阅读说明：本技术 制备光气的催化剂及其制备方法和光气制备与能源综合利用的方法 (Catalyst for preparing phosgene, preparation method thereof and method for preparing phosgene and comprehensively utilizing energy ) 是由 董超 赵东科 周宇杰 李超群 文放 王文博 张宏科 徐丹 李翀 石杰 于 2019-08-30 设计创作，主要内容包括：本发明提供制备光气的催化剂及其制备方法和光气制备与能源综合利用的方法。所述制备方法,包括如下步骤：1)将活性炭在改性溶液中搅拌浸泡,之后加入二甲基二氯化锡和氧化铬粉末进行反应,再加入氧化镍细粉,并进行超声震荡,制得预改性活性炭；2)将预改性活性炭烘干；3)将步骤2)烘干的预改性活性炭进行加热焙烧,制得所述催化剂。基于该制备方法,催化剂表面形成有磷酸铬锡和硅酸铬锡分别与Ni通过-O-Ni-O-键合而形成的薄层,能提高活性炭的耐高温和抗氧化性能,提高装置安全稳定运行水平；将光气生产与盐水蒸发浓缩工艺相耦合,并将蒸汽作为热源用于盐水蒸发浓缩,实现能源综合利用一体化的目的。(The invention provides a catalyst for preparing phosgene, a preparation method thereof and a method for preparing phosgene and comprehensively utilizing energy. The preparation method comprises the following steps: 1) stirring and soaking the activated carbon in a modified solution, adding dimethyltin dichloride and chromium oxide powder for reaction, adding fine nickel oxide powder, and performing ultrasonic oscillation to prepare pre-modified activated carbon; 2) drying the pre-modified activated carbon; 3) heating and roasting the pre-modified activated carbon dried in the step 2) to prepare the catalyst. Based on the preparation method, a thin layer formed by bonding chromium tin phosphate and chromium tin silicate with Ni through-O-Ni-O-respectively is formed on the surface of the catalyst, so that the high temperature resistance and the oxidation resistance of the activated carbon can be improved, and the safe and stable operation level of the device can be improved; phosgene production is coupled with a brine evaporation and concentration process, and steam is used for brine evaporation and concentration as a heat source, so that the purpose of energy comprehensive utilization integration is realized.)

1. A method for preparing a catalyst for use in the preparation of phosgene, the method comprising the steps of:

1) stirring and soaking activated carbon in a modified solution, adding dimethyltin dichloride and chromium oxide powder into the modified solution for reaction, adding heat-treated nickel oxide fine powder, and performing ultrasonic oscillation to prepare pre-modified activated carbon; the modified solution is a mixed acid solution containing phosphoric acid and silicic acid;

2) drying the pre-modified activated carbon obtained in the step 1);

3) under the protection of inert gas atmosphere, heating and roasting the pre-modified activated carbon dried in the step 2) to obtain the catalyst.

2. The preparation method according to claim 1, wherein in the step 1), the modified solution is obtained by dissolving phosphoric acid in water with stirring to obtain a phosphoric acid solution, then adding silicic acid into the phosphoric acid solution, and stirring uniformly to obtain the modified solution;

preferably, the mass concentration of the phosphoric acid solution is 5% -20%, preferably 7% -18%, more preferably 10% -15%;

preferably, the mass ratio of the amount of the silicic acid to the amount of the phosphoric acid is 1:1-1:5, preferably 1:2-1: 3.5.

3. The method for preparing according to claim 1 or 2, wherein in step 1), the activated carbon is selected from wood activated carbon and/or coconut shell activated carbon, and has a particle size of 2mm to 7mm, preferably 3mm to 5 mm.

4. The preparation method according to any one of claims 1 to 3, wherein in the step 1), the soaking time of the activated carbon in the modification solution is 5h to 20h, preferably 10h to 15 h;

in the step 1), the stirring speed is 20r/min-50r/min, preferably 30r/min-40 r/min;

preferably, in the step 1), the mass ratio of the activated carbon to the modification solution is 1:0.6-1: 2.

5. The production method according to any one of claims 1 to 4, wherein the dimethyltin dichloride in step 1) is added in an amount of 0.2 to 2.0mol/L, preferably 0.3 to 1.5mol/L, more preferably 0.5 to 1.0 mol/L;

the addition amount of the chromium oxide in the step 1) is 0.2-3.0mol/L, preferably 0.5-2.0mol/L, and more preferably 0.8-1.5 mol/L;

the reaction time of adding the dimethyltin dichloride and the chromium oxide powder in the step 1) to carry out the reaction is 1-5h, and preferably 2-3 h.

6. The method according to any one of claims 1 to 5, wherein in step 1), the nickel oxide fine powder is subjected to the heat treatment at a temperature of 400 ℃ and 600 ℃, preferably at a temperature of 450 ℃ and 550 ℃; the time of the heat treatment is 1-4h, preferably 2-3 h;

preferably, in the step 1), the particle size of the nickel oxide fine powder is 0.3-1.5 μm; the addition amount of the nickel oxide fine powder is 0.2-1.5mol/L, preferably 0.6-1.2 mol/L.

