US2141275A - Method for hydrating olefines - Google Patents

Description

Dec. 27, 1938.

w. K. LEWIS METHOD FOR HYDRATING .OLEFINES Filed Oct. 22, 1936 .SCE (In IIYG rower.

I A a/V (Ar/Myra; 114x110 man l RECOtfiRY TOM GR 2 Sheets-Sheet 2 .Z ISTILLATE OUT'AAT Patented Dec. 27, 1938 UNITED STATES nm'rnon roa nrmwrmc. omrmss Warren K. Lewis,

Newton, Mass., assignor to Standard Oil Development Company, a corporation of Delaware Application October 22, 1936, Serial No. 106,96!

' 13 Claims; (01. 260-641) The present invention relates to an improved process for utilizing hydrocarbon gases and liqu'ids for production of more valuable products, and particularly to an improved method for hydrating olefines for the production of alcohols, esters, and the like. The invention will be fully understood from the following description.

In the drawings Fig. 1 represents in semi-dia-.

grammatic form a suitable apparatus for converting light petroleum liquids and gases into alcohols, and

Fig. 2 shows another arrangement of the reaction vessel and the recovery equipment.

The present specification is a continuation in.

part of prior applications, Serial No. 688,035, filed September 2, 1933, and Serial No. 737,361 filed July 28, 1934. These cases relate to improved methods for hydrating olefines so as to produce alcohols. In its broadest sense the process for hydating olefines is known; for example, it is known to absorb olefines, either liquid or gaseous, in sulphuric acid of high strength or other similar absorbents'and then to dilute such absorbent to I a large extent and to distill off the alcohol. -In

such case the acid is not strictly a catalystbecause it emerges from the reaction in a more diluted form. In the present case as well as the applications referred to above, the process is strictly catalytic in that the absorption agent,

for example sulphuric acid, is maintained throughout in ,a relatively diluted form, which is well below the concentration known to be suitable for sulphation at atmospheric pressures.

Referring to the drawings, Fig. 1 shows a pipe I through which oil or hydrocarbon gases are passed at high velocity. The gas or oil is cracked.

in the heated coil 2 which is arranged in a furnace setting 3. The exit products are cooled in the worm 4 and are conducted to a purifier 6 by line 5. The purifier may be in the form of a towerwith inlet and outlet lines I and 8 for a suitable scrubbing liquid suchas hydrocarbon oil. If desired, the scrubbing tower maybe used to cool the cracked gases and suitable arrange-- ments, such as a series of partial coolers or con-" densers, may be provided'to segregate the normally liquid condensates such as gasoline, cracked gas oils, tar and the like, before the scrubbing steps. Such arrangements, being well known in the art, can be designed withoutdifllculty. Th

gaseous fractions are removed by line 9. u

The apparatus described in the foregoing paragraph is preferably operated at low or moderate pressures and the gases may be recompressed by the compressor ill before passing into the subse quent steps. The compressed olefine gas passes into a reheater II and into a pipe ll where it is admixed with superheated steam from pipe l3,

which is also under thesame high pressure.- If

60 olefine gas or light liquid olefines are available,

for .example, from ordinary cracking still, it is not necessary to use the prior cracking coil 2 as such gas or liquid may be introduced under high pressure through the pipe l2. It may be desirable to crack only a sufficient quantity of gas to enrich the cracked gases available from the commercial cracking stills.

The olefines and steam are now admitted to the base of the reaction chamber l5. The tower is preferably provided v with suitable means for maintaining it at a uniform temperature throughout, such as a jacket IE, but equivalent means such as electrically heated coils may be .used. The tower is fitted with contact means such as tower packing or plates l1, fitted with bubbling caps and overflow pipes. The catalyst, which is a dilute aqueous solution, the exact composition of which will be disclosed below, is introduced at the upper chamber l8, flowing downwardly in contact with the upfiowing stream of vaporized olefine and steam, and is drawn off at the base of the tower by a pipe 20 which carries the catalyst and such alcohol as is produced by the hydration of the olefines to the recovery equipment.

A reduction valve 2| is provided in the pipe 20 which reduces the pressure on the catalytic liquor before discharging into the recovery tower 22, which may be a simple distillation or stripping column provided with contact means 23, a closed heating coil 23a at the lower end and a pipe for the introduction of stripping gases. The alcohol is distilled over through a vapor pipe 25, to a condenser 26. The distillate is collected in re ceiving drum 21, and withdrawn to storage by pipe 28. A vent pipe 29 is provided on the re,- ceiver.

