DE937469C - Process for the production of silica-alumina catalysts - Google Patents

Description

Process for the production of silica-alumina catalysts The invention relates to a process for the production of Ki@es.elsäure-Aluminiumoxyd- catalysts, which are suitable for the splitting of hydrocarbons.

There are already various processes for the preparation of I <i @ eselsäure-aluminum oxide catalysts: ators suggested. According to one method, one poses by the action of vinegar fringes on aluminum amalgam, it washes an aluminum oxide sol with considerable amounts of water free of foreign salts and mixes it with, an IGes, elsäureso # l; that one through treatment obtained from a sodium silicate solution with a base exchanger, and dries finally the mixture. It has also been proposed by hydrolysis of aluminum alcoholate to produce an aluminum oxide sol, which .then with other catalytic substances can be mixed .. According to one embodiment of this method, mixing is carried out the alumina sol with a silica sol, which is preferably formed by cation exchange was obtained from a silicate solution, and then falls from this sol mixture mixed alumina-silica gel.

It is also known to produce silicic acid hydrosols by reacting sodium silicate and sulfuric acid. After the Kleselsäuirehydrosol has solidified to a hydrogel, aluminum sulfate or alum is added. The gel is then converted into aluminum oxide by adding aqueous ammonia. According to one method, the silica hydrogel is washed free of sodium sulfate before the alum is added, while in another method it is washed out only after the alum has been added. But in both cases it is necessary to wash out the catalyst. In all of these cases, however, the manufacture of catalysts is time consuming. Expensive systems are necessary and the floor space required is comparatively large. The maintenance costs of the apparatus increase in relation to the costs of the initial equipment. In addition, the yield of silica fringes and clay from the raw products used is too low. Ziur1 example, the losses with the known methods are: procedure No. x I No. 2 Clay amount spent. . . 100 0/0 100 0/1 Yield. . . . . . . . . . . . 610 / a 92% Loss ............... 390/0 8% Silica amount spent ... Zooo / 0 Zooo / 0 Yield. . . . . . . . . . . . . 850/0 930/0 Loss . . . . . . . . . . . . . . . 15% 70 / . 0 In these processes described above, sodium silicate, sulfuric acid, aluminum hydrate and ammonia are used as raw products.

According to the invention, a mixed gel of silicon oxide and aluminum oxide prepared by first hydrolyzing aluminum alcoholate to an alumina gel slurry wins and this with an aqueous slurry of finely divided silica gel mixes. This latter gel is made from a sodium silicate solution through cation exchange won, whereby initially a silicon dioxide sol is formed, whose pl, one on q. until 7 sets to accelerate freezing. During the freezing process, that becomes Sol vigorously stirred, causing the gel in the form of a slurry of tiny silica particles fails. Now stir the aluminum oxide and silicon dioxide gel slurry together, separates the mixed gel and dries @es.

This method offers a considerable advantage over the previous ones well-known processes, as one here is extraordinarily rhyme and correspondingly pure brine Gels of the oxides in question are obtained without washing out soot: further falling the silica gel slurry as a result of controlling the pH of the silica sol and of vigorous stirring during the sol-gel conversion in an extraordinarily fine manner So that the previously necessary, very expensive mechanical comminution comes in omission.

The costs for materials and equipment are included in the The method according to the invention is considerably lower, if only because it is not washed out. For a system of around 40,000 kg per day, the space requirement of the building in which the facility for silica and alumina production is housed, for example 15 to 200/0 less than the two methods mentioned above. You win more than 95% of the initial amount of silica and alumina in the form of catalyst.

According to the invention, the silicic acid hydrosol z. B. from an im Commercially available sodium silicate, or another. Silicate solution through base exchange z. B. made with a phenol or styrene copolymer exchanger, while the clay is obtained by hydrolysis of aluminum alcoholate.

In the drawings are two. Appendices shown that see how to carry out of the method of the invention.

