WO2016091058A1 - Method for preparing 3-pentanone from 2-pentene - Google Patents

Abstract

Disclosed is a method for preparing 3-pentanone from 2-pentene. The method comprises the following steps: 1) 2-pentene and acetic acid are mixed and an addition reaction takes place in a liquid phase through a catalyst bed, and special conditions are controlled so as to convert the 2-pentene and the acetic acid into amyl acetate; 2) the reaction liquid is rectified, unreacted 2-pentene and acetic acid are firstly recovered under normal pressure, and then amyl acetate with a mass fraction of 99.50% is obtained under reduced pressure; 3) methanol and the amyl acetate are subjected to a catalytic rectification reaction to obtain a mixture of 2-pentanol and 3-pentanol; 4) the mixture of 2-pentanol and 3-pentanol is rectified to obtain 3-pentanol with a mass percentage content of 99.5%; and 5) the 3-pentanol is subjected to a catalytic dehydrogenation and rectification reaction, so as to directly prepare 3-pentanone with a high purity. Compared with existing processes, the method has the advantages of a high conversion rate and a good selectivity; and the method not only has a production cost which is greatly reduced, but is also a green and environmentally friendly production process.

Description

Method for preparing 3-pentanone from 2-pentene Technical field

The present invention relates to a process for the preparation of 3-pentanone from 2-pentene, and in particular to a process for the preparation of 3-pentanone from 2-pentene by addition, transesterification and dehydrogenation.

Background technique

3-pentanone is an important intermediate in fine chemical products, mainly used in the preparation of pesticides, pharmaceuticals and other products. 3-pentanone can be obtained by high temperature decarboxylation of propionic acid. However, since the reaction is a process of reducing the molecular weight and it is required to carry out the reaction at a very high temperature, the reaction conditions are severe and the production efficiency is not satisfactory. In addition, 2-pentene obtained by processing petroleum to produce ethylene by-produced carbon five fractions as a raw material can also produce 3-pentanol by hydration reaction, including 2-pentene indirect hydration and direct hydration. Process, although indirect hydration has the advantages of high conversion rate and good selectivity, due to the need to use sulfuric acid in the preparation process, the corrosion resistance of the equipment is extremely high, and the environmental pollution is still serious, but the direct hydration process does not have these problems. It is an environmentally friendly technical route, but the shortcoming of this method is that the reaction conversion rate is too low, and the circulation amount of the raw material 2-pentene is extremely large. There have been no reports on the preparation of 3-pentanone by dehydrogenation of 3-pentanol.

Summary of the invention

The present invention provides a process for producing 3-pentanone from 2-pentene, which solves the technical problem of attempting to prepare 3-pentanone from 2-pentene by addition, transesterification and dehydrogenation.

The following is a technical solution of the present invention to solve the above technical problems:

A method for preparing 3-pentanone from 2-pentene, characterized in that the method comprises the steps of:

1) adding 2-pentene to acetic acid, and then performing an addition reaction in a liquid phase through a catalyst bed to convert 2-pentene and acetic acid into amyl acetate to obtain a reaction liquid; the acetic acid and 2-pentene The molar ratio is 2 to 5:1, the mass space velocity of the addition reaction is 1 to 3 hr ^-1 , the reaction temperature is 80 to 100 ° C, the reaction pressure is 0.8 to 2.0 MPa, and the catalyst in the catalyst bed Is a sulfonic acid cation exchange resin, the mass exchange capacity of the sulfonic acid cation exchange resin is 3 to 5.5 mmol / g;

2) The reaction liquid obtained in the step 1) is subjected to rectification in a rectification column having a theoretical plate of 30; first, unreacted 2-pentene and acetic acid are recovered under normal pressure; and the mass fraction is obtained at 99.50 under reduced pressure. % of amyl acetate; the obtained 2-pentene and acetic acid are recycled.

