CN115925505A - Process method for synthesizing chloroethylene by mercury-free catalysis - Google Patents

Abstract

The invention provides a process method for synthesizing chloroethylene by mercury-free catalysis, which relates to the technical field of acetylene method chloroethylene synthesis methods, and the process reduces the concentration of reactants in raw material gas by mixing and diluting inlet raw material gas by mixing part of crude chloroethylene at the outlet of a converter with inlet raw material or diluting the raw material gas by using inert gas; and a certain proportion of activated carbon is added into the inlet part of the converter, or a part of catalyst with lower active component is used in the inlet section of the converter, so that the activity of the catalyst in the inlet section of the converter is reduced. The method can effectively shorten the induction period time of the mercury-free catalyst at the initial use stage, reduce the deactivation caused by temperature runaway of the catalyst and prolong the service life of the catalyst.

Description

A kind of process method of mercury-free catalytic synthesis of vinyl chloride

technical field

The invention relates to the technical field of vinyl chloride synthesis method by acetylene method, in particular to a mercury-free catalytic method for synthesizing vinyl chloride.

Background technique

Polyvinyl chloride (PVC) is the second largest general-purpose synthetic resin. The synthesis methods of PVC polymerized monomer vinyl chloride are mainly ethylene method and acetylene method, among which the acetylene method is the most important production method. However, the existing acetylene process uses mercury catalysts, but it will cause a lot of pollution and mercury consumption. To solve such problems, new catalysts are urgently needed to reduce mercury consumption and pollution.

Mercury-free catalysts such as gold acetylene hydrochloride and ruthenium have benefited from their high activity, selectivity and stability in acetylene hydrochlorination, and have become the focus of research in the past few years, and have been developed by many enterprises and scientific research institutions A catalyst for acetylene hydrochlorination with excellent performance. As disclosed in Chinese patent CN 201910940508, a gold catalyst loaded with ionic liquid exhibits extremely high activity and stability. Chinese patent CN 202111422143 discloses a ruthenium acetylene hydrochloride-based catalyst, which has better HCl adsorption capacity and enables The catalyst has higher stability; at the same time, with the gradual maturity of mercury-free catalysts, some enterprises have carried out industrial-level tests and applications, and proposed many processes and technologies supporting mercury-free catalysts. For example, Chinese patent CN201911082316 discloses a mercury-free catalytic method for synthesizing vinyl chloride. By setting up a multi-stage mixing preheater and realizing series, parallel or series-parallel combination of front and rear converters, different operating modes can be flexibly used to effectively extend the mercury-free process. Catalyst operating life. Chinese patent CN 202021847169 discloses a vinyl chloride synthesis process device suitable for mercury-free catalysts. The copper-based catalyst is used in the front stage and the gold catalyst is used in the background to solve the problem of concentrated heat release in the initial stage of the gold catalyst, and the hot spots are difficult to control, which is likely to cause high temperature of the catalyst. inactivation problem.

However, regardless of the series or parallel process, highly active catalysts such as gold and ruthenium are highly active and react violently during the induction period, which is very easy to cause overheating. Generally, the operating temperature of the acetylene hydrochlorination catalyst is below 200°C, but in the actual production process, due to the high concentration of reactants in the raw material gas at the inlet section of the reactor and poor heat transfer, overheating often occurs. The factory generally controls the reaction temperature by gradually increasing the feed flow rate, but this method often takes as long as a month to bring the load to the normal level, which greatly affects the production efficiency, and this method cannot avoid local overheating of the catalyst. In addition, in the series process of acetylene hydrochlorination, the background catalyst that has been used for a period of time is often reloaded into the front-end converter for continued use, so that the role of the catalyst can be fully exerted and the service life of the catalyst can be extended. In the above-mentioned patented technology, a copper-based catalyst with a lower operating temperature is used in the foreground. Although the use of a gold catalyst in the background makes the temperature control of the foreground easier, local overheating is still unavoidable, which may easily cause the loss of the copper-based catalyst. At the same time, because the patented technology does not perform the operation of replacing the background catalyst to the front stage, the catalyst is not fully utilized, and the operating cost of the catalyst is increased instead.

Aiming at the problems in the prior art that the mercury catalyst is highly polluted, the induction period of the mercury-free catalyst is long, the activity is high during the induction period, and it is easy to deactivate due to overheating, it is necessary to find a process method for the synthesis of vinyl chloride without mercury. .

