Array ( [0] => {{short description|Process of increasing the rate of a chemical reaction}} [1] => {{Redirect|Catalyst|other uses}} [2] => {{Distinguish|Catalist|Cathalistis{{!}}''Cathalistis''}} [3] => {{For|the stage of metabolism|catabolism}} [4] => {{Use mdy dates|date=November 2020}} [5] => {{Use American English|date=November 2020}} [6] => [[File:Catalysts.JPG|thumb|300x300px|A range of industrial catalysts in pellet form]] [7] => [[Image:Low Temperature Oxidation Catalyst.jpeg|thumb|An [[air filter]] that uses a low-temperature oxidation catalyst to convert [[carbon monoxide]] to less toxic [[carbon dioxide]] at room temperature. It can also remove [[formaldehyde]] from the air.]] [8] => '''Catalysis''' ({{IPAc-en|k|ə|ˈ|t|æ|l|ə|s|ɪ|s}}) is the increase in [[reaction rate|rate]] of a [[chemical reaction]] due to an added substance known as a '''catalyst'''{{Cite book|title=IUPAC Compendium of Chemical Terminology |publisher=Blackwell Scientific Publications |year=2009 |isbn=978-0-9678550-9-7 |location=Oxford|chapter=Catalyst|doi=10.1351/goldbook.C00876|chapter-url=http://goldbook.iupac.org/C00876.html}}{{cite book|last=Masel |first=Richard I |year=2001 |title=Chemical Kinetics and Catalysis |publisher=Wiley-Interscience |location=New York |isbn=0-471-24197-0}} ({{IPAc-en|ˈ|k|æ|t|əl|ɪ|s|t}}). Catalysts are not consumed by the reaction and remain unchanged after it.{{cite book |last1=Steinfeld |first1=Jeffrey I. |last2=Francisco |first2=Joseph S. |last3=Hase |first3=William L. |title=Chemical Kinetics and Dynamics |date=1999 |publisher=Prentice Hall |isbn=0-13-737123-3 |page=147 |edition=2nd |quote=A catalyst is defined as a chemical substance which increases the rate of a chemical reaction without itself being consumed in the reaction.}} If the reaction is rapid and the catalyst recycles quickly, very small amounts of catalyst often suffice;{{cite web|url=http://www.anl.gov/articles/7-things-you-may-not-know-about-catalysis |title=7 things you may not know about catalysis |first=Louise |last=Lerner |publisher=[[Argonne National Laboratory]] |year=2011}} mixing, surface area, and temperature are important factors in reaction rate. Catalysts generally react with one or more reactants to form [[reaction intermediate|intermediates]] that subsequently give the final reaction product, in the process of regenerating the catalyst. [9] => [10] => The rate increase occurs because the catalyst allows the reaction to occur by an alternative mechanism which may be much faster than the non-catalyzed mechanism. However the non-catalyzed mechanism does remain possible, so that the total rate (catalyzed plus non-catalyzed) can only increase in the presence of the catalyst and never decrease.{{cite book |last1=Laidler |first1=Keith J. |last2=Meiser |first2=John H. |title=Physical Chemistry |date=1982 |publisher=Benjamin/Cummings |isbn=0-8053-5682-7 |quote= Inhibitors do not work by introducing a higher reaction path; this would not reduce the rate, since the reaction would continue to occur by the alternative mechanism |page=425}} [11] => [12] => Catalysis may be classified as either [[homogeneous catalysis|homogeneous]], whose components are dispersed in the same phase (usually gaseous or liquid) as the reactant, or [[heterogeneous catalysis|heterogeneous]], whose components are not in the same phase. [[Enzyme]]s and other biocatalysts are often considered as a third category. [13] => [14] => Catalysis is ubiquitous in [[chemical industry]] of all kinds.{{Cite journal |last1=Carroll |first1=Gregory T. |last2=Kirschman |first2=David L. |date=2023-01-23 |title=Catalytic Surgical Smoke Filtration Unit Reduces Formaldehyde Levels in a Simulated Operating Room Environment |url=https://pubs.acs.org/doi/10.1021/acs.chas.2c00071 |journal=ACS Chemical Health & Safety |language=en |volume=30 |issue=1 |pages=21–28 |doi=10.1021/acs.chas.2c00071 |s2cid=255047115 |issn=1871-5532}} Estimates are that 90% of all commercially produced chemical products involve catalysts at some stage in the process of their manufacture. [15] => [16] => The term "catalyst" is derived from [[Greek language|Greek]] {{lang|grc|[[wikt:καταλύω|καταλύειν]]}}, ''kataluein'', meaning "loosen" or "untie". The concept of catalysis was invented by chemist [[Elizabeth Fulhame]], based on her novel work in oxidation-reduction experiments.{{cite book|last1=Laidler|first1=Keith J.|chapter="Elizabeth Fulhame and the discovery of catalysis: 100 years before Buchner|last2=Cornish-Bowden|first2=Athel|editor-last1=Cornish-Bowden|editor-first1=Athel|title=New beer in an old bottle : Eduard Buchner and the growth of biochemical knowledge|date=1997|publisher=Universitat de Valencia|location=Valencia|isbn=9788437033280|pages=123–126|chapter-url=http://bip.cnrs-mrs.fr/bip10/newbeer/Fulhame.pdf|access-date=14 March 2021|archive-date=January 23, 2015|archive-url=https://web.archive.org/web/20150123224920/http://bip.cnrs-mrs.fr/bip10/newbeer/Fulhame.pdf|url-status=dead}}{{Cite book|title = Women in Chemistry: Their Changing Roles from Alchemical Times to the Mid-Twentieth Century|publisher = American Chemical Society|date = 2001|isbn = 978-0-8412-3522-9|first1 = Marelene|last1 = Rayner-Canham|first2 = Geoffrey William|last2 = Rayner-Canham|url-access = registration|url = https://archive.org/details/womeninchemistry0000rayn}} [17] => [18] => ==General principles== [19] => ===Example=== [20] => An illustrative example is the effect of catalysts to speed the decomposition of [[hydrogen peroxide]] into water and [[oxygen]]: [21] => :2 H{{sub|2}}O{{sub|2}} → 2 H{{sub|2}}O + O{{sub|2}} [22] => This reaction proceeds because the reaction products are more stable than the starting compound, but this decomposition is so slow that hydrogen peroxide solutions are commercially available. In the presence of a catalyst such as [[manganese dioxide]] this reaction proceeds much more rapidly. This effect is readily seen by the [[Effervescence (chemistry)|effervescence]] of oxygen.