3) The methanol and the amyl acetate obtained in the step 2) are subjected to catalytic transesterification to obtain a mixture of 2-pentanol and 3-pentanol; the transesterification reaction temperature is 62-80 ° C, and the molar ratio of methanol to amyl acetate The ratio is 2.0 to 5.0:1; the catalyst is sodium methoxide, the catalyst is added in an amount of 0.3 to 2% by mass of the amyl acetate, and the methyl acetate as a by-product of the transesterification is separated from the top of the rectification column to control the reflux ratio of the rectification column. 1:1 to 4:1;

4) The mixture of 2-pentanol and 3-pentanol obtained in the step 3) is subjected to rectification, and the rectification is carried out in a rectification column having a theoretical plate of 70; the temperature in the column is 118 to 125 ° C, and the reflux ratio is At 10 to 20:1, a fraction of 115 to 116 ° C is collected from the top of the column. A 3-pentanol having a content of 99.5% is obtained; when the temperature of the column is 126-130 ° C and the reflux ratio is 10-20: 1, a fraction of 118-119 ° C is collected from the top of the column, and the product is 99.5%. 2-pentanol.

5) The 3-pentanol obtained in the step 4) is directly subjected to catalytic dehydrogenation distillation to obtain high-purity 3-pentanone; the catalytic dehydrogenation reaction temperature is 113-118 ° C, the reaction pressure is normal pressure, and the catalyst 3 - The pentanol loading WWH is 2.5-5.5 hr ^-1 , and the dehydrogenation reaction uses a granular Raney nickel-type metal alloy as a catalyst, and its composition is:

Al-Ni-A

Wherein A is one selected from the group consisting of Ce and Bi; the dehydrogenation reaction product is discharged in a gas phase, and the gas phase reaction product is directly purified into a rectification column having a theoretical plate of 50 to obtain a high-purity 3-pentanone product, and the rectification is controlled. The reflux ratio is from 1:1 to 10:1.

The composition of the catalyst in the step 5) of the present invention is: Al-Ni-A, wherein A is one selected from the group consisting of Ce and Bi, and the weight ratio of each component is: Al:Ni:A=1:(0.8 ～0.94): (0.03 to 0.2); the catalyst has a particle size of 0.01 to 0.1 mm.

The component A in the catalyst for the catalytic dehydrogenation reaction in the step 5) of the present invention is selected from Ce; and the catalyst in the step 5) has a particle size of 0.02 to 0.08 mm.

The molar ratio of acetic acid to 2-pentene in the step 1) of the present invention is 2.5 to 3.5:1, the mass space velocity of the addition reaction is 1.5 to 2.5 hr ^-1 ; and the reaction temperature is 85 to 90 ° C; The reaction pressure is 0.9 to 1.5 MPa.

The catalyst sulfonic acid cation exchange resin described in the step 1) of the present invention has a mass exchange capacity of 4 to 5 mmol/g.

The transesterification reaction temperature in the step 3) of the present invention is 65 to 75 ° C, and the molar ratio of methanol to amyl acetate is 3.0 to 4.0:1.

The catalyst sodium methoxide described in the step 3) of the present invention is added in an amount of 0.5 to 1% by mass of the amyl acetate.

The reflux ratio of the rectification described in the step 3) of the present invention is from 2:1 to 3:1.

The catalyst described in the step 5) of the present invention has a 3-pentanol loading WWH of from 3 to 4 hr ^-1 .

The reflux ratio of the rectification described in the step 5) of the present invention is from 2:1 to 6:1.

The molar ratio of acetic acid to 2-pentene in the above step 1) is preferably 2.5 to 3.5:1; the mass exchange capacity of the sulfonic acid cation exchange resin is preferably 4 to 5 mmol/g; The reaction temperature is preferably from 1.5 to 2.5 hr ^-1 ; the reaction temperature is preferably from 85 to 90 ° C; and the reaction pressure is preferably from 0.9 to 1.5 MPa.

The molar ratio of methanol to amyl acetate in the above step 3) is preferably from 3.0 to 4.0:1; the reaction temperature is preferably from 65 to 75 ° C; and the amount of the catalyst is preferably from 0.5 to 1% by mass of the amyl acetate. The reflux ratio of the rectification is preferably from 2:1 to 3:1.

The rectification described in the above step 4) can be carried out in a continuous operation or a batch operation, and the obtained 2-pentanol is also a fine chemical intermediate having a higher added value.

In the above step 5), the component A in the dehydrogenation catalyst is preferably selected from Ce; the particle size of the catalyst is preferably 0.02 to 0.08 mm; the 3-pentanol load WWH of the catalyst is 3 to 4 hr ^-1 ; It is preferably from 2:1 to 6:1.

