US2045785A - Process for converting ethers to alcohols - Google Patents

Abstract

Ethers are converted to alcohols by hydration with a dilute aqueous acid catalyst such as sulphuric, phosphoric, hydrochloric or, less advantageously an organic acid such as acetic acid, or alternatively an acidic salt such as zinc or aluminium chloride at elevated temperature and pressure such that the bulk of the alcohol formed is retained in the liquid phase and preventing substantial increase in the concentration of the acid. The activity of the catalyst may be increased by adding other substances such as silver salts, or oily substances such as fatty or mineral oils or turkey red oil. Ether entering at 1, Fig. 1, is forced by a pump <PICT:0456547/IV/1> <PICT:0456547/IV/2> 2 through a heater 3 and steam may be added at 4. The vapour enters a packed tower 6 having a heating-jacket 9 and acid liquor is introduced at 7. Any olefine formed is withdrawn by a pipe 10 and passed through a condenser 11 to recover ether which separates from the water in a vessel 13. Acid liquor containing alcohol is withdrawn by a pipe 17 through a pressure-reducing valve 18 to a distilling column 19 having a cooling-coil 21 at the top, alcohol vapour containing some ether being drawn off at 22 to a column 23 for separation. In a modification, Fig. 2, the ether vapour meets sprayed acid liquor in an unpacked reaction vessel 106 having spraying nozzles 107. The temperature may be 200--300 DEG C. Some production of olefine may occur at 250 DEG C. and increases at higher temperatures; this may be checked by adding steam. The pressure may be 225--3000 lb. In the examples, sulphuric acid of 10 per cent and 5 per cent strength is used. The Specification as open to inspection under Sect. 91 states that the reaction temperature may be as low as 20 DEG C. This subject-matter does not appear in the Specification as accepted.

Description

hum-30 1936. w. K. LEWIS I 2,045,785 PROCESS FOR CONVERTING ETHERS TO ALgonoLs Filed Dec. 28,1954, Z'Sheets-Sheet 1 "L .L' \I. 27124 Z? 27% June 30, 1936. i w. K. Liz wls' 5 PROCESS FOR CONVERTING ETHERS 'TO ALCOHOLS Filed Dec. 28: 1 934 2 Sheets Shee t 2 71152 Luvs.)

REAC' TOR PatentedJune 30, 1936 UNITED STATES- PROCESS FOR CONVERTING ETHEBS T ALCOHOLS Warren K. Lewis, Newton, Mass.,' assignor to Standard Oil Development Company, a corporation of Delaware Application December 28, 1934, sem No. 159,559

17 Claims.

The present invention relates to a process for converting ethers to alcohols, and particularly to an advantageous method for. carrying out the conversion of ethyl ether to ethyl alcohol. The invention will be fully understood from the following description and the drawings.

In the drawings, Figure 1 represents in diagrammatic form an apparatus adapted to continuously convert ether to alcohol, and

Figure 2 represents a somewhat different arrangement of the apparatus the, same purpose.

While it has heretofore been considered desirable to convert alcohols to ethers, there is only a relatively small requirement for ethers and a relatively large demand for alcohol, and modern synthetic methods have considerably' increased the production of etheras a by-product, and it is therefore desirable to convert ethers to alcools.

It has been discovered that ethers generally, and ethyl ether in particular, can be converted to the corresponding alcohols by hydration throughcontact with dilute mineral acidic substances under particular conditions of temperat e and pressure. It has been found that the reaction is 1 smooth, resulting in a high yield of alcohol of a high'degree of purity,

