DE1006104B - Process for the catalytic reforming of gasoline-type hydrocarbon mixtures - Google Patents

Description

Process for the catalytic reforming of hydrocarbon mixtures Gasoline Type The invention relates to a method of catalytic reforming of gasoline-type hydrocarbon mixtures with a relatively low Naphthene content using platinum-containing catalysts.

As is well known, you can get a significant octane increase from Obtain gasolines through catalytic reforming. This is understood to be the catalytic Treatment of hydrocarbons in the presence of hydrogen at an elevated temperature and elevated pressure, usually not consuming hydrogen. Platinum-containing Catalysts are very suitable for this purpose, and a particularly cheap catalytic one Reforming process using such catalysts is the so-called Platform method that has recently been used to an increased extent. With this one Process one evaporates the gasoline to be reformed and brings it to an elevated temperature and under hydrogen pressure with the platinum-containing catalyst, e.g. B. one with 0.3 Percentage by weight of platinum on an aluminum oxide support, which may contain halogen or not, in touch.

When the hydrocarbon mixtures used as the starting material only a relatively low naphtha content, d. H. less than 30 percent by weight have such. B. many types of gasoline from crude oils from the Middle East, and the reforming is carried out under such conditions that above all a dehydration and an isomerization of the naphthenes and an isomerization of the paraffinic hydrocarbons take place, the resulting reformates generally have an octane number that is too low. This disadvantage can be overcome by reforming under such conditions that, in addition to the above-mentioned transformations, a hydrogenative cracking of the existing Paraffin hydrocarbon also takes place to a sufficient extent, with the larger molecules are split into smaller molecules and a saturation of the result resulting unsaturated hydrocarbons takes place. Since the hydrating Cracking hydrogen is consumed by itself through dehydrogenation reactions must be delivered and, in addition, the partial pressure of the hydrogen in the gas mixture in reaction must be kept at a high value, to prevent a decrease in the activity of the catalyst, it turns out for the implementation of the reforming process on a technical scale is very important, that the dehydrogenation reactions are in equilibrium with the hydrocracking reactions keep.

It was already known that in the dehydrogenation of lower aliphatic or cycloaliphatic hydrocarbons with metal oxide catalysts whose activity can be increased or maintained by adding to the reaction mixture adding an amount of water vapor, which preferably does not exceed 3 percent by volume and is usually between 0.03 and 0.2 percent by volume.

It was also known that in the catalytic reforming of paraffin and naphthenic liquid hydrocarbon mixtures using platinum-containing Catalysts the presence of water affects the extent of hydrative cracking, in the sense that the addition of water suppresses the reactions of the hydrogenating Krackens suppressed. In the patent literature, the use of proportional high water concentrations of e.g. B. 0.5 to 1.5 mole percent or even considerably more, calculated on the supply, mentioned. At these relatively high concentrations If a larger amount of water is added, the hydrogenating cracking occurs in a correspondingly smaller amount Extent instead.

It has now been found that it is in the catalytic reforming of gasoline-type hydrocarbons with less than 30 weight percent naphthenes using platinum-containing catalysts on a support with acid character is particularly advantageous with at least eight times the molar amount of hydrogen to hydrocarbon, a temperature between 480 to 510 ° and a pressure of 10 to 50 at to work, the water vapor content of the reaction mixture being low, and that is not kept above 0.03 percent by volume. If you have the Adjusts the water content so that it meets the specified limit of 0.03 percent by volume according to the invention does not exceed the extent of the hydrocracking reactions excellent control during catalytic reforming. Given the low naphthene content of the starting material, these reactions should proceed to a considerable extent, so that an end product with a sufficiently high octane number is obtained. The effect of the very small amounts of water in the reaction mixture is that with their increase the hydrogenating cracking is intensified and vice versa when the water content decreases decreases. This is the opposite of what is known to be taking place, if a considerably higher water vapor content than 0.03 volume percent is used. In this case, an increase in the water vapor content is from suppressing the accompanied by hydrating cracking.

If in the method according to the invention an increase in the already appears necessary, the reaction mixture cannot be used alone adjust to the required higher water content by adding water, but you can also add substances that are water under the reaction conditions form, e.g. B. alcohols such as isopropyl alcohol, butanols and the like.

