SE457727B - SET TO REFORM THE PULP WATER USING A LARGE ZEOLITE CATALYST - Google Patents

Description

457 127 2; 10 15 20 ZS 30 35 The catalysts used so far have given moderately satisfactory results with heavy paraffins but less satisfactory results with C6-C8 paraffins, especially C6 paraffins. Catalysts based on L-type zeolite are more selective with respect to the dehydrocyclization reaction; can be used to improve the conversion rate to aromatic hydrocarbons without requiring higher temperatures, which usually have a significant adverse effect on the stability of the catalyst; and produce excellent results with C6-C8 paraffins. However, running time and regenerability are problems and satisfactory regeneration procedures are not known.

In a method of dehydrocyclizing aliphatic hydrocarbons, hydrocarbons are contacted in the presence of hydrogen with a catalyst consisting essentially of a type L zeolite with exchangeable cations, at least 90 of which are alkali metal ions made of sodium, lirium, potassium. rubidium and / or cesium and containing at least one metal consisting of Group VIII metals in the Periodic Table of the Elements, tin and germanium, the metal or metals comprising at least one Group VIII metal in the Periodic Table having a dehydrating effect, for to convert at least some of the added material into aromatic hydrocarbons.

A particularly advantageous embodiment of this method is a type L platinum alkali metal allolite catalyst due to its excellent activity and selectivity for converting hexanes and peptanes to aromatic compounds, but the running time remains a problem.

The present invention overcomes the shortcomings of the prior art by using a catalyst comprising a large porous zeolite, an alkaline earth metal and a Group VIII metal to reform hydrocarbons at an extremely high selectivity for the conversion of alkanes to aromatic compounds.

The hydrocarbons are contacted with a catalyst comprising a large porous zeolite, at least one Group VIII metal (suitably platinum); and an alkaline earth metal, which is barium, strontium or calcium (preferably barium). In one aspect of the present invention, the process conditions are controlled so that the selectivity for n-hexane hydrocyclization is greater than 60%. In another aspect, the selectivity index of the catalyst is greater than 60%. The catalyst provides satisfactory driving time. 10 15 20 ZS 30 35 4.57 727 Preferably, large-pore zeolite is a type L zeolite, containing from 0.1 to 5% by weight of platinum and 0.1 to 35% by weight of barium. The hydrocarbons are contacted with the barium-exchanged type zeolite at a temperature of from 400 ° C to 600 ° C (preferably 430 ° C to 550 ° C); a liquid volume rate per hour of from 0.3 to 5 S; a pressure of from 98.1 kPa to an overpressure of 3.45 MPa (suitably overpressure from 0.345 to 2.07 MPa); and an H 2 / HC ratio of from 1: 1 to 10: 1 (preferably from 2: 1 to 6: 1).

In its broadest aspect, the present invention encompasses the use of a catalyst comprising a large pore zeolite, an alkaline earth metal and a Group VIII metal to reform hydrocarbons, in particular, the dehydrocyclization of alkanes, at an extremely high selectivity to convert hexanes to aromatic as well as innate compounds.

The term "selectivity" as used in the present invention is defined as the percentage of moles of paraffin converted to aromatic compounds relative to moles converted to aromatic and cracked products, 100 x moles of paraffins converted to aromatic compounds moles of para iners converted to aromatic compounds and cracked products, ie, selectivity = Isomerization reactions and alkylcyclopentane formation are not considered in determining selectivity.

The term "selectivity for n-hexane" as used in the present invention is defined as the percentage of moles of n-hexane that are converted to aromatic compounds relative to moles that are converted to aromatic compounds and cracked products.

The selectivity for converting paraffins to aromatic compounds is dull on the effect of the process of converting paraffins to desired and valuable products: aromatic compounds and hydrogen, as opposed to less desirable hydrocracking products.

A natural feature of any dehydrocyclization catalyst is the selectivity index. Selectivity index is defined as "the selectivity of n-hexane" using n-hexane as feedstock and operating at 490 ° C overpressure 0.689 MPa, 3 liquid volume rates per hour and 3 H 2 / HC after 20 hours. Highly selective catalysts produce more hydrogen than less selective catalysts because hydrogen is generated when paraffins are converted to aromatic compounds and hydrogen is consumed when paraffins are converted to cracked products. increasing the selectivity of the process increases the amount of hydrogen produced (more aromatization) and decreases the amount of hydrogen hydrogenated (less cracking).

