CATALYST FOR REMOVING NITROUS OXIDE AND METHOD OF REMOVING NITROUS OXIDE

METHODS FOR PROCESSING PLASTIC-DERIVED OILS AND WASTE PLASTICS

NH3 ABATEMENT WITH GREATER SELECTIVITY TO N2

CATALYST FOR THE MANUFACTURE OF ACRYLONITRILE

REDOX CATALYSTS AND PROCESSES FOR EFFICIENT OXIDATIVE DEHYDROGENATION OF ALKYLAROMATICS

CERIUM ZIRCONIUM MIXED OXIDE COMPOSITIONS

CATALYST AND METHOD FOR OXIDATIVE DEHYDROGENATION OF LOW-CARBON ALKANES TO LIGHT OLEFINS

CATALYST, AND METHOD FOR PRODUCING COMPOUND USING SAME

GRAIN BOUNDARY AND SURFACE-DOPED RARE EARTH MANGANESE-ZIRCONIUM COMPOSITE COMPOUND AND PREPARATION METHOD AND USE THEREOF

CATALYST, PRODUCTION METHOD FOR CATALYST, AND PRODUCTION METHOD FOR alpha,beta-UNSATURATED ALDEHYDE AND/OR alpha,beta-UNSATURATED CARBOXYLIC ACID USING SAME

CATALYST, AND METHOD FOR PRODUCING COMPOUND USING SAME

MOLYBDENUM-VANADIUM-IRON- AND/OR MOLYBDENUM-VANADIUM-ALUMINIUM-BASED OXIDATIVE DEHYDROGENATION CATALYST MATERIALS

MOLYBDENUM-VANADIUM-IRON- AND/OR MOLYBDENUM-VANADIUM-ALUMINIUM-BASED OXIDATIVE DEHYDROGENATION CATALYST MATERIALS

PRODUCTION OF ACROLEIN OR ACRYLIC ACID FROM ISO-PROPANOL WITH HIGH YEILD AND LOW COST

VISIBLE LIGHT-SENSITIVE PHOTOCATALYST COMPOSITION AND A VISIBLE LIGHT-SENSITIVE PHOTOCATALYST FILM COMPRISING THE SAME

PRODUCTION OF ACROLEIN OR ACRYLIC ACID FROM ISO-PROPANOL WITH HIGH YEILD AND LOW COST

EXHAUST GAS PURIFICATION CATALYST DEVICE

PHENOL ALKYLATION CATALYST PRECURSOR AND CATALYST, AND METHOD OF ALKYLATING PHENOL

ODH catalyst formulations

LOW-TEMPERATURE DENITRATION CATALYST

Method for preparing silicate/carbon composite from attapulgite, and use of silicate/carbon composite

Molybdenum-vanadium-iron- and/or molybdenum-vanadium-aluminium-based oxidative dehydrogenation catalyst materials

Hybrid catalysts comprising a mixed metal oxide component for production of C2 and C3 hydrocarbons

Systems for pyrolysis and increased production of pyrolysis gas

CATALYSTS FOR SINGLE STEP DOUBLE DEHYDROGENATION OF BUTADIENE FROM N-BUTANE

Mesoporous composite catalysts containing bismuth silicate and transition metal oxide

Catalyst for heavy oil upgradation

Method for producing catalyst and method for producing unsaturated nitrile

Cationically curable compositions with latent reducing agent demonstrating low cure temperature

Method for producing metal complex catalyst, and metal complex catalyst produced by same

Active perovskite-type catalysts stable to high temperature aging for gasoline exhaust gas applications

Prussian blue derived catalysts

Effects of catalyst concentration and solid activator on nickel-mediated olefin/carbon dioxide coupling to acrylates

Catalyst for electrochemical ammonia synthesis and method for producing the same

Method for preparing a carbon-supported, platinum-transition metal alloy nanoparticle fuel cell catalyst

Plasmonic nanoparticle catalysts and methods for producing long-chain hydrocarbon molecules

Redox catalysts for the oxidative cracking of hydrocarbons, methods of making, and methods of use thereof

Use of vanadates as oxidation catalysts

Highly active multimetallic materials using short-chain alkyl quaternary ammonium compounds

Highly active trimetallic materials using short-chain alkyl quaternary ammonium compounds