7. The method according to any one of claims 1 to 6, wherein in step 1), the ultrasonic oscillation has an ultrasonic pulse frequency of 10 to 30kHz, preferably 12 to 25kHz, more preferably 15 to 20 kHz; the pulse width is 50-500ms, preferably 100-450ms, more preferably 150-300 ms; preferably, the time of the ultrasonic oscillation is 1-5 h.

8. The method according to any one of claims 1-7, wherein in step 2), the temperature for drying is 150 ℃ to 200 ℃, and the drying time is 4h to 8 h;

in the step 3), the heating temperature of the heating roasting is 500-800 ℃, and preferably 600-700 ℃; the heating time is 5h-15h, preferably 8h-12 h.

9. The catalyst for preparing phosgene is characterized in that activated carbon is used as a carrier, and thin layers formed by bonding chromium tin phosphate and chromium tin silicate with Ni through-O-Ni-O-respectively are formed on the surface of the activated carbon;

preferably, the catalyst is prepared by the preparation method of any one of claims 1 to 8.

10. Use of a catalyst prepared by the process according to any one of claims 1 to 8 or a catalyst according to claim 9 for catalyzing the reaction of carbon monoxide and chlorine to produce phosgene; preferably, the total oxygen content in the raw material chlorine gas and the raw material carbon monoxide is controlled to 10-50mg/Nm³More preferably 10 to 20mg/Nm³。

11. A method for preparing phosgene and comprehensively utilizing energy is characterized by comprising the following steps:

mixing chlorine gas and carbon monoxide, introducing the mixture into a phosgene synthesis reactor filled with the catalyst prepared by the preparation method of any one of claims 1-8 or the catalyst of claim 9, and reacting the mixture under the action of the catalyst to synthesize the phosgene; the reaction pressure in the phosgene synthesis reactor is, for example, from 0.1 to 0.5MPag, and the inlet temperature of the phosgene synthesis reactor is, for example, from 10 to 60 ℃;

the phosgene synthesis reactor is provided with a coolant flowing space, and coolant flows through the coolant flowing space and is used for absorbing reaction heat generated by synthesizing phosgene; after absorbing the reaction heat, the coolant in the coolant flowing space is introduced into a steam generator and exchanges heat with water for converting into steam, so that steam is generated; returning the coolant, which has been heat-exchanged with the water for converting into steam, to a coolant circulation space of the phosgene synthesis reactor for continuously absorbing reaction heat generated by synthesizing phosgene;

supplying the steam to a brine evaporative concentration unit for evaporative concentration of brine, the steam serving as a heat source required for the evaporative concentration of brine;

preferably, concentrated brine obtained by evaporation concentration of a brine evaporation concentration unit is sent to a chlor-alkali electrolytic cell to obtain chlorine through electrolysis.

12. The method as claimed in claim 11, wherein the total oxygen content in the raw material chlorine gas and the raw material carbon monoxide is controlled to 10 to 50mg/Nm³Preferably 10-20mg/Nm³。

13. The method according to claim 11 or 12, characterized in that the coolant comprises one or at least two of the heat transfer oils of chlorobenzene, o-dichlorobenzene, carbon tetrachloride, decahydronaphthalene or alkylbenzene type, preferably comprises one or at least two of o-dichlorobenzene, xylene, carbon tetrachloride, decahydronaphthalene, further preferably o-dichlorobenzene and/or decahydronaphthalene, more preferably decahydronaphthalene.

14. The process according to any one of claims 11 to 13, characterized in that the phosgene synthesized in the phosgene synthesis reactor is fed to a phosgene synthesis protector for further reaction of unreacted chlorine and carbon monoxide;

preferably, the free chlorine content in the phosgene output from the outlet of the phosgene synthesis protector is less than 50mg/Nm³；

Preferably, the outlet temperature of the phosgene synthesis protector is controlled below 100 ℃; preferably, the outlet temperature is controlled to be between 50 ℃ and 80 ℃, more preferably between 60 ℃ and 70 ℃.

15. The method according to any one of claims 11-14, wherein the pressure of the steam generated in the steam generator is in the range of 0.2-1.6MPag, preferably 1.0-1.6 MPag;

and/or the brine used for evaporation concentration in the brine evaporation concentration unit is derived from waste brine generated in the production process of diphenylmethane diamine, polyphenyl methane polyamine, diphenylmethane diisocyanate or polyphenyl methane polyisocyanate, preferably the brine has the mass concentration of 5-23% of sodium chloride and the TOC content of 2-15 ppm;

and/or the saline water evaporation concentration unit adopts double-effect or multi-effect evaporation, preferably double-effect or triple-effect evaporation;

and/or the concentration of sodium chloride in the concentrated brine obtained by evaporation and concentration of the brine evaporation and concentration unit is controlled to be 300g/L-310 g/L;

and/or the phosgene synthesis reactor is a tubular reaction tube, a spiral tubular reactor, a fixed bed tubular reactor or a double-tube plate type fixed bed reactor, preferably a fixed bed tubular reactor.

