IE45113B1

IE45113B1 - Separation of hydrocarbons

Info

Publication number: IE45113B1
Application number: IE63/77A
Authority: IE
Original assignee: Snam Progetti
Priority date: 1976-01-14
Filing date: 1977-01-13
Publication date: 1982-06-30
Also published as: CA1091615A; DD128592A5; ZA7796B; ES455306A1; PT66065B; PL112578B1; GR59765B; IN145336B; PT66065A; HU178726B; YU39984B; FR2338235A1; SE423535B; CS200504B2; DE2701466A1; PH13737A; NO148370B; IE45113L; BE850400A; BR7700296A

Abstract

The novel solvent for the separation of hydrocarbons by extractive distillation, by gas-liquid scrubbing or by liquid-liquid scrubbing contains N-methyl-morpholin-3-one. The solvent can be used as a mixture with water and/or other organic solvents, for example ethylene glycol. The novel solvent is used above all for the separation of diolefins from mixtures containing them, and also for the separation of olefinic hydrocarbons from mixtures containing them, and likewise for the separation of aromatic hydrocarbons from mixtures containing them.

Description

This invention relates to the separation of hydrocarbons.

More particularly, the present invention relates to the separation of hydrocarbons using a heterocyclic solvent.

Still more particularly, but not exclusively, the present invention S relates to the separation of one or more hydrocarbons from mixtures which contain them, by extractive distillation, scrubbing of gas with a liquid or scrubbing of liquid with a liquid.

It is known to use heterocyclic compounds as extractive solvents in the separation of hydrocarbons from hydrocarbonaeeous mixtures by operations of IQ extractive distillation, gas-liquid scrubbing or liquid-liquid scrubbing.

When evaluating such compounds to the end of an industrial exploitation of same, numerous aspects must be considered, among which are selectively, ease of conveyance, stability, ease of synthesis, toxicity, vapour pressure, specific gravity, boiling point temperature and melting point temperature.

It has been found, and this is the basis of the present invention, that N-methy]-morpholine-3-one is a compound which satisfactorily fulfils, in general, all of these requirements and thus it can be used with advantage as an extractive solvent. - 2 •15113 According to the present invention, there is provided a process for the separation of hydrocarbons by extractive distillation, gas liquid scrubbing or liquid-liquid scrubbing which involves the use, as extractive solvent, of Nmethyl-morpholine-3-one, alonsor in admixture with another solvent.

N-methyl-morpholine-3-one can be used c:ther alone or in admixture with water and/or with another organic solvent, for example ethylene glycol. Preferably, based on the weight of the mixture of the N-methyl-morpholine-3-one and of water and/or other organic solvent, the water, when present, is present in an amount of up to 20% and the other organic solvent, when present, is present in an amount of up to 20%.

The solvent according to the invention can be exploited in particular for the separation of diolefin hydrocarbons from mixtures which contain them, more particularly of butadiene from a mixture of hydrocarbons, or of isoprene from a mixture of Cg hydrocarbons.

The process according to the present invention can also be used with advantage for the separation of mixtures of saturated, olefinic or aromatic hydrocarbons from mixtures which contain them, or also for the separation of an individual olefinic or aromatic hydrocarbon, respectively, from mixtures of olefins, saturated hydrocarbons and diolefins, or from mixtures of aromatic hydrocarbons.

More particularly, the present invention can be used for the separation of styrene, benzene, toluene and xylenes, either alone or in admixture with each other, from batches which contain them.

The present invention will now be illustrated by the following Examples which describe processes carried out in the plants shown schematically in Figures 1 to 8 of the accompanying drawings, in which Figures similar components are sometimes identified by identical reference numerals and sometimes by different reference numerals. - 3 4Sl'i3 EXAMPLE 1.

This process was carried out in the plant illustrated in Figure 1.