Referring to the drawings, in Figure 1 the pipe I is .the feed pipe for ether to the system. It is forced by pump 2 to a heating coil 3 which may be directly fired. steam heated-or raised by other means to an elevated temperature to cause vaporization under the elevatedpressure. Steam 'may be introduced by pipe 4 and passes through 'pipe '5 into the reaction zone 6, which may be of any particular form. It is desirable to produce as intimate a contact as possible between the ether vapor and' the dilute aqueous acidic liquid which is introduced by means of the pipe I. The catalytic contact zone 5 is preferably filled with acid resistant rings or other shapes indicated generally at} and may be heated by a jacket 9 or other equivalent means. The ether vapor with or without steam is forced into the reaction zone 6, maintaining pressure, and the conversion occurs therein. The alcohol produced may be largely retained in the acid liquor by suitable adjustment of temperature and pressure as will be disclosed below, and the liquor flows downwardly to the recovery equipment which will be described below.

When the temperature is to some degree by a subsequent reaction with the for accomplishing sufliciently high, say above 250' C., the alcohol produced is dehydrated production br-ol'efins, and these will ordinarily pass upwardly through. the reaction zone and collect in the upper part of the reaction zone. It

- which emerges from the reaction zone by a pipe l0 may becondensed preferably under full pressure in a condenser I l and is drawn off to separation tank 13. The condensate, which also contains condensed steam, may be discarded or may be separatedbystratification in separation tank I 3 from which water is withdrawn by pipe l4 and from which ether may be drawn by pipe l5 and returnedto the inlet of the coil 3 for recirculation in order to obtain a complete conversion. The olefin vapors which are uncondensed in cooler ill pass off by pipe It for fuel or to be otherwise utilized.

The-acid liquor which preferably contains the alcohol produced in the reaction zone is removed by a pipe I! and pressure is preferably reduced at the valve l8 so that the heated mixture is discharged at a lower pressure into the distillation unit which may be represented by a rectifying column l9; This is provided with heating coil 20 at its base and, a condenser 2! at the top from which the rectified alcohol, which contains some ether, maybe withdrawn by a vapor line 22 to a. second column 23 for separation of alcohol from unconverted ether. I This column is fitted with plates and refluxing coil in the usual manner. Alcohol is obtained as a residue, cooled in cooler 24 and withdrawn while ether vapor is taken overhead and condensed at 25. 'Theether may be returned to zone 6 forconversion. 5

The acid liquor is returned to reacton 6 by pipe 26 and pump 26a and water may-be added by pipe 21 to compensate for the water required in the reaction and to make up any loss which may have occurred.

Turning to Figure 2, a somewhat difierent operation is shown. The ether is fed by the pipe l0! through the coil and into the reactor I06 just as before. The'reaction vessel in this case is an unfilled drum fed with spray nozzles in? through which acid is forced so as to be dispersed in the form of fine liquid particles. I

' Vapor is withdrawn from the reactor I06 by means of a pipe I08 to the condenser I09. Ex-

olefin passes 05 by a; pipe As will be disclosed below, there are alternate operations depending upon the particular conditions maintained within the reactor. Sumce it to sayhere that relatively high temperatures in proportion to the pressure imposed cause the alcohol produced to be maintained completely or substantially in the vapor phase and in such case will be removed with the unconverted ether by pipe I08 and will be condensed with the alcohol and water vapor. The aqueous alcohol may be removed from the condenser at a lower level by means of pipe 2 and the mixture may be passed into the recovery equipment through the pressure reduction valve H3.

If desired, a relatively high pressure in relation to the temperature may be maintained in the reaction vessel and in this case, just as disclosed in connection with Figure 1, the bulk of the alcohol produced will be retained in the liquid products. In such case, the acid liquor containing the alcohol will be'removed by pipe Ill and conducted to the recovery equipment into which it discharges through the pressure reduction valve H6.

It will be understood that either of these operations is contemplated or, if desired, conditions may be held such that a portion of the .alcoholwill be carried overhead and the remainder will be-retained in the liquid products so that the alcoholic material will be recovered from both of these sources.

