MXPA00001667A

MXPA00001667A - Method for producing 1,6-hexanediol

Info

Publication number: MXPA00001667A
Application number: MXPA/A/2000/001667A
Authority: MX
Inventors: Boris Breitscheidel; Pinkos Rolf; Frank Stein; Liang Shelue; Hartmuth Fischer Rolf
Original assignee: Basf Ag 67063 Ludwigshafen De
Priority date: 1997-12-23
Filing date: 2000-02-17
Publication date: 2001-05-07

Abstract

The invention relates to a method for producing 1,6-hexanediol by hydrogenating adipic acid esters and/or 6-hydroxycarboxylic acid esters in the gaseous phase at an elevated temperature and pressure in the present of chromium-free catalysts. Hydrogenation is carried out a) using catalysts containing copper, manganese and aluminium as essential constituents or in the presence of Raney copper;b) at temperatures of between 150 and 230°C and pressures of between 10 and 70 bar;c) at a molar ratio of hyrogen to hydrogenating ester of between 150 to 1 and 300 to 1;and d) at a catalyst load of between 0.01 and 0.3 kg C3-ester per litre of catalyst and hour.

Description

PRODUCTION OF 1, 6-HEXANODIOL The present invention relates to an improved process for producing 1,6-hexanediol by hydrogenation in the gas phase of adipic diesters, 6-hydroxycaproic esters or mixtures thereof, in the presence of chromium-free catalysts containing mainly copper, manganese and aluminum , or in the presence of Raney-copper while maintaining certain hydrogenation conditions. Example 1 of WO 97/31882 discloses hydrogenating mixtures of dimethyl adipate and methyl 6-hydroxycaproate in liquid phase at 220 ° C / 220 bar, in the presence of catalysts, consisting of 70% by weight of CuO, 25% by weight of ZnO and 5% by weight of AI2O3, to hexanediol with selectivities above 99% (99.5% conversion). The disadvantage of this hydrogenation in the liquid phase is the high reaction pressure, which results in capital costs for the hydrogenation plant. This disadvantage can be eliminated by hydrogenation in gas phase, since generally distinctly lower reaction pressures, for example, pressures below 100 bar, are sufficient for the ester hydrogenated ones. However, for gaseous phase hydrogenations to be economical, the advantage of the cost of capital side should not be lost through other cost factors. The hydrogenation of the gas phase, therefore, must achieve high selectivity of hexanediol similar to hydrogenation in the liquid phase. Japanese Application open to the public S 64-85938 describes the hydrogenation of dimethyl adipate or diethyl adipate to hexanediol in the gas phase, in the presence of copper chromite catalysts at 160-250 ° C and from 10 to 70 atmospheres and molar ratios diester / hydrogen from 1: 100 to 1: 590. A hexane diol selectivity of more than 98% is obtained in only one of eleven operating examples, ie, a hexandiiol selectivity of 98.9% (conversion 97.5%) in Example 6. However, the hydrogen / diester molar ratio employed in 457 gives rise to very high energy costs. Finally, chromium-containing catalysts are undesirable because of the toxicity of chromium. The safe disposal of deactivated catalysts is very costly. U.S. 5,395,990 states that for the gas phase hydrogenation of dimethyl adipate of example 13, which is carried out at 180 ° C and 62 bar on a catalyst containing copper (41.1% by weight), manganese (6.2% by weight) ) and aluminum (20.4% by weight) with a hydrogen / diester ratio of 480 and a catalyst space velocity of 0.4 1 of the diester per 1 catalyst per hour, which results are similar to those of Example 11. however, Example 11, a gas phase hydrogenation of dimethyl maleate under identical conditions for example 13, does not report selectivity for butanediol. Example 13 of U.S. 5,406,004 describes the hydrogenation of dimethyl adipate to hexanediol at 220 ° C and 62 loar, the molar ratio of the diester / hydrogen between 248 and 383 and the spatial velocity of the catalyst of 0.4 1 of diester per 1 of the catalyst per hour in the presence of the catalyst that it is mentioned in Example 13 of US 5,395,990. The selectivity of hexanediol and the conversion of diester are not reported. It is merely stated that results similar to Examples 2 to 4 were observed. However, these examples do not take into account a real gas phase hydrogenation, since the temperature of the mixture at the reactor outlet is below its condensation temperature. . We have reported Example 13 of U.S. 5,395,990 and Example 13 of U.S. 5,406,004 (as Comparative Examples 14 and 15) and we have found that the selectivity of hexanediol is in each case different, less than 95%. There are two "groups of particular by-products that are responsible for the low selectivity of hexanediol: a) 5-membered cyclic compounds: 2-methylcyclopentanol (1), 2-methylcyclopentanone (2), cyclopentanol (3) and hydroxymethylcyclopentane (4), all of which can be formed from dimethyl adipate: (1) (2) (3) (4) The methanol released during the gas phase hydrogenation of dimethyl adipate can act as a methylating agent. For example, the 5-membered cyclic compounds are obtained in the proportions of 61% of (1), 29% of (2), 6% of (3) and 4% of (4), based on the total of the 5-membered cyclic compounds, in example 5. The process described in EP-A 251 111, which consists in the reaction of adipic diesters at 300-345 ° C in the gas phase on solid oxidic catalysts of the elements of the group Main I to V and transition groups I to VIII of the periodic table of the elements or oxides of rare earth metals, especially aluminum oxide, still favors cyclopentanone for the main product. b) Esters of C12 and C13 The transesterification of methyl 6-hydroxycaproate with hexanediol gives rise to 6-hydroxycaproate of 6-hydroxyhexyl (5%).

