3,086,932 ice Patented Apr. 23, 1963
2 and increases of the proportion of higher polyphenyls 3,086,932 PROCESS FOR PRODUtIiNG A RECOVERENG is an undesirable tendency. This is true as well for other ORGANIC NUCLEAR REACTOR COOLANT hydrocarbons, e.g., partially hydrogenated or alkylated MODERATGRS polyphenyls. Robert 0. Bolt, San Rafael, and William W. West, El The present invention is predicated on the discovery Cerrito, Cali?, assignors, by mesne assignments, to the that catalytic hydrogenolysis of ‘di?erent polyphenyls United States of America as represented by the United produces a marked reversion or conversion of higher States Atomic Energy Commission molecular weight constituents of aromatic and especially No Drawing. Filed Nov. 3%, 1959, Ser. No. 856,321 polyphenyl mixtures having undesirable characteristics 3 Claims. (Cl. Zita-493.2) 10 into lower molecular weight mixtures of more useful and The present invention relates, in general, to the pro desirable coolant-moderator types. Most unexpectedly duction and recovery of polyphenyl coolants from in hydrogenolysis, i.e., ring cleavage occurs with little ring tractable polyphenyl tars or residues and, more particu hydrogenation which might have been expected. Thus, larly, to the treatment of intractable, insoluble tarry resi highly damaged reactor coolant-moderator materials may dues obtained from coolants or moderators employed in 15 be reconditioned or various component fractions thereof nuclear reactors for conversion into useful moderator separated and treated to provide a material which is coolant products. highly satisfactory for reuse in the reactor. Varieties of aromatic hydrocarbons have been utilized Accordingly, it is an object of the present invention or have been proposed or investigated for use as coolants to provide a method for reconditioning coolant-moderator or moderators in nuclear reactors including polyphenyls, materials for use in a nuclear reactor. I aromatic condensed ring compounds, aromatic ethers and Another object of the invention is to employ a catalytic alkylated aromatic hydrocarbons. Polyphenyl hydro hydrogenolysis treatment for converting higher molecular carbons, especially biphenyl, the terphenyls and the qua weight reactor coolant-moderators into more desirable terphenyls are suitable for such use due to superior radio coolant~moderators. lytic and pyrolytic resistance and other requisite proper 25 Still another object of the invention is to provide a ties as disclosed in the ‘copending application of Rep method of converting high molecular weight intractable pino J. Fontana et al., S.N. 599,352, ?led July 23, 1956, tarry components of aromatic hydrocarbon coolant now abandoned. Ordinarily, mixtures of a ?uid nature moderators into coolant types suitable for use in a nuclear or low melting point solids corresponding to lower aver reactor. age molecular weights or eutectic mixtures are preferred. A further object of the invention is to employ a cat Upon long continued use in the high temperature intense alytic hydrogenolysis treatment for reconditioning poly radiation environment of the reactor the organic mixtures phenyl moderator-coolants for use in a nuclear reactor. show increases in viscosity with higher molecular weight Other objects and features of the invention will be materials being formed therein. Eventually, insoluble come apparent by consideration of the following de high molecular weight materials may form which ma- tailed description. terials precipitate to plug reactor passages and create a The present invention contemplates the treatment of hazard to further operation of the reactor. Accordingly, aromatic hydrocarbon mixtures employed as coolants and in conventional practice the mixture employed in the re moderators or higher molecular weight fractions obtained actor is periodically replaced or reconditioned by sep 40 therefrom by distillation, extraction, selective precipita arating the tarry constituents by distillation, precipitation, tion, etc. The process is especially