CA1155873A - Process and apparatus for the production of vinyltoluene - Google Patents
Process and apparatus for the production of vinyltolueneInfo
- Publication number
- CA1155873A CA1155873A CA000393024A CA393024A CA1155873A CA 1155873 A CA1155873 A CA 1155873A CA 000393024 A CA000393024 A CA 000393024A CA 393024 A CA393024 A CA 393024A CA 1155873 A CA1155873 A CA 1155873A
- Authority
- CA
- Canada
- Prior art keywords
- vinyltoluene
- crude
- inhibitor
- vaporous
- condensed
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- HJWLCRVIBGQPNF-UHFFFAOYSA-N prop-2-enylbenzene Chemical compound C=CCC1=CC=CC=C1 HJWLCRVIBGQPNF-UHFFFAOYSA-N 0.000 title claims abstract description 127
- 238000000034 method Methods 0.000 title claims abstract description 30
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 18
- 230000008569 process Effects 0.000 title claims description 25
- 239000003112 inhibitor Substances 0.000 claims abstract description 64
- 238000006116 polymerization reaction Methods 0.000 claims abstract description 26
- 238000006356 dehydrogenation reaction Methods 0.000 claims abstract description 24
- HYFLWBNQFMXCPA-UHFFFAOYSA-N 1-ethyl-2-methylbenzene Chemical compound CCC1=CC=CC=C1C HYFLWBNQFMXCPA-UHFFFAOYSA-N 0.000 claims abstract description 22
- 239000008346 aqueous phase Substances 0.000 claims abstract description 15
- 239000012074 organic phase Substances 0.000 claims abstract description 13
- 238000001914 filtration Methods 0.000 claims abstract description 5
- ISWSIDIOOBJBQZ-UHFFFAOYSA-N Phenol Chemical compound OC1=CC=CC=C1 ISWSIDIOOBJBQZ-UHFFFAOYSA-N 0.000 claims abstract description 3
- 238000004821 distillation Methods 0.000 claims description 38
- HIQCTHFRLRVNPP-UHFFFAOYSA-N 4-methyl-2,3-dinitrophenol Chemical compound CC1=CC=C(O)C([N+]([O-])=O)=C1[N+]([O-])=O HIQCTHFRLRVNPP-UHFFFAOYSA-N 0.000 claims description 3
- 238000004064 recycling Methods 0.000 claims description 3
- 238000000746 purification Methods 0.000 claims description 2
- 238000002360 preparation method Methods 0.000 claims 1
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 abstract description 27
- 229920000642 polymer Polymers 0.000 abstract description 26
- 239000000047 product Substances 0.000 description 18
- 230000015572 biosynthetic process Effects 0.000 description 13
- HOYRZHJJAHRMLL-UHFFFAOYSA-N 2,6-dinitro-p-cresol Chemical compound CC1=CC([N+]([O-])=O)=C(O)C([N+]([O-])=O)=C1 HOYRZHJJAHRMLL-UHFFFAOYSA-N 0.000 description 9
- 239000000203 mixture Substances 0.000 description 9
- 238000009835 boiling Methods 0.000 description 6
- 239000003054 catalyst Substances 0.000 description 6
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 6
- 238000010791 quenching Methods 0.000 description 5
- 230000003197 catalytic effect Effects 0.000 description 4
- 238000013461 design Methods 0.000 description 4
- 229930195733 hydrocarbon Natural products 0.000 description 4
- 150000002430 hydrocarbons Chemical class 0.000 description 4
- 230000035508 accumulation Effects 0.000 description 3
- 238000009825 accumulation Methods 0.000 description 3
- 230000002378 acidificating effect Effects 0.000 description 3
- 238000005194 fractionation Methods 0.000 description 3
- 238000002347 injection Methods 0.000 description 3
- 239000007924 injection Substances 0.000 description 3
- 230000003405 preventing effect Effects 0.000 description 3
- 239000000523 sample Substances 0.000 description 3
- 239000011269 tar Substances 0.000 description 3
- 238000012546 transfer Methods 0.000 description 3
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
- 235000002017 Zea mays subsp mays Nutrition 0.000 description 2
- 241000482268 Zea mays subsp. mays Species 0.000 description 2
- 239000002253 acid Substances 0.000 description 2
- VSCWAEJMTAWNJL-UHFFFAOYSA-K aluminium trichloride Chemical compound Cl[Al](Cl)Cl VSCWAEJMTAWNJL-UHFFFAOYSA-K 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 238000009833 condensation Methods 0.000 description 2
- 230000005494 condensation Effects 0.000 description 2
- 230000001276 controlling effect Effects 0.000 description 2
- 238000001816 cooling Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000004508 fractional distillation Methods 0.000 description 2
- 230000002829 reductive effect Effects 0.000 description 2
- 238000000926 separation method Methods 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- -1 vinyl- Chemical group 0.000 description 2
- UFBJCMHMOXMLKC-UHFFFAOYSA-N 2,4-dinitrophenol Chemical compound OC1=CC=C([N+]([O-])=O)C=C1[N+]([O-])=O UFBJCMHMOXMLKC-UHFFFAOYSA-N 0.000 description 1
- MAQGNTACXAOLNE-UHFFFAOYSA-N 2-hydroxy-5-methyl-3-nitrobenzoic acid Chemical compound CC1=CC(C(O)=O)=C(O)C([N+]([O-])=O)=C1 MAQGNTACXAOLNE-UHFFFAOYSA-N 0.000 description 1
- VGGSQFUCUMXWEO-UHFFFAOYSA-N Ethene Chemical compound C=C VGGSQFUCUMXWEO-UHFFFAOYSA-N 0.000 description 1
- 239000005977 Ethylene Substances 0.000 description 1
- 238000005727 Friedel-Crafts reaction Methods 0.000 description 1
- UBUCNCOMADRQHX-UHFFFAOYSA-N N-Nitrosodiphenylamine Chemical compound C=1C=CC=CC=1N(N=O)C1=CC=CC=C1 UBUCNCOMADRQHX-UHFFFAOYSA-N 0.000 description 1
- 229910021536 Zeolite Inorganic materials 0.000 description 1
- 150000001450 anions Chemical class 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 238000010790 dilution Methods 0.000 description 1
- 239000012895 dilution Substances 0.000 description 1
- KSHJAFFDLKPUMT-UHFFFAOYSA-N dinitro-ortho-cresol Chemical compound CC1=C(O)C=C([N+]([O-])=O)C=C1[N+]([O-])=O KSHJAFFDLKPUMT-UHFFFAOYSA-N 0.000 description 1
- HNPSIPDUKPIQMN-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Al]O[Al]=O HNPSIPDUKPIQMN-UHFFFAOYSA-N 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000012467 final product Substances 0.000 description 1
- 230000002401 inhibitory effect Effects 0.000 description 1
- 229910052500 inorganic mineral Inorganic materials 0.000 description 1
- 230000000670 limiting effect Effects 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 239000012263 liquid product Substances 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000036961 partial effect Effects 0.000 description 1
- 150000002989 phenols Chemical class 0.000 description 1
- 229920002102 polyvinyl toluene Polymers 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- ODLMAHJVESYWTB-UHFFFAOYSA-N propylbenzene Chemical class CCCC1=CC=CC=C1 ODLMAHJVESYWTB-UHFFFAOYSA-N 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 238000012719 thermal polymerization Methods 0.000 description 1
- 238000011144 upstream manufacturing Methods 0.000 description 1
- 230000008016 vaporization Effects 0.000 description 1
- 238000013022 venting Methods 0.000 description 1
