NO137986B - PROCEDURE FOR THE PREPARATION OF A BIFUNCTIONAL CATALYST SUITABLE FOR ISOMERIZATION AND HYDROCRACKING OF HYDROCARBONS - Google Patents

Abstract

Process for the preparation of a bifunctional catalyst suitable for the isomerization and hydrocracking of hydrocarbons.

Description

The present invention relates to a method for production

of a bifunctional catalyst suitable for the isomerization and hydrocracking of hydrocarbons, and the peculiarity of the progress

the method according to the invention is that it is produced from a carrier material selected from the group of natural and synthetic minerals of the clay type with a crystalline matrix with a planar non-porous structure and a high charge density (0.4 to

1.0 electron charges per half-cell Si^^g) such as beidelite and vermiculite, as centers with controlled acidity are formed on the surface of the carrier material, all the same, by neutralizing missing charges with the help of a cation

exchange of between 20 and 100% with cations of the elements in groups Illb, IVb, VIb, Vllb and VIII of the periodic table, after which the material is impregnated with a platinum or palladium salt in amounts of between 0.01 and 0.5% by weight and the material is then subjected to a thermal treatment at temperatures in the range of 300 to 600°C, preferably at 450°C,

for 10 hours.

The reactions that can be carried out using catalysts produced according to the invention are e.g. isomerization of hydrocarbons in general and among these in particular: a) selective isomerization of 2,2-dimethylbutane to 2,3-dimethylbutane, further

b) selective isomerization of heavy normal paraffins. Other reactions that are catalyzed by means of the catalysts prepared

according to the invention is hydrocracking of hydrocarbons.

Isomerization and hydrocracking of hydrocarbons are operations that are widely used in industry.

The first reaction enables the production of highly branched saturated hydrocarbons, which, when mixed with other hydrocarbons, increase the anti-knock properties of the paraffinic hydrocarbons and thereby enable the complete or partial avoidance of additives based on lead alkyl or of another kind.

Blending of branched hydrocarbons with hydrocarbon fractions for use as fuel for internal combustion engines makes it possible to significantly increase the octane number of the mixtures in a very simple and economical way.

But even if isomerization reactions take place, secondary reactions with hydrocracking also take place and this produces hydrocarbons with an undesirable low molecular weight.

In contrast, hydrocracking allows the production of certain light fractions that are rich in isoparaffins and therefore usable as motor gasoline by starting from heavy distillates or gas oils.

The above-described treatments are carried out using well-known techniques by allowing suitable petroleum fractions to react in the presence of hydrogen at high pressure, with catalysts in a reactor maintained at the desired temperature.

It is also necessary to point out that the working conditions where

the catalysts that are known in this branch of technology, can usually be used are very critical, especially in isomerization operations, due to the limited range of temperature

and print where there is optimal turnover and selectivity.

The catalysts produced according to the invention for the treatment of hydrocarbons, in particular for the isomerization of paraffinic hydrocarbons and for the hydrocracking of heavy fractions, enable the achievement of high selectivities at conversion rates that are very close to those that can be calculated thermodynamically.

The centers with controlled acidity are produced artificially by means of , charge transfer and the degree of acidity, which as mentioned is controlled, depends on the production system used to obtain the catalyst.

As mentioned, the acidity is produced by using a material with a chrysalline base mass, planar and non-porous, which in the chrysatal lattice has missing charges which, in order to achieve electrical neutralization, require a compensation from cations on the outer surface," and these requirements are satisfied by the natural or synthetic clay-type minerals with a high charge density

(0.4 - 1 electron charges per half-cell Si401Q) with substitution preferably tetrahedral, as it occurs in phyllosilicates.

Specifically, these minerals belong to the families:

smectites of the "beidellite" type (beidellites, non-tronites), limited expansion minerals of the "vermiculite" type (vermiculites, hydrobiotites, illites).

Such minerals in a finely divided state (particle size less than 40 are subjected to cationic exchange with bi- or polyvalent cations of the elements from groups Illb, IVb, VIb, Vllb and VIII in the periodic table and with the series of lanthanides (Handbook of Chemistry and Physics - 49. edition 1968 - 1969 - Chemical Rubber Publishing Company), and then preferred cations of lanthanum, cerium, titanium and manganese.

The precious metal present on the surface of the catalyst

according to the invention, the percentage is between 0.01 and 5% by weight and is introduced on the surface of the catalyst by means of impregnation with a compound of the mentioned metal.

In the case of platinum, the impregnation is carried out with I^PtClg or Pt(NH3)4(O<H>)2.

