KR20000005073A - Process for the purification of butane 1,4 diol - Google Patents

Abstract

PURPOSE: A method to provide a process for the purification of butane-1,4-diol with a minor amount of the cyclic acetic compound, 2-(4-hydroxybutoxy)-tetrahydrofuran. CONSTITUTION: Butane-1,4-diol with 2-(4-hydroxybutoxy)-tetrahydrofuran is fed into a hydrogenation zone such as a slurry bed or a fixed bed under the presence of a minor amount of water and of a hydrogenation catalyst. As the temperature and pressure of bed rises from 30°C to 170°C, from 10.43BAR to 68.95BAR, water, tetrahydrofuran, and butanol are recovered in a first distillatory column. Butane-1,4-diol containing heavy boiling compounds is recovered in the upper fraction of a second distillatory column, and butane-1,4-diol product containing a reduced content compared with the butane-1,4-diol butane fed is recovered in the middle fraction of a second column.

Description

Method for Purifying Butane-1,4-diol

Butane-1,4-diol is used as a monomer in plastic products such as polybutylene terephthalate. It is also used as an intermediate for the preparation of γ-butyrolactone and tetrahydrofuran, which is an important solvent.

One route of butane-1,4-diol involves the reaction of formaldehyde with acetylene by the Reppe reaction to provide butyne-1,4-diol, which is then hydrogenated. To prepare butane-1,4-diol.

Another method for preparing butane-1,4-diol uses maleic anhydride as starting material. It is esterified with C ₁ to C ₄ alkanols, such as alkanols, usually methanol or ethanol, to produce the corresponding dialkyl maleates which are then hydrogenated to produce butane-1,4-diol and alkanols, which are recycled to It will produce additional dialkyl maleates. Methods and facilities for the preparation of dialkyl maleates in maleic anhydride are disclosed, for example, in US-A-4795824 and WO-A-90 / 08127. Hydrogenation of dialkyl maleates to produce butane-1,4-diol is further disclosed in US-A-4584419, US-A-4751334 and WO-A-88 / 00937, which are incorporated herein by reference in their entirety. do.

In the hydrocracking of dialkyl maleates such as dimethyl maleate or diethyl maleate, it is possible to produce valuable byproducts of γ-butyrolactone and tetrahydrofuran. Since there is already a market for these by-products, butane-1,4-diol and mixed products are not disadvantageous. In addition, the hydrogenolysis product mixture will usually contain small amounts of the corresponding dialkyl succinate, n-butanol, the corresponding dialkyl alcohol succinate, for example diethyl ethoxysuccinate and water. .

Other small by-products are identified as compounds of the cyclic acetal, ie 2- (4'-hydroxybutoxy) -tetrahydrofuran (1-4'-hydrobytoxy) -tetrahydrofuran.

It is formed virtually by reaction of butane-1,4-diol with 4-hydroxy butyraldehyde, a potential intermediate in subsequent hydrocracking reactions, or dehydrogenation of butane-1,4-diol itself. It can be formed by. The mechanism of formation of all these products and byproducts is not fully understood. However, their preparation is the same as in the following scheme.

Cyclic acetal by-products, namely 2- (4'-hydroxybutoxy) -tetrahydrofuran, are problematic because the boiling point is very close to the boiling point of butane-1,4-diol and forms an invariable boiling mixture (azeotrope). do. Therefore, it is impossible or difficult to produce butane-1,4-diol free of this cyclic acetal in principle using conventional distillation. Butane-1,4-diol produced by the hydrocracking route usually contains from about 0.15% to about 0.20% by weight of cyclic acetal together with at least 0.02% by weight of other impurities. The presence of 2- (4'-hydroxybutoxy) -tetrahydrofuran, a compound with a small amount of cyclic acetal in butane-1,4-diol, is color forming in butane-1,4-diol because it is a color forming material It is disadvantageous by inducing.

This is described in US-A-4383895 as a color forming material present in the crude butane-1,4-diol produced by hydrogenation of butane-1,4-diol and the crude butane-1,4-diol. Distillation under conditions that first remove all water present in the, 4-diol and further distill the butane-1,4-diol with reduced water content to remove sufficient color forming material to provide the product for polyester production. Suggested.