- 239000010457 zeolite Substances 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C15/00—Cyclic hydrocarbons containing only six-membered aromatic rings as cyclic parts
- C07C15/40—Cyclic hydrocarbons containing only six-membered aromatic rings as cyclic parts substituted by unsaturated carbon radicals
- C07C15/42—Cyclic hydrocarbons containing only six-membered aromatic rings as cyclic parts substituted by unsaturated carbon radicals monocyclic
- C07C15/44—Cyclic hydrocarbons containing only six-membered aromatic rings as cyclic parts substituted by unsaturated carbon radicals monocyclic the hydrocarbon substituent containing a carbon-to-carbon double bond
- C07C15/46—Styrene; Ring-alkylated styrenes
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C7/00—Purification; Separation; Use of additives
- C07C7/20—Use of additives, e.g. for stabilisation
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (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)
Abstract
ABSTRACT OF THE DISCLOSURE
A process for preparing viny toluene comprising passing ethyltoluene through a dehydrogenation zone to form vaporous crude vinyltoluene, adding from about 50 to about 100 parts per million by weight of a polymeri-zation inhibitor such as a nitrated phenol to the vaporous crude vinyltoluene at a temperature between about 200 and about 300°C, condensing the vaporous crude vinyltoluene, maintaining the pH of the aqueous phase of the condensed crude vinyltoluene at a value between about 5.5 and about 6.5 sufficient to maintain the inhibitor in the organic phase of the condensed crude vinyltoluene, adding a second portion of polymeri-zation inhibitor to the condensed crude vinyltoluene until the inhibitor concentration totals about 500 parts per million by weight relative to the vinyltoluene content of the crude vinyltoluene, filtering the con-densed crude vinyltoluene to remove seed polymer, and distilling the condensed crude vinyltoluene to recover substantially pure vinyltoluene; and apparatus for carrying out said method.
A process for preparing viny toluene comprising passing ethyltoluene through a dehydrogenation zone to form vaporous crude vinyltoluene, adding from about 50 to about 100 parts per million by weight of a polymeri-zation inhibitor such as a nitrated phenol to the vaporous crude vinyltoluene at a temperature between about 200 and about 300°C, condensing the vaporous crude vinyltoluene, maintaining the pH of the aqueous phase of the condensed crude vinyltoluene at a value between about 5.5 and about 6.5 sufficient to maintain the inhibitor in the organic phase of the condensed crude vinyltoluene, adding a second portion of polymeri-zation inhibitor to the condensed crude vinyltoluene until the inhibitor concentration totals about 500 parts per million by weight relative to the vinyltoluene content of the crude vinyltoluene, filtering the con-densed crude vinyltoluene to remove seed polymer, and distilling the condensed crude vinyltoluene to recover substantially pure vinyltoluene; and apparatus for carrying out said method.
Description
1 1 ~ 5 ~3 7 3 PROCESS AND APPARAT~S FOR THE PRODUCTION OF
_ VINYLTOLUENE ':
BACKGROUND OF THE INVENTIO~
The present invention pertains to a process and apparatus for the production of vinyltoluene, and more specifically to a method and means for inhibiting the .i formation of undesirable thermal polymers in the manufacture of vinyltoluene.
Vinyltoluene is commonly prepared by the catalytic 1~ dehydrogenation of ethyltoluene, cooling of the saseous materials to condense the same and fractionally distil-ling the liquid product to obtain vinyltoluene. In the manufacture of vinyltoluene by the catalytic dehydro- -genation of ethyltoluene, considerable difficulty has been experienced prior to and during the distillation of the crude vinyltoluene product to obtain purified vinyltoluene, because of the production of thermal poly~ers. This problem manifests itself in a plugging of the equipment used for the manufacture of the vinyltoluene.
In order to prevent the formation of the thermal polymer during distillation of vinyltoluene, various types of known polymerization inhibitors have been em-ployed in connection with prior art distillation processes.-These inhibitors have been only partially effective in pre-25 venting the formation of the undesirable thermal polymerr in the distillation apparatus. However, since this normal addition of inhibitor to the crude vinyltoluene product takes place in or just prior to the distillation apparatus, the inhibitor does not prevent the formation 1 1 55~73
_ VINYLTOLUENE ':
BACKGROUND OF THE INVENTIO~
The present invention pertains to a process and apparatus for the production of vinyltoluene, and more specifically to a method and means for inhibiting the .i formation of undesirable thermal polymers in the manufacture of vinyltoluene.
Vinyltoluene is commonly prepared by the catalytic 1~ dehydrogenation of ethyltoluene, cooling of the saseous materials to condense the same and fractionally distil-ling the liquid product to obtain vinyltoluene. In the manufacture of vinyltoluene by the catalytic dehydro- -genation of ethyltoluene, considerable difficulty has been experienced prior to and during the distillation of the crude vinyltoluene product to obtain purified vinyltoluene, because of the production of thermal poly~ers. This problem manifests itself in a plugging of the equipment used for the manufacture of the vinyltoluene.
In order to prevent the formation of the thermal polymer during distillation of vinyltoluene, various types of known polymerization inhibitors have been em-ployed in connection with prior art distillation processes.-These inhibitors have been only partially effective in pre-25 venting the formation of the undesirable thermal polymerr in the distillation apparatus. However, since this normal addition of inhibitor to the crude vinyltoluene product takes place in or just prior to the distillation apparatus, the inhibitor does not prevent the formation 1 1 55~73
- 2 -of the undesirable thermal polymers in the equipment up stream of the distillation unit, such as in the condensers - and in the crude vinyltoluene drum. The occurrence of fouling in the condensers and drum due to polymer forma-5 tion represents a serious problem in the production of vinyltoluene.
SUM~RY OF THE INVENTION
It is therefore an object of the present invention to provide an improved process for the production of vinyl-10 toluene.
Another object of the invention resides in the provision of a method for preventing the formation of soluble and insoluble (cross-linked) thermal polymers during the processing and subseguent distillation of r 15 vinyltoluene feed stock prepared by the catalytic dehydro-genation of ethyltoluene.
