CN1292369A - Preparation method of high-purity cyclopentadiene - Google Patents

Abstract

The invention is a preparation method of high-purity cyclopentadiene. The crude dicyclopentadiene is mixed with the batching gas, and after preheating, it decomposes and reacts instantly in the gas phase depolymerization tower, and then enters a specially designed gas phase depolymerization product fractionation tower for separation and purification. The upper part of the tower is a constant temperature section, and the lower part is a rectification section. The separated and purified product is condensed to obtain high-purity cyclopentadiene. The invention has the advantages of fast reaction speed, high production capacity, saving energy consumption, reducing coking, prolonging the service life of equipment, etc., and improves the yield of cyclopentadiene, which can reach more than 97%, and the final cyclopentadiene product has a purity of 98% %above.

Description

Preparation method of high-purity cyclopentadiene

The invention relates to a method for preparing high-purity cyclopentadiene, in particular to a method for preparing high-purity cyclopentadiene obtained by mixing crude dicyclopentadiene obtained from the C5 secondary liquid of ethylene produced from petroleum cracking with steam and other ingredients. Process for the preparation of pure cyclopentadiene.

Cyclopentadiene (abbreviated as CPD) has a wide range of uses, such as the synthesis of pesticides, plastics, resins, rubber, phenocene compounds, and the production of anti-shock and anti-drying agents for liquid fuels that require a large amount of high-purity CPD. At present, manufacturers of CPD in my country generally adopt the method of directly heating dicyclopentadiene (DCPD for short) to distill and decompose (liquid phase depolymerization method) to decompose DCPD into CPD. However, due to the huge production equipment and slow decomposition speed of this process, Energy consumption and production process are long and economically uneconomical. There are also a few manufacturers who use the method of tubular gas phase depolymerization to decompose DCPD into CPD. Compared with the liquid phase depolymerization method, this process can save energy by 50%, increase the rate by 4 times, and the yield of CPD has also increased. However, this method has a comparative The biggest disadvantage is that it is easy to coke in the depolymerization tube, which affects the thermal conductivity. In addition, frequent decoking will also shorten the service life of the depolymerization tube.

Japan's Sumitomo Company discloses a method for preparing CPD (EP509445). This method uses DCPD to mix with ingredients and steam to depolymerize, and the concentration of CPD in the product can reach more than 96%. But this method has adopted two constant temperature condensers when the collection of depolymerization product CPD and concentration, the temperature of one constant temperature condenser is 60 ℃, to get rid of undecomposed DCPD and other polymers and water in the raw material, the other Only the temperature of the constant temperature condenser is 20°C to condense the CPD, and the efficiency of the recovery and enrichment system is only 78%.

Chinese patent (CN1150942A) discloses a method for preparing high-purity cyclopentadiene. Through a special device, a liquid trap is added between the ordinary column and the column, so that the vapor phase flows from the bottom to the bottom of the steam channel. and the liquid phase flowing down from above cannot flow back to the steam channel, so that the two processes of decomposition and purification can be carried out simultaneously and continuously in the same device, achieving the purpose of reducing the formation of polymers and increasing the yield of CPD. The concentration of CPD product is greater than 96%, and the yield is greater than 80%.

The purpose of this invention is to provide a kind of method for preparing high-purity cyclopentadiene, the fractionating tower of the reclaiming concentrated part of CPD is through special design, and the top of fractionating tower is designed a constant temperature section to strengthen internal reflux, and the bottom of fractionating tower is In the rectification section, the concentration of CPD discharged from the top of the tower is above 98%, the separation efficiency of the tower is above 95%, and the yield of CPD in the whole process is above 97%.

