US3579599A - Process for extract-separation of aromatic hydrocarbons - Google Patents

Process for extract-separation of aromatic hydrocarbons Download PDF

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Publication number
US3579599A
US3579599A US776728A US3579599DA US3579599A US 3579599 A US3579599 A US 3579599A US 776728 A US776728 A US 776728A US 3579599D A US3579599D A US 3579599DA US 3579599 A US3579599 A US 3579599A
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extract
xylene
aromatic hydrocarbons
mole
diluent
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US776728A
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Yoshiro Ito
Tamotsu Ueno
Takashi Nakano
Kazuo Okamoto
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Japan Gas Chemical Co Inc
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Japan Gas Chemical Co Inc
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    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C7/00—Purification; Separation; Use of additives
    • C07C7/10—Purification; Separation; Use of additives by extraction, i.e. purification or separation of liquid hydrocarbons with the aid of liquids

Definitions

  • a process for continuously extract-separating m-xylene from a mixture of xylenes containing m-xylene and at least one xylene isomer (inclusive of ethylbenzene) other than m-xylene comprising the steps of charging said xylene mixture, reflux m-xylene, diluent, BF, and liquid HF into an m-xylene extractor, and extracting m-xylene in a continuous countercurrent extraction method, characterized by selectively extracting m-xylene from said xylene mixture under such selected operating conditions of said extractor as the mole ratio of BF /HF in the HF extract withdrawn from said m-xylene extractor, that is, the concentration of xylene, in the hydrocarbon phase at the HF extract withdrawal section (final stage), and Brn, that is, the mole ratio of m-xylene/BF in the HF extract, will substantially satisfy the 'y-flm correlation on 'y-
  • This invention is based on the discovery that separation of aromatic hydrocarbons in a high yield and purity is possible without reflux of m-xylene a step heretofore been considered indispensable.
  • This invention relates to a process for extract-separating high basicity aromatic hydrocarbons into a hydrogen fluoride phase by allowing an extracting agent consisting of hydrogen fluoride and boron trifluoride to contact a mixture containing two or more aromatic hydrocarbons having ditferent basicity from each other.
  • This invention is applicable to a process for extract separating m-xylene from C aromatic hydrocarbon fraction; a process for extract-separating mesitylene from C aromatic hydrocarbon fraction; or a process for extractseparating aromatic hydrocarbons having a high boiling point from a mixture of xylenes and aromatic hydrocarbons having the high boiling point.
  • this invention provides a process for separating Patented May 18, 1971 aromatic hydrocarbons in a higher yield and purity than ever before without the refluxing heretofore considered necessary.
  • this invention is an improvement over the aforementioned process for extract-separating aromatic hydrocarbons.
  • This improvement eliminates the necessity of recovering excessive diluent and installing auxiliary equipment related to the reflux, and, accordingly, increases the capacity of the extracting system and reduces utility requirements, for its operation.
  • 2,727,- 078 (Shoemaker) relates to a process for separating mxylene from an isomeric mixture of xylenes by employing BF -HF extracting agent, however, the characteristic of this process lies in forming a complex mixture of mxylene and at least one xylene isomer other than m-xylene, with BF in HF to which m-xylene and diluent are added, thereby selectively decomposing complex mixtures of other isomers, leaving m-xylene as the only complex form. It is to be noted that in this process addition of m-xylene is an absolutely necessary factor.
  • US. Pat. 2,848,518 (Fragen) describes the total system related to a process for separating each constituent from a mixture of xylenes but description of said extraction process is extremely simple and covers no more than what is already described hereabove.
  • this invention relates to a process for extract-separating high basicity aromatic hydrocarbons into a hydrogen fluoride phase by allowing an extracting agent consisting of hydrogen fluoride and boron trifluoride to contact with a mixture containing two or more aromatic hydrocarbons having different basicity from each other, characterized by extract-separation of aromatic hydrocarbons without substantially refluxing aromatic hydrocarbons to be extracted.
  • this invention employing as raw material C aromatic hydrocarbon fraction (referred to as C fraction hereinafter) containing m-xylene and at least one, xylene isomer other than mxylene, and feeding said C fraction, diluent, BF and liquid HF to an m-xylene extractor, relates to a process for extract-separating m-xylene in a continuous countercurrent extraction, characterized by continuous extractseparation of m-xylene from said C fraction containing m-xylene and at least one xylene isomer other than mxylene without substantially refluxing m-xylene under such operating conditions of said extractor as the mole ratio of BF HF in the HF extract withdrawn from said m-xylene extractor, 'y, that is, the concentration of xylene in the hydrocarbon phase at the HF extract withdrawal section (final stage), and pm, that is, the mole ratio of total mxylene/BF in the HF extract, will substantially
  • C aromatic hydrocarbon fraction referred to in the specification means C aromatic hydrocarbon fraction obtained by separating from a petroleum constituent containing aromatic hydrocarbons, which was obtained by catalytic reforming, thermal cracking of petroleum or from a tar constituent containing aromatic hydrocarbons, normally contains m-xylene, o-xylcne, p-xylene and ethylbenzene as principal constituents and a small amount of benzene, toluene, etc.
  • xylene isomers other than m-xylene includes ethylbenzene in addition to o-xylene and pxylene.
  • raflinate means a hydrocarbon phase remaining without being extracted into the HF phase in the extractor, and when extracting m-xylene from C aromatic hydrocarbon fraction, it means a mixture of C aromatic hydrocarbon substantially not containing m-xylene, diluent added in the course of extracting mxylene, a very small amount of HF, BF benzene, toluene, etc. Accordingly, the diluent, a very small amount of HF, BF etc. are removed through distillation of the raflinate, and residual C aromatic hydrocarbon fraction is obtained.
  • extract product means aromatic hydrocarbons to be extracted in the HF extract.
  • extrac means the sum of extracting agent and extract product.
  • FIG. 1 is a highly simplified flow sheet to illustrate the principle of extraction.
  • FIG. 2 shows the -fim at temperature C. as BF HF in parameter between m, signifying correlation the mole ratio of m-xylene/B'F in the HF extract and y, signifying the concentration of xylene in the hydrocarbon phase at the HF extract withdrawal section (final stage).
  • FIG. 3 illustrates the same relation shown in FIG. 2 at C.
  • FIG. 4 also illustrates the same relation shown in FIG. 2 at +15 C.