Another advantage of using highly selective catalysts is that hydrogen catalysts are purer catalysts. This higher purity is the result, due to the production of more hydrogen, while less low-boiling hydrocarbons (cracked product hydrogen in reforming is critical, a complete refinery, er). ) alstras. The purity of generated as is usually the case in generated hydrogen is utilized in processes such as hydrotreating and hydrocracking, which require at least some minimal hydrogen partial pressures. If the purity becomes too low, the hydrogen can no longer be used for this purpose and must be used in a less valuable way, for example as fuel gas.

In the method of the present invention, supplied hydrocarbons suitably comprise non-aromatic hydrocarbons containing at least 6 carbon atoms. Suitably, added materials are substantially free of sulfur, nitrogen, metals and other known toxins for reforming catalysts.

The dehydrocyclization is carried out in the presence of hydrogen at a pressure controlled to promote the reaction thermodynamically and to limit undesirable hydrocracking reactions kinetically. The pressures used suitably range from 98.1 kPa to an overpressure of 3.45 MPa, more suitably from an overpressure of 0.345 to 2.07 MPa, the molar ratio of hydrogen to from 1: 1 to 1011, more suitably from 2: 1 to 6: 1.

Within the temperature range from 400 ° C to 60,000, the dehydrocyclization reaction occurs with acceptable speed and selectivity. hydrocarbons are suitable If the operating temperature is below 400 ° C, the reaction rate is insufficient and consequently the yield is too low for industrial purposes. Even the dehydrocyclization equilibrium is unfavorable at low temperatures. When the operating temperature is above 600 ° C, disturbing secondary reactions, such as hydrocracking and coking, occur, and substantially reduce the heat and increase the catalyst deactivation rate. It is therefore not advisable to exceed the temperature of 600 ° C.

The suitable temperature range (40 ° C to 11 5 ° C) for dehydrocyclization is that within which the process is optimal in terms of activity, selectivity and the stability of the catalyst.

The liquid volume rate per hour of the hydrocarbons is suitably between 0.3 and 10.

The catalyst according to the invention is a large-pore zeolite with one or more dehydrogenation constituents. The term "large pore zeolite" is defined as a zeolite having an effective pore diameter of 6 to 15 Angstroms; Among the large pore crystalline zeolites which have been found to be useful in the practice of the present invention, type L zeolite and synthetic zeolites with faujasite structure, such as zeolite X and zeolite Y, are the most important and obviously have pore sizes in the order of 7 to 9 composition of type L zeolite, expressed in the molar ratios of oxides, may correspond to the following: (0.9-1.3) M 0: Al 2 O 3 (S, 2-6.9) SiO 2: yH 2 O 2 / n wherein M represents a cation, n represents the valence of M, - and y can be any value from 0 to about 9. Zeolite L, its X-ray diffraction pattern, its properties and method of its preparation are described in detail in U.S. Pat. No. 3,216,789. U.S. Patent No. 3,216,789 is incorporated herein by reference to show the appropriate zeolite of the present invention. The actual form fl can vary without changing the crystal structure; for example, the molar ratio of silicon to aluminum (Si / A1) can vary from 1.0 to 3.5.

The chemical formula of zeolite Y expressed in the molar ratios of oxides can be written as: (0.7-1.1) Na 2 O: Al 2 O 3: x SiO 2: yH 2 O wherein x is a value greater than 3 up to about 6 and y may be a value up to about 9. Zeolite Y has a characteristic X-ray powder diffraction pattern, which can be used with the above formula for identification. Zeolite Y is described in more detail in U.S. Pat. No. 3,130,007. U.S. Pat. No. 3,130,007 is incorporated herein by reference to show a zeolite useful in the present invention.

Zeolite X is a synthetic crystalline zeolitic molecular sieve corresponding to the formula: (0.7-1.1) M2 / nO: Al2O3: (2.0-3.0) SiO2 .2H2 O wherein M represents a metal, especially alkali and alkaline earth metal. metals, n is the valence of M, and y can have any value up to about 8 depending on the identity of M and the degree of hydration of the crystalline zeolite. Zeolite X, its X-ray diffraction pattern, its properties and method of making the same are described in detail in U.S. Pat. No. 2,882,244.

