US2701266A - Separation of p-xylene by crystallization - Google Patents

Separation of p-xylene by crystallization Download PDF

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Publication number
US2701266A
US2701266A US175839A US17583950A US2701266A US 2701266 A US2701266 A US 2701266A US 175839 A US175839 A US 175839A US 17583950 A US17583950 A US 17583950A US 2701266 A US2701266 A US 2701266A
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US
United States
Prior art keywords
cooling
xylene
coil
crystallization
current
Prior art date
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Expired - Lifetime
Application number
US175839A
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English (en)
Inventor
Coats Robert Reid
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Imperial Chemical Industries Ltd
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Imperial Chemical Industries Ltd
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Filing date
Publication date
Application filed by Imperial Chemical Industries Ltd filed Critical Imperial Chemical Industries Ltd
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Publication of US2701266A publication Critical patent/US2701266A/en
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D9/00—Crystallisation
    • B01D9/005—Selection of auxiliary, e.g. for control of crystallisation nuclei, of crystal growth, of adherence to walls; Arrangements for introduction thereof
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C7/00—Purification; Separation; Use of additives
    • C07C7/14—Purification; Separation; Use of additives by crystallisation; Purification or separation of the crystals
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S585/00—Chemistry of hydrocarbon compounds
    • Y10S585/909—Heat considerations
    • Y10S585/911—Heat considerations introducing, maintaining, or removing heat by atypical procedure
    • Y10S585/913—Electric
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S585/00—Chemistry of hydrocarbon compounds
    • Y10S585/949—Miscellaneous considerations
    • Y10S585/95—Prevention or removal of corrosion or solid deposits

Definitions

  • production of the desired crystalline product is facilitated by intermittent heating of a cooling surface or surfaces by electrical means, e. g. by passing an electrical current through it or them, at selected time intervals, for short periods sutficient in duration to melt deposited solid adjacent to the aforesaid cooling surface or surfaces and removing said solid therefrom, e. g. by sloughing it off, to prevent deposition thereon.
  • electrical means e. g. by passing an electrical current through it or them, at selected time intervals, for short periods sutficient in duration to melt deposited solid adjacent to the aforesaid cooling surface or surfaces and removing said solid therefrom, e. g. by sloughing it off, to prevent deposition thereon.
  • the heating of the cooling surface is effected so rapidly that the amount of heat transferred to cooling fluid or cooled liquid during the heating period is kept as low as possible compatible with efiicient operation. This can be achieved by selecting suitable voltages, time intervals and incidence of heating.
  • One suitable method of' operation is to make the cooling coil part of an electric circuit and to pass a heavy electric current through it for a very brief interval so that heat is generated in the mass of the coil.
  • an alternating current of radio frequency it is possible to confine the heating eflfect substantially to the surface of the metal whereby it is more efficiently utilised and the coil more quickly resumes its own function of cooling. If a jacketed crystalliser is used the current can conveniently be produced inductively in the vessel wall;
  • One suitable arrangement comprises a jacketed cooling vessel provided with a stirrer and a worm coil of stainless steel, for example that sold under the registered trademark Staybrite, forming part of an electric circuit which includes the secondary coil of a transformer.
  • Current is supplied to the worm coil by closing the primary circuit of the transformer by means of a switch.
  • the current may be applied to the worm coil by means of a thyratron-switched circuit or an ignitron circuit triggered by a suitable timing means, for example a time switch-or a thyratron.
  • An ignitron circuit is desirable when highamperage currents are to be used.
  • the principle on which the invention is based is the application, at intervals, of short electrical pulses applied so that the heat developed and available for melting the solid interferes to the minimum extent with the cooling function of the coils
  • the invention is applicable to crystallisation processes conducted over a wide range of temperature, e. g. from +l00 C. down to 100 C., and is especially suitable for the separation of p-xylene from mixed xylenes at temperatures from +13 C. downwards.
  • the cooling elements e. g. coils
  • the duration of each pulse should be brief, e. g. up to 10, and preferably less than 5, seconds
  • the input of energy should be sufficient but not greatly in excess of that required to free the coil from depositron
  • the pulses should be sufliciently frequent to prevent the deposition of hard, thick incrustation, which would not readily slough off. 7
  • a suitable ignitron circuit for single phase operation is shown schematically in Figure 1 and comprises two ignitrons II, one to conduct each half cycle, with their igniters AA and metal rectifiers BB, and a suitable switch S.
  • '-L and N represent the line and neutral bus bars and W the output to the coil in the cooling vessel or transformer feeding said coil.
  • the switch S may suitably be a cam operated contact, preferably driven by a synchronous motor.
  • FIG. 3 The general arrangement of a simple and effective method of carrying the invention into practice is shown in Figure 3, which is self explanatory.
  • Alternating curand period a thyrarent from mains MM is supplied to the primary coil P of a transformer through an electrical process controller D which is set to give impulses of desired duration at specified time intervals, a suitable program being one impulse of one second duration per minute.
  • This causes a corresponding surge of current in the circuit comprising the secondary coil Y and the cooling coils Z which are electrically insulated by insulators F.
  • the liquid mixture of hydrocarbons containing p-xylene is introduced into crystallizer K provided with stirrer R through the pipe X.
  • the liquid mixture is cooled by cooling coils Z through which a coolant such as pentane is passed. Crystals rich in p-xylene are formed and removed from the crystallizer through the valved outlet pipe 0. Build-up of these crystals on the cooling surface ofthe coils Z is prevented by the periodic surges of current, sent as above described, through said cooling surface.
  • the invention is illustrated by the following example.
  • the mixture of xylenes contained sufficient p-xylene to give a slurry containing 20% by weight solids at 38 C., which was the operating temperature.
  • Methanol was pumped through the coil at a rate of 60 litres per hour
  • the duration of the pulses of the surge current and the number of pulses per minute were controlled by a press button contactor in the primary circuit of the transformer. The pulses were applied at equidistant time intervals.
  • Run I.-Thick deposition of p-xylene on the outer surface of the coils-Was present at 30 minutes and very heavy deposition at 45 minutes.
  • Run 5 The condition of the coils after minutes was similar to that in Run 4 after the same time.
  • amperages of 10 and more may be used, preferably the amperage of the current employed in the process is or more.

