Patent Application
20080251418
1. Field of the Invention
The present invention relates to the upgrading of petroleum residium (petroleum resid), bitumen, shale oil and/or other heavy oils by the removal therefrom of heavy, high molecular weight multi-ring aromatics and metals present in such petroleum resid, bitumen and/or heavy oils in the form of asphaltenes and/or heavy resins and/or polycyclic hetero (N,S,O) aromatics.
2. Description of the Related Art
Heavy, high molecular weight multi-ring aromatics, polycyclic hetero (N,S,O) aromatics and metals-containing molecules, e.g., porphyrins, are present in petroleum resid, bitumen and/or heavy oils largely in the form of a solubility class called asphaltenes or, depending on the feed, as individually identifiable molecular types, e.g., the asphaltene can comprise a mixture of such materials, or materials such as polycyclic hetero (N,S,O) aromatics and be present per se, in such feeds.
The asphaltene fraction present in such feeds contains the most polar molecules. Traditionally, to force such asphaltene materials out of the petroleum resid, bitumen and/or heavy oils, a process known as solvent deasphalting is practiced. In that process, an excess of non-polar solvent is added to the petroleum resid, bitumen and/or heavy oils (hereinafter collectively referred to as heavy hydrocarbon feed stream) to force the polar asphaltene material out of the heavy hydrocarbon feed stream. Current commercial deasphalting processes use liquid propane or liquid butane as the non-polar precipitation inducing solvent. Such processes are energy intensive requiring the refrigeration and compression/pressurization of the propane or butane to condense them into a liquid. Following the removal of the precipitated asphaltene from the now deasphalted heavy hydrocarbon feed stream containing the liquid propane or butane, the propane or butane is recovered by evaporation from the heavy hydrocarbon feed stream, necessitating the re-refrigeration and re-pressurization of the now gaseous propane or butane for re-condensation into liquid form for re-use. Another drawback of solvent deasphalting, in addition to the high energy costs involved, is the lack of selectivity in the solvent deasphalting process. The lack of selectivity of the solvents is evidenced by the co-precipitation of non-asphaltenic molecules along with the asphaltenes and the presence of residual asphaltene molecules in the deasphalted oil (DAO) fraction.
Alternatively, petroleum resid can be visbroken, coked or used as residual sulfur fuel oil (RSFO) or as asphalt without removal of the asphaltene fraction. Such processes are also either energy intensive, expensive or wasteful of high value hydrocarbons present in the petroleum resid feed stream.
More desirable are processes such as the solvent deasphalting previously described, which, following removal of the asphaltene fraction, produce a deasphalted oil (DAO) which has a higher value and is of higher quality residual sulfur fuel oil (RSFO) or as feedstock for fluid catalytic cracking (FCC) to force higher value liquids which could not be otherwise secured from the petroleum resid per se. The recovered asphaltene fraction is currently processed via high temperature thermal chemistry (coking and/or visbreaking) to form slightly higher value liquids and coke, or it is used as feedstock for asphalt production.
It would be highly desirable to develop a process for the removal of the heavy, high molecular weight multi-ring aromatics and/or resins and/or polycyclic hetero (N,S,O) aromatics (hereinafter collectively referred to as asphaltenes unless otherwise indicated) from petroleum resid, bitumen and/or heavy oils which is less energy intensive, e.g., uses little or no solvent, and is more selective.
Heavy, high molecular weight multi-ring aromatics, and/or resins, and/or polycyclic hetero (N,S,O) aromatics are separated from petroleum resid, bitumen, shale oil and/or other heavy oils (heavy hydrocarbon feed stream) by the process of selectively substituting polar substituents onto the aromatic rings of the heavy, high molecular weight multi-ring aromatics, and/or resins, and/or polycyclic hetero (N,S,O) aromatics (hereinafter collectively referred to for heavy feeds as asphaltenes) present in the heavy hydrocarbon feed stream via electrophilic aromatic substitution. Such a process utilizes little, if any, solvent, any solvent used being aromatic-containing diluent to control viscosity rather than liquid propane or butane, the aromatic diluent being easily recovered by one skilled in the art.
