# overview
Heterogeneous catalytic processes form the basis for much of the chemical and petroleum processing industries. Solid catalysts enable reactions to occur at sufficiently high rates to be commercially feasible. In many cases, proper selection of a suitable catalyst also permits reaction pathways and product selectivities to occur that would not be kinetically possible in the absence of the catalyst. In our laboratory, we employ kinetic measurements of selected reactions, in combination with a variety of optical and surface spectroscopic and physical characterization techniques, to investigate the surface properties and detailed modes of operation of zeolites, metal oxides and supported metal catalysts.

Among the more challenging problems in the field of heterogeneous catalysis is that of selectively oxidizing small alkanes to higher hydrocarbons and oxygenates in high yields. We are currently investigating, for example, the catalyzed oxidative coupling of methane to C2hydrocarbon products. We have established that this reaction occurs via a heterogeneous-homogeneous reaction mechanism, in which the first step is homolytic cleavage of a C-H bond in methane at an O-site on the oxide catalyst surface. The resulting methyl radicals then emanate into the gas phase where they either undergo coupling to the desired C2 products or enter into a series of chain branching homogeneous reactions that lead to the formation of undesired COx products. We are employing x-ray photoelectron, FT-IR and in situ Raman spectroscopies to characterize the nature of the active sites on the catalyst surfaces. Additional studies using isotopic labelling and laser-induced fluorescence spectroscopy are providing details about the mechanism of this complex reaction system. Other projects involve studies of the direct selective oxidation of methane to oxygenates, such as formaldehyde and methanol, and to aromatic products.

# hrJobTitle
Retired Professor and Associate Department Head

# keywords[]
Silver Ions, For Olefin Removal From Gas Stream

# keywords[]
Methane, Oxidative Coupling, Integrated Recycle System

# keywords[]
Effect Of Methane And Carbon Dioxide On Hydroxyl Radicals

# keywords[]
Formation Of Hydroxyl Radicals Over Lanthanum Oxide

# keywords[]
Laser-induced Fluorescence Of Hydroxyl Radicals

# educationAndTraining[].organization.label
Rice University - (Houston, Texas, United States)

# educationAndTraining[].organization.label
University of Wisconsin - Madison - (Madison, Wisconsin, United States)

# educationAndTraining[].organization.label
University of Wisconsin - Madison - (Madison, Wisconsin, United States)

# awardsAndHonors[].label
Association of Former Students College-Level Teaching Distinguished Achievement Award, The

# publications[].label
Steady-state conversion of methane to aromatics in high yields using an integrated recycle reaction system

# publications[].label
MECHANICAL STUDIES ON PROPYLENE OXIDATION ON BISMUTH MOLYBDATE

# publications[].label
CORRELATIONS BETWEEN THE PHYSICAL-CHEMICAL PROPERTIES AND CATALYTIC BEHAVIORS OF ALKALI-METAL GRAPHITE-INTERCALATION COMPOUNDS

# publications[].label
Nitric oxide decomposition and selective catalytic reduction by methane over BaO/MgO catalysts.

# publications[].label
Effect of CH4 and CO2 on the catalytic formation of OH  radicals over La2O3

# publications[].label
CATALYTIC PROPERTIES OF RARE-EARTH OXIDES

# publications[].label
Characterization of surface carbon formed during the conversion of methane to benzene over Mo/H-ZSM-5 catalysts

# publications[].label
AN INFRARED STUDY OF THE DEHYDROGENATION OF ETHYLBENZENE TO STYRENE OVER IRON-BASED CATALYSTS

# publications[].label
In situ Raman evidence for a barium solid state phase that is active in nitric oxide decomposition: influence of preparation parameters

# publications[].label
Destructive adsorption of carbon tetrachloride on lanthanum and cerium oxides

# publications[].label
Conversion of methane to benzene over transition metal ion ZSM-5 zeolites - I. Catalytic characterization

# publications[].label
Formation of hydroxyl radicals from the reaction of water and oxygen over basic metal oxides

# publications[].label
PARTIAL OXIDATION OF METHANE TO CARBON-MONOXIDE AND HYDROGEN OVER A NI/AL2O3 CATALYST

# publications[].label
REACTIONS OF METHYL RADICALS WITH METAL-OXIDES

# publications[].label
Steady-State production of olefins and aromatics in high yields from methane using an integrated recycle reaction system

