WO1992006938A1

WO1992006938A1 - Removal or aromatic color bodies from aromatic hydrocarbon streams

Info

Publication number: WO1992006938A1
Application number: PCT/US1991/007528
Authority: WO
Inventors: Stewart H. Presnall; Robert J. Haynal; Beverly B. Slimp, Jr.; Martin P. Grosboll; Pamela A. Yanchik
Original assignee: Lyondell Petrochemical Company
Priority date: 1990-10-12
Filing date: 1991-10-11
Publication date: 1992-04-30
Also published as: AU8901991A

Abstract

This invention relates to a method for removing oxygenated aromatic color bodies from a C8-11 aromatic hydrocarbon stream having a boiling range between 70-240 °C, and more particularly a styrenic fraction having a boiling range between 140-155 °C by contacting the aromatic hydrocarbon stream with a neutral attapulgite clay. The process is most effective if the aromatic hydrocarbon stream is first dried using a molecular sieve. The process is effective in reducing the APHA color value of a C8-11 aromatic stream to about 400 or less and reducing the APHA color value of a C8-11 styrenic stream to 50 or less.

Description

REMOVAL OF AROMATIC COLOR BODIES FROM AROMATIC HYDROCARBON STREAMS

This invention relates to a process for removing aromatic color bodies from aromatic hydrocarbon streams.

Crude petroleum oil is generally separated into various fractions having a specified boiling range and molecular weight. Each fraction is a complex mixture of compounds related generally by molecular weight and chemical class. One such hydrocarbon stream of interest here is derived from the cracking of petroleum or coal and subsequent distillation fractionation into boiling point ranges. The distillate having a boiling range between 160-460^βF (70- 240°C) is in major part composed of Cg__u aromatics, such as unsubstituted or alkyl substituted styrenes, indenes, benzenes and indanes (such streams hereinafter are called resin oils or aromatic hydrocarbon streams) .

In the bulk processing of crude oils to resin oils, there is generally unavoidable inclusion of aromatic color bodies. The color bodies which generally contaminate resin oils also exhibit a molecular weight similar to the desired components in resin oil and a boiling point within the specified 70-240°C range. These color bodies can be C₈__n oxygenated aromatics such as, for example, unsubstituted or alkyl substituted phenols and quinones including, without limitation, phenols, cresols, catechols, resorcinols, hydroquinones, naphthoquinones , and naphthols; or sulfur containing aromatics, including but not limited to thiol, thiophene, and mercaptan structures. Because the oxygenated aro atic color bodies are so similar in physical properties to the desired resin oil components, these color bodies were considered difficult to remove from the resin stream by typical adsorptive processes.

Aromatic hydrocarbon streams, which unfortunately contain these contaminants, are used in a wide variety of applications, for example, as a feedstock to manufacture hydrocarbon resins which are used as additives in printing inks, adhesives, and rubber. Important characteristics sought in commercial preparations of aromatic hydrocarbon streams are purity and lack of color. Thus, manufacturers of hydrocarbon streams are under pressure to rid their commercial hydrocarbon products of contaminants which either directly or indirectly affect the purity or color of the products. Sulfur containing compounds can cause the hydrocarbon stream to have a variety of undesirable characteristics, such as color or an unpleasant odor, and, because sulfur is reactive, sulfur containing compounds can poison and/or consume catalysts used in subsequent reactions to which the stream may be subjected. Consumers of aromatic hydrocarbon products prefer a hydrocarbon stream having a sulfur content of less than 100 ppm because at this level, the resin produced from this hydrocarbon stream can be hydrotreated to yield an essentially clear product.

An important component of C^- aromatic hydrocarbon streams in the 140-155°C (280-310°F) boiling range is styrene. Styrene is used in a wide variety of applications. For example, styrene is used to manufacture polystyrene products, such as cups, plates, packaging materials, and insulation. Important characteristics sought in a commercial styrene product are purity and lack of color. Thus, companies that produce styrene are under pressure to rid their styrene products of contaminants that increase the color or reduce the purity of the styrene. Styrene producers also are under pressure to rid their styrene products of contamination by sulfur, which can cause an unpleasant odor or undesirable color, and which can poison and/or consume catalysts used in subsequent reactions to which the styrene may be subjected.

