CONTENT AND FORMS OFADSORBED HYDROGEN ON METHANOL SYNTHESIS CATALYSTS CuO/ZnO/Al2O3

Abstract

The condition of hydrogen bound by the active centers of CuO/ZnO/Al2O3has been inves-tigated by the complex of thermal analysis and mass spectrometry. There are four forms of surface hydrogen: molecular weakly bound and three atomic strongly bound with desorption temperatures 200-900 °C. The presence of structural hydrogen in the active catalyst have been determineddue to the difference in the values of reactive and structural hydrogen. Desorption temperatures and heats have been determined for molecular and atomic forms of hydrogen in the studied catalytic systems. The effect of the catalyst structure obtained by various methods on the adsorbed hydrogen condition and reaction activity in methanol synthesis is shown. Also, studies of catalytic systems of the composition CuO/ZnO/Al2O3were carried out using the methods of X-ray phase and energy dispersive spectroscopy, temperature-programmed reduction in a hydrogen-containing gas, elec-tron microscopy, low-temperature nitrogen adsorption, and the selectivity of the catalyst for meth-anol, methane and dimethyl ether was determined in the temperature range of 200-300 °C and pressure in the system 3 MPa. The activity and selectivity of catalytic systems are compared with industrial analogues. The morphology of the catalyst surface have been analyzed at various accel-erating voltages of the electron microscope cathode. The absence of a direct relationship between the activity and selectivity values of the studied catalytic systems and the specific surface area has been experimentally proven. The operational properties of industrial and catalytic systems synthe-sized in the work are close. The difference in selectivity for methanol can be unambiguously ex-plained by the adsorption properties with respect to hydrogen.