JPH0331696B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for producing 1,5-pentanediol, and more specifically, hydrogenates dialkyl glutarate in the gas phase to produce 1,5-pentanediol with extremely high selectivity and yield through a one-step operation. This invention relates to an improved process for obtaining 5-pentanediol. 1,5-pentanediol is polyurethane,
Useful as a raw material for unsaturated polyester. (Prior Art) Many studies have long been conducted on methods of hydrogenating carboxylic acid esters to obtain corresponding alcohols. Perhaps the most commonly known book is "Organic Reactions" by H. Adkins, Vol., pp. 1-27 (1954). This book describes the hydrogenation of a number of carboxylic acid esters, and the catalyst used is a copper-chromium catalyst, which is very famous as the Adkins catalyst.
Examples of the hydrogenation reaction are described on pages 13 to 22 of the book, and the general reaction conditions are carried out in a liquid phase at a temperature of about 150° C. or higher and a pressure of about 140 atmospheres or higher. However, such reaction conditions vary depending on the type of raw ester, and in particular, high pressure is required for hydrogenation of dicarboxylic acid dialkyl ester, and for example, hydrogenation of glutaric acid ester requires approximately
Pressures of 250 to 350 atmospheres are used. In addition, as a method for hydrogenating carboxylic acid esters, for example, (1) using a catalyst containing Co, Zn, and Cu;
A method of hydrogenation under conditions of 150 to 450°C and 500 to 10,000 psig (Japanese Patent Publication No. 60-45940), (2) A method using a catalyst containing copper or copper oxide, zinc oxide, and silica (Japanese Patent Publication No. 58-50536) (3) A method using a Cu-Cr mixture and copper deposited on a carrier as a catalyst under conditions of 20 to 100 bar and 150 to 300°C (Japanese Unexamined Patent Publication No. 1983-
38333) and (4) a method of hydrogenating a dicarboxylic acid dialkyl ester using a catalyst containing copper and silicon oxide (Japanese Patent Application Laid-Open No. 178037/1983). However, in these technologies (1) to (4),
All reaction examples are carried out in a liquid phase, and in many cases it is preferable to carry out the reaction in a liquid phase.
Furthermore, there are no examples of hydrogenation of glutaric acid esters. On the other hand, attempts have also been made to hydrogenate carboxylic acid esters in the gas phase. US Patent No. 2079414
Lines 49 to 60 of the left column on page 9 of the specification of the No.
Hydrogenation at 300-400°C is disclosed.
In addition, in Japanese Patent Publication No. 1983-501104, Ru, Ni
Alternatively, a method for hydrogenating an ester in the gas phase in the presence of a specific catalyst consisting of Rh, a promoter, and carbon is disclosed, but it essentially relates to a method for producing ethanol from ethyl acetate. Furthermore, in this publication, the following statement is included in column 2, lines 16 to 24. "U.S. Pat. No. 4,346,240 discloses several known catalysts used to hydrogenate esters. These use temperatures above 150°C,
Furthermore, very high pressures (13.8-20.7 MPa) are used, so that the method is a liquid phase method. The catalysts mentioned are Raney nickel, copper chromite or zinc-chromium oxide. However, when catalysts of this type are used in gas phase rather than liquid phase processes, the high temperatures significantly reduce the results. Therefore, up to now it has not been possible to carry out satisfactorily the gas phase hydrogenation of esters to alcohols. '' This statement strongly hints at the difficulty of hydrogenating glutaric acid esters in the gas phase using copper-chromium catalysts. In addition, in Japanese Patent Publication No. 58-500993, a reduced mixture of copper oxide and zinc oxide is used as a catalyst to reduce the
