NO137985B - BYFUNCTIONAL CATALYST FOR ISOMERIZATION AND HYDROCRACKING OF HYDROCARBONS - Google Patents

Description

The present invention relates to bifunctional catalysts for the treatment of paraffinic hydrocarbons as individual components or as a mixture for the production of products with properties necessary for certain industrial applications.

The reactions that can be carried out using catalysts 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 catalysed using the catalysts according to the invention are 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 are mixed with others

hydrocarbons increase the anti-knock properties of the paraffinic hydrocarbons and make it possible to completely or partially avoid the use of additives based on lead alkyl or other compounds.

Mixing 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 convenient way.

Although isomerization reactions take place, there are also secondary reactions with hydrocracking taking place, which produces hydrocarbons with an undesired low molecular weight.

In contrast, hydrocracking allows the manufacture

of certain light fractions that are rich in isoparaffins and therefore usable as motor petrol by starting from heavy distillates or gas oils.

The treatments described above are carried out with the help of

of well-known technique 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 under which the catalysts 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 pressure where there is optimal conversion and selectivity.

The catalysts according to the invention for treatment

of hydrocarbons, in particular for the isomerization of paraffinic hydrocarbons and for the hydrocracking of heavy fractions, enables the achievement of high selectivities at conversion rates that are very close to those that can be calculated thermodynamically.

The invention thus relates to a bifunctional catalyst

for the isomerization and hydrocracking of hydrocarbons and the peculiarity of the catalysts according to the invention is that it is made from avl) a carrier material selected from natural or synthetic minerals of the clay type with a crystalline ground-mass structure in the form of planar and non-porous parallel layers with high charge density ( 0.4 to 1.0 electron charges per half-cell Si40lQ); in that the surface of the support material has centers with, for the respective purposes, the same set acidity, all equal, in that the acidity has been achieved by charge displacement or one of the type proton acid or Lewis acid, and 2) fine

dispersed platinum and/or palladium in an amount of between 0.01 and 0.5% by weight calculated on the whole catalyst.

These and other features of the invention appear in the patent claims.

The centers with controlled acidity are produced artificially by means of different methods and the degree of acidity, which can be controlled, depends on the production method used to obtain the catalyst.

The acidity produced artificially on the surface of the catalyst can be of different nature and in particular:

a) an acidity due to charge transfer

b) an acidity of the proton type

c) an acidity of the Lewis acid type.

The acidity mentioned under point a) is produced by using a

material with a planar and non-porous crystalline groundmass, which inside the crystal lattice has missing charges which, in order to achieve electrical neutrality, require a compensation from cations on the outer surface of the coating. These requirements are satisfied by the natural or synthetic minerals of the clay type and among these, phyllosilicates with a higher charge density (0.4 - 1 electron charges per half-cell Si^O^ with preferably tetrahedral substitution are particularly preferred.

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 p.) undergo cation exchange with bi- or polyvalent cations of the elements from groups Illb, IVb, VIb, Vllb, and VIII of the periodic table and with the series of lanthanides (Handbook of Chemistry and Physics - 49th edition 1968 - 1969 - Chemical Rubber Publishing Company), and then preferred cations of lanthanum, cerium, titanium and manganese.

The acidity mentioned under point b) is produced by

use the above-described minerals after exchange with ammonium ion and subsequent heating to a temperature sufficient for cleavage with the evolution of ammonia,

usually between 300 and 600°C and preferred at approx. 450°C

for 10 hours.

The acidity mentioned under point c) is produced by means of

of heating and partly by dehydration of hydroxyl groups linked to aluminum present in the octahedral layer of the materials described above. In particular, but not necessarily, such an acidity is produced by the metakaolinite obtained by heating between 350 and 450°C of kaolinite mineral.

The precious metal present on the surface of the catalyst

according to the invention, constitutes between 0.01 and 5 percent by weight and is introduced on the surface of the catalyst by impregnation with a compound of the said metal.

In the case of platinum, the impregnation is carried out with H2PtCl6

or Pt(NH3)4(O<H>)2.

The introduction of the noble metal is carried out in any case, regardless of the type of acidity present on the surface of the catalyst,

and therefore regardless of the procedure carried out to achieve this acidity.

The catalyst according to the present invention enables conversion and selectivity which are industrially very interesting. Furthermore, it brings remarkable economic advantages in comparison with the conventional catalysts

because of the cheap minerals used for the production or the very simple and cheap processing to which these are subjected, or because this catalyst gives

results of industrial interest with very small amounts of noble 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 obtain catalysts with different degrees of acidity simply by changing the starting material, the nature of the cation with which the exchange is carried out and the production method.

In reality, for the same starting material with a certain missing charge as previously discussed, the use of one or the other cation will make it possible to obtain different catalysts, which have different surface acidity (by acidity is meant either proton acidity or Lewis acidity or acidity due to charge transfer) and which from the same feed material and under the same reaction conditions will give different reaction products.

A different distribution of the reaction products is also achieved by

to change the starting material and by retaining the same cation. Different acidities can also be used in the case of a different production method as previously discussed.