It is a particular object of the present in-vention to provide a new and improved process for pre-venting the fouling of the crude vinyltoluene condensers 20 and drums used prior to distillation with undesirable thermal polymers.
A further object of the present invention is to provide a new and improved apparatus which is less prone to fouling with thermal polymers during the manufacture 25 of vinyltoluene.
In accomplishing the foregoing objects, there has been provided in accordance with the present invention a process for the production of vinyltoluene comprising .the steps of passing ethyltoluene through a dehydrogenation 30 zone to form vaporous crude vinyltoluene; adding a first portion of polymerization inhibitor to the vaporous crude vinyltoluene; condensing the vaporous crude vinyl-toluene; maintaining the pH of the aqueous phase of the condensed crude vinyltoluene at a value sufficient to 35 maintain the inhibitor in the organic phase of the condensed crude vinyltoluene; adding a second portion of polymerization inhibitor to the condensed crude vinyl-toluene; and distilling the condensed crude vinyltoluene under distillation conditions to recover pure vinyl- ~;
toluene. The condensed crude vinyltoluene may advantage-ously be filtered before distillation to remove polymer which may otherwise serve as "seed" polymer in the dis-tillation train. The polymerization inhibltor may comprise a nitrated phenol, preferably dinitro-para-cresol.
In accordance with a further aspect of the invention, the pH of the aqueous phase is adjusted to a level of from about S.5 to about 6.5. Additionally, the ; process may further comprise the step of recycling the aqueous phase back to the dehydrogenation step.
In accordance with a still further aspect of .
the invention, the first portion of polymerization in-hibitor is added when the vaporous crude vinyltoluene tem- r perature is from about 200C to about 300C. Also, the first portion of polymerization inhibitor is advantage-ously added in amounts of about 50 to 100 parts per million by weight relative to the vinyltoluene present, and the total of the first and second portions of the inhibitor added is preferably sufficient to bring the inhibitor concentration to a level of about 500 parts per million during the distillatior step.
In accordance with still another aspect of the present invention, there is provided an apparatus for manufacturing vinyltoluene, comprising means for de-hydrogenating ethyltoluene to form vaporous vinyltoluene;
first means for introducing a polymerization inhibitor into the vaporous vinyltoluene after the vaporous vinyl-toluene leaves the dehydrogenation means; means for condensing the vaporous vinyltoluene; means for collecting the condensed vinyltoluene; a second means for intro-ducing a polymerization inhibitor into the collected vinyltoluene; and means for purifving the vinyltoluene, preferably a distillation apparatus. Additionally, a filter for filtering the vinyltoluene may be included prior to the purification thereof.
1155~73 In the process according to the invention, a portion of the inhibitor is introduced directly into the stream of vaporous vinyltoluene as it leaves the dehydro-genation apparatus but immediately prior to its condensation.
5 The pH required to maintain the inhibitor in the organic phase of the vinyltoluene feed stock will vary depending upon the pXa of the inhibitor selected. It has been found that the pR required for DNPC is less than about 6.5 and typically between about 5.5 and about 6.5. However, if p-10 inhibitors other than DNPC are used during the processes, the pH required to maintain the inhibitor in the organic phase will depend on the acidic character of the inhibitor employed during the process. Any conventional filter may be utilized to filter the crude vinyltoluene feed stock 15 prior to distillation. It has been found that a filter ~
with passages Gf lessthan about 50 microns is the most r efficient size in removing any undesirable thermal polymer.
Through the use of the process according to the present invention, the amount of polymerization occur-20 ring before and during the distillation of vinylt~luene is significantly reduced in comparison to conventionally ~
employed methods. In addition, the amount of desired ._ distillation product is increased in proportion to the decrease in the amount of polymer formation. Still further, 25 , since the inhibitor is maintained in the organic phase of the vinyltoluene, the water can be reused, e.g., in the generation of dilution steam for dehydrogenating ethyl-toluene.
Other objects, features and advantages of the 30 invention will become apparent from the detailed description of the preferred embodiments which follows, when considered together with the attached figures of drawing.
BRIEF DESCRIPTION OF THE DRAWINGS
In the Drawings:
Figure 1 is a schematic diagram of a preferred embodiment of the apparatus employed in practicing the ~!
r:
1 15~73 , ' ~
present invention; and Figure 2 shows a schematic diagram of another apparatus which may be employed in practicing the invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
-Vinyltoluene is typically manufactured by reacting toluene with ethylene in the presence of an activated - Friedel-Crafts catalyst, such as aluminum chloride, or a zeolite catalyst, dehydrogenating the ethyltoluene by passing it together with steam through a dehydrogenation zone at a sufficient reaction temperature, and separating the dehydrogenated product by means of fractional distil-lation.
The present invention provides a process and apparatus for the production of vinyltoluene whereby the formation of the undesirable thermal polymer can be greatly inhibited or entirely prevented prior to and during distil- r lation of vinyltoluene feed stock prepared by the catalytic dehydrogenation of ethyltoluene. This is accomplished by adding an inhibitor immediately prior to the step of condensing the dehydrogenated vinyltoluene feed stock, adjusting the pH of the aqueous phase of the condensed feed stock to maintain the inhibitor substantially in the organic phase, and optionally filtering the feed stock prior to fractional distillation.
Toluene is alkylated to form ethyltoluene by any suitable method known to those of skill in the art.
The ethyltoluenes formed are dehydrogenated by vaporizing the hydrocarbons by means of heat exchangers, passing a stream of the vapors into admixture with steam to form a vapor mixture comprising from 1 to 10, advantageously from 2 to 3 parts ~y weight of steam per part of hydrocarbons, and passing the vapor mixture into a reactor containing a solid, .. ' 1 ~55873 granular dehydrogenation catalyst at a reaction temperature between 550 and 700C, preferably between 560 and 650C.
Any of the known catalysts which are suitable for use in dehydrogenating ethyltoluene may be used. A considerable number and variety of such catalysts are known and are commercially available. Catalysts of the self-regenerative type are preferably used.