The surface of the sulfonic acid cation exchange resin in the above step 1) contains a sulfonic acid group. When catalyzing the addition reaction of 2-pentene with acetic acid, it preferentially adsorbs acetic acid and forms a liquid crystal film of acetic acid on the surface of the catalyst. After the pentenene molecule diffuses to the surface of the liquid film, it must pass through the liquid film and adsorb on the surface of the catalyst in a chemical adsorption state, and then an electrophilic addition reaction of the positive carbon ion with the acetic acid occurs. For the addition reaction, acetic acid is more reactive than water, so that the conversion and selectivity of the reaction are significantly improved.

In the addition reaction in the above step 1), the addition reaction product of 2-pentene and acetic acid is a mixture of sec-amyl acetate and (3-pentyl) acetate, wherein sec-amyl acetate accounts for about 30% of the total mass. The (3-pentyl) acetate was 70%.

The above step 3) catalytic distillation reaction can be carried out in a catalytic rectification plant comprising two upper and lower portions, the upper part being a rectification part and the lower part being a reaction part. The reaction by-product methyl acetate is vaporized and then raised to the upper rectification column for rectification separation, methyl acetate is obtained at the top, and unreacted methanol is refluxed from the rectification portion to the transesterification reaction portion to continue the reaction. The methyl acetate produced by transesterification can be treated as a by-product.

In the transesterification reaction, no isomerization reaction was found, and the ratio of 2-pentanol to 3-pentanol produced was unchanged, and the 3-pentanol content was still 70%. The boiling point of 2-pentanol is 118.8 ° C, and the 3-pentanol is 115.3 ° C. By using the difference in boiling point between the two, 2-pentanol and 3-pentanol products having a content of 99.5% or more can be obtained, respectively.

The above step 5) catalytic rectification reaction can also be carried out in a catalytic rectification plant comprising two upper and lower portions, the upper part being a rectification part and the lower part being a reaction part. The reaction portion is a liquid phase slurry bed reactor, and the rectification portion may be a tray rectification column. After the reaction product is vaporized, it is raised to the upper rectification column for rectification, and a high-purity 3-pentanone product is obtained at the top of the column, and the unreacted 3-pentanol is directly refluxed from the rectification portion to the dehydrogenation reaction portion to continue the reaction.

In the above step 5), a good performance Al-Ni-Ce or Bi catalyst is selected in the 3-pentanol dehydrogenation reaction, and the reaction can be carried out at a lower temperature due to the high catalyst activity, and the catalyst is The treatment capacity is significantly improved while the product selectivity reaches 100%, which ensures that the reactants do not contain any by-products, and the conversion of 3-pentanol is the same as the purity of the product.

The key to the present invention is the development of a process for the preparation of 3-pentanone from 2-pentene. Compared with the existing process, it has the advantages of high conversion rate and good selectivity, which not only greatly reduces the production cost, but also is a green production process.

detailed description

The invention is further illustrated by the following examples, which are intended to illustrate the invention and not to limit the scope of the invention.

In each of the examples, the conversion and selectivity of the addition reaction, the transesterification reaction, and the dehydrogenation reaction were respectively calculated by the following formula. The transesterification reaction of the present invention is a catalytic transesterification distillation reaction, and the dehydrogenation reaction is a catalytic dehydrogenation rectification reaction.

The conversion rate of the addition reaction, the transesterification reaction and the dehydrogenation reaction, the raw materials and products in the above-mentioned various formulas refer to the raw materials and direct products in which the corresponding reactions occur, and the addition reaction, transesterification reaction and dehydrogenation in the above various formulas The raw materials, intermediate products, products, and catalysts involved in the conversion and selectivity of the reaction are all by mass.

[Examples 1 to 10]

Addition reaction:

Addition reaction: 2-pentene is mixed with acetic acid and then subjected to an addition reaction in a liquid phase through a catalyst bed to convert 2-pentene and acetic acid into amyl acetate to obtain a reaction liquid; wherein the acetic acid and 2 The molar ratio of pentene is 2 to 5:1, the mass space velocity of the addition reaction is 1 to 3 hr ^-1 , the reaction temperature is 80 to 100 ° C, and the reaction pressure is 0.8 to 2.0 MPa. The catalyst in the sulfonic acid-based cation exchange resin has a mass exchange capacity of 3 to 5.5 mmol/g.

The reaction liquid obtained above is subjected to rectification in a rectification column having a theoretical plate of 30, and unreacted 2-pentene and acetic acid are first recovered under normal pressure, and then the mass percentage is 99.50% or more under reduced pressure. Amyl acetate.