An extractive distillation column 9 was fed via a pipe 1 with a stream having the following composition:- 5 isoprene moles/hour 282.0 isopentane 13.2 pent-l-ene 39.7 2-methyl-but-l-ene 67.3 10 normal pentane 120.1. pent-2-ene-trans 29.4 pent-2-ene-iso 18.1 2-methyl-but-2-ene 11.3 .. cyclopenta-1,3-diene 1.7 15 and isopropenylacetylene 0.1 The operating conditions were as follows:- Head pressure 1.1 absolute atmospheres L/D ratio (also known as the reflux ratio) 0.9:1 20 Nc. of plates 65.

Column 9 was also fed, through a pipe 2, with 500 kg/hour of a solvent mixture composed of N-methyl-morpholine-3-one and water in the proportion of 94 to 6 by weight. From the head of column 9, there was discharged in a pipe 3 a stream having 25 the foil ov/ing composition:- moles/hour isoprene 5.6 isopentane 13.2 pent-Irene . 39.7 30 2-methyl-but-l-ene 67.3 normal pentane 120.1 pent-2-ene-trans 29.4 - 4 *»H 3 moles/hour pent-2-ene-cis 11.1 and 2-methyl-but-2-ene 11.0 A stream coming from the bottom of column 9 was sent in a pipe 4 to a second extractive distillation column 10, as was a stream of 60 kg/hour of the above-mentioned solvent in a pipe 5.

The column 10 was operated under the following conditions:Head pressure 1.1 abs. atmospheres L/D ratio 0.9:1 No. of plates 75.

From the head of column 10 was discharged in a pipe 6 a stream of high-purity isoprene, having the following composition:moles/hour isoprene 270.8 and 2-methyl-but-2-ene 0.3 From a lateral discharge pipe 7 were withdrawn in vapour phase the more polar hydrocarbons (i.e. cyclopenta-1,3-diene and isopropenyl acetylene), and from the bottom of column 10 in pipe 8 was withdrawn the solvent free of hydrocarbons, which was therefore recycled in pipes 2 and 5 to the extractive distillation columns 9 and 10, respectively.

EXAMPLE 2.

This process was also carried out in the plant illustrated in Figure 1. The extractive distillation column 9 was fed via pipe 1 with a 1 kg/hour stream having the following composition:- saturated hydrocarbons by weight 20% olefinic hydrocarbons 45% buta-1,3-diene 35% and Acetylenic compounds (such as vinyl acetylene) 1,000 ppm The operating conditions were as follows Head pressure L/D ratio ι No. of plates absolute atmospheres 0.9:1 70.

To the same column, through pipe 2 were sent 10 kg/hour of a mixture composed of N-methyl-l-morpholine-3-one and water in the proportion of 93:7 by weight.

From the head in pipe 3 a stream was discharged, at the rate of 0.65 kg/hours which substantially contained saturated and olefinic hydrocarbons.

The stream discharged in pipe 4 from the bottom of column 9, was sent to the second extraction column 10, together with a stream of 2 kg/hour (in pipe 5) of the above-mentioned solvent mixture.

The separation in the column 10 was carried out under the following conditions :Head pressure L/D ratio No. of plates 1.2 absolute atmospheres 0.9:1 80.

From the head was discharged in pipe 6 a stream of about 0.34 kg/hour of buta-1,3-diene with a high degree of purity and which contained only about 20 ppm (parts per million) of acetylenic compounds.

In the lateral discharge pipe 7 were withdrawn in vapour phase the majority of the acetylenic hydrocarbons originally fed, together with a negligible quantity of butadiene, whereas from the bottom of column 10 was discharged in pipe 8 the solvent mixture, which was substantially hydrocarbon-free, and which was recycled to the extraction columns 9 and 10.

EXAMPLE 3.

This process was carried out in a plant as illustrated in Figure 2.