16. A system for phosgene preparation and energy comprehensive utilization is characterized by comprising:

a phosgene preparation unit comprising a phosgene synthesis reactor for contacting chlorine gas and carbon monoxide with the catalyst prepared by the preparation method according to any one of claims 1 to 8 or the catalyst according to claim 9 and synthesizing phosgene under the action of the catalyst; the phosgene synthesis reactor is provided with a coolant circulation space for circulating coolant for absorbing reaction heat generated by the synthesis of phosgene;

a steam generating unit including a steam generator communicating with the coolant flow-through space, for receiving the coolant absorbing the reaction heat and heat-exchanging it with water for converting into steam, thereby generating steam; the coolant flow-through space of the phosgene synthesis reactor is also used for receiving a coolant which is subjected to heat exchange with the water for converting into steam;

the brine evaporation and concentration unit is connected with the steam generation unit to receive the steam generated by the steam generation unit and is used for evaporating and concentrating brine into concentrated brine by taking the steam as a heat source;

preferably, the chlorine-containing gas purification device further comprises an electrolysis unit comprising a chlor-alkali electrolysis cell for receiving the concentrated brine or dry salt resulting from crystallization of the concentrated brine and electrolyzing the concentrated brine or the dry salt to obtain chlorine gas;

preferably, the phosgene preparation unit further comprises a phosgene synthesis protector communicated with a phosgene outlet of the phosgene synthesis reactor and used for receiving phosgene output by the phosgene outlet and further reacting unreacted chlorine and carbon monoxide in the phosgene.

Technical Field

The invention belongs to the field of phosgene synthesis, and particularly relates to a catalyst for preparing phosgene and a technique for comprehensively utilizing synthetic energy of the phosgene.

Background

Phosgene is known as phosgene, apple taste is rotten, pure phosgene is colorless, an industrial product is light yellow or light green, and the chemical property is very active due to the existence of two acyl chlorides. Phosgene is a very important chemical raw material, has wide application in organic synthesis, and is widely applied to synthesis of pesticides, dyes, coatings, initiators, medicines, fine chemicals, isocyanate (R-NCO), diphenylmethane diisocyanate (MDI), Toluene Diisocyanate (TDI), Polyurethane (PU) and the like. With the rapid development of MDI, TDI, PU and special fine phosgene chemical markets in recent years, the demand of phosgene serving as a main raw material is rapidly increased. Therefore, the research on the yield, quality and energy comprehensive utilization of phosgene is particularly important.

The industrial production method of phosgene is mainly characterized by using carbon monoxide and chlorine as raw materials and using active carbon as catalyst to synthesize phosgene, and the commonly used active carbon is coconut shell carbon and coal-based carbon. The phosgene synthesis reaction belongs to a strong exothermic reaction, and the unit chlorine reaction heat is 116 kJ/mol. For such exothermic reactions, it is critical whether the heat of reaction is removed in time. If the reaction heat can not be removed in time, not only can a 'temperature runaway' be caused, but also the adiabatic temperature rise can reach more than 550 ℃, so that the reaction speed is increased, and the ablation and pulverization of the active carbon are serious; if a vicious circle is caused, even the reaction is out of control. In the case of phosgene synthesis reaction, phosgene can be decomposed into carbon monoxide and chlorine again at high temperature, the phosgene decomposition rate can reach more than 80%, excessive chlorine can cause excessive free chlorine at the outlet of a phosgene synthesis reactor, and the quality of phosgene products is seriously influenced. In the phosgenation reaction environment, excess chlorine gas reacts with amines to form chlorine-containing compounds. These chlorine-containing impurity compounds are difficult to remove by conventional methods such as rectification, recrystallization and the like, and the product quality is seriously affected. In addition, the temperature difference between the reactor and the shell is increased, and the equipment is damaged due to different thermal expansion degrees, for example, if steel equipment is adopted, the equipment is also damaged due to the reaction of chlorine and iron caused by high temperature.

At present, a phosgene synthesis reactor is mainly a vertical tubular fixed bed reactor with a tube side filled with an activated carbon catalyst and a shell side filled with a cooling medium, wherein the cooling medium is mainly low-boiling water, an organic solvent or high-boiling hot oil. Chlorine and carbon monoxide are mixed in advance in a mixer and enter the reactor from the bottom, and the cooling medium takes heat away uniformly in a cocurrent or countercurrent mode. Many attempts have been made by those skilled in the art to improve the process of phosgene synthesis to improve its economics and phosgene quality.

EP 1135329B 1 discloses a process for producing phosgene with low carbon tetrachloride content by using a carbon monoxide feedstock having a low methane content to reduce the amount of carbon tetrachloride formed by the reaction of methane and chlorine and to reduce the effect of carbon tetrachloride on the quality of the subsequent product. In fact, the content of methane in the raw material carbon monoxide is extremely low, and the generation amount of carbon tetrachloride is generated in part due to the reaction of chlorine and activated carbon under high temperature conditions.

US4231959 discloses a process for the preparation of phosgene by increasing the excess of carbon monoxide to reduce the residual chlorine content of phosgene and improve product quality. It is also mentioned here that, in addition to water as cooling medium, it is also possible to use boiling water on the shell side of the reactor, in which case usable steam is produced. However, the steam quality is low, the economy is not high, the heat exchange medium is water, equipment corrosion is caused due to gradual high temperature, water leaks into the reaction space to react with phosgene, the corrosion is further aggravated, and the safety risk is high.

