RU2228324C1 - Norbornadiene preparation method - Google Patents

Abstract

FIELD: organic synthesis. SUBSTANCE: norbornadiene, or bicyclo[2.2.1] hepta-2,5-diene, which can be used in production of high- efficiency insecticides, resins, polymer materials, and also as base material for high-density, energy-rich and high- calorie fuels, is prepared by reaction of cyclopentadiene or dicyclopentadiene with acetylene in a continuous liquid-phase process in presence of solvent at 200-240 C and pressure above 25 atm, wherein cyclopentadiene-to- acetylene molar ratio is 1:(1-1.8) and solvent is preliminarily saturated with acetylene. Reaction mixture is then subjected to rectification to norbornadiene, whereas solvent is recycled. Method is characterized by using dimethylformamide or N-methylpyrrolidone as solvent and preliminary dissolution of dicyclopentadiene followed by saturation of resulting solution with acetylene at 15-20 C and atmospheric pressure. After that, reaction mixture is passed into reactor upwards and temperature of mixture coming out of the reactor is lowered to 20-30 C and pressure is lowered below its atmospheric value using for this damping damper-throttling device, top part of which receives nitrogen at pressure equal to that in norbornadiene synthesis unit. EFFECT: improved technology enabling implementation of the method in industrial scale. 1 dwg, 1 tbl, 12 ex

Description

The invention relates to petrochemical synthesis, and in particular to a method for producing norbornadiene (NBD) or bicyclo [2.2.1] heptadiene-2.5, which can be used to obtain highly effective insecticides, resins, polymeric materials, and also as a basis for high-density, energy-intensive and high-calorie fuels.

There is a method of producing NBD by the diene synthesis reaction between cyclopentadiene (CPD) or its dimeric form - dicyclopentadiene (DCPD) and acetylene (MA Glikin and others. Phlegmatization of acetylene by cyclopentadiene. "Petrochemistry", V1, 1966, No. 1, p. 101, p. 101 )

The reaction is carried out in the gas phase at a temperature of 340 ° C and a pressure of 6-13 atm in the presence of a phlegmatizer, which reduces the likelihood of explosive decomposition of acetylene. Nitrogen, isopropane, cyclopentadiene are used as a phlegmatizer. However, this does not exclude the possibility of explosive decomposition of acetylene located in the gas phase at a pressure above the limiting pressure of explosive decay, which is 1.4 atm. In addition, all gas-phase versions of the process at elevated temperatures are accompanied by grinding of the reactor and periodic (after 20-60 hours) shutdown for burning coke with atmospheric oxygen at 500-550 ° C.

There is also a method of producing norbornadiene by the interaction of CPD or DCPD with acetylene in the gas phase at a temperature of 370-380 ° C and a pressure of 2.8-3 atm in the presence of a water vapor phlegmatizer with a ratio of CPD: acetylene: water equal to 1: (1.05- 1.1) :( 1-2) (ed. St. USSR No. 1004334, class C 07 C 13/39).

The main disadvantage of this method is the explosiveness of the process carried out at elevated pressure and temperature in the gas phase, where explosive decomposition of acetylene is possible. In addition, work with acetylene in the explosive area significantly complicates the technological design of the process, because the strength of all apparatuses and pipelines in this case, in accordance with the requirements for acetylene production, must correspond to 200 atm. At the same time, the diameter of pipelines and the speed of movement of acetylene along them are significantly limited; installation of explosive membranes and flame arresters is required. The need for periodic burning of resins leads to a constant violation of the synthesis regime of NBD and makes the installation more difficult to operate.

Closest to the claimed is a method for producing NBD by the interaction of CPD or DCPD with acetylene in the liquid phase, tested both in laboratory conditions and in a pilot plant. This method increases the explosion safety of the process in comparison with the process in the gas phase (V. M. Smagin et al. Liquid-phase production of norbornadiene from cyclopentadiene and acetylene. Chemical Industry, 1993, No. 6, pp. 25-26). The process is carried out in the liquid phase in a coil-type reactor under continuous operation in the presence of a solvent of dimethylacetamide or dimethyl sulfoxide at a temperature of 220-230 ° C and a pressure of 27-30 atm, with a molar ratio of CPD: acetylene equal to 1: (1.1-1.3 ) (in laboratory conditions) or at a temperature of 225-235 ° С, a pressure of 28-35 atm with a molar ratio of CPD: acetylene equal to 1: (1.5-3.5) (in the experimental setup), with preliminary saturation of the solvent with acetylene and subsequent rectification of the reaction mass with the release of norbornadiene.

