US 3136825 A
Description (OCR text may contain errors)
United States Patent 1 3,136,825 PROCESS FOR DISPROPORTIONATION F ISGPARAFFINIC HYDRGCARBONS Patrick W. Ryan, Chicago Heights, Ill., Ronald S. Bartlett, Lafayette, Ind, and Robert A. Sanforml-Iomewood, 11., assignors, by mesne assignments, to Sinclair Research, Inc., New York, N.Y., a corporation of Delaware No Drawing. Filed Oct. 20, 1960, Ser. No. 63,735 4 Claims. (Cl. 260-683A4) The present invention relates to a process for the conversion of low octane number paraffin feedstoclrs into higher octane rating motor fuel components. More particularly, the present invention relates to a process of parafiin disproportionation whereby higher molecular Weight paratfins react with lower molecular weight parafiins to produce intermediate molecular Weight parafiins boiling in the gasoline range.
In recent years the automobile manufacturers have steadily increased the compression ratios of their spark ignition engines as a means of obtaining more power and greater efficiency. As the compression ratios of the engines increase, the hydrocarbon fuel employed must be of higher octane value to provide efficient knock-free operation notwithstmding that fuel octane can be increased through the addition of tetraethyl lead; and other undesirable aspects of engine operation, for instance preignition, can be overcome by the use of other additive components. Thus the problem remains for petroleum refiners to produce higher octane base hydrocarbon fuels under economically feasible conditions.
These refiners now have installed a substantial number of units for reforming straight run petroleum fractions in the presence of free hydrogen and over a platinum metal-alumina catalyst to obtain relatively high octane products. Primarily these products, frequently called reformates, are blended with other gasoline components such as thermal and catalytically cracked gasolines, alkylate, etc., and additives such as tetraethyl lead in obtaining present-day motor fuels. The reforming operation has a number of disadvantages. First, as the octane requirements of the blended engine fuels rise, the octane quality of the reformate must also increase if the blends be otherwise unaltered. This increase results in a substantial reduction in yield particularly when obtaining reformates having octanes (RON neat) of the order of 90 to 95 or above. As the severity of the operation is increased, the platinum metal-containing catalyst becomes fouled more often with carbonaceous deposits which requires more frequent regenerations and/ or replacements. As the platinum metal-alumina catalysts are relatively expensive, either replacement or withdrawal from use during regeneration materially increases the cost of providing a given volume of reformate. These and other factors affecting the yield-octane number-cost relationship make it desirable for the refiner to consider various ways in which high octane hydrocarbon fuel components can be obtained by employing processing methods other than platinum metal-alumina catalyst reforming operations.
A source of further octane enhancement lies inupgrading relatively low octane parafiins as, for instance, by paraffin disproportionation. A number of catalyst systems are known as being useful in this type of operation and such catalyst systems include, for example AlCl /HCl, HF/BF and HF. These catalysts have not proven entirely satisfactory, however, in that they age rapidly and form large amounts of catalyst oil. The HP ctalyst-s systems have the additional disadvantages in that HP is highly corrosive and difiicult to handle.
The present invention relates to a process for upgrading low octane, normally liquid isoparaffinic feedstocks, for instance, having a neat octane rating (RON), up to about 75, preferably up to about 60, by Way of disproportionation in a boron trifluoride-phosphoric acid catalyst system. Generally, a gain in octane number of about or greater is obtained. The present process has particular advantage in that it can be utilized in conjunction with reforming systems employing gasoline feedstocks and platinum-alumina catalysts to upgrade the isoparafiinrich feeds commonly obtained from reformates, as, for example, by the Udex or other solvent extraction or separation processes. Moreover, since our process is selective in converting isoparafiins, any unreacted normal paraflins in the feedstock can be used as turbine engine fuels or recycled to reforming or isomerization systems for conversion into higher octane rating components.
