阅读说明：本技术 一种戊二氨基甲酸酯的催化合成方法 (Catalytic synthesis method of pentanedicarbamic acid ester ) 是由 王利国 惠祥 李会泉 徐爽 曹妍 于 2021-08-26 设计创作，主要内容包括：本发明提供了一种戊二氨基甲酸酯的催化合成方法,将戊二胺与羰化剂加入溶剂中溶解,通过二氧化钛催化剂进行催化合成反应,所述催化合成反应不仅使得戊二胺的转化率达到100％,戊二氨基甲酸酯的选择性≥90％,还具有条件温和,反应时间短,无污染,对设备要求低等优点,适用于工业化生产,而且所用二氧化钛催化剂合成简便,稳定不易分解,易于回收,可以重复使用。(The invention provides a catalytic synthesis method of pentamethylene dicarbamate, which comprises the steps of adding pentamethylene diamine and a carbonylation agent into a solvent for dissolving, and carrying out catalytic synthesis reaction by a titanium dioxide catalyst, wherein the catalytic synthesis reaction not only enables the conversion rate of pentamethylene diamine to reach 100 percent, but also has the advantages of no pollution, low equipment requirement and the like, is mild in condition, short in reaction time and suitable for industrial production, and the used titanium dioxide catalyst is simple and convenient to synthesize, stable, not easy to decompose, easy to recover and capable of being repeatedly used.)

1. A catalytic synthesis method of pentanedicarbamate is characterized by comprising the following steps:

adding pentanediamine and a carbonylation agent into a solvent for dissolving, and adding a titanium dioxide catalyst for reaction to obtain the pentanedicarbamate.

2. The catalytic synthesis method according to claim 1, wherein the titanium dioxide catalyst accounts for 1-30% by mass of the pentamethylenediamine.

3. The catalytic synthesis process according to claim 1 or 2, characterized in that the titanium dioxide catalyst is obtained by the following preparation method:

mixing a titanium source and a morphology control agent, and sequentially carrying out reaction and solid-liquid separation to obtain a solid product; and drying, grinding and calcining the solid product in sequence to obtain the titanium oxide catalyst.

4. The catalytic synthesis method of claim 3, wherein the titanium source is a titanium source solution;

preferably, the titanium source in the titanium source solution comprises any one or a combination of at least two of isopropyl titanate, tetrabutyl titanate, titanium trichloride or titanium tetrafluoride;

preferably, the solvent A in the titanium source solution is absolute ethyl alcohol;

preferably, the preparation method of the titanium source solution comprises the following steps: dissolving a titanium source in a solvent A, and dispersing under an ultrasonic condition;

preferably, the volume ratio of the titanium source to the solvent A in the titanium source solution is (0.5-2): 1.

5. The catalytic synthesis method according to claim 3 or 4, wherein the morphology controller comprises any one or a combination of at least two of deionized water, hydrochloric acid, hydrofluoric acid, formic acid, acetic acid, or sulfuric acid;

preferably, the volume of the morphology control agent is 5-100% of the volume of the titanium source;

preferably, the mixing is to slowly drop the morphology control agent to the titanium source under the ultrasonic condition;

preferably, the time of the ultrasound is 0.5 to 3 hours.

6. The catalytic synthesis process according to any one of claims 3 to 5, wherein the reaction temperature is 50 to 200 ℃;

preferably, the reaction time is 1-15 h;

preferably, the solid-liquid separation is suction filtration, washing with absolute ethyl alcohol and then with distilled water until the pH of the filtrate is 6.9-7.1, and then performing the drying.

7. The catalytic synthesis process of any one of claims 3-6, wherein the drying temperature is 60-150 ℃;

preferably, the drying time is 3-10 h;

preferably, the calcination is carried out in a muffle furnace;

preferably, the temperature of the calcination is 400-550 ℃;

preferably, the calcination time is 1 to 5 hours.

8. The catalytic synthesis method of any one of claims 1-7, wherein the carbonylation agent comprises any one or a combination of at least two of methyl carbamate, ethyl carbamate, propyl carbamate, butyl carbamate, dimethyl carbonate, diethyl carbonate, or urea;

preferably, the molar ratio of the carbonylation agent to the pentanediamine is (2-10): 1;

preferably, the solvent comprises any one of methanol, ethanol, propanol, n-butanol, toluene, chlorobenzene or dichlorobenzene or a combination of at least two thereof;

preferably, the molar ratio of the solvent to the pentanediamine is (5-50): 1.

