Optimization of a Nitration Reaction

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2 CBC-PROCOS S.p.A. - Research and Development Laboratory - Calorimetry Optimization of a Nitration Reaction Alessandro Barozza*, Paolo Paissoni, Jacopo Roletto barozza@procos.it Giornata di Studio sullo Sviluppo e Sicurezza dei Processi Chimici Milano, 24 Maggio 2011

3 Formation of a Nitroester Nitration to oxigen R OH R O NO 2 Process must be run on a multi-purpose plant Economical process Safe process

4 Economical process Cheap starting material Yields Productive process Fast and easy process Green process Safe process

5 Economical process Modified from T. Li Rathman & W.F. Bailey OPRD 2009, 13,

6 From Literature Nitration with HNO 3 /H 2 SO 4 /Water Large excess of HNO 3 (3.5 eq) Conversion about 70% T: 0-5 C Batch process charge of alcohol in one single portion

7 RADEX thermal stability of final sulphonitric MXR Tj Tr C 70 Systag RADEX calorimeter Steel High pressure vessel, glass lined φ about Time relative h Tr Tj

8 Searching a new method Reaction higher temperature (room temperature) Low excess of HNO 3 (stoichiometric!) or avoid its use

9 Alternative methods of nitration More expensive method vs. direct nitration Time Reaction steps Cost of reagents Stability problem of intermediate

10 Alternative methods of DIRECT nitration HNO 3 (fuming) in various solvents (CH 2 Cl 2, CH 3 COOH) High excess of Nitric Acid is required to obtain a good conversion (α>70%) Handling of fuming nitric acid is complicate Using of HNO 3 70% gives a very low conversion even if a large excess is used

11 Nitration in Acetic Anhydride Nitration in Acetic Anhydride with fuming HNO 3

12 Nitration in Acetic Anhydride Reaction is fast and can be conducted with a small excess eq of HNO RT Final MXR is thermally stable up to 60 C (stability problem of the final molecule molecule) Process needs to be controlled by dosage of Alcohol Preparation and handling of HNO 3 solution in Ac 2 O could be problematic* Acetyl derivative <1.5% *R.Andreozzi, Journal of Hazardous Materials A90 (2002)

13 Nitration in Acetic Anhydride Work-up The final reaction mass is quenched in aqueous Ammonia In presence of Ac 2 O the reaction is violent, Acetamide is formed and a strong amount of heat is released

14 Nitration in AcOH and Ac 2 O Ac 2 O is used stoichiometric to HNO 3 AcOH is used as solvent The solution of HNO 3 in Ac 2 O/AcOH could be unstable: a right concentration must be found-outout

15 Nitration in AcOH and Ac 2 O Choosing concentrations A high concentration lowers the final cost More productive process Less Ammonia in work-up Less wastes But it can be a problem from a safety point of view A Low concentration increases safety More stable solution Decrease adiabatic temperature rise due to decomposition Decrease plosive attitude But increases process costs How much?

16 Nitration in AcOH and Ac2O An economical consideration

17 Nitration in AcOH and Ac2O An economical consideration

18 How to choose the right concentration From literature Solutions of HNO 3 in Ac 2 O are not stable (may detonate RT) if the concentration is between 50% and 85% Chemistry in Britain 1967, 3, p.504 VERIFY data from literature!

19 Tr-Tj (filt.. K 1 Solution of FUMING HNO 3 in Ac 2 O dtr/dt K/m 0.01 Tj Tr C 200 and AcOH (c. 8.3%) Systag RADEX calorimeter Steel High pressure vessel, glass lined C 40 C 50 C 60 C 70 C Time relative h Tr Tj dtr/dt Tr-Tj (filtered)

20 Tr-Tj (filt.. K 1 Solution of dtr/dt K/m 0.01 HNO 3 (c.>90%) in Ac 2 O and AcOH (c. 8.3%) Tj Tr C 200 Systag RADEX calorimeter Steel High pressure vessel, glass lined C 40 C 50 C 60 C 70 C Time relative h Tr Tj dtr/dt Tr-Tj (filtered)

21 Stability of nitrating mixture It seems that the termal stability of the nitrating mixture could be related to the presence of nitric oxides To avoid the presence of nitric oxides, do not use fuming nitric acid Use HNO 3 69% It is cheaper than Fuming HNO 3 It is easily available for amounts of about kg But it contains about 31% of water!?!

