3,532,740 United States Patent 0 " IC€ Patented Oct. 6, 1970

1 2 5 3,532,740 CH2 0 0 OXIDATIVE DEHYDROGENATION PROCESS Charles W. Hargis, Johnson City, and Howard S. Young, Kingsport, Tenn., assignors to Eastman Kodak Com CH3 pany, Rochester, N.Y., a corporation of New Jersey 2 N 0 Drawing. Continuation-impart of application Ser. N 0. and 152,630, Nov. 15, 1961. This application May 18, 1966, Ser. No. 550,931 Int. Cl. C07c 45/12 US. Cl. 260-486 24 Claims 10 are oxidized to the corresponding alpha,beta-unsaturated derivatives This application is a continuation-in-part of our co pending application Ser. No. 152,630, ?led Nov. 15, 1961, now abandoned, which was copending with and a con tinuation-in-part of our application Ser. No. 10,107, ?led Feb. 23, 1960, now abandoned. This invention relates to selective oxidation of un 1 2 saturated aliphatic hydrocarbon derivatives. More par and ' ticularly the invention relates to selective oxidation of B a an alkyl derivative having a functional group in which functional unsaturation occurs, to produce a correspond ing ole?nic derivative. We have found that selective oxidation of the alpha, The principal object of the invention is to provide a beta-carbon atoms of the alkyl radical is accomplished method for selective oxidation of a compound consisting by action of an oxidizing agent consisting of one of, or of a lower alkyl radical attached to a functional group 25 a mixture of, the oxides of arsenic, antimony, and bis in which functional unsaturation occurs, and by such muth. When contacted with the “functionally unsatur oxidation to produce the corresponding alpha-beta un ated” organic compound at elevated temperatures, the saturated compound. Another object of the invention is metal oxide is reduced and yields oxygen which combines to provide a method for reacting an aliphatic derivative with hydrogen from the alpha and beta carbon atoms of with an oxide of antimony, arsenic bismuth to produce the oxidized compound. An alpha,beta-unsaturated com such alpha-beta unsaturated ole?nic derivatives. pound is produced. The invention provides a method for selective oxida Therefore, according to the invention, vapor of a com tion at the alpha and beta carbon atoms of the alkyl pound having the formula: radical in compounds consisting of a lower alkyl radical R1—CH—CH—X attached to a functional group in which functional un IIW Ila saturation occurs between the ?rst carbon atom and an wherein X is a functional group in which functional un— adjacent atom. saturation occurs between the ?rst carbon atom and an By “functional unsaturation” as the term is used in adjacent atom, is contacted at a temperature above 100° this speci?cation we mean an unsaturated linkage, either 40 C. with at least one memben selected from the group con a double bond or a triple bond, between two atoms of a sisting of oxides of arsenic, antimony, and bismuth. functional group (between the ?rst carbon atom and an In the foregoing formulae for the functionally unsatur adjacent atom of the functional group in the instance of ated compounds useful in the process of our invention the invention). To illustrate, in the functional group of the substituent X is typically of the formula: ketone 0 H C (10) functional unsaturation as we use the term occurs at the double bond between C and 0. or Functional unsaturation occurs between the ?rst car (c) bon atom and an adjacent atom in the following func tional groups for instance: ’ in 'which R4, when taken singly, is typically hydrogen, alkyl, hydroxy, or alkoxy. The substituents R1, R2, and R3, when taken singly are hydrogen or alkyl. The sub stituents R1 and R3, when taken collectively, represent joined alkylene groups completing a saturated carbo cyclic ring having 5 to 6, preferably 6, carbon atoms in the ring; and the substituents R1 and R4, when taken collectively, represent joined alkylene groups complet ing a saturated carbocyclic ring having 5 to 6, preferably 6, carbon atoms in the ring. The substituents R1, R2, R3 and R4, when alkyl, are typically alkyl of 1 to about 8 carbon atoms and are preferably lower alkyl, e.g., alkyl of 1 to about 4 carbon 65 atoms. When R4 is alkoxy, it typically contains an alkyl moiety of 1 to about 8 carbon atoms. The alkyl moiety of the alkoxy group represented by R4 is preferably lower alkyl, e.g., alkyl of 1 to about 4 carbon atoms. Typical of the alkyl groups represented by R1, R2, R3, 70 and R4 are methyl, ethyl, propyl, isopropyl, butyl, iso Thus, alkyl derivatives such as butyl, sec-butyl, tert-butyl, etc.'The substituent R4, when 3,532,740 4 