US3264211A

US3264211A - Pour point reduction process

Info

Publication number: US3264211A
Application number: US234539A
Authority: US
Inventors: Nager Maxwell
Original assignee: Shell Oil Co
Current assignee: Shell USA Inc
Priority date: 1962-10-31
Filing date: 1962-10-31
Publication date: 1966-08-02
Anticipated expiration: 1983-08-02
Also published as: CH451894A; BE639291A; GB994002A; DE1246918B; NL299837A; FI42351B

Description

United States Patent 3,264,211 POUR POINT REDUCTION PROQESS Maxwell Nager, Pasadena, Tex., assignor to Shell Oil Company, New York, N.Y., a corporation of Delaware No Drawing. Filed Oct. 31, 1962, Ser. No. 234,539 9 Claims. (Cl. 208-264) This invention relates to a process for the refining of petroleum and more particularly to the hydrotreating of that portion of petroleum falling into the kerosene and gas oil range.

In a conventional refining process petroleum is first separated into a number of different fractions such as, for example, a butane fraction, pen-tane fraction, straightrun gasoline, naphtha, kerosene, light gas oil, heavy gas oil, etc. These fractions are then suitably refined by various known refining methods to produce such products as gasoline, special solvents, paint thinner, kerosene and jet fuel, distillate fuels such as diesel fuel, range fuel and furnace oils, agricultural spray oils, etc. The distillation range of many of these products is substantially the same or overlap appreciably, consequently, the specific refining methods used are chosen to provide the particular performance characteristics desired for each product. Thus, each product is refined to meet a variety of specifications which include, for example, gravity, distillation, flash point, pour point, sulfur, viscosity, octane, diesel index or the like, which reflect the performance characteristics of the product. Since the demand and value for the various products differs appreciably, and may vary to a considerable extent as the result of seasonal or other factors, the refiner is frequently pressed to meet demand with minimum downgrading of material of higher value.

The advent of commercial jet aircraft, which consume kerosene type materials as fuels, has posed a major problem for refiners. In order to supply the demand for low pour point proper volatility materials for jet fuel, it has been necessary to rob these materials from furnace oil. Generally, furnace oil components have had to be undercut, i.e., reduce end point by lowering distillation cut point, in order to meet pour point specifications, too, the removal of low pour point from end material for jet fuel has aggravated this problem and has also added to the problem of meeting front end volatility requirement.

It has been found in accordance with this invention that it is possible to produce specification furnace oils from a wide variety of distillate stocks, both cracked and straightrun, with minimum use of undercutting or of light diluents. The process is a special hydrotreatment which is carried out with a hydrocarbon feed containing from about 50 to 600 ppm. total nitrogen at a temperature between about 650 to 850 F., a pressure of 450 to 1,500 p.s.i.g., a liquid hourly space velocity of 0.5 to 5, and a hydrogen to oil mole ratio of about 1 to 10. The catalyst used in the process is a dual function catalyst comprising a hydrogenative metal, i.e., one having high activity for hydrogenation reaction, of Group VI and Group VIII of the 'Periodic Table which is dispersed or combined with an acidic-type catalyst support, i.e., one which has cracking activity. The process is conducted in the presence of nitrogen compounds to effect minimum conversion to gases or hydrocarbons in the low gasoline boiling range.

Metals of Group VI which have hydrogenation activity "ice are tungsten, molybdenum and chromium. Of the Group VIII metals, cobalt, and nickel of the iron group are more widely known and used and are considerably less expensive than the noble metals such as the platinum and palladium group. These hydrogenative metals are active in the form of the metal, the oxide, or the sulfide. In the process of the invention, tungsten and nickel are in the form of the sulfide, the weight ratio of tungsten to nickel being 0.2 to about 4 or higher, preferably about 0.4 to 0.8. The amount of hydrogenative metal in the catalyst is usually between about 550% by weight, although larger amounts can be used if desired. The amount of nickel is generally at least about 5% and preferably no more than about 20% by weight. Supports having cracking activity are the inorganic refractory oxide materials such as silica-alumina, silica-magnesia, silica-alumina-zirconia, and the like. Silica-alumina containing from about 5- 40% by weight alumina is particularly suitable as a support in the present process. Catalysts containing about 0.1 to 2% w. fluoride can be employed if desired.