The disadvantage of the prototype is that in the description of the method there is no solution to a fundamental technological issue. Although carrying out the process in the liquid phase significantly increases the explosion safety of the process compared to carrying out the process in the gas phase, there is still a danger of explosive decomposition of acetylene, because an acetylene-containing phase may form in the system during depressurization to atmospheric pressure after the reactor. The disadvantages of the method also include the use of dimethylacetamide and dimethyl sulfoxide as solvents. The use of these solvents is difficult due to the complexity of the system for their regeneration due to the difficulty of separating them from the reaction products.

The objective of the invention is the creation of a more technologically advanced and explosion-proof as compared to the prototype process for obtaining NBD, feasible on an industrial scale.

The proposed method for producing NBD consists in the interaction of the CPD or DCPD with acetylene under continuous conditions in the reactor in the liquid phase in the presence of a solvent at a temperature of 200-240 ° C, pressure above 25 atm, with a molar ratio of CPD: acetylene equal to 1: (1-1 , 8), with preliminary saturation of the solvent with acetylene and subsequent rectification of the reaction mixture with the release of NBD and recycling of the solvent. The proposed method is characterized in that dimethylformamide (DMF) or N-methylpyrrolidone is used as a solvent, in which DCPD is first dissolved and then the resulting solution is saturated with acetylene at a temperature of 15-20 ° C and atmospheric pressure, after which the reaction mass is fed into the reactor from below up, followed by lowering the temperature after leaving the reactor to 20-30 ° C and lowering the pressure to atmospheric, using a damper-throttling device, to the upper part of which nitrogen is supplied with a pressure equal to the working pressure on the syn node eza NBD.

It should be noted that at an elevated temperature (above 170 ° C), DCPD monomerizes in the CPD and the CPD enters into the reaction of interaction with acetylene. Due to the fact that the reaction is reversible, as the temperature decreases, reverse dimerization of the unreacted CPP occurs.

The solvents used in the process DMF and N-methylpyrrolidone are available and are easier to separate from the reaction products during regeneration.

To obtain a BNP, a coil-type reactor with a horizontal pipe arrangement is used, in which the liquid moves from the bottom up, which eliminates the formation of gas voids. Because at a temperature of synthesis of NBD of 200-240 ° C, the partial pressure of acetylene is 17-25 atm, then when throttling this solution, it can transfer to the gas phase, which can lead to an explosion hazard of this operation. Therefore, to ensure explosion safety, the reaction mass after the reactor is cooled to a temperature of 20-30 ° C, at which the partial pressure of acetylene decreases to a pressure of less than 1.1 atm, the solution becomes explosion-proof. After cooling, the reaction mass enters a damper-throttling device, which is a column type apparatus, at the outlet of which there is a control valve. Nitrogen is supplied to the upper part of the apparatus with a pressure equal to the working one on the NBD synthesis unit. This excludes the possibility of the formation of a gas acetylene-containing phase in the reactor even in case of violations of the technological regime. The control valve opens depending on the pressure in the reactor.

Unreacted CPD and DCPD together with the solvent after separation of the NDB are returned to recycling without additional rectification of the solvent. Along with it, by-products of high boiling point are returned to the recycling - the TPS trimer, formed due to the trimerization of the initial TPS, as well as the adduct of the TPS and NBD. However, continuous accumulation of the CPD trimer and the adduct of the CPD and NBD does not occur as the number of recycles increases, because at 200-240 ° C, the trimer partially undergoes reverse decomposition to the initial CPD, and the adduct of CPD and NBD is converted to NBD by the disproportionation reaction with acetylene.

In order to prevent constant accumulation of high-boiling products in the system, a part of the bottom residue (5-10 wt.%) After separation of the NBD from the reaction mass is constantly removed from the system for regeneration. After 500 hours of continuous operation, tar deposits and coking are not detected on the walls of the reactor. The solvent is regenerated by its reevaporation in a rotary-film evaporator.

For a better understanding of the invention, the drawing shows the technological scheme for obtaining NBD.

The diagram shows the positions of the following devices: capacity 1; pump 2; absorber 3; pump 4; reactor 5; cooling device 6; damper-throttling device 7; valve 8; distillation column 9; pump 10.

