DE1933538A1 - Allyl alcohol prepn - Google Patents

Abstract

Allyl alcohol is prepared by passing propylene, O2 and CH3COOH in presence of water in gas phase at 50 degrees-250 degrees C over Pd catalysts, gaseous reactn. product is condensed and treated with an acid catalyst in liquid phase at 50 degrees-150 degrees C and resultant reactn. product is separated into a head product of allyl acetate, allyl alcohol and water, and a sump product of acetic acid, allyl alcohol and H2O. Lead product is recycled for treatment with the acid catalyst, the sump product is separated into a head product of allyl alcohol and H2O, and a sump product of CH3 COOH and H2O, this latter being recycled to reactn. of propylene with CH3COOH and O2, and if necessary water is removed from the allyl alcohol and H2O azeotrope.

Description

Process for producing allyl alcohol The present invention relates to an economical process for the production of allyl alcohol by reaction of propylene and oxygen.

It is known to produce allyl alcohol by hydrolysis of allyl chloride qder by isomerization of propylene oxide.

It has now been found that allyl alcohol is technically more advantageous Way from propylene and oxygen. If you can produce propylene, oxygen and acetic acid in the presence of water in the gas phase at temperatures of 50 - 2500 passes over palladium catalysts, the gaseous. Reaction product condenses, the condensation product formed essentially from allyl acetate, acetic acid and water wholly or partially with an acidic catalyst in the liquid phase at temperatures treated from 50-150 ° C and the reaction product obtained here after removal of the catalyst in a first distillation into an essentially of one ternary azeotrope consisting of allyl acetate, allyl alcohol and water and a product consisting essentially of acetic acid, allyl alcohol and water separates, and that the top product from this first distillation is wholly or partially returned to the treatment with the acidic catalyst, and that 4as the bottom product from the first distillation in a second distillation in a overhead product consisting essentially of the azeotrope of allyl alcohol and water and separates a bottom product consisting essentially of acetic acid and water, and that one converts the bottom product from the second distillation into the reaction of the propylene recycled with oxygen and acetic acid and optionally out of the azeotrope Allyla.kool and water removes the water by methods known per se In the process according to the invention, propylene is first reacted with the oxygen and acetic acid to allyl acetate. The condensation deq gaseous The reaction product can be made, for example, by cooling to temperatures below 50 ° 0. whereby a liquid phase is formed, that of the remaining gaseous Phase is separated.

The liquid phase consists essentially of allyl acetate and acetic acid and water, depending on the concentration ratios, a delamination can occur take place in an upper, organic phase, which consists essentially of allyl acetate, and a lower, aqueous phase consisting essentially of water and acetic acid. As mentioned, the upper, organic phase and the lower, aqueous phase can partially or treated entirely in the liquid phase with an acidic catalyst. This can be done at normal or increased pressure. In this treatment with the.

acidic catalyst, partial hydrolysis of the allyl acetate to allyl alcohol takes place. The catalyst is now removed from the reaction product. This can be done by neutralization, e.g. if sulfuric acid is used as the catalyst, or also by mechanical separation, e.g. if an acidic cation exchanger is used as the catalyst. at about 830 boiling ternary azeotrope consists of allyl acetate, allyl alcohol, water and acetic acid. The top product of this first column is returned to the reaction with the acidic catalyst. The bottom product of the first column is broken down in a second distillation column into a top product, which consists of the allyl alcohol-water azeotrope and a bottom product, which consists of water and acetic acid, and which converts propylene, oxygen and acetic acid in the presence is recycled from water to allyl acetate. This completes the acetic acid cycle. The only raw materials required for implementation are propylene and oxygen. The reaction can be given by the equation C3H6 + 1/2 02 Allyl alcohol can be exemplified.

When propylene is reacted with oxygen and acetic acid is formed as a by-product a small amount of carbon dioxide and water of reaction. Through this, The amount of water coupled with the formation of carbon dioxide would be complete Circulation increase the water content in the circuit. In general, however the amount of water in the form of the allyl alcohol-water azeotrope from the cycle is taken out, larger than this water of reaction. It is therefore in general necessary to add a small amount of water to the circulatory system to get a ensure constant water content. In the process described, the Allyl alcohol in the form of the water azeotrope boiling at 890, which is approx. 28% by weight of water contains, won.

