CN1733711A

CN1733711A - Biurea synthesis technology

Info

Publication number: CN1733711A
Application number: CN 200510017886
Authority: CN
Inventors: 杨金顺; 陈勇; 张品三
Original assignee: Kaifeng Dongda Chemical (group) Co Ltd
Current assignee: Kaifeng Dongda Chemical (group) Co Ltd
Priority date: 2005-08-12
Filing date: 2005-08-12
Publication date: 2006-02-15
Anticipated expiration: 2025-08-12
Also published as: CN1295210C

Abstract

The synthesis technique for LDA comprises, using hydrazine hydrate and urea as material, using pretreated HCl gas without excessive oxidizing substance to replace strong H2SO4 in existing technique and prepare the said product. To treat the waste liquid, according ammonia nitrogen content in waste, caltulating required vaporated water quantity to prepare NaCl and NH4Cl, crystallizing the NaCl and NH4Cl both of high purity by evaporation and condensation respectively, and the obtained water can be recycled; returning the last little waste liquid to system for treatment with new waste liquid. This invention has little corrosion to device and high product purity and yield, and ensures the no-pollutant discharge.

Description

Biurea synthesis process

Technical Field

The invention relates to a urea synthesis process, in particular to a biurea synthesis process.

Background

Thebiurea is an important intermediate for producing ADC foaming agent (chemical name: azodicarbonamide), and can also be used for skid resistance of runways, skid resistance of gears, fire prevention and dissolution prevention of high-grade cables and the like.

The structural formula of biurea is:

chemical engineeringThe industrial and traditional process for preparing biurea is mainly hydrazine hydrate (N)₂H₄·H₂O) and urea (CO (NH)₂)₂) Taking concentrated H as raw material according to the proportion of hydrazine hydrate and urea of 1: 3.75-3.9₂SO₄The preparation method is characterized in that the condensation is carried out under the acidic condition of controlling the pH value to be 4-5, and the preparation process mainly comprises the following reaction formula:

1. neutralization reaction

2. Condensation reaction

Because a large amount of waste liquid containing ammonia nitrogen is finally generated in the synthesis process, and the waste liquid also containsWith SO₄ ^-2、CL^-、Na⁺The biurea produced by the process has the highest purity of only 90 percent and lower purity, and the purity is improved by adopting a washing method, so that the water consumption is high, the cost is higher, and meanwhile, the adopted concentrated sulfuric acid not only seriously corrodes equipment in the production process, but also ensures that the yield of the biurea can only reach 80 to 85 percent due to the decomposition effect on urea and hydrazine hydrate, and the yield is lower, so the problem is a difficult problem which troubles the production enterprises for many years.

Disclosure of Invention

Aiming at the defects in the background technology, the invention provides the biurea synthesis process which has the advantages of simple process, small corrosion to equipment, higher product purity and yield, easy treatment of production waste liquid and capability of ensuring no pollution discharge.

The specific solution comprises the following steps:

(1) introducing HCL gas or adding hydrochloric acid into hydrazine hydrate and urea serving as raw materials, or introducing HCL gas and adding hydrochloric acid into hydrazine hydrate and urea to perform condensation reaction to prepare biurea;

(2) analyzing the content of ammonia and nitrogen in the production waste liquid, and calculating the NH content₄After the mass percent of CL is calculated, NaCL and NH prepared from the waste liquid are calculated₄The amount of water to be evaporated for CL, NaCL is crystallized by the heat of evaporation and NH is crystallized by condensation₄CL。

The HCL gas and the hydrochloric acid used for preparing the biurea in the step (1) are the HCL gas and the hydrochloric acid which are pretreated by filtering excessive oxidizing substances through a reducing agent.

