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3,168,584 United States Patent Office Patented Feb. 2, 1965 2 gree of dehydrogenation and the following formation of 3,168,584 iodide. It is especially important in determin MANUFACTURE OFAROMATIC HYDRO. CARBONS ing the overall course of the conversion since Maxwell Nager, Pasadena, Tex., assignor to Shell Oil the instantaneous concentration of iodine affects the in Company, New York, N.Y., a corporation of Delaware stantaneous concentrations of the various active hydro No Drawing. Filed Jan. 17, 1963, Ser. No. 252,051. carbon species in the reaction zone. 10. Claims. (C. 260-673) A number of advantages are obtained by the present process. Thus, whereas iodinative dehydrogenation of This application is a continuation-in-part of copending is endothermic, and when practiced inde application, Serial No. 43,647, filed July 18, 1960, now O pendently requires that the heat of reaction be supplied U.S. 3,080,435, issued March 5, 1963, which is directed from another source, the overall heat of the reactions in broadly to the iodative dehydrogenation of organic com volved in this process is exothermic, thereby avoiding the pounds by the use of and certain molten metal necessity of heat transfer to the reaction zone. More iodides. over, since the iodinative dehydrogenation reaction alone This invention relates to an improved process for the is equilibrium limited, rapid reaction of the hydrogen production of aromatic hydrocarbons, more particularly iodide with the metal oxide shifts the reaction to a higher dehydrocoupling and cyclizing of lower aliphatic hydro dehydrogenation conversion of the initial hydrocarbon; carbons. this is particularly valuable for the dehydrogenation of It has now been found that particular aromatic com light hydrocarbons wherein the temperatures normally pounds can be produced in high yields at moderate con 20 required for high equilibrium conversion are also conduc versions by dehydrogenating and cyclizing simple aliphatic tive to thermal and fragmentation. Furthermore, hydrocarbons. The present invention can, therefore, be the maintenance of only a very low concentration of hy used to manufacture aromatic compounds such as ben drogen iodide in the reaction zone by its reaction with zene, , xylenes, and in commercial metal oxide minimizes the necessity for a rapid quench of quantities using feed compositions of simple, non the reactor effluent as well as the recovery and recycling aromatic hydrocarbons. The process of the present in of the relatively large amounts of iodine species normally vention is particularly useful in the preparation of high required. Still further, the molten salt mass together purity para-xylene, although it may be adapted for the with the in situ formation of the iodine, provides for a preparation of various alkyl and alkenyl substituted aro highly effective contacting of the iodine and the hydro matic hydrocarbons of from 7 to 30 carbon atoms. 30 carbon, provides for quickly bringing the hydrocarbon According to the process of the present invention, Ca, reactant to the desired reaction temperature, and provides C4 or C5 acyclic hydrocarbons or mixtures composed pre an excellent heat transfer medium for transferring the dominantly of two or more of them and oxygen are excess heat from the reaction zone. Mixtures of salts intimately contacted with a molten alkali metal iodide to may be utilized which are either all in the molten state or simultaneously dehydrogenate, couple, cyclize, and aro 5 wherein at least one is molten and the remainder are matize the simpler hydrocarbons to aromatic compounds. Suspended in the molten plasma. In any case, the amount Thus, mixtures of two or more C to C5 acyclic hydro of Solid or molten iodide present in the molten salt mix carbons (including the dimers and trimers of such C to ture is sufficient to provide, when oxidized, the necessary Cs hydrocarbons) or a mixture of one or more of these amount of iodine for reaction and also metallic oxide acyclic hydrocarbons and a product of the dehydrocou 40 Sufficient to substantially completely remove hydrogen pling cycloaromatization of the hydrocarbon