WO2023245633A1

WO2023245633A1 - Process for producing chloroethane

Info

Publication number: WO2023245633A1
Application number: PCT/CN2022/101169
Authority: WO
Inventors: 许传久; 赵莹; 赵金刚; 王从春; 徐杰; 彭亮
Original assignee: 安徽金禾实业股份有限公司
Priority date: 2022-06-24
Filing date: 2022-06-24
Publication date: 2023-12-28
Also published as: CN115348956A

Abstract

The present invention provides a process for producing chloroethane, comprising the following steps: (1) separating sucralose tail gas to prepare concentrated hydrochloric acid; (2) desorption and concentration of the concentrated hydrochloric acid; and (3) synthesis and purification of chloroethane. The present invention utilizes the hydrogen chloride waste gas produced as a by-product in the production of sucralose and realizes the reuse of the by-product hydrogen chloride waste gas and the continuous production of chloroethane. This technique is characterized by high yield, low cost, little wastewater, low energy consumption, high chloroethane purity, and the like.

Description

A process for producing ethyl chloride

Technical field

The invention belongs to the field of chemical production, and specifically relates to a process for continuously producing ethyl chloride using hydrogen chloride tail gas as a by-product of sucralose production.

Background technique

At present, domestic synthesis of ethyl chloride includes hydrochloric acid method and hydrogen chloride method. The hydrochloric acid method commonly uses zinc chloride as a catalyst and is carried out at a temperature of 110°C to 145°C. This method consumes a lot of steam, has a lot of waste water, and the reaction system is unstable. It is mainly a kettle-type intermittent reaction and has low production efficiency. The hydrogen chloride method commonly uses zinc chloride as a catalyst, and the reaction temperature is between 100 and 145°C. This method has a high ethanol conversion rate, greatly reduces the amount of wastewater, low energy consumption, and high yield, but it is basically carried out in a kettle production method, with continuous The level of chemical production is not high.

The equipment used to synthesize ethyl chloride includes kettle type and tower type reactors. The patent application documents with publication numbers CN109503312A, CN106336341A, CN106831315A, and CN105254469A all use kettle reactors. Patent application documents with publication numbers CN206508975U and CN206519136U report tower reactors for synthesizing ethyl chloride, but their actual use effects are not reported. The patent application document with publication number CN106748633B reports a process for synthesizing ethyl chloride in a tower reactor. However, both ethanol and hydrogen chloride enter from the bottom of the synthesis reaction tower and react in the synthesis reaction tower. The pressure in the synthesis reaction tower is as high as 0.2 MPa~0.4MPa, and the yield of ethyl chloride has not been specifically reported.

Using the by-product hydrogen chloride gas to react with ethanol to synthesize ethyl chloride is one of the effective ways to reduce the cost of raw materials for ethyl chloride and solve the outlet of hydrogen chloride waste gas. The patent application document with publication number CN104311382A discloses a method for preparing ethyl chloride from hydrogen chloride, a by-product of the chlorination reaction, using 30% to 36% hydrochloric acid made from 95% ethanol and the by-product hydrogen chloride, which is passed into the reaction kettle, the gaseous mixture of ethyl chloride produced by the reaction is separated and refined through a secondary distillation tower. This patent actually still belongs to the category of synthesizing ethyl chloride using the hydrochloric acid method, which requires a large amount of steam and produces a large amount of hydrochloric acid-containing wastewater. The patent application document with publication number CN109503312A discloses a method for preparing ethyl chloride from hydrogen chloride, a by-product of the synthesis of chlorobenzene. It realizes the continuous production of ethyl chloride to a certain extent and finds a better way to solve the problem of tail gas in the production of chlorobenzene. There is a way out, but this method uses a kettle reaction system.

The tail gas produced during the production of sucralose contains 55% to 65% sulfur dioxide, 25% to 35% HCl, 3% to 8% DMF and trichloroethane, and 2% to 7% other impurities. Patent application documents with publication numbers CN108373139A, CN109724368A, CN112010268A, CN112221311A, and CN112221310A have successively disclosed several technologies for separating and purifying various components in the production of sucralose tail gas; although patent application documents with publication number CN109438169A disclose the use of three The hydrochloric acid produced by separating and purifying the exhaust gas produced during the sucralose process directly reacts with ethanol, and then undergoes deacidification, dehydration, dealcoholization, alkali washing, distillation and other processes to obtain ethyl chloride with a purity of 99.5%, but this patent It still belongs to the category of synthesis of ethyl chloride by hydrochloric acid method, and the conversion rate of ethanol has not been reported. There are no further reports on whether the hydrogen chloride gas obtained by the above patented technologies can be continuously used to efficiently synthesize ethyl chloride, and there are no reports on the recycling of tail gas resources from sucralose production.

In the past two years, judging from the actual situation of the applicant using the method of CN109438169A to produce ethyl chloride, the yield of ethyl chloride is not only as low as 80%, the purity is as low as 99.5%, but the amount of waste water is large and the energy consumption is high. Therefore, using the hydrogen chloride-containing tail gas produced in the production of sucralose to react with ethanol to achieve continuous synthesis of high-quality ethyl chloride and realizing clean production of recycling sucralose tail gas resources are important technical issues that applicants urgently need to solve. .

Application content

In view of the above problems, the present invention discloses a process for producing ethyl chloride to overcome the above problems or at least partially solve the above problems.

In order to achieve the above objects, the present invention adopts the following technical solutions:

A process for producing ethyl chloride, which includes the following steps:

(1) Separate sucralose tail gas to produce concentrated hydrochloric acid: use an organic solvent to absorb trichloroethane in the sucralose tail gas, then dry with concentrated sulfuric acid to remove the moisture in the sucralose tail gas, and then compress, condense, and liquefy Recover the sulfur dioxide in the sucralose tail gas to obtain separated hydrogen chloride gas, and then use dilute hydrochloric acid to absorb the hydrogen chloride gas to prepare concentrated hydrochloric acid;

(2) Analysis and concentration of concentrated hydrochloric acid: Hydrogen chloride gas is analyzed from the concentrated hydrochloric acid obtained in step (1). After analysis, the concentrated hydrochloric acid becomes dilute hydrochloric acid, which is sent to step (1). Absorb hydrogen chloride gas to produce concentrated hydrochloric acid, and the cycle repeats;

(3) Synthesis and purification of ethyl chloride: The desorbed hydrogen chloride gas and ethanol are used to prepare a mixed gas containing ethyl chloride, and the mixed gas containing ethyl chloride is purified to obtain the final ethyl chloride product.

