Miltitz Aromatics ’ general manager Dr Stefan Müller and Ronald Piech describe how pioneering technology can help overcoming particular problems in fine chemistry and terpenoid molecules
Controlling highly exothermic reactions in the manufacture of isoprene building blocks
Miltitz Aromatics ’ general manager Dr Stefan Müller and Ronald Piech describe how pioneering technology can help overcoming particular problems in fine chemistry and terpenoid molecules
Miltitz Aromatics is in many ways one of the spiritual heirs of the famous Schimmel & Co ., the pioneers who made Central Germany one of the most important cradles of the natural and synthetic flavour and fragrance ( F & F ) industry . With much of this industry migrating to Asia , the company has increasingly specialised in specific materials and technologies .
In the 1990s , Miltitz developed new methods to improve the energy and thus the cost-efficiency of metathesis processes , making them usable in F & F . The approach was patented and applied to large-scale fragrance production , which led to the construction of a major plant by a long-standing business partner . Where such reactions were not required as the first synthesis step of a multi-stage process , esterification , condensation and other me-too reactions were abandoned very early on and the focus was placed on hydrogenation and highend distillation .
Hydrogenation focus
Hydrogenation is a constantly evolving focus , with equipment based on multi-purpose loop reactor plants , with pressure ranges from 25 to 75 bar and with different heating systems using steam and heat transfer oil up to
280 ° C . As the process runs in semibatch mode , the catalyst remains within the system and is therefore separated from contact with the ambient air , which extends its lifecycle for most of the reactions taking place in the loop system .
By keeping the number of batches at a stable temperature level , the material is prevented from having to be repeatedly cooled and heated . A special licence also allows the use of carbon monoxide as a feedstock for one of the plants , creating opportunities for hydroformylation and carbonylation .
In order to accompany each new project from the feasibility stage , processes are closely monitored in terms of both chemistry and technology . For this purpose , Miltitz operates various laboratory hydrators in its own laboratory , as well as two pilot loop plants , each with 10 litres and 200 litre reactors , on site . Such test facilities are very rare in the industry .
Isoprene chemistry
In addition to hydrogenation , Miltitz Aromatics has focused on isoprene chemistry and its conversion into intermediate and end products from the very beginning . As an important F & F raw material , isoprene is the monomeric unit of the entire field
of terpenoid chemistry and thus an important building block of terpenes .
Due to its bifunctional structure with two reactive double bonds , isoprene is a platform molecule for chemical transformations such as di- and trimerisation and polymerisation . Its dimers and trimers are particularly interesting molecules in F & F chemistry . Initially , however , the aim of production was to obtain prenyl chloride as a base for end products such as prenyl acetate , prenyl salicylate and others .
Miltitz has invested in equipment for the handling and storage of isoprene in bulk and is also supplied with HCl via an on-site pipeline , which facilitates the synthesis of this intermediate , being very aggressive and highly corrosive to pipes and equipment . It is difficult to handle unless a further synthesis step is added on site to make transport safe .
Challenges of isoprene
After years of working with this difficult starting material , the company was challenged by enquiries from partners . They suggested combining isoprene expertise with the use of pyrophoric catalysts . Synthesising isoprene dimers and trimers on a production scale is not a trivial task for any chemical company .
54 SPECIALITY CHEMICALS MAGAZINE ESTABLISHED 1981