Fig. I shows a system, both as Alumittv.umoxydkompente one Alu-miniumoxyds, mud is used: and Fig. 2 shows a system in which the aluminum oxide component a hydzosol is used.

According to FIG. 1, metallic aluminum in the form of scrap, ingots, chips or turnings is introduced into the reaction vessel through the supply line 12. The catalyst, e.g. B. mercury salts, iodine, aluminum halide, preferably mercury chloride, fed through pipe 16 essentially anhydrous aliphatic alcohols are introduced. Although water-soluble alcohols, such as ethyl, isopropyl or tertiary butyl alcohol, can be used for this purpose, the water-insoluble alcohols are preferred. ° There are preferably C5 and higher aliphatic alcohols, z. B. amyl alcohol, which are liquid at the reaction temperature because they are less soluble in water and can be recovered more easily for reuse. Mixtures of such aliphatic alcohols, e.g. B. use a mixture of isomeric amyl alcohols, commercially available. If aliphatic C5 alcohols are used alone, the reaction vessel is usually operated at about 0.35 to 1.75 atmospheres, the pressure being regulated by means of a valve built into pipe 17.

In some cases, a carbon or a hydrocarbon fraction, z. B. a petroleum distillate, from a boiling range of 93 to 26o ° or higher water-insoluble alcohol can be added. It can also be hydrocarbons, such as Heptane, octane and octane mixtures can be used in the reaction vessel. The added one Hydrocarbon acts as a dilution agent and supports the steering the reaction between alcohol and aluminum. The hydrocarbon additive facilitates also the separation and recovery of the alcohol after hydrolysis of the aluminum alcoholate has taken place. In addition, the hydrocarbon serves as a. Solvent for that in the reaction formed aluminum alcoholate. If you put a mixture of aliphatic C5 alcohols together with: a pure hydrocarbon, such as Heptane, or with one If the hydrocarbon fraction is used, the amount of alcohol is reduced to: approx two thirds opposite: that one. Amount needed when alcohol is the only one Is liquid other than 1-19G12, which is fed to the reaction vessel.

In general, it is necessary to keep the mixture in the reaction vessel i o to heat to initiate the reaction between the aluminum and the alcohol. In the drawing, a steam-circulating heating coil 18 is shown as the heating device, but other heating devices can be used. The contents of the reaction vessel io is initially set to: a temperature of about 93 to 149, expediently about i 2c) ' heated. You can use steam or other heating means. After the reaction is initiated, the reaction rate increases very rapidly, so that cooled must become. The cooling can take place in that one passes through the pipe coil 18 : conducts a coolant in place of a heating medium to cause a temperature rise avoid. The reaction vessel is preferably held during the reaction: one -Temperature between 93 and about 149 °. You can also use several reaction vessels, when larger amounts of catalyst are produced in a steady process should.

Aluminum and alcohol react with one another to form aluminum alcoholate and hydrogen. The hydrogen gas and the alcohol and hydrocarbon vapors flow through the pipe 15 into: the reflux condenser 19, from which the condensed Liquid and the hydrogen are conveyed into the separator 2o. The essentially pure hydrogen is drawn off through the pipe 17 to my collecting tank and; separately recovered. A relief valve can be provided in pipeline 17 will. The condensate is through pipes 21 and 16 into the reaction vessel i o -returned and. promotes cooling in this: this reaction material.

Aluminum alcoholate and liquid alcohol mixture are pumped 25 withdrawn in pipe 24 from the reaction vessel io #. This mixture is made by Pipeline 26 is supplied with water to hydrolyze the alcoholate. The mixture is conveyed in: the mixing nozzle 28 or another mixing device to water and alcoholate to mix thoroughly. The mixture of aluminum hydroxide leaving the mixer 28, Alcohol, water, and optionally hydrocarbons, are fed into settling zone 32 promoted, in which the alcohol-hydrocarbon mixture the upper and the the Water containing alumina particles in the form of a slurry forms the lower layer forms. This sedimentation vessel can be heated by means of the heating coil 34 or other heating devices , to about 21 to 99 °: be heated.

