DE2513683A1 - CATALYSTS FOR THE MANUFACTURE OF ISOPRENE AND THEIR USE - Google Patents

Description

The invention relates to the production of isoprene by reacting isobutylene with formaldehyde Catalysts containing 1. silver ions, 2. aluminum oxide and 3. silicon oxide.

In response to the increasing demand for isoprene as a starting material for the production of synthetic rubbers and the like, it is desirable to easily use isoprene in high purity and to produce in good yield. For this purpose, the direct production (one-step process) recommended on the condensation between isobutylene and formaldehyde due to the simplified working method. Various catalysts have been used for this one-step process suggested, e.g. aluminum oxide, silicon dioxide-aluminum oxide, cadmium phosphate, silver oxide, Phosphoric acid-chromium oxides (or hydroxides), phosphoric acid-manganese oxides (or -hydroxides), silicon dioxide-antimony oxide and silica-bismuth oxide.

However, these known catalysts have the following disadvantages:

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1) The conversion of formaldehyde (the ratio of the amount of formaldehyde converted to the amount of formaldehyde used) is insufficient.

2) The selectivity of the conversion of formaldehyde to isoprene is not high. :

3) Since the activity of the known catalysts decreases rapidly due to carbon bonds, which are inevitably formed during the condensation reaction, the conversion of formaldehyde is considerably lower in the course of the reaction time. It is therefore necessary the regeneration of the catalysts by burning off the carbon compounds in a very short time To repeat time intervals.

A) The catalytic activity decreases with the repetition of the regenerations because of the heat resistance of the catalysts is bad, so that the life of the catalysts is short. '

In an effort to eliminate the aforementioned disadvantages and provide an advantageous method for large-scale Production by isoprene according to the "one-step process" to develop, it was surprisingly found that solid catalysts, the 1. silver ions, 2. Contain aluminum oxide and 3 · silicon oxide and furthermore, as a fourth component, at least one oxide and / or ion of one or more transition metal elements, alkaline earth metals, boron, thallium, tin, lead and phosphorus, these elements being present in a certain ratio, the above-mentioned Do not have disadvantages.

With the solid catalysts according to the invention thus isoprene is formed in high yield and high purity. Furthermore, the solid catalysts have good ones Heat resistance and therefore a very long life

_ 3 -

duration. \

The invention thus relates to the catalysts intended for the large-scale production of isoprene with the properties mentioned as well as a large-scale feasible process for the production of isoprene using these catalysts.

The solid catalysts according to the invention can be prepared by adding or mixing together a silver component with the aluminum component and silicon component and Calcining the resulting mixtures are prepared.

The silver-ammine complex ion, silver nitrate, silver acetate, silver cyanide, silver carbonate, silver fluoride, silver chloride and silver sulfate are, for example, suitable as silver components. As such, "all silver compounds can be used which can be converted into the silver ion by reaction or calcination in the presence of silicon oxide and / or aluminum oxide. However, the silver-ammine complex ion is generally preferred. \"

Examples of suitable silicon components are Silicon oxide (e.g. silica xerogel, silica hydrogel, Silica sol and crystalline silica), silica salts (e.g. potassium silicate and sodium silicate), silicon halides (e.g. silicon tetrachloride and silicon tetrafluoride), Silicic acid esters (e.g. tetraethylorthosilicate), other compounds that are formed by calcining easily converted into silicon dioxide, and Don minerals containing these compounds. That Silica, which is one of the constituents of the catalysts according to the invention, is preferably poor Alkalis, especially sodium. For example, the proportion of the alkali component, calculated as sodium ion, is preferably not more than 2% by weight, based on the

Silicon oxide. “When the catalyst is used, for example, by the ion exchange process described in detail later is to be produced, it is appropriate to use a silica xerogel. The usage of Silica hydrogel or silica hydrosol enables easy Mix with the active ingredients so that more homogeneous catalysts are obtained.

Aluminum compounds are used as the aluminum component which can easily be converted into aluminum oxide by calcining or hydrolysis, e.g. aluminum hydrate, aluminum chloride, polyaluminum chloride, aluminum sulfate, aluminum fluoride, aluminum isopropoxide, Aluminum hydroxide and various forms of aluminum oxide (e.g. aluminum oxide xerogel, aluminum oxide hydrogel, Aluminum oxide hydrosol and crystalline aluminum oxide).

