JPH0427970B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention generally relates to the purification of spent sulfuric acid streams produced in the production of alcohols by catalytic hydration of olefins. Each year, large quantities of alcohol are produced by the catalytic hydration of olefins, which involves absorbing a selected olefin feed into a stream of concentrated sulfuric acid to form the corresponding sulfate alkyl ester. Water is then mixed with the ester-containing liquid to hydrolyze the ester to form the desired alcohol, which is generally recovered by stripping with steam or other heating fluid. Thereby, a dilute sulfuric acid stream is produced which, for economic reasons, must be treated to concentrate with respect to its sulfuric acid content and then recycled to the absorption stage. Organic impurities in these various sulfuric acid streams accumulate due to this continuous acid recycling, and this accumulation deposits carbonaceous material on the interior surfaces of the process equipment.
These carbonaceous deposits resulting from thermal decomposition ("coking") of organic impurities can foul the equipment and severely reduce the flow rate of liquid through the equipment. Therefore, removal of these deposits is periodically necessary and requires facility interruptions as well as physical removal of these deposits, such as by manual scraping of soiled surfaces. This requires significant costs in manpower and plant interruptions, and results in a significant loss of annual plant capacity. Furthermore, the carbonaceous deposits thus removed are waste gases, and safe dumping of these waste gases is required, creating further costs and attendant environmental problems. Various methods have been developed to purify various spent sulfuric acid streams. Certain methods of regenerating used sulfuric acid by air oxidation of organic impurities are described in US Pat. No. 2,015,254. U.S. Pat. No. 3,145,080 discloses that after reacting dilute sulfuric acid with excess hydrogen sulfide in the presence of activated carbon,
A method is described for removing metal impurities from dilute sulfuric acid by decomposing excess hydrogen sulfide with hydrogen peroxide, also in the presence of activated carbon. Alkylated refinery sludge containing undesirable organics produced during petroleum refining is disclosed in U.S. Patent No.
No. 3,477,814, in which the alkylated sludge is first heated to dehydrate and desulfate the sludge, and then, in a series of complex steps, concentrated pure sulfuric acid is purified. generated and collected. The spent sulfuric acid stream produced in the nitration of aromatic hydrocarbons such as toluene is described in U.S. Pat.
No. 3,856,673 to completely oxidize nitrated organic compound impurities such as nitrocresol and other nitrophenolic compounds. Such oxidation is necessary to prevent the formation of trinitro-substituted aromatic compounds, which are highly unstable and can be violently explosive. U.S. Patent No. 4,085,016 relates to the electrolytic treatment of sulfuric acid streams produced from sulfur dioxide obtained by torrefaction of sulfide ores, using peroxy compounds of hydrogen peroxide and sulfuric acid to remove organic impurities from CO2. It states that it can be completely oxidized into _two gases and water. US Pat. No. 4,157,381 relates to a method for purifying a sulfuric acid stream containing organic impurities by the use of peracid steam atomization and multiple steam treatment stages. In this process, an oxidizing agent such as nitric acid, hydrogen peroxide, or caroic acid is added at any one of several stages. The impurity content of spent sulfuric acid streams produced by various processes and their critical process characteristics vary widely. Thus, the methods described above are unsuitable for direct use in the treatment of spent sulfuric acid streams produced in different processes, such as in the hydration of olefins for the production of alcohol. According to the invention, a spent sulfuric acid stream produced in the hydration of olefins for the production of alcohol and containing organic sulfonic acid impurities is treated with ozone, hydrogen peroxide, chlorates, peroxydisulfates, and The sulfonic acid impurity is partially oxidized by contacting with an oxidizing agent selected from the group consisting of mixtures thereof, using the oxidizing agent in an amount less than one stoichiometric equivalent per equivalent of the sulfonic acid impurity. carbonaceous solids are produced in an untreated spent sulfuric acid stream at a given temperature to remove harmful organic impurities. The inventors have discovered that the fouling problem associated with the formation of carbonaceous deposits in the sulfuric acid catalytic hydration process of olefins for alcohol production is due to the fact that the fouling problem associated with the formation of carbonaceous deposits is produced as a by-product in the hydration process and at high temperatures. This is due to the presence of chemically reactive organic sulfonic acid impurities in the spent sulfuric acid stream that readily decompose into coke and tar, and these can be reduced by the process of the present invention of partially oxidizing the organic sulfonic acid impurities. We have discovered the surprising fact that the staining problem can be eliminated or greatly reduced. The process of the present invention also provides a treated sulfuric acid stream with greatly improved thermal stability, and after concentration, the treated sulfuric acid stream is subjected to thermal decomposition of organic impurities in the sulfuric acid stream. It has been unexpectedly discovered that the amount of carbonaceous deposits produced can be greatly reduced while being recycled to the olefin hydration process. Treatment of the spent sulfuric acid stream resulting from the hydration of olefins in accordance with the method of the present invention eliminates or substantially minimizes equipment fouling problems associated with the deposition of carbonaceous impurities on process equipment interior surfaces. . The method of the invention will now be described with reference to the accompanying drawings. In the drawings, like numbers refer to the same or similar elements. Referring to Figure 1, an olefin, e.g. an aliphatic olefin having 2 to 8, preferably 2 to 4 carbon atoms per molecule (e.g. ethylene, propylene, butene, pentene, octene) is absorbed from line 2. in the absorption column 10, in contact with the concentrated sulfuric acid stream introduced from line 6 and (at least in part)