The present invention is achieved in this way: the preparation method of the high-purity cyclopentadiene of the present invention is to introduce crude DCPD and water vapor or nitrogen or toluene into the mixing tower 1 for mixing, and the mixing temperature in the mixing tower 1 is 98 to 120°C The ratio of water vapor or nitrogen or toluene and other ingredients to DCPD is (0.8-1.4): 1 (weight ratio), and the mixed gas is discharged from the top of the mixing tower 1 in the form of an azeotrope , enter the raw material preheater 2 from the bottom of the raw material preheater 2 for preheating, the temperature at the outlet of the raw material preheater 2 is 190-280°C, and the preheated raw material mixture gas is discharged from the top of the raw material preheater 2, Enter the gas phase depolymerization tower 3 from the upper part of the gas phase depolymerization tower 3, undergo instantaneous decomposition reaction, the reaction temperature is 300-350°C, the residence time is 0.6-1.4 seconds, and the depolymerization products after cracking enter the gas phase depolymerization Product fractionation tower 4 is separated, and the top of gas phase depolymerization product separation tower 4 is a constant temperature section 14, and the temperature of constant temperature section 14 is controlled at 30～50 ℃, and the bottom of gas phase depolymerization product fractionation tower 4 is rectification section 15, and the whole gas phase The temperature of the depolymerization product fractionation tower 4 is controlled at 45-60°C. The number of trays in the rectifying section 15 is 5-10. The separated product is condensed by the gas-phase depolymerization product condenser 5 to obtain high-purity liquid CPD.

The present invention will be described in detail below in conjunction with the accompanying drawings.

Fig. 1 is a process flow diagram of the present invention.

Fig. 2 is a structural schematic diagram of a gas phase depolymerization product fractionation tower of the present invention.

As shown in Figure 1 and Figure 2, crude DCPD is obtained from the C5 secondary liquid of petroleum cracking to ethylene through several crude processes, and the content of DCPD is more than 80%. The crude DCPD enters the middle of the mixing tower 1 from 6, and the ingredient gas such as water vapor enters the mixing tower 1 from the bottom of the mixing tower 1 through 7, and the ingredients such as DCPD and water vapor are fully mixed in the mixing tower 1. The ratio of ingredients such as water vapor to DCPD is (0.8-1.4): 1 (weight ratio). The temperature of the mixing tower 1 is controlled at 98-120°C, and it can be kept warm with a steam jacket. The mixed DCPD and water vapor and other ingredient gases are discharged from the top of the mixing tower 1 in the form of azeotrope. The temperature at the top of the mixing tower 1 should be controlled at about 120°C.

In addition to water vapor, other inert gases such as nitrogen, carbon dioxide, benzene or toluene can also be used as the batching gas. However, using water vapor as a batching gas has the following advantages: water has a large heat capacity, which is beneficial to raising the temperature of raw material gas DCPD and accelerating heat transfer; water is easy to separate from raw material gas DCPD and product CPD, and is easy to use; water can also form an azeotrope with DCPD, And enter the reaction zone in the form of DCPD·H ₂ O, the dispersion is uniform and the vaporization temperature is low, only 98°C. The weight ratio of the ingredients H ₂ O and DCPD can be between (0.8-1.4):1.

The mixed gas discharged from the top of the mixing tower 1 enters the raw material preheater 2 from the bottom of the raw material preheater 2 for preheating through 8, and the mixed gas is heated from 120°C to about 200°C in the raw material preheater 2. The raw material preheater 2 is a jacketed shell and tube preheater, and the heat transfer medium can be water vapor or heat transfer oil.

The mixed gas is discharged from the upper part of the raw material preheater 2, enters the gas phase depolymerization tower 3 from the top of the gas phase depolymerization tower 3 through 9, and reacts instantaneously. The reaction temperature in the gas phase depolymerization tower 3 is 300-350°C. The heating type of the gas phase depolymerization tower 3 can be electric heating or flue gas heating. The residence time of the mixed gas in the gas phase depolymerization tower 3 is 0.6-1.4 seconds.

The reaction temperature of the mixed gas in the gas-phase depolymerization tower is selected between 300 and 350°C. If the reaction temperature is too high, coking will easily occur; if the reaction temperature is too low, the reaction speed will drop significantly and affect the CPD yield. The residence time of the mixed gas in the gas-phase depolymerization tower is selected to be 0.6-1.4 seconds. If the residence time is too short, the CPD yield will drop more; if the residence time is too long, the CPD yield will also decrease. There will be a significant increase, and on the contrary, side reactions will increase, especially the increase in coking will affect the service life of the depolymerization tower.

