US2725344A - Upgrading of naphthas - Google Patents

Description

Nov. 29, 1955 M. R. FENsKE HAL UPGRADING OF NAPHTHAS Filed sept. 11, 1952 `REACTOR TUBE SEPARATOR u Llf L COOLING COIL PREHEATEx vAPomzER TRANSFER MEDIUM HYDROCARBON LAYER HYDROGEMATOR 4 HYnRocEnAToR AOUEOUS LAYER MERRELL R. FENSKE JENNINGS H. JONES FINISHED FUEL mvsnrons nv E1: #KM moanev 2,725,344 UPGRADING oF NAPHTHAS Merrell R. Fenske and Jennings H. Jones, State College',

Pa., assignors to EssoRe'sear'ch and Engineering Cempany, a corporation of Delaware i Application september 11, 1952', serial No; 309,144

11 claims. (ci. 19a- 142) thermally cracked naphthas, catalytic cracked naphthas,

or hydroformed naphthas.

It has been proposed in Patent No. 1,808,168 and elsewhere to dehydrogenate hydrocarbons by reacting them in vapor phase with oxygen at relatively low temperature. tain oleiins on a small scale by treating a virgin gasoline fraction with air at temperatures of about 265 C., the air being added in amounts equivalent to not more than about 1.5 atoms of oxygen per hydrocarbon molecule. This reaction has been known to be poisoned by solid packing or by liquid reux within the reactor, and also by active reactor surfaces; At best, this process was characterized by relatively low yields of v`oleiins, without any substantial formation of liquid oxygenated com pounds. On the other hand, when the reactor temperature was raised appreciably vabove the aforementioned value, and especially when high ratios of oxygen to hydrocarbon were used, all except the very light hydrocarbons were extensively degraded into carbon dioxide and water. Moreover, such liquid fuel product as was obtained, was of relatively low quality because of its gum-forming tendencies.

It is the object of the present invention to increase the oxidative conversion of hydrocarbons and particuiarly of naphthas so that low octane hydrocarbons are preferentially converted into oleiins and other products having superior anti-knock characteristics. A further object is the conversion of hydrocarbons into oxycompounds which either are suitable gasoline constituents or can be converted into such by selective hydrogenation, which yields alcohols, or by dehydration, which yields unsaturated hydrocarbons such as olelins. These and other objects as well as the nature of the invention will become apparent from the following description.

In the present invention naphtha is dehydrogenated and oxidized by reaction with about 0.3 to 1.2 or 1.5 moles or" oxygen per mole of hydrocarbon, depending on the reaction conditions, the nature of the feed, and the degrec of oxidation desired. Although it is greatly preferred to use substantially pure oxygen, air or any inert gas such as steam containing oxygen may be used. Use of oxygen in a purity of at least 90 mole per cent of a condensable gas rich in oxygen simplifies the recovery of the volatile products, for such products are then associated with fewer gaseous diluents. Also diluents may adversely affect the reaction.

It has thus been possible, for instance, to 'ob- Where extensive conversion is desired it is important that the oxidation be carried out in several successive steps. This can be done either by introducing the oxygen at several successive points, or by removing the oxidation product after one contact with oxygen, and preferably after separation of the resulting water layer and non-condensable -gas recycling the oxidation product to the reactionzone for'more contacts with oxygen. The reaction is carried out at temperatures of about 275 C. to 480 C., and at relatively low pressures of about 0 to p. s. i. g.,'preferably at about 350 to 400 C. and a pressure ofabout 0 to 5 p. s. i. g. Pressure tends to increase the yield of gas at the expense of useful products. Nevertheless, this may at times be desirable since the resulting oxidized hydrocarbon layer then also contains a substantially increased proportion of valuable oleins. The best pressure' 'to use depends on the temperature of reaction, the inherent oxidation rate of the hydrocar# bon, and the completeness of the recovery of the volatile productsV that is desired. The more reactive the hydrocarbon, the lower the pressure. Contact times in the range of about l to 5 seconds, and preferably not more than 3 seconds, may be employed. No catalyst is used and, as far as known, the reaction isa homogeneous one in the gas phase. The resulting products are a non-condensable gas, a hydrocarbon layer, and a water layer.

Heat transfer is an essential part of the present invention, for the reaction is highly exothermic. lt is necessary to remove this heat'from the reaction zone, to keep the reaction temperatures from rising to such high levels that many of the valuable reaction products would be lost by pyrolysis. To remove the reaction heat, the contents of the reaction Zone must be in good heat transfer relationship with another medium which is capable of absorbing this heat without jeopardizing the reactants or acting as an anti-catalyst for the reaction. in the present instance the reaction may be convenientlycarried out in empty tubes immersed in a thermostatic bath using liquid terphenylas the heat absorbing medium. However, other well-known stable media which are fluid and have an appreciable heat capacity in the proper temperature range such as mercuryV or molten salts such as mixtures of nitrates of sodium and potassium may be used similarly.

It is important that the materials constituting the reaction Zorie or surfaces present therein do not attain excessive temperatures. Otherwise, they tend to catalyze the formation of carbon dioxide and Water and other undesirable products. For this reason it is essential that the surfaces in contact with the reactants, but not necessarily the reactants themselves, have a heat transfer coeicient, in relation to the medium picking up the reaction heat, of at least 100 B. t. u. per hour per square foot of surface per degree Fahrenheit difference in temperature between these surfaces and the heat absorbing medium. Only in this way can the reaction temperatures be maintained within the desired range and the surfaces in contact with the reactants always kept low enough in temperatnre to avoid undesirable catalytic effects.

Since surface has an adverse effect on the homogeneous reaction which isthe basis of this invention, another important feature is to have the reaction zone contained by smooth walls or surfaces essentially free of reducible oxides, that'is, surfaces which are not altered readily either by an oxidizing or reducing environment, such as existswhen oxygen and hydrocarbon interact. When the surfaces are metallic, they should be selected from those metals that do not oxidize readily. When the surfaces contain oxides, the oxides should be selected from those that are not readily reduced, Vor prone to exert undesirable catalytic eiects. Examples of metallic surfaces are stainless steel, silver, and alloys of chromium or nickel.

