Petroleum distillate upgrading process

Abstract

A petroleum distillate feed is upgraded and a substantial C.sub.3 -C.sub.4 olefin product fraction produced by contacting the feed with ZSM-5 type zeolite at (1) a temperature in the 500.degree.-800.degree. F. range, (2) a pressure below about 13 atmospheres gauge, and (3) an LHSV in the 0.1-15 V/V/Hr range, and fractionating the effluent product stream.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

In the processing of petroleum distillates, the presence of paraffins is often undesirable. For example, when a distillate is hydrocracked, the paraffins will be cracked in significant and undesirable amounts to light paraffinic gases, which are usually burned or used as LPG fuels and which are not useful for further processing.

Because the losses to relatively low profit gases are significant, there is a continuing search for methods of dewaxing petroleum distillates by processes yielding chemical products which are amenable to further processing to more profitable products.

We have discovered that under certain processing conditions ZSM-5-type zeolites can be used to dewax, or to remove paraffins, from petroleum feedstocks by forming C.sub.3 -C.sub.4 olefins which are valuable chemicals amenable to further processing steps; further, the residual uncracked material has improved characteristics useful for reforming operations to make gasoline.

These benefits are achieved through a process which uses a ZSM-5-type catalyst in a matrix substantially free of hydrocarbon cracking activity with a low nitrogen feedstock. Additionally, the process of this invention is particularly useful because the coking and deactivation rate of the catalyst composite is exceptionally low leading to greater efficiency in refinery operations. Further, the process can be practiced at any stage of hydrocarbon processing where it is desired to remove normal or slightly branched paraffins without detrimentally affecting the other chemical components of a feed.

2. Background Art

Dewaxing of virgin petroleum distillates using a ZSM-5 catalyst is known in the literature (see, for example, U.S. Pat. Nos. 3,894,939--W. E. Garwood--and 4,067,797--N. Y. Chen et al). However, these known processes suffer from disadvantages, including (1) high catalyst fouling or deactivating rates and (2) little or none of the C.sub.3 -C.sub.4 product fraction is C.sub.3 -C.sub.4 olefins.

U.S. Pat. No. 3,758,403, Rosinski et al, Sept. 11, 1973, discloses the catalytic cracking of hydrocarbons with mixtures of ZSM-5 and other zeolite catalysts under cracking conditions.

It is an object of this invention to provide a novel process for carrying out the catalytic upgrading of petroleum distillates in a more effective and efficient manner.

It is an object of this invention to provide a process in which at least a substantial portion of the product produced by catalytically dewaxing a distillate using a ZSM-5-type zeolite is a C.sub.3 -C.sub.4 olefin fraction.

Other and additional objects of this invention will be clear from a consideration of the complete specification including the claims thereof.

TECHNICAL DISCLOSURE

The discovery of the present invention is embodied in a process for upgrading a petroleum distillate feed consisting essentially of hydrocarbons having a normal boiling point in the range of from about 180.degree. F. to about 1200.degree. F. and producing at least a substantial C.sub.3 -C.sub.4 olefin product fraction, by

(1) producing a process stream by contacting said feed with a catalyst comprising a ZSM-5-type crystalline aluminosilicate in a form which is substantially free of hydrogenation activity, said contacting being under conditions including (a) a temperature in the range of from about 500.degree. to 800.degree. F.; (b) a pressure below about 13 atmospheres gauge, and (c) a liquid hourly space velocity in the range of from about 0.1 to 20, said feed having a content of nitrogen-containing impurities, calculated by weight as nitrogen, below about 5 ppm; and

(2) recovering an upgraded effluent stream and olefin fraction by fractionating said process stream.

The present invention is further embodied in a petroleum distillate upgrading process wherein the portion of the catalyst, which is not a ZSM-5-type zeolite, is substantially free of hydrocarbon cracking activity.

The process of the present invention for upgrading petroleum distillate feeds can be used in conjunction with other processes known to the art such as hydrocracking and reforming. These well known processes typically occur under hydrogenation conditions and chemically change the contents of their feedstocks. Hydrocracking and catalytic reforming processes are typically operated under a significant partial pressure of hydrogen produced by a hydrogen-rich recycle gas rate of 500 or more SCF hydrogen per barrel of feed. Hydrogenation conditions are well known to the art and typically include, in addition to a significant hydrogen partial pressure, a moderate to high overall pressure as well as a catalyst having hydrogenation/dehydrogenation activity, e.g., nickel, palladium, and platinum catalysts.

The discovery of the present invention is further embodied in a process for increasing the effectiveness of petroleum processing, comprising:

(A) upgrading a petroleum distillate feed which consists essentially of hydrocarbons having a normal boiling point range in the range of from about 180.degree. to 1200.degree. F., through use of an upgrading process comprising,

(i) producing a process stream containing a C.sub.3 -C.sub.4 olefin product fraction, in an amount, based upon upgrading feed converted, in the range of from about 2 to 10 weight percent, by contacting said feed with a catalyst comprising a ZSM-5-type crystalline aluminosilicate zeolite in a form which is substantially free of hydrogenation activity, said contacting being under conditions including (a) a temperature in the range of from about 500.degree. to 800.degree. F.; (b) a pressure below about 13 atmospheres gauge; and (c) a liquid hourly space velocity in the range of from about 0.1 to 20, said feed having a content of nitrogen-containing impurities, calculated by weight as nitrogen, below about 5 ppm;

(ii) producing an upgraded effluent stream by removing the olefin product fraction from said process stream; and

(iii) recovering said upgraded effluent stream; in conjunction with

(B) hydrocracking or reforming a petroleum feedstock.

By use of the phrase "in conjunction with" is meant that the upgraded effluent can be the feedstock for a hydrocracking or reforming process, or, the effluent of the hydrocracking or reforming process can be the feed for the upgrading process, or, the upgrading process can be operated in a recycle mode with a hydrocracker or reformer.

By "recycle mode" as used herein is meant a processing scheme wherein effluent from the upgrading process is feedstock for the hydrocracking reforming process and effluent from the hydrocracking or reforming process is feed for the upgrading process, in the manner of FIGS. 4 and 5.

Intermediate process steps, such as stripping, splitting or fractionation, can be used to remove desirable chemicals from the process streams and to recover a desirable boiling range feed or feedstock for introduction into step (A) or (B).

The unique characteristic of using the upgrading process of the present invention in conjunction with processes of the art, such as hydrocracking and reforming, is that the overall effectiveness of the petroleum processing is increased since the hydrocracking and reforming steps do not operate on the normal or slightly branched paraffins. Those chemicals have been removed by the upgrading process as C.sub.3 -C.sub.4 olefins instead of as light gas paraffins. The C.sub.3 -C.sub.4 olefins are more valuable chemically than the corresponding light gas paraffins.

The great efficacy and attractiveness of the upgrading process is that it can be used at any stage of an oil refining operation where the feed to be upgraded is appropriate and where it is desirable to remove only straight and slightly branched chain paraffins with minimal capital expenditure. Because of the activity of the catalyst and its low deactivation rate, a fixed bed reactor can be used for extended periods of time without the necessity of the regeneration requirements of a Fluid Catalytic Cracking apparatus. By "nitrogen-containing impurities" as used herein is meant orgnaic nitrogen-containing compounds indigenous to crude petroleum and syncrude oils and/or as present in their conventionally hydroprocessed distillate fractions.

The Catalyst

The ZSM-5-type catalyst employed is a crystalline aluminosilicate zeolite having a silica to alumina ratio greater than 12 and preferably greater than 30 and is exemplified by ZSM-5, ZSM-8, ZSM-11, ZSM-12, ZSM-21 and other similarly-acting aluminosilicates described in the literature. For example, ZSM-5 is described in U.S. Pat. Nos. 3,702,886 and 3,770,614; ZSM-8 is described in U.S. Ser. No. 865,418 filed Oct. 10, 1969 (now abandoned), ZSM-11 is described in U.S. Pat. No. 3,709,979; ZSM-12 is described in U.S. Pat. No. 3,832,449, and ZSM-21 is described in U.S. Pat. No. 3,948,758. Relevant portions of these patents are incorporated herein by reference. The ZSM-5-type catalyst may be in the hydrogen form or in a metal cation or cation complex form which possesses little or no hydrogenation activity, such as a calcium, strontium, barium, zinc, copper, silver or rare earth form, with the hydrogen form being preferred. Hydrogenation activity of a catlyst is the capability of the catalyst to adsorb and dissociate molecular hydrogen.

