GB1574035A

GB1574035A - Process for continuously producing diisopropyl ether

Info

Publication number: GB1574035A
Application number: GB17479/77A
Authority: GB
Original assignee: Nippon Oil Corp
Current assignee: Eneos Corp
Priority date: 1976-04-28
Filing date: 1977-04-27
Publication date: 1980-09-03
Also published as: FR2349560B1; FR2349560A1; JPS5938213B2; NL7704558A; DE2719024A1; JPS52131508A

Abstract

PURPOSE:Diisopropylalcohol is made to react with propylene in the presence of a strongly acidic cation-exchange resin as a catalyst and diisopropylether is continuourly prepared in high yield by the distillation of the reaction solution after contacting with a granular olid acid as a neutralizing agent.

Description

(54) PROCESS FOR CONTINUOUSLY PRODUCING DIISOPROPYL ETHER (71) We, NIPPON OIL COMPANY LIMITED, a Japanese Company, of No. 3 12, I-chome, Nishi-Shimbashi, Minato-ku, Tokyo, Japan, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The invention relates to processes for continuously producing diisopropyl ether and to diisopropyl ether produced by such a process. The processes may be used for producing diisopropyl ether on an industrial scale.

Diisopropyl ether has been obtained industrially by separating and purifying the by-products of the hydration of propylene to give isopropyl alcohol.

According to the invention there is provided a process for continuously producing diisopropyl ether which process comprises reacting a mixture of isopropyl alcohol and propylene at a temperature of up to 1500C and a pressure of at least 20 atmospheres by passing the mixture through strong acid type cation exchange resin particles so as to give a reaction mixture containing diisopropyl ether, neutralizing the reaction mixture, flashing the neutralized mixture so as to remove propylene, distilling the flashed mixture to recover isopropyl alcohol from the residue and an azeotropic mixture of isopropyl alcohol and diisopropyl ether from the distillate, and removing isopropyl alcohol from the azeotropic mixture to give diisopropyl ether.

Preferably isopropyl alcohol is removed by extracting the azeotropic mixture with a solvent for selectively dissolving isopropyl alcohol or diisopropyl ether and distilling the phase containing diisopropyl ether.

Advantageously the mixture is reacted at at least 50"C.

Preferably the process comprises passing a mixture of isopropyl alcohol and propylene at a molar ratio of isopropyl alcohol to propylene of 1:0.4 to 1:4 through a first fixed bed of strong acid type cation exchange resin particles having a mean grain diameter of from 0.2 to 10 mm at a liquid space velocity of from 0.1 to 4 hr-l at from 50 to 1500C and 20 to 50 atmospheres; passing the resultant reaction mixture through a second fixed bed of water insoluble, particulate agent for neutralizing acid having a mean grain diameter of from 0.1 to 10 mm at from 10 to 1500C; introducing the resultant neutralized mixture into a flashing tower and flashing the mixture to remove unreacted propylene from the mixture; distilling the flashed mixture in a multistage distillation tower to recover unreacted isopropyl alcohol from the bottom of the distillation tower and obtain an azeotropic mixture of isopropyl alcohol and diisopropyl ether from an upper portion of the tower; contacting the azeotropic mixture with a hydrophobic or hydrophilic solvent to give a phase containing isopropyl alcohol and a phase containing diisopropyl ether; and distilling the phase containing diisopropyl ether. The phases may be in the form of distinct layers. The hydrophobic solvent is of course non-aqueous. The hydrophilic solvent may be water.

In the process of the invention, isopropyl alcohol and propylene are used as starting materials. As isopropyl alcohol starting material there may be used isopropyl alcohol commercially available containing preferably less than 1% by weight of moisture. The propylene starting material should preferably be of high purity, but may contain less than 500/ by weight of propane.

Isopropyl alcohol and propylene are heated to a temperature in the proximity of a reaction temperature separately or in a mixed condition and then introduced into the first bed with catalyst consisting of the strong acid type cation-exchange resin. The isopropyl alcohol and propylene are preferably fed at a ratio of 1:0.8 to 1:2.5 of isopropyl alcohol to propylene. Where the propylene value is less than 0.4, an increase in subsidiary reactions such as the dehydration of isopropyl alcohol as well as an increase in the quantity of unreacted isopropyl alcohol may result. Where the propylene value is in excess of 4, an increase in the quantity of unreacted propylene may result, which hinders subsequent refining steps. In addition, an increased quantity of the dimer of propylene is produced by a side reaction.