CN109289714A discloses a method for filling a catalyst for phosgene synthesis reaction, which reduces the loss of activated carbon by filling ceramic balls with larger particles of 100mm-300mm at the upper and lower positions of an activated carbon bed layer and covering 1-2 layers of screens. However, the reaction rate and the heat release rate cannot be reduced by the traditional filling method, the temperature runaway is avoided, and the situation of activated carbon powder ablation is still serious.

CN1765740A discloses a phosgene manufacturing method and apparatus, chlorine and carbon monoxide are reacted in a shell-and-tube reactor, which has a plurality of reaction tubes and a coolant space surrounding the reactor, and the coolant is evaporated for steam generation. However, only the steam-generating reactor device is introduced, the improvement of the hot spot temperature of the light gas synthesis reactor is not explained, the outlet temperature of the steam-generating reactor is higher, and the service life of the activated carbon catalyst is shorter.

At present, the industry mainly researches and improves the economy and the product quality of phosgene synthesis, and reports on the aspects of prolonging the service life of a phosgene synthesis reactor, reducing the operation cost and comprehensively utilizing energy are less. As for phosgene synthesis, one outstanding problem of the current process is that the activated carbon has poor high temperature resistance and oxidation resistance, the radial temperature difference of a reactor is large, the central hot spot temperature of the catalyst cannot be quickly removed, the activated carbon is ablated and pulverized at high temperature and is mixed with raw material chlorineThe gas and the trace oxygen in the raw material gas react to generate carbon tetrachloride or carbon dioxide, which causes serious loss of the activated carbon; and the raw material gas contains 100-300mg/Nm³Oxygen further accelerates the ablation and pulverization of the activated carbon, shortens the service cycle of the reactor and has poor running stability of the device. In addition, carbon tetrachloride in phosgene cannot be separated efficiently, resulting in poor downstream product quality.

A large amount of waste brine can be generated in the production process of diphenylmethane diisocyanate/polyphenyl methane polyisocyanate, and the waste brine is mostly adopted in the industry to remove organic matters and then is directly discharged to the sea, so that the waste of salt resources is caused.

Disclosure of Invention

In view of the above, the invention provides a preparation method of a catalyst for preparing phosgene, and based on the preparation method, the high temperature resistance and oxidation resistance of activated carbon can be improved, the service life of the catalyst can be prolonged, and the safe and stable operation level of a device can be further improved. The invention also provides a method for phosgene preparation and energy comprehensive utilization, in the phosgene preparation process, the catalyst has longer operation period, so that repeated shutdown and catalyst replacement can be avoided in the phosgene production process, and stable steam can be generated; the phosgene production and the brine evaporation and concentration process are coupled, the reaction heat of the phosgene production is used as a heat source to obtain steam, and the steam is used as the heat source for brine evaporation and concentration, so that the energy waste is solved, the problem of resource waste caused by the discharge of waste brine is avoided, and the purpose of energy comprehensive utilization integration is realized.

In order to achieve the purpose, the invention adopts the following technical scheme:

in one aspect, the present invention provides a method for preparing a catalyst for phosgene, the method comprising the steps of:

1) stirring (for example, uniformly stirring) and soaking activated carbon in a modification solution, then adding (for example, slowly adding) dimethyltin dichloride and chromium oxide powder into the modification solution to react, then adding the heat-treated nickel oxide fine powder, and carrying out ultrasonic oscillation to prepare pre-modified activated carbon; the modified solution is a mixed acid solution containing phosphoric acid and silicic acid;

2) drying the pre-modified activated carbon obtained in the step 1);

3) and (3) under the protection of inert gas (such as nitrogen, argon and other inert gases common in the field), heating and roasting the dried pre-modified activated carbon obtained in the step 2) (such as in a high-temperature furnace) to obtain the catalyst.

The preparation method is adopted to prepare the modified activated carbon catalyst, dimethyltin dichloride and chromium oxide powder are added into a mixed acid solution of phosphoric acid and silicic acid to fully react to prepare chromium tin phosphate and chromium tin silicate, nickel oxide has higher activity after heat treatment and reacts with the chromium tin phosphate and the chromium tin silicate in the solution to form-O-Ni-O-chain bridges, and the chain bridges are transversely and longitudinally bonded and continuously extended to form a space net structure, so that a compact polymerized thin layer is finally formed on the surface of the activated carbon. Therefore, the modified activated carbon catalyst obtained by the preparation method of the invention covers a thin polymerization layer formed by the chromium tin phosphate and the chromium tin silicate under the transverse and longitudinal bonding action of the-O-Ni-O-chain bridge on the surface of the activated carbon, so that the high temperature resistance and the oxidation resistance of the activated carbon are greatly enhanced, and the obtained catalyst has the characteristics of high mechanical strength, difficult pulverization, high temperature resistance and strong oxidation resistance.

In some embodiments, in step 1), the modification solution is obtained by dissolving phosphoric acid in water (e.g., pure water) with stirring to obtain a phosphoric acid solution, and then adding (e.g., slowly adding) silicic acid to the phosphoric acid solution, and stirring to be uniform. The phosphoric acid solution is prepared firstly, and then the silicic acid is added to prepare the modified solution, so that a better mixing effect can be achieved. In some embodiments, the phosphoric acid solution has a mass concentration of 5% to 20% (e.g., 5%, 7%, 10%, 13%, 15%, 18%, 20%), preferably 7% to 18%, more preferably 10% to 15%. In some embodiments, the ratio of the amount of silicic acid to the amount of phosphoric acid is 1:1 to 1:5 (e.g., 1:1, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:5) by mass, preferably 1:2 to 1: 3.5.

