CN115925505A

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

Info

Publication number: CN115925505A
Application number: CN202211429422.1A
Authority: CN
Inventors: 王振; 赵长森; 牛强; 王刚; 白雪
Original assignee: Ordos Hanbo Technology Co ltd; Inner Mongolia Erdos Electric Power Metallurgy Group Co Ltd
Current assignee: Ordos Hanbo Technology Co ltd; Inner Mongolia Erdos Electric Power Metallurgy Group Co Ltd
Priority date: 2022-11-15
Filing date: 2022-11-15
Publication date: 2023-04-07

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

Process method for synthesizing chloroethylene by mercury-free catalysis

Technical Field

The invention relates to the technical field of a method for synthesizing chloroethylene by an acetylene method, in particular to a process method for synthesizing chloroethylene by mercury-free catalysis.

Background

Polyvinyl chloride (PVC) is the second most common synthetic resin, and the synthetic methods of PVC polymerization monomer vinyl chloride are mainly ethylene method and acetylene method, of which acetylene method is the most important production method. However, the existing acetylene method processes all adopt mercury catalysts, but the mercury catalysts can cause a large amount of pollution and mercury consumption, and aiming at the problems, new catalysts are urgently needed to reduce the mercury consumption and pollution.

Mercury-free catalysts such as acetylene hydrochlorination gold and ruthenium have become important research points in the past few years due to the high activity, selectivity and stability of the catalysts in the acetylene hydrochlorination reaction, and acetylene hydrochlorination catalysts with excellent performance are developed by multiple enterprises and scientific research units. For example, a gold catalyst loaded with ionic liquid disclosed in Chinese patent CN 201910940508 shows extremely high activity and stability, and a ruthenium-based catalyst for acetylene hydrochlorination disclosed in Chinese patent CN 202111422143 has better HCl adsorption capacity, so that the catalyst has higher stability; meanwhile, with the gradual maturity of the mercury-free catalyst, industrial tests and applications are developed by part of enterprise units, and a plurality of processes and technologies matched with the mercury-free catalyst are provided. For example, chinese patent CN201911082316 discloses a process for synthesizing vinyl chloride by mercury-free catalysis, which effectively prolongs the operating life of a mercury-free catalyst by flexibly adopting different operating modes by arranging a multi-stage mixing preheater and realizing series, parallel or series-parallel combination of a front converter and a rear converter. Chinese patent CN 202021847169 discloses a vinyl chloride synthesis process device suitable for a mercury-free catalyst, wherein a process method that a copper-based catalyst is adopted in a foreground and a gold catalyst is adopted in a background is adopted, and the problems that heat release is concentrated in an initial stage of the gold catalyst, hot spots are difficult to control, and the catalyst is easily inactivated at a high temperature are solved.

However, no matter the series or parallel process, the high-activity catalysts such as gold, ruthenium and the like have high activity and violent reaction in the induction period, so the temperature runaway is easily caused. The operation temperature of the acetylene hydrochlorination catalyst is below 200 ℃, but in the actual production process, the temperature runaway phenomenon often occurs because the reactant concentration in the raw material gas at the inlet section of the reactor is high and the heat exchange is poor. The plant generally controls the reaction temperature by gradually increasing the feed rate, but this method often requires as long as a month to bring the load up to normal levels, greatly affecting the production efficiency, and the method cannot avoid the local overheating of the catalyst. In addition, the acetylene hydrochlorination series process usually recharges the background catalyst used for a period of time to the foreground converter for continuous use, so that the catalyst can be fully played, and the service life of the catalyst is prolonged. In the patent technology, the foreground uses a copper-based catalyst with lower operating temperature, and the background uses a gold catalyst, so that the foreground temperature is easier to control, but the local temperature runaway condition is still difficult to avoid, and the loss of the copper-based catalyst is easily caused. Meanwhile, the technology of the patent does not carry out the operation of replacing the background catalyst to the foreground, so that the catalyst is not fully utilized, and the running cost of the catalyst is improved.