NH3 ABATEMENT WITH GREATER SELECTIVITY TO N2

Method for producing ammoxidation catalyst and method for producing acrylonitrtie

Method for regeneration of used lubricating oils

Production of synthesis gas from natural gas with copper—iron—manganese oxide oxygen carriers/catalysts via partial oxidation and dry reforming processes

Metal oxide catalyst, method for producing same, and apparatus for producing same

Catalyst mixture for the treatment of waste gas

Catalysts for Pyrolysis

Catalyst for preparing 2,5-furancarboxylic acid and a method for preparing 2,5-furancarboxylic acid using the catalyst

METHOD FOR THE HYDROTHERMAL PREPARATION OF MOLYBDENUM-BISMUTH-COBALT-IRON-BASED MIXED OXIDE CATALYSTS

Plasmonic nanoparticle catalysts and methods for producing long-chain hydrocarbon molecules

Process for preparation of a supported cobalt-containing Fishcer-Tropsch synthesis

Macroporous catalyst for the preparation of aliphatic amines

Catalyst-containing oxygen transport membrane

Catalytic body coated with metal oxide, method of manufacturing the same, and method of preparing 1,3-butadiene using the same

Core-shell structure supported tungsten composite catalyst and preparation method and use thereof

Sustainable Oxygen Carriers for Chemical Looping Combustion with Oxygen Uncoupling and Methods for Their Manufacture

Process for production of ketones from secondary alcohols

Process for producing chlorotrifluoroethylene

Conversion of alcohols to hydrocarbons using a dual catalyst system comprising basic oxide on mixed oxide or mesoporous carrier and etched metal loaded zeolite catalyst

Production of biofuels with novel salts impregnated tire-derived carbon catalysts

Cluster supported catalyst and method for producing same

Metal catalyzed dearomative 1,2-carboamination

Methods for the oxidative dehydrogenation of butene to produce butadiene

Catalyst composition for inhibiting diesel engine white smoke emission

Gold-based catalyst for oxidative esterification of aldehydes to carboxylic acid esters

Method for producing ruthenium/iron/carbon carrier catalysts

Nitrogen Oxide Oxidation Activity of Pseudo-Brookite Compositions as Zero-PGM Catalysts for Diesel Oxidation Applications

ROBUST CATALYST FOR HYDROGEN PRODUCTION FROM P-FORMALDEHYDE

Method for preparing acetal carbonyl compound

CATALYST FOR THE DEHYDROGENATION OF HYDROCARBONS

Carbon nanotubes having larger diameter and lower bulk density and process for preparing same

MIXED METAL OXIDE AMMOXIDATION CATALYSTS

Segregation resistant perovskite oxides with surface modification

Catalyst for fixed bed aniline rectification residue recycling and preparation method

Mixed metal oxide ammoxidation catalysts

Process for producing chlorotrifluoroethylene

Pre calcination additives for mixed metal oxide ammoxidation catalysts

Catalyst composition for the synthesis of multi-walled carbon nanotubes

High molybdenum mixed metal oxide catalysts for the production of unsaturated aldehydes from olefins

Low cost lean NOreduction catalyst system

PREPARING CERIUM(III) COMPOUNDS

NOVEL FORMULATION OF HEXA-ALUMINATES FOR REFORMING FUELS

Mixed metal oxide catalysts

DEHYDROGENATION CATALYST OF ALKYL AROMATIC COMPOUNDS HAVING IMPROVED PHYSICAL STRENGTH, PROCESS FOR PRODUCING SAME, AND DEHYDROGENATION METHOD THEREOF

Mo-, Bi- and Fe-comprising multimetal oxide compositions

Spinel structured catalyst for aldehyde production

Process for continuously producing geometric shaped catalyst bodies K

HIGHLY ACIDIC COMPOSITIONS COMPRISING ZIRCONIUM AND SILICON OXIDES AND AN OXIDE OF AT LEAST ONE OTHER ELEMENT SELECTED FROM AMONG TITANIUM, ALUMINUM, TUNGSTEN, MOLYBDENUM, CERIUM, IRON, TIN, ZINC, AND MANGANESE

PROCESS FOR PRODUCING GEOMETRIC SHAPED CATALYST BODIES

ZrOx, Ce-ZrOx, Ce-Zr-REOx as host matrices for redox active cations for low temperature, hydrothermally durable and poison resistant SCR catalysts