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
  • Analytical Chemistry (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Water Supply & Treatment (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
  • Physical Or Chemical Processes And Apparatus (AREA)
US175839A 1949-08-12 1950-07-25 Separation of p-xylene by crystallization Expired - Lifetime US2701266A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB21037/49A GB698870A (en) 1949-08-12 1949-08-12 Improvements in and relating to crystallising processes

Publications (1)

Publication Number Publication Date
US2701266A true US2701266A (en) 1955-02-01

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US175839A Expired - Lifetime US2701266A (en) 1949-08-12 1950-07-25 Separation of p-xylene by crystallization

Country Status (5)

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US (1) US2701266A (is")
DE (1) DE841744C (is")
FR (1) FR1023931A (is")
GB (1) GB698870A (is")
NL (1) NL75853C (is")

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3513212A (en) * 1965-08-18 1970-05-19 Ici Ltd Recovery of paraxylene crystals under refrigeration and sonic vibration conditions

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3239603A1 (de) * 1982-10-26 1984-04-26 Linde Ag, 6200 Wiesbaden Verfahren zum gleichzeitigen entfernen von h(pfeil abwaerts)2(pfeil abwaerts)s, so(pfeil abwaerts)2(pfeil abwaerts) und elementarem schwefel aus gasgemischen

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1746144A (en) * 1927-03-08 1930-02-04 Gen Electric Production of piezo-electric elements
US1940065A (en) * 1927-12-15 1933-12-19 Ig Farbenindustrie Ag Separatrion and purification of ortho, meta and para xylene
US2491413A (en) * 1946-07-25 1949-12-13 Cutler Hammer Inc Welding controller
US2500298A (en) * 1944-09-29 1950-03-14 Philco Corp Defrosting system for refrigerating apparatus
US2570612A (en) * 1947-06-05 1951-10-09 Werkspoor Nv Method and apparatus for removing the crusts of the cooling elements of a continuously operating crystallizer

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1746144A (en) * 1927-03-08 1930-02-04 Gen Electric Production of piezo-electric elements
US1940065A (en) * 1927-12-15 1933-12-19 Ig Farbenindustrie Ag Separatrion and purification of ortho, meta and para xylene
US2500298A (en) * 1944-09-29 1950-03-14 Philco Corp Defrosting system for refrigerating apparatus
US2491413A (en) * 1946-07-25 1949-12-13 Cutler Hammer Inc Welding controller
US2570612A (en) * 1947-06-05 1951-10-09 Werkspoor Nv Method and apparatus for removing the crusts of the cooling elements of a continuously operating crystallizer

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3513212A (en) * 1965-08-18 1970-05-19 Ici Ltd Recovery of paraxylene crystals under refrigeration and sonic vibration conditions

Also Published As

Publication number Publication date
FR1023931A (fr) 1953-03-25
DE841744C (de) 1952-06-19
GB698870A (en) 1953-10-28
NL75853C (is")

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