DE1096888B - Process for the catalytic isomerization of hydrocarbon mixtures which are solid at normal temperature - Google Patents

Description

A process for catalytic isomerization of solid at normal temperature hydrocarbon mixtures The invention relates to the catalytic isomerization of solid at normal temperature hydrocarbon mixtures containing at least 50 percent by weight of paraffin, in particular to the use of catalysts which, in advance by heating to a temperature of at least 250 'C are pretreated in the presence of hydrogen and under pressure.

The expression "hydrocarbon mixtures solid at normal temperature" is intended to include solid paraffin-like products, such as those usually obtained from high-boiling natural or synthetic hydrocarbon mixtures are obtained and many times also normally contain liquid hydrocarbons.

The starting material should have a content of at least 50 percent by weight Have paraffin. This paraffin content is derived from the oil content of the hydrocarbon material determined, determined according to ASTM method D 721-51 T.

It is known,. that the normal or branched alkanes present in the paraffin can be converted into branched or more highly branched alkanes by subjecting the paraffin to a catalytic isomerization. According to an earlier patent 931826 , this isomerization can be carried out quickly and selectively by bringing the paraffin in vapor form together with hydrogen at a temperature between 300 and 550 ° C, preferably between 350 and 450 ° C, in contact with a catalyst that does not more than 1 percent by weight of platinum on a support, e.g. B. clay contains. According to patent 960273 , the desired isomerization can also be carried out with the aid of a similar catalyst, but the paraffin is treated in the liquid phase under otherwise identical conditions. Furthermore, according to patent 1033193, cheaper catalysts which do not contain platinum can be used for the isomerization of mixtures of hydrocarbons which consist of at least 20 percent by weight of paraffin-like hydrocarbons which are solid at normal temperature. These are those catalysts which are composed of one or more metals or metal compounds, in particular oxides or sulfides, of metals of VI. Group, left column, and / or the VIII. Group of the Periodic Table (with the exception of the platinum metals) consist, applied to a support with acidic character, which can be achieved or enhanced by introducing halogen, preferably fluorine.

It can be done with the help of these methods, which are carried out at elevated pressure, e.g. B. 10 to 40 at, a low melting product that is used as an ingredient can be used for high-quality lubricants and for diesel oils, from high-melting, paraffin-like raw materials that are solid at normal temperature are obtained, where practically the molecular weight of the starting materials is retained and the Isomerization without any significant degree of cleavage reactions occurring runs.

It has now been found that in the catalytic isomerization of Hydrocarbon mixtures which are solid at normal temperature and which are at least 50% by weight Containing paraffin, an increase in the conversion of the starting material into the desired isomerization can be achieved if you use a catalyst used, which was previously subjected to a pretreatment in a known manner, wherein this treatment consists of heating the catalyst in the presence of hydrogen under pressure to a high temperature of at least 250 ° C.

The duration of this pretreatment, which depends on the nature of the catalyst and the heating temperatures can vary quite considerably, is usually several hours, e.g. B. 5 to 10 hours. In the known isomerization processes, normally liquid hydrocarbons, e.g. B. petrol hydrocarbons, are processed, the catalysts are sometimes in a hydrogen atmosphere heated to the desired reaction temperature, with optionally a reduction of a metal oxide to which the metal is intended. The catalyst is here mostly brought to the reaction temperature very quickly. Such treatment is in the generally not with the conditioning treatment according to the invention, most of the time requires prolonged heating with hydrogen under pressure to compare. Man could not deduce from this that in the isomerization of normal Temperature solid hydrocarbons, so another starting material that Use of catalysts preheated for a long time under hydrogen pressure would be of particular benefit.

In the pretreatment of the catalyst to be used according to the invention hydrogen is passed through under pressure. If desired, the high can be over 250 ° C can be maintained for a longer period of time, and it corresponds expediently approximated to the temperature which is subsequently used in the isomerization will.

