III International Conference

PP-I-59THE CHARACTERISTICS OF INDIVIDUAL HYDROGEN FORMS CONNECTEDBY THE SURFACE OF THE SKELETAL NICKEL CATALYST IN SOLUTIONSBarbov A.V., Ulitin M.V., Shepelev M.V.The Ivanovo State University of Chemistry and Technology, Ivanovo, RussiaE-mail: physchem@isuct.ruThermodynamic characteristics of individual forms of hydrogen adsorbed on the surfaceof the skeletal nickel catalyst of various nature and structure solvents are calculated accordingto the data of adsorption–calorimetric experiment. The quantitative redistribution between theindividual forms of the adsorbed hydrogen is shown to be a principal cause of solvents natureand structure influence on the laws of adsorption.The numerous researches of real catalysts properties on the basis of metals and theiroxides, skeletal nickel catalysts included, have shown their surface to be energeticallyheterogeneous. The principal cause of power surface heterogeneity is the existence of variousforms of the reacting substances adsorbed on the active centers of the catalyst.Thermodynamic characteristics of the adsorption stages of hydrogen on catalytic activesurfaces are known to define the energy of intermediate interactions, speed and selectivity inliquid phase hydrogenation reactions.The analysis of literature data and the adsorption–calorimetric measurements evidencethat there are three individual forms of hydrogen on the surface of the skeletal nickel catalystat a room temperature – one molecular α 1 –form and two atomic γ– and β 2 –forms, the bondenergies with the surface being 20÷40, 60÷100 and 125÷250 kJ/mol, respectively. Nowadaysthermodynamic characteristics of adsorbed hydrogen individual forms have been obtained forthe processes, proceeding in a gas phase on ideal monocrystals surfaces. Moreover, thefindings are often unreasonably transferred to liquid phase catalytic systems. The laws ofhydrogen adsorption in liquid phase processes significantly depend on the nature and structureof a solvent. However, the reasons of solvent influence on the laws of hydrogen adsorption onthe surface of metals and catalysts in solutions remain obscure.Data about the quantity of the adsorbed hydrogen, sizes of adsorption at various pressuresof hydrogen, heats of adsorption depending on a coverage in various solvents at 303 K,obtained by an adsorption–calorimetric method, as well as literature data, allowed us tocalculate thermodynamic characteristics of the individual forms of the hydrogen. They wereadsorbed from solutions on the surface of skeletal nickel catalyst. These thermodynamic111