applicable to the extraction, etc. The tarry residues obtained in such re treatment of polyphenyl mixtures such as the damaged conditioning operations represent an expensive loss of the biphenyl-terphenyl coolant-moderator employed, e.g., in coolant or moderator material and the indicated changes the OMRE and to other mixtures including, initially, bi of composition of the coolant lead to greater pumping 45 phenyl, terphenyls and quaterphenyls. Usually such in cost, lower heat transfer as well as other higher oper itial mixtures are ?uid or have a low melting point and ating costs for such a reactor. may comprise a considerable proportion of biphenyl with Nuclear reactors employing organic moderators and terphenyl and quaterphenyls or eutectic mixtures. Alkyl coolants are well known in the art. A reactor employing ated biphenyl, terphenyls and minor amounts of quater biphenyl as a moderator is disclosed in vU.S. Patent No. 50 phenyls may likewise be employed. For the purposes of 2,708,656, issued May 17, 1955, to E. Fermi et al. The the invention, a radiation ‘damaged mixture is one that use of organic liquids as coolants is also disclosed in has a higher average molecular Weight or undesirable Chapter 8 of “Principles of Nuclear Reactor Engineer- _ amounts of high molecular compounds and evidencing ing,” Glasstone, Van Nostrand Co., Inc., 1955. A bibli~ variously higher insoluble tar content, higher viscosity, ography of publications relating to such reactors is pre 55 melting point, etc. Certain polyphenyl synthesis meth sented in “Selected Abstracts on the Use of Organic Ma ods may produce mixtures of too high a molecular weight terials as Reactor Moderator-Coolants,” G. Naish and which mixture may likewise be treated. A damaged re— .R. W. Bowring, AERE Report inf/Bib 105. Moreover, actor or coolant material of the character described may biphenyl-terphenyl mixtures have successfully been uti comprise discarded material, a bypass stream obtained lized in the OMRE (organic moderated reactor experi 60 from a reactor coolant system, residues obtained by selec ment). C.f. “Details of OMRE” Nucleonics, vol. 14, tive separation from a reactor coolant circuit, or the like. No. 5, page 22, May 1956. In accordance with the invention such a material is The reactions which occur upon radiolytic pyrolysis of V subjected to a hydrogenolysis treatment wherein a sub the initial coolant-moderator mixtures are complex but stantial portion of the higher molecular weight compo generally tend to increase molecular weight, e.g., by con 65 nents are converted into lower molecular weight com verting lower polyphenyls to higher, polymerizing or com ponents such as biphenyl, terphenyl and alkylated deriva tives thereof which constitute superior reactor coolant bining unsaturated radiolysis products, etc., to progres moderator types. With source materials not originally sively produce a less desirable coolant and tinally a too severely damaged the reaction product, after ?ltering material which is not suitable for further use and which 70 and ‘being separated from gaseous or low-boiling compo must be replaced. Any substantial change such as re nents, is reintroduced into the operating reactor as recon duction of the proportion of lower molecular polyphenyls ditioned material. With highly damaged materials, such 3,086,982 xii as the insoluble, intractable tarry residues the reaction cate ring cleavage which eitectively divides high molecu product may be fractionated, e.g., in distillation or lar piolyphenyls to provide the desired lower molecular vacuum distillation apparatus and the recovered lower coolant-moderator compounds. It will be understood molecular weight, components may be used as makeup from the foregoing that if the original mixture includes moderator-coolant or otherwise admixed with other com- 5 polyphenyls of a higher molecular Weight than terphenyl, ponents to provide moderator-coolants as in conventional e.g., quaterphenyls, et seq., a general lowering of molecu practice. la-r