KR20000065043A - Catalyst for Selective Aromatization - Google Patents

Abstract

The present invention relates in particular to catalysts for the selective preparation of aromatic compounds from hydrocarbon streams with straight, branched or cyclic alkyl or alkylene chains having 6 to 12 carbon atoms. Such catalysts on the oxides of transition metals in Group 4B of the periodic table, such as TiO ₂ or ZrO ₂ , include elements from one or more Group VIIB (eg palladium, platinum, rhodium), rhenium or tin, and optionally alkali metals Or compounds of alkaline earth metals, compounds of group 3A or 3B or zinc, or one or more compounds from the group of sulfur, tellurium, arsenic, antimony or selenium. The invention also relates to the use of such catalysts in the preparation of aromatic compounds such as ethyl benzene or xylenes from C ₆ to C ₁₂ -hydrocarbons.

Description

Catalyst for Selective Aromatization

The present invention relates to a noble metal containing catalyst on a ceramic support for the selective preparation of aromatic compounds from paraffinic / naphthenic hydrocarbon streams having straight, branched and / or cyclic alkyl or alkylene chains having 6 to 12 carbon atoms. will be. Specifically, the present invention relates to a method for preparing a C ₈ -aromatic compound.

The most important source of industrially important C ₆ -C ₈ -aromatic compounds such as benzene, xylene or ethylbenzene is catalytic catalytic reforming. In the reforming process, straight chain paraffinic hydrocarbons are converted into branched chain paraffinic hydrocarbons and aliphatic aromatic and aromatic hydrocarbons. This process, on the other hand, is used to increase the anti-knock capability of four-stroke engine fuels. That is, the reaction mixture obtained is generally used as such. On the other hand, the aromatic compounds formed are separated, for example, by distillation, and are used as intermediates and synthetic building blocks, for example, for producing synthetic rubbers and synthetic fibers. Ethylbenzene formed from components of the C ₈ moiety is required, for example, to produce styrene and polystyrene.

The modification process involves various reactions such as isomerization, aromatization (dehydrogenation) and cyclization. This process taking place at 450 to 550 ° C. and at a pressure of 15 to 70 bar is usually controlled by a platinum catalyst on a support.

Catalysts comprising other materials besides platinum, such as Pt-Re / Al ₂ O ₃ .SiO ₂ or Pt / Sn / Al ₂ O ₃ .SiO ₂ (known as binary metal catalysts), are likewise known. As an example of this, Pt / Sn / Al ₂ O ₃ based catalysts are described in J. Chem. Mol. Catal. 88 (1994) 359-376. The support material is typically aluminosilicate or zeolite. Pt-catalysts on L zeolites (Energy Progress 7, (1987), 215-222) have high aromatic selectivity due to the morphological selectivity of the support, but low disclosure yields. In contrast, Pt / Co / Nd (US Tuk He Pub No. 4 136 130) or Pt / Co / Re / Ge (US Pub No. 4 136 017) on a (non-zeolitic) chlorinated Al ₂ O ₃ support The same multicomponent catalyst shows higher activity, but tends to form cracked products, especially when compared to the formation of C ₈ -aromatic compounds (ethylbenzene, styrene, xylene), and therefore tends to exhibit lower aromatic selectivity. have.

It is an object of the present invention to provide a catalyst which is free from the above disadvantages or is of a relatively low degree and which converts a C ₆ -C ₈ -hydrocarbon stream into a high yield of aromatics. The specific purpose is to find a catalyst with specific selectivity to ethylbenzene among the C ₈ -aromatic compounds with the highest added values.

The inventors have found that the object is ceramic oxides of metals in one or more fourth transition group (Group 4B) elements, specifically precious metals selected from the Group 8 elements of the Periodic Table of the Elements on ZrO ₂ and TiO ₂ , specifically palladium, platinum or rhodium and It has been found to be achieved by a catalyst comprising (or) rhenium and / or tin.

