US3684691A - Dewaxing process wherein relatively small pore size crystalline aluminosilicate zeolites are used to chemically convert n-paraffins in hydrocarbon oils - Google Patents

Abstract

TACTED WITH SULFUR PRIOR TO USE. ZINC IS THE PREFERRED GROUP II-B METAL. THE CRYSTALLINE ZEOLITES ARE CONTACTED WITH A HYDROCARBON OIL IN THE PRESENCE OF HYDROCARBON AND AT ELEVATED TEMPERATURES AND PRESSURES. CRYSTALLINE ZEOLITIES HAVING AN AVERAGE, UNIFORM PORE SIZE FROM ABOUT 4 TO LESS THAN 6 ANGSTROM UNITS ARE DISCLOSED.

AN IMPROVED DEWAXING PROCESS WHEREIN CRYSTALLINE ALUMINOSILICATE ZEOLITES ARE EMPLOYED TO CHEMICALLY CONVER N-PARAFFINS IN HYDROCARBON OILS. THE CRYSTALLINE ZEOLITES ARE ION EXCHANGED WITH EITHER HYDROGEN OR ONE OR MORE METALS FROM GROUP II-B OR BOTH. WHEN THE ZEOLITE IS OF THE TYPE 5A, A MAJOR PORTION OF THE EXCHANGED IONS WILL BE OF THE GROUP II-B METALS. THE ZEOLITE MAY ALSO BE COMBINED WITH A HYDROGENATION COMPONENT AND CON-

Description

Aug. 15, 1972 DEWAXING PROCESS WHEREIN RELATIVELY SMALL PORE SIZE CRYSTALLINE ALUMINOSILICATE ZEOLITES ARE USED TO CHEMICALLY CONVERT n-PARAFFINS IN HYDROCARBON OILS Flled Doc. 29, 1969 v POUR POINT E OF 320E FRACTION w. F. AREY ETAL 3,684,691

2. Sheets-Sheet 1 FIGURE I ZEOLITIC TREATMENT VS. SOLVENT DEWAXING FOR POUR POINT REDUCTION FEED: ZELTEN GAS OIL FEED (550-650F.)

| I I b A ZEOLITIC TREATMENT O SOLVENT DEWAXING I I I 7O 8O 9O DEWAXED OIL YIELD, WT.

' (32OE+I WILLIAM F. AREY, JR. GLEN P. HAMMER RALPH B. MASON JAMES A. RIGNEY ATTORNEY INVENTORS Aug. 15, 1972 w. F. AREY ETAL 3,684,691

DEWAXING PROCESS WHEREIN BELATIVELY SMALL FORE SIZE CRYSTALLINE ALUMINOSILICATE ZEOLITES ARE USED TO CHEMICALLY CONVERT n-PARAFFINS IN HYDROCARBON OILS Filed Dec. 29, 1969 I 2 Sheets-Sheet 2 FIGURE II.

ZEOLITIC TREATMENT VS. SOLVENT DEWAXING FOR CLOUD POINT REDUCTION FEED: ZELTEN GAS o|| FEED (55O-650F.I I I I l CLOUD POINT, "E OF 320F. FRACTION A ZEOLITIC TREATMENT O SOLVENT DEWAXING 5I I I f 506O 7O 8O 90 I00 DEWAXED OIL YIELD, WT. (320E +I rams-ma RALPH 'a. mason JAMES A. msnav United States Patent 3,684,691 DEWAXING PROCESS WHEREIN RELATIVELY SMALL PORE SIZE CRYSTALLINE ALUMINU- SILICATE ZEOLITES ARE USED TO CHEMICAL- glIKLgONVERT N-PARAFFINS 1N HYDROCARBON William F. Arey, Jr., 1324 Belvedere Drive, and Glen P. Hamuer, 4754 Whitehaven, both of Baton Rouge, La. 70808; Ralph B. Mason, Rte. 2, Box 140, Denham Springs, La. 70726; and James A. Rigney, 47 Roper Drive, Charlottetown, Prince Edward Island, Canada Continuation-impart of application Ser. No. 518,680, Jan. 4, 1966. This application Dec. 29, 1969, Ser. No. 888,874

Int. Cl. 010g 13/02, 37/04; C01b 33/28 US. Cl. 208-59 11 Claims ABSTRACT OF THE DISCLOSURE An improved dewaxing process wherein crystalline aluminosilicate zeolites are employed to chemically convert n-paraflins in hydrocarbon oils. The crystalline zeolites are ion exchanged with either hydrogen or one or more metals from Group lI-B or both. When the zeolite is of the type 5A, a major portion of the exchanged ions will be of the Group II-B metals. The zeolite may also be combined with a hydrogenation component and contacted with sulfur prior to use. Zinc is the preferred Group II-B metal. The crystalline zeolites are contacted with a hydrocarbon oil in the presence of hydrogen and at elevated temperatures and pressures. Crystalline zeolites having an average, uniform pore size from about 4 to less than 6 angstrom units are disclosed.