Absorption into the sulfuric acid produces the corresponding sulfuric acid alkyl ester. The olefin to be sulfated can be obtained from any available olefin source, such as cracking distillation of carbonaceous materials, but especially from cracking of petroleum hydrocarbons, such as is carried out in petroleum refining of mineral oils. . The olefins used in the present invention are also typically obtained by careful fractional distillation of cracked petroleum gases and are preferably substantially free of highly unsaturated hydrocarbons, especially diolefins such as butadiene. Examples of olefins that can be used are lower branched and straight chain alkenes (ie, alkenes of 2 to 6 carbon atoms), such as ethylene, propylene, butene, and the like. The sulfuric acid stream 6 used to sulfate the selected olefin feed is a concentrated sulfuric acid stream, the exact sulfuric acid concentration depending on the olefin used, reaction temperature and other conditions. Generally, however, sulfuric acid stream 6 will contain about 45 to 99%, preferably about 65 to 95%, by weight sulfuric acid for the sulfation of ethylene or propylene, and will contain a butene or higher olefin feed. For the reaction, it contains about 55-85% by weight, preferably about 65-80% by weight of sulfuric acid. The temperature and pressure used in the absorption tower 10 are also
Varies depending on olefin, acid concentration and other factors. Generally, temperatures of about 20-120°C are used and pressures are sufficient to maintain the desired liquid phase within the absorption column. Typically, for example, propylene is
It is absorbed at a temperature of about 90-110°C and a pressure of about 7.03-28.12 Kg/cm ² gauge (100-400 psig). As shown in the drawing, the olefin and the sulfuric acid stream are contacted in a countercurrent manner, and the sulfuric acid stream is introduced into the top of the absorption column. Unabsorbed gas is discharged from the top of absorption column 10 through conduit 7 and can be recycled to conduit 2 if desired, or can be subjected to conventional treatment, such as treatment with a caustic solution. . A product stream, commonly referred to as "extractant", is discharged from the bottom of absorption column 10 through line 4;
Alkyl esters, such as diethyl sulfate when the olefin is ethylene, and di(isopropyl) sulfate in the case of propylene sulfation.
The concentration of alkyl ester in extract stream 4 is not critical and can vary within a wide range. That is, the extract generally contains lower alkenes (e.g. propylene,
butylene) absorption contains 15-30% by weight of total alkyl esters (mono- and dialkyl esters). In the second step of the hydration process, water is added to the extract in stream 4 through line 12 in order to hydrolyze the alkyl esters and liberate isopropanol from the corresponding alcohol, e.g. di(isopropyl sulfate). do. The method of contacting the water with the extract is not critical and is known in the art.
(1) an in-line addition method of water to the extract (as shown in the drawing), provided there is adequate conduit length to provide sufficient mixing and reaction time; and (2) a separate reactor. A variety of such methods have been used, including contacting the extract with water under stirring (not shown). The amount of water added to the extract is also not critical;
Can vary widely. Generally, about 0.3 to 1.0 parts by weight of water is added to the extract for each part by weight of alkyl ester in the extract. The important thing is not to add too much water. Addition of excess water only results in an increase in the dilution of the extract, as this excess water must then be removed in a concentration step, as will be explained in detail later. The dilute extract thus obtained generally has a concentration of about 30 to
60% by weight sulfuric acid, more preferably about 40-50% by weight
of sulfuric acid and is then sent via line 4 to a distillation column 20 (referred to herein as the "alcohol production column"), where the crude alcohol is recovered as an overhead product via line 18. be done. The overhead alcohol product is then sent to subsequent conventional processing steps to produce alcohol of the required purity. The bottoms product is discharged from alcohol production column 20 via line 24 and generally comprises a sulfuric acid stream containing about 40-55% by weight sulfuric acid, preferably about 45-50% by weight sulfuric acid. In a conventional process, the alcohol-producing column bottom product is sent directly to another distillation column (hereinafter referred to as the "column concentrator"), and this bottom acid stream is distilled in the acid concentrator column. Water is removed as an overhead product and a second bottoms product consisting of a concentrated acid stream is produced. These thick bottom products are generally sent to storage for cooling and eventual recycling to the absorption stage. According to the embodiment of the invention shown in FIG.
