CN215783355U - Device for continuously producing hydroxyl acetonitrile by using liquid-phase hydrocyanic acid - Google Patents

Abstract

The utility model discloses a device for continuously producing hydroxyl acetonitrile by liquid-phase hydrocyanic acid, which comprises a plurality of reactors connected in series in sequence, wherein a formaldehyde feeding pipe, a hydrocyanic acid feeding pipe and a catalyst feeding pipe which are used for continuous feeding are connected to the first reactor; the adjacent two stages of reactors are sequentially communicated in series through discharge pipes; a mixing mechanism is arranged in any stage of reactor; the reactor also comprises a neutralization tank and a storage tank which are communicated with the last-stage reactor in sequence; the neutralization tank is used for receiving a reaction liquid flowing out of the first final reactor; the storage tank is used for receiving the finished hydroxy acetonitrile product discharged from the neutralization tank; wherein, a heat exchange mechanism is connected on any stage of reactor and the storage tank. The device simple structure, operate steadily, be fit for industrial production and can guarantee the stability of product quality and yield.

Description

Device for continuously producing hydroxyl acetonitrile by using liquid-phase hydrocyanic acid

Technical Field

The utility model belongs to the technical field of chemical production, and relates to a device for continuously producing hydroxyacetonitrile by using liquid-phase hydrocyanic acid.

Background

Hydroxyacetonitrile (2-Hydroxyacetonitrile), which is soluble in water, is unstable to heat and alkali, is easy to polymerize, is easily decomposed into formaldehyde and hydrocyanic acid to initiate the polymerization of hydrocyanic acid, and has a darker color after polymerization, releases heat and further promotes the polymerization. Hydroxyacetonitrile is hydrolyzable to glycolic acid under acidic conditions; mixing with ammonia to spontaneously generate aminoacetonitrile, wherein the aminoacetonitrile can be condensed to prepare serine, and alkaline hydrolysis or hydrolysis is carried out to obtain glycine; reacting hydroxy acetonitrile with ammonia at high temperature to generate iminodiacetonitrile; reacting with aniline to obtain anilinoacetonitrile for producing indigo; synthesizing various compounds such as herbicides such as chloromethyl by esterification reaction; the hydroxy acetonitrile is also a main raw material of various chelating agents and is a good flotation agent.

The preparation method of the hydroxyacetonitrile mainly comprises an acetonitrile oxidation method and a hydrocyanic acid hydroxymethylation method, and the hydrocyanic acid hydroxymethylation method is mainly used in industrial production. The principle of the hydrocyanic acid hydroxymethylation method is as follows: under the condition of proper acid and alkali, formaldehyde and hydrocyanic acid are subjected to normal pressure addition reaction to generate hydroxyacetonitrile, a large amount of heat is released by the reaction, and the reaction equation is as follows:

HCN+HCHO→HOCH₂CN-Q

although the reaction principle is simple, hydrocyanic acid and hydroxyacetonitrile are very active in chemical properties and are easy to polymerize under alkaline conditions, normal temperature or long retention time. In addition, because hydrocyanic acid is extremely toxic, excessive industrial formaldehyde solution is generally adopted to react with hydrocyanic acid, more formaldehyde is remained in a hydroxyacetonitrile product, the remained formaldehyde is not effectively removed, further downstream production of the hydroxyacetonitrile (such as aminoacetonitrile and glycine) is influenced, side reactions and impurities are generated, and formaldehyde can also generate some colored impurities, so that the color of downstream products is darkened, and the product quality is influenced.

The methylolation of hydrocyanic acid may be divided into a gas phase method and a liquid phase method according to the phase state of the starting material hydrocyanic acid, the hydrocyanic acid in the gas phase method being in a gaseous state and the hydrocyanic acid in the liquid phase method being in a liquid state. In China, low-concentration gas-phase hydrocyanic acid is mostly used as a raw material to react with formaldehyde to produce the hydroxyacetonitrile, the gas-phase hydrocyanic acid is mostly prepared by using natural gas as a raw material to perform ammoxidation or light oil cracking ammoxidation, the hydrocyanic acid concentration is low, and a hydroxyacetonitrile product is obtained by absorbing formaldehyde solution, for example, Chinese patent document CN201410460442.4 discloses a method for industrially and continuously producing the hydroxyacetonitrile by using the gas-phase hydrocyanic acid, and Chinese patent document CN201610000966.4 discloses a method for preparing the hydroxyacetonitrile by using cyanogen-containing tail gas-phase hydrocyanic acid. Because the concentration of the gas-phase hydrocyanic acid is low, although the reaction is easy to control, the energy consumption is high, and the impurity content in the product is high.

The method for synthesizing the hydroxyacetonitrile by using the liquid-phase hydrocyanic acid is mainly a batch method, and the report of the industrial continuous production of the hydroxyacetonitrile by using the liquid-phase hydrocyanic acid is not found.

Chinese patent document CN201710313478.3 discloses an industrial preparation method of hydroxyacetonitrile, which adopts liquid hydrocyanic acid and formaldehyde to produce the hydroxyacetonitrile, the temperature of the formaldehyde is reduced to 20 ℃, then the hydrocyanic acid is dripped, the PH value of a dripper is controlled to be 6.5-7.5, the temperature is controlled and stirred for about 30min after the dripping is finished, the reaction is terminated by adding acid after the sampling analysis is qualified, and the hydroxyacetonitrile finished solution is transferred into a storage tank, wherein the formaldehyde content is not more than 0.2%, and the free hydrocyanic acid content is not more than 0.25%. The method is intermittent production, is not suitable for large-scale industrial continuous production, and has high formaldehyde content in the finished product and limited application of the hydroxyl acetonitrile product.