Contents of the invention

Aiming at the problems existing in the prior art, the present invention provides a mercury-free catalytic method for synthesizing vinyl chloride, which solves the problems that the mercury-free catalyst has a long induction period, high activity during the induction period, and is easily deactivated by overheating.

To achieve the above object, the technical scheme adopted in the present invention is as follows:

The present invention provides a process for synthesizing vinyl chloride. The vinyl chloride synthesis device includes a mixer 1, a converter 2, and a converter 3, and the converter 2 and the converter 3 are connected in parallel;

The imported raw material gas and inert gas are mixed in the mixer 1, and then enter the converter 2 and the converter 3. The reaction gas at the outlet of the converter 2 includes gas B and gas D; the reaction gas at the outlet of the converter 3 includes gas C and gas E, wherein both gas C and gas B enter the subsequent section, gas D and gas E are mixed into gas F and then circulated to the mixer 1 to be mixed with raw material gas and inert gas.

Further, the volume ratio of the gas D to the gas B is 0-10:1, and the volume ratio of the gas E to the gas C is 0-10:1.

Further, the imported raw material gas, inert gas and recycle gas f are mixed to obtain gas A; in terms of the ratio of substances, the proportion of recycle gas F in gas A is 0-100%, and the inert gas The proportion in gas A ranges from 0-100%.

In some specific embodiments, when the converter 2 and the converter 3 are connected in parallel, the reaction gas at the outlet of the converter 2 and the converter 3 is divided into two streams, wherein the gas D and E are mixed with the raw material as a cycle gas, and the gas C and B enters the follow-up section; in general, the concentration of vinyl chloride at the outlet of the converter is about 90%-100% in the parallel process, and the vinyl chloride at the outlet of the circulating converter can achieve the effect of diluting the concentration of the imported raw material gas under the condition of parallel operation.

When a new plant is started up, all converters are new converters, and at this time, no vinyl chloride at the outlet of the converters can be circulated and diluted. At this time, an inert gas can be introduced into the mixer 1, and mixed with the feed gas can also reduce the heat of reaction at the inlet of the converter during the initial start-up stage, shorten the induction period, and reduce the effect of catalyst runaway deactivation. When the system becomes stable, switch the inert gas to the circulating gas. This reduces excess inert gas in the system and lowers operating costs.

Further, the inert gas includes argon and/or nitrogen, and the imported raw material gas includes acetylene and HCl.

Further, the converters 2 and 3 both include a tube side 1 and a shell side 2, the tube side 1 includes section A and section B, the section A is filled with activated carbon and/or mercury-free catalyst, the section B Packed with mercury-free catalyst.

Preferably, the A section is filled with activated carbon and common mercury-free catalysts, or filled with low-activity mercury-free catalysts (i.e. catalysts with lower active component content, such as gold, copper, ruthenium catalysts, wherein gold, copper, ruthenium catalysts The active components are ions or compounds of gold, copper, ruthenium, etc.), and the B section is filled with common mercury-free catalysts.

It is worth noting that the low-activity mercury-free catalyst means that the active component mass content of the catalyst is 10-70% of that of ordinary mercury-free catalysts; for example, the low-activity mercury-free catalyst corresponding to 1‰ gold catalyst is 0.1-0.7‰ gold catalyst.

Further, the length of the section A is 10-40cm, and the mass content of activated carbon in the section A is 0-100%.

Further, the shell side 2 passes through a heat exchange medium, and the heat exchange medium includes one or more of hot water, heptane, and octane; the catalyst includes one or more of gold, ruthenium, and copper catalysts. Several kinds.

Further, in the converter, raw gas, inert gas and/or circulating gas go through the tube side 1, and the heat exchange medium goes through the shell side 2.

Since the heat exchange medium and the reaction raw materials are heat exchanged in countercurrent in the industry, the closer to the inlet section of the converter, the larger the proportion of the gas phase in the heat exchange medium, and the worse the heat transfer effect. The overall activity of the catalyst at the inlet can be reduced by mixing activated carbon and catalyst in section A, or loading a catalyst with a low content of active components, thereby reducing the intensity of the reaction at the inlet, and at the same time moving the position with the most intense reaction away from the inlet of the converter part, improve the heat removal capacity of the position.