The alcohol production column bottom product, consisting of an aqueous liquid containing 40-55% by weight H ₂ SO ₄ and organic sulfonic acid impurities, passes through line 24 to reaction zone 6.
0 and in reaction zone 60, the concentrated sulfuric acid stream is contacted with a controlled amount of oxidizing agent introduced into zone 60 from line 62. Organic sulfonic acid impurities are generally at least about 500 ppm by weight,
Usually at least about 700 ppm by weight, more typically about 9000-30000 ppm by weight, most typically about 12000
It is present in the alcohol producing column bottoms 24 in an amount of ˜20,000 ppm by weight. These alcohol producing bottom products to be treated in the process of the invention can contain up to 65000 ppm or more of organic sulfonic acid impurities. Organic sulfonic acid impurities are generally present in the organic moiety in an amount of 2 to 16 per molecule, more typically 2 to 16 per molecule.
8 carbon atoms and at least one per molecule;
More typically 1 to 2 sulfonic acid moieties (-
SO ₃ H). When an organic sulfonic acid impurity is represented by the formula RSO ₃ H, "R" is alkyl, aryl, alkenyl, alkynyl, alquaryl,
Aralkyl, cycloalkyl, polynuclear aryl,
consisting of one member carried from the group consisting of heterocyclic groups and derivative groups in which one or more carbons of those groups are substituted with a hydroxy group or a keto group or a carboxyl group or a sulfate group or a mercapto group or a sulfono group I can do it. When "R" is alkyl, the alkyl group is
Can be branched or straight chain, generally from 1 to
It can contain up to 12 carbon atoms, usually 1 to 6 carbon atoms. Examples of such alkyl groups are:
Methyl, ethyl, isopropyl, pentyl, octyl, and dodecyl. When "R" is cycloalkyl, the cycloalkyl group generally has 3 to 12
carbon atoms, typically 4 to 8 carbon atoms. Examples of such groups are cyclopropyl, cyclobutyl, cyclohexyl, cyclooctyl, cyclododecyl. An example where "R" is an aryl group is phenyl. “R”
When is a polynuclear aryl, the "R" group generally contains 2 to 4 aromatic rings. Examples of such polynuclear aryl groups are naphthenyl, anthracenyl, phenanthrenyl. When "R" is alkenyl, the alkenyl group generally contains 2 to 12 carbon atoms, usually 2 to 6 carbon atoms. Examples of such alkenyl groups are ethenyl, butenyl,
Hexenyl and decenyl. When "R" is alkynyl, the alkynyl group generally contains 2 to 12 carbon atoms, usually 2 to 6 carbon atoms. Examples of such alkenyl groups are ethynyl, butynyl, propynyl. When "R" is alkaryl, the aryl component generally consists of phenyl or tolyl and the alkyl component generally contains 1 to 12 carbon atoms, usually 1 to 6 carbon atoms. Examples of such alkaryl groups are tolyl, m-ethylphenyl, o-ethyltolyl,
m-hexyltolyl. When "R" is aralkyl, the aralkyl group generally consists of phenyl or alkyl-substituted phenyl as the aryl component and an alkyl component having 1 to 12 carbon atoms, usually 1 to 6 carbon atoms. . Examples of such aralkyl groups are benzyl, o-ethylbenzyl, 4-isobutylbenzyl. “R”
When is a heterocyclic group, the heterocyclic group generally consists of compounds having at least one 6-12 membered ring, in which one or more ring carbon atoms are replaced with oxygen or nitrogen. Examples of such heterocyclic groups are furyl, pyranyl, pyridine, piperidyl, dioxanyl, tetrahydrofuryl, pyrazinyl, 1,4
-Oxazinyl. Typical examples of such impurities are alkenyl sulfonic acids of 2 to 4 carbon atoms, hydroxy-substituted alkyl sulfonic acids of 2 to 4 carbon atoms, etc., and mixtures thereof. Examples of hydroxyalkylsulfonic acids are _CH3CH (OH)CH( _CH3 )
_SO3H , _{HOCH2CH2CH2SO3H , CH3CH (} OH _)
SO4H ,

[Formula] etc. Examples of alkenyl sulfonic acids are CH ₂ CH=CHCH ₂ SO ₃ H,
_CH2 = _CHSO3H , _CH3CH = _CHSO3H , etc. Most typical organic moieties have the number of carbon atoms in each organic moiety corresponding to the number of carbon atoms in the olefin feed introduced from conduit 2 to absorption column 10. The oxidizing agent consists of at least one member selected from the group consisting of ozone, hydrogen peroxide, chlorate, and peroxydisulfate. Chlorates and peroxydisulfates are added as soluble salts into the spent sulfuric acid stream being treated. Examples of such salts are _NH4 ⁺ ,
They are chlorate and peroxydisulfate compounds of alkali metals and alkaline earth metals. Examples of oxidizing agents are therefore O ₃ , H ₂ O ₂ , sodium chlorate, potassium chlorate, magnesium chlorate, persulfate.