It is also possible to use compounds that contain two or more elements in the catalyst of the present invention should be included. Examples of such compounds are silver aluminate, the one Connection of aluminum and silver, and aluminum silicate, a compound of aluminum and silicon.

The three components mentioned are prepared by mixing or reacting with one another by methods known per se put together. For example, a method in which an aqueous solution or colloidal aqueous solution of the silicon component with an aqueous one Solution of the silver component and an aqueous solution or colloidal aqueous solution of the aluminum component mixed and. the mixture then subjected to gel formation or precipitation with an alkali or an acid will; a process in which water-insoluble members of the components are converted into water-soluble components immersed or an ion exchange with the latter

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be subjected, or mechanical-chemical mixing processes in which kneaders, ball mills or others Apparatus are used.

This mixing or compounding can be done in any order, however, for example when using the ion exchange method, the silver ion is preferably added last.

If not silicon oxide, but a different silicon component or not aluminum oxide, but a different one Aluminum component is used, it is expedient that after the two components have been combined, one Hydrolysis is carried out with an aqueous solution of a mineral acid (e.g. hydrochloric acid or sulfuric acid) and / or the mixture is heated in the presence of oxygen. ';

The substances which are present in addition to the components of the catalysts according to the invention, e.g. nitrate and chlorine ions as well as the alkalis, acids or salts used in gel formation or hydrolysis preferably all removed by washing with water or otherwise. One way to remove of these undesirable impurities is decomposition or sublimation by heating.

In the catalysts according to the invention, the atomic ratio (ratio of the numbers of atoms) is Aluminum to silver about 1:10 to 30: 1, preferably about 1: 3 to 20: 1. The weight ratio of alumina to silicon oxide is about 1: 5000 to 2: 1, preferably about 1: 1000 to 1: 1.

The pooled in the manner described components are then at a temperature of about 100 ° to 1400 ⁰ C, preferably about 300 ° to 900 ⁰ C, calcined. That

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Calcining is usually carried out in the presence of air, inert gases (e.g. nitrogen and carbon dioxide), oxygen, Hydrogen, water vapor or mixtures of these gases. Has the presence of water vapor results in more effective activation and enables lower activation temperatures to be used. the Calcination time is about 1 to 24 hours, preferably about 2 to 10 hours. Since the condensation reaction to produce isoprene from isobutylene and Formaldehyde is usually carried out at a temperature above about 180 C, it is not necessary It is essential to carry out the calcination before using it for the reaction.

The solid catalysts prepared in the manner described contain silver ions, aluminum oxide and a silicon component. i

When using the solid catalysts of the invention the following can be assumed for the reaction to produce isoprene from isobutylene and formaldehyde become: The silver ion is effective as a mild acid and forms an active site for the isobutylene, the one is mild base; the silver ion mainly affects the isoprene yield. The silver ion as such is so thermally unstable that it has to be applied to a support such as silica. In the mixture of However, silver ion with silica, the stability of the silver ion is still poor, and the silver ion becomes Slightly reduced to silver metal in the course of the reaction. In addition, the silver ion takes care of it when it is dried or heated etc. to be converted into oxides, e.g. silver oxide. In the presence of aluminum oxide, the SiIb is ionized as such extremely stable. For example, even then the silver ion does not turn into silver oxide or silver metal transformed or decomposed when such a system is on

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800 ⁰ C is heated. It was also found that the silver ion is not reduced even in the course of the reaction. ;

The solid catalysts according to the invention can also contain the oxide and / or ion as a fourth component one or more elements from the transition elements (e.g. chromium, iron, cobalt, nickel, copper, Molybdenum, tungsten, zinc, zirconium, lanthanum, cesium and titanium), alkaline earth metals (e.g. beryllium, magnesium, Calcium, strontium and barium), boron, thallium, tin, lead and phosphorus. The incorporation of the fourth component or the fourth components does not stabilize the silver ion only further, but leads to improvements in the heat resistance and life of the catalysts.