  • This invention provides an efiective process for selectively extracting a certain specific hydrocarbon from a mixture of more than two aromatic hydrocarbons having diflerent basicity from each other.
  • the process is also effective for extract-separating mesitylene from a mixture current extracting system 1, and at the same time, hydrogen fluoride and boron trifluoride are fed through pipe 3 and pipe 4 respectively to the top of the extractor 1, and countercurrent contact of the HF-BF phase and C fraction phase is allowed to take place in the extractor.
  • diluent is fed into the extractor 1 through pipe 5 to improve its selectivity, and furthermore, a portion of extract-separated high purity m-xylene is fed back as reflux to the extractor 1 through pipe 6.
  • the extract and rafiinate are withdrawn from the extractor 1 through pipe 8 and pipe 7, respectively.
  • the amount of reflux is at a reflux ratio of 0.54, while in this invention without substantially refluxing means a reflux ratio of 0.2 or less (including 0.0).
  • the reflux ratio is a value meaning the value of said amount of reflux divided by the value of the total amount of extract product in the HF extract withdrawn from the extractor minus the amount of reflux to be fed back to the extractor as reflux.
  • Table 1 shows the result of measurement of mxylene/BF mole ratio in the HF extract in both cases using pure m-xylene only and using pure m-xylene and a known quantity of diluent added to the system.
  • diluent n-hexane is employed and the measured temperature is 0 C.
  • n and 'y are defined by the following formula: hydrocarbon having a high boiling point from a mixture to l a i v of xylene and aromatic hydrocarbons havmg said higher [3 3mm t c hydmfiarbons m HF extract (mole) boiling point.
  • this invention is particularly ef fective in providing an industrial process for extractseparating m-xylene from the C fraction.
  • the raw material C fraction is fed through pipe 2 into the center of the continuous counter- BE, in HF extract (mole) (flm: 5 in case where aromatic hydrocarbon is pure m-xylene) aromatic hydrocarbons in hydrocarbon phase 1: in equilibrium relation with HF extract (mole) aromatic hydrocarbons in hydrocarbon phase in equilibrium relation with HF extract (mole) diluent in hydrocarbon phase (mole)
  • the hydrocarbon phase means residual hydrocarbons not extracted in the HF extract phase (solution of aromatic hydrocarbons and diluent).
  • FIG. 2, FIG. 3, and FIG. 4 show the value when the measured temperature is C., 20 C. and C., respectively. In other words, notwithstanding a change in temperature and diluent employed, the result showing the same tendency is obtainable.
  • the -Bm correlation such as those shown in FIGS. 2-4 is particularly important for selective extraction of m-xylene from the C fraction. Namely, in order to selectively extract m-xylene present in the C fraction as a high purity m-xylene complex, and simultaneously leave substantially no m-xylene in the rafiinate, it is necessary to select the addition amount of HF and BE; (or, for example, the mole ratio of BF /HF and the amount of BF so as to allow the total m-xylene fed into the m-xylene extractor to be extracted in the withdrawn HF extract. To obtain high purity m-xylene and residual C fraction consisting substantially of xylene isomers other than m-xylene, these ratios must be determined highly precisely.
  • the BP /HF mole ratio of the with drawn HF extract must be first established within the range of 0.02-0.20, followed by determination of that is, the concentration of the aromatic hydrocarbon in the hydrocarbon phase at the HF extract withdrawal section (final stage). Should the BF /HF mole ratio be too low, the amount of needed HF would increase, hence increased amount of the extract subject to decomposition and increased heat load caused by the decomposition. Also, when the BF /HF mole ratio is increased, the pressure inthe' extractor will increase. For this reason, selection of the aforementioned range is desirable. The value of 'y is approximately 0.3 or less.
  • amount of diluent to be fed into extractor (mole) D varies somewhat depending upon the concentration of the extract product in the raw material; however, when there is absolutely no reflux (that is to say when the reflux ratio is zero), D is appropriate in the range of 0.7-10 with a 1-5 range being most desirable. When the reflux ratio is 0.2, D may be 0.5 or above.
  • the diluent is removed as raflinate.
  • Stable substances that do not substantially dissolve in extracting agent but form a uniform phase with ratfinate can be used as diluent, for example, aliphatic saturated hydrocarbons such as propane, n-butane, i-butane, n-pentane, and n-hexane; alicyclic saturated hydrocarbons such as cyclopentane, and cyclohexane; or halogenated hydrocarbons such as carbon tetrachloride. When carbon tetrachloride is used, the top and bottom positions of the raffinate and the extract are normally reversed. An extraction temperature of -20-+30 C. and pressure of 1-20 kg./cm.
  • the amount of hydrogen fluoride to be fed is 1.8-25 mole against one mole of the raw material aromatic hydrocarbon, while the abount of boron trifluoride is about 0.7-1.5 moles against one mole of the extract product in the raw material aromatic hydrocarbon. It is desirable to select the mole ratio of boron trifluoride/ hydrogen fluoride within the range of 002-020.
  • the types of extracting tower suitable for use include such as a packed tower, perforated plate tower, perforated plate pulse tower, extractor equipped with stirrer, and mixer settler.
  • high basicity aromatic hydrocarbons of high purity can be extract-separated in an extremely high yield without substantially refluxing the extract product.
  • this invention does not require reflux of the extract product, the amount of extract product at the extract withdrawal section is de creased, thereby decreasing the amount of feed diluent.
  • this decreases need for recovering excessive diluent and for installing the auxiliary equipment needed in connection with the reflux, nor will there be any substantial increase in the theoretical number of plates necessary for extraction, and significant benefits such as increased capacity of the extractor are obtained.
  • the theoretical number of plates of the extraction tower was 7.5.
  • EXAMPLE 3 The raw material C -C fraction containing 20% of 1,3,5-trimethyl benzene was fed so as to allow countercurrent contact to take place under normal pressure and at 8 C., all other conditions being identical with those described in Example 1.
  • the results obtained are as follows Extracting Raw agent material Diluent Ex- Rath- Substance supplied supplied supplied tract nate HF 691 2 B F 61 1 Ethyl benzene 0 6 p-Xylene 0. 1 45 m-Xylene- 11 125 o-igene. It i. .1 0. 2 4O 1 ime bsnz enefli 56.7 0. 2
  • a process for continuous countercurrent extractseparation of aromatic hydrocarbons into a hydrogen fluoride phase comprising:
  • the extract product is substantially 1,3,5-trimethylbenzene
  • the molar ratio of BF-,/ HF is from 0.02 to 0.20
  • the molar ratio of HF charge to the aromatic hydrocarbon mixture is from 1.8 to 25
  • the molar ratio of BF;,/ extract product is from 0.7 to
  • the molar ratio of a diluent charge to the extract product is from 0.5 to 10.