These include H ₂ S ₂ O ₄ and ammonium peroxydisulfate. The oxidizing agent chosen is in an amount of less than one fully oxidized stoichiometric equivalent per equivalent of sulfonic acid impurity;
Preferably less than 80% of the 1 complete oxidation stoichiometric equivalent, more preferably less than 50%, most preferably 10
used in amounts less than %. In this specification,
The term “complete oxidation stoichiometric equivalent” refers to the amount of selected oxidant required to completely oxidize the organic sulfonic acid in the acid being treated to produce carbon dioxide gas (CO ₂ ) and water. means the equivalent of Since the stoichiometric equivalents required for complete oxidation of organic sulfonic acid impurities vary depending on the oxidizing agent chosen, the exact sulfonic acid present, and other factors, the present invention provides The amount of oxidizing agent introduced also differs. The complete oxidation of typical alkenyl sulfonic acids to carbon dioxide and water by various oxidizing agents is shown in equations ()-() below. CH ₃ CH=CHCH ₂ SO ₃ H+12H ₂ O ₂ →4CO ₂ +15H ₂ O+H ₂ SO ₄ () CH ₃ CH=CHCH ₂ SO ₃ H+12O ₃ →4CO ₂ +3H ₂ O+H ₂ SO ₄ +12O ₂ () CH ₃ CH= CHCH ₂ SO ₃ H+12H ₂ S ₂ O ₈ +9H ₂ O →4CO ₂ +25H ₂ SO ₄ () CH ₃ CH=CHCH ₂ SO ₃ H+12K ₂ S ₂ O ₈ +9H ₂ O →4CO ₂ +25K ₂ SO ₄ () CH ₃ CH=CHCH ₂ SO ₃ H+12KClO ₃ →4CO ₂ +3H ₂ O+12KClO ₂ +H ₂ SO ₄
() Contacting the oxidizing agent with the spent sulfuric acid stream in zone 60 can be carried out in batch mode or in continuous mode or semi-continuous mode. The contact method is not strict. Thus, for example, a selected oxidizing agent can be added to a conduit containing a stream of spent sulfuric acid. In this case, zone 60 can be viewed as a tubular reactor. Alternatively, zone 60
may include a reactor into which the oxidizing agent and spent sulfuric acid are introduced. Preferably, an oxidizing agent is continuously introduced into the spent sulfuric acid stream to continuously partially oxidize organic impurities in the sulfuric acid and thus eliminate fouling problems associated with carbonaceous deposits on process equipment. to substantially prevent it. The temperature and pressure conditions required for the reaction of the oxidizing agent and non-volatile organic impurities can vary over a wide range, but are generally about 70-190°C, more preferably about 100-190°C.