U.S. Patent No. 2,882,244 is incorporated herein by reference to show a zeolite useful in the present invention. A suitable catalyst according to the invention is a type L zeolite with one or more dehydration constituents.

An essential element of the present invention is the presence of an alkaline earth metal in the large pore zeolite. The alkaline earth metal must be either barium, strontium or calcium, preferably barium. The alkaline earth metal can be incorporated into the zeolite by synthesis, impregnation or ion exchange. Barium is more suitable than the other alkaline earth metals because it results in a slightly less acidic catalyst. Strong acidity is undesirable in the catalyst because it promotes cracking, which results in lower selectivity. .

In one embodiment, at least in part, the alkali metal is exchanged for barium, using methods known for ion exchange of zeolites. This involves contacting the zeolite with a solution containing excess Ba ++ ions. Barium should make up from 0.01 to 35% by weight of the zeolite.

Dehydrocyclization catalysts of the present invention contain one or more Group VIII metals, for example nickel, ruthenium, rhodium, palladium, iridium or platinum.

Suitable Group VIII metals are iridium and especially platinum, which are more selective with respect to dehydrocyclization and are also more stable under the dehydrocyclization reaction conditions than other Group VIII metals. 10 15 20 25 30 35; 457,727 The appropriate percentage of platinum in the catalyst is between and 5%.

Group VIII metals are introduced into the large pore zeolite by synthesis, impregnation or exchange in an aqueous solution of a suitable salt. When it is desired to introduce two Group VIII metals into the zeolite, the operation can be performed simultaneously or sequentially.

For example, platinum can be introduced by impregnating zeolite with an aqueous solution of tetramminplatin- (II) nitrate, tetramminplatin- (II) hydroxide, dinitrodiamino-platinum in a 0.1% ion exchange process or tetramminplatin- (II) - chloride. For example, platinum can be introduced using cationic platinum complexes, such as tetramine platinum (II) nitrate.

An inorganic oxide can be used as a support to bind the large-pore zeolite containing the Group VIII metal and alkaline earth metal. The carrier can be a natural or synthetically generated inorganic oxide or a combination of inorganic oxides. Typical organic oxide substrates that can be used include clays, alumina and silica, in which the acidic sites are conveniently replaced with cations which do not give strong acidity (such as Na, K, Rb, Cs, Ca, Sr or Ba).

The catalyst can be used in any of the conventional types of equipment known in the art. It can be used in the form of pellets, pellets, granules, broken fragments or various special forms, arranged as a fixed bed within a reaction zone and added material can pass therethrough in liquid, vapor or mixed phase and in either upward or downward direction. flow. Alternatively, it may be prepared in a suitable form for use in moving beds or in fluid-solid phase processes in which feed is passed upwards through a turbulent bed of finely divided catalyst.

After the desired metal or metals have been introduced, the catalyst is treated in air at about 260 ° C and then reduced in hydrogen at temperatures from 200 ° C to 700 ° C, preferably 400 ° C to 50 ° C.

At this stage, it is ready for use in the dehydrocyclization process. In some cases, however, for example when the metal or metals have been introduced by an ion exchange process in process, it is convenient to eliminate any remaining acidity of the zeolite by treating the catalyst with an aqueous solution of a salt or hydroxide of a suitable alkali or alkaline earth element to neutralize any hydrogen ions formed during the reduction of metal ions with hydrogen.

In order to obtain optimal selectivity, the temperature must be regulated so that the reaction rate is considerable, but conversion is less than 98i% as excessive temperature and excessive reaction can have an adverse effect on the selectivity. Pressure must also be regulated within a correct range. Too high a pressure will place a thermodynamic (equilibrium) limit on the desired reaction, especially for hexane flavoring, and too much pressure can result in coking and deactivation. Although the primary advantage of the present invention lies in improving the selectivity for the conversion of paraffins (especially C6-C8 paraffins) to aromatic compounds, it has also surprisingly been found that the selectivity of the medium is high. to benzene is excellent. This reaction, which on conventional reforming catalyst based on chlorinated alumina comprises an acid catalyzed 'isomerization step', occurs on the catalyst of the present invention with selectivity as good as or better than prior art catalysts based on chlorinated alumina. Thus, the present invention can also be used to catalyze the conversion of materials high in S-linked ring alkyl naphthenes to aromatic compounds.

