What is the difference between catalyst and reagent

to directory mode

Area of ‚Äč‚ÄčExpertise - Inorganic chemistry, physical chemistry, interface chemistry

In heterogeneous catalysis, the reacting substances and the catalyst are in at least two separate phases. For example, in ammonia synthesis, the gas mixture of nitrogen and hydrogen is converted over a solid catalyst:

With regard to the phase state, the substances to be converted and the catalyst, the catalytic conversions are divided into homogeneous and heterogeneous systems.

Typical of heterogeneous catalysis are gaseous starting materials and solid catalysts, which - especially in technology - are also known as contacts. The catalysis takes place on the (outer and / or inner) surface of the catalyst, which is where the terms surface catalysis and contact catalysis come from. Diffusion processes as well as adsorption and desorption processes of the reactants and products are important for the entire reaction process. Typical reaction temperatures are 200-600. The reactions are often carried out under high pressures.

The reacting system of a heterogeneously catalyzed reaction is often composed of three phases in various combinations. For example, the catalyst can be in the solid state and the reagents can be in the gaseous and liquid phases. The heterogeneously catalyzed processes predominantly take place on solid catalysts.

If all reactants and the catalyst are present as gases, this is always a homogeneous catalysis, since the gases mix completely. In the case of a system made up of different liquids, this is not necessarily the case, since liquids need not be completely miscible with one another. It follows that such systems of several liquids could in principle be homogeneous or heterogeneous.

In principle, the following eight binary systems are possible with heterogeneous catalysis.

Tab. 1
System numberReagentscatalystabbreviation
1Gas phasesolid phaseV-S
2Gas phaseliquid phaseV-L
3liquid phaseGas phaseL-V
4liquid phaseliquid phaseL-L
5liquid phasesolid phaseL-S
6solid phaseGas phaseS-V
7solid phaseliquid phaseS-L
8solid phasesolid phaseS-S

See also: catalyst, catalysis, homogeneous catalysis, ammonia synthesis

Learning units in which the term is dealt with

Basics of heterogeneous reactors45 min.

chemistrytechnical chemistryReaction engineering

The learning unit gives an introduction to the technical implementation of chemical reactions. Different modes of operation are discussed.

Reactors for heterogeneous reactions90 min.

chemistrytechnical chemistryReaction engineering

Some fixed bed and fluidized bed reactors are presented and their mode of operation is explained.

catalysis45 min.

chemistryGeneral ChemistryReaction kinetics

Description of catalyst reactions using various examples.

Platinum as a catalyst45 min.

chemistryInorganic chemistryChemistry of the elements

This learning unit provides information on the subject of platinum as a catalyst. Applications from homogeneous and heterogeneous catalysis are discussed.

Introduction to Macrokinetics30 min.

chemistrytechnical chemistryReaction engineering

The learning unit describes the sub-steps of heterogeneous catalysis and the dependence of the effective reaction rate on the mass transport conditions.

Process of heterogeneous catalysis30 min.

chemistrytechnical chemistryReaction engineering

The learning unit describes the sub-steps of heterogeneous catalysis and the dependence of the effective reaction rate on the mass transport conditions.

Acid catalysts30 min.

chemistrytechnical chemistryReaction engineering

The learning unit describes acidic heterogeneous catalysts using the example of zeolites and their areas of application.

Selective oxidation30 min.

chemistrytechnical chemistryReaction engineering

The Mars-van-Krevelen mechanism is described using the selective oxidation of o-xylene to phthalic anhydride.

Catalyst deactivation15 minutes.

chemistrytechnical chemistryReaction engineering

The most important mechanisms of catalyst deactivation are presented.

Metal-containing catalysts45 min.

chemistrytechnical chemistryReaction engineering

In the learning unit, metal carrier and all-metal catalysts are presented. Ammonia synthesis is explained as the use of a full metal catalyst and steam reforming is explained as the use of a metal supported catalyst.

Shrinking core model90 min.

chemistrytechnical chemistryReaction engineering

In this learning unit you will learn how a reacting solid changes and what influence this has on the further progress of the reaction.

Heterogeneous catalysis10 min.

chemistrytechnical chemistryReaction engineering

In addition to a brief introduction to the subject of "heterogeneous catalysis", some historical discoveries and milestones in catalyst development are shown.

Basics of complex catalysis30 min.

chemistryInorganic chemistryHomogeneous catalysis

The basics and terms of catalysis, especially organometallic complex catalysis, are explained. The difference between homogeneous and heterogeneous catalysis is explained.

catalysis10 min.

chemistryPhysical chemistrykinetics

Entry pages for catalyst and catalysis; Overview

Introduction to homogeneous catalysis40 min.

chemistryInorganic chemistryHomogeneous catalysis

The learning unit introduces the topic of homogeneous catalysis and deals with the fundamentals and basic terms with special emphasis on organometallic complex catalysis.