A method of hydrogenation under conditions of about 100 Kg/cm ² and about 75 to 300° C. is disclosed. However, there are no examples regarding the hydrogenation of glutaric acid esters. As mentioned above, there is no example of hydrogenation of glutaric acid ester in the gas phase. (Problems to be Solved by the Present Invention) When trying to hydrogenate glutaric acid ester by the liquid phase method as shown in (1) to (4) above, in most cases high temperature and pressure are required and the reaction equipment etc. Not only does this increase the load on the liquid phase process, but it also causes considerable deterioration of the catalyst inherent in the liquid phase process. This is not only due to the high temperature and high pressure, but also because the catalyst is generally corroded by trace amounts of water and acid contained in the reaction solution or raw materials, and copper etc. are dissolved in the solution, which causes the reaction. This is because the catalyst itself cannot maintain a certain shape, such as becoming reduced copper and precipitating under certain conditions. The reality is that this problem must always be taken into account as long as the reaction is carried out using a liquid phase method. In addition, as mentioned above, there is no example of gas phase hydrogenation of glutaric acid ester, and in the hydrogenation of adipic acid ester exemplified in Japanese Patent Publication No. 58-500993, the conversion rate was low and unreacted materials were It is expected that a great deal of effort will be required to collect and reuse the
Practical methods for hydrogenating glutaric acid esters in the gas phase have been extremely difficult. Furthermore, a reduced mixture of copper oxide and zinc oxide is
It is generally known that catalyst performance is likely to deteriorate at high temperatures due to precipitation of reduced copper, sintering, etc., and careful attention must be paid to the occurrence of localized overheating due to the expected reaction heat in the reaction system. It has disadvantages such as being necessary. (Means for Solving the Problems) The present inventors conducted intensive studies to solve these problems, and found that under the extremely strictly controlled and relatively mild reaction conditions described below,
It was discovered that 1,5-pentanediol can be stably obtained with surprising selectivity, yield, and productivity, and the present invention was achieved. The present invention provides di-( _C1 - _C4 ) alkyl ester of glutaric acid in the presence of a copper-chromium catalyst.
This is a method for producing 1,5-pentanediol, characterized by hydrogenating the ester in the gas phase at a temperature range of 240°C and a pressure range of 10 to 70 atmospheres. By the method of the present invention, hydrogenation can be carried out efficiently, and in some cases, a yield of about 80% or more, preferably 90% or more, and even more preferably 95% or more can be achieved in a single-stage reaction. It is possible to stably obtain 1,5-pentanediol, and from an economic point of view, it is even possible to eliminate the need to circulate and reuse raw material esters and reaction intermediates, simplifying the manufacturing process. It has a huge effect. The present invention will be explained in detail below. In the present invention, di-(C ₁ to _{C 4} ) of glutaric acid
Alkyl ester is used as raw material. Specifically, dimethyl ester, diethyl ester, di-n-propyl ester, diisopropyl ester, di-n-butyl ester, diisobutyl ester, and di-tert-butyl ester of glutaric acid are used. When obtaining 1,5-pentanediol in high yield by the method of the present invention, it is recommended to use dimethyl glutarate or diethyl glutarate, which has a boiling point lower than that of the 1,5-pentanediol produced. It is preferable because it can be easily separated. _C5
The above-mentioned dialkyl esters have extremely low vapor pressures in the reaction temperature range of the present invention, and a huge amount of gas (mainly hydrogen) must be supplied to maintain the reaction system in the gas phase, making this an economical method. I can't say it anymore. Furthermore, there is no particular problem even if the glutaric acid ester contains a small amount of alcohol or a trace amount of water. As the copper-chromium catalyst used in the present invention, specifically, copper chromite known as the so-called Adkins catalyst, barium-stabilized copper chromate, barium oxide-activated copper chromite, etc. can be used. Copper-chromium catalysts containing manganese and zinc can also be used. Further, it may contain silica or alumina added for the purpose of molding the catalyst. The copper content in the catalyst is about 25-50% by weight, preferably about 30-40%, and the chromium content is about 20-50% by weight.