A temperature of 150°C, most preferably about 110-130°C is used. Temperatures outside these ranges can also be used. Sufficient pressure can be used to maintain the sulfuric acid stream being treated in a liquid state, thus atmospheric, subatmospheric, and superatmospheric pressures are suitable. For propene or butene absorption, approximately −
Pressures of 1.054 to 2.109 Kg/cm ² gauge pressure (-15 to 30 psig) are quite suitable. Zone 6 of used sulfuric acid
Residence time at zero is not critical and generally ranges from about 2 seconds to 2 hours, more preferably from about 10 seconds to 1 hour, for most effective utilization of the added oxidant. By the above method, organic sulfonic acid impurities are
The surprising fact has been discovered that organic sulfonic acid impurities are converted to oxidation products that are significantly more thermally stable than themselves. Thus, treated spent sulfuric acid streams containing these oxidation products have a significantly reduced tendency to form carbonaceous deposits in process equipment associated with alcohol production and recovery and sulfuric acid concentration and recirculation. shows. Of course, the exact oxidation product will vary depending on the type of organosulfonic acid impurity, the amount of oxidizing agent, and other factors. However, generally these oxidation products are
In addition to unknown organic oxidation products produced by carbon-carbon cleavage in molecules of organic sulfonic acid impurities, lower aliphatic carboxylic acids (e.g. acetic acid, propionic acid), sulfuric acid, carbon monoxide, carbon dioxide and Contains a mixture of. At least a portion of these oxidation products are substantially more volatile than the organic sulfonic acid impurities themselves. Thus, the treated spent sulfuric acid stream containing oxidation products may be further processed, such as by distillation or flashing under reduced pressure, to remove at least a portion (and preferably at least a large portion) of these more volatile oxidation products. part) can be removed. It has been surprisingly discovered that in order to obtain more thermally stable sulfonic acids, it is not necessary to remove oxidation products that are less volatile than organic sulfonic acid impurities. In the embodiment of FIG. 1, the treated alcohol-producing column bottoms is discharged from reaction zone 60 via line 64 and sent to concentrator column 30;
Within concentrator column 30, the treated spent sulfuric acid is contacted with a heating fluid, such as steam, introduced from light 34, water is removed as an overhead product from line 32, and a concentrated sulfuric acid stream is produced; This concentrated sulfuric acid stream is discharged through line 38. Concentration tower 30
The temperature and pressure conditions therein are not critical and vary widely depending on the alcohol stream being treated.
Thus, hydration of butene or pelopene requires approximately
A temperature of 80 to 180 °C, preferably about 80 to 130 °C, and a pressure of about -1.0545 to 7.03 Kg/ ^cm2 (-15 to
A pressure of 100 psig) is commonly used. The aqueous overhead vapor discharged from line 32 also contains at least a portion of the oxidation product that is sent to concentrator column 30 and vaporizes under the temperature and pressure conditions employed within concentrator column 30 . The concentrated sulfuric acid stream discharged from line 38 is recycled to vessel 50 for intermediate storage of concentrated sulfuric acid, after being cooled in heat exchanger 80, if desired.
This concentrated sulfuric acid is ultimately recycled to the absorption tower 10 through line 6, and supplementary sulfuric acid is added from line 5 as required. If desired, a portion or all of the effluent from reaction zone 60 is routed through conduit 39 to a separate distillation zone 40 to absorb volatile organic matter produced by partial oxidation in zone 60 and having a lower boiling point than water. Impurities can be removed from conduit 42 as an overhead product. The resulting liquid, thus reduced in volatile organic impurities compared to water, is passed to conduit 64 for primary introduction into concentrator column 30. In this embodiment, the aqueous overhead product 32 from concentration column 30 contains reduced amounts of organic impurities. It will be appreciated that if desired, a portion of the bottom product recovered from alcohol regeneration column 20 via conduit 24 can be sent directly as feed to concentrator column 30 via conduit 28.
Therefore, in this embodiment, the contact zone 60
The stream sent as a feed to the concentrator 30 can include a slip stream or side stream of alcohol bottom product that would otherwise be recycled as a feed directly to the concentrator column 30. Of course, the portion of the alcohol bottoms that is treated within zone 60 will depend on the amount of impurities in the alcohol bottoms, the desired level of purification to be achieved in the treated stream, and other factors. and can be adjusted by a valve 21. Generally, however, at least about 10% by volume, and preferably about 50-100% by volume, of the alcohol bottoms product is subjected to the process of the present invention in zone 60 due to partial oxidation of organic sulfonic acid impurities therein. It will be processed. Next, FIG. 2 will be explained. In Figure 2,
Concentrated sulfuric acid, e.g. containing 50-99% _by weight _H2SO4 and at least 1500 ppm, usually about 8000-30000 ppm
or more, more typically around 10000~
Contains 20000ppm organic sulfonic acid impurities,
The bottoms product from concentrator 30 is discharged through conduit 38 and at least a portion thereof is transferred to contact zone 7.