Styrene is one product resulting from the refinement of petroleum crude oil. For example, styrene is a byproduct in the thermal pyrolysis of hydrocarbon streams, particularly naphthas and distillates derived from crude oil, to produce ethylene and propylene. The styrene is recovered as part of a pyrolysis gasoline product, consisting of organic molecules having five to nine carbon atoms, and having a boiling range of 140-155°C. This styrene-rich hydrocarbon stream can be treated according to the present invention. Styrene also is produced at other points in the petroleum refining process. See U.S. Patent Nos. 3,684,665; 4,031,153; and 3,763,015; and Sato, M. , "Extract Styrene from Pyrolysis Gasoline", Hydrocarbon Processing (May 1973) pp. 141-144. In addition, styrene can be obtained from the pyrolytic treatment of coal, for example, through destructive distillation. Additionally, the styrene referred to herein can be styrene intentionally produced such as by a manufacturing process from benzene and ethylene feedstocks or similar feedstocks. Further, styrene produced by the dehydrogenation of ethyl benzene or dehydration of an α-methyl benzyl alcohol (α-MBA) can be used herein.

Various methods of purifying such aromatic hydrocarbon streams have been tried in the past; however, there is a need for an inexpensive, commercially feasible method for purifying such streams.

The present invention addresses the above problem by providing a less expensive, effective method for purifying such aromatic hydrocarbon streams while minimizing the amount of solid waste that is generated.

It has been discovered that aromatic color bodies present in such aromatic hydrocarbon streams can be removed by contacting the stream with a "neutral" attapulgite clay adsorbent. The present invention is most effective when the aromatic hydrocarbon stream is first passed through a molecular sieve.

For purposes of simplicity, the removal of aromatic color bodies from aromatic hydrocarbon streams according to the present invention hereinafter will be referred to as "purifying" or "purification" of the stream. A stream that has been treated using the present invention will be referred to as a "purified" aromatic hydrocarbon stream. The purity of an aromatic hydrocarbon stream treated according to the present invention is measured using a method known in the art as the American Public Health Association ("APHA") system: 1984 Am. Soc. of Testing Materials, Vol. 06.01, p. 146, D1209-84, Standard test method for color of clear liquids (platinum-cobalt scale) , incorporated herein by reference.

Any aromatic hydrocarbon stream having a boiling range of between 70-240°C can be purified according to the present invention. The aromatic hydrocarbon streams which are more particularly the subject of this invention comprise about 60% by weight or more of Cg__π aromatics. In general, the Cg__n aromatic fraction is composed of about 60-70% by weight of unsubstituted or alkyl substituted aromatic olefins such as styrenes and indenes and 30-40% by weight of alkyl substituted aromatics such as alkyl benzenes and indanes. The balance of the aromatic stream is typically Cg__n paraffins. An aromatic hydrocarbon stream taken directly from a steam cracking olefins unit generally has an APHA number of about 850-1100. A treatment according to the present invention is considered successful if the APHA number is reduced to about 400 or less. The lower the APHA number of the treated hydrocarbon stream, the more successful the treatment. Another goal of treatment is that the percent of useful desired components left in the hydrocarbon stream should not be reduced significantly, for example, by no more than 10%.

An aromatic hydrocarbon stream comprised in major part of styrenics (styrene and C₉._u alkyl substituted styrene) that is obtained directly from a resin oil tower generally has an APHA measurement of between about 600 and 650, and a boiling range of 280-310^βF (140-155°C) . Treatment of the stream according to the present invention is considered to be successful if the APHA number is reduced to 50, preferably to less than 50. The lower the APHA number, the more successful the treatment. The treatment of a hydrocarbon stream also is considered to be successful if the percent of styrenics in the resulting purified hydrocarbon stream does not fall below 50%, preferably remaining above 60% or more.

The preferred adsorbent for use in the present invention is neutral attapulgite clay. Attapulgite is a hydrated magnesium aluminum silicate mineral consisting of acicular-shaped particles with a mean particle size of about 0.1 micron existing naturally in aggregate form. Attapulgite is not a swelling clay. Domestic deposits are located chiefly in the Georgia-Florida region.

Acidic clays, especially acid treated clays, are not believed to be useful in the present invention because they tend to polymerize styrenic and other olefinic molecules, and the polymerized molecules then clog the pores of the clay and interfere with the purification process. In addition, such acid treated clays have been observed to generate exothermic reactions which interfere with the functioning of the invention.