Another advantage of the present invention is that the catalyst of the present invention is more stable than prior zeolite catalysts. The stability of the catalyst or the resistance to deactivation determines its useful running time. Longer running times result in less waste time and cost in regenerating and replacing the catalyst charge.

In one embodiment of the present invention, a hydrocarbon feed is contacted with a first catalyst, which is a conventional reforming catalyst, and a second catalyst, which is a dehydrocyclization catalyst comprising a large pore zeolite, an alkaline earth metal and a Group VIII metal. The use of a reforming catalyst comprising an alumina support, platinum and rhenium is fully discussed in U.S. Patent No. 3,415,737, which is hereby incorporated by reference to illustrate the use of a: conventional reforming catalyst. Other advantageous bimetallic catalysts include platinum tin, platinum germanium, platinum lead and platinum iridium.

The hydrocarbons can be contacted with the two catalysts in series, the hydrocarbons being first contacted with the first (conventional) reforming catalyst and then with the second (dehydrocyclization) catalyst; or wherein the hydrocarbons are first contacted with the second catalyst and then with the first catalyst. Also, the hydrocarbons can be contacted in parallel, with one fraction of the hydrocarbons being contacted with the first catalyst and another fraction of the hydrocarbons being contacted with the second catalyst. The hydrocarbons can also be brought into contact with both catalysts simultaneously in the same reactor.

EXAMPLES The present invention will be further illustrated by the following examples, which illustrate a particularly advantageous method and compositional embodiments. While the examples are provided to illustrate the present invention, they are not intended to limit it.

Example I - An Arabic light direct distillate, which had been hydroraffinated to remove sulfur, oxygen and nitrogen, was reformed at a pressure of 0.689 MPa, 2 liquid volume rates per hour and 6 H 2 / HC with three different catalysts. The feed contained 80.2% by volume of paraffins, 16.7% by volume of naphthenes and 3.1% by volume of aromatic compounds, and it contained 21.8% by volume of CS, 52.9% by volume of C6, 21.3% by volume of C7 and 3.2% by volume of C8.

In the first run, the Arabic light direct distillate was reformed at 499 ° C using a commercial sulfided platinum-rhenium alumina catalyst described in U.S. Pat. No. 3,415,737.

In the second experiment, the Arabic light direct distillate was reformed at 493 ° C using an L-type platinum-potassium zeolite catalyst formed by: (1) impregnating a potassium zeolite of type L with 0.8% platinum using tetramine platinum (II) nitrate; (2) drying the catalyst; (3) calcine the catalyst at 26,000 and (4) reduce the catalyst at 40 ° C to 50 ° C for 1 hour.

In the third experiment, the process of the present invention, the Arabic light direct distillate was reformed at 493 ° C using a type L platinum-barium zeolite catalyst formed by: (1) ion exchange of type L potassium zeolite with a sufficient volume of 0.17 molar barium nitrate solution to contain an excess of barium compared to the ion exchange capacity of the zeolite; (2) drying the obtained barium zeolite catalyst of exchange type L; (3) calcination of the catalyst at S90 ° C; (4) impregnating the catalyst with 0.8% platinum using tetramine platinum (II) nitrate; (S) drying the catalyst; at 260 ° C; and (7) reduction: 111 ° C for 1 hour.

The results of these three experiments are shown in Table I. (6) Calcination of the catalyst by the catalyst in hydrogen at 480 ° C Table I 499 ° C Pt / Re / 493 ° C 493 ° C Supply Aluminum oxide PT / K / L Pt / Ba / L C1 weight-8 of the feed 2.8 5.5 3.6 CZ 6.6 2.5 1.3 C3 9.3 3.2 1.5 104 0.1 5.8 0.9 0.5 NC4 0.5 6.8 3.8 2.4 íC5 5.1 13.6 6.7 5.6 NC5 11.3 9.8 12.6 12.6 c6 + P + N 81.3 13.4 7, 8 9.3 Benzene 1.5 15.1 40.6 43.8 C7 + aromatic compounds 0.8 15.8 12.7 15.0 CS + LV% yield 63 69.9 74.4 Hydrogen, SCF / B 470 1660 2050 Selectivity, mol% 20 72 87 C6 + P -> aromatic compounds 10 15 20 25 30 35 N 457 '727 This series of experiments shows that the use of type L platinum-barium zeolite catalysts in reforming gives a selectivity for converting hexanes to benzene remarkably superior to that of the prior art. Note that the associations with this superior selectivity are an increase in hydrogen generation, which can be used in other procedures. Also note that the hydrogen unit is higher for the Pt / Ba / L test because more hydrogen is generated and less C1 plus C2 is generated.