The strong acid type cation-exchange resin herein referred to includes a styrenesulphonic acid type resin or a phenolsulphonic acid type resin. The styrene-sulphonic acid type ion exchange resin may be of a sulphonated copolymer of styrene and a polyunsaturated compound such as divinylbenzene. The sulphonic acid type resin derived from a sulphonated copolymer of styrene and divinylbenzene is represented by the following formula:

wherein n and m each denote a positive integer.

This resin may have different degrees of bridging of adjacent polystyrene chains by divinyl benzene. The resin may have different physical structures including a gel type resin having merely three-dimensional structure and a porous type resin having macro-pores in its structure. Typical commercially available products are as follows: Styrene-sulphonic acid type resins Gel Type "Amberlite" IR-120 (Rohm & Haas) "Dowex" 50w-X4, X8, X10, X12 and X16 (Dow Chemical) Diaion SK 106, 110, 112 and 116 (Mitsubishi Chemical) All the products obtained under the above trade names can be used for the process of the invention.

The phenolsuphonic acid type resin is generally a condensate of phenolsulphonic acid with formaldehyde and is represented by the following formula:

wherein n denotes a positive integer.

The aforesaid strong acid type cationexchange resins used as a catalyst may be used in the form of a spherical or columnshaped particles having a mean grain diameter of 0.2 to 10 mm.

The particles of the catalyst may be charged into a cylindrical pressure vessel to form a fixed bed. The size of the bed may vary and is preferably from 0.2 to 20 m (metres) in height. It is possible to use a plurality of fixed beds arranged in series or in parallel relation to one another. Isopropyl alcohol and propylene are continuously fed bed the g ted bed through the top or bottom but preferably through the top 'quantity of isopropyl alcohol and Porous Type "Amberlyst" 15 (Rohm & Haas) "Amberlyst" XN-1004 (Rhom & Haas) Diaion PK 204, 208, 212, 216, 220 and 228 (Mitsubishi Chemical) propylene being fed should advantageously give a liquid space veloctiy in the range of 0.1 to 4 m3/m3xhr-1 i.e. (see following definition) preferably in the range of from 0.5 to 2 hr-1. The liquid space velocity herein referred to is the sum in volume (m3) of isopropyl alcohol and propylene, including both freshly supplied as well as recovered from the refining step hereinafter described and recycled, which are to be fed in liquid form to the fixed bed per cubic metre of the catalyst bed per hour, the volume being defined at a temperature of 20"C and a pressure of 10 kg per sq cm.

Inert solvent or diluent might be added to the starting materials, but the use of such an inert solvent is not desirable in the process of the invention.

If the quantity of starting materials being fed is below 0.1 hf' in liquid space velocity, reaction between the starting materials may progress sufficiently, but the quantity of diisopropyl ether may be reduced and decomposition of the diisopropyl ether produced may accelerate. If the quantity of starting materials being fed exceeds 4 litres/hr then the reaction results may not progress sufficiently thus hindering the succeeding refining step.

Preferably the reaction mixture emerging from the first bed is divided into a first and a second stream, the first stream being fed to the second bed and the second stream being recycled for passing through the first bed. In this case, the weight ratio of the quantity of fresh starting materials to the stream of the mixture being recycled should preferably be from 1:3 to 1:10.

The liquid space velocity representing the quantity of starting materials being fed is independent of the quantity of the mixture which is to be directly recycled to the first bed.

The use of the recycled stream enables an excess of starting materials to be supplied to the first bed which can help in dissipating the heat of the exothermic reaction between isopropyl alcohol and propylene and in reducing the speed of reaction. By the use of the recycled stream the reaction temperature can be conveniently maintained in a uniform manner through the bed and overheating, including local overheating avoided. The reaction temperature may also be controlled by special cooling means but the special cooling means may not be as efficient in overcoming local overheating.

The reaction pressure in the process of the invention is preferably maintained at from 20 to 50 atmospheres, most preferably at from 30 to 40 atmospheres. If the pressure is lower than 20 atmospheres, the reaction may be incomplete and if the pressure is higher than 50 atmospheres the pressure vessel and their accessory equipment may become unduly complicated.

