Abstract:
An inhibitor to suppress or inhibit the viscosity increase of a hydrocarbon, e.g. in a bottom section of an oil quench tower, featuring the use of a sulfonic acid and/or its salt as an effective inhibitor composition, which may optionally contain a polymerization inhibitor including one or more inhibitors selected from the group of aromatic amines, phenols and dialkyl hydroxyl amines. Furthermore, the method to inhibit the increasing viscosity of hydrocarbon, e.g. in a bottom section of a tower, may be accomplished by adding the hydrocarbon viscosity inhibitor to the feed oil, reflux oil or directly to the tower bottom oil in the tower. Such an oil quench tower is used for an olefin production process in which the hydrocarbon may include naphtha, light oil, natural gas, liquefied natural gas, etc. in the raw material.

Description:
This is a continuation-in-part of copending application Ser. No. 08/335,607 filed on Dec. 14, 1994, and now abandoned. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to hydrocarbon viscosity inhibitors or reducers and methods of inhibiting or reducing the viscosity of hydrocarbons, and more particularly relates to hydrocarbon viscosity inhibitors which also increase hydrocarbon product yield, improve the thermal effect of and stabilize operation by inhibiting or reducing the viscosity of a hydrocarbon. 
     BACKGROUND OF THE INVENTION 
     In the petrochemical industry, various types of olefins are usually produced by thermally decomposing naphtha. Naphtha together with diluting stream is thermally decomposed at about 800° to about 850° C. in a thermal decomposition furnace, abruptly cooled down to about 350° to about 400° C. at the outlet of the decomposition furnace and sent to an oil quench tower (also called a gasoline fractionator or gasoline splitter) in which the naphtha is divided into a light component with 9 or less carbon atoms, and a heavy component with more than 9 carbon atoms. The feed oil in the quench tower contains the aromatic unsaturated compounds of the styrene, methyl styrene, divinylbenzene, indene, etc., which can be undesirably polymerized by the heat throughout the oil quench tower thus increasing the viscosity of oil in the bottom section of the tower and thus cause contamination by polymerized materials in the tower. In the past, the contamination of the tower has been prevented by adding a polymerization inhibitor, but such a method showed only a limited preventative effect, and did not inhibit or reduce the viscosity of the oil from increasing in the tower. Therefore, the method commonly used for inhibiting the increase of viscosity of oil in the bottom section of the tower was to lower the temperature of tower bottoms. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide a chemical agent and a method which can inhibit the viscosity of hydrocarbon from increasing, e.g. in the bottom section of an oil quench tower in an olefins production process. 
     It is another object of the present invention to provide a hydrocarbon viscosity inhibitor or reducer which can be readily acquired or made. 
     In carrying out these and other objects of the invention, there is provided, in one form, a hydrocarbon viscosity inhibitor composition comprising a sulfonic acid or salt thereof of the formula: R&#39;--SO 3  (X) n . In this formula, R&#39; is selected from the group consisting of a straight or branched alkyl group of 4-32 carbon atoms; an alkyl-substituted benzene nucleus and an alkyl-substituted naphthalene nucleus, where the alkyl group in either is a straight or branched alkyl group of 4-32 carbon atoms; X is selected from the group consisting of hydrogen, alkali metal, and alkali earth metal, primary amine salt, secondary amine salt, tertiary amine salt; where any of the amine salts may be substituted with a straight or branched alkyl group of 1-22 carbon atoms, and further where the straight or branched alkyl group of 1-22 carbon atoms may contain a hydroxy or an alkoxy group, and n is selected from the group consisting of 1 or 1/2. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     It was assumed that the increase in viscosity of a hydrocarbon in, for example, the bottom of equipment such as an oil quench tower is caused by the thermal polymerization of aromatic unsaturated compounds of styrene, methyl styrene, divinylbenzene, indene, etc. contained in the feed oil. Based on this assumption, a very strenuous and diligent study was made regarding the inhibition of polymerization and increase in viscosity, which resulted in the discovery of a compound which can inhibit the viscosity of a hydrocarbon from increasing in the tower bottom. 
     The invention of inhibiting or suppresses the rising viscosity of hydrocarbon in the bottom section of an oil quench tower, e.g., features the use of one or more components of sulfonic acid or its salt of the formula (I): 
     