Examples of suitable heat resistant oxide surfaces are silica, alumina, and chromia.

In operating with multiple points of oxygen injection, the reaction temperature should be brought down to the 300 to 480 C. range before the next injection of oxygen takes place. This is accomplished by providing ample heat transfer surface, of the quality and character described, between the points of oxygen injection.

Essentially all the oxygen is used up in one pass through the reactor. The distribution of this oxygen to the various products is important for it shows what reactions are taking place. For an East Texas light virgin naphtha boiling between 158 and 216 F., the following typical oxygen distribution was obtained.

4 oxides of carbon, and the other to 30% as useful liquid oxygenated compounds. The formation of oxides of carbon represents unwanted side reactions which are wasteful of both hydrocarbon feed and oxygen. On the other hand, oxygen fixed in the hydrocarbon structure in the form of oxy compounds such as aldehydes, ketones, alcohols, and bridge-oxygen compounds or epoxides actually is desirable. Many of the formed oxygen compounds have characteristics which make them valuable fuel components, or their oxygen can be converted to water via dehydration, thereby adding to the selectivity to water and increasing the yield of desirable olefins or dioleiins. Or such oxygen compounds can be converted to alcohols by selective hydrogenation as hereafter dc- 15 scribed. TABLE I While only about of the reacted oxygen goes to useful oxygenated compounds, the actual production of these compounds is high because of their relatively large Total Wt. Liquid Percent Fue] molecular weight. For instance, 1t can be seen from 20 Table III below that the actual weight of the oxygenated Oxygen Distribution, compounds was 122.4 pounds/ 100 pounds of reacted To Non-Condensable Gaseous Products- Oxygen,

Carbon Wlioxide 1g Carbon l onoxlde r TABLE In v L P d t 26 25 Tot ater a er ro uc s watermi7 49 Productlon 0f liquid oxygenated compounds Forlmaelyde 1 ging; ogfgiitsd Material 1 1 [Basis: 100 lbs. 02 reacting; 386 lbsnaptha charged (178 lbs. naphtha 5s 9 To Hydrocarbon Layer Products-` 3() arbqyls t7) g o, Dismpox es constituent Iffljss'flgo butiomwt.

16 16 9 Percent To tal 100 25 Formaldehyde 10. 0 5. 3 other Aldehydes in Water Layer 13. 1 2. 9 gthler Oxly- Oonnunds i(n Water Lager. g (l) al' OIIYSIII ayer ESSllmlIlg 5 In general, about 25 to 70 we1ght percent of the naphtha Epoxides ,DHC Layer (assuming CM) 57. 5 s. s feed may be actually converted, As a result, about to percent by weight of the naphtha feed appears, in 1224 24'9 partially converted form, in the hydrocarbon layer, some 5 to 12% is converted to non-condensable gas; and about 3 to 8 percent is converted to give the water layer. Typical average compositions are shown in Table II.

TABLE II Product distribution Gas (Oz-free and Nz-free basis) Vol. percent CO About 40-60 CO2 About 10-25 C2H4 About 5-10 CsHfi About 8-15 Saturated hydrocarbons (C3 average) About 5-10 Hydrocarbon layer: Wt. percent Olelins (C4 to Cs) 12 to 16 Carbonyl compounds 1 5 to 9 Epoxides 2 v13 to 20 Unconverted feed hydrocarbons 60 to 65 tlAcetaldehyde, propionaldehyde, acetone, C5 to CS kctones, e c.

2 :Z5-dimethyl tetrahydrofuran, etc.

Water layer: Approx. wt. percent It is apparent that if the reaction were entirely one of dehydrogenation, all of the oxygen should appear as water. Actually, however, only about 40 to 55% of the original oxygen ends up as water, some 25 to 30% ends up aS In addition to the above products, about 40 pounds of valuable olefins are formed per pounds of oxygen reacting.

Although the data presented above were obtained for a light East Texas virgin naphtha, similar results are obtained from heavy virgin naphtha (200 to 430 F. boiling) range, Bradford Pennsylvania virgin naphtha to 259 F. boiling range) and also from pure hydrocarbons such as n-pentane, n-hexane, n-heptane, n-nonane, n-decane, n-hexadecane, cyclohexane, methyleyclohexane, methylcyclopentane, 1octene, 2-octene, etc. Thus, the invention is particularly applicable to virgin naphtha hydrocarbons boiling in the range of about 158 to 430 F. (70 to 220 C.). In general, pure aromatic hydrocarbons such as benzene and toluene, and highly branched paraffin hydrocarbons such as 2,3-dimethylbutane and isooctane, do not undergo appreciable reaction under the conditions outlined above.

In general, the liquid products resulting from the hydrov carbon oxidation consist of low molecular aldehydes (mainly formaldehyde, acetaldehyde, propionaldehyde, and some acrolein), lretones (acetone and ketones hav ing the same carbon content as the hydrocarbon oxidized), alcohols (methanol, ethanol, and higher aicchols having the same carbon content as the hydrocarbon oxidized), epoxides (such as tetrahydrofurans, trimethylene oxide derivatives, and ethylene oxide derivatives having the same carbon content as the hydrocarbon oxidized), olefins (a mixture of olens of the same carbon content as that of the hydrocarbon feed and lower molecular weight alpha olens), and unreacted hydrocarbon.

The low molecular weight aldehydes, ketones, and alcohols tend to be concentrated in the water layer whereas the epoxides and higher ketones and alcohols weer@ are concentrated in the hydrocarbon layer in admixture with the olens and unreacted hydrocarbon or naphtha portion.