In some embodiments, in step 1), the activated carbon is selected from wood activated carbon and/or coconut shell activated carbon, and has a particle size of 2mm to 7mm (e.g., 2mm, 3mm, 4mm, 5mm, 7mm), preferably 3mm to 5 mm.

In some embodiments, in step 1), the mass ratio of activated carbon to modification solution is 1:0.6 to 1:2 (e.g., 1:0.6, 1:0.8, 1:1, 1:1.2, 1:1.5, 1:1.8, 1:2), preferably 1:0.8 to 1: 1.5; the soaking time of the activated carbon in the modified solution is 5h-20h (for example, 5h, 10h, 13h, 15h, 18h and 20h), and preferably 10h-15 h; in some embodiments, in step 1), the stirring rate is from 20r/min to 50r/min, preferably from 30r/min to 40 r/min.

In some embodiments, the dimethyltin dichloride of step 1) is added in an amount of 0.2 to 2.0mol/L (e.g., 0.2mol/L, 0.3mol/L, 0.5mol/L, 0.7mol/L, 1.0mol/L, 1.3mol/L, 1.5mol/L, 2.0mol/L), preferably 0.3 to 1.5mol/L, more preferably 0.5 to 1.0 mol/L; the addition amount of the chromium oxide in the step 1) is 0.2-3.0mol/L (0.2mol/L, 0.3mol/L, 0.5mol/L, 0.8mol/L, 1.0mol/L, 1.3mol/L, 1.5mol/L, 2.0mol/L, 2.5mol/L, 3.0mol/L), preferably 0.5-2.0mol/L, more preferably 0.8-1.5 mol/L; the reaction time of adding dimethyltin dichloride and chromium oxide powder for reaction in the step 1) is 1-5h (1h, 2h, 3h, 4h and 5h), and preferably 2-3 h.

In some embodiments, in step 1), the nickel oxide fine powder is subjected to the heat treatment at a temperature of 400-; the heat treatment time is 1 to 4 hours (e.g., 1 hour, 2 hours, 3 hours, 4 hours), preferably 2 to 3 hours.

In some embodiments, in step 1), the nickel oxide fine powder has a particle size of 0.3 to 1.5 μm (e.g., 0.3 μm, 0.5 μm, 0.6 μm, 0.8 μm, 1.0 μm, 1.2 μm, 1.5 μm), preferably 0.5 to 0.8 μm; the adding amount of the nickel oxide fine powder is 0.2-1.5mol/L (0.2mol/L, 1.5mol/L, 0.4mol/L, 0.6mol/L, 0.8mol/L, 1.0mol/L, 1.2mol/L, 1.5mol/L), and preferably 0.6-1.2 mol/L; the reaction time of adding the nickel oxide fine powder in the step 1) for reaction is 1-5h (1h, 2h, 3h, 4h and 5h), preferably 2-3 h; the ultrasonic oscillation time is consistent with the reaction time of adding the nickel oxide fine powder.

In some embodiments, in step 1), the ultrasonic oscillation has an ultrasonic pulse frequency of 10 to 30kHz (e.g., 10kHz, 12kHz, 15kHz, 17kHz, 20kHz, 30kHz), preferably 12 to 25kHz, more preferably 15 to 20 kHz; the pulse width is 50-500ms (e.g., 50ms, 70ms, 100ms, 150ms, 200ms, 250ms, 300ms, 350ms, 400ms, 450ms, 500ms), preferably 100-; ultrasonic oscillation under the optimized condition is adopted, so that chemical modification can be better cured. As mentioned above, the ultrasonic oscillation time is consistent with the reaction time of adding the nickel oxide fine powder, and is preferably 1-5h (1h, 2h, 3h, 4h, 5 h). In some embodiments, the drying temperature in step 2) is 150-.

In some embodiments, in step 3), the heating temperature of the heating roasting is 500 ℃ to 800 ℃ (e.g., 500 ℃, 550 ℃, 600 ℃, 650 ℃, 700 ℃, 800 ℃), preferably 600 ℃ to 700 ℃; the heating time is 5h to 15h (e.g., 5h, 8h, 10h, 12h, 15h), preferably 8h to 12 h.

The operations (soaking, reaction, ultrasonic oscillation, and other links) related to the step 1) do not need to perform intervention control on the system temperature (for example, no additional intervention such as heating is needed), and only need to operate at an ambient temperature (or referred to as room temperature), for example, the step 1 is performed at an ambient temperature of 10 to 40 ℃ (specifically, for example, in the following examples 1 to 4, the links related to the step 1) are performed at an ambient temperature of 25 to 30 ℃, which will not be described in detail in the following examples 1 to 4).

The surface of the catalyst prepared by the preparation method is covered with a thin polymerization layer formed by bonding chromium tin phosphate, chromium tin silicate and Ni in the transverse direction and the longitudinal direction of an-O-Ni-O-chain bridge, and the cavitation action of ultrasonic waves is combined to promote the chemical modification of the solidified active carbon, so that the high temperature resistance and the oxidation resistance of the active carbon are greatly enhanced, and the obtained catalyst has the characteristics of high mechanical strength, difficult pulverization, high temperature resistance and strong oxidation resistance.