Aiming at the problems of heavy pollution of mercury catalysts, long induction period of mercury-free catalysts, high activity in the induction period, easy temperature runaway and inactivation and the like in the prior art, it is necessary to find a process method for synthesizing vinyl chloride by mercury-free catalysis.

Disclosure of Invention

The invention provides a process method for synthesizing chloroethylene by mercury-free catalysis, aiming at solving the problems of long induction period, higher activity in the induction period and easy temperature runaway and inactivation of mercury-free catalysts in the prior art.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

the invention provides a process method for synthesizing vinyl chloride, wherein a device for synthesizing vinyl chloride comprises a mixer 1, a converter 2 and a converter 3, wherein the converter 2 and the converter 3 are connected in parallel;

the method comprises the following steps that inlet raw material gas and inert gas enter a mixer 1 to be mixed and then enter a converter 2 and a converter 3, and reaction gas at the outlet of the converter 2 comprises gas B and gas D; the reaction gas at the outlet of the converter 3 comprises gas C and gas E, wherein the gas C and the gas B both enter the subsequent working section, and the gas D and the gas E are mixed into gas F and then are circulated to the mixer 1 to be mixed with the raw material gas and the inert gas.

Further, the volume ratio of the gas D to the gas B is 0-10.

Further, mixing the inlet feed gas, the inert gas and the circulating gas f to obtain a gas A; the proportion of the recycle gas F in the gas A is 0-100%, and the proportion of the inert gas in the gas A is 0-100%.

In some embodiments, when the converter 2 and the converter 3 are connected in parallel, the reaction gas at the outlets of the converter 2 and the converter 3 is divided into two streams, wherein the gases D and E are mixed with the raw material as the recycle gas, and the gases C and B enter the subsequent section; typically, the concentration of vinyl chloride at the converter outlet in the parallel process is about 90% to 100%, and the vinyl chloride passing through the recycle converter outlet can dilute the inlet feed gas concentration in the case of parallel operation.

When a new factory is started, all the converters are new converters, and chlorine-free ethylene at the outlet of the converters can be circularly diluted. At this time, inert gas can be introduced into the mixer 1 and mixed with the raw material gas, and the effects of weakening the reaction heat at the inlet of the converter, shortening the induction period and reducing the temperature runaway inactivation of the catalyst can be achieved at the initial start-up stage. When the system is stable, the inert gas is switched to the circulating gas. Therefore, redundant inert gas in the system can be reduced, and the operation cost is reduced.

Further, the inert gas comprises argon and/or nitrogen, and the inlet feed gas comprises acetylene and HCl.

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

Preferably, the section a is mixed and filled with activated carbon and a common mercury-free catalyst, or filled with a low-activity mercury-free catalyst (i.e. a catalyst with a lower content of active components, such as gold, copper, and ruthenium catalysts, wherein the active components of the gold, copper, and ruthenium catalysts are ionic or compounds of gold, copper, and ruthenium, respectively), and the section B is filled with a common mercury-free catalyst.

It is worth to be noted that the low-activity mercury-free catalyst means that the mass content of the active components of the catalyst is 10-70% of that of the common mercury-free catalyst; for example, a low activity mercury-free catalyst corresponding to a 1% gold catalyst is a 0.1-0.7% gold catalyst.

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

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

Further, in the converter, the feed gas, inert gas and/or recycle gas are led through a tube side 1, and the heat exchange medium is led through a shell side 2.

Because heat exchange medium and reaction raw materials carry out heat exchange in a countercurrent way in industry, the closer to the inlet section of the converter, the larger the gas phase proportion in the heat exchange medium is, and the worse the heat transfer effect is. The overall activity of the catalyst at the inlet can be reduced by filling the section A with the activated carbon and the catalyst or filling the catalyst with lower active component content, so that the intensity of the reaction at the inlet is reduced, and meanwhile, the most intense position of the reaction is moved to the part far away from the inlet of the converter, and the heat transfer capacity of the position is improved.