Studies of electrophilic aromatic substitution reactions/derivatizations on polycyclic aromatics and polycyclic heteroaromatics, both in model compounds and with resids have demonstrated selectivity for the removal of the heavy high molecular weight multi-ring aromatics, and/or resins and/or polycyclic hetero (N,S,O) aromatics. The chemistry favors selective attack of the more electron rich polycyclic aromatics and heteroaromatics. Increasing the number of fused polycyclic rings, and/or heteroatom content and/or extent of alkyl substitution, increases the electron density of the polycyclic aromatics and/or polycyclic heteroaromatics, making them more susceptible to the selective chemistry.
The substitution of polar substituents onto the aromatic rings of the asphaltenes changes (raises) the solubility parameters of the asphaltenes rendering them less soluble in the balance of the petroleum resid and/or bitumen and/or heavy oil (heavy hydrocarbon feed stream) which is non-polar or less polar by comparison, thereby resulting in the selective precipitation of the polar group functionalized asphaltene from the heavy hydrocarbon feed stream. The precipitated polar group functionalized asphaltenes can be recovered from the balance of the heavy hydrocarbon feed stream by centrifugation, decantation, filtration, etc., leaving behind a high quality deasphalted oil (DAO) suitable for further processing as desired by the practitioner.
In the present process, the heavy hydrocarbon feed stream, in liquid form, is contacted with a reagent suitable for selectively substituting polar group(s) onto the aromatic rings of the asphaltene material via electrophilic aromatic substitution. Electrophilic aromatics substitution reactions are exemplified by halogenation, nitration, sulfonation, Friedel-Crafts acylation and hydroxy alkylation.
Because electrophilic aromatic substitution occurs under liquid conditions the heavy hydrocarbon feed stream needs to be in the liquid form. If not already liquid at ambient condition, the heavy hydrocarbon feed stream can be heated to make it liquid, i.e., to a temperature of between about 50 to 200° C., preferably between about 100 to 175° C., more preferably between about 100 to 165° C. Alternatively, a light aromatic diluent such as toluene can be added to solvate the heavy hydrocarbon feed stream to reduce viscosity (i.e., make it liquid) and/or facilitate reaction. In another embodiment, both heating and an aromatic or aromatic-containing diluent can be employed.
In the present method, sufficient electrophilic aromatic substitution reagent is used to result in the addition of from about 1 to 8, preferably about 2 to 6, more preferable about 2 to 4 polar groups per asphaltene molecule. The asphaltene content of the subject feed can be determined by the application of ASTM method D3279. XPS and/or wt % C, H, N and S analysis was used; the XPS analysis identifies the functional groups while elemental analysis confirms the amount of the elements, e.g., sulfur, added. If sulfonation is employed, it is desirable to use the least amount of electrophilic aromatic substitution reagent possible (such as oleum or SO3) to increase the selectivity of the reaction for the least soluble, i.e., heaviest, asphaltene molecules. Thus, the use of sufficient electrophilic aromatic substitution reagent to add 2 to 4 polar groups to the asphaltene structure is desirable to achieve the selective reaction of the asphaltenes versus reaction with the smaller, lighter polycyclic aromatic molecules present in the heavy hydrocarbon feed stream. Generally, larger polycyclic aromatics and heterocyclic aromatics react preferentially in comparison to the smaller ring systems.
The selective electrophilic aromatic substitution reaction, well known in the literature, using, e.g. SO3, NO2, P2O5 halogenation, nitration, aldehyde condensation (HCHO), acylation etc. will result in the substitution of polar groups onto the aromatic rings of the asphaltene. Functionalization of asphaltene with SO3H group(s) can be followed by heating to drive dimerization/oligomerization of the functionalized asphaltene leading to the formation of still heavier polar molecules which even more easily precipitate out of the heavy hydrocarbon feed stream. The heating step to dimerize/oligomerize the polar functionalized asphaltene is effective only when the polar functionalizing group is sulfonic acid (—SO3H) or hydroxy alkyl (—R—OH). While the dimerization/oligomerization will not increase the polar species content on a polar species per 100 carbon atom basis, it will result in an at least doubling of the molecular weight of the molecule which increases solubility parameter and will help precipitation.
Practicing the electrophilic aromatic substitution reaction process on asphaltenes to deposit —SO3H or —ROH groups at temperatures of 120-165° C. could lead to the production of the above described dimers or oligomers without additional heating.