The hydrogen and other forms of the ZSM-5-type zeolite may be obtained by conventional base and/or ion-exchange methods routinely employed in the zeolite art, including customary drying and calcining steps. Preferably the ZSM-5-type zeolite catalyst herein has a minimal sodium content, for example, by weight less than 1 weight percent, more preferably less than about 100 ppm, although a ZSM-5-type zeolite having a larger sodium content exhibits a relatively useful catalytic activity for present purposes.

The ZSM-5-type catalyst can be in any convenient form, that is, as required for ordinary fixed-bed, fluid-bed or slurry use. The catalyst can be composited with binders or it can be tableted without binders. Preferably it is used in a fixed-bed reactor and in a composite with a porous inorganic binder or matrix in such proportions that the resulting product contains from 1% to 95% by weight, and preferably from 10% to 70% by weight, of the zeolite in the final composite. It is extremely desirable that the porous inorganic binder or matrix have substantially no hydrocarbon cracking activity, especially where fixed bed use is desired. Where the inorganic binder has little or no hydrocarbon cracking activity, the ZSM-5-type catalyst composite is unsuitable for use in cracking systems which require the formation of coke to maintain an economical heat balance between the cracking reactor and the regeneration reactor. Such a system is a Fluid Catalytic Cracking (FCC) system in which a substantial part of the heat required in the cracking bed is supplied by the burning of the coke from th FCC catalyst during regeneration.

The term "porous matrix" includes inorganic compositions with which a zeolite can be combined, dispersed, or otherwise intimately admixed wherein the matrix may be catalytically active in a hydrocarbon cracking sense, but preferably inactive. The porosity of the matrix can either be inherent in the particular material or it can be caused by mechanical or chemical means. Representative of satisfactory matrices include pumic, firebrick, diatomaceous earths, and inorganic oxides. Representative inorganic oxides incude alumina, silica, amorphous silica-alumina mixtures, naturally occurring and conventionally processed clays, for example bentonite, kaolin and the like, as well as other siliceous oxide mixtures such as silica-magnesia, silica-zirconia, silica-titania and the like. The preferred inorganic matrices are those having low acidity--hence low hydrocarbon cracking activity--unmixed metal oxides, for example alumina, silica, zirconia, titania, or magnesia rather than mixtures of oxides. Where mixtures of oxides are used, there is a greater tendency for the binder/matrix to itself have sufficient hydrocarbon cracking activity to cause substantial and undesirable increases in the coking rates, thereby losing a significant advantage for refinery operations.

The compositing of the zeolite with an inorganic oxide matrix can be achieved by any suitable known method wherein the zeolite is intimately admixed with the oxide while the latter is in a hydrous state, for example as a hydrosol, hydrogel, wet gelatinous precipitate, or in a dried state or combinations thereof. A convenient method is to prepare a hydrous mono or plural oxide gel or cogel using an aqueous solution of a salt or mixture of salts, for example aluminum sulfate, sodium silicate and the like. To this solution is added ammonium hydroxide, carbonate, etc., in an amount sufficient to precipitate the oxides in hydrous form. After washing the precipitate to remove at least most of any water-soluble salt present in the precipitate, the zeolite in finely divided state is thoroughly admixed with the precipitate together with added water or lubricating agent sufficient in amount to facilitate shaping of the mix as by extrusion.

Petroleum hydrocarbon distillates, and the like, containing at least a significant (5 volume percent) content of normal paraffins and/or slightly branched paraffins are satisfactory feeds for the upgrading process provided that they have a content of nitrogen-containing impurities, calculated as nitrogen, which is less than 5, preferably less than 1, ppmw.

