Multitrack reactor

Transient reactors, such as pulse (chromatographic) reactors, temporary analysis of products (TAP) reactors, multitrack reactors, and temperature-programmed reactors have been developed mainly to study gas-solid (catalyst) reactions. These are rather sophisticated techniques used to study mechanisms of catalytic processes at the molecular level in great detail. Since this is rarely done in the development of processes for the manufacture of fine chemicals and pharmaceuticals, these reactors are not discussed further. The interested reader is referred to works by Anderson and Pratt (1985) and Kapteijn and Moulijn (1997). 

We have applied our Multitrack reactor, an advanced TAP-like reactor system,23 to evaluate the number of redox-active Pt surface sites (Ptsurf redox) on Pt/A Os catalysts as a function of Pt dispersion. The number of Ptsurf redox sites was compared with the total number of Ptsurf sites determined by conventional volumetric CO chemisorption. 

The surface coverage on a catalyst can vary strongly as a function of the reactor position, even in a small reactor as used in Multitrack. 

The platinum catalyzed CO oxidation of carbon monoxide was studied using an advanced transient reactor system, referred to as Multitrack. The experiments indicate, that the reaction is taking place according to the Langmuir-Hinshelwood reaction model. The desorption of CO from the catalyst surface was shown to be a kinetically relevant step in the reaction. From experiments performed using it was shown that isotopic mixing occurs on the catalyst surface due to the decomposition of CO present on the catalyst surface. 

Figure 1. Schematical representation of the Multitrack system. Shown is the basic layout of the system, together with the typical gas pulse shapes as they are given to the reactor and measured at the analysis section.

The basic system of Multitrack consists of three vacuum chambers. The first contains a small reactor, which can be operated from 300 to 1273 K. The reactor used was 7 mm i.d. with a total bed height of 10 mm. The pressure in this vacuum chamber is about 10 mbar. To the reactor gas pulses can be given using high speed gas pulsing valves, with a pulse width of about 100 ps. For the experiments described here gas pulses of 10 to 10 molecules were applied. Using a flow valve it... 

The interaction of with a highly dispersed Pt/Al20s catalyst was studied at 523 K using Multitrack, a novel TAP-like reactor system. On a hydrogen reduced catalyst, initially i NO was rapidly decomposing, 3delding as main product, and only little amounts of The i NO-conversion decreased as the... 

In this contribution the application of an improved Temporal Analysis of Products (TAP) reactor system [7] in the analysis of NO-decomposition is described. The sensitivity of the Multitrack set-up (MULTIple Time Resolved Analysis of Catals ic Kinetics) is an important advantage compared to conventional TAP-reactors. The detection of small product amounts has become possible and thus, the analysis of low conversion reactions. Furthermore, without the necessity of averaging, transient processes can be monitored in real time. Here, we focused on the transformation of NO on reduced Pt-sites and the effect of the oxidation state of the Pt catalyst on N2O selectivity and (adsorbed) NO2 formation. 

In this study the Multitrack system, a TAP-like system [9], was used. In Figure 1 a schematical representation is given. A small reactor (7 mm inner diameter, bed height 10 mm) is located in an ultra-high vacuum system. Small amounts of reactants (lO -lO o molecules, 100 ps pulse width) can be pulsed into the reactor that typically operates at a pressure of 3 Pa. At the reactor exit the reaction products are analyzed by a quadrupole mass spectrometer. As this mass... 

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