In JP-A-61 / 197534, 2- (4'-hydroxybutoxy) -tetrahydrofuran, 2- (4'-oxobutoxy) -tetrahydrofuran and 1,4-di (2-tetrahydro Crude butane-1,4-diol containing at least one of the compounds of furoxy) -butane is hydrogenated in the presence of a hydrogenation catalyst such as a supported platinum catalyst. Crude butane-1,4-diol can be produced by diacetoxy butene by acetosylation of butadiene and then hydrogenated using a palladium or nickel catalyst and hydrolyzed in the presence of a strong acid cation exchange resin. . The present specification will disclose how water and acetic acid are removed by distillation in the resulting hydrolysis product to produce crude butane-1,4-diol, the starting material of the present purification process. Since water is removed by distillation, the starting material of the process product is substantially anhydrous. Since aldehydes and acetals in the crude butane-1,4-diol are disclosed to be converted into compounds which can be easily separated from butane-1,4-diol by hydrogenation using the purification method of the present invention. This document describes 2- (4'-hydroxybutoxy) -tetrahydrofuran, 2- (4'-oxobutoxy) -tetrahydrofuran and 1,4-di- (2-tetrahydrofuroxy) -butane This hydrogenation refers to conversion to tetrahydrofuran, butane-1,4-diol, butanol, ditetramethylene glycol and the like. The hydrogenated crude butane-1,4-diol is then subjected to distillation in two stages. The light boiling fraction containing water, tetrahydrofuran and butanol is recovered in the first distillation column. The second distillation column acts as a purifier, where butane-1,4-diol containing light boiling compounds is recovered at the top and bottomed butane-1,4-diol containing heavy boiling compounds. And the desired purified butane-1,4-diol is recovered at the side of the column.

It is therefore an object of the present invention to produce a butane-1,4-diol product stream which is in principle free of compounds of cyclic acetal, i.e. 2- (4'-hydroxybutoxy) -tetrahydrofuran. To provide an improved method for purifying diols.

Another object of the present invention is to form 2- (4'-hydroxybutoxy) -tetrahydrofuran as a by-product, which substantially prevents the loss of potentially valuable butane-1,4-diol butane-1,4- It is to provide an improved method of producing diols.

Another object of the present invention is to provide a process for converting trace amounts of 2- (4'-hydroxybutoxy) -tetrahydrofuran present in butane-1,4-diol to further butane-1,4-diol. It is.

The present invention relates to the product of butane-1,4-diol.

According to the invention, for the purification of substantially anhydrous butane-1,4-diol raw materials containing 2- (4'-hydroxybutoxy) -tetrahydrofuran, which is a small amount of cyclic acetal compounds, the butane Hydrogenating the -1,4-diol feedstock in the presence of a hydrogenation catalyst in the hydrogenation zone and butane-1 with a reduced amount of 2- (4'-hydroxybutoxy) -tetrahydrofuran in the hydrogenation zone Recovering the 4-diol product, wherein the hydrogenation is carried out in the presence of about 0.5% to about 5% by weight of water based on the weight of the butane-1,4-diol raw material. . In this method, the amount of water added will correspond to a molar ratio of water: 2- (4'-hydroxybutoxy) -tetrahydrofuran from about 20: 1 to about 500: 1.

Although the reaction mechanism has not been described in detail, a valid explanation is that the cyclic acetal is converted to hemiacetal in the presence of a small amount of water.

This hemiacetal is in equilibrium with 4-hydroxybutylaldehyde, which is itself an open chain compound.

It can then be hydrogenated with butane-1,4-diol.

It is possible that the crude butane-1,4-diol is distilled in advance to remove acetic acid and water so that 2- (4'-hydroxybutoxy) -tetrahydrofuran, a compound of the cyclic acetal, is converted into hemiacetal. It is contrary to the reaction disclosed in the purification method of JP-A-61-197534 with little or no.