# publications[].label
Skeletal isomerization of hexane over Pt/H-beta zeolites: Is the classical mechanism correct?

# publications[].label
Conversion of methane to benzene over transition metal ion ZSM-5 zeolites - II. Catalyst characterization by x-ray photoelectron spectroscopy

# publications[].label
Steady-state conversion of methane to C4+ aliphatic products in high yields using an integrated recycle reactor system

# publications[].label
Oxidative coupling of methane over Mn/Na2WO4/MgO and related catalysts.

# publications[].label
Characterization of a Mo/ZSM-5 catalyst for the conversion of methane to benzene

# publications[].label
THE ROLE OF SODIUM-CARBONATE AND OXIDES SUPPORTED ON LANTHANIDE OXIDES IN THE OXIDATIVE DIMERIZATION OF METHANE

# publications[].label
Low-temperature destructive adsorption of carbon tetrachloride on barium oxide.

# publications[].label
Rebuttal to the Comment on "The role of methyl radicals in the reduction of NO by CH4 over a Ba MgO catalyst"

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Effect of CH4 and CO2 on the catalytic formation of OH center dot radicals over La2O3

# publications[].label
REACTION OF STEAM WITH COKE ON SOLID SUBSTRATES.

# publications[].label
Characterization of Ga/ZSM-5 for the catalytic aromatization of dilute ethylene streams

# publications[].label
SITE DIFFERENTIATION IN HOMOLYTIC VS HETEROLYTIC ACTIVATION OF METHANE OVER BA MGO CATALYSTS

# publications[].label
Decomposition of nitric oxide over barium oxide supported on magnesium oxide .3. In situ Raman characterization of the role of oxygen

# publications[].label
The role of methyl radicals in the reduction of NO by CH4 over a Ba/MgO catalyst

# publications[].label
Catalytic reactions of NO over 0-7 mol% Ba/MgO catalysts - I. The direct decomposition of NO

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HYDROXYL RADICAL FORMATION DURING THE REACTION OF OXYGEN WITH METHANE OR WATER OVER BASIC LANTHANIDE OXIDE CATALYSTS

# publications[].label
NATURE OF ACTIVE-SITES ON CATALYTIC ALUMINA - INFORMATION FROM SITE POISONING BY SULFUR-CONTAINING MOLECULES

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KINETICS AND MECHANISM OF NORMAL-BUTENE ISOMERIZATION OVER ACTIVATED LANTHANUM OXIDE

# publications[].label
HYDROCARBON SYNTHESIS AND CARBON-DIOXIDE ADSORPTION ON IRON CATALYSTS

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PREPARATION AND CHARACTERIZATION OF CATALYTIC LANTHANUM OXIDE

# publications[].label
REACTION OF STEAM WITH COKE ON SOLID SUBSTRATES

# publications[].label
OXIDATIVE COUPLING OF METHANE OVER OXIDE-SUPPORTED SODIUM-MANGANESE CATALYSTS (VOL 155, PG 390, 1995)

# publications[].label
DOUBLE NATURE OF GAMMA ALUMINUM CATALYSTS - ISOMERIZATION AND D2 EXCHANGE-REACTIONS OF 1-BUTENE

# publications[].label
Characterization of Ga/ZSM-5 for the catalytic aromatization of dilute ethylene streams

# publications[].label
SECONDARY REACTIONS OF METHYL RADICALS WITH LANTHANIDE OXIDES - THEIR ROLE IN THE SELECTIVE OXIDATION OF METHANE

# publications[].label
CHARACTERIZATION OF CATALYTIC LANTHANUM OXIDE FOR DOUBLE-BOND ISOMERIZATION OF N-BUTENES

# publications[].label
PROPERTIES OF LANTHANIDE OXIDES AS SUPPORTS FOR DISPERSED IRON, COBALT, AND NICKEL-CATALYSTS

# publications[].label
The conversion of methane to benzene over Mo/ZSM-5 zeolites in the absence of an oxidant

# publications[].label
Catalytic conversion of methane and ethylene to propylene

# publications[].label
Catalytic Reactions of NO over 07 mol% Ba/MgO Catalysts

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Conversion of methyl radicals to methanol and formaldehyde over vanadium oxide catalysts