9. The catalytic synthesis process of any one of claims 1 to 8, wherein the reaction temperature of the reaction is 80 to 220 ℃;

preferably, the reaction time of the reaction is 0.5-10 h;

preferably, the reaction pressure of the reaction is 0.5-8 MPa;

preferably, the reaction is carried out under a protective gas atmosphere;

preferably, the shielding gas comprises any one of nitrogen, argon or neon or a combination of at least two thereof.

10. The catalytic synthesis method of any one of claims 1-9, wherein the catalytic synthesis method comprises:

adding pentanediamine and a carbonylation agent into a solvent for dissolving, adding a titanium dioxide catalyst into the solvent for reaction under the atmosphere of protective gas, controlling the reaction temperature to be 80-220 ℃, the reaction time to be 0.5-10h and the reaction pressure to be 0.5-8MPa, and obtaining the pentanedicarbamic acid ester;

wherein the preparation method of the titanium dioxide catalyst comprises the following steps: preparing a titanium source solution, slowly dropwise adding a morphology control agent to the titanium source under the ultrasonic condition, performing ultrasonic treatment for 0.5-3h, controlling the volume ratio of the titanium source in the titanium source solution to a solvent A to be (0.5-2):1, wherein the volume of the morphology control agent accounts for 5-100% of the volume of the titanium source in the titanium source solution, performing reaction on the obtained suspension at 50-200 ℃ for 1-15h, washing the solid product obtained by suction filtration with absolute ethyl alcohol, then washing with distilled water until the pH value of the filtrate is 6.9-7.1, then drying in an oven at 60-150 ℃ for 3-10h, and calcining the ground solid product in a muffle furnace at 400-550 ℃ for 1-5h to obtain a titanium dioxide catalyst;

the mass of the titanium dioxide catalyst accounts for 1-30% of that of the pentamethylene diamine; the carbonylation agent comprises any one or the combination of at least two of methyl carbamate, ethyl carbamate, propyl carbamate, butyl carbamate, dimethyl carbonate, diethyl carbonate or urea; the molar ratio of the carbonylation agent to the pentamethylene diamine is (2-10) to 1; the solvent comprises any one or the combination of at least two of methanol, ethanol, propanol, n-butanol, toluene, chlorobenzene or dichlorobenzene; the molar ratio of the solvent to the pentamethylene diamine is (5-50) to 1.

Technical Field

The invention relates to the field of chemical synthesis, in particular to a catalytic synthesis method of glutaric dicarbamate.

Background

Aliphatic isocyanates, due to their unique chemical structures, can impart excellent mechanical properties, outstanding chemical stability and excellent weatherability to polyurethane materials, and are widely used in building materials, coating materials, industrial equipment pipes and light industrial products, such as artificial leathers, shoes, etc. Among them, Pentamethylene Diisocyanate (PDI) belongs to a novel bio-based isocyanate product, contains 70% of renewable carbon, and the derivative thereof has the advantages of yellowing resistance, chemical resistance, wear resistance and the like, and has wide application prospects.

Among the reported techniques, PDI is synthesized mainly by the phosgene method. For example, CN103347852A proposes a method for preparing PDI, in which pentamethylene diamine is first prepared biologically, and then directly reacted with phosgene, but a large amount of acid chloride and other by-products are present in the product. CN106715384A discloses a method for efficiently synthesizing PDI by gas phase phosgene, but the technical barrier of the method is high. CN107602419A proposes that PDI is prepared by first using pentanediamine and carbon dioxide to form carbonate and then carrying out phosgenation.

However, with the increasing awareness of environmental protection, the use of highly toxic phosgene generates a large amount of waste acid and waste salt and increases the equipment investment, limiting further development in the future. Therefore, a process route for synthesizing PDI in a non-phosgene green environment has become a focus of research in recent years. CN106883150A discloses that PDI is prepared by reacting triphosgene with pentamethylene diamine, the method has mild conditions, is simple and safe, but the use of triphosgene and an acid-binding agent limits the industrialization of the method.

