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Special Methods


Thermal Gravimetry (TG) and Differential Thermal Analysis (DTA)

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Temperature-Programmed Methods: Reduction (TPR), Oxidation (TPO), Desorption (TPD)

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A Set of Calorimetric Methods for the Study of Dispersed Systems and Reaction Heats

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Differential Scanning Calorimetry

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Detection of Free Radicals in Gas Phase

Objects of study

Heterogeneous reactions with hydrocarbon participation accompanied by the formation of free radicals and excited molecules in gas phase. The following reactions are of interest: complete and partial oxidation, hydrogenation and dehydrogenation, catalytic pyrolysis, alkylation and others.

Applications

Free radicals and excited molecules formed on a catalyst surface can initiate parallel gas-phase conversion of reagents. This process must be taken into account in the study of kinetics and reaction mechanism. Two methods have been developed for detection of radicals in gas phase, namely matrix isolation technique with EPR and direct mass-spectrometric detection.

Instrument facilities

  1. Matrix isolation technique. Radicals are detected with EPR. To accumulate the radicals a gas mixture after the reactor is frozen out in a collector cooled by liquid nitrogen mounted in an EPR resonator. Then the frozen condensate is irradiated with UV light and the radicals formed in the photolysis are studied. Products incondensable at 77 K are analyzed with MX-7301 mass-spectrometer. A flow reactor of ideal mixing with the pressure range from 1 to 20 Pa is applied. The sensitivity of the method is 108 radicals/cm3.
  2. Direct mass-spectrometric detection of free radicals. Mass-spectrometric set-up UR-1 with variable energy of ionizing electrons has been assembled. This setup allows to detect both radicals and stable products of a chemical reaction. A molecular beam of reaction products is directed into a mass-spectrometer with a sampling time less than 0.1ms. Simultaneous detection of 10 components is possible during a kinetic measurement. The flow reactor of ideal substitution with the pressure range from 100 to 105 Pa is applied. The method sensitivity by the methyl radicals is 1011 radicals/cmsup>3.

Leading scientists and their research interests

A.Yu. Gladky. Alcohol oxidation, intermediates in steam conversion of methane, propane pyrolysis.


Radioisotope Methods for the study of the mechanisms and reactions kinetics

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