In carrying out the process the catalyst is usually employed in a fixed bed reactor. The catalyst is generally preformed, with lumps, extrudates, or pellets of about to inch size being particularly suitable. In a commercially available inch extruded catalyst containing 6% w. Ni and 19% w. W is a suitable catalyst for the process of the invention.

The catalyst used in the process of the invention can be prepared by any suitable means, the simple impregnation method being preferred. For example, a preformed acidic support is impregnated with an aqueous solution of a water soluble salt of the metal hydrogenation components, dried and calcined. To sulfide the catalyst, a mixture of hydrogen sulfide and hydrogen, preferably 10% v. hydrogen sulfide, is passed over the catalyst for a sufficient period of time, generally indicated by a breakthrough of hydrogen sulfide from the catalyst. An alternate means is to contact the catalyst with a sulfurcontaining hydrocarbon, usually feed into which is injected 2-3% by volume carbon disulfide or methyl disulfide, at a temperature of about 200 F. initially and which is gradually raised over a period of time to reaction temperature.

In the process of the invention, the hydrotreating operation is preferably effected at a temperature of about 700 to 800 F., a pressure of about 750 to 1,000 p.s.i.g., a space velocity of about 1 to 4, and hydrogen to oil mole ratio of about 2 to 5. The process can be carried out for a long period of time, although activity of the catalyst will tend to gradually decrease and incremental increases in operating temperature will be required to maintain the desired reduction in pour point of the oil. In general, use of high hydrogen partial pressures will tend to maintain catalyst activity. Eventually, however, it will be necessary to regenerate the catalyst to restore its ac tivity. This may be done by subjecting the catalyst to an oxidation with, for example, dilute air to remove the accumulated deposits,.followed by resulfiding of the catalyst after which hydrocarbon feed can again be continued.

In the process of the invention, volatility of hydrocarbon distillate is increased, pour point and cloud point are reduced, and sulfur and nitrogen compounds are substantially completely removed. Pour point is reduced at least 5 'F. and preferably at least 7 F. A wide variety of straight-run and catalytically cracked furnace oil components have been processed in once through operations at substantially constant catalytic activity. While these stocks spanned a wide range of pour point from 34 F. to +22 F., similar results were obtained with each. Reductions of 8-10 F. in pour point and 4050 F. inASTM 10% point were observed. Denitrification was substantially complete even with high nitrogen-containing feeds. The reduction in cloud point is important since commercially available pour point depressants are generally ineffective in reducing the cloud point of distillates. Moreover, low temperature filterability and pumpability characteristics of the distillates prepared by the process of the invention are much superior to the results obtainable through the use of additive alone. Stability characteristics of the furnace oil product is quite good.

Liquid yields in the process are quite high, being generally of the order of 100% by volume. The yield of 240 F.+furnace oil should be at least 85% by volume, preferably 90% by volume, and is generally around 95- 96% by volume. The small amount of feed converted to low boiling products, less than 10% by weight and preferably less than 5% by weight, is in contrast to other process such as hydrocracking processes which employ a cracking catalyst base. Moreover, the few light paraffins produced are about at the equilibrium iso/normal ratio which is in contrast to the very high iso/normal ratios obtained in hydrocracking. Light hydrocarbons in the product are removed, e.g., by distillation, to provide the proper flash point of the furnace oil.

Hydrogen consumption is generally in the range from about 100 to 750 standard cubic feet of hydrogen per barrel of feed and depends at least in part on the nature of the feed. With low boiling distillates hydrogen consumption will be in the order of 100-300 s.c.f. H lbbl. while with heavy distillates, such as heavy catalytically cracked gas oils which contain a substantial portion of polyaromatics the hydrogen consumption will be in the order of 400-650 s.c.f. Hg/bbl. and higher.

In the present process, the hydrotreatment is conducted in the presence of nitrogen compounds, the amount of nitrogen compounds being controlled to provide of about 50-600 p.p.m. N, preferably, 100-300 p.p.m. N, basis feed. The optimum nitrogen content for a feed will depend on the nature of the feed itself, with the particular catalyst used, and operating conditions. The importance of nitrogen compounds in the process can be seen from Table I which shows the results of hydrotreating cetane with sulfided nickel/tungsten (6.5% Ni, 10% W) on silica-alumina. The catalyst is maintained in the sulfide state by the addition of 1% S as dimethyl disulfide. Hydrotreating is conducted with and without the addition of triethylamine to provide 100 p.p.m. N. It will be noted that somewhat higher temperatures are employed with the nitrogen-containing feed.

