DD219184A1 - METHOD FOR THE CATALYTIC HYDROGENATION OF BUT-2-IN1,4-DIOL - Google Patents

Abstract

The invention relates to a process for the catalytic hydrogenation of but-2-yne-1,4-diol to butane-1,4-diol by a two-stage process. In a stirred reactor with a suspended nickel-tracer catalyst, the reaction is first carried out to a conversion of 90 to 98% of but-2-yne-1,4-diol. The catalyst is separated off continuously in a sedimentation vessel and returned to the stirred reactor as a recycle stream. The gas is introduced through a hollow stirrer. The second reaction stage is carried out in a fixed bed reactor.

Description

Title of the invention

Process for the catalytic hydrogenation of but-2-yn-1,4-diol

Field of application of the invention

The invention relates to a catalytic hydrogenation process for preparing butane-l, 4-diol from but-2-yn-1,4-diol by a two-stage process, wherein in the first stage, the hydrogenation in a stirred reactor with a supported supported nickel catalyst and the 2nd stage is carried out in a fixed bed reactor at elevated pressure.

Characteristic of the known technical solutions

Butane-1,4-diol is industrially produced by catalytic hydrogenation of but-2-yn-1,4-diol. The used but-2-in-l, 4-diol solution is obtained by catalytic reaction of aqueous formaldehyde and ethyne.

For the catalytic hydrogenation of but-2-yn-1,4-diol

^H 2 ^H 2

HIGH ₂ CsCCH ₂ OH HIGH ₂ CH »CHCHgOH H0 (CHg) ₄ OH

Many methods are known, which run in one or two stages. The one-stage hydrogenation and also the first stage of the two-stage hydrogenation can be carried out both in a stirred reactor with suspended catalyst and in a fixed bed reactor. Raney nickel (also modified with Mo, Cu, Mn, Al, Co, Cr), nickel-supported catalysts (the same modifications,

η γ

Support: Al oxide and silica gel) or noble metal catalysts (Pt, Pd) used. The first stage, the hydrogenation to but-2-en-i, 4-diol, in the temperature range of 15-180 ⁰ C (preferably at 50- 60 C) and in the pressure range (for stirred autoclave) from 0.1 to 4 MPa , The second stage is carried out at a pressure of 1-50 MPa. In the past, many process and catalyst changes have been made to improve process selectivity. The yield of butane-l, 4-diol is usually when using nickel catalysts at 80 - 90 % (US-PS 2,967,893, US-PS 3,449,445).

Main by-products of hydrogenation are ^ - hydro-. Xibutyraldehyde, which is formed during the first hydrogenation step by simultaneous hydrogenation and rearrangement of but-2-yn-i, 4-diol, an acetal of ^ -hydroxibutyraldehyde and butane-l, 4-diol and n-butanol. The aldehyde and its acetal may undergo side reactions to form nonvolatile residues. Like the unreacted but-2-en-1,4-diol, when present in substantial quantities in the butanediol they form a low quality product. Therefore, the second hydrogenation step is typically conducted at higher temperatures and / or pressures to reduce the majority of by-products to butane-1,4-diol. However, under unfavorable reaction conditions, the by-products mentioned can also react further to compounds which can not be converted to butane-1,4-diol and which are also relatively difficult to separate by distillation.

The butynediol hydrogenation-suspended catalyst processes described in patents and other publications are carried out batchwise because the continuous separation of the catalyst is known to cause great difficulties. However, the coupling with a downstream fixed bed reactor is only possible via larger storage tanks in order to ensure a continuous supply of

tion for the second stage (US Pat. No. 3,449,445, DE OS 2,926,641). Disadvantages in the realization of the first stage also in a fixed bed reactor, however, arise in heat removal due to the large exotherm and the greater reaction rate (DE OS 2 145 297, DE OS 2 004 611) and by the low catalyst utilization, also by the greater reaction rate conditionally.

For smaller reactors it is known that a good mass transfer or a high gas utilization can be achieved by the use of a hollow stirrer. For larger reactors, hollow stirrers are not suitable, according to the literature, because of insufficient gas flow, an external gas recirculation is required here.

Object of the invention

The aim of the invention is the catalytic hydrogenation of but-2-yn-1,4-diol using nickel catalysts, wherein a high productivity and yield of butane-i, 4-diol to be ensured. The advantages of using a slurry reactor with suspended catalyst, the good material and heat transfer, to be connected with those of the continuous operation and control of the process are made possible.

Explanation of the essence of the invention

The object of the invention is to develop a process for the hydrogenation of but-2-yn-1,4-diol which meets the object of the invention.

According to the invention, the hydrogenation of the but-2-yn-1,4-diol is carried out in two stages, the first stage in the continuously operated stirred reactor with suspended catalyst, the second stage in the fixed bed reactor, The catalyst is a supported nickel catalyst on SiO 2 for both stages - or Al 0 -

^V ^ Cm O

Base with 15 - 80 % nickel.

The operating parameters for the first stage are at temperatures of 50-150 ^° C., preferably 60-90 ° C. and pressures of 0.5-5 MPa _4, preferably 1-2.5 MPa, and for the second stage at temperatures of likewise 50 *. 150 ⁰ C, preferably 80-120 ⁰ C and pressures of 5 - 25 MPa. The entry concentration of but-2-yn-1,4-diol in the aqueous. Solution is 20-50 %, preferably 30-35%.

The gas input for the first stage via a Hohlrührer »It was surprisingly found that even at immersion depths far above ι m, a limit often mentioned in the literature, still a good gas input takes place and thus the hollow stirrer is also applicable to large reactors. By a promoted gas flow rate, which is at least 10 times the stoichiometrically necessary, a very good mass transfer and high utilization of the hydrogen is achieved.