Chinese patent document CN200610048135.0 discloses a method for preparing hydroxyacetonitrile by using acrylonitrile byproduct liquid hydrocyanic acid, which comprises the following steps of firstly adding a formaldehyde solution into a reactor, then adding a catalyst, cooling to 0-20 ℃, and starting to drip hydrocyanic acid: and (3) formaldehyde is 1: 1-1.5, then the addition reaction is carried out at 0-40 ℃ to generate hydroxyl acetonitrile, and after the reaction is finished, inorganic acid is used for adjusting the pH value to 2-5 to obtain a finished product. The method still belongs to a batch method, has a certain difference with large-scale industrial continuous production, does not determine the pH value of addition reaction, and has polymerization risk in industrial production.

As mentioned above, liquid phase hydrocyanic acid batch process production hydroxyacetonitrile, hydrocyanic acid feeding mainly adopt the dropwise add mode, and hydrocyanic acid is effectual with the material mixing, and it is few to release heat, and is even controllable, and reaction pH value is than higher, generally reaches 6.5 ~ 9. At present, the industrial production of the hydroxyl acetonitrile by the liquid phase hydrocyanic acid generally adopts a batch method, and the batch method mainly has the following characteristics: 1) the dripping feeding amount is small, the industrial production scale is small, and the labor intensity is high; 2) batch production, unstable quality; 3) the feeding materials are generally prepared by excessive formaldehyde, the content of residual formaldehyde in the hydroxyacetonitrile product is high, the residual formaldehyde is not effectively removed, the downstream production of the hydroxyacetonitrile (such as aminoacetonitrile and glycine) is influenced, side reactions and impurities are generated, formaldehyde can generate some colored impurities, the color of the downstream product is darkened, the product quality is influenced, and the application range of the hydroxyacetonitrile is limited.

In the continuous production of the hydroxyacetonitrile by the liquid-phase hydrocyanic acid, continuous feeding enables the reaction to be quicker, byproducts are more easily produced, the danger is enhanced, and the like, so that a great deal of difficulty exists in the continuous production of the hydroxyacetonitrile liquid-phase method, which is also the reason that the prior continuous production process of the hydroxyacetonitrile liquid-phase method which is suitable for industrialization does not exist.

Based on this, it is very necessary for those skilled in the art to provide a device for continuously producing hydroxyacetonitrile from liquid-phase hydrocyanic acid, which has a simple structure, is suitable for industrial production, and ensures product quality and yield.

Disclosure of Invention

Aiming at the defects in the prior art, the utility model provides the device for continuously producing the hydroxyacetonitrile by using the liquid-phase hydrocyanic acid, which has the advantages of simple structure, stable operation, suitability for industrial production and capability of ensuring the product quality and the yield stability.

The technical scheme provided by the utility model is as follows:

a device for continuously producing hydroxyl acetonitrile by liquid-phase hydrocyanic acid comprises a plurality of reactors which are sequentially connected in series, wherein a formaldehyde feeding pipe, a hydrocyanic acid feeding pipe and a catalyst feeding pipe which are used for continuous feeding are connected to the first reactor; the adjacent two stages of reactors are sequentially communicated in series through discharge pipes; a mixing mechanism is arranged in any stage of reactor;

the reactor also comprises a neutralization tank and a storage tank which are communicated with the last-stage reactor in sequence; the neutralization tank is used for receiving a reaction liquid flowing out of the first final reactor; the storage tank is used for receiving the finished hydroxy acetonitrile product discharged from the neutralization tank;

wherein, a heat exchange mechanism is connected on any stage of reactor and the storage tank.

Preferably, the heat exchange mechanism comprises an external circulation cooling loop which is connected with the primary reactor and is provided with a circulation pump and a circulation cooler, and the material at the outlet of the circulation cooler returns to the primary reactor through the external circulation cooling loop;

the heat exchange mechanism comprises other reactors connected with the first-stage reactor in series and a heat exchange coil in the neutralization tank, and a cooling medium circulates in the heat exchange coil.

Further, the heat exchange mechanism also comprises a heat exchange jacket connected to any stage of reactor, and a cooling medium is circulated in the heat exchange jacket.

Furthermore, the device also comprises a volatile gas condenser, wherein the volatile gas of the circulating cooler, the reactor, the neutralization tank and the storage tank is collected to the volatile gas condenser, and an outlet of the volatile gas condenser is connected to the first-stage reactor, so that the volatile gas is condensed and then returns to the first-stage reactor for recycling.

Furthermore, thermometers for monitoring the reaction temperature are respectively arranged on any stage of reactor, and a thermometer for monitoring the temperature of the reaction materials returned to each reactor is arranged at the outlet of the circulating cooler; wherein: the outlet temperature of the circulating cooler is controlled to be-5-10 ℃, the circulation ratio of the material flow returned to the first-stage reactor from the outlet of the circulating cooler to the material flow overflowing to the next-stage reactor is controlled to be 5-20, and the temperature in the reactor is controlled to be 10-25 ℃.

Further, a pH meter for monitoring the pH value of the reaction is arranged on the primary reactor; the catalyst feeding pipe is provided with a catalyst feeding valve, an outlet of the catalyst feeding pipe is connected to the first-stage reactor, and the PH value in the reactor is controlled to be 3-5.5 by adjusting the catalyst feeding valve.

Furthermore, the device also comprises a control system, and the thermometer, the PH meter and the catalyst feed valve are all electrically connected with the control system.

Preferably, the mixing mechanism comprises a stirrer arranged in each stage of reactor, and the stirrer is provided with at least 2 layers of stirring paddles.

Preferably, the neutralization tank is provided with at least 2 stages connected in parallel at the downstream of the last-stage reactor, and an online hydrocyanic acid analyzer, a formaldehyde analyzer, a mineral acid feeding pipe, a thermometer and a PH meter are connected to any one of the neutralization tanks.