The synthesis of isocyanate by urethane pyrolysis is a reaction route with great application prospect, and comprises the synthesis and pyrolysis of urethane. As a key intermediate, the synthesis of Pentanedicarbamate (PDC) is crucial, and CN108689884A discloses the synthesis of butyl carbamate by carbamate synthesis using zinc compounds (e.g., zinc acetate, zinc oxalate, etc.) to catalyze urea and pentanediamine extracts. However, most of the existing catalysts are homogeneous catalysts, so that the recovery is difficult, and the further application of the catalysts is limited.

In summary, few reports of the catalytic systems for synthesizing the pentamethylene dicarbamate by the non-phosgene method of pentamethylene diamine are disclosed in the prior art, and there is a need to develop a catalytic synthesis method of pentamethylene dicarbamate, wherein the catalyst in the catalytic synthesis method has the advantages of stability, difficulty in decomposition, easiness in recovery and reusability, and the catalytic reaction conditions are mild, the reaction time is short, no pollution is caused, the requirement on equipment is low, and the method is suitable for industrial production.

Disclosure of Invention

In order to solve the technical problems, the invention provides a catalytic synthesis method of pentamethylene dicarbamate, which comprises the steps of adding pentamethylene diamine and a carbonylation agent into a solvent for dissolving, and carrying out catalytic synthesis reaction by a titanium dioxide catalyst, wherein the catalytic synthesis reaction not only enables the conversion rate of pentamethylene diamine to reach 100% and the selectivity of pentamethylene dicarbamate to be more than or equal to 90%, but also has the advantages of mild conditions, short reaction time, no pollution, low equipment requirement and the like, is suitable for industrial production, and the used titanium dioxide catalyst is simple and convenient to synthesize, is stable, is not easy to decompose, is easy to recover and can be repeatedly used.

The invention aims to provide a catalytic synthesis method of pentanedicarbamic acid ester, which comprises the following steps:

adding pentanediamine and a carbonylation agent into a solvent for dissolving, and adding a titanium dioxide catalyst for reaction to obtain the pentanedicarbamate.

The catalytic synthesis method adopts the titanium dioxide catalyst to carry out catalytic synthesis reaction, not only ensures that the conversion rate of the pentanediamine reaches 100 percent and the selectivity of the pentanedicarbamate is not less than 90 percent, but also has the advantages of mild condition, short reaction time, no pollution, low requirement on equipment and the like, is suitable for industrial production, and the used titanium dioxide catalyst is simple and convenient to synthesize, stable, difficult to decompose, easy to recover and capable of being repeatedly used.

In a preferred embodiment of the present invention, the titanium dioxide catalyst is present in an amount of 1 to 30% by mass, for example, 1%, 2%, 3%, 5%, 8%, 10%, 12%, 15%, 17%, 20%, 23%, 25%, 28%, or 30% by mass based on the mass of the pentamethylenediamine, but the amount is not limited to the above-mentioned values, and other values not listed in the above-mentioned range are also applicable.

As a preferred technical scheme of the invention, the titanium dioxide catalyst is prepared by adopting the following preparation method:

mixing a titanium source and a morphology control agent, and sequentially carrying out reaction and solid-liquid separation to obtain a solid product; and drying, grinding and calcining the solid product in sequence to obtain the titanium oxide catalyst.

As a preferable technical scheme of the invention, the titanium source is a titanium source solution.

Preferably, the titanium source in the titanium source solution comprises any one of isopropyl titanate, tetrabutyl titanate, titanium trichloride or titanium tetrafluoride, or a combination of at least two of these, typical but non-limiting examples being: a combination of isopropyl titanate and tetrabutyl titanate, a combination of tetrabutyl titanate and titanium trichloride, a combination of titanium trichloride and titanium tetrafluoride, a combination of titanium tetrafluoride and isopropyl titanate, or the like.

Preferably, the solvent A in the titanium source solution is absolute ethyl alcohol.

Preferably, the preparation method of the titanium source solution comprises the following steps: dissolving a titanium source in a solvent A, and dispersing under the ultrasonic condition.