The catalyst produced according to the present invention enables conversion and selectivity which are industrially very interesting.

Furthermore, it entails remarkable economic advantages in comparison with the conventional catalysts due to the cheap minerals used for the production or the very simple and cheap processing to which these are subjected, or due to the fact that this catalyst gives results of industrial interest with very small amounts of precious metals , which in the case of isomerization is preferably 0.15% by weight, i.e.

much less than the amounts required in conventional catalysts. Furthermore, it is necessary to point out that it is

. possible.to achieve, catalysts with different degrees of acidity only by

to change the starting material, the nature of the cation with which the exchange is carried out and the method of preparation.

In reality, for the same starting material with a certain lack of charge as discussed earlier, the use of one or the other cation will allow the achievement of different catalysts, which have different surface acidity (acidity here means acidity due to charge transfer).

A different distribution of the reaction products is also achieved by changing the starting material and by retaining the same cation.

The catalysts will be described in more detail by means of a method for isomerization using the catalyst described above.

The process of isomerization of paraffinic hydrocarbons

as the only component or as a mixture and then in particular isomerization of 2,2-dimethylbutane to 2,3-dimethylbutane is carried out at different temperature conditions, pressure, relative volume velocities and percent conversion per passing. The temperature used is determined depending on the particular type of catalyst used and is always kept between 100°C and 600°C, preferably between 300 and 450°C.

The pressure is chosen so that it is ensured that the completion of the reaction with the reaction components takes place in the vapor phase and at the particular pressures used the pressure range is located between atmospheric pressure

2

and 150 kg/cm .

The relative volume velocity (HLSV) is between 0.1 and 20 h <1. >Relative, volume velocity here and in the following means the ratio between volumetric flow per hour of added liquid hydrocarbons and the catalyst volume.

The isomerization can be carried out either continuously or discontinuously.

The isomerization processes are particularly and preferably used to convert 2,2-dimethylbutane to 2,3-dimethylbutane due to the higher octane number of the latter product.

The isomerization process for 2,2-dimethylbutane is preferably carried out continuously in two zones. The supply consisting of the hexane fraction is isomerized in a first reaction zone containing the catalyst according to the invention.

A mixture in thermodynamic equilibrium with the C-C aliphatic hydrocarbons is obtained from which 2,2-dimethylbutane is separated by distillation.

The compound used is sent to another reaction zone containing the catalyst produced according to the invention where isomerization of 2,2-dimethylbutane to 2,3-dimethylbutane takes place.

The reaction products are sent to a separation column where 2,2-dimethylbutane which was not reacted is extracted from the top and re-circulated to the second isomerization reactor, while 2,3-dimethylbutane is taken out from the bottom of the column together with a controlled amount of 2-methyl - pentane.

With the aforementioned method, 2,3-dimethylbutane is obtained as the predominant product.

It is noted that both reaction zones can be operated with the catalyst produced according to the invention.

It is also possible that the first zone is operated using a catalyst of another type, e.g. the one described in Italian patent document 743,088. However, it is absolutely necessary that the second zone is operated with the catalyst manufactured according to the invention.

The catalyst produced according to the invention can also be used in hydrocracking processes and then the supply to be treated, which consists of liquid heavy hydrocarbons, is sent to a reactor which is filled with the catalyst produced according to the invention.

The conversion is carried out at a temperature between 150 and 450°C at

a pressure between 35 and 150 atmospheres.

Relative volume velocity is between 0.1 and 10 h ^. The products from the reactor are subjected to conventional treatments with de-butanisation and fractionation.

In the following, preferred embodiments of the invention will be described with the help of exemplary embodiments where the catalyst produced according to the invention is used.

In these examples, the term "conversion" means the ratio: and the term "selectivity" means the ratio:

Selective isomerization of 2,2-dimethylbutane.

Beidellite was used, characterized by an equivalent surface of 54 A 2. The term "equivalent surface" means the area available for a single monovalent cation. .10 grams of beidelite were subjected to ion exchange using the usual method with a 2N aqueous solution of lanthanum nitrate.

The process was repeated three times at a temperature of 60-70°C to ensure complete ion exchange.

The material obtained in this way, after thorough washing to remove all foreign ions present, was subjected to impregnation with a solution of chloroplatinic acid in such a quantity that it gave the finished catalyst a platinum content after drying and calcining at 350 °C of 0.15%.

Control of the degree of hydration of the catalyst under working conditions was carried out by adding suitable amounts of water dissolved in the feed hydrocarbons (50 - 100 ppm water).

The catalyst thus prepared was tested in a flow microreactor for the isomerization reaction of 2,2-dimethylbutane.

