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ice 3,086,932 Patented Apr. 23, 1963 2 3,086,932 and increases of the proportion of higher polyphenyls is an undesirable tendency. This is true as well for other PROCESS FOR PRODUtIiNG A RECOVERENG ORGANIC NUCLEAR REACTOR COOLANT MODERATGRS Robert 0. Bolt, San Rafael, and William W. West, El Cerrito, Cali?, assignors, by mesne assignments, to the hydrocarbons, e.g., partially hydrogenated or alkylated United States of America as represented by the United produces a marked reversion or conversion of higher polyphenyls. The present invention is predicated on the discovery that catalytic hydrogenolysis of ?di?erent polyphenyls 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 desirable coolant-moderator types. Most unexpectedly The present invention relates, in general, to the pro hydrogenolysis, i.e., ring cleavage occurs with little ring duction and recovery of polyphenyl coolants from in hydrogenation which might have been expected. Thus, tractable polyphenyl tars or residues and, more particu highly damaged reactor coolant-moderator materials may larly, to the treatment of intractable, insoluble tarry resi dues obtained from coolants or moderators employed in 15 be reconditioned or various component fractions thereof separated and treated to provide a material which is nuclear reactors for conversion into useful moderator highly satisfactory for reuse in the reactor. coolant products. Accordingly, it is an object of the present invention Varieties of aromatic hydrocarbons have been utilized to provide a method for reconditioning coolant-moderator or have been proposed or investigated for use as coolants materials for use in a nuclear reactor. I or moderators in nuclear reactors including polyphenyls, aromatic condensed ring compounds, aromatic ethers and alkylated aromatic hydrocarbons. Polyphenyl hydro Another object of the invention is to employ a catalytic hydrogenolysis treatment for converting higher molecular weight reactor coolant-moderators into more desirable coolant~moderators. Still another object of the invention is to provide a lytic and pyrolytic resistance and other requisite proper 25 carbons, especially biphenyl, the terphenyls and the qua terphenyls are suitable for such use due to superior radio ties as disclosed in the ?copending application of Rep pino J. Fontana et al., S.N. 599,352, ?led July 23, 1956, method of converting high molecular weight intractable tarry components of aromatic hydrocarbon coolant now abandoned. Ordinarily, mixtures of a ?uid nature or low melting point solids corresponding to lower aver age molecular weights or eutectic mixtures are preferred. moderators into coolant types suitable for use in a nuclear Upon long continued use in the high temperature intense radiation environment of the reactor the organic mixtures alytic hydrogenolysis treatment for reconditioning poly show increases in viscosity with higher molecular weight materials being formed therein. Eventually, insoluble reactor. A further object of the invention is to employ a cat phenyl moderator-coolants for use in a nuclear reactor. Other objects and features of the invention will be come apparent by consideration of the following de tailed description. The present invention contemplates the treatment of aromatic hydrocarbon mixtures employed as coolants and moderators or higher molecular weight fractions obtained high molecular weight materials may form which materials precipitate to plug reactor passages and create a hazard to further operation of the reactor. Accordingly, in conventional practice the mixture employed in the re actor is periodically replaced or reconditioned by sep 40 therefrom by distillation, extraction, selective precipita tion, etc. The process is especially applicable to the arating the tarry constituents by distillation, precipitation, treatment of polyphenyl mixtures such as the damaged extraction, etc. The tarry residues obtained in such re conditioning operations represent an expensive loss of the biphenyl-terphenyl coolant-moderator employed, e.g., in the OMRE and to other mixtures including, initially, bi