{{cite web|publisher=[[University of Minnesota]] |title=Genie in a Bottle |url=http://www.chem.umn.edu/services/lecturedemo/info/genie.htm |date=2005-03-02 |url-status=dead |archive-url=https://web.archive.org/web/20080405195443/http://www.chem.umn.edu/services/lecturedemo/info/genie.htm |archive-date=2008-04-05 }} The catalyst is not consumed in the reaction, and may be recovered unchanged and re-used indefinitely. Accordingly, manganese dioxide is said to ''catalyze'' this reaction. In living organisms, this reaction is catalyzed by [[enzyme]]s (proteins that serve as catalysts) such as [[catalase]]. [23] => [24] => ===Units=== [25] => The [[SI derived unit]] for measuring the '''catalytic activity''' of a catalyst is the [[katal]], which is quantified in moles per second. The productivity of a catalyst can be described by the [[turnover number]] (or TON) and the catalytic activity by the ''turn over frequency'' (TOF), which is the TON per time unit. The biochemical equivalent is the [[enzyme unit]]. For more information on the efficiency of enzymatic catalysis, see the article on ''[[Enzyme#Kinetics|enzymes]]''. [26] => [27] => ===Catalytic reaction mechanisms=== [28] => {{Main|catalytic cycle}} [29] => In general, chemical reactions occur faster in the presence of a catalyst because the catalyst provides an alternative [[reaction mechanism]] (reaction pathway) having a lower [[activation energy]] than the non-catalyzed mechanism. In catalyzed mechanisms, the catalyst is regenerated.{{cite book |last1=Laidler |first1=Keith J. |last2=Meiser |first2=John H. |title=Physical Chemistry |date=1982 |publisher=Benjamin/Cummings |isbn=0-8053-5682-7 |pages=424–425}}{{cite book |quote=The catalyst lowers the activation energy of the reaction by providing an alternative path that avoids the slow, rate-determining step of the uncatalyzed reaction |last1=Atkins |first1=Peter |last2=de Paula |first2=Julio |title=Atkins' Physical Chemistry |date=2006 |publisher=W.H.Freeman |isbn=0-7167-8759-8 |page=839 |edition=8th}}{{cite book |last1=Steinfeld |first1=Jeffrey I. |last2=Francisco |first2=Joseph S. |last3=Hase |first3=William L. |title=Chemical Kinetics and Dynamics |date=1999 |publisher=Prentice Hall |isbn=0-13-737123-3 |pages=147–150 |edition=2nd |quote=The catalyst concentration [C] appears in the rate expression, but not in the equilibrium ratio.}} [30] => [31] => As a simple example occurring in the gas phase, the reaction 2 SO2 + O2 → 2 SO3 can be catalyzed by adding [[nitric oxide]]. The reaction occurs in two steps: [32] => : 2{{nbsp}}NO + O2 → 2{{nbsp}}NO2 (rate-determining) [33] => : NO2 + SO2 → NO + SO3 (fast) [34] => The NO catalyst is regenerated. The overall rate is the rate of the slow step [35] => :v = 2k1[NO]2[O2]. [36] => [37] => An example of [[heterogeneous catalysis]] is the reaction of [[oxygen]] and [[hydrogen]] on the surface of [[titanium dioxide]] (TiO{{sub|2}}, or ''titania'') to produce water. [[Scanning tunneling microscopy]] showed that the molecules undergo [[adsorption]] and [[dissociation (chemistry)|dissociation]]. The dissociated, surface-bound O and H atoms [[diffusion|diffuse]] together. The intermediate reaction states are: HO{{sub|2}}, H{{sub|2}}O{{sub|2}}, then H{{sub|3}}O{{sub|2}} and the reaction product ([[Water dimer|water molecule dimers]]), after which the water molecule [[desorption|desorbs]] from the catalyst surface.{{cite news [38] => | first = Mitch [39] => | last = Jacoby [40] => | date = 16 February 2009 [41] => | title = Making Water Step by Step [42] => | newspaper = [[Chemical & Engineering News]] [43] => | page = 10 [44] => | url = http://pubs.acs.org/cen/news/87/i07/8707notw6.html [45] => }}{{cite journal [46] => | vauthors = Matthiesen J, Wendt S, Hansen JØ, Madsen GK, Lira E, Galliker P, Vestergaard EK, Schaub R, Laegsgaard E, Hammer B, Besenbacher F [47] => | year = 2009 [48] => | title = Observation of All the Intermediate Steps of a Chemical Reaction on an Oxide Surface by Scanning Tunneling Microscopy [49] => | journal = [[ACS Nano]] [50] => | volume = 3 [51] => | issue = 3 [52] => | pages = 517–26 [53] => | issn = 1520-605X [54] => | doi = 10.1021/nn8008245 [55] => | pmid = 19309169 [56] => | citeseerx = 10.1.1.711.974 [57] => }} [58] => [59] => ===Reaction energetics=== [60] => [61] => [[Image:CatalysisScheme-en.svg|thumb|upright=1.25|Generic potential energy diagram showing the effect of a catalyst in a hypothetical exothermic chemical reaction X + Y to give Z. The presence of the catalyst opens a different reaction pathway (shown in red) with lower activation energy. The final result and the overall thermodynamics are the same.]] [62] => Catalysts enable pathways that differ from the uncatalyzed reactions. These pathways have lower [[activation energy]]. Consequently, more molecular collisions have the energy needed to reach the transition state. Hence, catalysts can enable reactions that would otherwise be blocked or slowed by a kinetic barrier. The catalyst may increase the reaction rate or selectivity, or enable the reaction at lower temperatures. This effect can be illustrated with an [[Energy profile (chemistry)|energy profile]] diagram. [63] => [64] => 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. The ratio of the forward and the reverse reaction rates is unaffected (see also [[thermodynamics]]). The [[second law of thermodynamics]] describes why a catalyst does not change the chemical equilibrium of a reaction. Suppose there was such a catalyst that shifted an equilibrium. Introducing the catalyst to the system would result in a reaction to move to the new equilibrium, producing energy. Production of energy is a necessary result since reactions are spontaneous only if [[Gibbs free energy]] is produced, and if there is no energy barrier, there is no need