Surprisingly, other common adsorbent and filtering media are substantially less effective in removing the color bodies from the subject resin streams. Such adsorbents include activated charcoal, ion exchange resins, various zeolites, molecular sieves, silica gel and the like.

A clay is believed to be useful in this invention if, when 5 gm of the clay is mixed with 10 gm of distilled water and shaken, the pH of the resulting mixture is between 5-9, particularly between 6-8, and most particularly 7. Such clays herein are called "neutral" clays. In particular, the clay that has been found to be most ef ective is attapulgite clay.

Usable clays have a mesh between approximately 4-300, preferably between 30-60. Those of skill in the art will recognize that, as the mesh of the clay increases, a higher pressure is required to pass the aromatic stream through the clay. Clays useful in the invention can be obtained from a number of sources, such as Oil Dri Corporation of America, 520 North Michigan Avenue, Chicago, Illinois, 60611. Heating of the clay before use, e.g. by kilning, can be helpful to remove unwanted moisture; however, the clay should not be heated above 800°C, or the clay particles may fuse and clog, rendering the clay ineffective to purify the unsaturated hydrocarbon stream.

Purification of unsaturated hydrocarbon streams according to the present invention has been found to be most effective when the stream first is contacted briefly with a molecular sieve, particularly a 13x molecular sieve composed of alumina silicate. Such molecular sieves can be obtained from Davison Chemical, a Division of Grace Chemical, Baltimore, Maryland, 21203. Other molecular sieves, such as 4A and 5A molecular sieves, are preferred to remove water and then preferentially, a 13x molecular sieve can be used to remove water and color bodies conjunctively. Contacting the stream with a series of molecular sieves of increasing mesh size also may be an effective mode of practicing the invention.

Molecular sieves are used to remove water from the unsaturated hydrocarbon stream. Water may block the active sites in the adsorbent which are responsible for purification of the stream. Certain molecular sieves, such as the 13X molecular sieve obtained from Davison Chemical, also can remove color bodies according to the present invention; however, such molecular sieves are less effective and much more expensive than other adsorbents that are useful in the invention. Thus, such molecular sieves are not as efficient or economically desirable on a large scale as other, less expensive adsorbents.

Adsorbents used to purify unsaturated hydrocarbon streams according to the present invention have been found to be effective, without regeneration, up to approximately an 10:1 weight to weight ratio. For example, 100 gms of attapulgite clay are effective to clarify 1000 gms of unsaturated hydrocarbon stream. After this 10:1 ratio has been met, the clay is either disposed of or regenerated.

The invention will be more clearly understood with reference to the following examples: EXAMPLE 1 90 g of an aromatic hydrocarbon stream containing 63.5028% of styrenics and having an APHA number of 627 were passed through a separatory funnel containing a 13x molecular sieve obtained from Davison Chemical, a Division of Grace Chemical, Baltimore, Maryland, 21203 for a total average residence time of approximately 10 minutes. The effluent from the separatory funnel was passed through a column containing 15 g of Ultra-Clear® attapulgite clay obtained from Oil Dri Corporation of America, 520 North Michigan Avenue, Chicago, Illinois, 60611. After 15 minutes average residence time, the effluent was collected and the APHA number was measured at 40, the styrenic content at 63.0801%.

EXAMPLE 2 70 g of an aromatic hydrocarbon stream containing 63.5028% of styrenics and having an APHA number of 627 were passed through a separatory funnel containing a 13x molecular sieve obtained from Davison Chemical, a Division of Grace Chemical, Baltimore, Maryland, 21203 for a total average residence time of about 10 minutes. The effluent from the separatory funnel was passed through a column containing 10 g of Ultra-Clear® 30/60 attapulgite clay obtained from Oil Dri Corporation of America. After 15 minutes average residence time, the effluent was collected and the APHA number was measured at 40, the styrenic content at 63.1701%.

EXAMPLE 3

800 g of an aromatic hydrocarbon stream (boiling range between 70-240°C) containing greater than 85% Cg__n aromatic hydrocarbons and having an APHA number of approximately 950 were passed through a separatory funnel containing a 13x molecular sieve obtained from Davison Chemical, a Division of Grace Chemical, Baltimore, Maryland, 21203. The effluent from the separatory funnel was passed through a column containing 100 g of the materials listed on the following chart. After 45 minutes average residence time, the effluent was collected and the APHA numbers were measured using known methods. The following results were obtained:

Attapulgite Activated Molecular Molecular Clay Alumina Sieve (13X) Sieve (3x

4x, 5x)

APHA 340 800 490 950

The desirable hydrocarbon content of all samples was reduced by less than 10%.