Preferably, a first hydrogen cyanide distributor and a second hydrogen cyanide distributor are respectively arranged in the first-stage reactor; the first hydrogen cyanide distributor and the second hydrogen cyanide distributor are oppositely arranged at the upper side and the lower side of the mixing mechanism.

Further, the first hydrocyanic acid distributor comprises a first ring pipe, wherein the bottom of the first ring pipe is an open hole area along the radial cross section of the first ring pipe in the range of a fan-shaped included angle theta 1;

the second hydrogen cyanide distributor comprises a second ring pipe, and the lateral side of the outer side of the second ring pipe is an open hole area with a sector included angle theta 2 angle range along the radial section of the second ring pipe.

According to the device provided above, a process for continuously producing hydroxyacetonitrile by using liquid-phase hydrocyanic acid can also be provided, which comprises the following steps:

s1, formaldehyde solution, hydrocyanic acid and catalyst solution are respectively and continuously added into a first-stage reactor, wherein hydrocyanic acid is fed in a multi-layer manner, is rapidly mixed and reacts in the first-stage reactor, and simultaneously releases reaction heat, reaction liquid of the first-stage reactor overflows to a next-stage reactor through an overflow port at the upper part to continue reacting, and reaction liquid after the reaction in a last-stage reactor overflows to a neutralization tank through an overflow port at the upper part; wherein the reaction temperature of the reaction liquid in each reactor is controlled within the range of 10-25 ℃ by a heat exchange system; adding a catalyst solution into the first-stage reactor through a catalyst feeding pipe in the reaction process to adjust the pH value of the first-stage reactor to 3-5.5;

s2, analyzing residual amounts of hydrocyanic acid and formaldehyde in an overflow reaction liquid of the last-stage reactor in a neutralization tank, adding inorganic acid and controlling the pH value to be 1-2.5 by a pH meter if the residual amounts are qualified, and feeding the qualified acidified hydroxy acetonitrile finished product into a storage tank; if the residual value does not meet the requirement, adding a proper amount of formaldehyde or hydrocyanic acid to continuously react to reach the standard, and adding inorganic acid to transfer to a storage tank.

Preferably, in step S1: controlling the reaction temperature in each stage of reactor to be 17-23 ℃.

Preferably, in step S1: the pH value in the primary reactor is adjusted to 4-5.2.

Preferably, in step S1: controlling the molar ratio of hydrocyanic acid to formaldehyde in the reaction material to be 1-1.15: 1.

Compared with the technology for synthesizing the hydroxyl acetonitrile by using a gas phase hydrocyanic acid method, the liquid phase hydrocyanic acid method takes liquid hydrocyanic acid (with the purity of 99.5%) and formaldehyde solution (10-50% wt) as raw materials, the hydrocyanic acid raw material has high purity, the difficulty in removing reaction heat is large, the required precision of reaction control is high, but the liquid phase continuous production can be realized, and the beneficial effects of higher product purity can be obtained, more specifically, the following steps are as follows:

1) the utility model adopts a multistage reactor to form a series overflow fully-mixed reaction system, realizes the production of the hydroxyacetonitrile by a liquid phase hydrocyanic acid hydroxymethylation continuous method, greatly improves the production scale and can ensure the stable product quality. The formaldehyde solution, the hydrocyanic acid and the catalyst solution are respectively and independently and continuously added into a first-stage reactor, the formaldehyde solution, the hydrocyanic acid and the catalyst solution are quickly mixed under the action of a mixing mechanism in the first-stage reactor and finish a main reaction, and the mixture enters a next-stage reactor along with a discharge pipe, so that the unreacted hydrocyanic acid and formaldehyde are further contacted and reacted to generate the hydroxyacetonitrile; and moreover, after the heat is fully transferred by the heat exchange mechanism in the reaction process, the mass transfer and the heat transfer of the reaction system can be further enhanced, the polymerization risk is low, the industrial continuous production of the hydroxyacetonitrile is reliably realized, the production scale is greatly improved, and the product quality is stable.

2) In the first-stage reactor, a stirrer adopts a plurality of layers of stirring paddles, a hydrocyanic acid feeding pipe is designed with a plurality of layers of different-point feeding, so that hydrocyanic acid feeding can be quickly taken away by the stirrer to be mixed and diluted with materials in the reactor, and the circulation ratio is 15-30 by arranging an external circulation loop with a large circulation ratio, so that mixing is enhanced, the mixing effect is improved, the unevenness in the reactor is reduced, local over-concentration and over-temperature are avoided, side reactions are reduced, and the yield is improved; meanwhile, the probability of temperature runaway is reduced by combining the arrangement of the heat exchange jacket.

3) The utility model can realize closed clean production by uniformly collecting the gas phase at the top of the reactor, the neutralization tank and the storage tank and recycling the gas phase after condensation.

4) The utility model avoids polymerization accidents caused by over-temperature and over-high PH value by controlling the reaction conditions, and has stable and reliable industrial production and stable product quality.

In conclusion, by applying appropriate process conditions through the device, the stable quality and the low impurity content of the hydroxyl acetonitrile product produced continuously in the liquid phase can be ensured; and the device is arranged, so that the safety of the process is improved, and the method is suitable for industrial large-scale production.

Drawings

FIG. 1 is a schematic structural diagram of a device for continuously producing hydroxyacetonitrile from liquid-phase hydrocyanic acid.

FIG. 2 is a schematic structural diagram of a first hydrocyanic acid distributor adopted in a device for continuously producing hydroxyacetonitrile from liquid-phase hydrocyanic acid.

Fig. 3 is a cross-sectional view of section a-a in fig. 2.