for a catalyst. Then, removing the catalyst would also result in a reaction, producing energy; i.e. the addition and its reverse process, removal, would both produce energy. Thus, a catalyst that could change the equilibrium would be a [[perpetual motion machine]], a contradiction to the laws of thermodynamics.Robertson, A.J.B. (1970) ''Catalysis of Gas Reactions by Metals''. Logos Press, London. Thus, catalysts '''do not''' alter the equilibrium constant. (A catalyst can however change the equilibrium concentrations by reacting in a subsequent step. It is then consumed as the reaction proceeds, and thus it is also a reactant. Illustrative is the base-catalyzed [[hydrolysis]] of [[ester]]s, where the produced [[carboxylic acid]] immediately reacts with the base catalyst and thus the reaction equilibrium is shifted towards hydrolysis.) [65] => [66] => The catalyst stabilizes the transition state more than it stabilizes the starting material. It decreases the kinetic barrier by decreasing the ''difference'' in energy between starting material and the transition state. It '''does not''' change the energy difference between starting materials and products (thermodynamic barrier), or the available energy (this is provided by the environment as heat or light). [67] => [68] => ===Related concepts=== [69] => Some so-called catalysts are really '''[[precatalyst]]s'''. Precatalysts convert to catalysts in the reaction. For example, [[Wilkinson's catalyst]] RhCl(PPh{{sub|3}}){{sub|3}} loses one triphenylphosphine ligand before entering the true catalytic cycle. Precatalysts are easier to store but are easily activated [[in situ#Chemistry and chemical engineering|in situ]]. Because of this preactivation step, many catalytic reactions involve an [[induction period]]. [70] => [71] => In '''cooperative catalysis''', chemical species that improve catalytic activity are called '''cocatalysts''' or '''promoters'''. [72] => [73] => In [[tandem catalysis]] two or more different catalysts are coupled in a one-pot reaction. [74] => [75] => In [[autocatalysis]], the catalyst ''is'' a product of the overall reaction, in contrast to all other types of catalysis considered in this article. The simplest example of autocatalysis is a reaction of type A + B → 2 B, in one or in several steps. The overall reaction is just A → B, so that B is a product. But since B is also a reactant, it may be present in the rate equation and affect the reaction rate. As the reaction proceeds, the concentration of B increases and can accelerate the reaction as a catalyst. In effect, the reaction accelerates itself or is autocatalyzed. An example is the hydrolysis of an [[ester]] such as [[aspirin]] to a [[carboxylic acid]] and an [[Alcohol (chemistry)|alcohol]]. In the absence of added acid catalysts, the carboxylic acid product catalyzes the hydrolysis. [76] => [77] => A true catalyst can work in tandem with a [[Catalytic cycle#Sacrificial catalysts|sacrificial catalyst]]. The true catalyst is consumed in the elementary reaction and turned into a deactivated form. [78] => The sacrificial catalyst regenerates the true catalyst for another cycle. The sacrificial catalyst is consumed in the reaction, and as such, it is not really a catalyst, but a reagent. For example, [[osmium tetroxide]] (OsO4) is a good reagent for dihydroxylation, but it is highly toxic and expensive. In [[Upjohn dihydroxylation]], the sacrificial catalyst [[N-methylmorpholine N-oxide]] (NMMO) regenerates OsO4, and only catalytic quantities of OsO4 are needed. [79] => [80] => ===Classification=== [81] => Catalysis may be classified as either [[Homogeneity and heterogeneity|homogeneous or heterogeneous]]. A [[homogeneous catalysis]] is one whose components are dispersed in the same phase (usually gaseous or liquid) as the [[reactant]]'s molecules. A [[heterogeneous catalysis]] is one where the reaction components are not in the same phase. [[Enzyme]]s and other biocatalysts are often considered as a third category. Similar mechanistic principles apply to heterogeneous, homogeneous, and biocatalysis. [82] => [83] => ==Heterogeneous catalysis== [84] => {{Main|Heterogeneous catalysis}} [85] => [86] => [[File:Zeolite-ZSM-5-vdW.png|thumb|right|The microporous molecular structure of the [[zeolite]] ZSM-5 is exploited in catalysts used in refineries]] [87] => [[File:Ceolite nax.JPG|thumb|Zeolites are extruded as pellets for easy handling in catalytic reactors.]] [88] => Heterogeneous catalysts act in a different [[phase (matter)|phase]] than the [[reactants]]. Most heterogeneous catalysts are [[solid]]s that act on substrates in a [[liquid]] or gaseous [[reaction mixture]]. Important heterogeneous catalysts include [[zeolite]]s, [[alumina]],{{Cite journal|last1=Shafiq|first1=Iqrash|last2=Shafique|first2=Sumeer|last3=Akhter|first3=Parveen|last4=Yang|first4=Wenshu|last5=Hussain|first5=Murid|date=2020-06-23|title=Recent developments in alumina supported hydrodesulfurization catalysts for the production of sulfur-free refinery products: A technical review|journal=Catalysis Reviews|volume=64|issue=1 |pages=1–86|doi=10.1080/01614940.2020.1780824|s2cid=225777024 |issn=0161-4940|doi-access=}} higher-order oxides, graphitic carbon, [[transition metal]] [[oxide]]s, metals such as [[Raney nickel]] for hydrogenation, and [[vanadium(V) oxide]] for oxidation of [[sulfur dioxide]] into [[sulfur trioxide]] by the [[contact process]].