0 and is contacted within zone 70 with a selected oxidizing agent introduced into zone 70 from conduit 72, as described above. Liquid effluent passes through conduit 74 to zone 70
is discharged from. This oxidation zone effluent is then sent to a separate distillation zone 40 in which volatile organic impurities are removed as an overhead product through conduit 42, as described above. The resulting liquid, free of organic impurities more volatile than water, is then passed to conduit 39 and then
If desired, after cooling in heat exchanger 80, it can be recycled to vessel 50 as described above. Optionally, a portion (or all) of the liquid effluent in conduit 74 is recycled through conduit 73 to concentrator column 30 where the partially oxidized products, which are more volatile than the water produced in zone 70, are recycled. It can be vaporized and discharged along with the overhead product through conduit 32. To the extent that such recirculation through conduit 73 is used, the need for a separate distillation zone 40 is reduced or even eliminated. If desired, a portion of the concentrated sulfuric acid in conduit 38 can be sent directly through conduit 38a to conduit 39 for recycling to the process. In this case, the acid stream treated in zone 70 can be viewed as a slip stream of concentrated acid bottom product discharged from concentrator 30. Liquid flow to zone 40 and conduits 73 and 3
The relative flow rate of the liquid flow through 8a is determined by the respective valves 7
5,77,35. The method of the present invention will be further explained below with reference to Examples. In the examples, unless otherwise specified, parts are parts by weight. In the examples, total soluble organic carbon (TSOC) was measured using a glass fiber perdisc (Reeve Angel 934 AH,
Using a liquid sample that had been vacuum-filtered through a funnel equipped with a Beckman Total Organic Carbon Analyzer (Model 215B) to remove carbonaceous solid particles with a particle size greater than approximately 1.5 microns,
[Beckman Total Organic Carbon Analyzer
(Model 215B)]. In the example, the distillation of the sample was carried out using a thermometer and a length of 22.86
This is done by placing each sample into a 500 ml, 2 neck round bottom flask equipped with a 9 inch (cm) glass water condenser. The liquid is stirred with a magnetic stirrer and heated with an electric heating mantle. Distillation is carried out at a rate such that approximately 0.5 ml of water is recovered as condensate per minute at normal pressure. The pot temperature corresponds to the normal pressure boiling point of 72% by weight sulfuric acid. Stop the distillation when a temperature of 178°C is reached. After cooling to room temperature,
TSOC of condensate and liquid remaining in flask
Analyze. In addition, the condensate is analyzed by gas chromatography. In the heat soaking treatment in the Examples, the thus treated sample was measured with a thermometer and a
This is done by placing in a 250 ml two-neck round bottom glass flask equipped with a 9 inch glass water condenser and a magnetic stirrer.
Heat the flask with an electric heating mantle. next,
After distilling the liquid by completely refluxing the liquid for a predetermined period of time while stirring, the TSOC of this liquid is analyzed. Example 1 In Experiments 1-2, spent sulfuric acid (72 weight%
A 220 g sample of H ₂ SO ₄ ) was pressure-equalized, each containing a thermometer, a water-cooled condenser open to the atmosphere, a magnetic stirrer, and 40.7 ml of 30% hydrogen peroxide. Place in a separate 500ml 3-neck round bottom flask equipped with an addition funnel. In experiment 1, used acid was diluted with water to
Bring _the concentration to % _H2SO4 by weight. The liquid in each flask was heated with an electric heating mantle to a temperature of 125°C.
Hydrogen peroxide is added dropwise to the sulfuric acid in order to control the exothermic reaction that occurs and to maintain the liquid temperature at 125±3°C. After the hydrogen peroxide addition is complete in about 15 minutes, the resulting reaction mixture is cooled to room temperature and weighed. Take samples of the acid before and after addition of hydrogen peroxide,
Perform analysis of TSOC and organic sulfonic acid impurities. The liquid from Run 1 is then distilled to concentrate the acid to 72% by weight H ₂ SO ₄ using the method described above. This recycled acid was then removed from the reaction flask and placed in another flask where it was subjected to the heat soaking treatment described above for 4 hours at a temperature of 178°C to achieve "coking". That is, the amount of carbonaceous solids produced by thermal decomposition of TSOC in heat-treated sulfuric acid is measured. In Experiment 2, the liquid after adding H ₂ O ₂ was changed to
After dilution with enough water to bring it down _to 60% by weight _H2SO4 , this diluted sample was distilled using the method described above to reconcentrate the acid to 72% _by weight _H2SO4 ,
This gives a thermal history comparable to the acid sample of Example 1. This reconcentrated acid is then subjected to the same heat soaking treatment as in the experiment/description. containing the indicated concentrations of total soluble organic carbon and organic sulfonic acids to demonstrate the improvement obtained by the method of the present invention in reducing the amount of carbonaceous solids produced in such impure acids. Impure concentrated sulfuric acid (72% by weight) which has not been treated with the method of the present invention
H ₂ SO ₄ ) was first diluted with water to give 60% by weight H ₂ SO ₄
A separate series of experiments is performed in which the sample is concentrated and then distilled, thereby reconcentrating to 72% by weight to give a thermal history comparable to Experiments 1-2. The reconcentrated sample is then subjected to the heat soaking treatment described above, also at 178°C for 4 hours. The data obtained from these experiments are shown in Table 1 below.