may be em iodide from the reaction mixture as it is formed. ployed. Various sources of C to. C hydrocarbons may The process of the present invention is based upon the be utilized, such as the dimers and trimers of C, CA and discovery that the reactions involved can be controlled C5 hydrocarbons. These dimers and trimers may be so as to produce aromatic hydrocarbons directly from C. used directly in place of the Cato C5 hydrocarbons them to Csaliphatic hydrocarbons while virtually excluding the selves, or may be used in monomeric form. The simple production of other, less desirable, compounds. Previ hydrocarbon feed stream may contain saturated and/or ously, it had been observed that the production of aro unsaturated compounds such as , propylene, n matic hydrocarbons by dehydrocoupling and cyclization , isobutane, butene-1, butene-2, , iso of C3 to Cs hydrocarbons in a molten alkali metal iodide pentane, n-pentane, and isoamylenes. oxygen system was accompanied by the production of sub Although the exact nature of the reactions involved is stantial amounts of poly-olefins and tar-like materials be not completely understood, the results of studies of the cause of the random nature of the removal of hydrogen effect of varying different variables, such as contact time, atoms from the simple hydrocarbons. For example, in relative proportion of oxygen, temperature, relative copending application Serial No. 43,647 previously re amounts of metal oxide used, etc., indicate that three 5 5 ferred to, using an isobutane feed, a Li-LiO system, different reactions are involved in the process and are an air/butane ratio of 5-6 (volume basis), and a reactor occurring together in the reaction zone: (a) reaction of temperature of 1050 F., only small amounts of aromatic oxygen with the metal iodide to form free iodine and the hydrocarbons (mostly and toluene in amounts corresponding metal oxide, and/or hydroxide; (b) re of from 0.7% to 1.2% based upon the moles of iso action of the liberated free iodine with the feed hydro 60 butane fed to the reactor) were produced, the major prod carbon to form hydrogen iodide and hydrocarbon of lower lucts being butylenes and propylene. However, by em H:C ratio; and (c) reaction of the hydrogen iodide, with ploying a hydrocarbon feed composed of 75% by weight metal oxide to form metal iodide and water. Since the of isobutane and 25% by weight of isobutylene, with a (b) reaction may be controlled in part by the concentra reactor temperature of 1060 F., and a molar ratio of tion of free iodine, and this is dependent upon the pro 65 oxygen to feed of from 0.5 to 10, 18% by weight of the portion of oxygen and reaction (a), the extent of the reactor feed was converted to xylenes (mostly para (b) reaction may be controlled indirectly by varying the Xylene); only 0.2% by weight of toluene was produced. proportion of oxygen delivered to the molten iodide mass. By reversing the ratio of the feed reactants (25% by The proportion of oxygen added largely determines the weight of isobutane and 75% by weight of isobutylene), course and extent of the other reactions including the 70 but using the same reactor temperature (1060° F.), formation of metal oxide, the release of iodine, the de-- 17.6% by weight of xylenes were produced, indicating. 3,168,584 3 4. that for these particular feed components (isobutane and reactor temperatures of more than 1100 F. By “con isobutylene) the selectivity is not dependent upon the tact time' is meant the average residence time of the relative amounts of isobutane and isobutene in the feed. hydrocarbon reactant e.g., butane, isobutane, propane, Thus, the use of a smaller proportion of oxygen, rela propylene, isobutylene, diisobutylene or isoamylene in tive to hydrocarbon, resulted in a marked increase in contact with the molten salt in the reaction zone. In aromatic yield. For aromatic production, the oxygen 5 general, the purity of the p-xylene produced is improved to hydrocarbon feed ratio should be maintained for a by decreasing the residence time of the iso-C or total conversion per pass of less than 50%; a range of 30 iso-C4 (indicating an such 40% is particularly useful for