The catalyst for isomerization of n-paraffins, the method of its preparation and method of isomerization of n-paraffins

 

(57) Abstract:

Describes a catalyst for the isomerization of n-paraffins, comprising a compound of molybdenum. Its difference is that it is a mixture of molybdenum oxide and silicon oxide with a molar ratio MoO3/SiO2>0.2 and has a surface area of from 20 to 400 m2/g, pore volume is in the range from 0.05 to 1 cm3/g with a size of mesopores from 20 to 500 . Describes the method of its preparation and method of isomerization of n-paraffins. The technical result is the obtaining of a catalyst which can be used in the reaction of isomerization of n-paraffins without the need for special pre-treatment. 3 S. and 7 C.p. f-crystals, 1 table.

The invention relates to a catalyst based on molybdenum and silicon, the method of preparation of the catalyst and method of isomerization of n-paraffins.

More specifically, the present invention relates to a catalyst based on molybdenum and silicon and its use in isomerization reactions of n-paraffins with the number of carbon atoms greater than or equal to 5, preferably between 5 and 40.

The use of a catalyst based on molybdenum for the isomerization of n-paraffins is known in the literature. the materials associated with the formation of carbides or oxycarbides molybdenum, which, with regard to the source of the oxide have a higher surface area, the value of which is from approximately 4 m2/g (MoO3when 99.95%) to values that can reach 200 m2/,

The path from molybdenum oxide to the catalyst is labour intensive and can be achieved in various ways, as illustrated below.

"Journal of Solid State Chemistry" (59, 1985, 332, and 348) describes the processing of molybdenum oxide with a mixture of ammonia/hydrogen at 880oC to obtain the corresponding nitride, which is then converted into carbide by processing the methane/hydrogen at 900oC. Obtained by this method carbides have a surface area 140-180 m2/,

Another method described in "Journal of Catalysis" (106, 1987, 125). In this method, the molybdenum oxide is treated with a stream of methane/hydrogen with increasing temperature.

In "Journal of Catalysis"(112, 1988, 44) oxide may be pre-impregnated with 0.25 weight. % platinum, which acts as a catalyst carbosilane, which takes place at temperatures rising up to 700oC. the Final solids have surface area of about 200 m2/,

On the contrary, according to what is described in "Journal of Catalysis" (117, 1989, the 100oC. Or the reaction carburatore can be done using a pair of MoO3on charcoal, receiving materials with a surface area of 100-200 m2/g, as described in the European patent N 396475.

Synthesis of oxycarbides molybdenum in situ has been recently described, starting with MoO3processed at low temperature (350oC) in a stream of hydrogen/n-octane in 24 hours ("Catalysis Today", 35, 1997, 51).

The applicant has discovered a new catalytic structure based on molybdenum oxide and silicon dioxide, which as such can be used in the reaction of isomerization of n-paraffins without the need for special pre-treatment.

The present invention therefore relates to a catalyst based on molybdenum and silicon, having a surface area in the range from 20 to 400 m2/g, and the molar ratio of Mo/Si > 0,2.

Another objective of the present invention relates to a catalyst based on molybdenum and silicon, which can be obtained by a method that includes:

a) dissolving a soluble salt of molybdenum in aqueous solution containing at least one basic compound selected from ammonium hydroxide having the General formula (I)

Restablet aliphatic group, containing from 1 to 7 carbon atoms,

b) adding to the solution from stage (a) at least one silicon compound capable of either hydrolyzed to SiO2in such amounts to give a molar ratio Mo/Si is greater than 0.2, and, optionally, an aliphatic alcohol.

C) gelation thus obtained mixture, and calcining the obtained gel in air at a temperature in the range from 500 to 600oC.

In the method of producing catalyst according to the present invention can be used any salt of molybdenum, soluble in water or in an alkaline environment. Practical examples are halogenated derivatives of molybdenum, for example, those having the formula: MoO2X2where X represents halogen, such as chlorine, bromine or fluorine, or those having the formula: MoOX4where X represents a chlorine atom or fluorine, molybdenum trioxide, molybdenum acid tetrahydrate of heptamolybdate ammonium.

