JPS6332334B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field of the Invention] This invention relates to a method of using a novel platinum group metal catalyst supported on a novel form of carbon. In particular, it relates to hydrogen transfer reactions such as dehydrogenation of hydrocarbons and/or dehydrocyclization reactions. [Objective and gist of the invention] According to an aspect of the invention, (1) the carrier has (a) a basic planar surface area of at least 100 m ² /g, and (b)
(c) a graphite-containing carbon having a ratio of BET surface area to basal planar surface area of not greater than 5:1; and (2) a graphite-containing carbon having a ratio of basal planar surface area to edge surface area of at least 5:1; of weight
0.01 to 10% by weight, preferably 0.1 to 5% by weight
A catalyst comprising a supported platinum group metal is provided. By platinum group metals is meant ruthenium, rhodium, palladium, osmium, iridium, platinum and gold. Preferred metals are platinum itself and iridium. The basic planar surface area of the graphite-containing carbon is preferably in the range of 150 m ² /g to 1000 m ² /g. If this area is larger than 1000 m ² /g, it does not have sufficient strength as a catalyst carrier. The closer the ratio of BET surface area to basic planar surface area is to the theoretical minimum value of 1, the higher the quality of the material. That is, the proportion of crystalline substances becomes high and the proportion of amorphous substances becomes low. For practical reasons, this ratio is preferably in the range 2:1 to 1.01:1. Preferably, the ratio of base planar surface area to edge surface area is greater than 10:1, and most preferably greater than 300:1. The graphite-containing carbon carrier preferably has a pH in the range of 5 to 9, preferably 6 to 8.
more preferably a pH of about 7, and preferably contains less than 1% by weight of adsorbed oxygen, more preferably less than 0.5% by weight of adsorbed oxygen. The lower the adsorbed oxygen, the closer the pH will be to 7. The graphite-containing carbon must be of high purity. For example, the ash content should be 0.1% by weight or less, preferably 0.05% or less, and more preferably 0.02% or less. Preferably, the catalyst composition also contains a small proportion of modifying metal ions selected from alkali metal ions and alkaline earth metal ions. Modifying metal ions significantly increase the dehydrocyclization activity of platinum group metals. The preferred amount of modifying metal is
10 to 300 atomic percent of platinum group metals.
Although any alkali metal is suitable, sodium is preferred. Alkaline earth metals are magnesium, calcium, strontium or barium. The particle size of the graphite-containing carbon is not critical and can be controlled in known ways in relation to its intended use. Fine particle ranges are used in slurry processes, and granular forms are used in fixed bed processes. Graphite is (a) activated carbon derived from coconut charcoal, coal, peat, etc., (b) carbon blacks, (c) carbons produced by coking petroleum residue, and (d) British Patent No. 1168785. It can be made from many different forms of carbon, including lipophilic graphite as made by the described method. The support is made of carbon having a BET surface area in the range of 100 to 3000 m ² /g in an inert atmosphere.
900℃ to 3300℃, preferably 1500℃ to 2700℃
can be produced by heating at a temperature of 100 ml for a time sufficient to form graphite-containing carbon. The carbon used as a starting material must be heated to at least 500°C at about 1000°C before the heat treatment described above.
Preference is given to those having a BET surface area of m ² /g. The preparation of the graphite-containing carbon is a combination of the selected carbon type and heat treatment under inert and oxidizing conditions selected to optimize the ratio of BET to base planar surface area and base planar surface area to edge surface area. Varies depending on use. Heating in an inert gas increases the proportion of graphitic material. That is, the first ratio decreases and the second ratio increases. Although most forms of carbon have a significant reduction in total surface area by this treatment, this is not always the case, and some forms of carbon exhibit relatively little reduction in surface area upon heating. Oxidation under carefully controlled conditions increases surface area in comparison. Preparation of carbon supports typically and generally involves three steps. (1) an initial heat treatment at a temperature between 900°C and 3300°C in an inert gas, (2) an oxidation step at a temperature between 300°C and 1200°C, and (3) 1000°C in an inert gas. A second heat treatment at a temperature between 3000°C and preferably no higher than the temperature of the first heat treatment. In steps (1) and (3), an atmosphere suitable for use at temperatures up to 1000°C is nitrogen. Above this temperature, it is preferable to use, for example, argon or helium as inert gas. Suitable oxidizing media in step (2) include air, water vapor and carbon dioxide. If air is used, 300℃ to 450℃
When using water vapor or carbon dioxide, temperatures within the range of 800°C to 1200°C are preferred. During heating in an inert atmosphere, it is believed that at least a portion of the carbon is converted to graphite and adsorbed organic oxygen-containing groups such as ketones, hydroxyls, carboxylic acids and the like are removed. No organic oxygen-containing groups present in the treated carbon (1% or less)
This is important in relation to the selectivity of catalysts using carbon as a carrier. This is because oxygen-containing groups have been reported to promote side reactions. The catalyst is prepared by impregnating a graphite-containing carbon support with a solution of a reducible platinum group metal compound and reducing the reducible compound to the metal. Suitable solutions include aqueous solutions of platinum tetramine chloride, platinum tetramine hydroxide, and chloroplatinic acid. Appropriate impregnation conditions include a temperature of 20°C to 90°C;
The impregnation time is 1 to 6 hours and the concentration of the solution is 10 ^-4 to 1 molar. After each impregnation, the catalyst is dried, for example, at 100°C to 250°C for 1 to 24 hours. The amount of modifying metal ions that can be added to the catalyst is much higher for catalysts made from chloroplatinic acid or similar compounds than for catalysts made from tetramine complexes. The highest activity is retained in the former up to about 300 atomic percent and in the latter up to about 150 atomic percent. Before use, the platinum group metal is heated at 200°C to 700°C, preferably 300°C, for example in a reducing atmosphere, preferably in a flowing hydrogen stream of 500 to 10,000 V/V/h.
Preferably, the reduction is carried out by heating at 1 to 600°C for 1 to 5 hours. Preferably, the alkali or alkaline earth metal ions are added before reducing the platinum group metal. The catalyst is particularly suitable for dehydrating acyclic, linear hydrocarbons having at least 6 carbon atoms, or hydrocarbons having a linear structure having at least 6 carbon atoms that can be cyclized in their structure. Suitable for elementary cyclization. Preferred hydrocarbons are paraffins, but olefins may also be used. Particularly suitable feedstocks are C _6-10 paraffinic hydrocarbons which, when used, provide good yields of benzene and/or lower alkyl aromatics with minimal side reactions. Can be done. The feedstock may be pure hydrocarbons or a mixture of non-linear hydrocarbons. Such mixtures may also contain naphthenes and aromatics, for example petroleum distillates, especially from 60 to 250°C.
It may also be a petroleum fraction that boils within this range. Sulfur compounds in the feedstock are generally undesirable for platinum group metal catalysts. The sulfur content in the feedstock should not exceed 10 ppm (by weight), especially 1 ppm (by weight)
It is preferable that Thus, according to another aspect of the invention, there is provided a process for hydrogen transfer of hydrocarbons, which comprises contacting the hydrocarbons with the above-mentioned catalyst under conversion conditions. Broad and preferred ranges of operating conditions for dehydrogenation and/or dehydrocyclization are as follows.