The fourth component mentioned above can be added to the catalyst to be produced in various forms which can easily be converted into the ion and / or oxide by heating or hydrolysis, for example as nitrate, chloride, sulfate, salt of an organic acid or ammonium salt of the corresponding elements . The weight ratio of the element or elements of the fourth constituent to silicon dioxide can be within a wide range. In general, the proportion is not more than 20% by weight, preferably not more than 10% by weight. The fourth component is generally added to the solid catalyst according to the invention prior to calcination. \

The isoprene yield can be increased further by adding the fourth component to the catalyst.

The production of isoprene using the solid catalysts according to the invention can be carried out by Condensation reaction between isobutylene and form

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aldehyde. The process as such can be carried out in a manner similar to a known process for catalytic Condensation of isobutylene and formaldehyde can be carried out. Here, the molar ratio of Isobutylene to formaldehyde can be varied depending on the reaction conditions, however Isobutylene is preferably used in excess, for example of more than 3 moles per mole of formaldehyde.

The two starting materials are preferably reacted in the vapor phase at a temperature lying above 180 ⁰ G, preferably at a temperature of about 200 ° to 400 ⁰ C in the presence of a catalyst according to the invention. The reaction can be carried out under normal pressure, reduced pressure or increased pressure, but taking into account the yield of isoprene, it is advantageous to work under slightly increased pressure. The amount of the gaseous reactants fed in (space flow rate) is generally about 1 to 1000 mol, preferably about 10 to 500 mol / hour / l of catalyst.

When carrying out the method according to the invention, certain gaseous substances can not cause the reaction disturb, are added to the reaction system as a diluent or an extender of the starting materials. Suitable inert gaseous substances are, for example, water vapor, methanol, nitrogen, air and carbon dioxide and paraffinic hydrocarbons (e.g. methane, ethane and Propane). The presence of water vapor is particularly desirable in order to avoid a sudden drop in activity to prevent the catalyst and to increase the selectivity of the converted formaldehyde to isoprene. In in this case the weight ratio of water to formaldehyde is preferably about 1: 4 to 20: 1.

Since in the reaction described above, the

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The heat of reaction is relatively low, there are no special precautionary measures for regulating the temperature of the catalyst bed required. Hence, an adiabatic reactor certainly serves the purpose.

If the activity is of the solid catalyst in the course of a long reaction time like with regard to conversion and selectivity, the catalyst is regenerated by in the presence of air, oxygen or Ϋ / asserdampf to about 300 to 800 C, preferably to about 400 to 700 ⁰ G is heated, whereupon it is ready for the condensation reaction again.

The shape of the catalyst can vary according to the reactor used. For example, can the catalyst in one for plague bed reactors, fluidized bed reactors, moving bed reactors and transported Transporting-bed type reactors. For example, using of silica sol as a silicon oxide component and by spray drying the mass easily into the form a form suitable for fluidized bed reactors or transport bed reactors. Catalysts For reactors with moving bed or fixed bed reactors can use silica sol or silica hydrogel as a silicon oxide component according to an ITass deformation process can also be easily manufactured.

If the reaction is carried out in a fixed bed, a plurality of reactors are preferably used so that the reaction and the regeneration of the catalyst can be carried out alternately. It is also possible to use a fluidized bed reactor, a reactor with a moving bed or a transport bed reactor, whereby slight circulation of the catalyst is possible and only a simple regeneration is required .

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The reaction product is either condensed or absorbed in a suitable solvent and in on itself, as is known, by fractionation or others usual procedures isolated. Unreacted isobutylene and unreacted formaldehyde can be separated off and recycled to the condensation reaction as starting materials.

In this way, isoprene is formed with high conversion and with high selectivity. The isoprene obtained has a very high purity of more than. 99%.