The preparation method of the titanium dioxide catalyst creatively adds the morphology control agent into the titanium source solution under the ultrasonic condition, so that the titanium source and the morphology control agent can be fully contacted, the pre-reaction can be effectively carried out, and the time of the subsequent reaction can be shortened.

Preferably, the volume ratio of the titanium source to the solvent A in the titanium source solution is (0.5-2):1, for example, 0.5:1, 0.8:1, 1:1, 1.2:1, 1.5:1, 1.8:1 or 2:1, etc., but is not limited to the recited values, and other values not recited within this range of values are equally applicable.

As a preferred embodiment of the present invention, the morphology controlling agent includes any one or a combination of at least two of deionized water, hydrochloric acid, hydrofluoric acid, formic acid, acetic acid, or sulfuric acid, and typical but non-limiting examples of the combination are: a combination of hydrochloric acid and hydrofluoric acid, a combination of hydrofluoric acid and formic acid, a combination of formic acid and acetic acid, a combination of acetic acid and sulfuric acid, or a combination of hydrochloric acid and sulfuric acid, and the like.

It should be noted that the morphology control agents such as hydrochloric acid are all commercially available products, and are not described herein again.

Preferably, the volume of the morphology controlling agent is 5-100% of the volume of the titanium source, such as 5%, 10%, 20%, 30%, 50%, 60%, 70%, 80%, 90%, or 100%, but not limited to the recited values, and other values not recited within this range are equally applicable.

Preferably, the mixing is slowly dropping the morphology control agent to the titanium source under ultrasonic conditions.

Preferably, the sonication time is 0.5 to 3 hours, such as 0.5 hours, 1 hour, 1.5 hours, 2 hours, 2.5 hours, or 3 hours, etc., but is not limited to the recited values, and other values not recited within the range of values are equally applicable.

In a preferred embodiment of the present invention, the reaction temperature is 50 to 200 ℃, for example, 50 ℃, 60 ℃, 70 ℃, 80 ℃, 90 ℃, 100 ℃, 110 ℃, 120 ℃, 130 ℃, 140 ℃, 150 ℃, 160 ℃, 180 ℃, 190 ℃ or 200 ℃, but is not limited to the recited values, and other values not recited in the range of the values are also applicable.

Preferably, the reaction time is 1 to 15 hours, such as 1 hour, 2 hours, 4 hours, 5 hours, 7 hours, 10 hours, 12 hours, 14 hours, or 15 hours, but not limited to the recited values, and other values not recited within the range of values are also applicable.

Preferably, the solid-liquid separation is suction filtration, washing with absolute ethyl alcohol and then with distilled water until the pH of the filtrate is 6.9-7.1, and then performing the drying.

It is worth to be noted that the absolute ethyl alcohol washing and the distilled water washing are respectively carried out at least three times to ensure the cleaning effect.

In a preferred embodiment of the present invention, the drying temperature is 60 to 150 ℃, for example, 60 ℃, 70 ℃, 80 ℃, 90 ℃, 100 ℃, 110 ℃, 120 ℃, 130 ℃, 140 ℃ or 150 ℃, but the drying temperature is not limited to the recited values, and other values not recited in the range of the values are also applicable.

Preferably, the drying time is 3 to 10 hours, such as 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, or 10 hours, but not limited to the recited values, and other values not recited within the range of values are also applicable.

Preferably, the calcination is carried out in a muffle furnace.

Preferably, the temperature of the calcination is 400-550 ℃, such as 400 ℃, 430 ℃, 450 ℃, 460 ℃, 480 ℃, 500 ℃, 510 ℃, 530 ℃ or 550 ℃, etc., but is not limited to the recited values, and other unrecited values within the range of values are equally applicable.

Preferably, the calcination is carried out for a period of time of 1 to 5 hours, for example 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours or 5 hours, etc., but not limited to the recited values, and other values not recited within the range of values are also applicable.

As a preferred embodiment of the present invention, the carbonylating agent includes any one or a combination of at least two of methyl carbamate, ethyl carbamate, propyl carbamate, butyl carbamate, dimethyl carbonate, diethyl carbonate, or urea, and typical but non-limiting examples of the combination are: a combination of methyl carbamate and ethyl carbamate, a combination of butyl carbamate and dimethyl carbonate, a combination of dimethyl carbonate and diethyl carbonate, or a combination of diethyl carbonate and urea, and the like.