The reaction temperature in the process of the invention is suitably from 50"C to 1500C to ensure sufficient reaction whilst reducing side reactions such as: .lae dehydration of isopropyl alcohol: the dimerization of propylene; the effusion of acidic material from the strong acid type cation-exchange resin used as the catalyst; and deterioration of the catalyst. Preferably, a reaction temperature is from 100" to 130"C.

In the process of the invention side reactions may be largely avoided and a large quantity of water, esters, or polymers of olefins are not produced as by-products of the reaction. However, under some reaction conditions, a small quantity of water (for example, in the order of 2% of water with respect to diisopropyl ether produced) may be created because of the following reactions:

IPA < propylene+H20 2IPAPE+H2O where IPA is isopropyl alcohol and IPE diisopropyl ether.

A small amount of strongly acid material may be eluted from the strong acid type cation-exchange resin and be included in .he reaction mixture. Should the reaction mixture be fed directly to a succeeding refining step for distillation and heating (which is usually required for the distillation) to separate unreacted material from the mixture and to purify the product, further side reactions could then result, such as decomposition of diisopropyl ether and dehydration of unreacted isopropyl alcohol. Undesirable by-products could thus be produced which also lower the yield of diisopropyl ether. The acidic materials thus elt.ted and the small quantity of water produced as by-product, also act together to corrode the reaction apparatus.

The eluted strongly acid material could be neutralized with an aqueous solution containing a strongly basic material such as NaOH, CaO, or Ca(OH)2. Neutralization could then be followed by the separation of the salts produced by neutralization reaction. The salt separation however is difficult and the quantity of the basic material should be controlled to allow for the concentration of acid material effused which in turn depends to a considerable extent upon the kind of catalysts used, the reaction temperature, the flow rate of the starting materials and the reaction time. If the quantity of base added is smaller than required, insufficient removal of the strongly acid material results, while if an excess of the basic material is fed, the succeeding refining step must be carried out under conditions for strongly treating the basic material. Furthermore, the presence of strongly basic material in any material recycled to the first bed would lower the activity of the strong acid type resin from which H+ would be exchanged with alkali metal. Thus unreacted material containing a strongly basic material cannot be recycled without first being neutralized with the acid.

An additional neutralizing step would be required to remove excess of the basic material.

The eluted strongly acid material could be neutralized by NaOH or CaO in a solid form but since a small quantity of water is present in the reaction mixture as a result of the side-reaction some NaOH or CaO would be slowly dissolved during the continuous use of the process leading to the complications previously described.

The eluted strongly acid material could be absorbed on, for example, activated carbon. The adsorbing capacity of such an adsorbent is low and if the concentration of acid to be adsorbed is lowered, the acidadsorbing ability of the adsorbent is greatly lowered.

Preferably the reaction mixture is therefore passed through the second fixed bed filled with a water-insoluble, solid particulate acid-neutralizing agent having a mean grain diameter of 0.1 to 10 mm, so that the mixture and the acid-neutralizing agent are brought into contact with each other.

The water-insoluble, solid particulate acid neutralizing agent herein referred to may be an inorganic solid particulate material with an extremely low solubility in water (such as those having a solubility of less than 0.1 g/100 g of water under the normal application conditions) and with an acid neutralization capacity of more than 1.0 mmoVg. The acid neutralization capacity can be determined by adding the solid material to an aqueous solution containing 1 " by weight of sulphuric acid allowing the aqueous solution to stand for 10 hours at SO"C, removing said solid material from the solution, and calculating the number of mmol of sulphuric acid removed from the aqueous solution per gram of the solid material.

The water-insoluble, solid particulate acid neutralizing agents include magnesium oxide, alumina. silica or a complex oxide or hydrate containing magnesium oxide, alumina or silica including magnesiumaluminium double oxides and hydrates thereof (magnesium and/or aluminium), complex oxides and hydrates of magnesium and/or aluminium with at least one additional element selected from Na, K, C, Si, Ca, Ba and Sr, for example, such as MgO, MgO . mH2O (m=0 to 0.5), Awl203 hydrotalcite (6MgO . Al203 . CO2. 12H2O), Al2O3 . mSiO2 . nH2O. (m=0.5 to 3, n=l to 6), Al203 . nH2O, 2.5 MgO . Awl203 . nH2O, Na2O . Al203 . nH2O, 2MgO . 6SiO2 . nH2O (in any compound, n=l to 6). Of these compounds, hydrotalcite and MgO are preferably used.