In accordance with the present invention an isoparaffinic feedstock of about 6 to 12 carbon atoms and isobutane are contacted with a boron trifluoride-phosphoric acid catalyst in a disproportionation zone and a product boiling in the gasoline range having an increased octane rating is obtained. The disproportionation is at a temperature of about 30 F. to 350 F., preferably about 200 to 275 F.; and a 131- partial pressure sufficient to maintain the hydrocarbon mixture at least partially in a liquid state, for instance, about 100 to 5000 p.s.i.g., preferably about 600 to 1200 p.s.i.g. The hydrocarbons are contacted with the catalyst for a time sufficient to substantially increase the octane rating of the resultingproduct boiling in the gasolinerange. Normally, this period will be dependent on the stirring efficiency, temperature and BF partial pressure but will generally fall within the range of about 15 minutes to 5 or more hours, preferably about 1 to 2 hours. The ratio of the heavier isoparaflin to isobutane is generally about 0.1:1 to 10:1, preferably about 0.7:1 to 2:1. Advantageously, these reaction conditions are selected to provide conversion of at least about 60%, preferably at least about or of the heavier isoparaiiinic feed to lower boiling hydrocarbons.
The phosporic acid catalyst of the present invention is employed in effective catalytic amounts and will usually be present in the disproportionation zone in a weight ratio of about 0.1:1 to 10:1 of total hydrocarbon to catalyst, preferably in a weight ratio of about 0.3:1 to 2:1. The process may be carried out in a batch operation or in a continuous operation which provides for recycle of the catalyst and isobutane. In conducting the reaction, an overall isobutane consumption is preferred, for example, about 1 to 25%, preferably about 5 to 10% based on the isobutane charged.
= The hydrocarbon product and the phosphoric acidboron trifluoride catalyst layers resulting on completion of the reaction can be separated by any manner desired. When agitation of the reaction mixture is stopped, it will separate into two phases'in the reactor or in any other vessel into which it is transferred as in a continuous or batch operation. These phases can be separated by simple decantation.
The reaction mixture can be allowed to separate into a lower layer of catalyst containing unsaturated oil including aromatics. The upper hydrocarbon layer formed can be freed from the catalysts by distillation and/or Washing with Water or passed through a column of basic ion exchange resin or other solid absorbent such as charcoal, potassium sulfate, sodium sulfate, etc. The unsaturated oil (catalyst oil) appearing in the catalyst layer can be separated through discharge into water followed by extraction with a solvent, e.g. ether or pentane. Small traces of fluoride remaining in the hydrocarbon material can be removed as by contact with alumina at about 200 to 500 F. Various drying procedures can be employed to separate the water from the hydrocarbon materials. Preferably the reaction product is characterized, aside from the C s, by predominantly a C to fraction with C being a major component.
As aforementioned, the disproportionation reaction of the present invention is conducted under a BF partial pressure of about 100 to 5000 p.s.i.g. In operation, therefore, phosphoric acid is saturated with ER, and the reaction medium provided with excess BF to give the required partial pressure. It is preferred that the phosphoric acid saturated with BF be about 40 or 50% to 100% concentration in water. The more concentrated phosphoric acid is preferred, e.g. at least about 80% since with increasing concentration there is less consumption of boron trifluoride. With 100% phosphoric acid, for instance, one mole of boron trifiuoride is absorbed per mole of acid while in the case of aqueous solutions both the phosphoric acid and water absorb boron trifluoride approximately mole for mole. The phosphoric acid-boron trifluoride catalyst system may be preformed, that is, formed prior to addition of the hydrocarbon reactants or formed in situ, that is, after addition of the hydrocarbon reactants and phosphoric acid to the reaction zone.
The hydrocarbon feed of the present invention contains an isoparaflin feed of about 6 to 12 carbon atoms. Although pure isoparaffins either alone or mixed with each other can be used, advantageously, petroleum fractions in the C to C boiling range having at least about 50% by weight isoparafiins, preferably at least about 65% by weight in admixture with normal parafiins, and perhaps other hydrocarbons, of similar boiling range can be employed. Such materials are found in various petroleum refinery streams and can be separated in more or less pure form. If desired, large amounts of olefins may be excluded from our reaction system and we prefer an essentially olefin-free feedstock, for instance, having not more than about 5% olefins.
A particularly suitable feedstock is a paraflinic concentrate derived from the 0 liquid product contained in the effluent of reforming systems employing petroleum gasoline feedstocks and platinum-alumina catalysts. As an example, most if not all of the aromatics of the reformate can be separated as by adsorption, extractive distillation, or any other procedure desired. The paraffinic materials resulting are predominantly isoparaffinic containing in admixture about 15 to 35 weight percent normal parafiins with minor amounts of olefins, aromatics and naphthenes. To obtain this feedstock from the reformate, the aromatics can be adsorbed on silica gel; or separated by solvent extraction through the use of a solvent selective for aromatics, e.g. phenol, or by any other desirable procedure.