The reagents used in the above experiments were obtained from the following sources: Ultra-Clear® attapulgite clay having a typical analysis of 65.98% Si0₂, 13.09% A1₂0₃, 4.97% Fe^, 1.51% CaO, 5.32% MgO, 1.21% K₂0, 0.23% Na₂0, 0.03% S0₃, 0.78% P₂0₅, and 4.64% LOI and a mesh of 30/60 was obtained from Oil Dri Corporation of America, 520 North Michigan Avenue, Chicago, Illinois, 60611; activated alumina having a mesh of 12/32 was obtained from EM Science, a Division of EM Industries, Inc. , an associate of E. Merck of Germany, Cherry Hill, NJ, 08034; and, molecular sieves were obtained from Davison Chemical, a Division of Grace Chemical, Baltimore, Maryland, 21203.

Two other materials also were tested for their clarification abilities—an acid treated clay and an amberlyst ion exchange resin. The results for these materials are not shown because the acid treated clay caught fire, and the amberlyst melted.

EXAMPLE 4 800 g of an aromatic hydrocarbon stream (boiling range between 70-240^βC) containing greater than 85% C₈._n aromatic hydrocarbons and having an APHA number of approximately 950 and containing 134 ppm of organically bound sulfur were passed through a separatory funnel containing a 13x molecular sieve obtained from Davison Chemical. The effluent from the separatory funnel was passed through a column containing 100 g of Ultra-Clear® attapulgite clay having a mesh of 30/60. After 45 minutes average residence time, the effluent was collected and the APHA number and sulfur content was measured using known methods. The APHA number of the treated hydrocarbon stream was 220, and the sulfur content was reduced to 94 ppm.

EXAMPLE 5

750 g of an aromatic hydrocarbon stream (boiling range between 70-240°C) containing greater than 85% Cg__π aromatic hydrocarbons and were passed over a column packed with 100 g

Oil Dri Ultra-Clear® 30/60 attapulgite clay. The initial

APHA reading of the hydrocarbon stream was 864. After a residence time of 30 minutes, an initial effluent was collected and tested. The hydrocarbon stream after treatment had a APHA reading of 100.

Further, the oxygenate content of the hydrocarbon stream before and after clay treatment was measured on a Hewlett Packard gas chromatograph. FIGS, la and lb show the comparison of oxygenate content before and after clay treatment of the C_g__π aromatic hydrocarbon stream. The top chromatograph on each of FIGS, la and lb is a representation of the relative oxygenate content of the aromatic stream after clay treatment; and the bottom chromatograph is representative of the aromatic stream before treatment.

EXAMPLE 6 100 g of resin oil containing greater than 85% by weight Cg__n aromatic hydrocarbons were admixed with 10 g of Oil Dri Ultra-Clear® 30/60 attapulgite clay and continuously shaken. The initial APHA reading of the untreated resin oil was 1020. After two minutes of shaking, a sample of resin oil was tested and the APHA reading was 440. After a total of 7-1/2 minutes of shaking, the treated resin oil was tested and had an APHA reading of 76.

* * *

A simple gravity driven or batch procedure can be used, or a pump or ebullient bed can be used to force the unsaturated hydrocarbon stream through the adsorbent. The resulting purified stream can be collected by any known method, including, for example, collection in a pipeline so that the resulting stream can be transferred to another location.

While the invention has been described with respect to various specific examples and embodiments, it is to be understood that the invention is not limited thereto. Many variations and modifications may be made upon the specific examples disclosed herein, and the appended claims are intended to cover all of these variations and modifications.

Claims

CLAIMS:

1. A process for removing oxygenated aromatics from an aromatic hydrocarbon stream comprising in major part of styrenics and having a boiling range between 140-155°C comprising the steps of contacting said aromatic hydrocarbon stream with an adsorbent consisting essentially of a neutral attapulgite clay for a time sufficient to purify said aromatic hydrocarbon stream, and collecting a purified aromatic hydrocarbon stream.