Optionally, the concentrated hydrochloric acid analysis in step (2) adopts a hydrochloric acid analysis and purification system. The hydrochloric acid analysis and purification system includes a double-effect heat exchanger, a desorption tower, a reboiler, a primary condenser, a desulfurization tower, a secondary The desulfurization tower contains an organic solvent for desulfurization and purification of hydrogen chloride gas. The organic solvent is one or a mixture of two of white oil and liquid paraffin with a melting point below 40°C.

Optionally, a water separation system is installed at both the bottom of the desulfurization tower and the bottom of the buffer tank.

Optionally, in step (3), the synthesis of ethyl chloride adopts a tower reaction device, which includes a preheating tower, a synthesis reaction tower, a gas-liquid separator and a condenser, so The preheating tower is equipped with a catalyst, so that after the ethanol is preheated and activated by the preheating tower, it catalytically reacts with the hydrogen chloride gas coming out of the buffer tank in the synthesis reaction tower to synthesize ethyl chloride to obtain ethyl chloride. A mixture of alkane and impurity gases.

Optionally, hydrogen chloride gas enters from the upper end of the synthesis reaction tower, and preheated and activated ethanol enters from the lower end of the synthesis reaction tower. The hydrogen chloride gas and the preheated and activated ethanol are counter-currently mixed, and a catalyst is installed in the synthesis reaction tower. And complete the catalytic reaction in the synthesis reaction tower.

Optionally, the preheated and activated ethanol vapor is introduced into the synthesis reaction tower through a distributor arranged at the bottom of the synthesis reaction tower; the hydrogen chloride gas coming out of the buffer tank is placed in the synthesis reaction tower from the top of the synthesis reaction tower. The air guide pipe and another distributor in the tower lead into the synthesis reaction tower.

Optionally, the mixed gas containing ethyl chloride is further allowed to enter a primary water washing tower, a secondary water washing tower, and an alkali washing tower for washing, and the ethyl chloride after water washing and alkali washing enters a rectification tower for distillation to obtain Crude ethyl chloride, wherein the hydrochloric acid wastewater produced by washing in the primary water washing tower and the dilute hydrochloric acid analyzed in step (2) are returned to step (1) to absorb hydrogen chloride gas and produce concentrated hydrochloric acid.

Optionally, in the synthesis reaction tower, the catalyst is selected from one or two types of zinc chloride and aluminum trichloride, and the catalyst concentration accounts for the total mass of all materials in the synthesis reaction tower in mass percentage. 50%~80%.

Optionally, in the step (3), the molar ratio of the hydrogen chloride gas to the ethanol is 1/1 to 1.3/1.

Optionally, when the hydrochloric acid content of the first-level water washing tower is 10% to 15%, the washing water is replaced, and the replaced first-level washing water is combined with the dilute hydrochloric acid after the concentrated hydrochloric acid has been resolved and sent to the step (1). Absorb hydrogen chloride gas to prepare concentrated hydrochloric acid; when the pH value of the solution in the secondary water washing tower is 2 to 4, the washing water is replaced, and the replaced secondary washing water is used to replace the washing water in the primary water washing tower; when the alkali When the pH value of the solution in the washing tower reaches 7 to 8, replace the alkali solution.

It can be seen that the present invention utilizes the by-produced hydrogen chloride waste gas in the production of sucralose, and realizes the reuse of the by-produced hydrogen chloride waste gas and the continuous production of ethyl chloride. This technology has the characteristics of high yield, low cost, less waste water, low energy consumption, and high purity of ethyl chloride.

Description of the drawings

Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are for the purpose of illustrating preferred embodiments only and are not to be construed as limiting the invention. Also throughout the drawings, the same reference characters are used to designate the same components. In the attached picture:

Figure 1 is a process flow diagram of the production method of the present invention;

Figure 2 is a diagram of the continuous tower reaction device of the present invention.

Specific embodiments

The invention provides a process for producing ethyl chloride, which includes the following steps: (1) Separating sucralose tail gas to produce concentrated hydrochloric acid: using an organic solvent to absorb trichloroethane in the sucralose tail gas, and then using concentrated Drying with sulfuric acid removes the moisture in the sucralose tail gas, then compresses and condenses, liquefies and recovers the sulfur dioxide in the sucralose tail gas to obtain separated hydrogen chloride gas, and then uses dilute hydrochloric acid to absorb the hydrogen chloride gas to obtain concentrated hydrochloric acid; (2) Analysis and concentration of concentrated hydrochloric acid: hydrogen chloride gas is analyzed from the concentrated hydrochloric acid obtained in the step (1). After analysis, the concentrated hydrochloric acid becomes dilute hydrochloric acid, which is sent to the step (1) to absorb hydrogen chloride. The gas is used to produce concentrated hydrochloric acid, and the cycle repeats; (3) Synthesis and purification of ethyl chloride: Utilize the desorbed hydrogen chloride gas and ethanol to prepare a mixed gas containing ethyl chloride, and process the mixed gas containing ethyl chloride for Purification to obtain the final ethyl chloride product.

The process of continuously producing ethyl chloride using hydrogen chloride, a by-product of sucralose production, according to the present invention will be described in detail below.

As shown in Figure 1, the process flow of the production method of the present invention includes the following steps:

(1) Separate sucralose tail gas to produce concentrated hydrochloric acid: absorb the hydrogen chloride tail gas by-product of sucralose production through an organic solvent to remove organic matter, dry and remove water with concentrated sulfuric acid, compress and liquefy to recover sulfur dioxide, obtain hydrogen chloride residual gas, and finally analyze it with hydrochloric acid The 18% to 24% dilute hydrochloric acid after column analysis absorbs the above hydrogen chloride residual gas to produce 30% to 36% concentrated hydrochloric acid.