In many cases of chemical processing, the allyl alcohol can be used directly in the form of this water azeotrope. If necessary, the allyl alcohol can be freed from water by known processes and obtained in this way in dry form. ~ Combine the fashion. Main reaction of the formation of allyl alcohol according to the equation 03H6 + +02 Allyl alcohol with the formation of carbon dioxide as a side reaction due to the combustion of propylene according to the equation 03H6 + 4.5 02 3 C02 + 3 H20 it can be seen that allyl alcohol, carbon dioxide and water are formed as a total reaction from propylene and oxygen, this water being the water of reaction resulting from the combustion of propylene to carbon dioxide. Two substances, namely propylene and oxygen, have to be added to the overall reaction system. Three reaction components, namely allyl alcohol, carbon dioxide and water, are to be extracted from the overall reaction system. Carbon dioxide is separated from the cycle gas or a substream of the cycle gas in a technically known manner and released in practically pure form from the reaction system as exhaust gas. If allyl alcohol were to be isolated in anhydrous form in the process, the water of reaction resulting from the formation of carbon dioxide would have to be withdrawn from the liquid cycle, for example in the form of an aqueous acetic acid, such as that obtained at the bottom of the second distillation column. With the removal of acetic acid-containing wastewater, however, a loss of acetic acid would be associated, which is generally not economically viable. Special measures would therefore be required in order to recover the acetic acid from this acetic acid-containing wastewater. In the procedure according to the invention, the problem of working up wastewater containing acetic acid is solved in that this water of reaction is removed as the top product of the second distillation column in the form of the allyl alcohol-water azeotrope. In practice, instead of three reaction products (allyl alcohol, water, carbon dioxide), two reaction products are extracted from the reaction system: carbon dioxide and the allyl alcohol-water azeotrope. Since more water is removed with the allyl alcohol-water azeotrope when the process is carried out in practice than corresponds to the formation by combustion of the propylene to form carbon dioxide and water, the difference will be added to the system as a prischarge. It is particularly advantageous to feed this amount of water into the hydrolysis of the allyl acetate.

There is a preferred mode of operation of the method according to the invention in that one hourly the following amounts for the implementation of propylene, Oxygen and acetic acid used to make allyl acetate: 5 - 20 ml water / mol acetic acid, 1 - 5 mol oxygen / mol acetic acid and 4 - 40 mol propylene + inert / mol oxygen, and that such a temperature is set in the range between 50 and 2500C that 80 - 100% of the acetic acid used is converted in a single pass. At the Cooling of the gaseous reaction product to temperatures below 500 is obtained then a liquid, upper phase, which consists essentially of allyl acetate, and a liquid, lower phase consisting essentially of water.

The palladium contained in the catalyst can be as metal or in the form of compounds, which are preferably essentially free of phenolic, sulfur and nitrogen are present, e.g. B. as palladium acetate, palladium benzoate, palladium propionate, Palladium acetylacetonate, palladium hydroxide.

The catalyst advantageously contains activators such as e.g.

Alkali acetates or alkali compounds under the reaction conditions at least partially convert into alkali acetates, e.g. formates, propionates, hydroxides, Carbonates, phosphates, borates, citrates, tartrates, lactates. Suitable alkali compounds are compounds of potassium 9, sodium, lithium, rubidium and cesium.

Metals or compounds can also be added to the catalyst that affect the activity and selectivity of the catalyst, suitable Additives are e.g.

Metals of groups V to VIII of the periodic table and / or gold and / or copper, the metals also being compounds that are essentially free of IIalogens, sulfur, nitrogen, may be present. Examples are as Additives called: gold, platinum, iridum, ruthenium, rhodium as metal or oxide or Hydroxide, as well as oxides, hydroxides, acetates, acetylacetonates, or decomposition or Conversion products of this, the elements iron, manganese, chromium, tungsten, molybdenum. Preferably iron compounds that are essentially free of halogen, sulfur and nitrogen are used as additives.

The catalysts are preferably on supports.

The following can be used as a catalyst carrier, for example: silica, natural and synthetic silicates, activated carbon, aluminum oxide, spinels, pumice stone, Titanium dioxide.