CROSS REFERENCES TO RELATED APPLICATIONS This application is a continuation-in-part of US. Ser. No. 518,680, filed Jan. 4, 1966, and now abandoned.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to a process for dewaxing petroleum oils and fractions thereof. Particularly, it relates to an improved process for removing normal paraffinic hydrocarbons from petroleum oils in which they are present in admixture with other hydrocarbons, in order to lower the pour point of such oils. More particularly, the invention relates to an improved process for removing normal paraffinic hydrocarbons from petroleum oils 'by contacting such oils with specific types of crystalline aluminosilicate zeolites having uniform pore openings in the order of about 5 angstrom units.

Description of the prior art It is well known in the art to form various lubricating oils, commonly referred to as lubes, from hydrocarbon fractions derived from petroleum crudes. With particular reference to the relatively inexpensive lube oils, a common procedure known in the art is to extract these hydrocarbon fractions with various solvents so as to give a raflinate of a desired high viscosity index, such material being resistant to changes in viscosity with changes in temperature and thus being useful under varying operating conditions. Moreover, it is particularly desired that 'ice.

the lube oil have a low pour point so that it can be effectively used at low temperature conditions, since excessive thickening at low temperatures is often unacceptable. A further common requirement for an acceptable lube oil is that it have a .low cloud point, determined in accordance with the ASTM Cloud Point Test, which fixes the temperature at which wax first starts to precipitate within the oil.

The present invention is concerned with an improved process for dewaxing normal parafiin-containing oils which is more economical than conventional solvent dewaxing procedures and which, with certain feedstocks, produces a higher product yield with equivalent or higher pour point reduction.

Briefly, the present process employs the use of certain forms of crystalline alumino-silicate zeolites which have been treated in such a manner as to achieve optimum dewaxing results. In addition to the particular form of the zeolitic material, certain temperature and pressure conditions and the presence of hydrogen during the contacting of the zeolite material and the paraffin-containing oil have been found to be essential.

The scientific and patent literature contains numerous references to the composition and adsorbing action of alumino-silicate zeolites. Recently the catalytic activity of these materials has drawn wide attention. In general, these crystalline zeolites contain alkali or alkaline earth metal, aluminum, silicon and oxygen. They maybe either natural or synthetic in origin and may have uniform pore openings of from about 3 to about 15 angstrom units, depending upon their composition and the conditions under which they were formed. Those crystalline zeolites, having uniform pore openings in the order of about 5 angstrom units, are highly useful for separating normal parafiins from branched chain and cyclic compounds. Among the natural zeolites having these properties may be mentioned chabazite, erionite and clinoptillolite. Synthetic zeolites having uniform pore openings of about 5 angstroms are also available. For example, a suitable starting material, referred to as Zeolite A in US. Pat. No. 2,882,243, has a molar formula in the dehydrated form of 1.0 :e 0.2M O:A12Os:1.85 a: 0.5 etc,

wherein M is a metal usually sodium and n is its valence. It may be prepared by heating a mixture containing Na O, A1 0 Si0 and H 0 (supplied by suitable source materials) at a temperature of about C. for 15 minutes to 90 hours or longer. Suitable ratios of these reactants are fully described in the aforementioned patent.

One suitable process for preparing such materials syn thetically involves, for example, the mixing of sodium silicate, preferably sodium metasilicate, with sodium aluminates under carfully controlled conditions. The amounts of the sodium silicate and sodium aluminate solutions employed are preferably such that the ratio of silica to alumina in the final mixture ranges from about 0.8 to 1 to about 3 to 1., and more preferably from about 1 to 1 to about 2 to 1. The aluminate preferably is added to the silicate at ambient temperature with sutficient agitation to produce a homogeneous mixture, after which the mixture is heated to a temperature of from about to about 215 F. and held at that temperature for a period of from about 0.5 to about 3 hours or longer. During the crystallization step, the pH of the solution is preferably maintained on the alkaline side at about 12 or higher.

The products produced by the above typical procedure will have uniform pore openings of about 4 angstroms as produced in the sodium form. They may then be converted to products having uniform pore openings of about 5 angstroms by replacement of sodium via conventional ion-exchange techniques with various cations.

Despite the excellent selective adsorption properties of these crystalline aluminosilicate zeolite materials (molecular sieve), certain difficulties are encountered in applying them to large scale removal of normal paraflins from branched chain and cyclic hydrocarbons. For example, it is usually necessary to employ a two-step cyclic process wherein the normal parafiins are first selectively adsorbed and then desorbed in a separate operation. The desorption step is usually carried out by steaming the used adsorbent or by passing a suitable desorbent through the zeolitic bed. The capacity of the molecular sieve adsorbent when used in this manner is usually low, and, therefore, such cyclic processes are relatively expensive because of the frequency with which the sieve must be desorbed. The desorption methods available are further only partially effective, and selectivity and capacity rapidly decline with use. A further difficulty is that carbonaceous deposits rapidly build up on the surface of the sieve requiring frequent regeneration.

SUMMARY OF THE INVENTION The present invention provides a new and improved method for removal of normal paraffins from hydrocarbon oils by means of molecular sieves, which process is free from many of the disadvantages heretofore encountered. The present process differs from prior adsorption processes in that the molecular sieves are employed to effect chemical conversion of the normal paraffins on a selective basis as opposed to a mechanical separation. It has thus been found that normal paraflins present in a hydrocarbon oil can be selectively converted to lower boiling products by contacting the oil with certain types of crystalline aluminosilicate zeolite materials, to be hereinafter defined, in the presence of hydrogen and at critical conditions of temperature, pressure, feed rate and hydrogen rate. The process is preferably accomplished in partial or total vapor phase using a fixed-bed catalyst system.

