FI96320C - Method for oligomerization of alkenes - Google Patents

Abstract

The invention relates to a process for the oligomerization of light alkenes, in particular butenes, for the preparation of diesel oil and lubricating oil fractions having an improved cetane number and an improved viscosity index, in the presence of a chromium-containing ZSM-5 zeolite catalyst in temperature and pressure conditions which maintain oligomerization. The catalyst used in the process is an HZSM zeolite to which chromium in an amount of 0.7-5 wt.% of the weight of zeolite has been added by the impregnation technique or the dry ion exchange technique.

Description

96320

A process for the oligomerization of ai ee

The present invention relates to a process for the oligomerization of light alkenes, in particular butenes 5, in the presence of ZSM-5 zeolite catalysts to diesel and lubricating oil fractions with improved properties, in particular an improved cetane number and a viscosity index.

Light alkenes can be oligomerized to heavier hydrocarbons with zeolites in acid form 10. The temperature must be sufficiently high (above 170 ° C) and it is also advantageous to use high pressure for oligomerization. Although petrol-grade hydrocarbons (boiling below 180 ° C) are always produced as an oligomerization product, in the oligomerization of light alkenes, it makes sense to maximize the proportion of more valuable products such as high quality diesel, paraffinic solvents and lubricating oils.

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When alkenes are oligomerized with a zeolite catalyst, the cold properties of the product are generally good. However, the quality of the products is strongly influenced by the degree of branching of the products. If a non-form-selective catalyst is used as the catalyst, the branching is strong. Branching lowers the cetane number of diesel and the value of the viscosity index of lubricating oil 20. Thus, it is preferable to use a shape-selective zeolite catalyst with which the branching of the oligomerization products can be reduced. Particularly suitable catalysts are zeolite catalysts with a pore size close to that of ZSM-5 (5.1 * 5.5 Å). The use of the HZSM-5 catalyst as an oligomerization catalyst is also • justified by its low coke formation and stability at high temperatures. The quality and yield of the oligomerization products can be affected by changing either the reaction conditions or the properties of the oligomerization catalyst.

The use of HZSM-5 zeolite as an oligomerization catalyst is well known. HZSM-5 zeolite: the properties have been influenced e.g. by varying its aluminum content and particle size 30 (US 4,517,399), the amount of metal ions in the crystal (US 4,554,396) and ion exchange sites (US 4,542,251). In addition, the acidity distribution of HZSM-5 zeolite has been modified, for example, by dealumination (U.S. Pat. No. 5,043,307) or by selective destruction of acid sites on the outer surface (U.S. Pat. No. 4,520,221).

2,96320

It is also known to modify the ZSM-5 zeolites used in oligomerization by replacing a certain amount of the original cations, e.g. Zn, Ni, Pt, Pd, Re and Cr cations. Typically, lice replacement is performed by an ion exchange technique in which the zeolite is treated with a dilute aqueous solution of a salt containing an exchangeable cation. Thus, for example, U.S. Pat. No. 3,960,978 discloses ZSM-5 catalysts containing small amounts of chromium and zinc, which have been applied to the oligomerization of light alkenes, mainly propylene, to gasoline fractions.

The present invention relates to a process for the oligomerization of light alkenes, in particular butenes, using chromium-containing HZSM-5 zeolites as catalyst. According to the invention, it has surprisingly been found that the addition of at least a certain amount of chromium to HZSM-5 zeolite and the application of the catalyst thus obtained for the oligomerization of light alkenes, in particular butenes or butene-containing hydrocarbon mixtures, gives in good yield The viscosity index.

The method according to the invention is mainly characterized by the features set forth in claim 1.

It is not possible to obtain the desired amount of chromium ions from the solution phase by ion exchange to ZSM-5 zeolite because they form large complexes with water molecules. Therefore, according to the invention, chromium is added to the HZSM-5 zeolite in two alternative ways. In the impregnation technique, the zeolite is treated with a chromium salt solution with a volume at most equal to the total pore volume of the zeolite. Preferably, a volume of solution approximately equal to said pore volume is used. The zeolite is then rebelled in a manner known per se by heating to a temperature of 300-800 ° C. In this case, the so-called kuivaimpregnointitekniikka.

Alternatively, the chromium salt is dry blended with the zeolite to form a homogeneous mixture. The zeolite is then rebelled in a manner known per se, in which case some of the cations of the zeolite are replaced by chromium. In this case, the so-called , the dry-onivaihtotekniikka.