The upper layer of alcohol-carbon dioxide is made by pipeline 36 withdrawn and by means of the pump 38 through the heat exchanger 4o for indirect Exchange promoted in order to preheat the mixture, and further in: a dewatering or Distillation tower 4z to water in the form of an azeotropic mixture or a solution to remove amyl alcohol and water. Heat is given to tower 42 by the heating coil 44 or other heating devices. This is where the contents of the tower become heated to about 127-138 °.

The vapors of water, alcohol and carbon: -hydrogen * flow through Pipeline 46 and cooler 48 from. The condensate is conveyed into the separator 52 and separates in this into an alcohol-hydrocarbon mixture as the upper layer 53 and water as the lower layer 53 '. The alcohol-hydrocarbon mixture will withdrawn through pipeline 54 and returned to the drainage tower 42. water is withdrawn through pipe 56 and into pipe 26 in the return of the mixing nozzle or hydrolysis zone 28 is fed back. The dehydrated alcohol-hydrocarbon mixture is by means of pump 57 'from the bottom of the tower 42 through pipe 57, the heat exchanger 4o and pipeline 16 fed back to the reaction vessel i o. When passing through the heat exchanger 4o is used to cool the liquid and that through pipeline 36 the tower 42 flowing mixture is heated.

From the bottom of the settling zone 32, a pump 59 flows into pipeline 58 a suspension of the alumina particles in water is drawn off in the form of a slurry and fed to the upper part of the stripping tower 62. Its content is determined by the Heating coil 64 heated to 93 to 10 4 '. The tower can be designed as a packed tower be. In the supply line 58, the heating element 65 is installed, which also bypassed by the secondary line 65 'can verden. In the tower 62 the alcohol-hydrocarbon mixture is separated from most of the water by taking the former mixture in vapor form flows through pipe 66, but some water vapor is entrained. the Pipeline 66 is equipped with: a cooler 68 in which the vapors are cooled and from which the condensate is conveyed into separator 72 by being drawn into : separates an upper alcohol-hydrocarbon layer and a lower water layer. The alcohol-hydrocarbon layer is drawn off in pipeline 74 by means of pump 76 and fed back to the dewatering tower 42 through the heat exchanger 40. From the The bottom of the separator 72 is at least one by means of a pump 79 with pipeline 78 Part of the water is drawn off and fed to the upper part of the stripping tower 62. Some of the water can be removed from the separator through pipeline 77 by means of pump 8i 72 and feed it back into the pipeline 56 to the mixing nozzle or hydrolysis zone 28.

Through pipeline 82 from the bottom of the stripping tower 62 is the aqueous Slurry of alumina with about 3 to 25 weight percent A120g withdrawn and conveyed through pipeline 84 into the stirred vessel 86, or they can be conveyed through pipeline 88 and filter device 92 conduct to remove some of the water, and through pipe ducts 94 can be withdrawn from the system. Part of the whole Water withdrawn through conduit 94 can pass through conduit 56 to the hydrolyzing zone 28 can be returned for reuse. The alumina particles in the filter cake are then conveyed into the stirring vessel 86 by means of a conveying device 95.

The silicic acid hydroisole is replaced by percolates of alkali silicate, in particular Natriuun'-silica.t, produced by an ion exchanger. Acid-genenderbane @ organic Cation exchangers are known, they can be made from sulphurous acid-treated coal, Wood, crude oil scrap or lignite or on various synthetic resins be produced, e.g. B. the resins made from polyhydric phenol and formaldehyde Tann; "- formaldehyde and from phenolsulfonic acid-formaldehyde.

The concentration of sodium silicate should preferably be above 29 g Si02 per liter lie. At concentrations above about 225 g Si02 per liter, the Sodium silicate solution too - viscous and the ioxnene exchanger to remove Sodium not effective enough. The process is below about 29g Si02 per liter no longer economical.

