CN103288585B - A kind of method of separating phenylethylene from carbon eight cut - Google Patents

Abstract

The invention discloses a kind of method of separating phenylethylene from carbon eight cut, comprise: carbon eight cut isolating vinylbenzene in extractive distillation column after extracting rectifying, adopt all or part of replacement of aqueous phase to raffinate oil as the liquid-phase reflux of described extractive distillation column internal solvent recovery zone, described aqueous phase is the return tank water bag of extracting rectifying column overhead or the free-water of the interior separation of point flow container or supplements the de-salted water added.Method of the present invention reduces the concentration of o-Xylol in extractive distillation column mutually by recirculation water, reduces solvent ratio, reduces reflux ratio, reduces vinylbenzene loss, increases turndown ratio.

Description

A kind of method of separating phenylethylene from carbon eight cut

Technical field

The present invention relates to chemical field, say further, relate to a kind of method of separating phenylethylene from carbon eight cut.

Background technology

Along with the construction of megaton ethene, from carbon eight cut pyrolysis gasoline, reclaim vinylbenzene technique, have a good application prospect and economic benefit.Because in pyrolysis gasoline carbon eight cut, the boiling point of vinylbenzene and other aromatic hydrocarbons is more or less the same, particularly vinylbenzene differs less than 1 DEG C with the boiling point of o-Xylol, and the relative volatility both time solvent-free, close to 1.0, cannot adopt conventional rectification to be separated.The method of usual employing extracting rectifying, changes o-Xylol and cinnamic relative volatility by solvent, isolates polymerization-grade vinylbenzene from pyrolysis gasoline.

Conventional process continues to use the flow process of conventional extractive distillation column as shown in Figure 1, solvent enters extractive distillation column from 5-15 block plate tower top, C8 raw material enters in the middle part of tower, stripped vapor adds from tower reactor or reboiler, overhead vapours is after condensation, part is raffinated oil backflow, and water stripping is discharge after water bag is collected.

The main purpose of extractive distillation column trim the top of column is the existence keeping solvent recuperation section liquid phase, prevents solvent from overhead loss.In common process, a large amount of o-Xylols is enriched during tower top is raffinated oil (oil phase), extractive distillation column is entered as backflow, add the content of o-Xylol in extractive distillation column internal recycle (as shown in square frame in figure), thus add o-Xylol and cinnamic separating difficulty.

Summary of the invention

For solving problems of the prior art, the invention provides a kind of method of separating phenylethylene from carbon eight cut.Reduced the concentration of o-Xylol in extractive distillation column by recirculation water mutually, reduce solvent ratio, reduce reflux ratio, reduce vinylbenzene loss, increase turndown ratio.

The object of this invention is to provide a kind of method of separating phenylethylene from carbon eight cut.

Comprise: carbon eight cut isolating vinylbenzene in extractive distillation column after extracting rectifying,

Wherein, all or part of replacement of aqueous phase is adopted to raffinate oil as the liquid-phase reflux of described extractive distillation column internal solvent recovery zone.

Described aqueous phase is the return tank water bag of extracting rectifying column overhead or the free-water of the interior separation of point flow container or supplements the de-salted water added.

The present invention is achieved through the following technical solutions: the free-water be separated by return tank water bag or point flow container or the de-salted water etc. supplementing interpolation, raffinating oil as backflow in part replacement (or all replacing) traditional extraction rectification process, as the liquid phase of solvent recuperation section, to reduce in extractive distillation column the content of the particularly o-Xylol of raffinating oil.

The operational condition of extractive distillation column can adopt common operational condition in prior art.In the present invention, extractive distillation column is preferably in negative pressure state operation, and pressure maintains 10-15KPa.A.

Specifically can comprise following steps:

(1) extractive distillation column operates in negative pressure state, and pressure maintains 10-15KPa.A;

(2) extraction solvent enters extractive distillation column from tower top 5-15 block plate;

(3) C8 cut enters from appropriate location in the middle part of tower;

(4) stripped vapor is added in tower reactor or reboiler;

(5) overhead extraction uses the water bag on return tank, or gun barrel or decanting vessel etc., is separated and raffinates oil and water;

(6) oil-containing water or fresh deionized water, partly or entirely replaces backflow of raffinating oil;

(7) tower top obtains product of raffinating oil;

(8) obtain at the bottom of tower containing cinnamic rich solvent.

Effect of the present invention is: the concentration being reduced o-Xylol in extractive distillation column by recirculation water mutually, and the method has the following advantages:

1. can reduce the content of raffinating oil in extractive distillation column, particularly decrease the content of o-Xylol.Containing vinylbenzene 35wt% in certain pyrolysis gasoline composition, o-Xylol 15%, reflux ratio 0.55, vinylbenzene in tower: o-Xylol=1.25: 1; According to whole water phase backflow, vinylbenzene in tower: o-Xylol=2.3: 1.

2. traditional oil phase reflow method is compared, and whole water phase or some aqueous phase backflow can reduce solvent ratio;

3. traditional oil phase reflow method is compared, and whole water phase or some aqueous phase backflow can reduce vinylbenzene loss;

4. can reduce reflux ratio, traditional oil phase reflow method reflux ratio is at about 0.9-1.2, and adopting whole water phase to reflux can control of reflux ratio about 0.2.

5. can increase turndown ratio, traditional oil phase backflow, when quantity of reflux exceedes normal value about 1.5 times, the excess backflow of non-aromatic component can destroy full tower balance, and in bottom product, the content of o-Xylol increases, and adopts whole water phase backflow, increase quantity of reflux 2-3 doubly, bottom product quality can not be affected.