FIG. 4 is a schematic structural diagram of a second hydrocyanic acid distributor used in a device for continuously producing hydroxyacetonitrile from liquid-phase hydrocyanic acid according to the present invention.

Fig. 5 is a cross-sectional view of section a-a in fig. 4.

The notations in the figures have the following meanings:

1-reactor, 10-first-stage reactor, 100-formaldehyde feed pipe; 101-hydrocyanic acid feed pipe; 102-catalyst feed pipe, 1020-catalyst feed valve, 103-first hydrogen cyanide distributor, 104-second hydrogen cyanide distributor, S1/S2-open area, 1040-discharge hole; 11-a second-stage reactor, 12-a third-stage reactor; 2-mixing mechanism, 20-stirrer; 3-a neutralization tank, 30-an inorganic acid feeding pipe, 31-an online hydrocyanic acid analyzer, 32-an online formaldehyde analyzer, 33-a neutralization circulating cooling loop, 330-a neutralization circulating pump and 331-a neutralization circulating cooler; 4-storage tank, 40-cooling coil; 5-heat exchange mechanism, 50-external circulation cooling loop, 51-circulating pump, 52-circulation cooler, 53-heat exchange coil and 54-heat exchange jacket; 60/61/62-thermometer; 70/71-PH meter; 8-a volatile gas condenser; 9-control system.

Detailed Description

The technical solution of the present invention will be clearly and completely described below with reference to the specific embodiments. The following examples are only for illustrating the technical solutions of the present invention more clearly, and the protection scope of the present invention is not limited thereby.

Further, in the description of the present application, "multi-stage, multi-layer" means at least two stages/layers, e.g., two stages/layers, three stages/layers, etc., unless specifically limited otherwise.

According to an embodiment of the present invention, shown in fig. 1, a device for continuously producing hydroxyacetonitrile with liquid phase hydrocyanic acid comprises a multistage reactor 1 connected in series in sequence, wherein a formaldehyde feeding pipe 100, a hydrocyanic acid feeding pipe 101, and a catalyst feeding pipe 102 are connected to the first stage reactor 10 for continuous feeding; the adjacent two-stage reactors 1 are sequentially communicated in series through discharge pipes; a mixing mechanism 2 is arranged in any stage of reactor 1;

the reactor also comprises a neutralization tank 3 and a storage tank 4 which are communicated with the last-stage reactor in sequence; the neutralization tank 3 is used for receiving a reaction liquid flowing out of the last-stage reactor I; the storage tank 4 is used for receiving the hydroxy acetonitrile finished product discharged from the neutralization tank 3;

wherein, the reactor 1 of any stage, the neutralization tank 3 and the storage tank 4 are connected with a heat exchange mechanism 5.

According to the device structure of the embodiment, the multistage series full-mixing reaction structure is adopted in the utility model to realize multistage series overflow reaction, specifically, formaldehyde solution, hydrocyanic acid and catalyst solution are respectively and independently continuously added into a first-stage reactor 10, and are rapidly mixed and reacted under the action of a mixing mechanism 2 to release a large amount of heat, and the heat is fully transferred by a heat exchange mechanism 5 and then enters a next-stage reactor along with a discharge pipe, so that unreacted hydrocyanic acid and formaldehyde are further subjected to contact reaction to generate hydroxyacetonitrile, and finally, the industrial production of the hydroxyacetonitrile by a liquid-phase hydrocyanic acid hydroxymethylation continuous method is realized, the production scale is greatly improved, and the product quality is stable.

As a preferred embodiment, the heat exchange mechanism 5 comprises an external circulation cooling loop 50 which is connected with the primary reactor 10 and is provided with a circulating pump 51 and a circulation cooler 52, and the material at the outlet of the circulation cooler 52 is returned to the primary reactor 10 through the external circulation cooling loop 50. In actual use, chilled brine may be used as the cooling medium in the external circulation cooling loop 50. The function of the external circulation cooling loop 50 is to enhance mixing and remove the heat of reaction.

The heat exchange mechanism 5 further comprises heat exchange coils 53 arranged in the other reactors connected in series with the first-stage reactor 10, the neutralization tank 3 and the storage tank 4, and cooling media circulate in the heat exchange coils 53.

In order to further improve the heat transfer effect and improve the equilibrium of the reaction inside the reactor, the heat exchange mechanism 5 further comprises a heat exchange jacket 54 connected to any stage of reactor 1, and a cooling medium is circulated in the heat exchange jacket 54. In practical use, the cooling medium is frozen saline.

In the above embodiment, the mixing mechanism 2 comprises the stirrer 20 arranged in each stage of the reactor, and the stirrer 20 is provided with at least 2 layers of stirring paddles, preferably a propeller type or a paddle type. Preferably, the stirrers 20 are arranged in each stage of the reactor 1 at intervals of 0.8 to 1.2D (D is the diameter of the reactor).

A first hydrogen cyanide distributor 103 and a second hydrogen cyanide distributor 104 (not shown in fig. 1) are respectively arranged in the first-stage reactor 10, and the first hydrogen cyanide distributor 103 and the second hydrogen cyanide distributor 104 are respectively arranged in the first-stage reactor; the first hydrogen cyanide distributor 103 and the second hydrogen cyanide distributor 104 are disposed opposite to each other on the upper and lower sides of the mixing mechanism 2. It should be noted that, when the stirrer 20 of the mixing mechanism 2 is provided with at least 2 layers of stirring paddles, the upper side of the mixing mechanism 2 refers to the upper side of the stirring paddles except for the bottommost stirring paddle; the lower side of the mixing mechanism 2 is below the lowermost paddle.