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The amount of chromium in the zeolite can be controlled by changing the amount of chromium in the impregnation solution or chromium salt-zeolite mixture. The amount of chromium in the zeolite can also be varied by using different chromium salts in the starting mixture. According to the invention, the amount of chromium in the HZSM-5 zeolite is between 0.7 and 5% by weight, preferably 1 to 3% by weight, based on the weight of the zeolite. As the chromium source, water-soluble chromium salts, for example chlorides or nitrates, can be used in the dry impregnation. Any suitable chromium compounds can be used in the dry ion exchange technique.

After the addition of chromium, silica can be added to the zeolite as a support, which makes the catalyst harder and mechanically more durable. The addition of silica is preferably carried out by mixing silica with zeolite as a colloidal solution before calcining the catalyst.

The cetane number of the diesel fraction of the oligomerization product obtained by using HZSM-5 zeolite to which chromium has been added as the oligomerization catalyst is considerably higher than when using the corresponding HZSM-5 zeolite as the catalyst. Correspondingly, the viscosity index of the lubricating oil fraction of the oligomerization product is high.

The process according to the invention makes it possible to oligomerize light alkenes, such as Q-C6 alkenes or mixtures thereof. The feedstocks can be pure or they can be refinery streams containing 20 different alkenes and alkanes. Preferably, the process according to the invention is suitable for the oligomerization of butene-containing hydrocarbon mixtures for diesel and lubricating oil fractions.

The oligomerization is usually carried out at a temperature of 160 to 350 ° C, preferably 200 to 310 ° C, preferably 10 to 80 bar. 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 achieve a uniform degree of conversion.

It is also possible to apply the process according to the invention in such a way that the catalyst is placed in two or more separate reactors. Particularly preferably, the zeolite catalysts modified according to the invention can be applied in an oligomerization plant according to Finnish patent application FI925608, in which 4,963,20 two or more side reactors are connected to the distillation column. The catalyst is then placed in side reactors, which can be in series or in parallel. In this case, substantial further improvements are obtained in the cetane numbers and viscosity indices of the diesel and lubricating oil fractions. The invention is described in more detail below with reference to the following examples.

Example 1

A zeolite of the ZSM-5 type was prepared by the following method known per se (US 10,392,782). 5.25 kg of water glass and 6.57 kg of water were mixed together. The second solution was prepared by mixing together 322 g of Al 2 (SO 4) 3 * 18 H 2 O, 657 g of tetrapropylammonium bromide, 1965 g of NaCl, 473 g of 95% H 2 SO 4 and 9 kg of water. The solutions were mixed. The combined solution was placed in an autoclave. The reaction temperature was 100 ° C and the reaction time was 6 days. After washing and calcination, the sodium ions of the zeolite were exchanged for ammonium ions using NH 4 NO 3 solution, after which the NH 4 -ZSM-5 zeolite was calcined at 500 ° C for 2 hours. In this case, ammonium ions decompose and H-ZSM-5 zeolite is formed. The aluminum content of the H-ZSM-5 zeolite was 1.6% by weight. The zeolite was screened to a grain size of 0.15 to 0.35 mm. This zeolite was used as a reference catalyst.

20 Example 2

The HZSM-5 zeolite prepared according to Example 1 was impregnated with a chromium nitrate solution. The HZSM-5 zeolite was dried at 400 ° C. To the dry HZSM-5 zeolite was added an amount of chromium solution corresponding to the total pore volume of the zeolite. One mole per mole of aluminum in HZSM-5 zeolite was added to the chromium 25 zeolite. After the addition of the chromium solution, the zeolite was calcined at 500 ° C for two hours. The zeo compound contained 2.4 wt% chromium after calcination. Chromium zeolite was screened to a grain size of 0.15-0.35 mm.

30 Example 3

The HZSM-5 zeolite prepared according to Example 1 was impregnated using a chromium chloride solution. The impregnation was performed according to Example 2. The zeolite contained 2.1 wt% chromium after calcination. The aluminum in the zeolite was 1.5% by weight. Chromium zeolite was screened to a grain size of 0.15 to 0.35 mm.