Preferably, the molar ratio of the carbonylation agent to pentanediamine is (2-10):1, such as 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1 or 10:1, but not limited to the recited values, and other values not recited within this range are equally applicable.

Preferably, the solvent comprises any one of methanol, ethanol, propanol, n-butanol, toluene, chlorobenzene or dichlorobenzene, or a combination of at least two of the following typical but non-limiting examples: a combination of methanol and ethanol, a combination of propanol and n-butanol, a combination of toluene and chlorobenzene, or a combination of chlorobenzene and dichlorobenzene, and the like.

Preferably, the molar ratio of the solvent to the pentanediamine is (5-50):1, for example 5:1, 10:1, 15:1, 20:1, 25:1, 30:1, 35:1, 40:1, 45:1 or 50:1, but is not limited to the recited values and other values not recited within this range are equally applicable.

In a preferred embodiment of the present invention, the reaction temperature of the reaction is 80 to 220 ℃, for example, 80 ℃, 90 ℃, 100 ℃, 120 ℃, 140 ℃, 150 ℃, 160 ℃, 170 ℃, 180 ℃, 190 ℃, 200 ℃, 210 ℃ or 220 ℃, but the reaction temperature is not limited to the recited values, and other values not recited in the range of the values are also applicable.

Preferably, the reaction time of the reaction is 0.5 to 10 hours, such as 0.5h, 1h, 2h, 3h, 4h, 4.5h, 5h, 6h, 6.5h, 7h, 8h, 9h or 10h, etc., but is not limited to the recited values, and other values not recited within the range of values are equally applicable.

Preferably, the reaction pressure of the reaction is 0.5 to 8MPa, for example, 0.5MPa, 1MPa, 1.5MPa, 2MPa, 3MPa, 4MPa, 5MPa, 5.5MPa, 6MPa, 6.5MPa, 7MPa or 8MPa, but is not limited to the recited values, and other values not recited within the numerical range are also applicable.

Preferably, the reaction is carried out under a protective gas atmosphere.

Preferably, the shielding gas comprises any one of nitrogen, argon or neon or a combination of at least two of these, typical but non-limiting examples being: a combination of nitrogen and argon, a combination of nitrogen and neon, or a combination of argon and neon, and the like.

As a preferred technical solution of the present invention, the catalytic synthesis method comprises:

adding pentanediamine and a carbonylation agent into a solvent for dissolving, adding a titanium dioxide catalyst into the solvent for reaction under the atmosphere of protective gas, controlling the reaction temperature to be 80-220 ℃, the reaction time to be 0.5-10h and the reaction pressure to be 0.5-8MPa, and obtaining the pentanedicarbamic acid ester;

wherein the preparation method of the titanium dioxide catalyst comprises the following steps: preparing a titanium source solution, slowly dropwise adding a morphology control agent to the titanium source under the ultrasonic condition, performing ultrasonic treatment for 0.5-3h, controlling the volume ratio of a titanium source in the titanium source solution to a solvent A to be (0.5-2):1, wherein the volume of the morphology control agent accounts for 5-100% of the volume of the titanium source in the titanium source solution, performing reaction on the obtained suspension at 50-200 ℃ for 1-15h, washing the solid product obtained by suction filtration with absolute ethyl alcohol for at least three times, then washing with distilled water for at least three times until the pH value of the filtrate is 6.9-7.1, then drying in an oven at 60-150 ℃ for 3-10h, and calcining the ground solid product in a muffle furnace at 400-550 ℃ for 1-5h to obtain a titanium dioxide catalyst;

the mass of the titanium dioxide catalyst accounts for 1-30% of that of the pentamethylene diamine; the carbonylation agent comprises any one or the combination of at least two of methyl carbamate, ethyl carbamate, propyl carbamate, butyl carbamate, dimethyl carbonate, diethyl carbonate or urea; the molar ratio of the carbonylation agent to the pentamethylene diamine is (2-10) to 1; the solvent comprises any one or the combination of at least two of methanol, ethanol, propanol, n-butanol, toluene, chlorobenzene or dichlorobenzene; the molar ratio of the solvent to the pentamethylene diamine is (5-50) to 1.