{{cite book |last1=Housecroft |first1=Catherine E. |last2=Sharpe |first2=Alan G. |title=Inorganic Chemistry |date=2005 |publisher=Pearson Prentice-Hall |isbn=0130-39913-2 |page=805 |edition=2nd}} [89] => [90] => Diverse mechanisms for [[reactions on surfaces]] are known, depending on how the adsorption takes place ([[Langmuir-Hinshelwood-Hougen-Watson|Langmuir-Hinshelwood]], [[Eley–Rideal mechanism|Eley-Rideal]], and Mars-[[Dirk Willem van Krevelen|van Krevelen]]).Knözinger, Helmut and Kochloefl, Karl (2002) "Heterogeneous Catalysis and Solid Catalysts" in Ullmann's ''Encyclopedia of Industrial Chemistry'', Wiley-VCH, Weinheim. {{doi|10.1002/14356007.a05_313}} The total surface area of a solid has an important effect on the reaction rate. The smaller the catalyst particle size, the larger the surface area for a given mass of particles. [91] => [92] => A heterogeneous catalyst has '''active sites''', which are the atoms or crystal faces where the substrate actually binds. Active sites are atoms but are often described as a facet (edge, surface, step, etc.) of a solid. Most of the volume but also most of the surface of a heterogeneous catalyst may be catalytically inactive. Finding out the nature of the active site is technically challenging. [93] => [94] => For example, the catalyst for the [[Haber process]] for the synthesis of [[ammonia]] from [[nitrogen]] and [[hydrogen]] is often described as [[iron]]. But detailed studies and many optimizations have led to catalysts that are mixtures of iron-potassium-calcium-aluminum-oxide.{{cite book |doi=10.1002/14356007.a02_143.pub2 |date=2006 |last1=Appl |first1=Max |chapter=Ammonia |title=Ullmann's Encyclopedia of Industrial Chemistry |isbn=3527306730 }} The reacting [[gas]]es [[Adsorption|adsorb]] onto active sites on the iron particles. Once physically adsorbed, the reagents partially or wholly dissociate and form new bonds. In this way the particularly strong [[triple bond]] in nitrogen is broken, which would be extremely uncommon in the gas phase due to its high activation energy. Thus, the activation energy of the overall reaction is lowered, and the rate of reaction increases.{{Cite web |date=2013-10-03 |title=Chemistry of Vanadium |url=https://chem.libretexts.org/Bookshelves/Inorganic_Chemistry/Supplemental_Modules_and_Websites_(Inorganic_Chemistry)/Descriptive_Chemistry/Elements_Organized_by_Block/3_d-Block_Elements/Group_05%3A_Transition_Metals/Chemistry_of_Vanadium |access-date=2022-07-08 |website=Chemistry LibreTexts |language=en}} Another place where a heterogeneous catalyst is applied is in the oxidation of sulfur dioxide on [[vanadium(V) oxide]] for the production of [[sulfuric acid]]. Many heterogeneous catalysts are in fact nanomaterials. [95] => [96] => Heterogeneous catalysts are typically "[[catalyst support|supported]]," which means that the catalyst is dispersed on a second material that enhances the effectiveness or minimizes its cost. Supports prevent or minimize agglomeration and sintering of small catalyst particles, exposing more surface area, thus catalysts have a higher specific activity (per gram) on support. Sometimes the support is merely a surface on which the catalyst is spread to increase the surface area. More often, the support and the catalyst interact, affecting the catalytic reaction. Supports can also be used in nanoparticle synthesis by providing sites for individual molecules of catalyst to chemically bind. Supports are porous materials with a high surface area, most commonly [[alumina]], [[zeolites]] or various kinds of [[activated carbon]]. Specialized supports include [[silicon dioxide]], [[titanium dioxide]], [[calcium carbonate]], and [[barium sulfate]].{{Cite journal |last1=Chadha |first1=Utkarsh |last2=Selvaraj |first2=Senthil Kumaran |last3=Ashokan |first3=Hridya |last4=Hariharan |first4=Sai P. |last5=Mathew Paul |first5=V. |last6=Venkatarangan |first6=Vishal |last7=Paramasivam |first7=Velmurugan |date=2022-02-08 |title=Complex Nanomaterials in Catalysis for Chemically Significant Applications: From Synthesis and Hydrocarbon Processing to Renewable Energy Applications |journal=Advances in Materials Science and Engineering |language=en |volume=2022 |pages=e1552334 |doi=10.1155/2022/1552334 |issn=1687-8434|doi-access=free }} [97] => [98] => ===Electrocatalysts=== [99] => {{Main|Electrocatalyst}} [100] => In the context of [[electrochemistry]], specifically in [[fuel cell]] engineering, various metal-containing catalysts are used to enhance the rates of the [[half reaction]]s that comprise the fuel cell. One common type of fuel cell electrocatalyst is based upon [[nanoparticles]] of [[platinum]] that are supported on slightly larger [[carbon]] particles. When in contact with one of the [[electrode]]s in a fuel cell, this platinum increases the rate of [[oxygen]] reduction either to water or to [[hydroxide]] or [[hydrogen peroxide]]. [101] => [102] => ==Homogeneous catalysis== [103] => {{Main|Homogeneous catalysis}} [104] => Homogeneous catalysts function in the same phase as the reactants. Typically homogeneous catalysts are dissolved in a solvent with the substrates. One example of homogeneous catalysis involves the influence of [[hydrogen|H]]{{sup|+}} on the [[esterification]] of carboxylic acids, such as the formation of [[methyl acetate]] from [[acetic acid]] and [[methanol]].Behr, Arno (2002) "Organometallic Compounds and Homogeneous Catalysis" in Ullmann's ''Encyclopedia of Industrial Chemistry'', Wiley-VCH, Weinheim. {{doi|10.1002/14356007.a18_215}} High-volume processes requiring a homogeneous catalyst include [[hydroformylation]], [[hydrosilylation]], [[hydrocyanation]]. For inorganic chemists, homogeneous catalysis is often synonymous with [[organometallic chemistry|organometallic catalysts]].Elschenbroich, C. (2006) ''Organometallics''. Wiley-VCH: Weinheim. {{ISBN|978-3-527-29390-2}} Many homogeneous catalysts are however not organometallic, illustrated by the use of cobalt salts that catalyze the oxidation of [[p-xylene]] to [[terephthalic acid]]. [105] => [106] => === Organocatalysis === [107] => {{Main|Organocatalysis}} [108] => [109] => Whereas transition metals sometimes attract most of the attention in the study of catalysis, small organic molecules without metals can also exhibit catalytic properties, as is apparent from the fact that many [[enzyme]]s lack transition