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

the method comprises the following steps that inlet raw material gas and inert gas enter a mixer 1 to be mixed and then enter a converter 2, reaction gas at the outlet of the converter 2 comprises gas b and gas d, wherein the gas b enters a converter 3 to continue to react; the reaction gas at the outlet of the converter 3 comprises gas c and gas e, wherein the gas c enters the subsequent working section, and the gas d and the gas e are mixed into gas f and then recycled to the mixer 1 to be mixed with the raw material gas and the inert gas.

Further, the volume ratio of the gas d to the gas b is 0-10.

In some embodiments, when the converter 2 is connected in series with the converter 3, the reaction gas at the outlet of the converter 2 is divided into two parts, b and d, wherein the gas b enters the converter 3 to continue the reaction, and the gas d is recycled to the mixer 1 to be mixed with the raw material gas and then enters the converter 2 again; the reactor at the outlet of the converter 3 is divided into two parts c and e, wherein the gas e is recycled to the mixer 1 to be mixed with the raw material gas and then enters the converter 2 again, and the gas c enters the subsequent working section. In industrial production, raw material gas at the inlet of a converter is generally acetylene and HCL (concentration ratio is 1.1), main components at the outlet of the converter are chloroethylene, the concentration of chloroethylene at the outlet of a front-stage converter is about 50-70% in a general series process, and the concentration of chloroethylene at the outlet of a rear-stage converter is about 90-100%, so that the outlet of the converter is circulated and then mixed with the raw material gas, the effect of diluting the concentration of the raw material gas at the inlet can be achieved, meanwhile, the unreacted raw material gas at the outlet of the converter is further reacted, the conversion rate at the outlet of a reactor is ensured to meet the system requirement, the reaction heat release at the inlet of the converter can be effectively weakened, the induction period time is shortened, and the deactivation caused by the temperature runaway of a catalyst is reduced.

The technical effects obtained by the invention are as follows:

1. through diluting the catalyst at the section A of the inlet of the converter, the intensity of the reaction at the inlet is effectively reduced, and meanwhile, the most intense position of the reaction is moved to the part far away from the inlet of the converter, so that the heat transfer capacity of the hot spot position is improved, the service life of the catalyst is effectively prolonged, and the operation cost is reduced.

2. The inert gas is used for diluting the inlet feed gas, so that the reaction heat at the inlet of the converter can be effectively weakened, the induction period time is effectively shortened, the inactivation caused by temperature runaway of the catalyst is reduced, and the service life of the catalyst is prolonged.

3. The outlet gas of the converter is partially circulated to the inlet to be mixed with the raw material gas, so that the concentration of acetylene in the raw material gas can be effectively diluted, and the reaction intensity at the inlet is reduced. Meanwhile, unreacted acetylene in the circulating feed gas is further reacted, and the acetylene yield can be improved.

4. The problem of easy temperature runaway and inactivation of the catalyst in the induction period can be effectively solved by using a single catalyst, the process operation difficulty is reduced, and the service life of the catalyst is prolonged.

Drawings

FIG. 1 is a series process flow of the present invention, in which 1-mixer; 2-a converter; 3-a converter; a. b, c, d and e are all gases; f is circulating gas;

FIG. 2 is a parallel process flow of the present invention, in which 1-mixer; 2-a converter; 3-a converter; A. b, C, D, E is gas; f is circulating gas;

FIG. 3 is a schematic view of the structure of a converter according to the present invention, in which 1-pass is shown; 2-shell layer; A. b is respectively A section and B section.

Detailed Description

The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention.

Before the present embodiments are further described, it is to be understood that the scope of the invention is not limited to the particular embodiments described below; it is also to be understood that the terminology used in the examples herein is for the purpose of describing particular embodiments only, and is not intended to limit the scope of the present invention.

When numerical ranges are given in the examples, it is understood that both endpoints of each of the numerical ranges and any value therebetween can be selected unless the invention otherwise indicated. 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 should be noted that the raw materials used in the present invention are all common commercial products, and thus the sources thereof are not particularly limited.