In addition to the above elements, rhenium and / or tin may additionally be used as added to further elements, specifically Group 8 elements. In addition, an important component of the present invention is a compound of the third main group or transition group (Group 3A or 3B), or a basic compound such as an alkali metal oxide, alkaline earth metal oxide or rare earth oxide, or a corresponding oxide at 400 ° C. or higher. It may be added or doped with any of the compounds of these elements which may be. Simultaneous doping by a plurality of these elements or compounds thereof is possible. For example, potassium and lanthanum compounds are very suitable. In addition, the catalyst can be mixed with sulfur, tellurium, arsenic, antimony, or selenium containing compounds, which frequently result in increased selectivity, perhaps by partial poisoning (reducing agents).

Compared with the catalysts known in the prior art, the advantage of the catalyst of the invention is that the overall selectivity is higher for aromatic compounds, in particular for C ₈ -aromatic compounds. In addition, the catalysts of the present invention allow for higher conversion of aromatic compounds and higher yields in this regard than prior art catalysts.

The catalyst of the present invention can be prepared using amphoteric ceramic oxides, in particular oxides of zirconium and titanium or mixtures thereof. Also suitable are those compounds which can be converted to these oxides by firing. They can be prepared by known methods, for example by sol-gel processes, precipitation of salts, dehydration of the corresponding acid, dry mixing, slurrying or spray drying.

Suitable supports are all variants of zirconium and titanium oxides. However, in preparing a ZrO ₂ based catalyst, it has been found that the ratio of monoclinic ZrO ₂ is 90% or more as measured by X-ray diffraction. In the X-ray diffraction pattern, monoclinic ZrO ₂ is characterized by two strong signals at 2θ values of about 28.2 and 31.5.

Doping with a basic compound may be carried out during preparation, for example by co-precipitation, or after, for example, impregnating the ceramic oxide with an alkali metal or alkaline earth metal compound, or a compound of a third transition group element or a rare earth metal compound. have.

The content of the metal, rare earth metal or zinc in the alkali metal or alkaline earth metal, 3A or third transition group is generally at most 20% by weight, preferably 0.1 to 15% by weight, particularly preferably 0.5 to 10% by weight. Use as compounds for feeding alkali and alkaline earth metals generally consists of compounds which can be converted to the corresponding oxides by firing. Suitable compounds are, for example, hydroxides, carbonates, oxalates, acetates, nitrates, or mixed hydroxycarbonates of alkali and alkaline earth metals.

If the ceramic support is additionally or only doped with metals in the 3A or third transition group, the compounds used as starting materials should also be compounds which can be converted to the corresponding oxides by firing. If lanthanum is used, examples of suitable compounds include lanthanum compounds comprising lanthanum oxide carbonate, La (OH) ₃ , La ₂ (CO ₃ ) ₃ , La (NO ₃ ) ₃ , or organic anions (eg Lanthanum acetate, lanthanum formate or lanthanum oxalate).

The precious metal component can be applied in a variety of ways. That is, for example, the support may be impregnated or sprayed with a solution of a noble metal or a suitable compound of rhenium or tin. Suitable metal salts for preparing such solutions are, for example, nitrates, halides, formates, oxalates or acetates of precious metals. Complex ions or acids of these complex ions (eg H ₂ PtCl ₆ ) may also be used. Compounds found to be particularly suitable for preparing the catalysts of the present invention are PdCl ₂ , Pd (OAc) ₂ , Pd (NO ₃ ) ₂ and Pt (NO ₃ ) ₂ .

The catalyst according to the invention can also be obtained using a noble metal sol comprising at least one component in which the active component is present in a fully or partially reduced state.

When using noble metal sol, they are reduced in a conventional manner, for example by reducing the metal salt or a mixture of a plurality of metal salts in the presence of a stabilizer such as polyvinylpyrrolidone, followed by impregnation of the support or spraying of the support. It is prepared in advance by applying to. The method of preparation is described broadly in German patent application no. 1 95 00 366.7, which was not published before the present application.

The content of group 8 elements or rhenium or tin in the catalyst may be, for example, 0.005 to 5% by weight, preferably 0.01 to 2% by weight, particularly preferably 0.1 to 1.5% by weight. If rhenium or tin are further used, their ratio to the precious metal component may be, for example, 0.1: 1 to 20: 1, preferably 1: 1 to 10: 1.