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

The process for the isomerization of paraffinic hydrocarbons as a single component or as a mixture, and in particular the isomerization of 2,2-dimethylbutane to 2,3-dimethylbutane, is carried out at different temperature conditions, pressure, relative volume rates 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 reaction with the reaction components takes place in the vapor phase and at the particular pressures used, the pressure range is between atmospheric pressure and 150 kg/cm 2.

The relative volume velocity (HLSV) is between 0.1 and

20 h-"'". 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 octane11 for the latter product.

The isomerization process for 2,2-dimethylbutane is preferably carried out continuously in two zones. The product made up 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 said compound is sent to another reaction zone containing the catalyst according to the invention where isomerisation 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 recovered from the top and recycled 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

predominantly product.

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

The catalyst according to the invention can also be used

in hydrocracking processes and then the feed to be treated, which consists of liquid heavy hydrocarbons, is sent to a reactor which is filled with the catalyst in

- according to the invention.

The reaction 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<-1>. The products from the reactor are subjected to conventional treatments with debutanisation and fractionation.

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

In these examples, the term "conversion" means the ratio between the number of molecules that are converted

number of molecules added

and by the term "selectivity" is meant the ratio between molecules of the desired product

number of molecules converted.

Example 1.

Selective isomerization of 2,2-dimethylbutane.

Beidellite, characterized by an equivalent, was used

and 2

surface of 54 A . The term "equivalent surface area" refers to the area available to a single monovalent cation.

10 grams of beidellite were subjected to ion exchange using

by 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 calcination 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 prepared in this way was tested in a flow microreactor for the isomerization reaction of 2,2-dimethylbutane.

The reaction conditions were as follows:

Table 1 shows the results obtained. As the desired product in this case is 2,3-DMB, it must be included

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

Example 2.

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

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 manner with chloroplatinic acid so that there was a content of 0.15% by weight of platinum in the finished catalyst. So in this case, an appropriate amount of water was added to the hydrocarbon supply.

The reaction conditions were as follows:

Example 3.

To show the great importance of the specific combination between trivalent cations and clay minerals to achieve

a high selectivity for the desired product 2,3-dimethylbutane, the previous example using verraikulite was referred to.

In the present example, the vermiculite was replaced with

an ammonium salt (nitrate or acetate) and subjected to a further calcination (between 400 and 500°C) to effect removal of NH3 and consequent formation of an acidity of

the proton type.

Finely divided 10 grams of vermiculite was subjected to an ion exchange with a solution of ammonium acetate by the usual method.

After the exchange and washing, the obtained material was heated for three hours at a temperature of 450°C.

Finally, introduction of 0.15% by weight Pt was carried out as described in the previous example.

The reaction conditions were as follows:

Example 4.

10 grams of kaolinite purified by sedimentation and subsequent washing to remove possible dissolved impurities and added with appropriate amounts of platinum (see examples 1, 2 and 3) were heated at a temperature of 420°C for 15 hours.

In this way, a catalyst was obtained in the form of kaolinite in a metastable state containing 0.15% by weight of platinum by means of a partial dehydration.

The reaction conditions were as follows:

Example 5.

Selective isomerization of normal hexadecane with 20 grams of 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>

HLSV = 1

^/hydrocarbon ratio = 5

The following data is obtained:

By C^-C^-f raks ions is meant all products that write

from the hydrocracking 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, they are "signs of the course of the reaction which are considered percent hydrocracking and the ratio between iso-hexadecanes and the sum of all C^-components.

Example 6.

Selective isomerization of heavy paraffin fractions.

20 grams of catalyst in the form of 0.15% by weight Pt supported on 99.85% vermiculite exchanged with titanium for reaction with selective isomerization of normal heavy paraffins in a gas oil fraction with boiling temperatures from 250 to 350°C

with the aim of lowering the pour point for the fraction itself.

The reaction conditions and product properties are as follows:

Reaction conditions:

T = 340°C

2

P = 50 kg/cm

HLSV

I^/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:

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

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

Example 7.

Normal hexadecane hydrocracking.

20 grams of catalyst in the form of vermiculite yielded with titanium with 0.15% by weight of Pt were; tested for hydrocracking reaction of n-hexadecane.

The data obtained are as follows:

Reaction conditions:

T = 350°C

2

P = 50 kg/cm

HLSV =0.5

H2/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.

Claims (4)

1. Bifunctional catalyst for the isomerization and hydrocracking of hydrocarbons, characterized by the fact that it is made up of 1) a carrier material selected from natural or synthetic minerals of the clay type with a crystalline groundmass structure in the form of planar and non-porous parallel layers with a high charge density (0.4 to 1.0 electron charges per half-cell S^O.^); in that the surface of the carrier material has centers with, for the respective purposes, the same set acidity, all equal, in that the acidity is obtained by charge displacement or is of the type proton acid or Lewis acid, and 2) finely dispersed platinum and/or palladium in an amount of between 0.01 and p.5 percent by weight calculated on the entire catalyst. 2. Bifunctional catalyst as stated in claim 1, characterized in that the clay-type mineral is a smectite of the beidelite type, preferably beidelite or nontrolite. 3. Bifunctional catalyst as stated in claim 1, characterized in that the mineral of the clay type is a semi-expanded mineral of the vermiculite type, preferably vermiculite, hydrobiotite or illite. 4. Bifunctional catalyst as stated in claim 1, characterized in that the clay-type mineral is meta-kaolinite.