Otherwise the temperature measured may not be

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Unformatted text preview: ation of the furnace Considerable temperature gradients in the catalyst bed must be avoided as much as possible when catalysts are tested. Otherwise the temperature measured may not be representative for the whole system and the catalytic tests would have only limited validation. A reactor with a small temperature gradient may also provide that the gas stream is preheated to the reaction temperature before it gets in contact with the catalyst, hence minimising any temperature gradient, especially at the beginning of the catalyst bed. Therefore it is of great importance that a furnace is used that provides such an isothermal zone in the reactor (no temperature gradient). A long isothermal 69 2. Experimental ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffyfffffffffffffffffffffffffffffffffffffffff zone is also beneficial if larger amounts of catalysts are employed (long catalyst bed), ensuring a negligible temperature gradients due to the reactor itself. The temperature gradient of a given reactor in the absence of a reaction is determined by the furnace. Therefore a furnace must be chosen that provide no or little temperature gradients under the reaction conditions. The original furnace consisted of a cylindrical electrical heating element hollow in the middle (outer diameter 4.4 cm, inner diameter 1.6 cm). The heating element consisted of a ceramic element and a heating wire. The whole element itself was surrounded for electrical and thermal isolation by a thin layer of synthetic kaolinite wool and suited in a metal container (Fig. 8). Original and modified furnace Rebuild furnace Thermoelement (reactor) Thermoelement (heating element) Kaolinith wool Electrical heating element Kaolinith wool plug (modified original furnace only) Quartz tube Quartz reactor Fig. 8 Proportional drawings of the original, the modified and the rebuild furnace 70 2. Experimental The reactor (outer diameter 6 mm, inner diameter 4 mm) was place...
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