An extractive distillation column 8 was fed via a pipe 1 with a reformed gasoline stream having the following composition:- 6 ύ i»l J g Benzene kg/hour 1.50 Toluene 2.00 Xylenes 3.50 Non-aromatic hydrocarbons 3.00 The operating conditions were as follows.- Head pressure 1.1 absolute atmospheres L/D ratio 0.7:1 No. of plates 55. The same column was fed through a pipe 2 with 30 kg/hour of a mixture of N-methyl-morpholine-3-one and ethylene glycol in the proportion of 95;5 parts fay weight.

From the head of column 8 was discharged in a pipe 3 a stream of 3.05 kg/hour which substantially contained all the non-aromatic hydrocarbons fed to the column 8. In a pipe 6 is condensate refluxed at the head of column 8.

The bottom product from column 8 was sent in a pipe 4 to a stripping column 9 which was operated under the following conditions:Head pressure 0.2 absolute atmospheres L/D ratio 0.2:1 No. of plates 25.

From the head of column 9 was withdrawn in a pipe 5 a stream of aromatic hydrocarbons which had a preselected quantity of saturated compounds, whereas from the bottom of column 9 the solvent was recovered, which was recycled to the column 8. In a pipe 7 is condensate refluxed at the head of column 9.

The stripping of the stream discharged from the bottom of the column 8 was, in a modified process, carried out in two stages, as indicated by Figure 3 which illustrates the appropriately modified plant.

In such a case, as shown in Figure 3, the same bottom product in pipe 4 was sent to a first stripping column 9 which was operated under the following conditions:- 7 1.1 absolute atmospheres Head pressure L/D ratio 0.2:1 No. of plates 25.

From the head of column 9 was discharged in a pipe 5 a stream having a specified content of saturated compounds and which was composed as follows:kg/hour Benzene 1.49 Toluene 1.99 Xylenes ' 0.47 From the bottom of column 9 in pipe 6 v/as discharged a stream which was sent to a second stripping column 10 v/hich v/as operated under the following conditions :Pressure 0.2 absolute atmospheres L/D 0.1:1 No. of plates 15.

From the head of column TO in a pipe 7 was discharged a stream of xylenes according to a preselected specification (3.03 kg/hr), and from the bottom of column 10 v/as recovered the solvent which was recycled to column 8.

EXAMPLE 4.

This process was carried out in a plant as illustrated in Figure 4.

An extractive distillation column 9 v/as fed via a pipe 1 with a stream of 100 kg/ hour of a Cg cut v/hich had the following composition:- Co saturated and olefinic G hydrocarbons 3.5 £-xylene 17.OS ra-xyl ene and £-xylene 43.IS ethylbenzene 8.6S and styrene 27.8S The operating conditions were as follows:- 8 -2 iS 1 ί 3 Head pressure 140 mmHg (absolute) L/D ratio 5:1 No. of plates 80.

The same column was fed through a pipe 2 with 1,300 kg/hour of a mixture composed of N-methyl-morpholine-3-one and water in the ratio of 96:4 by weight.

From the head of column 9 in a pipe 3 was discharged water and a stream of organic refined mixture which had the following composition:kg/hour Cg saturated and olefinic ° hydrocarbons 3.5 16.9 43.1 8.6 o-xylene m-xylene and £-xylene ethylbenzene and stryene 0.3 This stream was sent to a demixer 11 to separate water, which was drawn off in a pipe 17, from the refined mixture which was withdrawn through a pipe 16.

From the bottom of column 9 was discharged in pipe 4 a stream which was sent to an extraction column 10 together with a stream of 150 kg/hour of the same solvent mixture in pipe 5. The separation in the column 10 was carried out under the following conditions:Head pressure 160 mmHg (absolute) L/D ratio 2.5:1 No. of plates 60.

From the head of column 10 a stream was removed in a pipe 6, which comprised o-xylene and styrene which were recycled to the column 9, whereas from the bottom of column 10 was discharged a stream in a pipe 7 which was fed to a stripping column 12, which operated under the following conditions:- 9 - Λ 13 ¢13 i * Head pressure 190 mmHg (absolute) No. of plates 30.