metals. Typically, organic catalysts require a higher loading (amount of catalyst per unit amount of reactant, expressed in [[mol%]] [[amount of substance]]) than transition metal(-ion)-based catalysts, but these catalysts are usually commercially available in bulk, helping to lower costs. In the early 2000s, these organocatalysts were considered "new generation" and are competitive to traditional [[metal]](-ion)-containing catalysts. Organocatalysts are supposed to operate akin to metal-free enzymes utilizing, e.g., non-covalent interactions such as [[hydrogen bonding]]. The discipline organocatalysis is divided into the application of covalent (e.g., [[proline]], [[4-Dimethylaminopyridine|DMAP]]) and non-covalent (e.g., [[thiourea organocatalysis]]) organocatalysts referring to the preferred catalyst-[[Substrate (chemistry)|substrate]] [[binding (molecular)|binding]] and interaction, respectively. The Nobel Prize in Chemistry 2021 was awarded jointly to Benjamin List and David W.C. MacMillan "for the development of asymmetric organocatalysis."{{cite web |title=The Nobel Prize in Chemistry 2021 |url=https://www.nobelprize.org/prizes/chemistry/2021/summary/ |website=NobelPrize.org}} [110] => [111] => ===Photocatalysts=== [112] => {{main|Photocatalysis}} [113] => Photocatalysis is the phenomenon where the catalyst can receive light to generate an [[excited state]] that effect redox reactions.{{Cite journal|doi= 10.1021/acs.chemrev.1c00993|title= Introduction: Photochemical Catalytic Processes|year= 2022|last1= Melchiorre|first1= Paolo|journal= Chemical Reviews|volume= 122|issue= 2|pages= 1483–1484|pmid= 35078320|s2cid= 246287799|doi-access= free}} [[Singlet oxygen]] is usually produced by photocatalysis. Photocatalysts are components of [[dye-sensitized solar cell]]s. [114] => [115] => ===Enzymes and biocatalysts=== [116] => {{Main|Enzyme catalysis}} [117] => [118] => In biology, [[enzyme]]s are protein-based catalysts in [[metabolism]] and [[catabolism]]. Most biocatalysts are enzymes, but other non-protein-based classes of biomolecules also exhibit catalytic properties including [[ribozyme]]s, and synthetic [[deoxyribozyme]]s.Nelson, D.L. and Cox, M.M. (2000) ''Lehninger, Principles of Biochemistry'' 3rd Ed. Worth Publishing: New York. {{ISBN|1-57259-153-6}}. [119] => [120] => Biocatalysts can be thought of as an intermediate between homogeneous and heterogeneous catalysts, although strictly speaking soluble enzymes are homogeneous catalysts and [[Biological membrane|membrane]]-bound enzymes are heterogeneous. Several factors affect the activity of enzymes (and other catalysts) including temperature, pH, the concentration of enzymes, substrate, and products. A particularly important reagent in enzymatic reactions is water, which is the product of many bond-forming reactions and a reactant in many bond-breaking processes. [121] => [122] => In [[biocatalysis]], enzymes are employed to prepare many commodity chemicals including [[high-fructose corn syrup]] and [[acrylamide]]. [123] => [124] => Some [[monoclonal antibodies]] whose binding target is a stable molecule that resembles the transition state of a chemical reaction can function as weak catalysts for that chemical reaction by lowering its activation energy.[https://web.archive.org/web/20130821044547/http://www.documentroot.com/2010/03/catalytic-antibodies-simply-explained.html Catalytic Antibodies Simply Explained]. Documentroot.com (2010-03-06). Retrieved on 2015-11-11. Such catalytic antibodies are sometimes called "[[abzymes]]". [125] => [126] => ==Significance== [127] => [128] => [[File:Verbrennung eines Zuckerwürfels.png|thumb|Left: Partially caramelized [[cube sugar]], Right: burning cube sugar with ash as catalyst]] [129] => [[File:TiCrPt micropump3.webm|thumb|A Ti-Cr-Pt tube (~40 μm long) releases oxygen bubbles when immersed in [[hydrogen peroxide]] (via catalytic decomposition), forming a [[micropump]].{{cite journal|doi=10.1039/C1CP20542K|pmid=21505711|url= http://nanomem.fudan.edu.cn/79solovev2011.pdf |archive-url=https://web.archive.org/web/20190328131026/http://nanomem.fudan.edu.cn/79solovev2011.pdf |archive-date=2019-03-28 |url-status=live |title=Tunable catalytic tubular micro-pumps operating at low concentrations of hydrogen peroxide|journal=Physical Chemistry Chemical Physics|volume=13|issue=21|pages=10131–35|year=2011|last1=Solovev|first1=Alexander A.|last2=Sanchez|first2=Samuel|last3=Mei|first3=Yongfeng|last4=Schmidt|first4=Oliver G.|bibcode=2011PCCP...1310131S}}]] [130] => [131] => Estimates are that 90% of all commercially produced chemical products involve catalysts at some stage in the process of their manufacture."Recognizing the Best in Innovation: Breakthrough Catalyst". ''R&D Magazine'', September 2005, p. 20. In 2005, catalytic processes generated about $900 billion in products worldwide.[http://www.climatetechnology.gov/library/2005/tech-options/tor2005-143.pdf 1.4.3 Iindustrial Process Efficiency] {{webarchive|url=https://web.archive.org/web/20080517071700/http://www.climatetechnology.gov/library/2005/tech-options/tor2005-143.pdf |date=2008-05-17 }}. climatetechnology.gov Catalysis is so pervasive that subareas are not readily classified. Some areas of particular concentration are surveyed below. [132] => [133] => ===Energy processing=== [134] => [135] => [[Petroleum]] refining makes intensive use of catalysis for [[alkylation]], [[catalytic cracking]] (breaking long-chain hydrocarbons into smaller pieces), [[Petroleum naphtha|naphtha]] reforming and [[steam reforming]] (conversion of [[hydrocarbon]]s into [[synthesis gas]]). Even the exhaust from the burning of fossil fuels is treated via catalysis: [[Catalytic converter]]s, typically composed of [[platinum]] and [[rhodium]], break down some of the more harmful byproducts of automobile exhaust. [136] => :2 CO + 2 NO → 2 CO{{sub|2}} + N{{sub|2}} [137] => [138] => With regard to synthetic fuels, an old but still important process is the [[Fischer-Tropsch synthesis]] of hydrocarbons from [[synthesis gas]], which itself is processed via [[water gas shift reaction|water-gas shift reactions]], catalyzed by iron. The [[Sabatier reaction]] produces [[methane]] from carbon dioxide and hydrogen. [[Biodiesel]] and related biofuels require processing via both inorganic and biocatalysts. [139] => [140] => [[Fuel cell]]s rely on catalysts for both the anodic and cathodic reactions. [141] => [142] => [[Catalytic heater]]s generate flameless heat from a supply of combustible fuel. [143] => [144] => ===Bulk chemicals=== [145] => [[File:CataylstExampleSulfuricAcidPlant.jpg|alt=Typical vanadium pentoxide catalyst used in sulfuric acid production for an intermediate reaction to convert sulfur dioxide to sulfur trioxide.