Method for producing catalyst for use in production of unsaturated aldehyde and/or unsaturated carboxylic acid, and method for producing unsaturated aldehyde and/or unsaturated carboxylic acid

Mixed Oxide Catalysts Made of Hollow Shapes

Catalyst, its preparation and use

Process for producing composite oxide catalyst

Method for producing unsaturated aldehyde and unsaturated carboxylic acid

Process and apparatus for depositing nanostructured material onto a substrate material

Carbon monoxide combustion catalyst and a process of preparation thereof

PROCESS FOR THE PREPARATION OF A CATALYTIC SPECIE USING ELECTRO-DEPOSITION

Process for producing hydrogenolysis products of polyhydric alcohols

Catalyst and methods for producing multi-wall carbon nanotubes

PRODUCTION PROCESS OF CONJUGATED DIENE

Mixed metal oxide ammoxidation catalysts

Fuel additive containing lattice engineered cerium dioxide nanoparticles

Oxidation catalyst and method for producing the oxidation catalyst

Processes and systems for producing syngas from methane

METHOD FOR SYNTHESIZING COMPOUND AND CATALYST FOR SYNTHESIS REACTION

Method for production of conjugated diolefin

Process for preparing acrylic acid from methanol and acetic acid

CATALYST AND METHOD FOR PARTIALLY OXIDIZING HYDROCARBONS

Exhaust gas purifying catalyst and method for manufacturing the same

Titania-metal composite and method for preparation thereof, and film forming method using dispersion comprising the composite

Composition including a lanthanum perovskite on an alumina or aluminium oxyhydroxide substrate, preparation method and use in catalysis

Titania-metal composite and method for preparation thereof, and film forming method using dispersion comprising the composite

TITANIA-METAL COMPOSITE AND METHOD FOR PREPARATION THEREOF, AND FILM FORMING METHOD USING DISPERSION COMPRISING THE COMPOSITE

Catalyst for removing nitrogen oxides

Self sustained electrochemical promotion catalysts

Catalyst for purifying exhaust gas

FISCHER-TROPSCH SYNTHESIS CATALYST, PREPARATION AND APPLICATION THEREOF

Exhaust gas treating catalyst and exhaust gas purification apparatus using the same

Redox material for thermochemical water splitting, and method for producing hydrogen

Addition of (A) blocking agent(s) in a ceramic membrane for blocking crystalline growth of grains during atmospheric sintering

Catalyst for producing unsaturated aldehyde by oxidation of lower olefin at high space velocity

Mixed oxide catalysts for catalytic gas phase oxidation

Multi-metal oxide catalyst and method for producing (meth)acrylic acid by using the same

Multi-metal oxide catalyst and method for producing (meth)acrylic acid by using the same

Attrition resistant mixed metal oxide ammoxidation catalysts

Process for preparing improved mixed metal oxide ammoxidation catalysts

Mixed metal oxide ammoxidation catalysts

ZrOx, Ce-ZrOx, Ce-Zr-REOx as host matrices for redox active cations for low temperature, hydrothermally durable and poison resistant SCR catalysts

High efficiency ammoxidation process and mixed metal oxide catalysts

Method for producing amines

Dehydrogenation catalyst for alkyl aromatic compounds exhibiting high performance in the presence of high-concentration CO

METHOD FOR MANUFACTURING UNSATURATED HYDROCARBON AND OXYGENATED COMPOUND, CATALYST, AND MANUFACTURING METHOD THEREFOR

REDOX MASSES HAVING A SPINEL TYPE STRUCTURE AxA'x,ByB'y,O4 AND USE IN A CHEMICAL LOOPING COMBUSTION PROCESS

Supported Catalyst for Synthesizing Carbon Nanotubes, Method for Preparing the Same and Carbon Nanotubes Made Using the Same

Process for producing phenol

CATALYTIC LAYER FOR OXYGEN ACTIVATION ON IONIC SOLID ELECTROLYTES AT HIGH TEMPERATURE

Dehydrogenation Catalyst of Alkylaromatic Compounds Having High Redox Ability, Process for Producing Same, And Dehydrogenation Method Using Same

Fixed-bed reactor and process for producing acrylic acid using the reactor

Oxide catalyst, process for producing acrolein or acrylic acid and process for producing water-absorbent resin