5 Example 4

To the HZSM-5 zeolite prepared according to Example 1 was added chromium in the solid phase. The chromium nitrate salt and HZSM-5 zeolite were mixed thoroughly. The mixture of chromium nitrate and HZSM-5 zeolite was made by adding one mole of chromium nitrate chromium per mole of aluminum in HZSM-5 zeolite. The mixture was then treated at 500 ° C under a stream of nitrogen for two hours. After the heat treatment, the zeolite was washed three times with distilled water. 5 g of wash water per gram was used in one wash. The chromium zeolite was then dried at 400 ° C. The chromium in the zeolite was 2.5% by weight after drying. Chromium zeolite was screened to a grain size of 0.15-15.35 mm.

Example 5

To the HZSM-5 zeolite prepared according to Example 1, chromium was added in a solid phase using a chromium chloride salt. Solid ion exchange was performed according to Example 4. The chromium in the zeolite after drying was 1.7% by weight. The aluminum in the zeolite was 1.4% by weight. Chromium zeolite was screened to a grain size of 0.15 to 0.35 mm.

Example 6 A sample was prepared from the zeolite described in Example 2 by adding colloidal SiO 2 solution Ludox AS-40. To 20 g of zeolite was added 27 ml of colloidal solution. The catalyst was shaped,. dried and crushed to a grain size of 0.15 to 0.35 mm and calcined at 500 ° C. The catalyst content of the catalyst was 35% by weight.

30

Example 7

The zeolite of Example 1 was tested in a microreactor at a pressure of 50 bar to a temperature of 230 ° C at a temperature of 6,963,20. The zeolite was diluted 1: 3 by volume with silicon carbide. The WHSV was 5 g feed / h / g catalyst. The feed was an oil refining stream with the following composition in weight percent:

Propane 1.15 wt% 5 Butanes 57.5 wt%

Butenes 42.3 wt%

The conversions of butenes during the run were as follows: 10 Catalyst age 19.1 30.5 38.0 121.4 134.0 142.9 153.0 g feed / g catalyst

Conversion, p% 99 99 99 96 93 93 92

The GC cetane number was determined from the collected samples. The GC cetane number is the value calculated from the GC analysis, which corresponds to the motor cetane number. The GC-cetane numbers determined from the samples were 48-49. 11% by weight of coke had formed in the catalyst.

Example 8 The zeolite of Example 2 was tested in a microreactor as in Example 7. At a catalyst age of 39 g feed / g catalyst, the WHSV was changed from 5 to 2 g feed / h / g catalyst.

The conversions of butenes during the run were as follows:

Catalyst age 19.1 29.0 38.9 91.0 97.7 102.3 g feed / g catalyst: Conversion, wt% 73 67 65 74 84 92 30 The GC-cetane numbers determined from the samples ranged from 52 to 53. Coke to the catalyst had formed 9% by weight.

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Example 9 7 96320

The zeolite of Example 3 was tested in a microreactor as in Example 7. With a catalyst age of 119 g feed / g catalyst, the WHSV was changed from 5 to 3 g feed / h / g 5 catalyst.

The conversions of butenes during the run were as follows:

Catalyst age 20.9 31.2 42.4 118.5 127.6 132.9 139.1 10 g feed / g catalyst

Conversion, wt% 91 89 87 83 88 91 92 The GC-cetane numbers determined from the samples were 50-51. 12% by weight of coke had formed in the catalyst.

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Example 10

The zeolite of Example 4 was tested in a microreactor in the same manner as in Example 7.

20 The conversions of butenes during the run were as follows:

Catalyst age 21.5 31.4 40.1 117.0 126.6 137.6 147.3 g feed / g catalyst

Conversion, wt% 99 99 99 95 91 91 89 25 The GC-cetane numbers determined from the samples ranged from 48 to 49. 10% by weight of coke had formed on the catalyst.

Example 11 30

The zeolite of Example 5 was tested in a microreactor as in Example 7. The conversions of butenes during the run were as follows: 8,96320

Catalyst age 21.6 31.8 39.4 120.0 136.5 146.6 g feed / g catalyst

Conversion, wt% 98 96 94 85 76 72 5 The GC-cetane numbers determined from the samples ranged from 49 to 50. 9% by weight of coke had formed on the catalyst.