alkoxy, is typically methoxy, ethoxy, propoxy, isopro the ratio of bulk contact mass volume (for instance in poxy butoxy, isobutoxy, sec-butoxy, tert-butoxy, etc. cubic feet) to reactant vapor feed rate (for instance in When R1 and R3 collectively represent joined alkylene cubic feet per second). This is to be distinguished from groups completing a carbocyclic ring, the carbocyclic exposure time for the metal oxide which is the total rings so represented are typically cyclopentyl or cyclo time a sample of solid metal oxide is exposed to reactants hexyl. When R1 and R4 collectively represent joined in the reaction zone. alkylene groups completing a carbocyclic ring, the carbo To the extent found necessary, temperature in the re cyclic rings so represented are typically cyclopentyl or action zone may be regulated by controlling feed tem cyclohexyl. _ perature and, when a diluent is used, by controlling the The alpha,beta-unsaturated compounds formed in the 10 ratio of diluent to reactant in the feed stream. The reac process of our invention can be represented by the for tion proceeds at a temperature above about 100° C. and mula: reactions conducted at temperatures between about 325° C. and 475° ‘C. give good product yields. Good yields are obtained at atmospheric pressure which is pre ferred for economic reasons, but the pressure in the re in which R1, R21, R3 and X are as de?ned hereinbefore, action zone may be varied. when the functionally unsaturated compound employed The oxide or mixture of oxides selected for a particular has only one alpha-beta position capable of being 0x1 reaction and the valence state of the oxide or mixture datively dehydrogenated. of oxides must be considered as factors having marked When the functionally unsaturated compound has two 20 in?uence on the choice of operating conditions. An oxide or more alpha-beta positions capable of being oxidatrvely in which the metallic element is present in a higher val dehydrogenated, dehydrogenation can occur at both POSI ence state, a valence of 5 for example, is more vigorous tions. Thus, diethyl ketone can react with antimony in oxidative action than one in a lower valence state. tetroxide to form divinyl ketone. In a particularly in Less severe operating conditions such as lower reaction teresting embodiment of this aspect of our invention, temperature and decreased contact time can therefore be cyclohexanone reacts with an inorganic oxide apparently employed when an oxide of the higher valence state is to form 2,5-cyclohexadiene-1-one or 2,4-cyclohexadiene used. Also, oxidation activity of the metal oxides in a l-one which immediately rearranges to phenol. given valence state tends to increase as oxides of metal Typical of the functionally unsaturated compounds in descending order in the periodic series are selected. which are useful in the process of our invention are com 30 For example, arsenic pentoxide requires higher operating pounds such as propionaldehyde, methyl ethyl ketone, temperatures and/or more prolonged contact times for propionic acid, methyl propionate, cyclohexanone, ethyl a comparable production of unsaturates than does anti benzene, l-butene, cyclohexanecarboxaldehyde, methyl mony pentoxide. The ?exibility in operating conditions cyclohexanecarboxylate, cyclohexanecarboxylic ac1d, made possible by varying degrees of oxidation activity cyclohexyl benzene, etc. 03 Gr of the oxides or mixtures thereof can be of considerable The process of our invention involves a reaction be importance in selection of a suitable oxide and suitable tween the functionally unsaturated compound and the operating conditions, since the heat stability and reac selected metal oxide or oxy-acid thereof. For example, tion stability of the various organic compounds which isobutyraldehyde, reacts with arsenic pentoxide to form may be oxidized will differ. methacrolein, water, and a reduced form of the arsenic 40 Some of the organic compounds which may be oxidized pentoxide, e.g., arsenic trioxide or elemental arsenic. according to the invention possess suf?cient stability to The mechanics of the process consist simply of con allow feeding of some air into the reaction zone with tacting the organic compound to be oxidized with a the organic compound. The advantage of introducing metal oxide in a reaction zone at a temperature between air with the feed stream is that the exposure time for the 100° C. and 600° C., preferably between 150° C. and oxidizing agent is extended because some of the reduced 500° C. This is conveniently done by passing a stream metal oxide in the reaction zone is