Compared with the prior art, the invention has at least the following beneficial effects:

(1) the catalytic synthesis method of the invention not only enables the conversion rate of the pentamethylene diamine to reach 100%, but also enables the selectivity of the pentamethylene dicarbamate to be more than or equal to 90%;

(2) the catalytic synthesis method has the advantages of mild conditions, short reaction time, no pollution, low requirement on equipment and the like, and is suitable for industrial production;

(3) the titanium dioxide catalyst adopted by the catalytic synthesis method has the advantages of simple synthesis, stability, difficult decomposition, easy recovery, repeated use and the like.

Detailed Description

For the purpose of facilitating an understanding of the present invention, the present invention will now be described by way of examples. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.

The following examples refer to the following gas chromatographic conditions:

chromatographic column model RTX-5;

the column temperature is initially 50 ℃, kept for 1min, heated to 150 ℃ at the speed of 20 ℃/min, kept for 1min, heated to 220 ℃ at the speed of 20 ℃/min, and kept for 12min at the temperature of 220 ℃;

the control mode is pressure control, the pressure is 110kPa, the purging flow is 3mL/min, and the split ratio is 25;

the gasification temperature was 250 ℃.

Example 1

The embodiment provides a catalytic synthesis method of pentanedicarbamate, which comprises the following steps:

in a reaction kettle, 1.0118g of pentamethylene diamine and 5.324g of ethyl carbamate are added into 9mL of absolute ethyl alcohol for dissolution, then 0.10118g of titanium dioxide catalyst is added, air in the reaction kettle is replaced by nitrogen, after the sealing is confirmed to be good, the reaction is carried out in the nitrogen atmosphere, the reaction temperature is controlled to be 180 ℃, the reaction time is 4 hours, and the reaction pressure is 3 MPa; after the reaction is finished, naturally cooling the reaction kettle to room temperature, releasing gas in the reaction kettle, opening the reaction kettle, centrifugally separating out the titanium dioxide catalyst, taking supernatant, and analyzing the composition by using gas chromatography, wherein specific results are listed in table 1;

wherein the titanium dioxide catalyst is prepared by the following preparation method:

putting 5mL of tetrabutyl titanate into a 100mL reaction kettle with polytetrafluoroethylene as a lining, slowly dropping 4mL of hydrochloric acid solution dropwise, namely, the volume of the morphology control agent accounts for 80% of the volume of the titanium source, sealing the reaction kettle, putting the reaction kettle into an oven for hydrothermal reaction, heating the reaction kettle at 180 ℃ for 24 hours, performing suction filtration after the hydrothermal reaction is finished to obtain a white solid, cleaning the white solid with distilled water until the pH value of the filtrate is 7, drying the neutral white solid at 80 ℃ for 10 hours, grinding the dried solid, and calcining the solid in a muffle furnace at 550 ℃ for 3 hours to obtain the titanium oxide catalyst.

Example 2

This example provides a catalytic synthesis of pentanedicarbamate, except that the ethyl carbamate described in example 1 was replaced by an equimolar amount of propyl carbamate, the conditions were otherwise identical to those of example 1, and the composition of the supernatant was analyzed by gas chromatography, with the specific results shown in Table 1.

Example 3

This example provides a catalytic synthesis method of glutarocarbamate, which is identical to example 1 except that the reaction temperature in the catalytic synthesis method described in example 1 is changed from 180 ℃ to 200 ℃, and the composition of the supernatant is analyzed by gas chromatography, and the specific results are shown in table 1.

Example 4

This example provides a catalytic synthesis method of pentamethylene dicarbamate, except that the titanium dioxide catalyst obtained by the following preparation method was used, other conditions were completely the same as those in example 1, the composition of the supernatant was analyzed by gas chromatography, and the specific results are listed in table 1;

the preparation method of the titanium dioxide catalyst comprises the following steps:

putting 5mL of tetrabutyl titanate into a 100mL reaction kettle with polytetrafluoroethylene as a lining, slowly dropping 4mL of hydrofluoric acid solution dropwise, namely, the volume of the morphology control agent accounts for 80% of the volume of the titanium source, sealing the reaction kettle, putting the reaction kettle into an oven for hydrothermal reaction, heating the reaction kettle at 180 ℃ for 24 hours, performing suction filtration after the hydrothermal reaction is finished to obtain a white solid, cleaning the white solid with distilled water until the pH value of the filtrate is 7, drying the neutral white solid at 80 ℃ for 10 hours, grinding the dried solid, and calcining the solid in a muffle furnace at 550 ℃ for 3 hours to obtain the titanium oxide catalyst.