aromatic xylene produc as isobutylene) in the molten salt reaction zone and/or tion. For 100% conversion of i-butane to xylene the 0 by decreasing the temperature. These conditions were Stoichiometric oxygen requirement would be 1.25 mole also unexpectedly found to result in an increase in the oxygen per mole of i-butane. Thus, a preferred O/i-C conversion of the iso-C4's for a given i-CA/O ratio. The molar ratio is from about 0.25 to about 0.5. improvement in purity is believed to be due to minimiz Similarly, p-Xylene is produced from diisobutylene by ing purely thermal conversion while increase in conver heating it at temperatures of from 850° to 1050 F. 15 sion is attributable in large part to improved gas-liquid using a feed ratio, moles of oxygen per moles of diiso contacting at the higher gas velocities used to obtain butylene, of from 0.2 to 1.0 in a LiI molten salt system. shorter residence times. Some xylene may be produced Selectively (for the production of p-xylene) is favored thermally (without the interaction with iodine or the by the injection of steam into the system. The steam Li salt) and the mole ratio of the para-xylene to the produces LiCH so that a Li-LiOH system is involved. 20 meta-xylene produced by this reaction (P/M) is only According to a preferred embodiment of the inven in the order of from 1.5 to 2. The purity of the final tion, p-Xylene is manufactured by iodative (iodinative) p-Xylene product can be increased by conducting the dehydrogenation and coupling of isobutane. Isobutyl reaction so as to avoid this thermal reaction. ene may be supplied as feed or produced as an inter The important of controlling the relative amount of mediate in the reaction from isobutane. the thermal reaction is apparent from a comparison of Various methods of contacting the hydrocarbon feed the results of Examples 3 and 4 given in Table I which (containing either a saturated or unsaturated hydrocar is a summary of several runs using an isobutylene feed. bon) with the molten metal iodide may be employed. For the same mole ratio of oxygen to feed and with the One simple method comprises merely bubbling the hy same residence time, significantly higher conversion is drocarbon and oxygen in the vapor phase into the 30 obtained at the higher temperature. However, this in molten metal iodide (for example, lithium iodide) and crease in conversion (from 33.1% to 40.8%) is accom recovering the vaporous products (principally new hy panied by a decrease in p-xylene purity; this decrease is drocarbon and water). Various types of molten salt a measure of the nonselective thermal formation of reactors may be used as will readily occur to those skilled xylene. Only small amounts of normal butane and in the art. Reactors employing a dispersed liquid-in-gas 35 butenes (up to about 1.0% by weight) were in the feed system have been found to be particularly suitable for initially, and only small amounts of these compounds the process of the present invention. Reactors employ are formed by isobutylene isomerization in the molten ing concurrent plug flow of the fluids (molten salt and salt reaction Zone. vaporous reactants) with a high degree of gas-liquid con TABLE I tacting have been found to be especially useful. The 40 process may be operated continuously or batchwise. Para-xylene from isobutylene-baffled reactor-2% The preferred melt which is advantageously employed w. LiOH/98% LiI - in the present invention is composed initially of from 75 to 99 percent by weight of lithium iodide and from Example No.------2 3 4 5 6 1 to 25 percent by weight of lithium oxide and/or lithium Reactor Temperature, F------900 5 1, O O 5 95 O hydroxide. A low concentration of LiOH favors the Residence time, Sec.---- 4.2 - o4. g 5 production of high purity p-Xylene. Anhydrous salts Ofici, moleratio--- 0.42 : 0 42 o 4 10.43 H2O/O2, mole ratio- 2 are used, but reagent grade lithium iodide (which con Para-xylene purity, percent m-- 94.79 5. : tains about 29 percent by weight of water) may also be Conversion, percent W------36.5 32. 3.0 3. 3. 