         R&#39;--SO.sub.3 (X).sub.n                                     (I) 
    
     where R&#39; is selected from the group consisting of 
     a straight or branched alkyl group of 4-32 carbon atoms; 
     an alkyl-substituted benzene nucleus, where the alkyl group is a straight or branched alkyl group of 4-32 carbon atoms; and 
     an alkyl-substituted naphthalene nucleus, where the alkyl group is a straight or branched alkyl group of 4-32 carbon atoms; 
     X is selected from the group consisting of hydrogen, alkali metal, and alkali earth metal, primary amine salt, secondary amine salt, tertiary amine salt; where any of the amine salts may be substituted with a straight or branched alkyl group of 1-22 carbon atoms, and further where the straight or branched alkyl group of 1-22 carbon atoms may contain a hydroxy or an alkoxy group; and 
     n is selected from the group consisting of 1 or 1/2. 
     It will be appreciated that when X is hydrogen, the above formula (I) is a sulfonic acid, and when X is other than hydrogen, it is a salt form that is being referred to. 
     Furthermore, this is an inhibitor composition which suppresses the rising viscosity of the aforementioned hydrocarbon, a feature of which is to mix one or more polymerization inhibitors selected from the aromatic amine family of polymerization inhibitors, the phenol family of polymerization inhibitors and the dialkyl hydroxylamine family polymerization inhibitor with the R&#39;--SO 3  (X) n  component. This invention is also related to a method to inhibit an increase in viscosity of a hydrocarbon, such as in the bottom section of oil quench tower, involving addition of the subject viscosity inhibitor to the tower bottom oil using the effective component of sulfonic acid or its salt of formula (I). In one embodiment, the proportion of sulfonic acid or its salt or the composition containing the same is from about 10 ppm to about 10,000 ppm based on the amount of oil in the tower bottom or other hydrocarbon. 
     In non-limiting, more specific examples of suitable components of this invention are the sulfonic acid or its salt shown in formula (1) where R includes, but is not limited to, nonyl, decyl, dodecyl, octadecyl, petroleum sulfonic acid residue, dodecyl benzene, tridecyl benzene, dibutyl benzene, octyl benzene, nonylbenzene, or nonyl naphthenate. In the formula (I), X can be hydrogen or alkaline metals such as lithium, sodium, potassium, etc., or alkaline earth metals such as magnesium, barium, calcium, etc. or alkyl amine salts such as propyl amine salt, diisopropyl amine salt, diisobutyl amine salt, sec-butyl amine salt, di-sec-butyl amine salt, 1,2-dimethyl propyl amine salt, hexyl amine salt, cyclohexyl amine salt, heptyl amine salt, 2-ethyl hexyl amine salt, di(2-ethylhexyl) amine salt, octyl amine salt, nonyl amine salt, decyl amine salt, undecyl amine salt, dodecyl amine salt, tetra decyl amine salt, hexadecyl amine salt, octadecyl amine salt, coco amine salt, mono-ethanol amine salt, etc. More specific examples include, but are not limited to dodecyl benzene sulfonic acid sodium, petroleum sulfonic acid sodium, dodecyl benzene sulfonic acid coco amine salt, dodecyl benzene sulfonic acid mono-ethanol amine salt, etc. Each of these sulfonic acids and their salts may be used individually alone or in combination of two or more suitable sulfonic acids or their salts, and this invention does not restrict or limit the mixed use of these acids and salts. 