The process of the invention has numerous advantages over prior processes which have been proposed for dewaxing hydrocarbon oils. The normal paraffins which would otherwise be adsorbed by the molecular sieve materials are continuously converted to lower boiling gaseous products which are not retained by the sieve, thereby leaving the pores of the zeolite relatively free of hydrocarbons. Accordingly, a desorption step is unnecessary, and the various difficulties encountered in desorption operations are avoided. Furthermore, the lower boiling products, such as kerosene, naphtha, butane, etc., can readily be separated from the normally liquid portions of the dewaxed effluent and recovered as valuable by-products. The simplified procedure employed herein makes the present process considerably more economically attractive than prior processes.

DETAILED DESCRIPTION The crystalline alumino-silicate zeolite materials used in the dewaxing process of the invention will be characterized by having relatively small uniform pore openings. By relatively small is meant a pore size of below about 6 angstrom units, particularly 4 to less than 6 angstroms, e.g., about 5 angstroms. More particularly, the zeolites employed will have pores capable of affording entry to the objectionable normal parafiinic hydrocarbons but incapable of admitting the more valuable branched and cyclic hydrocarbons. Preferred crystalline alumino-silicate zeolites in the present invention will include the aforedescribed Zeolite A and the natural or synthetic form of erionite. Other relatively small size zeolites can also be employed. The naturally-occurring mineral erionite has elliptical pore openings of about 4.7 to 5.2 angstroms on its major axis. The synthetic form or erionite can be prepared by known methods, such as those disclosed in US. Pat. No. 2,950,952. It is characterized by pore openings of approximately 5 angstromi units and differs from the naturally-occurring form in its potassium content and the absence of extraneous metals.

The relatively small pore size crystalline aluminosilicate zeolite materials used in the present process are usually produced or found naturally in the alkali metal cation form. These zeolites are customarily base exchanged with other cations to replace alkali metal and/or to alter the pore size of the zeolites. In accordance with the invention, it has been found that indiscriminate cationic exchange is not suitable for the intended purposes, but that, depending on the particular type of relatively small pore size zeolite used, either hydrogen cations, cations of metals in Group lL-B- of the Periodic Table (Handbook of Chemistry and Physics, 38th edition, Chemical Rubber Publishing Company) or mixtures thereof are peculiarly adapted to the practice of the process described herein. Representative metal cations include cadmium and zinc cations, with zinc cations being particularly preferred.

Where the zeolite used in the present invention is of the synthetic S-angstrom type; i.e. Zeolite A or Type A zeolite, it will most preferably have been exchanged with the Group II-B metal cations to result in the relatively small uniform pore openings. The preferred cation solutions will be aqueous solutions of suitable salts, such as chloride, acetate, nitrate, etc. The extent of the ion exchange should be sufficient to reduce the alkali metal; e.g. sodium content of the zeolite, to less than 10 wt. percent, and preferably less than 5 wt. percent. The ion ex change is preferably conducted to cause at least 25%, and more preferably greater than 50%, of the exchangeable cation content to be divalent by replacement with the Group II-B metal cation. It will be understood, however, that although the most preferred zeolites will be prepared by using the Group II-B- cation as the sole exchanging cation, the presence of this cation together with other exchanging cations, such as hydrogen cation, will also be highly useful. Thus, the present invention contemplates the use of a Type A 5-angstrom zeolite, preferably containing zinc or cadmium cation. More preferably, the zeolite 'will have a major portion of its cation content supplied by zinc and/or cadmium with perhaps minor portions of residual sodium, as well as minor portions of other ions which may also have been introduced via ion exchange for various purposes. Partial incorporation of hydrogen cation is readily accomplished by treating the Group II-B metal cation zeolite with ammonium ion with subsequent calcination to liberate ammonia, leaving hydrogen ions.

Where the zeolite used in the present invention is of the naturally-occurring variety or a synthetic facsimile thereof, such as erionite and the like, suitable forms will further include those which have been exchanged with a hydrogen or hydrogen-containing cation such as ammonium ion. This is readily accomplished via treatment with an ammonium salt such as the chloride, nitrate, sulfate, etc., or via a mild acid treat. Where ammonium ion exchange is used, subsequent calcination results in liberation of ammonia and formation of the hydrogen form of the zeolite. In either case, the extent of exchange should be sufficient to achieve the aforementioned levels of sodium content. Thus, for example, with natural or synthetic erionite, exchange with either hydrogen-containing (or hydrogen) cations, mixtures of the latter with Group II-B cations or Group H-B cations alone will be suitable, and the order of decreasing preference will be as just stated. In the case of the Type A zeolites, the order of preference will be just the reverse (i.e. Group II-B metal cationsmixtures of Group II-B metal and hydrogen cations-hydrogen cations), with the Group II-B cations being most preferred.

