FI88682B - FOERFARANDE FOER RAFFINERING AV OLJA - Google Patents

Abstract

The invention relates to a process for preparing a diesel oil fraction with a high cetane number. According to the invention a charge containing light olefins is oligomerized in the presence of a zeolite catalyst to prepare a product composition which at least partially comprises C3/4 theta hydrocarbons. The product composition thus obtained is hydrogenated to form a diesel oil fraction. According to the invention the catalyst used comprises a ZSM-5 zeolite catalyst, whose hydroogen ions have, at least partially been exchanged for Ca<2> &copy& ions. By means of the invention it is possible to prepare diesel oil fraction with a cetane number higher than 49.

Description

68682

The present invention relates to a process for refining oil according to the preamble of claim 1.

According to such a process, the starting material containing light olefins in particular is oligomerized in the presence of a zeolite catalyst to produce a diesel oil product.

10 ZSM-5 zeolite has extensive use as a catalyst for the oil industry. Thus, it is used e.g. as an additive or promoter in a cracking catalyst (FCC), in the manufacture of synthetic gasoline (MTG), in the conversion of propane and butane to aromatics (Cyclar), and in the selective hydrocracking of n-paraffins (M-forming and Dewaxing). In addition, zeolites and in particular ZSM-5 are known to act as catalysts for the alkylation of aromatics and the oligomerization of olefins.

By the latter process, a mixture of light olefins rich in C 1-4 hydrocarbons can be prepared, from which, after hydrogenation, diesel-grade products are obtained.

The use of ZSM-5 zeolite as a catalyst for oil refining is mainly based on its shape selectivity and its low coke formation rate compared to other zeolites.

The lattice structure of the zeolite is formed by silicon and aluminum cations connected tetrahedrally by an oxygen bridge. Since the charge of silicon in zeolite is +4 and that of aluminum is +3, a third cation is needed to stabilize the lower positive charge relative to aluminum silicon. The stabilizing cation may be e.g. sodium, potassium or hydrogen. ZSM-5 is normally prepared with sodium as its stabilizing cation at the ion exchange site. Because the ZSM-5 zeolite in this form is not catalytically active, the sodium ion must be at least partially converted to a hydrogen ion, creating acid sites in the zeolite that catalyze several reactions typical of oil refining.

Of the numerous patents dealing with the preparation of conventional ZSM-5 basic zeolites, mention should be made in particular of U.S. Pat. No. 3,702,886.

It is known that in addition to the alkali metals mentioned above, other basic cations, such as Ca, Cs, Sr and Ba, can be ion-exchanged in the zeolite. The catalytic properties of the zeolite can be affected by ion exchange. Thus, for example, Ca ion has been found to improve the stability of zeolite catalyst 2 88682 when converting methanol to gasoline. U.S. Patent No. 4,675,460 discloses the use of a Ca-modified ZSM-5 zeolite catalyst in a process in which light olefins are first oligomerized with a Ca-modified (or other basic cation-modified gas-catalyzed) ZSM-5 zeolite catalyst to further gasoline grade.

The present invention is based on the surprising finding that the use of Ca-modified ZSM-5 zeolite as a catalyst for the oligomerization of light olefins gives a product mixture having a higher cetane number after hydrogenation than a product mixture prepared using 0 unmodified ZSM-5 zeolite.

More specifically, the method according to the invention is mainly characterized by what is set forth in the characterizing part of claim 1.

Significant advantages are achieved by the invention. Thus, by using Ca-modified ZSM-5 zeolite, it is possible to significantly increase the cetane number of the hydrogenated diesel product obtained in the oligomerization of light olefins. As can be seen from the application examples below. was the engine cetane number of the hydrogenated diesel product without Ca modification from 45 to 47 when the Ca-modified zeolite catalyst was used. Therefore, according to the invention, the need for additives normally used to increase the cetane number can be substantially reduced or even eliminated.

In particular, it should be noted that the increase in cetane number is not due to an increase in average molecular size. The experimental runs shown below were carried out in such a way that the average carbon number of the product obtained with the Ca-modified zeolite catalyst-5 was lower or at most equal to that of the product obtained with the unmodified catalyst.

The invention will now be examined in more detail by means of a detailed description and a few application examples.

A. Preparation of the catalyst

The Ca-modified catalyst base zeolite used in the invention is prepared, for example, as described in U.S. Patent No. 3,88682. The base zeolite is required to have an optimal pore size for shape selectivity when oligomerizing light olefins to hydrocarbons, which can be separated by distillation of, for example, high quality diesel fuel or isoparaffinic solvent. The Si / Al ratio of the base zeolite and at the same time also the Ca-modified zeolite is preferably less than 5 to 400, more preferably about 30 to 200.

