A method for preparing vinyl chloride by catalytic hydrochlorination of acetylene with low cost and without mercury

Abstract

The present invention provides a method for preparing vinyl chloride by mercury-free catalytic hydrochlorination of acetylene at low cost, which relates to the technical field of vinyl chloride synthesis and includes the steps of: (1) mixing hydrogen chloride and acetylene to obtain a mixed gas; (2) preheating the mixed gas and then introducing it into a converter filled with a catalyst for vinyl chloride synthesis to produce crude vinyl chloride; (3) washing the crude vinyl chloride with water, washing it with alkali, and rectifying it to obtain refined vinyl chloride. The method of the present invention can achieve mercury-free substitution for vinyl chloride production with minimal technical transformation investment under the existing device conditions by using a gold-based catalyst to replace the low-mercury catalyst. By adopting the operation mode of series connection of front and back converters, preferably controlling the acetylene space velocity range, controlling the bed temperatures of the front and back stages and the acetylene content at the outlet, and preferably controlling the catalyst loading amount, the service life of the catalyst can reach more than 13,000 h, the production of vinyl chloride monomer can exceed 10,500 tons, and the catalyst usage cost can be controlled below 150 yuan / ton of vinyl chloride. The present invention realizes the production of vinyl chloride at low cost and without mercury.

Description

Technical Field

[0001] The present invention belongs to the technical field of vinyl chloride synthesis, and particularly relates to a method for preparing vinyl chloride by non-mercury catalytic acetylene hydrochlorination with low cost. Background Art

[0002] Polyvinyl chloride (PVC) is one of the five general-purpose resins, with advantages such as flame retardancy, chemical corrosion resistance, wear resistance, excellent electrical insulation, and relatively high mechanical strength. It is the most common basic raw material and polymer material, widely used in major fields such as agriculture, petrochemical industry, light industry, chemical building materials, electric power, metallurgy, national defense and military industry, building materials, food processing, etc., and occupies a very important position in economic development and people's daily life.

[0003] Polyvinyl chloride is a thermoplastic resin polymerized from vinyl chloride (VCM) under the action of an initiator and is a homopolymer of vinyl chloride. At present, according to the different sources of its raw materials, the VCM production route is mainly divided into the ethylene method and the calcium carbide method. Due to reasons such as raw material conditions, the vast majority in China uses the acetylene method to prepare vinyl chloride, that is, a synthesis reaction occurs between acetylene gas and hydrogen chloride gas under the action of a carrier and a mercuric chloride catalyst.

[0004] Chinese invention patent CN108373400A discloses an acetylene method vinyl chloride synthesis process, which is divided into a front converter and a rear converter. 20 - 90% of the mixed gas first reacts in the front converter, and then after being preheated with the remaining mixed gas, they are mixed and reacted in the rear converter to produce crude vinyl chloride. Although the equipment operation rate of the present invention is relatively high, it is beneficial to increase the product conversion rate and extend the service life of the catalyst. However, the catalyst contains a mercuric chloride catalyst.

[0005] Scholars in this field have done a lot of research on the non-mercury catalytic preparation of vinyl chloride. Chinese invention patent CN105330512A discloses a method for non-mercury preparation of vinyl chloride from acetylene hydrogen chloride. After acetylene and hydrogen chloride are mixed and preheated, they are introduced into a first-stage reactor filled with a carbon-supported non-mercury base metal catalyst to obtain a gas-phase product, and the product vinyl chloride is obtained by condensation; the uncondensed mixed gas is introduced into a second-stage reactor filled with a carbon-supported non-mercury base metal catalyst, and another part of the product is obtained after freezing. After two-stage separation, the conversion rate of acetylene is greater than 97.7%, and the selectivity of vinyl chloride is greater than 98%. However, the preparation of vinyl chloride requires intermittent two-stage reactors, and intermediate condensation and collection of crude vinyl chloride are required, and the operation is relatively complex.

[0006] Chinese invention patent CN103894208A discloses a mercury-free catalyst system. The catalyst consists of an activated carbon carrier and a mixed active component composed of one or more noble metal compounds and one or more common metal compounds in a certain proportion. The noble metals are gold, palladium, ruthenium, platinum, and iridium, and the common metals are iron, zinc, and copper. However, using noble metals as the active component of the catalyst results in a high cost, which requires people to study a mercury-free vinyl chloride preparation process that can slow down catalyst deactivation and reduce production costs.