reoxidized by the air of vapor of the organic compound through a reaction introduced with the feed stream. But in some-cases pres vessel packed with particles of the selected metal oxide. ence of air will cause excessive side reactions which will Fine particles of the metal oxide are preferred because reduce the product yield substantially. Ethylbenzene is more surface area per unit of volume will be available ' an example of a compound with which air may be intro for contact with the organic vapor. In some cases it duced in carefully controlled amounts. The optimum may be advantageous to dilute the vapor stream with Volume of air to be used will depend upon the particular nitrogen or other inert gas to control the temperature reactants selected as well as the operating conditions. in the reaction zone, to reduce the rate of side-reactions, Usually the optimum will be in the range from 0 to 0.8 and to facilitate removal of reaction products from the - volumes of air per volume of organic vapor. reaction zone. The optimum ratio of the volume of _ The following examples are given to illustrate the diluent gas per volume of organic vapor will depend invention. upon the reactants being used and the reaction tempera EXAMPLE 1 ture and contact time but will usually be within the Over a period of two hours, 0.373 mole of isobutyr range from 0 to 2.0 volumes inert gas per volume of or 60 aldehyde was passed over granular antimony pentoxide ganic vapor. The process is operable within wide ranges contained in a 1-inch diameter Vycor tube 33 inches of temperature, pressure and contact time. However, long, at a temperature of 325° C. and a contact time of because of sensitivity of organic compounds to changes 15.5 seconds. The reaction product, which was com in temperature under oxidative conditions, consideration posed of an aqueous phase and an organic phase, was must be given to the relation of operating variables. For collected in traps, cooled to 10° C. and —80° C. The instance, the permissible range of contact time Will be organic reaction product amounted to 97.5 percent of different at various temperatures within the preferred the weight of the liquid feed which had been metered temperature range. With increase in temperature, the to the reactor during the run. Analysis of the product contact time must be decreased commensurately to avoid showed 0.075 mole of methacrolein and 0.281 mole of excessive consumption of organic feed stock in side unreacted isobutyraldehyde. The conversion of isobutyr reactions. The optimum contact time will be a function aldehyde feed to methacrolein was 20.1 percent and the of the organic and metal oxide reactants chosen and of yield of methacrolein based on isobutyraldehyde con the reaction temperature but will usually fall within the sumed was 81.5 percent. The organic product contained range from about 0.1 to about 75 seconds. The term traces of biacetyl. “contact time” as used in this speci?cation is de?ned as Vycor is a trademark for heat- and chemical-resistant 3,532,740 5 6 glassware of various compositions and physical properties, The particular solid oxidant selected for use may be ob all characterized by extremely low coefficients of expan tained in various ways such as by oxidation of the free sion. metal or a mixture of free metals taken alone or in any EXAMPLE 2 desired proportions, by known chemical methods. Or, in termediate or lower oxides or their mixtures may be Over 3 Period of one hour, a mixture c°nSiSt_ing of- 5 formed by thermal decomposition and/or chemical reduc 0-20 mole of isobutyraldehyde and 0-20 H1916 of mtrogen tion of higher oxides or suitable mixtures thereof. Meth Was Ptlssed Over granular antlmony tetroxld‘? at 450° C‘ ods for affecting these various transpositions are a matter and a contact time of 7.4 seconds. The tetroxide had been of record and may be found by reference to the usual Prepared by heating a sample of antlmeny pentoxlde m 10 sources such as textbooks or inorganic chemistry. In the air at 780° c- The two'phase hqmd reaction Product Was same manner, samples of oxidant that have lost dehydro eoheeted as in EXamPIe 1- The °_rgamc Phase amouflted genating activity due to conversion to a lower oxide or to 92 Percent of the liquid fed dunng the run‘ Analysls 9f other inactive species can be regenerated by suitable chem the 01" genie Product Showed 0-084 mole of methacrolem ical treatment to form the starting oxidant. In this respect and 0.10 mole of unreacted isobutyraldehyde, correspond- 15 antimony tetroxide has preveh to he a particularly useful ing to a conversion