Solid acid

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Solid acids are acids that are insoluble in the reaction medium. They are often used as heterogeneous catalysts.

Examples[edit]

Most solid state acids are organic acids such as oxalic acid, tartaric acid, citric acid, maleic acid, etc. Examples of inorganic solid acids include silico-aluminates (zeolites, alumina, silico-aluminophosphate), and sulfated zirconia. Many transition metal oxides are acidic, including titania, zirconia, and niobia.[1] Such acids are used in cracking. Many solid Brønsted acids are also employed industrially, including polystyrene sulfonate, solid phosphoric acid, niobic acid, and heteropolyoxometallates.[2]

Applications[edit]

Solid acids are used in catalysis in many industrial chemical processes, from large-scale catalytic cracking in petroleum refining to the synthesis of various fine chemicals.[3]

One large scale application is alkylation, e.g., the combination of benzene and ethylene to give ethylbenzene. Another application is the rearrangement of cyclohexanone oxime to caprolactam.[4] Many alkylamines are prepared by amination of alcohols, catalyzed by solid acids.

Zeolite, ZSM-5 is widely used as a solid acid catalyst.

Solid acids can be used as electrolytes in fuel cells.[1]

References[edit]

  1. ^ a b Boysen, Dane A.; Uda, Tetsuya; Chisholm, Calum R. I.; Haile, Sossina M. (2004-01-02). "High-Performance Solid Acid Fuel Cells Through Humidity Stabilization" (PDF). Science. 303 (5654): 68–70. Bibcode:2004Sci...303...68B. doi:10.1126/science.1090920. ISSN 0036-8075. PMID 14631049. S2CID 10829089.
  2. ^ Busca, Guido (2007-11-01). "Acid Catalysts in Industrial Hydrocarbon Chemistry". Chemical Reviews. 107 (11): 5366–5410. doi:10.1021/cr068042e. ISSN 0009-2665. PMID 17973436.
  3. ^ "Solid Acid Catalysis: From Fundamentals to Applications". CRC Press. Retrieved 2016-09-15.
  4. ^ Röper, Michael; Gehrer, Eugen; Narbeshuber, Thomas; Siegel, Wolfgang (15 June 2000), "Acylation and Alkylation", Ullmann's Encyclopedia of Industrial Chemistry, John Wiley & Sons, Ltd, doi:10.1002/14356007.a01_185, ISBN 978-3-527-30673-2, retrieved 2022-01-18