Example 1

The series process flow shown in figure 1 is adopted, the filling mode of the catalyst in the converter is shown in figure 3, the catalyst adopted in the section B is 1 per mill fresh gold catalyst, and the section A is as follows: 0cm, the mass percent of the A section of the active carbon is 0 percent. The ratio of the amounts of acetylene and HCl materials as raw materials is 1:1.1, the space velocity of acetylene is 50h ^-1 Inert gas is nitrogen and is present in 0% of the feed a, recycle gas f is present in 0% of the converter feed a, the ratio between the flow rates of gas d and gas b is 0:1, the ratio of the flow rates of the gas e and the gas c is 0:1.

example 2

The difference from example 1 is that the recycle gas f is present in 15% of the converter feed a, the ratio between the gas d and gas b flow is 0:1, the ratio of the flow rates of the gas e and the gas c is 2:1.

example 3

The difference from example 1 is that the inert gas is nitrogen and 15% is present in feed a.

Example 4

The parallel process flow shown in fig. 2 is adopted, the filling mode of the catalyst in the converter is shown in fig. 3, the catalyst adopted in the section B is 1 per mill of fresh gold catalyst, and the section A is as follows: 0cm, the mass percent of the A section of the active carbon is 0 percent. The ratio of the amounts of acetylene and HCl substances as raw materials is 1:1.1, the acetylene space velocity is 30h ^-1 Inert gas in feed A is 0%, recycle gas F in converter feed A is 0%, and the ratio of gas D to gas B flow is 0:1, the ratio of the flow rates of the gas E and the gas C is 0:1.

example 5

The difference from example 4 is that the recycle gas F represents 15% of the feed A to the converter, the ratio between the flow rates of gas D and B is 2:1, the ratio of the flow rates of the gas E and the gas C is 2:1.

example 6

The difference from example 4 is that the inert gas is nitrogen and 15% of the feed A is present.

Example 7

The difference from the embodiment 1 is that the A section length is as follows: the mass percent of the A section of the activated carbon is 50 percent, the rest part is filled with 1 thousandth of gold catalyst, and the B section is filled with 1 thousandth of gold catalyst.

Example 8

The difference from the embodiment 1 is that the A section length is as follows: 40cm, the mass percent of the A section of activated carbon is 50%, the rest part is filled with 1 thousandth of gold catalyst, and the B section is filled with 1 thousandth of gold catalyst.

Example 9

The difference from the embodiment 1 is that the A section length is as follows: the mass percent of the activated carbon at the A section is 100 percent, and the catalyst of 1 per mill gold is filled at the B section, which is 20 cm.

Example 10

The difference from the embodiment 1 is that the A section length is as follows: 2 cm, 0.5 per mill of gold catalyst is filled in the section A, and 1 per mill of gold catalyst is filled in the section B.

Example 11

The difference from the embodiment 4 is that the A section length is as follows: the mass percent of the A section of the activated carbon is 50 percent, the rest part is filled with 1 thousandth of gold catalyst, and the B section is filled with 1 thousandth of gold catalyst.

Example 12

The difference from the embodiment 4 is that the A section length is as follows: 40cm, the mass percent of the A section of activated carbon is 50%, the rest part is filled with 1 thousandth of gold catalyst, and the B section is filled with 1 thousandth of gold catalyst.

Example 13

The difference from the embodiment 4 is that the A section length is: 20cm, the mass percent of the A section of active carbon is 100 percent, and the B section is filled with 1 ‰ gold catalyst.

Example 14

The difference from the embodiment 4 is that the A section length is as follows: 2 cm, 0.5 per mill of gold catalyst is filled in the section A, and 1 per mill of gold catalyst is filled in the section B.

Tests were conducted using the above protocol, and the temperature of the converter was measured using a jacketed thermocouple inserted into the tube side, and the results are shown in table 1.

TABLE 1

For the series process, the service life of the catalyst is the running time of the catalyst when the conversion rate of the catalyst is reduced to 65% under the conditions of corresponding space velocity and raw material gas ratio when the converter is used as a front stage.

