Catalysis

catalyzescatalysescatalystcatalyticcatalyzecatalystscatalyzedcatalysecatalyzingcatalytic activity
Not to be confused with catabolism (often catalysis aids catabolism).wikipedia
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Catalyst poisoning

poisoningpoisonspoisoned
The effect of a catalyst may vary due to the presence of other substances known as inhibitors or poisons (which reduce the catalytic activity) or promoters (which increase the activity and also affect the temperature of the reaction).
Catalyst poisoning refers to the partial or total deactivation of a catalyst by a chemical compound.

Heterogeneous catalysis

heterogeneous catalystheterogeneous catalystsheterogeneous
In heterogeneous catalysis, the diffusion of reagents to the surface and diffusion of products from the surface can be rate determining.
Heterogeneous catalysis is the type of catalysis where the phase of the catalyst differs from the phase of the reactants or products.

Nanomaterial-based catalyst

Nanomaterial based catalystcatalystnanocatalyst
A nanomaterial-based catalyst is an example of a heterogeneous catalyst.
These catalysts can play two different roles in catalytic processes: they can be the site of catalysis or they can act as a support for catalytic processes.

Catalytic converter

catalytic converterscatalystDiesel Oxidation Catalyst
Catalysis is relevant to many aspects of environmental science, e.g. the catalytic converter in automobiles and the dynamics of the ozone hole.
A catalytic converter is an exhaust emission control device that reduces toxic gases and pollutants in exhaust gas from an internal combustion engine into less-toxic pollutants by catalyzing a redox reaction (an oxidation and a reduction reaction).

Green chemistry

greensustainable chemistrygreener
Catalytic reactions are preferred in environmentally friendly green chemistry due to the reduced amount of waste generated, as opposed to stoichiometric reactions in which all reactants are consumed and more side products are formed.
Green chemistry emerged from a variety of existing ideas and research efforts (such as atom economy and catalysis) in the period leading up to the 1990s, in the context of increasing attention to problems of chemical pollution and resource depletion.

Ozone depletion

ozone holeozone layer depletionozone-depleting
Catalysis is relevant to many aspects of environmental science, e.g. the catalytic converter in automobiles and the dynamics of the ozone hole.
Once in the stratosphere, they release halogen atoms through photodissociation, which catalyze the breakdown of ozone (O 3 ) into oxygen (O 2 ).

Reaction rate

raterate of reactionrates
Catalysis is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst, which is not consumed in the catalyzed reaction and can continue to act repeatedly.
When a catalyst is used the reaction rate may be stated on a catalyst weight (mol g −1 s −1 ) or surface area (mol m −2 s −1 ) basis.

Chemical kinetics

kineticsreaction kineticskinetic
Kinetically, catalytic reactions are typical chemical reactions; i.e. the reaction rate depends on the frequency of contact of the reactants in the rate-determining step.
The main factors that influence the reaction rate include: the physical state of the reactants, the concentrations of the reactants, the temperature at which the reaction occurs, and whether or not any catalysts are present in the reaction.

Reaction inhibitor

inhibitorinhibitioninhibitors
An added substance which does reduce the reaction rate is not considered a catalyst but a reaction inhibitor (see below).
An inhibitor can reduce the effectiveness of a catalyst in a catalysed reaction (either a non-biological catalyst or an enzyme).

Katal

kat
Catalytic activity is usually denoted by the symbol z and measured in mol/s, a unit which was called katal and defined the SI unit for catalytic activity since 1999.
The katal (symbol: kat) is the unit of catalytic activity in the International System of Units (SI).

Alkene

olefinalkenesolefins
Catalysts may bind to the reagents to polarize bonds, e.g. acid catalysts for reactions of carbonyl compounds, or form specific intermediates that are not produced naturally, such as osmate esters in osmium tetroxide-catalyzed dihydroxylation of alkenes, or cause dissociation of reagents to reactive forms, such as chemisorbed hydrogen in catalytic hydrogenation.
The reaction is carried out under pressure at a temperature of 200 °C in the presence of a metallic catalyst.

Osmium tetroxide

OsO 4 Osmic acidOsmium tetraoxide
Catalysts may bind to the reagents to polarize bonds, e.g. acid catalysts for reactions of carbonyl compounds, or form specific intermediates that are not produced naturally, such as osmate esters in osmium tetroxide-catalyzed dihydroxylation of alkenes, or cause dissociation of reagents to reactive forms, such as chemisorbed hydrogen in catalytic hydrogenation.
However its reactions are made catalytic by adding reoxidants to reoxidise the Os(VI) by-product back to Os(VIII).

