FI97027C - Hydrate cracking catalyst for medium distillate using low acidity Y zeolite - Google Patents

Description

97027

This invention relates to a highly selective middle distillate hydrocracking catalyst. More specifically, the invention relates to a catalytic hydrocracking process which is selective in the conversion of heavy hydrocarbon oils to middle distillates boiling in the range of 149-37 ° C. The invention is characterized in that a new low acid Y zeolite is used.

Hydrocracking is an oil refining process in which the molecules of a hydrocarbonaceous substance are partially decomposed in the presence of hydrogen to give a more desirable low molecular weight hydrocarbon product. As a result of the increased demand for middle distillates, such as jet turbine and diesel fuels, commercial interest in hydrocracking has increased as this process decomposes less feedstock into gas and coke and thus provides a higher yield of liquid products from the boiling range of middle distillates than heat or non-hydrogen consuming.

The crucial aspect of a competitive hydrocracking process is the use of a special catalyst that is highly active in both cracking and hydrogenation. A large number of these dual-acting catalysts are known in Alal-la.

• · ·

In general, the cracking activity, i.e. the measure of the conversion of the feedstock to the product, usually depends on the solid oxygen components present in the catalyst base. Hyd- • · ·; * j *; The roughness activity, on the other hand, usually depends on the different metals present in the catalyst support. These metals; # · # Are mostly metals belonging to groups VIB and VIII of the Periodic Table of the Elements.

35 Catalysts commonly used in the hydrocracking industry to produce middle distillates comprise a metal or metals and / or metal compounds selected from metals of groups VIB or VIII of the Periodic Table of the Elements which are on an amorphous refractory inorganic oxide support such as with mixtures of alumina and alumina. Recently, significant commercial activity has focused on the development of hydrocracked-5 catalysts comprising crystalline aluminosilicates on a catalyst base.

In general, zeolite aluminosilicates have a higher total acidity than amorphous oxides and therefore have better cracking activity. Because of this property, zeolites are believed to provide better catalytic performance in the conversion of hydrocarbons. In a study to develop zeolite hydrocracking catalysts, special attention has been paid to the Y-type zeolite originally described in U.S. Patent 313,0007. The catalytic mechanism of the Y-type zeolite has not yet been fully elucidated. However, it has been found that a Y-zeolite-containing hydrocracking catalyst is not only more active in the production of middle distillates, but is also more selective for the desired middle-distillate product.

The current state of the art in hydrocracking catalysts containing zeolite comprises Y-zeolite or various modifications of Y-zeolite with a refractory inorganic. '· With 25 oxide matrices. The y-zeolite can be converted, for example, # t * j ‘by increasing the molar ratio of silica to alumina’ ** and reducing the size of the elementary box.

• · • · · • · • · • ··. * · *. U.S. Patent 4,419,271 discloses a hydrocarbon conversion catalyst useful in hydrocracking comprising one or more hydrogenation components on a support. . containing crystalline aluminosilicate zeolite active in hydrocarbon cracking and a silica-alumina dispersion in an alumina matrix. The holder of the patent 35 states that the replacement of alkali metals with polyvalent metal-containing cations, hydrogen ions or hydrogen ion precursors, which is usually carried out by ion exchange techniques, is necessary in order to obtain a zeolite having the desired cracking activity. By reducing the alkali metal content to less than 5% by weight and preferably to less than 0.5% by weight (calculated as alkali metal oxides), a substance with considerable cracking activity is obtained. According to the patent holder, the most preferred zeolite-5 ti for use as a component in the hydrocracking catalyst mixture is a modified Y zeolite having a silica to alumina ratio of about 3.5-6.0, a surface area of about 500-700 m 2 / g, a primer size of about 2.425- 2.435 nm (24.25-24.35 angstroms), a water adsorption capacity of less than about 8% by weight of the zeolite (at a water vapor partial pressure of 4.6 mm and at 25 ° C) and an ion exchange capacity of less than 20% sodium. Y-zeolite, where the ratio of silica to alumina is comparable.

U.S. Patent 4,401,556 discloses a hydrocarbon conversion catalyst comprising an ultrahydrophobic Y zeolite (UHP-Y) and characterized in that it has a molar ratio of silica to alumina of 4.5 to 35, has an essential Y zeolite 20-connector X-ray chart, with an ion exchange capacity not exceeding 0,070, a primer size of 2,420 to 2,445 nm (24,20 to 24,45 angstroms), an area of not less than 350 m2 / g (BET), a water vapor sorption capacity at 25 ° C and 0,10: np / p ° of less than 5.00% by weight and a residual butanol test value of not more than 0.40% by weight. "25 per cent.

U.S. Patent 4,517,073 discloses a hydrocracking catalyst containing an active hydrogenation component on a support comprising a silica-alumina dispersion in alumina and a Y-type zeolite and wherein the molar ratio of silica to alumina is greater than about. ^ 6.0. The zeolites used in the hydrogen cracking process of the patent holder in the catalysts in question have the essential crystal structure of Y-zeolite, it contains less than 1.5% by weight of alkali metals (calculated as total monoxides) and its elemental copolymer. the size is usually less than 2.465 nm (24.65 angstroms). The best observed molar ratios of silica to alumina are 6-20 and 4,97027 when the molar ratio is less than 20, the water vapor adsorption capacity of the zeolites referred to by the patent holder at 25 ° C and 4.6 mmHg water vapor partial pressure is at least 20% by weight based on the dry weight of the zeolite its oxygen ad-5 sorption capacity at 100 mmHg and -83 ° C is at least 25% by weight.