Exhaust gas purifying catalyst

AMMONIA DECOMPOSITION CATALYSTS AND THEIR PRODUCTION PROCESSES, AS WELL AS AMMONIA TREATMENT METHOD

Membrane with a stable nanosized microstructure and method for producing same

Composite oxide for exhaust gas purification catalyst, method for manufacturing the same, coating material for exhaust gas purification catalyst, and filter for diesel exhaust gas purification

CATALYSTS FOR NOX REDUCTION EMPLOYING H2 AND A METHOD OF REDUCING NOX

Catalyst composition for selective catalytic reduction of exhaust gases

Catalyst And Method For Producing Unsaturated Aldehyde And Unsaturated Carboxylic Acid

Deodorizing catalyst, deodorizing method using the same, and method for regenerating the catalyst

Process for preparing (meth)acrolein by heterogeneously catalyzed gas phase partial oxidation

CATALYST FOR PRODUCING ACROLEIN AND/OR ACRYLIC ACID AND PROCESS FOR PRODUCING ACROLEIN AND/OR ACRYLIC ACID USING THE CATALYST

Iron- and manganese-comprising heterogeneous catalyst and process for preparing olefins by reacting carbon monoxide with hydrogen

Iron- and copper-comprising heterogeneous catalyst and process for preparing olefins by reacting carbon monoxide with hydrogen

Method for the production of a nanocrystalline molybdenum mixed oxide

Mixed Metal Oxide Ingredients for Bulk Metal Oxide Catalysts

Method and use of providing photocatalytic activity

Carbon nanofiber, producing method and use of the same

Process for the preparation of phenol

Method for the production of nanocrystalline bismuth-molybdenum mixed oxide

Process for producing complex oxide catalyst

Method of producing propylene glycol

Method for producing hydrogenolysis product of polyhydric alcohol

Catalyst support and method of producing same

COATED CATALYSTS COMPRISING A MULTIMETAL OXIDE COMPRISING MOLYBDENUM, BISMUTH AND IRON

Process for preparing catalysts

Coated catalysts comprising a multimetal oxide comprising molybdenum

Cyclic catalytic upgrading of chemical species using metal oxide materials

METHOD FOR PRODUCING CARBONYL COMPOUND

Oxygen storage catalyst with decreased ceria reduction temperature

Process for the preparation of a catalytic specie using electro-deposition

METHOD OF LOADING SOLID PARTICLES INTO A FIXED-BED MULTITUBULAR REACTOR

Process for producing acetone from bioethanol

Process for production of carbonyl compound

MOLDING AND METHOD FOR PRODUCING THE SAME, AND CATALYST AND METHOD FOR PRODUCING THE SAME

MIXED OXIDE CATALYSTS MADE OF HOLLOW SHAPES

Preparation process of a catalyst used for gas phase oxidation of light alkenes to unsaturated aldehydes

Exhaust gas purifying catalyst

Slurry bed fischer-tropsch catalysts with silica/alumina structural promoters

Catalyst System, Oxidation Reactor Containing The Same, And Preparation Method For Acrolein And Acrylic Acid Using The Same

Mixed oxide catalysts for catalytic gas phase oxidation

Mixed manganese ferrite catalysts, method of preparing thereof and method of preparing 1,3-butadiene using thereof

Catalyst for production of nitric oxide

Method for producing an amine

Processes for preparing amines and catalysts for use therein

Purifying catalyst

Metal Nano Catalyst, Method for Preparing the Same and Method for Controlling the Growth Types of Carbon Nanotubes Using the Same

Process for producing light olefins from synthesis gas using dual sequential bed reactor

Method of preparing multicomponent bismuth molybdate catalysts comprising four metal components and method of preparing 1,3-butadiene using said catalysts

HIGHLY ACIDIC COMPOSITIONS COMPRISING ZIRCONIUM AND SILICON OXIDES AND AN OXIDE OF AT LEAST ONE OTHER ELEMENT SELECTED FROM AMONG TITANIUM, ALUMINUM, TUNGSTEN, MOLYBDENUM, CERIUM, IRON, TIN, ZINC, AND MANGANESE

Catalyst for preparing carbon nanotube comprising multi-component support materials containing amorphous silicon particles and the bulk scale preparation of carbon nanotube using the same