Example II A second series of experiments was performed to show that the present invention could work with other large pore zeolites in addition to type L zeolite. The selectivity index was measured for four catalysts.

This second series of experiments was performed using n-hexane as the feedstock. All experiments in this series were performed at 49 ° C, overcryek o, es9 MPa, s water flow rate per hour and 3 H 2 / HC. .

The first experiment used a type L platinum-potassium zeolite which had been prepared by the methods shown in the second procedure of Example I.

The second experiment used a type L platinum-barium zeolite which had been prepared by the procedures shown in the third procedure of Example I except that the barium nitrate solution was 0.3 molar instead of 0.17 molar.

The third experiment used a platinum-sodium zeolite Y, which had been prepared by impregnating a sodium zeolite Y with Pt (NH 3) 4 (NO 3) 2 to give 0.8% platinum, then drying, calcining the catalyst at 260 ° C and reduction in hydrogen V at 40-50 ° C.

The fourth experiment used a platinum-barium zeolite Y 1 which had been prepared by ion exchange of a sodium zeolite Y with 0.3 molar barium nitrate at 80 ° C, drying and calcination at 590 ° C, then impregnation of the zeolite with Pt ( NH 3) 4 (NO 3) 2 to give 0.8% tower at 260 ° C and reduction in hydrogen at 480-00 ° C. The results of platinum, then drying, calcination of the catalyst of these experiments are given below in Table II. 10 15 20 25 30 1-7 457 727 Table 11 o ~ .nvand1íng_ 'sèlèkfívitetsindex sh '20 h P: / K / L 10 59 79 P: / sa / L ss ss 92 P: / Na / Y sz 79 54 P : / Ba / Y 74 pp. Thus, in operation, the incorporation of barium into large pore zeolite, such as type Y zeolite, causes a dramatic improvement in the selectivity of n-hexane. Note that the stability of platinum-barium zeolite type L is excellent. After 20 hours, there was no decrease in the conversion when type L platinum-barium zeolite catalyst was used.

Example III A third series of experiments was performed to show the effect of adding additional ingredients to the catalyst.

This third series of experiments was performed using a feedstock which had been hydrorefined to remove sulfur, oxygen and nitrogen, and which contained 80.9% by volume of paraffins, 16.8% by volume of naphthenes and 1.7% by volume of aromatic compounds. The feedstock also contained 2.6% by volume CS, 47.6% by volume C6, 43.4% by volume C7 and 6.3% by volume C8. All experiments in this series were performed at 490 ° C, overpressure 0.689 MPa, 2.0 liquid volume rate per hour and 6.0 Hz / HC.

In the first experiment, a platinum-sodium zeolite Y was prepared by the procedures shown in the third procedure of Example II.

In the second experiment, a platinum-barium zeolite Y was prepared by the procedures shown in the fourth procedure of Example II.

In the third experiment, a platinum rare earth zeolite Y was prepared by impregnating a commercial rare earth zeolite Y obtained from Strem Chemicals Inc to give 0.8% Pt using Pt (NH 3) 4 (NO 3). ) 2, then the zeolite was dried, calcined at 260 ° C and reduced at 480-500 ° C. ZS 457 727f In the fourth experiment, a platinum rare earth metal barium zeolite Y was prepared by ion exchange of a commercial Strem Chemical Inc. rare earth metal zeolite Y with a 0.3 molar Ba (NO 3) 2 solution at 809, drying and calcining the zeolite at 590 ° C, impregnating the zeolite with Pt (NH 3) 4 (NO 3) 2 to give 0.8% Pt, then drying, calcining the zeolite at 260 ° C and reducing at 480-500 ° C. The results of these experiments are given below in Table III.