Table 1 As can be seen from the data presented in Table 1, the hydrogen peroxide partial oxidation treatments of Experiments 1 and 2 produce sulfonic acids with greatly enhanced thermal stability. Only 11% by weight of the TSOC in the sulfuric acid subjected to the H ₂ O ₂ treatment in Runs 1 and 2 pyrolyzes to insoluble activated carbonaceous solids in the subsequent heat soaking treatment.
In contrast, approximately 54-76% by weight of the TSOC present in the spent sulfuric acid streams of Runs 3-8, which were not treated according to the present invention, pyrolyzes to insoluble carbonaceous solids upon heat soaking. . Furthermore, the coking rates (i.e., grams of carbonaceous solids produced per hour in 1000 grams of solution in the heat soak test) for Experiments 1 and 2 also differed from those containing much higher initial TSOC levels. It is much lower than the coking rate of the heat soaked sulfuric acid streams of Runs 3-5, and still lower than the coking rate of the heat treatment numbers of Runs 6 and 7, which contain lower TSOC levels. Therefore, at equal TSOC levels, the process of the present invention, which can be used batchwise or semi-continuously or continuously, is more effective than can be tolerated in the presence of acids with such improved thermal stability. also allows the olefin hydration process to be carried out with less attendant coking and therefore less carbonaceous deposits fouling the process equipment. As a result, the method of the present invention eliminates “dirty acids”.
acid)” for example in the effluent from the reaction zone.
Up to 20000ppm, preferably about 500-15000ppm,
More preferably with an acid having about 1000-10000 ppm total organic carbon (calculated as elemental carbon),
It allows olefin hydration processes to be carried out without significant carbonaceous fouling problems. Thus, the present invention was considered essential in the prior art. “White acid” removes all soluble organic carbon to prevent staining problems.
Preferably, the acid stream treated with the method of the invention, when exposed to high temperatures (e.g. 150-180°C), eliminates the need for treatment of used sulfuric acid to produce
Carbonaceous solids are produced at a rate that is at least about 50%, and more preferably at least about 90% less than the rate at which carbonaceous solids are produced in the raw acid stream under such conditions. It will be obvious that various changes and modifications may be made without departing from the invention. Accordingly, all matter contained in the above description should be construed as illustrative only and not as limiting. For example, in one alternative to the embodiment shown in FIG. 2, as well as in one preferred embodiment of the present invention, at least about 500 ppm
A sidestream acid containing organic sulfonic acid impurities is discharged from condensation column 30 above or below acid feed conduit 24 and, as described above, is processed by the method of the present invention.
contact zone 70 for treatment with a selected oxidizing agent;
to produce partially oxidized organic compounds from organic sulfonic acid impurities. The acid stream thus treated can then be sent from zone 70 back to concentrator column 30 through conduit 73, as described above. In yet another most preferred embodiment of the invention, the selected oxidizing agent is added directly to one or more points of the acid concentrator, such as the concentrator of the embodiment of FIG. 1 or 2. can do. In this case, the desired partial oxidation of the organic sulfonic acid impurity is
The more volatile oxidation by-products are then removed from the acid concentrator as an overhead product and concentrated sulfuric acid is produced and discharged as a bottom product. Ru.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing one embodiment of the method of the invention, and FIG. 2 is a schematic illustration of another embodiment of the method of the invention.
1 is a schematic diagram showing two embodiments; FIG. Explanation of drawing numbers 4...Extract liquid flow, 6...Sulfuric acid flow,
DESCRIPTION OF SYMBOLS 10... Absorption column, 20... Distillation column, alcohol production column, 24... Alcohol production column bottom product, line, 30... Concentration column, 40... Separate distillation zone, 5
0... Container, 60... Reaction zone, 70... Contact zone, 80... Heat exchanger.