In a typical process according to the invention, the butane-1,4-diol feedstock contains from about 0.05% to about 1.0% by weight of 2- (4'-hydroxybutoxy) -tetrahydrofuran, usually about 0.1% by weight % To about 0.4% by weight.

The hydrogenation catalyst is preferably a Group 8 metal-containing hydrogenation catalyst. Such Group 8 metal containing catalysts typically contain from about 0.1% to about 2% by weight of Group 8 metals. As examples of Group 8 metals, mention may be made of nickel, palladium, platinum, rhodium, iridium, rhenium and mixtures of two or more thereof. Group 8 metals are applied on inert supports such as graphite, alumina, silica alumina, silica, zirconia, thoria, diatomaceous earth, and the like. Particularly preferred catalysts are nickel catalysts. It may contain, for example, about 10% by weight to about 60% by weight or more of nickel. The other is a palladium-on-carbon catalyst, preferably containing from 0.1% to about 4% by weight of palladium. Suitable nickel catalysts are commercially available at Kvaerner Process Technology, W2 6LE Isborn Terrace 30, London, UK, at 86/4.

Although the hydrogenation reaction can be carried out in the vapor phase, it is more preferred to be carried out in a liquid phase reaction using either a slurry of catalyst or more preferably a fixed bed of catalyst. When working with a fixed bed of catalyst, the catalyst particles preferably have a particle size in the range of about 0.5 mm to about 5 mm. Convenient forms, such as particles, can be any of spherical, pellet, ring, or saddle shaped. If a fixed bed of catalyst is used, the reactor can be a shell-and-tube reactor that can be operated substantially isothermally, but an adiabatic reactor is preferred. The use of the adiabatic reactor is advantageous because its capital cost is much cheaper than that of the cell-tube reactor and is generally easy to replenish the selected catalyst in the reactor.

The process of the present invention requires the presence of a small amount of water. Although the crude butane-1,4-diol stream contains significant amounts of water, for example from 0.1% to about 0.5% by weight, the process of the present invention is a finishing step with γ-butyrolactone, tetrahydrofuran, Preference is given to carrying out at least one previous distillation step for separating water, alkanols (for example methanol or ethanol) and other byproducts such as n-butanol from butane-1,4-diol. The butane-1,4-diol raw material used in the process of the invention will in principle be anhydride. Therefore, it will be necessary to add a small amount of water to it. Preferably, a molar ratio of water: 2- (4′-hydroxybutoxy) -tetrahydrofuran of at least about 1: 1 to about 1000: 1, more preferably from about 20: 1 to about 500: 1. Water will be added.

Hydrogenation is preferably carried out by raising the temperature, for example from about 30 ° C to about 170 ° C. The supply temperature of the hydrogenation zone is preferably in the range of about 50 ° C to about 125 ° C. Similarly, it is preferably performed by increasing the pressure, for example from about 50 psia (about 3.45 bar) to about 2000 psia (about 137.90 bar), preferably from about 150 psia (about 10.34 bar) to about 1000 psia (about 68.95 bar). Do.

Butane-1,4-diol raw material is from about 0.1h to about 4.0h ^{-1 -1} range, preferably from about 0.5h ^-1 to a liquid hourly space velocity in the range from about 1.5h ^-1 (liquid hourly space velocity) of It is preferable to supply to the hydrogenation region at. It may be premixed with an inert diluent before entering the hydrogenation zone. Conveniently the diluent comprises the butane-1,4-diol product recycled at the outlet end in the hydrogenation zone. In this case, the ratio of inert diluent to fresh feed material is preferably in the range of about 1: 1 to about 1000: 1, for example in the range of about 5: 1 to about 100: 1.

After the hydrogenation step, butane-1,4-diol products, which are essentially free of 2- (4'-hydroxybutoxy) -tetrahydrofuran, are preferred to remove the remaining traces of water and "heavy". The final distillation step will be carried out in an atmosphere of inert gas.