The invention is further illustrated by the following examples. In these examples the sales are so7 / ie the selectivity to isoprene is given as the mean value within the stated reaction time.

example 1

Sodium silicate (NapO.nSiOp.HpO; 28-30% 9 - 10% NaPO) was hydrolyzed with sulfuric acid and then well washed to remove the Na ⁺ ions with water. 30 ml of an aqueous aluminum chloride solution (0.05 mol / l) were added to 333 g of the silica hydrogel thus prepared (with 9.0% by weight SiO _{2 on a dry basis at 110 ° C.).} While the mixture was well kneaded in an automatic kneader, 30 ml of an aqueous solution of silver-ammine complex ion (0.05 mol / l) prepared by adding aqueous ammonia to an aqueous silver nitrate solution was added. Then, an aqueous ammonium chloride solution (2 mol / l) was added, whereby the gel, which had been partially converted to a sol, was restored to the original hydrogel form. ;

This gel was dried ^{at 100 ° C. overnight.} The xerogel obtained was comminuted and the sieve fraction

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Screened out 0.59 to 1.68 mm (10 to 28 mesh). ^{This xerogel was calcined at 500 °} C. for 4 hours in a mixture of air and steam. The catalyst prepared in this way looked white. Its X-ray diffraction pattern showed no sign of silver oxide.

In a conventional fixed bed reactor 10 cnr of this Catalyst filled. At normal pressure and 300 ° C, a 40% aqueous solution of formaldehyde and isobutene was in an amount of 3.22 g / hour. or 0.3 mol / hour. introduced. The reaction was carried out for 4 hours.

The isoprene formed as reaction products and unreacted isobutene were removed by cooling in a cold trap separated with dry ice-methanol, while unreacted formaldehyde and other water-soluble; Components have been absorbed in water. "|

In the experiment described above, 90% of the formaldehyde was converted. The selectivity too Isoprene was 72%.

Example 2 <

2 Granular silica gel (specific surface area 380 m / g, mean pore diameter 96 S) was comminuted to 0.84 to 2.0 mm. 50 g of the crushed gel were immersed in aqueous 3N ammonia for 24 hours, whereby the protons on silicon dioxide in NIL. ⁺ Ions were converted. Then 100 ml of silver-ammine complex ions (0.05 mol / l) were added to the gel in order to exchange the NIL ⁺ into Ag (NH,) p. The silica gel with Ag ions was air-dried and then immersed in 170 ml of aqueous aluminum nitrate (0.03 mol / l) for 24 hours. The gel obtained was ^{dried at 100 ° C. overnight and calcined at 500 °} C. for 8 hours in a gaseous mixture of air and steam. Just like that

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Catalyst prepared according to Example 1 also showed no sign of silver oxide in this catalyst composition. When the reaction was carried out under the same conditions as for the preparation of the catalyst of Example 1, the conversion of formaldehyde was 94 % and the selectivity to isoprene was 70 %.

Example 3

To 200 ml of silica hydrosol (SiOp concentration 20 to 21% by weight; pH value 3 to 4; particle diameter 100 to 200 S) were added 4 ml of aluminum nitrate (0.5 mol / 1) and 20 ml of silver-ammine complexion ( 0.1 mol / l), whereupon 2 mol / l ammonium chloride and aqueous 3N ammonia were added. The gel obtained was ^{dried overnight at 100 °} C., comminuted and sieved to obtain the 0.5 to 1.19 M fraction. The crushed gel was then calcined for 3 hours at 700 ⁰ G in a stream of a gaseous mixture of air and water vapor. As in Example 1, there was no evidence of silver oxide that might have been formed. When the reaction was carried out using the catalyst prepared in the manner described under the conditions mentioned in Example 1, the conversion of formaldehyde was 93 % and the selectivity for isoprene was 69 %. \

Examples 4 to 7 . j

Catalysts were prepared in the manner described in Example 3. The same reaction was taking Use of catalysts with different content of Ag ion and AlpO ^ carried out. The results are listed in the following table. The result of the reaction with an AIpO -, - free one is also for comparison Called a catalyst.

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Example set of

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Ag ⁺ , meq. / G meq. / G % catalyst catalyst

Selectivity, %

4th 0.02 0.60 75 73 5 0.10 0.45 96 67 6th 0.50 2.00 '97 65 7th 1.0 3.00 100 60 3 0.05 0.15 93 69 control
I. x 0.05 0 58 59

The catalyst had a brownish tinge due to the partial formation of silver oxide.

Examples 8 to 25

To the same silica hydrogel as used in Example 1, Ag ⁺ and AlpO were added in the same manner as in Example 1. Finally, an aqueous solution of the fourth ingredient listed in the table below was added. The gel obtained was dried and then calcined at 700 ° C. for 3 hours. The amounts of Cr, Fe, Co, Ni, Cu, Zn, Zr, La, Ce, Mg, Ca, B, Tl, Sn, Pb, P, Mo and W as oxides added in this way were always 0.001 mol / g Catalyst.