Sulfonation of aromatic compounds by concentrated or fuming sulfuric acid, or pure sulfur trioxide or its pyridine complex, are of known industrial importance due to the availability and low cost of the reagents. Using sulfuric acid has some disadvantages: higher reaction temperature, longer reaction time, formation of waste acid due to the production of water, and pollution to the environment. The use of sulfur trioxide (SO3) i.e., pure reagent, or oleum reagent, preferably SO3 pure reagent as the sulfonating agent is more efficient because only direct addition of the SO3 group is involved and there is no formation of water during the reaction. Other advantages of SO3 include faster reaction, obviation of waste acid disposal and minimal environmental impact. Moreover, using SO3-nitrobenzene has advantage in that a significant body of kinetics under these conditions exists for model compounds in the literature.
Aromatic sulfonation by sulfuric acid has been known to be complicated by temperature dependent isomerization, reversibility, further sulfonation, as well as by water produced by the reaction, but all of these are reported in the literature and known to those skilled in the art and can be taken into consideration and compensated for by the practitioner.
While halogenation will result in the addition of polar moieties onto the asphaltene molecule and will result in the precipitation of the thus polar substituted asphaltene, it is not a preferred technique because the presence of the halogen could lead to corrosion problems elsewhere in the refinery.
The heavy hydrocarbon feed stream is, as previously indicated, a petroleum resid, shale oil, bitumen or heavy oil.
Petroleum resid is a high boiling fraction recovered from crude distillation at 900-1050° F., preferably 900-1030° F., more preferably 980-1030° F. at atmospheric pressure or at the vacuum distillation temperature equivalent thereof.
Petroleum resid is commonly made-up of asphaltenes, which are heavy, high molecular weight (˜1500 Mn) polar aromatic molecules which also contain metals; other polar molecules such as resins contain minimal metals but which do contain sulfur and nitrogen are smaller than asphaltenes; other polycyclic aromatics; naphthalene aromatics; naphthalenes; and paraffins. Resins are lower molecular weight versions of asphaltenes with their polar functionality located at one end of the molecule rather than being distributed homogenously throughout the molecule. The resins act as surfactant “like” molecules, stabilizing and dispersing the polar asphaltenes in the relatively less polar hydrocarbon matrix which is the bulk of petroleum crude oil, resids and bitumens.
In the present specification “bitumen” means the heavy oil recovered from tar sands while “heavy oils” include resids, heavy Venezuelan, Russian, Brazilian, arctic etc. oils not necessarily associated with sands, but which have greater than about 20% boiling above 10001F.
In addition to removing asphaltenes per se from petroleum resid, bitumen and/or heavy oils, materials such as pyrrolic N-containing N heterocyclic and polycyclic aromatic analogues, which contain at least one unsubstituted available aromatic carbon such as the carbazole and indole moiety-containing aromatic molecules and polycyclic aromatic analogues thereof can be removed from lighter oil feed streams, which do not contain asphaltenes, other than just from the aforesaid heavy hydrocarbon feed streams, which similarly contain pyrollic-N—containing nitrogen compounds; e.g., other lighter oil feed streams such as from a VGO or shale oil derived feeds, by functionalization with polar substituents via electrophilic aromatic substitution because of the high selectivity of the electrophilic aromatics substitution reaction for these pyrrolic nitrogen containing heterocyclic aromatics in preference over non-heterocyclic aromatics, the sulfur containing heterocyclic aromatic and even non-pyrrolic nitrogen containing heterocyclic aromatics and their polycyclic aromatic analogues. Because of this selectivity, the amount of electrophilic aromatic substitution reagent employed to remove pyrrolic N-containing nitrogen heterocyclic compounds and/or polycyclic aromatic analogue thereof can be less than that needed to remove asphaltenes from petroleum resid, bitumen and/or heavy oils, the amount of electrophilic aromatic substitution reagent employed in such cases being as little as just sufficient to add one functionalizing polar substituent group to the pyrrolic-N-containing nitrogen heterocycle compounds and/or polycyclic aromatic analogue thereof. Thus, for feeds which contain asphaltenes and pyrrolic-N-containing nitrogen compounds associated with the asphaltene fraction, for feeds which contain both pyrrolic-N-containing nitrogen compounds associated with the asphaltene fraction as well as pyrrolic-N-containing nitrogen compounds which are not part of the asphaltene fraction as well as for the lighter feeds which contain non-asphaltenic pyrrolic-N-containing nitrogen compounds, the electriphilic aromatic substitution reagent can be used in amounts just sufficient to preferentially and selectively remove the pyrrolic-N-containing nitrogen compounds from such feeds. The removal of the pyrrolic N-containing N-heterocyles and polycyclic analogues thereof from feeds such as lighter hydrocarbon streams, e.g., VGO, shale oil etc. which is sent to subsequent catalytic cracking or hydrotreating such as hydrodesulfurization reduces the rate of deactivation of the hydrotreating catalysts.