From the head of column 12 vras withdrawn a stream which was sent to a demixer 13, from which through a pipe 8 was obtained styrene having a purity of more than 99.8%, whilst water was discharged through a pipe 18.

From the bottom of column 12 was discharged in a pipe 14 the solvent, which, after it had been mixed in a mixer 15 with tempered v/ater in pipes 17 and 18, was recycled in pipes 2 and 5 to columns 9 and 10 respectively.

EXAMPLE 5.

This process was carried out in a plant as illustrated in Figure 5.

A gas-liquid scrubbing column 9 was fed through a pipe 1 with a stream of 1 kg/hour of the following composition:by weight buta-1,3-diene 35% saturated hydrocarbons about 20% C„ monolefinic hydrocarbons about 45% The operating conditions were as follov/s:Kaad pressure 5 abs. atmospheres No. of plates 40.

The same column was fed through a pipe 2 with about 8.5 kg/hour of a mixture composed by N-methyl-morpholine-3-one and water in the proportions of 94:6 by weight.

From the head of column 9 v/as discharged in pipe 3 a gas stream of 0.65 kg/hour, v/hich substantially contained saturated and olefinic hydrocarbons and from the bottom of column 9 a stream in a pipe 4 which was sent to a stripping column 10 v/hich was operated as follows.— Head pressure 5.5 abs. atmospheres No. of plates 45.

From the head of column 10 in a pipe 5 was discharged a gas stream of olefins and buta-1,3-diene v/hich v/as recycled to the column 9, whereas from the - 10 4 3 11 3 bottom of column 10 was discharged a stream in a pipe 6 which was fed to a second stripping column 11 which was operated under the following conditions:Head pressure 1.1 abs. atmospheres No. of plates 30.

The gaseous stream discharged from the head of column 11 was sent to a compressor 12, from which in a pipe 8, upon condensation, were withdrawn about 0.35 kg/hour of buta-1,3-diene containing only slight amounts of saturated and olefinic compounds (at a purity of more than 99.5% by wt.), whereas through a pipe 7 part of the aforementioned stream was recycled to the column 10.

From the tail of column 11 was withdrawn the solvent, which was recycled to column 9.

EXAMPLE 6.

This process was carried out in a plant as illustrated in Figure 6. Through a pipe 1 was fed a gasoline charge which had the following composition:- benzene by weight 15% toluene 25% xylenes 25% and 20 saturated hydrocarbons 35% This charge was fed to a liquid-liquid extraction column 14 having 60 plates, at a rate of flow of 5 kg/hour. Through a pipe 13 were sent to column 14 13 kg/hour of a mixture of N-methyl-morpholine-3-one and water in the ratio of 95:5 by weight, the entire column being maintained at 40°C - 45°C, with a head pressure of about 2 atmospheres absolute.

From the head of the column 14 was discharged in a pipe 3 a stream which was essentially composed of the saturated compounds which were present in the original charge.

The extract emerging from the bottom of column 14 was fed to the head of a column 15 which was operated with a head pressure of about 1.2 atmospheres absolute and with 30 plates. - 11 The head product of the column 15 was withdrawn in a pipe 5 and was condensed in two consecutive stages in condensers 17 and 18. The stream which was condensed above 120°C was sent via a pipe 6 and remixed v/ith the original charge, whereas the stream in pipe 7 from condenser T8 was recycled to the base of the liquid-liquid extractor 14.

The stream discharged from the bottom of the column 15 was sent in a pipe 8 to a column 16 operated at a head pressure of 1.2 absolute atmospheres and with 30 plates.

From the head of column 16 was discharged a stream which was demixed in separator 9 such that through a pipe 10 v/as withdrawn a stream of about 3.05 kg/hour of aromatics having a specified content of saturated compounds, whereas from the bottom of the separator 9 v/as withdrawn an aqueous stream which is partly refluxed to column 16 (at a rate of 1.5 kg/hour) and partly recycled to column 14 (at 0.7 kg/hour). The solvent discharged from the bottom of column 16 was recycled to the liquid-liquid extractor 14 via pipe 13.