The catalytic liquor stripped of alcohol flows through pipe 36 to pump 3| and thence back to pipe i8 for' reuse in the hydration tower.

\ In Fig. 2 a somewhat different arrangement ,of the reaction tower and recovery stream is shown. The same reference numerals are used throughout, where possible. The olefine and steam are introduced as before at pipes I la and I3 respectively. The reaction tower I5 is fitted with alternate plates Ila and "b and the overflow pipes are arranged so as to conduct the liquor on the various plates, not to the plate directly below but to the nextv lower plate. In this manner two separate streams of liquor flow downward through the tower, the gas and. vapor rise through plates continuously and alternately contact with the two liquids, which, however, do not mix at any point. The catalytic liquor; is introduced by the .pipe 18 while the second liquid streamJpreferably a noncatalytic liquor, is introduced through a pipe l8.

Separate recovery andscrubbing towers 22 and 220. are provided for the two liquor streams 20 and 20a provided with reducing valves 2| and 2la andeach is a, substantial duplicate of the other and of the tower shown as 22 in Fig. 1. The stripped liquors flow down through the towers 22 and 22a and are separately recirculated to pipes i8 and I811. respectively so as to provide two complete but uncomr'nunicating liquor circulation streams.

olefines, for example ethylenef thepropylenes, butylenes and higher homologues, either in, a pure state or admixed with. each other for with other gases, into corresponding alcohols. Cracked gases-preferably crack A t pressures below 100 lbs. per square inch, tori-example, and even as low as atmospheric pressure, are preferred. The tops from stabilized cracked naphthas consisting of 60 to 70% propane, after removal of propylene with sulphuric acid, may serve as an excellent cracking stock, and when cracked at 700 or 800 C. at low pressure, yields a considerably larger volume of a gaseous product containing 20 to 35% ethylene and 2 to 7% propylene. Such a material can be recompressed and fed directly to thereaction tower i5 for the production of ethyl and isopropyl alcohols.

It will be understood that water must be furnished in order to hydrate the oleilnes and this may be furnished in different ways, for example, it may be included with the gases in the form of steam and where the gases are very rich incleflnes it is desirable to use this method since the steam assists as a heat carrier. Water may be added to the dilute acid catalyst at the top of the tower l6, if desired in the proper proportion. The amount of water and steam to be added should be sufflcient first, for the hydration reaction and second, to keep the of! gases saturated -so that the catalyst is not concentrated during the-reaction by evaporation and loss of water. The amount of steam will depend on temperature and pressure conditions although it is generally several times in excess of the amount of oleflnes present, say 2 or 3 or even 5 mols of steam added per mol of olefine.

The reaction temperature is below 350 0.; how much lower depending on factors such as catalyst, the time for conversion desired, degree of agitation of the reactants, and the rapidity of withdrawal of the alcohol from the tower. A rapid reaction is obtained at 250 0., it is reasonably rapid at 120 to 150 C. and quite perceptible rates are foundas low as 80 C. although, perhaps, too low for commercial application.

The temperature and pressure also depend on the particular olefine or oleilne mixture being reacted. In general the temperature should'be decreased for higher olefines and this is especially true of reactive oleilnes containing a tertiary carbon atom combined with an adjacent carbon atom having a double bond, such as in the case 01 isobutylene. Such oleflnes. have a marked tendency to polymerize and the temperature for alcohol production should be quite low for example about 120 C. or lower and under a suitable pressure for example for this particular temperature of about 150 atmospheres.

The pressure utilized in the present process depends on the particular temperature used, higher pressures being necessary as higher temperatures are used, but should in every case be sumcient to prevent anysubstantlal evaporation of water and alcohols from the dilutecatalytic' tallied and with the large volume of gas blown through it, there will be a tendency to evaporate, but the amount of steam used and the pressure imposed should be adjusted to substantially offset this tendency, and while variations in concentration of the catalytic liquor may be evident from time to time due to the difiiculty in balanc- One object of the present proc'essis' to convert ing all of these factors exactly, the object of the adjustment is to ,maintain as close a balance as possible to prevent evaporation of the catalyst and to maintain the alcohol formed in a liquid condition throughout the tower or at least to maintain then-acid throughout at catalytic strength as will be defined below. For illustra- $1011 it may be stated that the pressure is above atmospheres and it is preferable to operate at {100 to 200 or even at 1000 atmospheres, it being understood thatzthe yields decrease with pres- ;sure reduction. On the other hand, pressures above 400 atmospheres do not give proportional advantages.