In general, the supply of sodium silicate is interrupted when the pH of the product exceeds a predetermined value. The exact value of this pH depends somewhat on the origin and purity of the silicate. For example was when using a commercially available silicate, the feed to the ion exchanger interrupted when the pH of the product reached 3. The exchanger is then through dilute sulfuric acid or hydrochloric acid is regenerated and then the acid is regenerated with water -washed. Before the acid regeneration, it is advisable to rinse with water to remove the remaining Remove residues of silica hydrosol. The wash water can in turn be used for dilution the sodium silicate solution fed to the exchanger can be used.

In some cases it may be useful to have more than one reaction vessel to use in one treatment stage and the solution through several interconnected Conduct reaction vessels in the same way as if only a single exchange vessel would exist.

The diluted sodium silicate solution with a content of 29 to 225g SiO2 per liter is passed through pipe 98 through exchanger 102. That outflowing silicic acid hydrosol has a concentration of. -about 3 to 2o percent by weight Si02, and such a pü that it does not exist for a period of 1 hour or more solidified into a hydrogel. It is extracted from the heat exchanger 102 through pipeline 104 withdrawn and fed into the mixing nozzle io6, which through pipeline io8 in sufficient Amount of ammonium hydroxide or anhydrous ammonia is added to adjust the pH of the To increase silica hydrosol to such a value that it in a time of solidified to a hydrogel from a few seconds to 5 minutes. In a critical PH range - from about 4 to 7, the silicic acid hydrosol solidifies in a time between a few seconds and about 5 minutes to the hydrogel. Becomes the pH of the silica hydrosol increased to about 8, at some concentrations of silica gelation takes hours or even days. This is the peculiar property of silica hydrosol used to solidify it quickly and thereby an excellent gap contact to obtain. Silicic acid hydrosol and ammonium hydroxide are supplied by pipeline 112 conveyed raw from the mixing nozzle into the stirring vessel 86 and in this while stirring gewaltexL This mixing vessel is about two thirds full. Then you lead the Stream of the silica hydrosol into another, not shown, stirred vessel, which has the same dimensions as stirred vessel 86. The contents of the stirred vessel 86 is then stirred until all particles of the silica hydrosol form hydrogel are rigid. By stirring the lües, els acid hydrogel in the state of its formation wind formed a slurry that can be conveyed by pumping. After that entire Kiiesel @ säumehydrosol is converted into hydrogel, the stirred vessel 86 through conduit 84 a calculated amount of an alumina slurry was added. Continue stirring the vessel 86 until the clay and silica are thorough are mixed.

The stirred vessel 86 can -with a vertical, centrally arranged Be equipped with agitator shaft, which has one or more horizontally mounted agitator arms wearing. Instead of adding all of the silica seams before adding clay, you can this measure can also be carried out in stages, by initially adding a part. the Silicic acid, then the required clay, then again further silicas and again more alumina are added alternately until the stirring vessel 86 is filled. .

The silica fringing sol leaving the Awstaws.che r i o2 should no longer be as 0.5% soda (Na20), expediently not more than about 0.2% soda (dry weight) contain.

Instead of mixing all of the ammonium hydroxide with the kvesic acid hydrosol in the mixing nozzle 106, all or part of the ammonium hydroxide can be conveyed through the pipe 114 into the stirred vessel 86. The pipe 114 can also be used to introduce additional ammonia or ammonium hydroxide after the alumina slurry has been added to adjust the pH of the mixture to the same value as the final value of the silicic acid hydroisol alone. The slurry of Kveselsäurehydrogel and alumina is then withdrawn by means of pump 8 i 1 through conduit 116 and the Rührgefäß86 Zerstäuberi22 supplied which is disposed in the upper part of the container 124th The container 124 contains a liquid which consists of a petroleum fraction at a temperature of about 66 to 93 ° as the upper layer 126 and water as the lower layer 128. As a result of the atomization at 122, small droplets of silica-alumina gel particles are formed, which fall into the heated oil bath i26 and are aged in it. The particle size of the dry product can range from microspheres to the size of pearls.