[Table] This catalyst can also be used for the hydrogenation of aromatic hydrocarbons such as benzene and other compounds such as olefins and acetylenes. For reference, a broad range of operating conditions and a preferred range of operating conditions for hydrogenation are as follows.

[Embodiments of the invention]

The present invention will be further explained below with reference to Examples and Reference Examples. Example 1 Production of carbon Cabot Corporation (Cabot
Corporation) from “Black Perls 71”
45 g of carbon black, sold under the tradename Black Pearls 71, was heated to 1000° C. under a nitrogen atmosphere to remove volatiles and cooled to room temperature (11.4% weight loss). The sample was then heated from room temperature to 2700°C in an argon atmosphere, held at this temperature for approximately 30 minutes, and then cooled (further
2.3% weight loss). This second heating and cooling process took approximately 3 hours. After cooling, the carbon had a mottled black and gray appearance and had the following analytical values: BET surface area 180m ² /g Base surface area 150m ² /g Edge surface area 0.36m ² /g BET/base ratio 1.2:1 Base/edge ratio 427:1 PH 7 (measured as a slurry with water) % Graphite 30wt % (X-ray diffraction) % Amorphous carbon 70% by weight Total metal content 13 ppm Ash content 0% Adsorbed oxygen 0 As a result of the heat treatment, the total weight loss was 13.7% by weight. The carbon is believed to be spherical with a diameter of 200-400 Å and has an external graphite skin. Preparation of the catalyst 0.7% by weight of platinum was deposited on the support by impregnation with an aqueous solution of 1/10 mol Pt(NH ₃ ) ₄ (OH) ₂ for 4 hours at 90°C, followed by drying for 2 hours at 120°C. Added. A portion of this impregnated material was then impregnated for 2 hours at 90°C with an aqueous solution containing 0.74 grams of sodium carbonate per portion, and then dried at 110°C for 2 hours to form a 40-100 BBS. Sieve into mesh size, then heat at 500℃.
Reduction was carried out for 2 hours in a flowing hydrogen stream of 4000 V/V/h. The resulting catalyst contained 600 ppm sodium. This corresponds to 73 atomic percent of platinum. The catalyst was continuously stirred throughout the platinum and sodium impregnation and subsequent water removal to ensure uniform distribution of both components in and between the catalyst pellets. Use of the carbon produced as described above as a catalyst support (1) 0.225 g of catalyst was added to
℃, under atmospheric pressure, with a molar ratio of hydrogen to n-hexane of 7:1 and a liquid hourly space velocity of 4 V/V/h, n
-Used in the dehydrocyclization reaction of hexane. The microreactor had a catalyst capacity of 0.45 ml. (2) A portion of the above-mentioned catalyst, in which the sodium addition step was omitted, was also tested under the same conditions. The results are as follows.

