Efficient multiphoton dissociation of CF 2 HCl in waveguide reactors with high selectivity

Parthasarathy, V.; Sethi, S.; Gantayet, L.M.; Biswas, Dhruba J.; Iyer, N. V.; Rao, K. Annaji; Sarkar, S.K.

doi:10.1016/s1010-6030(97)00153-6

Cited by 11 publications

(1 citation statement)

References 25 publications

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“…Subsequently we focused our attention to aspects other than the laser chemistry which would enhance the overall throughput of an enriched product. These include MPD studies in waveguide reactors, 21 use of short duration pulses for excitation 22 etc.…”

Section: Br2mentioning

confidence: 99%

Control strategies for laser separation of carbon isotopes

2002

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Laser isotope separation (LIS) by infrared laser chemistry of polyatomic molecules has come a long way since its discovery. The last decade has seen considerable efforts in scaling up of the process for light elements like carbon, oxygen and silicon. These efforts aim at ways to improve both the enrichment factor and the throughput. The achievement is quite significant especially for carbon isotope separation wherein macroscopic operating scales have been realized. We report our studies on the IR laser chemistry of two promising systems, viz. neat CF 2 HCl and CF 3 Br/Cl 2 . We have investigated conditions for optimizing the dissociation yield and selectivity using natural samples containing 1⋅1% C-13. We also highlight our current efforts for scaling up the process. These include the design aspects of a photochemical reactor with multipass refocusing Herriott optics for efficient photon utilization, development of a cryogenic distillation set up and a preparative gas chromatograph for large scale separation/collection of the isotopically enriched photoproduct in the post-irradiation stage.

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Section: Br2mentioning

confidence: 99%

Control strategies for laser separation of carbon isotopes

2002

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Yield and enrichment studies of C-13 isotope by multi-photon dissociation of Freon-22 at low temperatures

et al. 2003

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Multi-photon dissociation of Freon-22 (CF 2 HCl) at low temperatures has been carried out to separate the C-13 isotope using a TEA CO 2 laser. Yield and enrichment of C-13 isotope in the product C 2 F 4 are studied at 9P(22) laser line as a function of temperature (-50°C to 30°C). It is observed that at a given fluence when the temperature is lowered the yield decreases and the enrichment factor of C-13 increases. Room temperature irradiation of CF 2 HCl towards the blue edge of C-13 absorption (i.e. at 9P(20) laser line) gives low yield of the product (C 2 F 4) at a fluence, which produces the desired enrichment factor of 100. An increase in fluence gives very high yield of C 2 F 4 but the enrichment factor is very low. Irradiating CF 2 HCl at a temperature of-10°C enhances the enrichment factor to 100 and the yield obtained is comparable to that towards the red edge of C-13 absorption (i.e. at 9P(26) laser line). At a given enrichment factor higher enrichment efficiency is achieved when CF 2 HCl is irradiated at lower temperature.

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Maximization of yield of C-13 isotope by multiphoton dissociation of Freon-22 using high average power TEA CO2 laser

et al. 2002

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Selective multi-photon dissociation (MPD) of Freon-22 (CF 2 HCl) molecules has been carried out using a TEA CO 2 laser at various CO 2 laser lines (9P(20)-9P(26)) in order to maximize the yield of C-13 isotope in the product (C 2 F 4) at an enrichment factor of 100. The effects of laser pulse tail due to the presence of N 2 in the laser mixture on the enrichment factor and yield of C-13 are investigated. It is found that the addition of a small amount of N 2 is possible in the laser mixture without a significant drop in the yield at desired enrichment factor. Addition of a small amount of N 2 improves the laser efficiency considerably. At a given pulse energy, a slight change in the near field intensity distribution of a laser severely affects the selectivity of C-13 isotope. The computed far-field intensity distributions of the measured near-field intensities show marked spatial variation in the focal spots that leads to a drop in selectivity. For macroscopic production of C-13 isotope a simple and novel multi-pass cavity has been designed and tested to focus the energy repeatedly keeping the optimum fluence constant at each focal spot.

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Efficient multiphoton dissociation of CF 2 HCl in waveguide reactors with high selectivity

Cited by 11 publications

References 25 publications

Control strategies for laser separation of carbon isotopes

Control strategies for laser separation of carbon isotopes

Yield and enrichment studies of C-13 isotope by multi-photon dissociation of Freon-22 at low temperatures

Maximization of yield of C-13 isotope by multiphoton dissociation of Freon-22 using high average power TEA CO2 laser

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