DD226872A1 - METHOD FOR CATALYTIC HYDROGENATION IN THE LIQUID PHASE - Google Patents

Abstract

The invention relates to a process for carrying out catalytic liquid phase hydrogenations including highly exothermic, such as. B. from nitroaromatics to the corresponding amines, by gaseous hydrogen to suspended catalysts, preferably under pressure and at elevated temperature under preferably continuous Prozeßfuehrung. The process is carried out in a tubular reactor in which sgn. Static mixing elements are fixed and in which the 3-Phasenproduktstroemung of gas, liquid and solid is superimposed on a pulsation, whereby it is achieved that the reaction proceeds in the quasi-kinetic range. The heat dissipation takes place via a heating / cooling jacket. According to the modular principle, it is possible to combine any number of reactor tubes into one reaction unit.

Description

1ΓΒΒ CHEMICAL COMPETITOR BITTERSELD

2547

Catalan hydrogenation in the liquid phase

Field of application of the invention

The invention relates to a process for carrying out catalytic hydrogenations in the liquid phase with gaseous hydrogen on suspended catalysts.

Characteristic of the known technical solutions

Pure hydrogen peroxide hydrogenation with gaseous hydrogen in the presence of suspended catalysts, there are a number of technically introduced process.

λ -i; · :. Π Ί ί Χ /

- 2 - 2547

The majority runs in autoclaves, with effective mixing equipment, eg. B. with high-speed stirrers and baffles and with heating or · cooling options in the form of z. B. Kuhl- / Heizmantel, inner coil, device for evaporative cooling are equipped. Pur continuous process control, several autoclaves can be combined to form a reactor cascade or the reactor cascaded into several stages. (Chem Eng J_ £ Hov 6, (1967) p 251;..... Chem. Eng 2 £> ⁰ ^ x 9 "(1967) p 249) Also for the continuous operation * was described autoclave To combine a special Absichtsbehälter for the catalyst and to circulate the reaction solution by means of the agitator or by Mammutpumpenwirkung according to the principle of the loop reactor. (DE-AS 1 542 544, DE-AS 1 947 851, DD-PS 126 891) The most important condition which must be fulfilled in the hydrogenation with suspended catalyst, is an intensive mixing of the three phases T / hydrogen gas, liquid substrate and solid, finely divided catalyst. The rapid transport of the reactants to and from the active sites of the catalyst must be ensured. (Ullmanns Encyclopedia of Industrial Chemistry Vol 4 ed. 7, pp. 400, Weinheim / Bergstrasse fi 9747) Hur so the hydrogenation reaction in the kinetic region of the tart is feasible

 As mixing organs z. B · Turbine stirrer, disc stirrer and paddle stirrer proven, but less a Propeiler stirrer. But also combinations of self-priming stirrers with turbines and of tubular and propeller stirrers have become known. (Ulimann 4 · Aufl., Bd, 3 (1973) p. 506 ff)

- 3 -. 2547

In this case, a high number of revolutions of the stirrer is usually required, which brings problems of shaft seal with it. Therefore, rotary or reciprocating mixers with magnetic force transmission are often used in the laboratory and in small plants for bypassing shaft seals, as described in DE-OS 2 217 229, DE-OS 2 753 153 and DE-OS 2 919 943. The devices described, however, is liable to the defect that the hydrogenation processes occurring therein are limited by substance transition inhibitions, so that they are usually far away from the kinetic range.

In many cases, the possible dissipation of heat does not satisfy, so that it can act throughput-limiting in the case of strongly exothermic reactions. In the case of Ver. Turning of Innehschlangeh and the use of Hubrührern also makes annoying noticeable that the catalyst settles on emptying the reactor on the horizontal surfaces, which in particular when using pyrophoric Metallkatalysatören KömplikatiÖrieh can cause.