It has also been observed that there is a definite equilibrium alcohol concentration in the liquor within the tower and if this is reached the olefines pass through the tower without further conversion. This equilibrium concentration depends on the conditions of temperature and pressure to some extent, but principally on the olefine concentration of the gas. For example, if the olefine concentration in the gas is ethylene, andthe equilibrium concentration of ethyl alcohol is from 4 to 5%, when the ethylene concentration is about 20%-,at the same pres sure and temperature the alcohol concentration for equilibrium is about 8 to 10%. It is highly desirable to always keep the alcohol concentration in-the dilute acid liquor at a value well below the equilibrium concentration, and this may be accomplished in several different ways. For example, it has been found that if the acid catalyst is passed through the tower with suflicient rapidity, it is possible to decrease the alcoholic content to about one-half or less of the equilibrium concentration under the particular conditions of operation, and under these conditions the conversion is rapid and altogether the operation is highly successful.

Another means for controlling the alcohol concentration in the catalytic liquor, is by use of the mechanical arrangements shown in Fig. 2. In this case two separate streams of liquor flow through the tower without intercommunication; the one is, of course, the dilute catalytic liquor and the other is a liquor capable of absorbing alcohol, but preferably non-catalytic in character. Of the latter type examples may be given. Hydrocarbon oils, for instance petroleum oils, may be used especially where the olefine is sufficiently high boiling to yield higher alcohols. I

Highly aromatic oils, phenols, especially alkyl phenols, which are liquid and readily dissolve distilled away at the temperature and pressure imposed, and for this purpose it has been found desirable to add very soluble salts to'increase the boiling point, for example sodium or potass'ium sulphate or calcium chloride may be used for this p p se. It will be understood that a portion of ,the alcohol will be held in the catalytic liquor but it will be also understood that the alternate stream will also absorb a substanformation. If desired, a sumcient quantity of the fatty acid, for example acetic'orhigher acids, may be added to'esterify substantially ,all of the alcohol formed, or lesser quantities may be used so as to obtain alcohols and esters in any desired proportion. It is particularly desirable to use the apparatus illustrated inFig. 2 in such a scheme, the fatty acid being admittedby pipe i8a for example. In this way is ispossible to obtain alcohols and esters as separate cuts.

As to the time of contact, it will be understood that it is difiicult to give clear-cut illustrations,

but that the larger the tower and more contact surface, the greater will be the proportion of olefine converted. Using a single 6" depth 'of dilute sulphuric acid, 40% of ethylene (pure ethylene) bubbled therethrough was converted to ethyl alcohol at a temperature of 250 C., while at 140 C. about 11% of the ethylene was so converted. It will be understood that thisfactor is so closely related to temperature, catalyst and other conditions that it may vary greatly, depending on particular installation. In order to obtain good yields it is essential to obtain a series of contact steps such as are obtained in a tower, especially when dilute olefine gases are treated.

The catalysts which may be employed are of several types, most of which have been previously used at low pressure in highconcentraand other halide acids may be used but the less volatile and more stable mineral acids, such as sulphuric and phosphoric are preferred. -Organic acids such asacetic and oxalic are useful but metal halides; such as those of cadmium, zinc, ammonium and aluminum are better. In

general it may be said that the higher the acid strength of the catalyst, the lower is its effective concentration in the present process.

With different catalysts, different concentrations are preferable. For example, with phosphoric acid concentration rapidly increases the yield for ethylene-up to a maximum at about 15% but beyond that concentration theactivity decreases markedly. The activity with 5% phosphoric acid is much greater at 300 C. and,400 atmospheres than with the stronger acids as used in the prior art. Six percent sulphuric acid is satisfactory, although it may be used in lower concentrations, say from 1 to 4% or 10% or somewhat higher, but always well below 1.6 specific gravity which is the lower limit for absorption at normal or moderate pressures. Again,

however. high pressures appear to favor the low acid concentrations which are useless at atmospheric and moderate pressure. Some of the catalysts effect considerable polymerization and of these sulphuric acid is one. Phosphoric acid on the other hand, while apparently somewhat less active, does not effect polymerization of the oleflne toanything like the same extent. Ten

per cent acetic acid is not so good as 2% hydrochloric acid and boric acid has been found to be even less active. With various metal salts the concentrations are likewise varied and a few tests are required to show the optimum concentration. With aluminum chloride (A1C13.6H2O) 15 to 20% solution gives an optimum output at 300 C. while zinc chloride is apparently the best at about 50%.