More specifically, the first hydrocyanic acid distributor 103 includes a first loop pipe, the diameter of the first loop pipe is about 1.2-1.5D (diameter of the stirring paddle), the first loop pipe is arranged above the stirring paddle (except for the bottommost layer) of the mixing mechanism 2 by about 0.1-0.5D (diameter of the stirring paddle), the bottom of the first loop pipe is an open area S1 with a sector included angle θ 1 along a radial cross section of the first loop pipe, as shown in fig. 2 and 3, and holes are arranged in a regular triangle on the open area S1. Based on this, hydrocyanic acid passing through the first hydrocyanic acid distributor 103 is sprayed downward, is rapidly taken into the agitator and mixed. In practical application, in order to obtain a more excellent uniform reaction effect, the included angle theta 1 is 90-150 ℃, the aperture diameter phi of the opening is 4-10 mm, the hole spacing is 1-5 times of the aperture diameter, and the bottom of the first ring pipe is uniformly distributed with the openings in the area of the radial cross section within the range of the fan-shaped included angle theta 1.

The second hydrogen cyanide distributor 104 comprises a second ring pipe, the diameter of the second ring pipe is about 1.2-1.5D (diameter of the stirring paddle), the second ring pipe is arranged below the stirring paddle at the bottommost layer by about 0-0.5D (diameter of the stirring paddle), the outer side of the second ring pipe is an opening area S2 along the radial cross section of the second ring pipe with an included angle theta 2 of a fan shape, holes are only arranged on the outer side, and drain holes 1040 are arranged at intervals of 20 degrees at the lowest point of the second ring pipe to prevent hydrogen cyanide from accumulating, as shown in fig. 4 and 5 in detail, the holes are arranged in a regular triangle on the opening area S2. Based on this, hydrocyanic acid which passes through the bottom-layer second hydrogen cyanide distributor 104 is mainly sprayed horizontally from the side through the lateral openings of the second loop, and rapidly mixed with the high-speed horizontal flow below the bottom-layer stirrer. In practical application, in order to obtain a more excellent uniform reaction effect, the included angle theta 2 is 0-30 degrees, the aperture diameter phi of the opening is 4-10 mm, the hole distance is 1-5 times of the aperture diameter, and the bottom of the second ring pipe is uniformly distributed with the openings in the area of the fan-shaped included angle theta 2 along the radial section.

The first hydrogen cyanide distributor 103 and the second hydrogen cyanide distributor 104 may be respectively provided with a plurality of layers as required.

As a preferred embodiment, thermometers 60 for monitoring the reaction temperature are respectively provided on any one of the reactors 1. And, the outlet of the circulation cooler 52 is provided with a thermometer 61 for monitoring the temperature of the reaction material returned to the primary reactor 10; wherein: the outlet temperature of the circulating cooler is controlled to be-5-10 ℃, the circulation ratio of the material flow returned to the first-stage reactor 10 from the outlet of the circulating cooler 52 to the material flow overflowing to the next-stage reactor is controlled to be 5-20, if the circulation ratio is too low, the mixing effect and the cooling effect are poor, the circulation ratio is too high, energy is wasted, and the circulation ratio is 5-20 preferably 10-15; the circulating pump 51 is a centrifugal pump, and the circulating cooler 52 is a shell-and-tube heat exchanger. Therefore, the temperature in the reactor is controlled to be 10-25 ℃, and the preferable temperature is 17-23 ℃, so that hydrocyanic acid and formaldehyde solution are fully and uniformly reacted, the conversion rate is improved, and the risk of temperature runaway polymerization is reduced.

The primary reactor 10 is provided with a PH meter 70 for monitoring the PH value of the reaction; the catalyst feeding pipe 102 is provided with a catalyst feeding valve 1020, an outlet of the catalyst feeding pipe 102 is connected to the primary reactor 10, and the pH value in the primary reactor is controlled to be 3-5.5 by adjusting the catalyst feeding valve 1020. More preferably 4 to 5.2. The catalyst may be sodium sulfite or its acid salt or hydrogen salt solution. By controlling the pH value of the reaction to be appropriate, the materials can be well mixed, the reaction heat release rate is reduced on the whole, and the stability of the reaction and the product quality are ensured after the temperature is controlled.

The device also comprises a volatile gas condenser 8, the volatile gas of the circulating cooler 51, the reactor 1, the neutralization tank 3 and the storage tank 4 is collected to the volatile gas condenser 8, and the outlet of the volatile gas condenser 8 is connected to the first-stage reactor 10, so that the volatile gas is condensed and then returns to the first-stage reactor 10 for recycling.

The temperature gauge 60/61, the pH gauge 7, and the catalyst feed control valve 1020 of the above-described embodiment are all connected to the control system 9. The control system 9 may adopt a PLC or DCS control system.

The neutralization tank 3 is provided with at least 2 stages connected in parallel at the downstream of the last stage reactor (for example, a three-stage reactor 12 in fig. 1), and an on-line hydrocyanic acid analyzer 31, an on-line formaldehyde analyzer 32, an inorganic acid feeding pipe 30, a thermometer 62 and a PH meter 71 are connected to any neutralization tank 3. And the on-line hydrocyanic acid analyzer 31, the on-line formaldehyde analyzer 32, the inorganic acid feeding pipe 30, the thermometer 62 and the pH meter 71 are all commercially available instruments and are electrically connected to the control system 8, so that the automatic treatment efficiency of the whole device is improved. Wherein, the number of the neutralization tanks is at least 2, when the liquid level of one reaction liquid reaches the set liquid level, the other neutralization tank 3 is switched to continue to receive the overflow reaction liquid from the last-stage reactor, and the treatment efficiency is improved.

Further, a neutralization circulation cooling circuit 33 having a neutralization circulation pump 330 and a neutralization circulation cooler 331 is provided in the neutralization tank 3 for controlling the temperature in the neutralization tank 3 to prevent polymerization. In practical applications, 1 neutralization circulation cooler 331 is provided for every 2 neutralization tanks 3, and 1 neutralization circulation cooler 331 may be provided for each neutralization tank 3.