The character of the epoxidesproduced depends on the molecular weight and the type of hydrocarbon oxidized. Thus, for example, n-hexane yields anV epoxide portion containing chieiiy 2,5dimethyltetrahydrofuran, Z-ethyltetrahydrofuran, 2,4-epoxyhexane, and 2,3-epoxyhexane. Similarly, pure n-heptane yields .an epoxide mixture containing chiey Z-methyl-S-ethyl tetrahydrofuran, 2-propyltetrahydrofuran, 2,4-epoxyheptane, and 3,4-epoxyheptane. The higher hydrocarbons such as n-nonane, n-decane, n-hexadecane, etc. 'also yield an epoxide portion containing similar products. On the other hand, naphthene hydrocarbons yield an epoxide portion Acontaining mainly epoxynaphthenes. Thus, vfor example, cyclohexane yields 1,2-epoxycyclohexane and 1,4-epoxycyclhohexane while methylcyclohexane yields a complex mixture of epoxymethylcyclohexanes.

The various epoxides are useful as solvents and also as chemical intermediates in that they maybe Vconverted to diolens, alcohols, glycols, ketones, phenols, polymers, chlorohydrins, esters, etc.

The olens present in the liquid products` consist, in general, of a mixture of olensof the-same @carbon Acontent as the hydrocarbonfeed and lower molecular lweight alpha olens. Thus, for example, n-decane on oxidation yields a mixture of vdecenes, l-h'exene, 1-heptene, and 1-octene. Similarly, n-heptane yields .heptenes, l-butene, l-pentene, and l-hexene. Cyclohexane yields mainly cyclohexene together some r`lower molecular Weight alpha olens. Thus, the described process is-a'lso takeplace results mostly in saturated and unsaturated gaseous hydrocarbons containing, on the average, be-

` tween 2 and 3 carbon atoms per molecule.

The liquid hydrocarbon and water layers obtained in the oxidation can be lightly hydroiined to convert the v aldehydes and a portion of the ketones to alcohols, but

without affecting epoxides or oleiins. The alcohols and any ltetones or epoxides, etc. can then be distilled from the Water layer and combined with the oxidized hydrocarbon layer. The resulting fuel mixture, stiil having a boiling range closely similar to that of the naphtha charged, may have the following typical composition (by volume); 9% alcohols and ketones, 14% olefins, 17% epoxides and 60% hydrocarbons. The research octane number of the resulting mixture may be about 80 to 85 without the addition of tetraethyl lead (clear/. The yield of fuel including the oxidized hydrocarbon layer and the hydrogenated material from the water layer may amount to about 80 to 90% by weight of the original naphtha.

vSimilar results are obtained for other feeds such as narrow-boiling hydrocarbon fractions or pure hydrocarbons. For example, n-hexane when oxidized to the extent vof about 72 percent gives a 72 percent by weight yield of a liquid having the following composition (after y a light hydrofiningtreatment).

suitable for the production A'of alpha olens of .lower Research Octane No. of feed 38.9 Research Octane No. of unoxidized hydrocarbon portion of the liquid product obtained by sulfuric acid extraction to remove oxygenated and rolenic materials (about 37 percent of the naphtha underwent oxidation) 53.3

To illustrate further the selective nature of .theoxidation reaction, it has been found that the .comparative ease of oxidizing various pure yhydrocarbons under the conditions described herein decreases in the following gorder:

1. n-Hexadecane 8. Isopentane 2. n-Decane 9. l-pentene 3. n-Heptane 10. Z-pentene 4. Z-methylpentane l1. Trimethylethylene 5. Methylcyclopentane 12. ABenzene 6. Cyclohexane 13. vToluene 7. Methylcyclohexane 14. -Isooctane The three last-named hydrocarbons 'are essentially nonreactive. l

From a fuel standpoint the finishing of y"the liquid 'products obtained in the selective oxidation is `important in determining the yield of liquid fuel and "its-anti-kno'cl; quality. The volatility Aof 'the liquid product 'is usually not much greater than that of thefeed for vthere is not much hydrocarbon cracking during the oxidation -as carried out under this invention. "Such cracking as' does Liquid product wt. per cent i Hexenes 4 Oxygenated compounds from hydrocarbon layer (largely epoxides) 32 Oxygenated compounds from water layer (about 70% C1 and C2 alcohols7 remainder epoxides) 26 n-lHexane, unreacted 38 The octane number (Research, clear) of the above liquid product was found to be 76.5. The research octane number of n-hexane is 24.8. This further iilustrates the usefulness vof this process in upgrading hydrocarbons to malte them more suitable as fuels for spark ignition engines.

The oxidized hydrocarbon layer may be selectively hydrogenated to convert undesirable Vcarbonyl compoundsy into alcohols. This selective hydrogenation may be carried out either 'simultaneously with the aforementioned hydrogenation of the water layer, or preferably the two layers may be hydrogenated separately .as described later.

In the alternative, the oxidized hydrocarbons including alcohols and epoxides can be dehydrated to olens or di-Y olens Yby passage over synthetic or natural alumina in the form of clay or bauxite, for instance, at atmospheric pressure and 350 to 450 C.

T-he following specil'ic runs will serve to illustrate the operation and advantages of the invention more clearly, vthough it will be understood that the scope of the inven tion is not limited thereto.

For carrying out the oxidation a tubular reactor has been used. This consisted lessentially of twelve 0.5-inch andfsix-'OJS-inch diameter stainless steel tubes, Yany nurnber .of which could be lconnected in series in a serpentine path and immersed vin an agitated bath of molten myterphenyl which Was 'used as a heat transfer fluid. Each vof the tubes Was about 20 inches long. Variable lengths vof treactorstubing vwere used in different runs in order to provide different .reaction times as ldesired. Side lines of stainless steel tubing were tapped into the tubular reactor v at 'the vttl-bends connecting .the several tubes so as to allowaddition .of oxygen yat .numerous points in the reaction zone. The reactor was fitted with thermocouples which extended through a ypacking nut in each arm of the serpentine tubing.

Data of typical runs are summarized inTable `IV b e- TABLE IV Oxidation of hydrocarbons E t T L h V HEast ,Iixas i as exa-s ig t irgin eavy irgin H5 dmcmbon Fwd Naphtha (06.2000 FJ (A) Naphthag) N Henne (ZOO-430 F.)