In the final distillation step, despite the step for deoxygenation, probably due to the presence of trace amounts of the product of 4-hydroxybutylaldehyde, 2-hydroxytetrahydrofuran and / or 2-ethoxytetrahydrofuran Cyclic acetals tend to spontaneously remodel. However, the increase in the cyclic acetal content is significantly smaller than that observed when distilling the untreated butane-1,4-diol feedstock. The butane-1,4-diol product recovered with 2- (4'-hydroxybutoxy) -tetrahydrofuran, a compound of about 0.03% by weight of the cyclic acetal in the hydrogenation zone, at 160 ° C. for 5 hours. If heated under nitrogen, it was observed that the cyclic acetal content increased to about 0.06% by weight.

The invention is further illustrated in the following examples, where all percentages are by weight unless otherwise indicated.

Example 1

Continuously operable laboratory scale hydrogenation test rigs are obtained from crude butane-1,4-diol production plants where diethyl maleate undergoes hydrocracking using a reduced copper chromium catalyst in the vapor phase. It was used for the hydrogenation of samples of -1,4-diol. Crude butane-1,4-diol contained 0.21% 2- (4'-hydroxybutoxy) -tetrahydrofuran and a trace, usually about 0.02% water. The sample was recovered as a vapor stream obtained from a distillation column set up to separate unconverted diethyl succinate and γ-butyrolactone from crude butane-1,4-diol (then water in the raw reaction mixture obtained in the hydrocracking zone). Volatile components including ethane, n-butanol and tetrahydrofuran are removed by distillation).

The catalyst used in this example consists of a 1/16 "(1.59 mm) nickel / alumina sphere sold under the trade name DRD 86/4 by Kvaerner Process Technology Limited, 30, Eastbourne, London, England. It contains 48.3% by weight of nickel, including%, and has a bulk density of 0.96 g / cm 3; and also passes through a No. 20 net (US Standard Sieve) (ie <850 mm), but 90% of the particles. % Passed through No. 8 of the US Standard Sieve (ie <2.36 mm) and only 0.08% of the particles remaining on No. 14 of the US Standard Sieve (ie <1.40 mm) 200 ml of catalyst was supplemented to a reactor made of stainless steel and had a heating jacket set to provide isothermal reaction conditions through the reactor with an inner diameter of 1.065 inches (27.05 mm). 600NLPH (abbreviation NLPH of the ₂ "normalised liters per hour (normalized liters per hour)", that is, 0 ℃ Under a flow of means a per liter measured at 1bar) was activated by gradually heating to 100 ℃. After rises gradually, the reactor temperature up to 140 ℃, it was introduced into the gas flow during the 0.1 vol% H ₂ 1 sigan. H _{The 2} concentration was then raised from 0.1% by volume to 1% by volume for 1 hour at which the reactor temperature was maintained at 140 ° C. The H ₂ concentration in the gas stream then slowly rose to 10% at 140 ° C. and slowly to 100% by weight. The pressure was then raised to 900 psia (62.05 bar) and the reactor maintained at 140 ° C. at this pressure.

Initially enough water was added to the crude butane-1,4-diol feed to raise the water content to 4% (the stoichiometric content required to hydrolyze the cyclic acetal was 0.05%). The results obtained at different working temperatures, water contents and hourly liquid space velocity (LHSV) are shown in Table 1 below. It will be appreciated that raising the temperature by 10 ° C. from 110 ° C. to 120 ° C. will increase the productivity of the catalyst by about 2 to about 3. Appropriate results were observed at about 2% water content.

Table 1

Note of Table 1: THF = tetrahydrofuran

GBL = γ-butyrolactone

BDO = butane-1,4-diol

HVS = "heavy"

Acetal = 2- (4'-hydroxybutoxy) -tetrahydrofuran

LHSV = liquid space velocity per hour (h ^-1 )

Example 2

Further experimental tests similar to those used in Example 1 except for the facility for recycling the butane-1,4-diol product obtained at the outlet end of the hydrophobic region for dilution of the crude butane-1,4-diol stock Leagues were used in this example. 250 ml (237.4 g) of the same catalyst as used in Example 1 was used and activated in the same manner. Twelve jobs were executed. Analysis of the wet butane-1,4-diol raw material obtained by adding water to the crude butane-1,4-diol of the type used in Example 1 is set in Table 2.