A particularly useful method for accomplishing this separation employs a glycol-water extraction medium. As commercially licensed, one such system is known as Udexing. By regulation of conditions such as a glycol to water ratio, the extraction and solvent stripping temperature, and the character of the glycol, a Udex rafiinate varying in paraffinicity is obtained. The manner of controlling these factors is known in the art and it is sufficient to say that the preferred glycol materials are the glycols such as diethylene and dipropylene glycols and their mixtures.
In a preferred embodiment this invention provides a method of obtaining higher octane fuels for spark ignition engines involving the use of separate reaction zones in which are employed catalysts of different properties. In this method a gasoline, including naphtha, is contacted with a platinum metal alumina catalyst in the presence of free hydrogen under conditions which provide a substantial increase in the octane number of the petroleum hydrocarbon material. A low octane isoparaffin fraction,
4 for instance, boiling predominantly in the C -C range, of the resulting reformate is separated and then contacted with isobutane and with the boron trifluoride-phosphoric acid catalyst in a disproportionation zone to give a product boiling in the motor fuel which is of substantial octane rating.
The hydrocarbon feedstocks charged to the reaction zone containing the platinum-metal-alumina catalyst are petroleum fractions boiling primarily in the gasoline range, for instance in the range from about 175 to 450 F., but somewhat higher or lower boiling constituents can be included if desired. Preferably, the feedstock boils primarily in the range of about 200 to 400 F. Although the hydrocarbons passing to the platinum metal-alumina catalyst reaction system may be composed of predominantly saturated or straight run naphtha material, additional components can be used by themselves or in admixture. Such components include thermal and catalytically cracked stocks, particularly when hydrogenated, recycled reformate fractions of these cracked and reformed materials, etc. The reaction conditions observed or maintained in the platinum metal-alumina catalyst system include those suggested for present commercial reforming operations such as temperatures from about 750 to 1000 F., preferably about 825 to 975 F., and pressures from about 50 to 1000 p.s.i.g., preferably about to 500 p.s.i.g. The free hydrogen supplied to this reaction system usually is in the form of hydrogen-rich recycle gases and generally provides about 2 to 20 moles of hydrogen per mole of hydrocarbon feed; preferably this ratio is about 4 to 10:1. The space velocity usually lies in the range of about 0.5 to 10 WHSV (weight of feed per weight of catalyst per hour) preferably about 2 to 5 WHSV.
The platinum metal-alumina catalysts employed in the method of this invention include a number of compositions. Generally, the platinum metal is a minor amount of the catalyst, e.g. about 0.1 to 1.5 weight percent of the final composition. Platinum is the most commonly employed metal present in these reforming catalysts although other useful platinum metals include rhodium, palladium, iridium which, along with platinum, are the face centered cubic crystallite types of the platinum family as distinct from the hexagonal types ruthenium and osmium which appear to be of lesser value.
A paraffin-rich fraction of the liquid reformate from the platinum metal catalyst operation is obtained as a Udex rafiinate as noted above and contains predominantly isoparaffins together with about 15 to 35 weight percent of normal paratfin constituents with minor amounts of naphthenes, aromatics and olefins. The feedstock boils primarily in the motor fuel range, for instance, from C up to about 425 PI, although heavier constituents can be included.
This paraflin-rich feed obtained as a Udex raflinate is then contacted with the phosphoric acid-boron trifluoride catalyst system in the presence of isobutane as previously described. Normal paraffins may be present since they do not inhibit the reaction. In the system of the present invention primarily the isoparafiins of the feedstock react, with their being preferably little, if any, conversion of normal parafiins.
The disproportionate may be further processed in several ways. For instance, the disproportionate may be subjected to distillation to recover isobutane which could then be recycled. The (1 fraction which has a high octane number could be sent to the gasoline pool or could be passed over a 5 A. molecular sieve in order to obtain a high octane C -C gasoline and recover the unreacted C and C normal components.
If desired the C disproportionate could be further processed as, for example, by subjecting it to further distillation to obtain a high octane C -C out which can be sent directly to the gasoline pool and a bottoms fraction which contains small amounts of isoparafiinic C s and C s and larger amounts of normal C and C paraffins.