The reducing agent adopted for pretreating HCL gas and hydrochloric acid is FeCl₂、FeSO₄、Na₂SO₃。

The invention uses hydrazine hydrate and urea as raw materials, and uses HCL gas and hydrochloric acid to replace concentrated H in the prior art₂SO₄The biurea prepared by condensation has greatly reduced material components in the waste liquid and almost no SO₄ ^-2Therefore, not only the corrosion to the equipment is greatly reduced, but also the treatment difficulty of the production waste liquid is greatly reduced,in addition, the prepared biurea is higher in purity and easier to wash, the production cost is greatly reduced, and NaCL and NH are prepared from the production waste liquid by calculation according to the content of ammonia nitrogen in the production waste liquid₄The CL requires the amount of evaporated water, high-purity NaCL is crystallized by evaporation heat, and high-purity NH is crystallized by condensation₄CL can not only obtain certain economic benefit, but also ensure pollution-free discharge of production. Meanwhile, excessive oxidizing substances are eliminated by adopting HCL gas and hydrochloric acid through pretreatment, so that the reaction yield can reach more than 90%. The invention is a green biurea synthesis process with high reaction yield and purity, thorough waste liquid treatment and no pollution discharge.

Detailed Description

Example 1:

the production method comprises the following production steps:

1. pretreatment of HCL gas

Introducing HCL gas into the reaction kettle and filling FeCl serving as a reducing agent into the reaction kettle₂Is pretreated to eliminate the presence of excess oxidizing species.

2. Synthesis of biurea

Adding 500ml hydrazine hydrate (hydrazine content is 30g/L) into a 1000ml four-neck round-bottom flask with amechanical stirrer, a thermometer, a reflux condenser tube and a gas guide tube, simultaneously adding 57g urea according to the hydrazine content in a ratio of 1: 3.8, then introducing pretreated HCL gas through the gas guide tube until the pH value is 4, heating to 108 ℃, adjusting the introduced amount of the HCL gas, keeping the pH value and the reaction temperature to the reaction end point (namely, the hydrazine content in the solution is less than 0.1g/L), finally washing, filtering and drying to obtain 51.93g biurea with the purity of 98%, and calculating the reaction yield (calculated according to the hydrazine hydrate) to be 92%.

The reaction formula in the biurea preparation process is as follows:

(1) neutralization reaction

(2) Condensation reaction

3. The method for treating the production waste liquid comprises the following steps:

(1) 460ml of the once-through waste liquid after washing and filtering is analyzed to obtain the product with 24.053g/L ammonia nitrogen content and CL content^-188g/L, calculation of NH content₄7.856% of CL, 17.926% of NaCL and H₂The mass percent of O is 74.218 percent, and NaCL and NH prepared from the primary production waste liquid are calculated according to the data₄The amount of water required to be evaporated for CL was 315 g.

(2) Adding the waste liquid into the reactor with mechanical stirringA thermometer, a four-neck flask which is additionally provided with a distillationhead and a condenser pipe is heated and evaporated, the heating temperature is 100-120 ℃, when the evaporation capacity reaches 308.2g (partial vapor is not condensed and lost), 82.6g of NaCL crystal with the purity of 96.8 percent is obtained by filtering the primary production waste liquid while the primary production waste liquid is hot, and when the secondary production waste liquid after filtering the thermal crystal NaCL is cooled to 15 ℃, NH with the purity of 95.2 percent can be obtained by filtering₄24.3g of CL crystal, the final three production waste liquid can be returned to a four-neck bottle for retreatment, and the evaporated water can be returned to the production system for use or discharge.

The NaCL obtained from the production waste liquid can be used as a raw material for producing caustic soda in a chlor-alkali plant and can also be used for producing soda in a combined soda production process in a soda plant to obtain NH₄CL is a high-quality farmland fertilizer. In addition, a small amount of the tertiary production waste liquid finally can be returned to the waste liquid treatment system to be treated together with the new production waste liquid in the large-scale production process.

Example 2

The production method comprises the following production steps:

1. pretreating hydrochloric acid

Introducing HCL gas into the reactor and filling FeSO serving as a reducing agent into the HCL gas₄The filter tank is pretreated to eliminate the excessive oxidizing substances, and then the pretreated HCL gas is absorbed by water to prepare saltAnd (4) acid.

