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Nottingham engineers came up with a novel safety valve design. At the end of the reaction, after the pressure had been released and the pressure gauge read zero, a valve could be removed to leave behind a hole of a few millimetres in diameter ensuring any residual pressure would be released. A further safety feature was that the head of the safety valve also operated as the key which had to be physically inserted into the clamp to undo and remove it. Therefore it would not be possible to manipulate the clamp in any way without firstly removing the safety key and hence releasing any unexpected residual pressure in the reactor.
This simple yet highly effective safety feature, inherent in the design of the new reactor is shown in Figure 1.
To ensure the operational integrity of the new design, the PressureSyn reactors have been extensively tested and used by various research groups in the School of Chemistry at the University of Nottingham. Using a wide range of standard operating procedures developed for specific experimental conditions there have been no safety incidents reported, which proves testament to the safety key design. A variety of reactions carried out in the PressureSyn reactor have been reported in the literature [1, 2]. In a recent publication by Howdle et al (J. Am. Chem. Soc. 2012, 134, 4772-4781) work towards the synthesis of structured block copolymers which are important in myriad applications from catalyst supports to data storage was reported. The known synthetic routes to these important materials had limitations which hindered industrial scale manufacture. Using the PressureSyn reactor, Professor Howdle developed a new reliable and controllable route via reversible addition-fragmentation chain
transfer (RAFT) dispersion polymerisation in supercritical CO2 to give access to these materials in a versatile one-pot process.
Additional Reactions Carried out in the PressureSyn Reactor
The flexibility of the design enables the PressureSyn reactor be utilised in a wide range of high pressure reactions. The reactor head is fitted with a number of ports including pressure gauge, pressure relief valve/bursting disk safety features, outlet valve, thermocouple, gas inlet value and safety valve. As an alternative configuration, replacement of the gas inlet valve with a blanking valve would allow the PressureSyn to be utilised as a standard autoclave. PressureSyn reactors are produced as standard in durable SS316 stainless steel however the same design can be used to manufacture units in acid resistant alloys such as Hasteloy.
Figure 1. PressureSyn safety key
Each key in the new design is individually engineered to fit only one clamp therefore it is not possible to undo the clamp using another key whilst there is the possibility of the reactor being under pressure. In order to ensure that the clamp did not introduce areas of stress into the body of the reactor, measurements were made of the complete assembly. As shown in Figure 2 there are no significant stress seen in the area where the clamp is fixed onto the reactor body.
If required, the reactor can be fitted with a magnetic stirrer bar and used in collaboration with a metal heating jacket and placed on a stirrer hotplate as shown in Figure 3. The specification of the reactor enables reactions to be performed up to maximum working pressure of 100barg @200°C.
Figure 2. Stress measurement patterns on PressureSyn reactor body
Figure 3. PressureSyn Reactor on stirrer hotplate
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