Hydrotalcite herein referred to usually has a molar ratio of magnesium to aluminium of 3. Hydrotalcite may be synthesized with a widely varying molar ratio of magnesium to aluminium depending upon the production process. Some of the hydrotalcites having a molar ratio of magnesium to aluminium ranging from 1 to 10 show an X-ray diffraction pattern having a peak arising from hydrotalcite whose molar ratio of magnesium to aluminium is approximately 3. Hydrotalcites having a molar ratio of magnesium to aluminium of 1 to 10 are effective for the purpose of neutralization.

The aforesaid solid particulate acidneutralizing agent is used as a fixed bed using particles of spherical, flake or columnar shape having a mean grain diameter of 0.1 to 10 mm.

The reaction mixture may be caused to pass continuously through the second fixed bed in a pressure vessel filled with the acidneutralizing agent, conveniently at a temperature of from 10 to 150 C. A temperature lower than 10"C may result in incomplete removal of the acidic material results and a need to cool the reaction mixture from the first bed with an attendant loss of heat. A temperature of over 1500C may cause undesirable reactions such as decomposition of the mixture obtained by reaction, and dehydration of the isopropyl alcohol. Preferably the temperature should be from 90 to 1200C. The quantity of the mixture which is to pass through the fixed bed usually has a liquid space velocity of from 0.1 to 20 her1. . The neutralized reaction mixture is introduced into a flashing tower for flashing treatment. The flashing tower is normally a multi-stage tower, in which volatile, low boiling point compounds, in this case essentially unreacted propylene, are removed from the neutralized mixture by flashing and discharged from the top of the tower. Two or three flashing towers may be arranged in series and used as a multi-stage tower.

Propylene separated by flashing from the mixture may be recycled to the first reaction container.

The flashed mixture is fed to a multi-stage distillation tower typically having from 5 to 40 stages. Unreacted isopropyl alcohol is recovered from the bottom of the distillation tower. The recovered isopropyl alcohol thus recovered may be recycled to the first reaction vessel. A small quantity of unreacted propylene is recovered from the top of the distillation tower while an azeotropic mixture of isopropyl alcohol and diisopropyl ether is obtained from the upper portion of the distillation tower, the portion being located advantageously at a level higher than the middle stage. The azeotropic mixture herein referred to is usually a mixture containing isopropyl alcohol and diisopropyl ether in a ratio of 1:5.1 by weight but may include a mixture containing isopropyl alcohol and diisopropyl ether at a ratio varying from 1:4.7 to 1:5.5. The small quantity of water produced by the side reaction is usually contained in the azeotropic mixture.

Suitably the unreacted isopropyl alcohol recovered from the multi-stage distillation tower is recycled to the first fixed bed and discharged together with the azeotropic mixture from the upper portion of the tower.

The azeotropic mixture may then be brought into contact with a hydrophobic or hydrophilic solvent. Suitable hydrophobic solvents may be hydrocarbons. In the case of a hydrocarbon solvent, the diisopropyl ether contained in the azeotropic mixture is extracted from the mixture by the solvent to give a layer of diisopropyl ether in the solvent and a layer of isopropyl alcohol.

Typical examples of hydrophilic solvents are water and lower alcohols having a carbon number of 1 to 4, such as methanol.

In the case of hydrophilic solvent, isopropyl alcohol is separated from the azeotropic mixture and extracted by the solvent, to give a layer of isopropyl alcohol in a solvent and a layer of diisopropyl ether are formed in like manner. The quantity of solvent is normally in the range of 0.3 to 20 times by volume the quantity of azeotropic mixture.

Water is preferably used as the solvent. In this case, in order to hold the loss of diisopropyl ether to a minimum, the quantity of water should preferably be in the range of 0.5 to 3 times the quantity of the azeotropic mixture by volume.

The layer of diisopropyl ether is then distilled to separate it from any solvent and from impurities to give diisopropyl ether of high purity.