The hydrogen pressure is z. B. 5 11t or more, with in general Pressures between about 25 and 100 11t are preferred: The hydrogen is not required to be pure, and hydrogen-free gases can also be used and their other components such as hydrocarbon gases and nitrogen, among Pretreatment conditions are inert.

The hydrogen pressure in the pretreatment of the catalyst can be the same or not equal to the pressure at which the isomerization of the paraffin-like, is carried out at normal temperature solid hydrocarbons, but is preferred lower.

It was found to be conditioned upon isomerization with the Catalyst is often beneficial, the pressure during the isomerization after the expiration a relatively short operating period, e.g. B. from 50 to 150 hours, to lower, z. B. from 40 to 50 to 25 to 35 11t, as this is often a considerable further Increase in conversion is accompanied, which is thus noticeably higher than when one begins immediately at the lower pressure, with otherwise unchanged conditions. This advantage is obtained especially when one is at a lower pressure pretreated catalyst is used as the pressure that the subsequent isomerization is equivalent to.

The isomerization itself can be carried out both in the vapor phase and in the liquid phase. Working in the liquid phase, in which the so-called trickle technique can be used with advantage, in which the material to be isomerized trickles in a thin layer over a fixed catalyst (cf. the older patent 1000 017), is particularly useful for a starting material with such high molecular weight that it cannot be vaporized without cleavage or extreme difficulty, e.g. B. paraffins with an average molecular weight over 350 and with a boiling range over 300 ° C.

The most favorable conditions for isomerization vary somewhat depending on the starting material to be isomerized and the catalyst used. The isomerization is generally particularly advantageous, especially when working in the liquid phase. at a temperature of 400 to 440 ° C, a pressure between 20 and 40 11t, a contact time of 0.5 to 10 minutes and a throughput of 1 to 5 kg of starting material per liter of catalyst per hour, the molar ratio of hydrogen to starting material of 10: 1 to 60: 1 fluctuates.

The process according to the invention has been found to be particularly useful when isomerization catalysts are used which contain no more than 1% by weight of platinum on a support having an acidic character, e.g. B. alumina containing a small amount of chlorine or fluorine, since the effect of conditioning is usually greatest with these catalysts. However, it is not limited to these and can also be used advantageously with other catalysts with isomerizing, dehydrogenating properties and also acidic nature, e.g. B. those protected in the patent 1033 193, especially in the case of molybdenum-alumina fluorine catalysts with less than 5 percent by weight of fluorine, evenly distributed over the active surface of the support.

With the help of the method according to the invention, considerably higher Yields of isomerized products are obtained than when working with one unconditioned catalyst under otherwise identical reaction conditions. So if paraffins boiling above 300 ° C (average molecular weight above 350) isomerized using platinum catalysts, yields obtained in oil with a boiling range above 300 ° C, which, depending on the conditions, below which the catalyst was pretreated, approximately 10 to 2011 / o higher than the yield when using the non-pretreated catalyst. Fission reactions, which lead to the formation of low molecular weight products occur only to a small extent Extent on, and the degree of conversion, d. H. the percentage (percent by weight) isomerized product with the same molecular weight as the starting material, based on the total of the converted starting material, which is 85 to 90% or can be even more, is at least as high as if an untreated one Catalyst is used while the properties, such as viscosity, viscosity index and pour point, of the oils obtained in both cases only insignificant differences exhibit.

The invention is further illustrated in the following examples: Example I A solid paraffin, melting at 54 ° C and with an oil content of 4.7 percent by weight, Boiling above 300 ° C and with an average carbon number of 27, was at a throughput of 2 kg per liter of catalyst and hour together with 10 mol of hydrogen per mole of paraffin at 420 ° C and a pressure of 35 11t from top to bottom over one granular technical so-called platforming catalyst passed, whereby the molten paraffin trickled over the catalyst particles in a thin layer. The catalyst was heated from room temperature in 8 hours before adding the paraffin preheated to 420 ° C, with hydrogen at atmospheric pressure in an amount of 1000 normal liters per liter of catalyst and hour was passed through.