Therefore, when one works according to the invention, it is by adjusting of the reaction mixture to a certain water content possible, the hydrogenating Precisely control cracking reactions that take place during catalytic reforming, d. H. to accelerate or suppress them as desired, depending on the requirements of the final product. This increases the adaptability of the reforming process considerably. If it z. B. when reforming a certain starting material it is desired to achieve the greatest possible octane yield, d. H. the greatest possible Sum of reformate yield and its octane number, this can be achieved by the water content of the reaction mixture to a maximum value of about 0.01 Holds percentage by volume. Hydrogen cracking then takes place in a relatively limited manner Measure takes place, and as a result, the percentage of components of the Reformau, which boil up to 100 °, relatively low, z. B. 15 to 20 percent by volume. if on the other hand it is desirable to have a product with greater volatility with the same To produce octane number, for which one accelerates the hydrogenating cracking reactions should, one can do this by a considerably higher content of water vapor reach, e.g. B. of 0.02 percent by volume or above, but not more than 0.03 percent by volume. In addition, this method of operation has the advantage that the temperature to be maintained can be lower, e.g. B. 8 to 10 ° lower, with the remaining reaction conditions stay the same. If necessary, you can determine the octane number of the reformate a similar increase in the water content and by carrying out the reaction increase at the same temperature.

The maximum limit of 0.03 percent by volume is for the water content set to which the reaction mixture is adjusted according to the invention, since it It has been found that when the water content is increased above this limit can only achieve a small increase in octane number, and this cancels out the decreased Yield of reformate does not increase. In addition, this limit is set because at a higher content of water vapor depending on the reaction conditions used can be cracked so strongly that the life of the platinum catalyst is reduced considerably, which of course is undesirable. On the other hand, at a maximum water content of 0.03 volume percent the original activity and Selectivity of the platinum catalyst in use is almost completely preserved, so that you can use him continuously for long periods of work of z. B. 2000 hours and above can use.

If you have the water content according to the method according to the invention setting the correct value, it is possible to carry out the reforming process in such a way that that in each individual case the best compromise between process selectivity, that of the yield of liquid product and hydrogen at a certain octane number depends, and the life of the catalyst on the one hand and the properties of the obtained products on the other hand.

In view of the relatively low naphthene content of the starting material Hydrocarbon mixture used in the process according to the invention should one quite sharply defined reaction conditions, such as. B. Temperatures of about 480 to 500 degrees or even above, and relatively low space velocities use in order to obtain reformates with a sufficiently high octane number. In this case It is important that the hydrogen in the reforming treatment in large molar Amount is present, at least in eightfold or z. B. ten times the molar amount, based on the hydrocarbon, since the catalyst when using less Amount of hydrogen loses its activity fairly quickly, so you only get it can use for a relatively short time.

The hydrogen in the presence of which the reforming treatment takes place, does not need to be pure and can therefore be in the form of a hydrogen-rich Gas are supplied. In practice, it is preferable to use a portion of the hydrogen-rich Gas that is formed in the reforming process, use for this purpose and it is therefore circulated in a circular process.

The starting material to be reformed usually has a low one Water content usually not more than 0.01 percent by volume. When setting the Water content of the mixture of hydrogen and hydrocarbons to be reformed you should of course have this low water content of the added mixture and also consider the water content of the circulating gas. It goes without saying that the water content of the mixture fed is an independent variable. Of the On the other hand, the water content of the circulating gas may differ from that of the supplied mixture depend, although this does not always have to be the case, as the water content of the circulating Gas may also depend in part or entirely on how the gas is being used an aqueous solution of amines or amino alcohols, e.g. B. mono-, di- or triamines or other suitable basic substances to remove all hydrogen sulfide, is treated.

Adjusting the water vapor content of the reaction mixture to the value required for the result desired in reforming, one can Depending on the circumstances, by drawing off water or adding small amounts of water or a substance that forms water under the reforming conditions. These Regulation can be carried out in any convenient way.

The method according to the invention is preferably carried out in such a way that that the hydrogen-rich gas that is obtained in the reforming process before you put it back in the process, to such a thing Water content sets that the water vapor content of the mixture of circulating gas and hydrocarbon, that is introduced into the reforming zone no longer has the required value than 0.03 percent by volume.