(2) Analysis, purification and concentration of concentrated hydrochloric acid: The concentrated hydrochloric acid prepared above is passed through a double-effect heat exchanger, a desorption tower, a reboiler, a primary condenser, a desulfurization tower, and a secondary condenser to produce hydrogen chloride gas. The desulfurization tower is equipped with an organic solvent for desulfurization and purification of the passing hydrogen chloride gas (that is, organic solvent absorption). The desulfurization and purification of the hydrogen chloride gas enters the buffer tank through the secondary condenser for subsequent synthesis of ethyl chloride. The analyzed 18% to 24% dilute hydrochloric acid is condensed and sent to the tail gas treatment section of the sucralose workshop. It is enriched with the hydrogen chloride residual gas separated and purified in the aforementioned (1) process to obtain 30% to 36% concentrated hydrochloric acid. By repeating this cycle, a hydrochloric acid analysis, purification and concentration circulation system is constructed to provide a stable source of hydrogen chloride for the synthesis of ethyl chloride.

(3) Synthesis and separation of ethyl chloride: Pass the ethanol into the preheating tower, and the preheated and activated ethanol after one-stage preheating passes through the distributor and the hydrogen chloride gas coming out of the buffer tank passes through the distributor in the synthesis reaction tower. Catalytic reaction to synthesize ethyl chloride. The generated ethyl chloride, ether, water and unreacted hydrogen chloride, a small amount of ethanol, and a small amount of sulfur dioxide pass through the gas-liquid separator, first-level condenser, second-level condenser, third-level condenser and alcohol separator to contain a small amount of ethanol, Ethyl chloride gas mixture of ether, water, hydrogen chloride and sulfur dioxide.

(4) Purification of ethyl chloride: The mixed gas containing ethyl chloride enters the first-level water washing tower, the second-level water washing tower, and the alkali washing tower for washing to remove impurities such as ethanol, hydrogen chloride, and sulfur dioxide, and then the washed The ethyl chloride is sent to the distillation tower for distillation to obtain crude ethyl chloride gas.

(5) Refining of ethyl chloride. The crude ethyl chloride is passed through a first-level molecular sieve adsorption tower, a second-level molecular sieve adsorption tower, a first-level modified zeolite molecular sieve tower, and a second-level modified zeolite molecular sieve tower to remove residual ethanol, water and other impurities to obtain fine ethyl chloride, with a purity of > 99.90%, moisture <0.02ppm, ethanol <0.04%, comprehensive yield of ethyl chloride>94.0%.

Here, the present invention can produce hydrogen chloride gas with a purity of 95% to 99% after separating and purifying the tail gas of sucralose production according to the process (1).

The hydrochloric acid analysis and purification device of the present invention consists of a double-effect heat exchanger, a desorption tower, a reboiler, a primary condenser, a desulfurization tower, a secondary condenser and a buffer tank. The temperature at the top of the analytical tower is controlled at 80°C ~ 105°C, and the pressure is 0.08MPa ~ 0.15MPa; the outlet temperature of the primary condenser is controlled at 45°C ~ 65°C, and the outlet temperature of the secondary condenser is controlled at 10°C ~ 35°C; The desulfurization tower is placed between the primary condenser and the secondary condenser. The desulfurized hydrogen chloride is removed from the precipitated sulfur through the desulfurization tower. The temperature of the desulfurization tower is between 40°C and 55°C. The desulfurization tower is equipped with an organic solvent. The organic solvent used is one or a mixture of liquid paraffin or white oil. Liquid paraffin with a melting point below 40°C is preferably used. The desulfurized hydrogen chloride gas is further cooled to 10-35°C by the secondary condenser and enters the buffer tank to provide hydrogen chloride gas with stable flow and low water content for the synthesis of ethyl chloride. A water separation system is installed at the bottom of the desulfurization tower and buffer tank to facilitate the timely discharge of condensed sulfur-containing water or hydrochloric acid-containing water out of the system to ensure the continuous operation of the hydrogen chloride analysis and purification system.

The present invention carries out the synthesis and separation of ethyl chloride according to the process (3). As shown in Figure 2, the tower reaction device used includes a preheating tower, a synthesis reaction tower, a gas-liquid separator, a primary condenser, and a secondary condensation condenser, three-stage condenser and alcohol separator. The preheating tower is filled with catalysts of the same type and concentration as those in the synthesis tower. The catalyst used is one or a combination of zinc chloride and aluminum trichloride. When the reaction starts, the catalyst concentration accounts for 40% to 80% (mass percentage) of the total mass of the materials in the synthesis reaction tower. During the continuous reaction, the liquid level height in the synthesis reaction tower is controlled to be 40% to 40% of the internal height of the synthesis reaction tower. 80%. The temperature of the preheating tower is controlled at 90°C ~ 120°C, the temperature of the synthesis reaction tower is controlled at 125°C ~ 140°C, and the pressure is controlled at 0.04MPa ~ 0.08MPa.

The present invention carries out the synthesis and separation of ethyl chloride according to the process (3). The ethanol enters from the bottom of the preheating tower. After preheating, it enters the bottom of the synthesis reaction tower from the top of the preheating tower in the form of steam. The bottom of the synthesis reaction tower is equipped with distributor to control the uniform distribution of ethanol molecules. Hydrogen chloride gas enters the interior of the synthesis reaction tower through a pipeline from the top of the synthesis reaction tower. A distributor is installed at the bottom of the pipeline and is submerged under the liquid surface of the synthesis reaction tower to control the uniform distribution of hydrogen chloride molecules in the catalytic system. Hydrogen chloride gas and evenly distributed activated ethanol molecules meet in countercurrent in the synthesis reaction tower and undergo a catalytic reaction to obtain ethyl chloride.

The present invention carries out the synthesis and separation of ethyl chloride according to the process (3). Hydrogen chloride:ethanol is 1/1 to 1.3/1 (molar ratio). By excess hydrogen chloride, the ethanol molecules react as completely as possible, thereby reducing the amount of ethanol recovery. , improve the primary conversion rate of ethyl chloride, thereby further reducing its energy consumption and waste water volume.