HO-CH2- (CH2) 4-C-0- (CH2) 5OH (5) Although in a much smaller amount than (5_), the 6-hydroxyhexyl methyl adipate (6) is apparently formed through the transesterification of dimethyl adipate with hexanediol. 0 O CH3O-C- (CH2) 4- C -O- (CH2) 5OH (6) The molar ratio of (5) to (6) is approximately 90:10.

The quantitatively dominant byproduct (5) has a significantly higher molecular weight (PM 232) and therefore a different boiling point than dimethyl adipate (MW 174) and methyl 6-hydroxycaproate (MW 146). The higher the production of (5) and (6), the higher the temperatures and / or hydrogen rates necessary to vaporize and hydrogenate in gaseous phase (5) and (6). And the separation of (5) and (6) of the stream leaving the hydrogenation reactor, for recycling, is complicated. Therefore, unless they can be hydrogenated, they should be considered as byproducts. An object of the present invention is to provide a process for the gas phase hydrogenation of adipic diesters, 6-hydroxycaproic esters or mixtures of adipic diesters and 6-hydroxycaproic esters to hexanediol in the presence of mainly copper catalysts with hexanediol selectivities not less than 95%, especially more than 98%, coupled with Ce ester conversions not less than 90%, especially not less than 95%. We have found that this objective is achieved according to the present invention by a process for producing hexanediol by hydrogenation of adipic esters and / or hydroxycaproic esters at elevated temperature and pressure in the presence of chromium free catalysts, which consists of hydrogenating: a) a catalyst that contains copper, manganese and aluminum as essential constituents or on copper Raney. b) at a temperature from 150 to 230 ° C and a pressure from 10 to 70 bar, c) at a molar ratio of hydrogen to ester to be hydrogenated within the range from 150: 1 to 300: 1, and d) at a rate of the catalyst from 0.01 to 0.3 kg of the Cg ester per liter of catalyst per hour.