The present invention also provides a process for synthesizing vinyl chloride, the device for synthesizing vinyl chloride includes a mixer 1, a converter 2, and a converter 3, and the converter 2 and the converter 3 are connected in series;

The imported raw material gas and inert gas are mixed in the mixer 1, and then enter the converter 2. The reaction gas at the outlet of the converter 2 includes gas b and gas d, wherein, the gas b enters the converter 3 to continue the reaction; the outlet of the converter 3 The reaction gas includes gas c and gas e, wherein gas c enters the subsequent process section, gas d and gas e are mixed into gas f and then circulated to the mixer 1 to be mixed with raw gas and inert gas.

Further, the volume ratio of the gas d to the gas b is 0-10:1, and the volume ratio of the gas e to the gas c is 0-10:1.

Further, the imported raw material gas, inert gas and recycle gas f are mixed to obtain gas a; in terms of the ratio of substances, the proportion of recycle gas f in gas a is in the range of 0-100%, and the inert gas The proportion in gas a ranges from 0-100%.

In some specific embodiments, when the converter 2 and the converter 3 are connected in series, the reaction gas at the outlet of the converter 2 is divided into two streams b and d, wherein the gas b enters the converter 3 to continue the reaction, and the gas d circulates to the mixer 1 is mixed with the feed gas and enters the converter 2 again; the outlet reactor of the converter 3 is divided into two streams c and e, in which the gas e circulates to the mixer 1 and mixes with the feed gas and then enters the converter 2 again, and the gas c enters the Subsequent section. In industrial production, the raw material gas at the inlet of the converter is generally acetylene and HCL (concentration ratio 1:1.1), while the main component of the outlet of the converter is vinyl chloride. Generally, the concentration of vinyl chloride at the outlet of the former converter in the series process is about 50-70%. The concentration of vinyl chloride at the outlet of the first-stage converter is about 90%-100%. Therefore, by circulating the outlet of the converter and mixing it with the raw material gas, it can dilute the concentration of the imported raw material gas, and at the same time unreacted raw material gas at the outlet of the converter Further reaction ensures that the conversion rate at the outlet of the reactor meets the system requirements, which can effectively reduce the heat of reaction at the inlet of the converter, shorten the induction period, and reduce deactivation caused by catalyst overheating.

The technical effect that the present invention obtains is:

1. By diluting the catalyst in section A of the inlet of the converter, the intensity of the reaction at the inlet is effectively reduced, and at the same time, the position of the most intense reaction is moved to a part far away from the inlet of the converter, so as to improve the heat removal capacity of the hot spot and effectively improve the operation of the catalyst life and reduce operating costs.

2. Diluting the imported raw material gas with inert gas can effectively reduce the reaction heat at the inlet of the converter, effectively shorten the induction period, reduce the deactivation caused by the catalyst overheating, and prolong the service life of the catalyst.

3. By recirculating part of the outlet gas of the converter to the inlet and mixing it with the feed gas, it can effectively dilute the acetylene concentration in the feed gas and reduce the intensity of the reaction at the inlet. At the same time, the unreacted acetylene in the circulating raw material gas is further reacted, which can also increase the yield of acetylene.

4. The use of a single catalyst can effectively improve the problem that the catalyst is prone to overheating deactivation during the induction period, reduce the difficulty of process operation, and increase the service life of the catalyst.

Description of drawings

Fig. 1 is the serial process flow among the present invention, and among the figure, 1-mixer; 2-reverter; 3-converter; a, b, c, d, e are gas; f is cycle gas;

Fig. 2 is the parallel process flow among the present invention, and among the figure, 1-mixer; 2-reverter; 3-converter; A, B, C, D, E are gas; F is cycle gas;

Fig. 3 is the schematic structural diagram of the converter in the present invention, in the figure, 1-tube side; 2-shell layer; A, B are A section and B section respectively.

Detailed ways

Embodiments of the present invention are described below through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation modes, and various modifications or changes can be made to the details in this specification based on different viewpoints and applications without departing from the spirit of the present invention.

Before further describing the specific embodiments of the present invention, it should be understood that the protection scope of the present invention is not limited to the following specific specific embodiments; it should also be understood that the terms used in the examples of the present invention are to describe specific specific embodiments, It is not intended to limit the protection scope of the present invention.