Further because of the reactivity and selectivity of the electrophilic aromatic substitution reaction for the asphaltenic type molecules in the various feeds, it is possible to produce and/or recover asphaltenes from what have heretofore been classified as non-asphalt resids. Some resins when functionalized by polar groups and/or oligomerized move from the resin solubility class to the asphaltene solubility class. This would increase the asphaltene content of the resid or bitumen. Higher asphaltene contents result in more feedstocks for higher value asphalt.
The value of the electrophilic aromatic substitution of polar group(s) onto the asphaltenes in petroleum resid, and/or bitumen, and/or heavy oil is because in the petroleum resid, and/or bitumen and/or heavy oil the electrophilic aromatic substitution is selective with respect to the asphaltene molecules present in the heavy hydrocarbon feed stream. The asphaltenes in the heavy hydrocarbon feed stream react much more readily and completely than do the lighter, smaller polycyclic aromatics in the heavy hydrocarbon feed stream. This selectivity in a mixed polycyclic aromatics-containing stream is crucial for the process to be viable. Selective separation of the asphaltenes from the feed with the substantial exclusion of the lighter, smaller polycyclic aromatics results in the recovery of an asphaltene suitable for the production of higher grade asphalt as a consequence of its lower light aromatic content, and in the recovery of a DAO containing more of the more valuable light polycyclic aromatics which makes the DAO such a valuable feed for upgrading in, e.g., fluid catalytic cracking and hydrotreating.
The heptane asphaltenes from a heavy Canadian vacuum resid was reacted with 20% oleum in toluene. Asphaltenes (1.0 g) was dissolved in toluene (25 mL) and stirred at room temperature under nitrogen. 20% oleum (2.5, 1.0 or 0.5 mL) was added slowly by syringe to the asphalatene solution at 0° C. The reaction mixture was warmed to room temperature and allowed to stir for 24, 2 or 0.25 h. A precipitate formed early during the addition of the oleum. When the reaction time was complete, water (10 mL) was added and the entire reaction mixture was suction filtered through a fritted glass filter. The filtered precipitate (Toluene Insoluble asphaltenes) was air dried and then dried to constant weight in a vacuum oven at 120° C. Unfunctionalized asphaltenes are toluene soluble but heptane insoluble. Here, adding polar functionality makes them also toluene insoluble (TI). Because the H/C atomic ratio of the asphaltenes has not been significantly changed by functionalization, they are still asphaltenes, as opposed to “coke” which is traditionally defined as toluene insoluble material but with a much lower H/C ratio. The yield of sulfonated asphaltenes is shown in Table 1. The filtrate was washed with water three times in a separatory funnel. The filtrate (Tolene Solubles) was dried over anhydrous sodium sulfate overnight, suction filtered and evaporated to dryness. The yield is shown in Table 1.
A complete heavy Canadian vacuum resid was reacted with 20% oleum in toluene.
Heavy Canadian vacuum resid (2.26 g) was dissolved in toluene (25 mL) and stirred at room temperature under nitrogen. Oleum (20%, 0.5 mL) was added slowly by syringe to the resid solution at 0° C. The addition is usually at a rate of 1-2 drops per second. The temperature of the reaction mixture is monitored during addition to make sure that the addition is slow enough not to cause a rapid rise in temperature. The reaction mixture was warmed to room temperature and allowed to stir for 2 or 4 h. A precipitate formed early during the addition of the oleum. When the reaction time was complete, water (10 mL) was added and the entire reaction mixture was suction filtered through a fritted glass filter. The filtered precipitate (Toluene Insoluble asphaltenes) was air dried and then dried to constant weight in a vacuum oven at 120° C. The yield of sulfonated asphaltenes is shown in Table 1. The filtrate (Toluene Solubles) was washed with water three times in a separatory funnel. The filtrate was dried over anhydrous sodium sulfate overnight, suction filtered and evaporated to dryness. The yield is shown in Table 1.