Those carriers which have a high chemical resistance are preferred against water and acetic acid, such as silica.

The catalyst can be in the form of pills, sausages or balls, for example be used. e.g. in the form of balls with a diameter of 4 - 6 mm.

The catalysts can be prepared in a wide variety of ways. For example, compounds of the metals can then be dissolved in a solvent soak on the carrier. and then dry. But you can also use the components soak one after the other on the carrier and, if necessary, by intermediate treatment, such as annealing, chemical reactions, such as treatment with solutions of alkali metal hydroxides, Convert alkali carbonates, reducing agents.

In the preparation of the catalysts, one can start from compounds the sulfur, nitrogen or halogen contain, such as sodium palladium chloride, Tetrachloroauric acid, ferric chloride, copper nitrate, manganese sulfate, and then these compounds convert on the support into insoluble compounds that are essentially free of Are sulfur, nitrogen and halogen, such as palladium metal, palladium oxide, Iron hydroxide, gold hydroxide, copper hydroxide, manganese oxide, and then by washing free the catalyst from nitrogen, sulfur and halogen compounds.

For example, organic palladium and iron compounds can be used together soak in an organic solvent, dry, for example drying temperatures from 50 - 1500C can be used, then alkali acetates from aqueous solution soak and dry at temperatures of 50 - 2000C. In the drying conditions can be a partial or complete decomposition or transformation of the organic Palladium and iron compounds take place.

The catalyst obtained in this way can be mixed with liquid or gaseous methanol, Ethylene, propylene are treated, the palladium compounds to the palladium metal be reduced. You can also use the catalyst before the reaction with propylene, Acetic acid and oxygen to allyl acetate in the gas phase with propylene and water, optionally treat acetic acid and / or nitrogen and / or carbon dioxide, wherein a partial or complete reduction of the palladium compound to the metal occur can. The process according to the invention can be carried out at normal pressure or elevated pressure, preferably 3 - 15 atm.

A preferred procedure in the preparation of the catalysts consists in that one palladium acetylacetonate and optionally iron acetylacetonate Dissolves in benzene, soaks it on the catalyst support, dries at 80 - 10000, then Potassium acetate impregnated from aqueous solution, the catalyst of a thermal treatment at 100-130 ° C subjects and then the catalyst in the gas phase at 50-2500C - if necessary under pressure - with propylene and water and if necessary Acetic acid treated. It is technically advantageous to have this treatment in the reactor before the actual conversion to allyl acetate, i.e. before the addition of oxygen, perform.

Another preferred preparation of the catalysts consists in that the carrier is soaked with an aqueous sodium palladate solution and then the sodium palladate is reduced to the palladium metal with alkaline-aqueous hydrazine.

The catalyst is then washed with water and dried and then topped with potassium acetate.

The finished catalyst advantageously contains, calculated as Metal, 1-10 g Pd, and 1-50 g alkali acetate per liter of catalyst. For the Case that other metals resp.

Metal compounds are used as additives, the finished catalyst can these metals - calculated as metal - e.g. contained in quantities of 0.1 - 10 g. the Raw materials required for the production of the allyl acetate should preferably be free of halogen, sulfur and nitrogen compounds.

The gas entering the reactor can, in addition to propylene, oxygen, Acetic acid and water inert components such as propane, carbon dioxide, nitrogen, Argon.

The oxygen concentration at the entrance to the reactor is advantageous chosen so that one is below the explosion limit of the gas mixture in the reactor lies.

The amounts of acetic acid and water are chosen so that under the reaction conditions the reactants are in the gas phase.

While using small amounts of water, the alkali acetates Gradually leaving the catalyst, this is the case with the procedure according to the invention largely not the case, a renewed addition of the alkali acetates is therefore usually, not necessary or only at longer intervals. If necessary, can the addition can be done, for example, by placing in the hot gas stream before entering the reaction there are small amounts of alkali acetates, e.g. in the form of a dilute solution of alkali acetates in water and / or acetic acid. You can use the solution in the liquid phase directly inject into the hot gas stream and evaporate here.

The reaction is advantageously carried out in tubular reactors. Suitable dimensions of the reaction tubes are, for example, lengths of 4-8 m and internal diameters from e.g.