[Table] Example 2 A sample of carbon black sold by Kabot Corporation under the trade name "Black Pearls 2" was prepared as described in Example 1.
Heated and cooled in stages (total weight loss 32% by weight). After cooling, the carbon had a mottled black and gray appearance and had the following analytical values: BET surface area 235m ² /g Base surface area 230m ² /g Edge surface area 0.3m ² /g BET/base ratio 1.02:1 Base/edge ratio 766:1 PH 7 Total metal content 13ppm Ash content 0% Adsorbed 0.7% by weight of platinum and 0.7% by weight of platinum and
A catalyst containing 600 ppm sodium was prepared. (1) n-hexane was dehydrocyclized as described in Example 1. (2) A catalyst prepared as described above but omitting the sodium addition step was also tested under the same conditions. The results were as follows.

[Table] Example 3 The sodium-containing catalyst described in Example 2 was used in Example 1.
was used for the dehydrocyclization of n-hexane to benzene under operating conditions of 42 hours continuously. The results obtained during this reaction were as follows.

[Table] Reference Example 4 Several different commercially available dehydrocyclization catalysts were tested under the operating conditions of Example 1, and their activities and benzene yields were compared to the sodium-containing catalysts described in Example 2. compared with those of catalysts. The results are as follows.

[Table] Reference Example 5 Sodium-treated catalysts similar to those in Example 2 were subjected to various reactions under atmospheric pressure in a microreactor at a hydrogen to hydrocarbon ratio of 6:1 and a liquid hourly space velocity of 1 V/V/h. It was used to hydrogenate benzene at temperature. Instead of reducing at 500°C for 2 hours, it was reduced at 250°C for 30 minutes. The following transformations were achieved.

[Table] Reference Example 6 A catalyst similar to that of Reference Example 5 was used for the hydrogenation of benzene under the same conditions and at 75°C. In this reference example, the catalyst was reduced for 1/4 hour at 225°C. The following transformations were achieved.

Reference Example 7 Reference Example 5 was repeated using a reforming catalyst containing 0.35% Pt on commercially available alumina that was reduced at 250° C. for 1 1/2 hours. The following transformations were achieved.

Reference Example 8 Reference Example 7 was repeated using a reforming catalyst containing 0.35% Pt on commercially available alumina that was reduced at 500° C. for 1 1/2 hours. The following transformations were achieved.

TABLE It will be noted that all hydrocarbon conversions were carried out in a microreactor with a catalyst capacity of 0.45 ml. This volume corresponds to 0.225 g of graphite-containing carbon-based catalyst and 0.45 g of alumina-based catalyst. In order to ensure a comparison of the platinum content in the reactor, it is necessary to load the carbon-based catalyst with twice the platinum content of the alumina-based catalyst. Example 9 A comparative test was conducted on carbon containing graphite as a carrier whose surface properties were within and outside the specifications of the present invention. Three types of heat treatments were performed on activated carbon sold as AC40. 9- Heating to 900°C in argon, then in air
Heated at 450°C for 5 hours. 9- Heat treatment was carried out in the same manner as in 9-, and then heated to 1500°C in an inert gas. 9- Heat treatment was performed in the same manner as in 9-, and then heated to 1700°C in an inert gas. A 0.7% platinum-supported catalyst was prepared on the carbon thus obtained, filled in a microreactor, and n-hexane and hydrogen were introduced to perform dehydrocyclization. Reaction conditions: Liquid hourly space velocity of n-hexane (V/V/hour) 2 Temperature (°C) 500 Pressure (absolute bars) 1 H ₂ /hexane (molar ratio) 10:1 Display of reaction results: Activity (%) ) = Total yield x 100 / Total yield + Remaining amount Selectivity (%) = Benzene x 100 / Total yield Benzene yield (%) = Benzene x 100 / Total effluent amount Cracking (%) = (C ₁ - C ₄ ) ×100/total runoff volume The results are as follows.

[Table] It has been shown that non-standard carbons with a base plane surface area/edge surface area of 5 or less have poor catalytic performance and poor benzene yield.

Claims (1)

[Claims] 1. contacting a hydrocarbon feedstock under hydrogen transfer conditions with a platinum group metal supported catalyst, the support having a basal planar surface area of at least 100 m ² /g;
In a method for transferring hydrogen from a hydrocarbon, the C ₆ ~ _C10 n-paraffin at 200~650℃
at a temperature within the range of, under a pressure within the range of 1 to 210 bar gauge pressure, a liquid hourly space velocity within the range of 0.01 to 20 V/V/hr, and a hydrogen to hydrocarbon molar ratio of 0.01:1 to
A hydrogen transfer method characterized in that dehydrogenation and/or dehydrocyclization is carried out by contacting with a catalyst at a ratio of 20:1.