As a slowing additive (partially poisoning of the catalyst according to the concept of the invention), compounds of sulfur, tellurium, arsenic, selenium can be used if necessary. It is also possible to add carbon monoxide while using the catalyst. It has been found to be particularly suitable to use sulfur, which is advantageously applied in the form of ammonium sulfide, ie (NH ₄ ) ₂ S. The molar ratio of the noble metal component to the catalyst poison can vary from 1: 0 to 1:10, preferably 1: 1 to 1: 0.05.

The catalyst may be used as a fixed bed in the reactor, or for example in a fluidized bed, and may have a suitable physical appearance. Suitable forms are, for example, granules, pellets, monoliths, spheres or extrudates (extruded rods or pellets, car wheels, stars, rings).

The catalyst formulation has a BET surface area of 500 m ² / g or less, generally 10 to 300 m ² / g, particularly preferably 20 to 300 m ² / g. The pore volume is generally 0.1 to 1 ml / g, preferably 0.15 to 0.6 ml / g, particularly preferably 0.2 to 0.4 ml / g. The average pore diameter of mesopores that can be measured by Hg penetration analysis is generally 8 to 60 nm, preferably 10 to 40 nm. The proportion of pores having a diameter of 20 nm or more generally varies from 0 to 60%. It has been found advantageous to use a support having a proportion of macropores (ie, pores having a diameter of 20 nm or more) of 10% or more.

The specific reaction is from 0.01 to 100 h ⁻¹ , preferably from 300 to 800 ° C., preferably from 400 to 600 ° C., specifically from 400 to 550 ° C., at a pressure of 100 millibar to 100 bar, preferably 1 to 40 bar. Preferably at an LHSV of 0.1 to 20 h ⁻¹ . Apart from the hydrocarbon mixture being dehydrogenated, it is possible to have diluents such as CO ₂ , N ₂ , noble gases or streams. Similarly, hydrogen can be added if necessary in a volume ratio of hydrogen to hydrocarbon (gas), which can be from 0.1 to 100, preferably from 1 to 20. The added hydrogen can be used to remove the carbon that accumulates on the surface of the catalyst as the reaction time increases.

In addition to continuously adding gases which prevent the deposition of carbon during the reaction, hydrogen or air can sometimes be passed over them to regenerate the catalyst. Regeneration is carried out at 300 to 900 ° C., preferably at 400 to 800 ° C., using a free oxidant, preferably air, or under reducing atmosphere, preferably with hydrogen. Regeneration can be performed at atmospheric, negative or overpressure. Suitable pressures are, for example, in the range of 500 millibars to 100 bar.

Catalyst manufacturing

Examples 1 and 2

6.38 g of Pd (OAc) ₂ was dissolved in 500 mL of water while 5 g of polyvinylpyrrolidone was added. 500 ml of 0.34 M sodium citrate solution was added to the solution, and the mixture was refluxed for 4 hours. This resulted in a transparent Pd sol.

Analysis: Pd 0.3%

Palladium sol was sprayed onto 200 g of ZrO ₂ pellets (5 × 3 mm pellets) on heated rotating metal plates using a two-fluid nozzle. The pellets were then dried at 120 ° C. for 72 hours and then impregnated with a solution of 2.96 g of K ₂ CO _{3 in} 47 ml of water for 1 hour according to their water absorption (23.5 g / 100 g). They were shaken several times during impregnation and then dried at 120 ° C. for 18 hours.

1.1 g of a 40 wt% solution of ammonium sulfide ((NH ₄ ) ₂ S) was diluted with water to a 47 mL solution, the pretreated pellet was impregnated with it and dried at 120 ° C. for 16 h.

Analysis: Pd 1.3%, K 0.96%, S 0.17%

Examples 3, 4, 5

5.6 g of oxalic acid were dissolved in 55 mL of water. 4.27 g of Pd (OAc) ₂ was added to this solution, and the mixture was slowly heated to 50 ° C to dissolve and stirred vigorously.

The zirconium dioxide used was extrudate, had a BET surface area of 92 m ² / g, a pore volume of 0.25 ml / g (Hg porosimetry), and a proportion of pores having a diameter of at least 0.02 μm. In each case 200 g of ZrO ₂ were impregnated (approximately 30 minutes) with a liquid of concentrated palladium according to their water absorption (27.2 g / 100 g). The extrudate was then dried at 80 ° C. in a rotary evaporator. They were then dried at 120 ° C. for 16 hours.

