XPS, UPS and TDS studies of CO adsorption on platinum

XPS, UPS and TDS studies of the adsorption of carbon monoxide on partially recrystallized platinum foil at 300 K indicate that the adsorption is of nondissociative character and there are two CO_ads states.

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300 K. , . CO.

     

The application of XPS to the determination of the kinetics of the co oxidation reaction over the Ir(111) surface

The coverages of adsorbed oxygen and CO on an Ir(111) surface have been determined using X-ray photoelectron spectroscopy (XPS) during the steady-state catalytic production of CO₂. Correlating the coverages of the reacting adsorbates with the rate of CO₂ production allows the kinetics of the CO oxidation reaction to be determined. The reaction is found to obey a Langmuir-Hinshelwood rate expression of the form , where R_CO2 is the rate of CO₂ production, k⁰ is the pre-exponential factor of the reaction rate coefficient, [CO] and [O] are the surface coverages of CO and oxygen, respectively, and E_a is the activation energy for the oxidation reaction. The activation energy for this catalytic oxidation reaction is found to be approximately 9 $\text{kcal}\text{mole}$.     

State of components in supported catalysts prepared via interaction of platinum-tin complexes with Al2O3 surface

The interaction of platinum-tin complexes with the OH groups of Al₂O₃ is shown to lead to the formation of surface complexes in which tin ions bonded to the support are not reduced to metal and inhibit platinum agglomeration.

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OH- Al₂O₃ , .

     

Use of time-of-flight mass spectrometry for monitoring helium microcontamination in the industrial manufacture of extra high purity inert gases

A time-of-flight EMG-20-9 mass spectrometer was designed for the online monitoring of helium impurity at the 0.05 ppm level. The spectrometer was introduced for the continuous control of the gas mixture composition in the technology of neon purification from the helium impurity in spite of the large difference in the concentrations of components. The instrument was certified as a measuring facility and introduced into the State Register of Measurement Instrumentation of the Russian Federation. The characteristics of the mass spectrometer and its modifications were overviewed and its possibilities for monitoring xenon and krypton production from air were shown.     

Artificial ribonucleases. 5. Synthesis and ribonuclease activity of tripeptides composed of amino acids involved in catalytic centers of natural ribonucleases

The characteristic features of the spatial arrangement of the main functional groups involved in catalytic centers of ribonucleases and nucleases were revealed by computer analysis of the catalytic centers of these enzymes. Based on the results of computer simulation, tripeptides containing Lys, Arg, His or Hia, Thr, and Asn in different combinations were synthesized. In these tripeptides, the distances between the corresponding functional groups are equal to those observed in natural enzymes. The efficacy of RNA cleavage with Arg- and His-containing tripeptides depends on their structure and correlates with the overall positive charge of these compounds. Of all the tripeptides under consideration, compounds bearing the overall charge of +4 exhibit the highest ribonuclease activity.