Adding more catalyst increases the reaction rate by providing more active sites, despite the catalyst not being consumed.

Beyond Thermal Limits: Manipulating Reactive Intermediate Coverages and Turnover Rates via Visible Photon-Mediated Catalysis on Rh-Doped Perovskite Oxides. 2026. https://doi.org/10.1021/jacs.6c11493

Catalyst behavior depends on surface adsorbate energetics that are constrained by scaling relationships on metal surfaces. External stimuli (e.g., photons), however, can disrupt these limitations by modulating key intermediate coverages via non-thermal reaction pathways. Here, low-energy visible photon fluxes are utilized to selectively control coverages of strongly bound intermediates on isolated Rh active sites doped within a semiconductor perovskite oxide host (SrTiO 3 ). Red light (632 nm) facilitates selective photolytic CO desorption from rhodium gem-dicarbonyl (Rh(CO) 2 ) species that are ubiquitous reaction intermediates, including for the probe reaction studied herein CO oxidation to CO 2 . Thermochemical CO 2 formation rates (408 K) on Rh-doped SrTiO 3 are limited by adsorbed CO, exhibiting a negative apparent CO rate order (−0.6) and a positive O 2 rate order (+0.4). Arrhenius analyses, anaerobic CO oxidation measurements, and in situ spectroscopies assert that, thermochemically, lattice oxygens from the doped perovskite contribute to CO 2 formation rates. Notably, under red light illumination (0.76–2.02 W cm –2 ), the apparent CO rate order shifts to positive (+1). This, combined with decreasing apparent activation energies and CO coverages (wavelength-agnostic) with increasing photon flux, indicates that photons act selectively toward driving Rh(CO) 2 photolysis, even within complex reaction networks, thereby enhancing Rh accessibility, O 2 dissociation, and cons

Contact with Electrically Conductive Inert Solids Alters Intrinsic Heterogeneous Brønsted Acid Catalysis. 2025. https://doi.org/10.1021/jacs.5c12973

Interfacial electric fields at heterogeneous catalyst surfaces have been demonstrated to alter kinetics of liquid-phase reactions. In these systems, electric fields are generated from applying a potential to the catalyst through connection to a potentiostat or through electron transfer from redox-active species in solution. Here, we demonstrate that catalyst polarization can also occur by simply contacting electrically conductive inert solids, leading to the counterintuitive conclusion that a catalyst particle touching an inert solid can alter intrinsic reaction rates. Using dehydration of 1-methylcyclopentanol to 1-methylcyclopentene catalyzed by Brønsted-acidic carboxylic acid groups on carbon nanotubes as a proof-of-concept probe reaction, we show that catalyst contact with inert, thermally reduced carbon nanotubes leads to order-of-magnitude changes in reaction rate. Furthermore, we demonstrate that these contact-induced effects can also be observed under standard laboratory reaction conditions, where particle-to-particle contact in stirred catalyst powder suspensions is sufficient to demote rates by ∼8-fold. This work provides the foundation for a new method of reaction rate control, which could have implications whenever heterogeneous catalyst particles are in contact with inert materials for liquid-phase reactions in the presence of electrolyte.