In addition, the liquid separated by the gas-liquid separator returns to the preheating tower to continue the reaction to achieve continuous reaction; a small amount of condensate that enters the alcohol separator after being condensed by the primary, secondary, and tertiary condensers is collected to a certain amount. Finally, concentrated distillation is performed to recover ethanol, which can be recycled as ethanol raw material.

The present invention carries out the purification of ethyl chloride according to (4), so that the mixed gas of ethyl chloride enters the primary and secondary water washing towers for water washing to mainly remove hydrogen chloride and a small amount of ethanol. When the hydrochloric acid content of the primary water washing tower is 10 to 15%, the washing water is replaced. When the pH value of the secondary water washing tower is 2 to 4, the washing water is replaced. The wash water replaced from the secondary water washing tower is used for the primary water washing tower. replace. The water-washed gas containing ethyl chloride enters the alkali washing tower for washing to remove residual sulfur dioxide and residual hydrogen chloride. When the pH of the aqueous solution reaches 7 to 8, replace 20% to 40% sodium hydroxide solution. The replaced primary water washing tower washing water (10% to 15% dilute hydrochloric acid) and (2) 18% to 24% dilute hydrochloric acid after process analysis are sent to the tail gas treatment section of the sucralose production workshop, and the separated The hydrogen chloride tail gas is enriched to produce concentrated hydrochloric acid (30% to 36% concentrated hydrochloric acid), thereby realizing the recycling of the excess hydrogen chloride gas introduced.

The present invention is based on (5) refining of ethyl chloride. The crude ethyl chloride is passed through a first-level molecular sieve adsorption tower, a second-level molecular sieve adsorption tower, a first-level modified zeolite molecular sieve tower, and a second-level modified zeolite molecular sieve tower to remove residual ethanol and ether. and water to obtain fine ethyl chloride, with purity >99.90%, moisture <0.02ppm, ethanol <0.04%, and comprehensive yield of ethyl chloride >94.0%. When the purity of fine ethyl chloride is <99.90%, moisture is >0.02ppm, and ethanol is >0.04%, replace the molecular sieve or modified zeolite molecular sieve. The replaced molecular sieves and modified zeolite molecular sieves are regenerated and continue to be recycled.

The invention separates and purifies the tail gas of sucralose production to obtain hydrogen chloride gas to make concentrated hydrochloric acid, and then parses out the hydrogen chloride gas for synthesizing ethyl chloride, and returns the parsed dilute hydrochloric acid to the tail gas treatment section of the sucralose production workshop. Concentrate to obtain concentrated hydrochloric acid, so that the analyzed dilute hydrochloric acid can be recycled. The hydrogen chloride gas and ethanol obtained by analysis are subjected to continuous catalytic reaction, separation, purification and refinement in the synthesis reaction tower to obtain fine ethyl chloride, which realizes the continuous production of ethyl chloride by utilizing hydrogen chloride-containing waste gas resources. This ethyl chloride is further used in the production of the applicant's ethyl maltol (as an ethylation reagent), thereby building a "bridge" in the production of the applicant's sucralose and ethyl maltol, which not only satisfies the It meets the needs of industries such as spices and dyes, and meets the quality requirements of ethyl chloride in industries such as dyes.

Compared with the existing technology for synthesizing ethyl chloride, the innovation and beneficial effects of this invention are as follows:

(1) Use the tail gas of sucralose production for separation and purification to obtain hydrogen chloride gas to make concentrated hydrochloric acid, and then analyze and purify the hydrogen chloride gas for the synthesis of ethyl chloride, and the analyzed 18% to 24% dilute hydrochloric acid and primary The 10% to 15% dilute hydrochloric acid obtained by washing with water is returned as base acid to the tail gas treatment section of the sucralose production workshop to absorb the separated hydrogen chloride gas to obtain concentrated hydrochloric acid, so that the analyzed dilute hydrochloric acid and the washed dilute hydrochloric acid can be recycled . By repeating this cycle, the hydrogen chloride-containing tail gas in the production of sucralose is continuously used to synthesize ethyl chloride. This technology not only solves the problem of treating the hydrogen chloride-containing tail gas generated in the production of sucralose, but also reduces the cost of raw materials for synthesizing ethyl chloride. The existing method of synthesizing ethyl chloride using the tail gas of sucralose production is still limited to the hydrochloric acid method. A large amount of low-concentration hydrochloric acid wastewater has not been recycled, resulting in large wastewater volume, high energy consumption, low yield, and low product quality.

(2) The hydrogen chloride gas desorbed from concentrated hydrochloric acid is desulfurized and purified by an organic solvent, and then enters the buffer tank. This not only avoids the deposition of sulfur at the bend connecting the primary and secondary condensers, blocking the pipeline, causing shutdown and maintenance, and even causing safety hazards. It also provides a stable flow hydrogen chloride gas source for synthesizing ethyl chloride, which is conducive to continuous production and obtaining high-quality ethyl chloride products. A water separation system is installed at the bottom of the desulfurization tower and the bottom of the buffer tank, which can discharge the condensed sulfur-containing water or hydrochloric acid-containing water out of the system in a timely manner, effectively ensuring the continuous operation of the hydrogen chloride analysis and purification system, and providing continuous and stable operation for the synthesis reaction. Stable supply of hydrogen chloride gas.

(3) Preheat ethanol to 90°C to 120°C through a preheating tower. The preheating tower is equipped with a high-concentration catalyst, which prolongs the activation time of ethanol molecules and maximizes the activation of ethanol molecules into ethyl cations, and It quickly completes the catalytic reaction with the hydrogen chloride gas molecules entering from the upper end of the synthesis reaction tower (countercurrent mixing) in the synthesis reaction tower, effectively improving the catalytic efficiency of the catalyst, speeding up the ethanol reaction rate, and reducing the escape percentage of ethanol molecules, thus improving The primary conversion rate of ethanol is increased, thereby reducing the load of subsequent separation, purification and refinement of ethyl chloride. However, the existing preheating is limited to preheating ethanol molecules and does not have the effect of efficiently preactivating ethanol molecules, which easily causes some ethanol molecules to escape from the catalytic system and reduces the primary ethanol conversion rate.

