papers by Gérard Delahay

Light hydrocarbons ammoxidation into acetonitrile over Mo–ZSM-5 catalysts: Effect of molybdenum precursor

by mourad Mhamdi, Gérard Delahay, and A. Ghorbel

Microporous and Mesoporous Materials, 2016

Effect of the chromium precursor nature on the physicochemical and catalytic properties of Cr-ZSM-5 catalysts: Application to the ammoxidation of ethylene

by mourad Mhamdi, A. Guerrero-ruiz, Gérard Delahay, and A. Ghorbel

Journal of Molecular …, Jan 1, 2011

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Sol�gel derived mesoporous Cr/Al 2 O 3 catalysts for SCR of NO by ammonia

by mourad Mhamdi and Gérard Delahay

J Porous Mat, 2010

Catalytic performances of Cr/Al 2 O 3 catalysts were investigated in Selective Catalytic Reductio... more Catalytic performances of Cr/Al 2 O 3 catalysts were investigated in Selective Catalytic Reduction (SCR) of NO by NH 3 in the presence of oxygen. Solids were prepared either by sol-gel method or by impregnation and were characterized by different techniques such as chemical analysis, N 2 physisorption, XRD, 27 Al MAS NMR, DRIFT, UV-Vis Diffuse Reflectance (DRS), Raman Spectroscopy and Temperature Programmed Reduction by H 2 (H 2 -TPR). The physisorption of N 2 at 77 K reveals that solids are mesoporous. On the other hand, XRD shows that xerogels are amorphous but supercritical drying leads to a nanosized crystallite state. No crystalline a-Cr 2 O 3 was found which indicate that metal species reside essentially on the surface of Al 2 O 3 and their size measured less than 4 nm. Furthermore, 27 Al MAS NMR reveals that part of chromium ions occupies sites on/in Al 2 O 3 in close vicinity of tetrahedral 27 Al. This, apparently, is not the case for aerogels. DRIFT results show that there is a consumption of hydroxyl groups of alumina after calcination. The esterification reaction between hydroxyl groups and chromium oxide during calcination leads to the formation of anchored (poly-)chromates according to DRS, Raman, and H 2 -TPR results. The catalysts are active in the studied reaction by NH 3 and the activity is principally governed by preparation method and operating conditions. When compared to xerogels, aerogels are more active in NO reduction and less selective toward N 2 O. Preparation method and drying mode seem to involve the predominance of active species which are essentially mono and polychromates but Cr 3? ions incorporated inside alumina seem to be inactive.

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Solid–State Ion Exchange of Molybdenum ( VI ) Acetylacetonate into ZSM-5 Zeolite

by mourad Mhamdi, Gérard Delahay, and A. Ghorbel

Thermochimica Acta, 2017

Selective catalytic reduction of NOx by NH3 on V-Mo-zeolite prepared by solid-state ion exchange method

by Gérard Delahay, mourad Mhamdi, and A. Ghorbel

Studies in Surface Science and Catalysis, 2008

V-Mo-Zeolite catalysts prepared by solid-state ion exchange were studied in the selective catalyt... more V-Mo-Zeolite catalysts prepared by solid-state ion exchange were studied in the selective catalytic reduction of NOx by ammonia. The catalysts were characterized by chemical analysis, X-ray powder diffraction, N2 adsorption (BET), DRIFT, UV-Vis and Raman, spectroscopy and H2 TPR. Catalytic results show that upon addition of Mo to V-ZSM-5, catalytic performance was enhanced compared to V-ZSM-5.

