Background
At present, the plasticizer is the largest additive variety in the modern plastic industry, plays a decisive role in promoting the development of the plastic industry, particularly the polyvinyl chloride PVC industry, and has wide application in the fields of synthetic rubber, paint, adhesive, sealing material and the like. Researches show that the traditional production device for preparing the plasticizer has the advantages of long reaction time, high energy consumption, low yield per unit time, unstable product quality, high water content and high acid value of a product detection result. And the prepared o-benzene plasticizer has toxicity and carcinogenicity.
In the process of preparing the cyclohexane plasticizer by liquid phase hydrogenation of the phthalic plasticizer, phthalic acid ester can generate benzoic acid monoester and corresponding alcohol or olefin through intramolecular elimination reaction at higher temperature, DOP can be decomposed into phthalic anhydride, 2-ethylhexyl alcohol and 2-ethyl hexene by heating, the olefin can be further changed into alkane under hydrogen atmosphere, one ester bond in two ester bonds of DOP is broken to generate benzoic acid (2-ethylhexyl) ester and 2-ethyl hexene, and the 2-ethyl hexene is hydrogenated to generate 3-methylheptane. The existence of the benzoic acid monoester can reduce the performance of preparing the cyclohexane plasticizer, and the alcohols and alkanes with low boiling points can cause the cyclohexane plasticizer to generate pungent odor, reduce the flash point of the cyclohexane plasticizer and finally reduce the comprehensive performance of the cyclohexane plasticizer, so that the research on the separation and purification of products of preparing the cyclohexane plasticizer by the liquid-phase hydrogenation of the o-benzene plasticizer is developed, and the industrialization is realized.
Disclosure of Invention
The invention aims to provide a production process for preparing cyclohexane plasticizer by performing liquid phase hydrogenation on o-benzene plasticizer capable of purifying cyclohexane plasticizer, which adopts the following technical scheme:
the production process of cyclohexane plasticizer by liquid phase hydrogenation of o-benzene plasticizer includes the following steps:
1) introducing heated inert gas to the bottom of the reduced pressure distillation tower in a pulse pneumatic transmission mode;
2) and the plasticizer product enters the bottom of the reduced pressure distillation tower after being preheated, and the inlet of the plasticizer product on the reduced pressure distillation tower is higher than the inlet of the inert gas, so that the plasticizer product is mixed and heated with the rising inert gas flow in the downward flowing process, and the target product and the by-product are separated.
The invention also aims to provide a system special for the production process of the cyclohexane plasticizer by the liquid-phase hydrogenation of the o-benzene plasticizer, and the technical scheme is as follows:
the production system for preparing the cyclohexane plasticizer by liquid-phase hydrogenation of the o-benzene plasticizer comprises a primary reduced pressure distillation tower and a secondary reduced pressure distillation tower which are connected in series through a separator, wherein the separator comprises a sleeve communicated between the tower bottom of the primary reduced pressure distillation tower and the tower top of the secondary reduced pressure distillation tower, a central pipe with a closed upper end and an open lower end is connected in the sleeve through a spoke-shaped support frame, the top of the central pipe extends out of the upper end of the sleeve and extends into the tower bottom of the primary reduced pressure distillation tower, an air release port is arranged on the pipe wall of the extending part, an inner baffle fixed on the pipe wall of the central pipe and an outer baffle fixed on the pipe wall of the sleeve are connected in an annular space between the central pipe and the sleeve, the inner baffle and the outer baffle are both inclined downwards and suspended, the inner baffle; the tower bottom of the first-stage reduced pressure distillation tower is provided with a plasticizer product inlet below the gas release port, the tower bottom of the second-stage reduced pressure distillation tower is provided with an inert gas inlet, the inert gas inlet is connected with an inert gas heater, and the inlet of the inert gas heater is connected with a gas source device controlled by a pulse generator.
Preferably, the vent holes are inclined holes which are inclined downwards from the tube cavity of the central tube, and the vent holes are positioned between two adjacent inner baffles and close to the upper baffle.
Preferably, the relief opening is an oblique hole sloping downward from the lumen of the central tube.
Preferably, the upper end of the central tube is conically shaped with the edge of the tap extending from the circumference of the central tube.
Preferably, the central tip of the tap cone is spherical crown shaped.
Preferably, the lower end of the central tube projects from the lower end of the sleeve and is provided with a flared air-receiving opening.