to methacrolein of 42.0 percent and form of oxidant Since the Spent oxidant can be readily a Yield of 84-0 Percent _ regenerated by heating in air as in Example 2. The Same Sample of oxidant was then used for 2} Fee‘ Although we have not made an extensive study of the 0nd 1-hour Period of Operation under the Same condltloes reduction product of the metal oxides we know the action without regenerative treatment of the oxidant. Analysis 20 of the oxides is that of an oxidizing agent rather than that of the organic liquid product obtained mdicated a con- Of a catalyst This is Clearly indicated by presence of Version Of 20-3 Percent and a Yleld 0f 85-4 Percent Thus water in the reaction product as well as by visible evidence during the second 1-hour period of oxidant use, the metha- of lower Oxides, and in ‘some cases metals, in the spent ereleih Prodhetion fate was 01113’ about half of that Ob‘ solid materials. For example prolonged exposure of bis taihed on initial use- i _ 25 muth trioxide with the organic reducing medium resulted The used oxidant Was regenerated by treatmg Wlth a in the formation of the metal, along with water and the IhiXtUfe of nitrogen and ail‘ at a furnace temperature of ethylenically unsaturated compound. To prevent this oc 450° C- The eeheehtl‘atleh of Oxygen in the Tegeheratmg currence with subsequent loss of metal from the reaction mixture was adjusted to maintain a temperature In Fhe zone, we prefer to treat the oxidant before excessive re hottest Point in the OXidaHt bed below 545 ° C- Heatlng 30 duction has occurred, with air in a separate operation. in the nitrogen-ail‘ mixture Was Continued until no further When the operation is carried out in this manner no visible heat of reaction could be detected. The regenerated OXI- signs of metal in the Spent Solids are seen following par dent was then used for a 1-hour Period at the initial test- tial reduction of the oxidant. Possibly a lower oxide was ihg eenditiohs- The Conversion and Yield of methaereleih formed or microscopic particles of metal in readily oxidiz as determined by product analysis were 41.5 percent and 35 able form were dispersed in the solid, 82.4 percent respectively. Thus the initial activity of the The Oxides selected for use in the process of the in. oxidant bed had been restored by the regenerative treat- vention may be used in the form of solid particles of the ment. oxide or may be suspended on a carrier such as silica gel, Using the apparatus and procedural methods of Ex- alumina or silica by conventional procedures. Small par amples I and II, a number of lower aliphatic derivatives 40 ticles of the selected oxide can conveniently be used in a were reacted with oxides of arsenic, antimony, and biS- conventional circulating-?uidized-bed reactor with the muth to produce the corresponding alpha-beta unsatu- advantage that fresh oxides may be continuously intro rated derivative. Data and results of these reactions are duced into the reaction zone as spent solids are removed tabulated in Table I. for regeneration.

TABLE I Reaction Contact Conver Ex. Oxidizing zone time, sion, Yield, No. Alkyl derivatives agent temp. sec. Product percent percent Remarks

3 .... ._ Is0butyraldehyde_____ 813204 450 7.4 Methact'olein ______. 45.5 79.2 Equimolar quantity of Nzfed _ with the aldehyde feed. 4 ______Isobutyraldehyde_____ 131203 450 7.4 Methacrolein ______. 41. 3 68. 9 Equimolar quantity of N2 fed with the aldehyde feed. 5 ...... __do ______.- AS205 350 13.6 Methacrolein ______31.4 85.5 Some sublimed AS203 carried over with product; equimolar quantity of N2 fed with organic feed. 6__.--__ n-Butyraldehyde ______810204 480 6. 6 Crotonaldehyde _____ -_ 20. 0 73. 5 Equimolafr tiluantity of N 2 fed with or anic ce . 7 ______Isobutyric acid ______-- A5205 450 23 Methacry1icacid__ _. 10.5 35.5 g 8 __ n-Bntyn'c acid ______AS205 450 23 Crotcnic acid ______8.5 42.3 _ Methylisobutyrate___. AS205 450 12.5 Methyl methacry1ate__ 10.3 49.5 10_.___ Propionaldehyde .... -. S1120; 475 6.8 Acrolein ______. 5.2 61.8 11_____ Ethylbenzene ______.- S1320; 505 5.9 Styrene ______19.1 73.2 0.33 mole air and 0.33 mole N2 fed with 0.48 mole of organic feed. 12_____ Methyl ethyl ketone_- Sb204 455 10.4 Methyl vinyl ketone_. 33.1 ______-_ Yield not determined. Methyl vinyl ketone identi?ed by gas chroma tography. 13_____ Diethyl ketone ______Sb2O4 455 11.2 Ethyl vinyl ket0ne__._ 51.2 ______Yield not determined. Ethyl vinyl ketone identi?ed by infrared. 14_____ Butane-1 ______Biz03 500 11. Butadiene ______4.7 ______Yield not determined. Butadiene identi?ed by gas chromatography.