As a further step in the preparation of the zeolitic materials used in the present process, the exchanged zeolite is preferably combined with an active hydrogenation metal component chosen from Groups V-B, VI-B, VII-B or VIII of the Periodic Table. Such hydrogenation components are suitably exemplified by the metals cobalt, nickel, platinum, palladium, etc. These metals may exist in the form of the free metal; or the oxide or sulfide as in the case of cobalt, etc.; or mixtures of such metals, oxides or sulfides. Platinum group metals (i.e. metals of the platinum and palladium series) will be preferred in the present invention, with palladium being particularly preferred. Incorporation of the active metal may be accomplished by any conventional technique, such as by ion exchange followed by reduction, impregnation, etc. When palladium is employed, the zeolite is preferably impregnated with an ammoniacal solution of palladium chloride sufficient to produce the desired amount of palladium in the final product, and then dried and calcined at a temperature of 800 to 1000 F. Thus, where the zeolite has been previously exchanged with ammonium ion, calcination at this point serves to liberate ammonia and produce the hydrogen form of the zeolite. In the case of platinum group metals, a reduction step will usually be further necessary as, for example, by treatment with hydrogen. The amount of the active hydrogenation metal component may range from about 0.1 to about wt. percent, based on the weight of the final product. In the case of platinum group metals, e.g. palladium, the preferred amount will be in the range of about 0.1 to 6, e.g., 0.5 to 3 wt. percent, based on dry zeolite.

Incorporation of the active hydrogenation metal component as described above is optional, although it will be preferred for enhanced activity and prolonged life of the zeolite in the present process. In the case of the hydrogen forms of the zeolites, presence of the hydrogenation metal will be more preferred than in the case of the Group II B metal-containing zeolite forms described previously. As a general rule, therefore, the lower the Group II-B metal content of the zeolite, the more preferred the presence of the hydrogenation metal. It will thus be more advantageous to combine the hydrogen form of natural or synthetic erionite with the hydrogenation metal than in the case of the Group II-B metal form of the Type A zeolite. Thus, the zeolitic materials used in the dewaxing process of the present invention will have been base exchanged with the cations previously enumerated and will, in addition, preferably contain an active metal having hydrogenation properties, such as a platinum group metal of which palladium will be particularly preferred.

As an additional embodiment of the present invention, it has been found that the activity and effectiveness of the cation-exchanged zeolites hereinabove described can be substantially improved by contact with sulfur prior to their use in the treatment of the paraffin-containing hydrocarbon oils. The zeolite is preferably sulfactivated to enhance its parafiin removal properties by contact either with sulfur-containing feed or, if the feed has a low sulfur content, with hydrogen sulfide or an added sulfur compound which is readily convertible to hydrogen sulfide at the conditions employed, e.g. carbon disulfide and the like. The extent of this sulfactivation treatment should be sufficient to incorporate about 0.5 to 15 wt. percent sulfur into the zeolitic material In carrying out the process of the present invention, the conditions under which the hydrocarbon feed stream is contacted with the aforedescribed crystalline aluminosilicate zeolite are to be regarded as critical. The feed stream is contacted, preferably in fixed-bed downflow operation, and in total or partial vapor phase, with the crystalline zeolite material at a temperature of from about 650 to 900 F., preferably 700 to 850 F.; a pressure of to 5000 p.s.i.g., preferably 400 to 1000 p.s.i.g.; a space velocity of 0.1 to 10, preferably 0.5 to 2, volumes of feed per volume of crystalline zeolite per hour; and in the presence of hydrogen which is preferably introduced concurrently with the feed at a. rate of about 500 to 10,000, preferably 1000 to 3000, standard cubic feet per barrel of feed. For the treatment of a preferred middle distillate feedstock, boiling substantially between 300 and 650 F. and having a pour point above about +30 F., the preferred operating conditions will include a temprature of between about 700 and 850 'F., a pressure of between about 400 and 1000 p.s.i.g., a space velocity of between 0.5 and 2.0 v./v./hour and a hydrogen rate of about 1000 to 3000 s.c.f./b. of feed. For a preferred gas oil feedstock having a boiling range of between 400 and 1100 F., the operating conditions will include a temperature of about 700 to 850 F., a pressure of about 400 to 1000 p.s.i.g., a space velocity of about 0.5 to 1.0 v./v./hour and a hydrogen rate of about 2000 to 10,000 s.c.f./b. of feed.

In accordance with the present invention, the feedstock is preferably preheated to the contacting temperature and introduced into contact with the crystalline zeolitic material, preferably in vapor phase or mixed vapor-liquid phase (in the case of a high boiling gas oil feed) and fixed-bed operation, concurrently with a hydrogen-containing gas stream. Preferably the feed stream will pass downwardly through the zeolitic bed and in so doing the normal parafiins present therein are selectively hydrocracked to lower molecular weight products. The efiiuent is removed from the zeolitic contacting zone and passed to a vapor-liquid separation zone wherein the lower boiling normally gaseous hydrocarbons are removed and the normally liquid bottoms product is recovered and preferably further fractionated into light ends, naphtha and dewaxed fractions having desired boiling range.

The feedstocks adapted for treatment in accordance with the present invention may be generally defined as hydrocarbon oils boiling in the range of about 300 to about 1100 F., and particularly between about 400 and about 650 F. Such oils will include heavy naphthas, kerosenes (e.g., boiling between. 300 and 500 F), diesel fuels, jet fuels, heating oils, gas oils, middle distillates, lube base stocks, etc. The process of the invention is particularly effective for removing wax and similar normal parafiinic constituents from middle distillate and gas oil fractions, in order to reduce their pour point, cloud point, haze point and solidification tendency; and it is in this area that the process of the invention will rfind its widest application. Preferably, the preferred middle distillate fractions will have a total n-parafiin content within the range of about 5 to 50 wt. percent, particularly 10 to 30 wt. percent; and the preferred gas oil fractions will have a total n-paraffin content within the range of about 10 to 50 wt. percent, particularly 20 to 30 wt. percent. Parafiin contents outside these ranges will be operable but the advantages derived from the present process may not be as readily recognized.

