Offline    1.412.963.6385

Build My System

Notes

MEASURING ACIDITY IN ZEOLITES USING TPD

Temperature-programmed desorption (TPD) of basic molecules from the surface of zeolites has been extensively used to measure their acid properties. The TPD experiment consists of sorbing a base molecule on the material of interest and, while flushing the surface with an inert gas, linearly ramping the temperature and measuring the desorption of the base. By quantitatively measuring the amount of base desorbed and noting the temperature(s) of desorption, information can be obtained on both the intrinsic and extrinsic acid properties in a single experiment (See Figure 1).

EFFECT OF SOME EXPERIMENTAL PARAMETERS ON TPR PROFILES

Temperature-programmed reduction (TPR) techniques can yield direct information on the reducibility of catalysts and catalyst precursors and is an excellent technique for characterizing a variety of catalysts. The technique consists of exposing the sample to a flowing mixture of a reducing agent, such as hydrogen, in an inert gas while linearly ramping the temperature. The rate of consumption of the reducing agent is monitored and related to the rate of reduction of the sample. Figure 1 shows the TPR profile obtained for a 10% NiO/Si02 catalyst using a 10% H2/Ar mixture at a flow rate of 30 ml/min and a linear heating rate of 20 K/min. Such a signal gives information concerning the ease of reducibility (temperature at maximum) as well as the extent of reducibility (signal area) of the material being studied. An excellent comprehensive description of this technique is found in the book "TemperatureProgrammed Reduction for Solid Materials Characterization" by A. Jones and B.D. McNicol (Marcel-Dekker, Inc., 1986).
 
 

INTRODUCTION TO SLURRY REACTORS

Many industrial processes involve multi-phase systems, and perhaps the most complex is the gas-liquid-solid or slurry reactor. The complexity of this system arises from the simultaneous presence of mass and heat transport involving all three phases in addition to reaction. Although the transport phenomena can often be theoretically evaluated, by assuming limiting cases, the addition of the reactor operating characteristics and slurry physical properties introduces further complexities. Empirical correlation based on a particular reactor at actual operating conditions must then be utilized.