The Ca ion exchange is performed on the zeolite in the H + form. It does not matter whether the zeolite is converted to the H + form already at the synthesis stage or only by ion exchange after synthesis. In addition, the zeolite may contain small amounts of Na ions, preferably less than 1000 ppm.

10

Ca ion exchange can be performed in either the liquid phase or the solid phase. Typically, however, it is done with a calcium salt dissolved in water. The technique is well known. Typically salts used are chlorides, nitrates, sulfates and acetates. In the present invention, the Ca ion is exchanged for zeolite from a calcium acetate solution. The amount of calcium 15 in solution relative to the zeolite depends essentially on the zeolite used and is typically between 1 and 10,000 μ 000ηοΐ Ca 2+ / g zeolite, preferably 5 to 2,000 μπιοί Ca 2+ / g zeolite. The molarity of the calcium acetate solution is typically between 0.005 and 1 M, preferably between 0.05 and 0.5 M.

The ion exchange is carried out with good stirring at a temperature of 25 to 100 ° C, preferably 40 to 90 ° C.

The ion exchange time is 0.1 to 4 h, preferably 0.5 to 2 h. The ion-exchanged zeolite is washed with hot water. The sample is dried at 100-120 ° C overnight. The calcination is performed at 500 ° C, 3 h. The calcination can be performed in air, vacuum or in an inert gas.

After drying and calcination, the amount of deionized or impregnated calcium in the zeolite is 0.01 to 1.0% by weight, preferably 0.05 to 0.5% by weight. Too high amounts of calcium may impair the activity of the catalyst. However, within the concentration limits given above, calcium does not impair the activity of the zeolite, but on the contrary may in some cases even improve it.

Once the zeolite is ion-exchanged Ca and calcined, it can be used as the active part of the catalyst. Because the catalyst is often required to have certain physical, thermal, and mechanical properties, the zeolite is mixed with a support that is generally inert to the reaction. The support can also act catalytically in some cases. Typical carriers include 4,886,882 various clays, silica, aluminas and other metal oxides. They can be naturally occurring or synthetic. The carrier may also be a mixture of several metal oxides. Various organic and inorganic additives and binders can also be used in the preparation of the catalyst, for example methylcellulose. The size of the catalyst particles varies depending on the reactor type and the diameter. Catalyst particles with a size of 0.149-0.350 mm were used in the microreactors. Experimental runs were also performed in a larger reactor with a catalyst particle size of 0.35 to 1.0 mm or 1.0 to 2.0 mm. The catalyst was typically 2 to 20 g in the microreactor and typically 50 to 200 g in the larger reactor.

0 B. Oligomerization

The present invention uses Ca-modified ZSM-5 zeolite as a catalyst in the oligomerization of light C2-C6 olefins, preferably n-butene, to C5-Cn hydrocarbons. The products are typically mixtures of branched olefins. Aromatics are not present in the products or are present in an amount of less than 0.2% by weight. Gasoline, kerosene and diesel fractions are separated from the oligomerization product by distillation. For the purposes of this application, diesel fraction means a fraction distilling between 200 ° and 320 ° C. It should also be noted that several different solvents containing branched paraffinic hydrocarbons can be distilled from the oligomerization product.

The oligomerization is carried out at a temperature of 160 ° to 350 ° C, preferably 200 ° to 310 ° C and a pressure of 1 to 150 bar, preferably 10 to 80 bar. It has been found that pressure promotes the reaction. As the pressure increases, special requirements are placed on the reaction equipment to such an extent that it is generally not appropriate to use pressures above 150 bar. Likewise, raising the temperature increases the conversion. However, too high temperatures may result in an excessive cracking and aromatization reaction instead of oligomerization. Flow rates vary depending on the oligomerization reactor. In a conventional tubular reactor, the WHSV is generally 0.5 to 10, preferably about 1 to 5. Flow rates and temperatures can also be changed during the reaction to provide a uniform degree of conversion.

0 Ca modification increases the cetane number of the hydrogenated diesel fraction compared to the unmodified ZSM-5 catalyst. The cetane number improves by at least 2 units, usually from a level of about 45 to a level of about 50. The cetane numbers mentioned in the examples below are defined as so-called motor cetane numbers.