After applying palladium, the extrudate was slurried in a solution of 3.61 g of K ₂ CO _{3 in} 55 mL of water and dried again at 80 ° C. on a rotary evaporator after about 30 minutes. The extrudate was then dried at 120 ° C. for 28 hours.

1.1 g of a 40% by weight solution of ammonium sulfide were diluted with 55 mL of water, the pretreated extrudate was impregnated and dried at 80 ° C. in a rotary evaporator and then at 120 ° C. for 65 hours.

Analysis: Pd 0.97%, K 0.98%, S 0.13%, Remaining ZrO ₂

Examples 6, 7, 8

5.6 g of oxalic acid were dissolved in 60 mL of water. 4.27 g of Pd (OAc) ₂ was added to the solution, dissolved with vigorous stirring, and slowly heated to 50 ° C. 200 g of ZrO ₂ extrudates having a BET surface area of 70 m ² / g, a pore volume of 0.28 ml / g, and a proportion of pores having a pore of at least 20 nm of about 30% were added to their water absorption (30.6 g / 100 g of water). Thus impregnated with a palladium solution. After about 30 minutes, the extrudate was dried at 80 ° C. in a rotary evaporator. They were then dried at 120 ° C. for 24 hours.

After applying palladium, the extrudate was slurried in a solution of 3.61 g of K ₂ CO _{3 in} 60 mL of water and dried again at 80 ° C. on a rotary evaporator after about 30 minutes. The extrudate was then dried at 120 ° C. for 28 hours.

1.1 g of a 40% by weight solution of ammonium sulfide were diluted with 55 mL of water. The pretreated extrudate was impregnated with dilute solution and dried at 80 ° C. on a rotary evaporator. The extrudate was then dried at 120 ° C. for 70 hours.

Analysis: Pd 0.98%, K 0.94%, S 0.11%

Examples 9 and 10

5.6 g of oxalic acid were dissolved in 52 mL of water. 4.27 g of Pd (OAc) ₂ was added to this solution, dissolved with vigorous stirring, and slowly heated to 50 ° C.

The zirconium dioxide used was extrudate, had a BET surface area of 46 m ² / g, a pore volume of 0.23 ml / g (Hg porosimetry), and a proportion of pores having a pore size of at least 0.02 μm. 200 g of extrudate were impregnated with a palladium solution according to their water uptake (26 g / 100 g of water). After about 30 minutes, the extrudate was dried at 80 ° C. in a rotary evaporator. The extrudate was then dried at 120 ° C. for 14 hours.

After applying palladium, the extrudate was slurried in a solution of 3.61 g of K ₂ CO _{3 in} 52 ml of water and dried again at 80 ° C. on a rotary evaporator after about 30 minutes. The extrudate was then dried at 120 ° C. for 20 hours.

1.1 g of a 40% by weight solution of ammonium sulfide were diluted with 52 mL of water, the pretreated extrudate was impregnated with it and dried on a rotary evaporator and initially dried at 80 ° C. for 65 hours.

Analysis: Pd 0.92%, K 0.89%, S 0.11%

Example 11

0.181 g of Pt (NO ₃ ) ₂ (commercial product # 006438) dissolved in 2.7 ml of water, and 0.100 g of Sn (OAc) ₂ dissolved in 2.6 ml of water were added as an extrudable zirconium dioxide (commercial product of Nortonton # 93163335). , BET surface area 40 m ² / g, water absorption 26 g / 100 g) 10 g continuously applied at 1 hour intervals, after an additional 1 hour the extrudate is dried at 120 ℃ for 16 hours, calcined at 650 ℃ I was. The catalyst thus obtained comprises 1% platinum and 0.5% tin.

Example 12

0.181 g of Pt (NO ₃ ) ₂ (commercial product as in Example 11) dissolved in 3.06 ml of water, and 0.100 g of Sn (OAc) ₂ dissolved in 3.06 ml of water were added to zirconium dioxide (Norton's commercial product). # 93163321, BET surface area 49 m ² / g, water absorption 30.6 g / 100 g) 10 g continuously applied at 1 hour intervals, after an additional 1 hour the extrudate is dried at 120 ℃ for 16 hours, 650 ℃ Calcined at. The catalyst thus obtained comprises 1% platinum and 0.5% tin.