1 used. Excess water may be boiled off at about 400° C. 50 Selectivity, percent w; After the process has been operated for a short period of CH4------time, the molten salt mass will contain varying amounts of other constituents. Ordinarily, it is desirable to keep such additional melt constituents to a minimum concen i tration (not more than about 10 percent of the total 5 5 melt by weight). The hydrocarbon and oxygen may 6 - - 7 be fed into the melt separately or may be mixed (with y le leS 7 6 6 or without an inert gas such as ) and the mix --CH i Methylnaphthalene ture contacted with the melt. When a hydrocarbon-air 2,7-dimethylnaphthalene---C7Hil------mixture is employed, the gaseous mixture may be bub 60 Cil------bled into the melt by introducing the mixture below C2-Il C3=Il the surface of the meit. The product stream is removed, iC4 ce---- condensed, and separated as desired by any suitable Teavy en CO... CaS. CO2------The temperature at which the process is carried out is Oxygen balance, percent m----- O 9 1. o 9 normally held within the range of from 800 F. to 1100 F. Within this temperature range, p-Xylene may be 1. Oxygen used in this run. In all other runs in Table I air was used. produced from iso-Ca hydrocarbons in good yields with 2 Dimethalyl (2,5-dimethyl-1,5-hexadiene). short contact times (from 0.1 to 5.0 seconds). It has Other factors also are to be considered in relation to been found that the use of short contact times and tem the selectivity of the process for the production of peratures of 800 F. to 1100 F. favors the production p-xylene. For example, the substitution of oxygen for of para-xylene of from 90 to 99 mole percent purity. air (still maintaining the same oxygen/feed molar ratio) Contact times of from 0.1 to 3.0 seconds generally give in the oxidation zone seems to have only a slight, if any, a somewhat higher purity p-xylene (93 to 99 mole per affect on the ratio of p-xylene to m-xylene in the prod cent) than contact times of from 3 to 8 seconds at 75 uct stream (see Examples 3 and 4 of Table I). In 3,168,584 5 6 creasing the oxygen/feed molar ratio within limits al tivity achieved for the production of p-xylene is quite ready discussed also causes a small increase in the p unexpected. The process of the present invention pro Xylene purity. In the commercial preparation of very duces p-xylene of very high purity in spite of the wide pure p-Xylene these factors become increasingly im variety of side products. By employing a different feed, portant. " " " - . . . . . ' , " , , , , , it is possible to tailor the process for the production of Table II illustrates the conversion of diisobutylene to other specific aromatic compounds. (See Table IV.) para-xylene using temperatures of from 875° C. to 1000 For example, using a propylene feed and temperatures F. and mole ratios (oxygen/feed) of from 0.5 to 0.95. above 600 C. with a lithium iodidelithium hydroxide TABLE II - - - - melt (or initially even with lithium iodide alone), ben 0. zene is the major product. Conversion of disobutylene top-xylene TABLE IV Example No.- Reaction studies-coupling

Temperature, F 7 15. Example No.------14 15 6 7 OfFeed, mole ratio O 95 Steam input, cc.fmin------si Feed Hydrocarbons-- Iso- 50-Iso- 50-Propane, 75-Propy Yieli percent w.noloss bases - butylene butane, 50-Iso- lene 2------50-n-Butane, butylene 25-Toluene

20 OldC, mole ratio. 0.3 0.8 1.0 0.3 i 80. O 7 Reactor tempera- ', Toluene... ture, F------975 980 1,000 1,030. Xylenes.------Conversion, percent Carbon (from CO and CO) m------23 1 40 274 321 Carbon (tarry residue).----- 3 Selectivity, percent Measured recovery, percent w 92 O 1. m: Iodine in product, percent w. 0.5 Conversion, percent mill------2 22 25 1.1 Selectivity, percent In------0.6 Average reactor contact time (sec.).------1.3 0.3 26, 8 Largely isobutylene. 7.6 2Largely p-xylene. 44.9 3. Not determined. in-C4H10------4. Not corrected for iodides in product. 30 ... 2 Benzene- ... 1 Table II summarizes the results obtained when iso Toluene.-- -- 0.6 butylene and mixtures of isobutane and isobutylene were Cs aromatics----- 6.0 reacted in a molten salt reactor containing about 90 to CNapthalene------aromatics------2-methylnaph 95 percent by weight of Li and from 5 to 10 percent by 35 thalene------weight of LiOH (added directly to the molten reactor 2,7-dimethyl-, naphthaleine... 