The low octane bottoms fraction from this distillation is a poor recycle stock due to its high content of normal parafiins. However, it can be further processed by sending it as a feed to a catalytic reformer where the normal parafiins are converted to aromatic and isoparafiins. The resulting reformate could then be recycled and disproportionated, or first, dearomatized and the rafiinate subjected to further disproportionation. Other processing alternatives obvious to those skilled in the art can be employed.
The following examples wil serve to further illustrate the present invention and the improved results obtained thereby.
EXAMPLE I A boron trifiuoride saturated solution of 100% phosphoric acid was charged to a 1-gallon autoclave. The
temperature was raised to approximately 252 F. and a mixture of isobutane and a C to C sulfuric acid-treated naphtha reformate cut was pressured into the reactor by means of a calibrated blowcase. The C to C reformate cut employed analyzed as follows:
Paraifins, vol. percent 82.9 Olefins, vol. percent 0.0 Naphthenes, vol. percent 14.6 Aromatics, vol. percent 2.5 Composition, vol. percent:
C 3.2 1C7 55.0 iC 29.4 RC3 8.0 iCg 4.4 nC
Octane number (RON-I-3 cc. TEL added/gal)--- 73.8
The reactor was then pressured up with BF, to approximately 985 p.s.i.g. and stirred for 2 hours after which stirring was stopped. The reactor wasthen cooled. The contents of the reactor were drained into a room temperature trap, which was in reality a separatory funnel. The room temperature trap was connected to a series of four cold traps where condensible gases were collected. After the catalyst was collected in the room temperature trap it was drained and stored in a tapered stoppered bottle. The hydrocarbon in the room temperature trap was collected and weighed. The hydrocarbon present in each of the four cold traps was also weighed. The total hydrocarbon weight (447 g.) showed a weight percent recovery of 90.2% (excluding catalyst oil).
The hydrocarbon products (excluding catalyst oil) were combined and analyzed. The results of the run are shown in Table I.
Table 1 Run number 41. Feedstock Acid treated reformate. iC /t0ta1 HC wt. ratio 0.471. Catalyst 100% H PO /BF Catalyst gain, g 165. Catalyst/total HC wt. ratio 1. Temperature, F 252. Pressure 985. Product g. (wt. percent) 447 (90.2). Debutanized product analyses,
IBP 94. 118 50 183 90 468. EP -500. Percent rec 90.5. Percent res. Percent loss Octane No. (RON +3 cc.
The data clearly shows that low octane number isoparaflinic feedstocks may be advantageously dispropor-. tionated in the presence of isobutane and a phosphoric I acid-boron trifluoride catalyst system to yield a higher octane product. EXAMPT E H A straight-run naphtha is obtained by distillation from crude oil, and the naphtha typically has an ASTM distillation boiling range of about 209 to 381 F., a RON (neat) of about 47.2, and a gravity API at 60 F. of about 56.7. This naphtha is fed to a reforming unit containing three essentially adiabatic reactors each having a fixed bed of a platinum-alumina reforming catalyst. This system is equipped with means for heating the charge to each reactor and the heaters and reactors are arranged for serial fiow. The catalyst employed is a platinum-alumina reforming catalyst containing about 0.6 weight percent platinum, and manufactured in accordance with US. Patent No. 2,838,444. The inlet temperature of the feed to each of the three catalyst beds is 940 F., while the pressure is about 500 p.s.i.g. Free hydrogen is supplied to the feed passing to the heater before the first reactor and the hydrogen is supplied to the feed passing to the heater before the first reactor and the hydrogen is obtained by recycle from the third reactor efiluent stream. The molar ratio of hydrogen-rich recycle gas (72.7% H to hydrocarbon feed is approximately 5.5 to 1, while the overall space velocity is about 2.34 WHSV. The efiluent from the last reactor is conveyed to a flash drum operating at 500 p.s.i.g. and is then treated or depropanized to remove C and lighter hydrocarbons by distillation.