The above addition reaction was carried out in a tubular fixed bed reactor having a size of φ25 mm × 1500 mm. The reactor was charged with 100 g of a spherical sulfonic acid cation exchange resin catalyst having a particle diameter of 0.40 to 1.25 mm to constitute a fixed bed catalyst bed, and the mass exchange capacity of the resin was 3 to 5.5 mmol/g. The reactor is equipped with a circulating hot water temperature control jacket, and a temperature measuring platinum resistor is installed on the upper, middle and lower sides of the catalyst bed. The reaction feed is controlled by the feed pump and the system pressure is regulated by the back pressure valve.

The reaction raw material is reacted through a fixed bed at a set feed amount, and an addition reaction is carried out under the reaction conditions set as described above. The addition reaction products obtained in each of Examples 1-10 were subjected to component analysis by a chromatographic method, and the conversion ratio and product selectivity of the addition reactions of the respective examples were respectively calculated. The reaction conditions and results of the respective examples are shown in Table 1.

Table 1

[Examples 11 to 20]

Transesterification

Transesterification reaction: a mixture of methanol and pentyl acetate obtained in Examples 1 to 10, respectively, is subjected to catalytic transesterification to obtain a mixture of 2-pentanol and 3-pentanol; wherein the molar ratio of methanol to amyl acetate a ratio of 2.0 to 5.0:1, a reaction temperature of the catalytic transesterification reaction is 62 to 80 ° C, a catalyst is sodium methoxide, and a catalyst is added in an amount of 0.3 to 2% by mass of the amyl acetate; The methyl acetate, a by-product of the catalytic transesterification distillation reaction, is discharged in a vapor phase, and the gas phase reaction product directly enters the distillation column of the theoretical plate of 30 and is separated from the top of the rectification column, and the reflux ratio of the controlled rectification is 1:1. ~4:1.

The obtained mixture of 2-pentanol and 3-pentanol was separately subjected to rectification in a rectification column having a theoretical plate of 70. Wherein, when the temperature of the column is 118 to 125 ° C and the reflux ratio is 10 to 20:1, the fraction of 115 to 116 ° C is collected from the top of the column to obtain a content of 99.5% 3-pentanol; when the temperature of the column is 126-130 ° C and the reflux ratio is 10-20:1, the fraction of 118-119 ° C is collected from the top of the column, and the fraction product is 99.5 by mass. More than % of pentaerythritol.

The above transesterification reaction is carried out in a reactive rectification unit consisting of a transesterification reactor and a rectification column. The reactor was a 1000 ml glass reactor. The top of the reactor is connected to the rectification column. The number of theoretical plates of the rectification column is 30, and a condensing reflux device with a discharge port is arranged at the top of the rectification column.

130 grams of amyl acetate and a quantity of methanol were added to the reactor, and a sodium methoxide catalyst was added to the reactor. The reactor is heated and heated to carry out a reaction, and the reflux ratio of the rectification is controlled. The methyl acetate produced by the reaction is removed by collecting the outlet material at the top of the rectification column. When the methyl acetate was not collected at the top outlet of the rectification column, the reaction was completed. The reaction solution was cooled to room temperature, and the liquid material was subjected to rectification to obtain 2-pentanol and 3-pentanol in an amount of 99.5% or more, respectively. 3-pentanol can be used as a raw material for the preparation of 3-pentanone by dehydrogenation.

The transesterification reaction products obtained in Examples 11 to 20 were subjected to component analysis by chromatography, and the conversion of the reaction and the selectivity of the product were calculated. The reaction conditions and results of the respective Examples 11 to 20 are shown in Table 2.

Table 2

[Examples 21 to 30]

Dehydrogenation reaction

Dehydrogenation reaction: The 3-pentanol obtained in Examples 11 to 20 was directly subjected to a catalytic dehydrogenation distillation reaction to obtain a high purity of the 3-pentanone. The reaction temperature of the catalytic dehydrogenation distillation reaction is 113-118 ° C, the reaction pressure is normal pressure, the 3-pentanol load WWH of the catalyst is 2.5-5.5 hr ^-1 , and the catalytic dehydrogenation distillation reaction adopts the granular Raney nickel type. The metal alloy is used as a catalyst, and its composition is: Al-Ni-A, wherein A is one of Ce and Bi, and the weight ratio of each component is: Al:Ni:A=1:(0.8-0.94):(0.03 ~0.2). The particle size of the catalyst is generally from 0.01 to 0.1 mm.