The aforementioned patents are considered to describe the prior art in hydrocracking catalysts containing Y-type 10 zeolites. Prior art Y-type zeolites for use in hydrocracking have been characterized by terms such as silica to alumina molar ratio, elementary body size, ion exchange capacity, surface area, and water sorption capacity. Bifunctional catalysts used in hydrocracking provide both cracking and hydrogenation activity, and it is well known in the art that the degree of acidity of a catalyst component affects the cracking activity of the catalyst. For example, the articles by Dwyer and Newsam cited below discuss the cause and effect of zeolite acidity. However, despite the tremendous efforts of skilled researchers in hydrocracking, the effect of hydroxyl content, which is directly related to the degree of acidity of the cracking component (such as Y-type zeolite), selectivity itself, has been neglected in 25 cases.

IM *

Dehydroxylation has generally been scarce in the literature. One exception to this is the publishing group, which includes • · ·, ···. U.S. Patent 4,790,928. This publication relates to the improvement of the performance of ZSM-5 and other medium-sized zeolites with selective dehydroxylation. . put out. The resulting zeolite, when compounded with a · ♦ * ··: catalyst, is said to be useful for dewaxing oil fractions such as reduced crude oils or vacuum gas oils. Dehydroxylation is accomplished by calcination above 600 ° C (1172 ° F) without water.

Il 97027 5

Studies on the hydroxyl group content and calcination effects of Y zeolites are discussed in American Chemical Society Monograph 171, June A. Rabo, eds., Pages 140-147.

5

The use of low acidity catalysts in hydrogen cracking is discussed in U.S. Patent 4,263,129. However, this publication is considered limited to the use of zeolite in ZSM-5 form with a molar ratio of silica to alumina of more than 12. Preferably, low acidity is achieved by extensive zeolite sodium exchange with an alkali metal to give high sodium contents, although evaporation to reduce acidity is also referred to. The process of the invention differs from this publication in that it uses Y zeolites with a low sodium content and a low molar ratio of silica to alumina.

U.S. Patent 3,929,672 compares the effect of the steam and dry calcinin-20 pathways on Y zeolites. Dry calcinations are said to lead to loss of crystallinity.

This invention relates, in its broadest sense, to a process for the selective hydrocracking of middle distillates using a catalyst comprising a hydrogenic crystalline Y-type zeolite having an elementary booth size of about 2.42-2.44 nm ** ': (24.20-24, 40 angstroms) and has a sufficiently low level of surface hydroxyl groups to give an NH3-TPD acidity level of less than about 2.00. The zeolite is preferably dehydroxylated by dry calcination.

• · ·. . The invention can be characterized as a hydrocracking catalyst, * · *. ' which is selective in the production of middle fraction distillates and which comprises in combination: (i) a hydrogenation component, (ii) a refractory inorganic oxide matrix containing alumina, and (iii) a crystalline hydrogen Y-type aluminosilicate zeolite having an initial size of 97027 6 kop is 2.42-2.44 nm and the NH3-TPD acidity value is less than 1.50.

It is an object of the present invention to provide improved hydrogen-5 cracking catalysts and processes. Another object of the present invention is to provide an improved hydrocracking catalyst with better activity and selectivity in providing middle distillate products.

It has now been found that a hydrogen Y-type zeolite having low bonded hydroxyl groups on the surface of the zeolite provides a better hydrocracking catalyst. It has been found that this catalyst, which can be characterized by the ammonia temperature programmed desorption method (NH3-TPD), is much more selective in the hydrocracking process producing middle distillates.

The hydrocracking composition of the present invention comprises a crystalline Y-type zeolite. Y-type zeolite is generally discussed in U.S. Patent 313,0007, which is incorporated herein by reference.

The chemical formula of the y zeolite, expressed as moles of oxide, can be written as follows: 0.9 ± 0.2 Na 2 O: Al 2 O 3: wSiO 2: xH 2 O * · · where w is from 3 to about 6 and x can be any number about 9 · ** '; until.

30

«T I

The classical structure of the γ-zeolite is a three-dimensional crystal, a network formed by a tetrahedron containing SiO 4 and AlO 4, crossed by the distribution of oxygen atoms. The electron valence of an aluminum-containing tetrahedron is stabilized by such cations as metal ions, rare earth metals. ·; the presence of ions, early metal ions, ammonium ions, amine complexes and hydrogen ions. The cavities of the structure can be filled with water molecules. Usually, the crystalline zeolite ti 97027 7 is present or prepared in the alkali metal form. The classification of a substance as a Y-zeolite is in principle based on the above formula and on the presence of a known X-ray pattern in the substance. The structure of γ-zeolite-5 may include germanium, gallium, phosphorus or boron together with or instead of traditional silica and alumina.

The "acidity" of the zeolite has been the subject of considerable research 10 and speculation. For example, the effect of acidity on catalytic activity and the acidity ratio of the mixture to zeolites is discussed in John Dwyer's article on page 258 in Chemistry and Industry, April 2, 1984. The article states that it appears obvious that hydroxyl groups in zeolite channels form active Bronsted sites. It describes two types of hydroxyls: surface or terminal hydroxyls and bridge-forming hydroxyls in larger pores. The article deals extensively with the degree of acidity, the mixture, the activity of the catalyst, and the selectivity of the catalyst. It should be noted that product selectivity is said to be determined by the shape and size of the pores and its effect on limiting diffusion to selective internal sites rather than being determined or affected by acidity.

