Phenol is an important industrial chemical and serves as an intermediate product for example in the manufacture of plastics such as phenolic and epoxy resins as well as adhesives, solvents, wood preservatives and insecticides. Today's preferred industrial method of producing phenol is phenol synthesis in the three-stage Hock process from isopropyl benzene (cumene), which is first formed from benzene and propene. The cumene is oxidised first by means of atmospheric oxygen to form its hydroperoxide, which in a second stage, under the influence of strong acids, breaks down into phenol and acetone These two substances can then be separated at the end into two consecutive distillation chains. The simultaneous development of two easily separable, valuable products makes this environmentally-friendly process particularly cost-effective.

Today, the process focuses on increased product yield of the two co-products, as well as avoiding unusable by-products and volumes of sewage. Modern techniques can increase the oxidation degree of cumen by around 50% and thereby reduce the amounts of cumen to be recycled. However, this requires accurate process control. KROHNE offers a multitude of suitable measuring systems such as ultrasonic flowmeters with temperature and pressure sensors, that are directly connected to the device, thus allowing a high level of flexibility. These include pressure transmitters for complex process pressure and level applications such as absolute and relative pressure measurement in open tanks and – as a dual variant – for electronic differential pressure measurement.