The invention also provides a catalyst for preparing phosgene, which takes active carbon as a carrier, and a thin layer formed by bonding chromium tin phosphate and chromium tin silicate with Ni through-O-Ni-O-respectively is formed on the surface of the active carbon; specifically, the surface of the carrier activated carbon is covered with a polymeric thin layer formed by chromium tin phosphate and chromium tin silicate under the transverse and longitudinal bonding action of an-O-Ni-O-chain bridge. The catalyst can be prepared by the preparation method described above.

The invention also provides an application of the catalyst, wherein the catalyst is used for catalyzing carbon monoxide and chlorine to react to prepare phosgene; preferably, the total oxygen content in the raw material chlorine gas and the raw material carbon monoxide is controlled to 10-50mg/Nm³(e.g., 10 mg/Nm)³、15mg/Nm³、20mg/Nm³、25mg/Nm³、40mg/Nm³、50mg/Nm³) Preferably 10-20mg/Nm³. The chlorine and the trace oxygen in the carbon monoxide can react with the activated carbon at high temperature to generate carbon dioxide, so that the high-temperature heat loss of the activated carbon is caused, the height of a bed layer of the reactor is reduced, the service life is shortened, the reaction heat release is unstable, and the quality of steam and the operation stability of the device are influenced; the present inventors have found that it is preferable to control the total oxygen content in the raw materials chlorine and carbon monoxide to 10 to 50mg/Nm³More preferably 10 to 20mg/Nm³The method can effectively improve the defects, is beneficial to prolonging the service life of the catalyst and obtaining stable reaction heat release, thereby improving the steam quality and the stability of the operation of the device.

When phosgene is prepared, the catalyst obtained by the preparation method is an activated carbon catalyst which is coated with a polymerization thin layer formed by transverse and longitudinal bonding of chromium tin phosphate, chromium tin silicate and Ni through an-O-Ni-O-chain bridge on the surface and is cured by ultrasonic modification, and has improved high temperature resistance and oxidation resistance. In a preferred embodiment, the oxygen content is 10-20mg/Nm³The chlorine and the carbon monoxide are reacted to prepare the phosgene, so that the reaction rate of the catalyst, the raw material chlorine and trace oxygen in the raw material gas can be greatly reduced, the high-temperature ablation or pulverization condition of the activated carbon can be obviously slowed or eliminated, and the service life of the catalyst is prolonged.

The invention also provides a method for phosgene preparation and energy comprehensive utilization, which comprises the following steps:

mixing chlorine and carbon monoxide, feeding the mixture into a phosgene synthesis reactor filled with the catalyst prepared by the preparation method or the catalyst, and reacting under the action of the catalyst to synthesize phosgene; the reaction pressure in the phosgene synthesis reactor may be from 0.1 to 0.5MPag, preferably from 0.2 to 0.4 MPag; the inlet temperature in the phosgene synthesis reactor (the temperature in the reactor after mixing of CO and chlorine) can be controlled to be 10-60 ℃, preferably 20-40 ℃; the total oxygen content in the raw material chlorine and the raw material carbon monoxide is preferably controlled to be 10-50mg/Nm³(e.g., 10 mg/Nm)³、15mg/Nm³、20mg/Nm³、25mg/Nm³、40mg/Nm³、50mg/Nm³) More preferably 10 to 20mg/Nm³；

The phosgene synthesis reactor is provided with a coolant flowing space (such as the shell side of the phosgene synthesis reactor, specifically the space surrounding the tubes in the phosgene synthesis reactor), and coolant flows through the coolant flowing space and is used for absorbing reaction heat generated by synthesizing phosgene; after absorbing the reaction heat, the coolant in the coolant flowing space is introduced into a steam generator and exchanges heat with water for converting into steam, so that steam is generated; returning the coolant, which has been heat-exchanged with the water for converting into steam, to a coolant circulation space of the phosgene synthesis reactor for continuously absorbing reaction heat generated by synthesizing phosgene;

the steam is supplied to a brine evaporative concentration unit for evaporative concentration of brine, and the steam is used as a heat source required for the evaporative concentration of brine.

In some preferred embodiments, the concentrated brine obtained by evaporation concentration in the brine evaporation concentration unit is sent to a chlor-alkali electrolytic cell to obtain chlorine gas by electrolysis.

In the method for preparing phosgene and comprehensively utilizing energy provided by the invention, the catalyst obtained by the method is an active carbon catalyst which is formed by forming a polymerization thin layer on the surface of chromium tin phosphate, chromium tin silicate and Ni under the transverse and longitudinal bonding action of an-O-Ni-O-chain bridge and is modified and solidified by ultrasonic waves, so that the high temperature resistance and the oxidation resistance of the active carbon are improvedPerformance; in a preferred embodiment, the oxygen content is preferably 10-20mg/Nm³The chlorine and the carbon monoxide greatly reduce the reaction rate of the catalyst, the raw material chlorine and trace oxygen in the raw material gas, obviously slow down or eliminate the high-temperature ablation or pulverization of the activated carbon, and prolong the service life of the catalyst. Simultaneously producing high-quality phosgene with low free chlorine and low carbon tetrachloride; the phosgene preparation process is coupled with the steam generating device and the brine evaporation and concentration process, so that the improved phosgene production device is safe and stable in operation level, and byproduct steam can be stabilized while phosgene is produced; the byproduct steam is used as a heat source for evaporating brine (such as waste brine generated in the production process of diphenylmethane diamine/polyphenyl methane polyamine or diphenylmethane diisocyanate/polyphenyl methane polyisocyanate), and the brine can be sent to a chlor-alkali electrolytic cell for electrolysis to produce chlorine after being concentrated, so that the integration of comprehensive utilization of energy is realized.

