CN112174780B

CN112174780B - Control method for improving UV value of ethylene glycol product through low-pressure catalytic hydrogenation

Info

Publication number: CN112174780B
Application number: CN202011032301.4A
Authority: CN
Inventors: 于广臣; 刘连忠; 彭义秋
Original assignee: Individual
Current assignee: Yu Guangchen
Priority date: 2020-09-27
Filing date: 2020-09-27
Publication date: 2021-07-20
Anticipated expiration: 2040-09-27
Also published as: CN112174780A

Abstract

The invention relates to a control method for improving the UV value of an ethylene glycol product through low-pressure catalytic hydrogenation, which comprises the following steps: step S1: adding a catalyst; step S2: adding a hydrogenation reaction kettle to enable a double-bond compound in the ethylene glycol to perform addition reaction with hydrogen under the action of a nickel catalyst, so that the ultraviolet light transmittance of the ethylene glycol product is improved; step S3: sending hydrogen into a hydrogenation reaction kettle, opening a hydrogen control valve of the hydrogenation reaction kettle, introducing the hydrogen, and controlling the pressure to be 0.6-10MPag, wherein the introduced hydrogen is excessive gas, and the excessive hydrogen returns to the inlet of a hydrogen compressor through a recovery pipeline; controlling the hydrogen flow according to the pressure of the hydrogenation reaction kettle; step S4: feeding ethylene glycol by adopting a bottom spraying mode; step S5: extracting the materials; the invention has the advantages that: and a small amount of catalyst is adopted, the catalyst can be used for a long time in the later period, the continuous production is met, no hazardous substance is buried, and the burying cost is saved. And the catalyst can be recovered and reused after processing.

Description

Control method for improving UV value of ethylene glycol product through low-pressure catalytic hydrogenation

Technical Field

The invention relates to the technical field of ethylene glycol production processes, in particular to a control method for improving a UV value of an ethylene glycol product through low-pressure catalytic hydrogenation.

Background

Ethylene Glycol (MEG) is an important organic chemical feedstock downstream of EO for the production of polyester, synthetic fibers, and the like. One important index for testing the quality of ethylene glycol products is ultraviolet transmittance (referred to as UV value).

According to the regulation of the national standard GB4649-2008, the indexes of polyester grade glycol are shown in a table 1.1

TABLE 1.1 polyester grade ethylene glycol index

Wavelength of UV value	220nm	275nm	350nm
				UV transmittance%	≥75	≥92	≥99

As the adopted raw materials are diversified, such as ethylene glycol prepared by a petroleum ethylene method, ethylene glycol prepared by coal, ethylene glycol prepared by a biological method and different process routes, trace impurities are generated simultaneously in the process of producing ethylene glycol, and the important index of polyester grade ethylene glycol, such as large UV value fluctuation, unstable product quality and the like, are caused by the change of the raw materials and the operation conditions.

In the existing production process package for preparing ethylene glycol by a known petroleum ethylene method in the market at present, hydrogenation reaction kettle unit equipment is not adopted in ethylene oxidation technologies of three companies, namely Shell, SD and UCC, and due to the lack of hydrogenation reaction equipment, a post-stage aldehyde removal resin tank technology is generally adopted at present.

The technology of the formaldehyde-removing resin tank is that the extracted product is firstly put into a formaldehyde-removing system, enters a product intermediate tank after impurities are removed, and enters a product storage tank after an analysis result is qualified. But has the following disadvantages:

1) the dealdehyding resin is expensive and needs to be replaced after the resin is saturated after being used for a certain period.

2) The replaced resin belongs to dangerous compounds and must be buried in a specified burying plant, and the burying cost is high.

3) The new dealdehyding resin is put into a dealdehyding tank and needs to be soaked by glycol for 24 hours, and the soaked glycol contains more impurities and can only be treated as waste, so that the glycol loss is caused.

While ethylene is oxidized to produce Ethylene Oxide (EO) in an EO production process, the molecular skeleton of ethylene is easily destroyed, and deep oxidation occurs to produce carbon dioxide and water and EO is isomerized to produce trace amounts of acetaldehyde and formaldehyde as by-products. The quality of the ethylene glycol product is influenced, the polyester grade standard is not reached, and the indexes of the polyester product such as color, fiber strength and the like are influenced.

Disclosure of Invention

In view of the above problems, the present invention provides a control method for increasing the UV value of ethylene glycol product by low-pressure catalytic hydrogenation, which is used to increase the UV value of ethylene glycol product, so as to overcome the above disadvantages of the prior art.