It is surprising that it is possible to maintain the sum total of the 5-membered sub-produced cyclic compounds and the 6-hydroxyhexyl esters of Ce acid below 5 mole%, especially 2 mole% (based on the adipic diester feed and of the 6-hydroxycaproic ester) to thus obtain a selectivity of the hexanediol not less than 95%, especially not less than 98%. The gas phase hydrogenation of methyl adipate and methyl 6-hydroxycaproate, as mentioned at the beginning, sub-produced (presumably by methyl cyclopentanone-2-carboxylate and cyclopentanone 2-methylcyclopentanol, 2-methylcyclopentanone, cyclopentanol and hydroxymethylcyclopentane. These byproducts are usually from the hydrogenation of esters of monocarboxylic acids and / or dicarboxylic acids of Ce - Therefore, these are not observed in the hydrogenation of alpha, omega-diesters of acids of C4 / Cs, C and Cs. its quantity increases with the increase in temperature.Gase phase hydrogenation of adipic diesters also subproduces the esters 6-hydroxycaproate 6-hydroxyhexyl and methyl adipate 6-hydroxyhexyl high boiling point.These are increasingly hydrogenated to hexanediol , the product of value, with increasing temperature.

Despite the mutually opposite response of the two groups of by-products to changes in temperature, it is surprisingly possible to obtain the desired selectivity of 95% to 98%. Nor was it predictable that, despite the formation of the by-product, the catalyst would have a long effective life. In addition, the higher selectivities of hexanediol and the long lives of the catalyst are surprisingly obtained with the use of mixtures of adipic diesters / 6-hydroxycaproic ester produced in accordance with DE-A 19 607 954, which includes numerous other compounds. The starting materials for the process of the present invention can be pure adipic esters, for example, dialkyl (of C? -C4) diesters, 6-hydroxycaproic esters, for example, alkyl (C1-C4) esters, or mixtures of the same. Preferably, it is possible to use mixtures of esters such as those obtained in the esterification with C1-C4 alcohols of carboxylic acid mixtures byproducted in the oxidation of cyclohexane to cyclohexanone / cyclohexanol. These mixtures may also include, for example, glutaric diesters, 5-hydroxyvaleric esters, 2-oxocaproic esters and dihydromuconic diesters. The process of the present invention preferably operates using methyl and ethyl esters of the aforementioned carboxylic acids as the starting materials. The hydrogenation is carried out catalytically in the gas phase. Suitable catalysts are chromium-free catalysts which contain mainly copper, manganese and aluminum with or without minor amounts of zinc, zirconium and / or silicon. These include, in particular, catalysts such as those described in EP 0 552 463. These are catalysts which, in the oxidized form, have the composition: CuaAlbZrcMndOx where a > 0, b > 0, c = 0, d > 0, a > b / 2, b > a / 4, a > c, a > d and x is the number of necessary oxygen ions, per unit formula, to preserve electrical neutrality. A specific example of a suitable catalyst is composed of about 70% by weight of CuO, 20% by weight of I2O3 and 10% by weight of Mn2? 3. The catalysts can be prepared, for example, according to EP 0 552 463, by precipitation of the sparingly soluble compounds of the solutions containing the corresponding metal ions in the form of their salts. Examples of suitable salts are halides, sulfates and nitrates. Suitable precipitants include all agents that give rise to the formation of these insoluble intermediates as they are convertible to the oxides by heat treatment. Particularly suitable intermediates are hydroxides and carbonates or bicarbonates, so that the precipitants used are particularly preferably alkali metal carbonates or ammonium carbonates. An important step in the preparation of the catalysts is the thermal treatment of the intermediates at temperatures between 500 ° C and 1000 ° C. The BET surface area of the catalysts is within the range of 10 to 150 m / g. Otherwise, it is possible to use Raney copper as the catalyst; Raney copper is traditionally prepared by treatment of copper-aluminum alloys with alkali metal hydroxide and is used in the form of parts. The catalysts can be placed in a fixed bed reactor or in a fluidized bed reactor. The hydrogenation can be carried out in a downflow or upflow mode. It is advantageous to use at least sufficient hydrogen as a hydrogenating agent and carrier gas to prevent the starting materials, intermediates and products from liquefying during the reaction. Excessively preferred hydrogen is recycled, although a small portion can be removed from the system as exhaust gas so that inerts, for example methane, can be removed. It is possible to use a reactor or a plurality of reactors connected in series or in parallel.