20-50 mm. The heat of reaction can advantageously by boiling Cooling liquids that surround the reaction tubes on the shell side, e.g. pressurized water, be discharged.

The reaction can be carried out, for example, in such a way that one essentially consists of propylene, oxygen and inerts such as carbon dioxide, Propane, nitrogen, argon, existing cycle gas under pressure through an evaporator that contains acetic acid and water, and that one by the temperature in the evaporator the cycle gas is loaded with the desired amount of acetic acid and water. The gas mixture is then heated under pressure to the reaction temperature and that for the reaction Required oxygen added to prevent any formation and enrichment that may occur to encounter higher boiling compounds in the sump of the acetic acid water evaporator, you can continuously or discontinuously small amounts of the bottom of the acetic acid-water evaporator take off, whereby these may be returned after purification, e.g. redistillation can be.

The resulting from the condensation after separation of the liquid components The gaseous phase consists essentially of unreacted propylene and unreacted Oxygen and formed carbon dioxide and possibly inerts such as propane, nitrogen, Argon. Depending on the temperature and pressure at which the deposition of the liquid Proportions occurs, the gas phase contains certain proportions of the condensable reaction products, such as water, allyl acetate, acetic acid.

The gaseous phase can now be used directly as cycle gas under reaction pressure return to the reaction or to the acetic acid-water evaporator. One can but also further liquid components by changing the temperature and / or the pressure win and return the gas only after separating these liquid components.

The expansion gas produced when the pressure is released from the liquid phase can be compressed and recycled in a suitable manner.

This is a by-product of the conversion of propylene to allyl acetate The resulting carbon dioxide can be fed back into the reaction. To one too To counteract strong accumulation of carbon dioxide, one can use a partial flow of the Remove cycle gas from the return and in this way a constant Carbon dioxide content in the cycle gas, e.g. B. 20 - 30 $, based on the cycle gas, set. After the carbon dioxide has been separated off, the substream can be returned to the cycle gas will.

The upper, organic phase obtained by the process, which is essentially consists of allyl acetate, and the lower, aqueous phase, which consists essentially of Water is now wholly or partially combined and in the liquid phase treated with an acidic catalyst. In this treatment with the acid catalyst you can too the liquid condensate directly without phase separation input.

The hydrolysis of the allyl acetate to allyl alcohol is in the presence of a acid catalyst carried out. For example, you can use liquid mineral acids, such as.

Sulfuric acid. In this case the catalyst is after Completed reaction removed or ineffective by neutralization, e.g. with sodium hydroxide solution made. The hydrolysis of the allyl acetate is advantageously carried out in the presence of an acidic cation exchanger. When the reaction is complete, the catalyst becomes mechanically separated, for example by sedimentation, filtration or centrifugation, and the catalyst-free reaction product is processed by distillation given. The hydrolysis of the allyl acetate can advantageously be carried out in a range from 50 - 150 ° C. You can do the reaction at normal pressure or also perform with increased pressure.

During the hydrolysis of the allyl acetate, an equilibrium is formed, the reaction product consists of allyl alcohol, water, acetic acid and unreacted Allyl acetate. The equilibrium can be achieved by increasing the water-allyl acetate ratio be shifted in favor of allyl alcohol.

The reaction product freed from the catalyst is in a first Distillation column in a top product that boils at 82.8 ° C and that from a ternary azeotrope consists of allyl acetate, allyl alcohol and water, and a bottom product that consists of allyl alcohol, water and acetic acid, separately. The one taken overhead The ternary azeotrope has the following composition, for example: Allyl alcohol 9% by weight, water 20% by weight and allyl acetate 71% by weight. After condensation, it breaks down into two phases. The water phase contains 7% by weight of allyl alcohol, 89.9% by weight of water and 3.1% by weight of allyl acetate and the organic phase consists of 9.5% by weight allyl alcohol, 5% by weight water and 85.5 wt. Allyl acetate.

You can now either use part of the two phases as a return give to the column or only a part of the upper phase as reflux to Column and the lower phase completely add to the hydrolysis.

The upper phase is returned to the hydrolysis of the allyl acetate. The bottom product of the first column is separated into a second column azeotrope consisting of allyl alcohol and water with a boiling point of 89 and a bottom product consisting of water and acetic acid. This bottom product will returned to the acetic acid-water evaporator and here to the propylene-containing one Circulating gas stream evaporates and the reaction of propylene with oxygen and acetic acid fed again.