In practical application, the storage tank 4 is a normal pressure storage tank, and 1-2 storage tanks can be arranged, and the cooling coil 40 is arranged in the storage tank to maintain the storage temperature.

In the above embodiment, the number of stages of the reactor 1 and the neutralization tank 3 may be adjusted adaptively according to the actual application. As shown in FIG. 1 of the present invention, a 3-stage reactor 1, a 2-stage neutralization tank 3 can be optionally provided.

According to the above embodiment provided by the present invention, a process for continuously producing hydroxyacetonitrile from liquid phase hydrocyanic acid can be further implemented, comprising the following steps:

s1, adding formaldehyde solution, hydrocyanic acid and catalyst solution into a first-stage reactor 10 continuously, wherein hydrocyanic acid enters in a multilayer mode, is rapidly mixed and reacts in the first-stage reactor 10, releases reaction heat at the same time, reaction liquid of the first-stage reactor overflows to a next-stage reactor through an overflow port in the upper part to continue reacting, and reaction liquid after the reaction in a last-stage reactor overflows to a neutralization tank 3 through an overflow port in the upper part; the reaction temperature of the reaction liquid in each reactor 1 is controlled to be within the range of 10-25 ℃ through the heat exchange mechanism 5, the external circulation cooling loop 50 can not only cool, but also enhance the material circulation in the reactor, and is superposed with the mechanical stirring action of the mixing mechanism 2, so that the mixing effect is better, and the phenomena of over-temperature and over-concentration of local alkalinity in the reactor are further eliminated, so as to avoid polymerization; adding a catalyst solution through a catalyst feeding pipe 102 in the reaction process to adjust the pH value in each reactor 1 to 3-5.5;

s2, analyzing residual amounts of hydrocyanic acid and formaldehyde in an overflow reaction liquid of the last-stage reactor in the neutralization tank 3, if the residual amounts are qualified, adding inorganic acid, controlling the pH value to be 1-2.5 and optimally 1.3-2 by a pH meter 71, and feeding the qualified finished product of the acidified hydroxyacetonitrile into a storage tank 4; if the residual value does not meet the requirement, adding a proper amount of formaldehyde or hydrocyanic acid to continuously react to reach the standard, and then adding sulfuric acid to transfer to a storage tank 4.

According to the embodiment, the formaldehyde and the liquid-phase hydrocyanic acid are all continuously fed into the first-stage reactor 10, the reaction speed is high, almost most of the reaction is completed in the first-stage reactor 10 under the reaction condition (the conversion rate is higher than 90%), so that the thermal effect of the reaction kettle is large, the required heat transfer area is large, the temperature control difficulty is large, and temperature runaway is easily caused. Through hydrocyanic acid multilayer distribution feeding, and combine heat transfer mechanism to improve and remove thermal efficiency, reduce the probability that the temperature runaway takes place, in view of the above, accomplish more than 90% conversion rate in reactor 1 through controlling hydrocyanic acid, accomplish remaining 10% hydrocyanic acid conversion in the remaining reactor that connects in series in proper order, make reaction system design more reasonable.

In step S2, the number of the neutralization tanks 3 is set to at least 2, and when the reaction liquid level of one of the neutralization tanks reaches the set liquid level, the other neutralization tank 3 is switched to continue to receive the overflow reaction liquid from the last reactor, thereby improving the treatment efficiency. In order to ensure the reaction efficiency and the product quality, in step S1, the reaction temperature in the reactor is controlled to be 17-23 ℃.

In step S1, the opening of the catalyst feed valve 1020 may be adjusted by the control system 6 to adjust the PH in the primary reactor to 4 to 5.2, thereby reducing the risk of polymerization.

In step S2, adding sulfuric acid into the neutralization tank 3 to make the pH in the tank less than 2, terminating the reaction, freezing and cooling to obtain the finished product, and transferring the finished product into a storage tank 4.

In addition, the catalyst solution is 1-30% wt of aqueous solution. Specifically, the catalyst adopts: and sodium sulfite is diluted to be prepared into 8-10% wt.

The mass concentration of the formaldehyde solution is 10-50 wt%; if the concentration of formaldehyde is too high, polymerization is easy, and if the concentration of formaldehyde is too low, the concentration of the finished product of the hydroxy acetonitrile is low, and further purification is needed.

Hydrocyanic acid: 90-100% wt; the proportion of slight excess hydrocyanic acid is adopted, the molar ratio (percent) of hydrocyanic acid to formaldehyde of reaction materials is controlled to be (1-1.15) to 1, and preferably (1-1.05): 1. avoiding the formaldehyde residue, leading to more reaction impurities and influencing the product quality.

Above, control basicity, temperature, hydrocyanic acid concentration, the proportion of reaction raw materials in hydroxyacetonitrile production, promote product quality, reduce impurity by a wide margin, be fit for large-scale industrial production.

Specific examples of industrial production are provided below:

comparative example 1

Raw materials: 437kg/h of hydrocyanic acid (concentration 99.5 wt%), 1256kg/h of formaldehyde solution (concentration 37 wt%), hydrocyanic acid: formaldehyde (mol) ═ 1.04; the catalyst is prepared into 8 wt% sodium sulfite solution by using sodium sulfite.