Using an appropriate process according to the invention high purity diisopropyl ether can be obtained industrially in a high yield, with only small amounts of byproducts, with a simple purification and with a small incidence of corrosion.

The invention is described with reference to the Figure which shows a schematic flow diagram of the process of the invention.

Propylene starting material is fed through a line 1. The other starting material, isopropyl alcohol, is fed through a line 3 for mixing with the propylene. If necessary unreacted propylene and isopropyl alcohol, which have been recovered in later stages of the process, are circulated for re-use through lines 2 and 4 respectively. The liquid starting materials join with fluid flowing through a recycling line 6 and pass through a line 5. Then the liquid flowing through the line 5 is heated in a heat exchanger E-l, which is maintained at a desired reaction temperature, and introduced into a reaction tower D-l, which contains a fixed bed of particles of a strong acid type cation-exchange resin. The fluid leaving the reaction tower D-l is divided into two streams. One stream is recycled through the line 6 by means of a recycling pump P to join with the fresh starting materials from the lines 1 and 3 as described previously for recycling to the reaction tower D-l. The recycling through the line 6 may he omitted where the tower D-l has special cooling means. The other stream of the fluid leaving the reaction tower D-l is introduce d through a line 7 into a neutralizirits tower D-2 which contains a fixed bed of water-insoluble, particulate, acid neutralizing agent. Fluid from the neutralizing tower D-2 is introduced through a line 8 into a first flashing tower D3. The pressure is reduced in the tower D-3 compared with that in the towers D-2 and D-l. The pressure in the reaction tower D-l and the neutralizing tower D-2 is controlled by a pressure controlling valve PCV at a predetermined level. A gas consisting essentially of unreacted propylene is passed through a line 9 out of the top of the first flashing tower D-3, while liquid is taken from the bottom of the flashing tower D-3.

After cooling in a heat exchanger E-2, the liquid is introduced through a line 10 into a second flashing tower D-4. A gas consisting essentially of pure propylene is discharged from the top of the second flashing tower D4 tr pass through a line 11, while a liquid is taken from the bottom of the tower D-4 and introduced through a line 12 into a first distillation tower C-l. From the topmost portion of the distillation tower C-1 a gas consisting essentially of residual propylene is discharged. The discharged gas is passed through a line 13 to join with the gas streams coming out of the lines 9 and 11, and the resultant single stream is returned through a line 14 and through the line 2, respectively to join the propylene starting material fed through the line 1. A liquid stream consisting essentially of unreacted isopropylalcohol discharged from the bottom of the distillation tower C-l may if desired, be recycled through a line 15 and then the line 4 directly to join with the isopropyl alcohol starting material fed through the line 3.

A liquid fluid consisting essentially of an azeotropic mixture of isopropyl alcohol and diisopropyl ether is taken out of an upper portion of the distillation tower C-I (that upper portion being located at a level higher than the middle stage of the tower) and then introduced through a line 16 into a rinsing or liquid extraction tower C-2 in which the liquid fluid is contacted with solvent. Water may be used as the solvent which is supplied through a line 17 to the extraction tower. In the tower C-2, unreacted isopropyl alcohol is selectively transferred to the water phase.

A liquid fluid containing water and isopropyl alcohol is taken out of the bottom of the tower C2, and discharged through a line 18 to the exterior of the apparatus. A liquid fluid, containing diisopropyl ether and substantially no isopropyl alcohol, is taken out of the top of the tower C-2, and introduced through a line 19 into a second distillation tower C-3. From the top of the distillation tower C-3, a liquid fluid containing the azeotropic mixture of water and diisopropyl ether is discharged through a line 20 to the exterior. If desired, the liquid fluid from the top of the tower C-3 may be recycled through a line 21 to join with the line 16 for being subjected once more to extraction with water. Diisopropyl ether of high purity is taken as a product from the bottom of the distillation tower C-3 through a line 22.

The invention is further illustrated by the Examples.

Example 1 Diisopropyl ether was continuously produced according to the procedures described below in the apparatus shown in the drawing.

