Solid acid

A solid material that donates protons, accepts electron pairs, or both. Solid acids often catalyze reactions while remaining in a separate phase from the reacting mixture.

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Brønsted–Lowry acid: A species that donates a proton to another species. Brønsted-acid sites on solids donate protons to adsorbed reactants.
Zeolite: A crystalline, microporous aluminosilicate with a regular network of molecular-sized pores. Many zeolites contain proton-donating framework sites and are widely used as solid acids.
Fluid catalytic cracking: A petroleum-refining process that converts heavy hydrocarbons into lighter products over circulating powdered catalyst. Acidic zeolite catalysts crack heavy oil into fuels and petrochemical feedstocks.
Homogeneous acid catalysis: Acid-catalyzed reactions in which catalyst and reactants occupy the same phase. Unlike dissolved acids, solid acids can often be separated from products by physical means.
Catalyst deactivation: The loss of catalytic activity or selectivity during use. Coke, poisoning, and structural changes can block or weaken solid-acid sites.
Lewis acid: A species that accepts an electron pair to form a bond. Lewis-acid sites accept electron pairs from reactants bound at the solid surface.
Silica–alumina: An amorphous or poorly crystalline material composed mainly of silicon and aluminum oxides. Its surface hydroxyl groups and coordinatively unsaturated aluminum can provide acidic sites.
Methanol-to-hydrocarbons process: A catalytic process that converts methanol into mixtures of hydrocarbons, including gasoline-range compounds and olefins. Zeolite acid sites rearrange methanol-derived intermediates into hydrocarbon products.
Sulfuric acid: A strong diprotic mineral acid with the formula H₂SO₄. It is a familiar liquid-acid catalyst whose corrosiveness and separation differ from solid-acid use.
Coke (catalysis): Carbon-rich deposits formed during catalysis that accumulate on catalyst surfaces or in pores. Coke can obstruct the pores that make many solid acids selective and active.