The product of the catalytic dehydrogenation distillation reaction is discharged in a gas phase, and the gas phase reaction product directly enters a rectification column having a theoretical plate of 50 for rectification and purification to obtain a high purity of the 3-pentanone product, and the rectification is controlled by rectification. The reflux ratio is from 1:1 to 10:1.

The above reaction is carried out in a reactive rectification unit consisting of a dehydrogenation reactor and a rectification column. The reactor is a 1000ml glass reactor. The reactor is equipped with a mechanical stirring device, a thermometer, a feed port and a rectification column. The external heating device has a theoretical plate number of 60 on the rectification column and a zone on the top of the rectification column. There is a condensing return device for the vent and the discharge port. In the reactor, 700 g of 3-pentanol was first added, and then 50 g of a Raney nickel catalyst having a particle size of 0.03 to 0.05 mm was introduced into the reactor. The reactor was heated to 113 to 118 ° C, and then maintained at this temperature. 3-pentanol was continuously pumped into the reactor for reaction. The reaction pressure is normal pressure, the catalyst has a 3-pentanol loading WWH of 2.5 to 5.5 hr ^-1 , the number of theoretical plates of the rectification column is 50, and the reflux ratio of the controlled rectification is 1:1 to 10:1. The hydrogen produced by the dehydrogenation is discharged through the vent at the top of the rectification column, and the outlet material at the top of the rectification column is collected as a product. It should be noted that the 3-pentanol feed amount and the product discharge amount should be controlled to balance each other to maintain the stability of the system. The compositions of the catalysts of Examples 21 to 30, specific reaction conditions, 3-pentanol conversion and 3-pentanone selectivity of the dehydrogenation reaction, and the purity of the product are shown in Tables 3 and 4.

table 3.

	Catalyst component	Weight ratio of each component	temperature reflex	WWH(hr -1 )
Example 21	Al-Ni-Ce	1:0.8:0.2	113	2.5
Example 22	Al-Ni-Bi	1:0.94:0.03	118	5.5
Example 23	Al-Ni-Ce	1:0.94:0.05	114	3.6
Example 24	Al-Ni-Ce	1:0.94:0.07	115	3.8
Example 25	Al-Ni-Bi	1:0.94:0.1	116	3.2
Example 26	Al-Ni-Ce	1:0.94:0.13	117	3.0
Example 27	Al-Ni-Bi	1:0.8:0.18	116	3.5
Example 28	Al-Ni-Bi	1:0.94:0.06	117	4.0
Example 29	Al-Ni-Bi	1:0.8:0.17	118	3.5
Example 30	Al-Ni-Bi	1:0.8:0.15	116	3.0

Table 4.

	3-pentanol conversion rate (%)	3-pentanone selectivity (%)	Reflux ratio	3-pentanone purity (%)
Example 21	99.9	100	1:1	99.8
Example 22	99.8	100	10:1	99.7
Example 23	99.9	100	2:1	99.9
Example 24	99.8	100	3:1	99.8

Example 25	99.9	100	6:1	99.9
Example 26	99.8	100	5:1	99.9
Example 27	99.9	100	4:1	99.8
Example 28	99.7	100	3:1	99.8
Example 29	99.9	100	3:1	99.8
Example 30	99.8	100	5:1	99.8

Claims (10)

1. A method for preparing 3-pentanone from 2-pentene, characterized in that the method comprises the steps of:

   1) adding 2-pentene to acetic acid, and then performing an addition reaction in a liquid phase through a catalyst bed to convert 2-pentene and acetic acid into amyl acetate to obtain a reaction liquid; the acetic acid and 2-pentene The molar ratio is 2 to 5:1, the mass space velocity of the addition reaction is 1 to 3 hr ^-1 , the reaction temperature is 80 to 100 ° C, the reaction pressure is 0.8 to 2.0 MPa, and the catalyst in the catalyst bed Is a sulfonic acid cation exchange resin, the mass exchange capacity of the sulfonic acid cation exchange resin is 3 to 5.5 mmol / g;

   2) The reaction liquid obtained in the step 1) is subjected to rectification in a rectification column having a theoretical plate of 30; first, unreacted 2-pentene and acetic acid are recovered under normal pressure; and the mass fraction is obtained at 99.50 under reduced pressure. % of amyl acetate; the obtained 2-pentene and acetic acid are recycled.