5 * 5 8 682

In the context of the invention, it has been found that with a Ca-modified zeolite catalyst, the desired high cetane number diesel products can be produced in high yield by a process in which the starting product consisting mainly of light olefins is contacted with said zeolite at least twice. The process according to the invention is carried out, for example, in that the olefin feed is first pre-oligomerized in the presence of a Ca-modified zeolite in order to increase the proportion of the C8 + fraction, after which the actual oligomerization is carried out. Alternatively, the product from the oligomerization can be fed a second time through the same catalyst bed to increase the diesel yield. The invention differs in this respect from, for example, the prior art according to U.S. Pat. No. 4,675,460, in which the product obtained from the first oligomerization must be alkylated in the presence of a Friedel-Crafts catalyst in order to obtain diesel-grade products.

According to an alternative, the process according to the invention is carried out in several successive, series-connected reactors, all of which use a similar Ca-modified zeolite-15 ladder catalyst.

In a process based on recycling or several successive oligomerization reactors, the first oligomerization of the C4 fraction results in a product stream containing 10 to 90% by weight, preferably 40 to 80% by weight of C5 + olefins. The product stream then contains at least some, usually about 5 to 50% by weight of C8 + components, and also contains C '+ fractions (about 5 to 25%). The latter are thus formed already in the first oligomerization step and their proportion increases when the mixture is re-contacted with the catalyst.

The product mixture obtained from the oligomerization is hydrogenated in a manner known per se, e.g. with hydrogen gas in the presence of a nickel catalyst, to form a diesel-class product.

It should also be noted that although the experimental results presented below have been obtained in laboratory reactors fed almost 100% olefins, the method also works on an industrial scale. wherein the olefin content of the feed is 20 to 100%, usually about 30 to 95%.

3G Paraffins that may be present in the feed stream do not interfere with oligomerization to a greater extent.

The product according to the invention can be used as such as diesel fuel or it can be mixed with conventional amounts of straight-run fractions.

The invention will now be examined in more detail by means of application examples.

5 Example 1

Preparation of Ca-Modified Zeolite Catalyst ZSM-5 zeolite was prepared as described in U.S. Patent No. 3,702,886. Na-ZSM-5 was ion-exchanged three times with NH 3 NO (3 M) solution with constant stirring. For each gram of zeolite, 15 g of ammonium nitrate solution was used. One ion exchange lasted 1.5 hours. The temperature of the ion exchange solution was 80 ° C. After ion exchanges, the zeolite was washed with hot water, 100 ml water / 1 g zeolite. Drying was performed at 110 ° C overnight. Calcination was performed at 540 ° C for 3 hours.

The 5 Ca ion exchange was performed after the ammonium nitrate ion exchanges described above. The ion exchange solution was made by stirring 100 ml of calcium acetate solution (1 M) in 900 ml of water. 50 g of zeolite were mixed into the solution. During the ion exchange, the solution was stirred continuously. The temperature of the solution was 80 ° C and the ion exchange time was 1 hour. After ion exchange, the zeolite was washed with hot water, 100 g water / 1 g zeolite. The zeolite was then dried at 110 ° C. The stirring was performed at 0,500 ° C for 3 hours. After ion exchange, the calcium content of the zeolite was 0.24% by weight.

35% by weight of SiO 2 support (Silica gel, Ludox AS-40) was added to the zeolite. After addition of support, the catalyst was dried and stirred (540 ° C, 3 h). The catalyst was screened to a particle size of 1.0 to 2.0 mm.

j

Example 2

Preparation of Ca-modified zeolite catalyst

Zeolite preparation and NH 4 NO 2 ion exchange were performed in the same manner as in Example 1. Ca 2+ ion exchange was performed by stirring 25 ml of calcium acetate solution (1 M) in 975 ml of water. 50 g of zeolite were mixed into the solution. The ion exchange was performed as in Example 1. The Ca content of the zeolite after ion exchange was 0.092 wt%. Addition of carrier as in Example 1.

Example 3 (comparison)

Use of unmodified zeolite catalyst in oligomerization; Properties of the diesel fraction Fraction 7 83 682 5 200 g of catalyst were charged to a 30 mm diameter steel tube reactor. The size of the catalyst particles was 1.0 to 2.0 mm. First, 1-butene was fed through the catalyst bed. To increase the diesel yield, the product obtained was fed once more through the same catalyst. Liquid supply composition C4 = 42.2%, Cg = 42.4%, C11 + = 11.3%, Cs + C6 + C7 + C9 + C10 = 4.1% 10

Test conditions

Reactor temperature (° C) 240-280

Pressure (bar) 50 WHSV (h1) 1 15 Catalyst unmodified ZSM-5

The product was collected in a refrigerated container. The product was distilled at the following cutting points:

Distillation fractions 20 TA-30 ° C total gases 30-180 ° C petrol 180-200 ° C kerosene 200-285 ° C diesel 285-TL base 25