Large scale sulfonation of Heavy Canadian vacuum resid heptane asphaltenes is the third experimental procedure. Asphaltenes (300.78 g) was dissolved in 60 L of toluene and stirred at room temperature under nitrogen. 20% oleum (150 mL) was added slowly (1.5 drops/second) by syringe to the asphaltene solution at 0° C. An exotherm was observed as the temperature of the asphaltene solution rose to 7° C. The reaction mixture was warmed to room temperature and allowed to stir for 0.25 hours. A precipitate formed early during the addition of the oleum. When the reaction time was complete, the entire reaction mixture was suction filtered through a fritted glass filter. The filtered precipitate (Toluene Insolubles) was washed with distilled water (900 mL), air dried and then dried to constant weight in a vacuum oven at 120 degrees centigrade. The water layer was submitted for acid titration. The yield of sulfonated asphaltenes is shown in Table 1. The filtrate (Toluene Solubles) was washed in a separatory funnel with water (3000 mL) three times. The filtrate was dried over anhydrous sodium sulfate overnight, suction filtered and evaporated to dryness. The yield is shown in Table 1. Each of the Toluene Solubles and Toluene Insolubles products were subjected to a series of tests and analyses outlined in detail below. The TIs did not melt in either the Penetration (D5-25) or Softening (D36) Point tests and therefore was deemed unfit for asphalt use.
A European vacuum resid (96.13 g, FST-4262) was heated to 160° C. in a 500 mL three necked flask under a nitrogen atmosphere. The flask was equipped with a mechanical stirrer. The resid was fluid enough to stir at 165° C. Sulfur trioxide (5.76 g, 0.072 moles, 3 mL) was slowly added to the hot, stirring resid under nitrogen. When addition of the sulfur trioxide was complete, the reaction mixture was allowed to stir at 160° C. for 1 hour under a nitrogen atmosphere. The reaction mixture was cooled to room temperature and toluene (700 mL) was added and the mixture was allowed to sit overnight. The reaction mixture was suction filtered and the filtered solids were washed with toluene. The solids were dried in a vacuum oven at 110° C. overnight to yield (4.43 g) of toluene insolubles (TIs). The toluene filtrates were evaporated to dryness, using a rotary evaporator and dried in a vacuum oven to constant weight to yield (97.02 g) of toluene solubles (TSs). Total yield was 101.45 g (106% based on starting resid). The TIs did not melt in either the Penetration (D5-25) or Softening (D36) Point tests and therefore was deemed unfit for asphalt use.
The European vacuum resid (99.79 g, FST-4262) was dissolved in dry methylene chloride (100 mL) and poured into a 500 mL three necked flask under a nitrogen atomosphere in a dry box at room temperature. The flask was equipped with a mechanical stirrer. Sulfur trioxide (1.92 g, 0.024 moles, 1 mL) was slowly added to the stirring resid at room temperature. When addition of the sulfur trioxide was complete, the reaction mixture was allowed to stir at room temperature for 1 hour under a nitrogen atmosphere. The reaction mixture was evaporated to dryness, using a rotary evaporator and dried in a vacuum oven to constant weight to yield 100.65 g of product (101% yield based on starting resid). The product had a Penetration and Softening (98 MM/10 and 46.4° C.) Point different than the starting resid (92 MM/10 and 38° C.).
The products of these experimental procedures were subjected to some or all of the following tests and analyses. The results of the following analyses appear later in the text as they are discussed in detail.