Sol–gel derived mesoporous Cr/Al2O3 catalysts for SCR of NO by ammonia

by mourad Mhamdi and Gérard Delahay

Journal of Porous Materials, 2010

Catalytic performances of Cr/Al2O3 catalysts were investigated in Selective Catalytic Reduction (... more Catalytic performances of Cr/Al2O3 catalysts were investigated in Selective Catalytic Reduction (SCR) of NO by NH3 in the presence of oxygen. Solids were prepared either by sol–gel method or by impregnation and were characterized by different techniques such as chemical analysis, N2 physisorption, XRD, 27Al MAS NMR, DRIFT, UV–Vis Diffuse Reflectance (DRS), Raman Spectroscopy and Temperature Programmed Reduction by H2

Influence of the V+Mo/Al ratio on vanadium and molybdenum speciation and catalytic properties of V–Mo–ZSM-5 prepared by solid-state reaction

by Gérard Delahay, mourad Mhamdi, and A. Ghorbel

Catalysis Today, 2009

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Selective catalytic reduction of NO with NH3 over HZSM-5-supported fe-cu nanocomposite catalysts: The fe-cu bimetallic effect

by mourad Mhamdi, Gérard Delahay, and A. Ghorbel

Ammoxidation of ethylene to acetonitrile over Cr-ZSM-5 catalysts

by mourad Mhamdi, Gérard Delahay, and A. Ghorbel

Studies in Surface Science …, Jan 1, 2008

A series of Cr/Al 2 O 3 and Co/Al 2 O 3 catalysts were tested in the selective ammoxidation of et... more A series of Cr/Al 2 O 3 and Co/Al 2 O 3 catalysts were tested in the selective ammoxidation of ethylene to acetonitrile. Catalysts were prepared either by sol-gel method or by impregnation with chromium or cobalt acetylacetonate salts. Physicochemical properties of catalysts were accomplished by several techniques such as chemical analysis, physisorption of N 2 , X-ray diffraction (XRD), 27 Al MAS NMR, UV-Visible diffuse reflectance (DRS) and Raman spectroscopy and temperature programmed reduction of H 2 (H 2 -TPR). Textural analysis reveals that mesoporous materials with pronounced surface areas were obtained using sol-gel procedure while impregnation of the support produces a moderate decrease of its surface area and pore volume. XRD analysis confirms the presence of highly dispersed metal species which reside essentially on the surface and measure less than 4 nm. Furthermore, 27 Al MAS NMR shows that for xerogels, part of metal species occupies sites on/in A1 2 O 3 in close vicinity of octahedral 27 Al. This, apparently, is not the case for aerogels. For Cr/Al 2 O 3 catalysts, isolated Cr 6? , mono and polychromate species were identified using DRS, Raman Spectroscopy and H 2 -TPR which seem to play a key role in the ammoxidation of ethylene. Furthermore, for cobalt doped catalysts, CoAl 2 O 4 was identified as active phase on the basis of DRS and H 2 -TPR results. From the supercritical drying, it results generally better catalysts than catalysts calcined by ordinary procedure which leads to inactive agglomerated Co 3 O 4 and CoO-Al 2 O 3 phase.

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Cr-ZSM-5 catalysts for ethylene ammoxidation: Effects of precursor nature and Cr/Al molar ratio on the physicochemical and catalytic properties

by mourad Mhamdi, Gérard Delahay, and A. Ghorbel

Microporous and Mesoporous Materials, 2013

Cr-ZSM-5 catalysts prepared by solid-state ion exchange with different Cr/Al molar ratios were ch... more Cr-ZSM-5 catalysts prepared by solid-state ion exchange with different Cr/Al molar ratios were characterized and tested in ethylene ammoxidation to acetonitrile in the temperature range 425-500°C. Starting from Cr acetate like precursor and lower Cr load (Cr/Al = 0.5), small amount of chromate species, sited inside the zeolite matrix, exhibited lower catalytic activity in ammoxidation (12.5% of CH 3 CN yield). Increasing the Cr amount (Cr/Al = 1) does not significantly improve the catalytic properties since agglomerates of amorphous Cr 2 O 3 inhibited the accessibility of chromate species to the reactants. However, at higher Cr amount (Cr/Al = 1.5), crystalline Cr 2 O 3 particles reduced the diffusion of reactants to the internal active sites. Starting from Cr chloride like precursor, the corresponding solids are low-exchanged since CrCl 3 evaporates. At Cr/Al molar ratios of 0.5 and 1, chromate species, sited in the exchange sites, exhibited interesting catalytic properties (18.5 and 25% of CH 3 CN yield at 500°C, respectively). Nevertheless, at higher metal load (Cr/Al = 1.5), the excess of Cr transforms into crystalline Cr 2 O 3 which inhibits the diffusion of reactants to the active sites and enhances the hydrocarbon oxidation mainly at low temperatures. As ethylene ammoxidation required ammonia activation over (poly)chromate sites, a possible pathway of such a step has been proposed on the basis of NH 3 -TPD results.