Although representative feeds include atmospheric or vacuum gas oils and fractions and mixtures thereof, for example having normal boiling point ranges in the range 400.degree. F. to 1200.degree. F., preferably 500.degree. F. to 850.degree. F., feeds can include distillates having a boiling point range of 180.degree.-1200.degree. F.

The feed may contain sulfur-containing impurities. However, the resulting product, in general, will also contain undesirable sulfur-containing impurities to some degree. Preferably the feeds for the present process contain, calculated as sulfur, less than 20 ppmw of sulfur-containing impurities.

Process Conditions

The process conditions satisfactory for use in the process of the invention may vary, depending upon such factors as the feed, the conversion desired, the catalyst age and the like. In general, satisfactory conditions include:

______________________________________ Broad Preferred Range Range______________________________________Temperature, .degree.F. 500-800 550-750Pressure, psig <200 0-25______________________________________

The space velocity, LHSV, V/V/Hr. can be in the range of 0.5-15, preferably 0.5-10, more preferably 2-10, and most preferably 2-4.

The yield of C.sub.3 -C.sub.4 olefins has been found to be very sensitive to the system pressure. Thus, at about 500 psig, the yield of these olefins is negligible. As the pressure is decreased below 500 psig, an increasingly significant yield of C.sub.3 -C.sub.4 olefins is produced. These olefins are especially desirable and are valuable for many well-known uses in the petroleum and chemical processing arts, whereas their alkane counterparts are far less desirable products. The yield of C.sub.3 -C.sub.4 olefins varies, depending upon the particular feed, conditions and catalyst employed, in the range of from about 2 to 10 weight percent of the feed converted.

DESCRIPTION OF THE FIGURES

FIG. 1 shows the effect of nitrogen on the activity of a ZSM catalyst.

FIG. 2 shows the effect of pressure on light gas yield.

The following figures illustrate the use of the upgrading process of the present invention in conjunction with other standard refining processes such as hydrocracking. For simplicity, standard equipment, such as compressors, pumps, and separators, are not illustrated.

FIG. 3 illustrates the sequential use of the upgrading process with a hydrocracker. The low nitrogen feed is introduced into the upgrading zone (2) via line (1). The upgraded effluent is removed from the upgrading reactor via a line (3) which introduces the upgraded effluent into a distillation zone (4) which separates the light gases and light olefins as well as the olefinic naphtha from the remainder of the upgraded effluent. The remainder of the effluent passes via a line (5) to a conventional hydrocracking zone (6) the effluent of which is removed and treated conventionally.

FIG. 4 illustrates the use of the upgrading process in a recycle mode with a conventional hydrocracker. The low nitrogen feed is introduced to the upgrading zone (12) via a line (11). The upgraded effluent passes from the upgrading reactor via a line (13) to a stripping zone (14) which removes the light paraffinic gases and olefins. The stripper bottoms pass by line (15) to a distillation zone (16) which separates the different petroleum fractions of boiling point less than 400.degree. F. The portion boiling above 400.degree. F. is split into two streams, one of which passes through a line (17) and is recycled into the feed line (11). The second stream passes by line (18) into a hydrocracking zone (19) whose effluent passes into line (20) and is mixed with the upgraded effluent of line (15) before introduction into the distillation zone (16).

In FIG. 5, the denitrified feed is introduced into the upgrading zone (32) via a line (31). The upgraded effluent recovered from the upgrading zone is introduced via a line (33) into a distillation zone (34) to remove the light olefins and paraffins. The lower boiling effluent, typically less than 400.degree. F., is introduced via line (35) into a standard hydrocracking zone (36). The hydrocracker effluent is conducted via a line (37) to a distillation zone (38), typically having a 450.degree. F. cut point. The heavy cut is recycled via a line (39) into the denitrified feed of line (31).

The following specific examples will serve to further illustrate the process of the present invention and the advantages thereof.

