Novel Process Window for the safe and continuous synthesis of tert. Butyl peroxy pivalate with micro process technology

Transcription

1 Novel Process Window for the safe and continuous synthesis of tert. Butyl peroxy pivalate with micro process technology Segmented flow- & first Hyper SADT Experiments DBU file number: 20007/894 T. Illg 1,2, V. Hessel 1,2,Patrick Löb 1 J. C. Schouten 2 1 Institut für Mikrotechnik Mainz GmbH Mixing and Fine Chemistry Department 2 Eindhoven University of Technology Department of Chemical Engineering and Chemistry Laboratory of Chemical Reactor Engineering IMM, 2009 IMM -1

2 The motivation 1 st Reaction step: Synthesis of tert.-butyl potassium peroxid (TBKP) H KH aq 298 K K H 2 ΔT ad = 25 K SADT = 361 K noncritical / single phase reaction 2 nd Reaction step: Synthesis of tert.-butyl peroxy pivalate (TBPP) K Cl aq 293K KH aq ΔT ad = 72 K SADT = 298 K critical / biphasic reaction IMM, 2009 SADT = (Self Accelerating Decomposition Temperature) IMM -2

3 State of the art Continuous batch IMM, 2009 IMM -3

4 Drawing conclusions from the state of the art Hold-up of reactive peroxide is enormous Reaction temperature is mostly limited by the SADT (Self Accelerating Decomposition Temperature) Nonessential long reaction times High dilution is used to remove the heat of reaction Good mixing is necessary to avoid accumulation Surface to volume ratio deteriorates with increasing reaction volume Benzoyl peroxide explosion at the Catalyst Systems Inc. (Gnadenhutten, hio, 2003) Goals: Transfer of both reaction steps into continuous processes using the benefits of micro process technology. Finding a New Process Window for TBPP synthesis to compete with the conventional process and to achieve advantages in process safety. IMM, 2009 IMM -4

5 Considerations The necessity of good heat management Avoidance of heat accumulation Avoidance of hot spot formation The presence of the biphasic second reaction step Avoidance of phase separation Avoidance of reactant accumulation in product phase Supply of sufficient interfacial area A highly corrosive reactant (pivaloyl chloride) The suppression of side reactions e.g. Hydrolysis of pivaloyl chloride in alkaline aqueous reaction mixture Thermal decomposition of reactant and product Use of Segmented Flow to synthesise TBPP Use of Dispersed Flow to synthesise TBPP IMM, 2009 IMM -5

6 The two concepts for TBPP synthesis (focus 2 nd step) Why Segmented Flow? Highly ordered flow pattern Defined interfacial areas Facilitates kinetic analysis Determination of mass transfer coefficients Foster perester formation vs. hydrolysis of acid chloride Enhanced mass transfer due to internal circulations Why Dispersed Flow? Easier to scale up Multistage dosing to manage heat of reaction Hyper-SADT is feasible J. R. Burns, C. Ramshaw, Lab Chip, 2001, 1, influenced by many parameters consecutive coalescence must be avoided IMM, 2009 IMM -6

7 Segmented Flow Influencing parameters Inlet geometry Channel dimension Pressure fluctuations caused by pumping equipment Ratio of aq/org flow Physical properties interfacial forces wetting behaviours gravitational forces inertial forces Thermal effects PoP unreactive system H 2 /n-c 7 Water / PIVCl (99%) KH (22.7%) / PIVCl (99%) Flow rate ratio aq/org: 1 and 3.6 M. N. Kashid, D. W. Agar, Chem. Eng. J., 2007, 131, 1 13 V. Hessel, A. Renken, J. C. Schouten, J. Yoshida, Micro Process Engineering, A Comprehensive Handbook, Volume 1 Fundamentals, perations and Cataysts, Chapter 1 Multiphase flow, Wiley-VCH, 2009 IMM, 2009 IMM -7

8 Short review on obtained segmented flow results Screening of different types of mixers to generate a stable flow pattern gave irregular flow pattern low interfacial tension but promising results increase of concentration to achieve a better aq/org ratio: γ 12 [mn/m] Water/n-C7 Literature value [8] Water/n-C7 KH-22.7wt%aq/PIVCl-50wt% n-c7 KH-2.3wt%aq/PIVCl-50wt% n-c7 TBKP-31wt%aq/PIVCl-50wt% n-c7 TBKP-31wt%aq/PIVCl-99wt% Conversion / Yield [%] Conversion PIVCl [%] Yield TBPP [%] Retention time [min] IMM, 2009 IMM -8

9 Indicating mass transfer limitations first conclusions- Cl Teflon tubing K Thermostat TIC τ = 12 s τ = 24 s τ = 42 s Conversion / Yield [%] Conversion PIVCl [%] Yield TBPP [%] Conversion / Yield [%] Conversion PIVCl [%] Yield TBPP [%] Conversion / Yield [%] Conversion PIVCl [%] Yield TBPP [%] Total flow velocity [cm/min] Total flow velocity [cm/min] Total flow velocity [cm/min] Rough estimation on obtained results (neglecting irregular flow pattern) Conversion increases with increasing velocity possibly indicating mass transfer limitations Residence time takes influence on conversion / yield More regular flow pattern will lead to a better interpretation of obtained results IMM, 2009 IMM -9