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Selective catalytic reduction of NOx by NH 3 on V-Mo-zeolite prepared by solid-state ion exchange method

by Gérard Delahay, mourad Mhamdi, and A. Ghorbel

Studies in Surface Science and Catalysis, 2008

Selective catalytic reduction of nitric oxide with ammonia on copper (II) ion-exchanged offretite

by Gérard Delahay and A. Ghorbel

Catalysis Communications, 2005

Copper K-offretite catalysts prepared by ion exchange were characterized by XRD, H2-TPR and evalu... more Copper K-offretite catalysts prepared by ion exchange were characterized by XRD, H2-TPR and evaluated in the selective catalytic reduction of NO (NO-SCR) by ammonia. Despite several successive exchanges, the quantity of copper introduced remains low and the exchange ratio does not exceed 50%. The NO conversion profiles have a sigmoid curve shape. Full NO conversion in N2 is reached above

Recent Advances in Cu I/II Y: Experiments and Modeling

Catalysis Reviews-science and Engineering, 2006

An overview of the CuY material is performed on the basis of the results obtained during the last... more An overview of the CuY material is performed on the basis of the results obtained during the last 5 years on their structure (nature of the Cu species, siting, coordination …), their use and reactivity, based on TPR, XRD and various ex situ and in situ spectroscopies such as XAS, IR and EPR. A brief summary of previous work is

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N 2O decomposition in the presence of ammonia on faujasite-supported metal catalysts

Applied Catalysis B-environmental, 1999

The reduction of N2O to N2 was carried out by temperature programmed surface reaction (TPSR) from... more The reduction of N2O to N2 was carried out by temperature programmed surface reaction (TPSR) from 473 to 873K in He, He+3% O2, He+0.02% NH3 and He+3% O2+0.02% NH3 on H–FAU supported transition metal catalysts. In the absence of oxygen, the addition of NH3 considerably shifts the N2O conversion profile towards lower temperatures. This is particularly true for the Ru–

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EPR Investigation of Fe-Exchanged Beta-Zeolites

by Gérard Delahay and Antoine Aboukaïs

Langmuir, 2003

ABSTRACT

Selective catalytic reduction of NO by NH3 on Cu-faujasite catalysts: an experimental and quantum chemical approach

Chemphyschem : a European journal of chemical physics and physical chemistry, Jan 16, 2002

The selective catalytic reduction (SCR) of NO by NH3 in the presence of O2 on Cu-faujasite (Cu-FA... more The selective catalytic reduction (SCR) of NO by NH3 in the presence of O2 on Cu-faujasite (Cu-FAU) has been studied. Substitution of some Cu2+ with H+ and Na+ cations, compensating for the negative charge of the zeolite framework, forms the various CuHNa-FAU studied. The amount of Cu was held constant and the proportion of H+ and Na+ varied in the sample. The substitution of Na+ for H+ increases sharply the SCR rate by lowering the temperature of reaction by about 150 K. It is proposed that the rate increase mainly comes from an unhindered migration of Cu from hidden to active sites and a modification of the redox properties of Cu species. The former was demonstrated by diffuse reflectance IR spectroscopy of adsorbed CO. The change in redox properties was demonstrated by a faster oxidation of Cu+ to Cu2+ (rate-determining step). Quantum chemical calculations on model clusters of CuHNa-FAU indicate that the faster rate of oxidation can be explained by a higher lability of protons in...