EXAMPLE 7.

This process was carried out in a plant as illustrated in Figure 7.

As a charge there v/as used (in pipe 1) a reformed gasoline which had the following composition:by weight benzene 4% toluene 15% xylenes 20% saturated 61% ' This charge was sent to a first liquid-liquid extraction column 12 which had 40 plates, at a rate of flov/ of 100 kg/hour. Through a pipe 5 were sent about 250 kg/hour of N-methyl-morpholine-3-one, whereas through a pipe 10 were sent to the same column 40 kg/hour of pentane; the extractor was maintained at 25°C and with a head pressure of 3 atmospheres absolute. - 12 The stream discharged in a pipe 2 from the head of column 12 was sent to the distillation column 13 from the head of which, via a pipe 8, the pentane was recovered which was required for the operation of the extractor 12, and from the bottom of which, via a pipe 9, was discharged a stream of about 61.3 kg/hour, 5 composed essentially of the saturated hydrocarbons which were contained in the original charge in pipe 1.

The bottom stream from the extractor 12 was sent via a pipe 3 to a second liquid-liquid extractor 14 together with about 220 kg/hour of pentane sent via a pipe 11. Extractor 14 had 20 plates and operated constantly at °C and 2.0 atmospheres absolute.

The stream discharged in a pipe 4 from the head of column 14 was sent to a distillation column 15, from the head of which there was recovered in pipe 6 the pentane which was necessary for operating the extractors 12 and 14, and from the bottom of which was discharged via a pipe 7 a stream of about 38.7 kg/hour of a mixture of benzene, toluene and xylene having a specified percentage of saturated compounds.

From the bottom of the second extractors 14 was recovered the solvent which was recycled via pipe 5 to column 12.

EXAMPLE 8.

This process was carried out in the plant illustrated in Figure 8.

A liquid-liquid extraction column 12 was fed with a stream having the same composition as that fed to column 9 in Example 1.

To the column 12, which had 50 plates and operated at a pressure of 1.2 atmosphere absolute was also fed, through a pipe 7, 150 kg/hour of a mixture composed of N-methyl-morpholine-3-one and water in the proportion of 95:5 by weight.

From the head of column 12 a stream was discharged through a pipe 2, which, upon stripping of the solvent contained therein (an operation which is not shown in the drawings), was composed of:- 13 - moles/hour 8.4 2-methyl-but-1-ene isoprene . isopentane pent-l-ene 13.2 39.7 67.3 normal pentane pent-2-ene-trans pent-2-ene-cis and 2-methyl-but-2-ene 120.1 29.4 18.1 .8 The stream discharged from the bottom of column 12 via a pipe 3 was fed to a stripping column 13 which had a head pressure of about 1.5 atmospheres absolute and 30 plates.

From the head of column 13, in a line 4, was discharged a stream of olefins and isoprene, which was recycled to the extractor 12, whereas from the bottom of column 13 in a pipe 5 was discharged a stream which was fed to a second stripping column 14 which had a head pressure of about 1.2 atmospheres absolute, 20 plates, and'a L/D ratio of 0.2:1.

From the head of column 14 via a pipe 6 was recovered isoprene having a specified content of monoolefins and saturated compounds, which was sent to the extractive distillation column 11 for removing the polar hydrocarbons, whereas from the bottom of column 14 via a pipe 7 was recovered the solvent which was recycled to the column 12.

The column 12 operated under the following conditions.— Head pressure L/D ratio No. of plates 1.1 absolute atmospheres 0.9:1 75.

From the head of column 11, via a pipe 8, was discharged a stream of highly pure isoprene, which, more particularly, was composed of.— moles/hour isoprene 268.0 and 2-methyl -2-butene moles/hour 1 3 0.5 From a lateral withdrawing pipe 9 were withdrawn in the vapour phase most of the polar hydrocarbons (i.e. cyclopenta-1,3-diene and isopropylacetylene), and from the bottom of column 11 was discharged via a pipe 10 the solvent, which was free from hydrocarbons and was recycled to column 11.