Simple English Wikipedia: Catalysis. https://simple.wikipedia.org/wiki/Catalysis

Catalysis Catalysis is the process of change in rate (speed) of a chemical reaction due to the help of a catalyst. Unlike other chemicals which take part in the reaction, a catalyst is not consumed by the reaction itself. A catalyst may participate in many chemical reactions. Catalysts that speed the reaction are called positive catalysts. Catalysts that slow the reaction are called negative catalysts, or inhibitors. Substances that increase the activity of catalysts are called promoters, and substances that deactivate catalysts are called catalytic poisons. In chemistry A catalyst is something which changes the rate of a chemical reaction. An example is when manganese oxide (MnO2) is added to hydrogen peroxide (H2O2), and the hydrogen peroxide starts to break up into water and oxygen. Catalysts are either of natural or synthetic origin. Catalysts are useful because they leave no residue in the solution they have sped up. A catalyst can also be used in a reaction again and again as it is not used up. There are many catalysts in our body which play an important part in many biochemical reactions. These are called enzymes. Catalysis (, kə-TAL-iss-iss) is the increase in rate of a chemical reaction due to an added substance known as a catalyst ( KAT-əl-ist). Catalysts are not consumed by the reaction and remain unchanged after the reaction. If the reaction is rapid and the catalyst is recycled quickly, a very small amount of catalyst often suffices; mixing, surface area, and temperature are important factors in reaction rate. Catalysts generally react with one or more reactants to form intermediates that subsequently give the final reaction product, in the process of regenerating the catalyst. The rate increase occurs because the catalyst allows the reaction to occur by an alternative mechanism which may be much faster than the noncatalyzed mechanism. However the noncatalyzed mechanism does remain possible, so that the total rate (catalyzed plus noncatalyzed) can only increase in the presence of the catalyst and never decrease. Catalysis may be classified as either homogeneous, whose components are dispersed in the same phase (usually gaseous or liquid) as the reactant, or heterogeneous, whose components are not in the same phase. Enzymes and other biocatalysts are often considered as a third category. Furthermore, a nanocatalyst is a nanosize catalyst used in the field of applied nanoscience. Catalysis is nearly ubiquitous in the chemical industry. Estimates are that 90% of all commercially produced chemical products involve catalysts at some stage in the process of their manufacture. The term "catalyst" is derived from Greek 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. Catalysts enable pathways that differ from those of uncatalyzed reactions. These pathways have lower activation energy. Consequently, more molecular collisions have the energy needed to Heterogeneous catalysts act in a different phase than the reactants. Most heterogeneous catalysts are solids that act on substrates in a liquid or gaseous reaction mixture. Important heterogeneous catalysts include zeolites, alumina, higher-order oxides, graphitic carbon, transition metal oxides, metals such as Raney nickel for hydrogenation, and vanadium(V) oxide for oxidation of sulfur dioxide into sulfur trioxide by the contact process. Diverse mechanisms for reactions on surfaces are known, depending on how the adsorption takes place (Langmuir-Hinshelwood, Eley-Rideal, and Mars-van Krevelen). 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. 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. 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. The reacting gases 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. 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. Heterogeneous catalysts are typically "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.

Zirconocene catalyst with boron cocatalyst for methyl methacrylate polymerization. 2025. https://doi.org/10.58837/chula.the.2001.977