Table 2

Operation 1-8 Action 9-12 water 3.92 4.03 ethane 0.013 0.013 Tetrahydrofuran 0.003 0.003 γ-butyrolactone 0.444 0.443 Butane-1,4-diol 94.985 94.876 Diethyl succinate 0.013 0.013 2- (4'-hydroxybutoxy) -tetrahydrofuran 0.175 0.175

The effect of the liquid recycled to the four first work was observed by using a hydrogen flow velocity of the pressure and temperature of 24NLPH, 900psia (62.05bar) of LHSV, 110 ℃ of 1.0h ^-1. Was Task 1 recycle ratio 2㎏ h ^-1, the work 2 was 1㎏ h ^-1, in the operation 3 was 0.6㎏ h ^-1, and it was a task 4, 0㎏ h ^-1. In operations 5-12 the effect of hydrogen flow rate was observed. Task 9 pauses the league over the weekend, then repeats the conditions of Task 8. Operations 10-12 used low hydrogen flow rates. The results are summarized in Table 3 below.

Table 3

Job number Temperature H ₂ flow NLPH LHSV h ^-1 Liquid recirculation kg / h ^-1 Supply H ₂ O Weight% Supply Acetal Weight% Product Acetal Weight% One 110 20 1.0 2 4.0 0.17 0.063 2 110 24 1.0 1.0 4.0 0.165 0.057 3 108 24 0.8 0.6 4.0 0.17 0.050 4 107 24 1.1 0 4.0 0.17 0.058 5 109 6 1.01 0 4.0 0.17 0.070 6 110 36 1.05 0 4.0 0.17 0.048 7 110 12 1.07 0 4.0 0.17 0.059 8 110 24 0.88 0 4.0 0.17 0.039 9 111 24 1.18 0 4.0 0.7 0.049 10 110 3 0.8 0 4.0 0.17 0.036 11 110 1.5 0.8 0 4.0 0.17 0.030 12 110 0.5 0.8 0 4.0 0.17 0.025

Note: NLPH = normalized liters per hour

LHSV = liquid space velocity per hour

Acetal = 2- (4'-hydroxybutoxy) -tetrahydrofuran

Example 3

Samples of crude butane-1,4-diol, the feed material of Example 2, and samples of the butane-1,4-diol product after treatment by the method described in Example 2, were each transferred to respective round bottom flasks filled with nitrogen. . The temperature of the flask was raised to 160 ° C. so that water and “light” were distilled off. Samples were obtained for analysis at intervals after the temperature reached 160 ° C. The results are shown in Table 4 below.

Table 4

sample Raw material product time Acetal 0 0.033 0.03 40 0.06 0.04 100 0.16 0.05 160 0.17 0.057 300 0.17 0.057

Note: Acetal = 2- (4'-hydroxybutoxy) -tetrahydrofuran

Example 4

The general method of Example 1 is repeated using a 2% palladium on carbon catalyst after the process has activated the catalyst as recommended by the supplier. Similar good results were obtained at temperatures between 100 and 125 ° C. with an oxygen pressure of 200 psia (13.79 bar) to 900 psia (62.05 bar).

Example 5

In this example, the results of varying the amount of water added using the same catalyst as the apparatus of Example 2 and using the butanetan-1,4-diol in the form used in Example 1 were observed. The results obtained are shown in Table 5.

In the comparison of operations 1, 3 and 9 of Table 5, the water content of the feedstock decreased from 4.03% to 2.3% and from 0.98%, and the acetal from the product from 0.035% to 0.052% and 0.08% if the other conditions were the same. Each increases. The results shown in Table 5 also indicate that the H ₂ flow rate decreased from 3.0 NLPH (normalized liters per hour, ie liters per hour at 0 ° C. and 1ata (1.01 bar)) to 0.5 NLPH, with acetal removal at three water contents tested. Show minimal effect.