The following conclusions can be drawn from the comparative examples 1 to 14:

1. comparing examples 1-3 and examples 4-6, it can be seen that the hot spot temperature is significantly reduced and the induction period time is greatly shortened after the raw gas is diluted, regardless of the serial or parallel process. For gold catalysts, when the hotspot temperature is higher than 200 ℃, the catalyst is accelerated to be deactivated, resulting in shortened service life.

2. Examples 7-9 or examples 11-13 show that mixing activated carbon with mercury-free catalyst in the front stage of the converter in both series and parallel processes can reduce the hot spot temperature while shortening the induction period. The main reason is that the converter is countercurrent heat exchange, the closer to the inlet of the raw material gas, the weaker the heat transfer capacity of a heat exchange medium is, the reaction heat release is reduced by reducing the loading amount of the catalyst at the front section of the converter, and the hot spot temperature can be effectively reduced. It can also be found that the longer the length of the mixed activated carbon, the greater the proportion of the mixed activated carbon, the lower the hot spot temperature and the shorter the induction period of the catalyst. However, the catalyst loading length cannot be increased without limit because the more activated carbon is loaded, the less the catalyst is loaded in the converter, and the longer the catalyst loading per unit mass is, the shorter the life of the converter is.

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 also reduces the hot spot temperature and shortens the induction period. The principle is consistent with that of mixed active carbon.

Finally, it should be noted that the above-mentioned contents are only used for illustrating the technical solutions of the present invention, and not for limiting the protection scope of the present invention, and that the simple modifications or equivalent substitutions of the technical solutions of the present invention by those of ordinary skill in the art can be made without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A process for synthesizing vinyl chloride, which is characterized in that: the device for synthesizing vinyl chloride comprises a mixer 1, a converter 2 and a converter 3, wherein the converter 2 and the converter 3 are connected in series;

the method comprises the following steps that inlet raw material gas and inert gas enter a mixer 1 to be mixed and then enter a converter 2, reaction gas at the outlet of the converter 2 comprises gas b and gas d, and the gas b enters a converter 3 to continue to react; the reaction gas at the outlet of the converter 3 comprises a gas c and a gas e, wherein the gas c enters the subsequent section, and the gas d and the gas e are mixed into a gas f and then recycled to the mixer 1 to be mixed with the raw material gas and the inert gas.

2. The process of claim 1, wherein: the volume ratio of the gas d to the gas b is 0-10.

3. The process according to claim 1, characterized in that: mixing the inlet feed gas, the inert gas and the circulating gas f to obtain a gas a; the proportion of the recycle gas f in the gas a is 0-100%, and the proportion of the inert gas in the gas a is 0-100%.

4. A process for synthesizing vinyl chloride, which is characterized in that: the device for synthesizing vinyl chloride comprises a mixer 1, a converter 2 and a converter 3, wherein the converter 2 and the converter 3 are connected in parallel;

5. The process of claim 4, wherein: the volume ratio of the gas D to the gas B is 0-10.

6. The process of claim 4, wherein: mixing the inlet feed gas, the inert gas and the circulating gas f to obtain a gas A; the proportion of the recycle gas F in the gas A is 0-100%, and the proportion 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 comprises argon and/or nitrogen, and the inlet feed gas comprises acetylene and HCl.

8. The process according to claim 1 or 4, characterized in that: the converters 2 and 3 both comprise a tube side 1 and a shell side 2, the tube side 1 comprises a section A and a section B, the section A is filled with activated carbon and/or mercury-free catalyst in a mixed mode, and the section B is filled with mercury-free catalyst.

9. The process of claim 8, wherein: the length of the section A is 10-40cm, and the mass percentage of the activated carbon in the section A is 0-100%.

10. The process of claim 8, wherein: the shell pass 2 passes through a heat exchange medium, and the heat exchange medium comprises one or more of hot water, heptane and octane; the mercury-free catalyst comprises one or more of gold, ruthenium and copper catalysts.