When the examples give numerical ranges, it should be understood that, unless otherwise stated in the present invention, the two endpoints of each numerical range and any value between the two endpoints can be selected. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

It is worth noting that the raw materials used in the present invention are all common commercially available products, so their sources are not specifically limited.

Example 1

Adopt the serial process flow shown in Figure 1, the loading mode of catalyst in the converter is as shown in Figure 3, the catalyst that B section adopts is 1‰ fresh gold catalyst, and described A section length is: 0cm, the mass percent of A section activated carbon is 0%. The ratio of raw material acetylene to HCl is 1:1.1, the space velocity of acetylene is 50h ^-1 , the inert gas is nitrogen and its proportion in feed a is 0%, and the proportion of cycle gas f in feed a of converter is 0 %, the flow rate ratio of gas d and gas b is 0:1, and the flow rate ratio of gas e and gas c is 0:1.

Example 2

Same as Example 1, the difference is that the recycle gas f accounts for 15% of the reformer feed a, the flow ratio of gas d and gas b is 0:1, and the flow ratio of gas e and gas c is 2:1.

Example 3

Same as Example 1, the difference is that the inert gas is nitrogen and its proportion in feed a is 15%.

Example 4

Adopt the parallel process flow shown in Figure 2, the loading mode of catalyst in the converter is as shown in Figure 3, the catalyst that B section adopts is 1‰ fresh gold catalyst, and described A section length is: 0cm, the mass percent of A section activated carbon is 0%. The ratio of raw material acetylene to HCl is 1:1.1, the space velocity of acetylene is 30h ^-1 , the proportion of inert gas in feed A is 0%, the proportion of recycle gas F in feed A of converter is 0%, and the gas The ratio of D to gas B flow rate is 0:1, and the ratio of gas E to gas C flow rate is 0:1.

Example 5

Same as Example 4, the difference is that the recycle gas F accounts for 15% of the converter feed A, the flow ratio of gas D and gas B is 2:1, and the flow ratio of gas E and gas C is 2:1.

Example 6

Same as Example 4, the difference is that the inert gas is nitrogen and its proportion in the feed A is 15%.

Example 7

With embodiment 1, its difference is that described A section length is: 20cm, and the mass percent of A section activated carbon is 50%, and remaining part is filled with 1‰ gold catalyst, and B section is filled with 1‰ gold catalyst.

Example 8

With embodiment 1, its difference is that described A section length is: 40cm, and the mass percent of A section activated carbon is 50%, and remaining part is loaded with 1‰ gold catalyst, and B section is filled with 1‰ gold catalyst.

Example 9

Same as Example 1, the difference is that the length of section A is 20cm, the mass percentage of activated carbon in section A is 100%, and section B is filled with 1‰ gold catalyst.

Example 10

Same as Example 1, the difference is that the length of section A is 20 cm, section A is filled with 0.5‰ gold catalyst, and section B is filled with 1‰ gold catalyst.

Example 11

With embodiment 4, its difference is that described A section length is: 20cm, and the mass percent of A section activated carbon is 50%, and remaining part is loaded with 1‰ gold catalyst, and B section is filled with 1‰ gold catalyst.

Example 12

With embodiment 4, its difference is that described A section length is: 40cm, and the mass percent of A section activated carbon is 50%, and remaining part is loaded with 1‰ gold catalyst, and B section is filled with 1‰ gold catalyst.

Example 13

Same as Example 4, the difference is that the length of section A is 20cm, the mass percentage of activated carbon in section A is 100%, and section B is filled with 1‰ gold catalyst.

Example 14

Same as Example 4, the difference is that the length of section A is 20 cm, section A is filled with 0.5‰ gold catalyst, and section B is filled with 1‰ gold catalyst.

The above scheme was used to carry out the test, and the temperature of the converter was measured by inserting a thermocouple with a jacket into the tube side. The results are shown in Table 1.

Table 1

For the series process, the above-mentioned catalyst life refers to the operation time of the catalyst when the conversion rate drops to 65% under the conditions of the corresponding space velocity and feed gas ratio when the converter is the foreground.

Can draw the following conclusions by comparative example 1-14:

1. Comparing Examples 1-3 and Examples 4-6, it can be found that, regardless of the series or parallel process, after the raw material gas is diluted, the temperature of the hot spot is significantly reduced, and the induction period is greatly shortened. For gold catalysts, when the hot spot temperature is higher than 200 °C, the catalyst will accelerate deactivation, resulting in a shortened service life.