Table 1 Temperature, F

750 Feed N, p.p.m 100 Yields, percent \v.:

1- 5 30. 5 6. 2 C6C13 25.9 12. 6 ISO-Cm- 5. 4 21. 8 11-015 38. 1 58. 5

nitrogen compounds. This results in a decrease in activity, thus the necessity for higher temperatures, but improves selectivity since the remaining active sites promote the favorable reactions. The presence of excess nitrogen tends to decrease activity with little further benefit in selectivity. Although most if not all hydrocarbon distillates contain some naturally occurring nitrogen compounds, the nitrogen content varies considerably and in many cases will be of a relatively low value. In such cases the nitrogen content can be controlled by the addition of suitable nitrogen compounds to the nitrogen deficient distillate, the inexpensive and readily available organic amines being quite suitable. Cyclic compounds containing nitrogen, within or without the ring, are suitable but are generally more expensive. The more volatile nitrogen compounds can be added to the recycle hydrogen stream if desired. In determining the amount of extraneous nitrogen compounds which are to be added to provide the desired nitrogen level, the ammonia content of the recycle hydrogen should be taken into account as ammonia is also etfective in the process of the invent-ion.

It is generally advantageous to include in the feed to the process gas oils which are higher boiling than those normally included in furnace oil. The high boiling gas oils generally contain relatively large amounts of nitro gen compounds and thus serve as a source of nitrogen compounds to provide optimum nitrogen content. In addition the yield of low pour point furnace oil is markedly increased. This is because the pour point reduction of the furnace oil component in the process of the invention reduces or eliminates the need for undercutting which heretofore has been necessary to meet pour point specification, thus more of the higher boiling oil can be included in the furnace oil component. Additional yield is obtained as the result of pour point reduction and molecular weight reduction of the heavy gas oil components which permits a portion of the heavy gas oil to be used in the furnace oil. By hydrotreating heavy gas oil components in admixture with the furnace oil components, e.g., a full range catalytical- 1y cracked or straight-run gas oil, furnace oil yield can be increased by as much as 15% for a fixed pour point furnace oil.

Heavy gas oils generally boil up to about 950 F., preferably 850 F. A full range gas oil, comprising light and heavy gas oils, suitable as feed to the process of the invention will boil in the temperature range from about 350 to 850 F.

There is also indication that inclusion of heavy gas oil in the hydrotreating process improves catalyst stability although the reason for this is not readily apparent. The heavy gas oil product is deeply hydrogenated and substantially free from nitrogen and, therefore, is an excellent feed to a cracking process, either catalytic cracking or hydrocracking, both of which are well known to the art. 'For example, 640 F.+heavy gas oil product from the process of the invention, when catalytically cracked, produces more gasoline and less coke compared with the corresponding product obtained from conventional hydrogenation at the same processing conditions (Ni-4Mo/Al O catalyst at 725 F., 900 p.s.i.g. 4/1H /oil mole ratio, and 1 LHSV).

EXAMPLE I Silica-alumina (approximately 25% alumina) cracking catalyst was tableted and impregnated with an aqueous solution of nickel nitrate and silicotungstic acid, in an amount calculated to provide 6.5% w. nickel and 10% w. tungsten. The impregnated pellet-s were allowed to stand 16-20 hours and then dried under a heat lamp. The catalyst was stirred during the initial drying. The catalyst was dried an additional three hours in vacuum at 265 F. and calcined 20 hours at 500 F., followed by an additional five hours at 860 F. The catalyst was sulfided prior to use by injecting 3% by volume carbon disulfide (or dimethyl disulfide) in the feed at a temperature of 200 R, which was raised to reaction temperature at the rate of 50-100 per hour.