The reaction conditions were the following:

In table 1, the obtained results are shown.

As the desired product in this case is 2,3-DMB, selectivity must mean the ratio

(DM = dimethyl, DMB = dimethylbutane; MP = methyl pentane; Cg = hexane) as other cracking products or hydrocracking products were not present.

EXAMPLE 2

A vermiculite with an equivalent surface area of 37 A 2 was used. The vermiculite had been finely ground to particles less than 40 microns in diameter.

The material obtained in this way was, after several washings to remove possible soluble impurities, subjected to cation exchange with a 2N solution of lanthanum nitrate as in example 1. Impregnation was then carried out in a similar way with chloroplatinic acid as follows that there was a content on

o.15 weight percent platinum in the finished catalyst. Also in this case, an appropriate amount of water was added to the hydrocarbon feed.

The reaction conditions were the following:

EXAMPLE 3

Selective isomerization of normal hexadecane with 20 grams

catalyst in the form of 0.15% by weight Pt supported on 99.85% vermiculite exchanged with titanium and testing of selective isomerization reaction for normal hexadecane.

The operating conditions and the data obtained were as follows:

Reaction conditions:

T = 330°C

P = 50 kg/cm<2>

HIS V = 1

H2/hydrocarbon ratio = 5

The following data is obtained:

Reaction product:

Hydrocarbons C3_c^5 (mol percent) 15%

Ratio iso-C,,

16

Total C,c 85%

16

By C3~C^5_ fractions is meant all products that write seq

from the hvdrocracking reaction and which it is desirable to limit within relatively narrow limits.

The products of interest in this case are the hydrocarbons with the same molecular weight as the feed but with a branched structure; Therefore, the signs of the course of the reaction considered are percent hydrocracking and the ratio between iso-hexadecanes and the sum of all C^g components.

EXAMPLE 4

Selective isomerization of heavy paraffin fractions.

20 grams of catalyst in the form of 0.15 weight percent Pt carried on

99.85% vermiculite yielded with titanium for reaction with selective isomerization of normal heavy paraffins in a gas oil fraction with boiling temperature from 250 to 350°C with the aim of lowering the pour point of the fraction itself.

The reaction conditions and product properties are as follows

Reaction conditions:

T = 340°C

2

P = 50 kg/cm

HLSV = 1

H2/hydrocarbon ratio = 5.

Reaction products:

a) With cooking temperature up to 250°C = 22 percent by weight.

b) With a boiling temperature higher than 250°C (250°C+) = 78 percent by weight.

Product features:

Feed (250°C+): d15 = 0.804; pour point = +19°C

Product (250°C+) : d15 = 0.795; pour point - + 3°C

EXAMPLE 5

Normal hexadecane hydrocracking. 20 grams of catalyst *in the form of vermiculite supplemented with titanium with 0.15 wt% Pt was tested for the hydrocracking reaction of n-hexadecane.

The data obtained are the following:

Reaction conditions:

T = 350°C

2

P = 50 kg/cm

HLSV =0.5

I^/hydrocarbon ratio = 10

Product features:

Conversion = 80%

Molar distribution of the reaction products:

In the above, C^, C^, C,-, etc., represent isoparaffinic and paraffinic hydrocarbons with the specified number of carbon atoms.

EXAMPLE 6

Selective isomerization of normal hexadecane

20 g of catalyst consisting of 0.15% by weight Pt supported on 99.85% vermiculite exchanged with elements of groups Illb, VIb and VII of the periodic table was tested for selective isomerization reaction for the normal hexadecane, under the following operating conditions: 2

Pressure: 50 kg/cm

Temperature: varying from 330 to 390°C

HLSV = 1

I^/hydrocarbon ratio = 5

The results obtained are indicated in the following table

Claims (1)

Process for the production of a bifunctional catalyst suitable for the isomerization and hydrocracking of hydrocarbons, characterized in that it is produced from a carrier material selected from the group of natural and synthetic minerals of the clay type with a crystalline matrix with a planar non-porous structure and a high charge density ( 0.4 to 1.0 electron charges per half-cell SI^iq) such as beidelite and vermiculite, as centers with controlled acidity are formed on the surface of the carrier material, all equal, by neutralizing missing charges using of a cation exchange of between 20 and 100% with cations of the elements in groups Illb, IVb, VIb, Vllb and VIII in the periodic table, after which the material is impregnated with. a platinum or palladium salt in amounts of between 0.01 and 0.5% by weight and the material is then subjected to a thermal treatment at temperatures in the range of 300 to 600°C, preferably at 450°C, for 10 hours.