Run N o 73 85 94 78 88 89 104 104/5 Feed Conversion, Percent 46 46 58 55 42 52 48 72 Total Oz/HC Feed Ratio (in 0.64 0. 78 1.07 0. 99 0.81 1.08 0. 75 1.49 Maximum Og/HC Feed Ratio (in moles) 0.31 0.26 0.27 0.50 0. 27 0. 27 0. 19 0. 19 Percent of Theor. O2 for Complete Combu ion. 6. 4 7. 8 10. 7 9. 9 5. 9 7. 8 7. 8 15. 7 O2 Roasting, Perccnt 99 94. 5 100 96 98. 5 99. 4 99.9 100 No. Points of O2 Injection 3 3 4 2 4 8 HC Feed Rate, Lbs./Hr 5.83 2. 09 2.07 Temperature of Bath, C 359 362 360 362 `360 360 361 361 [emDerature of Reaction, Max. 450 400 400 490 420 415 456 456 Total Contact Time, Secs 2 3 4 2. 5 3 5 4. 8 9. 5 HC Layer/Water Layer, Wt. Rntlo 4. 2 3. 9 2. 6 3.1 6. 5 4. 6 1. 14 3. 04 C,H,O Product Distribution, Wt. Percent on Total 0,110 Charged:

HC Layer 65 Water Layer 16 Non-Coudensable Gas 13 Analysis of HC Layer:

Acids, gm. 02/100 gm. HG Layer 0.14 Carbonyls, gm. 02/100 gm. HC Layer 2.0 Bromine No., gm. Bri/100 gm. HC Layer 31. 7 Acid Solubility:

Vol. Percent Sol. 95% H2304 33 Vol. Percent Sol. 90% HBP O4 22 Density 60 F 0.743 0.746 0.756 0. 818 0. 701 0. 731 Analysis of Water Layer:

Acids, gm. 0;/100 gm. W. L 1. 1 1. 7 1. 2 1. 3 1. 01 Carbonyls, gm. 02/100 gm. W. L 11. 6 10. 7 10.0 10.0 13. 8 13. 6 CHZO, Wt. Percent 12.1 11. 7 11. 8 24.0 Analysis of Non-Cond. Gas, Wt. Percent:

CO 48. 3 47. 1 51. 8 52. 2 14. 7 13. 3 18. 2 20. 8 13. 7 15. 2 20. 0 17. 1 17. 2 18. 9 19. 0 18. 5 6.7 6.0 6.7 6.3 6.3 6.2 (JO/CO2 Ratio 3. 3 3. 5 2. 9 2.0 3. 3 3.4 Yield, Wt. percent on HC Feed:

HO Layer B 81. 5 84. 6 76. 2 78. 7 94. 0 90. 4 Oxygen Material from Water Layer B. 5.1 5. 8 7; 1 6. 7 2. 9 1. 6 'lotcl Organic Liquid 86. 6 90. 4 83.3 85. 4 96. 9 95. 0 C-l-H in Non-Cond. Gas 9. 3 15.6 4. 9 9. Octane No., Research, Clear:

Combined Product C C 83.1 84. 5 C 71. 5 C 79. 5 Original Feed 64.4 64. 4 43. 0 43.0

. Light Heavy A Properties of Feed Naphtha Naphtm Acid Solubility:

Vol. Percent Sol. 95% H2804, 4. 0 11. 0 Vol. Percent Sol. 90% H3PO4 0 1.0 Density at 60 F 0.709 0. 765 Octane No., Res., Clear 64. 4 43.0

B After light hydrogenation.

C Hydror'lned HC layer plus organic material The data representing the percentage of naphtha undergoing oxidation was based on the solubility of the hydrocarbon layer products in 95% sulfuric acid (the acid insoluble portion was assumed to represent the proportion of unreacted naphtha present, after correction for the small soluble portion of the original naphtha). Solubility of the product in phosphoric acid has been used as a measure of the proportion of oxygenated material present in the hydrocarbon layer.

The percentage of oxygen reacting was found by making an oxygen balance based on the amount of oxygen appearing in the non-condensable gaseous products and the volume of gas produced. 98% oxygen was used.

Contact times were calculated from known low rates and known reactor Volume, assuming that no reaction occurred. Since the formation of water and gaseous products leads to shorter reaction times, the calculated values represent maximum, rather than exact actual contact times. Where multiple injections of oxygen were used, the tabulated contact times represent the sum of several calculations.

The temperatures are those of the bath and of the maximum temperature found in the reaction zone.

ln several early runs in which the oxygen was preheated to about 300 F. before entering the reactor, excessive;

recovered from water layer after hydrogenation.

temperatures as high as about l000 C. were observed near the entrance point where the oxygen rst contacted the hydrocarbon. These excessive temperatures could be minimized by diluting the hydrocarbon with steam, but even this proved unnecessary by omitting preheating of the oxygen and introducing the latter into the reactor without preheating, i. e., at temperatures below about 50 C.

In order to initiate the vapor phase oxidation of the naphtha a minimum bath temperature of about 325 to 330 C. is required. However, bath temperatures of about 360 C. are preferred since the reaction develops at an earlier point in the reactor and the maximum temperature peak is lower. Once the oxidation reaction begins, a high temperature develops and is maintained substantially constant and at about the same point in the reactor, depending on the conditions being employed.

The maximum proportion of oxygen that may be injected into or be present in the reactor at any one point while oxidizing hydrocarbons such as light virgin naphtha is about 40 moles of O2 per 100 moles of naphtha. At a contact time of about 3 seconds this oxygen ratio produces a maximum reaction temperature of 450 to 470 C. Still further increases in local oxygen/naphtha Yratio to about 0.45 or 0.5 are less desirable, as this has tended arcuate.

9 to produce excessive temperatures of 500 to 600 C. and made temperature control quite diicult. In the present equipment under the 'conditioiis described oxygen/naphtha molal ratios of about 0.3 to 0.4 are preferred, in order of useful product.

desired products.

any one point.