Zirconocene catalyst, rac-Et(Ind)2ZrCl2 was alkylated with Grignard reagent, then combined with a boron cocatalyst: B(C6F5)3, Ph3C+B(C6F5)4- or PhNMe2H+B(C6F5)4-. To perform the polymerization of methyl methacrylate monomer, Zn(C2H5)2 which is a Lewis acid, was used to complex with methyl methacrylate before adding the catalyst to the reaction in order to protect the zirconocene catalyst from being poisoned with a polar functional group of the monomer. The role of Lewis acid presumably involved in the initiation step of polymerization. The reaction can be carried out over a range of polymerization temperature from -78 degree celcius to 30 degree celcius. The polymer obtained was isotactic poly(methyl methacrylate) (PMMA) with high molecular weight, revealed from NMR spectrum and GPC measurement. In addition, the glass transition temperature of the polymer from DSC measurement was around 50 degree celcius. The catalytic activity increases with an increase of catalyst concentration. The polymer yield increases with polymerization time, which indicates that the propagation rate is independent on monomer concentration. The optimum mole ratio of MMA/Zn is 4. In this study, the narrow molecular weight distribution, a characteristic demonstrated by metallocene catalyst is also shown (Mw/Mn<2.5). Chula DigiVerse: Digital Preservation of Chulalongkorn University --> --> Zirconocene catalyst with boron cocatalyst for methyl methacrylate polymerization Peerawat Kajornkiratikul Boron ,Polymerization ,Methyl methacrylate ,Zirconocene หน้าหลัก Collections {{biblio_info.main_cat_name_en}} {{biblio_info.cat_name}} --> {{date_view}} {{counter_view}} Report a problem --> Report a problem --> Collections {{biblio_info.main_cat_name}} {{biblio_info.main_cat_name_en}} {{biblio_data.cat_info.cat_name}} {{biblio_data.cat_info.cat_name_en}} {{key}} -1 || key == 'เลขประจำเอกสารดิจิทัล'" href="http://Doi.Org/{{value}}" target="_blank">{{value}} EndNote OpenURL 0"> Digital File 0"> E-book 0"> Media {{value.file_name_original}} 0"> ( {{value.num_page}} Pages ) {{value.file_size}} --> vertical_align_bottom Download {{value.file_name_original}} {{v.file_name_original}} {{v.file_size}} --> vertical_align_bottom Download listLimit" ng-click="changeDigitalFileList(false)"> Show More Close {{value.file_name_original}} 0"> ( {{value.num_page}} Pages ) {{value.file_size}} galleryLimit" ng-click="changeDigitalFileMobile(false)"> Show More Close galleryLimit" ng-click="changeDigitalFile(false)"> Show More Close 0"> ไม่มีข้อมูล View as E-Book 0"> ไม่มีข้อมูล {{value.file_name_original}} ( {{value.file_size}} ) ( Duration: {{value.vedio_duration}} ) --> visibility View {{value.file_name_original}} {{value.file_size}} ( Duration: {{value.vedio_duration}} ) galleryLimit" ng-click="changeDigitalFileMobile(false)"> Show More Close galleryLimit" ng-click="changeDigitalFile(false)"> Show More Close Login For Download Digital File >>> 'Default_Bio' --> {{key | uppercase}} --> Recommended Reference Exif File {{value.description}} {{value.exif_data}} - Data Not found - Back Exift File &times; 0"> Member item (hasPart) = 6" data-ng-href="{{base_url + 'info/relationItem/' + 1 + '/dc:' + bibid}}" class="link-title" target="_blank"> All {{value.title}} 0"> Main item (isPartOf) = 6" data-ng-href="{{base_url + 'info/relationItem/' + 2 + '/dc:' + bibid}}" class="link-title" target="_blank"> All {{value.title}} 0"> Main format (isFormatOf) = 6" data-ng-href="{{base_url + 'info/relationItem/' + 3 + '/dc:' + bibid}}" class="link-title" target="_blank"> All {{value.title}} 0"> First-version item record (isVersionOf) = 6" data-ng-href="{{base_url + 'info/relationItem/' + 4 + '/dc:' + bibid}}" class="link-title" target="_blank"> All {{value.title}} 0"> Alternative format (hasFormat) = 6" data-ng-href="{{base_url + 'info/relationItem/' + 5 + '/dc:' + bibid}}" class="link-title" target="_blank"> All {{value.title}} 0"> Related Books Related items = 6 && cat_order == 1" id="show-btn-list" data-ng-href="{{base_url + 'info/listItem/' + cat_id}}" class="link-title" target="_blank"> All --> {{value.title}} --> ปิดหน้าต่าง -->

Catalytic gasification characteristics of mixed black liquor and calcium catalyst in mixing (air/steam) atmosphere. 2008. https://doi.org/10.1016/s1872-5813(08)60025-0

Abstract The catalytic effect of single and mixed catalysts including two single catalysts with 3% Ca and 5% Na-BL, and one 3% Ca+5% Na-BL mixed catalyst on carbon conversion, gasification reaction rate, relative amount of harmful pollutant like sulphur containing gases under temperature ranging from 750°C to 950°C and ambient pressure conditions were investigated by thermogravimetry in mixing (air/steam) gasification for three high-metamorphous anthracites of Longyan, Fenghai, and Youxia coals. The mixed BL+Ca catalyst has a synergetic effect in comparison with only using single BL and Ca catalyst. At mixing gasification the mixed catalyst of 3% Ca+5% Na-BL greatly increases the carbon conversion and reaction rate by accelerating the reactions of C+CO2→2CO and C+H2O→CO+H2 because of the presence of alkali surface compounds [COM] and [CO2M], and exchanged calcium phenolate and calcium carboxylate (COO)2. This catalytic action is stronger than steam gasification. By adding CaCO3 into BL catalyst in gasification less than 900°C, the catalytic ability is improved with increasing coal conversion and effective desulphurization.