After the reacted depolymerization product is discharged from the bottom of the gas phase depolymerization tower 3, it enters the rectification section 15 in the middle of the gas phase depolymerization product fractionation tower 4 through 10. The gas-phase depolymerization product fractionation tower 4 is a specially designed fractionation tower, and a constant temperature section 14 is designed on the top of the fractionation tower 4 to strengthen internal reflux. The temperature of the constant temperature section 14 is controlled at 30-60°C. If the temperature of this constant temperature section is too low, then CPD will not be effectively discharged from the top of the fractionation tower 4, but will be discharged from the bottom 12 of the gas phase depolymerization product fractionation tower 4 together with the oil and water phase, reducing the CPD yield; and the constant temperature section If the temperature is too high, the separation efficiency will decrease and the product quality will be affected. The lower part of the fractionation tower 4 is a rectification section 15, the temperature of the rectification section 15 is controlled at 45-60° C., and the number of trays of the rectification section 15 is 5-10. This special design is to prevent excessive polymerization of CPD due to too long residence time when the reflux ratio is too high; it can also avoid the purpose of effectively separating CPD from H2 _O and a small amount of unreacted DCPD from other impurities due to too fast distillation .

In the gas phase depolymerization product fractionation tower 4, the depolymerization product CPD is separated from impurities such as the ingredient H ₂ O and a small amount of unreacted DCPD and CPD copolymer dimer, and the separation efficiency is greater than 95%. The CPD discharged from the top of the gas-phase depolymerization product fractionation tower 4 is condensed through the gas-phase depolymerization product condenser 5 through 11 and then discharged through 13 to obtain high-purity liquid CPD, and the CPD concentration can reach more than 98%.

What is discharged from the bottom of the gas-phase depolymerization product fractionation tower 4 through 12 is the ingredient H ₂ O and high-boiling organic impurities. The oil-water phase is separated through an oil-water separator 16, wherein the water phase can be reused as the ingredient H2O through 18, and there is still a certain amount of DCPD and CPD copolymer dimer in the oil phase, and part of the CPD can also be depolymerized and recovered through 17.

Compared with the prior art, the present invention has the following advantages: 1. The high-purity CPD is prepared by the gas phase depolymerization method, which improves the reaction speed and production capacity and saves energy consumption compared with the liquid phase depolymerization method. 2. Adding water vapor to the gas phase depolymerization raw material gas as a batching gas can reduce coking, promote heat conduction, easily separate from the product, prolong the service life of the equipment, and increase the yield of CPD products. 3. The gas-phase depolymerization products are separated by a specially designed fractionation tower, which increases the separation efficiency. The separation efficiency reaches more than 95%, and the highest yield can reach more than 97%.

The following are specific examples of the present invention, and the examples are further elaborations of the present invention, rather than limitation of the present invention.

Example 1:

97 grams of crude DCPD per hour, the DCPD content is 94% (weight), sent into the mixing tower 1 by metering pumps, while the batching H of 138 grams per hour ₂ O enters the mixing tower 1 in the form of water vapor, H ₂ O and DCPD The proportioning ratio is 1.4:1 (by weight). The temperature of the mixing tower 1 is controlled at 120°C, the temperature of the DCPD·H ₂ O mixed gas exiting the mixing tower 1 is 120°C, preheated by the raw material preheater 2, and the DCPD·H ₂ O mixed gas exits the raw material preheater 2 The temperature is 210°C, the mixed gas enters the gas phase depolymerization tower 3, the temperature of the gas phase depolymerization tower 3 is controlled at 350°C, and the residence time of the DCPD·H ₂ O mixture in the gas phase depolymerization tower 3 is 1.4 seconds. The depolymerization product enters the gas phase depolymerization product fractionation tower 4 for fractionation, the temperature of the constant temperature section 14 in the gas phase depolymerization product fractionation tower 4 is controlled at 30°C, the temperature of the rectification section 15 is controlled at 45°C, and the number of trays in the rectification section is 10. After the fractionation, the product is discharged from the top of the gas-phase depolymerization product fractionation tower 4, and after being condensed by the gas-phase depolymerization product condenser 5, a high-concentration liquid CPD product with a CPD content of 98% is obtained. The output is 88 grams per hour, and the CPD is paid in full. rate at 97%. The high boiler oil phase is discharged from the bottom of the gas phase depolymerization product fractionation tower 4, and the recovery rate per hour is 9 grams.