[0007] In summary, there is an urgent need in the art to develop a process for preparing vinyl chloride that has low cost, good reaction activity, long catalyst life, mercury-free catalysis, and high product yield. This is also a top priority for the sustainable development of the PVC industry. Summary of the Invention

[0008] In view of the problems existing in the prior art, the present invention provides a method for preparing vinyl chloride by mercury-free catalytic acetylene hydrochlorination at low cost. A gold-based catalyst with excellent catalytic performance is selected to replace the mercury catalyst, and a series operation mode of front and back converters is adopted. By optimizing the acetylene space velocity range, controlling the front and back bed temperatures, controlling the acetylene content, and the catalyst loading amount, the service life of the catalyst can be greatly improved, the production cost of vinyl chloride can be reduced, and mercury-free catalytic production of vinyl chloride can be achieved.

[0009] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0010] First, the present invention provides a method for preparing vinyl chloride by mercury-free catalytic acetylene hydrochlorination at low cost, comprising the following steps:

[0011] (1) Mix hydrogen chloride and acetylene to obtain a mixed gas;

[0012] (2) After preheating the mixed gas, introduce it into a converter filled with a catalyst to carry out vinyl chloride synthesis to produce crude vinyl chloride;

[0013] (3) Wash the crude vinyl chloride with water, wash it with alkali, and rectify it to obtain pure vinyl chloride.

[0014] Preferably, in step (1), the volume ratio of hydrogen chloride to acetylene is 1 - 1.1:1.

[0015] More preferably, the volume ratio of hydrogen chloride to acetylene is 1.05:1.

[0016] Preferably, in step (1), the purity of hydrogen chloride ≥ 95%, the purity of acetylene ≥ 99.5%, and the water content of the mixed gas ≦ 100 ppm.

[0017] Preferably, in step (2), the preheating temperature is 90 - 140 °C.

[0018] Further preferably, the temperature of preheating is 110-130°C.

[0019] Even more preferably, the temperature of preheating is 120°C.

[0020] Preferably, in step (2), the catalyst is a gold-based catalyst, selected from at least one of gold chloride, auric trichloride, and chloroauric acid.

[0021] Further preferably, the catalyst is auric trichloride, the loading amount of auric trichloride is 1-2‰, the catalyst is in sheet or column shape, the particle size is 3-6 mm, and the bulk density is 0.46-0.50 g / cm 3 。

[0022] Even more preferably, the catalyst is auric trichloride, the loading amount of auric trichloride is 1.5‰, the catalyst is in sheet or column shape, the particle size is 4.5 mm, and the bulk density is 0.48 g / cm 3 。

[0023] Preferably, in step (2), the acetylene space velocity passing through the converter filled with the catalyst is 40-50 h -1 。

[0024] Further preferably, the acetylene space velocity passing through the converter filled with the catalyst is 45 h -1 。

[0025] Preferably, in step (2), the converter is a converter in which the front stage and the back stage are connected in series, a shell-and-tube fixed-bed reactor, with 2,880 tubes, and heptane is used for heat removal.

[0026] Preferably, in step (2), the ratio of the front stage to the back stage of the converter is 1:0.8-1.2; the bed temperature of the front stage is controlled at 130-200°C, and the bed temperature of the back stage is controlled at 130-180°C; the outlet of the total acetylene pipe of the front stage is controlled at 10-20%, and the outlet of the total acetylene pipe of the back stage is controlled at 4-6%.

[0027] Further preferably, the ratio of the front stage to the back stage of the converter is 1:0.5-1.5; the bed temperature of the front stage is controlled at 130-190°C, and the bed temperature of the back stage is controlled at 140-170°C; the outlet of the total acetylene pipe of the front stage is controlled at 12.8-17.5%, and the outlet of the total acetylene pipe of the back stage is controlled at 4-6%.

[0028] Even more preferably, the ratio of the front stage to the back stage of the converter is 1:1; the bed temperature of the front stage is controlled at 160-180°C, and the bed temperature of the back stage is controlled at 150-160°C; the outlet of the total acetylene pipe of the front stage is controlled at 15%, and the outlet of the total acetylene pipe of the back stage is controlled at 5%.

[0029] Preferably, in step (2), for the synthesis of vinyl chloride, the residence time of the mixed gas in the converter is 80 s.

[0030] Preferably, in step (3), the water washing, caustic washing, and rectification are carried out using the technology of Goodyear of the United States.