For many reactions, especially those with strong heat of reaction, loop reactors with an externally arranged heat exchanger are known (DE-OS 2 339 242). They are preferably equipped with jet nozzles for the material union, which suck the hydrogen with the liquid driving jet (fats ,. soaps, paints 6, (1969) ,, 441; Chem Ing Tech & 2 (1970), 474 u ££ (1972.... ), 367 and 899. Chem. Eng * Progr. (1980), June, 53; DE-PS 1 109 818; DE-AS 1 793 452). Although these methods avoid the drawbacks of classical autoclave chemistry, they have, in their two essential equipments, circulation pumps and jet nozzles - parts which are subject to heavy wear due to erosion by the entrained solid particles.

- 4 - 2547

The so-called fluidized bed reactions also include the type of catalyst with suspended catalyst. One possible embodiment for a fluidized bed reactor has been described in DS-OS 2 551 641; Thereafter, in a tubular reactor, the coal particles to be hydrogenated and the catalyst, suspended in an oil, are held in suspension by pulsation. Further development of this principle provides that a "quasi-compact bed of reaction-promoting lumpy particles" is flowed through by the reactants, wherein the fluid phase is pulsed (DS-OS 2 555 938), an essential feature of these methods is in that the solid is removed by suitable means, e.g. B. by limiting sieve bottom, is enclosed in the reactor and therefore can only perform a relative movement. Br is subject to a strong abrasion. As a result, hydrogenation processes in the fluidized bed are limited in their applicability. They are generally technically difficult to control and have become established only in special cases, in the so-called Η-Coal and H-Oil process (Dllmann Bd. 10 (1975), 697, and Vol. 13 (1977), 543).

ZJeI ₁ the invention

The aim of the invention is a process for carrying out catalytic hydrogenation with hydrogen in fluid phase using suspended catalysts including highly exothermic hydrogenations, eg. As that of nitro compounds to develop, which overcomes the Hachteile the known technical solutions, technically feasible with simple means and so thorough cross-mixing of all reactants mass transfers causes can be worked under quasi-kinetic conditions.

- 5 - 2547

Explanation of the essence of the invention

The object of the invention is to carry out liquid-phase hydrogenations with gaseous hydrogen peroxide in the presence of suspended catalysts, in which the reaction volume is reduced at the same throughput rate and made safer by a larger heat exchange surface per unit volume. According to the invention, the process for carrying out catalytic hydrogenations with hydrogen gas in a fluid phase using finely divided catalyst suspended in the fluid is carried out in a preferably loop-type device according to FIG. 1, the essential part of which is any ITEigungswinlcel, preferably vertical reaction tube 1 under eiüem which is supplied with the sluid and the hydrogen gas. This reaction tube is provided with an optionally in several independent heating or cooling zones divided jacket space 2 for heat exchange. It has been found that the hydrogenation reaction proceeds in the quasi-kinetisehen area, if one arranges in the reaction tube mounting elements 3, which are effective as a static mixer and at the same time the reactor contents via a pulsation generator 6 vibrated. The hydrogenation process can also be carried out continuously in this apparatus and, depending on the required reaction conditions, under pressure or under pressure and / or at elevated temperatures.

Depending on their suitability, the static mixer elements 3 can optionally be the same or different type of construction and completely or only partially fill the length of the reaction tube; only their effectiveness with the lowest possible flow resistance is essential.

- 6 -. 2547

The reaction tube 1 is acted upon by means of a metering device via a feed line 4 with the liquid to be hydrogenated or dissolved in a suitable liquid or finely divided compound, via line 5 with hydrogen gas and via the feed line 11 with fresh catalyst, which is in suspension with reaction product and / or a suitable solvent is present ·

After hydrogenation, the reaction product is optionally at 9 relaxed, removed from the reactor and fed to the workup. The catalyst is preferably separated before the expansion at 7 of the main amount of the reaction product and recycled with a portion of the reaction product for the most part back into the reaction tube · It can be partially or completely removed and replaced by fresh catalyst or replaced.