Accompanying drawing explanation

Extracting, rectifying and separating phenylethylene schema in Fig. 1 prior art

Fig. 2 extracting, rectifying and separating phenylethylene schema of the present invention

Description of reference numerals:

1-extractive distillation column; 2-reboiler; 3-condenser; 4-return tank; 5-extraction distillation solvent; 6-carbon eight raw material; 7-stripped vapor; 8-rich solvent; 9-raffinates oil; 10-liquid-phase reflux; 11-aqueous phase

Embodiment

Below in conjunction with embodiment, further illustrate the present invention.

Embodiment:

As shown in Figure 2, from the pyrolysis gasoline that cracker comes, through cut cutting, obtain C8 cut, its composition is in table 1, and temperature is 60 DEG C.Carbon eight cut enters in tower in the middle part of extractive distillation column, extraction distillation solvent enters from tower top, stripped vapor enters in tower reactor or reboiler, carbon eight cut and extraction distillation solvent carry out extracting rectifying in tower, extractive distillation column overhead vapours enters return tank after condensation, isolatedly raffinate oil as product extraction, isolated aqueous phase returns extracting rectifying top of tower as liquid-phase reflux.The rich solvent of extractive distillation column tower reactor rich in styrene, a part enters reboiler, return after components vaporize in tower, gas phase in tower is provided, another part extraction is in follow-up solvent recovery tower, continue separating phenylethylene and solvent, flow and the working pressure formed in table 2. extractive distillation column of each logistics are 15kPa.A

The composition (weight percentage) of table 1 carbon eight cut

C8 alkane	C8 alkene	Toluene	Ethylbenzene	P-Xylol	M-xylene	O-Xylol	Vinylbenzene
								2.5	2.5	1	18	5	25	12	34

The each logistics flux of table 2 aqueous-phase reflux and composition

Logistics number	6	7	8	9	10
						Logistics describes	Raw material C8 cut	Stripped vapor at the bottom of tower	Rich solvent	Raffinate oil	Aqueous-phase reflux
Phase	Liquid	Steam	Liquid	Liquid	Liquid
						Temperature DEG C	75	110	137	45	45
Mass rate kg/hr	10000	1712	62876	6650	1566
						Mass percentage
C8 alkane	2.50	0.00	0.00	3.76	0.00
						The non-aromatic alkene of C8	2.50	0.00	0.00	3.76	0.00
Toluene	1.00	0.00	0.00	1.50	0.00
						Ethylbenzene	18.00	0.00	0.00	27.06	0.00
P-Xylol	5.00	0.00	0.00	7.52	0.00
						M-xylene	25.00	0.00	0.00	37.59	0.01
O-Xylol	12.00	0.00	0.00	18.00	0.00
						Vinylbenzene	34.00	0.00	5.34	0.75	0.00
Solvent	0.00	0.00	94.56	0.00	0.00
						Water	0.00	100.00	0.10	0.06	99.99

Comparative example:

As shown in Figure 1, except employing is raffinated oil as liquid-phase reflux, all the other same embodiments.The flow composition of each logistics is in table 3.

Table 3 oil phase refluxes each logistics flux and composition

Logistics number	6	7	8	9	10
						Logistics describes	Raw material C8 cut	Stripped vapor at the bottom of tower	Rich solvent	Raffinate oil	Oil phase refluxes
Phase	Liquid	Steam	Liquid	Liquid	Liquid
						Temperature DEG C	75	110	137	45	45
Mass rate kg/hr	10000	1688	62857	6678	7564
						Mass percentage
C8 alkane	2.5	0	0	3.74	3.74
						C8 alkene	2.5	0	0	3.74	3.74
Toluene	1	0	0	1.50	1.50
						Ethylbenzene	18	0	0	27.00	27.00
P-Xylol	5	0	0	7.51	7.51
						M-xylene	25	0	0	37.45	37.45
O-Xylol	12	0	0	17.97	17.97
						Vinylbenzene	34	0	5.31	1.04	1.04
Solvent	0	0	94.59	0.00	0.00
						Water	0	100	0.1	0.06	0.06

From the data of table 2 and table 3, when C8 charging, solvent ratio are identical, the quantity of reflux of oil phase backflow is 7564kg/h, and oil phase reflux ratio is 0.9, and the quantity of reflux of aqueous-phase reflux is 1566kg/h, and aqueous-phase reflux ratio is 0.16, and comparatively oil phase backflow reduces greatly; In raffinating oil, cinnamic rate of loss is refluxed by oil phase 2.04%, be reduced to 1.46% of aqueous-phase reflux, the vinylbenzene that about can reduce per hour loses 20kg.

Claims (3)

1. the method for separating phenylethylene from carbon eight cut, comprising: carbon eight cut isolating vinylbenzene in extractive distillation column after extracting rectifying, is characterized in that:

The all or part of replacement of aqueous phase is adopted to raffinate oil as the liquid-phase reflux of described extractive distillation column internal solvent recovery zone;

Comprise the following steps:

(1) extracting rectifying is carried out with the extraction distillation solvent entered from the top of extractive distillation column in the middle part that carbon eight cut enters extractive distillation column, and stripped vapor is added by tower reactor;

(2) overhead vapours is isolated and is raffinated oil and aqueous phase after condensation, and aqueous portion or all replacement are raffinated oil as tower top liquid-phase reflux;

(3) obtain raffinating oil as product output, extractive distillation column tower reactor obtains containing cinnamic rich solvent.

2. the method for separating phenylethylene from carbon eight cut as claimed in claim 1, is characterized in that:

Described aqueous phase is the return tank water bag of extracting rectifying column overhead or the free-water of the interior separation of point flow container or supplements the de-salted water added.

3. the method for separating phenylethylene from carbon eight cut as claimed in claim 1, is characterized in that:

The working pressure of described extractive distillation column is 10-15kPa.A.