     The optional polymerization inhibitor of this invention may be generally defined as an oxidation inhibitor which reacts based on the radical chain inhibiting reaction. The aromatic amine family of polymerization inhibitors include, but are not necessarily limited to, p-phenylenediamines such as N,N&#39;-di-di-isopropyl-p-phenylenediamine; N,N&#39;-di-sec-butyl-p-phenylenediamine; N,N&#39;-diphenyl-p-phenylenediamine; N-(1-methylheptyl)-p-phenylenediamine; etc.; and secondary amines such as 4,4-dicumyl-diphenyl amine; 4,4-dioctyl diphenyl amine; p-methoxy phenylmethylamine; 4,4-dinonyl diphenylamine; diphenylamine; phenyl-α-naphthylamine; phenyl-β-naphthylamine; etc. Suitable polymerization inhibitors from the phenol family include, but are not necessarily limited to, the following various types of phenols: phenol; 2-methyl phenol; 4-methyl phenol; 2,6-dimethyl phenol; 2,4,6-trimethyl phenol; 2,6-ditertiary butyl phenol; 2,4-ditertiary butyl phenol; 2-methyl-4-tertiary butyl phenol; 2,6-diisopropyl phenol; 2,6-dimethyl-4-tertiary butyl phenol, 4-methoxyl phenol, etc. and various catechols including, but not limited to, 4-tertiarybutyl catechol, and various hydroquinones including, but not necessarily limited to, hydroquinone; 2-methyl hydroquinone; 2-tertiary butyl hydroquinone; 2,5-di-tertiary butyl hydroquinone; 2,5-di-tertiary amyl hydroquinone, etc. The dialkyl hydroxyl amine family of polymerization inhibitors includes, but is not limited to such materials as diethylhydroxylamine; dipropylhydroxylamine, etc. 
     In one embodiment of the invention, a dialkylhydroxylamine is explicitly absent, and in particular, diethylhydroxylamine (DEHA) is explicitly absent. 
     Each of these polymerization inhibitors may be used singly with the viscosity inhibitor or in combination of two or more inhibitors together with the sulfonic acids or salts thereof. This invention is not limited to any particular mixture of these inhibitors or mixture of inhibitors with the viscosity inhibitors of this invention. 
     The optional polymerization inhibitor of this invention may be used by mixing it with the viscosity inhibitor sulfonic acid or its salt, where the ratio of polymerization inhibitor to the sulfonic acid of formula (I) or its salt is 10 to 1 or less, by weight. The hydrocarbon viscosity inhibitor composition of this invention is added to the oil in the bottom of an oil quench tower or other hydrocarbon in a proportion of about 10 to about 10,000 ppm, preferably about 10 ppm to about 2,000 ppm, based on the amount of hydrocarbon. Normally amounts in these ranges are expected to be effective, although other proportions are also anticipated to be effective. However, in general, if the proportion is less than about 10 ppm, an effective result normally cannot be ensured, and if the proportion is more than 10,000 ppm, the effect may be sufficient, but not in a cost effective proportion to the amount added. 
     In the practice of the method of this invention, the hydrocarbon viscosity inhibitor composition may be added at other positions, but in the oil quench tower application, it is normally added to the tower feed oil or return oil, or directly to the oil in the bottom of an oil quench tower. 
     When adding the viscosity inhibitor of this invention, each effective component of the inhibitor may be added separately, or may alternatively be mixed at the specified proportions before adding. For easy addition, it is usually better to measure the amount of each effective component and dissolve it in an appropriate solvent before injecting. 
     Since it is assumed that the increase in the viscosity of tower bottom oil flowing out of oil quench towers after distilling is caused by the polymerization of aromatic unsaturated compounds such as ethylene, methyl ethylene, divinylbenzene, indene, etc., the viscosity increase may be inhibited by suppressing the polymerization. However, the effective viscosity inhibition has not been made with the conventional polymerization inhibitors alone. The viscosity inhibitors of this invention are believed to prevent the viscosity from increasing as the inhibitor adheres to the initially formed polymer and disperses the formed polymer, thus preventing the polymerization from further progressing and the formed polymer from branching and bridging. However, the inventors do not wish to be limited by any particular theory. 
     This invention is explained further and in more detail by the following examples of actual application, but is not limited to the illustrated examples alone. 
     