Catalyst Composition

Alumina-Based Perovskite Catalysts and Catalyst Supports

PEROVSKITE CATALYST SYSTEM FOR LEAN BURN ENGINES

Catalyst composition for the synthesis of thin multi-walled carbon nanotube and its manufacturing method

Exhaust gas-purifying catalyst

METHOD OF CHARGING CATALYST TUBES OF A BUNDLE OF CATALYST TUBES IN A STRUCTURED FASHION

CATALYST FOR VAPOUR CONVERSION OF CARBON MONOXIDE METHODS FOR THE PRODUCTION AND FOR THE USE THEREOF

TEMPLATED CATALYST COMPOSITION AND ASSOCIATED METHOD

Method of preparing heteropoly acid catalyst

Electrode catalyst for fuel cell, method for producing the same, and fuel cell using the electrode catalyst

Exhaust gas purification catalyst and exhaust gas purification honeycomb structure with catalyst

Catalyst composition for preparing carbon nanotube

Process for continuously producing geometric shaped catalyst bodies K

PARTICULATE CARBON CARRYING FINE PARTICLE THEREON, PROCESS FOR PRODUCTION THEREOF, AND ELECTRODES FOR FUEL CELLS

Method of preparing multicomponent bismuth molybdate catalysts with controlling pH and a method of preparing 1,3-butadiene using thereof

Zinc ferrite catalysts, method of preparing thereof and method of preparing 1,3-butadiene using thereof

Process for producing hydrogenolysis products of polyhydric alcohols

Single-walled carbon nanotube catalyst

Composite oxide for use as exhaust gas purification catalyst and filter

POLYNARY VANADYL PYROPHOSPHATE

POLYNARY METAL OXIDE PHOSPHATE

Complex oxide catalyst of Bi/Mo/Fe for the oxidative dehydrogenation of 1-butene to 1,3-butadiene and process thereof

CATALYST FOR DEHYDROGENATION OF ALKYL AROMATIC COMPOUND WHICH HAS IMPROVED PHYSICAL PROPERTIES, METHOD FOR PRODUCTION OF THE CATALYST, AND DEHYDROGENATION METHOD

Single-walled carbon nanotube catalysts and method for preparing same

Process for preparing multimetallic anionic clays and products thereof

Process for producing geometric shaped catalyst bodies

Process for producing geometric shaped catalyst bodies

POLYNARY METAL OXIDE PHOSPHATE

Heteropoly acid catalyst and method of preparing the same

Catalysts comprising a combination of oxidized metals and a method for cleaving phenylalkyl hydroperoxides using the catalysts

Vanadium-free catalyst for selective catalytic reduction and process for it's preparation

Process for producing a ringlike oxidic shaped body

Exhaust gas purifying catalyst and production process thereof

Stable ferrous-ferric nitrate solutions for fischer-tropsch catalyst preparation

Multi-metal oxide catalyst and method for producing (meth)acrylic acid by using the same

Method for producing catalyst for use in production of unsaturated aldehyde and/or unsaturated carboxylic acid, and method for producing unsaturated aldehyde and/or unsaturated carboxylic acid

Exhaust Gas Purification Catalyst and Exhaust Gas Purification Catalyst Member

SINGLE-WALLED CARBON NANOTUBE CATALYST

Exhaust gas purifying catalyst

Catalyst Consisting of a Solid Support, an Oxide and a Metal Active Phase Which is Grafted on the Oxide, a Method for the Preparation and the Use Thereof

Fluidized bed catalyst for producing acrylonitrile and process for producing acrylonitrile

Oxidic Metal Composition, Its Preparation And Use As Catalyst Composition

Purification Device and Method for Purifying a Fluid Stream

Catalyst

Method of producing unsaturated aldehyde and/or unsaturated acid

Catalyst for synthesizing acrylonitrile and process for producing acrylonitrile

PARTICULATE COMBUSTION CATALYST, PARTICULATE FILTER, AND EXHAUST GAS CLEAN-UP SYSTEM

Method for producing unsaturated aldehyde and unsaturated carboxylic acid

Catalyst for producing acrylonitrile and process for producing acrylonitrile

Hydrogen production using complex metal oxide pellets

METHOD FOR PRODUCING A MULTI METAL OXIDE CATALYST, METHOD FOR PRODUCING UNSATURATED ALDEHYDES AND/OR CARBOXYLIC ACIDS AND BAND CALCINATION DEVICE