Dihydroxylation

di-hydroxylation
Catalysts may bind to the reagents to polarize bonds, e.g. acid catalysts for reactions of carbonyl compounds, or form specific intermediates that are not produced naturally, such as osmate esters in osmium tetroxide-catalyzed dihydroxylation of alkenes, or cause dissociation of reagents to reactive forms, such as chemisorbed hydrogen in catalytic hydrogenation.
The metal is often used as a catalyst, with some other stoichiometric oxidant present.

Rate-determining step

rate-limiting steprate determining steprate-limiting
For example, if the rate-determining step in the above reaction scheme is the first step
The concept of the rate-determining step is very important to the optimization and understanding of many chemical processes such as catalysis and combustion.

Polymer

polymershomopolymerpolymeric
In heterogeneous catalysis, typical secondary processes include coking where the catalyst becomes covered by polymeric side products.
Synthetic polymerization reactions may be carried out with or without a catalyst.

Activation energy

energy barrieractivation energiesactivation barrier
In general, chemical reactions occur faster in the presence of a catalyst because the catalyst provides an alternative reaction pathway with a lower activation energy than the non-catalyzed mechanism.
A substance that modifies the transition state to lower the activation energy is termed a catalyst; a catalyst composed only of protein and (if applicable) small molecule cofactors is termed an enzyme.

Hydrogen peroxide

H 2 O 2 H2O2HO
The disproportionation of hydrogen peroxide creates water and oxygen, as shown below.
It begins with the reduction of an anthraquinone (such as 2-ethylanthraquinone or the 2-amyl derivative) to the corresponding anthrahydroquinone, typically by hydrogenation on a palladium catalyst.

Stoichiometry

stoichiometricstoichiometric coefficientstoichiometries
Catalytic reactions are preferred in environmentally friendly green chemistry due to the reduced amount of waste generated, as opposed to stoichiometric reactions in which all reactants are consumed and more side products are formed.
A stoichiometric reactant is a reactant that is consumed in a reaction, as opposed to a catalytic reactant, which is not consumed in the overall reaction because it reacts in one step and is regenerated in another step.

Hydrogen

HH 2 hydrogen gas
As an example of a detailed mechanism at the microscopic level, in 2008 Danish researchers first revealed the sequence of events when oxygen and hydrogen combine on the surface of titanium dioxide (TiO 2, or titania) to produce water.
Catalysts for the ortho-para interconversion, such as ferric oxide, activated carbon, platinized asbestos, rare earth metals, uranium compounds, chromic oxide, or some nickel compounds, are used during hydrogen cooling.

Raney nickel

Raney-Nickelcatalyst for hydrogenationspongy nickel
Examples are nickel, such as Raney nickel for hydrogenation, and vanadium(V) oxide for oxidation of sulfur dioxide into sulfur trioxide by the so-called contact process.
This third metal is called a "promoter".

Chemical equilibrium

equilibriumchemical equilibriaequilibria
In the catalyzed elementary reaction, catalysts do not change the extent of a reaction: they have no effect on the chemical equilibrium of a reaction because the rate of both the forward and the reverse reaction are both affected (see also thermodynamics).
Adding a catalyst will affect both the forward reaction and the reverse reaction in the same way and will not have an effect on the equilibrium constant.

Enzyme

enzymologyenzymesenzymatic
Enzymes and other biocatalysts are often considered as a third category.
Enzymes are both proteins and biological catalysts (biocatalysts).

Substrate (chemistry)

substratessubstratesubstrate specificity
Analogous events associated with substrate binding and product dissociation apply to homogeneous catalysts.
Enzymes catalyze chemical reactions involving the substrate(s).

Ruthenium

RuRu(NH 3 ) 6 3+ ruthenate
Many catalytic processes, especially those used in organic synthesis, require "late transition metals", such as palladium, platinum, gold, ruthenium, rhodium, or iridium.
A minor application for ruthenium is in platinum alloys and as a chemistry catalyst.

Iridium

IrIr-192Ir(III)
Many catalytic processes, especially those used in organic synthesis, require "late transition metals", such as palladium, platinum, gold, ruthenium, rhodium, or iridium.
The most important iridium compounds in use are the salts and acids it forms with chlorine, though iridium also forms a number of organometallic compounds used in industrial catalysis, and in research.