The device comprises the following steps: as shown in FIG. 1, a primary reactor 10 is provided, which has a size of about phi 1200x2000mm, a secondary reactor 11 has a size of about phi 1200x2000mm, a tertiary reactor 13 has a size of about phi 1600x2100mm, the stirrers 20 in the primary reactor 11 are provided with 2 layers of stirring paddles, hydrocyanic acid feed pipes 101 of the primary reactor 10 are respectively communicated with 2 layers of circular pipes to serve as a first/second hydrocyanic acid distributor 103/104, the first hydrocyanic acid distributor 103 is arranged 400mm above the upper layer of stirring paddle, and the second hydrocyanic acid distributor 104 is arranged 200mm below the lower layer of stirring paddle; first stage reactor 10 configuration: an external circulation cooling circuit 50 with a circulation pump 51 and a circulation cooler 52, and a heat exchange jacket 54; the second stage three stage reactor is provided with heat exchange jacket 54 and heat exchange coil 53. The first-stage reactor 10 is also provided with a catalyst feeding pipe 102;

the technological parameters are as follows: the reaction pH is 4.9, the temperature of the primary reactor 10 is 30 ℃, the temperature of the secondary reactor 11 and the tertiary reactor is 20 ℃, the reaction time is 5.2h, and the reaction pressure is normal;

the process comprises the following steps: pre-starting all cooling media (frozen brine) in the stirrer 20, the heat exchange jacket 54, the circulating cooler 52 and the heat exchange coil 53, monitoring the reaction conditions in the primary reactor 10 by using a pH meter 70 and a thermometer 60, continuously pumping 1256kg/h of formaldehyde solution into the primary reactor 10, simultaneously continuously pumping 437kg/h of hydrocyanic acid into the primary reactor 10, simultaneously starting a circulating pump 51 and a catalyst feed valve 1020 (the addition amount of the catalyst sodium sulfite solution is controlled according to the pH value measured by the pH meter), controlling the pH value in the primary reactor to be 4.9, controlling the temperature process parameters to be reached, gradually increasing the liquid level, sequentially overflowing into the secondary reactor 11, the tertiary reactor 12 and the neutralization tank 3, and adjusting the pH value to be 1.8 by adding sulfuric acid through an adjusting valve 300 when the pH value is qualified, the reaction is terminated and sent to the product tank 40 upon cooling.

As a result: the temperature of the primary main reactor 10 rises uncontrollably rapidly and rises to 98 ℃ rapidly, the process is stopped, and the materials in the reactor are polymerized and are brown.

Comparative example 2

Raw materials: as in comparative example 1.

The device comprises the following steps: the same as comparative example 1;

the technological parameters are as follows: pH 6.7, temperature 20 ℃ in the first to third reactors, otherwise the same as in comparative example 1;

the process comprises the following steps: the pH in the first stage reactor was controlled to 6.7 by adjusting the catalyst feed valve 1020, otherwise the same as in comparative example 1;

as a result: the temperature runaway occurred in the first-stage reactor 10, and the materials in the reactor polymerized to be brown.

Example 1

Raw materials: as in comparative example 1.

The device comprises the following steps: the same as comparative example 1;

the technological parameters are as follows: the temperature in the first, second and third reactors is controlled to be 20 ℃, and the rest is the same as the comparative example 1;

the process comprises the following steps: the same as comparative example 1;

as a result: hydrocyanic acid and formaldehyde solution are continuously fed for 5.2h to obtain 4579kg of colorless and transparent hydroxyacetonitrile finished product (folding hundred), the yield of the hydrocyanic acid is 95.9 percent, the concentration of the hydroxyacetonitrile is 51.6 percent by weight, the formaldehyde residue is 0.042 percent, and the hydrocyanic acid residue is 0.04 percent.

Example 2

Raw materials: the same as in example 1.

The device comprises the following steps: the same as example 1;

the technological parameters are as follows: the temperature of the first, second and third reactors was controlled at 17 ℃ and the rest was the same as in example 1.

The process comprises the following steps: the same as example 1;

as a result: hydrocyanic acid and formaldehyde solution are continuously fed for 5.2h to obtain 4541kg of colorless and transparent finished hydroxyacetonitrile product (Sanbao), the yield of the hydrocyanic acid is 95.1 percent, the concentration of the hydroxyacetonitrile is 51.2 percent, the formaldehyde residue is 0.047 percent, and the hydrocyanic acid residue is 0.043 percent.

Example 3

Raw materials: as in comparative example 1.

The device comprises the following steps: the same as comparative example 1;

the technological parameters are as follows: the temperature in the first, second and third reactors is controlled to be 23 ℃, and the rest is the same as the comparative example 1;

the process comprises the following steps: the same as comparative example 1;

as a result: hydrocyanic acid and formaldehyde solution are continuously fed for 5.2h to obtain 4532kg of colorless and transparent hydroxyacetonitrile finished product (Sanbao), the yield of the hydrocyanic acid is 94.9 percent, the concentration of the hydroxyacetonitrile is 51.3 percent, the formaldehyde residue is 0.048 percent, and the hydrocyanic acid residue is 0.045 percent.

Example 4

Raw materials: the same as in example 1.

The device comprises the following steps: the hydrocyanic acid feed pipe 100 is not connected with the first/second hydrocyanic acid distributor 103\104 of the loop, and the rest is the same as the embodiment 1;

the technological parameters are as follows: the same as example 1;

the process comprises the following steps: the same as example 1;

as a result: hydrocyanic acid and formaldehyde solution are continuously fed for 5.2h to obtain 4225kg of light yellow finished hydroxyacetonitrile (Sanba), wherein the yield of the hydrocyanic acid is 88.5 percent, the concentration of the hydroxyacetonitrile is 48.0 percent, the residual formaldehyde is 0.26 percent, and the hydrocyanic acid is 0.12 percent.

Example 5

Raw materials: the same as in example 1.