The invention provides a control method for improving the UV value of an ethylene glycol product through low-pressure catalytic hydrogenation, which comprises the following steps: the method comprises the following steps:

step S1: addition of catalyst

Step S11: introducing materials, and simultaneously opening a valve on a material pipe between the bottom of a communicated drying tower and a catalyst preparation tank and a valve on a pressure balance pipeline between the side of the communicated drying tower and the catalyst preparation tank to enable the materials to enter the catalyst preparation tank, and closing the two valves when the liquid level of the catalyst preparation tank is 50-60%, wherein the valve on the pressure balance pipeline between the side of the communicated drying tower and the catalyst preparation tank is used for balancing the pressure balance of the drying tower and the catalyst preparation tank, so that the materials can flow downwards;

step S12: opening a feed hole of a catalyst preparation tank, and manually adding a catalyst, wherein the ratio of ethylene glycol (containing 2-3 percent of water) to the catalyst is about 30: 1;

step S13: opening a feeding hole of a catalyst preparation tank, pouring a catalyst, opening a valve on a pipeline connected between the catalyst preparation tank and a catalyst feeding pump, starting the feeding pump, opening a circulating valve on a circulating pipe connected with the catalyst preparation tank, fully mixing and circulating ethylene glycol and the catalyst in the catalyst preparation tank and the circulating pipe, and then closing the circulating valve;

step S2: adding a hydrogenation reaction kettle to enable a double-bond compound in the ethylene glycol to perform addition reaction with hydrogen under the action of a nickel catalyst, so that the ultraviolet light transmittance of the ethylene glycol product is improved;

step S21: opening a valve connected with a pipeline of the ethylene glycol hydrogenation reaction kettle, and feeding the fully mixed catalyst solution into the ethylene glycol hydrogenation reaction kettle; repeating the operation of step S1;

step S22: when the liquid level of the hydrogenation reaction kettle reaches 50-60%, closing the feeding pump, stopping adding the catalyst, and finishing the preparation; starting a hydrogenation reaction kettle stirrer, keeping the catalyst and ethylene glycol to be uniformly stirred, and preventing the catalyst from sinking to the bottom and influencing the catalyst efficiency;

step S3: sending hydrogen into a hydrogenation reaction kettle, opening a hydrogen control valve of the hydrogenation reaction kettle, introducing the hydrogen, and controlling the pressure to be 0.6-10MPag, wherein the introduced hydrogen is excessive gas, and the excessive hydrogen returns to the inlet of a hydrogen compressor through a recovery pipeline; controlling the hydrogen flow according to the pressure of the hydrogenation reaction kettle;

step S4: the feeding method adopts a bottom spraying mode, the ethylene glycol enters the hydrogenation reaction kettle after being pressurized by a feeding pump from the drying tower, the feeding method adopts a bottom spraying mode, the bottom catalyst can be blown by feeding through the bottom spraying mode, so that the materials and the catalyst are fully mixed, the catalyst is prevented from being accumulated at the bottom, and the catalyst is ensured to be in a rotary flow state;

step S5: the method comprises the following steps of (1) extracting materials, namely, alternately extracting the materials by using a double-row cylindrical filter designed in a hydrogenation reaction kettle, and blowing a catalyst adsorbed on the double-row cylindrical filter into the reaction kettle by matching with a hydrogen back-blowing pipeline, wherein the time can be set to be 15-30 seconds or is prolonged; thereby ensuring the normal extraction of the materials;

step S51: the cylindrical filters are of two rows, each row is connected with a plurality of cylindrical filters in parallel, and the catalyst is retained outside the filter screen by the plurality of cylindrical filters; the ethylene glycol passes through the filter screen gap under the action of pressure to reach the interior of the cylindrical filter, then is converged into the extraction main pipe and is sent out, and solid catalyst particles are intercepted on the surface of a filter medium;

step S52: in step S51, when the catalyst is excessively adsorbed on the surface of the cylindrical filter, the filter differential pressure increases; the back-flushing device and the differential pressure controller of the cylinder type filter are used for switching and controlling the back-flushing time and speed of the hydrogen; when the pressure difference of the cylindrical filter reaches a set value, the differential pressure transmitter transmits an electric signal to a controller of the cylindrical filter, a valve on a main material extraction pipeline is closed, a hydrogen pressure control valve is opened, the external hydrogen pressure is higher than the internal pressure of the hydrogenation reaction kettle, the internal part of the cylindrical filter is blown outwards, a catalyst adsorbed in gaps of the cylindrical filter is blown out completely, after a filter screen is cleaned, the pressure difference is reduced to the minimum value, the system returns to the initial filtering state, the system returns to normal operation, and one back blowing filtering cycle is completed;

step S53: ethylene glycol enters the cylindrical filter from the outside of each single cylindrical filter gap, and then is gathered to the main pipe of the produced material and then enters the next ethylene glycol rectifying tower by means of pressure difference; because the ethylene glycol refining tower is operated under negative pressure, the flow control valve controls the extracted flow, and the ethylene glycol enters the ethylene glycol refining tower to carry out the next rectification operation.