weight will be obtained with substantial amounts of In the hydrogenolysis treatment the damaged coolant- biphenyl and ter-phenyl being produced. Such mixtures moderator mixture is contacted with hydrogen in the would correspond or could be easily blended to corre presence of a hydrogenolysis catalyst under high pres- 10 spond to the superior coolant-moderators disclosed in sure and at elevated temperatures in appropriate batch the aforesaid copending application of Fontana et a1. or continuous flow high pressure equipment of conven- and publications supra. Hydrogenated polyphenyls tional design. Generally speaking, it is contemplated that which are produced under indicated conditions are less so-ca,11ed “acid” cracking and mild hydnogenation cata- desirable compounds since radiation damage resistance is lysts are effective in producing hydrogenolysis of higher 15 lower. polyphenyls. More speci?cally A1203 (alumina) and Further details will be presented in the following certain mixtures of A1203 with CuO have been so em— speci?c example illustrating the manner of operating the ployed. Suitable operating conditions are presented in process ‘of the invention: Table I, infra. EXAMPLE TABLE I 20 Standardized amounts of terphenyl representative of higher molecular weight polyphenyls were reacted with Conditions Bmad range Preferred range hydrogen under high pressure ‘and at an elevated tem 0 perature with various combinations of cracking and hy Timerhmns-?o------01-8-0 ------4-181)- drogenation catalysts. The reagents comprised Mon in‘iil'de?ggsr?ie,gjsiignwni ______'_'_' Egg-£8881 25 Same m-terphenyl recrystallized from ethyl alcohol; Ram 0‘ “mpwnd: A1103‘ FY2°5I_%,825=°-25=° 't° 112333651211 to aluminum oxide powder (Baker, reagent grade) as crack Cuo' ' ' ' ' ' ' ing catalyst; and copper oxide powder (Mallincrodt GP.) as hydrogenation catalyst. The reagents were charged General comments as to the effects of the speci?c into a hydrogenation bomb and the bomb pressurized se catalyst type are summarized in the following chart: 30 'quentially to 500' and 250 p.s.i.g. with H2 to eliminate
Chart
Catalyst Effect on biphenyl formation E?eet on ring hydrogenation E?ect on higher polyphenyl formation
Hydrogenation (OuO) _ _ Increasing amounts decrease biphenyl Increasing amounts increase ring hydro Increasing amounts probably reduce rmation. genation. h’gher polyphenyl formation. Cracking (A1203) ...... Increasing amounts probably increase No ring hydrogenation obtained with Increasing amounts probably increase biphenyl formation. cracking catalysts alone. higher polyphenyl formation.
Norm-General comments: (1) Both ring-hydrogenation and hydrogenolysis reactions are strongly a?ected by temperature and reaction time. (2) It is likely that the catalyst for optimum operation (low conversions to higher polyphenyls and hydrogenated polyphcnyls and high conversions to biphenyl) will be primarily a cracking catalyst, with a small amount of a mild hydrogenation catalyst.
Poly-phenyls can be represented by the formula air and ?nally the ‘desired hydrogen pressure was intro duced. The bomb was then placed in a rocking hydro C(iH5(C6H4)nC6H5 50 genation furnace ‘and heated to the desired temperature wherein It may be zero or a larger integer, i.e., 1, 2, 3 with reagent proportions and other conditions as sum Presumably, polyphenyl tars contain substantial marized for several runs in the following Table II:
TABLE II Summary of Conditions for T erphenyl Hydrogenolysis Runs
Conditions 6064-35 6064-39 6064-42 6106445 6064-47
Time, hours ______._ 4 ______3. Temperature, ° F__. _ 800 900. Initial pressure, D.S.i.g_ _ 1,500 ______5G0 ______-_ 500 ______500 _ 1,000. Terphenyl . ______. . . _ _ . _ __ m-TerphenyL. m~Terphenyl__ o-TerphenyL- o-Terphenyl__ o-Terphenyl. Terphenyl charge, g. ______2 __ _._- 25 ____ 5 ____ 50. Cat ______1312090110-... AlzO3-C110_-__ AlzOa-CuO.___ A1203 ______A1203. Catalyst charge, g.: A1203...“ ______.. __-_ 8. CuO ______. 1 _ 0. Ratio of compound: AhOyCuO charges ...... _ 25:420.
