阅读说明：本技术 一种连续合成氨基甲酸酯的工艺 (Process for continuously synthesizing carbamate ) 是由 周玉文 于 2019-10-23 设计创作，主要内容包括：本发明涉及一种催化精馏连续合成氨基甲酸酯的工艺,采用管式反应器,通过预先装载复合型催化剂,通过控制反应温度和原料流速,可实现尿素、甲醇和碳酸二甲酯的连续反应,实现了氨基甲酸酯的连续化制备,尿素转化率在98％以上,氨基甲酸选择性在98.2％以上,附产氨的选择性在1.8％以下。(The invention relates to a process for continuously synthesizing carbamate by catalytic distillation, which adopts a tubular reactor, can realize the continuous reaction of urea, methanol and dimethyl carbonate by pre-loading a composite catalyst and controlling the reaction temperature and the flow rate of raw materials, realizes the continuous preparation of carbamate, and has the advantages of urea conversion rate of more than 98 percent, carbamate selectivity of more than 98.2 percent and ammonia by-product selectivity of less than 1.8 percent.)

1. A process for the continuous synthesis of carbamates, characterized in that: dissolving urea in methanol to form a methanol solution, feeding the urea methanol solution and dimethyl carbonate into a static mixer for mixing, preheating by a preheater, and feeding into a tubular reactor by a feeding pump, wherein the tubular reactor is loaded with a high-efficiency catalyst, and the urea and the dimethyl carbonate are subjected to alcoholysis reaction in the tubular reaction to obtain carbamate, and the reaction formula is as follows:

NH2-CO-NH2+OCH3-CO-OCH3→2NH2-CO-OCH3

and distilling to obtain the carbamate after the reaction is finished, wherein the catalyst is Na-ZnO-ZrO 2/gamma-Al 2O 3.

2. The process for the continuous synthesis of carbamates according to claim 1 wherein: the concentration of urea in the urea methanol solution is 1-30 wt%, and the feeding molar ratio of urea to dimethyl carbonate is 1: 1.1-2.5.

3. The process for the continuous synthesis of carbamates according to claim 1 wherein: the preheating temperature of the preheater is 100-120 ℃, and the reaction temperature is 150-210 ℃.

4. The process for the continuous synthesis of carbamates according to claim 1 wherein: further, the feed rate was 0.1-0.8ml/gcat min.

5. The process for the continuous synthesis of carbamates according to claim 1 wherein: the preparation method of the catalyst comprises the following steps:

s1, dissolving soluble zinc salt and soluble zirconium salt in a certain amount of deionized water according to a certain proportion, fully stirring and uniformly mixing, adding an alumina carrier, adjusting pH, carrying out ultrasonic dispersion for 2-5 hours, carrying out dipping reaction for 2-3 hours, drying at 80-120 ℃ for 5-10 hours, and finally roasting at high temperature to obtain a catalyst precursor;

s2, adding the catalyst precursor and sodium metal into a vacuum grinding reactor according to a certain proportion, and grinding for 3-5 hours to obtain the high-efficiency solid-phase catalyst Na-ZnO-ZrO 2/gamma-Al 2O 3.

6. The process for the continuous synthesis of carbamates according to claim 5 wherein: in the step S1, the soluble zinc salt is zinc nitrate or zinc chloride, and the soluble zirconium salt is zirconium nitrate, zirconium chloride or zirconium sulfate; the mol ratio of the soluble zinc salt to the soluble zirconium salt is 1: 20-50.

7. The process for continuously synthesizing carbamates according to claim 5 wherein the pH value in step S1 is preferably in the range of 1 to 3.

8. The process for the continuous synthesis of carbamates according to claim 5 wherein: in the step S1, the high-temperature roasting temperature is 500-1200 ℃, and the roasting time is 2-12 hours.

9. The process for the continuous synthesis of carbamates according to claim 5 wherein: the amount of the metal added in step S2 is 1.5-10% by mass of the catalyst precursor.

10. The process for the continuous synthesis of carbamates according to claim 5 wherein: the temperature of the polishing reaction in step S2 is 200-300 ℃.

Technical Field

The invention belongs to the field of organic synthesis, and particularly relates to a process for continuously synthesizing carbamate.

Background

Carbamates are an important class of organic synthetic reagents and raw materials for the manufacture of pharmaceuticals. The thermal cracking method of carbamate is adopted to synthesize isocyanate, which has no environmental pollution, low requirement on equipment, great flexibility in building factories and good application prospect. In the presence of a phosphorus pentoxide dehydrating agent, the acetanilide and carbamate react to generate quinazolinone, so that the reaction yield is low. The carbamate compound reacts with acetonyl acetone to obtain the N-substituted 2, 5-dimethylpyrrole with excellent uvioresistant performance and good compatibility with rubber, plastic and various resins. The carbamate and the polyalcohol undergo ester exchange reaction to obtain the polyalcohol carbamate compound, and the structure of the polyalcohol carbamate compound is similar to that of the polyamide. The urethane of polyol and aldehyde are cross-linked to produce a polymer having a polyaminoester structure, which is useful as a coating material, an adhesive, etc. The polyurethanes synthesized by the above-described process do not contain residual toxic isocyanate groups and are referred to as non-toxic polyurethanes. Methyl carbamate and olefin are subjected to addition reaction to synthesize the N-substituted carbamate compound. Styrene and carbamate are subjected to addition reaction in the presence of mercuric nitrate to obtain N-phenethyl carbamate, and the yield is 99%. The carbamate and the isobutene are catalyzed by acidic ion exchange resin to obtain the N-tertiary butyl ethyl carbamate with the yield of 93 percent. After the benzyl carbamate, aldehyde and triphenyl phosphate react, the obtained product is reacted with hydrogen bromide to obtain aminomethyl diphenyl phosphate, and then the aminomethyl diphenyl phosphate reacts with chloroacetyl chloride to obtain the phosphorus-containing dipeptide through condensation.