40%, preferably about 25-35%. If the catalyst is suddenly exposed to the reaction conditions described below, the temperature will rise rapidly due to the heat of reduction of copper, damaging the catalyst. It is desirable to carry out pretreatment such that the reduction conditions are gradually brought closer to the reaction conditions. In the present invention, the reaction is carried out at a temperature range of 160 to 240°C, preferably 170 to 230°C, more preferably 180 to 230°C, 10 to 70 atm, preferably 15 to 60 atm, more preferably 20 to 60 atm. Hydrogenation is carried out in the gas phase in the pressure range. At reaction temperatures below 160°C, the reaction rate is extremely low and an extremely large amount of gas (mainly hydrogen) is required to maintain the reaction system in the gas phase.
This is undesirable because it requires the supply of raw materials, and also, at a reaction temperature exceeding 240°C, side reactions rapidly increase, resulting in a decrease in raw material utilization efficiency, which is undesirable. In addition, pressures below 10 atm are unfavorable because the reaction rate decreases and side reactions increase. At pressures above 70 atm, the amount of gas supplied to maintain the gas phase increases, and the surface of the reactor increases. However, it also requires a high degree of pressure resistance, which means that it loses its advantages. The conditions for keeping the reaction system in the gas phase vary depending on the temperature, pressure, type of raw material ester, production ratio of 1,5-pentanediol, etc., and the conditions for maintaining the reaction system in the gas phase vary depending on the temperature, pressure, type of raw material ester, production ratio of 1,5-pentanediol, etc. 80% or more), the vaporization conditions are close to the reaction temperature and reaction pressure of the produced 1,5-pentanediol. In such a case, the amount of hydrogen supply required to maintain the gas phase (abbreviated as the required amount of hydrogen) can be roughly determined by the following equation. (Required amount of hydrogen) / (Raw material ester) (Molar ratio) ≒ (Total pressure of reaction system (atm)) / (P (atm)) Here, P is the total amount of raw material ester (dimethyl glutarate or diethyl glutarate). The vapor pressure of 1,5-pentanediol at the reaction temperature t° C. when converted to 1,5-pentanediol is approximately determined by the following formula. P (atm) = 1/760exp {20.07-5463/162.7+t} In addition, when the raw material is a C ₃ or C ₄ dialkyl ester of glutaric acid, the vapor pressure of these esters at the reaction temperature is 1,5-pentanediol. The amount of hydrogen required is determined by the vaporization conditions of the ester. The reaction can be carried out while supplying hydrogen in an amount of about 1 to several hundred times the required amount of hydrogen, but if the amount of hydrogen supplied is too large, hydrogen supply operations, temperature raising operations, and product cooling operations may be necessary. etc. become complicated,
In addition, there are cases where the contact time between the raw material and the catalyst becomes too short and the reaction yield tends to decrease.
In order to obtain 1,5-pentanediol in a high yield and economically in a one-stage reaction, it is preferable to carry out the reaction while supplying about 1 to 20 times the amount of hydrogen required, and about 1 to 10 times the amount of hydrogen required. It is more preferable to carry out the reaction under double hydrogen supply. The liquid hourly space velocity (LHSV) of the raw material ester relative to the catalyst phase may be determined appropriately depending on the situation, but is usually 0.1 to 10 hr ^-1 , preferably 0.2.
It is carried out at about 3hr ^-1 . (Effects of the Invention) The present invention efficiently hydrogenates glutaric acid ester with high selectivity and yield by using a highly stable copper-chromium catalyst under strictly controlled conditions. 1,5-pentanediol can be obtained. This is an extremely useful method from a practical point of view. (Examples) The present invention will be described in more detail below with reference to Examples, but the present invention is not limited to these Examples in any way. All reactions in the examples were carried out in the following manner. A preheated tube made of SUS316 in which a mixture consisting of a predetermined amount of glutaric acid di-(C ₁ - _{C 4} ) alkyl ester and a predetermined amount of hydrogen is sequentially wound into a coil under a predetermined pressure and heat is supplied from the outside. The gas is supplied to a vessel, heated to a predetermined temperature, and vaporized.