|thumb|Typical vanadium pentoxide catalyst used in sulfuric acid production for an intermediate reaction to convert sulfur dioxide to sulfur trioxide.]] [146] => Some of the largest-scale chemicals are produced via catalytic oxidation, often using [[oxygen]]. Examples include [[nitric acid]] (from ammonia), [[sulfuric acid]] (from [[sulfur dioxide]] to [[sulfur trioxide]] by the [[contact process]]), [[terephthalic acid]] from p-xylene, [[acrylic acid]] from [[propylene]] or [[propane]] and [[acrylonitrile]] from propane and ammonia. [147] => [148] => The production of ammonia is one of the largest-scale and most energy-intensive processes. In the [[Haber process]] [[nitrogen]] is combined with hydrogen over an iron oxide catalyst.{{cite book |last1=Smil |first1=Vaclav |title=Enriching the Earth: Fritz Haber, Carl Bosch, and the Transformation of World Food Production |date=2004 |publisher=MIT |location=Cambridge, MA |isbn=9780262693134 |edition=1st}} [[Methanol]] is prepared from [[carbon monoxide]] or carbon dioxide but using copper-zinc catalysts. [149] => [150] => Bulk polymers derived from [[ethylene]] and [[propylene]] are often prepared via [[Ziegler-Natta catalysis]]. Polyesters, polyamides, and [[isocyanate]]s are derived via [[acid-base catalysis]]. [151] => [152] => Most [[carbonylation]] processes require metal catalysts, examples include the [[Monsanto acetic acid process]] and [[hydroformylation]]. [153] => [154] => ===Fine chemicals=== [155] => Many [[fine chemicals]] are prepared via catalysis; methods include those of heavy industry as well as more specialized processes that would be prohibitively expensive on a large scale. Examples include the [[Heck reaction]], and [[Friedel–Crafts reaction]]s. Because most bioactive compounds are [[Chirality (chemistry)|chiral]], many pharmaceuticals are produced by enantioselective catalysis (catalytic [[asymmetric synthesis]]). (R)-1,2-Propandiol, the precursor to the antibacterial [[levofloxacin]], can be synthesized efficiently from hydroxyacetone by using catalysts based on [[BINAP]]-ruthenium complexes, in [[Noyori asymmetric hydrogenation]]:{{cite journal |doi=10.1038/s41570-018-0049-z|title=The role of the metal-bound N–H functionality in Noyori-type molecular catalysts|year=2018|last1=Dub|first1=Pavel A.|last2=Gordon|first2=John C.|s2cid=106394152|journal=Nature Reviews Chemistry|volume=2|issue=12|pages=396–408}} [156] => [[File:levofloxacin3.png|center|632px|levofloxaxin synthesis]] [157] => [158] => ===Food processing=== [159] => [160] => One of the most obvious applications of catalysis is the [[hydrogenation]] (reaction with [[hydrogen]] gas) of fats using [[nickel]] catalyst to produce [[margarine]].{{cite web | publisher = Chemguide | title = Types of catalysis | url = http://www.chemguide.co.uk/physical/catalysis/introduction.html |first = Jim|last = Clark|date = October 2013}} Many other foodstuffs are prepared via biocatalysis (see below). [161] => [162] => ===Environment=== [163] => Catalysis affects the environment by increasing the efficiency of industrial processes, but catalysis also plays a direct role in the environment. A notable example is the catalytic role of [[chlorine]] [[free radical]]s in the breakdown of [[ozone]]. These radicals are formed by the action of [[ultraviolet]] [[radiation]] on [[chlorofluorocarbon]]s (CFCs). [164] => :Cl{{sup|'''·'''}} + O{{sub|3}} → ClO{{sup|'''·'''}} + O{{sub|2}} [165] => :ClO{{sup|'''·'''}} + O{{sup|·}} → Cl{{sup|'''·'''}} + O{{sub|2}} [166] => [167] => ==History== [168] => [169] => The term "catalyst", broadly defined as anything that increases the rate of a process, is derived from [[Greek language|Greek]] [[wikt:καταλύω|καταλύειν]], meaning "to annul," or "to untie," or "to pick up". The concept of catalysis was invented by chemist [[Elizabeth Fulhame]] and described in a 1794 book, based on her novel work in oxidation–reduction reactions.Bård Lindström and Lars J. Petterson (2003) "[http://image.sciencenet.cn/olddata/kexue.com.cn/upload/blog/file/2008/10/200810102212944318.pdf A brief history of catalysis]" ''Cattech'', '''7''' (4) : 130–38. The first chemical reaction in organic chemistry that knowingly used a catalyst was studied in 1811 by [[Gottlieb Kirchhoff]], who discovered the acid-catalyzed conversion of starch to glucose. The term ''catalysis'' was later used by [[Jöns Jakob Berzelius]] in 1835Berzelius, J.J. (1835) ''Årsberättelsen om framsteg i fysik och kemi'' [Annual report on progress in physics and chemistry]. Stockholm, Sweden: Royal Swedish Academy of Sciences. After reviewing Eilhard Mitscherlich's research on the formation of ether, Berzelius coins the word ''katalys'' (catalysis) on [https://books.google.com/books?id=1DM1AAAAcAAJ&pg=PA245 p. 245]: [170] =>
Original: ''Jag skall derföre, för att begagna en i kemien välkänd härledning, kalla den kroppars'' katalytiska kraft, ''sönderdelning genom denna kraft ''katalys, ''likasom vi med ordet analys beteckna åtskiljandet af kroppars beståndsdelar medelst den vanliga kemiska frändskapen.''