                                           TABLE I__________________________________________________________________________Viscosity Inhibitors Used for TestsViscosityinhibitor  Viscosityshorthand  inhibitor type            Viscosity inhibitor description__________________________________________________________________________A      Sulfonic acid            Dodecyl benzene sulfonic acid (branched type)            free acidB      Sulfonic acid salt            Dodecyl benzene sulfonic acid (branched type)/            tetradecyl amine salt; prepared by dissolving            equimolar amounts of the sulfonic acid and the            amine in xylene; kept at 60° C. for 2 hours,            thus            forming salt. For this testing, the xylene            solution as simply added.C      Sulfonic acid salt            Dodecyl benzene sulfonic acid (branched type)/            cocoamine saltD      Sulfonic acid salt            Dodecyl benzene sulfonic acid (branched type)/            2-ethylhexyl amine saltB      Sulfonic acid salt            Dodecyl benzene sulfonic acid (branched type) /            dibutyl amine saltF      Sulfonic acid salt            Dodecyl benzene sulfonic acid (branched type)/            ethylene diamine saltG      Sulfonic acid salt            Dodecyl benzene sulfonic acid (branched type) /            monoethanol amine saltH      Sulfonic acid salt            Dodecyl benzene sulfonic acid (straight chain            type)/tetradecyl amine saltI      Sulfonic acid salt            Tridecyl benzene sulfonic acid (branched type)/            tetradecyl amine saltJ      Sulfonic acid salt            Tetradecyl benzene sulfonic acid (branched            type)/n-butyl amine saltK      Sulfonic acid salt            Petroleum sulfonic acid/sodium saltL      Sulfonic acid salt            Petroleum sulfonic acid/sodium salt__________________________________________________________________________ 
    
     
                                           TABLE II__________________________________________________________________________Polymerization Inhibitors Used for TestsAbbrev.,                       Trade name,if any Full name   Source       if any__________________________________________________________________________TBC   4-tert-butyl catechol             Dainippon Ink &amp;                          DIC-TBC             Chemicals Inc.BHT   2,6-dimethyl-p-cresol             Kawaguchi Chemicals Inc.                          Antage BHTBPA   N,N&#39;-di-sec-butyl-p-             Sumitomo Chemicals Inc.                          Sumlizer phenylenediamine         BPADEHA  Diethyl hydroxylamine             Toka Idenka Kogyo Inc.                          DEHADPA   Diphenylamine             Seiko Chemicals Inc. Polymethacrylate family             Texaco Chemical Co. of dispersion agents__________________________________________________________________________ 
    
     
                       TABLE III______________________________________Raw Materials Used in Polymerization Inhibitors Used for Tests                       Trade name,Full name         Source    if any______________________________________Dodecyl benzene sulfonic acid             Teika     Teika Power B-120(branched type)Dodecyl benzene sulfonic acid             Teika     Teika Power L-120(straight chain type)Tridecyl benzene sulfonic acid             Teika     Teika Power B-130(branched type)Petroleum sulfonic acid sodium salt             Matsumura Sulforl 500             SekiyuTetra decyl amine Nihon Yushi                       Amine MBCoco amine        Nihon Yushi                       Amine FB______________________________________ 
    
     Other reagents such as 2-ethylhexyl amine; dibutyl amine, ethylene diamine, monoethanolamine and n-butyl amine were all made by Tokyo Kasei. 
     EXPERIMENTAL PROCEDURE 
     The test oil (100 ml) was poured into a 200 ml glass container; the specified quantity of viscosity inhibitor was added to the container and heated to 180° C. for 15 hours. When the test oil was cooled to 25° C., its viscosity was measured with a BL type revolving viscometer (made by Tokyo Keiki). The test oil was quench oil obtained from an ethylene plant (containing less than 0.1 wt. % styrene; less than 0.1 wt. % methylstyrene; less than 0.1 wt. % divinylbenzene and less than 0.1 wt. % indene). The tower bottom oil and oil quench tower reflux oil (containing 30 wt. % styrene; 14.5 wt. % methylstyrene; 0.2 wt. % divinylbenzene and 9.0 wt. % indene) were mixed at the mixing ratio of 9:1 (in volume). The results of these tests are shown in Tables IV and V. 
     