Activity and stability of the catalyst were determined with a blend consisting of 65% v. catalytically cracked light gas oil and 35% mixed sour straight-run gas oil, which are considered as representative of major furnace oil components. To meet a F. pour point and 460 F. maximum ASTM 10% point specification, 25-30% v. of kerosene or range fuel would have to be added to this blend. The blend, containing 200 p.p.m. total nitrogen, was hydrotreated for an extended period with the above catalyst. The liquid product was distilled in a 1 inch 30-plate Oldershaw column at 10:1 reflux. Operating conditions and results are shown in Table II.

Table II Operating Conditions:

Pressure, p.s.i.g 900 900 LHSV 1 1 Hg/Oil, mol 3.9 4. 4 Temperature, F 720 725 Hz Consumption, s.e.t./bbl 397 425 Hours on Stream 326 710 Yields, percent v. Basis Oil Charge Feed 240 F+Produet Properties:

Gravity, .API at 60 F 30. 6 35. 7 35. 9 Flash point, F M 218 145 146 Your Point, F..- +10 +2 +1 +22 +16 43. 0 52. 3 52. 6

434 338 364 495 420 445 556 524 519 619 601 604 646 606 042 0. 98 0.05 Total N, p.p.m 200 1 1 *S.e.f./bbl.

It is to be noted from the above table that the desired furnace oil specification could substantially be achieved, after cutting the product at 240 F. to meet the flash specification, with substantially no added kerosene. The light gasoline fraction, i.e., C 240 P. fraction, removed to meet flash point contains about 60% ring hydrocarbons and therefore is an excellent feed to a catalytic reforming process.

EXAMPLE II Blends of light and heavy gas oil were hydrotreated with a sulfided tungsten/nickel on silica-alumina catalyst similar to that described in Example I. Feed A, consisting of 80% v. light gas oil, 20% v. heavy gas oil, required a 625 F. cut point for a 0 F. pour point, the furnace oil yield at this out point being 78% v. Feed B, containing 60% v. light gas oil, 40% v. heavy gas oil, required a 618 P. out point for a 0 F. pour point furnace oil, the yield of furnace oil at this cut point being 69% v. Operating conditions and results are shown in Table III for feed A containing 210 p.p.m. total nitrogen and feed B containing 260 p.p.m. total nitrogen.

Table III 80% v. LGO 60% v. LGO 20% v. HGO 40% v. HGO

Operating Conditions:

Reactor Temperature, F. 750 775 Reactor Pressure, p.s.i.g 900 900 LHSV 1.0 1. 0 Hydrogen-to-Oil, Molar... 5. 0 6. 0 Catalyst Age, hours 2, 050 2, 220 10 Hydrogen Consumption, s.e.i./

bbl 500 430 Feed Product Feed Product Yielgs, percent v. basis feed:

15 Metiih'ri (SEXY/5153f. "I "i611 Ethane (s.e.f./l)bl.) 17.8

Propane O. 9 Isobutane. O. 6 n-Butane 0.6 Isopentane 0. 3

2O n-Pentane 0. 1 C -240 F 2. 2 240-675 F." 240-040--. 78. 5 675+ F 640+ F 19. 3

Total s. 102. 5

Furnace Oil, 240 F. to 640 Pour Point 0 Specific Gravity.-- 0. 8676 Flash Point, F

3O EXAMPLE III A stove oil having the properties listed in Table IV Was employed in hydrotreatin g experiments with a sulfided tungsten/ nickel on silica-alumina cracking catalyst 3 similar to that described in Example I.

Table IV Gravity, API -2 40.1 ASTM dist, F;

IBP 340 10% 40s EP 590 Sulfur, w. 0.15 Nitrogen, p.p.m. W. 29 Pour point, F. 25 Cloud point, F. -15 Diesel index 60.6 Flash point, F. (TCC).

An organic nitrogen compound (triethylamine or tri-n butylamine) was added to the stove oil to provide varying levels of nitrogen content. Operating conditions were 900 p.s.i.g., 725 F., 1 LHSV, and 5 H /oil mole EXAMPLE IV For comparison, a blend of furnace oil components was hydrotreated with a commercial hydrodesulfurization catalyst comprising obalt molybdenum on alumina. Pour point and cloud point of the blend were +6 and +15, respectively. As shown in Table VI, .pour point and cloud point of the product are little affected by the hydrotreatment.