Alkyl derivatives having functional groups Without Salts of the oxy-acids or arsenic, bismuth, and anti functional unsaturation were substituted in the process mony appear to be equivalent in oxidizing effect to the and although oxidation occurred there was a marked lack oxides from which the salts have been derived. Calcium of speci?city of reaction. A number of useful oxidation arsenate when used as the oxidizing agent appears to be . products were produced. Isobutyl alcohol was oxidized to 70 reduced in the process to calcium oxide and arsenic tri— a mixture including substantial amounts of isobutyralde oxide. In experiments in which calcium arsenate from hyde, methacrolein, methallyl alcohol, as well as some ortho-arsenate was used, arsenic trioxide was found sub other products not identi?ed. Similarly, arrays of oxida limed on condenser surfaces outside the reaction cham tion products were obtained from n-propyl alcohol and ber, indicating a reduction of arsenic valence from 5 to ethyl chloride. 75 3 as when arsenic pentoxide was used. The following ex— 3,532,740 7 8 ample illustrates a preferred embodiment of the inven R2 R3 tion in which an oxy-acid of antimony is the oxidizing agent. IU-(‘lH-(‘lH-X EXAMPLE 15 in which X is a functionally unsaturated group selected from those of the formula: During a period of 7 hours and 15 minutes, a sample of granular potassium pyroantimonate, K4Sb2O7 having a volume of 85 ml. and heated to a temperature of 455° C. in the Vycor tube of Example 1 was contacted with 90.3 g. of isobutyraldehyde. Methacrolein was produced throughout the entire period of operation as shown by 10 chromatographic examination of product samples taken periodically throughout the run and by the continuous production or organic-aqueous reaction effluent. The or each of R1, R2 and R3 when taken singly, is selected ganic product weighed 85.8 g. and contained 30 g. of from: methacrolein. (a) hydrogen Su?des of arsenic, antimony, and bismuth can be used or instead of the oxides of oxy-acid salts as the oxidizing (b) alkyl; agent in the process, though we prefer to use oxides or R4, when taken singly, is selected from salts of oxy-acids of those metals. (a) hydrogen In all of the above examples only one alpha-beta posi (b) alkyl tion could be oxidized to form a double bond. With com (c) hydroxy pounds in which oxidation to form a double bond can or occur at two alpha-beta positions, both positions may be (d) alkoxy; oxidized by the process of this invention. Some examples R1 and R3, when taken collectively, represent joined alk— of such compounds are dialkylketones such as diethyl ylene groups completing a saturated carboxycyclic ring ketone, dialkylthioketones, dialkylvinyl compounds and having 4 to 6 carbon atoms in the ring; and R1 and R4, dialkyl benzenes, These are oxidized by the process of when taken collectively, represent joined alkylene groups the invention to the corresponding dialkenyl derivatives. completing a saturated carbocyclic ring having 4 to 6 The reaction product may contain some or both the carbon atoms in the ring. singly and the doubly oxidized derivatives. 2. The process of claim 1 in which the reaction is car ried out by contacting the oxide or oxy-acid salt of ar EXAMPLE 16 senic, antimony, or bismuth with the functionally unsat During a period of 30 minutes, 13.8 g. of diisobutyl urated compound for about 0.1 to about 75 seconds at a ketone was passed over a sample of 4 x 20 mesh arsenic temperature above 100° C. pentoxide having an initial volume of 50 ml. and heated 3. The process of claim 2 in which the functionally to a temperature of 450° C. in the Vycor tube of Ex unsaturated compound is isobutyraldehyde and the prod ample 1. Phorone and isophorone were identi?ed in the ucts of the reaction include methacrolein and water. organic phase of the two-phase liquid product. The for 4. The process of claim 2 in which the functionally mation of phorone further demonstrates the principle of 40 unsaturated compound is n‘butyraldehyde and the prod extended dehydrogenation where more than one alpha ucts of the reaction include crotonaldehyde and Water. beta position is available for reaction. Isophorone would 5. The process of claim 2 in which the functionally be expected from a Michael’s reaction involving conju~ unsaturated compound is isobutyric acid and the prod gate addition of an active methylene component to an ucts of the reaction include methacrylic acid and water. 