The invention has the beneficial effects that:
the process and the system of the invention adopt a pulse mode to send heated inert gas to the reduced pressure distillation tower, and utilize the characteristic that the time of the inert gas is large and small to better simulate fluidization mixing heating at the bottom of the reduced pressure distillation tower, thereby realizing better mixing heating and separation and purification effects on the plasticizer product, and having better separation and purification effects.
Detailed Description
Referring to fig. 1, a schematic diagram of a production system for producing cyclohexane plasticizer by liquid phase hydrogenation of o-benzene plasticizer according to the present invention is shown, and the specific structure is as follows:
the device comprises a feeding preheater 1, a reduced pressure distillation tower 2, an extraction separation tower 3, a solvent regeneration tower 4, a light component tank 5, a heavy component tank 6, a first condenser 7, a second condenser 8, a first vacuum pump 9 and a second vacuum pump 10. The feeding preheater 1 is provided with a first feeding hole A, a first discharging hole B communicated with the first feeding hole A, a second feeding hole C and a second discharging hole D communicated with the second feeding hole C; the first condenser 7 and the second condenser 8 are respectively provided with a water inlet E, a water outlet F communicated with the water inlet E, a feed inlet G and a discharge outlet H communicated with the feed inlet G; an inert gas inlet K is formed in the bottom of the reduced pressure distillation tower 2, a heat conduction oil pipe 21 is arranged in an inner cavity of the bottom of the reduced pressure distillation tower 2 above the inert gas inlet K, and an oil inlet M and an oil outlet N of the heat conduction oil pipe 21 are both positioned outside the reduced pressure distillation tower 2; the reboiler 41 is connected to the bottom of the solvent regeneration column 4. The first discharge hole B of the feeding preheater 1 is connected to the middle part of the reduced pressure distillation tower 2, the tower bottom of the reduced pressure distillation tower 2 is connected with a distillation tower pump 22, the distillation tower pump 22 is connected to the second feed hole C of the feeding preheater 1, and the second discharge hole D of the feeding preheater 1 is divided into two branches which are respectively connected to the product tank 11 and the tower top of the reduced pressure distillation tower 2. The top of the reduced pressure distillation tower 2 is connected to the lower part of the extraction separation tower 3, the top of the extraction separation tower 3 is connected to the feed inlet G of the first condenser 7, the discharge outlet H of the first condenser 7 is connected to the light component tank 5, and the first condenser 7 and the light component tank 5 are connected to the first vacuum pump 9. The tower bottom of the extraction separation tower 3 is divided into two branches which are respectively connected to the tower top of the reduced pressure distillation tower 2 and the tower top of the solvent regeneration tower 4, the tower bottom of the solvent regeneration tower 4 is connected with a regeneration tower pump 42, the regeneration tower pump 42 is connected to the tower top of the extraction separation tower 3, the tower top of the solvent regeneration tower 4 is connected to a feed inlet G of the second condenser 8, a discharge hole H of the second condenser 8 is connected to the heavy component tank 6, and the second condenser 8 and the heavy component tank 6 are simultaneously connected to the second vacuum pump 10. The first vacuum pump 9 and the second vacuum pump 10 are both connected to the extraterrestrial region.
The vacuum distillation tower 2 includes a first vacuum distillation tower 25 and a first vacuum distillation tower 23 connected in series via a separator 24. Referring to fig. 2, the separator 24 includes a sleeve 241 communicated between the bottom of the first-stage vacuum distillation tower 25 and the top of the first-stage vacuum distillation tower 23, a central tube 242 with a closed upper end and an open lower end is connected to the sleeve 241 through a spoke-shaped support frame, the top of the central tube 242 extends from the upper end of the sleeve 241 and into the bottom of the first-stage vacuum distillation tower 25, and the wall of the extending part is provided with an air release opening 243, an inner baffle 244 fixed on the wall of the central tube 242 and an outer baffle 245 fixed on the wall of the sleeve 241 are connected to the annular space between the central tube 242 and the sleeve 241, the inner baffle 244 and the outer baffle 245 are both suspended in a downward inclined manner, the inner baffle 244 and the outer baffle 245 are alternately distributed from top to bottom, and a vent hole 246 located; the tower bottom of the first-stage reduced pressure distillation tower 25 is provided with a plasticizer product inlet positioned below the air release port 243, the tower bottom of the first-stage reduced pressure distillation tower 23 is provided with an inert gas inlet, the inert gas inlet is connected with an inert gas heater 27, and the inlet of the inert gas heater 27 is connected with a gas source device 26 controlled by a pulse generator.