The hydrolysis of allyl acetate in the liquid phase with, an acidic Cation exchangers can be carried out batchwise or continuously. The continuous working method is used for the technical implementation of the process preferred. One can work here in such a way that one is provided with a stirrer Pressure vessel continuously pumps in product containing allyl acetate and water, reacted in the reaction vessel with suspended catalyst and out of the reaction vessel continuously withdraws a corresponding amount of reaction product. Used a coarse-grained ion exchanger, e.g. B. in a grain size of 0.5 - 1 mm, so you can achieve the separation of the catalyst from the reaction product by that it is drawn off through a frit. But you can also use a finely ground Ion exchangers work and the catalyst-containing reaction product in a centrifuge into a catalyst-free overflow and a catalyst-containing underflow, the is returned to the reaction, separate. When working with a coarse-grained Ion exchangers can also work in such a way that the catalyst is filled into a reaction tube through which the feedstock flows from bottom to top will. The speed of the liquid flow can be adjusted so that the Catalyst layer is more or less loosened, but that in overflow no Catalyst is included, in this procedure you can also use part of the Recycle the reaction product into the reaction and only a partial stream out take from this cycle. It is also possible to connect several reactors in series switch.

Example 1 The production of allyl alcohol by reacting propylene and oxygen will be explained by way of an example, the one described below Try using Fig. 1 described in more detail, In the evaporator V is located the bottom product of column D 2, which consists of acetic acid and water. Through the Vaporizer V is propylene (which is passed through 1) at a pressure of 5 atm directed. The temperature of the acetic acid-water mixture in the evaporator V is 1200. In the evaporator V the propylene flow is corresponding to the vapor pressure with Load acetic acid and water. The mixture of propylene, water and acetic acid flows through power 5 to the superheater H, in which it is heated to 1700. Behind Small samples of the gaseous mixture can be taken from the superheater H. and the molar ratio of water to acetic acid in the feed mixture to the reactor R. Oxygen is added through line 2 before reaction R. The reactor consists of a jacketed and heated with boiling pressurized water Pressure pipe with a length of 2.50 m and an inner diameter of 25 mm. In the reactor there is 1 liter of catalyst in the form of spheres with a diameter of 5 mm. The catalyst consists of silica spheres with an inner surface of 120 m which contains 3.3 g of palladium in the form of palladium metal and 30 g of potassium acetate / Ntr. Catalyst included. Of the The reactor is kept at a temperature of 1680. The gaseous reaction product is under the reaction pressure of 5 atm in the cooler K to 200 cooled, in the subsequent separation vessel S there is a separation into a gas phase and a liquid phase takes place. The gas phase is taken off via line 4. she consists of the unreacted propylene and the unreacted oxygen. she also contains small amounts of carbon dioxide, which is a by-product in the reactor have formed. After removing the carbon dioxide formed during the reaction one can get the unreacted propylene and the unreacted oxygen from electricity Feed 4 back into the reaction via bed 1.

The liquid reaction product from the separation vessel S, which is made of allyl acetate, Acetic acid and water are placed in three stirred autoclaves in series A 1, h 2 and A 3 are pumped. In each of these stirred autoclaves there are 100 g more acidic Cation exchanger (polystyrene sulfonic acid, crosslinked with 8% divinylbenzene, H-form). The conversion of the liquid reaction product from the separation vessel S into the stirred autoclave A 1, A 2 and A 3 are carried out at 1000 and a pressure of 3 atmospheres in the liquid phase. The reaction product, free of catalyst, is withdrawn from the autoclave via frits. The catalyst-free reaction product from the autoclave A 3 is in a distillation column D 1 separated into a top product boiling at 830 and a bottom product.

The top product is returned to autoclave A 1 via output 6. The bottom product of the column 1 is in the column D 2 in a boiling at 89 ° Top product and a bottom product broken down. The top product consists of the azeotrope from allyl alcohol and water. It is passed over from the system as the desired end product Power 3 pulled out.

The bottom product of the column D 2 is via line 7 into the evaporator V returned.

A dilance test of 500 hours was carried out.