A tubular reactor with well-controlled temperature in an oil bath (catalyst with particle size adjusted to 15 to 32 mesh)
(filled with 15ml). The product-containing gas coming out of the reactor is passed through a tubular condenser.
The gas is cooled to 40°C and the liquefied components are collected in a sample receiver, and the gas is further cooled to -15°C and the liquefied components are collected again. Excess hydrogen gas is released to atmospheric pressure through a pressure regulating valve. The liquefied components are taken out and mixed at each reaction time, and the conversion rate of the raw materials, the selectivity and yield of 1,5-pentanediol, and the amount of by-products are determined by gas chromatography. Here, the selectivity and yield of 1,5-pentanediol are expressed by the following formula. (1,5-pentanediol is abbreviated as PD) PD selectivity (%) = (Number of moles of PD generated) / (Number of moles of raw material ester consumed) x 100 PD yield (%) = (Rate of raw material ester conversion (%) ×PD selectivity (%)) ×1/100 Example 1 Dimethyl glutarate 7.95ml/hr, hydrogen 260N
/hr to the aforementioned preheater and raise the temperature to 200℃,
Copper chromite catalyst (manufactured by Girdler, product name: G-13, 15~) that has been sufficiently treated with hydrogen in advance
15 ml of the powder (pulverized to 32 mesh) was supplied to a filled reaction tube, and the reaction was carried out continuously at 200°C and 30 atm. LHSV is 0.53hr ^-1 . After the reaction was allowed to stabilize for a while, a gas chromatography analysis of the liquefied sample taken 4 to 5 hours after the start of the reaction revealed that the conversion rate of dimethyl glutarate was 99.9%, the PD selectivity was 95.7%, and the PD yield was 95.6. It was %. Also, after conducting this reaction for 100 hours, the reaction results between 100 and 101 hours were as follows:
They were 99.8%, 95.4%, and 95.3%. From this,
It can be seen that 1,5-pentanediol can be stably obtained with extremely high selectivity and yield. Examples 2 to 7 As shown in Table 1, the reaction temperature, reaction pressure and
The same operation as in Example 1 was performed except that LHSV, hydrogen supply amount, etc. were changed, and the reaction results were analyzed for 4 to 5 hours from the start of the reaction. Table 1 shows the results.
Shown below. It can be seen that in both cases, the selectivity and yield of 1,5-pentanediol are extremely high. Comparative Example 1 The same operation as in Example 1 was performed except that the reaction temperature was 250°C. The results are shown in Table 1. Comparative example 2 Reaction temperature was 150℃, hydrogen supply amount was 2000N
The same operation as in Example 1 was performed except that /hr was changed. The results are shown in Table 1. Comparative Example 3 The same operation as in Example 1 was carried out except that the hydrogen supply amount was 180 N/hr, but the reaction system gradually turned into a liquid phase and stable results could not be obtained. Comparative Example 4 The same operation as in Example 1 was performed except that the reaction pressure was 5 atm. The results are shown in Table 1.

【table】

[Table] Examples 8 and 9 Barium-activated copper chromite catalyst (manufactured by Girdler, product name: G-22), or barium-manganese stabilized copper-chromium catalyst (manufactured by Girdler, product name: G-22) The same operation as in Example 1 was performed except that G-99B) was used. The results are shown in Table 2.

[Table] Examples 10 to 12 Changing the raw material ester and changing the hydrogen supply amount to 1200N/
The same operation as in Example 1 was performed except that hr was changed. The results are shown in Table 3.

【table】

Claims (1)

[Claims] 1. Hydrogenating the di-( _C1 - _C4 ) alkyl ester of glutaric acid in the gas phase in the presence of a copper-chromium catalyst at a temperature range of 160-240°C and a pressure range of 10-70 atm. A method for producing 1,5-pentanediol, characterized by: