Catalysis and catalysts
CATALYSIS AND CATALYSTS 8
Acatalyst describes a compound, which when added to a chemicalreaction, the rate of the reaction increases however, the compoundremains unchanged at the conclusion of the chemical reaction. Acatalyst usually accelerates a reaction through forming bonds withthe reacting species. In almost 90% of the chemical industry productscatalytic processes are exceedingly indispensable (Spivey &Dooley,2011. Pp 38). For example, in the production of fine and bulkchemicals and production of transportation fuels catalytic processesare vital. Therefore, in chemical industry, it is remarkably hard toignore the contributions of catalysts. In fact, one of the mostreasons why catalysts are utilized in the chemical industries is tomitigate the cost of production. This is because as rates ofreactions are increased, less time and cost is realized in obtaininga certain product. Catalysis is therefore, the phenomenon where acatalyst accelerates a chemical reaction. Catalysis may entail biocatalysis, heterogeneous and homogeneous catalysis. The aim of thisessay will be discussing Maxwell Boltzmann distribution diagram andenthalpy diagram indicating activation complex. Furthermore, examplesof homogeneous and heterogeneous catalysts and their mechanism ofwork will also be addressed in the essay.
MaxwellBoltzmann Distribution Diagram, Collision Theory and Concept ofActivation Energy
Accordingto the collision theory, reacting species need to collide with oneanother in order for a reaction to occur. However, it is not allcollisions that result to a chemical change. A collision can only beeffecting in resulting to a chemical change if the species collidinghave a given minimum amount of internal energy, which is equivalentto the activation energy of a reaction. Besides, the speciescolliding should become oriented in a way favorable to the basicrearrangement of electrons and atoms. Therefore, according to thetheory, the rate of a chemical reaction is equivalent to thefrequency of effective collisions.
Theparticles, which are represented under the area to the right of theactivation energy, have the capacity to react upon collision.However, a great majority do not possess sufficient energy, whichwill make them simply bounce apart. In order to speed up thereaction, one would require augmenting the number of particles havingenergies greater than or equaling the activation energy.
EnthalpyDiagram Showing Activation Complex Catalyst Pathway
Anactivated complex describes an intermediate state, which becomesformed during the process of converting reactants into products(Spivey &Dooley,2011. Pp 57). It is the structure, which results at the highestenergy point in the reaction path. In an exothermic reaction, some ofthe reactants’ enthalpy becomes released to the surroundings in theform of heat. As a consequence, the enthalpy of the reactants is morethan that of the products. The following enthalpy diagram depicts theactivated complex in an exothermic reaction.
Onthe other hand, heat is usually taken from the surrounding, when itcomes to endothermic reactions. This energy is transferred to theproducts therefore, the enthalpy of the reactants is usually lesscompared to that of the products. The enthalpy diagram for such areaction is as depicted below.
Incatalysis, a homogeneous catalyst describes a catalyst that is in thesame phase as the reacting species. The working of a homogeneouscatalyst is such that one of the reactants reacts with thehomogeneous catalyst, leading to the creation of an intermediatesubstance. Then, the intermediate product reacts with the otherreactant, forming a final product. In the process, the homogeneouscatalyst retains its original form. An example of a homogeneouscatalyst is iron (II) ions in a reaction between iodide ions andpersulphate ions. In this reaction, the reactants and the catalystare in the same phase. In this reaction, iron (II) ions becomeoxidized to iron (III) ions by the persulphate ions (Bhaduri& Mukesh, 2000. Pp 127). However, since iron (III) ions arestrong oxidizing agents, they oxidize the iodide ions to iodine. Inthis process, the iron (III) ions are reduced back to iron (II) ions.Therefore, at the conclusion of the reaction, iron (II) ions, whichare the catalyst, remain unchanged. Another example of a homogeneouscatalyst entails the chlorine atom in the decomposition of the ozone.In this case, the catalyst and the reactants exist in the gas phase,which qualify the chlorine atom to be viewed as a homogeneouscatalyst in the process. Although ozone can decompose under theinfluence of atmospheric light, the decomposition process becomesaccelerated by a chlorine atom. In the decomposition process, thechlorine atom keeps on being regenerated. Therefore, at theconclusion of the reaction, the chlorine atom remains unaltered.
Aheterogeneous catalyst describes a catalyst, which has a differentphase from the reactants. For instance, the catalyst may have a solidphase while the reactants have a liquid phase. The working of oneheterogeneous catalyst is the same for all heterogeneous catalysts.During heterogeneous catalysis, one or more reactants become adsorbedon the surface of the active sites of a catalyst. The interaction ofthe reactant molecules and the active sites of the catalyst make thereactants become more reactive. The catalyst then desorbs the productmolecules this makes the active sites free and available for newreactant molecules (Ross,2012. Pp 62). An example of a heterogeneous catalyst entails nickelcatalyst in the reaction between hydrogen and ethene. In thisreaction, the ethene molecules become adsorbed on the surface of thecatalyst nickel. The double bond amid the carbon atoms splits and theelectrons are utilized in bonding it to the nickel surface. Hydrogenmolecules also become adsorbed on the surface of nickel. Then, theproduct molecules break off from the surface of nickel, leavingactive sites available for other new molecules. Another example of aheterogeneous catalyst entails iron in the process of making ammonia,where nitrogen and hydrogen gas react (Thomas &Thomas,1997. Pp 102). In this case, iron, which is in solid phase, catalyzesa reaction between reactants that are in gas phase. This makes ironto qualify as a heterogeneous catalyst in the process.
Exampleof Catalytic Poisoning
Catalyticpoisoning describes a situation, where reacting substances orreaction products form substances that result in the reduction of theeffectiveness of a catalyst. An example of catalytic poisoningentails lead on catalysts in hydrogenation reactions.
Catalysisprocess emerges as an indispensable process in the chemicalindustries due to its benefits. A key benefit of the catalysisprocess is the reduction of both operation and investment costs inthe chemical processes. Besides, catalysts are significant in thechemical industry because they accelerate reactions enablingindustrial vital reactions become carried out efficiently inpractically attainable conditions.
Bhaduri,S., & Mukesh, D. 2000, HomogeneousCatalysis: Mechanisms and Industrial Applications,Hoboken, NJ: John Wiley & Sons.
Ross,J. R. H. 2012, Heterogeneouscatalysis: Fundamentals and applications,Amsterdam: Elsevier.
Spivey,J. J., & Dooley, K. M. 2011, Catalysis.Vol. 23: A review of recent literature,Cambridge: Royal Society of Chemistry.
Thomas,J. M., & Thomas, W. J. 1997, Principlesand practice of heterogeneous catalysis,New York: VCH.