The recovery'equipment shown in the drawings is substantially the same as that shown in Figure 1 and need not be described in detail. The acid liquor is withdrawn from the base of the recovery tower and is returned by a pipe II! to the spray nozzles I06 after the addition of water to make up for that consumed in the reaction and otherwise'lost. In case the conditions are maintained within the reactor such as to cause a complete or substantially complete vaporization of the alcohol formed, it will be understood that the acid liquor need not be passed through the recovery system but may be forced by the pump H5 directly to the spray nozzles by means of a by-pass line 8.

The above descriptions are of the most desirable types of apparatus particularly suited for large scale continuous operation, but the operations maybe conducted in batch in a single contact stage if desired. In such a system the acid may be placed in the reaction zone and left there for the reaction period, ether. being pumped in continuously or from time to time to maintain pressure. The advantages of the preferred operation, which involves flow of acid through several contact stages, are better absorption of ether, greater yield of alcohol and less loss due to olefin formation.

The conditions under which the conversion of ether to alcohol is accomplished are quite varied.

Temperature may be even as low as 20 C., but

it is greatly preferred to use higher temperatures,

temperatures. This can be offset to a considerable degree by the addition of steam-as has been described above, but it is not necessary to introduce steam and by an intimate degree of contact at high temperature, the time of reac- 5 tion may be quite short, say 10 to 60 minutes which may be sumcient only for a relatively small loss to olefin. 1

It is also required that a. substantial pressure be used during the reaction and such pressure is used as will substantially prevent evaporation of water from the aqueous catalyst. The lower limitof pressure appears to be about 225 pounds per square inch at a temperature of about 200 C., but pressures much in excess of this are preferred, for example, from 500 to 1000 or even 3000 pounds per square inch.

It has already been disclosed that the catalyst is an acidic substance and a great many aqueous solutions can be used for this purpose, especially 20 the mineral acids such as sulfuric, phosphoric, hydrochloric and the like. Acetic and otherorganic acids may be used but they are less effective. Of all these catalysts, sulfuric acid is perhaps the most attractive commercially, especially 25 at a concentration of about 10% where its activity appears to be at its height. Most of the acids are found to show optimum catalytic prop erties at definite concentrations, and the most effective concentration varies inversely with the 30 strength of the particular acid. The acid strength is such that alcohol mixed therewith is largely in the form of alcohol and not as an alkyl ester, so that it can be removed by distillation without further dilution. For example, as has 35 been said before, sulfuric acid at about 10% is at its best, whereas the best concentration of hydrocholric acid is below 10% or from 5 to 6%, while with phosphoric acid the optimum is say 15 to 20%. With the other weaker acids mentioned the concentration is even higher.

Under the pressures imposed and the temperature used aqueous catalysts do not tend to appreciably concentrate. There may be some slight concentraton from time to time, but the object is to maintain the catalyst at substantially the same concentration throughout. Ifthe catalyst is allowed to continuously concentrate it is found that a large loss in the form of olefins results.

It is not necessary to use acids for the catalysts and substances which give an acid reaction in aqueous solution may also be used such as, for example, aluminum chloride, zinc chloride, or other salts of the same general nature. In describing the catalysts, it may be said that they 5 r are dilute aqueous acidic substances and by this is meant substances which give a fairly strong acid reaction in the aqueous solution. They should have in every case'a concentration of less than 50% by weight and preferably even less 60 than this. Two or more catalysts may be used, if desired, in admixture and substances may be added to the catalyst to increase its activity such as silver salts or oily substances, either mineral oils or fatty oils, Turkey-red oil and the like. a 65 It has been found to be desirable to maintain an appreciable amount of ether passing out of the top of the reactor and the rate of flow is so adjusted with the temperature and pressure and catalyst so as to obtain this result. A good share 70 of the ether purged in this manner may be recovered by cooling and condensation or by other means. The condensate contains some olefin and this amount of olefin should be kept at a low figure, say of the order of 1% of the ether re- 76 turned to the reaction zone. In order to maintain this condition there is an optimum cooler recovery temperature and pressure. For the-optimum ether recovery for the above conditions,

' assuming 10% of the volume of vapors leaving the reaction zone to be oleflns, the optimum recovery of 94% of the purged .ether is obtained by cooling to 170 C. under a pressure of 1200 pounds per square inch.