10 Visualization of segmented break-up undiluted fluid system- K fluid interface Cl Fluid system used: TBKP-31 wt%aq PIVCl-99 wt% Ratio aq/org: 3.57 Interfacial tension: ~4 mn / m (for comparison H 2 / n-c 7 : 51 mn / m) LTF Glass T-mixer dimensions: 0.8 mm ID Channel length 6 cm after mixing zone Manipulation of fluid system to increase surface tension and to achieve an advanced segmented break up IMM, 2009 IMM -10

11 Manipulation of fluid system to increase interfacial tension TBKP- 3 to 5 wt% aq cons PIVCl- 5 to 12.5 wt% in n-c 5 LTF Glass T-mixer ID 1.6 mm pros Removal of n-c 5 is necessary for HPLC analysis Stripping with N 2 still under improvement Low conversion rate due to high dilution Increase in reaction time by reducing the total flow rate resulted in floating of organic segments Regular segments Yield 8 15%; τ = 20s Smaller channel size Higher flow velocity Longer residence time Enable segmented flow? IMM, 2009 IMM -11

12 Dispersed Flow - Hyper SADT concept What is Hyper SADT? Definition of SADT: Self Accelerating Decomposition Temperature. Lowest temperature at which a packaging size will undergo a self accelerating decomposition reaction. SADT is inversely proportional to packaging size. Limiting parameter for peroxide production due to high hold up! Definition of Hyper SADT : Running the process at or above the limiting SADT without losses in process safety, based on a small reaction volume enabled by using micro process technology. Resulting in shorter processing times and higher space time yields. IMM, 2009 IMM -12

13 Hyper SADT first promising results Cl Teflon tubing K Thermostat TIC Reaction conditions: V TBKP-31 wt%aq : 0.5 ml/min V PIVCl-99 wt% : ml/min τ: 31 s RT: 23 to 60 C Conversion / Yield / % ΔT τ=31s Conversion tert.-butyl hydroperoxide Conversion pivaloyl chloride Yield tert.-butyl peroxy pivalate Reaction temperature / C ΔT after mixer outlet / C IMM, 2009 IMM -13

14 Hyper SADT mean values over four experiments Mean Conversion / Mean Yield / % τ = 31s 23 Mean conversion tert.-butyl hydroperoxid Mean conversion pivaloyl chloride Mean yield tert.-butyl peroxy pivalate Reaction temperature / C 70 ccurring coalescence causes inhomogeneous flow profile Directly affecting the sampling Mean values over 4 repetitions is still showing the positive trend No significant impact on yield by further temperature increase Implementation of static mixing devices Different concepts under discussion Generation of a better pre-dispersion by change of mixing device (smaller channel geometry) IMM, 2009 IMM -14

15 Hyper-SADT approximate benchmarking Hyper SADT [1] (micro processing) µ-mixer tube set-up RT: 23 C up to 60 C Y TBPP : 50 % and 65 % Reaction time: 31 s has to be improved in terms of avoidance of coalescence avoidance of hot spot formation better process control shorter reaction time increased yield ~ 12 faster than ~ 190 faster than Hypo-SADT below SADT [1] (micro processing) µ-mixer tube set-up RT: 10 C Y TBPP : 40 % Reaction time: 84 s Conventional (micro processing) [2] RT: 10 to 20 C Y TBPP : 93 % Reaction time ~6 min 3 x 350 L Cascade (~1 m 3 ) [2] RT: 10 to 20 C Y TBPP : 84% [1] Illg et al, unpublished results, 2009 [2] Azzawi et al. Method for the production of organic peroxide by means of micro Reaction time ~100 min reaction technique, IMM, 2009 US , 2009 IMM -15

16 Conclusions Two concepts to synthesize TBPP Dispersed Flow and Segmented Flow First promising results on Hyper-SADT processing First indication of mass transfer limitations Visualization of segmented break-up in non-manipulated system, as an explanation for irregular flow patterns obtained in previous experiments Impact of manipulation by dilution of fluid system resulted in a better segmented flow IMM, 2009 IMM -16

17 utlook Additional segmented flow experiments with new glass micro mixer Diluted and undiluted systems Change of mixing element with longer reaction zone to achieve higher conversion Mixing element with smaller channel diameters to increase flow velocity and thus internal circulations ptimization of dispersed system How can coalescence be avoided? Different concepts under discussion Temperature control at mixing point? Material for reactor development? Measurement of kinetics Improvement of HPLC method Sample pre-treatment has to be improved (diluted fluid system) IMM, 2009 IMM -17

18 IMM, 2009 IMM -18