The yield of the diesel fraction was 23.1%. The diesel fraction was hydrogenated before analyzing the product properties. The engine fraction of the diesel fraction (TA 200 ° C, TL 285 ° C) was 45. The average carbon number was 13.25. The other product analyzes were as follows:

product Analysis

Density (15 ° C, kg / m3) 778.2

Bromine number 0.3

Viscosity (mm2 / s, 20 ° C) 2.08 35 Cloud point (° C) (-50 Freezing point (° C) (-50

Filterability (° C) (-50 8 88682

Example 4 (comparison)

Properties of the distillate fraction distilled at different intersections

The product obtained from the tubular reactor of Example 3 was distilled at different intersections.

5

The product was collected in a refrigerated container. The product was distilled at the following cutting points:

Distillation fractions 0 AL-30 ° C total gases 30-180 ° C petrol 180-200 ° C kerosene 200-315 ° C diesel 315-LP base: 5

The yield of the diesel fraction was 23.1%. The diesel fraction was hydrogenated before the analysis of the product properties. The engine fraction of the diesel fraction (TA 200 ° C, TL 315 ° C) was 46. The average carbon number was 13.45. Other product analyzes were as follows: o

product Analysis

Density (15 ° C, kg / m3) 798.8

Bromine number 0.4

Viscosity (mm2 / s, 20 ° C) 2.60 '5 Cloud point (° C) (-50 Freezing point (° C) (-50

Filterability (° C) (-50

Example S

Use of Ca-modified zeolite in oligomerization; diesel (grain fraction properties 200 g of catalyst were charged to a 30 mm diameter steel tube reactor. Catalyst particles ranged in size from 1.0 to 2.0 mm. First, 1-butene was fed through the catalyst bed. To increase the diesel yield, the resulting product was fed once more through the same catalyst. Composition C4 = 43.9%, CK = 40.6%, Cn + = 11.2%, C5 + C6 + C7 + C9 + C10 = 4.3% 9 88682

Test conditions:

Reactor temperature (° C) 240-270

Pressure (bar) 50 WHSV (h1) 1 5 Catalyst Ca-modified ZSM-5

The product was collected in a refrigerated container. The product was distilled at the following cutting points:

Distillation fractions 10 TA-30 ° C total gases 30-180 ° C petrol 180-200 ° C kerosene 200-318 ° C diesel 318-TL base 15

The yield of diesel was 23.4%. The diesel fraction was hydrogenated before analyzing the product properties. The engine fraction of the diesel fraction (TA 200 ° C, TL 318 ° C) was 50. The average carbon number was 13.10. The other product analyzes were as follows:

product Analysis

Density (15 ° C, kg / m3) 783.6

Bromine number 1.8

Viscosity (mm2 / s, 20 ° C) 2.74 25 Cloud point (° C) (-50 Freezing point (° C) (-50

Filterability (° C) (-50

Example 6 (Comparative) Use of an unmodulated zeolite catalyst in oligomerization; diesel (grain fraction properties 50 g of catalyst was charged to a 30 mm diameter steel tube reactor. The size of the catalyst particles was 0.5 to 1.0 mm. First 1-butene was fed through the catalyst bed. To increase the diesel yield, the obtained product was fed once more through the same catalyst. Liquid supply composition C4 = 55.0%, Cs = 33.2%, C11 + = 9.3%, C5 + C6 + C7 + C, + C, O = 2.5% 10 83682

Test conditions:

Reactor temperature (° C) 210 - 235 5 Pressure (bar) 50 WHSV (h1) 10 - 3

Catalyst unmodified ZSM-5

The product was collected in a refrigerated container. The product was distilled at the following cut points: 0

Distillation fractions TA-30 ° C total gases 30-180 ° C petrol 180-200 ° C kerosene 5 200-317 ° C diesel 317-TL base

The yield of the diesel fraction was 37%. The diesel fraction was hydrogenated before analyzing the product properties. The engine fraction of the diesel fraction (TA 200 ° C, TL 318 ° C) was 46. The average carbon number was 13.23. Other product analyzes were as follows:

product Analysis

Density (15 ° C, kg / m3) 784.4 Bromine number 0.4

Viscosity (mm 2 / s, 20 ° C) 2.68

Cloud point (° C) (-50 Freezing point (° C))

Filterability (° C) (-50; 0

Example 7 (comparison)

Properties of the diesel fraction distilled at different points S The product obtained from the tubular reactor of Example 6 was distilled at different points.

