Photochemical Processes in Stirred Tank Reactors

• Published in: Chemical Engineering 2018-04, Vol.125 (6), p.42-57
• Main Authors: Himmelsbach, W, Rojan, P, Multner, B, Last, W, Braun, A M, Peschl, A
• Format: Magazinearticle
• Language: English
• Subjects: By products; Chemical engineering; Chemical industry; Chemical reactors; Control equipment; Cooling; Corrosion; Engineers; Equipment and supplies; Gases; Investigations; Laboratories; Materials; Organic chemistry; Photochemical reactions; Photochemistry; Production processes; Radiation; Reactors; Temperature; Thermal energy
• ISSN: 0009-2460; 1945-368X

Photochemical processes complement or may even substitute conventional (thermal) processes. The radiant energy initiates the reaction, for example by forming radicals, and in most cases, no thermal energy is needed to overcome the energy barrier according to Arrhenius' law. Photochemical reactions are usually kept well below 100°C, hence leading to far fewer side reactions and formation of byproducts than thermal reactions. Except for photocatalyzed processes, no expensive catalysts with their elaborate handling requirements are needed. In most cases, photochemical processes are performed in immersion-type tubular reactors in which turbulence is achieved and maintained by circulating the reaction system or by the production or the introduction of gases. Only recently have stirred-tank reactors -- still the "workhorse" of the chemical industry -- been adapted to the requirements of photochemical processes. This article describes the basics of industrial photochemistry and the present state-of-the-art for the design of stirred-tank photochemical reactors.