Salt of molybdenum is dissolved in an aqueous solution of basic compounds having General formula (I). Of these main ingredients is preferred hydroxide of tetrapropylammonium.

When a salt of molybdenum dissolved, the solution add a connection to astasia the invention is tetrachlorosilane silicon, in which the alkyl group contains from 1 to 4 carbon atoms, such as, for example, tetraethylorthosilicate.

The alcohol is preferably selected from aliphatic alcohols, in particular C2-C6-alkyl monohydroxy alcohols.

Preparation capable of gelation of the solution based on molybdenum, stage (a) and (b) mainly takes place at room temperature, measuring the ingredients of the reaction so that they comply with the following molar ratios:

Mo/Si is more than 0.2;

OH-(Si + Mo) more than 0.1;

H2O(Si + Mo) more than 5;

Alcohol/H2O between 0 and 20.

More specifically, the ingredients are preferably metered in order to obtain the following molar relationship:

Mo/Si between 1 and 100;

HE-/(Si + Mo) is between 0.2 and 5;

H2O/(Si + Mo) between 10 and 100;

Alcohol/H2O between 0.5 and 2.

When the reaction mixture has cooked, gelation begins. It can be done at room temperature or at a temperature in the range from room temperature values up to 100oC.

Gelation may require time in the range from several minutes to several hours (even up to 100) and can occur both in paramashiva is whether opaque. The formation of the settled phase was never observed.

At the end of phase gelling the resulting gel is dried at 100oC for several hours and then calcined in air at 500 to 600oC.

The catalyst of the present invention is formed in the form of a solid substance having a surface area in the range from 20 to 400 m2/g, pore volume in the range from 0.5 to 1 cm3/g, the distribution is concentrated in the area of mesopores.

The catalyst of the present invention are useful in the reaction of isomerization of n-paraffins, in particular n-paraffins with the number of carbon atoms greater than or equal to 5, preferably between 5 and 40.

Another objective of the present invention, therefore, relates to a method of isomerization of n-paraffins, characterized in that the isomerization reaction is carried out in the presence of a catalyst, which can be obtained by a method that includes:

a) dissolving a soluble salt of molybdenum in aqueous solution containing at least one basic compound selected from ammonium hydroxide having the General formula (I)

R1R2R3R4N+OH-< / BR>
where the group R1-R4tienie to the solution from stage (a) at least one silicon compound, can either hydrolyzed to SiO2and, optionally, aliphatic alcohol;

C) gelation thus obtained mixture, and calcining the obtained gel in air at a temperature in the range from 500 to 600oC.

The preferred catalyst for the isomerization reaction is a catalyst based on molybdenum and silicon, having a surface area in the range from 20 to 400 m2/g, and the molar ratio of Mo/Si > 0,2.

Isomerization of n-paraffins can be carried out in a reactor of any type. Preferably, however, to work with reactors fixed bed or fluidized bed continuous or periodic operation.

The isomerization reaction is carried out in the presence of hydrogen, at a temperature in the range from 200 to 550oC, preferably between 250 and 450oC and at a pressure of hydrogen in the range from atmospheric pressure to 10 MPa, preferably from 2 to 6 MPa.

Several illustrative, but not limiting examples are provided for better understanding of the present invention and its implementation.

Example 1.

20 g of tetrahydrate of heptamolybdate ammonium (EMA) rastvorami of 53 g of tetraethylorthosilicate (TPP) and 160 g of ethanol.

After about 7 minutes there is the presence of a homogeneous opaque gel without separation of the settled phase. He was left alone at room temperature overnight and then dried at 100oC for 15 hours and calcined at 550oC for 6 hours in air.

The obtained solid substance has the following composition, wt.%: MoO350; SiO250. It has a surface area of 161 m2/g, pore volume of 0.53 cm3/g, an average pore diameter of 126 nm, calculated from the desorption isotherm.

Example 2.