The product was distilled at the following cut points: i 11 88682

Distillation fractions TA-30 ° C total gases 5 30-180 ° C petrol 180-205 ° C kerosene 205-318 ° C diesel 318-TL base 10

The yield of the diesel fraction was 31.7%. The diesel fraction was hydrogenated before analyzing the product properties. The engine fraction of the diesel fraction (TA 205 ° C, TL 318 ° C) was 47. The average carbon number was 13.61. Other product analyzes were as follows: 15 Product analysis

Density (15 ° C, kg / m3) 788.9

Bromine number 1.4

Viscosity (mm2 / s, 20 ° C) 2.75 20 Cloud point (° C) (-50 Freezing point (° C) (-50

Filterability (° C) (-50 25 Example 8

Use of a Ca-modified zeolite catalyst in oligomerization; properties of the diesel fraction 50 g of catalyst were charged to a 30 mm diameter steel tube reactor. The size of the catalyst particles was 0.35 to 1.0 mm. First, 1-butene was fed through the catalyst bed. To increase the diesel yield, the product obtained was fed once more through the same catalyst. Liquid feed composition C4 = 56.1%, C8 = 34.3%, C11 + = 6.8%, C3 + C6-1-C7-1-C9-1-C10 = 2.8%.

Experimental conditions: 35 Reactor temperature (° C) 260-305

Pressure (bar) 50 WHSV (h ') 8 - 2

Catalyst Ca-modified ZSM-5 40 The product was collected in a refrigerated vessel. The product was distilled at the following cutting points: 12 H S 6 ö 2

Distillation fractions TA-30 ° C light gas 30-180 ° C petrol 180-200 ° C kerosene 5 200-317 ° C diesel 317-TL base

The yield of the diesel fraction was 41%. The diesel fraction was hydrogenated before analyzing the product properties.

0 The engine fraction of the diesel fraction (TA 200 ° C, TL 317 ° C) was 50. The average carbon number was 13.32. Other product analyzes were as follows:

Product analysis 5 Density (15 ° C, kg / m3) 774.4

Bromine number 1.2

Viscosity (mm 2 / s, 20 ° C) 2.64

Cloud point (° C) (-50 Freezing point (° C) (-50 0 Filterability (° C) (-50

Claims (13)

13 88 682 A process for preparing a high cetane number diesel oil fraction, which process comprises 5. oligomerizing a light olefin-containing feedstock in the presence of a zeolite catalyst to form a product mixture consisting at least in part of CM + hydrocarbons, and - hydrogenating the product mixture thus obtained to produce a diesel oil fraction a ZSM-5 zeolite catalyst is used in which at least some of the hydrogen ions have been converted to Ca 2+ ions. Process according to Claim 1, characterized in that a diesel oil fraction having a Cetane number of more than 47, preferably more than 49, is prepared. Process according to Claim 1 or 2, characterized in that a Ca-modified ZSM-5 zeolite is used in which the Si / Al ratio is less than 400, preferably 30-200. Process according to one of Claims 1 to 3, characterized in that a Ca-modified ZSM-5 zeolite is used which contains 0.01 to 1.0% by weight, preferably 0.05 to 0.5% by weight, of ion-exchanged calcium. Process according to one of the preceding claims, characterized in that the oligomerization is carried out at a temperature of 160 ° to 350 ° C, preferably 200 ° to 310 ° C and 1 to 150 bar, preferably 10 ° C. ... at a pressure of 80 bar. Process according to one of the preceding claims, characterized in that a starting material containing 20 to 100% by weight, preferably 30 to 95% by weight, of olefins is introduced into the oligomerization. 30: Process according to one of the preceding claims, characterized in that a hydrocarbon fraction containing from 10 to 95% by weight, preferably from 40 to 80% by weight, of C 5+ olefins is used as starting material. 14 S 8 682 Process according to Claim 7, characterized in that the starting material contains at least some, preferably 5 to 50% by weight, of C 8+ olefins. Process according to Claim 7 or 8, characterized in that the starting material for oligomerization 5 is obtained by pre-oligomerizing a hydrocarbon fraction consisting of at least substantially light hydrocarbons in the presence of a Ca-modified ZSM-5 zeolite catalyst. Process according to Claim 9, characterized in that a catalyst similar to that used in the actual oligomerization is used in the pre-oligomerization. 0 Process according to one of the preceding claims, characterized in that the oligomerization starting material is obtained by combining part of the oligomerization product mixture with a fresh feed containing light olefins. . 5 Process according to Claim 6, characterized in that the oligomerization is carried out in a single reactor in which part of the oligomerization product stream is recycled and combined with the fresh feed of light olefins. Process according to Claim 6, characterized in that the oligomerization. i> 5 S8682 Paten tkrav: