Science · Chemistry

Catalysis

1835 (named by Berzelius)

Chemistry — reaction kinetics and industrial chemistry

Catalysis is the speeding up of a chemical reaction by a substance that offers the reactants a lower-energy route and is regenerated unchanged at the end. Jöns Jacob Berzelius gathered a ragbag of puzzling observations under the name in 1835; Wilhelm Ostwald gave the modern definition and won the 1909 Nobel Prize in Chemistry largely for it. The key point, and the one most often got wrong, is that a catalyst changes only the rate at which equilibrium is reached, never where that equilibrium lies. Almost all industrial chemistry depends on it — ammonia over iron, sulfuric acid over vanadium oxide, polymers over Ziegler–Natta systems, car exhausts over platinum, palladium and rhodium — and every living cell runs on the protein version, enzymes.

How to spot them

▸A substance that speeds a reaction and is left unchanged at the end
▸Named by Berzelius in 1835; defined by Ostwald, who won the 1909 Nobel Prize
▸It lowers activation energy but cannot shift an equilibrium
▸Enzymes are the biological form; about nine in ten manufactured chemicals involve it
▸The platinum, palladium and rhodium honeycomb in a car exhaust

Key facts

Jöns Jacob Berzelius coined the name for it in 1835, from the Greek for 'loosening down' (1835)

He grouped together fermentation, the decomposition of hydrogen peroxide on metals and several other oddities under one heading.

Wilhelm Ostwald won the 1909 Nobel Prize in Chemistry for the work that defined it (1909)

His definition: a substance that alters the rate of a reaction without appearing in the final products.

It offers a lower-energy path — lowering the activation energy — while leaving the position of equilibrium exactly where it was

It speeds the forward and reverse reactions by the same factor.

Enzymes are nature's version, and some accelerate their reactions by a factor of 10^17

Enzyme names almost all end in -ase; James Sumner crystallised the first, urease, in 1926.

The honeycomb of platinum, palladium and rhodium in a car's exhaust does this to carbon monoxide, unburnt fuel and nitrogen oxides

Leaded petrol poisoned these converters, which is the main reason lead was removed from fuel.

Ziegler and Natta shared the 1963 Nobel Prize in Chemistry for the version of it that makes polyethylene and polypropylene (1963)

Titanium-based systems let polymers be built with controlled structure at low pressure.

It is split into homogeneous and heterogeneous kinds, according to whether it shares a phase with the reactants

Heterogeneous — usually a solid surface with gas or liquid flowing past — dominates heavy industry because the product is easy to separate.

Key ideas

Heterogeneous versions work by adsorbing reactants on a surface, weakening their bonds and holding them in the right orientation. The Sabatier principle says the surface must bind them neither too weakly to react nor so strongly that the product never leaves.
Autocatalysis, where a product of the reaction catalyses the reaction, gives the characteristic S-shaped rate curve and is one of the ingredients of origin-of-life chemistry.

Quick-fire facts

•Berzelius named it in 1835; the term comes from Greek kata (down) and lyein (to loosen).
•Wilhelm Ostwald took the 1909 Nobel Prize in Chemistry; Paul Sabatier shared the 1912 prize for hydrogenation over finely divided nickel.
•The contact process makes sulfuric acid over vanadium(V) oxide; the Ostwald process makes nitric acid by passing ammonia over platinum–rhodium gauze.
•Catalytic converters became compulsory on new American cars in 1975 and across the EU in 1993.
•Rhodium is so valuable — at times several times the price of gold — that converter theft became a significant crime.
•James Sumner won a share of the 1946 Nobel Prize in Chemistry for showing that enzymes are proteins.
•Efficiency is measured by turnover number (molecules converted per catalyst site) and turnover frequency (per site per second).
•Common misconception: a catalyst does not increase the yield of an equilibrium reaction, and it is not 'used up but replaced' — it is genuinely regenerated, though real ones degrade and are poisoned over time.

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Sources

The Nobel Foundation — The Nobel Prize in Chemistry 1909 — Wilhelm Ostwald
International Union of Pure and Applied Chemistry — Compendium of Chemical Terminology (the 'Gold Book'), entry 'catalyst' IUPAC's formal definition; the Gold Book site blocks automated access, so no URL is cited.
The Nobel Foundation — The Nobel Prize in Chemistry 1963 — Ziegler and Natta