Preferably, in step S2, the stirrer of the hydrogenation reactor is used to prevent the catalyst from accumulating at the bottom, and because the specific gravity of the catalyst is high, the catalyst will gradually accumulate at the bottom of the reactor in the hydrogenation reactor for a long time without being stirred, and the function of the catalyst will be lost.

Preferably, in step S5, the blowing time of the catalyst is set to be between 15 and 30 seconds.

Preferably, in step S5, the cylindrical filter has a spiral filter mesh with a mesh size of 130 μm to 200 μm.

Preferably, in step S5, two rows of cylindrical filters are adopted, and when one row of filters is subjected to a back-flushing cleaning process, the other row of produced filters normally produces materials without affecting the normal discharge of the materials.

Preferably, in step 1, the catalyst is a nickel catalyst, and the nickel-aluminum alloy is treated with a sodium hydroxide solution, in the process, most of aluminum reacts with the sodium hydroxide to dissolve away, so that dried activated raney nickel is left, and the raney nickel has micropores with different sizes, because the raney nickel is fine gray powder on the surface, but each tiny particle in the powder is a three-dimensional porous structure from the microscopic perspective, the porous structure greatly increases the surface area, and the extremely large surface area brings high catalytic activity.

Preferably, the nickel-aluminum alloy 2Ni — Al +2NaOH +2H2O ═ 2Ni +2NaAlO2+3H 2; raney nickel is mainly used for unsaturated compounds including: hydrogenation of olefins, alkynes, nitriles, dienes, aromatics, carbonyl-containing materials, and polymers having unsaturated bonds.

The invention has the advantages and positive effects that:

1. the invention adds a hydrogenation reaction kettle with a stirring type, so that double-bond compounds in ethylene glycol generate addition reaction with hydrogen under the action of a nickel catalyst, and the ultraviolet light transmittance of ethylene glycol products is improved. Through the actual operation analysis test of the ethylene glycol device, impurities in the ethylene glycol solution react with hydrogen under the action of a nickel catalyst, and unsaturated bonds of trace impurities in the ethylene glycol solution contain carbonyl or conjugated double bonds, -c ═ o, — -c ═ o, —, and H2 undergo an addition reaction and are converted into saturated bonds which do not absorb ultraviolet rays, so that the product quality is greatly improved, the process conditions such as temperature, pressure and liquid level are easy to control, no adverse side reaction is generated, and the original process operation conditions are not influenced.

2. The ethylene glycol enters the hydrogenation reaction kettle after being pressurized by the pump from the drying tower, the feeding mode adopts a bottom spraying mode for feeding, the advantage 1 is that the bottom catalyst is blown to fully mix the materials and the catalyst, and the advantage 2 is that the catalyst is prevented from being accumulated at the bottom, so that the catalyst is ensured to be in a rotary flow state.

3. The invention solves the problem that the catalyst is accumulated at the bottom and can be slowly accumulated at the bottom of the reactor for a long time in the reaction hydrogenation kettle due to the large specific gravity of the catalyst, and the effect of the catalyst is lost by adopting the reaction hydrogenation kettle with a stirrer and a bottom feeding injection mode.