The present process is subject to numerous variations without departing from the scope intended herein. For example, the feedstock can be treated without preliminary hydrofining or may be hydrofined prior to contacting with the zeolitic material. Nitrogen or sulfur removal by hydrofining or acid treating of the feed will be preferred wtih high nitrogen or high sulfur feedstocks, as will be hereinafter illustrated. Such preliminary treatment will be desired where the sulfur and nitrogen levels of the feedstock are sufficiently great to impair the performance of the crystalline zeolite. Additionally, the liquid efliuent product issuing from the zeolitic contacting zone can be hydrofined for further sulfur and nitrogen removal as well as color and stability improvement, utilizing conventional hydrofining catalysts, such as supported cobalt, molybdate, nickel sulfide and the like, at

conventional hydrofining conditions. Hydrofining at this point accomplishes hydrogenation of aromatics to naphthenic components and contributes to further lowering of pour point and cloud point. Also, by further lowering of the sulfur and nitrogen content of the efiiuent, product stability is improved. An optional mild acid treatment may also be used to remove undesirable components causing product instability.

DESCRIPTION OF THE PREFERRED EMBODHWENT In the event that the dewaxing process of the present invention is not capable of the desired degree of pour point reduction, owing to the heavy nature of the particular feedstock, it is further within the contemplation of the present invention to combine the present process with subsequent conventional solvent dewaxing stages. In this embodiment the product from the zeolitic contacting stage is fractionated into a light out having acceptable pour point, and a heavier out having excessively high pour point. Additional solvent dewaxing is conducted on the heavier fraction with subsequent combination of the acceptable light fraction and the improved heavy fraction to thereby result in an overall pour point lowering of the final product. The details of the solvent dewaxing stage are well known in the art and will not be dealt with here at length. Solvent mixtures such as methyl ethyl ketone-toluene, methyl ethyl ketone-methyl isobutyl ketone, etc., can be used in known manner. Through this particular embodiment, a large proportion of the feed is excluded from the conventional solvent dewaxing facility, thereby adding to the economic attractiveness of the zeolitic treating and solvent dewaxing combination. The intermediate fractionating cost (between the zeolitic contacting stage and solvent dewaxing stage) is more than offset by increased throughput in the solvent dewaxing operation. To further demonstrate this embodiment, the following is a representative example:

A gas oil feed boiling in the range of 650 to 1050 F. containing fractions suitable for lubricating oil use, is contacted with a relatively small pore size crystalline zeolite of the type hereinbefore described and at the operating conditions hereinbefore set forth capable of removing the waxy components of the feed. The gas oil feed can first be phenol treated for aromatics removal prior to the zeolitic contacting stage. The etfiuent from the zeolitic contacting stage is passed to a high temperature separator wherein 650 -F. and lighter fractions are recovered and 650 -F.+ fractions are separated and passed to a vacuum distillation tower. In the distillation zone a 650 to 700 F. fraction is removed as overhead, a low pour point 700 to 850 F. lube fraction is removed as a sidestream for subsequent blending and 850 F.+ fractions are recovered as bottoms and sent to a solvent dewaxing zone. In the latter, chilled solvent, which may be either a methyl ethyl ketone-methyl isobutyl ketone and/or propane mixture, is utilized in conventional manner to" dewax the 850 -F.+ fraction. Depending upon the type of finished lube base desired, the pour point of the lube fraction from the solvent dewaxing zone may be within the range of 20 to +20 F. In this manner, improved solvent dewaxing capacity is realized through the processing of a feed that has already been treated to partially remove components causing fine wax crystal formation in conventional solvent dewaxing processes. The dewaxed fractions from the solvent dewaxing zone are then blended with the low pour point fractions recovered from the distillation tower.

A further embodiment contemplated herein comprises the stage-wise contacting of the waxy feed with the crystalline zeolite material. It has been observed that contact of the typical waxy feeds herein contemplated with the described crystalline zeolite at the operating conditions hereinbefore set forth cause conversion of the feed to naphtha and C gaseous components, predominantly propane. It has been further observed that this conversion proceeds in a step-wise manner; that is, a naphtha is first produced and then breaks down to propane and gaseous product. Since, with feedstocks having very high wax contents, high severity operating conditions are required in the zeolitic contacting zone to achieve desired levels of pour point reduction, a substantial loss in naphtha yield results through its conversion to the lighter fractions, such as propane. In order to maximize naphtha yield by curtailing conversion to C and lighter products, a stage-wise operation can be conducted wherein the conversion of the feedstock in the first zeolitic contacting stage is controlled, for example, in the range of about 10 to 30%. Naphtha fractions in the effluent from the first stage are separated by fractionation, and the naphthafree gas oil bottoms are then passed to subsequent zeolitic contacting stages. Alternatively, a single zeolitic contacting stage can be used together with a fractionation stage as above, with the fractionator bottoms being recycled back to the same zeolitic contacting stage. In both cases, the valuable naphtha fractions are removed from the processing system before their conversion to lower boiling, less desired materials. Where extensive dewaxing is required due to the nature of the feedstocks, the multiple stage system can be conducted so that the initial stages operate at temperatures and pressures in the lower portions of the ranges hereinbefore set forth, with subsequent stages being operated at higher values or under such conditions as would normally be required for a severity level equivalent to the single stage process.

