Laser production of carbon-13 based on CF2 HCl

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FIG. 1 is a block diagram of the two stage process

LASER PRODUCTION OF CARBON-13 BASED ON involving chemical exchange, and CF2HCL FIG. 2 is a more detailed flow-diagram of the pro

CCSS.

This invention relates to a method for isotope enrich Referring to FIG. 1, an IR laser 10 irradiates a feed ment by laser radiation and more particularly to a stock of CF2HCl in reaction chamber 11 to give HCl method of producing carbon-13 by multiphoton decom and CF2 enriched in C-13. The products from this stage position of CF2HCl. (CF2HCl, HCl, C2F4) are passed to separation stage 13 The use of carbon-13 as an industrial compound is not 10 where the HCl and the CF2HCl (depleted in C-13) are widespread at the present time but is expected to in removed. The remaining component, C2F4 is passed to crease. Extensive application of carbon-13 to medical enriched in C-13 is stage chemical exchange 14 from which a CO2 product obtained.

screening programs is anticipated. The present method Referring to FIG. 2, the feedstock of gaseous of production is by low temperature distillation of car CF2HCl is irradiated in an appropriate cell 11 by the IR bon monoxide and this process is expensive, provides 15 laser 10. The small throughput, needs large inventory of starting and has noneCF2HCl is a cheap commercial substrate materials, and must be symbiotic with a liquid airplant. ously suggested substrate such asassociated of the problems with previ

CF3I, CF3Br, etc. The

A method of isotopic separation by photopredissocia substrate pressure is in the range 10-100 Torr, depend tion is described in U.S. Pat. No. 3,983,020, issued Sept. ing upon laser pulse length. The IR laser operates in the 28, 1976 to C. B. Moore and E. S. Young. A photo 20 frequency range 1040-1080 cm -1 (wavenumbers) chemical method for carbon isotopic enrichment is with a fluence greater than 5 J cm-2. The photolysis disclosed in U.S. Pat. No. 4,120,767 issued Oct. 8, 1978 selectively decomposes the CF2HCl and is operated for to S. N. Bittenson and P. Houston. This patent describes a sufficient time to give C2F4 enriched in C-13 to ap a process using, as a starting material, a gaseous mixture proximately 25-35% along with CF2HCl and HCl. of at least two isotopic CF3I species and irradiating this 25 These products are passed to absorber stage 15 where mixture in a reaction zone with laser radiation at a pres the HCl is removed and then to freon separation stage sure below about 10 Torr to cause relative enrichment 16 where the CF2HCl which is depleted in C-13 is re of one of the species. The enriched residual substrate is moved. The C2F4 remaining is passed to oxidation stage 13CF3I. This process is effective but yields are low and 30 passed to itchemical 17 where is oxidized to provide a CO2 product that is exchange stage 18. This is a CO2 therefore production costs are high.

In co-pending United States application No. 25,886 and the 12CO2 to givereaction carbamate exchange that separated the 3CO2

filed Apr. 2, 1979 in the name of Peter A. Hackett, Clive We claim:

Willis and Michel Gauthier, now abandoned, a method 1. A method of producing carbon-13 by multiphoton of producing of carbon-13 by multiphoton dissociation 35 decomposition of CF2HCl, said material containing of CF3Br or CF3Cl is disclosed. In a paper in The Jour carbon-12 and carbon-13 isotopic species, comprising: nal of Chemical Physics July 1, 1979, Vol. 71, No. 1, by (a) irradiating gaseous CF2HCl in a reaction chamber Peter A. Hackett, Clive Willis and Michel Gauthier, a at a pressure in the range 10-100 Torr with an method of producing carbon-13 by multiphoton disso infra-red laser beam at a frequency in the range ciation of CF3COCF3 is described. 40 1040-1080 wavenumbers to selectively decompose In co-pending United States application No. 132,656, the CF2HCl to give C2F4 enriched to a first level of filed Mar. 21, 1980, in the name of Peter A. Hackett, carbon-13, CF2HCl, and HCl, Wing S. Nip and Clive Willis, now U.S. Pat. No. (b) passing these products through an absorber to 4,328,078, a method of producing carbon-13 by multi 45 remove the HCl and a separation stage to remove photon dissociation of perfluoropropene (C3F6) is de the CF2HCl depleted in carbon-13, scribed. (c) oxidizing the C2F4 to form CO2, and It is another object of the present invention to pro (d) passing the CO2 through a second exchange stage vide an inexpensive method of carbon-13 production. to separate the 13CO2 and the 12CO2 and give a This and other objects of the invention are achieved 50 CO2 product containing approximately 90-99%

by a method of producing carbon-13 using CF2HCl as 2. A method of producing carbon-13 as in claim 1 the feedstock (substrate) material in which the CF2HCl wherein the CO2 is passed through a chemical exchange is enriched up to a first level of C-13 by I.R. laser photo stage to separate the 13CO2 and the 12CO2 and give a dissociation and then to 90-99% C-13 by a second ex CO2 product.

change. In the preferred arrangement the second stage 55 3. A method of producing carbon-13 as in claim 1 or is a chemical exchange process. claim 2 wherein the CF2HCl is decomposed to give In drawings which illustrate an embodiment of the C2F4 enriched to approximately 25-35% carbon-13. invention, ck ck ck : t