Example 13

0.65 g of Pt (NO ₃ ) ₂ (commercial product as in Example 11) dissolved in 21.4 mL of water, 3.27 g of palladium (II) nitrate solution (concentration of 11% by weight in water), and 21.4 mL of water. 1.42 g of Sn (OAc) ₂ is applied continuously to 70 g of extrudates of zirconium dioxide (commercial product # 93163321 as described above) at 1 hour intervals, and after an additional 1 hour the extrudate is applied at 120 ° C. for 16 hours. Dried and calcined at 650 ° C. The catalyst thus obtained comprises 1% platinum and 0.5% tin.

Example 14

0.65 g of Pt (NO ₃ ) ₂ (commercial product as in Example 11) dissolved in 21.4 mL of water, 3.27 g of palladium (II) nitrate solution (concentration of 11% by weight in water), and 21.4 mL of water. 1.42 g of Sn (OAc) ₂ was continuously applied to 10 g of extrudable zirconium dioxide (commercial product # 93163321, such as Norton Inc.) at an hourly interval, and after an additional hour, the extrudate was applied at 120 ° C. for 16 hours. Dried and calcined at 650 ° C. The catalyst thus obtained comprises 1% platinum and 0.5% tin.

Example 15

0.182 g of Pt (NO ₃ ) ₂ (commercial product as above) dissolved in 12 ml of water was added to powdered titanium dioxide (Finnti S 140 # 71077 from Kemira, B77 surface area 277 m ² / g, Water absorption 120 g / 100 g) was applied to 10 g and the material was dried at 120 ° C. and calcined at 500 ° C. The catalyst thus obtained comprises 1.15% platinum.

Example 16

0.182 g of Pt (NO ₃ ) ₂ (commercial product as such) dissolved in 12 ml of water was applied to 10 g of powdered titanium dioxide (BET surface area 90 m ² / g, water absorption 94 g / 100 g), The material was dried at 120 ° C and calcined at 500 ° C. The catalyst thus obtained contained 1.1% platinum.

Example 17

0.087 g of Pd (NO ₃ ) ₂ and 0.066 g of Pt (NO ₃ ) ₂ (commercial product as described above) dissolved in 3.06 mL of water were added to an extruded zirconium dioxide (BET surface area of 70 m ² / g, pore volume of 0.28 mL). / g, a proportion of pore having a diameter of 20 nm or less, 30%, crystalline monoclinic system, water absorption 30.6 g / 100 g) 10 g), the extrudate was dried at 120 ℃ and calcined at 500 ℃. The catalyst thus obtained comprises each 0.5% platinum and palladium.

Experiment in pulse reactor

Aromatization of the C ₈ -hydrocarbons (Examples 1-16) to C ₉ -hydrocarbons (Example 17) was carried out in a micro fixed bed pulse reactor. About 0.6 g of catalyst were weighed in the reactor and treated with pure n-octane (pulse (atmospheric pressure without hydrogen addition)). Between two successive n-octane pulses (about 1.5 minutes), helium gas was flowed into the reactor. The flow rate of the carrier gas is about 21.5 ml / min. A single pulse contains about 100 μg n-octane. The reaction product was quantitatively determined for each pulse using on-line GC-MS.

The results obtained are shown in Table 1 and Table 2. The selectivity shown is based on the maximum conversion period in each case. Commercial reforming catalysts of known composition were used for comparison.

