A process for the synthesis of 3-methyl-2-buten-1-ol

Abstract

The application provides a method for synthesizing 3-methyl-2-buten-1-ol, and belongs to the technical field of isopentenol synthesis. The method comprises the following steps: introducing 3-methyl-3-buten-1-ol and an atmosphere containing hydrogen into a fixed bed reactor, and performing a hydrogenation isomerization reaction under the action of a Pd / Al2O3 catalyst to generate 3-methyl-2-buten-1-ol; wherein the content of formaldehyde in the 3-methyl-3-buten-1-ol is 0.03-0.15%. The application adopts a fixed bed reactor to perform continuous production, adopts a Pd / Al2O3 catalyst with low palladium content as the catalyst, the preparation method is simple, the price is relatively low, and the content of formaldehyde in the 3-methyl-3-buten-1-ol is controlled to inhibit a side reaction, so that the reaction conversion rate and the product selectivity are high.

Description

Technical Field

[0001] This invention relates to the field of isopentenol synthesis technology, and in particular to a method for synthesizing 3-methyl-2-buten-1-ol. Background Technology

[0002] Isopentenol (3-methyl-2-buten-1-ol) is a colorless, oily liquid with a strong, pungent odor. It is mainly used in the synthesis of citral, vitamin E, vitamin A, pyrethroid insecticide intermediates such as benzoyl ester, and downstream products such as dichloroquine ester and DV chrysoyl chloride. With the continuous deepening of research on isopentenol synthesis technology, its application range is becoming wider and wider, and the demand is also increasing significantly. Therefore, research on isopentenol synthesis technology is of great significance.

[0003] Currently, isopentenol is mainly prepared industrially using the chloroisopentene method and the 3-methyl-3-buten-1-ol hydroisomerization method. The chloroisopentene method uses chloroisopentene as a raw material, where 1-chloro-3-methyl-3-butene undergoes a transposition to 1-chloro-3-methyl-2-butene, which then reacts with sodium acetate to form the corresponding acetate ester, followed by hydrolysis to obtain isopentenol. This process requires a high water content in the sodium acetate, necessitating dehydration before use; otherwise, the selectivity of isopentenol will decrease. Furthermore, the process is complex and generates a large amount of wastewater. The hydroisomerization method uses 3-methyl-3-buten-1-ol as a raw material, where a double bond isomerization reaction occurs under a catalyst and hydrogen atmosphere to prepare isopentenol. This method is economical and environmentally friendly, attracting considerable attention from researchers. However, it is prone to saturated hydrogenation of the double bonds during application, resulting in low product selectivity and numerous side reactions. Moreover, it typically employs a batch reactor, resulting in low continuity, and the catalysts are mostly palladium on carbon with a palladium content of 5%, making them expensive. Summary of the Invention

[0004] The purpose of this invention is to provide a method for synthesizing 3-methyl-2-buten-1-ol, which uses a fixed-bed reactor for continuous production and employs Pd / Al2O3 with low palladium content as a catalyst. The preparation method is simple and inexpensive. At the same time, by controlling the formaldehyde content in 3-methyl-3-buten-1-ol, side reactions are suppressed, resulting in high reaction conversion rate and product selectivity.

[0005] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:

[0006] This invention provides a method for synthesizing 3-methyl-2-buten-1-ol, comprising the following steps:

[0007] 3-Methyl-3-buten-1-ol and a hydrogen-containing atmosphere are introduced into a fixed-bed reactor, and a hydroisomerization reaction is carried out under the action of a Pd / Al2O3 catalyst to produce 3-methyl-2-buten-1-ol; wherein the formaldehyde content in the 3-methyl-3-buten-1-ol is 0.03-0.15%, preferably 0.05-0.1%.