EXAMPLE I

In a preferred embodiment a gas oil is dewaxed with a significant concurrent production of a C.sub.3 -C.sub.4 olefin product fraction in good yield. A typical oil has the following characteristics:

Boiling Point Range (ASTM D-1160), .degree.F.: 445 to 820 Gravity, .degree.API: 37.8 Aniline Point, .degree.F.: 200 Total Nitrogen, ppmw as N: 0.5 Sulfur, ppmw as S: 20. Ramsbottom Carbon: 0.5 Refractive Index (80.degree. C.): 1.4375 Density (70.degree. C.): 0.798 Average Molecular Weight: 275 Paraffins: 52.7 Naphthenes: 36.6 Aromatics: 10.7

The contacting of the feed with a catalyst consisting of a composite of ZSM-5-type zeolite in a porous alumina matrix (65/35 weight ratio of zeolite to matrix) is carried out in a fixed-bed reactor under conditions including:

Temperature, .degree.F. (average): 750 Space Velocity, LHSV, V/V/Hr: 2.0 Total Pressure, psig: 25 Hydrogen Partial Pressure, psia: 0 Recycle Gas, SCF/B: 0

Typical results from use of the above-described representative feed and conditions include the following weight percent yields

C.sub.1 : 0.0 C.sub.2 (total): 0.01 C.sub.3 (total): 2.86 Propene: 1.59 C.sub.4 (total): 9.66 Butenes: 7.03 C.sub.5 -180.degree. F.: 12.19 180.degree.-380.degree. F.: 6.54 380.degree.-500.degree. F.: 7.14 500.degree. F.-End Point: 61.60 Total C.sub.5 +: 87.49

Under the above conditions and using a low-nitrogen feedstock, the above catalyst experiences a fouling rate of only 0.02.degree. F. per hour. This rate, surprisingly, is but about one-fifth the expected rate in view of the prior art, for example: (1) U.S. Pat. No. 4,067,797, N. Y. Chen et al; and (2) the article entitled "New Process Cuts Pour Point of Distillates" by N. Y. Chen et al, The Oil and Gas Journal, June 1977, pp. 165-170.

EXAMPLE II

A comparison test was run to determine the effect of nitrogen on a ZSM catalyst. A raw Arabian light oil and a hydrodenitrogenated (HDN) Arabian light oil having the following properties:

______________________________________ Raw Arabian Light HDN Arabian Light______________________________________Gravity .degree.API 27.4 37.5Aniline point, .degree.F. 176.4 182.3Sulfur, wt% 2.06 0.0037Total N, ppm 445 0.74D-1160 Distillation10%/30% .degree.F. 693/733 464/56650%/70% .degree.F. 756/776 641/69990%/EP .degree.F. 809/870 761/837% Paraffinic Carbon 65 63% Naphthenic Carbon 16 25% Aromatic Carbon 19 12______________________________________ were contacted over a catalyst containing 65% H-ZSM-5 and 35% alumina at atmospheric pressure, with no hydrogen or recycle gas, an LHSV=2, and a temperature adjusted to maintain a 17% conversion. The results of the test as shown in FIG. 1, indicate that initially the raw oil fouls the catalyst four times as fast as the denitrified oil, until equilibrium is reached. After equilibrium is reached, the catalyst which processes dentirified oil is about 150.degree. F. more active than the catalyst which processes the raw oil, indicating the use of a ZSM-5-type catalyst with a denitrified oil will exhibit a much longer run life than catalyst processing raw oil.

EXAMPLE III

This experiment was carried out to show the effect of pressure on the yields of light paraffinic and olefinic gases. A hydrogenitrogenated gas oil having the following characteristics:

______________________________________Gravity, .degree.API 34.1Aniline point, .degree.F. 170.3Sulfur wt % 0.0019Total N, ppm 0.63D-1160 Distillation10%/50%/90% .degree.F. 377/654/796Carbon Type,%P/%N/%A 48.9/41.5/9.5______________________________________ was contacted with a catalyst consisting of 65% H-ZSM-5 and 35% alumina at mild conversion conditions including 600.degree. F., LHSV=2, 2000 SCF/BBL recycle gas, and at the following pressures: 500 psig, 200 psig, 100 psig and 25 psig. The results, as shown in FIG. 2, indicate that the amount of olefins in the light product gas increases dramatically as the pressure is decreased--for example, at 500 psig, the ratio of the wt % C.sub.4 =(C.sub.4 olefins) to total C.sub.4 is 0.08, whereas at 100 psig, it is 0.46, and at 25 psig, it is 0.56. Thus, low pressure enhances the relative proportion of olefins produced in the light product gas.