4. The ethylene glycol extraction filter adopts a double-row spiral cylindrical filter, and the cylindrical filter has the advantage of large surface area. The cylindrical filter adopts two rows, each row is connected with a plurality of filters in parallel, and the catalyst is trapped outside the filter screen. The glycol passes through the gap under the action of pressure to reach the interior of the filter, and then is collected into the main production pipe to be sent out. Solid catalyst particles are trapped on the surface of the filter medium. When the catalyst is excessively adsorbed on the filter surface, the filter pressure difference may increase. The back flushing mechanism and the differential pressure controller can automatically switch and control the back flushing time and speed of the hydrogen. When the pressure difference reaches a set value, the differential pressure transmitter transmits an electric signal to the controller, a valve on a main material extraction pipeline is closed, a hydrogen pressure control valve is opened, the external hydrogen pressure is higher than the internal pressure of the tower kettle, the inside of the filter blows outwards to blow and clean the catalyst absorbed in gaps of the filter, after a filter screen is cleaned, the pressure difference is reduced to a minimum value, the system returns to an initial filtering state, the system returns to normal operation, and one back-blowing filtering cycle is completed. The ethylene glycol enters the filter from the outside of each single filter gap, and then is gathered to the main pipe of the produced material and enters the next ethylene glycol rectifying tower by the pressure difference. Because the ethylene glycol refining tower is operated under negative pressure, the flow control valve controls the extraction flow, and the ethylene glycol can easily enter the ethylene glycol refining tower to carry out the next rectification operation. The blowing time of the catalyst can be set between 15 and 30 seconds or can be prolonged or shortened according to actual conditions. And adjusting the instrument control system. The cylindrical filter adopts a high-strength framework, a support and a spiral filter screen, is efficient and accurate in filtering, ensures that only ethylene glycol can enter an internal system of the filter screen, and adopts a filter screen with the specification of 130 mu-200 mu. (depending on the catalyst particle size). Two rows of filters are adopted, when one row of filters is subjected to a back flushing cleaning process, the other row of extraction filters normally extract materials, and normal material discharging is not influenced. The two rows of filters can simultaneously extract materials and also can switch to extract the materials.

4. The invention adopts a small amount of catalyst, can be used for a long time in the later period, accords with continuous production, has no danger compound to be buried, and saves the burying cost. And the catalyst can be recovered and reused after processing. Drawings

Other objects and results of the present invention will become more apparent and more readily appreciated as the same becomes better understood by reference to the following description taken in conjunction with the accompanying drawings. In the drawings:

fig. 1 is an overall flow chart according to an embodiment of the present invention.

Fig. 2 is a structural view of a cylindrical filter according to an embodiment of the present invention.

Detailed Description

In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of one or more embodiments. It may be evident, however, that such embodiment(s) may be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form in order to facilitate describing one or more embodiments.

Example 1

Fig. 1-2 show an overall structural schematic according to an embodiment of the present invention.

As shown in fig. 1-2, the control method for increasing the UV value of an ethylene glycol product through low-pressure catalytic hydrogenation provided by the embodiment of the present invention includes: the method comprises the following steps:

step S1: addition of catalyst

step S13: opening a feeding hole of the catalyst preparation tank, pouring the catalyst, opening a valve on a pipeline connected between the catalyst preparation tank and the catalyst feeding pump, starting the catalyst feeding pump, opening a circulating valve on a circulating pipe connected with the catalyst preparation tank, fully mixing and circulating the ethylene glycol and the catalyst in the catalyst preparation tank and the circulating pipe, and then closing the circulating valve;

In step S2, the stirrer of the hydrogenation reactor is used to prevent the catalyst from accumulating at the bottom, and because the specific gravity of the catalyst is high and the stirrer is not arranged, the catalyst will slowly accumulate at the bottom of the reactor in the hydrogenation reactor for a long time, and the function of the catalyst will be lost.

In this embodiment, in step S5, the blowing time of the catalyst is set to be between 15 and 30 seconds.

In step S5, the cylindrical filter is a spiral filter with mesh size of 130 μm to 200 μm.

In step S5, two rows of cylindrical filters are used in the present embodiment, and when one row of the cylindrical filters is subjected to the back-flushing cleaning process, the other row of the extraction filters normally extract the material without affecting the normal material discharge.

In step 1, the catalyst is nickel catalyst, the nickel-aluminum alloy is treated with concentrated sodium hydroxide solution, in the process, most of aluminum reacts with sodium hydroxide to dissolve away, dried activated raney nickel is left, and the raney nickel has micropores with different sizes.

The nickel-aluminum alloy 2Ni — Al +2NaOH +2H2O in this example is 2Ni +2NaAlO2+3H 2; raney nickel is mainly used for unsaturated compounds including: hydrogenation of olefins, alkynes, nitriles, dienes, aromatics, carbonyl-containing materials, and polymers having unsaturated bonds.