   3) The methanol and the amyl acetate obtained in the step 2) are subjected to catalytic transesterification to obtain a mixture of 2-pentanol and 3-pentanol; the transesterification reaction temperature is 62-80 ° C, and the molar ratio of methanol to amyl acetate The ratio is 2.0 to 5.0:1; the catalyst is sodium methoxide, the catalyst is added in an amount of 0.3 to 2% by mass of the amyl acetate, and the methyl acetate as a by-product of the transesterification is discharged in the vapor phase, and the gas phase reaction product directly enters the distillation column. The top of the distillation column is separated, and the reflux ratio of the controlled rectification is 1:1 to 4:1;

   4) The mixture of 2-pentanol and 3-pentanol obtained in the step 3) is subjected to rectification, and the rectification is carried out in a rectification column having a theoretical plate of 70; the temperature in the column is 118 to 125 ° C, and the reflux ratio is When 10 to 20:1, a fraction of 115 to 116 ° C is collected from the top of the column to obtain 3-pentanol having a content of 99.5%; when the temperature of the column is 126 to 130 ° C and the reflux ratio is 10 to 20:1, A fraction of 118 to 119 ° C was collected from the top of the column, and the product was a 2-pentanol having a content of 99.5%.

   5) The 3-pentanol obtained in the step 4) is directly subjected to catalytic dehydrogenation distillation to obtain high-purity 3-pentanone; the catalytic dehydrogenation reaction temperature is 113-118 ° C, the reaction pressure is normal pressure, and the catalyst 3 - The pentanol loading WWH is 2.5-5.5 hr ^-1 , and the dehydrogenation reaction uses a granular Raney nickel-type metal alloy as a catalyst, and its composition is:

   Al-Ni-A

   Wherein A is one selected from the group consisting of Ce and Bi; the dehydrogenation reaction product is discharged in a gas phase, and the gas phase reaction product is directly purified into a rectification column having a theoretical plate of 50 to obtain a high-purity 3-pentanone product, and the rectification is controlled. The reflux ratio is from 1:1 to 10:1.
2. The method for preparing 3-pentanone from 2-pentene according to claim 1, wherein the composition of the catalyst in the step 5) is: Al-Ni-A, wherein A is selected from the group consisting of Ce, One of Bi, the weight ratio of each component is: Al: Ni: A = 1: (0.8 - 0.94): (0.03 - 0.2); the catalyst has a particle size of 0.01 - 0.1 mm.
3. The method for preparing 3-pentanone from 2-pentene according to claim 2, wherein component A in the catalyst for catalytic dehydrogenation in step 5) is selected from Ce; in step 5) The catalyst has a particle size of 0.02 to 0.08 mm.
4. The method for preparing 3-pentanone from 2-pentene according to claim 1, wherein the molar ratio of acetic acid to 2-pentene in the step 1) is 2.5 to 3.5:1. The mass space velocity of the addition reaction is 1.5 to 2.5 hr ^-1 ; the reaction temperature is 85 to 90 ° C; and the reaction pressure is 0.9 to 1.5 MPa.
5. The method for preparing 3-pentanone from 2-pentene according to claim 1, wherein the catalyst sulfonic acid cation exchange resin in the step 1) has a mass exchange capacity of 4 to 5 mmol/g. .
6. The method for preparing 3-pentanone from 2-pentene according to claim 1, wherein the transesterification temperature in the step 3) is 65 to 75 ° C, and the molar ratio of methanol to amyl acetate The ratio is 3.0 to 4.0:1.
7. The method for preparing 3-pentanone from 2-pentene according to claim 1, wherein the catalyst sodium methoxide in the step 3) is added in an amount of 0.5 to 1% by mass of the amyl acetate.
8. A method for producing 3-pentanone from 2-pentene according to claim 1, wherein the reflux ratio of the rectification in the step 3) is from 2:1 to 3:1.
9. A method for producing 3-pentanone from 2-pentene according to claim 1, wherein the catalyst in the step 5) has a 3-pentanol loading WWH of from 3 to 4 hr ^-1 .
10. A method for producing 3-pentanone from 2-pentene according to claim 1, wherein the reflux ratio of the rectification in the step 5) is from 2:1 to 6:1.