Carbamates are important pharmaceuticals and pesticides. For example, urethane is a sedative and hypnotic, under the drug name urethane; polyurethanes (polyurethanes for short) obtained by the polymerization of difunctional isocyanates with diols (see polymerization) are used as synthetic leather, synthetic fibers, paints, foams and adhesives.

The carbamate pesticide has the characteristics of strong selectivity, high efficiency, broad spectrum, low toxicity to people and livestock, easy decomposition and less residual toxicity, and is widely applied to the aspects of agriculture, forestry, animal husbandry and the like. More than 1000 carbamate pesticides exist, the using amount of the carbamate pesticides exceeds that of organophosphorus pesticides, and the sale amount of the carbamate pesticides is second to that of pyrethroid pesticides. The carbamate pesticide is used in large amount such as Metolcarb, Carbaryl, Aldicarb, Carbofuran, IsoprOCarb and Pirimicarb. The carbamate pesticide is generally stable under acidic conditions, is easy to decompose when meeting alkali, is easy to decompose when being exposed to air and sunlight, and has a half-life period of several days to several weeks in soil.

Carbamates can be prepared by reacting a chloroformate with ammonia or an amine, or by reacting a carbamoyl chloride with an alcohol or a phenol. The reaction of isocyanates with alcohols or phenols is also a simple process for the preparation of carbamates.

The urea alcoholysis method is a novel synthesis method developed in recent years, has cheap raw materials and simple reaction process, and is the main direction for researching the synthesis of carbamate at present. At present, the yield of carbamate is improved by discharging ammonia through cold energy in the reaction process, but an absorption tower and cooling equipment are required to be additionally arranged, so that the equipment cost and the energy consumption are high, and the industrial production is not facilitated.

Disclosure of Invention

Aiming at the problems of low urea conversion rate and high ammonia discharge energy consumption in the prior art, the invention aims to provide the method for continuously preparing the carbamate, which takes the dimethyl carbonate and the urea as raw materials, does not generate by-products in the reaction process, has good atom economy, and is beneficial to alcoholysis reaction and synthesis in industrial production.

The invention provides a process for continuously synthesizing carbamate, which comprises the steps of dissolving urea in methanol to form a methanol solution, feeding the urea methanol solution and dimethyl carbonate into a static mixer for mixing, preheating by a preheater, and feeding into a tubular reactor by a feeding pump, wherein the tubular reactor is loaded with a high-efficiency catalyst, and carrying out alcoholysis reaction on the urea and the dimethyl carbonate in the tubular reaction to obtain the carbamate, wherein the reaction formula is as follows:

NH₂-CO-NH₂+CH₃O-CO-OCH₃→2NH₂-CO-OCH₃

distilling to obtain carbamate after the reaction is finished, wherein the catalyst is Na-ZnO-ZrO₂/γ-Al₂O₃。

According to the invention, dimethyl carbonate is used as a reaction raw material for urea alcoholysis, so that the raw material for urea alcoholysis is provided in the reaction process, and carbamate can be obtained by reacting with ammonia byproduct in the alcoholysis reaction. In chemical production, a continuously operated tubular reactor with a relatively large length and diameter can be approximately regarded as an ideal displacement flow reactor (Plug flow reactor, PFR for short). Has the advantages of small volume, large specific surface, less back mixing, continuous change of reaction parameters and easy control.

Furthermore, the concentration of the urea in the urea methanol solution is 1-30 wt%, and the feeding molar ratio of the urea to the dimethyl carbonate is 1: 1.1-2.5.

Further, the preheating temperature of the preheater is 100-120 ℃, the reaction temperature is 150-210 ℃, and the reaction pressure is 1-5 MPa.

Further, the feed rate was 0.1-0.8ml/gcat min.

Further, the preparation method of the catalyst comprises the following steps:

s1, dissolving soluble zinc salt and soluble zirconium salt in a certain amount of deionized water according to a certain proportion, fully stirring and uniformly mixing, adding an alumina carrier, adjusting pH, carrying out ultrasonic dispersion for 2-5 hours, carrying out dipping reaction for 2-3 hours, drying at 80-120 ℃ for 5-10 hours, and finally roasting at high temperature to obtain a catalyst precursor;

s2, adding the catalyst precursor and sodium metal into a vacuum grinding reactor according to a certain proportion, and grinding for 3-5 hours to obtain the high-efficiency solid-phase catalyst Na-ZnO-ZrO 2/gamma-Al 2O 3.

