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Notes

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.

LABORATORY AND COMMERCIAL-SCALE CATALYTIC REACTORS

Designing and using laboratory-scale reactors for studying catalysts can be a very confusing process. Laboratory catalytic reactors are used for a variety of objectives including catalyst screening and evaluation, determination of reaction data, simulation of commercial process conditions, studies of catalyst pretreatments or aging, etc. Each of these objectives lends itself to a specific design of the reactor in order to achieve results which are meaningful. This Altamira Note discusses three common applications of laboratory-scale reactors and the suitability of various reactor types for these different research and development applications.