Industrial Applicability

The benefits of the present upgrading process go far beyond the recovery of valuable olefins where only less valuable light paraffin gases had previously been produced. The feedstocks for reforming operations preferably have a low content of paraffins. Although under reforming conditions some paraffins are converted to aromatics, many more are cracked to shorter chain length paraffinic gases. The result is that energy has been used to heat paraffins and drive their cracking instead of to drive the reforming reactions which produce the desired aromatics. Because these paraffins have been removed from the effluent of the present upgrading process, when that effluent is introduced into a reformer a significant efficiency increase and energy saving is achieved. The feedstock for the catalytic reforming process is typically the 180.degree.-400.degree. F. fraction, or a portion thereof, of the upgraded effluent. An especially desirable reforming feedstock is the 180.degree.-400.degree. F. fraction of hydrocracker effluent where the hydrocracker feedstock is the upgraded effluent stream.

The upgrading process can also be used to increase the efficiency and effectiveness of hydrocarbon cracking processes through use of the upgrading process in conjunction with a standard hydrocracking process loop. FIG. 4 illustrates the low pressure upgrading process in a process loop with a conventional hydrocracker.

The low nitrogen feed is subjected to the low pressure ZSM-5-type catalyst upgrading process, a light gas fraction (C.sub.4.sup.-) comprising about 60% olefins, a gasoline fraction of improved octane and a heavy non-paraffinic fraction are split from the effluent. The heavy non-paraffinic fraction is subjected to a conventional hydrocracker which cracks the mixture to a naphthenic naphtha. A C.sub.4.sup.- paraffin gas fraction is recovered while the C.sub.5 + fraction can be recycled into the upgrading reactor. Removal of shorter, normal or slightly branched hydrocarbons through upgrading makes the hydrocracking process more profitable, as olefins are produced from the paraffins instead of the usual paraffinic gases. The amount of hydrogen required for processing a unit of feed is also reduced while the liquid yield is increased.

EXAMPLE IV

An experiment was performed to compare the results of a standard hydrocracking process in conjunction with an inactive upgrading reactor, to a process loop with the upgrading reactor activated. The process loop is illustrated in FIG. 5. The hydrodenitrified feed was an Arabian Light Gas Oil having the following characteristics:

______________________________________Gravity, .degree.API 37.5Aniline point, .degree.F. 182.3Sulfur, ppm 37Total nitrogen, ppm 0.74D-1160 distillation, .degree.F.10%/50%/90% 464/641/761Carbon Type %P/%N/%A 63.1/24.9/11.9______________________________________ The reaction conditions in the hydrocracking and upgrading reactors were as follows: ______________________________________ Standard Standard & Upgrading______________________________________HydrocrackerTemperature, .degree.F. 600 590Pressure, psig 1,350 1,350LHSV 1.4 1.4Upgrading ReactorTemperature, .degree.F. 300 (inactive) 700 (active)Pressure, psig 0 0LHSV 6.3 6.3Overall conversionper pass (LV%) 80.0 80.0Yields as % of Feed (w/w)C.sub.2 -C.sub.4 alkane 16.7 13.6C.sub.2 -C.sub.4 alkene 0 11.0C.sub.5 -380.degree. F. 85.7 77.0Octane C.sub.5 -180.degree. F.(Research, clear) 85.7 92.9Hydrogen consumption SCFB 1,237 922______________________________________ As can be seen from the data, there were decreases in light paraffin gas production and hydrogen consumption, and increases in C.sub.5 -180.degree. F. octane and C.sub.2 -C.sub.4 alkene production. Additionally, the activity of the standard hydrocracking catalyst was improved by 10.degree. F. when the upgrading reactor is activated.