The invention will be further understood by reference to the following examples which are given for illustrative purposes.

EXAMPLE 1 This example illustrates the preparation and use of a Group II-B metal cation containing crystalline aluminosilicate zeolite combined with palladium and having uniform pore openings of about 5 angstroms which was used in the dewaxing process of the invention.

A charge of 500 grams of commercial sodium Zeolite A (supplied by the Linde Division of the Union Carbide Corporation) having pore openings of about 4 angstroms was suspended in 2000 cc. of water, and a solution containing one pound of zinc chloride in 500 cc. of Water was added slowly with good stirring at ambient temperature. Agitation was continued at ambient temperature for at least 4 hours. The suspension was allowed to settle; the mother liquor was removed by filtration. This procedure was performed on the wet solids two more times so that the total number of exchanges was three. After the third exchange the product was water washed by reslurrying in about 2000 cc. of water for about one hour followed by removal of the wash liquid by filtration. The wash was repeated two times and the product dried. Analysis of the product showed 0.83 wt. percent sodium, 20.8 wt. percent zinc, 38.1 wt. percent SiO and 30.8 wt. percent A1 0 The product was then combined with palladium by adding 133 cc. of an ammoniacal palladium chloride solution having a palladium content of 37.5 milligrams per cc. to 500 grams of product suspended in water. The final product, after drying, had a palladium content of 0.89% and was pelleted and charged to a small pilot plant reactor where it was heated in a hydrogen stream at atmospheric pressure and 850 F. It was finally sulfactivated by contact with a heavy naphtha feed containing an appreciable amount of sulfur, e.g., 16

wt. percent.

EXAMPLE 2 A gas oil feed derived from a Zelten Crude was treated with the palladium-zinc-5 A. zeolite of Example 1. The

Zelten gas oil feed had a boiling range of between about 560 and 650 F. and the following inspections:

This gas oil feed was passed downwardly through a fixed bed of the sulfided palladium-zinc zeolite at a temperature of about 800 F., a pressure of 1000 p.s.i.g., a space velocity of 0.5 v./v./hr., and in the presence of added hydrogen at a rate of 200 s.c.f./b. of feed. After about 6 hours of operation, the feed flow was discontinued and the yield, pour point and cloud point of the liquid product, i.e. material boiling above 320 F., were determined. The data obtained were compared to conventional dewaxing operation using a mixed solvent of methyl ethyl ketone-methyl isobutyl ketone (in 3:1 ratio) in the ratio of 3 parts (by volume) of solvent to 1 part gas oil feed. In these runs the gas oil feed was heated to 150 F. and chilled slowly while incrementally adding the solvent mixture. After the minimum temperature, the wax was filtered and the dewaxed oil recovered. The minimum temperature for three difierent runs was +20 F., F. and 45 F., respectively.

The results obtained by the dewaxing process of the invention in comparison to those obtained by conventional solvent dewaxing are shown graphically in the attached FIG. I, with the supporting data for the former shown below:

oil yield, the process of the invention is shown to produce a markedly lower pour point. (The term dewaxed oil" is applied to gas oils of high pour point that have been reduced to the desired level, e.g. 0 to +20 F., by conventional solvent dewaxing processes in which the wax constituents are removed by filtration at a predetermined temperature. The wax components are predominantly normal paraflins.)

In addition to the lowering of the pour point achieved by the present invention, cloud point reduction was found to be about equivalent to that attainable by the solvent dewaxing procedure. The comparison of the two techniques for cloud point reduction is shown in the accompanying FIG. II. As indicated in FIG. II, essentially no difference in cloud point reduction was observed between the present process and the conventional solvent dewaxing technique as applied to the Zelten gas oil feed.

The superiority of the present process over conventional dewaxing techniques is thus demonstrated.

EXAMPLE 3 This example compares the use of Group II-B metal cations in the crystalline zeolite used in the dewaxing process of the invention to the use of other cations. A specially prepared Zelten gas oil containinglow sulfur 10 ppm.) and essentially no nitrogen 2 ppm.) was employed as feed. This purification was accomplished by hydrofining with cobalt molybdate-alumina catalyst at 700 F., 1 v./v./hour and 1000 p.s.i.g. at a hydrogen rate of 2000 s.c.f./ b. of feed. A S-angstrom crystalline zeolite was prepared in accordance with the procedure of Example 1, except that zinc nitrate was used as the ion exchange medium The performance of this zeolite, after sulfactivation, is compared below to the calcium and magnesium forms of the same zeolite, the latter being conventional modifications. Process conditions included a temperature of 800 F., a pressure of 500 p.s.i.g., a feed TABLE I Dewaxing of Zelten gas oil with palladium-zinc 5 A.

zeolite at- 775-850 F., 0.5-1.0 2 000 s.c.f.

v. v./hr. 5001,000 p.s.i.g. hydrogen bbl.