coolant or moderator material and the indicated changes of composition of the coolant lead to greater pumping 45 phenyl, terphenyls and quaterphenyls. Usually such in itial mixtures are ?uid or have a low melting point and cost, lower heat transfer as well as other higher oper may comprise a considerable proportion of biphenyl with ating costs for such a reactor. terphenyl and quaterphenyls or eutectic mixtures. Alkyl Nuclear reactors employing organic moderators and ated biphenyl, terphenyls and minor amounts of quater coolants are well known in the art. A reactor employing biphenyl as a moderator is disclosed in vU.S. Patent No. 50 phenyls may likewise be employed. For the purposes of the invention, a radiation ?damaged mixture is one that 2,708,656, issued May 17, 1955, to E. Fermi et al. The has a higher average molecular Weight or undesirable use of organic liquids as coolants is also disclosed in amounts of high molecular compounds and evidencing variously higher insoluble tar content, higher viscosity, ing,? Glasstone, Van Nostrand Co., Inc., 1955. A bibli~ ography of publications relating to such reactors is pre 55 melting point, etc. Certain polyphenyl synthesis meth Chapter 8 of ?Principles of Nuclear Reactor Engineer- _ ods may produce mixtures of too high a molecular weight which mixture may likewise be treated. A damaged re? actor or coolant material of the character described may .R. W. Bowring, AERE Report inf/Bib 105. Moreover, comprise discarded material, a bypass stream obtained biphenyl-terphenyl mixtures have successfully been uti lized in the OMRE (organic moderated reactor experi 60 from a reactor coolant system, residues obtained by selec tive separation from a reactor coolant circuit, or the like. ment). C.f. ?Details of OMRE? Nucleonics, vol. 14, In accordance with the invention such a material is No. 5, page 22, May 1956. subjected to a hydrogenolysis treatment wherein a sub The reactions which occur upon radiolytic pyrolysis of V stantial portion of the higher molecular weight compo the initial coolant-moderator mixtures are complex but nents are converted into lower molecular weight com 65 generally tend to increase molecular weight, e.g., by con ponents such as biphenyl, terphenyl and alkylated deriva verting lower polyphenyls to higher, polymerizing or com 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 sented in ?Selected Abstracts on the Use of Organic Ma terials as Reactor Moderator-Coolants,? G. Naish and duction of the proportion of lower molecular polyphenyls ditioned material. With highly damaged materials, such 3,086,982 xii cate ring cleavage which eitectively divides high molecu as the insoluble, intractable tarry residues the reaction lar piolyphenyls to provide the desired lower molecular product may be fractionated, e.g., in distillation or coolant-moderator compounds. It will be understood vacuum distillation apparatus and the recovered lower 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 convenand 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 catadesirable 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)- in?iil'de?ggsr?ie,gjsiignwni drogenation catalysts. _______ __'_'_' Egg-�81 Ram 0? ?mpwnd: A1103? FY2�_%,825=�-25=� 't� 112333651211 to Cuo' ' ' ' The reagents comprised Mon 25 Same m-terphenyl recrystallized from ethyl alcohol; aluminum oxide powder (Baker, reagent grade) as crack ' ' ' 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 Hydrogenation (OuO) _ _ Increasing amounts decrease biphenyl Cracking (A1203) ...... .. Increasing amounts probably increase biphenyl formation. rmation. E?eet on ring hydrogenation E?ect on higher polyphenyl formation Increasing amounts increase ring hydro genation. Increasing amounts probably reduce h?gher polyphenyl formation. Increasing amounts probably increase No ring hydrogenation obtained with 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 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: C(iH5(C6H4)nC6H5 TABLE II Summary of Conditions for Terphenyl Hydrogenolysis Runs Conditions 6064-35 Time, hours _________________________________ ._ 6064-39 6064-42 6106445 4 ____________ __ 3. Temperature, � F__. _ 800 Initial pressure, D.S.i.g_ _ 1,500 ________ __ 5G0 __________ -_ . _ _ . _ __ m-TerphenyL. m~Terphenyl__ o-TerphenyL- 2 __ 25 Terphenyl . _ _ _ _ _ _ _ _ . . Terphenyl charge, g. Cat _____________________________________ __ A1203...? 