EXAMPLE V

A similar experiment to that of Example IV was conducted using a less paraffinic, denitrified Empire Gas Oil having the following characteristics:

______________________________________Gravity .degree.API 34.1Aniline point, .degree.F. 170.3Sulfur, ppm 19Total nitrogen, ppm 0.63D-1160 distillation, .degree.F.10%/50%/90% 477/654/796Carbon type %P/%N/%A 48.9/41.6/9.6______________________________________ The reactor conditions in the hydrocracking and upgrading reaction were as follows: ______________________________________ Standard Standard & Upgrading______________________________________HydrocrackerTemperature, .degree.F. 596 607Pressure, psig 1,200 1,200LHSV 1.0 1.0Upgrading reactorTemperature, .degree.F. (Not in process 700Pressure psig loop) 0LHSV 6.3Overall conversionper pass (LV%) 70.0 70.0Yields as % of Feed (W/W)C.sub.2 -C.sub.4 alkane 14.5 13.1C.sub.2 -C.sub.4 alkene 0 4.4C.sub.5 -380.degree. F. 87.6 81.5Octane C.sub.5 -180.degree. F.(Research, clear) 85 90Hydrogen consumption SCFB 1,167 1,093______________________________________ As can be seen from the experiment, alkane production and hydrogen consumption were decreased while C.sub.5 -180.degree. F. octane and olefin production were increased where the present upgrading process is used in conjunction with a conventional hydrocracker.

EXAMPLE VI

A pilot plant was set up to illustrate the use of the upgrading process in conjunction with a standard hydrocracking process. The flow chart for the pilot plant was as illustrated in FIG. 5. In general, the denitrified feed was introduced into the upgrading reactor. The upgraded effluent was passed to a first still from which the 380.degree. F. and above effluent was recovered and introduced, with hydrogen-rich recycle gas, into a hydrocracker. The hydrocracker effluent was introduced first, into a high pressure separator to obtain the recycle gas and second, into a still to separate fractions boiling above and below 450.degree. F. The fraction boiling above 450.degree. F. was recycled into the feed for the upgrading reactor. The fraction boiling below 450.degree. F. was further fractionated into a C.sub.5 -180.degree. F. 180.degree.-230.degree. F., 230.degree.-380.degree. F., and 380.degree.-450.degree. F. jet cut fractions.

The feed used had the following characteristics:

______________________________________Gravity, .degree.API 33.9Aniline point, .degree.F. 162.6Sulfur, ppm 10Nitrogen, ppm 0.30D-1160 distillation .degree.F.10/50/90 483/633/781Carbon type%P/%N/%A 53.5/32.2/14.3______________________________________

For the first part of the experiment (100 hours) the upgrading reactor was maintained at 300.degree. F. so that it remained inactive although still within the process loop. The hydrocracker was maintained at 588.degree. F., LHSV 0.6, total psig 1200, hydrogen pressure 1024 psia. For the second part of the experiment, the temperature of the upgrading reactor was raised to 700.degree. F. for operation; all other conditions in the upgrading reactor remained identical to those of the first part of the experiment. The conversion rate, in LV%, increased from 62.8 to 66.8 even though the hydrocracker gained 20.degree. F. in activity (hydrocarbon catalyst temperature was reduced to 568.degree. F.). The hydrogen consumption also declined from 1150 SCFB in the first part of the experiment to 842 SCFB in the second.

After 3000 hours operation of the pilot plant with the upgrading reactor active, there was no discernible decrease in the activity of the catalysts used in the process loop. Yields were:

______________________________________ Hydrocracker Hydrocracker & Upgrader______________________________________C.sub.1 (Wt %) 0.01 0.03C.sub.2 -C.sub.3 alkane (Wt %) 2.06 3.63C.sub.2 -C.sub.3 alkene (Wt %) 0 3.45C.sub.4 alkane (Vol %) 16.23 13.21C.sub.4 alkene (Vol%) 0 6.83Compositions (V %) of the higher boiling fractions were:C.sub.5 -180.degree. F.: P 84.8 32.0 O 0.0 20.0 N 14.0 37.7 A 0.6 10.4180- 230.degree. F.: P 48.2 31.3 O 0.0 14.3 N 48.3 45.3 A 3.5 9.1230- 380.degree. F.: P 39.2 22.0 O 0.0 4.3 N 52.5 58.8 A 8.2 14.9380- 450.degree. F.: P 27.7 10.3 O 0.0 0.4 N 55.7 78.0 A 16.7 11.3______________________________________ (P = paraffins; N = naphthenes; O = olefins; A = aromatics) It can be seen from the data there was a significant improvement in the yield of olefins as well as an overall decrease in paraffin content.

The jet cut, a 380.degree.-450.degree. F. fraction recovered after the hydrocracking step, contained fewer paraffins, thus yielding both a lower smoke point and a lower freezing point. Additionally, the jet cut had a very low olefin content, all olefins having been hydrogenated in the hydrocracker.

The light naphtha fraction (C.sub.5 -180.degree. F.), useful for gasoline, had a higher aromatic and olefin content, with a lower paraffin content, therefore a higher octane rating than when the upgrading reactor was inactive. The cuts boiling below 400.degree. F. are particularly suitable for use in reformers because of their lower paraffin content.

Claims

1. A process for increasing the effectiveness of petroleum processing, comprising:

(A) upgrading a petroleum distillate feed which consists essentially of hydrocarbons having a normal boiling point range in the range of from about 180.degree. to 1200.degree. F., through use of an upgrading process comprising,

(i) producing a process stream containing a C.sub.3 -C.sub.4 olefin product fraction in an amount, based upon upgrading feed converted, in the range of from about 2 to 10 weight percent, by contacting said feed with a catalyst comprising a ZSM-5-type crystalline aluminosilicate zeolite in a form which is substantially free of hydrogenation activity, said contacting being under conditions including (a) a temperature in the range of from about 500.degree. to 800.degree. F.; (b) a pressure below about 13 atmospheres gauge; and (c) a liquid hourly space velocity in the range of from about 0.1 to 20, said feed having a content of nitrogen-containing impurities, calculated by weight as nitrogen, below about 5 ppm;

(ii) producing an upgraded effluent stream by removing the olefin product fraction from said process stream; and

(iii) recovering said upgraded effluent stream; in conjunction with

(B) hydrocracking or reforming a petroleum feedstock.

2. A process according to claim 1 wherein the process of Step (B) is a hydrocracking process.

3. A process according to claim 2 wherein the effluent from said hydrocracking process is the feed for said upgrading process.

4. A process according to claim 2 wherein said upgraded effluent stream is the feedstock for said hydrocracking process.

5. A process according to claim 2 wherein said upgrading process and said hydrocracking process are operated in a recycle mode.

6. A process according to claim 1 wherein the process of Step (B) is a reforming process and the feed for said reforming process is selected from the 180.degree.-400.degree. F. fraction, or portion thereof, of said upgraded effluent.

7. A process according to claim 1 wherein the catalyst of Step (A)(i) comprises a ZSM-5-type crystalline aluminosilicate zeolite composited with a porous inorganic matrix wherein said matrix is substantially free of hydrocracking activity.

8. A process for upgrading a petroleum distillate feed consisting essentially of hydrocarbons having a normal boiling point in the range of from about 180.degree. F. to about 1200.degree. F. and producing at least a substantial C.sub.3 -C.sub.4 olefin product fraction, by

(1) producing a process stream by contacting said feed with a catalyst comprising a ZSM-5-type crystalline aluminosilicate in a form which is substantially free of hydrogenation activity, said contacting being under conditions including (a) a temperature in the range of from about 500.degree. to 800.degree. F.; (b) a pressure below about 13 atmospheres gauge, and (c) a liquid hourly space velocity in the range of from about 0.1 to 20, said feed having a content of nitrogen-containing impurities, calculated by weight as nitrogen, below about 5 ppm; and

(2) recovering an upgraded effluent stream and olefin fraction by fractionating said process stream.