The air release hole 243 and the air vent hole 246 are inclined holes inclined downward from the lumen of the central tube 242, and the air vent hole 246 is located between two adjacent inner baffle plates 244 at a position near the upper one. The upper end of the central tube 242 is conically tapered with the edge of the taper extending from the periphery of the central tube 242. The central tip of the shunting cone is in a spherical crown shape. The lower end of the center tube 242 protrudes from the lower end of the sleeve 241 and is provided with a flared air-receiving opening.
The production process comprises the following steps:
(1) introducing heated N2 gas to the bottom of the reduced pressure distillation tower 2 in a pulse pneumatic conveying mode, introducing heat conduction oil into a heat conduction oil pipe 21, adding an extraction solvent N, N-Dimethylacetamide (DMAC) into the extraction separation tower 3, starting a reboiler 41 of a solvent regeneration tower 4, and introducing circulating water into a first condenser 7 and a second condenser 8 respectively; the operating temperature of the reduced pressure distillation tower 2 is controlled to be 260 ℃, the operating temperature of the extraction separation tower 3 is controlled to be 140 ℃, and the operating temperature of the solvent regeneration tower 4 is controlled to be 200 ℃; the interior of a reduced pressure distillation tower 2, an extraction separation tower 3, a solvent regeneration tower 4, a light component tank 5, a heavy component tank 6, a first condenser 7 and a second condenser 8 are all kept in a negative pressure state, and the pressure is-0.08 MPa;
(2) sampling and analyzing a hydrogenation product, detecting the conversion rate of a raw material DOP and the selectivity and yield of a product DEHCH by using gas chromatography, confirming that the conversion rate of the DOP reaches 100%, carrying out settling separation, allowing the hydrogenation product without the catalyst to enter a feeding preheater 1 from a first feeding hole A of the feeding preheater 1, preheating, then allowing the hydrogenation product to enter a reduced pressure distillation tower 2 from a first discharging hole B, carrying out mass transfer heating on a downward flowing and rising N2 gas flow, and separating a target product from a byproduct;
(3) the target product enters the bottom of the reduced pressure distillation tower 2, is extracted from the bottom of the tower and is sent to a second feed inlet C through a distillation tower pump 22 to enter a feed preheater 1 to exchange heat with the hydrogenation product, the target product after heat exchange is detected to be qualified and is sent to a product tank 11, and if the target product is not qualified, the target product is sent to the top of the reduced pressure distillation tower 2 to enter the reduced pressure distillation tower 2 again for distillation treatment; the by-product enters the extraction separation tower 3 along with the tower top N2 gas of the reduced pressure distillation tower 2, and after being extracted and separated by an extraction solvent N, N-Dimethylacetamide (DMAC) in the extraction separation tower 3, light components and heavy components in the by-product are separated;
(4) the light components enter a first condenser 7 along with part of N2 gas from the top of the extraction separation tower 3, the light components enter a light component tank 5 after being condensed by circulating water introduced into the first condenser 7, and N2 gas is pumped out by a first vacuum pump 9 as non-condensable gas and is sent to an out-of-range area; heavy components and N, N-Dimethylacetamide (DMAC) enter a solvent regeneration tower 4 from the bottom of an extraction separation tower 3, the heavy components and the N, N-Dimethylacetamide (DMAC) are separated and then enter a second condenser 8 along with part of N2 gas, the heavy components and the N, N-Dimethylacetamide (DMAC) are condensed and liquefied by circulating water introduced into the second condenser 8 and then enter a heavy component tank 6, and N2 gas serving as non-condensable gas is pumped out by a second vacuum pump 10 and sent to an out-of-range area; the N, N-dimethylacetamide DMAC is regenerated and returned to the top of the extraction separation tower 3 through a regeneration tower pump 42, the N, N-dimethylacetamide DMAC is returned to the top of the reduced pressure distillation tower 2 from the bottom of the extraction separation tower 3 for recycling, and the N, N-dimethylacetamide DMAC and the byproduct enter the extraction separation tower 3 together with the N2 gas at the top of the reduced pressure distillation tower 2 after being treated by the reduced pressure distillation tower 2;
wherein, the light component refers to low boiling point alcohol and alkane, and the heavy component refers to cyclohexane monoacid ester.
The above description is only about the preferred embodiment of the present invention, but it should not be understood as limiting the claims, and the present invention may be modified in other structures, not limited to the above structures. In general, all changes which come within the scope of the invention are intended to be embraced therein.