Example 5

This example provides a catalytic synthesis method of pentamethylene dicarbamate, except that the titanium dioxide catalyst obtained by the following preparation method was used, other conditions were completely the same as those in example 1, the composition of the supernatant was analyzed by gas chromatography, and the specific results are listed in table 1;

the preparation method of the titanium dioxide catalyst comprises the following steps:

putting 5mL of titanium isopropoxide into a 100mL reaction kettle with polytetrafluoroethylene as a lining, slowly dripping 5mL of hydrochloric acid solution dropwise, namely, the volume of the morphology control agent accounts for 100% of the volume of the titanium source, sealing the reaction kettle, putting the reaction kettle into an oven for hydrothermal reaction, heating the reaction kettle at 180 ℃ for 24 hours, performing suction filtration after the hydrothermal reaction is finished to obtain white solid, cleaning the white solid by using distilled water until the pH value of the filtrate is 7, drying the neutral white solid at 80 ℃ for 10 hours, grinding the dried solid, and calcining the ground solid in a muffle furnace at 550 ℃ for 3 hours to obtain the titanium oxide catalyst.

Example 6

The embodiment provides a catalytic synthesis method of pentanedicarbamate, which comprises the following steps:

in a reaction kettle, 1.0118g of pentamethylene diamine and 5.324g of ethyl carbamate are added into 9mL of absolute ethyl alcohol to be dissolved, 0.10118g of titanium dioxide catalyst is added, the mass of the titanium dioxide catalyst accounts for 10% of that of the pentamethylene diamine, the molar ratio of the carbonylation agent to the pentamethylene diamine is 6.0:1, the molar ratio of the solvent to the pentamethylene diamine is 15.6:1, air in the reaction kettle is replaced by nitrogen, after the sealing is confirmed to be good, the reaction is carried out in the nitrogen atmosphere, the reaction temperature is controlled to be 190 ℃, the reaction time is 2 hours, and the reaction pressure is 3 MPa; after the reaction is finished, naturally cooling the reaction kettle to room temperature, releasing gas in the reaction kettle, opening the reaction kettle, centrifugally separating out the titanium dioxide catalyst, taking supernatant, and analyzing the composition by using gas chromatography, wherein specific results are listed in table 1;

wherein the titanium dioxide catalyst is prepared by the following preparation method:

dissolving 10mL of isopropyl titanate in 5mL of absolute ethyl alcohol, dispersing the isopropyl titanate in 5mL of absolute ethyl alcohol by using an ultrasonic cleaning machine to obtain a titanium source solution, slowly dropwise adding 2mL of deionized water to the titanium source under the ultrasonic condition, performing ultrasonic treatment for 1h, controlling the volume ratio of the titanium source to the solvent A in the titanium source solution to be 2:1, controlling the volume of the morphology control agent to be 20% of the volume of the titanium source in the titanium source solution, performing reaction on the obtained suspension at 80 ℃ for 3h, washing the solid product obtained by suction filtration with absolute ethyl alcohol for at least three times, washing with distilled water for at least three times until the pH value of the filtrate is 7, then drying in an oven at 150 ℃ for 3h, and calcining the ground solid product in a muffle furnace at 550 ℃ for 3h to obtain the titanium dioxide catalyst.

Example 7

This example provides a catalytic synthesis of pentanedicarbamate, except that the ethyl carbamate described in example 6 was replaced by an equimolar amount of propyl carbamate, the conditions were otherwise identical to those of example 1, and the composition of the supernatant was analyzed by gas chromatography, with the specific results shown in Table 1.

Example 8

This example provides a catalytic synthesis method of glutarocarbamate, which is identical to example 1 except that the reaction temperature in the catalytic synthesis method described in example 1 is changed from 190 ℃ to 210 ℃, and the composition of the supernatant is analyzed by gas chromatography, and the specific results are shown in table 1.