Claims (1)

[Scope of Claims] 1. A process for improving the thermal stability of a spent sulfuric acid stream produced in the catalytic hydration of olefins for the production of alcohol and containing organic sulfonic acid impurities, the process comprising: The stream is treated with an oxidizing agent selected from the group consisting of ozone, hydrogen peroxide, a chlorate source, peroxydisulfate, and mixtures thereof, and the oxidizing agent is added to one equivalent of the sulfonic acid impurity in the spent sulfuric acid stream. The treated sulfuric acid stream is used in less than one full oxidation stoichiometric equivalent to produce partially oxidized organic compounds from the sulfonic acid impurities and thereby has improved thermal stability. An improvement method characterized by giving. 2 The organic sulfonic acid impurity is at least about 500%
The improved method of claim 1, wherein the spent sulfuric acid is present in the spent sulfuric acid stream in an amount of ppm by weight. 3. The improvement of claim 1, wherein the treated spent sulfuric acid stream containing the partially oxidized organic compounds is treated at an elevated temperature to vaporize and remove at least a portion of the partially oxidized organic compounds. Method. 4 The spent sulfuric acid stream is approximately 45-99% by weight H ₂ SO ₄
The improvement method according to claim 1, comprising: 5. The improved method of claim 1, wherein a temperature of about 70-190°C is used in contacting with the oxidizing agent. 6. The improved method of claim 1, wherein the organic sulfonic acid impurity comprises hydroxyalkylsulfonic acid or alkenylsulfonic acid or a mixture thereof. 7. The improved method according to claim 1, wherein the number of carbon atoms in the organic moiety of the organic sulfonic acid impurity corresponds to the number of carbon atoms in the olefin. 8 (a) absorbing an olefin in a concentrated aqueous sulfuric acid solution in an absorption zone to form a sulfate alkyl ester corresponding to the olefin; and (b) absorbing a liquid stream containing the sulfate alkyl ester. (c) directing the resulting dilute liquid to an alcohol production zone for recovering the alcohol as a gaseous product; , thereby producing a spent sulfuric acid stream containing about 40-55% by weight sulfuric acid and at least about 500 ppm by weight organic sulfonic acid impurities, the method comprising: (d) contacting at least a portion of the spent acid in a contact zone with an oxidizing agent selected from the group consisting of ozone, hydrogen peroxide, a chlorate source, peroxydisulfate, and mixtures thereof; ) recovering an acid stream containing the partially oxidized organic compound from the contacting zone and combining the recovered stream with a remaining portion of the spent sulfuric acid stream that was not processed in the contacting zone to an acid concentrator; , removing aqueous vapor in an acid concentrator to produce a concentrated sulfuric acid stream of increased thermal stability suitable for recycling to an absorption zone. 9. The improved method of claim 8, wherein a temperature of about 70-190°C is used in contacting with the oxidizing agent. 10. The improved method of claim 8, wherein the organic sulfonic acid impurity comprises hydroxyalkylsulfonic acid or alkenylsulfonic acid or a mixture thereof. 11. The improved method according to claim 8, wherein the number of carbon atoms in the organic moiety of the organic sulfonic acid impurity corresponds to the number of carbon atoms in the olefin. 12 (a) absorbing an olefin in a concentrated aqueous sulfuric acid solution in an absorption zone to form a sulfate alkyl ester corresponding to the olefin; and (b) absorbing a liquid stream containing the sulfate alkyl ester. (c) directing the resulting dilute liquid to an alcohol production zone for recovery of the alcohol as a gaseous product; , thereby producing a spent sulfuric acid stream; (d) sending the spent sulfuric acid stream to an acid concentrator, in which the spent sulfuric acid is distilled to remove aqueous vapors; and producing concentrated used sulfuric acid containing about 45 to 99% by weight of sulfuric acid, the method comprising:
After steps a, b, c, d, step e or f or g below: (e) removing an acid side stream containing at least about 500 ppm by weight of organic sulfonic acid impurities from the acid concentrator; The acid side stream is treated with ozone,
contacting with an oxidizing agent selected from the group consisting of hydrogen peroxide, a chlorate source, peroxydisulfate, and mixtures thereof, and recycling at least a portion of the so-treated sulfuric acid sidestream to the acid concentrator. , or (f) at least approximately
into the acid concentrator column which receives a spent sulfuric acid stream containing 500 ppm by weight of organic sulfonic acid impurities;
or (g) directing at least a portion of the concentrated spent sulfuric acid stream containing at least about 1500 ppm by weight of organic sulfonic acid impurities to a contacting zone and in the contacting zone introducing an oxidizing agent as described above; contacting the sulfuric acid stream with an agent, and at least a portion of the sulfuric acid stream thus treated is adapted to vaporize and remove at least a portion of the partially oxidized organic compound that is more volatile than water or co-distilled with water. An improved process characterized in that it is processed at temperature and pressure conditions such that a sulfuric acid stream with increased thermal stability is suitable for recycling to the absorption zone. 13. The improved method of claim 12, wherein a temperature of about 70-190°C is used in contacting the oxidizing agent. 14. Claim 12, wherein the organic sulfonic acid impurity comprises a hydroxyalkyl sulfonic acid or an alkenyl sulfonic acid or a mixture thereof.
Improvement method described in section. 15. The improved method according to claim 12, wherein the number of carbon atoms in the organic moiety of the organic sulfonic acid impurity corresponds to the number of carbon atoms in the olefin.