Example 2:

95 grams of crude DCPD per hour, the DCPD content is 94% (weight), sent into the mixing tower 1 by metering pumps, while the batching H of 114 grams per hour ₂ O enters the mixing tower 1 in the form of water vapor, H ₂ O and DCPD The proportioning ratio is 1.3:1 (by weight). The temperature of the mixing tower 1 is controlled at 120°C, the temperature of the DCPD·H ₂ O mixed gas exiting the mixing tower 1 is 120°C, preheated by the raw material preheater 2, and the DCPD·H ₂ O mixed gas exits the raw material preheater 2 The temperature is 280°C, the mixed gas enters the gas phase depolymerization tower 3, the temperature of the gas phase depolymerization tower 3 is controlled at 350°C, and the residence time of the DCPD·H ₂ O mixture in the gas phase depolymerization tower 3 is 1.0 second. The depolymerization product enters the gas phase depolymerization product fractionation tower 4 for fractionation, the temperature of the constant temperature section 14 in the gas phase depolymerization product fractionation tower 4 is controlled at 35°C, the temperature of the rectification section 15 is controlled at 60°C, and the number of trays in the rectification section is 5. After the fractionation, the product is discharged from the top of the gas-phase depolymerization product fractionation tower 4, and after being condensed by the gas-phase depolymerization product condenser 5, a high-concentration liquid CPD product with a CPD content of 98% is obtained. The output is 85 grams per hour, and the CPD is paid in full. The rate is above 98%. The high boiler oil phase is discharged from the bottom of the gas phase depolymerization product fractionation tower 4, and the recovery rate per hour is 10 grams.

Example 3:

The thick DCPD of 115 grams per hour, DCPD content is 81% (weight), is sent into mixing tower 1 by metering pump, simultaneously the batching H of 120 grams per hour ₂ O enters mixing tower 1 with the form of steam, H ₂ O and The ratio of DCPD is 1.3:1 (by weight). The temperature of the mixing tower 1 is controlled at 120°C, the temperature of the DCPD·H ₂ O mixed gas exiting the mixing tower 1 is 120°C, preheated by the raw material preheater 2, and the DCPD·H ₂ O mixed gas exits the raw material preheater 2 The temperature is 193°C, the mixed gas enters the gas phase depolymerization tower 3, the temperature of the gas phase depolymerization tower 3 is controlled at 350°C, and the residence time of the DCPD·H ₂ O mixture in the gas phase depolymerization tower 3 is 1.0 second. The depolymerization product enters the gas phase depolymerization product fractionation tower 4 for fractionation, the temperature of the constant temperature section 14 in the gas phase depolymerization product fractionation tower 4 is controlled at 30°C, the temperature of the rectification section 15 is controlled at 45°C, and the number of trays in the rectification section is 10. After the fractionation, the product is discharged from the top of the gas-phase depolymerization product fractionation tower 4, and after being condensed by the gas-phase depolymerization product condenser 5, a high-concentration liquid CPD product with a CPD content of 98% is obtained. The output is 93 grams per hour, and the CPD is paid in full. The rate is above 98%. The high boiler oil phase is discharged from the bottom of the gas phase depolymerization product fractionation tower 4, and the recovery rate per hour is 21 grams.

Example 4:

100 grams of crude DCPD per hour, with a DCPD content of 85% (weight), is sent into the mixing tower 1 by a metering pump, while 110 grams of ingredients per hour H ₂ O enters the mixing tower 1 in the form of water vapor, H ₂ O and DCPD The proportioning ratio is 1.2:1 (weight ratio). The temperature of the mixing tower 1 is controlled at 98°C, the temperature of the DCPD·H ₂ O mixed gas exiting the mixing tower 1 is 98°C, preheated by the raw material preheater 2, and the DCPD·H ₂ O mixed gas exits the raw material preheater 2 The temperature is 190°C, the mixed gas enters the gas phase depolymerization tower 3, the temperature of the gas phase depolymerization tower 3 is controlled at 350°C, and the residence time of the DCPD·H ₂ O mixture in the gas phase depolymerization tower 3 is 1.1 seconds. The depolymerization product enters the gas phase depolymerization product fractionation tower 4 for fractionation, the temperature of the constant temperature section 14 in the gas phase depolymerization product fractionation tower 4 is controlled at 50°C, the temperature of the rectification section 15 is controlled at 45°C, and the number of trays in the rectification section is 10. After the fractionation, the product is discharged from the top of the gas-phase depolymerization product fractionation tower 4, and after being condensed by the gas-phase depolymerization product condenser 5, a high-concentration liquid CPD product with a CPD content of 98% is obtained. The output is 92 grams per hour, and the CPD is paid in full. The rate is above 98%. The high boiler oil phase is discharged from the bottom of the gas phase depolymerization product fractionation tower 4, and the recovery rate per hour is 8 grams.

Example 5:

120 grams of crude DCPD per hour, the DCPD content is 89% (weight), sent into the mixing tower 1 by metering pumps, while the batching H of 88 grams per hour ₂ O enters the mixing tower 1 in the form of water vapor, H ₂ O and DCPD The proportioning ratio is 0.8:1 (weight ratio). The temperature of the mixing tower 1 is controlled at 120°C, the temperature of the DCPD·H ₂ O mixed gas exiting the mixing tower 1 is 120°C, preheated by the raw material preheater 2, and the DCPD·H ₂ O mixed gas exits the raw material preheater 2 The temperature is 250°C, the mixed gas enters the gas phase depolymerization tower 3, the temperature of the gas phase depolymerization tower 3 is controlled at 300°C, and the residence time of the DCPD·H ₂ O mixture in the gas phase depolymerization tower 3 is 0.6 seconds. The depolymerization product enters the gas phase depolymerization product fractionation tower 4 for fractionation, the temperature of the constant temperature section 14 in the gas phase depolymerization product fractionation tower 4 is controlled at 30°C, the temperature of the rectification section 15 is controlled at 45°C, and the number of trays in the rectification section is 10. After the fractionation, the product is discharged from the top of the gas-phase depolymerization product fractionation tower 4, and after being condensed by the gas-phase depolymerization product condenser 5, a high-concentration liquid CPD product with a CPD content of 98% is obtained. The output is 102 grams per hour, and the CPD is paid in full The rate is above 98%. The high boiler oil phase is discharged from the bottom of the gas phase depolymerization product fractionation tower 4, and the recovery rate per hour is 12 grams.

Claims (7)

1, a kind of preparation method of high-purity cyclopentadiene, it is characterized in that: after thick dicyclopentadiene (DCPD) and batching air water steam or nitrogen or toluene enter mixing column [1] mixing, incoming stock preheater [2] preheating, after the moment decomposition reaction, enter gas phase depolymerization product separation column [4] at gas phase cleavage column [3] then and separate, by obtaining the liquid cyclopentadiene (CPD) of high purity after gas phase depolymerization product condenser [5] condensation.

2, preparation method according to claim 1 is characterized in that entering the batching gas of mixing column [1] and the proportioning of dicyclopentadiene is (0.8～1.4): 1 (weight ratio), described batching gas are water vapor or nitrogen or toluene.

3, preparation method according to claim 1 and 2 is characterized in that dicyclopentadiene and batching gas blended temperature in mixing column [1] are 98～120 ℃.

4, preparation method according to claim 1 is characterized in that the temperature in the feed preheater [2] is 190～280 ℃.

5, preparation method according to claim 1 is characterized in that the temperature of reaction of material mixed gas in gas phase cleavage column [3] is 300～350 ℃, and the residence time is 0.6～1.4 second.

6, preparation method according to claim 1, the top that it is characterized in that described gas phase depolymerization product separation column [4] is a constant temperature zone [14], the temperature of constant temperature zone [14] is controlled at 30～50 ℃, the bottom of gas phase depolymerization product separation column [4] is rectifying section [15], and the temperature of rectifying section [15] is controlled at 45～60 ℃.

7, preparation method according to claim 6 is characterized in that the stage number of the interior rectifying section of described gas phase depolymerization product separation column [4] [15] is 5～10.

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