The hydrocarbons boiling below 300.degree. C. (about 6 percent by weight of the starting paraffin) were distilled off from the product obtained, whereupon the product, which boiled above 300.degree. C., was dewaxed at -5.degree. The oil obtained in this way in a yield of 46.6 percent by weight, based on the starting paraffin , had a pour point of 8 ° C, a viscosity index of 157, a viscosity of 11.6 cSt at 38 ° C and 3.2 cSt at 99 ° C. The paraffin to oil conversion was 88%.

The isomerization was carried out under the same conditions and under Repeatedly using the same catalyst, but at a pressure of 35 at with hydrogen to a temperature of 420 ° C, but otherwise as stated above, has been preheated. The oil thus obtained in a yield of 55 percent by weight had a pour point of 8 ° C, a viscosity index of 156, a viscosity of 11.5 cSt at 38 ° C and 3.0 cSt at 99 ° C.

The degree of conversion of the paraffin into oil was 90%.

Example II The starting material was the same paraffin as in the example I, the same catalyst was used, which in 8 hours to 420 ° C v was preheated while 1000. ', normal liters of hydrogen per liter of catalyst and passed for one hour at a pressure of 35 atm. The isomerization took place under the same conditions as in Example I instead of with the difference that the pressure was initially kept at 50 atm and then reduced to 35 atm after about 70 hours became. The obtained product was also made in the same manner as in Example I worked up. During the initial period at 50 atm the yield of oil became gradual up to a value of 47.2 percent by weight, based on the starting paraffin. After the pressure was reduced to 35 atm, the yield increased considerably; H. to 66 percent by weight. The degree of conversion of the paraffin into oil was then 90%, while the oil obtained has a pour point of -I-8 ° C, a viscosity index of 151 and had a viscosity of 11.9 cSt at 38 ° C and 3.2 cSt at 99 ° C.

If the same platinum catalyst was previously heated to 420 ° C, while you get 1300 normal liters of hydrogen per liter of catalyst and hour with a A pressure of 50 atm was passed through and the isomerization was carried out under a pressure of 50 at worked, a yield of dewaxed, over 300 ° C boiling Oil obtained increasing from 48% to 51% in the course of about 130 hours. If then the isomerization at a pressure reduced to 35 atm, but otherwise unchanged Conditions were continued, a yield of 61% was obtained. The degree of conversion the paraffin in oil was then 90%. The oil obtained had a pour point of -i-5 ° C, a viscosity index of 148 and a viscosity of 11.5 cSt at 38 ° C and 3.1 cSt at 99 ° C.

Claims (5)

PATENT CLAIMS: 1. Process for the catalytic isomerization of Hydrocarbon mixtures which are solid at normal temperature and which are at least 50% by weight Containing paraffin, taking the starting material in the presence of hydrogen at temperatures from 300 to 550 ° C and an elevated pressure with a solid isomerization catalyst brings into contact, characterized in that a catalyst is used, that previously by heating to a temperature of at least 250 ° C in the presence has been pretreated by hydrogen and under increased pressure in a known manner is. 2. The method according to claim 1, characterized in that the to be used The catalyst has been gradually heated to a temperature which approximates that in the subsequent isomerization. 3. The method according to claim 1 and 2, characterized in that the catalyst to be used at a lower Pressure has been pretreated as that intended for the subsequent isomerization is. 4. The method according to claim 1 to 3, characterized in that the to be used Catalyst has been pretreated at a pressure between 25 and 100 atm. 5. Procedure according to claim 1 to 4, characterized in that during the isomerization of Pressure is reduced after a relatively short period of operation. Into consideration pulled documents: U.S. Patent Nos. 2,479,110, 2,589,189. Contemplated Older patents drawn: German patents No. 1000 017, 1033193.