A vapor mixture containing steam and vinyltoluene then leaves the dehydrogenation reactor and passes through one or more heat exchangers. A polymerization inhibitor is then injected into the vaporous mixture. Any of the inhibitors which are suitable for use in preventing the formation of undesirable thermal polymers in vinyltoluene and are soluble in the organic phase of the mixture may lS be utilized. Nitrated phenols are preferred, for example, dinitro-ortho-cresol, dinitro-para-cresol, meta-nitro-para-cresol, dinitro phenol, N-nitroso diphenyl amine, 4-halo-3,5-dinitro toluene, 3-nitro-2,5-cresotic acid and the like. The temperature of the vaporous mixture, at the time of the injection of the inhibitor, is prefer-ably between about 200C and 300C in order to prevent rapid decomposition of the inhibitor and to assure maximum --effectiveness of the inhibitor. If DNPC is utilized as an inhibitor, it is preferably added to the vaporous stream of crude vinyltoluene in amounts of between about 50 - 100 parts per million by weight relative to the vinyltoluene in the stream. The mixture is then cooled to condense the product, and the pH of the aqueous pha~e is adjusted, if necessary, to maintain the inhibitor in the organic phase. The pH needed to maintain the inhibitor in the organic phase will depend on the pKa of the inhibitor used. For instance, if DNPC is used as an inhibitor, a pH of 5.5 - 6.5 is sufficient to prevent the formation of the enolate anion, which is water soluble, and thus to maintain the DNPC substantially in the organic phase. Of course, if an inhibitor is selected which has a pKa different from that of DNPC, a different pH will be required to maintain the inhibitor in the organic phase of the vinyltoluene. The water collected may be recycled for use in future dehydrogenation reactions.
The dehydrogenation mixture may optionally and preferably be filtered to prevent transfer of any undesir-able insoluble polymers into the distillation apparatus.
~ Such polymers, unless removed, serve as seed polymers for ; the formation of large quantities of insoluble polymer in the distillation columns.
Additional polymerization inhibitor is added to the crude vinyltoluene prior to entry into the distillation apparatus in order to prevent any undesirable polymer formation during distillation of the vinyltoluene. Typically, .
an amount of inhibitor is added which is sufficient to raise the total concentration of the inhibitor to a level of about 500 parts per million by weight relative to the vinyltoluene. This has been found to be sufficient to prevent the formation of undesirabie insoluble pclymers during the distillation process. -The dehydrogenation mixture is fractionally distilled in a series of fractionating columns. The distillation is preferably conducted under reduced pressure r to further reduce the tendency of the vinyltoluene to polymerize. Lower boiling portions are separated from the vinyltoluene. The vinyltoluene is then removed from the heavier boiling fractions. Typical operating conditions for the distillation process include a temperature from about 65 to about 138C, and a subatmospheric pressure from about 10 to about 200 mm Hg absolute. The specific operating conditions produce a final product of commercial grade vinyltoluene which satisfies industry standards for ~:`
quality and purity.
Referring to the drawings, Figure 1 illustrates one embodiment for carrying out the process of the present invention. An ethyltoluene feed stock is introduced into a dehydrogenation apparatus 10 to form vinyltoluene. The vinyltoluene feed stock is injected with a polymeri-zation inhibitor 12 immediately prior to condensing thevinyltoluene. The vinyltoluene feed stock is condensed in ~ condenser 14, then transferred via line 16 to crude vinyltoluene drum 18. The condenser 14 may comprise a condenser using a fan or water for cooling. Alternatively, any çondenser suitable for condensing vaporous crude vinyltoluene may be utilized. The inhibitor 12 is preferably added as close to the quench nozzle of the condensing apparatus as possible in order to prevent decompasition of the inhibitor and to prevent the formation of undesirable ' ~r polymers in the condenser 14 or the drum 18. The pH
of the aqueous phase is adjusted to a pH which is suf-ficiently acidic to substantially maintain the inhibitor in the organic phase of the vinyltoluene feed stock.
A convenient means of controlling the pH of the aqueous phase in the crude drum comprises the following arrangement. Preferably, a partial stream of quench water is recycled from the crude drum to the condensing apparatus. A pH probe 19 is located in this recycle line, and downstream of the probe an inlet nozzle is provided for selectively injecting a pH control agent 20 when necessary. In order to maintain the aqueous phase slightly acidic, it is preferred to selectively add an inorganic mineral acid to the recycle stream, most preferably hydrochloric or sulfuric acid.
. The aqueous phase of the feed stock is withdrawn from the crude vinyltoluene drum through line 21 and is recycled for water treatment and use in the boilers used in the dehydrogenation of ethyltoluene.
1 1~5~73 t, _ 9 _ The product remaining in the vinyltoluene drum 18 is pumped through line 22 via pump 24 through filter 26 into a conventional vinyltoluene distillation train.
Additional inhibitor 28 is injected into the vinyltoluene feed stock in line 30 in order to ensure the presence of a sufficient amount of inhibitor during the distillation process.
In this embodiment, the vinyltoluene feed stock is introduced into the intermediate portion of recycle column 32 which is preferably of the parallel distillation path design. Reboiler 34 provides the necessary heat for distillation in column 32.
An overhead product comprising toluene and ethyl-toluene is withdrawn through line 5 for subsequent ~, fractionation in distillation column 36. In column 36, r toluene and other light distillates are withdrawn through line 38. An ethyltoluene bottoms product is withdrawn through line 40 and is recycled for use in the ethyltoluene dehydrogenation reactor 10. Reboiler 42 provides the bottoms with the necessary heat for the distillation.
The recycle bottoms product, containing vinyl- ~~
toluene inhibitor and polyvinyltoluene is withdrawn from .
the recycle column 32 through 44 u~ing pump 46 and is charged into the middle portion of finishing column 48.
A reboiler circuit comprising a reboiler 50 and an air feed line 52 is attached to the finishing column 48 for supplying the necessary heat and for establishing a counter-flow of air within the column. The purified vinyltoluene overhead product is withdrawn through line 54.
The finishing column bottoms product is di-rected to flash pot 56 via line 58 and pump 60. The flash pot 56 has a reboiler 62 to facilitate the fractiona- _ tion of the bottoms. The tar produced during the distillation ,.
,, , process is withdrawn through li~e 64 by pump 66 for proper disposal.
Figure 2 illustrates the application of the pro-cess of the present invention to another distillation train for vinyltoluene. An ethyltoluene feed stock is introduced into a dehydrogenation apparatus 110 to form vinyltoluene. The vinyltoluene feed stock is in-jected with a polymerization inhibitor 112 prior to the condensation of the vinyltoluene as explained in con-nection with Figure 1. The vinyltoluene feed stock is then condensed in condenser 114,and the condensed vinyl-toluene flows via line 116 to a crude vinyltoluene drum 118.
The pH of the aqueous phase is regulated by means of pH .
probe 119 and acid 120 as explained in connection with ~
Figure 1. The aqueous phase of the feed stock is withdrawn r through line 121 and is recycled back to the dehydrogenation apparatus 110. ~he product remaining in the crude vinyl-toluene drum 118 is pumped through line 122 via pump 124 through filter 126 into the vinyltoluene distillation ;.
train. Additional inhibitor 128 is added through line 122 into the vinyltoluene feed stock as explained in connection with Figure 1.
The vinyltoluene feed stcck is introduced into the intermediate portion of column 130 through feed line 122. The column 130 may be of any suitable design known to those skilled in the art and may contain any suitable number of vapor-liquid contracting devices, such as a sufficient number of bubble cap trays, perforated trays, valve trays, etc., to separate lower boiling fractions frim vinyltoluene. Alternatively, a packed column may be utilized to effect the separation. Column 130 is also equipped with a suitable reboiler 132 for supplying heat r thereto.