                                           TABLE IV__________________________________________________________________________Inventive Examples                Tested oilViscosity inhibitor composition                        Mixture of tower   Sulfonic Polymerization                Tower bottom oil,                        bottom oil and   acid or salt       inhibitor                Viscosity                        reflux oil;Ex.   (dosage: ppm)       (dosage: ppm)                (cp, 25° C.)                        Viscosity (cp, 25° C.)__________________________________________________________________________1  A  (1000)       --       12,300  1,9502  B  (100) --       14,000  2,6003  B  (500) --       9,500   1,9504  B  (1000)       --       8,800   1,3505  B  (10,000)       --       5,200   7506  C  (500) --       10,500  1,8007  C  (1000)       --       9,000   1,4508  D  (1000)       --       9,200   1,5509  E  (1000)       --       10,400  1,80010 F  (1000)       --       11,500  1,85011 G  (1000)       --       9,800   1,75012 H  (1000)       --       9,000   1,50013 I  (1000)       --       9,600   1,75014 J  (1000)       --       13,700  2,05015 K  (1000)       --       11,200  1,90016 A  (300) --       9,200   1,800   B  (500)17 A  (500) --       9,900   1,640   C  (500)18 B  (800) TBC  (200)                9,200   85019 B  (800) BHT  (200)                9,100   1,00020 B  (800) BPA  (200)                8,800   85021 B  (800) DEHA (200)                9,000   70022 B  (800) DPA  (200)                9,000   90023 B  (800) TBC  (100)                8,700   850   B  (800) BPA  (100)__________________________________________________________________________ 
    
     
                                           TABLE V__________________________________________________________________________Comparative Examples                Tested oilViscosity inhibitor composition                        Mixture of tower   Sulfonic Polymerization                Tower bottom oil,                        bottom oil and   acid or salt       inhibitor                Viscosity                        reflux oil;Ex.   (dosage: ppm)       (dosage: ppm)                (cp, 25° C.)                        Viscosity (cp, 25° C.)__________________________________________________________________________24 None     --       17,900  3,15025 L  (1000)       --       17,300  3,00026 L  (800) TBC  (200)                17,500  2,85027 L  (800) DPA  (200)                17,200  2,90028 --       TBC  (200)                17,800  2,70029 --       DEHA (1000)                17,300  1,55030 --       DPA  (1000)                17,600  2,85031 --       TBC  (500)                17,000  2,600       BPA  (500)32 -- Polymethacrylate family                18,400  3,300 dispersant (1000)__________________________________________________________________________ 
    
     As a result of the above experiments, it was confirmed that the increase viscosity of hydrocarbon in the bottom section of oil quench tower was effectively inhibited by adding the combination of sulfonic acid or its salt and polymerization inhibitor, as described in this invention, to the test oil. Note that Example 24 serves as the control against which inventive Examples 1-23 may be compared. The results of Examples 1-23 show considerably greater reduction in viscosity than do the results of Examples 25-32. 
     With the hydrocarbon viscosity inhibitor or reducer composition of this invention and the method employing it, the viscosity of hydrocarbon treated, such as in the bottom section of an oil quench tower, e.g., can be reduced and its increase inhibited. Further, gasoline yield is increased, the load on the bottom mp is reduced, pipings are prevented from clogging, refluxing rate in the oil ench tower is reduced, the temperature of the tower bottom section is increased to reduce the amount of heating steam used for the succeeding processes, etc., thus improving the economic effect of the entire process. 
     In the foregoing specification, the invention has been described with reference to specific embodiments thereof. However, it will be evident that various modifications and changes can be made thereto without departing from the broader spirit or scope of the invention as set forth in the appended claims. Accordingly, the specification is to be regarded in an illustrative rather than a restrictive sense. For example, specific viscosity inhibitors falling within the claimed parameters, but not specifically identified or tried are anticipated to be within the scope of this invention. Further, specific combinations of viscosity inhibitors and polymerization inhibitors within the claimed scope but not specifically identified or experimented with are anticipated to be within the scope of this invention.