25 J.M. Newsam's article, published March 7, 1986 in Science (Vol. 231, p. 1093), states that: ***: in most catalytic cracking reactions

Mixtures include acid sites in the zeolite. Such Bronsted acidity is mainly due to the hydroxyl groups that form the bridge. Acid sites are considered si-. . to a protonated aluminum tetrahedron in a silicon-rich structure.

35 As shown in the information below, it has been found that the selectivity of the hydrogen Y-zeolite in the preparation of middle distillate products directly correlates with the degree of acidity of the zeolite, which in turn is determined by the concentration of hydroxyl groups on the surface of the zeolite. the use of a roxyl zeolite-containing hydrocracking catalyst composite and the mixture containing it are believed to be novel.

5

Since it is currently not possible to directly measure the content of hydroxyl groups, this measurement must be made indirectly. The best method of analysis is to measure the acidity of the zeolite. This is believed to correlate directly with the hydroxyl group-10 peak content.

Ammonia temperature-programmed desorption (NH3-TPD) is widely used and is considered an effective procedure for determining the acidity of zeolites. (See Hidalgo, 15 CV, et al., Measurement of the Acidity of Various Zeolites by Temperature-Programmed Desorption of Ammonia, J. Catalysis, Vol. 85, No. 2, pp. 362-369 (1984), the contents of which are incorporated herein by reference). reference). Ammonia is an excellent test molecule in the TPD process. The small size of the molecule allows exceptionally good penetration into the pores, while its strong basicity allows easy stabilization at acid sites. The TPD procedure is considered the best because it is relatively simple, takes as little time as possible, and can be repeated accurately.

25 ·; · In this NH3-TPD procedure, a sample of 0.250 ± 0.001 g of zeolite is pretreated by first heating • ·. * ··. in air at 500 ° C and a flow rate of 60 cm3 / min for 75 minutes- • · ·. ···. and then in helium at 500 ° C and a flow rate of 60 to 30 cm 3 / min for 15 minutes. The pretreated zeolite is then cooled to room temperature over about 20 minutes with helium. . jacket. To bring to equilibrium, the zeolite sample • · · · ”· is then saturated 5 times with 100 cm3 aliquots (normal under dissolution conditions) of ammonia gas. The saturated zeo-35 paste is then purified with helium at room temperature and a flow rate of 60 cm 3 / min for 35 minutes. Immediately thereafter, the gas stream is directed to the gas chromatograph while the sample is heated to the programmed temperature, while the sample is heated at the programmed rate of temperature rise of 8.33 ° C / min to a maximum of 650 ° C. Ammonia desorption is then monitored by a recorder at 25-500 ° C for 75 minutes.

5

The area included in the desorption curve produced by the gas chromatography recorder correlates with the total amount of ammonia desorbed. Analysis of the exhaust gases by mass spectrometry revealed a slight desorption of impurities in the temperature range of 25-500 ° C. To standardize the desorption curve, the desorbed ammonia was taken up in 10% H 2 SO 4 solution and quantified by methods known in the art. The amount of desorbed ammonia per unit area of the desorption curve was determined to be 0.038 + 0.004 millimoles / unit area.

The NH3-TPD acidity value was determined by integrating the desorption curve between 25-500 ° C. The area under the curve was then multiplied by a factor of 0.038 millimoles / unit area and divided by the weight of the sample (0.250 g) to give the NH3-TPD-20 acidity value in millimoles / gram. Thus, for example, if integration between 25-500 ° C gives a total surface unit of 10.0, the NH3-TPD acidity value would be calculated as 10 surface units x 0.038 millimoles NH3 / surface unit / 0.250 gram sample = 1.52 millimoles / gram sample.

'. 25 ·; · All NH3-TPD acidity values contemplated by this invention are expressed in basic units in millimoles / gram of sample. For the sake of simplicity, the NH3-TPD values mentioned herein. ··· Reproducing the acidity data by the NH3-TPD method requires an accurate replication of the experiments, such as the rate of temperature rise, the sample size, the gas flow and the equilibrium temperature, so that different methods can • • · · '··: In any case, it is clear that the acidity values considered in this invention cover not only the values determined by the NH3-TPD test described above, but also the corresponding values that would be obtained from another similar sample using another method. .

97027 10 The Y zeolites which can be used in the process in question have (as a limitation) a molar ratio of silica to alumina of less than 6.0.

The Y-type zeolites useful in this invention have an alcope size of 2.42 to 2.44 nm, and preferably about 2.43 nm. It should be noted that when it is said in the prior art that zeolite-containing hydrocracking catalysts are sensitive to changes in the size of the zeolite elemental box, the acidity us-10 is independent of this parameter. The decrease in acidity as the size of the elementary box decreases is due to the decrease in the aluminum content of the zeolite and this effect is not related to the different acidity values of zeolites having the same molar ratio of silica to alumina and / or elementary box size.

The Y-type zeolite in question in the present invention should have an NHj-TPD acidity value of at most about 2.00. The acidity value is preferably less than about 1.50, very preferably less than about 1.50, and most preferably in the range of about 0.1 to about 0.70.