amounts of materials in which n is 2, 3 or larger while Following hydrogenolysis the reaction products were in desirable moderator-coolants n is 0, 1 with at most removed from the bomb whereupon it was noted that the minor amounts of quaterphenyls (11:2). The term CuO in each instance was reduced to the metallic state. “hydrogenolysis” as employed herein is intended to indi Catalyst was separated from the mixture and the mix 3,086,932 5 6 ture analyzed by means of a mass spectrograph with containing higher polyphenyls, the steps comprising with results presented below in Table III: drawing said damaged moderator-coolant from the
TABLE III Summary of Mass Spectrometer Analysis of Terphenyl H ydrogenolysis Runs
Mass Probable identi?cation 6064-35! 6064-392 6064-422 6064-45I 6064-47
7S____ Benzene ______‘l52____ Biphenylene aeenaphthy lene___. ___ 154--“ Biphenyl ‘ijiinieiiizi-Ec'e't‘ii'e this} cene phenanthrene_
230-.. 'I‘erphenyl ______234-___ Tetrahydro-terphenyl 236____242.-“ Hexahydro-terphenylDodeeahydro-terphenyl ______"=0 Benzpyrene 276"“ ______278______306..-- Quaterphenyl___ 382____ Quinquephenyl_-. ___ 458____ Hexap‘nenyl ______535-___ Heptap‘nenyl
1 In calculating the components in 6064-35, certain assumptions concerning sensitivities had to be made. These assumptions are listed on 6205-15. 1’ Polyphenyl values for 6064-39, —42, and —45 are normalized to 100%. These poly phenyls comprise approximately 96% of the total product for these three runs. 3 x denotes peak presence in small but undetermined amounts. NOTE.-—Figures in table refer to liquid volume percent concentration.
in practice the small proportions of polyphenyls above nuclear reactor, contacting an admixture of said damaged quaterphenyls shown would not seriously detract from reactor coolant-moderator and hydrogen simultaneously with a catalyst including an alumina acid cracking catalyst the e?ectiveness of the mixtures as coolant-moderators, 35 particularly when the mixtures are employed for makeup. and Q10 mild hydrogenation catalyst present in the ratio The lower boiling materials ‘could, of course, be sepa range of 25:2:1 to 25:4:0, respectively, at a temperature rated, e.g., as by distillation and employed as coolants in the range of about 800 to 1000" F. and a pressure in and the higher boiling material reprocessed. the range of 500 to 1000 p.s.i.g. to cause hydrogenolysis While there has been described in the foregoing what 40 of said higher polyphenyls to produce lower molecular may be considered to be preferred embodiments of the Weight polyphenyls and alkylated derivatives thereof in invention, modi?cation may be made therein without the reaction mixture, and then returning said coolant departing from the spirit of the invention and it is intended moderator mixture to the reactor. to cover all such as fall within the scope of the appended 3. The process as de?ned in claim 2 wherein there is claims. included the operation of fractionating said reaction mix vWhat is claimed is: ture prior to return to said reactor. 1. In a process for producing a polyphenyl moderator References Cited in the ?le of this patent coolant from a mixture including higher polyphenyls, the steps comprising contacting an admixture of said higher UNITED STATES PATENTS polyphenyl mixture and hydrogen simultaneously with a 50 2,033,878 Burk ______Mar. 10, 1936 catalyst including an alumina acid cracking catalyst 2,297,769 Ipatieff et al. ______Oct. 6, 1942 together with a lesser proportion of CuO as a mild 2,344,258 Miles ______Mar. 14, 1944 hydrogenation catalyst in the ratio range of 25 :2:1 to 2,355,219 Ipatieff et al. ______Aug. 8, 1944 25:4:(), respectively, at a temperature in the range of 2,364,719 Jenkins ______Dec. 12, 1944 about 800 to 1000° F. and a pressure in the range of 2,800,518 Pitzer ______July 23, 1957 500 to 1,000 p.s.i.g. to cause hydrogenolysis of said higher 2,921,891 Colichman ______Jan. 9, 1960 polyphenyls to produce lower molecular “weight poly phenyls and alkylated derivatives thereof in the reaction OTHER REFERENCES mixture, and fractionating said lower molecular weight Atomic Energy Commission Document: ANL—5121, polyphenyls from said reaction mixture. Engineering Properties of Diphenyl, Anderson, Aug. 11, 2. In a process for reconditioning a radiation damaged 1953, pp- 14 and 15. polyphenyl nuclear reactor coolant-moderator mixture Catalysis, Sophia Berkman et al., pp. 629 and 847.