I claim as my invention:

1. A process -fior reducing the pour point of hydrocarbon distillate which comprises passing a hydrocarbon distillate together with hydrogen and in the presence of from about 50 to about 600 p.p.m. total nitrogen over a catalyst comprising the sulfides of nickel and tungsten supported on an acid-acting cracking catalyst at a temperature of about 650 to 850 F., a pressure of about 450 to 1,500 p.s.i.g., a liquid hourly space velocity of 0.5 to 5, and a hydrogen to oil mole ratio of 1 to 10, and recovering a hydrocarbon fraction boiling in the temperature range between about 240 F. and 675 F. and having a pour point of at least F. below that of the corresponding hydrocarbon fraction in the feed.

2. A process *for reducing the pour point of a hydrocarbon distillate which comprises passing a hydrocarbon distillate boiling in the range from about 350 to 850 F. together with hydrogen and in the presence of from about 50 to about 600 p.p.m. total nitrogen over a catalyst comprising the sulfides of nickel and tungsten supported on an acid-acting cracking catalyst at a temperature of about 650 to 850 F., a pressure of about 450 to 1,500 p.s.i.g., a liquid hourly space velocity of 0.5 to 5, and a hydrogen to oil mole ratio of 1 to 10, and recovering a hydrocarbon fraction boiling in the temperature range between about 240 F. and 675 F. and having a pour point of at least 5 F. below that of the corresponding hydrocarbon fraction in the feed.

3. A process for reducing the pour point of a hydroarbon distillate which comprises passing a hydrocarbon distillate together with hydrogen and in the presence of about 100 to 300 p.p.m. total nitrogen over a catalyst comprising the sulfides of nickel and tungsten supported on silica-alumina cracking catalyst at a temperature in the range from about 700 to 800 F., a pressure from about 750 to 1,000 p.s.i.g., a liquid hourly space velocity from about 1 to 4, and a hydrogen to oil mole ratio of about 2 to 5, and recovering a hydrocarbon fraction boiling in the temperature range between about 240 F. and 675 F. and having a pour point of at least 5 F. below that of the corresponding fraction in the feed.

4. A process for reducing the pour point of a hydrocarbon distillate which comprises passing a hydrocarbon distillate boiling in the range from about 350 to 850 F. together with hydrogen and in the presence of 100 to 300 p.p.m. total nitrogen over a catalyst comprising the sulfides of nickel and tungsten supported on silica-alumina cracking catalyst at a temperature in the range from about 700 to 800 F., a pressure from about 750 to 1,000 p.s.i.g., a liquid hourly space velocity from about 1 to 4, and hydrogen to oil mole ratio of about 2 to 5, and recovering a hydrocarbon fraction boiling in the temperature range between about 240 F. and 675 F. and having a pour point of at least 5 F. below that of the corresponding fraction in the feed.

5. A process for reducing the pour point of a hydrocarbon distillate which comprises passing a hydrocarbon distillate boiling in the range from about 350 to 850 F. together with hydrogen and in the presence of 100 to 300 p.p.m. total nitrogen over a catalyst comprising the sulfides of nickel and tungsten supported on silica-alumina cracking catalyst at a temperature in the range from about 700 to 800 F., a pressure from about 750 to 1,000 p.s.i.g., a liquid hourly space velocity from about 1 to 4, and a hydrogen to oil mole ratio of about 2 to 5, and recovering a hydrocarbon fraction boiling in the tempera ture range between about 240 F. and 675 F. and having a pour point of at least 5 F. below that of the corresponding fraction in the feed and a heavy gas oil fraction boiling above 675 F. which is catalytically cracked.

6. A process for reducing the pour point of a hydrocarbon distillate which comprises passing a hydrocarbon distillate boiling in the range from about 350 to 850 F. together with hydrogen and in the presence of 100 to 300 p.p.m. total nitrogen over a catalyst comprising the sulfides of nickel and tungsten supported on silica-alumina cracking catalyst at a temperature in the range from about 700 to 800 F., a pressure from about 750 to 1,000 p.s.i.g., a liquid hourly space velocity from about 1 to 4, and a hydrogen to oil mole ratio of about 2 to 5, and recovering a hydrocarbon fraction boiling in the temperature range between about 240 F. and 675 F. and having a pour point of at least 5 F. below that of the corresponding fraction in the feed and a heavy gas oil fraction boiling above 675 F. which is hydrocracked.