[0031] Secondly, the present invention also provides a vinyl chloride prepared by the low-cost mercury-free catalytic hydrochlorination of acetylene, which is prepared by the above method.

[0032] Preferably, the purity of the vinyl chloride is ≥99.99%, the acetylene content is ≤5 ppm, the content of high-boiling substances is ≤10 ppm, and the water content is ≤100 ppm.

[0033] Finally, the present invention also provides the application of the above method in the preparation of vinyl chloride with high purity and high conversion rate.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] Starting from the catalytic mechanism of acetylene hydrochlorination, the present invention selects a gold-based catalyst with excellent catalytic performance to replace the low-mercury catalyst, and can achieve mercury-free replacement with the minimum technological transformation investment under the existing device conditions. Through the research on the characteristics of the gold-based catalyst, the series operation mode of the front and back converters is adopted, the acetylene space velocity range is optimized, the bed temperatures of the front and back stages and the outlet acetylene content are controlled, and the catalyst loading of the gold-based catalyst is optimized. The service life of the catalyst can reach more than 13,000 h, more than 10,500 tons of vinyl chloride monomer can be produced, and the catalyst usage cost is controlled below 150 yuan / ton of vinyl chloride. Specific Embodiments

[0036] The following non-limiting examples can enable those of ordinary skill in the art to understand the present invention more comprehensively, but do not limit the present invention in any way. The following content is only an exemplary illustration of the scope claimed in the present application. Those skilled in the art can make various changes and modifications to the invention of the present application based on the disclosed content, and it should also fall within the scope claimed in the present application.

[0037] The present invention will be further described below by way of specific examples. All the chemical reagents used in the examples of the present invention are obtained through conventional commercial channels unless otherwise specified.

[0038] Example 1

[0039] (1) Mix hydrogen chloride and acetylene gases evenly. The volume ratio of hydrogen chloride to acetylene is 1.05:1, the purity of hydrogen chloride is 95%, and the purity of acetylene is 99.5% to obtain a mixed gas with a water content of ≤100 ppm;

[0040] (2) The mixed gas is preheated and then fed into a converter (a shell-and-tube fixed-bed reactor with a design pressure of 3 kg, a volume of 10.89 m³, 2,880 tubes, and heat removal using heptane). The temperature of the preheated mixed gas is 120 °C, and the acetylene space velocity is 40 h -1 , and the converter adopts a front-back stage series connection mode. The ratio of the front stage to the back stage is 1:1. The temperature of the front stage bed is controlled at 130 - 150 °C, and the temperature of the back stage bed is controlled at 140 - 150 °C. The outlet of the front stage acetylene main pipe is controlled at 12.5%, and the outlet of the back stage acetylene main pipe is controlled at 4%. A gold trichloride catalyst with a content of 1‰ is used (in the shape of flakes or columns, with a particle size of 3 mm and a bulk density of 0.46 g / cm³). After non-mercury catalysis for 80 s, crude vinyl chloride is produced;

[0041] (3) The crude vinyl chloride is washed with water, washed with alkali, and rectified using the technology of Goodrich of the United States to obtain refined vinyl chloride.

[0042] Example 2

[0043] (1) The hydrogen chloride and acetylene gases are mixed evenly. The volume ratio of hydrogen chloride to acetylene is 1.05:1, the purity of hydrogen chloride is 95%, the purity of acetylene is 99.5%, to obtain a mixed gas with a water content ≤ 100 ppm;

[0044] (2) The mixed gas is preheated and then fed into a converter (a shell-and-tube fixed-bed reactor with a design pressure of 3 kg, a volume of 10.89 m³, 2,880 tubes, and heat removal using heptane). The temperature of the preheated mixed gas is 120 °C, and the acetylene space velocity is 50 h -1 , and the converter adopts a front-back stage series connection mode. The ratio of the front stage to the back stage is 1:1. The temperature of the front stage bed is controlled at 170 - 190 °C, and the temperature of the back stage bed is controlled at 160 - 180 °C. The outlet of the front stage acetylene main pipe is controlled at 17.5%, and the outlet of the back stage acetylene main pipe is controlled at 6%. A gold trichloride catalyst with a content of 2‰ is used (in the shape of flakes or columns, with a particle size of 6 mm and a bulk density of 0.50 g / cm³). After non-mercury catalysis for 80 s, crude vinyl chloride is produced;

[0045] (3) The crude vinyl chloride is washed with water, washed with alkali, and rectified to obtain refined vinyl chloride.