IV, run No. 104/5.

preferable.

reaction zone.

by comparing runs 78, 85 and 94.

monoxide are worthy of note.

alcohols, ketones, and epoxides.

covered as distillate.

10 the yield of luseful' liquid products. Thus, in run 85 the water layer upon hydrogenation and *distillation yielded 27 weight percent of re'-A zorable organic material, Yor about 6 pounds per 100 pounds of naphtha charged, not

Temperatures above to avoid reaction temperatures of 450 C. or higher 5 counting an additional 6% o'f the water layer which which tend to produce tar-like material at the expense consisted of a high-boiling Water soluble product.

Above 500 C. even some carbon is produced and this still further decreases the yield of Hydmgenatmn of wam layer Of course, a total oxygen ratio greatly The Water layer products are hydrogenated at low temin excess of the foregoing limits can be tolerated, 'p1-0- 10 perature, i. e. predominantly below about 60 C. in order vided that the oxygen is injected into the reactor in sucto avoid condensation reactions and the formation of :high cessive portions without exceeding the stated limits at boiling, Water Soluble Producte- Thus, While oxygen is preferably added about 60 C. are undesirable at the start, since they tend in a total amount of about 0.3 to 1 mole per mole 0f to Cause Polymerization of formaldehyde However, in hydrocarbon feed, as much as about 1.5 moles of oxygen 1I5 the latter Stages of the hydrogeuatiorl it may he, advarv per mole of feed is useful as indicated above in Table tageous t0 raise the temperature, e. e. to Sti-100 C., S0

as to facilitate complete hydrogenation of acetaldehyde. In general, the regions of maximum temperature may Raney nickel is a particularly useful catalyst for this range from l inch to 12 inches in length or more. When hydrogerlatioh, though other highly aCtlVe hydrogerlatioh the hot point is Very high in temperature, it tends tobe eatalyStS Suoh aS Platinum or Palladium may be used short in length, and when the temperature is more moder- Similarly Orl the other hallo, riieliel Supported oh kieSelate, the maximum temperature Zone tends te be more guhr or other less active catalysts are not so desirable, extensive, the latter type of temperature distribution lbeing Silloe they require relatively high hydrogeuatiori temperatures, e. g., 140 C. But at such high temperatures the Use of diluents such as steam or nitrogen in general forrhatior1 of undesirable high boiling residue due t0 has been found undesirable with naphtha-type feeds since Polymerization iS much higher than at loW temperature, it delays the start of the oxidation reaction and actually aud eVeu theh the oorlVerSioh of formaldehyde doeS not increases the tendency to form localized hot spots in the readily go to Completion However, for the ease 0f certain higmy in typical runs of this invention the water layer was reactive feeds the use of an inert diluent may be desirable. 53'() hydrogenated in a Shaking autoclave at about 1000 P- S- Multiple oxygen injection, on the other hand, 'tends to i' g- The temperature WaS maintained at about 50 to minimize hot points and is also desirable in that it pro- 60 C- for the i'lrSt tWo to three hours, WhereuPoI1 it WaS duces a greater yield of oxidized products as indicated raised to about 90 C- fOr another two hours or so.

Raney nickel was 'used as catalyst 'in Van amount equal to atom the data of Table IV it may be noted that, de- 10 weight percent 0n feed. The catalyst was prepared pending on reaction conditions, about 5 to 20 percent of aS deSeribed by Adkins et al, l- A. C *Se 70, 595 (i948) the hydrocarbon feed is converted to gas. The high ratio W4 oatalySte of C2 and C3 oleins to saturated hydrocarbons (about The hydrogerlatiou results are iSurruriariZed in SubS6- 3:1) in the gas, as Well as the high percentage of carbon fluent Table y A A comparison of runs 84-A and 84-B fshows the ad- The Water layer oxidation products contain relatively Vantage 0f Ralley hiolel cata'lySt over nickel oh 'leieSel large proportions of low molecular Weight oxygenate'd guhl When hydrogenating a water layer of the type .proeompomds, mainly vas C1 to C3 aldehydes, and some duced in the present invention. Specifically it is noted lf the water layer is that Raney nickel ,yields more than twice -the amount subjected to distillation, the majority of the oxygenated 0f Valuable -ProduCtS Suoh -aS alcohols, Whereas at the compounds, with the exception of 'formaldehyde and 45 temperatures required with nickel on kieselguhr the some polymers formed during distillation, may be re- .yield 0f alcoholsis Vlow and asubst-antial .proportion tof On the other hand, if the Water the organic material is turned `into 4an undesirable ihigh layer is lirst hydrogenated to convert the aldehydes to boiling residue. the corresponding alcohols, the formaldehyde may be re- Y vA comparison Yof .runs SS-A and -B shows .the ad- Since formaldehyde may "50 covered as methyl alcohol. represent about 40 percent of the entire oxygenated organic material present in -the Water layer, its recovery by conversion to methyl alcohol contributes .materially to vantage of finishing the hydrogenation -at .a `higher teinperature, which completely eliminates any acetaldehyde from the product while tncreasing the useful distillate yield.

TABLE V Hydrogena'tion of water layer Run No Analytical Data on Water Layer:

Formaldehyde, Wt. Percent Carbonyl-Number (Grn. Ott/ Gm Caroonyl Number Due to HCHO C3 Aldehydcs and Ketones, Wt. Percent;

Hydrogenatlon Conditions:

Oata1yst RaneyNi.

catalyst Ueedwt. Percent 1o 1o. Time and Temperature 6 Hrs a t 6 Hrs at 5 Hrs. at `3 Hrs.'55. 50' T55 C. l2 Hts.-'85. Ctmpiosltion of Water Layer (By Distlllaton) Wet Y as s: I Formaldehyde, Wt. Percent N one, None None v Acetaldehyde, Wt. Percent.-. None None L l0f8 'ggg Methyl Alcohol, Wt. Percent. 4. 6 v12.8 12:6 12. 1 Mttl. B. P. (i5-80 9,1 :Wt Perce 6. 7 10.2 `10.0Y -11. 3 -Mtr1.B.vP.so-95 C;2-Wt. Percent 4. o 13:5 350 '16.1

Total 'Dietmate n15. 3' 36. 5` 26. 4. a9. 5

High Bolling' Residue, Wt. Percent.......