300 litres of a styrene type cationexchange resin (Amberlyst 15 having an average grain diameter of 0.5 mm approximately, a product of Rohm and Haas Company) was charged as catalyst into the reaction tower D-l, and 50 litres of hydrotalcite (6MgO . Awl203. CO2. 12H2O having a mean grain diameter of 0.7 mm) was charged into the neutralizing tower D-2.

Fresh propylene having a purity of 97% by weight was fed through the line 1 at a flow velocity of 20.4 kglhr and fresh isopropyl alcohol having a purity of 99.9% by weight was fed through the line 3 at a flow velocity of 33.2 kg/hr to the reaction system.

Propylene and isopropyl alcohol recycled through the lines 2 and 4 join with fresh propylene and isopropyl alcohol supplied.

The flow rate of propylene at the joint of line 1 with line 2 was 90.6 kg/hr. (2.16 kg mol/hr) and of isopropyl alcohol at the joint of line 3 with line 4 was 129.4 kg/hr (2.16 kg mol/hr). The pressure within the reaction system was maintained at 40 kg per sq cmG by means of the valve PCV. The materials thus mixed were introduced together with fluid coming through the recycling line 6 into the reaction tower D-l through the line 5. The temperature at the entrance of the reaction tower D-l was controlled by the heat exchanger E-l so as to maintain the mixed materials at 1070C. The recycle flow rate of the fluid in line 6 was controlled to be 7 times as great as the rate of flow of fluid running through the line 7 by adjustment of the recycling pump P. (The latter rate is equal to the rate at which starting materials were fed through the line 5). The flow rate of the fluid from the reaction tower D-l passing through the line 7 was 220 kg/hr.

The fluid contained 32.5 /" by weight of propylene, 46.4% by weight of isopropyl alcohol and 21.1% by weight of diisopropyl ether. The concentration of acid in the fluid was 2.4x 10-3 equivalents per litre (eq/litre).

The fluid leaving the neutralizing tower D-2 was introduced through the line 8 into the first flashing tower D-3 in which the pressure was maintained at 13.5 kg per sq cm G. From the top of the flashing tower D3, a gaseous fluid consisting essentially of 85.5 /" by weight of propylene and for the remainder of isopropyl alcohol and a small quantity of diisopropyl ether was flashed at a flow rate of 48.7 kg/hr. The fluid removed from the bottom of the first flashing tower D-3 was cooled in the heat exchanger E-2, and thereafter introduced by way of the line 10 into the second flashing tower D-4. From the top of the flashing tower D-4, a stream consisting essentially of 77.0% by weight of propylene and consisting for the rest of isopropyl alcohol and a small quantity of diisopropyl ether was flashed at a flow rate of 30.2 kg/hr, while a liquid taken out of the bottom of the tower D-4 at a flow rate of 140.7 kg/hr was introduced into the first, 25stage distillation tower C-l. The liquid fluid being introduced into the distillation tower C-l contained 66.9% by weight of isopropyl alcohol, 28.7% by weight of diisopropyl ether and a small quantity of propylene, and contained 1.2x10-7 eq/litre of acid. From the topmost portion of the distillation tower C-l, propylene was discharged at a flow rate of 7.2 kg/hr, while unreacted isopropyl alcohol was taken out from the bottom of said distillation tower C-I at a flow rate of 90.1 kg/hr. Streams of gas taken out of the tops of the respective flashing towers D-3, D-4 and discharged from the top of the distillation tower C-l join one another. Part of the streams of fluid so joined was flashed and removed to the exterior of the reaction system, while the greater remaining part was streamed through the lines 14 and 2 to join the stream of the fresh propylene introduced through the line 1 as described previously. Isopropyl alcohol taken out of the bottom of the distillation tower C-l was partly discharged to the exterior of the reaction system, while the greater remaining part was streamed through the lines 15 and 4 to join with the stream of fresh isopropyl alcohol introduced through the line 3 as described previously. From the upper portion of the distillation tower C-1 (the fifth stage counted from above), a liquid fluid containing 12.0% by weight of isopropyl alcohol and 88.0% by weight of diisopropyl ether was taken out at a flow rate of 43.4 kg/hr. The fluid thus taken out was introduced through the line 16 into the rinsing tower C-2 into which water was charged through the line 17 at a rate of 80 kg/hr. The fluid containing the mixture of isopropyl alcohol and diisopropyl ether was rinsed in the rinsing tower C-2, and an aqueous solution containing extracted isopropyl alcohol was discharged from the bottom of the tower to the exterior of the apparatus. The liquid flu