If the substance to be reformed has a normal water content of around Has 0.01 weight percent, the water content of the circulating gas must be reduced to one Set a maximum value of 200 mg per Nm 3, depending on the one to be produced Reformat established requirements and the ratio of hydrogen to the Hydrocarbon mixture to be reformed, in which the reforming treatment takes place.

Since the hydrogen-rich gas generally has a water content of has more than 200 mg per Nm3, it is usually necessary to have this water content before the gas is recycled. For this purpose one can use the gas treat with one or more desiccants designed to reduce the Water content.

In practice you can easily reduce the water vapor content to about Reduce 200 mg per Nm3 by passing the gas through a drying device, the glycol or a glycol derivative, such as. B. diethylene glycol contains.

any further required reduction in the water content in the circulating gas can be achieved by drying with glycol or a glycol derivative or a similar drying agent, a further treatment with a solid substance can follow, which has a high water-binding force, z. B. with bauxite, activated Alumina, silica gel and the like have been found to be able to be used in this manner can easily reduce the water content of the gas to 25 to 50 mg per Nm3.

If the starting material to be reformed and the resulting hydrogen-rich Gas should have such a low water content that when returning the Gas the water content of the mixture introduced into the reforming zone below of the desired value, the salary can be increased to the correct value, by adding the required small amount of water or a water-supplying substance, such as B. isopropyl alcohol, sec. or tert. Butanol and the like, the circulating gas or to the feed mixture or the mixture of the two.

The method according to the invention can be used for reforming any liquid Use gasoline-type hydrocarbons that are relatively low Has naphthene content, namely less than 30 percent by weight, e.g. B. 20 to 25 percent by weight or below, such as B. Heavy gasoline or heavy gasoline fractions obtained by Distillation of crude oils from the Middle East.

In the method according to the invention, use is made of those containing platinum Catalysts that are common in catalytic reforming processes. These catalysts can from a small amount, e.g. B. 0.1 to 1 weight percent platinum on one Carrier, such as B. alumina, silica-alumina or silica-magnesia exist. As far as they are aluminum oxide-containing carriers, you can use them with little Quantities, not more than 1 percent by weight, of one or more halogens, in particular activate with chlorine and fluorine.

The temperature to be used during reforming, which depends on the Starting material and the catalyst can change something is at least about 470 ° and is preferably between 480 and 510 °. The pressure is usually between 10 and 100 at, preferably between 20 and 50 at, while a relatively employs low space velocity, usually less than about 5 and preferably between 2 and 2.51 liquid starting material per liter of catalyst per hour.

The use of a pressure of less than 30 atm can be advantageous, since in this way one can obtain products with a slightly higher octane number, the yield remaining the same or only slightly lower than when the reforming treatment is carried out at a pressure greater than about 30 at. In this case it is expedient to use a molar ratio of hydrogen to hydrocarbon of more than 10: 1 e.g. B. 12: 1 to use in order to avoid the risk of a decrease in catalyst activity. In this case it is furthermore desirable to adjust the water content of the reaction mixture to a value of less than 0.02 volume percent, since it has been found that the octane yield increases at these lower pressures and a water content of 0.02 to 0.03 percent by weight drops sharply, while the life of the catalyst is also reduced.

The method according to the invention is further carried out by the following Examples explained: Example 1 A heavy gasoline obtained in the distillation of crude oil with a boiling range between 110 and 190 °, the 60 percent by weight paraffins, 24 percent by weight Naphthenes and 16 percent by weight aromatics and an F-2 octane number of about 30 and a water content of about 0.01 percent by weight, was about a commercial catalyst for normalization with a space velocity of 2.31 per liter of catalyst and hour together with such a large amount of 85 percent by volume Hydrogen-containing gas passed that the molar ratio of hydrogen to Hydrocarbon was 10: 1 at an inlet temperature of the catalyst bed of 495 ° and a pressure of 40 at.

