In the first of this two part of the series, we will show two continuous chemical processes that utilize process intensification for chemical reaction systems and unit operations. The original processes were typically large bulky and spread out over significant plot space and also may have had high profiles.
By introducing PI to these technologies a decrease in equipment occurs, a smaller lower cost plant can be build that achieves all the benefits process intensification that includes:
- Reduced energy use;
- Decreased capital expenditure;
- Lower plant profile (height);
- Smaller plant footprint (area);
- Environmental advantages; and
- Safety benefits.
In the first process, we will show the continuous photochlorination of toluene for the production of Benzyl Chloride. Photochlorinations are some of the most interesting reactions in organic chemistry in that the catalyst is ultra violet (UV) light only.
Liquid toluene enters the bottom of a vertical HOLL-REACTOR® reactor while chlorine enters the side of the unit where the stator is metal. Just above this metal section the stator is glass. This is necessary because the glass allows 454 angstrom UV light to catalyze the reaction. The HOLL-REACTOR® produces such high shear that the bubbles generated are extremely small. Since this reaction is driven by gas liquid contact it occurs very fast and within a short vertical reactor with the interstitial surface area generated. Depending on the molar ratio of chlorine to toluene besides benzyl chloride, benzal chloride and benzotrichloride can be produced. In addition, there may be unreacted toluene coming out of the reactor. The discharge of the reactor flows to a knockout pot and the vapor flows to an HCl adsorption system and any residual chlorine goes to a caustic scrubber. The mixed chlorides liquid is pumped to a divided wall distillation system. Here the toluene comes off the top of the column and is recycled back to the front of the process. Product comes out of the 2nd outlet and benzal chloride and benzotrichloride come out of the 3rd and 4th outlets respectively. Depending on the molar ratios one product can be favored over the other. With Micromotion mass flow meters the molar ratio can easily be adjusted on the fly to optimize one product over the other. Typically the number of distillations needed to perform a separation are n-1 where n is the number of components. Thus in a traditional plant we would need 3 columns because there are 4 components. With the divided wall column we need 1 column.