6. The process of claim 2 in which the functionally alpha,beta-unsaturated compound. 45 In cyclohexanone an interesting double alpha-beta oxi unsaturated compound is n-butyric acid and the products dation occurs to form an unstable alpha-beta diene deriv of the reaction includes crotonic acid and water. ative that rearranges to phenol. 7. The process of claim 2 in which the functionally unsaturated compound is methyl isobutyrate and the products of the reaction include methyl methacrylate and water. 8. The process of claim 2 in which the functionally unsaturated compound is propionaldehyde and the prod ucts of the reaction include acrolein and water. 9. The process of claim 2 in which the functionally EXAMPLE 17 unsaturated compound is ethylbenzene and the products During a period of 30 minutes, a sample of 4 x 20 of the reaction include styrene and water. mesh arsenic pentoxide having an initial volume of 50 10. The process of claim 2 in which the functionally ml. and heated to a temperature of 445° C. in the Vycor unsaturated compound is cyclohexanone and the prod tube of Example 1 was contacted with 6.2 g. of gaseous 60 ucts of the reaction include phenol and water. cyclohexanone and 300 ml. of nitrogen. From the two 11. A process for the production of an alkenyl ben phase liquid product was isolated 1.2 g. of phenol in ad zene which comprises reacting an alkyl benzene in which dition to unreacted cyclohexanone. Arsenic trioxide and the alkyl side chains contain separately at least two car water were also products of the reaction. bon atoms at an elevated temperature in the vapor phase, Though the invention has been described with refer with a gas consisting essentially of molecular oxygen or ence to certain preferred embodiments, it will be under molecular oxygen in combination with an inert diluent stood that variations and modi?cations can be made with over an oxidation catalyst selected from the group con in the scope of the invention as de?ned in the following sisting of (i) antimony oxide alone and (ii) in combina claims. tion with an oxide of a polyvalent metal selected from We claim: arsenic and bismuth, whilst maintaining the conditions 1. The process which comprises reacting at least one of reaction such that oxidation of the starting material compound from the group of oxides or oxy-acids salts to acidic reaction products is substantially avoided. of arsenic, antimony, or bismuth in the absence of ac 12. A process as claimed in claim 11 wherein the poly tivated alumino with a functionally unsaturated com valent metal is bismuth. pound of the formula: 13. A process as claimed in claim 11 wherein the cata 3,532,740 9 10 lyst is heated in a molecular oxygen containing gas to a 22. A process as claimed in claim 11 carriedout at temperature of 780° C. before use. temperatures in the range 200 to 600 °- C. 14. A process as claimed in claim 11 wherein the cata 23. A process as claimed in claim 22 carried out at lyst is deposited on a support material. temperatures in the range 375 to 500° C. 1 15. A process as claimed in claim 14 wherein the sup 24. A process as claimed in claim 11 carried out with port material is selected from the group consisting of a contact time within the range 0.5 to 30 seconds. silica and alumina. , 16. A process as claimed in claim 14 wherein the sup I References Cited port material is heated before deposition of the catalyst. UNITED STATES PATENTS 17. A process as claimed in claim 11 wherein the alkyl 10 1,636,952 7/1927 Craver ______.._Y_ 260—603 benzene is ethyl benzene. 2,101,820 12/1937 Woodhouse ______260-603 18. A process as claimed in claim 11 wherein the pro 2,378,209 6/ 1945 Fuller et a1. ______260—673.5 portions of alkyl benzene in the feed is in the range about 2,945,057 7/1960 McDaniel ______260-486 26% to about 30% ‘by volume. 19. A process as claimed in claim 11 wherein the con 15 PAUL M. COUGHLAN, JR., Primary Examiner centration of oxygen in the reaction mixture is in the range 5 to 9% by volume. C. R. DAVIS. Assistant Examiner 20. A process as claimed in claim 11 wherein the feed contains a gaseous diluent which is inert under the con US. Cl. X.R. ditions of the reaction. 20 260-——396, 405.5, 468, 514, 526, 586, 598, 601, 621, 669 21. A process as claimed in claim 20 wherein the gase 680 011s diluent is nitrogen.