The heat removal is implemented via the shell of the reactor mounted half-pipe coils and built-in Steilrohr- or Spi / Ralrohrwärmeubertrager, which also serve as a flow breaker. The continuous catalyst separation is achieved according to the invention by a coupling of the reactor and sedimantation vessel. The sedimentation vessel has approximately the same cross section as the reactor. The recycle stream, which is recycled back to the process together with the catalyst separated from the product stream, should be 5 to 10 times the product stream. The achievable degree of separation is more than 99 %,

It has been found that the possibility of eliminating the by-products formed during the first stage, in particular the γ-hydroxibutyraldehyde, by further hydrogenation in the second stage, is stronger from the amount of butanediol formed in the first stage than the amount of by-product formed itself depends. For higher purity requirements, it proves to be favorable, the two

Hydrogenation steps to separate relatively accurately, ie, the first hydrogenation to operate approximately to a butynediol conversion of 90-98%, preferably 95 %) . As a result, an acetal formation is largely prevented and the degradation of the aldehyde in the second stage is easy.

However, experience has shown that such a precise control of the conversion is complicated, since the reactor is operated in the unstable region due to the low overall conversion. A surprisingly simple solution to this problem results from the solution according to the invention: keeping the hydrogen supply constant in the size corresponding to the desired conversion. This can be coupled, with a regulation of coolant throughput and / or coolant temperature,

Exemplary embodiments Example 1:

800 g of a 32% but-2-yn-1,4-diol solution in water were mixed with 5.9 g of a nickel-supported catalyst (40 % Ni on SiO 2) at T »80 C and ρ * 1.57 MPa in a discontinuous laboratory stirred autoclave implemented. The time course was determined by gas chromatographic analysis of samples taken from the reactor.

[min] c _BI [mol / l] ^C

_HBA

0 3.72 0.021

8.5 3.45 0.023

24.5 2.92 0.034

34.5 2.49 0.046

60.5 1.08 0.095

71.5 0.62 0.161

'86, 5 0 0.165 (BI: but-2-yn-l, 4-diol, HBA: y -hydroxibutyraldehyde)

Example 2:

To a continuously operated, stirred catalyst stirred tank reactor, was added 700 ml / hr of a 32% sut-2-in-1,4-diol solution. At T = 80 ^° C., ρ = 1 MPa and a catalyst mass of 9.5 g (40 % Ni on SiO 2), the following concentrations were established:

C- '' '

But-2-yn-1,4-diol = 0.366 mol / l

, ^C But-2-en-l, 4-diol 3.260 mol / 1 ^C butane-l * 4-diol. · 0.028 mol / 1

⁰ HBA ^S 0.066 mol / 1

Example 3: '. ·

A packed bed reactor filled with a nickel-supported catalyst (about 18 % Ni on Al-O) was added with a solution of but-2-yn-1,4-diol, but-2-ene-i, 4-diol, butane-i, 4-dxol and γ -hydroxibutyraldehyde supplied in water. At a temperature of T "100 ⁰ C and a pressure of ρ» 24.5 MPa were for two compositions of the feed mixture, the 70 % and 97 % conversion of but-2-in-l, 4-diol in the l. Hydrogenation correspond, obtained the following results:

Trial A Trial B

OV Γ 9 Ί 1500 1500

V fml / hl 350 350

mass fraction

♦ But-2-yn-l, 4-diol. But-2-en-1, 4-diol. Butane-i, 4-diol

; γ- hydroxibutyral.

.Butanol

Commitment- product commitment product qemisch mixture 10.1 0 1.0 0 20.4 0.01 29.6 0.02 0.4 31.8 1.0 32.3 2.0 0 1.9 0.02 - 1.1 .1,16

Claims (4)

^: · ' ⁹ '. ' invention claims 1. A process for the catalytic hydrogenation of but-2-in-l, 4- _v diol to butane-l, 4-diol by a two step process wherein the first stage is carried out in a stirred reactor with suspended nickel catalyst, the gas entry in the stirred reactor is carried out by means of a Hohlrührers and the second stage takes place in a fixed bed reactor, characterized in that the first stage in a continuously operated stirred reactor to a conversion of 90 - 98% of the but-2-in-l, 4-diol by controlling the process is carried out via a hydrogen flow control and / or additional control of the coolant flow or the coolant temperature, the catalyst is continuously separated in a sedimentation vessel downstream of the stirred reactor and continuously recycled from this as a circulation stream in the stirred reactor. 2. A process for the catalytic hydrogenation of but-2-in-i, 4-diol Punkt'1, characterized in that the first stage at a temperature of 50 - 150 ° C, preferably 60-90 ⁰ C and a pressure of 0.5-5 MPa, preferably 1- 2.5 MPa, and the second stage at a temperature of also 50-150 ⁰ C, preferably 80-120 ⁰ C, and a pressure of 5-25 MPa operated and that the aqueous but-2-one-l, 4-diollösung 20 -, 50 %, preferably 30 - 35 % but-2-in-l, 4-diol. 3. A process for the catalytic hydrogenation of but-2-in-l, 4-diol according to item 1 and 2, characterized in that the continuous stirred reactor is coupled to a downstream Sedimentatiohsgefäß of about the same cross section as the reactor and from this a circulation stream , animal which is 5 to 10 times the product flow, is returned to the stirred reactor. 4. A process for the catalytic hydrogenation of but-2-one-l, 4-diol according to item l and 2, characterized in that the hydrogen is introduced into the stirred reactor using a Hohlrührers, wherein the delivered hydrogen stream at least 10 times the stoichiometrically necessary is. ,