6.71 parts by volume of the resulting reformate are passed at a temperature of 222 F to a distillation column having a top temperature of 215 F. and a bottom temperature of 336 F. to remove light gasoline boiling in a range of about 118 to 216 F. as overhead. 3.17 parts by volume of the bottoms of this distillation column are charged at 316 F. to another distillation column having a top temperature of 279 F. and a bottom temperature of 348 F. to remove a heavier gasoline fraction and an overhead fraction having a boiling range of about 250 to 284 F. 1.622 parts by volume of the overhead from the latter distillation column is sent to an extractor having a tower top and bottom temperature of 280 F. into which is fed 8.16 parts by volume of an extractive medium containing about 17% by volume of dipropylene glycol,
' 55 75.5% by volume of diethylene glycol and 77.5% by volume of water. The rafiinate obtained as overhead from the extractor analyzed as follows:
Octane number (RON +3 cc. TEL added/gal.) 60.8
The raffinate feedstock was then disproportionated in the presence of isobutane and either or H PO B1 according to the method of Example I under the conditions shown in Table II below. The results are also shown in Table II.
.7 Table 11 Run number 32 36 Catalyst 85% 100% HaP04/BF3 HsPO4/BF3 1C4 extract feed wt. ratio 1 1 Catalyst total HG wt ratio 1 1 Temperature- 245 220 Pressure 1, 040 1, 060 Wt. percent recovery. 98. 9 99. 6 Wt. percent catalyst oil 4. 7 7. Product distribution:
3.1 2. 6 47. 3 18. 8 23. 6 26. 1 10. 9.0 3. 6 3.1 2. 6 2. 1 7. 3 5. 8 1. 4 1.1 0.6 1. 3 Wt. percent conversion 77. 3 80.8 C5, C6, 01 yield 72.0 71.2 Octane No. RON 3 cc.'s TEL/gal 87.7 87. 5 Vol. percent yield 107. 5 105. 6 iCr c0nsumption 11.0 10.3 Selectivity 93. 1 88. 1
The data demonstrates the particular advantages of utilizing the present process in conjunction with reformin g systems employing straight-run naphtha feedstocks and platinum-alumina catalysts to upgrade the isoparaffin-rich feeds obtained from the reformate. The catalyst oil produced in the two runs was only 4.7 and 7.0 weight percent.
EXAMPLE III Five hundred and five grams of a boron trifluoride saturated solution of 50% phosphoric acid was charged to a l-gallon stirred autoclave. The temperature was raised approximately 250 F., and 815 ml. (513 g.) of a mixture of 50 weight percent isobutane and 50 weight percent of an isoparaflinic feedstock consisting of mainly C and C isoparaffins was pressured into the reactor by means of a calibrated blowcase. The reactor was then pressured up to approximately 1000 p.s.i.g. and allowed to stir for hwo hours after which stirring was stopped, and the reactor was cooled. The contents of the reactor were drained into a room temperature trap, which was in reality a separatory funnel. The room temperature trap was connected to a series of four cold traps where condensible gases were collected. After the catalyst was collected in the room temperature trap it was drained and stored in a tared stoppered bottle. The hydrocarbon in the room temperature trap was collected and weighed. The hydrocarbon present in each of the four cold traps was also weighed. The total hydrocarbon weight (476 g.) showed a weight percent recovery of 92.8% (excluding catalyst oil).
The catalyst was decomposed by first heating to 250 F. to remove excess boron trifluoride, followed by dilution of five times its volume with water. Ether extraction of this aqueous material and subsequent removal of this ether by distillation gave 26 g. (5.1 weight percent) of catalyst oil. This brought the total recovery to 97.9 weight percent.
The hydrocarbon products (excluding catalyst oil) were combined and analyzed by vapor phase chromotography. Correcting for the isobutane charged the product distribution based upon a 92.8 weight percent recovery of total product is as follows:
Product: Weight percent 8 3'3 0: II: LI: 4317 C 16.5 C 7.4 i-C 4.6 nC 13.0 iC 2.4 ll-Cg 8 EXAMPLE iv The raflinate feedstock of Example II was disproportionated in the presence of isobutane and H PO /BF according to the method of Example I but under the conditions shown in Table'III below. The results are also shown in Table III.
Table III Run No 22. Catalyst 85% H PO /BF iC. /total HC wt. ratio 49.6. Catalyst Wt, g 500. Catalyst wt. gain 82. Catalyst/ total H'C wt. ratio 1. Temperature, F 253. Pressure, p.s.i.g 480. Products:
Wt. percent rec. 94.8.