The actual process by which the lower Y acid zeolite with lower acidity is prepared is not believed to be critical to the present invention. The hydrocracking catalyst in question can be prepared from »··· ***. from any of the starting materials disclosed in U.S. Patent No. 313,0007. X-ray pattern of the essential Y zeolite. The starting material can. ···. can be converted by any acidity reduction technique known in the art to obtain the desired hydrogen zeolite. Thus, conversion techniques such as hydrothermal treatment at elevated temperatures, calcination, impregnation or reaction with an antacid, crystallization, and any combination thereof.

Neither the zeolite conversion method nor the method of preparation is believed to be essential for the present invention. Any hydrogen Y-zeolite material having a suitably low hydroxyl group content can be used as the zeolite component in this hydrocracking catalyst.

5

One method of reducing the acidity is by hydrothermal treatment above 500 ° C for at least 0.5 hours.

One proven method of reducing the acidity is dry calcination at more than 500 ° C for at least 0.5 hours.

One highly preferred method of performing the desired dehydroxylation is to keep the zeolite at a temperature of at least 70 ° C for at least one hour substantially free of water. The use of any particular conversion method is not known to be critical to the invention. Ar-15 suggests that two or more different conversion techniques could be used.

The hydrocracking catalyst composite of the present invention should contain 2 to 20% by weight of the Y-20 type zeolite in question, and preferably 2 to 10% by weight. The present mixture also comprises a porous refractory inorganic oxide matrix which may comprise from 2 to 98% by weight and preferably from 5 to 95% by weight of the support of the finished catalyst composite. The matrix may contain any of the known refractory inorganic oxides, such as alumina, magnesia, silica, titanium oxide, zirconia, and alumina and the like, and combinations thereof. romp.

• · · t: 1 !! ^ 30 One proven matrix comprises silica-alumina or alumina. The most preferred matrix forms a mixture of silica-alumina and alumina, wherein said silica-alumina comprises 45-90% by weight of said matrix. It is also preferred that the support comprises from about 5% to about 45% by weight of alumina.

97027 12

The silica-alumina component can be prepared by any of a number of methods well defined in the art. Such methods include acid treatment of a naturally occurring clay or sand, simultaneous or sequential precipitation from hydrosols. These techniques are often combined with one or more activation treatments, such as hot oil aging, evaporation, drying, oxidation, reduction, calcination, etc. The pore structure of the substrate or support, commonly defined as surface area, pore diameter, or pore volume, can be developed. within certain limits by any suitable means, such as aging the hydrosol and / or hydrogel under controlled acid or base conditions at room temperature or elevated temperature, or by gelling the carrier at a critical pH or by treating the carrier with various inorganic or organic reagents.

The finished catalyst suitable for use in the hydrocracking process should have a surface area of about 200-700 square meters / gram, a pore diameter of about 2-3 nm, a pore volume of about 0.10 to about 0.80 millimeters / gram, and a bulk density of about 0.50 to about 0.90 grams / cubic centimeter. Areas larger than 350 m2 / g are highly recommended.

25 ·; · The alumina component of the catalyst may be

IMI

sa various alumina hydroxides or alumina • ·. ···. gels such as alpha-aluminum monohydroxide having a boeme • · mite structure, alpha-aluminum trihydroxide having a gibb- • φ III 30 penite structure, beta-aluminum trihydroxide having a bait • • · * barite structure, and the like. A particularly preferred alumina is known as Ziegler alumina and is characterized in U.S. Pat. No. 3,852,190 and U.S. Pat. No. 4,012,313 as a by-product of a Ziegler higher alcohol synthesis reaction described in U.S. Pat. No. 2,892,858 to Ziegler. One proven alumina is currently available from Conoco Chemical Division of the Continental Oil Company under the trade name 97027 13 "Catapal". The substance is an alpha-aluminum monohydroxide (boemite) of extreme purity, which has been shown to give very pure gamma-alumina after high temperature calcination.

5

It is to be understood that the precise physical properties of the carrier, such as shape and surface area, are not considered to limit the scope of the present invention. For example, the catalyst may be in the form of pills, pellets, granules, crushed particles, spheres, or various other forms, such as triangular extrudates arranged as solid beds in the reaction zone. Alternatively, the catalyst may be prepared in any suitable form for use in mobile-jet reaction zones in which the feed hydrocarbon feedstock and catalyst move either countercurrently or parallel to each other, or in fluidized bed processes in which the feedstock is suspended in a finely divided catalyst. in processes in which the catalyst is slurried in the feedstock and the resulting mixture is transferred to the reaction zone. The feedstock can be passed through the reactor (s) in a liquid, vapor or mixed phase and in either an upward or downward flow.

The catalyst particles can be prepared in any manner known in the art, including well-known oil droplet and extrusion methods. In the case of the oil droplet ···· process, the catalyst particles can be prepared first • ·. * ··. by suspending the selected zeolite powder in a suitable salt- • · · ···. liin. Active metal components can also be connected to • · 30 sols. The sol mixture is then directed as drops into an oil bath, which is maintained at an elevated temperature and allowed to stand in an oil bath until the sol droplets have turned into gelatinous spheres. The spherical particles can then be removed from the oil bath and then aged in a suspension medium at an elevated temperature for a suitable time.

