FLAVOURS & FRAGRANCES
Firstly , the storage of isoprene in large quantities must be mastered . The highly flammable liquid ( boiling point 34 ° C ) needs to be stored at cold temperatures . In addition , isoprene tends to polymerise slowly during storage if traces of air or moisture are present , creating polyisoprene ( synthetic rubber ) which can block valves and pipes . Isoprene is therefore stored under strictly inert conditions .
Secondly , Ziegler-Natta type catalysts , which use organoaluminium compounds as cocatalysts , are highly pyrophoric and will spontaneously burst into flames if they come into contact with water or air . They require appropriate safety and precautionary measures , especially as the production of the target products takes place under very exothermic conditions that require effective cooling of the vessels .
Although isoprene intermediates like isoprene dimers and trimers are an important raw material in the F & F industry , their availability is restricted because of their special process conditions . However , in the search for new materials , isoprene-based molecules are often considered . Their limited supply is a handicap for intended expansions of isoprenebased productions and this has encouraged an intensive search for flexibly manageable alternatives .
Move into flow
To address this , Miltitz and Dutch flow chemistry specialist FlowID looked into a technological conversion of batch processes for the production of prenyl chloride in flow . Within a short space of time , procedures were agreed and a test plant was subsequently set up in the laboratory . There , an adapted flow process finally ensured the reactions analogue to the sequences in the classic process and fulfilled the expectations .
This enabled us to convert a highly exothermic reaction into a continuous process at a much more energetically favourable temperature level . We used FlowID ’ s SpinPro R10 , whose technology is essentially geared towards the realisation of multi-phase syntheses with predominantly liquid , gaseous substances or mixtures of substances .
The result of these tests not only brought an innovation prize but also opened up the possibility of considering other syntheses and ultimately led to the decision to invest in FlowID ’ s R300 production system and , in view of the aggressiveness of prenyl chloride , to use it in a version designed with Hastelloy .
Energy savings of up to 80 % can be expected , as the reaction process in the flow reactor itself requires significantly less energy . The reduced reaction exotherm in the flow process also significantly reduces the effort required to cool the process . The supply to the continuous reaction with the raw material feed takes place on a much smaller volume basis , which also minimises the safety risks of the process steps when handling hazardous substances .
In addition , the significantly smaller reactor system makes it easier to realise thermal reactions and reactions that require pressure . Based on existing findings , a significant increase in capacity can be expected as a result of the technological processes in the flow reactor . The modular flow skid that is used generally also makes chemistry with organo-metallic catalysts or nitration and halogenation appear possible under far more favourable conversion conditions than before .
In addition , the closed circuits provide excellent mass and heat transfer systems . Overall , the small size of the reactors ensures comparatively higher plant and process safety and - based on an adapted laboratory flow reactor - significantly improves the scale-up to the size of industrial process engineering .
A SpinPro R10 will also be available to Miltitz for laboratory work in the future . Together with FlowID , the company will realise its own and third-party projects in which it sees itself as an industrial cooperation partner , also for other areas of fine chemistry - without withdrawing from the world of F & F , of course . ●
Dr Stefan Müller
GENERAL MANAGER
MILTITZ AROMATICS GMBH k + 49 3494 668 99-10 J s t e f a n . m u e l l e r @ m i l t i t z - a ro m a t i c s . d e j www . miltitz-aromatics . de
MAR / APR 2024 SPECCHEMONLINE . COM
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