Catalyst oil, g.
Total wt. percent rec. iC consumption 3.2. Product distribution by V.P.C.:
C 1.7. C; 48.0 C 16.0 C 5.2. O; 2 8
II-Cg We claim:
1. In a method of converting low octane parafiinic feedstocks, the step comprising contacting a hydrocarbon feedstock consisting essentially of isoparalfinic hydrocarbons of 6-12 carbon atoms and isobutane with a catalytic amount of phosphoric acid-boron trifluoride catalyst in a reaction zone at a temperature of about 30 to 350 F. and having a boron trifluoride partial pressure of about to 5000 p.s.i.g. and sufiicient to maintain the hydrocarbon mixture at least partially in the liquid state, the weight ratio of said feedstock to isobutane being about 0.1 to 10:1, to obtain a hydrocarbon product of increased octane number rating boiling in the gasoline range.
2. In a method of converting low octane paraifinic feedstocks, the step comprising contacting a hydrocarbon feedstock consisting essentially of isoparaffinic hydrocarbons of C to C carbon atoms and isobutane with phosphoric acid-boron trifluoride catalyst in a reaction zone at a temperature of from 200 to 275 F. and having a boron trifluoride partial pressure of about 600 to 1200 p.s.i.g. and sufficient to maintain the hydrocarbon mixture at least partially in the liquid state, the weight ratio of said feedstock to isobutane being about 0.7 to 2:1, the weight ratio of total hydrocarbon to phosphoric acid catalyst being about 0.3 to 2:1 to obtain hydrocarbon product of increased octane number boiling in the gasoline range.
3. In a method of converting a hydrocarbon fraction boiling in the gasoline range, the steps comprising reforming said hydrocarbon by contact with a platinum metalalumina catalyst in the presence of free hydrogen at a temperature of about 750-1000 F. to provide a product of increased octane value boiling in the gasoline range, separating from this product a hydrocarbon feedstock consisting essentially of isoparafiinic hydrocarbons boiling primarily in the C C range, contacting said isoparafiinic feedstock and isobutane with a catalytic amount of phosphoric acid-boron trifluoride catalyst in a reaction zone at a temperature of about 30 to 350 F. and having a boron trifluoride partial pressure of about 100 to 5000 p.s.i.g. and sufiicient to maintain the hydrocarbon mixture at least partially in the liquid state, the weight ratio of said feedstock to isobutane being about 0.1 to 10:1, to obtain a hydrocarbon product of increased octane number rating boiling in the gasoline range.
4. In a method of converting a hydrocarbon fraction boiling in the gasoline range, the steps comprising reforming said hydrocarbon by contact with a platinum metalalumina catalyst in the presence of free hydrogen at a temperature of about 7501000 F. to provide a product of increased octane value boiling in the gasoline range, separating from this product a hydrocarbon feedstock consisting essentially of isoparaffinic hydrocarbons boiling primarily in the (I -C range, contacting said hydrocarbon feedstock consisting essentially of isoparaflinic hydrocarbons of C to C carbon atoms and isobutane with phosphoric acid-borontrifluoride catalyst in a reaction zone at a temperature of from 200 to 275 F. and having a boron trifiuoride partial pressure of about 600 to 1200 p.s.i.g. and sufficient to maintain the hydrocarbon mixture at least partially in the liquid state, the weight ratio of said feedstock to isobutane being about 0.7 to 2:1, the weight ratio or" total hydrocarbon to phosphoric acid catalyst being 10 about 0.3 to 2:1, to obtain a hydrocarbon product of increased octane number boiling in the gasoline range.
References Cited in the file of this patent UNITED STATES PATENTS 2,216,274 Grosse Oct, 1, 1940 2,349,458 Owen et al. May 23, 1944 2,358,011 Ipatielf et al Sept. 12, 1944 2,363,222 Beyerstedt Nov. 21, 1944 2,402,051 Ipatieff et al. June 11, 1946 2,405,993 Burk Aug. 20, 1946 2,849,509 Slaughter et al. Aug. 26, 1958 2,947,682 Friedman Aug. 2, 1960 OTHER REFERENCES Booth et al.: Boron Trifiuoride and Its Derivatives; John Wiley and Sons, Inc., New York (1949); pages 166171 and 194.