2. Examples 7-9 or Examples 11-13 show that mixing activated carbon and mercury-free catalyst in the front section of the converter in the series and parallel processes can reduce the hot spot temperature and shorten the induction period. The main reason is that the converter is a counter-current heat exchange, the closer to the feed gas inlet, the weaker the heat transfer capacity of the heat transfer medium is, and the hot spot temperature can be effectively reduced by reducing the amount of catalyst loaded in the front stage of the converter to reduce the heat release of the reaction. It can also be found that the longer the length of the mixed activated carbon, the larger the proportion of mixed activated carbon, the lower the hot spot temperature, and the shorter the catalyst induction period. However, the length of catalyst mixing cannot be increased without limit. This is because the more activated carbon is loaded, the less catalyst is in the converter, and the increase in catalyst load per unit mass leads to a decrease in its life.

3. Examples 7 and 10 or Examples 11 and 14 show that loading a low-activity mercury-free catalyst in the front section of the converter can also reduce the hot spot temperature and shorten the induction period. Its principle is consistent with that of mixed activated carbon.

Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, rather than to limit the scope of protection of the present invention. Simple modifications or equivalent replacements to the technical solution of the present invention by those skilled in the art will not depart from the present invention. The essence and scope of the technical solution of the invention.

Claims (10)

1. A process for synthesizing vinyl chloride, characterized in that: the device for synthesizing vinyl chloride comprises a mixer 1, a converter 2, and a converter 3, and the converter 2 and converter 3 are connected in series; The imported raw material gas and inert gas are mixed in the mixer 1, and then enter the converter 2. The reaction gas at the outlet of the converter 2 includes gas b and gas d, wherein, the gas b enters the converter 3 to continue the reaction; the outlet of the converter 3 The reaction gas includes gas c and gas e, wherein gas c enters the subsequent process section, gas d and gas e are mixed into gas f and then circulated to the mixer 1 to be mixed with raw gas and inert gas. 2. The process according to claim 1, characterized in that: the volume ratio of the gas d to the gas b is 0-10:1, and the volume ratio of the gas e to the gas c is 0-10:1. 3. The process according to claim 1, characterized in that: said imported feed gas, inert gas and recycle gas f are mixed to obtain gas a; The proportion range is 0-100%, and the proportion range of the inert gas in gas a is 0-100%. 4. A process for synthesizing vinyl chloride, characterized in that: the device for synthesizing vinyl chloride comprises a mixer 1, a converter 2, and a converter 3, and the converter 2 and converter 3 are connected in parallel; The imported raw material gas and inert gas are mixed in the mixer 1, and then enter the converter 2 and the converter 3. The reaction gas at the outlet of the converter 2 includes gas B and gas D; the reaction gas at the outlet of the converter 3 includes gas C and gas E, wherein both gas C and gas B enter the subsequent section, gas D and gas E are mixed into gas F and then circulated to the mixer 1 to be mixed with raw material gas and inert gas. 5. The process according to claim 4, characterized in that: the volume ratio of the gas D to the gas B is 0-10:1, and the volume ratio of the gas E to the gas C is 0-10:1. 6. The process according to claim 4, characterized in that: the imported raw gas, inert gas and recycle gas f are mixed to obtain gas A; The proportion range is 0-100%, and the proportion range of the inert gas in the gas A is 0-100%. 7. The process according to claim 1 or 4, characterized in that: the inert gas includes argon and/or nitrogen, and the imported raw material gas includes acetylene and HCl. 8. The process according to claim 1 or 4, characterized in that: the converters 2 and 3 both include a tube pass 1 and a shell pass 2, and the tube pass 1 includes a section A and a section B, and the A section Section B is filled with activated carbon and/or mercury-free catalyst, and section B is filled with mercury-free catalyst. 9. The process according to claim 8, characterized in that: the length of the section A is 10-40cm, and the mass percentage of activated carbon in the section A is 0-100%. 10. The process according to claim 8, characterized in that: the shell side 2 passes through a heat exchange medium, and the heat exchange medium includes one or more of hot water, heptane, and octane; Mercury-free catalysts include one or more of gold, ruthenium, and copper catalysts.

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