Example 9

This example provides a catalytic synthesis method of pentamethylene dicarbamate, except that the titanium dioxide catalyst obtained by the following preparation method was used, other conditions were completely the same as those in example 1, the composition of the supernatant was analyzed by gas chromatography, and the specific results are listed in table 1;

the preparation method of the titanium dioxide catalyst comprises the following steps:

dissolving 10mL of isopropyl titanate in 5mL of absolute ethyl alcohol, dispersing the isopropyl titanate in 5mL of absolute ethyl alcohol by using an ultrasonic cleaning machine to obtain a titanium source solution, slowly dropwise adding 2mL of deionized water to the titanium source under the ultrasonic condition, performing ultrasonic treatment for 1h, controlling the volume ratio of the titanium source to the solvent A in the titanium source solution to be 2:1, controlling the volume of the morphology control agent to be 20% of the volume of the titanium source in the titanium source solution, performing reaction on the obtained suspension at 100 ℃ for 3h, washing the solid product obtained by suction filtration with absolute ethyl alcohol for at least three times, washing with distilled water for at least three times until the pH value of the filtrate is 7, then drying in an oven at 150 ℃ for 3h, and calcining the ground solid product in a muffle furnace at 550 ℃ for 3h to obtain the titanium dioxide catalyst.

Example 10

This example provides a catalytic synthesis method of pentamethylene dicarbamate, except that the titanium dioxide catalyst obtained by the following preparation method was used, other conditions were completely the same as those in example 1, the composition of the supernatant was analyzed by gas chromatography, and the specific results are listed in table 1;

the preparation method of the titanium dioxide catalyst comprises the following steps:

dissolving 10mL of isopropyl titanate in 20mL of absolute ethyl alcohol, dispersing the isopropyl titanate in 20mL of absolute ethyl alcohol by using an ultrasonic cleaning machine to obtain a titanium source solution, slowly dropwise adding 2mL of deionized water to the titanium source under the ultrasonic condition, performing ultrasonic treatment for 1h, controlling the volume ratio of the titanium source to a solvent A in the titanium source solution to be 0.5:1, controlling the volume of a morphology control agent to be 20% of the volume of the titanium source in the titanium source solution, performing reaction on the obtained suspension at 80 ℃ for 3h, washing a solid product obtained by suction filtration with absolute ethyl alcohol for at least three times, washing with distilled water for at least three times until the pH value of the filtrate is 7, then drying in an oven at 150 ℃ for 3h, and calcining the ground solid product in a muffle furnace at 550 ℃ for 3h to obtain the titanium dioxide catalyst.

Comparative example 1

This comparative example provides a catalytic synthesis of pentanedicarbamate under exactly the same conditions as example 1 except that the titanium dioxide catalyst described in example 1 was replaced with an equimolar amount of commercially available nickel oxide catalyst, and the composition of the supernatant was analyzed by gas chromatography, with the specific results shown in table 1.

Comparative example 2

This comparative example provides a catalytic synthesis of pentanedicarbamate under exactly the same conditions as example 1 except that the titanium dioxide catalyst described in example 1 was replaced with an equimolar amount of commercially available titanium dioxide catalyst, and the composition of the supernatant was analyzed by gas chromatography, with the specific results shown in table 1.

TABLE 1

In conclusion, the catalytic synthesis method provided by the invention not only enables the conversion rate of the pentamethylene diamine to reach 100% and the selectivity of the pentamethylene dicarbamate to be more than or equal to 90%, but also has the advantages of mild conditions, short reaction time, no pollution, low equipment requirement and the like, is suitable for industrial production, and the titanium dioxide catalyst used is simple and convenient to synthesize, stable, not easy to decompose, easy to recover and capable of being reused.

The applicant states that the present invention is illustrated by the above examples to show the detailed process equipment and process flow of the present invention, but the present invention is not limited to the above detailed process equipment and process flow, i.e. it does not mean that the present invention must rely on the above detailed process equipment and process flow to be implemented. It should be understood by those skilled in the art that any modification of the present invention, equivalent replacement of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.