The sulfonation of the heptane asphaltenes from Heavy Canadian vacuum resid in toluene at ambient temperature (See Examples 1A to 1D in Table 1) demonstrates that the asphaltenes react with the SO3 in oleum at ambient temperatures. The results also demonstrate that the sulfonated asphaltenes are insoluble in toluene which indicates that they are not very soluble in the resid. The sulfonated asphaltenes are similar to the unreacted asphaltenes as illustrated by the Thermogravimetric analyses (TGAs) in
The unreacted asphaltenes (
Examples 1A to 1D in Table 1 indicate that about 10% of the sulfonated asphaltenes are still soluble in toluene. This suggests the possibility that some of the asphaltenes may have fewer sulfonic acid functions added which would be an indication of selectivity. The other possibility is that the toluene soluble asphaltenes are sulfonated to the same degree as the insoluble product, but this is not adequate to make them insoluble in toluene.
The sulfonation of Heavy Canadian vacuum resid (experiment 2, Table 1) demonstrates two points. One is that the asphaltenes react with oleum in the presence of the rest of the resid molecules and the added toluene solvent at ambient temperature. The second point is that the sulfonated asphaltenes are insoluble in the resid and toluene mixture. This also indicates that sulfonated asphaltenes should be insoluble in the resid in the absence or presence of toluene solvent. This observation will extend the definition of asphaltenes as a heptane insoluble. toluene soluble, solubility class.
The yields in grams of the sulfonated asphaltenes (Examples 1A-1D, 2, 3, 4 and 5) suggest that the number of sulfonic acid groups added per average asphaltene molecule (average molecular weight 1500 amu and presuming about 40% of the asphaltene carbons are aromatic ring carbons) ranged from about seven tenths (0.7-SO3H/average asphaltene molecule) to thirty-five (35-SO3H/average asphaltene molecule), depending on the amount of oleum used and the reaction time. For Examples 2, 4 and 5, the values were corrected for the fact that resid only contains about 25 wt % asphaltenes and the —SO3H groups per average asphaltene molecule are calculated from yield (in grams) on the whole resid. It was presumed that all the —SO3H groups have gone only to asphaltene molecules.
The wt % C, H, N and S analysis of the sulfonated asphaltenes (Examples 1A to 1D, 2 and 3) indicates that the number of sulfonic acid groups added range from about 2 to 4.6 per 100 carbon atoms (Table 2, average MW˜1847). Corrected to MW˜1500 amu the range changes from 1.8-3.8 per average asphaltene molecule. There are significantly fewer added sulfonic acid groups according to the wt % analysis than the yield (in grams) data above suggested. The data indicates that it is likely that the increased SO3H group content in the yield (in grams) analysis is due to the occlusion of unreacted oleum with the product and/or the formation of salts carried over into the recovered product and included in the yield (in grams) data and not exclusively due to the addition of—sulfonic acid groups to the asphaltene molecule. There is, however, a consistency in the chemical makeup of toluene insolubles (TIs) isolated from the sulfonation reaction whether one starts with the resid or the asphaltenes.
X-ray photoelectron spectroscopy (XPS) indicates that the number of sulfonic acid groups added per asphaltene molecule in Examples 1A to 1D, 2 and 3 ranges from 0.1 to 4.8 which is directionally more consistent with the wt % C, H, N and S data than it is with the yield data. Quarternary ammonium salts of the nitrogen species were also observed. The range of salt formation goes from 17 to 63% of the total nitrogen species. These would be quaternary ammonium salts formed by the reaction of sulfuric acid (H2SO4) from the oleum with basic nitrogen species.
The toluene solubles (TSs) from the sulfonation of Heavy Canadian vacuum resid were compared to the DAO recovered by heptane deasphalting of the unreacted Heavy Canadian vacuum resid. The TSs are very similar in quality to the conventional heptane DAO. The number of atoms per 100 carbon atoms (100 C) were calculated from the wt % C, H, N and S analysis of a heptane DAO from an unreacted Heavy Canadian vacuum resid and the TSs from the sulfonation of Heavy Canadian vacuum resid (Table 3). Oxygen content was calculated by differene. The data in Table 3 illustrates how similar these two materials are in H/C ratio, nitrogen, sulfur and oxygen content. Apparently there are no molecules in the TSs that contain added sulfonic acid groups (—SO3H). This indicates that the sulfonation reaction was highly selective.
The TGA analysis (
A small scale Fluid Catalytic Cracking (FCC) unit was used to evaluate the catalytic cracking behavior of the TSs and the DAO. Table 4 shows that the overall conversion and gasoline yield is higher for the DAO than it is for the TS.