900. ____ __ Catalyst charge, g.: ______ .. 6064-47 1312090110-... _._- AlzO3-C110_-__ 500 ____ __ _ ____ AlzOa-CuO.___ 500 _ o-Terphenyl__ 5 ____ A1203 _______ __ __-_ CuO _____________________________________ _. 1,000. o-Terphenyl. 50. A1203. 8. 1 Ratio of compound: AhOyCuO charges ..... ._ amounts of materials in which n is 2, 3 or larger while in desirable moderator-coolants n is 0, 1 with at most minor amounts of quaterphenyls (11:2). The term ?hydrogenolysis? as employed herein is intended to indi _ 0. 25:420. Following hydrogenolysis the reaction products were removed from the bomb whereupon it was noted that the CuO in each instance was reduced to the metallic state. Catalyst was separated from the mixture and the mix 3,086,932 6 5 ture analyzed by means of a mass spectrograph with results presented below in Table III: containing higher polyphenyls, the steps comprising with drawing said damaged moderator-coolant from the TABLE III Summary of Mass Spectrometer Analysis of Terphenyl Hydrogenolysis Runs Mass 7S____ Probable identi?cation 6064-35! 6064-392 6064-422 6064-45I 6064-47 Benzene ___________________ __ ?l52____ Biphenylene aeenaphthy lene___. ___ 154--? Biphenyl ?ijiinieiiizi-Ec'e't?ii'e this} cene phenanthrene_ 230-.. 'I?erphenyl ________________ __ 234-___ Tetrahydro-terphenyl 236____ Hexahydro-terphenyl _____ __ "=0 Benzpyrene 242.-? Dodeeahydro-terphenyl 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. nuclear reactor, contacting an admixture of said damaged reactor coolant-moderator and hydrogen simultaneously the e?ectiveness of the mixtures as coolant-moderators, 35 with a catalyst including an alumina acid cracking catalyst and Q10 mild hydrogenation catalyst present in the ratio particularly when the mixtures are employed for makeup. range of 25:2:1 to 25:4:0, respectively, at a temperature The lower boiling materials ?could, of course, be sepa in the range of about 800 to 1000" F. and a pressure in rated, e.g., as by distillation and employed as coolants the range of 500 to 1000 p.s.i.g. to cause hydrogenolysis and the higher boiling material reprocessed. While there has been described in the foregoing what 40 of said higher polyphenyls to produce lower molecular Weight polyphenyls and alkylated derivatives thereof in may be considered to be preferred embodiments of the the reaction mixture, and then returning said coolant invention, modi?cation may be made therein without moderator mixture to the reactor. departing from the spirit of the invention and it is intended in practice the small proportions of polyphenyls above quaterphenyls shown would not seriously detract from to cover all such as fall within the scope of the appended claims. vWhat is claimed is: 1. In a process for producing a polyphenyl moderator coolant from a mixture including higher polyphenyls, the steps comprising contacting an admixture of said higher 3. The process as de?ned in claim 2 wherein there is included the operation of fractionating said reaction mix ture prior to return to said reactor. References Cited in the ?le of this patent UNITED STATES PATENTS polyphenyl mixture and hydrogen simultaneously with a 50 catalyst including an alumina acid cracking catalyst 2,033,878 Burk ______________ __ Mar. 10, 1936 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 25:4:(), respectively, at a temperature in the range of 2,355,219 Ipatieff et al. ________ __ Aug. 8, 1944 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 mixture, and fractionating said lower molecular weight polyphenyls from said reaction mixture. 2. In a process for reconditioning a radiation damaged polyphenyl nuclear reactor coolant-moderator mixture OTHER REFERENCES Atomic Energy Commission Document: ANL?5121, Engineering Properties of Diphenyl, Anderson, Aug. 11, 1953, pp- 14 and 15. Catalysis, Sophia Berkman et al., pp. 629 and 847.