(4) After ethanol is preheated and enters the bottom of the synthesis reaction tower from the top of the preheating tower, a distributor is installed at the bottom of the synthesis reaction tower to control the uniform distribution of ethanol molecules in the catalytic system; while hydrogen chloride gas is self-synthesizing in the reaction tower The top enters the interior of the synthesis reaction tower through a pipeline. A distributor is also installed at the bottom of the pipeline, which can also control the uniform distribution of hydrogen chloride molecules in the catalytic system. The uniformly distributed hydrogen chloride gas and the uniformly distributed activated ethanol vapor flow are used in the synthesis reaction Countercurrent intersection occurs in the tower, which increases the probability and time of contact between each other, greatly promotes the efficiency of the catalytic reaction, improves the primary conversion rate of ethanol, avoids excessive ethanol molecules entering the water washing system and increases the consumption of ethanol tons, thereby improving The yield of ethyl chloride.

(5) The "preheating tower-synthesis reaction tower" integrated equipment is used to replace the traditional reactor system, and hydrogen chloride gas replaces industrial hydrochloric acid to catalyze the synthesis of ethyl chloride reaction, which is not only conducive to the continuity of the synthesis of ethyl chloride reaction, but also improves the The recovery rate of ethyl chloride per unit time, and avoids the need to use hydrochloric acid to evaporate water from the synthesis reaction tower to generate more steam, and avoids large fluctuations in catalyst concentration that affect the catalytic efficiency, and also eliminates a large amount of ethanol-containing The generation of acidic wastewater realizes the efficient synthesis of ethyl chloride.

(6) Using a first-level water washing tower and a second-level water washing tower to wash the ethane-containing chlorine mixed gas is conducive to timely removal of excess hydrochloric acid in the mixed gas. The generated high-concentration hydrochloric acid wastewater and the analyzed dilute hydrochloric acid are returned to sucralose. The workshop that absorbs tail gas to produce concentrated hydrochloric acid realizes the recycling of hydrogen chloride resources and greatly reduces wastewater emissions. Using an alkali washing tower to wash the ethyl chloride mixed gas can not only remove the residual hydrogen chloride gas, but also remove the sulfur dioxide gas that was not completely separated in the separation of sucralose tail gas, thereby improving the quality of ethyl chloride and avoiding the subsequent use of ethyl chloride. The adverse effects caused by the synthesis reaction of alkane.

(7) The present invention continuously introduces ethanol and hydrogen chloride gas into the reaction system, and the water produced by the reaction is taken out with the excess hydrogen chloride and the generated ethyl chloride, thereby keeping the catalyst concentration in the reaction system relatively stable and achieving continuity. Production of ethyl chloride.

The present invention will be further described in detail below with reference to accompanying drawings 1, 2 and specific examples. The raw materials required for the examples are all commercially available industrial products.

Example 1

(1) Separate sucralose tail gas to produce concentrated hydrochloric acid: The tail gas in sucralose production (sulfur dioxide 57%, HCl 33%, trichloroethane and DMF 6%, other impurities 4%) enters the primary and secondary absorption towers, Secondary white oil is used as the absorption liquid. The absorbed tail gas (60% sulfur dioxide, 35% HCl, 2% trichloroethane, and 3% other impurities) enters the sulfuric acid drying tower (92% sulfuric acid) for drying and water removal; The gas (moisture content 324 ppm) is compressed by the liquid ring pump, condensed and liquefied to recover sulfur dioxide. The gas after recovering sulfur dioxide (sulfur dioxide 2.5%, HCl 95.5%, trichloroethane 1%, other impurities 1%) enters the spray tower and is recycled. 20.5% ~ 22.5% dilute hydrochloric acid is absorbed to obtain (0.28% sulfur dioxide, 0.32% trichloroethane) 32.6% ~ 33.5% concentrated hydrochloric acid.

(2) Analytical purification and concentrated hydrochloric acid: Pass 32.6% to 33.5% concentrated hydrochloric acid through a double-effect heat exchanger, desorption tower, reboiler, primary condenser, desulfurization tower (equipped with liquid paraffin), and secondary condenser , a hydrochloric acid analysis and purification device composed of a buffer tank, control the top temperature of the analysis tower to be 90°C ~ 93°C, and the top pressure of the tower to be 0.108MPa ~ 0.116MPa for analysis, and control the temperature of the desulfurization tower to be 45°C ~ 50°C to perform desulfurization and purification, thereby Purified hydrogen chloride gas is obtained for subsequent synthesis of ethyl chloride. The 20.6% to 22.4% dilute hydrochloric acid after analysis is mixed with the 12.2% to 13.6% dilute hydrochloric acid obtained from the first-level water washing tower and sent to the hydrochloric acid concentration process of the sucralose production workshop for thickening, and 32.6% to 33.5% is obtained. of concentrated hydrochloric acid.

(3) Synthesis of ethyl chloride: Pour 95% ethanol into the first-level preheating tower at 600Kg/h and preheat it to 108°C ~ 112°C. The preheated ethanol enters the synthesis reaction tower from the bottom of the synthesis reaction tower. At the same time, the hydrogen chloride gas in the buffer tank is passed from the top of the synthesis reaction tower to the catalyst zinc chloride at a rate of 520Kg/h (the molar ratio of hydrogen chloride to ethanol is 1.15:1.00) (zinc chloride accounts for all the gas in the synthesis reaction tower) In the synthesis reaction tower (the mass percentage concentration of the total mass of the material is 64.2%), control the temperature of the synthesis reaction tower to 134°C ~ 136°C and the pressure

Carry out synthesis reaction. The generated ethyl chloride, ether, water and unreacted hydrogen chloride, a small amount of ethanol, and a small amount of sulfur dioxide are condensed through the gas-liquid separator, first-level condenser, second-level condenser, and third-level condenser, and then enter the alcohol separator to obtain ethyl chloride. Alkane mixture (containing a small amount of ethanol, ether, water, hydrogen chloride and sulfur dioxide). The liquid in the gas-liquid separator returns to the preheating tower, and the liquid level height in the synthesis reaction tower is controlled to be 50% to 65% of the internal height of the synthesis reaction tower. The condensate (containing ethanol, water and hydrogen chloride) in the alcohol separator enters the condensate storage tank. After accumulating to a certain amount, ethanol is distilled and recovered as a raw material for the reaction.