22 Producing the nitrating mixture The amount of Ac 2 O must be in relation to the amount of HNO 3 and to the amount of Water and the mixing procedure is reactive! Is it better to: Add HNO or HNO 3 (69%) (69%) to Add Ac 2 O to HNO to Ac 2O+AcOH HNO 3 (69%) (69%)+AcOH Use METTLER RC1

23 Addition of HNO HNO 3 (69%) to to Ac 2O+AcOH Isothermal 20 C METTLER TOLEDO RC1e reaction calorimeter SV01 glass 800mL reactor

24 Addition of Ac 2 O to HNO HNO 3 (69%) (69%)+AcOH Isothermal 20 C METTLER TOLEDO RC1e reaction calorimeter SV01 glass 800mL reactor T ad 0.3K T ad 83K

25 Thermal stability of final nitrating mixture Tr-Tj (filt.. K dtr/dt K/m Tj Tr C Systag RADEX calorimeter Steel High pressure vessel, glass lined C 40 C 50 C 60 C 70 C Time relative h Tr Tj dtr/dt Tr-Tj (filtered)

26 Choosing a safe concentration of HNO 3 using CHETAH software Chetah is able to perform an estimation of the plosive attitude of a mixture of compounds, starting from structures of its component and their heats of formation From CHETAH v.7.3 manual Criterion 5: "Over-all Energy Release Potential This criterion combines the four individual criteria and the number of peroxide bonds into a single "HIGH" or "LOW" rating. This over-all criterion is known to be one of the most accurate for the classification of substances for their ability to be plosive and eliminates the ambiguity which sometimes arises when the four individual criteria give different ratings (e.g. "HIGH", "LOW", "MEDIUM"). The weights assigned to the individual criteria were derived by members of ASTM Committee E-27, using sophisticated pattern recognition techniques (linear discriminant analysis) with a large database of impact-testedtested materials.

27 CHETAH ERP criterion Over-all Energy relea ase potential Green: Ac 2 O+AcOH Blue: AcOH only Final Mixture HNO 3 +AcOH+Ac 2 O Starting Point HNO 3 +AcOH+H 2 O ERP = HIGH ERP = LOW % 5% 10% 15% 20% 25% 30% 35% 40% 45% % of HNO 3 into the mixture

28 Charge Acetic Acid Proposed method Charge Nitric Acid (2.2 eq) Charge Ac 2 O maintaining 20 C Stoichiometric to (Alcohol+Water) +10% Feed controlled Final MXR thermally stable up to 40 C c. HNO 3 =21% w/w Charge the Alcohol (solid solid) in 8 identical portions, each one every 5 minutes, maintaining C Wait about 1 hour Quench the system with aqueous ammonia

29 Preparation of HNO 3 solution in AcOH Power METTLER TOLEDO RC1e reaction calorimeter SV01 glass 800mL reactor 600 Power (W) Isothermal 20 C Reaction mass (g) Reaction mass Time (minutes) Reaction Limits with baseline No. Baseline Enthalpy start start Tad Interpolation kj kg kj/(kg K) K 1 Conversion Formula Qr = Qflow + Qaccu + Qdos Calculation with mean temperature values: No

30 Addition of Ac 2 O Power (W) METTLER TOLEDO RC1e reaction calorimeter SV01 glass 800mL reactor Power Reaction Limits with baseline Isothermal 20 C Time (minutes) Dosing ramp Theoretical Stoichiometric point 1:1 mol:mol Ac 2 O/H 2 O No. Baseline Enthalpy start start Tad Interpolation kj kg kj/(kg K) K 2 Conversion Ac 2 O dosage (eq Ac 2 O / eq Water) T ad.accu = Q accumulation m stoichiometric Cp stoichimetric = ( ) J g 2.05 J/(g K) = 2.95 K

31 Addition of Alcohol Power METTLER TOLEDO RC1e reaction calorimeter SV01 glass 800mL reactor Power (W) Dosing Ramp Calorimetric conversion Dosing ramp (g) Isothermal 20 C Time (minutes) Reaction Limits with baseline No. Baseline Enthalpy start start Tad Interpolation kj kg kj/(kg K) K 1 Conversion

32 Thermal stability of final MXR Tr-Tj (filt.. K dtr/dt K/m Tj Tr C Systag RADEX calorimeter Steel High pressure vessel, glass lined C 40 C 50 C 60 C 70 C Time relative h Tr Tj dtr/dt Tr-Tj (filtered)

33 Results

34 Process Before Optimization Results Process After Optimization -31% -40% -44% -19% -21% % Required time: 400 hours Required time: 280 hours

35 Optimization of a Nitration Reaction Alessandro Barozza, Paolo Paissoni, Jacopo Roletto barozza@procos.it Giornata di Studio sullo Sviluppo e Sicurezza dei Processi Chimici Milano, 24 Maggio 2011

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