The spherical particles can then be dried and calcined. If it is desired to prepare an alumina or silica-alumina matrix, the oil droplet process may be carried out in accordance with U.S. Pat. No. 2,620,314 or U.S. Pat. No. 3,003,972, respectively, which are incorporated herein by reference.

One preferred method of preparing the catalyst mixture of the present invention is to grind the selected zeolite simultaneously with both alumina and silica-alumina. Prior to mixing, the components of the mixture are preferably crushed into a powder. The active metal components can also be combined in the mixture at this stage. After grinding, the mixture is extruded through a die having a suitable orifice, such as a round or cloverleaf orifice, to provide an extrusion material of the desired shape. The extrudate can be cut to lengths of 1/2 to 1/4 inch and then dried and calcined at elevated temperatures and under conditions known in the art.

Although the hydrogenation components may be added before or during the oil droplet or extrusion processes, the hydrogenation component is preferably incorporated into the catalyst by impregnation after the selected zeolite and refractory inorganic oxide material have been formed, dried and calcined. The impregnation of the metal hydrogenation component into the particles can be performed in any manner known in the art, including evaporation, immersion, and vacuum impregnation techniques. Generally, the dried and calcined particles are contacted with one or more solutions containing i ··· * · *. contain the desired hydrogenation components in solution. Suitable • ·, ···. after the contact time, the composite particles are dried and • · calcined to produce the finished catalyst particles. Additional illumination to prepare a suitable catalyst is available from a number of references, including U.S. Patent Nos. 4,588,496 and 4,600,498, which are incorporated herein by reference for their contents as regards Y- zeolite-containing preparation and use of hydrocracking catalysts 35.

Suitable hydrogenation components are the catalytically active components selected from the metals of groups VIB and III7070 VIII and their compounds. In general, the hydrogenation components are present in the finished catalyst mixture little compared to the amount of other components defined therein as defined above. The Group VIII component is generally present in an amount of from about 0.1% to about 30% by weight, preferably from about 1% to about 15% by weight of the finished catalyst composite, based on the elements. The Group VIB component is from about 0.05% to about 30% by weight, preferably from about 0.5% to about 15% by weight, based on the elements of the finished catalyst composite. Suitable hydrogenation components include one or more metals selected from the group consisting of molybdenum, tungsten, chromium, iron, cobalt, nickel, platinum, palladium, iridium, osmium, rhodium, rudinium, and mixtures thereof.

15

The hydrogenation components may most likely be in the oxide form after calcination in air and may be converted to the sulfide form, if desired, by contacting them at elevated temperatures with a reducing atmosphere containing hydrogen sulfide, a mercaptan or other sulfur-containing compound. The catalyst can be sulfurized in situ by contacting it with a sulfur-containing feedstock, or it can be sulfurized before it comes into contact with the feedstock by exposing the composite to a reducing atmosphere immediately after calcination.

• · · • · · • · ···. If desired, a phosphorus component can also be added to the catalyst. The phosphorus addition can be performed either by mixing the carriers with a phosphorus-containing compound before forming the particles or by incorporating phosphoric acid into the impregnation solution. Usually phosphorus: is present in the catalyst from 1 to 30% by weight and preferably from 3 to 15% by weight: calculated as P2O5.

’: 35

In addition, the catalyst composite may also contain boron. Boron can be incorporated into the composite in any elemental or compound form and by any of the methods described above. That is, it may be included in the particle formation step, or boron may be present as a compound, such as boric acid, added to the impregnation solution. Boron can also be incorporated into the structure of selected zeolites 5. In the latter case, it is a question of converting the Y-type zeolite and then forming a silica-alumina-boronizoleite.

The catalysts in question are particularly useful in hydrocracking a hydrocarbon feedstock into a more valuable product with a lower average boiling point and lower average molecular weight. The catalysts are particularly useful in the preparation of middle distillate fractions boiling at about 149-371 ° C as determined by a suitable ASTM test procedure. In addition, the above-mentioned catalysts can also be used for hydrogenation reactions such as hydrodenitrification and hydrodesulfurization. Typical feedstocks are, in fact, all heavy mineral and synthetic oils and their fractions. Thus, feedstocks such as straight run gas oils, vacuum gas oils, demetallized oils, atomic residues, deasphalted vacuum distillate residue, coke distillates, catalytic cracking distillates, whale oil, tar pitch oil, carbonaceous matter and the like. The preferred raw materials are gas oils, the components of which: · at least 50% by volume boils above 371 ° C. Ve- ···· ***. the raw material fed to the cracker may contain nitrogen, • «. ···. which is usually present as organo-nitrogen compounds 1 ppm to 1.0 ···. in% by weight. The feed usually contains sulfur-containing compounds sufficient to give a sulfur content of more than 0.15% by weight. It may also contain mono- and / or polynuclear aromatic compounds in amounts of 80% by volume * «« ϊ · ί · and above.

35 The hydrocracking conditions used in the process in question are the same as those normally used in hydrocracking processes in the art. The hydrocracking reaction temperatures are 204-649 ° C, preferably 316-510 ° C. The reaction pressures tl 97027 17 are about 24132 kPa g of normal pressure, preferably 1379-20685 kPa g. The contact times usually correspond to a liquid flow rate (LHSV) through the catalyst of about 0.1 h'1 to 15 h'1, preferably 0.2-3 h'1. The hydrogen circulation rates are in the range 178-5 8,888 standard m3 / m3, preferably 355-5,333 standard m3 / m3.