[0008] The following is a detailed explanation:

[0009] The raw material 3-methyl-3-buten-1-ol in this invention refers to 3-methyl-3-buten-1-ol containing a trace amount of formaldehyde in an aqueous solution. Specifically, the 3-methyl-3-buten-1-ol used needs to contain a certain amount of formaldehyde, with the formaldehyde content controlled between 0.03% and 0.15% (e.g., 0.05%, 0.06%, 0.07%, 0.08%, 0.1%, 0.12%, 0.13%, 0.14%, etc.), preferably 0.05% to 0.1%. There are no particular restrictions on the source of the 3-methyl-3-buten-1-ol, as long as the formaldehyde content is within the above range. Including but not limited to the following situations: If the formaldehyde content in commercially available or self-prepared 3-methyl-3-buten-1-ol is within the above-mentioned range, it can be used directly; if the formaldehyde content in commercially available or self-prepared 3-methyl-3-buten-1-ol is higher than the above-mentioned range, further purification is required to ensure the formaldehyde content meets the requirements; if the formaldehyde content in commercially available or self-prepared 3-methyl-3-buten-1-ol is lower than the above-mentioned range, formaldehyde needs to be added (in the form of an aqueous solution) to ensure the formaldehyde content meets the requirements. Commercially available formaldehyde is usually present in the form of an aqueous solution or dispersed in organic matter. The formaldehyde content refers to the mass percentage of formaldehyde in the 3-methyl-3-buten-1-ol liquid (including alcohol, water, etc.).

[0010] The atmosphere containing hydrogen in this invention can be hydrogen gas, or a mixture of hydrogen and nitrogen gas, wherein the volume content of hydrogen is 10-100%, preferably 30-70%.

[0011] In some embodiments, the palladium (Pd) content in the Pd / Al2O3 catalyst is 0.25-0.5%, which may be derived from one or more of palladium chloride, palladium nitrate, and palladium hydroxide, preferably palladium chloride;

[0012] In some embodiments, the alumina (Al2O3) in the Pd / Al2O3 catalyst may be derived from microporous or macroporous boehmite, preferably macroporous boehmite; more preferably, the pore volume of the macroporous boehmite is ≥0.9 cm³. 3 / g, specific surface area ≥290m 2 / g, Na2O≤0.05wt%, dry basis content≥68wt%, SiO2<0.2wt%;

[0013] In some embodiments, the bulk density of the Pd / Al2O3 catalyst is 0.5–0.6 g / mL.

[0014] In some embodiments, the Pd / Al2O3 catalyst can be prepared by the following methods:

[0015] (1) Preparation of carrier: Mix macroporous boehmite and guar gum powder evenly, add 2-3% citric acid aqueous solution for kneading, and then extrude it into clover-shaped or toothed spheres of 2-3 mm by an extruder. Dry at 150-200℃ for 4-6 h and calcine at 850-950℃ for 4-6 h to obtain the carrier. The mass ratio of guar gum powder to macroporous boehmite is 2-4:100, and the mass ratio of citric acid aqueous solution to macroporous boehmite is 80-100:100.

[0016] (2) Catalyst preparation: The catalyst is prepared by excess impregnation. The support is added to the impregnation solution containing palladium ions and impregnated for 30-40 min. After draining the water, the impregnated catalyst is dried at 150-200℃ for 4-6 h and calcined at 400-500℃ for 4-6 h to obtain the oxidized catalyst. The mass ratio of impregnation solution to support is 90-110:100.

[0017] In some embodiments, the fixed-bed reactor is a bubble-bed reactor; the hydroisomerization reaction is carried out continuously in the bubble-bed reactor;

[0018] In some embodiments, the liquid hourly space velocity (LHSV) of 3-methyl-3-buten-1-ol is 1–3 h⁻¹. -1 Preferably 1.5 to 2 hours -1 ; and / or

[0019] The molar ratio of hydrogen to 3-methyl-3-buten-1-ol is 0.01 to 0.15:1, preferably 0.02 to 0.12:1;

[0020] In some embodiments, the reaction pressure is atmospheric pressure to 0.2 MPa, and the reaction temperature is 50 to 90°C.

[0021] The present invention features mild reaction conditions, high reaction conversion and product selectivity, and a catalyst with excellent stability. The single-pass conversion of 3-methyl-3-buten-1-ol is ≥50%, and the selectivity of 3-methyl-2-buten-1-ol is ≥97%.

[0022] Beneficial effects

[0023] The method of this invention uses a low-palladium-content Pd / Al2O3 catalyst for the hydroisomerization of 3-methyl-3-buten-1-ol to synthesize isopentenol. The catalyst preparation method is simple and the catalyst price is low. At the same time, by controlling the formaldehyde content in 3-methyl-3-buten-1-ol, side reactions are suppressed, resulting in high reaction conversion rate and product selectivity. The use of a bubble bed reactor allows for continuous production.