The device comprises the following steps: the hydrocyanic acid feed pipe 100 is not connected to the first hydrocyanic acid distributor 103 of the loop, and the other steps are the same as those of example 1;

the technological parameters are as follows: the same as example 1;

the process comprises the following steps: the same as example 1;

as a result: hydrocyanic acid and formaldehyde solution are continuously fed for 5.2h to obtain a faint yellow hydroxyacetonitrile finished product (Sanba) of 4359kg, the yield to hydrocyanic acid is 91.3 percent, the concentration of the hydroxyacetonitrile is 49.5 percent, the residual formaldehyde is 0.11 percent, and the hydrocyanic acid is 0.06 percent.

Example 6

Raw materials: the same as in example 1.

The device comprises the following steps: the hydrocyanic acid feed pipe 100 is not connected to the second hydrocyanic acid distributor 104 of the loop, and the other steps are the same as those of example 1;

the technological parameters are as follows: the same as example 1;

the process comprises the following steps: the same as example 1;

as a result: hydrocyanic acid and formaldehyde solution are continuously fed for 5.2h to obtain a faint yellow finished product (Sanba) of hydroxyacetonitrile 4383kg, the yield to hydrocyanic acid is 91.8 percent, the concentration of the hydroxyacetonitrile is 49.7 percent, the residual formaldehyde is 0.08 percent, and the hydrocyanic acid is 0.05 percent.

It should be noted that the above embodiments can be freely combined as necessary. The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.

Claims (10)

1. The utility model provides a device of continuous production hydroxyacetonitrile of liquid phase hydrocyanic acid which characterized in that:

the device comprises a multistage reactor which is connected in series in sequence, wherein a formaldehyde feeding pipe, a hydrocyanic acid feeding pipe and a catalyst feeding pipe which are used for continuous feeding are connected to the first-stage reactor; the adjacent two stages of reactors are sequentially communicated in series through discharge pipes; a mixing mechanism is arranged in any stage of reactor;

the reactor also comprises a neutralization tank and a storage tank which are communicated with the last-stage reactor in sequence; the neutralization tank is used for receiving reaction liquid flowing out of the last-stage reactor; the storage tank is used for receiving the finished hydroxy acetonitrile product discharged from the neutralization tank;

wherein, a heat exchange mechanism is connected on any stage of reactor and the storage tank.

2. The apparatus for continuously producing hydroxyacetonitrile according to claim 1, wherein:

the heat exchange mechanism comprises an external circulation cooling loop which is connected with the primary reactor and is provided with a circulating pump and a circulation cooler, and the material at the outlet of the circulation cooler returns to the primary reactor through the external circulation cooling loop;

the heat exchange mechanism also comprises heat exchange coil pipes arranged in the rest reactors and the neutralization tank, and cooling media are circulated in the heat exchange coil pipes.

3. The apparatus for continuously producing hydroxyacetonitrile according to claim 2, wherein:

the heat exchange mechanism also comprises a heat exchange jacket connected with any stage of reactor, and a cooling medium is circulated in the heat exchange jacket.

4. The apparatus for continuously producing hydroxyacetonitrile according to claim 2, wherein:

the device also comprises a volatile gas condenser, wherein the volatile gas of the reactor, the circulating cooler, the neutralization tank and the storage tank is collected to the volatile gas condenser, and an outlet of the volatile gas condenser is connected to the first-stage reactor, so that the volatile gas is condensed and then returns to the first-stage reactor for recycling.

5. The apparatus for continuously producing hydroxyacetonitrile according to claim 2, wherein:

thermometers for monitoring the reaction temperature are respectively arranged on any stage of reactor, and thermometers for monitoring the temperature of the reaction materials returned to each reactor are arranged at the outlets of the circulating coolers;

wherein:

the outlet temperature of the circulating cooler is controlled to be-5-10 ℃, the circulation ratio of the material flow returned to the first-stage reactor from the outlet of the circulating cooler to the material flow overflowing to the next-stage reactor is controlled to be 5-20, and the temperature in the reactor is controlled to be 10-25 ℃.

6. The apparatus for continuously producing hydroxyacetonitrile according to claim 5, wherein:

a PH meter for monitoring the PH value of the reaction is arranged on the primary reactor;

be provided with the catalyst feed valve on the catalyst inlet pipe, just the exit linkage to first order reactor of catalyst inlet pipe, PH is 3 ~ 5.5 in the first order reactor of regulation catalyst feed valve control.

7. The apparatus for continuously producing hydroxyacetonitrile according to claim 6, wherein:

the device also comprises a control system, and the thermometer, the PH meter and the catalyst feed valve are all electrically connected with the control system.

8. The apparatus for continuously producing hydroxyacetonitrile according to claim 1, wherein:

the mixing mechanism comprises a stirrer arranged in each stage of reactor, and the stirrer is provided with at least 2 layers of stirring paddles;

and/or;

the downstream of the last-stage reactor of the neutralization tank is set to be at least 2 stages connected in parallel, and an online hydrocyanic acid analyzer, an online formaldehyde analyzer, an inorganic acid feeding pipe, a thermometer and a PH meter are connected to any neutralization tank.

9. The apparatus for continuously producing hydroxyacetonitrile according to claim 1, wherein:

a first hydrogen cyanide distributor and a second hydrogen cyanide distributor are respectively arranged in the first-stage reactor; the first hydrogen cyanide distributor and the second hydrogen cyanide distributor are oppositely arranged at the upper side and the lower side of the mixing mechanism.

10. The apparatus for continuously producing hydroxyacetonitrile according to claim 9, wherein:

the first hydrocyanic acid distributor comprises a first ring pipe, wherein the bottom of the first ring pipe is an open hole area along the radial cross section of the first ring pipe in the range of a fan-shaped included angle theta 1;

the second hydrogen cyanide distributor comprises a second ring pipe, and the lateral side of the outer side of the second ring pipe is an open hole area with a sector included angle theta 2 angle range along the radial section of the second ring pipe.

Images