Example type T U ^a) Selectivity [%] number [℃] [%] EB o-? ? ^b) ∑Ar ^c) ∑C ₈ ^d) One Pd / K / ZrO ₂ 450 62.27 11.1 6.7 5.4 86.6 23.2 2 Pd / K / ZrO ₂ 500 62.25 3.28 9.4 12.3 89.3 24.9 3 Pd / K / ZrO ₂ 450 75.1 21.8 32.1 - 74.6 53.9 4 Pd / K / ZrO ₂ 500 67.3 5.0 24.3 1.23 91.1 30.5 5 Pd / K / ZrO ₂ 450 66.0 16.5 37.1 2.1 90.8 55.7 6 Pd / K / ZrO ₂ 450 82.3 20.4 21.2 3.73 88.0 45.3 7 Pd / K / ZrO ₂ 450 76.3 14.4 14.0 6.2 86.1 34.6 8 Pd / K / ZrO ₂ 500 97.5 4.0 11.2 5.0 97.5 20.2 9 Pd / K / ZrO ₂ 450 51.4 8.3 11.7 13.6 80.6 33.6 10 Pd / K / ZrO ₂ 500 32.3 4.7 8.8 7.4 85.8 20.9 11 Pt / Sn / ZrO ₂ 500 97.8 33.4 52.9 2.8 96.9 89.1 12 Pt / Sn / ZrO ₂ 500 99.7 29.4 51.3 4.0 85.4 85.4 13 Pt / Pd / Sn / ZrO ₂ 500 100 28.5 50.5 5.6 94.4 86.4 14 Pt / Sn / ZrO ₂ 500 99.6 32.1 59.4 1.6 98.4 94.8 15 Pt / TiO ₂ 500 100 37.1 48.7 5.4 96.3 91.3 16 Pt / TiO ₂ 500 100 37.8 50.0 2.3 97.5 90.9 Notice composition Pt / Sn / Al ₂ O ₃ 500 75.1 3.0 37.6 10.9 72.0 51.5 a) conversion based on n-octane (percent of GC per area) b) sum of m- and p-xylene c) sum of all aromatic compounds measured d) sum of all C ₈ -aromatic compounds (EB + xylene)

At the same temperature, the catalyst of the present invention exhibits higher selectivity relative to the overall yield of aromatic compounds than the comparative catalyst. A striking result is the high proportion of ethylbenzene, the product with the highest added value.

Example type T U ^a) Selectivity [%] [℃] [%] EB Xylene toluene ∑C ₈ ^b) ∑C ₈ ^c) 17 Pt / Pd / ZrO ₂ 500 95 9.6 6.2 21.7 15.8 31 a) Conversion based on n-octane (GC percentage per area) b) Sum of all aromatic compounds measured c) Sum of all C ₉ -aromatic compounds (1,2,4-trimethylbenzene, indane, n-propyl Benzene + indene)

Claims (15)

Straight, branched and / or bonded carbon, especially having from 6 to 12 carbon atoms, comprising at least one element selected from Group 8 elements of the Periodic Table of the Elements on the oxide of the Group 4B transition metal and / or rhenium and / or tin Catalyst for the selective preparation of aromatic compounds from hydrocarbon streams with click alkyl or alkylene chains. The catalyst of claim 1 comprising TiO ₂ and / or ZrO ₂ as transition metal oxides. The catalyst of claim 2 comprising mainly TiO ₂ as anatase. The catalyst of claim 2 comprising mainly ZrO ₂ in monoclinic variant. The catalyst of claim 1 comprising from 0.005 to 5% by weight of palladium, platinum, rhodium and / or rhenium. The catalyst of claim 1 further comprising a compound of an alkali or alkaline earth metal, a compound of group 3A or a third transition group and / or zinc. The catalyst of claim 6 comprising sodium or potassium as alkali metal. The catalyst of claim 6 comprising a lanthanum, yttrium, gallium, indium or thallium compound as the compound of 3A or third transition group. The catalyst of claim 1 comprising at least one compound selected from the group consisting of sulfur, tellurium, arsenic, antimony and / or selenium. The catalyst of claim 1 wherein the BET surface area is from 10 to 500 m ² / g. The catalyst of claim 1 wherein the pore has a diameter of from 8 to 60 nm, at least 10% of the pore having a diameter of at least 20 nm, and the volume of the particular pore is from 0.1 to 1 ml / g. The process of claim 1, comprising applying palladium, platinum, rhodium and / or rhenium to the support as a sol. Use of a catalyst according to claim 1 in the preparation of aromatic compounds from hydrocarbons having straight, branched and / or cyclic alkyl or alkylene chains having 6 to 12 carbon atoms. Use of the catalyst according to claim 1 in the preparation of ethylbenzene and / or xylene. Use of a catalyst according to claim 1 in the preparation of C ₉ -aromatic compounds.