[171] =>
''Translation'': I shall, therefore, to employ a well-known derivation in chemistry, call [the catalytic] bodies [i.e., substances] the ''catalytic force'' and the decomposition of [other] bodies by this force ''catalysis'', just as we signify by the word ''analysis'' the separation of the constituents of bodies by the usual chemical affinities.
 to describe reactions that are accelerated by substances that remain unchanged after the reaction. [[Elizabeth Fulhame|Fulhame]], who predated Berzelius, did work with water as opposed to metals in her reduction experiments. Other 18th century chemists who worked in catalysis were [[Eilhard Mitscherlich]]{{cite journal|author=Mitscherlich, E. |year=1834|url=https://books.google.com/books?id=wCUAAAAAMAAJ&pg=PA273 |title=Ueber die Aetherbildung|trans-title=On the formation of ether|journal=Annalen der Physik und Chemie|volume=31|issue=18|pages=273–82|bibcode=1834AnP...107..273M|doi=10.1002/andp.18341071802}} who referred to it as ''contact'' processes, and [[Johann Wolfgang Döbereiner]]{{cite journal|author= Döbereiner |year=1822|url=http://babel.hathitrust.org/cgi/pt?id=nyp.33433069069148;view=1up;seq=107 |title=Glühendes Verbrennen des Alkohols durch verschiedene erhitzte Metalle und Metalloxyde|trans-title=Incandescent burning of alcohol by various heated metals and metal oxides|journal=Journal für Chemie und Physik|volume=34|pages= 91–92}}{{cite journal|author=Döbereiner |year=1823|url=http://babel.hathitrust.org/cgi/pt?id=nyp.33433069069189;view=1up;seq=341 |title=Neu entdeckte merkwürdige Eigenschaften des Platinsuboxyds, des oxydirten Schwefel-Platins und des metallischen Platinstaubes|trans-title=Newly discovered remarkable properties of platinum suboxide, oxidized platinum sulfide and metallic platinum dust|journal=Journal für Chemie und Physik|volume=38|pages=321–26}} who spoke of ''contact action. ''He developed [[Döbereiner's lamp]], a [[Lighter (fire starter)|lighter]] based on [[hydrogen]] and a [[platinum]] sponge, which became a commercial success in the 1820s that lives on today. [[Humphry Davy]] discovered the use of platinum in catalysis.{{cite journal|author=Davy, Humphry |year=1817|url=https://books.google.com/books?id=xohJAAAAYAAJ&pg=PA77|title=Some new experiments and observations on the combustion of gaseous mixtures, with an account of a method of preserving a continued light in mixtures of inflammable gases and air without flame|doi=10.1098/rstl.1817.0009|journal=Philosophical Transactions of the Royal Society of London|volume=107|pages= 77–85|s2cid=97988261 |doi-access=}} In the 1880s, [[Wilhelm Ostwald]] at [[Leipzig University]] started a systematic investigation into reactions that were catalyzed by the presence of acids and bases, and found that chemical reactions occur at finite rates and that these rates can be used to determine the strengths of acids and bases. For this work, Ostwald was awarded the 1909 [[Nobel Prize in Chemistry]].{{cite journal | author =Roberts, M.W. | title = Birth of the catalytic concept (1800–1900) | journal = [[Catalysis Letters]] | volume = 67 | issue = 1 [172] => | year = 2000 | doi = 10.1023/A:1016622806065 | pages= 1–4| s2cid = 91507819 }} [[Vladimir Ipatieff]] performed some of the earliest industrial scale reactions, including the discovery and commercialization of oligomerization and the development of catalysts for hydrogenation.{{cite journal |last1=Nicholas |first1=Christopher P. |title=Dehydration, Dienes, High Octane, and High Pressures: Contributions from Vladimir Nikolaevich Ipatieff, a Father of Catalysis |journal=ACS Catalysis |volume=8 |issue=9 |date=21 August 2018 |pages=8531–39 |doi=10.1021/acscatal.8b02310|doi-access=free }} [173] => [174] => ==Inhibitors, poisons, and promoters== [175] => An added substance that lowers the rate is called a [[reaction inhibitor]] if reversible and [[Catalyst poisoning|catalyst poisons]] if irreversible. Promoters are substances that increase the catalytic activity, even though they are not catalysts by themselves.{{Cite book|last1=Dhara SS|url=https://books.google.com/books?id=fF1jDwAAQBAJ|title=A Textbook of Engineering Chemistry|last2=Umare SS|publisher=S. Chand Publishing|year=2018|isbn=9789352830688|location=India|pages=66}} [176] => [177] => Inhibitors are sometimes referred to as "negative catalysts" since they decrease the reaction rate. However the term inhibitor is preferred since they do not work by introducing a reaction path with higher activation energy; this would not lower the rate since the reaction would continue to occur by the non-catalyzed path. Instead, they act either by deactivating catalysts or by removing reaction intermediates such as free radicals.Laidler, K.J. (1978) ''Physical Chemistry with Biological Applications'', Benjamin/Cummings. pp. 415–17. {{ISBN|0-8053-5680-0}}.Laidler, K.J. and Meiser, J.H. (1982) ''Physical Chemistry'', Benjamin/Cummings, p. 425. {{ISBN|0-618-12341-5}}. In [[heterogeneous]] catalysis, [[coking]] inhibits the catalyst, which becomes covered by [[polymer]]ic side products. [178] => [179] => The inhibitor may modify selectivity in addition to rate. For instance, in the hydrogenation of [[alkyne]]s to [[alkene]]s, a [[palladium]] (Pd) catalyst partly "poisoned" with [[lead(II) acetate]] (Pb(CH{{sub|3}}CO{{sub|2}}){{sub|2}}) can be used[[Lindlar catalyst|(Lindlar catalyst]]).