Example 12 The catalyst of Example 6 was tested in a bench-scale oligomerization apparatus consisting of a distillation column and associated side reactors. The reaction apparatus is described in patent application F1 925608. The apparatus comprises a distillation column and two or more side reactors. Fresh feed and recycle feed from different altitudes of the distillation column are fed to the side reactors. The column pressure is typically less than 5 bar and the reactor pressure is typically more than 50 bar. The bench-scale experiment used three side reactors. Two of the reactors were connected in series and each contained 60 g of HZSM-5 catalyst. The first of these reactors was fed to a distillation column feed with a shear point mostly below 200 ° C. In addition, a refinery feed according to Example 7 was fed to both reactors. The third reactor contained 120 g of the catalyst prepared according to Example 6. A distillation column feed with a distillation range of mostly 120-250 ° C was fed to these 20 reactors. In addition, a refinery feed with 20 wt% propane and 80 wt% propylene was fed to this reactor. The reactor temperatures were 210-250 ° C in time and the pressures were 50 bar. The refinery feed flow rate to the first series-connected reactor was 280 g / h. The flow rate to the second series-connected reactor was 130 g / h. 150 g / h of refinery feed was fed to the third reactor 25. The product obtained on the basis of the distillation column was distilled. The results were as follows:

Distillation range, ° C TA-30 30-180 180-200 200-350 350-410 410+

Jae, p-% 6.0 18.5 10.6 53.9 8.6 2.5

The fraction was hydrogenated at 200-350 ° C. The product was then assigned an engine uncle number,

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30,996,320 which was 55. From the fraction 410 ° C + the viscosity was determined at 100 ° C and 40 ° C, from which the viscosity index was then calculated. The viscosity at 100 ° C was 6.71 mm 2 / cm and at 40 ° C 42.9 mm 2 / cm. The calculated viscosity index was 111. The fraction at 410 ° C + pour point was -48 ° C.

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Example 13

The catalyst of Example 6 was tested in the apparatus described in Example 12. The conditions were similar except for the refinery feed flow rates. The flow rates of the refinery feed 10 were: 280 g / h for the reactor connected to the first series, 60 g / h for the reactor connected to the second series and 90 g / h for the third reactor. The proportions of product obtained on the basis of the distillation column were as follows:

Distillation range ° C TA-30 30-180 180-200 200-350 350-410 410 + 15 Fraction, p -% __ 4.8 31.5 13.4 41.6 4.0 2.0

The fraction was hydrogenated at 200-350 ° C. The product was then subjected to a motor cetane number of 57. The viscosity of the fraction 410 ° C + was determined at 100 ° C and 40 ° C, from which the viscosity index was then calculated. The viscosity at 100 ° C was 7.07 mm 2 / cm and at 20 ° C 47.98 mm 2 / cm. The calculated viscosity index was 105.

Example 14

The commercial ZSM-5 catalyst was tested in the same experimental equipment under the conditions of Example 13. 90 g of catalyst were packed in each of the reactors connected in series. 316 g of catalyst were packed in the third reactor. The proportions of product obtained on the basis of the distillation column were as follows:

Distillation range, ° C TA-200 200-350 350-410 410+ 30 Fraction, wt% 19.7 54.7 17.5 5.0 10 96320

The fraction was hydrogenated at 200-350 ° C. The product was then subjected to a motor cetane number of 53. The viscosity was determined from the fraction 410 ° C + at 100 ° C and 40 ° C, from which the viscosity index was then calculated. The viscosity at 100 ° C was 7.54 mm 2 / cm and at 40 ° C 55.206 mm / cm. The calculated viscosity index was 98. The pour point was -45 ° C.

5

Example 15

The catalyst of Example 6 was tested in the apparatus described in Example 12. The conditions were similar except for the refinery feed flow rates. The flow rates at the refinery feed 10 were: 180 g / h for the reactor connected to the first series, 130 g / h for the reactor connected to the second series and 90 g / h for the third reactor. The proportions of product obtained on the basis of the distillation column were as follows:

Distillation range ° C TA-30 30-180 180-200 200-350 350-410 410+ 15 Fraction, p-% 3.5 20.2 8.6 57.3 7.4 2.5

The fraction was hydrogenated at 200-350 ° C. The product was then subjected to a motor cetane number of 55. The viscosity was determined from the fraction 410 ° C + at 100 ° C and 40 ° C, from which the viscosity index was then calculated. The viscosity at 100 ° C was 5.6 mm 2 / cm and at 20 ° C 32.4 mm 2 / cm. The calculated viscosity index was 111.