17.9 l, 4 mass or formed in situ by the injection of steam). trans-Stilbene------Temperatures employed were varied from 1000 F. to Heavy ends 4 48 1.8 1100. F. CO------1, 1 CO2------9.0 3.7 TABLE III 40 Cs aromatic dis tribution, per cent m: . Conversion of isobutylene and isobutane Ethyl to p-xylene benzene p-Xylene n-Xylene Example No.------10 1. 12 3 o-Xylene. Feed------Iso- Iso- 25%, Iso-C4/75% Iso-Ca? Styrene i. C. C. 75%. Iso-C4 - 25%, Iso-C4" 1 Combined conversion of i-C and n-C4°: Conversion ratio, iC4fnC4 Temperature, F------1,100 1,020 1,060. 1,060 =1.32. - OfFeed, mole------... 0,5 : 0.5 0.625 0.875 2 Combined conversion of C3° and iC: Conversion ratio, Ca?iC Yields, percent w., no - loss basis: 50 &mbined conversion of Cat and toluene: Conversion ratio, Cal 0.9 1.1 3.7 3. Tolueneas. 0.8 1.0 1.2 1. 4 Believed to contain 3,6-dimethylphenanthrene and trans-P-P- 68.4 72.7 69.5 72. dimethylstilbene, 2.0 1.2 3.9 1. 5 includes heavy ends. 0.3 0.2 0. 0. 0.4 0.2 0.3 0. Even more complex aromatic compounds may be pro 23.4 19.8 17.6 18. duced in significant yields under proper reaction condi 3.8 3.8 3.7 3. tions: Another example of the production of such a com pound is the preparation of 2,7-dimethylnaphthalene 1.2 - 1.6 1.2 (18 mole percent selectivity) from isobutylene using a 96.3 96.4 97.4 99 Conversion,2 percentral. 29.6 26.1 26.5 26 molar feed ratio (oxygen/isobutylene) of about 0.3 with Selectivity,2 percent mill. 83.5 80.2 71.8 73 a molten Lil-LiOH system at a temperature of about Average reactor contact : 975° F (see Table IV). , time (sec.)------1.4 1.5 1.2 When isobutane or isobutylene is fed to a molten salt 1. Largely p-xylene...... reactor according to the present invention, a whole series 2 Basis total C4 charged and not corrected for iodides in product. of coupled products may be obtained by proper control Included among the identified side products in the of the dehydrogenation coupling rate. The results indi reaction product obtained from the dehydrocoupling of cate that the coupling probably takes place via the meth iso-butene are 2,5-dimethyl-1,5-hexadiene, 1,1,3-trimeth ally free radical. For example, para-xylene produced in ylcyclopentane, benzene, toluene, naphthalene, 2-methyl the process reacts with iso-butylene or isobutane to pro naphthalene, 2,7-dimethylnaphthalene, trans-p-methyl duce dimethylnaphthalene (C12H12). The dimethyl stilbene, trans-p-p'-dimethylstill bene, methylphenanthrene, naphthalene reacts with another mole of isobutylene or 3,6-dimethylphenanthrene, 2 - methyl-7-(trans-p-methyl isobutane to produce dimethylphenanthrene (C16H14) in styryl)-naphthalene, iodomethane, vinyl iodide, 2-iodo preference to 2,6-dimethylanthracene, and repetition of , 2-methyl-1-iodopropene, iodobenzene, p-iodo the process two more times produces C20H16 and C2H18. toluene, and iodomethylnaphthalene. From the wide hydrocarbons, respectively, but in smaller quantities. variety of possible products, it is clear that the selec 75 The successive reactions can be represented by the follow 3,168,584 7 8 ing equations in which the ring- have been TABLE V-Continued omitted as customary for simplification: iC5H8 ------1.3 Benzene ------1.4 (H, Toluene ------2.0 P-Xylene ------23.2 -- iC 2-methyl-4-(meta-tolyl)-butene-1------2.0 oe and g-methylnaphthalene ------1.3 1,7-dimethylnaphthalene ------12.2 (H, 2,6-dimethylnaphthalene ------12.2 Para- - O 2,7-dimethylnaphthalene ------0.1 xylene C3H10 Cis-meta, meta'-dimethylstilbene ------2.7 C16H18 2 ------1.3 CH CEI Trans-meta, eta'-dimethylstibene ------17.2 Nonvolatile residue ------1.3 - iC4 -- iC 5 CO------6.0 -- -rm CO2 ------2.7 Total conversion-conversion ratio isobutylene/ra-Xylene This is probably a mixture of meta- and para-substituted ditolyl ethanes. CH3 20 Further details of the examples are as follows: EXAMPLES 1-6 2,7-dimethyl- - 3,7-dimethyl- six-la-> napthalene Isobutylene was fed to a molten salt composition con C12H12 C1Eis taining 2% LiOH and 98% LiI (percentages by weight). Reaction conditions and product distribution are sum marized in Table I. ce EXAMPLES -9 A Li-LiOH melt was prepared by mixing Li.3H2O (H, CH3 Hi? and LiOH.H2O in correct proportions to give 95% LiI-5% LiOH in the hot anhydrous melt. Table II tabulates the 30 results obtained by dehydrocyclizing diisobutylene to para xylene under varying temperatures and with different O -- iC 5 molar feed ratios (oxygen/hydrocarbon feed). EXAMPLES 10-13 A molten mixture of 90-95% Li and 5-10% LiOH (C was employed as reaction and contacting medium and C206 C24H18 iodine supply and hydrogen iodide acceptor. The feed In a similar fashion, isobutylene and m-xylene co-react, compositions, reaction conditions, and product distribu probably through the intermediates methallyl and m tions are given in Table III. The feed compositions were methlbenzyl free radicals, to produce corresponding di 40 as follows: methyl-naphthalenes. Thus, when an equimolar mixture Example 10-Isobutylene. of isobutylene and m-xylene was iodatively dehydrogen Example 11-Isobutylene. ated under conditions as set out in Table V by passing Example 12-A mixture of 25% isobutane and 75% iso the feed components through a horizontal pipe containing butylene (molar). molten LiI/LiOH and baffled with baffle plates to insure Example 13-A mixture of 75% isobutane and 25% iso intimate mixing of the feed components and the molten butylene (molar). mass followed by gas-liquid separation, the dimethyl naphthalene fraction separated from the product stream EXAMPLES 14-1 contained equivalent amounts of 1,7- and 2,6-dimethyl Using a Li-LiOH melt composition (98% by weight naphthalenes, showing that ring closure of the coupled LiI and 2% by weight of LiOH) and an average residence occurs at the same rate at the two available positions. time in the reactor of from 1 to 4 seconds, the following Other results given in Table V show that isobutylene was feed hydrocarbons were sent to the reactor: also converted in high yield to p-xylene and that a large Example 14-Isobutylene. proportion of the converted m-xylene produced meta, Example 15-50% isobutane and 50% n-butane (molar). meta'-dimethylstilbene, which was predominately the Example 16-50% propane and 50% isobutylene trans-isoner. Toluene similarly gives rise to stilbene (molar). (see Table IV) and p-xylene gives rise to p,p'-dimethyl Example 17-75% propylene and 25% toluene (molar). still bene. Results, showing the distributions of the aromatic com pounds formed, conversions, selectivities, oxygen/hydro TABLE V 60 carbon molar feed ratios, and reactor temperatures are Coupling reactions-m-xylene and isobutylene summarized in Table IV. The symbol i-CA in Table IV melt: 95-98% wt. LiI, 2-5% wt. LiOH indicates isobutane (a saturated CA hydrocarbon). Simi Reactor-horizontal baffled-pipe: larly, the symbol iC represents isobutylene. The other Temperature, F. ------1000 abbreviations used are self-explanatory. Residence time, Sec. ------1.5 EXAMPLES 18-28 O3/feed, mole/mole (air) ------0.3 The reactor (which may be a riser type or a simple H2O/O2, mole/mole ------2.0 stirred pot apparatus) was charged with 141 grams of Isobutylene/m-Xylene, mole/mole ------O reagent grade lithium iodide which contained about 29 Conversion, percent W.' ------15 70 percent Water. Most of the water was boiled off attem Selectivity, percent W. carbon peratures of up to 400 C., and then 14 grams of lithium CH4 ------0.6 hydroxide was added. The mixture was then heated to the C2H4 ------1.3 reaction temperature (400° C. to 650° C.) and nitrogen C3H6 ------5.3 was bubbled through the melt until the reactants were iC4H10 ------0.6 75 charged. The reactor was heated by an electric furnace. 9 Air and the organic compound were introduced below the iodide and a minor proportion of alkali metal base, while surface of the melt through a common inlet. Provision intimately contacting the molten salt with an amount of was made for withdrawing gaseous spot samples imme oxygen to give from about 10% to 50% conversion of diately following the receiver for analysis by gas-liquid the hydrocarbon, the molar ratio of said oxygen to said chromatography, during the run. Table VI is a summary 5 acyclic hydrocarbon being from about 0.25 to about of eleven runs using a propylene/oxygen mole ratio of 8.

. A process in accordance with claim 1, wherein the TABLE VI alkali metal iodide is lithium iodide and the alkali metal Melt composition 89% by weight lithium base is lithium hydroxide...... iodide-1.1% by weight lithium hydroxide O 3. A process for the preparation of a product containing Propylene/oxygen mole ratic-c 8 a major percentage of para-xylene which comprises inti nately contacting C.His to C4H10 hydrocarbon at a tem Molar Moleratio of C3 Example Reactor Temp., percent of equivalently perature of about 800-1100°. F. for 0.1 to 5 seconds No. type oC. propylene With an essentially homogeneous molten sait composition converted consisting essentially of a major proportion of lithium Benzene Bially Ethere iodide and a minor proportion of lithium hydroxide, while 550 . . . . 23- 1.5 1.3 intimately contacting the molten salt with an amount of 590 19. 1: ... 3 1.1 oxygen to give from 30% to 40% conversion of the hy 640. . . 16. 1: ... 0.5 1.0. 590: . 24. 1 - 1.5.1.5 drocarbon the molar ratio of said oxygen to said hydro 514/554- 14 2.0 . .2 20 carbon being from about 0.25 to about 0.5. ' ' '...' : .. 500 14 2.50.7 450 6 3.5 0.3 4. A process in accordance with claim 3, wherein the .400 8 (2) (2) ; (2) hydrocarbon feed is essentially isobutane. Stirred 450,495 rvé 1 0.8 pot. , . , ' 5. A process in accordance with claim 3 wherein the 278--...-do. . . 460 ra-2 (4) (4) (4) hydrocarbon feed is essentially isobutylene. 28------do... . . 485 -2 3. 6. A process for the preparation of dimethylnaphthalene which comprises intimately contacting an equimolar mix 1 C3 equivalent=moles of benzene (or biallyl) in product X2 or ture of a C4-hydrocarbon having a ratio of hydrogen to :

moles of ethene X%. 2 odopropene is the major product. carbon of at least. 2 and at least 1 xylene , at a 3 Melt composed of lithium iodide alone. temperature of about 800-1100°F. for 0.1 to 5 seconds 4 Benzene is the major product. with an essentially homogeneous molten salt composition ble VI shows that temperatures above 400° C. favor consisting essentially of a major proportion of lithium the formation of benzene, with better conversions in the iodide and a minor proportion of lithium hydroxide, while temperature range of from about 500° C. to 650° C., ben intimately contacting the molten salt with an amount of. zene being the major product above 600° C. The aromatic oxygen to give from about 10% to about 50% conversion (benzene) fraction may be separated by the use of ex 35 of the hydrocarbon, the molar ratio of said oxygen to said tractive solvents or by distillation. Higher O/Ca ratios, mixture being from about 0.25 to about 0.5. . . . . such as 0.25 and 0.5 in the riser operation give higher 7. A process in accordance with claim. 6, wherein the C,

conversions and higher proportions of benzene. In the hydrocarbon is isobutylene and the xylene isomer is para riser reactor, the hydrocarbon and oxygen feed mixture Xylene, and the dimethyl naphthalene is 2,7-dimethyl was fed into the lower end of an upright elongated tubul 40 naphthalene...... " lar vessel which opened at its lower end into a body of 8. A process in accordance with claira 6, wherein the molten lithium iodide-lithium hydroxide disposed in a . C. hydrocarbon- is isobutane and the xylene isomeri larger tubular- vessel surrounding- the riser- - tube- and dis para-xylene. . . laced from the upper open end of the riser tube. The 9. A process in accordance with claim. 6, wherein the velocity of the feed mixture was controlled to disperse Ca hydrocarbon is isobutylene and the xylene isomer is . . a portion of the molten mass in it and carry it with the meta-xylene...... gaseous mixture out the top of the riser tube. The dis 10. A process in accordance with claim 6, wherein the persed melt was separated by gravity: from the gaseous C4 hydrocarbon is isobutane and the xylene isomer is meta materials and returned to the body of molten material at Xylene. : . . i. the lower end of the riser tube. 50 claim as my invention: References Cited in the file of this patent 1. A process for the selective conversion of Ca to Cs. :... "

UNITED STATES PATENTS cyclic hydrocarbons represented by the formula CH o CnH2n-2 to a product containing a major percentage 3,080,435 3/63 Nager ... of aromatic hydrocarbon which comprises intimately con 3,106,590 10/63. Bittner tacting said acyclic hydrocarbon at a temperature of from FOREIGN PATENTS aboutessentially 800 homogeneousF-1100 F. molten for 0.1 salt to composition5 seconds withconsist an 793,214 4/58. Great Britain. ing essenti a substantial proportion of alkali metal ALPHONSO D. SULLIVAN; Primary Examine