Example 2 As a catalyst in the reaction tower D-l there was used 300 litres of sulphonated resin having a grain diameter of from 20 to 50 mesh, the resin having been obtained by polymerizing styrene containing 12% of divinylbenzene. Propylene was fed through the line 1 at a flow rate of 29.8 kg/hr, and isopropyl alcohol was fed through the line 3 at a flow rate of 56.7 kg/hr to the reaction system. The temperature of the mixture at the entrance of the reaction tower D-l was controlled by the heat exchanger E-l at 118"C. The other procedures were the same as in Example 1. The fluid coming out of the reaction tower D-l and passing through the line 7 contained 29.0% by weight of propylene, 36.4 ,; by weight of isopropyl alcohol, 33.8% by weight of diisopropyl ether and 0.8% by weight of water, and was 1.2x10-2 eq/litre in concentration of acid.

The liquid fluid introduced into the distillation tower C-I contained 1.1x10-7 eq/litre of acid. Diisopropyl ether of 99.9% by weight in purity was taken from the bottom of the distillation tower C-l, at a flow rate of 59.7 kg/hr.

Example 3 The same procedure as in Example 2 was repeated except that 300 litres of a styrene type cation-exchange resin (obtained by ionexchanging Amberlite IR-121 of Rohm and Haas Company with H+ and having a mean grain diameter=0.6 mm) was used; propylene was fed through the line 1 at a flow rate of 27.4 kg/hr; isopropyl alcohol was fed through the line 3 at a flow rate of 26.8 kg/hr; and the heat exchanger E-l was controlled so that the temperature of the mixture at the entrance of the reaction tower D-l was 105"C. A liquid flow into the distillation tower contained l.lx 10-' eq/litre of acid. Diisopropyl ether of 99.8% by weight in purity was taken from the bottom of the distillation tower C-3 at a flow rate of 41.3 kg/hr.

Having regard to the provisions of Section 9 of the Patents Act 1949, attention is directed to the claims of Patent No.

1,459,242.

WHAT WE CLAIM IS: 1. A process for continuously producing diisopropyl ether which process comprises reacting a mixture of isopropyl alcohol and propylene at a temperature of up to 1500C and a pressure of at least 20 atmospheres by passing the mixture through strong acid type cation exchange resin particles so as to give a reaction mixture containing diisopropyl ether, neutralizing the reaction mixture, flashing the neutralized mixture so as to remove propylene, distilling the flashed mixture to recover isopropyl alcohol from the residue and an azeotropic mixture of isopropyl alcohol and diisopropyl ether from the distillate, and removing isopropyl alcohol from the azeotropic mixture to give diisopropyl ether.

2. A process according to claim 1 in which isopropyl alcohol is removed by extracting the azeotropic mixture with a solvent for selectively dissolving isopropyl alcohol or diisopropyl ether and distilling the phase containing diisopropyl ether.

o. A process for continuously producing diisopropyl ether which process comprises: passing a mixture of isopropyl alcohol and propylene at a molar ratio of isopropyl alcohol to propylene of 1:0.4 to 1:4 through a first fixed bed of strong acid type cation exchange resin particles having a mean grain diameter of from 0.2 to 10 mm at a liquid space velocity of from 0.1 to 4 hr-1 at from 50 to 1500C and 20 to 50 atmospheres; passing the resultant reaction mixture through a second fixed bed of water insoluble, particulate agent for neutralizing acid having a mean grain diameter of from 0.1 to 10 mm at from 10 to 1500C; introducing the resultant neutralized mixture into a flashing tower and flashing the mixture to remove unreacted propylene from the mixture; distilling the flashed mixture in a multistage distillation tower to recover unreacted isopropyl alcohol from the bottom of the distillation tower and obtain an azeotropic mixture of isopropyl alcohol and diisopropyl ether from an upper portion of the tower; contacting the azeotropic mixture with a hydrophobic or hydrophilic solvent to give a phase containing isopropyl alcohol and a phase containing diisopropyl ether; and distilling the phase containing diisopropyl ether.