2. A process for removing aromatic color body contaminants from an aromatic hydrocarbon stream comprising in major part of styrenics and having a boiling range between 140-155°C comprising the steps of contacting said aromatic hydrocarbon stream with an adsorbent consisting essentially of a neutral attapulgite clay for a time sufficient to purify said aromatic hydrocarbon stream, and collecting a purified aromatic hydrocarbon stream.

3. A process for reducing the APHA reading of an aromatic hydrocarbon stream comprising in major part of styrenics and having a boiling range between 140-155°C comprising the steps of contacting said aromatic hydrocarbon stream with an adsorbent consisting essentially of a neutral attapulgite clay for a time sufficient to reduce the APHA reading of said aromatic hydrocarbon stream to about 50 or less, and collecting said purified aromatic hydrocarbon stream.

4. The process of claims 1, 2, or 3 wherein said aromatic hydrocarbon stream is first contacted with a molecular sieve.

5. The process of claim 4 wherein said molecular sieve is 4A, 5A or 13X.

6. The process of claims 1, 2, or 3 wherein said aromatic hydrocarbon stream had an initial APHA reading of between about 600 and about 650 and the purified aromatic stream has an APHA reading of less than 50.

7. A purified aromatic hydrocarbon stream comprising in major part of styrenics and having a boiling range between 140-155^βC and an APHA reading of about 50 or less produced by a process comprising the steps of contacting said aromatic hydrocarbon stream with an adsorbent consisting essentially of a neutral attapulgite clay for a time sufficient to reduce the APHA reading of said aromatic hydrocarbon stream to 50 or less, and collecting said purified aromatic hydrocarbon stream.

8. The product of claim 7 wherein during said process, said aromatic hydrocarbon stream is first contacted with a molecular sieve.

9. The product of claim 8 wherein said molecular sieve is 4A, 5A or 13X.

10. A process for removing aromatic color bodies from an aromatic hydrocarbon stream comprising 60% or more of C_g__n aromatics and having a boiling range between 70-240°C comprising the steps of contacting said aromatic hydrocarbon stream with an adsorbent consisting essentially of a neutral attapulgite clay for a time sufficient to purify said aromatic hydrocarbon stream, and collecting a purified aromatic.

11. A process for removing oxygenated aromatics from an aromatic hydrocarbon stream comprising 60% or more of Cg__u aromatics and having a boiling range between 70-240^βC comprising the steps of contacting said aromatic hydrocarbon stream with an adsorbent consisting essentially of a neutral attapulgite clay for a time sufficient to purify said aromatic hydrocarbon stream, and collecting a purified aromatic.

12. A process for reducing the APHA reading of an aromatic hydrocarbon stream comprising 60% or more of Cg__u aromatics and having a boiling range between 70-240°C comprising the steps of contacting said aromatic hydrocarbon stream with an adsorbent consisting essentially of a neutral attapulgite clay for a time sufficient to reduce the APHA reading of said aromatic hydrocarbon stream to about 400 or less, and collecting said purified aromatic.

13. The process of claims 10, 11, or 12 wherein the aromatic hydrocarbon stream comprises 85% or more of Cg__π aromatics.

14. The process of claims 10, 11, 12 or 13 wherein the C^n aromatics comprise a mixture of alkyl substituted benzenes, indanes, styrenes and indenes.

15. The process of claims 10, 11, 12 or 13 wherein said aromatic hydrocarbon stream is first contacted with a molecular sieve.

16. The process of claim 15 wherein said molecular sieve is 4A, 5A or 13X.

17. A purified aromatic hydrocarbon stream comprising 60% or more of C₈._u aromatics and having a boiling range between 70-240°C and an APHA reading of about 400 or less, said purified aromatic produced by a process comprising the step of contacting an aromatic hydrocarbon stream with an adsorbent consisting essentially of a neutral attapulgite clay for a time sufficient to reduce the APHA reading of said aromatic hydrocarbon stream to about 400 or less, and collecting said purified aromatic.

18. The product of claim 17 wherein the aromatic hydrocarbon stream comprises 85% or greater of Cj__u aromatics.

19. The product of claims 17 or 18 wherein the Cg._n aromatics comprise a mixture of alkyl substituted benzenes, indanes, styrenes and indenes.

20. The product of claims 17 or 18 wherein during said process, said aromatic hydrocarbon stream is first contacted with a molecular sieve.

21. The product of claim 20 wherein said molecular sieve is 4A, 5A or 13X.