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EXPOSED ALUMINUM IONS AS ACTIVE-SITES ON GAMMA-ALUMINA

# publications[].label
CONVERSION OF BENZENE TO SUBSTITUTED AROMATIC PRODUCTS OVER ZEOLITE CATALYSTS AT ELEVATED PRESSURES

# publications[].label
Steady-state production of olefins in high yields during the oxidative coupling of methane: Utilization of a membrane contactor

# publications[].label
Activation studies with a promoted precipitated iron Fischer-Tropsch catalyst

# publications[].label
Destructive adsorption of carbon tetrachloride on alkaline earth metal oxides

# publications[].label
Reaction of steam with coke on solid substrates

# publications[].label
BINDER SUPPORT EFFECTS ON THE ACTIVITY AND SELECTIVITY OF IRON CATALYSTS IN THE FISCHER-TROPSCH SYNTHESIS

# publications[].label
Catalytic conversion of methane into aromatic hydrocarbons over iron oxide loaded ZSM-5 zeolites

# publications[].label
Low-temperature destructive adsorption of carbon tetrachloride on barium oxide

# publications[].label
SPECTROSCOPIC CHARACTERIZATION OF SURFACE OXYGEN SPECIES ON BARIUM-CONTAINING METHANE COUPLING CATALYSTS

# publications[].label
OXIDATIVE COUPLING OF METHANE OVER NA2WO4/CEO2 AND RELATED CATALYSTS

# publications[].label
CHEMISTRY OF ORGANOCHROMIUM COMPLEXES ON INORGANIC OXIDE SUPPORTS .4. STUDY OF ETHYLENE POLYMERIZATION OVER CHROMOCENE ON SILICA CATALYSTS

# publications[].label
Decomposition of nitric oxide over barium oxide supported on magnesium oxide .1. Catalytic results and in situ Raman spectroscopic evidence for a barium-nitro intermediate

# publications[].label
ORIGIN OF CARBON OXIDES DURING THE OXIDATIVE COUPLING OF METHANE

# publications[].label
MECHANISTIC STUDIES OF PROPYLENE OXIDATION ON BISMUTH MOLYBDATE

# publications[].label
THE EFFECT OF CHLORIDE-IONS ON A LI+-MGO CATALYST FOR THE OXIDATIVE COUPLING OF METHANE

# publications[].label
ACTIVATION STUDIES WITH A PRECIPITATED IRON CATALYST FOR FISCHER-TROPSCH SYNTHESIS .1. CHARACTERIZATION STUDIES

# publications[].label
Decomposition of nitric oxide over barium oxide supported on magnesium oxide .2. In situ Raman characterization of phases present during the catalytic reaction

# publications[].label
OXIDATIVE COUPLING OF METHANE OVER OXIDE-SUPPORTED BARIUM CATALYSTS

# publications[].label
CONVERSION OF METHYL RADICALS TO METHANOL AND FORMALDEHYDE OVER MOLYBDENUM OXIDE CATALYSTS

# publications[].label
Reactions of methyl radicals with metal oxides

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The catalytic hydrolysis of CCl4 to HCl and CO2 over magnesium oxide

# publications[].label
STEAM VAPORIZATION OF COKE WHICH HAS PRECIPITATED UPON SOLID SUBSTANCES

# publications[].label
Decomposition of nitric oxide over barium oxide supported on magnesium oxide. 4. In situ Raman characterization of oxide phase transitions and peroxide species by O-18-labeling

# publications[].label
OXIDATIVE COUPLING OF METHANE OVER OXIDE-SUPPORTED SODIUM-MANGANESE CATALYSTS

# publications[].label
Origin of first-order kinetics during the bimolecular cracking of n-hexane over H-ZSM-5 and H-beta zeolites

# publications[].label
The role of surface-generated gas-phase methyl radicals in the reduction of NO by CH4 over a Sr/La2O3 catalyst

# publications[].label
Effect of laser heating on the local temperature and composition in Raman spectroscopy: A study of Ba(NO3)(2) and BaO3 decomposition

# publications[].label
Intrinsic catalytic cracking activity of hexane over H-ZSM-5, H-beta and H-Y zeolites

# publications[].label
BISMUTH MOLYBDATE CATALYSTS - KINETICS AND MECHANISM OF PROPYLENE OXIDATION

# publications[].label
Catalytic reactions of NO over 0-7 mol% Ba/MgO catalysts - II. Reduction with CH4 and CO

# publications[].label
In-situ Raman spectroscopy characterization of catalysts during the decomposition of nitric oxide.