4. A process according to claim 3 in which the reaction mixture emerging from the first bed is divided into a first and a second stream, the first stream being fed to the second bed and the second stream being recycled for passing through the first bed, the weight ratio of the first stream to the second stream being from 1:3 to 1:10.

5. A process according to claim 3 or claim 4 in which the acid neutralizing agent is magnesium oxide, alumina, silica or a complex oxide or hydrate containing magnesium oxide, alumina, silica for example hydrotalcite.

6. A process according to any of claims 3 to 5 in which in distilling the flashed mixture, unreacted propylene is recovered from the topmost portion of the tower, and the upper portion of the tower for obtaining the azeotropic mixture is located at a level higher than the mid-portion of the tower but lower than said topmost portion.

7. A process according to any of claims 3

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. Example 2 As a catalyst in the reaction tower D-l there was used 300 litres of sulphonated resin having a grain diameter of from 20 to 50 mesh, the resin having been obtained by polymerizing styrene containing 12% of divinylbenzene. Propylene was fed through the line 1 at a flow rate of 29.8 kg/hr, and isopropyl alcohol was fed through the line 3 at a flow rate of 56.7 kg/hr to the reaction system. The temperature of the mixture at the entrance of the reaction tower D-l was controlled by the heat exchanger E-l at 118"C. The other procedures were the same as in Example 1. The fluid coming out of the reaction tower D-l and passing through the line 7 contained 29.0% by weight of propylene, 36.4 ,; by weight of isopropyl alcohol, 33.8% by weight of diisopropyl ether and 0.8% by weight of water, and was 1.2x10-2 eq/litre in concentration of acid. The liquid fluid introduced into the distillation tower C-I contained 1.1x10-7 eq/litre of acid. Diisopropyl ether of 99.9% by weight in purity was taken from the bottom of the distillation tower C-l, at a flow rate of 59.7 kg/hr. Example 3 The same procedure as in Example 2 was repeated except that 300 litres of a styrene type cation-exchange resin (obtained by ionexchanging Amberlite IR-121 of Rohm and Haas Company with H+ and having a mean grain diameter=0.6 mm) was used; propylene was fed through the line 1 at a flow rate of 27.4 kg/hr; isopropyl alcohol was fed through the line 3 at a flow rate of 26.8 kg/hr; and the heat exchanger E-l was controlled so that the temperature of the mixture at the entrance of the reaction tower D-l was 105"C. A liquid flow into the distillation tower contained l.lx 10-' eq/litre of acid. Diisopropyl ether of 99.8% by weight in purity was taken from the bottom of the distillation tower C-3 at a flow rate of 41.3 kg/hr. Having regard to the provisions of Section 9 of the Patents Act 1949, attention is directed to the claims of Patent No. 1,459,242. WHAT WE CLAIM IS:

1. A process for continuously producing diisopropyl ether which process comprises reacting a mixture of isopropyl alcohol and propylene at a temperature of up to 1500C and a pressure of at least 20 atmospheres by passing the mixture through strong acid type cation exchange resin particles so as to give a reaction mixture containing diisopropyl ether, neutralizing the reaction mixture, flashing the neutralized mixture so as to remove propylene, distilling the flashed mixture to recover isopropyl alcohol from the residue and an azeotropic mixture of isopropyl alcohol and diisopropyl ether from the distillate, and removing isopropyl alcohol from the azeotropic mixture to give diisopropyl ether.

7. A process according to any of claims 3

to 6 in which the solvent is water and the azeotropic mixture of isopropyl alcohol and diisopropyl ether is contacted with water in a quantity of from 0.3 to 20 times the amount of azeotropic mixture by volume whereby said mixture is separated into a layer containing isopropyl alcohol and water, and a layer containing diisopropyl ether.

8. A process according to any of claims 3 to 7 in which the unreacted propylene removed by flashing is recycled to the first fixed bed.

9. A process according to any of claims 3 to 8 in which the unreacted isopropyl alcohol recovered from the multi-stage distillation tower is recycled to the first fixed bed.

10. A process for continuously producing diisopropyl ether substantially as described with reference to the drawing.

11. A process for continuously producing diisopropyl ether substantially as described in Example 1, 2 or 3.

12. Diisopropyl ether produced by a process according to any of the preceding claims.