20 g of EMA dissolved in 200 g of a 15% by weight aqueous solution of TPAN. Then add a solution consisting of 53 g of TPP and 160 g of ethanol.

After about 7 minutes there is the presence of a homogeneous opaque gel without separation of the settled phase. He was left alone at room temperature overnight and then dried at 100oC for 15 hours and calcined at 550oC for 6 hours in air.

The obtained solid substance has the following composition, wt.%: MoO350, SiO250. It has a surface area of 116 m2/g, pore volume of 0.45 cm3/g, an average pore diameter of 204 nm, calculated from the desorption isotherm.

Example 3.

After about 15 hours at room temperature observe the formation of a transparent gel, which is dried at 100oC for 22 hours and calcined at 550oC for 6 hours in air.

The obtained solid substance has the following composition, wt.%: MoO350; SiO250. It has a surface area of 48 m2/g, pore volume of 0.11 cm3/g, an average pore diameter of 72 nm, calculated from the desorption isotherm.

Example 4.

The synthesis described in example 3, again without alcohol.

The obtained solid substance has the following composition, wt.%: MoO350, SiO250. It has a surface area of 53 m2/g, pore volume of 0.08 cm3/,

Example 5.

20 g of EMA dissolved in 200 g of 35% by weight aqueous solution of TPAN. Then add a solution consisting of 53 g of TPP and 160 g of ethanol.

After about 60 hours at room temperature observe the formation of a transparent gel, which is dried at 100oC for 15 hours and calcined at 550oC for 6 hours in air.

The obtained solid substance has the following composition, wt.%: MoO350, SiO250. It has a surface area of 54 m2/g, pore volume of 0.09 cm3/g SREN g of 40% by weight aqueous solution of TPAN. Then add a solution consisting of 53 g of TPP and 160 g of ethanol.

After about 7 hours at room temperature observe the formation of a transparent gel, which is dried at 100oC for 15 hours and calcined at 550oC for 6 hours in air. The obtained solid substance has the following composition, wt.%: MoO350; SiO250. It has a surface area of 50 m2/g, pore volume of 0.08 cm3/,

Example 7.

20 g of EMA dissolved in 150 g of 40% by weight aqueous solution of TPAN. Then add a solution consisting of 53 g of TPP and 230 g of ethanol.

After about 60 hours at room temperature observe the formation of a transparent gel, which is dried at 100oC for 15 hours and calcined at 550oC for 6 hours in air.

The obtained solid substance has the following composition in weight. %: MoO350, SiO250.

Example 8.

20 g of EMA dissolved in 150 g of 40% by weight aqueous solution of TPAN. Then add a solution consisting of 24 g of TPP and 160 g of ethanol.

After about 24 hours at room temperature observe the formation of a transparent gel, which is dried at 100oC for 15 hours and calcined at 550368,8; SiO231,2.

Example 9.

20 g of EMA dissolved in 150 g of 40% by weight aqueous solution of TPAN. Then add a solution consisting of 5 g of TPP and 160 g of ethanol.

After about 24 hours at room temperature observe the formation of a transparent gel, which is dried at 100oC for 15 hours and calcined at 550oC for 6 hours in air.

The obtained solid substance has the following composition, wt.%: MoO391,4; SiO28,6.

Example 10 (for comparison).

20 g of EMA dissolved in 230 g of 23% by weight aqueous solution of NH4OH. Then add a solution consisting of 50 g of TPP and 160 g of ethanol.

Formed suspension, similar to milk, which after about 16 hours at room temperature gives a white solid separation settled layer of a solution. The product is dried at 100oC for 15 hours and calcined at 550oC for 6 hours in air.

The obtained solid substance has the following composition, wt.%: MoO351,5; SiO248,5. The surface area is 4 m2/,

Example 11 (for comparison).

Example 9 is repeated without TPP. Get the ultimate solid, Serov comparison 10 and 11, the morphological characteristics of the materials of the present invention related to the simultaneous presence in the reaction mixture of tetraalkylammonium hydroxide and silicon compounds.

Example 12.