. ',~.
Vnder the distillation conditions imposed in column 130, an overhead stream of low-boiling hydrocarbons comprising mainly toluene is removed from column 130 via line 134. These low-boiling hydrocarbons are sub-sequently condensed and passed into storage for further use. The bottoms product of the column 130 is then intro-duced into the recycle column 136 by means for line 138 and pump 140.
The recycle column 136 may be of any suitable design known to those skilled in the art. In one embodi-ment, the recycle column is of the parallel path design, i.e., two parallel distillation paths descending through the column. In this embodiment, it is necessary that the .~-recycle column contain a sufficiently large number of trays to permit a proper separation between the similar boiling vinyltoluene and ethyltoluene. Alternatively, the recycle column 136 may comprise a packed column.
The recycle column 136 is eguipped with a suitable re-boiler 142.
The ethyltoluene overhead product of the recycle column 136 is withdrawn through line 144 and is subsequently condensed for reuse in the ethyltoluene dehydrogenation apparatus 110. The recycle bottoms is withdrawn from the recycle column 136 through line 146. The recycle bottoms product is fed by pump 148 into finishing column 150 via line 146. The finishing column 150 is equipped with a reboiler 152. Inhibitor protection is adequately provided in this column and the recycle column 136 because of the prior additional of the polymerization inhibitor.
; 30 The purified vinyltoluene overhead product is withdrawn through line 154 from the finishing column. The purified vinyltoluene product will comprise commercial quality vinyltoluene. The finishing column bottoms product is withdrawn through line 156 via pump 158 into flash pot 160. The flash pot 160 has a reboiler 162 to facilitate the fractionation of the bottoms. The tar produced during the distillation process is withdrawn through line 164 by pump 166 for proper disposal. However, recycling these inhibitor-bearing tars into the recycle column is also contemplated as an optional step.
The use of the process of the present invention ,~~
enables an apparatus for the production of vinyltoluene to operate at an increased rate and significantly reduces the amount of unwanted thermal polymerization normally occurring during the production of vinyltoluene.
The invention will now be further illustrated ,i~
by the following non-limiting examples. ~-EXAMPLE I
Following several vinyltoluene production runs during which insoluble popcorn-type polymer accumulated regularly (i.e., every 1 to 3 weeks) in the primary condenser system and the crude vinyltoluene drum., a mechanism for injecting a solution of DNPC just upstream of the quench nozzle was installed. It was found that 100 ppm DNPC relative to the vinyltoluene present was effective in controlling the fouling problem caused by polymer accumulation. ~tilizing the DNPC injection just prior to the quench nozzle, as described, the system has operated more than sixty days without the occurrence of significant fouling.
~XAMPLE II
Because of the ability of even vary small amounts of popcorn (insoluble) polymer to serve as seed for accumulations of additional insoluble polymer, a filter system was installed between the crude vinyltoluene ~!
drum and the distillation train of the system of Example ~
I to prevent the forward transfer of solids. The filter system has been found to successfully accumulate the limited amounts of popcorn which remain notwithstanding the injection of the inhibitor just prior to the quench nozzle. As a~-consequence, the transfer of seed polymer into the distil- ~-lation train has been precluded, resulting in a significant decrease in the rate of accumulation of insoluble polymer therein.
While the invention has been described in terms of various embodiments and illustrated by specific examples, ,~-various modifications, substitutions and changes can ~-be made without departing from the spirit of the invention.
Accordingly, it is intended that the scope of the present invention be ascertained solely with reference to the following claims.
,
SUM~RY OF THE INVENTION
It is therefore an object of the present invention to provide an improved process for the production of vinyl-10 toluene.
Another object of the invention resides in the provision of a method for preventing the formation of soluble and insoluble (cross-linked) thermal polymers during the processing and subseguent distillation of r 15 vinyltoluene feed stock prepared by the catalytic dehydro-genation of ethyltoluene.
It is a particular object of the present in-vention to provide a new and improved process for pre-venting the fouling of the crude vinyltoluene condensers 20 and drums used prior to distillation with undesirable thermal polymers.
A further object of the present invention is to provide a new and improved apparatus which is less prone to fouling with thermal polymers during the manufacture 25 of vinyltoluene.
In accomplishing the foregoing objects, there has been provided in accordance with the present invention a process for the production of vinyltoluene comprising .the steps of passing ethyltoluene through a dehydrogenation 30 zone to form vaporous crude vinyltoluene; adding a first portion of polymerization inhibitor to the vaporous crude vinyltoluene; condensing the vaporous crude vinyl-toluene; maintaining the pH of the aqueous phase of the condensed crude vinyltoluene at a value sufficient to 35 maintain the inhibitor in the organic phase of the condensed crude vinyltoluene; adding a second portion of polymerization inhibitor to the condensed crude vinyl-toluene; and distilling the condensed crude vinyltoluene under distillation conditions to recover pure vinyl- ~;
toluene. The condensed crude vinyltoluene may advantage-ously be filtered before distillation to remove polymer which may otherwise serve as "seed" polymer in the dis-tillation train. The polymerization inhibltor may comprise a nitrated phenol, preferably dinitro-para-cresol.
In accordance with a further aspect of the invention, the pH of the aqueous phase is adjusted to a level of from about S.5 to about 6.5. Additionally, the ; process may further comprise the step of recycling the aqueous phase back to the dehydrogenation step.
In accordance with a still further aspect of .
the invention, the first portion of polymerization in-hibitor is added when the vaporous crude vinyltoluene tem- r perature is from about 200C to about 300C. Also, the first portion of polymerization inhibitor is advantage-ously added in amounts of about 50 to 100 parts per million by weight relative to the vinyltoluene present, and the total of the first and second portions of the inhibitor added is preferably sufficient to bring the inhibitor concentration to a level of about 500 parts per million during the distillatior step.
In accordance with still another aspect of the present invention, there is provided an apparatus for manufacturing vinyltoluene, comprising means for de-hydrogenating ethyltoluene to form vaporous vinyltoluene;
first means for introducing a polymerization inhibitor into the vaporous vinyltoluene after the vaporous vinyl-toluene leaves the dehydrogenation means; means for condensing the vaporous vinyltoluene; means for collecting the condensed vinyltoluene; a second means for intro-ducing a polymerization inhibitor into the collected vinyltoluene; and means for purifving the vinyltoluene, preferably a distillation apparatus. Additionally, a filter for filtering the vinyltoluene may be included prior to the purification thereof.
1155~73 In the process according to the invention, a portion of the inhibitor is introduced directly into the stream of vaporous vinyltoluene as it leaves the dehydro-genation apparatus but immediately prior to its condensation.