[0024] The present invention has been described in detail above; however, the above embodiments are merely illustrative in nature and are not intended to limit the invention. Furthermore, this document is not limited to the foregoing prior art or the invention itself, or to any theory described in the following embodiments. Detailed Implementation

[0025] The present invention will be further described below with reference to the embodiments. It should be noted that the following embodiments are provided for illustrative purposes only and do not constitute a limitation on the scope of protection of the present invention.

[0026] Unless otherwise specified, the raw materials, reagents, and methods used in the embodiments are all conventional raw materials, reagents, and methods in the art.

[0027] The raw materials involved in the examples are as follows:

[0028] The macroporous pseudoboehmite was sourced from Zibo Hengyi Chemical Technology Co., Ltd., with a pore volume of 0.91 cm³. 3 / g, specific surface area 297m 2 / g, Na2O content 0.02wt%, dry basis content 69.2wt%, SiO2 content 0.13wt%.

[0029] 3-Methyl-3-buten-1-ol was obtained from Zhongchumei Huabang (Dongying) Co., Ltd., with a content of 99.85wt%, formaldehyde content <20ppm, and no peroxides.

[0030] The analytical methods for the products involved in the examples are as follows:

[0031] Product composition analysis: SP-7890Plus gas chromatograph, PEG-20M column (50m length, 0.32mm inner diameter, 0.25μm film thickness), high-purity nitrogen as carrier gas, split ratio 1:50, programmed temperature rise: initial temperature 90℃ stabilized for 5 min, temperature rised to 150℃ at a rate of 10℃ / min stabilized for 10 min, temperature rised to 180℃ at a rate of 10℃ / min stabilized for 20 min.

[0032] Water content analysis of the product: Coulometric moisture analyzer was used.

[0033] Formaldehyde content analysis in the product: A C18 liquid chromatography column was used at a constant temperature of 30℃, with acetonitrile as the mobile phase and a detection wavelength of 358nm.

[0034]

[0035]

[0036] Preparation of Catalyst in Example 1

[0037] The steps are as follows:

[0038] Carrier preparation:

[0039] 1) Add 80 kg of macroporous pseudoboehmite and 2.4 kg of guar gum powder to a 200 L kneader and knead for 10 min;

[0040] 2) Slowly add 65 kg of 2.5% citric acid solution to the mixed material and continue kneading for 30 minutes;

[0041] 3) The kneaded material is extruded into a 3mm clover shape using an extruder. The shaped carrier is dried at 150℃ for 4 hours and calcined at 900℃ for 4 hours to obtain the carrier with a bulk density of 0.54g / mL.

[0042] Catalyst preparation:

[0043] 1) Add 84g of palladium chloride to a 50L plastic bucket, add 10Kg of deionized water and 30g of 65-68% nitric acid, stir until completely dissolved to obtain the impregnation solution;

[0044] 2) Pour 10 kg of the calcined carrier into the above impregnation solution, impregnate for 30 min, and then drain the water;

[0045] 3) The impregnated catalyst is dried at 150°C for 4 hours and calcined at 400°C for 4 hours to obtain the oxidized catalyst, wherein the palladium content is 0.5 wt%.

[0046] Example 1

[0047] A fixed-bed isothermal reactor was loaded with 100 mL of catalyst and a bubbling bed reaction was adopted. 3-methyl-3-buten-1-ol containing trace amounts of formaldehyde (formaldehyde aqueous solution needs to be added separately, and the formaldehyde content after addition is shown in the table below), a mixture of hydrogen and nitrogen (volume ratio of hydrogen to nitrogen 1:1) was introduced into the reactor from the bottom. The feed rate of 3-methyl-3-buten-1-ol was 200 mL / h, the hydrogen flow rate was 44 mL / min (molar ratio of hydrogen to 3-methyl-3-buten-1-ol was 0.06:1), the reaction pressure was atmospheric pressure, and the reaction temperature was 60℃. The experimental results are shown in the table below.

[0048]

[0049] Note: The light component in the product is the total content of hydrocarbons such as isobutylene, isoprene, and C10 components.