Operations 10 to 14 in Table 5 were to double the liquid hourly space velocity (LHSV) per hour to stimulate the result of a 50% reduction in catalyst activity until the product had the same acetal content obtained in the low acetal content of the product. The catalyst temperature was raised. This allowed the acetal content of the product to increase from 0.052% to 0.099%. While the other conditions remained substantially constant, the catalyst temperature rose by 5 ° C. The results indicate that raising the temperature by 10 ° C. will compensate for 50% loss in catalytic activity.

At temperatures above 120 ° C., the acetal content began to increase; The content of tetrahydrofuran also increased as a result of the dehydrogenation of butane-1,4-diol.

Operations 15-17 in Table 5 show that changing the pressure under substantially the same conditions affects the acetal content of the product. Task 17 pointed out that the same acetal content as Task 14 was produced in principle and there was no significant loss of catalytic activity during the period of operation at high temperatures.

In operations 18 and 19 in Table 5, the activity of the catalyst was confirmed.

The γ-butyrolactone content of the feed material was increased by 6% in task 20 of Table 5. This indicates that the presence of γ-butyrolactone does not inhibit the removal of acetal in the purified butane-1,4-diol product.

Table 5

Claims (13)

It contains a small amount of cyclic acetal compound 2- (4'-hydroxybutoxy) -tetrahydrofuran, and is substantially a method for purifying anhydrous butane-1,4-diol raw material, a) butane-1,4-diol raw material in the presence of a hydrogenation catalyst in the hydrogenation region Hydrogenating; And b) butane with reduced content of 2- (4'-hydroxybutoxy) -tetrahydrofuran Recovering the -1,4-diol product from the hydrogenation zone Including, The hydrogenation step is carried out in the presence of about 0.5% to about 5% by weight of water based on the weight of the butane-1,4-diol raw material. The method of claim 1, Wherein said butane-1,4-diol feedstock contains from about 0.1% to about 0.4% by weight of 2- (4'-hydroxybutoxy) -tetrahydrofuran. The method according to claim 1 or 2, The butane-1,4-diol feedstock hydrocracking di- (C ₁ to C ₄ alkyl) maleate and separating components comprising water and alkanol formed by the hydrocracking in the hydrocracking reaction product. Purifying method is a substantially anhydrous raw material obtained by distilling the hydrocracking reaction product in order to. The method according to any one of claims 1 to 3, Wherein said hydrogenation step is performed at a feed temperature in a range from about 50 ° C. to about 125 ° C. and a feed pressure in a range from about 150 psia (about 10.34 bar) to about 1000 psia (about 68.95 bar). The method according to any one of claims 1 to 4, Wherein said hydrogenation step is carried out using a water content wherein the molar ratio of water: 2- (4′-hydroxybutoxy) -tetrahydrofuran is from about 20: 1 to about 500: 1. The method according to any one of claims 1 to 5, The hydrogenation catalyst is a Group 8 metal-containing catalyst. The method of claim 6, Wherein said hydrogenation catalyst is a palladium-on-carbon catalyst containing from about 0.1% to about 4% by weight of palladium. The method of claim 7, wherein The hydrogenation catalyst is a nickel catalyst. The method according to any one of claims 1 to 8, The butane-1,4-diol product obtained in the hydrogenation step is distilled in an inert gas atmosphere to remove traces of water remaining from the butane-1,4-diol product. The method according to any one of claims 1 to 9, Wherein said butane-1,4-diol feedstock is fed to the hydrogenation zone at a rate corresponding to an hourly liquid space velocity of about 0.5 h ⁻¹ to about 4.0 h ⁻¹ . The method according to any one of claims 1 to 10, A purification method in which the butane-1,4-diol raw material is diluted with an inert diluent before entering the hydrogenation zone. The method of claim 11, And said inert diluent comprises butane-1,4-diol product recovered at the outlet end of the hydrogenation zone. The method according to claim 11 or 12, wherein And a volume ratio of said inert diluent: butane-1,4-diol raw material ranges from about 5: 1 to about 100: 1.