The 3-phase gas of solid, liquid and gas present in the reaction tube 1 is oscillated by means of a pulsator β with oscillations of variable amplitude and variable frequency of 30,000 min.sup.-3, particularly of 30-3,000 min.sup.-1 Depending on the frequency and amplitude of the pulsation, a high-to-very high relative speed, which is superimposed on the flow velocity, is preceded by very large shearing forces, the possibility of changing the amplitude and / or the frequency of the pulsation as well as the type and length of the static mixers in the reaction tube allow an optimal adaptation of the reaction conditions to any hydrogenation task and ensures intensive mixing regardless of the proportions and viscosities of the feedstock and end products. «

- 7 - 2547

In this case, all phases are contacted so intensively that the reaction proceeds in the quasi-kinetic range. In addition, due to the intensive mixing, the hydrogen is optimally consumed for the hydrogenation. It requires only a very small excess of gas and can work with very low hydrogen flow rates. This eliminates the need to circulate hydrogen. In the technical application then the corresponding devices, especially the compression device, can be omitted. In the continuous implementation of the process according to the invention, the product flow passes, after passing through the reaction tube 1, into a separation device 7, from which the residual gas is at equilibrium, the reaction product at 9 via an expansion element in such an amount for processing is passed, as substrate is metered in 4, and the sedimented catalyst is recycled to the reaction tube with a portion of the reaction product via lines 8 and 4. When needed, spent catalyst at 12 discharged and fresh catalyst at 11 as a suspension in With the aid of the amount of substrate metered in at 4, virtually any desired mean residence time in the hydrogenation reactor can be achieved by the process according to the invention due to very low backmixing , overall has the character of a plug flow. The heat supply and removal takes place via heating / cooling jacket 2, which can be divided into several, possibly independently acted upon zones. Depending on the geometric shape of the reaction tube, the effective exchange surface is variable. In order to maximize the exchange

- 8 - 2547

can achieve an arbitrary number of individual reaction tubes parallel and / or connected in series to form a reactor unit, where they can have a common jacket for heat exchange, or are individually sheathed. They are optionally equipped with a common or with several independently operating pulsation devices. In addition to the advantages of the method according to the invention, reference should also be made to the safety aspect. By reducing the reaction volume at the same throughput and at the same time much larger heat exchange surface per unit volume of the risk of a runaway reaction is virtually eliminated.

embodiments

The following examples are intended to illustrate the essence of the invention, but without limiting its scope.

Example 1 (continuous mode)

In a 1 000 ml reaction tube according to Figure 1 (ds 4, cm, 1 s 80 cm), the dissolved or suspended in the solvent substrate and the contact suspended in the solvent is fed and rinsed after cooling first with Hg and then with H ₂ . The Hg flow is adjusted so that after the start of the hydrogenation via the valve 10 only about 10 % of the supplied hydrogen escape. When using noble metal catalysts, the H ₂ pressure is 0.1 to 2.5 MPa, when using nickel catalysts 1.5 to 5 »MPa, preferably 2.0 to 3.0 MPa.

- 9 - 2547

The hydrogenation is started by setting the pulsator β and heating the reaction mixture to the hydrogenation temperature. The hydrogenation starts immediately. Via the substrate line 4, as much substrate solution is now fed to the reactor as is removed via the product line. The catalyst largely sediments in the decanter 10 and flows with a portion of the hydrogenation solution over 8 in the reactor. In the following experimental examples, the contact used at the beginning of the experiment is worked until its activities noticeably subsided and no IFrisch contact above 11 is added. In a continuous operation, a part of the contact via valve 12 is continuously or at certain intervals auszuschleusen and replaced by an equivalent amount of fresh contact. The amount of product fed in via 4 and / or 9 removed is determined by the residence time required until complete hydrogenation. After removal of non-sedimented contact traces, the hydrogenation solution removed at 9 is worked up in a known manner continuously or batchwise.