Feed Product distribution, weight percent on output basis:

0 0.6 0.2 0.5 0.6 0.5 0.4 0.3 1.3 1.0 0.4 0. 7 1. 0 0. 7 0.5 0.5 1.6 6. 6 4.3 5. 1 7.0 8.0 1.0 2. 6 9. 1 1. 6 3.3 2.4 3. 1 7. 2 0.8 1.0 4.4. 7.1 10.0 3.1 7.1 12.7 4.8 5.4 6.9 F.+, 83. 1 81. 6 88. 2 81. 2 70. 9 92. 5 90. 2 76.9 Inspections on 320 F. plus traction:

Gravity, API at 60 F 35. 7 32. 33. 33. 6 32. 9 33. 0 35.9 34. 7 33. 5 Pour point, F. 25 10 30 40 30 0 Cloud point, F 44 26 24 6 42 38 18 ASTM distillation (D15 IB I F 566 550 504 463 539 374 424. 5% 584 570 642 532 568 526 48s 10', 588 680 562 552 575 554 530 50? 602 602 596 597 601 595 593 624 626 632 631 628 632 620 632 632 644 64.2 639 644 640 FBP, 636 638 648 644 643 650 646 Recovery, ml. 98 98 98 98 98 97 97 Residue, ml 1 2 2 2 1 1 1 As indicated in the accompanying FIG. I, the dewaxing process of the present invention which involves removal of the normally paraffinic wax constituents of the gas oil feed by treatment at conversion conditions with the 5- angstrom zeolite catalyst is superior to the conventional solvent dewaxing technique. The process of the invention is shown to produce a higher yield of dewaxed oil at the same level of pour point reduction. At the same dewaxed rate of 0.5 v./v./hour and a hydrogen rate of 2000 s.c.f./ b. of feed. Four zeolites were tested: (1) calcium 5- angstrom zeolite; (2) magnesium 5-angstrom zeolite; (3) zinc-palladium S-angstrom zeolite;. (4) sulfactivated zincpalladium S-angstrom zeolite. In the latter case, the zeolite was pretreated at 850 F. with a C to C naphtha feed containing added carbon disulfide (as in Example 1). The results of these runs are shown in the following table.

TABLE II Dewaxing oi hydrofined Zelten gas gas oil a Sulfided Zn-Pd- Zn-Pd- Zeolite (Ia- A; Mg-5 A. 5 A. 5 A Feed Product distribution, weight percent:

01 and lighter 1. 4 2. 9 10. 4 10. 9 04 0. 7 1. 7 8. 6 4. 6 C 320 F. 4. 1 5.0 15. 7 11. 3 320 F.+ 93. 8 90. 4 05. 3 73. 2 100 Product inspections, 320 F lus fraction:

Gravity, API. 36. 5 36. 4 .0 34. 9 36.9 Pour point, F- -60 Cloud point, F 32 38 -4 14. 44. ASTM distillation, D-l58:

IBP 840 320 340 350 560 448 480 478 430 584 531 54.0 542 520 588 501 595 590 592 602 619 620 624 622 624 626 625 630 635 632 633 630 638 640 636 Recovery, perce 96. 5 96. 5 96. 0 99 98 2. 5 2. 5 3. 0 1 1 Residue, percent-.-

"Pre-sulfided in hydro operation at 850 F. with 0 -0 feed plus CS As indicated, the zinc cation modification produced ex tremely low pour and cloud points. The eifect of sulfiding the zeolite prior to contact with the waxy feed is further concentrated by the additional pour and cloud point lowering achieved.

EXAMPLE 4 This example illustrates the performance of an erionite type zeolite with the Zelten gas oil feed. A commerciallyavailable sample of synthetic erionite was first exchanged with ammonium ion and then with zinc cation (ZnCl solution) and finally combined with palladium as in Example 1. The resultant zeolite by analysis showed:

Wt. percent Zinc 6.8 Alkali metal 2.6 Silica 67.5 Alumina n- 19.1 Palladium 0.4

The conditions used and results obtained are shown in Table 1 H.

TABLE IIL-DEWAXING 0F HYDROFINED ZELTEN GAS OIL FEED WITH PALLADIUM ZINC ERIONITE [Process conditions: 500 p.s.i.g., 0.5 v./v.lhr., 4,000 s.c.t. Hz/bbl-l Temperature, F.

700 750 Feed Product distribution, weight percent:

C1 0. 7 2. 4 C2--- 0. 8 2. 4 Ca-.. 6. 9 11. 6 C4 2. 1 3. 2 C5 320 F.. 3.0 4. 9 320 F 86. 5 75. 5 Inspections on 320 F plus fractio Gravity, API 35. 7 85.1 Pour point, F. 20. 0 5.0 22.0 12. 0

Cloud point, F

The utility of erionite in the present process is thus demonstrated.