(4) Purification and distillation of ethyl chloride: The mixed gas containing ethyl chloride enters the first-level water washing tower, the second-level water washing tower for water washing, and the alkali washing tower (containing sodium hydroxide solution) for alkali washing to remove acid gases, etc. . When the hydrochloric acid content of the primary water washing tower is 12.2% to 13.6%, the washing water is replaced. The replaced primary water washing tower washing water is mixed with the analyzed 20.6% to 22.4% dilute hydrochloric acid and sent together to the exhaust gas treatment of the sucralose production workshop. The process section is thickened to produce 32.6% ~ 33.5% concentrated hydrochloric acid; when the pH value of the secondary water washing tower is 3 ~ 4, the washing water is replaced, and the washing water replaced by the secondary water washing tower is used to replace the primary water washing tower. When the pH of the aqueous solution in the alkali washing tower reaches 8, replace it with 30% sodium hydroxide solution. Then the washed ethyl chloride is sent to the distillation tower for rectification to obtain crude ethyl chloride gas.

(5) Refining of ethyl chloride. The crude ethyl chloride gas enters the first-level molecular sieve adsorption tower, the second-level molecular sieve adsorption tower, the first-level modified zeolite molecular sieve tower, and the second-level modified zeolite molecular sieve tower for adsorption and impurity removal to obtain fine ethyl chloride with a purity of 99.93%. ~99.97%, moisture 0.003ppm~0.010ppm, ethanol 0.005%~0.015%, sulfur dioxide was not detected, and the comprehensive yield of ethyl chloride was 96.2% (the comprehensive yield after continuous 168).

The synthesized high-quality ethyl chloride is used to synthesize ethyl maltol, and the quality and yield of the obtained ethyl maltol meet the requirements of technical indicators.

Comparative example 1

Different from Example 1, a hydrochloric acid analysis and purification system is not used. Instead of hydrogen chloride gas, 32.6% to 33.5% concentrated hydrochloric acid recovered from the tail gas of sucralose production is used. 95% ethanol and recovered hydrochloric acid are mixed together in the preheating tower. The rest of the process is the same as in Example 1 to obtain fine ethyl chloride, with a purity of 98.55% to 99.16%, a moisture of 0.007ppm to 0.025ppm, an ethanol of 0.06% to 0.24%, and a comprehensive yield of ethyl chloride of 81.6% (continuous for 168 hours). the final comprehensive yield).

The results show that the yield of ethyl chloride in Comparative Example 1 is obviously not as good as that of Example 1 (14.6% lower), and the quality of ethyl chloride (purity 98.55% to 99.16%) is also not as good as that of Example 1 (purity 99.93). %～99.97%), this is because the hydrochloric acid recovered from the exhaust gas of sucralose production in Comparative Example 1 contains sulfur dioxide, chloroform and other unknown substances.

Example 2

(1) Separation and purification of tail gas: The tail gas in the production of sucralose (60% sulfur dioxide, 30% HCl, 5% trichloroethane and DMF, 5% other impurities) enters the primary and secondary absorption towers, using liquid paraffin as the absorption liquid , the absorbed tail gas (sulfur dioxide 59.4%, HCl 35.0%, trichloroethane 2.6%, other impurities 3%) enters the sulfuric acid drying tower (sulfuric acid with a mass concentration of 88%) for drying and water removal; the dried gas (moisture content) 346ppm) is compressed by a liquid ring pump, condensed and liquefied to recover sulfur dioxide. The gas after recovering sulfur dioxide (sulfur dioxide 3%, HCl 95.4%, trichloroethane 0.6%, other impurities 1%) enters the spray washing tower, and the recovered 20.5 %~21.8% dilute hydrochloric acid absorbs hydrogen chloride to produce 30.5%~32.4% concentrated hydrochloric acid (containing 0.40% sulfur dioxide, 0.3% trichloroethane).

(2) Desorption and concentration of hydrochloric acid: Pass 30.5% to 32.4% concentrated hydrochloric acid through a double-effect heat exchanger, desorption tower, reboiler, primary condenser, desulfurization tower (equipped with secondary white oil), and secondary condensation A hydrochloric acid analysis device composed of a reactor, a buffer tank, etc., controls the temperature at the top of the analysis tower to be 86°C ~ 90°C, and the pressure at the top of the tower is 0.095MPa ~ 0.100MPa, and the hydrogen chloride gas is analyzed for subsequent synthesis of ethyl chloride, and the analyzed 20.2 % ~ 21.3% dilute hydrochloric acid is mixed with 11.2% ~ 13.3% dilute hydrochloric acid recovered from the first-level water washing tower and then sent together to the hydrochloric acid concentration process of the sucralose production workshop for thickening to obtain 30.5% ~ 32.4% concentrated hydrochloric acid.

(3) Synthesis of ethyl chloride: Pour 95% ethanol into the preheating tower at 600Kg/h and preheat it to 118°C ~ 120°C. The preheated ethanol is fed from the bottom of the synthesis reaction tower, and at the same time, it will be passed from the buffer The hydrogen chloride gas coming out of the tank is passed into the synthesis reaction tower from the top of the synthesis reaction tower at a rate of 552Kg/h (the molar ratio of hydrogen chloride to ethanol is 1.22:1.00). The synthesis reaction tower is equipped with a zinc chloride-aluminum trichloride catalyst. The mass percentage concentration of zinc-aluminum trichloride in the total mass of all materials in the synthesis reaction tower is 54.5% (the mass ratio of zinc chloride/aluminum trichloride is 9:1), and the temperature of the synthesis reaction tower is controlled to 130 ℃ ~ 134 ℃ for catalytic synthesis reaction. The generated ethyl chloride, ether, water and unreacted hydrogen chloride, a small amount of ethanol, and a small amount of sulfur dioxide are passed through a gas-liquid separator, a first-level condenser, a second-level condenser, a third-level condenser, and an alcohol separator to obtain ethyl chloride. Mixed gas (containing a small amount of ethanol, ether, water, hydrogen chloride, sulfur dioxide). The liquid in the gas-liquid separator returns to the preheating tower, and the liquid level height in the synthesis reaction tower is controlled to be 55% to 70% of the internal height of the synthesis reaction tower. The condensate (containing ethanol, water and hydrogen chloride) in the alcohol separator enters the condensate storage tank. After accumulating to a certain amount, the ethanol is distilled and recovered.