1. Hydrogenation of 4-iiitrotoluene to 4-toluidine

There are within 5 hours 10 1 of a methanolic solution containing 453 g 4 Hitrotoluen per liter, in the presence of 10 g of Kt 6500 (commercial Uickelträger catalyst of VSB Leuna works) at TOO ⁰ C and a pressure of 3.0 MPa at a pulsation frequency of 300 min and an amplitude of 5 mm hydrogenated with hydrogen. After work-up in the usual manner, 3397 g of 4-toluidine are obtained with a content of 99.6 %, in which thin-layer chromatography is no longer detectable. This corresponds to a yield of 96 % of theory.

- 10 - - 2547

2. Hydrogenation of 1,2-phenylenediamine from 2-lfitroaniline

There are hydrogenated in 6 hours 10 1 of a reaction mixture, each containing 1345 g of 2-lIitroanilin in methanol. The amount of catalyst used is 5 g of Kt 6500, reaction temperature 90 ^° C., pressure 2.7 MPa, pulsation frequency 500 minutes, amplitude 3 mm, after distillation the 1,2-phenylenediamine is as a pale yellowish crystals with Pp 102 to 103 ⁰ C and a Content of 99 % , yield 90 % of theory.

3. Hydrogenation of 4-Hitrophenol-Ua to 4-Aminophenol

10 1 of an aqueous solution of 2000 g of 4-H "itrophenol-la are in the presence of 4 g Kt 6500 at a metering rate of 1 l / h at 90 ⁰ C, 3 MPa pressure, a pulsation frequency of 100 min" and an amplitude of 25 mm hydrogenated. There are obtained 4-aminophenol with 38 to 99% purity in 92 % yield in which no more Uitrophenol is detectable.

Example 2 (discontinuous driving style)

In the case of batchwise operation, work is carried out in a horizontal reactor which, moreover, is the same as that used in Example 1. The hydrogen is periodically pressurized either when the valve 10 is closed in proportion to its consumption until there is no more pressure drop over time or at constant pressure, whereby the supplied quantity H is measured After the hydrogenation has ended, the mixture is decompressed and ¹ J by means of the decanter

- 11 -

- 11 - 2547

the catalyst is separated off and the reaction solution is emptied. The workup is carried out in a known manner depending on the properties of the reaction mixtures.

1. Hydrogenation of 2-ITitrotoluenes

Bs are hydrogenated 800 ml of a solution containing 425 g of 2-Nitrotoluen and are suspended in the β g Kt 6500, reaction temperature 100 ⁰ C, pressure 3.0 MPa, pulsation frequency 40 min "", amplitude 30 mm. After 25 minutes, the solution no longer absorbs hydrogen. By distillation, 2-toluidine is obtained with a content of 99.8 % , in the thin layer chrömatögräphisch "no Ausgerügsprodukt is detectable yield 98 # of theory.

Claims (5)

-12-. 2547 invention claim - 1 -1 of 30,000 min, preferably 30-3,000 min generated at optionally variable amplitude. A process for the liquid phase hydrogenation with suspended catalyst and hydrogen gas, characterized in that the compound to be hydrogenated is in fluid form together with catalysts dispersed in finely divided state and with hydrogen gas in a loop-type device, which consists of a single angle of inclination arranged, provided with a jacket for heat exchange and charged with static mixing elements reaction tube in which the content is caused by a pulsator to vibrate, is brought without pressure or under pressure in contact · 2. The method according to item 1, characterized in that the hydrogenation is carried out continuously and the catalyst is largely reintroduced into the reaction tube with a partial flow of the reaction product, wherein it is partially or completely removed from the system and supplemented or replaced by fresh catalyst. 3 · Method according to item 1, characterized in that the static mixing elements of the same or different construction type and over the full length or only part of the length of the reaction tube are arranged. - 13 - -13- 2547 4. The method according to item 1, characterized in that the pulsator oscillates at a frequency 5. The method according to points 1-4, characterized in that a plurality of reaction tubes with separate or possibly common 7 / ärmeaustauschmänteln to each other and / or possibly consecutively combined to form a reactor unit, optionally a common or more independent pulsators can be used , For this 1 page drawing