[0046] Example 3

[0047] (1) The hydrogen chloride and acetylene gases are mixed evenly. The volume ratio of hydrogen chloride to acetylene is 1.05:1, the purity of hydrogen chloride is 95%, the purity of acetylene is 99.5%, to obtain a mixed gas with a water content ≤ 100 ppm;

[0048] (2) The mixed gas is preheated and then fed into a converter (a shell-and-tube fixed-bed reactor with a design pressure of 3 kg, a volume of 10.89 m³, 2,880 tubes, and heat removal using heptane). The temperature of the preheated mixed gas is 120 °C, and the acetylene space velocity is 45 h -1 , and the converter adopts a series connection method of front and back stages. The ratio of the front stage to the back stage is 1:1. The temperature of the front-stage bed is controlled at 160 - 180 °C, and the temperature of the back-stage bed is controlled at 150 - 160 °C. The outlet of the front-stage acetylene main pipe is controlled at 15%, and the outlet of the back-stage acetylene main pipe is controlled at 5%. A gold trichloride catalyst with a content of 1.5‰ is used (in the shape of flakes or columns, with a particle size of 4.5 mm and a bulk density of 0.48 g / cm³). After mercury-free catalysis, crude vinyl chloride is produced;

[0049] (3) The crude vinyl chloride is washed with water, washed with alkali, and rectified to obtain refined vinyl chloride.

[0050] Example 4

[0051] Different from Example 3, in step (1), the volume ratio of hydrogen chloride to acetylene is 1.1:1.

[0052] The remaining steps and parameters are the same.

[0053] Example 5

[0054] Different from Example 3, in step (2), the temperature of the preheated mixed gas is 100 °C, and the ratio of the front stage to the back stage is 0.8:1.

[0055] The remaining steps and parameters are the same.

[0056] Comparative Example 1

[0057] The difference between this comparative example and Example 3 is only that a single converter is used for operation, and the space velocity is halved to 22.5 h -1 . The remaining steps and parameters are the same.

[0058] Comparative Example 2

[0059] The difference between this comparative example and Example 3 is only that the acetylene space velocity is 30 h -1 . The remaining steps and parameters are the same.

[0060] Comparative Example 3

[0061] The difference between this comparative example and Example 3 is only that the acetylene space velocity is 60 h -1 . The remaining steps and parameters are the same.

[0062] Comparative Example 4

[0063] The difference between this comparative example and Example 3 is only that the outlet of the front-stage acetylene main pipe is controlled at 5%. The remaining steps and parameters are the same.

[0064] Comparative Example 5

[0065] The difference between this comparative example and Example 3 is only that the outlet of the front-stage acetylene main pipe is controlled at 25%. The rest of the steps and parameters are the same.

[0066] Comparative Example 6

[0067] The difference between this comparative example and Example 3 is only that the outlet of the back-stage acetylene main pipe is controlled at 3%. The rest of the steps and parameters are the same.

[0068] Comparative Example 7

[0069] The difference between this comparative example and Example 3 is only that the outlet of the back-stage acetylene main pipe is controlled at 7%. The rest of the steps and parameters are the same.

[0070] Comparative Example 8

[0071] The difference between this comparative example and Example 3 is only that a gold trichloride catalyst with a content of 0.5‰ is used. The rest of the steps and parameters are the same.

[0072] Comparative Example 9

[0073] The difference between this comparative example and Example 3 is only that a gold trichloride catalyst with a content of 2.5‰ is used. The rest of the steps and parameters are the same.

[0074] Table 1

[0075]

[0076] Table 1 compares the technical effects of the catalyst service life, production, cost, and by-product generation amount of Examples 1-5 and Comparative Examples 1-9, and it can be known that:

[0077] (1) By comparing Examples 1-5, it can be obtained that the vinyl chloride monomer prepared by the preparation method of the present invention shows a lower production cost;

[0078] (2) By comparing Example 3 with Comparative Example 1, it can be obtained that the production cost of vinyl chloride monomer by using the operation mode of high space velocity front-stage and back-stage in series is lower than that of low space velocity single-stage operation. This is mainly because the series operation of the front-stage and back-stage can make the space velocity of the fresh gold-based catalyst in the back-stage lower, and the raw material gas is more easily converted; the front-stage adsorbs most of the harmful substances and the vinyl chloride inert gas entering the back-stage makes the bed temperature control more stable, extending the service life of the gold-based catalyst in the back-stage and the entire life cycle, resulting in cost reduction;

[0079] (3) By comparing Comparative Examples 2-3 with Example 3, it can be obtained that the acetylene space velocity is 40-50h -1Outside this range, the production cost of vinyl chloride monomer increases. This is mainly because when the acetylene space velocity is too high, the catalyst life is too short and the vinyl chloride output is low; when the acetylene space velocity is too low, although the catalyst life is extended, the output of vinyl chloride monomer per converter is reduced.