[0050] Comparative Example 1

[0051] A Pd / Al2O3 catalyst with a palladium content of 3% was prepared using a similar preparation method to that in Example 1. The catalyst was evaluated according to the evaluation method in Example 1, and the test results are shown in the table below.

[0052]

[0053] The experimental results show that the low-palladium-content Pd / Al2O3 catalyst can achieve the same reaction effect as the 3% palladium-content Pd / Al2O3 catalyst in the hydroisomerization reaction of 3-methyl-3-buten-1-ol, and it is also beneficial to the selectivity of isopentenol (3-methyl-2-buten-1-ol). Adding a trace amount of formaldehyde aqueous solution to 3-methyl-3-buten-1-ol can inhibit the saturated hydrogenation reaction to a certain extent and improve the selectivity of isopentenol (3-methyl-2-buten-1-ol). However, the amount of formaldehyde added needs to be controlled within an appropriate range. Excessive formaldehyde will result in a low reaction conversion rate, a decrease in product yield, and increased difficulty in subsequent separation.

[0054] The above embodiments are merely illustrative of the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein, without departing from the spirit and substance defined by the claims of the present invention; and such modifications or substitutions are still within the scope defined by the claims of the present invention.

Claims

1. A process for the synthesis of 3-methyl-2-buten-1-ol, characterized in that, The method comprises the following steps: 3-methyl-3-buten-1-ol and hydrogen-containing atmosphere are introduced into a fixed bed reactor to generate 3-methyl-2-buten-1-ol by hydrogen isomerization under the action of a Pd / Al2O3 catalyst; wherein the content of formaldehyde in the 3-methyl-3-buten-1-ol is 0.03-0.15%; The Pd / Al2O3 catalyst is prepared by the following method: (1) Preparation of the carrier: mix the macroporous pseudo-boehmite and the sesbania powder uniformly, add 2-3% of the aqueous solution of citric acid for mixing and kneading, then extrude into 2-3mm three-leaf clover shape or tooth ball shape through an extruder, dry at 150-200°C for 4-6h, and calcine at 850-950°C for 4-6h to obtain the carrier, wherein the mass ratio of the sesbania powder to the macroporous pseudo-boehmite is 2-4:100, and the mass ratio of the aqueous solution of citric acid to the macroporous pseudo-boehmite is 80-100:100; wherein the macroporous pseudo-boehmite has a pore volume ≥0.9cm 3 / g, a specific surface area ≥290m 2 / g, Na2O≤0.05wt%, a dry basis content ≥68wt%, SiO2<0.2wt%; (2) Catalyst preparation: the catalyst is prepared by an excessive impregnation method, the carrier is added into an impregnation solution containing palladium ions, after impregnation for 30-40 min, the water is drained, the impregnated catalyst is dried at 150-200 ℃ for 4-6 h, and is calcined at 400-500 ℃ for 4-6 h to obtain the catalyst; wherein the mass ratio of the impregnation solution to the carrier is 90-110:100; wherein the content of palladium in the Pd / Al2O3 catalyst is 0.25-0.5%, and the bulk density of the Pd / Al2O3 catalyst is 0.5-0.6 g / mL.

2. The method of claim 1, wherein, The content of formaldehyde in the 3-methyl-3-buten-1-ol is 0.05-0.1%.

3. The method of claim 1, wherein, The hydrogen-containing atmosphere is hydrogen, or a mixture of hydrogen and nitrogen, wherein the volume content of hydrogen is 10-100%.

4. The method of claim 3, wherein, The volume content of hydrogen is 30-70%.

5. The method of claim 1, wherein, The fixed bed reactor is a bubbling bed reactor.

6. The method of claim 1, wherein, 3-methyl-3-buten-1-ol at a liquid hourly space velocity of 1 to 3 h -1 ; The molar ratio of hydrogen to 3-methyl-3-buten-1-ol is 0.01-0.15:

1.

7. The method of claim 6, wherein, 3-methyl-3-buten-1-ol at a liquid hourly space velocity of 1.5 to 2 h -1 ; The molar ratio of hydrogen to 3-methyl-3-buten-1-ol is 0.02-0.12:

1.

8. The method of claim 1, wherein, The reaction pressure is normal pressure-0.2 MPa, and the reaction temperature is 50-90 ℃.

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