Process for producing catalyst

Process for making olefin oligomers and alkyl benzenes in the presence of mixed metal oxide catalysts

Iron-based water gas shift catalyst

Method for preparation of ethylene and propylene by catalytic cracking using a fluid-bed catalyst

EXHAUST GAS-PURIFYING CATALYST

PURIFICATION CATALYST FOR EXHAUST GAS, PRODUCTION METHOD THEREFOR, AND PURIFICATION CATALYST EQUIPMENT FOR EXHAUST GAS

CATALYST FOR PURIFYING EXHAUST GAS AND METHOD FOR PRODUCING TETRAGONAL SYSTEM COMPOSITE OXIDE

Oxidic Metal Composition, Its Preparation And Use As Catalyst Composition

METHOD OF ISOMERIZATION OF LIGHT GASOLINE FRACTIONS

Catalyst composition and producing process thereof for use in manufacturing methacrolein

METHOD FOR PRODUCING FATTY ACID ALKYL ESTERS AND/OR GLYCERIN

Catalyst, its preparation and use

Catalyst, its preparation and use

Method for producing methacrolein and/or methacrylic acid

Ozone-decomposing agent

Complex metal oxide catalyst with high (meth) acrylic acid selectivity

Catalyst for methanation of carbon oxides, preparation method of the catalyst and process for the methanation

Catalysts with slow, passive release of alkali ions

Mixed oxide catalysts for the catalytic gas-phase oxidation of olefins and processes for producing them

Synthesis reaction catalyst and method of synthesizing compound using the same

Catalyst Composition

Purification catalyst for exhaust gas, production method therefor, and purification catalyst equipment for exhaust gas

Process of catalytic ammoxidation for hydrogen cyanide production

Process for charging a reactor with a fixed catalyst bed which comprises at least annular shaped catalyst bodies K

Composite oxide catalyst and method of producing the same

DeNOx catalyst preparation method

Process for preparing multimetallic anionic clays and products thereof

Process for starting-up a heterogeneously catalyzed partial gas phase oxidation of acrolein to acrylic acid or of methacrolein to methacrylic acid

PRODUCTION OF LOWER MOLECULAR WEIGHT HYDROCARBONS

FISCHER-TROPSCH CATALYST SUPPORT AND CATALYST

Process for charging a longitudinal section of a catalyst tube

Method for vapor phase catalytic oxidation

Catalyst for removing nitrogen oxides

Oxide catalyst, process for producing acrolein or acrylic acid and process for producing water absorbent resin

Method for vapor phase catalytic oxidation

Catalyst for hydrogen production from water gas shift reaction

Process for Producing (Meth)Acrylic Acid or (Meth)Acrolein

Catalyst and Methods for Producing Maleic Anhydride

Method for vapor phase catalytic oxidation

Catalyst system for a multi-walled carbon nanotube production process

Method of synthesizing compound

Process for preparing shaped catalyst bodies whose active composition is a multielement oxide

CARBON FIBER AND CATALYST FOR MANUFACTURE OF CARBON FIBER

SINGLE-WALLED CARBON NANOTUBE CATALYSTS AND METHODS FOR PREPARING SAME

Exhaust gas purifying catalyst and producing method thereof

Cyclic catalytic upgrading of chemical species using metal oxide materials

Inorganic colors and related nanotechnology

CATALYST FOR PURIFICATION OF EXHAUST GAS

Process for the preparation of phenol

Composite oxide catalyst and method of producing the same

Composite oxide catalyst and method of producing the same

Ce-Zr-R-O CATALYSTS, ARTICLES COMPRISING THE Ce Zr R O CATALYSTS AND METHODS OF MAKING AND USING THE Ce-Zr-R-O CATALYSTS

Inorganic material that has metal nanoparticles that are trapped in a mesostructured matrix

Catalyst and Method for Hydrogenation of Carbonyl Compounds

Process for producing (meth)acrolein or (meth)acrylic acid

Nitrogen oxide removal catalyst system and nitrogen oxide removal method

Nanolayer catalysts useful in promoting oxidation, and their manufacture and use

Reactor for gas phase catalytic oxidation and a process for producing acrylic acid using it

Pilot test method for multitubular reactor

Process for regenerating catalyst