Ozonolysis of 2-Butenes

Ozonolysis

1. Ozonolysis of 2-methyl 2-butene and 2,3-dimethyl 2-butene Group Meeting Fall 2014

2. Outline Motivation Experimental Setup Results 2-methyl 2-butene 2,3-dimethyl 2-butene Future Work

3. Motivation One of the most important processes of Volatile Organic Carbons (VOCs) in the atmosphere is oxidation. One of the main oxidation reactions of VOCs is ozonolysis .

4. Carbonyl oxides, also know as Criegee Intermediates (CIs), are produced by ozonolysis through the breaking of a primary ozonide (POZ).

5. R earrangement, decomposition, or reaction of carbonyl oxides in the atmosphere produces secondary organic aerosols, OH radicals, peroxy radicals, etc.

6. CIs are formed with a energy distribution that results in only a fraction undergoing reactions or rearrangements. Resulting in short lifetimes.

7. Experimental Setup Ozonolysis of alkenes is done using a flow reactor: Reaction products are measured using cavity ring-down spectroscopy (CRDS). Spectra of the main products is subtracted in order to look for CI features.

8. CRDS: Suitable for atmospheric measurements due to: Long sample path (high sensitivity). Real time measurements. Portability (in situ measurements).

9. Spectra analysis:

10. Results 2-Methyl-2-Butene + O 3 + +

11. Comparison of f( λ ). Why?

12. 2,3-Dimethyl-2-Butene + O 3 +

13. Difference spectrum: First attempt

14. Scavenging with HFA

15. The choice of N ac and f( λ ) greatly effect the difference spectrum. N ac values need to be constrained: Optimization of the ozonolysis reaction using kinetic simulations. Comparison of product yields with literature values.

16. Simulation of the reaction in a flow reactor. The system of ODEs is solved using an approximation method by the kinetic simulator KINTECUS.

17. Concentration profiles in the reactor.

18. Product yields for different reaction conditions Alkene / Ozone O 3 reacted/ O 3 initial Baseline f( λ ) O 3 meas / O 3 sim Ac meas / Ac sim Ac sim / O 3 sim Ac meas / O 3 meas Y Ac Y HCHO (Exp) Y HCHO (Ref) 16.5 0.6 0.1285 3.2 2.2 10.5 7.2 5 0.53 ~0.40* 6.45 0.47 0.1620 3.8 0.65 8.6 1.4 1.6 0.65 ~0.41* 10.24 0.43 0.1134 4 1.41 8.9 3.1 4 0.8 ~0.40* 30.9 0.75 0.1712 2.31 2.1 14 12.7 4.3 0.55 ~0.38* 14.56 0.67 0.2612 2.97 1.31 13.2 5.8 2.8 0.48 ~0.40* 19.85 0.78 0.2312 2.02 1.73 13.6 11.6 3.3 0.52 ~0.41* 10.33 1 0.3322 2.3 13.6 NA 3.4 0.36 0.38 ± 0.04 12.36 1 0.2922 2.26 14 NA 3.4 0.42 0.38 ± 0.04

19. Future Work Improve the measurement of remaining ozone. Look into the ozone and acetone reactions: Re-analyze data of TME with HFA using literature yields for acetone. Run TME ozonolysis with HFA under optimized conditions.