5 The pH required to maintain the inhibitor in the organic phase of the vinyltoluene feed stock will vary depending upon the pXa of the inhibitor selected. It has been found that the pR required for DNPC is less than about 6.5 and typically between about 5.5 and about 6.5. However, if p-10 inhibitors other than DNPC are used during the processes, the pH required to maintain the inhibitor in the organic phase will depend on the acidic character of the inhibitor employed during the process. Any conventional filter may be utilized to filter the crude vinyltoluene feed stock 15 prior to distillation. It has been found that a filter ~
with passages Gf lessthan about 50 microns is the most r efficient size in removing any undesirable thermal polymer.
Through the use of the process according to the present invention, the amount of polymerization occur-20 ring before and during the distillation of vinylt~luene is significantly reduced in comparison to conventionally ~
employed methods. In addition, the amount of desired ._ distillation product is increased in proportion to the decrease in the amount of polymer formation. Still further, 25 , since the inhibitor is maintained in the organic phase of the vinyltoluene, the water can be reused, e.g., in the generation of dilution steam for dehydrogenating ethyl-toluene.
Other objects, features and advantages of the 30 invention will become apparent from the detailed description of the preferred embodiments which follows, when considered together with the attached figures of drawing.
BRIEF DESCRIPTION OF THE DRAWINGS
In the Drawings:
Figure 1 is a schematic diagram of a preferred embodiment of the apparatus employed in practicing the ~!
r:
1 15~73 , ' ~
present invention; and Figure 2 shows a schematic diagram of another apparatus which may be employed in practicing the invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
-Vinyltoluene is typically manufactured by reacting toluene with ethylene in the presence of an activated - Friedel-Crafts catalyst, such as aluminum chloride, or a zeolite catalyst, dehydrogenating the ethyltoluene by passing it together with steam through a dehydrogenation zone at a sufficient reaction temperature, and separating the dehydrogenated product by means of fractional distil-lation.
The present invention provides a process and apparatus for the production of vinyltoluene whereby the formation of the undesirable thermal polymer can be greatly inhibited or entirely prevented prior to and during distil- r lation of vinyltoluene feed stock prepared by the catalytic dehydrogenation of ethyltoluene. This is accomplished by adding an inhibitor immediately prior to the step of condensing the dehydrogenated vinyltoluene feed stock, adjusting the pH of the aqueous phase of the condensed feed stock to maintain the inhibitor substantially in the organic phase, and optionally filtering the feed stock prior to fractional distillation.
Toluene is alkylated to form ethyltoluene by any suitable method known to those of skill in the art.
The ethyltoluenes formed are dehydrogenated by vaporizing the hydrocarbons by means of heat exchangers, passing a stream of the vapors into admixture with steam to form a vapor mixture comprising from 1 to 10, advantageously from 2 to 3 parts ~y weight of steam per part of hydrocarbons, and passing the vapor mixture into a reactor containing a solid, .. ' 1 ~55873 granular dehydrogenation catalyst at a reaction temperature between 550 and 700C, preferably between 560 and 650C.
Any of the known catalysts which are suitable for use in dehydrogenating ethyltoluene may be used. A considerable number and variety of such catalysts are known and are commercially available. Catalysts of the self-regenerative type are preferably used.
A vapor mixture containing steam and vinyltoluene then leaves the dehydrogenation reactor and passes through one or more heat exchangers. A polymerization inhibitor is then injected into the vaporous mixture. Any of the inhibitors which are suitable for use in preventing the formation of undesirable thermal polymers in vinyltoluene and are soluble in the organic phase of the mixture may lS be utilized. Nitrated phenols are preferred, for example, dinitro-ortho-cresol, dinitro-para-cresol, meta-nitro-para-cresol, dinitro phenol, N-nitroso diphenyl amine, 4-halo-3,5-dinitro toluene, 3-nitro-2,5-cresotic acid and the like. The temperature of the vaporous mixture, at the time of the injection of the inhibitor, is prefer-ably between about 200C and 300C in order to prevent rapid decomposition of the inhibitor and to assure maximum --effectiveness of the inhibitor. If DNPC is utilized as an inhibitor, it is preferably added to the vaporous stream of crude vinyltoluene in amounts of between about 50 - 100 parts per million by weight relative to the vinyltoluene in the stream. The mixture is then cooled to condense the product, and the pH of the aqueous pha~e is adjusted, if necessary, to maintain the inhibitor in the organic phase. The pH needed to maintain the inhibitor in the organic phase will depend on the pKa of the inhibitor used. For instance, if DNPC is used as an inhibitor, a pH of 5.5 - 6.5 is sufficient to prevent the formation of the enolate anion, which is water soluble, and thus to maintain the DNPC substantially in the organic phase. Of course, if an inhibitor is selected which has a pKa different from that of DNPC, a different pH will be required to maintain the inhibitor in the organic phase of the vinyltoluene. The water collected may be recycled for use in future dehydrogenation reactions.
The dehydrogenation mixture may optionally and preferably be filtered to prevent transfer of any undesir-able insoluble polymers into the distillation apparatus.
~ Such polymers, unless removed, serve as seed polymers for ; the formation of large quantities of insoluble polymer in the distillation columns.
Additional polymerization inhibitor is added to the crude vinyltoluene prior to entry into the distillation apparatus in order to prevent any undesirable polymer formation during distillation of the vinyltoluene. Typically, .
an amount of inhibitor is added which is sufficient to raise the total concentration of the inhibitor to a level of about 500 parts per million by weight relative to the vinyltoluene. This has been found to be sufficient to prevent the formation of undesirabie insoluble pclymers during the distillation process. -The dehydrogenation mixture is fractionally distilled in a series of fractionating columns. The distillation is preferably conducted under reduced pressure r to further reduce the tendency of the vinyltoluene to polymerize. Lower boiling portions are separated from the vinyltoluene. The vinyltoluene is then removed from the heavier boiling fractions. Typical operating conditions for the distillation process include a temperature from about 65 to about 138C, and a subatmospheric pressure from about 10 to about 200 mm Hg absolute. The specific operating conditions produce a final product of commercial grade vinyltoluene which satisfies industry standards for ~:`
quality and purity.
Referring to the drawings, Figure 1 illustrates one embodiment for carrying out the process of the present invention. An ethyltoluene feed stock is introduced into a dehydrogenation apparatus 10 to form vinyltoluene. The vinyltoluene feed stock is injected with a polymeri-zation inhibitor 12 immediately prior to condensing thevinyltoluene. The vinyltoluene feed stock is condensed in ~ condenser 14, then transferred via line 16 to crude vinyltoluene drum 18. The condenser 14 may comprise a condenser using a fan or water for cooling. Alternatively, any çondenser suitable for condensing vaporous crude vinyltoluene may be utilized. The inhibitor 12 is preferably added as close to the quench nozzle of the condensing apparatus as possible in order to prevent decompasition of the inhibitor and to prevent the formation of undesirable ' ~r polymers in the condenser 14 or the drum 18. The pH
of the aqueous phase is adjusted to a pH which is suf-ficiently acidic to substantially maintain the inhibitor in the organic phase of the vinyltoluene feed stock.