# publications[].label
KINETICS AND MECHANISM OF PROPYLENE OXIDATION OVER BISMUTH-MOLYB-DATE CATALYSTS - PHYS

# publications[].label
REACTION OF STEAM WITH COKE ON SOLID SUBSTRATES

# publications[].label
THE CATALYTIC CONVERSION OF METHYL RADICALS ON METAL-OXIDE SURFACES

# publications[].label
THE EFFECT OF CHLORIDE IONS ON A LI+-MGO CATALYST FOR THE OXIDATIVE DEHYDROGENATION OF ETHANE

# publications[].label
Catalytic conversion of methane to benzene over Mo/ZSM-5

# publications[].label
EFFECT OF COBALT SOURCE ON THE REDUCTION PROPERTIES OF SILICA-SUPPORTED COBALT CATALYSTS

# publications[].label
Catalytic reactions of NO over 0-7 mol% Ba/MgO catalysts: I. The direct decomposition of NO

# publications[].label
THE ROLE OF CL- IN A LI+-ZNO-CL- CATALYST ON THE OXIDATIVE COUPLING OF METHANE AND THE OXIDATIVE DEHYDROGENATION OF ETHANE

# publications[].label
ACTIVATION STUDIES WITH A PROMOTED PRECIPITATED IRON FISCHER-TROPSCH CATALYST

# publications[].label
Nitric oxide decomposition and selective catalytic reduction by methane over Ba/MgO catalysts

# publications[].label
Isomerization of n-hexane over chlorinated Pt/gamma-Al2O3 catalysts

# publications[].label
HYDROGENATION OF CARBON-MONOXIDE OVER ALKALI METAL-GRAPHITE INTERCALATES - REACTION SELECTIVITY AND CATALYST DEACTIVATION CHARACTERISTICS

# publications[].label
ORIGIN OF KINETIC ISOTOPE EFFECTS DURING THE OXIDATIVE COUPLING OF METHANE OVER A LI+ MGO CATALYST

# publications[].label
DUAL-SITE NATURE OF GAMMA ALUMINA CATALYSTS - ISOMERIZATION VS D2 EXCHANGE REACTIONS OF 1-BUTENE

# publications[].label
EFFECT OF CARBON-DIOXIDE ON THE ACTIVATION-ENERGY FOR METHYL RADICAL GENERATION OVER LI/MGO CATALYSTS

# publications[].label
Quantification of acid sites in H-ZSM-5, H-beta, and H-Y zeolites

# publications[].label
Characterization of surface carbon formed during the conversion of methane to benzene over Mo/H-ZSM-5 catalysts

# publications[].label
IR STUDY OF CARBON-DIOXIDE ADSORPTION ON LANTHANUM SESQUIOXIDE AND TRIHYDROXIDE

# publications[].label
ISOTHERMS AND ENERGETICS OF CARBON-DIOXIDE ADSORPTION ON GAMMA-ALUMINA AT 100-300 DEGREES

# publications[].label
CATALYTIC CONVERSION OF METHANE AND PROPYLENE TO 1-BUTENE

# publications[].label
CATALYTIC PARTIAL OXIDATION OF METHANE OVER BA-PB, BA-BI, AND BA-SN PEROVSKITES

# publications[].label
DUAL-SITE NATURE OF GAMMA ALUMINA CATALYSTS - ISOMERIZATION VS D2 EXCHANGE REACTIONS OF 1-BUTENE

# publications[].label
Reactions of hydroxyl radicals on titania, silica, alumina, and gold surfaces

# publications[].label
ARE THE EQUILIBRIUM CONCENTRATIONS OF CO AND H-2 EXCEEDED DURING THE OXIDATION OF CH4 OVER A NI/YB2O3 CATALYST

# publications[].label
THE NATURE OF CATALYTIC SITES ON LANTHANUM AND NEODYMIUM OXIDES FOR DEHYDRATION DEHYDROGENATION OF ETHANOL

# publications[].label
FROM CH4 REFORMING WITH CO2 TO PYROLYSIS OVER A PLATINUM CATALYST

# publications[].label
Oxidative coupling of methane over Mn/Na<inf>2</inf>WO<inf>4</inf>/MgO and related catalysts

# streetAddress
Texas A&M University; Chemistry; 3255 TAMU