As indicated above,-temperature and pressure conditions may be adjusted so as to maintain the bulk of the alcohol formed either in the liquid tially no alcohol was obtained in the vapor. If,

however, the pressin'e is substantially reduced with the same temperature and catalyst conditions, the bulk of the alcohol obtained is in the vapor phase and only a trace was obtained in the withdrawn liquid;

From what has been said above,it will be understood that the reaction vessel must be adapted to withstand elevated pressures of the order of 2,000 to 3,000 pounds per square inch and temperatures up to say 300 C. and perhaps higher. The apparatus must be acid resistant and may be'made of suitable metal alloys such as chrome steels and the like, or lined with such alloys or with copper, or with enamel, or constructed ofstone ware, acid resistant brick and the like.

Example I Ether is vaporized and passed into a 'reaction vessel containing 10% sulfuric acid and maintained at a temperature of 272 C. Ether is,

forced in to maintain a pressure of 2,000 pounds per square inch during total time of contact of 25 minutes. The liquor withdrawn at the end of the experiment showed 22% ethyl alcohol which was recovered from the acid .by distillation at normal pressure. This represented a conversion of over.

% of the ether fed.

Example II The time of contact was increased over that shown in the above experiment to minutes and the conditions were otherwise maintained. It wasobserved that the concentration of alcohol fell to 16% and an equivalent amount of ethylene was found.

Example III A reaction vessel was filled two-thirds full of 10% sulfuric acid, heated to 240 C., and ether vapor pumped in slowly so as to maintain a pressure of approximately 2,000 pounds per square inch. The only agitation was that caused by gently rocking the reaction vessel.- After a time of 60 minutes the concentration of alcohol was found to be 25% of the liquid. At 207" C. with the same'catalyst and pressure the alcohol concentration rose to 15% in 60 minutes and l'7 in minutes. Ethylene formation was observed to begin at about 250 C.

I EzampleIV In the following tests a pressure of 1,800

pounds per square inch was maintained throughout and a catalyst comprising 8% sulfuric acid was used. The sulfuric acid was dropped continuously through a reactor in the form of a vertical tube 1%" LB. and 18" high. The rate of feed of the acid was 24 cc. per minute through a I. D. tube. The temperature was held at 207 C. and ether was continuously pumped in to maintain the pressure. The acid liquor was withdrawn as quickly as possible from the bottom of the tube continuously and it was found to contain from -4 to 6%of ethyl alcohol and a trace of ether.

A batch experiment in which acid was maintained in a bomb without agitation under the same temperature-and pressure conditionsused above showed 4 to 6% alcohol was built up in 10 minutes. These two experiments show the effect of increasing the area of contact. 'In the first experiment thedroplets were relatively small giving a substantial area, but the time of con- .tact was merely that required for the drop to fall through the 18", space. In 'the second experiment the area of contact (surface of the acid pool) was very much smaller and 10 minutes were required to build up the same concentration. By increasing the agitation or degree of contact between the acid and the ether, time of contact may be greatly reduced.

The present invention is not limited to any theory of the mechanism of the reaction in question, nor tothe conversion of any particular ether into alcohol, nor to any particular catalytic agent or method for carrying out the reaction, but only to the following claims in which it is desired to claim all novelty inherent in the in vention. I claim: I 1. A process for converting aliphatic ethers to alcohols comprising subjecting an ether to hydration in the presence of a dilute aqueous acidic, catalyst at an elevated temperature and a pressure in excess of 225 lbs. per square inch sufiiclent to substantially prevent concentration of the acidic catalyst.