[0080] (4) Comparing Comparative Examples 4-5 with Example 3, it is found that when the outlet control of the front-stage acetylene main pipe is outside the range of 10-20%, the production cost of vinyl chloride monomer increases. This is mainly because when the outlet control of the front-stage acetylene main pipe is too high, the life of the back-stage catalyst is significantly reduced, and then the life of the catalyst throughout its life cycle is shortened, resulting in a reduction in output; when the outlet control of the front-stage acetylene main pipe is too low, the life of the front-stage catalyst is significantly reduced, and then the life of the catalyst throughout its life cycle is shortened, resulting in a reduction in output.

[0081] (5) Comparing Comparative Examples 6-7 with Example 3, it is found that when the outlet control of the back-stage acetylene main pipe is outside the range of 4-6%, the production cost of vinyl chloride monomer increases. This is mainly because when the outlet control of the back-stage acetylene main pipe is too high, although the increase in output reduces the production cost, due to the high content of unreacted raw gas in the crude vinyl chloride, the subsequent treatment cost increases significantly, resulting in an increase in the overall production cost; when the outlet control of the back-stage acetylene main pipe is too low, the life of the catalyst throughout its life cycle is shortened, resulting in a significant reduction in output and an increase in production cost.

[0082] (6) Comparing Comparative Examples 8-9 with Example 3, it is found that when the loading of the gold-based catalyst is outside the range of 1-2‰, the production cost of vinyl chloride monomer increases. This is mainly because when the catalyst loading is too high, although the increase in output reduces the production cost, the cost of the catalyst increases significantly, resulting in an increase in the overall production cost; when the catalyst loading is too low, the life of the catalyst throughout its life cycle is shortened, resulting in a significant reduction in output and an increase in production cost.

[0083] 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 protection scope of the present invention. Any simple modification or equivalent replacement of the technical solution of the present invention by those of ordinary skill in the art shall not depart from the essence and scope of the technical solution of the present invention.

Claims

1. A method for preparing vinyl chloride by catalytic hydrochlorination of acetylene with low cost and without mercury, characterized in that, It includes the following steps: (1) Mix hydrogen chloride and acetylene to obtain a mixed gas; (2) After preheating the mixed gas, introduce it into a converter equipped with a catalyst for vinyl chloride synthesis to produce crude vinyl chloride; (3) The crude vinyl chloride is washed with water, washed with alkali, and rectified to obtain refined vinyl chloride; Among them, the acetylene space velocity passing through the converter filled with the catalyst in step (2) is 40 - 50 h -1 , the converter is a converter in which the front stage and the back stage are connected in series, and the ratio of the front stage to the back stage of the converter is 1:0.8 - 1.2; the outlet of the front-stage acetylene main pipe is controlled at 10 - 20%, and the outlet of the back-stage acetylene main pipe is controlled at 4 - 6%; the catalyst is a gold-based catalyst with a loading of 1 - 2‰, the catalyst is in the shape of flakes or columns, the particle size is 3 - 6 mm, and the bulk density is 0.46 - 0.50 g / cm 3 ; the bed temperature of the front stage is controlled at 130 - 200 °C, and the bed temperature of the back stage is controlled at 130 - 180 °C.

2. The method according to claim 1, wherein In step (1), the volume ratio of the hydrogen chloride to acetylene is 1 - 1.1:

1.

3. The method according to claim 1, wherein In step (2), the preheating temperature is 90 - 140 °C.

4. The method according to claim 1, wherein The ratio of the front stage to the back stage of the converter is 1:1; the bed temperature of the front stage is controlled at 160 - 180 °C, and the bed temperature of the back stage is controlled at 150 - 160 °C; the outlet of the acetylene main pipe of the front stage is controlled at 15%, and the outlet of the acetylene main pipe of the back stage is controlled at 5%.

5. Use of the method according to any one of claims 1 - 4 in the preparation of vinyl chloride with high purity and high conversion rate.

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