Further, in step S1, the soluble zinc salt is zinc nitrate or zinc chloride, and the soluble zirconium salt is zirconium nitrate, zirconium chloride or zirconium sulfate; the mol ratio of the soluble zinc salt to the soluble zirconium salt is 1: 20-50;

further, the pH value in step S1 is preferably between 1 and 3.

Further, the high-temperature calcination temperature in the step S1 is 500-1200 ℃, and the calcination time is 2-12 hours.

Further, the amount of the metal added in step S2 is 1.5-10% by mass of the catalyst precursor.

Further, the temperature of the milling reaction in step S2 is 200-300 ℃.

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

by adopting a tubular reactor, the continuous reaction of urea, methanol and dimethyl carbonate can be realized by pre-loading a composite catalyst and controlling the reaction temperature and the flow rate of raw materials, the continuous preparation of carbamate is realized, the conversion rate of urea is more than 98%, the selectivity of carbamate is more than 98.2%, and the selectivity of by-product ammonia is less than 1.8%.

Detailed Description

The technical solutions in the embodiments of the present invention are clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.

[ example 1 ]

S1, dissolving 1mol of zinc nitrate and 20mol of zirconium nitrate in 5L of deionized water, fully stirring and uniformly mixing, adding 500g of alumina carrier, adjusting the pH to 1 by using dilute sulfuric acid, performing ultrasonic dispersion for 3 hours, performing immersion reaction for 2 hours, drying at 120 ℃ for 5 hours, and finally calcining at 1200 ℃ for 3 hours to obtain a catalyst precursor;

s2, adding 100g of catalyst precursor and 1.5g of metallic sodium into a vacuum grinding reactor, and grinding and reacting for 4 hours at 300 ℃ to obtain the high-efficiency solid-phase catalyst Na-ZnO-ZrO₂/γ-Al₂O₃Namely catalyst C1.

[ example 2 ]

S1, dissolving 1mol of zinc chloride and 30mol of zirconium chloride in 6L of deionized water, fully stirring and uniformly mixing, adding 500g of alumina carrier, adjusting the pH to 1 by using dilute sulfuric acid, performing ultrasonic dispersion for 2 hours, performing immersion reaction for 3 hours, drying at 80 ℃ for 10 hours, and finally calcining at 1000 ℃ for 5 hours to obtain a catalyst precursor;

s2, adding 100g of catalyst precursor and 5g of metallic sodium into a vacuum grinding reactor, and grinding and reacting for 3 hours at 300 ℃ to obtain the high-efficiency solid-phase catalyst Na-ZnO-ZrO₂/γ-Al₂O₃And is denoted as catalyst C2.

[ example 3 ]

S1, dissolving 1mol of zinc nitrate and 50mol of zirconium nitrate in 6L of deionized water, fully stirring and uniformly mixing, adding 300g of alumina carrier, adjusting the pH to 2, ultrasonically dispersing for 2 hours, carrying out dipping reaction for 3 hours, drying at 120 ℃ for 5 hours, and finally roasting at 800 ℃ for 12 hours to obtain a catalyst precursor;

s2, adding 100g of catalyst precursor and 8g of metallic sodium into a vacuum grinding reactor, and grinding and reacting for 3 hours at 200 ℃ to obtain the high-efficiency solid-phase catalyst Na-ZnO-ZrO 2/gamma-Al 2O3, which is marked as catalyst C3.

[ example 4 ]

S1, dissolving 1mol of zinc nitrate and 20mol of zirconium nitrate in 5L of deionized water, fully stirring and uniformly mixing, adding 500g of alumina carrier, adjusting the pH to 1 by using dilute sulfuric acid, performing ultrasonic dispersion for 3 hours, performing immersion reaction for 2 hours, drying at 120 ℃ for 5 hours, and finally calcining at 1200 ℃ for 3 hours to obtain a catalyst precursor;

s2, adding 100g of catalyst precursor into a vacuum grinding reactor, and grinding and reacting for 4 hours at 300 ℃ to obtain the high-efficiency solid-phase catalyst ZnO-ZrO₂/γ-Al₂O₃Namely catalyst D1.

[ example 5 ]

Preparation of carbamate:

dissolving urea in methanol to form a urea methanol solution with the mass concentration of 20%, feeding the urea methanol solution and dimethyl carbonate into a static mixer according to the molar ratio of 1:1.5, mixing, preheating to 110 ℃ by a preheater, and feeding into a tubular reactor by a feeding pump, wherein a high-efficiency catalyst is loaded in the tubular reactor, urea and dimethyl carbonate are subjected to alcoholysis reaction in the tubular reaction to obtain carbamate, the reaction temperature is 180 ℃, the reaction pressure is 3MPa, and the detection and analysis results of the reaction mixture after the reaction are shown in Table 1.

The foregoing description has disclosed fully preferred embodiments of the present invention. It should be noted that those skilled in the art can make modifications to the embodiments of the invention without departing from the scope of the claims. Accordingly, the scope of the appended claims is not to be limited to the specific embodiments described above.