A convenient means of controlling the pH of the aqueous phase in the crude drum comprises the following arrangement. Preferably, a partial stream of quench water is recycled from the crude drum to the condensing apparatus. A pH probe 19 is located in this recycle line, and downstream of the probe an inlet nozzle is provided for selectively injecting a pH control agent 20 when necessary. In order to maintain the aqueous phase slightly acidic, it is preferred to selectively add an inorganic mineral acid to the recycle stream, most preferably hydrochloric or sulfuric acid.
. The aqueous phase of the feed stock is withdrawn from the crude vinyltoluene drum through line 21 and is recycled for water treatment and use in the boilers used in the dehydrogenation of ethyltoluene.
1 1~5~73 t, _ 9 _ The product remaining in the vinyltoluene drum 18 is pumped through line 22 via pump 24 through filter 26 into a conventional vinyltoluene distillation train.
Additional inhibitor 28 is injected into the vinyltoluene feed stock in line 30 in order to ensure the presence of a sufficient amount of inhibitor during the distillation process.
In this embodiment, the vinyltoluene feed stock is introduced into the intermediate portion of recycle column 32 which is preferably of the parallel distillation path design. Reboiler 34 provides the necessary heat for distillation in column 32.
An overhead product comprising toluene and ethyl-toluene is withdrawn through line 5 for subsequent ~, fractionation in distillation column 36. In column 36, r toluene and other light distillates are withdrawn through line 38. An ethyltoluene bottoms product is withdrawn through line 40 and is recycled for use in the ethyltoluene dehydrogenation reactor 10. Reboiler 42 provides the bottoms with the necessary heat for the distillation.
The recycle bottoms product, containing vinyl- ~~
toluene inhibitor and polyvinyltoluene is withdrawn from .
the recycle column 32 through 44 u~ing pump 46 and is charged into the middle portion of finishing column 48.
A reboiler circuit comprising a reboiler 50 and an air feed line 52 is attached to the finishing column 48 for supplying the necessary heat and for establishing a counter-flow of air within the column. The purified vinyltoluene overhead product is withdrawn through line 54.
The finishing column bottoms product is di-rected to flash pot 56 via line 58 and pump 60. The flash pot 56 has a reboiler 62 to facilitate the fractiona- _ tion of the bottoms. The tar produced during the distillation ,.
,, , process is withdrawn through li~e 64 by pump 66 for proper disposal.
Figure 2 illustrates the application of the pro-cess of the present invention to another distillation train for vinyltoluene. An ethyltoluene feed stock is introduced into a dehydrogenation apparatus 110 to form vinyltoluene. The vinyltoluene feed stock is in-jected with a polymerization inhibitor 112 prior to the condensation of the vinyltoluene as explained in con-nection with Figure 1. The vinyltoluene feed stock is then condensed in condenser 114,and the condensed vinyl-toluene flows via line 116 to a crude vinyltoluene drum 118.
The pH of the aqueous phase is regulated by means of pH .
probe 119 and acid 120 as explained in connection with ~
Figure 1. The aqueous phase of the feed stock is withdrawn r through line 121 and is recycled back to the dehydrogenation apparatus 110. ~he product remaining in the crude vinyl-toluene drum 118 is pumped through line 122 via pump 124 through filter 126 into the vinyltoluene distillation ;.
train. Additional inhibitor 128 is added through line 122 into the vinyltoluene feed stock as explained in connection with Figure 1.
The vinyltoluene feed stcck is introduced into the intermediate portion of column 130 through feed line 122. The column 130 may be of any suitable design known to those skilled in the art and may contain any suitable number of vapor-liquid contracting devices, such as a sufficient number of bubble cap trays, perforated trays, valve trays, etc., to separate lower boiling fractions frim vinyltoluene. Alternatively, a packed column may be utilized to effect the separation. Column 130 is also equipped with a suitable reboiler 132 for supplying heat r thereto.
. ',~.
Vnder the distillation conditions imposed in column 130, an overhead stream of low-boiling hydrocarbons comprising mainly toluene is removed from column 130 via line 134. These low-boiling hydrocarbons are sub-sequently condensed and passed into storage for further use. The bottoms product of the column 130 is then intro-duced into the recycle column 136 by means for line 138 and pump 140.
The recycle column 136 may be of any suitable design known to those skilled in the art. In one embodi-ment, the recycle column is of the parallel path design, i.e., two parallel distillation paths descending through the column. In this embodiment, it is necessary that the .~-recycle column contain a sufficiently large number of trays to permit a proper separation between the similar boiling vinyltoluene and ethyltoluene. Alternatively, the recycle column 136 may comprise a packed column.
The recycle column 136 is eguipped with a suitable re-boiler 142.
The ethyltoluene overhead product of the recycle column 136 is withdrawn through line 144 and is subsequently condensed for reuse in the ethyltoluene dehydrogenation apparatus 110. The recycle bottoms is withdrawn from the recycle column 136 through line 146. The recycle bottoms product is fed by pump 148 into finishing column 150 via line 146. The finishing column 150 is equipped with a reboiler 152. Inhibitor protection is adequately provided in this column and the recycle column 136 because of the prior additional of the polymerization inhibitor.
; 30 The purified vinyltoluene overhead product is withdrawn through line 154 from the finishing column. The purified vinyltoluene product will comprise commercial quality vinyltoluene. The finishing column bottoms product is withdrawn through line 156 via pump 158 into flash pot 160. The flash pot 160 has a reboiler 162 to facilitate the fractionation of the bottoms. The tar produced during the distillation process is withdrawn through line 164 by pump 166 for proper disposal. However, recycling these inhibitor-bearing tars into the recycle column is also contemplated as an optional step.
The use of the process of the present invention ,~~
enables an apparatus for the production of vinyltoluene to operate at an increased rate and significantly reduces the amount of unwanted thermal polymerization normally occurring during the production of vinyltoluene.
The invention will now be further illustrated ,i~
by the following non-limiting examples. ~-EXAMPLE I
Following several vinyltoluene production runs during which insoluble popcorn-type polymer accumulated regularly (i.e., every 1 to 3 weeks) in the primary condenser system and the crude vinyltoluene drum., a mechanism for injecting a solution of DNPC just upstream of the quench nozzle was installed. It was found that 100 ppm DNPC relative to the vinyltoluene present was effective in controlling the fouling problem caused by polymer accumulation. ~tilizing the DNPC injection just prior to the quench nozzle, as described, the system has operated more than sixty days without the occurrence of significant fouling.