2. Synthesis of biurea

Adding 500ml of hydrazine hydrate (the hydrazine content is 29g/L) into a 1000ml four-neck round-bottom flask with a mechanical stirrer, a thermometer, a reflux condenser and a constant-pressure dropping funnel, simultaneously adding 55.825g of urea according to the proportion of 1: 3.85 of the hydrazine content, then dropwise adding pretreated hydrochloric acid (31% -36%) into the flask through the constant-pressure dropping funnel until the pH value is 5, heating the mixture to 108 ℃, adjusting the addition amount and the dropping speed of the hydrochloric acid, keeping the pH value and the reaction temperature to the reaction end point, and finally washing, filtering and drying the mixture to obtain 49.60g of biurea with the purity of 97%, wherein the calculated yield is 90%.

(1) 590ml of the primary production waste liquid after washing and filtering is analyzed to obtain the product with 22.25g/L ammonia nitrogen content and CL content^-170.8g/L, calculating NH content₄7.342% by mass of CL, 16.31% by mass of NaCL and H₂The mass percent of O is 76.347 percent, and NaCL and NH prepared from the primary production waste liquid are calculated according to the data₄The amount of water required to be evaporated for CL was 420 g.

(2) The method and the equipment in the corresponding steps of the embodiment 1 are adopted to heat and evaporate the primary production waste liquid, the heating temperature is 100-120 ℃, 93.64g of NaCL crystal with the purity of 95.2 percent can be obtained when the evaporation amount reaches 410.3g, the secondary production waste liquid after being filtered by thermal crystallization NaCL is cooled and crystallized, and NH with the purity of 94.9 percent is obtained by filtration₄CL28.07g。

The undescribed portion of this example is the same as example 1.

Example 3

The production method comprises the following production steps:

1. HCL gas and hydrochloric acid were pretreated in the same manner as in examples 1 and 2, respectively, except that Na was used as the reducing agent₂SO₃。

2. Synthesis of biurea

Adding 500ml hydrazine hydrate into a 1000ml four-neck round-bottom flask with a mechanical stirrer, a thermometer, a reflux condenser and a gas guide tube, simultaneously adding 56.7g of urea according to the proportion of 1: 3.78, introducing pretreated HCL gas through the gas guide tube until the pH value is 5, replacing the gas guide tube with a constant-pressure dropping funnel for dropping hydrochloric acid inwards, heating to 107 ℃, adjusting the dropping hydrochloric acid amount and dropping speed, keeping the pH value and the reaction temperature to the reaction end point (hydrazine content is less than 0.1g/L), washing, filtering and drying to obtain 51.63g of biurea with the purity of 97.5%, and calculating the yield of 91% (based on the hydrazine hydrate).

(1) analyzing the 520ml of the once-through waste liquid after washing and filtering to obtain the product with 23.103g/L ammonia nitrogen content and CL content^-174.4g/L meterCalculating NH content₄7.601% of CL, 16.483% of NaCL and H₂The mass percent of O is 75-916%, and NaCL and NH prepared from the primary production waste liquid are calculated according to the data₄The amount of water required to be evaporated in the case of CL was 345 g.

(2) The method and the equipment in the corresponding steps of the embodiment 1 are adopted to heat and evaporate the primary production waste liquid, the heating temperature is 100-120 ℃, 93.50g of NaCLcrystal with the purity of 95.8 percent can be obtained when the evaporation amount reaches 335.4g, and NH with the purity of 95.09 percent can be obtained by cooling, crystallizing and filtering the secondary production waste liquid after filtering the thermal crystallization NaCL₄CL22.97g。

The undescribed portion of this example is the same as example 1.

Claims

1. A biurea synthesis process is characterized by comprising the following steps:

2. The biurea synthesis process according to claim 1, wherein the HCL gas and hydrochloric acid used to prepare biurea is pretreated with a reducing agent to remove excess oxidizing species.

3. The biurea synthesis process of claim 2, wherein the reducing agent used to pretreat the HCL gas and hydrochloric acid is FeCL₂、FeSO₄、Na₂SO₃。