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
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  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
US776728A 1967-11-21 1968-11-18 Process for extract-separation of aromatic hydrocarbons Expired - Lifetime US3579599A (en)

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US (1) US3579599A (de)
BE (1) BE724148A (de)
DE (1) DE1810029A1 (de)
FR (1) FR1604275A (de)
GB (1) GB1238474A (de)
NL (1) NL163202C (de)
SU (1) SU416934A3 (de)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20040088785A1 (en) * 2002-10-23 2004-05-13 Walker Victor Lee Curvilinear spa
WO2018232218A1 (en) 2017-06-16 2018-12-20 United States Gypsum Company No fiber calcination of gypsum for gypsum fiberboard

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20040088785A1 (en) * 2002-10-23 2004-05-13 Walker Victor Lee Curvilinear spa
US20070118984A1 (en) * 2002-10-23 2007-05-31 Dimension One Spas, A California Corporation Curvilinear spa
US9125794B2 (en) 2002-10-23 2015-09-08 New Dimension One Spas, Inc. Water feature for a spa
WO2018232218A1 (en) 2017-06-16 2018-12-20 United States Gypsum Company No fiber calcination of gypsum for gypsum fiberboard

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NL6816604A (de) 1969-05-23
NL163202C (nl) 1980-08-15
GB1238474A (de) 1971-07-07
BE724148A (de) 1969-05-02
SU416934A3 (ru) 1974-02-25
FR1604275A (de) 1971-10-11
DE1810029A1 (de) 1969-06-19

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