Influence of co-cations in the selective catalytic reduction of NO by NH3 over copper exchanged faujasite zeolites

The effect of a co-cation (Cs, Ba, Ca, Sr, Ba, La, Ce, Sm, Dy, Yb) on the properties of Cu exchan... more The effect of a co-cation (Cs, Ba, Ca, Sr, Ba, La, Ce, Sm, Dy, Yb) on the properties of Cu exchanged faujasite catalysts in the selective catalytic reduction (SCR) of NO by NH 3 in an oxidising atmosphere has been studied. Temperature programmed reduction (TPR) by H 2 of Cu-faujasite (Cu-FAU) was used as a tool to identify and quantify the nature and location of Cu species. The 'blocking' of sodalites cages of Cu-FAU by alkali earth or lanthanide ions enhanced the SCR activity at low temperature (LT) and made the reaction fully selective towards N 2 in the whole temperature range studied (up to 773 K). The formation of N 2 O in Cu-FAU zeolites results from the reaction between nitrogen monoxide and ammonia on next-nearest-neighbour (NNN) Cu ions located in sodalite cages.

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Influence of the preparation method on the properties of Fe-ZSM-5 for the selective catalytic reduction of NO by n-decane

The selective catalytic reduction of NO by n-decane was studied on Fe-ZSM5 catalysts prepared by ... more The selective catalytic reduction of NO by n-decane was studied on Fe-ZSM5 catalysts prepared by chemical vapor deposition and solidstate ion exchange from FeCl 3 , ligand exchange from iron acetylacetonate in toluene, and impregnation or ion exchange with iron nitrate in water. These catalysts were characterized using a wide variety of techniques. Activity tests were carried out by temperature-programmed surface reaction (TPSR) or at steady state. The most active materials were those characterized by the presence of iron species reducible at approximately 640 K, and assigned to cationic iron oxo species such as [(OH)-Fe-O-Fe-(OH)] 2+ . The NO conversion during steady-state experiments was lower than in TPSR tests, due to the build-up of a carbonaceous deposit. Water and SO 2 reversibly poisoned the NO conversion. #

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The simultaneous catalytic reduction of NO and N 2O by NH 3 using an Fe-zeolite-beta catalyst

Applied Catalysis B-environmental, 2000

An Fe-Zeolite-beta (Fe-BEA) catalyst, composed only of Fe cations or oxocations in charge compens... more An Fe-Zeolite-beta (Fe-BEA) catalyst, composed only of Fe cations or oxocations in charge compensation sites of the zeolite, is active in the simultaneous removal of NO (1500ppm) and N2O (1000ppm) by NH3 (2500ppm) in the presence of O2 (3vol.%). In temperature-programmed surface reaction (TPSR) experiments (ramp: 10Kmin−1 from 423 to 823K, space velocity: 200,000h−1), the light-off temperature, at 50% conversion,

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Selective Catalytic Reduction of Nitrous Oxide by Ammonia on Iron Zeolite Beta Catalysts in an Oxygen Rich Atmosphere: Effect of Iron Contents

Journal of Catalysis, 2001

A series of iron-exchanged zeolite beta (BEA) has been characterized by temperature programmed de... more A series of iron-exchanged zeolite beta (BEA) has been characterized by temperature programmed desorption (TPD) of oxygen and tested in the catalytic reduction of N2O by NH3. TPD of O2 has clearly shown that iron-oxo species formed upon reoxidation by nitrous oxide of Fe2+-BEA are more labile than those generated by calcination in air. In the selective catalytic reduction of

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Light hydrocarbons ammoxidation into acetonitrile over Mo–ZSM-5 catalysts: Effect of molybdenum precursor

by mourad Mhamdi, Gérard Delahay, and A. Ghorbel

Microporous and Mesoporous Materials, 2016

Effect of the chromium precursor nature on the physicochemical and catalytic properties of Cr-ZSM-5 catalysts: Application to the ammoxidation of ethylene

by mourad Mhamdi, A. Guerrero-ruiz, Gérard Delahay, and A. Ghorbel

Journal of Molecular …, Jan 1, 2011

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Sol�gel derived mesoporous Cr/Al 2 O 3 catalysts for SCR of NO by ammonia

by mourad Mhamdi and Gérard Delahay

J Porous Mat, 2010

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