The hydrogenation temperature is within the range of 150 ° C to 230 ° C, preferably within the range of 160 ° C to 200 ° C, particularly preferably within the range of 170 ° C to 190 ° C. The reaction pressure is within the range of 10 bar to 70 bar, preferably in the range of 20 bar to 60 bar, particularly preferably in the range of 30 bar to 50 bar. The molar ratio of hydrogen to the sum total of the esters used is within the range of 150 to 300, preferably ^ within the range of 170 to 290, particularly preferably within the range of 180 to 280. The space velocity of the catalyst is within the range of 0.01 to 0.3, preferably within the range of 0.05 to 0.2, particularly preferably within the range of 0.05 to 0.15 kg of the Ce ester to be hydrogenated per 1 catalyst per hour. . The conversion, based on the sum total of hexane diol forming Ce compounds such as adipic diesters, 6-hydroxycaproic esters, caprolactone and dihydromucone diesters, should be greater than 90%, especially greater than 95%. Hydrogenation is advantageously carried out as a continuous process. The hydrogenation exit streams are condensed and preferably treated by distillation. The hydrogenation exit stream consists mainly of 1,6-hexanediol and the alcohol corresponding to the ester group. Other constituents, in particular with the use of ester mixtures produced in accordance with DE-A 19607954, are 1,5-pentanediol, 1,4-butanediol, 1,2-cyclohexanediols and also monoalcohols having from 1 to 6 carbon atoms and water. The unconverted initial compounds present in the hydrogenation exit stream can be removed by distillation and recycled to the hydrogenation step.

Examples A) Apparatus for hydrogenation: Continuous processes were carried out in the apparatus the hydrogenation represented schematically in Figure 1. This consists of a vaporizer (E), a tubular reactor of 1.4 1 (30 x 2000 mm) (R), two condensers Ci and C2 and a pressure separator (S) to recover the condensable components of the hydrogen stream, a cyclic gas compressor (K) to recycle the cyclic hydrogen gas (3) and a discharge vessel T to collect the effluent from the reaction (4).

Process : Examples 1-12 and Examples 14-15 were each performed using a CuO (70% by weight) / M 2? 3 (10% by weight) / Al 203 (20% by weight) catalyst from Süddchemie (T4489), which was activated in the reactor at 160-200 ° C using mixtures of hydrogen / nitrogen in a volume ratio from 1:99 to 100: 0. The zone of the catalyst was joined by a layer of quartz rings at the end of the updraft and at the end of the downstream. The gas in the cycle was used in all cases, although 10% of the gas in cycle (5) was bled from the system and replaced by the same amount of fresh hydrogen. Example 13 was made using Raney copper catalyst A 3900 from Activated Metals. The initial compounds esters of & (1) were dosed with a pump (P) in the vaporizer, where they were vaporized and passed in gaseous form and mixed with preheated hydrogen (2) in the reactor. The molar ester / hydrogen ratio was determined by weighing the feed stream of the initial material by inhibiting the hydrogen currents. The discharge stream of the hydrogenation was weighed after condensation. Its composition was determined quantitatively by gas chromatography using an internal standard (diethylene glycol dimethyl ether). Each run was operated for approximately four days without change before the discharge stream of the hydrogenation was analyzed.

