Reactor contacting

The chloride is usually (but not always) stabilised in storage by addition of aqueous alkali or anhydrous amines as acid acceptors. A 270 kg batch which was not stabilised polymerised violently when charged into a reactor. Contact of the chloride (slightly hydrolysed and acidic) with rust led to formation of ferric chloride which catalysed an intermolecular Friedel-Craft reaction to form polybenzyls with evolution of further hydrogen chloride. Contact of unstabilised benzyl chloride with aluminium, iron or rust should be avoided to obviate the risk of polycondensation. See Benzyl bromide Molecular sieve... 

Figure 3.11 Propane metathesis catalyzed by (=SiO)2TaH (3) in a continuous flow reactor. Contact time effect (520mg of 5.3% Ta/SiOj 1 atm, 150 C, 1 to lOOmLmin or VHSV = 38 to 3800 h ) (a) alkane selectivity (b) alkene selectivity (c) hydrogen selectivity (d) alkane alkene ratio.

In other situations, contact time is not equal to detention time. For example, in the case of the activated sludge reactor, contact time is the rise time of the bubbles to the surface, whereas detention time is the average time of travel of the water between the inlet to the outlet of the reactor. Contact time refers solely to the bubbles contacting the water during the time they were rising from the diffusers. Hydraulic detention time, in this case, has no relation to the contact time. 

V. Hessel, P. Angeli, A. Gavriilidis, H. Lowe, Gas-Liquid and Gas-Liquid-Solid Micro-structured Reactors Contacting Principles and Applications, Ind. Eng. Chem. Res. 44 (2005) 9750. 

The Exxon donor solvent, direct liquefaction process also used hot oil drying. In this process, LRC is dried by a high-pressure hydrogenation reactor contact with hot recycle hydrogen donor solvent prior to entering. Unfortunately, no data were developed for solvent recovery after drying becanse the dried coal and vehicle solvent were reacted immediately with hydrogen in the Uqnefaction reactor. 

Hessel, V., Angeli, P., Gavriilidis, A., Lowe, H. (2005). Gas-liquid and gas-liquid-solid microstructured reactors Contacting principles and applications. Industrial and Engineering Chemistry Research, 44, 9750-9769. 

Lowe, H. (2005) Gas-liquid and gas-liquid-solid microstructured reactors contacting principles and applica- 50-... 

V. HesseL P. Angeh, A. Gavriilidis, H. Lowe, Gas-4iquid and gas-4iquid-sohd microstructured reactors contacting principles and appUcations. Industrial and En neering Chemistry Research, 2005, 44, 9750-9769. 

The features of the original proeess as reported by Kunii and Levenspiel (1991a) and some recent developments follow. Reaetor operating eonditions are 400 to 500°C at about 1.7 atmosphere, with a reactor contact time of 5 to 20 seconds. In addition to acrylonitrile, carbon monoxide, carbon dioxide and water, small quantities of hydrogen cyanide, acetonitrile, and acrolein are also produced. The original plants were designed to operate at around 52 cm/s superficial velocity. Modern plants are now operating with fines... 

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