Hydrogen production from NaBH₄ hydrolysis over chemically reduced TiO₂-based Ru nanocomposites and their antimicrobial performance.. 2026. https://doi.org/10.1038/s41598-026-42735-1

Herein, Ru⁰/TiO₂ nanocomposites containing 0.5 wt% Ru were prepared via a simple wet-impregnation route followed by chemical reduction and were thoroughly characterized by XRD, FTIR, SEM, TEM, and EDS analyses. The nanocomposite exhibits high activity toward the hydrolysis of NaBH₄ in water under relatively mild conditions (300 mM NaBH₄, without added base). Systematic variation of NaBH₄ concentration and catalyst loading shows that the hydrogen generation rate is essentially first order in both NaBH₄ and Ru⁰/TiO₂, yielding hydrogen generation rates in the range of ≈ 335.6 mL·min⁻¹·g_cat⁻¹ and turnover frequencies (TOF) of ≈ 938.30 h⁻¹ between 25 and 40 °C. Temperature-dependent kinetic measurements afforded an apparent activation energy of 32.37 kJ·mol⁻¹ together with ΔH‡ = 29.82 kJ·mol⁻¹ and ΔS‡ = -143 J·mol⁻¹·K⁻¹, indicating an energetically accessible yet highly ordered transition state at the Ru/TiO₂ interface. The catalyst retains ~ 36% activity after 4 cycles. In addition, Ru⁰/TiO₂ nanocomposites display strong antibacterial activity against both Gram-positive and Gram-negative bacteria, achieving growth inhibition above 90% at 500 µg·mL⁻¹. The dual functionality of Ru⁰/TiO₂ in highly efficient NaBH₄ hydrolysis and pronounced antimicrobial behavior highlights this nanocomposite as a versatile platform for practical chemical hydrogen storage and integrated energy and environmental applications.

LibreTexts: Catalytic Hydrogenation of Alkenes. https://chem.libretexts.org/Bookshelves/Organic_Chemistry/Supplemental_Modules_(Organic_Chemistry)/Alkenes/Reactivity_of_Alkenes/Catalytic_Hydrogenation_of_Alkenes

This reaction is exothermic. It will occur, but it is very slow without a catalyst. The Catalyst A catalyst increases the reaction rate by lowering the activation energy of the reaction. Although the catalyst is not consumed in the reaction, it is required to accelerate the reaction sufficiently to be observed in a reasonable amount of time. Catalysts commonly used in alkene hydrogenation are: platinum, palladium, and nickel. The metal catalyst acts as a surface on which the reaction takes place. This increases the rate by putting the reactants in close proximity to each other, facilitating interactions between them. With this catalyst present, the sigma bond of H2 breaks, and the two hydrogen atoms instead bind to the metal (see #2 in the figure below). The \(\pi\) bond of the alkene weakens as it also interacts with the metal (see #3 below). Since both the reactants are bound to the metal catalyst, the hydrogen atoms can easily add, one at a time, to the previously double-bonded carbons (see #4 and #5 below). The position of both of the reactants bound to the catalyst makes it so the hydrogen atoms are only exposed to one side of the alkene.

Statistical screening analysis of the chemical composition and kinetic study of phenol-formaldehyde resins synthesized in the presence of polyamines as co-catalysts. 2018. https://doi.org/10.1371/journal.pone.0195069

The physico-chemical and application properties of phenol-formaldehyde resins used in the production of laminated plastics depend on such factors as: type and amount of catalyst, formaldehyde-to-phenol mole ratio, temperature and time of the synthesis process. The special impact on the reaction mechanism and kinetics, e.g. on the formation of mono-, di- and trihydroxymethyl derivatives of phenol (PhOH) is a consequence of the type and amount of the catalyst. This paper presents the results of optimisation research of resol resin synthesis catalysed by trimethylamine (TEA) carried out according