The material exiting the reaction zone is normally transferred from the catalyst bed, subjected to partial condensation and vapor-liquid separation, and then fractionated to recover the various components. Hydrogen and, if desired, some or all of the unchanged heavier materials are recycled back to the reactor.

The process in question can thus be characterized as a hydrocracking process which is selective in the preparation of middle distillates and in which a hydrocarbon feed stream containing at least 50% by volume of components boiling above 370 ° C is contacted with a catalyst mixture comprising: (i) a hydrogenation component, (ii) a refractory inorganic oxide matrix comprising alumina, and (iii) a crystalline hydrogenated aluminosilicate zeolite having an essential X-ray pattern of the Y zeolite and having an ion exchange capacity greater than 0, 07, with a pot size of about 2.42-25 to 2.44 nm and an NH3-TPD acidity value of less than about 1.50, ·; · and which zeolite has been contacted with steam • «** '; 676-780 ° C for 2-12 hours, followed by • ♦, 11. it is dehydroxylated by dry calcination at a temperature of * ··. is at least 426 ° C for at least one hour, keeping the li! 30 talc under hydrocracking conditions, and the product stream is recovered «» «*.

· »« «·· -‘ The following examples are presented to illustrate the invention and are not intended to limit the scope of the invention.

35

Example 1 This example compares the effects of two different techniques for reducing the acidity of a zeolite. In Part A, the starting zeolite 97027 18 is heated in the presence of steam, after which it is dry calcined, while in Part B, the starting zeolite is heated in dry air. The acidity values of the zeolites were determined by the NH3-TPD experiment described above. In the ran-5 g of the starting zeolites, the molar ratio of silica to alumina was 5: 1 to 8: 1. A web with a molar ratio of silica to alumina of about 6: 1 is preferred. This relationship does not correspond to the so-called. bulk silica: alumina-molar ratios sometimes reported in publications. The zeolites contained less than 10% by weight of sodium.

Part A

Samples were used which were ammonia-exchanged Y-type zeolite powder previously sold by Union Carbide 15 Corporation and currently sold by UOP and referred to in the literature as LZ-Y82. A zeolite having a starting NH3-TPD acidity value of 2.60 and an elementary booth size of 2.456 nm was placed in a heating tube equipped with external heating means. Depending on the desired acidity value, the zeolite was contacted with pure steam generated from demineralized water at 1 atm absolute pressure and 676-788 ° C for 2-12 hours. At the end of the selected heating time, the steam flow was turned off and the batch temperature was reduced to room temperature in a dry stream of air for an additional 4 hours. During this step, the zeolite was maintained at a temperature of at least 426 ° C, «M · * '*. for at least one hour.

9 · * · • «* ··> Five zeolite samples (A, B, C, D and F) were prepared as described above with the temperature and time parameters S · · 'being listed in Table 1. Analysis of the product samples showed that they had an essential X-ray pattern of the zeolite • · · ϊ ·! ’And that their elementary box size and NH3-TPD acidity values were listed in Table 1.

The results show that the acidity of the zeolite can be changed (reduced) to a preselected value, while the alcove well sizes are obtained in the desired range of 2.42-2.44 nm. NH3- 35 97027 19 The TPD acidity can thus be adjusted by the Part A procedure, which involves dry calcination after steam treatment.

5 Table 1

Zeolite Evaporation conditions Elemental Acidity sample Time (h) Temperature (° C) degree of boiling in moles size (nm) NH3 / g 10 A 2 676 2,436 1.50 B 2 732 2,435 1.13 C 2 788 2,429 0.65 D 12,788 2,425 0.14 15 E - - 2,436 1,30 F 6 676 2,435 1.25

Part B

A sample of a variety of ammonia-exchanged Y-type zeolite powder (often referred to as LZ-20, formerly sold by Union Carbide Corporation and now sold by UOP) with an NH3-TPD acidity of 2.18 and a primer size of 2.437 nm was placed muffle furnace (no steam is present in this 25 procedure). This starting material is believed to represent the prior art zeolites intended

MM

"*, for use in selective middle distillation catalysts treated with steam, such as the zeolite mentioned in U.S. Patent 4,419 •. 271. The zeolite was heated to 704 ° C, maintained at this temperature. For 1 hour and then allowed to cool to room temperature, analysis of the product showed that it had a characteristic X-ray pattern of Y-zeolite, a primer size of 2.436 nm and an NH3-TPD acidity value of This zeolite corresponds to sample E in Table 35 1.

97027 20

The results show that dry calcination reduced the NH3-TPD acidity of the zeolite E of sample E without significantly affecting the elementary box size.

5 It is noteworthy that in the treatment of Part A, both the elemental box size and the NH3-TPD acidity of the starting zeolite changed. In Part B, however, only the NH3-TPD acidity value decreased, while the elemental box size of the starting zeolite remained somewhat unchanged (2.437 nm vs. 2.436 nm).

10

Heating the zeolite at a high temperature or calcination in a relatively dry environment, for example in a nitrogen-containing gas stream without additional steam, has thus proven to be an effective method which is likely to reduce the hydroxyl group content of the zeolite. Thus, this technique can be incorporated into a general catalyst preparation process when such a low degree of acidity and low hydroxyl group content are desired.