Example 16

The catalyst of Example 6 was tested in the apparatus described in Example 12. Conditions 25 were similar except for refinery feed flow rates. The refinery feed flow rates were: 180 g / h for the first series reactor, 60 g / h for the second series reactor and 150 g / h for the third reactor. On the basis of the distillation column: the proportions of the product obtained were as follows: 30 Distillation range ° C TA-30 30-180 180-200 200-350 350-410 410+

Jae, p-% 6.7 23.6 11.0 51.8 4.1 2.4 11 11 96320

The fraction was hydrogenated at 200-350 ° C. The product was then subjected to a motor cetane number of 55. The viscosity was determined from the fraction 410 ° C + at 100 ° C and 40 ° C, from which the viscosity index was then calculated. The viscosity at 100 ° C was 7.03 mm 2 / cm and at 40 ° C 47.5 mm 2 / cm. The calculated viscosity index was 105. The fraction at 410 ° C + pour point 5 was -48 ° C.

Example 17

The commercial ZSM-5 catalyst was tested in the same experimental equipment under the conditions of Example 16. 90 g of catalyst were packed in each of the reactors connected in series. 300 g of catalyst were packed in the third reactor. The proportions of product obtained on the basis of the distillation column were as follows:

Distillation range, ° C TA-200 200-350 350-410 410 + _ 15 Fraction, p-% 16.2 68.1 7.8 5.6

The fraction was hydrogenated at 200-350 ° C. The product was then subjected to a motor cetane number of 51. The viscosity was determined from the fraction 410 ° C + at 100 ° C and 40 ° C, from which the viscosity index was then calculated. The viscosity at 100 ° C was 7.84 mm 2 / cm and at 40 ° C 62.9 mm / cm. The calculated viscosity index was 87. The pour point was -42 ° C.

Example 18 The catalysts of Example 16 were regenerated at 500 ° C until all of the catalyst coke had been removed. The test run with regenerated catalyst was performed in a reactor apparatus,. which is described in Example 12. The regenerated catalysts were packed as follows: In two reactors connected in series, 60 g of the regenerated catalyst prepared according to Example 6 were packed in each. 120 g of HZSM-5 catalyst was packed in the third reactor. A reactor packed with 120 g of catalyst was fed to a distillation column feed with a distillation range of mostly 30 to 200 ° C. In addition, 500 g / h of the refinery feed according to Example 7 was fed to the reactor. A 500 g / h feed with a distillation range of mostly 120-150 ° C was fed to the first reactor connected in series from the distillation column. In addition, 80 g / h of the refinery feed of Example 12 were fed to both reactors connected in series. The temperatures in the reactors ranged from 230 to 280 ° C. The pressure in the reactors was 50 bar. The composition of the product obtained from the distillation column was as follows:

Distillation range ° C TA-30 30-180 180-200 200-350 350-410 410+

Jae, p-% 1.7 16.7 47.6 21.0 8.1 3.7 10

The fraction was hydrogenated at 200-350 ° C. The product was then subjected to a motor cetane number of 55. The viscosity was determined from the fraction 410 ° C + at 100 ° C and 40 ° C, from which the viscosity index was then calculated. The viscosity at 100 ° C was 5.077 mm 2 / cm and at 40 ° C 27.588 mm 2 / cm. The calculated viscosity index was 112. The pour point was -57 ° C. 15 il

Claims (7)

96320 A process for the oligomerization of light alkenes, in particular butenes, for the preparation of diesel and lubricating oil fractions with an improved cetane number and a viscosity index of 5 in the presence of a chromium-containing ZSM-5 zeolite catalyst under oligomerization conditions. or by dry ion exchange technique from 0.7 to 5% by weight of zeolite by weight of chromium. 10 Process according to Claim 1, characterized in that the HZSM-5 zeolite contains 1 to 3% by weight of chromium. Process according to Claims 1 to 2, characterized in that the chromium is added by impregnating the HZSM-5 zeolite with an aqueous solution of a chromium salt having a volume corresponding at most to the total pore volume of the zeolite and calcining the zeolite thus obtained at a temperature of 300 to 800 ° C. Process according to Claims 1 to 2, characterized in that the chromium is added by mixing the chromium salt and the zeolite together into a dry homogeneous mixture and calcining the zeolite thus obtained at a temperature of 300 to 800 ° C. Process according to one of the preceding claims, characterized in that a colloidal SiO 2 solution is added to the zeolite after the addition of chromium. 25 Process for the oligomerization of hydrocarbons or mixtures containing light alkenes, in particular butenes, to diesel and lubricating oil fractions with a high cetane number and a viscosity index according to one of the preceding claims, characterized in that the catalyst 30 is arranged in one or more side reactors connected to the distillation column. Process according to Claim 6, characterized in that part of the catalyst is chromium-modified HZSM-5 zeolite and part of unmodified ZSM-5 zeolite. 96320