1 Contains some ethyl alcohol and isopropyl alcohol. 2 Contains some low molecular Weight epoxldes.

to 15 wt. percent 50 to 92 C./l2 mm. Hg.

25 to 40 wt. percent 92 to 107 C./12 mm. Hg. 25 to 30 wt. percent 107 to 131 C./12 mm. Hg. 25 to 30 wt. percent Above 131 C./l2 mm. Hg.

The approximate composition of the organic material recovered by distillation from the water layer after hydrogenation over Raney nickel catalyst was as follows:

Hydrogenaton of hydrocarbon layer The presence of low molecular weight aldehydes in the oxidized hydrocarbon products is generally undesirable because of their irritating odor and, especially where the product is to be used as a motor fuel, because of their tendency to form gummy condensation products. Accordingly, it is desirable to convert the aldehyes to the corresponding alcohols so as to eliminate the formation of condensation products, and also to further increase the octane number of the product. However, conventional hydrogenation of the oxygenated hydrocarbon product, while eliminating the undesirable aldehydes, has also tended to saturate the valuable olens, thereby detracting from the anti-knock characteristics of the nal product.

According to the present invention it has been found that copper chromite catalyst can be used under proper conditions to bring about a selective hydrogenation of the undesirable aldehydes and ketones, without saturating the desired olelins admixed with the aldehydes in the oxidation product. The desired selective hydrogenation over the copper chromite catalyst is carried out at temperatures of about 100 to 160 C. and pressures of about 500 to 1500 p. s. i. g., preferably at about 140 yC. and at pressures of the order of about 1000 p. s. i. g. Selective hydrogenation is obtained by interrupting the reaction after the desired proportion of hydrogen has been absorbed, i. e. until the carbonyl number of the product has been reduced to a value less than 1.0. A suitable barium-promoted copper chromite catalyst is available from the Harshaw Chemical Co. (Code 469,931).

The advantages of the novel hydrogenation with the aid of copper chromite, as compared with the more `conventional hydrogenation using nickel on kieselguhr is illustrated in Table VI below. This table contains data obtained on the hydrocarbon layer of oxidation 85, showing properties before and after hydrogenation. ln

each hydrogenation run about 10 wt. percent of catalyst (based on feed) was used and the hydrogenation was carried out over a period of 3 to 4 hours at 1000 p. s. i. g.

TABLE v1 Hydrogenaton of hydrocarbon layer l Copper Chromite Nickel on Kiesel- Properties of Liquid Before Alter Before After Solubility in- 90% H3PO4. 25 25 25 22 Bromne No. 29. 6 27. 9 29. 6 10 Carbonyl No. 2. 2 0. 74 2. 2 0. 76

It is apparent that hydrogenation in the presence of copper chromite effectively reduces the aldehyde content, as shown by the decrease in carbonyl number, without materially affecting the olen content as indicated by the substantially unchanged sulfuric acid solubility and bromine number. ln contrast, the nickel catalyst, While effective in reducing the aldehyde content, also brings about a major decrease in brornine number as well as in acid solubility, thus indicating that olefins have been undesirably reduced. This saturation of oleiins becomes even more complete at higher temperatures. The boiling range of the hydrogenated product was in each instance similar to that of the starting oxygenated material. rhe approximate composition of the oxidized hydrocarbon layer from run 85, before and after selective hydrogenation with the aid of copper chromite is shown in Table VII.

TABLE VII Composition before and after hydrogenation Before After Hydro- Hydrogenation, genation, Wt. Per- Wt. Percent cent Carhonyls:

C4 and Higher .5 Alcohols, Cz'and Higher. U 5 Olelltsy: C d C 90% C@ and 61--.- .i 12 12 Epoxidcs 16. 5 1G. 5 Unoxidized Naphtha 63. 5 63. 5

The maximum yield of useful liquid products is obtained by combining the selectively hydrogenated hydrocarbon layer product and the hydrogenated material recovered from the water layer product. ln a typical :un the combined product may be composed of about 5 to l0 weight percent of organic material recovered from the Water layer while the other 90 to 95 weight percent rep resent the hydrogenated hydrocarbon layer. The boiling range of the combined product is similar to the hydrocarbon layer product alone, but somewhat richer in light ends than the original naphtha. The approximate composition of the combined hydrogenated product from run was:

Wt. percent Methanol 3 Ethanol, isopropanol-l-other Oxy-compounds from silica gel which adsorbs the oxygenated compoundsin a preference to the hydrocarbons, (2) by extractionv'vith a polar solvent such as hot water, 'a glycol, a glycol-Water mixture, ammonia, etc. to separate the oxygenated materials, (3) by first 'converting the tlirneithyl'ene oxide derivatives and ethylene oxide derivatives "t'o "glycols by means of dilute acid and then extracting 'the' oxygenated compounds by means of apelar solvent, V(4) 'for the case of certain pure or narrow-boiling hydrocarbon feeds, dis'- tillation may be Iused to separate the varius 'oxygenated compounds, for the latter 'mostly boilb'low and above the boiling point of the hydrocarbon beinig'bxidied.

Delzydra'tion of hydrocarbon l[ayer loxidation.product,

Instead of selectively hydrogenating the oxidation prod- 25 tion productfrom Ymn 85 was passedpover commercial alumina catalyst (fI-Iarshaw Chemical Co.) 'at a temperature of about 400 C. and a contact time of about`40 to 60 seconds at atmospheric pressure. As a result, the epoxides present in the oxidation product `gave principally conjugated and non-conjugated di'oleiins, with small amounts of olefin. The aldehydesfalso gave principally oleiins and diolens. The following "yields of products were obtained:

The following properties of `the liquid hydrocarbon product before and after dehydration were determined:

Before tter Bromine No 31.7 l5.3.l Carbonyl No 2.281 Negligible.