In addition to the above, it should also be noted that silver salts can be used for catalytic purposes, and while perhaps not so satisfactory alone,

- they are decidedly advantageous when added to other catalysts, for example, to sulphuric acid. Hydrocarbon oils may also be added to the catalytic liquor to assist in the absorption of the olefines, or Turkey red oil and similar materials may be used in its stead.

It is believed that the operation of the reaction vessel will be fully understood from the above description and little need be said as to the'operation of the recovery steps. This recovery is merely a distillation of the alcohol or ester that is formed from the catalytic liquor. The distillation' is conducted at a pressure below that at which reaction is obtained, but it is not necessary tooperate under vacuum or even at atmospheric pressure and it is usually, in fact, desirable to distill under a positive pressure, such pressure being'selected so that the distillation of the alcohol can be accomplished at approximately the same temperature as is maintained in the reaction tower. In this way waste heat is reduced to a minimum and the operation is conducted under the most favorable conditions.

The apparatus must, of course, be designed to Example 1 In the following first two experiments the gas used has the following compositions:

. Per cent Cam 39 CsHa 3.6 N: 57.4

In the first test the gas was bubbled in a single stream of bubbles through a glass lined reaction vessel containing 8% sulphuric acid in a single pool of 8 inch depth. The rate of gas flow was 2.5 to 3.5 volumes (at Standard conditions) per m nute/volume of reaction space, which was undera total pressure of 3000 lbs. and at temperature of approximately 255 C. The gas was continuously removed and it is found that 34% of the ethylene was converted to ethyl alcohol,

i. e. approximately 15 pounds of ethyl alcohol per 1000 cu. ft. of gas.

Example 2 To contrast with the above procedure the acidwas now allowed to flow through the reaction vessel in intimate counter-current contact with the rising gas. before and that of the acid was about 900 pounds/1000 cu. ft. of inlet gas. The alcohol concentration of the exit acid liquor Varied from about 5 to 6 gr./100 c. c. The conversion of ethylene proceeded smoothly to the extent of approximately giving a yield of about 45 pounds/ 1000 cu. ft. of gas and was removed from the acid liquor by distillation under reduced pressure. The exit gas contained from 3 to 4% ethylene and a trace of ethyl alcohol.

The effects of temperature and pressure on the operation of the process are shown by the following experiments:

Example 3 Gas containing 35% ethylene was bubbled once Example 4 Pure ethylene when reacted with 10% sulphuric acid maintained at a temperature of approximately 176 C. and undera pressure of approximately 197 atmospheres produces a solution containing 94 grams of ethyl alcohol per liter.

Example 5 Hydration of propylene to isom' mll alcohol.

At a temperature 01' approximately 138 C. and

a pressure of approximately 184 atmospheres with a catalyst of 12.1% HaPO4, the following yields of isopropyl alcohol were obtained from propylene.

Grams isopropyl alcohol per liter produced -Time of contact in hours Example 6 The rate of flow of gas was as" Pressures Time of contact in hours 95 184 272 503 atmosatmosatmosatmosphems phcres pheres phcres 35 415 72 W 61 70 187 so 86 136 164 92 U 152 176 101 IN 160 183 134 181 204 1% 146 189 212 Example 7' A C4 cut containing 17% isobutylene in the liquid phase when contacted with 3% hydrochloric acid at a temperature of 128 C. and under a pressure of atmospheres produced61 grams of tertiary butyl alcohol per liter in one hour.

Example 8 N-bntylenes when contacted with 3% hydrochloric acid at a temperature of 147? C. and under apressure of 150 atmospheres produced 45 grams of alcohol per liter in one hour.

The invention is not to be limited to any theory of the chemical reactions or of thei'unctions of the several steps, nor to the use of any particular olefine or mixture of oleflnes or particular catalyst but only to the following claims in which it is desired to claim all novelty in the invention.

I claim:

1. An improved process for hydrating oleflnes comprising passing an oleflne in vapor phase upwardly through a reaction zone in countercurrent contact with aqueous sulphuric acid of less than sulphating strength, the reaction being conducted at a temperature between about 350 and about 128 C. and at a pressure above about 100 atmospheres, maintaining a partial pressure of water to substantially maintain the concentration of the acid during reaction, maintaining the alcohol in liquid phase, dissolved in the aqueous sulphuric acid at a concentration below the equilibrium concentration, withdrawing a mixture oi alcohol and dilute sulphuric acid and distillingthe former from the latter at a pressure below that prevailing during reaction.