{{OrgSynth | author1= Lindlar H. | author2=Dubuis R. | title = Palladium Catalyst for Partial Reduction of Acetylenes | collvol = 5 | collvolpages = 880 | year = 2016 | doi=10.15227/orgsyn.046.0089}} Without the deactivation of the catalyst, the alkene produced would be further hydrogenated to [[alkane]].Jencks, W.P. (1969) ''Catalysis in Chemistry and Enzymology'' McGraw-Hill, New York. {{ISBN|0-07-032305-4}}Bender, Myron L; Komiyama, Makoto and Bergeron, Raymond J (1984) ''The Bioorganic Chemistry of Enzymatic Catalysis'' Wiley-Interscience, Hoboken, U.S. {{ISBN|0-471-05991-9}} [180] => [181] => The inhibitor can produce this effect by, e.g., selectively poisoning only certain types of active sites. Another mechanism is the modification of surface geometry. For instance, in hydrogenation operations, large planes of metal surface function as sites of [[hydrogenolysis]] catalysis while sites catalyzing [[hydrogenation]] of unsaturates are smaller. Thus, a poison that covers the surface randomly will tend to lower the number of uncontaminated large planes but leave proportionally smaller sites free, thus changing the hydrogenation vs. hydrogenolysis selectivity. Many other mechanisms are also possible. [182] => [183] => Promoters can cover up the surface to prevent the production of a mat of coke, or even actively remove such material (e.g., rhenium on platinum in [[catalytic reforming|platforming]]). They can aid the dispersion of the catalytic material or bind to reagents. [184] => [185] => ==See also== [186] => {{cmn| [187] => * [[Chemical reaction]] [188] => ** [[Substrate (chemistry)|Substrate]] [189] => ** [[Reagent]] [190] => ** [[Enzyme]] [191] => ** [[Product (chemistry)|Product]] [192] => * [[Abzyme]] [193] => * [[Acid catalysis]] (includes Base catalysis) [194] => * [[Autocatalysis]] [195] => * [[BIG-NSE]] (Berlin Graduate School of Natural Sciences and Engineering) [196] => * ''[[Catalysis Science & Technology]]'' (a chemistry journal) [197] => * [[Catalytic resonance theory]] [198] => * [[Electrocatalyst]] [199] => * [[Environmental triggers]] [200] => * [[Enzyme catalysis]] [201] => * [[Industrial catalysts]] [202] => * [[Kelvin probe force microscope]] [203] => * [[Limiting reagent]] [204] => * [[Murburn concept]] [205] => * [[Pharmaceutic adjuvant]] [206] => * [[Phase-boundary catalysis]] [207] => * [[Phase transfer catalyst]] [208] => * [[Photocatalysis]] [209] => * [[Ribozyme]] (RNA biocatalyst) [210] => * [[SUMO enzymes]] [211] => * [[Temperature-programmed reduction]] [212] => * [[Thermal desorption spectroscopy]] [213] => }} [214] => {{Portal bar|Chemistry|Biology}} [215] => [216] => ==References== [217] => * {{GoldBookRef | title = catalyst | file = C00876}} [218] => {{reflist}} [219] => [220] => ==External links== [221] => [222] => {{Wiktionary|catalysis}} [223] => {{Commons category|Catalysis}} [224] => {{EB1911 poster|Catalysis}} [225] => * [https://web.archive.org/web/20080530162951/http://scienceaid.co.uk/chemistry/inorganic/catalysis.html Science Aid: Catalysts] Page for high school level science [226] => * [http://aci.anorg.chemie.tu-muenchen.de/wah/vortraege/catalysis.pdf W.A. Herrmann Technische Universität presentation] {{Webarchive|url=https://web.archive.org/web/20051028140531/http://aci.anorg.chemie.tu-muenchen.de/wah/vortraege/catalysis.pdf |date=October 28, 2005 }} [227] => * [http://www.tuat.ac.jp/~kameyama/ Alumite Catalyst, Kameyama-Sakurai Laboratory, Japan] [228] => * [http://www.inorganic-chemistry-and-catalysis.eu/ Inorganic Chemistry and Catalysis Group, Utrecht University, The Netherlands] [229] => * [http://www.biw.kuleuven.be/ifc/cok/home.htm Centre for Surface Chemistry and Catalysis] [230] => * [http://www.udec.cl/~carbocat Carbons & Catalysts Group, University of Concepcion, Chile] [231] => * [http://www.nsfcentc.org Center for Enabling New Technologies Through Catalysis, An NSF Center for Chemical Innovation, USA] [232] => * [http://www.sciencenews.org/view/generic/id/42507/title/Bubbles_turn_on_chemical_catalysts "Bubbles turn on chemical catalysts"] {{Webarchive|url=https://web.archive.org/web/20120722092341/http://www.sciencenews.org/view/generic/id/42507/title/Bubbles_turn_on_chemical_catalysts |date=July 22, 2012 }}, Science News magazine online, April 6, 2009. [233] => [234] => {{Branches of chemistry}} [235] => {{Reaction mechanisms}} [236] => {{Galvanic cells}} [237] => [238] => {{Authority control}} [239] => [240] => [[Category:Catalysis| ]] [241] => [[Category:Chemical kinetics]] [242] => [[Category:Articles containing video clips]] [] => )
good wiki

Catalysis

Catalysis is the process of increasing the rate of a chemical reaction by the presence of a substance called a catalyst. A catalyst facilitates the reaction without being consumed in the process, thus enabling the reaction to occur more quickly and efficiently.

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A catalyst facilitates the reaction without being consumed in the process, thus enabling the reaction to occur more quickly and efficiently. This process is widely used in various fields, such as industrial manufacturing, energy production, and environmental remediation. Catalysis plays a crucial role in accelerating chemical reactions that would otherwise be slow or energetically unfavorable. It lowers the activation energy required to initiate the reaction, allowing molecules to overcome the barrier and form products more easily. Catalysts can work by providing an alternative reaction pathway, stabilizing reactive intermediates, or enhancing reactant binding, among other mechanisms. Catalysis can occur in heterogeneous systems, where the catalyst and reactants exist in separate phases, or in homogeneous systems, where both catalyst and reactants are in the same phase. Different types of catalysts, including metals, metal oxides, enzymes, and organic compounds, can be employed depending on the nature of the reaction and the required conditions. Applications of catalysis range from large-scale industrial processes, such as petroleum refining and pharmaceutical synthesis, to smaller-scale applications like catalytic converters in vehicles that reduce harmful emissions. Catalysts are also used in the production of fertilizers, plastics, and chemicals, as well as in the development of more efficient energy sources, including fuel cells and solar cells. Catalysis has a significant impact on environmental sustainability by reducing waste generation, improving energy efficiency, and mitigating pollution. Research and development in this field continuously strive to discover new catalysts and optimize existing ones for improved performance and selectivity. Overall, catalysis is a fundamental process that enables numerous chemical reactions to occur efficiently, making it an indispensable tool in modern industrial processes and scientific research.

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