The above shows that simple `dehydration eiliectivly removes the undesired carbonyl compounds and materially increases the unsaturation of the product. The approximate original composition of the hydrocarbon layer oxidation product, as well as its composition after dehydration and after selective hydrogenation are compared in Table VIH.

afnam 14., TABLE V111 Product composition g Original fAiter After Oxidation Hydroehy- Product, genation, Vdration,

Wt... .Wu Percent Percent P ercent Carbonyls 8 3 2 0 5 0 12 `12 18 0 'o 1o 16. 5 16. 5 2 Unoxidlzed Naphtha 63. 5 63. 5 `68 MIt will be observed that dehydration, as compared with selective hydrogenation, produces a greatly increased yield of unsaturates, a very substantial yield of diolens, and only a very small yield of oxygenate'd compounds.

When the above-described `dehydrated product (V10 pounds) was combined with a proportionate amount v(0.75 pound) of organic material recovered from the hydrogenated water layer described earlier herein, the resulting yield of useful liquid products amounted to about 83 Weight percent (8l volume percent), based on the naphtha charged. This compares with a combined yield of about 90 weight percent (85 volume percent) in the case Where the hydrocarbon layer was selectively hydrogenated. The clear-research octane number of the combined dehydrated product was about 81-82, as compared with '64.4 'for the naphtha charged, and 83.1 for the 'comparable 'combined 'product resulting from the selective hydrogenation. Iny the 'attached drawing a simplified flow diagram illustrates the combined steps of operation. The hydro'- "carbon Ifeed vfrom storage vessel 1 passes through vaporizer 2, 'then through reactor tube 3 with admixedA oxygen from inlets 4. The oxidation vapor products are condensed 'in 5. The-condensate separates into a'hydrocarbon Ilayer and an aqueous layer in separator 6, The hydrocarbon layer may be rvsubjected to hydrogenation `or Vdehydration lur'lit 7. The aqueous layer may be subjected to hydro- Egjfzn'a'tio'n in vunit S., The combined 'organic products vfrom l" units 7 and 8 may be used to obtain a finished fuel 9.

From the standpoint Aof octane improvement in va A"naphthia, the over-all effect of 'the selective oxidation lis 'one of dehydrogenation. The hydrogen is removed f'either directly as Water, or the original molecule is changed into s'ch a form 'that it can give water `upon dehydration, e. g., b 'y lcatalytic treatment with dehydrating agents, `such 'as alumina. For example, it has been shown :herein that about half of the oxygen charged goes to water. And when the potential Water is actually removed from the various :Oxy-compounds by dehydration, then the yover-al1 oxygen 'selectivity to water (and hence its selectivity jin "eliminating hydrogen from the feed) is around 70%. In `rother words, it is apparent that only about 25 to 30% of 'the oxygen is used up to make oxides of carbon, which are not 'usable vin a liquid fuel. But if the carbon monoxide is considered useful, as in OXO synthesis, then carbon dioxide represents the only waste of` oxygen and 'thusan oxygen efliciency of about 90% can be obtained. Also, it is understood, of course, that elimination of all oxygenfroin the Oxy-compounds formed in the oxidation step is `not 'essential to the main purpose hereof. On the contrary, with the exception of aldehydes, 'the Oxy-compounds generally aid in making naphthas more suitable as 'affuel AYfor internal combustion engines in terms of cleanllilne'ss, volatility and anti-knock quality. Also the freezing Ypoint is reduced, which may be of particular benefit vin jet fuels.v The remarkable upgrading lin anti-knock quality obtainable 'by means of the present inventionis 'due 'princpally to the selective oxidation of the poor quality components of the feed such as n-hexane (octane no. 24.8) to epoxides such as 2,5-dirnethyl tetrahydrofuran (octane no. 92.2) and to the presence in the final product of olens and alcohols such as methanol which have a good blending anti-knock value.

Having given a general description of the invention as Well as specific illustrations of various phases thereof, these are not to be considered as limitations thereof. On the contrary, variations and modiications not expressly described herein may be made by persons skilled in the art without departing from the present invention, the scope and spirit of which is particularly pointed out in the appended claims.

We claim:

1. A process for upgrading a naphtha hydrocarbon feed containing normally liquid hydrocarbons of the class conl sisting of normal parafns and cycloparains to form oleins and epoxides of the same number of carbon atoms as the feed hydrocarbon as principal conversion products thereof by non-catalytic oxidation, which comprises passing a stream of the hydrocarbon feed in Vapor phase through a conversion zone maintained at a pressure between and 100 p. s. i. g. and a reaction temperature between 275 C. and 480 C., injecting oxygen gas into the stream of hydrocarbon vapor in the conversion zone to form a mixture having a molal oxygen to hydrocarbon ratio at any `point not above 0.5, the total amount of oxygen so admixed and reacted with said hydrocarbon feed being between about 0.3 and 1.5 moles of oxygen per mole of hydrocarbon, maintaining the hydrocarbon in contact with the admixed oxygen for a calculated total reaction period of about 1 to 5 seconds until about 25 to 70 weight percent of the hydrocarbon feed is converted, cooling the conversion zone at a suiciently high rate of heat transfer to maintain the reaction temperature within the stated range, condensing the vapor products leaving the conversion zone, and separating the resulting liquid condensate into an aqueous phase and an organic phase product comprising principally unconverted hydrocarbon feed containing dissolved therein olens and epoxides of the same number of carbon atoms as the feed hydrocarbon.