2. An improved process for the hydration of oleflnes which comprises continuously passing an olefine into contact with a dilute aqueous hydration catalyst providing intimate contact in a series'of steps at a reaction temperature between about 350 C. and about 250 C. while under a reaction pressure above atmospheric and exceeding the vapor pressure of alcohol formed by the reaction, maintaining a partial pressure of water by addition thereof to prevent substantial concentration of the catalytic solution, whereby the oleflne is hydrated forming alcohol, cont-inuously withdrawing the dilute catalytic solution containing alcohol dissolved therein at a concentration below the equilibrium concentration and recovering the alcohol therefrom by distillation at a pressure below that prevailing during reaction.

3. Processaccording to claim 2 in which the olefine is passed upwardly in contact with the downwardly flowing stream of the dilute aqueous catalyst.

4. Process according to claim 2 in which the oleflne in vapor form is passed upwardly in countercurrent contact with the downwardly flowingstream of the dilute aqueous catalyst, the pressure andtemperature of the operation being interadjusted so as to obtain the alcohol in liquid phase, separating the alcohol from the acid liquor and recirculating the latter.

5. An improved process for hydrating olefines comprising passing an olefine in vapor phase upwardly through a reaction zone in countercurrent contact with aqueous sulphuric acid of less than sulphating strength, the reaction being conducted at a temperature between about 350 and about 250 C. and at a pressure above about 100 atmospheres, maintaining a partial pressure of water to substantially maintain the concentration of the acid during thereaction, maintaining the alcohol in-liquid pha'se dissolved in the aqueous sulphuric acid at a concentration below the equilibrium. concentration, withdrawing a mixture of alcohol and dilute sulphuric Lil providing intimate contact in a series of steps at acid and distilling the former from the latter at a pressure below that prevailing during the reaction.

6. Process according to claim in which the acid strength is maintained constantly at from about 1 to p 7. Process according to claim 5 in which the alcohol concentration in the acid catalytic liquor is maintained well below the equilibrium value.

8. Process according to claim 5 in which the alcohol concentration in the acid catalytic liquor is maintained well below the equilibrium value by maintaining a rapid flow of acid through 'the reaction zone.

9. Process according to claim 5 in which the alcohol concentration in the acid catalytic liquor is maintained well below the equilibrium value by introducing a non-catalytic liquor, maintaining it out of contact with the sulphuric acid, withdrawing the same and recovering alcohol therefrom.

10. Process according to claim 5 in which the alcohol concentration in the acid catalytic liquor is maintained well below the equilibrium value by adding an esterifying organic acid to the reaction zone and thereby esterifying a portion of the alcohol formed.

' 11. Process according to claim 5 in which the alcohol concentration in the acid catalytic liquor is maintained well below the equilibrium value by adding a fatty acid to the reaction zone.

12. An improved process for the hydration of olefines which comprises continuously passing cracked gases produced by cracking petroleum hydrocarbons at elevated temperatures into contact with a dilute aqueous hydration catalyst a reaction temperature between about 250 and about 350- C., while under a reaction pressure above atmospheric and exceeding the vapor pressure of alcohols formed by the reactions, maintaining a partial pressure of water by addition thereof to prevent substantial concentration of the catalytic solution, whereby the olefines are hydrated forming alcohols, continuously withdrawing cracked gases substantially free of alcohol forming olefines and their derivatives, continuously withdrawing the dilute catalytic solution containing alcohols dissolved therein ata concentration below the equilibrium concentration and recovering the alcohols therefrom by distillation at a pressure below that prevailing during the reactions.

13. An improved process for the hydration of olefines which comprises continuously passing an olefine into contact with a dilute aqueous hydration catalyst providing intimate contact in a series of steps at a reaction temperature between about 350 C. and about 80 C. while under a reaction pressure above atmospheric and exceeding the vapor pressure of alcohol formed .by the reaction, maintaining a partial pressure of water by addition thereof to prevent substantial concentration of the catalytic solution, whereby the. olefine is hydrated forming alcohol, continuously withdrawing the dilute catalytic solution containing alcohol dissolved therein at a concentration below the equilibrium concentration and recovering the alcohol therefrom by distillation at a pressure below that prevailing during reaction.

WARREN K; LEWIS.

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