The small spherical solid gel particles sink into the aqueous one Layer 128 held at about 66 to 121 'to keep the oil from the particles to separate the hydrogel. The slurry of kvesic acid-alumina particles becomes withdrawn through conduit 132 from the aqueous layer 128 and the filter device 134 supplied. The filtered particles are passed through conduit 138 into the dryer 136 conveyed and withdrawn from there in pipeline 142.

The container 124 can be bypassed by the secondary line i 17. Filter 134 removes some of the water from the hydrogel. The filter cake will dried in dryer 136, after which the catalyst particles are on suitable Size ground. You can also feed the hydrogel directly into the dryer instead feed it through pipe 117 to the filter.

The separated water is removed from filter 134 through conduit 144 and conveyed by means of pump 146 through the heat exchanger 148 in order to prevent it from being supplied again in the aqueous layer 128 of the container 124 to be heated.

Oil is withdrawn from the oil layer 126 through pipeline 152 and conveyed into the drain tank 156, from which it is returned to the oil layer 126 of the container 124 by means of pump 158 after reheating in the heat exchanger 162 in pipeline 164. In this case, the heat exchanger 162 can be bypassed with the entire circulating oil or only a part of it by means of secondary line 166. At 168, replacement for used oil can be supplied.

By changing the quantitative proportions of alumina slurry and silica hydrosol, which are introduced into the stirring vessel 86, may contain the alumina can be changed in the dried silica-alumina catalyst. He should be between about 5 to 70 percent by weight, preferably from 10 to 50 percent.

Fig. 2 shows an apparatus for implementing another embodiment of the process for the production of silica-alumina catalysts. This method is more expensive than the method according to FIG. i, but better ones can be achieved in this way Manufacture catalysts. In Fig. 2, 172 designates a reaction vessel which corresponds to the reaction vessel i o of FIG. Metallic aluminum is made by Pipe 174, catalyst through pipe 176, and anhydrous alcohol Pipeline 178 introduced. A heating coil is expedient in the interior of the reaction vessel 182 is provided, and a hydrogen outlet is arranged at 184. The anhydrous Aluminum alcoholate is peptized with acetic acid before it is hydrolyzed, so that one does not get an alumina slurry, as in the procedure according to Fig. i, but an alumina hydrosol. When working, a will also be more expedient Alcohol used alone instead of an alcohol-hydrocarbon mixture.

1Y by means of pump 187 are out of the reaction vessel through pipe 186 172 Aluminum alcoholate and excess alcohol deducted. This reaction material Glacial acetic acid is added through pipe 188 as a peptizer. The resulting Mixture is fed into the mixing nozzle 192 and the ingredients thoroughly together mixed. More than one mixing nozzle can be provided, and one can use the acetic acid partly, z. B. half, the first mixer and the rest of the second mixer to add. You can also use all or part of the acetic acid together with introduce the water, which in the hydrolysis stage to be described below is needed. The amount of acetic acid introduced can be between i: i o and 2 : i parts by weight of acetic acid to clay vary.

The mixture exits mixer 192 through conduit 194 and becomes mixed with water from pipe 196. This mixture now flows further into the Mixing nozzle 198, which represents the hydrolysis zone for the alcoholate. The amount of water used in the hydrolyzing zone can range from about 99: i to about 94: 6 parts by weight of water to clay. Peptization and hydrolysis at about 18 to 10 4, expediently carried out at 82 °. The hydrolyzed mixture is now conveyed in pipeline 202 into the stripping tower 204, which with the heating coil 2o6 is equipped and acts in the same way as the tower 62 of FIG. The vapors flowing out of the stripping tower through pipeline 2o8 get into the cooler 212, the condensate from it in the separators 214. Through pipe 216 the separated alcohol is drawn off from this and fed into the drainage tower 218 promoted. A portion of the aqueous layer is refluxed through conduit 222 fed back to the tower 204, the remaining part through pipeline 224 and pipeline 196 returned to hydrolysis.