The initial solution of DCPD in DMF from the tank 1 by the pump 2 is fed into the upper part of the absorber 3, in which the solution is saturated with acetylene supplied countercurrently to the lower part of the absorber. The undissolved acetylene from the top of the absorber is recycled, and the acetylene-saturated solution of DCPD in DMF is pumped into the reactor 5, heated by an organic high-boiling coolant, for example, oil, where at 200-240 ° С the DCPD monomers in the CPD, which interacts with acetylene.

Then, the reaction mass through a cooling device 6 enters the damper-throttling device 7, from which through the valve 8 after depressurizing to atmospheric, the reaction mass is fed to a distillation column 9, where low-boiling by-products and BND are distilled off, which are then sent to further isolate the commodity NBD. A portion of the bottom residue (5-10 wt.%) After separation of low-boiling products and BND is removed from the installation to prevent the accumulation of soluble high-boiling products in the system, and the rest of the bottom residue containing unreacted CPD, DCPD, the trimer of CPD, the adduct of CPD and DMF are returned pump 10 into recycling. To replenish the losses, fresh DCPD and DMF are fed into the bottoms fed for recycling.

The proposed method is illustrated by a number of examples.

Example 1

In an oil-heated coil-type reactor 5 with a volume of 120 l, metering pump 4 is supplied at a speed of 180 l / h with a 7% solution of DCPD in DMF pre-saturated with acetylene in absorber 3 at a temperature of 15-20 ° C and atmospheric pressure. The solubility of acetylene is 37 cm ³ / ml DMF, which corresponds to a molar ratio of CPD: acetylene 1: 1.34. Insoluble acetylene from the top of the absorber is recycled. The reaction time is 0.66 h, the pressure in the reactor supported by the control valve 8 is 28 atm, and the temperature is 235 ° C. As a result of the synthesis, a reaction mass of the following composition is obtained, wt.%: CPD 0.62; DCPD 1.53; TPS trimer 0.31; NBD 4.14; adduct CPD and NBD 0.13; unidentified high boilers 0.13; the rest is DMF.

Then the reaction mass, passing through the cooling device 6, is cooled to a temperature of 20-30 ° C due to the supply of a cooling agent, then passes the damper-throttling device 7 and valve 8 to reduce the pressure to atmospheric. Nitrogen is supplied to the upper part of the damper-throttling device under a pressure of 28 atm. Then, the reaction mixture is fed to distillation column 9, where raw NBD is distilled off, and the bottom residue containing unreacted CPD, DCPD, CPD trimer, adduct CPD and NBD and DMF solvent, after separation of 5-10%, are returned by pump 10 to recycling. To replenish the losses, fresh DCPD and DMF are fed into the bottoms fed for recycling.

As a result of the synthesis, the conversion of the DCPD is 71%, the yield of the NDB based on the reacted CPD and DCPD is 57%, the yield of the NDC taking into account the recycling of the TPS trimer and the adduct of the CPD and NDB 61.5%.

After the subsequent rectification of raw NBD, a sample of NBD with a purity of 99.5% (bp = 89.5-90 ° C / 760 mm Hg) was isolated, the extraction of which from the reaction mixture was more than 90%.

Similarly, other examples were carried out, the results of which are given in the table.

Thus, the proposed method is more technological in comparison with the prototype, it allows to increase the explosion safety of the process. Moreover, the method can be used on an industrial scale, because the danger of explosive decomposition of acetylene is almost completely eliminated.

Claims (1)

The method of producing norbornadiene by the interaction of cyclopentadiene or dicyclopentadiene with acetylene in the reactor in the liquid phase in the presence of a solvent at a temperature of 200-240 ° C and pressure above 25 atm, with a molar ratio of cyclopentadiene: acetylene equal to 1: (1-1.8), with continuous mode with preliminary saturation of the solvent with acetylene and subsequent distillation of the reaction mixture with the release of norbornadiene and recycling of the solvent, characterized in that the solvent used is dimethylformamide or N-methylpyrrolidone, in which first, dicyclopentadiene is dissolved, and then the resulting solution is saturated with acetylene at a temperature of 15-20 ° C and atmospheric pressure, after which the reaction mass is fed into the reactor from the bottom up, followed by a decrease in temperature after leaving the reactor to 20-30 ° C and a decrease in pressure to atmospheric using a damper-throttling device, in the upper part of which nitrogen is supplied under a pressure equal to the worker on the norbornadiene synthesis unit.