2. A process for converting aliphaticethers to alcohols comprising subjecting an ether to hydration in the presence of a dilute mineral acid at temperature above-the critical temperature of the ether while under pressure in excess of 225 lbs. per square inch suilicient to substantially prevent concentration of the acidic catalyst.

3. A process for converting aliphatic ethers to alcohols comprising subjecting an ether to hydration in the presence of a dilute mineral acid' catalyst while at temperature in excess of the critical temperature of ether and under pressure in excess of 225 pounds per square inch and sumcient to prevent concentration of the catalyst.

4. Process according to claim 3 in which the temperature and time of reaction are adjusted so as to favor'formation of alcohol rather than 5. Process acco;.iing to claim 3 in which the temperature is adjusted between approximately 200 and 300 C. and the time of reaction is interadjusted therewith so as to produce a major quantity of alcohol and a minor quantity oi olefin. A

6. Process according to claim 3 in which the catalyst comprises a dilute aqueous mineral acid selected from the group of sulfuric, phosphoric and hydrochloric.

7. Process according to claim 3 in which the catalyst is dilute aqueous sulfuric'acid.

8. Process according to claim 3 in which the catalyst is sulfuric acid of the order of 10% conentration. 9.A continuous process for converting ether to alcohol comprising contacting ether vapor with dilute aqueous mineral acid at temperature between about 200 and 300 C. while under pressure in excess of 225 pounds per square inch and adapted to substantially prevent concentration of the acid catalyst, continuously withdrawing alcohol and recovering the same.

10. Process according toclaim 9 in which the temperature and pressure conditions are adapted to maintain a substantial portion of the alcohol formed in vapor phase, in which a vaporized mixture comprising ether and alcohol is removed and alcohol is recovered therefrom.

11. Process according to claim 9 in which the pressure and temperature are adjusted to maintain a substantial portion of alcohol in the vapor phaseand in which the vaporized mixture comprising alcohol and ether are removed, separated and the ether is returned for further reaction.

12. Process according to claim 9 in which pressure and temperature are inter-adjusted to maintain the bulk of the alcohol in the liquid phase and in which the dilute aqueous catalytic solution containing alcohol is continuously fed into contact with the ether, is continuously withdrawn and alcohol recovered therefrom.

13. Process according to claim 9 in which pres sure and temperature are inter-adjusted to maintain the bulk of the alcohol in the liquid phase and in which the dilute aqueous catalytic solution is continuously fed into multiple stage contact with the ether vapor,- is continuously removed in solution therein and alcohol recovered by distillation.

14. Process according to claim 9 in which pressure and temperature are inter-adjusted to maintain the bulk of the alcohol in the liquid phase andin which the dilute aqueous catalytic solution containing alcohol is continuously withdrawn and alcohol recovered by distillation and the dilute acid liquor is returned for further reaction. 7

15. An improvediirocess for converting ethyl ether to alcohol comprising vaporizing ether and forcing it into a multiple contact zone maintained undera temperature or 200 to 300 C. and under a pressure of the order of 500 to 3,000 pounds per'square inch, passing a dilute aqueous mineral acid through the reaction zone so as to come into direct and intimate contact with the ether vapor in several stages, adjusting conditions'so as to substantially'prevent concentration of the dilute acid and to retain the major proportion of the alcohol produced in liquid phase, continuously withdrawing the dilute aqueous catalyst containing alcohol and distilling the alcohol therefrom.

16. Process according to claim 15 in which the catalyst is dilute aqueous sulfuric acid and said catalyst is recirculated through the reaction zone and continuously withdrawn to recover alcohol so as to provide insufiicient time to allow a substantzal formation of olefins.

17. Process according to claim 15 in which the catalyst is dilute aqueous sulfuric acid and said catalyst is recirculated through the reaction zone, continuously withdrawn to recover alcohol, providing insuflicient time to allow a substantial formation of oleflns, and bleeding of the oleflns which are so formed.

WARREN K. LEWIS.

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