In order to show the effect of minimal amounts of water vapor, the water content of the reaction mixture passed over the catalyst was changed. This was achieved by drying the circulating gas almost completely and adding a small amount of isopropyl alcohol to the hydrocarbon mixture fed. With a water vapor content of the circulating gas of less than 50 to 400 mg per Nm3, corresponding to a total water content of the reaction mixture of about 0.01 to 0.05 percent by volume, the following results were obtained, the figures given for the octane yield being the sum of the reformate yield (C5 +) and its octane number. Water content of the circulating gas 50 100 200 400 mg,: Vm Reformate yield (C, +) Weight percent ......... 88.6 85.8 84.3 83.1 F-2 octane number ............ 73.9 76.4 77.6 77.9 Octane yield ............ 162.5 162.2 161.9 161.0 Low-boiling component with Kp. up to 100 °, in volume percent of reformate ... 16.0 21.0 25.0 27.0 Yield of aromatics in Weight percent of feed 40.7 41.0 40.9 40.7 Produced gas (containing 85 percent by volume H2) 1 / kg Feed ................. 104.0 95.0 88.0 78.0 These results show that if the reaction conditions remain the same, the water content has almost no effect on the formation of aromatics, but that the hydrogenating cracking increases in accordance with the increase in the water content, especially in the range in which the water content of the circulating gas is 200 mg / Nm3, which means the yield of the reformate falls and the octane number increases.

Example 2 The starting material and the reaction conditions were the same as in Example 1 with the exception that the inlet temperature of the catalyst bed was changed to keep the octane number of the reformate constant between 77.5 and 78 keep.

The results obtained with different water contents were as follows: Inlet temperature ('C) 503 498 495 492 Water content of the circulating gas <50 100 200 400 in mg / Nm 3 Reformat- (C5 +) yield in Weight percent ......... 85.8 84.7 84.3 83.8 Low-boiling component with bp up to 100 'in volume percent of reformate ... 20.0 23.0 25.0 27.0 Yield of aromatics in Weight percent feed 43.5 42.0 40.9 39.5 Produced gas (containing 85 percent by volume H2) 1 / kg Feed ................. 120.0 100.0 88.0 76.0 These results clearly show the effect of the water content on the process temperature required to maintain a certain level of octane number and on the properties of the product obtained.

Example 3 The same heavy gasoline as in Example 1 was about a Commercial platform catalyst conducted at a space velocity of 2.31 per liter of catalyst per hour, together with such a large amount of hydrogen-rich Circulating gas that the molar ratio of hydrogen to hydrocarbon mixture is 12: 1 at a catalyst bed inlet temperature of 495 'and a pressure of 27.2 at. Before recycling, the circulating gas was brought to a water content set of less than 50 mg / Nm3 by drying with activated aluminum oxide.

The yield of reformate (C, +) obtained in this way was 87.1 percent by weight and the F-2 octane number is 78.7. The content of the components of the reformate with Kp. Bis 100 ° was 16 percent by volume.

If the space velocity was reduced to 2, but the reaction conditions were otherwise the same, then the reformate obtained in a yield of 86.1 percent by weight had an F-2 octane number of 80.6 and a content of components with a boiling point of up to 100 ° 18 percent by volume. After the process had been carried out continuously for 670 hours, the inlet temperature of the catalyst bed being increased to 501 ' , the reformate yield was still 85.3 percent by weight and the octane number was 81.2.

If you repeated the experiment described in the previous paragraph, However, the water content of the circulating gas is 200 mg / Nm3 and the temperature is 485 ° a reformate yield of 83.7 percent by weight with an octane number was obtained of 79.6 and a content of components with bp to 100 'of 25 percent by volume. In this case, the octane yield fell accordingly from 166.7 to 163.3.

Claims (4)

PATEN TA NS PRÜCHr #, - 1. A process for the catalytic reforming of hydrocarbon mixtures of the gasoline type with a naphthene content of less than 30 percent by weight, in which the starting material to be reformed is brought into contact together with a catalyst which contains platinum on a support with acidic properties, characterized in that the reforming reaction is a temperature between 480 and 510 °, a pressure between 10 and 50 at and a molar ratio of hydrogen to hydrocarbon of at least 8: 1, the water vapor content of the reaction mixture being set to a low value not exceeding 0.03 percent by volume. 2. The method according to claim 1, characterized in that "that the water vapor content of the forming during reforming Gas that is rich in hydrogen and is recycled before the Return is set to a value of less than 200 mg / Nm3. 3. Procedure according to claim 1 or 2, characterized in that the reforming treatment at a pressure of less than 30 at and a molar ratio of hydrogen Hydrocarbon greater than 10: 1 and a water content less than 0.02 By volume. 4. The method according to claim 1 to 3, characterized in that that the catalyst used for reforming does not exceed 1% by weight Contains platinum on an aluminum oxide carrier and is activated with halogen.