Example 2

Referring to fig. 1 and 2, in the present embodiment, step S1: feeding the ethylene glycol aqueous solution from a front process pipeline into an ethylene glycol drying tower, heating by a reboiler to remove most of water in the ethylene glycol, and extracting light components mainly containing water and a small amount of entrained ethylene glycol from the top of the tower to return to a process water recovery system. And step S2, feeding the concentrated ethylene glycol at the bottom of the ethylene glycol drying tower into an ethylene glycol hydrogenation reaction kettle through a valve 5 and a pipeline and a feeding pump of the drying tower. And step S3, in the ethylene glycol hydrogenation reaction kettle, under the action of a catalyst, impurities in the ethylene glycol and hydrogen are subjected to addition reaction, wherein unsaturated bonds are converted into saturated bonds which do not absorb ultraviolet rays, so that the effect of improving the UV value of the product is achieved. In step S4, the excessive hydrogen in the ethylene glycol hydrogenation reaction kettle is returned to the inlet of the hydrogen compressor through the pressure regulating valve 9. And step S5, collecting the reacted glycol solution in a hydrogenation reaction kettle through a double-row filter by means of pressure difference, and then converging the glycol solution into a material header pipe, and feeding the glycol solution into a glycol refining tower for next rectification operation. And step S6, continuously extracting the ethylene glycol solution after the hydrogenation reaction through a material extraction filter, and feeding the ethylene glycol solution into an ethylene glycol refining tower after the ethylene glycol solution is collected. Step S7 catalyst preparation and feeding procedure see example 1.

Example 3

Test results of the control method for improving the UV value of the ethylene glycol product by low-pressure catalytic hydrogenation

Wavelength of UV value	220nm	275nm	350nm
				UV transmittance%	>75	>92	≈100

Labeling: the test results implement the national standard, GB4649-2008, industry ethylene glycol standard.

Analysis and test: through practical operation analysis tests of example 1, impurities in the ethylene glycol solution react with hydrogen under the action of the catalyst, and trace impurities in the ethylene glycol solution are compounds of which unsaturated bonds contain carbonyl groups or conjugated double bonds, -c ═ o, -c ═ o and H2 to undergo addition reaction and are converted into saturated bonds which do not absorb ultraviolet rays, so that the product quality is greatly improved, the process conditions such as temperature, pressure and liquid level are easy to control, no adverse side reaction is generated, the original process operation conditions are not influenced, and the UV value of the product is improved. Ultraviolet transmittance (UV value) of ethylene glycol product: 220nm > 75%; 275nm > 92%; 350nm is approximately equal to 100 percent; higher than the polyester grade index.

And (4) conclusion: compared with the adsorption technology of adding and removing aldehyde resin, the ethylene glycol hydrogenation technology has the advantages of better superiority, stable product quality, larger improvement range of the index UV value of the ethylene glycol product, and contribution to the production of large-scale devices. The apparatus of example 1 operated for a long period and was stable, and the quality of the ethylene glycol product was in accordance with the polyester grade index.

The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and the changes or substitutions should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A control method for improving the UV value of an ethylene glycol product through low-pressure catalytic hydrogenation is characterized by comprising the following steps:

step S1: addition of catalyst

step S12: opening a feed hole of a catalyst preparation tank, and manually adding a catalyst, wherein the ratio of glycol containing 2-3% of water to the catalyst is 30: 1;

step S5: the method comprises the following steps of (1) extracting materials, namely, alternately extracting the materials by using a double-row cylindrical filter designed in a hydrogenation reaction kettle, and blowing a catalyst adsorbed on the double-row cylindrical filter into the reaction kettle by matching with a hydrogen back-blowing pipeline for 15-30 seconds or prolonging the time; thereby ensuring the normal extraction of the materials;

2. The control method for increasing the UV value of an ethylene glycol product through low-pressure catalytic hydrogenation according to claim 1, wherein in step S2, the agitator of the hydrogenation reactor is used for preventing the catalyst from accumulating at the bottom.

3. The control method for increasing the UV value of an ethylene glycol product through low-pressure catalytic hydrogenation according to claim 1, wherein in step S5, the blowing time of the catalyst is set to be between 15 and 30 seconds.

4. The method as claimed in claim 1, wherein in step S5, the cylindrical filter has a spiral filter screen with a mesh size of 130 μm to 200 μm.

5. The method according to claim 1, wherein in step S5, two rows of cylindrical filters are used, and when one of the rows of cylindrical filters is subjected to a blowback cleaning process, the other row of cylindrical filters is used to collect the material normally without affecting the normal discharge of the material.

6. The control method for improving the UV value of the ethylene glycol product through low-pressure catalytic hydrogenation according to claim 1, characterized in that in step 1, the catalyst is a nickel catalyst, and the nickel-aluminum alloy is treated with a concentrated sodium hydroxide solution.