The metals content of the TSs are compared to those of the DAO from the heptane deasphalting of Heavy Canadian vacuum resid in Table 5. The TSs from the sulfonation reaction have somewhat higher concentrations of metals than the DAO from heptane deasphalting of Heavy Canadian vacuum resid. The TSs from selective sulfonation are still reasonable feedstocks for FCC.
Because of difficulties anticipated in separating the spent oleum and sulfuric acid from the product, liquid sulfur trioxide (SO3) was substituted. A European Vacuum Resid (EVR) was also substituted for Heavy Canadian Vacuum Resid because it was identified as a poor feed stock for asphalt. The purpose was to take a non asphalt resid, treat it chemically with liquid SO3 and produce a good asphalt feedstock. More value was anticipated from this than working on a resid that is already a good feedstock for asphalt production.
The sulfonation reactions were also conducted at the melting point of the resid to determine if the reaction could be done without the use of solvent. One experiment was carried out by reacting liquid sulfur trioxide (SO3) with EVR at it's melt temperature (˜165° C.). The product was cooled to room temperature and toluene was added. The toluene was stirred with the sulfonated product overnight and then suction filtered to separate TSs and TIs. This reaction was difficult to run because of the reactivity of pure SO3 at 165° C. Elemental analyses of the TIs from this experiment are summarized in Table 6 and compared to heptane asphaltenes from unreacted EVR. The TIs from this experiment as well as from the previous experiments on Heavy Canadian Vacuum Resid with 20% oleum were found to have quality issues as discussed in the next section on the quality of sulfonated asphaltenes. The reaction of EVR with SO3 at 165° C. was extremely exothermic. The yield of TIs was 4.2 wt %. The yield of heptane asphaltenes from unreacted EVR is 5.5 wt %. The yields are similar and this indicates that only the asphaltenes in EVR are targeted by the sulfonation chemistry, even at 165° C. The presence of SO3 groups and oxidation products of organic carbon were not found in abundance for this sample by XPS. The surface of this sample may be depleted in sulfonation reaction products.
The TGA wt % coke @ 525° C. (
The TSs from the sulfonation of EVR @ 165° C. are also very similar in elemental analysis (Table 7) to the heptane DAO of the unreacted EVR. This is another indication.
of the selectivity of the sulfonation chemistry. Very little of the heptane DAO reacts. Only 0.17-SO3H groups are added per 100 carbon atoms. The TGA data (
It was anticipated that a better asphalt feedstock would result from sulfonating a non asphaltic resid such as EVR without removing the sulfonated asphaltenes. The experiment was repeated with liquid SO3 and EVR but this time at room temperature in a solvent (methylene chloride). The reaction appeared to be selective at 165° C. and this was an attempt to obtain a sulfonated product without having to do the reaction at 165° C. Methylene chloride was used in place of toluene to avoid sulfonating the toluene solvent. The elemental analysis of the product is compared to unreacted EVR in Table 8. The materials are similar and it can be seen that about 0.2-SO3H groups have been added per 100 carbon atom. The quality issues are discussed in the next section. The TGA (
Pyrolysis Gas Chromatography with Mass Spectral detection (GCMS) qualitatively demonstrates the evolution of SO2 but the temperature at which this occurs is unknown (
The results on a Heavy Canadian vacuum resid sample are for the asphaltenes that precipitate after sulfonation (also known at TIs or Toluene Insolubles). The presence of methylbenzene and benzene 2-Methyl Thiol are indicative of reaction and incorporation of the toluene solvent during the sulfonation. These two chemical features do not appear in the unreacted asphaltenes. It is not known how much toluene reacts and incorporates into the asphaltenes as the results represent a percentage of the total volatile molecules identified in the GCMS. The same thing is true of the SO2.