7. A process for reducing the pour point of a hydrocarbon distillate which comprises passing a hydrocarbon distillate together with hydrogen and in the presence of from about 50 to about 600 p.p.m. total nitrogen over a catalyst comprising the sulfides of nickel and tungsten supported on an acid-acting cracking catalyst at a temperature of about 650 to 850 F., a pressure of about 450 to 1,500 p.s.i.g., a liquid hourly space velocity of 0.5 to 5, and a hydrogen to oil mole ratio of 1 to 10, hydrogen consumption being about 100 to 750 standard cubic feet per barrel of feed, and recovering a hydrocarbon fraction boiling in the temperature range between about 240 F. and 675 F. and having a pour point of at least 5 F. below that of the corresponding hydrocarbon fraction in the feed.

8. A process for reducing the pour point of a hydrocarbon distillate which comprises passing a hydrocarbon distillate together with hydrogen and in the presence of from about 50 to about 600 p.p.m. total nitrogen over a catalyst comprising the sulfides of nickel and tungsten supported on an acid-acting cracking catalyst at a temperature of about 65 0 to 850 F a pressure of about 450 to 1,500 p.s.i.g., a liquid hourly space velocity, of 0.5 to 5, and a hydrogen to oil mole ratio of 1 to 10, hydrogen consumption being about 100 to 750 standard cubic feet per barrel of feed, and recovering in an amount of at least by volume, basis feed, a hydrocarbon fraction boiling in the temperature range between about 240 F. and 675 -F. and having a pour point of at least 5 F. below that of the corresponding hydrocarbon fraction in the feed.

9. A process for reducing the pour point of a hydrocarbon distillate which comprises passing a hydrocarbon distillate together with hydrogen and in the presence of from about 50 to 600 p.p.m. total nitrogen over a catalyst comprising the sulfides of nickel and tungsten supported on silica-alumina cracking catalyst at a temperature of about 650 to 850 F., a pressure of about 450 to 1,500 p.s.i.g., a liquid hourly space velocity of about 0.5 to 5, and a hydrogen to oil mole ratio of 1 to 10, hydrogen consumption being about 100 to 750 standard cubic feet per barrel of feed, and recovering a hydrocarbon fraction in an amount of at least by volume, basis feed, and boiling in the temperature range between about 240 F. and 675 F. and having a pour point of at least 5 F. below that of the corresponding hydrocarbon fraction in the feed.

References Cited by the Examiner UNITED STATES PATENTS 2,839,450 6/1958 Oettinger 208-254 2,894,903 7/1959 McGrath et a1 208-254 2,904,505 9/1959 Cole 208-264 2,943,047 6/1960 Reeg et al. 208254 3,058,896 10/1962 Nahin 208254 3,078,221 2/1963 Beuthes et al 208264 3,078,222 2/1963 Henke et a1. 208264 DELBERT E. GANTZ, Primary Examiner. ALPHONSO D. SULLIVAN, Examiner. S. P. JONES, Assistant Examiner.

Claims

1. A PROCESS FOR REDUCING THE POUR POINT OF HYDROCARBON DISTILLATE WHICH COMPRISES PASSING A HYDROCARBON DISTILLATE TOGETHER WITH HYDROGEN AND IN THE PRESENCE OF FROM, ABOUT 50 TO ABOUT 600 P.P.M. TOTAL NITROGEN OVER A CATALYST COMPRISING THE SULFIDES OF NICKEL AND TUNGSTEN SUPPORTED ON AN ACID-ACTING CRACKING CATALYST AT A TEMPERATURE OF ABOUT 650 TO 850*F., A PRESSURE OF ABOUT 450* TO 1,500 P.S.I.G. A LIQUID HOURLY SPACE VELOCITY OF 0.5 TO 5, AND A HYDROGEN TO OIL MOLE RATIO OF 1 TO 10, AND RECOVERING A HYDROCARBON FRACTION BOILING IN THE TEMPERATURE RANGE BETWEEN ABOUT 240*F. AND 675*F. AND HAVING A POUR POINT OF AT LEAST 5*F. BELOW THAT OF THE CORRESPONDING HYDROCARBON FRACTION IN THE FEED.