The catalyst described in example 3 was evaluated in the reaction of hydroisomerization n-heptane. The reactor is a tubular reactor with a fixed bed having an inner diameter of 1 cm and a length of 35 cm To the reactor was loaded with 5 g of catalyst sieved to 20-40 mesh.

The isomerization reaction is initiated, causing the temperature of the reactor to a temperature of about 100oC in a stream of nitrogen, then filed a mixture of hydrogen/n-heptane in a molar ratio of 30/1 and the temperature was raised to 350oC for a period of about 1 hour.

The reaction conditions were as follows: T = 350oC, P = 2 MPa, H2/n-C7= 30 mol/mol, TTS = 1 h-1.

TTS (weight average hourly feed rate) refers to n-heptane and expressed as grams of heptane per gram of catalyst per hour.

The isomerization reaction was carried out for 50 hours, observing that the conversion and selectivity remain constant during this time period. In particular, the conversion of n-heptane was 79.5% of the selectors is the iMER 2, evaluated in the reaction of hydroisomerization n-hexadecane. The reactor is a tubular reactor with a fixed bed having an inner diameter of 1.2 cm and a length of 45 cm In the reactor was loaded with 9 grams of catalyst sieved to 20-40 mesh.

The isomerization reaction was initiated, feeding a mixture of hydrogen/n-hexadecane in a molar ratio of 32/1, and the temperature was raised to 350oC for a period of approximately 2 hours.

The reaction conditions were as follows:

T = 350oC, P = 5 MPa, H2/n-C16= 32 mol/mol, TTS = 1 h-1.

The isomerization reaction was carried out for 60 hours, observing that the conversion and selectivity remain constant during this time period. In particular, the conversion of n-hexadecane was 94% with a selectivity to ISO-C16equal to 75%.

Example 14 (comparison).

The isomerization reaction described in example 12 was repeated using the catalyst of example 11 comparison.

The following table shows the test results from the point of view of conversion and selectivity.

1. The catalyst for isomerization of n-paraffins, comprising a compound of molybdenum, characterized in that it is a mixture of the oxide molybde is 2/g, pore volume is in the range from 0.05 to 1 cm3/g with a size of mesopores from 20 to 500 .

2. The method of preparation of the catalyst under item 1, which consists in dissolving a soluble salt of molybdenum in the aqueous solution containing a basic compound selected from hydroxides of ammonium General formula R1R2R3R4N+OH-where R1- R4- same or different, represent aliphatic groups containing from 1 to 7 carbon atoms, adding a silicon compound capable of either hydrolyzed to SiO2in an amount to provide a molar ratio MoO3/SiO2>0,2, and optional aliphatic alcohol, the gelation of the mixture, drying the gel and calcination at 500 - 600oC.

3. The method according to p. 2, in which an aqueous solution containing a basic compound, representing tetrapropylammonium.

4. The method according to p. 2, in which the soluble salt of molybdenum is selected from halogenated derivatives of molybdenum, for example, those having the formula: MoO2X2where X is a halogen, such as chlorine, bromine or fluorine, or those having the formula: MoOX4where X represents a chlorine atom or fluorine, molybdenum trioxide, molybdenite a product of hydrolysis of tetrachlorosilane silicon, in which the alkyl group contains from 1 to 4 carbon atoms.

6. The method according to p. 2, which is capable of gelation of the mixture has the following molar composition: MoO3/SiO2more than 0.2, OH/(Si+Mo) is more than 0.1, H2O/(Si+Mo) more than 5 alcohol/H2O between 0 and 20.

7. The method according to any of paragraphs.2 to 6, in which the gelation is carried out at room temperature or at a temperature between room values and 100oC.

8. Method of isomerization of n-paraffins in the presence of a catalyst, characterized in that the used catalyst under item 1.

9. The method according to p. 8, in which the reaction is carried out in the presence of hydrogen at a temperature in the range from 200 to 550oC, when the hydrogen pressure in the range from atmospheric pressure to 10 MPa.

10. The method according to p. 8 or 9, in which the n-paraffins have the number of carbon atoms equal to or more than 5.

 

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