Further experiments on the thermal stability of sulfonated asphaltenes were conducted by pyrolyzing the sulfonated asphaltenes at 250° C. for one hour instead of flash pyrolysis (
Thus it is seen that:
It was anticipated that sulfonated products may have residual or occluded sulfuric acid and/or SO3 which could be leached out by water during the preparation or use of asphalt. This section summarizes the results of acid leaching experiments performed on sulfonated Heavy Canadian vacuum resid heptane asphaltenes and on virgin Heavy Canadian vacuum resid heptane asphaltenes. The sulfonated Heavy Canadian vacuum resid heptane asphaltenes were generated on a large scale by dissolving virgin Heavy Canadian vacuum resid heptane asphaltenes in toluene and sulfonating them with 20% oleum at room temperature (Example 3). The solid that precipitated from the toluene during the reaction (TIs) was suction filtered and washed with water (this is the first water wash).
The sulfonation reaction described above yielded three products: the TIs (sulfonated Heavy Canadian vacuum resid heptane asphaltenes), Toluene Solubles (TSs) and first water wash. The first water wash was titrated for acid content. The TIs were submitted for a second water wash. The second water wash involved stirring the TIs with distilled water overnight, suction filtering and sending the second water wash for acid titration.
Acid Leaching Results
Penetration Point and Softening Point—The TIs from the sulfonation of Heavy Canadian vacuum resid heptane asphaltenes with oleum at room temperature in toluene would not melt or soften at the temperatures needed to conduct these two tests. The same was true of the TIs from the sulfonation of EVR at 165° C. with no toluene. Therefore it can be concluded that these sulfonated products are not suitable feedstocks to make asphalt. The last experiment was to test the sulfonation product of EVR without removing the TIs. This experiment was done at room temperature in methylene chloride to generate a sulfonated product and to avoid the drastic reaction conditions encountered at 165° C. (Table 8,
Samples of naphthalene, phenathrene, pyrene, benzothiophene, dibenzothiophene, carbazole, indole and perylene were subjected to sulfonation using sulfur trioxide in nitrobenzene. Relative reactivities were obtained by direct competition between two aromatic compounds in nitrobenzene. Reactions were started by addition of 0.5 equiv of SO3 to sample pairs of aromatic compound solutions under ice cooling. Although the reaction was rapid, the analyses of the reaction mixture were delayed until after 4 h of mixing of reagents at room temperature. The reaction mixture was filtered and the filtrate was analyzed using a gas chromatograph-mass spectrometer (Hewlett-Packard Model 5972 Series). The filtrate (1 μL) was injected at an injection port temperature of 250° C. and an oven temperature of 100° C.; after an initial hold time of 3 min at 100° C., the oven temperature was programmed at 110° C./min until 250° C. The distribution of the un-reacted compound 1 and unreacted compound 2 in the filtrate and relative ratio with respect to dibenzothiophene (considered as 1) are summarized in Table 9.
aRatio of the un-reacted compound 1: un-reacted compound 2 based on GC-MS analysis of the filtrate,
bRelative ratio of the un-reacted compounds to Dibenzothiophene considered as 1.
dPyrene was not detected;
ePhenanthrene was not detected.
Reactivity order of the compounds towards sulfonation using SO3-nitrobenzene is arranged as follows: (Table 10).
Thus it is seen that the pyrrolic N containing N-heterocyclic aromatic compounds are much more susceptible to sulfonation than are ordinary polycyclic aromatics and even sulfur containing heterocyclic aromatics.
In regard to the relative reactivity of pyrene with respect to naphthalene and phenanthrene the results obtained are in line with the results reported in the literature for the nitration of such molecules, and in regard to the relative reactivity of phenanthrene with respect to naphthalene the results obtained are in line with the results reported in the literature for the acylation of such molecules.
The discovery that the pyrrolic N containing nitrogen heterocyclic aromatic compounds are more reactive than ordinary aromatic compounds and even sulfur containing heterocyclic aromatic compounds towards electrophilic aromatic substitution (as exemplified by sulfonation) indicates that this technique can be employed to remove pyrolic N-containing nitrogen heterocyclic aromatic compounds from hydrocarbon streams which are intended for further processing in catalytic hydrotreating. The removal of the pyrrolic N-containing nitrogen heterocyclic aromatic compounds from feeds destined for catalytic hydrotreatment results in reducing the catalyst deactivation normally caused by such nitrogen heterocyclic compounds in the feed streams.
This Application claims the benefit of U.S. Provisional Application 60/922,206 filed on Apr. 6, 2007, herein incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| 60922206 | Apr 2007 | US |