2. A process for upgrading a naphtha hydrocarbon feed boiling in the range of about 70 to 220 C. and containing normally liquid hydrocarbons of the class consisting of normal parains and cycloparafns, which comprises passing a stream ofthe hydrocarbon feed in vapor phase once through a conversion zone at a pressure between about 0 and 5 p..s. i. g. and a reaction temperature between about 350 and a maximumof about 480 C., injecting oxygen gas of at least 90% purity at a temperature not above 50 C. into the stream of hydrocarbon vapor feed at a plurality of successive spaced points in amounts adapted to give at said injection points a mixture having a local molal oxygen to hydrocarbon ratio not in excess of 0.4 and to give a total amount of about 0.3 to 1.0 mole of oxygen per mole of hydrocarbon feed, maintaining the hydrocarbon in contact with the admixed oxygen for a calculated reaction period of about l to 3 secv onds, cooling the conversion zone at a suiliciently high rate of heat transfer to keep the reaction temperature from exceeding the stated maximum, condensing the conversion zone effluent, and separating tne resulting condensate into an aqueous phase and a hydrocarbon-rich organic product having a research octane number of at least 80 and comprising principally unconverted hydrocarbon feed containing dissolved therein olens and epoxides of the same carbon content as the original hydrocarbon feed.

3. A process according to claim 2 wherein the separated organic product is contacted with hydrogen under pressure at a temperature of about 100 to 160 C. in the presence of a copper ehromite catalyst until the aldehyde content of the product is selectively reduced to a carbonyl value less than 1.

4. A process for upgrading a light naphtha hydrocarbon feed containing normally liquid hydrocarbons of the class consisting of normal parafiins and cycloparans to form olens and epoxides as principal conversion products thereof by non-catalytic vapor-phase oxidation, which comprises passing a stream of the hydrocarbon feed in vapor phase once through a conversion zone at a pressure between 0 and 100 p. s. i. g. and a reaction temperature between 275 and 480 C., injecting oxygen into the stream of hydrocarbon vapor feed passed through the reaction zone to form a mixture having a molal oxygen to hydrocarbon ratio at any point not above 0.5, restricting the total amount of oxygen admixed and reacted with said hydrocarbon feed to about 0.3 to 1.2 moles of oxygen per mole of hydrocarbon, maintaining the hydrocarbon in contact with the admixed oxygen for a reaction period of about 1 to 5 seconds while cooling the reaction zone at a sufficiently high rate of heat transfer to maintain the reaction temperatures therein, condensing the resulting vapor products that leave the reaction zone to obtain liquid hydrocarbon-rich and water phases and separating the hydrocarbon-rich phase characterized by a solution of principally oletins and epoxides with a minor amount of carbonyl compounds in a portion of the feed hydrocarbon left unoxidized in one passage through the conversion zone.

5. The process according to claim 4, wherein portions of the total oxygen reacted are injected at a plurality of successive spaced points into the hydrocarbon vapor stream as it passed once through the conversion zone in an amount adapted to keep the oxygen-naphtha molal ratio from exceeding 0.4 at any point and to keep the maximum reaction temperature from exceeding 450 C.

6. The process according to claim 4 wherein a normal parain is converted more selectively to an olen and epoxide of the same number of carbon atoms per molecule and a branched paran in the feed remains substantially less reacted.

7. The process according to claim 4 wherein the hydrocarbon vapor feed is a light virgin naphtha fraction boiling between about to 110 C. containing normal and monomethyl substituted parans.

8. The process according to claim 4, wherein the hydrocarbon-rich liquid phase separated from the water phase is chemically treated to lower its carbonyl content.

9. The process according to claim 4, wherein the separated hydrocarbon-rich phase is chemically treated by selective catalytic hydrogenation of aldehydes therein.

10. The process according to claim 4, wherein the separated hydrocarbon-rich phase is chemically treated by catalytic dehydration to lower its carbonyl content.

11. The process according to claim 4, wherein the aldehydes in the separated water phase are hydrogenated, and organic material containing the hydrogenated aldehydes from the water phase is blended with organic compounds from the hydrocarbon-rich phase.

References Cited in the le of this patent UNITED STATES PATENTS 1,517,968 Ellis Dec. 2, 1924 1,735,486 Young Nov. 12, 1929 1,976,696 Ellis Oct. 9, 1934 1,995,324 Penniman Mar. 26, 1935 2,079,607 Ellis May 11, 1937 2,132,968 Penniman Oct. 11, 1938 p 2,321,311 Mottlau June 8, 1943 2,369,710 Bludworth Feb. 20, 1945 2,580,528 Dice et al. Jan. 1, 1952 2,689,253 Robertson et al. Sept. 14, 1954

Claims (1)

1. A PROCESS FOR UP GRADING A NAPHTHA HYDROCARBON FEED CONTAINING NORMALLY LIQUID HYDROCARBONS OF THE CLASS CONSISTING OF NORMAL PARAFFINS AND CYCLOPARAFFINS TO FORM OLEFINS AND EPOXIDES OF THE SAME NUMBER OF CARBON ATOMS AS THE FEED HYDROCARBON AS PRINCIPAL CONVERSION PRODUCTS THEREOF BY NON-CATALYTIC OXIDATION, WHICH COMPRISES PASSING A STREAM OF THE HYDROCARBON FEED IN VAPOR PHASE THROUGH A CONVERSION ZONE MAINTAINED AT A PRESSURE BETWEEN 0 AND 100 P.S.I.G. AND A REACTION TEMPERATURE BETWEEN 275* C. AND 480* C., INJECTING OXYGEN GAS INTO THE STREAM OF HYDROCARBON VAPOR IN THE CONVERSION ZONE TO FORM A MIXTURE HAVING A MOLAL OXYGEN TO HYDROCARBON RATIO AT ANY POINT NOT ABOVE 0.5, THE TOTAL AMOUNT OF OXYGEN SO ADMIXED AND REACTED WITH SAID HYDROCARBON FEED BEING BETWEEN ABOUT 0.3 AND 1.5 MOLES OF OXYGEN PER MOLE OF HYDROCARBON, MAINTAINING THE HYDROCARBON IN CONTACT WITH THE ADMIXED OXYGEN FOR A CALCULATED TOTAL

Images