EXAMPLE 9.

This process was carried out in the plant illustrated in Figure 5. The gas-liquid scrubbing column 9 was fed with a stream constituted by:- moles/hour normal butane 89.5 isobutane 22.4 but-l-ene 285.2 but-2-ene-trans 117.6 but-2-ene-cis 91.0 and buta-l,3-diene 6.8 The working conditions in column 9 were as follows:- Head pressure 5 atmospheres absolute No. of plates 40.

The column 9 was also fed, through the pipe 2, with 1,200 kg/hour of a mixture constituted by N-methyl-morpholine-3-one and water in the proportion of 93:7 by weight.

The bottom product from column 9 was sent via pipe 4 to the first stripping column 10, whereas from the head of column 9 was discharged a gas stream composed by:- moles/hour normal butane 87.7 isobutane 22.4 and but-l-ene 5.7 The operation of the column 10 was characterized by:Head pressure 5.5 atmospheres absolute No. of plates 40.

From the head of column 10 was discharged a gaseous stream of olefins and saturated hydrocarbons which was recycled to the column 9 via pipe 5, whereas from the bottom of column 10 was discharged a stream in pipe 6 which was fed to the second stripping column 11 which was operated under the following conditions:Head pressure 1.1 absolute atmospheres No. of plates 30.

The gaseous stream from column 11 was sent to the compressor 12; and from pipe 8, after condensation, a stream was withdrawn which was composed by:moles/hour normal butene 1.8 but-l-ene 279.5 but-2-ene-trans 117.6 but-2-ene-cis 91.0 and ί buta-1,3-diene 6.8 A portion of the above-mentioned stream sent to the compressor was recycled through the pipe 7 to the column 10.

From the tail of column 11, the solvent was recovered via pipe 2 to the column 9.

Having regard to the provisions of Section 14 of the Patents Act, 1964, attention is directed to the claims of our Patent No. 38,964.

Claims

1. Λ process for the separation of hydrocarbons by extractive distillation, gas-liquid scrubbing or liquid-liquid scrubbing, which involves the use, as extractive solvent, of N-methyl-morpholine-3-one, alone or in admixture with another solvent.

2. A process according to Claim 1, wherein the N-methyl-morpholine-3-one is used in admixture with water and/or another organic solvent.

3. A process according to Claim 2, wherein, based on the weight of the mixture of N-methyl-morpholine-3-one and of water and/or the other organic solvent, the water, when present, is present in an amount of up to 20% and the other organic solvent, when present, is present in an amount of up to 20%.

4. A process according to Claim 2 or 3, wherein the other organic solvent is ethylene glycol.

5. A process according to any preceding claim, for the separation of a diolefin from a mixture including the same.

6. A process according to Claim 5, wherein the diolefin to be separated is butadiene and the mixture which contains it is a mixture of C^ hydrocarbons.

7. A process according to Claim 5, wherein the diolefin to be separated is isoprene and the mixture which contains it is a mixture of Cg hydrocarbons.

8. A process according to any one of Claims 1 to 4, for the separation of an olefinic hydrocarbon from a mixture containing the same.

9. A process according to any one of Claims 1 to 4, for the separation of an aromatic hydrocarbon from a mixture containing the same.

10. A process according to Claim 9, wherein the aromatic hydrocarbon is styrene and the mixture which contains it is a cut of pyrolytic gasolines.

11. A process according to Claim 9, wherein the aromatic hydrocarbons are benzene, toluene, and the xylenes, alone or in admixture with each other, and the separation is carried out on cracking or reforming gasolines.

12. A process according to Claim 1, substantially as described in any one of the foregoing Examples. - 17

13. A hydrocarbon, whenever separated by a process according to any preceding claim.