Reactant dosing

Continuous in-line measurements and control of the mass material balance in the process, with automatic feedback to the reactants dosing devices (performed either by computerized system or by traditional flow control loops). 

Example 2 Reactant Dosing with Membranes ( Distributor )... 

Also chain growth to oligomerization is not uncommon, coating and blocking reactors by precipitation. Furthermore, the insolubility of fluorine in most solvents challenges reactant dosing because the gas-liquid interface, typically not well defined, is now the means to determine and control mass transfer and reaction rate and selectivity. 

A typical instrument for XRD of a working catalyst consists of a (commercial) powder diffraction instrument, a reaction cell, and the auxiliary equipment for reactant dosing and product analysis. It is desirable to use a computer system that simultaneously controls all these functions or at least records the sample temperature and experiment time together with the diffraction information. A single experiment characterizing a catalyst under working conditions typically produces a large amount of data, the analysis of which consumes much more time than the experiment. Thus, accurate documentation is mandatory and is best supported by automatic routines. 

Typical thermal and photolytic techniques may be used but a common method is to fill an ampoule, fitted with a break-seal, with the reactant or reactants, dose, quench in liquid nitrogen, and reattach to the vacuum. This is followed by conventional analysis. Facilities for heating the sample at the radiation source can be employed. RV s are constructed from Pyrex or metal " and may in some cases be coated with graphite. However, with different surfaces, different products can result . Thin-walled RV s have to be used for a-particle-induced reactions . In the radon-sensitised reaction of Hj and O2, Lind has shown that the rate coefficient is inversely proportional to the square of the diameter of a spherical RV. 

TS) and outer side (shell side, SS) of the membrane. The membrane itself is considered to be catalytically inert. The reactants are converted on the alternatively also catalyst particles, positioned in the tube side of the membrane (e.g., catalyst can be placed in the shell side). The dead-end reactor configuration shown in the figure (i.e. closed shell-side outlet) allows dosing reactants through the membrane in a controlled manner, with predefined flow rates. All reactants dosed have to permeate through the membrane. The products and the unconverted reactants leave the reactor at the tube side outlet. The PBMR shown in Fig. 

Hamel, C., Thomas, S., Schadlich, K. and Seidel-Morgenstern, A., 2003. Theoretical Analysis of Reactant Dosing Concepts to Perform Parallel-Series Reactions. Chemical Engineering Science, 58(19) 4483 -4492. 

Thomas, S., Pushpavanam, S. and Seidel-Morgenstem, A., 2004. Performance Improvements of Parallel-Series Reactions in Tubular Reactors Using Reactant Dosing Concepts. Industrial ... 

The saturation of the support surface with the reactant was followed by taking samples from the top and bottom parts of the support bed. Figure 1 shows the achievement of surface saturation as a function of reactant dose. Saturation of bonding sites proceeds from the top of the support bed towards the bottom, i.e. in the direction of the reactant flow. 

Figure 1. Surfiice saturation (mmol/g) as a function of the reactant dose (mmol/g). Metal determinations in samples taken from the top and the bottom of the fixed bed were made.

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