The coolant can be one or at least two of chlorobenzene, o-dichlorobenzene, carbon tetrachloride, decalin or alkylbenzene type heat transfer oil, preferably comprises one or at least two of o-dichlorobenzene, xylene, carbon tetrachloride and decalin, further preferably is o-dichlorobenzene and/or decalin, and more preferably is decalin.

In some embodiments, the phosgene produced in the phosgene synthesis reactor is fed to a phosgene synthesis protector, which is a device well known to those skilled in the art. The phosgene synthesis protector is filled with the catalyst (namely, the catalyst filled in the phosgene synthesis reactor) in a loose pile, and the reaction pressure in the phosgene synthesis protector can be 0.1-0.5MPag, and preferably 0.2-0.4 MPag; the unreacted chlorine and carbon monoxide are allowed to further react. Preferably, the outlet temperature of the phosgene synthesis protector is controlled below 100 ℃, preferably the outlet temperature is controlled between 50 ℃ and 80 ℃, and more preferably between 60 ℃ and 70 ℃. The outlet temperature of the phosgene synthesis protector is controlled under the preferred temperature condition, so that the phosgene can be effectively prevented from being decomposed into CO and chlorine, and the content of free chlorine in the phosgene output from the outlet of the phosgene synthesis protector is favorably lower than 50mg/Nm³。

In some embodiments, the pressure of the steam generated in the steam generator is in the range of 0.2-1.6MPag (e.g., 0.2MPag, 0.5MPag, 1.0MPag, 1.3MPag, 1.6MPag), preferably 1.0-1.6MPag of high quality steam.

In some embodiments, the brine used for evaporation concentration in the brine evaporation concentration unit is derived from waste brine generated in the production process of diphenylmethane diamine, polyphenyl methane polyamine, diphenylmethane diisocyanate or polyphenyl methane polyisocyanate, and preferably, the brine has the sodium chloride concentration of 5-23% by mass and the TOC (total organic carbon) content of 2-15ppm, so that the operation and economic benefit of the brine evaporation concentration unit can be improved, and the service life of an ionic membrane of an electrolytic unit can be prolonged.

In some embodiments, the brine evaporative concentration unit employs double or multiple effect evaporation, preferably double or triple effect evaporation, well known to those skilled in the art; the concentration of sodium chloride in the concentrated brine obtained by evaporation and concentration of the brine evaporation and concentration unit is controlled to be 300-310 g/L, and the concentrated brine can be directly sent to a chlor-alkali electrolytic cell for electrolysis to produce chlorine.

In some embodiments, the phosgene synthesis reactor is a tubular reactor, a spiral tubular reactor, a fixed bed tubular reactor, a double tube plate fixed bed reactor, preferably a fixed bed tubular reactor widely used in the art. Specifically, in the phosgene synthesis reactor, the catalyst is packed in the tubes, and the coolant flow space is located on the shell side of the phosgene synthesis reactor (the space surrounding the tubes in the phosgene synthesis reactor). The diameter of the phosgene synthesis reactor tube array may be from 25mm to 70mm, preferably from 30mm to 50mm, and the length of the tube array may be from 2500mm to 7000mm, preferably from 3500mm to 6000 mm.

In some embodiments, the carbon monoxide and chlorine are thoroughly mixed in the gas mixture in advance before entering the bottom of the phosgene synthesis reactor. The mixing manner of carbon monoxide and chlorine gas may be line mixing, nozzle mixing, stirring mixing, static mixer mixing, etc., preferably stirring mixing and static mixer mixing, more preferably static mixer mixing. The molar ratio of chlorine to carbon monoxide may be in the range 0.8 to 1.0, preferably 0.85 to 0.98, more preferably 0.90 to 0.95.

The invention also provides a system for phosgene preparation and energy comprehensive utilization, which comprises:

a phosgene preparation unit, which comprises a phosgene synthesis reactor and is used for contacting chlorine and carbon monoxide with the catalyst and synthesizing phosgene under the action of the catalyst; the phosgene synthesis reactor is provided with a coolant circulation space for circulating coolant for absorbing reaction heat generated in the synthetic phosgene reactor;

a steam generating unit including a steam generator communicating with the coolant flow-through space, for receiving the coolant absorbing the reaction heat and heat-exchanging it with water for converting into steam, thereby generating steam; the coolant flow-through space of the phosgene synthesis reactor is also used for receiving coolant which exchanges heat with the water for converting into steam, namely, the coolant circulates between the coolant flow-through space of the phosgene synthesis reactor and the steam generator;

and the brine evaporation and concentration unit is connected with the steam generation unit to receive the steam generated by the steam generation unit and is used for evaporating and concentrating the brine into concentrated brine by taking the steam as a heat source.