Examples of inventiveness 1-12 These examples were made using 500 ml of CuO / Mn2? 3 / Al2? 3 catalyst. Pure dimethyl adipate was used (density d = 1063 according to page 36 of the Aldrich-Chemie catalog, 1994, Steinheim). In Example 12, the dimethyl adipate was replaced by a mixture, produced according to DE-A 19 607 954, of dimethyl adipate, methyl 6-hydroxycaproate and other esters. The composition of the mixture was 52.3% dimethyl adipate, 9.1% methyl 6-hydroxycaproate, 5.2% caprolactone, 4.1% dimethyl dihydromuconate, 1.5% dimethyl succinate, 2.5% valerolactone 2.2% ester 5 -hydroxyvalent, 2.7% 2-oxocaproic ester and 6.4% dimethyl glutarate (by weight in each case).

Example of the invention 13 Pure dimethyl adipate was used. 500 ml of Raney copper was used as a catalyst.

Comparative examples 14 - 16 Comparative Example 14 was repeated from Example 13 of U.S. 5,395,990 and Comparative Example 15 was repeated from Example 13 of U.S. 5,406.004: 220 ° C; molar ratio of dimethyl adipate / hydrogen = 1: 248. 150 ml of CuO / Mn2? 3 / Al2? 3 catalyst was used. All results are as shown in the following in Table 1.

/ * Hydrogenation of dimethyl adipate in gas phase on T 4489 catalyst 15 1) 2-methylcyclopentanol + 2-methylcyclopentanone + cyclopentanol hydroxymethylcyclopentane 2) 6-hydroxycaproate 6-hydroxyhexyl + 6-hydroxyhexyl methyl adipate 3) hydrogenation of one mole of C12-C13 ester yields two moles of hexanediol 4) use of mixtures of dimethyl adipate / methyl 6-hydroxycaproate in lug ^ r of pure dimethyl adipate using Raney copper instead of T 4489

Claims

/to CLAIMS A process for producing 1,6-hexanediol by hydrogenation of adipic esters, and / or 6-hydroxycaproic esters in the gas phase, at elevated temperature and elevated pressure, in the presence of chromium-free catalysts, consisting of hydrogenating. a) on a catalyst containing copper, manganese and aluminum as essential constituents or on Raney copper. b) at a temperature from 150 to 230 ° C and a pressure from 10 to 70 bar, c) in a molar ratio of hydrogen to ester to be hydrogenated within the range from 150: 1 to 300: 1, and d) at a rate of the catalyst from 0.01 to 0.3 kg of the C6 ester per liter of catalyst, per hour. The process as recited in claim 1, wherein the catalyst further contains zinc, zirconium and / or silicon. The process as mentioned in claim 1, wherein the space velocity of the catalyst used is in the range from 0.05 to 0.2 kg of Ce ester per liter of catalyst per hour. The process as recited in claim 1, wherein the space velocity of the catalyst used is in the range from 0.05 to 0.15 kg of the ester of c¿ per liter of catalyst per hour. The process as recited in claim 1, wherein the molar ratio of hydrogen to Ce ester is within the range of 170 to 290. 6. The process as recited in claim 1, wherein the molar ratio of Hydrogen to the Ce ester is within the range from 180 to 280. 7. The process as recited in claim 1, wherein the temperature is within the range of from 160 ° C to 200 ° C. 8. The process as recited in claim 1, wherein the temperature is within the range of 170 ° C to 190 ° C. 9. The process as recited in claim 1, wherein the pressure is within the range of 20 to 60 bar. 10. The process as mentioned in claim 1, wherein the pressure is within the range of 30 to 50 bar. The process as recited in claim 1, wherein the ester to be hydrogenated consists of a mixture of adipic diester and 6-hydroxycaproic ester. 12. The process as recited in claim 1, wherein the starting materials used are alkyl (of C? -C4) monoesters of 6-hydroxycaproic acid and / or alkyl (of C1-C4) diesters of adipic acid. - The process as mentioned in claim 1, wherein the initial materials to be hydrogenated are mixtures of esters such as those generated by the esterification of mixtures of carboxylic acids obtained as by-products in the production of cyclohexanol / cyclohexanone by oxidation of cyclohexane with gases containing oxygen.