~XAMPLE II
Because of the ability of even vary small amounts of popcorn (insoluble) polymer to serve as seed for accumulations of additional insoluble polymer, a filter system was installed between the crude vinyltoluene ~!
drum and the distillation train of the system of Example ~
I to prevent the forward transfer of solids. The filter system has been found to successfully accumulate the limited amounts of popcorn which remain notwithstanding the injection of the inhibitor just prior to the quench nozzle. As a~-consequence, the transfer of seed polymer into the distil- ~-lation train has been precluded, resulting in a significant decrease in the rate of accumulation of insoluble polymer therein.
While the invention has been described in terms of various embodiments and illustrated by specific examples, ,~-various modifications, substitutions and changes can ~-be made without departing from the spirit of the invention.
Accordingly, it is intended that the scope of the present invention be ascertained solely with reference to the following claims.
,
Claims (12)
1. A process for the preparation of vinyltoluene, comprising the steps of:
passing ethyltoluene through a dehydro-genation zone to form vaporous crude vinyltoluene;
adding a first portion of polymerization inhibitor to said vaporous crude vinyltoluene;
condensing said vaporous crude vinyltoluene;
maintaining the pH of the aqueous phase of said condensed crude vinyltoluene to a value sufficient to maintain said inhibitor in the organic phase of said con-densed crude vinyltoluene;
adding a second portion of polymerization inhibitor to said condensed crude vinyltoluene; and distilling said condensed crude vinyltoluene under distillation conditions to recover pure vinyltoluene.
passing ethyltoluene through a dehydro-genation zone to form vaporous crude vinyltoluene;
adding a first portion of polymerization inhibitor to said vaporous crude vinyltoluene;
condensing said vaporous crude vinyltoluene;
maintaining the pH of the aqueous phase of said condensed crude vinyltoluene to a value sufficient to maintain said inhibitor in the organic phase of said con-densed crude vinyltoluene;
adding a second portion of polymerization inhibitor to said condensed crude vinyltoluene; and distilling said condensed crude vinyltoluene under distillation conditions to recover pure vinyltoluene.
2. The process of Claim 1, further comprising the step of filtering said condensed crude vinyltoluene before distillation thereof.
3. The process of Claim 1, wherein said polymeri-zation inhibitor comprises a nitrated phenol.
4. The process of Claim 3, wherein said polymeri-zation inhibitor comprises dinitro-para-cresol.
5. The process of Claim 3, wherein the pH of said aqueous phase is adjusted to a level of from about 5.5 to about 6.5.
6. The process of Claim 2, further comprising the step of recycling said aqueous phase back to said dehydrogenation step.
7. The process of Claim 1 or 2, wherein said first portion of polymerization inhibitor is added when said vaporous crude vinyltoluene temperature is between about 200°C and about 300°C.
8. The process of Claim 4, wherein said first portion of polymerization inhibitor is added in an amount of from about 50 to 100 parts per million by weight rela-tive to the vinyltoluene content of said crude vinyl-toluene.
9. The process of Claim 4, wherein said first portion of polymerization inhibitor and said second portion of polymerization inhibitor total about 500 parts per million by weight relative to the vinyltoluene content of said crude vinyltoluene.
10. An apparatus for manufacturing vinyltoluene comprising:
means for dehydrogenating ethyltoluene to form vaporous vinyltoluene;
first means for introducing a polymerization inhibitor into said vaporous vinyltoluene after said vaporous vinyltoluene leaves said dehydrogenation means;
means for condensing said vaporous vinyl-toluene to produce an aqueous crude vinyltoluene feed stock;
means for adjusting the pH of the aqueous phase of the condensed crude vinyltoluene feed stock;
means for collecting said condensed crude vinyltoluene feed stock;
a second means for introducing a polymeri-zation inhibitor into said collected crude vinyltoluene feed stock; and means for purifying said vinyltoluene.
means for dehydrogenating ethyltoluene to form vaporous vinyltoluene;
first means for introducing a polymerization inhibitor into said vaporous vinyltoluene after said vaporous vinyltoluene leaves said dehydrogenation means;
means for condensing said vaporous vinyl-toluene to produce an aqueous crude vinyltoluene feed stock;
means for adjusting the pH of the aqueous phase of the condensed crude vinyltoluene feed stock;
means for collecting said condensed crude vinyltoluene feed stock;
a second means for introducing a polymeri-zation inhibitor into said collected crude vinyltoluene feed stock; and means for purifying said vinyltoluene.
11. The apparatus of Claim 10, further comprising means for filtering said vinyltoluene prior to the puri-fication thereof.
12. The apparatus of Claim 10, wherein said purifying means is a distillation apparatus.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US221,662 | 1980-12-30 | ||
| US22166280A | 1980-12-31 | 1980-12-31 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1155873A true CA1155873A (en) | 1983-10-25 |
Family
ID=22828774
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000393024A Expired CA1155873A (en) | 1980-12-30 | 1981-12-22 | Process and apparatus for the production of vinyltoluene |
Country Status (7)
| Country | Link |
|---|---|
| JP (1) | JPS57134424A (en) |
| BE (1) | BE891574A (en) |
| CA (1) | CA1155873A (en) |
| DE (1) | DE3151976A1 (en) |
| FR (1) | FR2497193B1 (en) |
| GB (1) | GB2090282B (en) |
| IT (1) | IT1142638B (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4558169A (en) * | 1980-12-31 | 1985-12-10 | Cosden Technology, Inc. | Process for the production of vinyltoluene |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR1074757A (en) * | 1952-02-28 | 1954-10-08 | Dow Chemical Co | Improvements in the preparation of methylstyrene |
| US4105506A (en) * | 1977-02-24 | 1978-08-08 | Cosden Technology, Inc. | Polymerization inhibitor for vinyl aromatic compounds |
-
1981
- 1981-12-22 GB GB8138592A patent/GB2090282B/en not_active Expired
- 1981-12-22 CA CA000393024A patent/CA1155873A/en not_active Expired
- 1981-12-22 BE BE2/206898A patent/BE891574A/en not_active IP Right Cessation
- 1981-12-24 IT IT25852/81A patent/IT1142638B/en active
- 1981-12-24 JP JP56208264A patent/JPS57134424A/en active Pending
- 1981-12-30 FR FR8124477A patent/FR2497193B1/en not_active Expired
- 1981-12-30 DE DE19813151976 patent/DE3151976A1/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| FR2497193A1 (en) | 1982-07-02 |
| GB2090282A (en) | 1982-07-07 |
| IT8125852A0 (en) | 1981-12-24 |
| JPS57134424A (en) | 1982-08-19 |
| FR2497193B1 (en) | 1985-06-28 |
| GB2090282B (en) | 1983-11-02 |
| IT1142638B (en) | 1986-10-08 |
| BE891574A (en) | 1982-04-16 |
| DE3151976A1 (en) | 1982-08-12 |
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