In some preferred embodiments, further comprising an electrolysis unit comprising a chlor-alkali electrolysis cell for receiving said concentrated brine or a dry salt resulting from crystallization of said concentrated brine and electrolyzing said concentrated brine or said dry salt to obtain chlorine gas; in some embodiments, the concentrated brine is crystallized to form dry salt, and then enters a chlor-alkali electrolytic cell for electrolysis.

In some embodiments, the phosgene preparation unit further comprises a phosgene synthesis protector in communication with the phosgene outlet of the phosgene synthesis reactor for receiving phosgene output from the phosgene outlet and further reacting unreacted chlorine and carbon monoxide therein.

In some embodiments, the phosgene preparation unit further comprises a mixer in communication with the phosgene synthesis reactor for mixing chlorine gas and carbon monoxide to obtain a mixed gas to be supplied to the phosgene synthesis reactor.

In some embodiments, the steam generation unit further comprises a gas bag and a boiler water conveying pipe, wherein a steam inlet of the gas bag is communicated with a steam outlet of the steam generator, a condensed water outlet of the gas bag is communicated with a water inlet of the steam generator, and the water inlet of the steam generator is also communicated with the boiler water conveying pipe; the condensed water and the boiler water enter the steam generator as water for converting into steam to exchange heat with the coolant from the phosgene synthesis reactor. Specifically, the steam outlet of the air bag is connected with the brine evaporation and concentration unit, so that steam is supplied to the brine evaporation and concentration unit to provide a heat source.

The phosgene production and energy-integrated system mentioned here is particularly suitable for carrying out the phosgene production and energy-integrated method described above. The preferred features mentioned above in the method for phosgene production and energy integration are also applicable to the system for phosgene production and energy integration herein, and will not be described in detail herein.

The technical scheme provided by the invention has the following beneficial effects:

the preparation method of the invention can improve the high temperature resistance and oxidation resistance of the active carbon, and the prepared catalyst has the characteristics of high mechanical strength, good heat conductivity, difficult pulverization, high temperature resistance and strong oxidation resistance.

The novel modified activated carbon catalyst provided by the invention has strong oxidation resistance, greatly reduces the reaction rate of activated carbon, chlorine and trace oxygen in raw material gas at high temperature, and is favorable for reducing the content of carbon tetrachloride (for example, less than 50 mg/Nm) in phosgene at the outlet of a phosgene synthesis protector³) And the quality of phosgene products is improved. When the method is applied to phosgene production, the oxygen content of the raw materials chlorine and carbon monoxide is preferably controlled to 10-20mg/Nm³The reaction rate of the catalyst, raw material chlorine and trace oxygen in the raw material gas can be greatly reduced, the high-temperature ablation or pulverization condition of the activated carbon is obviously slowed or eliminated, the service life of the catalyst is prolonged, and the safe and stable operation level of the device is improved; production of low free chlorine and low tetrachloroHigh quality phosgene of carbon.

The invention couples the phosgene production process based on the catalyst with the steam evaporation and brine evaporation concentration process, and can realize long-period operation due to the excellent characteristics of the catalyst, so that the reaction heat generated in the phosgene production can be utilized to stabilize byproduct steam, the steam can be further used as a heat source to be supplied to the brine evaporation concentration process, waste brine is evaporated and concentrated, and the obtained concentrated brine can be crystallized into dry salt or directly used for producing chlorine through electrolysis; therefore, the invention can recycle the reaction heat of phosgene synthesis, solve the problems of energy waste and waste brine discharge resource waste, and realize the purpose of energy comprehensive utilization integration.

Drawings

FIG. 1 is a process flow diagram of phosgene preparation and energy integration in one embodiment,

FIG. 2: thermogravimetric characterization results (air atmosphere) of example 5;

FIGS. 3-4: SEM characterization results for the modified activated carbon and unmodified coconut shell activated carbon of example 3, respectively;

FIG. 5: XRD patterns for unmodified coconut shell activated carbon and the modified activated carbon of example 3.

In fig. 1, 1: a chlorine feed line; 2: a carbon monoxide feed line; 3: a mixer; 4: a phosgene synthesis reactor; 5: a steam generator; 6: air bags; 7: a phosgene synthesis protector; 8: a coolant input line; 9: a boiler water delivery pipe; 10: a phosgene output line; 11: a first-stage brine evaporator; 12: a primary brine flash evaporator; 13: a primary brine pump; 14: a spent brine input line; 15: a secondary brine evaporator; 16: a secondary brine flash evaporator; 17: a secondary brine pump; 18: a third-stage brine evaporator; 19: a tertiary brine flash evaporator; 20: a tertiary brine pump; 21: a condenser; 22: a vacuum pump inlet gas line; 23: a crystallizer; 24: a dry salt output line; 25-29: a pipeline; 30: a coolant flow-through space; 31: and (4) arranging pipes.

Detailed Description

In order to better understand the technical solution of the present invention, the following examples are further provided to illustrate the present invention, but the present invention is not limited to the following examples. The test methods used in the following examples are conventional methods known to those skilled in the art unless otherwise specified; the equipment and reagents involved are conventional in the art, unless otherwise specified.