20 Without wishing to be bound by theory, it is believed that the degree of acidity does not depend on the size of the elementary box and can thus be tailored by various heating combinations in the presence of steam and dry air. However, the exact effects of heating with and without steam on the acidity of the zeolite are not known.

• · • ·. ···. The preferred method of preparation gives hydrogen zeolites with substantially unchanged alli! emperor size compared to untreated zeolite.

* · "30 The dry calcination method in question is preferably used as the only way to reduce the acidity and • ·: hydroxyl group content of the zeolite. If other methods such as • · ·: dealumination or ion exchange are used, they are used: preferably before the dry heat treatment in question. preferably prior to incorporation of the treated zeolite into the catalyst particles formed.

97027 21

In hydrothermal treatments, steam is believed to prevent "dehydroxylation" of the zeo-connector. Steam is obviously desirable when the purpose of the treatment is to change the rudimentary size of the zeolite. The method in question relates to the use of pi-5 low hydroxyl zeolites rather than steam-treated zeolites.

Many zeolites used in prior art catalysts are characterized by their ability to adsorb water. This property and a test for its determination are described, for example, in the aforementioned U.S. Pat. No. 4,401,556. Zeolites are characterized by their water vapor adsorption capacity of less than 5.00% by weight at 25 ° C and 0.10% w / w. No experiments on these values were performed on the test materials in these 15 examples. However, similarly treated materials from the same sources were subsequently subjected to such experiments. The material corresponding to zeolite C and receiving the same hydrothermal treatment as it (used in Catalyst 3 below) had a water adsorption capacity of about 2.5% by weight. The water adsorption capacity of the crude Part A starting material (Catalyst No. 7) was about 18% by weight. This value is not available for the starting material in Part B. The adsorption capacity of water appears to decrease in proportion to the intensity of the hydrothermal treatment.

· 25

Example 2 # · * ·. The purpose of this example is to examine both elementary booth size II! the NH3-TPD acidity effects of the finished catalyst! road selectivity and activity.

• · · v * 30

Catalyst mixtures were prepared by mixing a zeolite powder with a refractory oxide matrix mixture containing alumina and silica-alumina in such amounts as to obtain a catalyst containing 5 to 35% by weight of oxides containing 95% by weight of volatile substances and no volatile substances. The resulting mixture was extruded into cylindrical pieces measuring approximately 0.16 x 1.27 cm. The extrusion material was dried and si 97027 22 was then calcined in air at 343 ° C for 2 hours. The calcined particles were then impregnated by co-evaporation with aqueous ammonia methatungstate and nickel nitrate (Ni (NO 2) 2.6H 2 O) present in amounts sufficient to provide a finished catalyst containing 1.0% by weight of elemental nickel and 10.0% by weight of elemental nickel. % elemental tungsten. The impregnated catalyst was then calcined for 45 minutes at 343 ° C and then for 90 minutes at 593 ° C. As described above, six catalyst mixtures were prepared, each containing the Y-zeo attachments prepared in Example 1. Table 2 details the properties of catalysts Nos. 1 to 6, which contain zeolites A-F, respectively.

The catalysts were prepared as described above using the starting zeolite materials used in Parts A and B of Example 1. Catalyst No. 7 was prepared using the starting zeolite of Part A (elemental box size = 2.456 nm, NH3-TPD = 2.60) and Catalyst No. 8 was prepared using the starting zeolite of Part B (al-20 box size = 2.437 nm, NH3-TPD = 2.18). The properties of catalysts Nos 7 and 8 in question are also shown in Table 2.

25 Table 2. · **. Catalyst Zeolite Primary NH3 - TPD - • · VV. n size size (nm) value • ♦ • · • · * ♦ ** • · · '· 30 1 A 2,436 1.50 2 B 2,435 1.13 • ·: 3 C 2,429 0.65 4 D 2.425 0 , 14: 5 E 2,436 1.30 35 6 F 2,435 1.25 7 Part B starting material 2,456 2.60 8 Part B starting material 2,437 2.18 97027 23

For each of the above catalysts, activity and selectivity were tested by the following method. A preheated vacuum gas oil having the chemical and physical properties shown in Table 3 was passed on a one-time-5 basis through an isothermal reactor containing 75 cm 3 of catalyst particles mixed with about 29 cm 3 of 60-80 mesh quartz. The operating conditions were: pressure 13790 kPa g, LHSV 1.0, hydrogen recycle flow 1 778 standard di-m3 / m3 with a purity of 90-95% and a running length of about 4 days. The reactor temperature was adjusted to give 85% by weight conversion to products with a boiling point below 371 ° C. The conversion percentage is calculated by liquid chromatography analysis of the boiling range of the product.

15

Table 3

Properties of steam gas oil 20

Specific gravity @ 15.6 ° C 0.9248 Distillation, ° C

Net weight ° API @ 15.6 ° C 21.5 IPB 280 Freezing point, ° C 26.7 5/10% 340/372

Aniline point, ° C 75.0 20/30 398/419 25 Sulfur (LECO),% by weight 2.24 40/50 439/455 ···. Nitrogen (Kjeldahl), ppm 1100 60/70 437/490. Carbon,% by weight 85.82 80/90 514/544

Hydrogen, wt% 11.64 EP 582

Bromine No. 5.0% Rec. 99.0 • · · '· 1 1 30 Viscosity, ® 98.9 ° C, CST 6.954

Conradson carbon,% by weight 0.42 • ·. · · · • · · · · · · · · · · ·. . The results of the above experiments are summarized in Table 4.