During this time, the feedstock was analyzed the superheater H constantly the ratio of water to Acetic acid im Controlled feedstock, and it was by adding small amounts of water to the Feed product of the evaporator Y has a ratio of (7-2) moles of water per 1 mole Acetic acid adjusted. Within the 500-hour test, a total of 46.2 kg was gained Propylene and 15.2 kg of oxygen reacted. At the top of the column 2 were calculated obtained on anhydrous allyl alcohol, 58 kg of allyl alcohol.

This corresponds to the equation propylene + 1/2 oxygen = Allyl alcohol with a yield of 90 based on propylene and 52.6 based on on the oxygen used.

Example 2 The procedure is as in Example 1, but instead of the stirred autoclave A1, A2 and A3 uses two reaction tubes with an ion exchanger (Polystyrene sulfonic acid, cross-linked with 8 divinylbenzene, H-form) with a grain size of 0.5 -1.2 mm are filled. Flows in through the first reaction tube from bottom to top 105 and a pressure of 3 atü a mixture of liquid reaction product from the Separation vessel S, from top product from column D1 and returned reaction product from the first reaction tube. The ratio of return to fresh product and Top product from column D1 is chosen so that the two phases are at room temperature are homogeneously mixed. According to the amount of product supplied from the separation vessel S and top product from D1, reaction product is taken off behind the first reaction tube and at a pressure of 3 atm and a temperature of 100 ° through the second reaction tube passed from the bottom to the top and then fed into the distillation column D1.

Within a 500-hour test, 46.0 kg of propylene and 15.0 kg kg of oxygen converted. Calculated on anhydrous allyl alcohol, 58 kg of allyl alcohol were calculated obtain.

Claims (9)

claims: 1) Process for the production of allyl alcohol, characterized in that that one propylene, oxygen and acetic acid in the presence of water in the gas phase at temperatures of 50 - 250 ° over palladium catalysts, the gas-ready Reaction product condenses, the. Ini. essentially from allyl acetate1 acetic acid and water existing condensation product wholly or partially with an acidic Catalyst treated in the liquid phase at temperatures of 50 - 15 ° C and that reaction product obtained in this way after removal of the catalyst in a first Distillation into an essentially from a ternary azeotrope of allyl acetate, Allyl alcohol and water and an overhead product consisting essentially of acetic acid, Allyl alcohol and water existing bottom product separates, and that the top product from this first distillation in whole or in part into the treatment with the acidic Recycle catalyst, and that the bottom product from the first distillation in a second distillation into an essentially from the azeotrope of allyl alcohol an overhead product that requires water and an essentially composed of acetic acid and water existing bottom product separates, and that the bottom product from the second distillation in the reaction of propylene with oxygen and acetic acid and given if the water is known per se from the azeotrope of allyl alcohol and water Procedure removed. 2) Method according to claim t), characterized in that the palladium catalysts Additions of alkali acetates or alkali compounds to the 8iC. under the reaction conditions at least partially in Alkaliao-etat. convert, included 3) Process according to claim 1) and 2), characterized in that the palladium catalyst, calculated as metal, 1 - 10 g Pd and 1 - 50 g alkali acetate per liter of catalyst contains, 4) Method according to claim 1) to 3), characterized in that the gaseous reaction product is cooled under pressure to a temperature below 500 and separates the resulting liquid product from the gaseous product. 5) Method according to claim 1) to 4), characterized in that a ratio of 5-20 moles of water per mole of acetic acid is established in the feed product and selects such a reaction temperature in the range of 50-2500 that 80-100 % of the acetic acid are converted in a single pass. 6) Method according to claim 1) to 5), characterized in that an acidic cation exchanger is used as the acidic catalyst, 7) Procedure according to claim 1) to 6), characterized in that the treatment of the condensation product with the acid catalyst in continuous operation in several series-connected Performs reactors. 8) Method according to claim 1) to 7), characterized in that fresh water is used to maintain the water content in the entire reaction system in the hydrolysis of the allyl acetate. 9) Method nach.Anspruch 1) to 8), thereby gekenxazeiehnet that in the first distillation, the top product is condensed into an organic upper and separating an aqueous lower phase, andthat part of the upper phase is used as Return to the column and the lower aqueous phase directly; for hydrolysis there. L e r s e i t e