The product of the dehydration tower containing the dehydrated alcohol 218 is returned through pipe 226, heat exchanger 228 and pipe 178 fed back to the reaction vessel 172. The top product of the tower 218 flows through Pipeline 232 and cooler 234 in the separators 236. This is from the upper Layer of alcohol in the circuit through pipe 23 8 to the tube 218 as reflux again supplied and water from the aqueous layer through pipes 242 and 196 to the Recirculated hydrolysis. If there is excess water available, this can can be withdrawn through pipe 243.

Tanerdehydrosol with about 3 to 25 percent by weight A1203 is withdrawn from the bottom of the tower 204 through pipe 252 and conveyed into the storage container 254, from which it is guided through pipe 256 into the mixing nozzle 258. The stripping urin 204 of FIG. 2 can be used, like the tower 62 of FIG. 1, to concentrate the alumina hydrosol.

The way in which the silicic acid hydrosol is made is essential the same as with the working method according to -Fig. i. Passes through pipe 262 one dilutes sodium silicate, cat over the acid regenerable placed in container 264 Cation exchanger, and the resulting silicic acid hydrosol through pipeline 266 into the mixing nozzle 268, in which a sufficient amount of Ammonilunhydroxyd 'or ammonia is added to bring the PH down to about? 4 to 7 increase. It forms the silica hydrosol at a time. from a few seconds to about 5 minutes a hydrogel. Ammonium hydroxide is fed in through pipe 272. As with the Operation according to FIG. I can. All or part of the ammonium hydroxide or ammonia can be conveyed directly into the stirred vessel 27-6 through the pipe 274. 'The small particles of the silica hydrogel. leave the stirred vessel 27'6 Pipeline 278 and are in the above-mentioned mixing nozzle 258 thoroughly with alumina hydrosol mixed. 'This mixture is now through pipe 282 into the stirred vessel 28-4 promoted, - to which a small amount of ammonium hydroxide is added through pipe 287, to solidify the alumina hydrosol to form an alumina gel. In a mixing vessel. 284 will the mixture was stirred thoroughly until a homogeneous mass was obtained. Instead of the alumina hydrosol To add the silicic acid hydrosol and then the ammonia or ammonium hydroxide one can also add the ammonia or ammonium hydroxide to the alumina hydrosol and then add this mixture to the Keselsäuxehydrogel. ' The former Method is preferable.

As shown in Fig.2, the slurry of the particles is from. Alumina and pebbles from the stirred vessel .284 through pipe 288 into the spray dryer 292 promoted, in which tiny dry spheres of silica-alumina catalyst .be obtained. The partially dried particles are then sprayed in the dryer 292 dried and withdrawn through pipe 296. By using alternating Quantities of silica and alumina hydrosol can be used in catalysts from 5 to 70 - Percentage by weight of clay, the remainder being leselic acid.

Instead of spray drying, when working according to Fig. 2 also the method of oil drying according to zig. i used. Vice versa In the case of the method of operation according to FIG. 1, spray drying can also be used instead of oil drying according to. Fig. 2 apply.

Claims (1)

PATENT CLAIM: Process for the production of IGes @ elic acid Using alumina catalysts of ion exchangers, characterized in that da: ß a) by hydrolysis of aluminum alcoholate an aqueous sus- pension made from hydrated alumina is placed :, b) a suspension of the smallest Silica hydrogel particles in an aqueous Medium is created by treating a diluted. Sodium silicate solution with a acid-regenerated cation exchangers, set the obtained silica sol to pH 4 up to 7 and constant stirring during the stamens ,. c) the suspensions. of hydrating tem aluminum oxide and the suspension of the Silica hydrogel particles mixed and that obtained mixture is stirred to a sus- pension of Yieselsäur-e-Aluminumoxyrl.-Teil- to obtain the secluded and to be dried. Referred publications: French patent specification No. 968879, 952 i9 ?; German patent specification No. 82o893.