EXAMPLE 5 Gravity, A-PI at 60 F. 33.3 Pour point, F. 40 Cloud point, F. 40 Sulfur, wt. percent 0.126 Nitrogen, wt. percent 0.005

ASTM Distillation (D-158):

As a result of the acid treating, the nitrogen content of the feed was reduced from 50 p.p.m. to less than 2 p.p.m. The operating conditions and results of these tests are summarized in the following table:

TABLE V [Pour and cloud point reduction otnpretreated Louisiana-Mississippi gas 01 Pretreatment of feed H1804 Feed None Feed treated 1 Temperature, F 800 800 850 Pressure, p.s.i 1, 000 500 600 Gas rate, cfJbhl 2,000 2, 000 4 000 Prod uct yield, weight percent,

320 F 91. 4 87. 8 74. 5 Inspections on 320 F.+:

Gravity, API at 60 F 33. 3 33. 3 33. 3 33. 1 33. 9 Pour point, F.. 4 35 40 15 15 Cloud point, F 36 40 28 24 Sulfur,p p m 40 Nitrogen, p n m 2 1 Gas oi l feed treated with 10% of 98 weight percent H2804 at 100 F. to reduce its mtrogen content.

As indicated above pretreatment of the feedstock to reduce the nitrogen level had a marked effect upon the ultimate reduction in pour point and cloud point.

While nitrogen removal was accomplished above by acid treatment, hydrofining of the feed prior to the zeolitic contacting is also effective. This was demonstrated in a run made with a severely hydrofined, light catalytic cycle oil feed which contained negligible nitrogen and sulfur (less than 2 p.p.m.). The hydrofined feedstock was contacted with the same erionite catalyst used above (in the case of the acid-treated gas oil feed), at operating conditions similar to those shown in Table IV with the following results:

TABLE V.-POUR POINT AND CLOUD POINT REDUCTION HYDROFINED LIGHT CATALYTIC CYCLE STOCK [850 F., 0.5 v./v./hr., 500 p.s.i.g., 4,000 ofJbbl. H2]

Feed Product Again a substantial pour point and cloud point reduction was realized.

EXAMPLE 6 In order to compare the specific hydrogen erionite catalyst of the present invention with those catalysts described in British Pat. No. 908,948 as useful for the pour point reduction of petroleum distillate fractions, by the selective adsorption of normal parafiins, the following catalysts were compared, several angstrom catalysts were compared at identical process conditions. The 5 A. sieves of the British patent are represented by zeolites 4A and 5A, as prepared by the Linde Division of Union Carbide Corporation. Both these zeolites and the erionite of the present invention were ion-exchanged to their hydrogen forms.

Thus, the hydroselective cracking of a gas oil feed was carried out utilizing a specific hydrogen erionite catalyst, namely, hydrogen-palladium erionite, and with the hydrogen-palladium forms of both 5 angstrom catalysts heretofore described. The results obtained are contained in Table VI.

14 therefrom, and subsequently contacting the resulting naphtha-free product with a zeolite of the same type at similar conversion conditions.

4. A process for dewaxing a hydrocarbon oil which comprises contacting said oil with a crystalline aluminosilicate zeolite having uniform pore openings of about 4 to less than 6 angstrom units and having the crystal structure of erionite, in the presence of hydrogen and at conversion conditions of from 650 to about 900 F., said zeolite containing hydrogen, and being combined with a metallic hydrogenation component.

5. The process of claim 4, wherein said hydrocarbon oil is a petroleum fraction selected from the group consisting of middle distillates and gas oils.

6. The process of claim 4, wherein said hydrocarbon oil is hydrofined prior to contacting with said zeolite.

7. The process of claim 4, wherein said oil is acid treated prior to contacting with said zeolite.

8. The process of claim 4 which. additionally comprises contacting said zeolite with sulfur prior to its contact with said oil.

9. The process of claim 4, wherein said conversion conditions include a pressure within the range of 100 to 5000 p.s.i.g., and wherein said hydrogen is introduced at a rate of about 500 to 10,000 standard cubic feet per barrel of said oil.

10. The process of claim 4, wherein said zeolite contains a Group II-B metal.

TABLE VL-"HYDROSELECTIVE CRACKING 01% GAS OIL FEED FOR POUR POINT Pd-H-5 A. Catalyst (zeolite source) Feed (Linde 4A) Feed Process conditions:

Pd-H-5 A. Pd-H Pd-H (Linde 5A) Feed erionite Feed erionite These results not only clearly demonstrate the dramatic superiority of the erionite catalysts of the present invention in obtaining substantial pour point reductions, but further indicate that the use of the 5 augstrom zeolites of British Pat. No. 908,948 do not at all make satisfactory hydroselective cracking catalysts.

What is claimed is:

1. A process for dewaxing petroleum oil fractions containing straight chain hydrocarbons which comprises contacting said fractions at conversion conditions including a temperature of from 650 to about 900 F., in the presence of hydrogen with a crystalline alumino-silicate zeolite having uniform pore openings of about 4 to less than 6 angstrom units, said zeolite being combined with a metallic hydrogenation component and further containing hydrogen, and recovering dewaxed normally liquid product of substantially reduced pour point.

2. The process of claim 1 which additionally comprises fractionating said product into a low pour point light fraction and a high pour point heavy fraction, subjecting said heavy fraction to a solvent dewaxing treatment and combining the dewaxed efiiuent from said solvent dewaxing step with said light fraction.

3. The process of claim 1 which additionally comprises fractionating said product to remove naphtha fractions 11. The process of claim 1, wherein said hydrogenation component comprises a Group VIII metal.

References Cited DELBERT E. GANTZ, Primary Examiner G. E. SCHMITKONS, Assistant Examiner US. Cl. X.R.

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