Table III Activity of aromatic compounds at 3 h, Selectivity, C + .. _ _ Target-e, 'of Wtin introduction into V14 3 h Pt / Na / Y 36 46 Pt / Ba / Y _ 54 68 Pt / rare earth metal / Y 22 (Too low to measure) Pt / Ba / rare earth metal / Y 36 27 This series of experiments shows that the addition of rare earth metal to the catalyst has an adverse effect on selectivity.

Example Gel IV An arabic naphtha, which had been hydrorefined to remove sulfur, oxygen and nitrogen, was reformed at a pressure of 0.689 MPa, 3 liquid volume rates per hour and 3 H 2 / HC to produce a C5 + product containing 82 aromatic compounds. weight percent by two different procedures. The feedstock was a hydrorefined arabic naphtha, which contained 67.9% paraffins, 23.7% naphthenes and 8.4% aromatic compounds. The distillation results with the D86 method were: start - 95 ° C, 5% -104, 10% -107, 30% -120, 50% -129, 70% -144, 90% -161, 95% -169, end point 188 ° C.

In the first process, arabic naphtha was reformed at 516 ° C in a reactor using a conventional reforming catalyst comprising 0.3 Pt, 0.6 Re, 1.0 Cl weight percent) on alumina. It was presulfided separately.

In the second process, the arabic naphtha was reformed at 493 ° C in the same reactor, wherein the top half of the reactor contained the same type of catalyst as that of the first process and the bottom half of the reactor contained a platinum-barium zeolite type L catalyst. , formed by the procedures 457 727 shown in Example I.

The results of these two experiments are shown in Table IV.

Deactivation rate C5 + yield, LV% hydrogen yield, scP / n Table IV PT / RE / 1/2 Pt / Re / aluminum- alumina oxide - 1/2 Pt / Ba / L 2.0 1.9 68.9 71 While the present invention has been described with reference to specific embodiments, the present invention is intended to cover the various changes and substitutions that may be made by those skilled in the art without departing from the spirit and scope of the appended claims.

Claims (9)

1; 457 727 PATENT CLAIMS A method of reforming hydrocarbons, characterized in that the hydrocarbons are contacted with a catalyst comprising an ethereal zeolite containing: (a) at least one Group VIII metal and (b) an alkaline earth metal consisting of: barium, strontium; or calcium, wherein the selectivity index of the catalyst is greater than 60 X or wherein the process conditions are controlled so that the selectivity for n-hexane hydrocyclation is greater than 60% and first, simultaneously or finally optionally bringing the hydrocarbons in reforming conditions and in the presence of hydrogen , which comprises a metallic oxide support which has incorporated therein in intimate mixture platinum and rhenium. 2. A method of reforming hydrocarbons according to claim 1, characterized in that the alkaline earth metal is barium and in which the Group VIII metal is platinum. 3. A process for reforming hydrocarbons according to claim 2, characterized in that the catalyst has from 0.1 to 35% by weight of barium and from 0.1 to 5% by weight of platinum. 4. A method of reforming hydrocarbons according to claim 1, characterized in that the ethereal zeolite has an apparent pore size of from 7 to 9 Å. 5. A method of reforming hydrocarbons according to claim 1, characterized in that the large-pore zeolite is selected from zsolite X, zeolite Y and zeolite of type L. 6. A method of reforming hydrocarbons according to claim 5, characterized in that the large-pore zeolite is zeolite Y. 7. A method of reforming hydrocarbons according to claim 5, characterized in that the large-pore zeolite is zeolite of type L. 457 727 '' B. A method of reforming hydrocarbons according to claim 1, characterized in that the contacting occurs at a temperature of from 40U ° C to 600 ° C, hot per hour of from 0.3 to 5; overpressure 3.45 MPa; l0: 1. a liquid volume rate - a pressure from 98.1 kPa to and an H2 / HC ratio of from 1: 1 to 9. A method of reforming hydrocarbons according to claim 8, characterized in that the contacting occurs at a temperature of 430 to 550 ° C, an overpressure of -0.345 to 2.07 MPa; and an H2 / HC ratio from 2: 1 to 6: 1.