The reaction was described in Example 1 Way done. The results are in the following Called table.

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example
No. Watery Solution of the additive Amount added,
ml / 50 g silicon
dioxide sales
% ' selectivity
% 8th For the manufacture
use the solution
detes reagent = Concentration
Mon 1/1 60 ■ 86 78 9 (NH ^) ₂ CrO ₄ 0.05 30th 93 63 10 FeCjZ, · 6H ₂ O 0.1 30th 92 70 11 Co (NO ₃ ) ₂ • 6H ₂ O 0.1 30th 96 64 12 · Fi (NO ₃ ) ₂ • 6H ₂ O 0.1 30th 94 61 13th CuCJ ₂ * 2H ₂ O 0.1 30th 91 71 14th Zn (NO ₃ ) ₂ • 6H ₂ O 0.1 60 90 68 15th ZrO (NO ₃ ) ₂ · 2H ₂ O 0.05 60 90 69 16 La (NO ₃ ) ". 6H ₂ O 0.05 60 87 73 17th Ce (CH ₃ COO) ₃ ^ H ₂ O 0.05 30th 91 69 18th Mg (NO ₃ ) ₂ • 6H ₂ O ■ 0.1 30th 97 67 19th CaC ^ "2H ₂ O O.i 30th 96 64 20th H ₃ BO ₅ 0.1 120 88 71 TJ ^ o ₃ 0.025

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example
No. Watery Solution of the additive Amount added,
ml / ^ O .g silicon
dioxide sales selectivity 21 Purely the production
use the solution
detes reagent ⁵ concentration
Minor 60 96 61 22nd SnQg ₀ '2H ₀ O 0.05 60 80 78 23 Pb (NO ^) ₂ 0.05 30th 62 84 24 ' H ₃ PO ₄ aq. (85 fo) 0.1 60 95 69 25th (ΝΗ ₄ ) ₆ Μο ₇ 0 ₂₄ 4Η ₂ 0 0.05 60 91 70 (NH ₄ ) ₁₀ W ₁₂ O ₄₁ «5H ₂ O 0.05

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Example 2 6

To 100 g of silica (SiO ^ concentration 30% by weight; pH value 9.6; particle diameter 1JO to 140 A) were added 60 ml of silver-ammine complex ion (0.05 mol / l) and 40 ml of aqueous aluminum chloride ( 0.1 mol / l). Then 30 ml of aqueous iron chloride (0.1 mol / l) and 6 ml of aqueous phosphoric acid (0.5 mol / l) were added. After further addition of aqueous 3N ammonia, the gel formed was wet shaped into granules of about 3 mm 3 mm. After drying at 100 C, the granules in an air stream for 3 hours at 800 ⁰ G was calcined, when the reaction was carried out using this catalyst under the above conditions of Example 1, the conversion was of formaldehyde 88% and the selectivity of the reaction for isoprene 70 %.

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Claims (4)

Claims (ΛΪ Solid catalysts for the production of isoprene by. Reaction of isobutylene with formaldehyde, containing a) silver ions, b) aluminum oxide and c) silicon oxide, the atomic ratio of aluminum to silver being about 1:10 to 30: 1 and the weight ratio of aluminum oxide to silicon oxide is about 1: 5000 to 2: 1. 2. Catalysts according to claim 1, characterized in that that the atomic ratio of aluminum to silver is about 1: 3 to 20: 1 and the weight ratio of aluminum oxide to silicon oxide is about 1: 1000 to 1: 1. 3. Catalysts according to claim 1 and 2, characterized in that they also as a fourth component at least one oxide and / or ion of elements from the transition elements, alkaline earth metals, boron, Thallium, tin, lead or phosphorus group consisting of the weight ratio of the element or the elements of the fourth constituent to silicon oxide not more than about 1: 5 », preferably not more than about 1:10. 4. Use of the catalysts according to claim 1 to 3 for the production of isoprene by catalytic condensation between isobutylene and formaldehyde. 509842/0902