(4) Purification of ethyl chloride: The mixed gas containing ethyl chloride enters the first-level water washing tower, the second-level water washing tower, and the alkali washing tower for washing. When the hydrochloric acid content of the primary water washing tower is 11.2 to 13.3%, the washing water is replaced, and the replaced primary water washing tower washing water is sent to the tail gas treatment section of the sucralose production workshop to thicken concentrated hydrochloric acid; when the pH value of the secondary water washing tower The washing water is replaced at 3 to 4 hours, and the washing water replaced by the second-level water washing tower is used to replace the first-level water washing tower. When the pH of the aqueous solution in the alkali washing tower reaches 7 to 8, replace it with 30% sodium hydroxide solution. Then the washed ethyl chloride enters the distillation tower for rectification to obtain crude ethyl chloride.

(5) Refining of ethyl chloride: Make the crude ethyl chloride gas enter the first-level molecular sieve adsorption tower, the second-level molecular sieve adsorption tower, the first-level modified zeolite molecular sieve tower, and the second-level modified zeolite molecular sieve tower to further remove impurities to obtain fine chlorine The purity of ethane is 99.92% to 99.96%, moisture is 0.007ppm to 0.012ppm, ethanol is 0.006% to 0.020%, and the comprehensive yield of ethane chloride is 96.0% (comprehensive yield after 168 hours of continuous operation).

The synthesized ethyl chloride is used to synthesize N,N-diethyl-m-acetamidoaniline, and the quality and yield of the obtained N,N-diethyl-m-acetamidoaniline meet the technical requirements.

Example 3

Different from Example 2, in the analysis and purification concentrated hydrochloric acid system, the resolved hydrogen chloride gas does not pass through the desulfurization tower equipped with liquid paraffin or white oil, but directly enters the buffer tank. The rest of the process is the same as in Example 2, and fine ethyl chloride is obtained. Its purity is 98.91% to 99.22%, moisture is 0.006ppm to 0.017ppm, ethanol is 0.005% to 0.025%, and the comprehensive yield of ethyl chloride is 92.6% (comprehensive yield after 168 hours of continuous operation).

The results show that: the yield of ethyl chloride in Example 3 is 3.4% lower than that in Example 2; the quality of ethyl chloride in Example 3 (purity is 98.91%-99.22%) is not as good as the quality in Example 2 (99.92%-99.92%). 99.96%). It can be seen that whether the desulfurization tower in the analytical purification concentrated hydrochloric acid system is installed or not has an impact on the quality of synthesized ethyl chloride.

Example 4

According to the process of Example 1, replace the 64.2% zinc chloride solution with 54.5% zinc chloride solution, and the other processes are the same. The purity of the refined ethyl chloride obtained is 99.91% ~ 99.95%, moisture 0.006 ~ 0.012ppm, and ethanol 0.01% ~ 0.04%, sulfur dioxide was not detected, and the comprehensive yield of ethyl chloride was 94.2% (comprehensive yield after 168 hours of continuous operation).

The results show that: compared with Example 1, the concentration of the catalyst zinc chloride solution became lower and the yield of ethyl chloride also decreased, but the quality of ethyl chloride remained basically unchanged.

Comparative example 2

Different from Example 4, a hydrochloric acid analysis and purification system is not used. Chlor-alkali industrial synthesis of 32.2% hydrochloric acid is used instead of hydrogen chloride gas. 95% ethanol and 32.2% hydrochloric acid are mixed together in the preheating tower. The rest of the process is the same as (3) in Example 1. , (4) and (5) processes are the same to obtain fine ethyl chloride, with a purity of 99.92% ~ 99.97%, moisture 0.006ppm ~ 0.016ppm, ethanol 0.01% ~ 0.04%, and a comprehensive yield of ethyl chloride 83.3% (continuous Comprehensive yield after 168 hours).

The results show that: the ethyl chloride yield of Comparative Example 2 is obviously not as good as the yield of Example 4, nor as good as the yield of Example 1, but the quality of ethyl chloride is close to that of Example 1 and Example 4. It can be seen that the present invention can effectively improve the comprehensive yield of ethyl chloride, and more importantly, greatly reduce the amount of waste water.

Example 5

According to the process of Example 1, 480Kg/h hydrogen chloride is used instead of 520Kg/h hydrogen chloride (the molar ratio of hydrogen chloride to ethanol is 1.06:1.00). The rest of the process is the same, and the purity of the refined ethyl chloride is 99.91% to 99.95%, and the moisture is 0.004ppm. ~0.013ppm, ethanol 0.006%~0.02%, and sulfur dioxide were not detected, and the comprehensive yield of ethyl chloride was 94.2% (continuous for 120 hours).

The results show that by reducing the molar ratio of hydrogen chloride to ethanol in ethanol, the yield of ethyl chloride is slightly lower than in Example 1, but the quality of ethyl chloride remains basically unchanged.

Example 6

According to the process of Example 1, a concentrated sulfuric acid (98% H2SO4) tower is used for acid washing, instead of an alkali washing tower for alkali washing. When the concentrated sulfuric acid concentration is reduced to 85%, the concentrated sulfuric acid is replaced. The remaining processes are the same to obtain the fine product of ethyl chloride. The purity is 99.72% to 99.88%, moisture is 0.004ppm to 0.012ppm, ethanol is 0.007% to 0.018%, sulfur dioxide is 0.05% to 0.09%, and the comprehensive yield of ethyl chloride is 95.3% (comprehensive yield of continuous operation for 120 hours).