Catalysts 1-4 and 6 are derived from the material of Example 1, Part A. Data for these five catalysts show that with a smaller elemental box size of the zeolite: (1) the activity of the catalyst decreases and (2) the selectivity increases.

24 97027

Table 4

Activity (° C) Selectivity 5 (Reactor time, (% by weight)

where 149-371 ° C is obtained

Catalyst 85% conversion) Product 85% NH3-TPD- by conversion) value 10 1 412 59 1.50 2 414 59 1.13 3 419 61 0.65 4 425 63 0.14 5 417 60 1.30 15 6 417 59 1.25 7 405 55 2.60 8 417 56 2.18 20 These data also reveal that catalysts Nos. 1-6 of this invention are much better in terms of combined overall activity and selectivity than Catalysts Nos. 1 to 6. 7 and 8, which contain an untreated highly acid catalyst. Verification of catalysts Nos. 1 to 6 and Nos. 7 and 8 ver-25 shows that a better catalyst is obtained when the NH3-TPD acidity value of the zeo- ··, composite component is less than y. · 'About 2.00. More specifically, although the ac- * · I ”density of catalyst No. 7 is relatively high (405 ° C), the selectivity is not I | ;;; not acceptable (55% by weight). It should be noted, however, that the size of the zeolite contained in Catalyst No. 7 is 2.56 nm, which is outside the preferred range of 2.420-2.445 nm of the aforementioned U.S. Patent No. 4,401 • · * 556.

• · · • · · • ·

However, Catalyst No. 8, which has an initial zeolite size of 2.437 at 35 nm within this range, has a comparable activity of 417 ° C but poor selectivity (56% by weight). From the above examples, it is clear that

II

97027 25 that the degree of NH3-TPD acidity of the zeolite component affects the overall performance of the hydrocracking catalyst.

The zeolite starting material of Part B is, as previously stated, clearly within the best value ranges for the zeolite described in the aforementioned prior art patent US-4,401,556. It is a commercially available substance with an elementary beaker size of 2.437 nm and has undergone hydrothermal treatment.

A deviation from the zeolite of the present invention, which fits within the limits best found in said publication, has an ion exchange capacity of 0.171 as determined by said publication. This material was used in Catalyst No. 8. The said publication states that the ion exchange capacity should not exceed 0.07.

The dry calcination in question converts the substance used in catalyst 8 into a catalyst used for the preparation of catalyst 5. The selectivity of the catalyst 5 is better with the same activity and is therefore a better catalyst. However, the difference in the elementary box sizes of the zeolites of catalysts 5 and 8 is almost insignificant. Therefore, the process of the invention improves the selectivity of the catalyst by a factor much higher than would be predictable based on the change in cone size. In a better catalyst. !! The ion exchange capacity of the zeolite E used was 0.091.

• · • «* · .1 This exceeds the upper limit mentioned in the said publication by 28 • · '···'%.

0 • · '· · · • · * 00 00 · · · • ·

Claims (8)

A hydrocracking process for the production of medium distillates having boiling points of 149-371 ° C, wherein a hydrocarbon feed stream is passed into contact with a catalyst composition comprising a refractory inorganic oxide matrix and a hydrogen-shaped Y-type zeolite having a unit cell size between 2 , 42 and .25 2.44 nm, in hydrogen cracking conditions and a product stream is recovered, characterized by using a low acidity zeolite having an ion exchange capacity greater than 0.07, and the content of bound hydroxyl groups sufficient * to provide an NH3-TPD acidity strength value less than 2.00. 2. The process according to claim 1, characterized in that a: hydrocarbon feed stream containing at least 50% by volume of components boiling above 371 ° C is contacted with a catalyst composition containing as combination (i) a hydrogenating component , (ii) an oxide matrix comprising aluminum oxide and (iii) a hydrogen Y-type aluminum silicate zeolite having an NH3-TPD acidity strength value of less than 1.50. 97G27 Method according to claim 2, characterized in that said composition comprises between 2% by weight and 20% by weight of said zeolite. 5 Method according to claim 2, characterized in that said refractory inorganic oxide matrix comprises a mixture of alumina and silica-alumina. Process according to claim 4, characterized in that said matrix comprises between 45% by weight and 90% by weight silica-alumina and also comprises between 5 and 45% by weight alumina. Process according to claim 2, characterized in that said hydrogen component is selected from the group VIB metals, group VIII metals and combinations thereof. Process according to claim 2, characterized in that the group VIB component is selected from the group consisting of molybdenum, tungsten and compounds thereof and the group VIII metal component is selected from the group consisting of nickel, cobalt and compounds thereof. 8. Average distillate selective hydrocracking catalyst composition, characterized in that it comprises in combination: (i) a hydrogen component, (ii) a refractory inorganic oxide feed containing alumina, and (iii) a crystalline. #> / • · * ··· 'Hydrogenated Y-type aluminum silicate zeolite having a typical X-ray diffraction pattern for zeolite Y and an ion exchange capacity greater than 0.07, a unit cell size between 2 , 42 and 2.44 nm and an NH3-TPD acidity strength value of less than 1.50. · «« · * ·· e · «(« t, I