Enzyme. https://en.wikipedia.org/wiki/Enzyme

protein, that acts as a biological catalyst, accelerating chemical reactions without being consumed in the process. The molecules on which enzymes act are An enzyme is a biological macromolecule, usually a protein, that acts as a biological catalyst, accelerating chemical reactions without being consumed in the process. The molecules on which enzymes act are called substrates, which are converted into products. Nearly all metabolic processes within a cell depend on enzyme catalysis to occur at biologically relevant rates. A metabolic pathway is typi An enzyme is a biological macromolecule, usually a protein, that acts as a biological catalyst, accelerating chemical reactions without being consumed in the process. The molecules on which enzymes act are called substrates, which are… Enzymes are generally globular proteins, acting alone or in larger complexes. The sequence of the amino acids specifies the structure which in turn determines the catalytic activity of the enzyme. Although structure determines function, a novel enzymatic activity cannot yet be predicted from structure alone. Enzyme structures unfold (denature) when heated or exposed to chemical denaturants and this disruption to the structure typically causes a loss of activity. Enzyme denaturation is normally linked to temperatures above a species' normal level; as a result, enzymes from bacteria living in volcanic environments such as hot springs are prized by industrial users for their ability to function at high temperatures, allowing enzyme-catalyzed reactions to be operated at a very high rate. Enzymes are usually much larger than their substrates. Sizes range from just 62 amino acid residues, for the monomer of 4-oxalocrotonate tautomerase, to over 2,500 residues in the animal fatty acid synthase. Only a small portion of their structure (around 2–4 amino acids) is directly involved in catalysis: the catalytic site. This catalytic site is located next to one or more binding sites where residues or An enzyme is a biological macromolecule, usually a protein, that acts as a biological catalyst, accelerating chemical reactions without being consumed in the process. The molecules on which enzymes act are called substrates, which are converted into products. Nearly all metabolic processes within a cell depend on enzyme catalysis to occur at biologically relevant rates. A metabolic pathway is typically composed of a series of enzyme-catalyzed steps. The study of enzymes is known as enzymology, and a related field focuses on pseudoenzymes—proteins that have lost catalytic activity but may retain regulatory or scaffolding functions, often indicated by alterations in their amino acid sequences or unusual 'pseudocatalytic' behavior. Enzymes are known to catalyze over 5,000 types of biochemical reactions. Other biological catalysts include catalytic RNA molecules, or ribozymes, which are sometimes classified as enzymes despite being composed of RNA rather than protein. More recently, biomolecular condensates have been recognized as a third category of biocatalysts, capable of catalyzing reactions by creating interfaces and gradients—such as ionic gradients—that drive biochemical processes, even when their component proteins are not intrinsically catalytic. Enzymes increase the reaction rate by lowering a reaction's activation energy, often by factors of millions. A striking example is orotidine 5′-phosphate decarboxylase, which accelerates a reaction that would otherwise take millions of years to occur in milliseconds. Like all catalysts, enzymes do not affect the overall equilibrium of a reaction and are regenerated at the end of each cycle. What distinguishes them is their high specificity, determined by their unique three-dimensional structure, and their sensitivity to factors such as temperature and pH. Enzyme activity can be enhanced by activators or diminished by inhibitors, many of which serve as drugs or poisons. Outside optimal conditions, enzymes may lose their structure through denaturation, Enzymes are generally globular proteins, acting alone or in larger complexes. The sequence of the amino acids specifies the structure which in turn determines the catalytic activity of the enzyme. Although structure determines function, a novel enzymatic activity cannot yet be predicted from structure alone. Enzyme structures unfold (denature) when heated or exposed to chemical denaturants and this disruption to the structure typically causes a loss of activity. Enzyme denaturation is normally linked to temperatures above a species' normal level; as a result, enzymes from bacteria living in volcanic environments such as hot springs are prized by industrial users for their ability to function at high temperatures, allowing enzyme-catalyzed reactions to be operated at a very high rate. Enzymes are usually much larger than their substrates. Sizes range from just 62 amino acid residues, for the monomer of 4-oxalocrotonate tautomerase, to over 2,500 residues in the animal fatty acid synthase. Only a small portion of their structure (around 2–4 amino acids) is directly involved in catalysis: the catalytic site. This catalytic site is located next to one or more binding sites where residues orient the substrates. The catalytic site and binding site together compose the enzyme's active site. The remaining majority of the enzyme structure serves to maintain the precise orientation and dynamics of the active site. In some enzymes, no amino acids are directly involved in catalysis; instead, the enzyme contains sites to bind and orient catalytic cofactors. Enzyme structures may also contain allosteric sites where the binding of a small molecule causes a conformational change that increases or decreases activity. A small number of RNA-based biological catalysts called ribozymes exist, which again can act alone or in complex with proteins. The most common of these is the ribosome which is a complex of protein and catalytic RNA components.