The results show that when concentrated sulfuric acid is used instead of alkali washing tower washing, the comprehensive yield of high-quality ethyl chloride is basically close, but the purity of ethyl chloride decreases slightly, and sulfur dioxide is detected, which is detrimental to the subsequent synthesis of ethylated products. Influence. Therefore, it is preferable to purify the ethyl chloride mixed gas by alkali washing in the continuous production of ethyl chloride from the tail gas of sucralose production.

It can be seen that the process of this embodiment utilizes the tail gas of sucralose production, and separates the sucralose tail gas system, hydrochloric acid analysis and purification-enrichment system, catalytic synthesis-separation system, water washing-alkali washing-distillation tower purification system, and The molecular sieve-modified zeolite molecular sieve refining system realizes the continuous production of high-quality ethyl chloride.

The above descriptions are only embodiments of the present invention and are not intended to limit the scope of the present invention. Any modifications, equivalent replacements, improvements, expansions, etc. made within the spirit and principles of the present invention are included in the protection scope of the present invention.

Claims

A process for producing ethyl chloride, characterized in that it includes the following steps:

(1) Separate sucralose tail gas to produce concentrated hydrochloric acid: use an organic solvent to absorb trichloroethane in the sucralose tail gas, then dry with concentrated sulfuric acid to remove the moisture in the sucralose tail gas, and then compress, condense, and liquefy Recover the sulfur dioxide in the sucralose tail gas to obtain separated hydrogen chloride gas, and then use dilute hydrochloric acid to absorb the hydrogen chloride gas to produce concentrated hydrochloric acid;

(2) Analysis and concentration of concentrated hydrochloric acid: Hydrogen chloride gas is analyzed from the concentrated hydrochloric acid obtained in step (1). After analysis, the concentrated hydrochloric acid becomes dilute hydrochloric acid, which is sent to step (1). Absorb hydrogen chloride gas to produce concentrated hydrochloric acid, and the cycle repeats;

(3) Synthesis and purification of ethyl chloride: The desorbed hydrogen chloride gas and ethanol are used to prepare a mixed gas containing ethyl chloride, and the mixed gas containing ethyl chloride is purified to obtain the final ethyl chloride product.
The process for producing ethyl chloride according to claim 1, characterized in that the concentrated hydrochloric acid analysis in step (2) adopts a hydrochloric acid analysis and purification system, and the hydrochloric acid analysis and purification system includes a double-effect heat exchanger and a desorption tower. , reboiler, primary condenser, desulfurization tower, secondary condenser and buffer tank. The desulfurization tower contains an organic solvent for desulfurization and purification of hydrogen chloride gas. The organic solvent is white oil with a melting point below 40°C. One or a mixture of two liquid paraffins.
The process for producing ethyl chloride according to claim 2, characterized in that a water separation system is installed at the bottom of the desulfurization tower and the bottom of the buffer tank.
The process for producing ethyl chloride according to claim 2, characterized in that, in the step (3), the synthesis of the ethyl chloride adopts a tower reaction device, and the tower reaction device includes a preheating tower , synthesis reaction tower, gas-liquid separator and condenser, the preheating tower is equipped with a catalyst, so that after the ethanol is preheated and activated by the preheating tower, it reacts with the hydrogen chloride gas coming out of the buffer tank in the synthesis reaction A catalytic reaction is carried out in the tower to synthesize ethyl chloride, and a mixed gas containing ethyl chloride with impurity gases is obtained.
The process for producing ethyl chloride according to claim 4, characterized in that hydrogen chloride gas enters from the upper end of the synthesis reaction tower, and preheated and activated ethanol enters from the lower end of the synthesis reaction tower, and the hydrogen chloride gas and the preheated activation The final ethanol is counter-currently mixed, a catalyst is installed in the synthesis reaction tower and the catalytic reaction is completed in the synthesis reaction tower.
The process for producing ethyl chloride according to claim 5, characterized in that the preheated and activated ethanol vapor is passed into the synthesis reaction tower through a distributor arranged at the bottom of the synthesis reaction tower; the hydrogen chloride gas coming out of the buffer tank is It is introduced into the synthesis reaction tower from the top of the synthesis reaction tower through an air guide pipe and another distributor provided in the synthesis reaction tower.
The process for producing ethyl chloride according to claim 4, characterized in that the mixed gas containing ethyl chloride enters a primary water washing tower, a secondary water washing tower, and an alkali washing tower for washing, and is washed with water and alkali. The washed ethyl chloride enters the rectification tower for rectification to obtain crude ethyl chloride, in which the hydrochloric acid wastewater produced by washing in the first-level water washing tower is returned to the step (2) together with the analyzed dilute hydrochloric acid in the step (2). 1) Absorb hydrogen chloride gas and produce concentrated hydrochloric acid.
The process for producing ethyl chloride according to claim 5, characterized in that, in the synthesis reaction tower, the catalyst is selected from one or both of zinc chloride and aluminum trichloride, and the catalyst concentration accounts for the synthesis reaction The total mass of all materials in the tower is 50% to 80% in terms of mass percentage.
The process for producing ethyl chloride according to claim 1 or 2, characterized in that, in the step (3), the molar ratio of the hydrogen chloride gas and the ethanol is 1/1 to 1.3/1.
The process for producing ethyl chloride according to claim 7, characterized in that when the hydrochloric acid content of the first-level water washing tower is 10% to 15%, the washing water is replaced, and the replaced first-level washing water is analyzed with concentrated hydrochloric acid. The final dilute hydrochloric acid is combined and sent to the step (1) to absorb hydrogen chloride gas to prepare concentrated hydrochloric acid; when the pH value of the solution in the secondary water washing tower is 2 to 4, the washing water is replaced, and the replaced secondary washing water is used for Replacement of washing water in the first-level water washing tower; replacing the alkali solution when the pH value of the solution in the alkali washing tower reaches 7 to 8.