RU2313391C2 - Catalyst and gasoline-alkylate production process - Google Patents

Abstract

FIELD: petrochemical process catalysts.

SUBSTANCE: invention relates to chemistry of heterogeneous catalysts and is directed to production of high-octane gasoline component via alkylation of isobutane with butane-butylene fraction on heterogeneous catalysts. Solid catalyst represents porous superacid based on zirconium and/or hafnium metallosilicates promoted with salts of double- or triple-charged metal cations with double-charged anions and depicted by general formula (EO₂·aSiO₂)·b(M_cX_d) wherein E = Zr and/or Hf, a=17-34; b=0.5 when c=1 and d=1, M= Ni²⁺, Zn²⁺, or ZrO²⁺, X=SO₄ ^2- or ZrF₆ ^2-; or b=0.1666 when c=2 and d=3, M=Sc³⁺, Y³⁺, or Ga³⁺ and X= SO₄ ^2-, parameter "a" being allowed to deviate from indicated value to larger or lesser side by 20% and parameter "b" by 5%. High-octane gasoline component is produced as indicated above at temperature 348 to 375 K, pressure 1.7 to 2.5 MPa, isobutane-to-butenes molar ratio 10-15, and volume feed supply velocity between 6.4 and 8.5 g/mL catalyst/h. Catalyst can optionally be regenerated.

EFFECT: enhanced conversion, yield of alkylate, productivity, and prolonged catalyst lifetime.

7 cl, 4 tbl, 11 ex

Description

The invention relates to the chemistry of heterogeneous catalysis, in particular to processes for producing a high-octane component of gasoline, referred to in the refining industry as "alkylate". The alkylate production process is based on the alkylation reaction of isoparaffins (isobutane) with lower olefins (propene, butenes). Industrial alkylation catalysts are anhydrous hydrogen fluoride or concentrated sulfuric acid. The technological design of the reaction has been brought to a high degree of perfection: no more than 0.4 kg of hydrogen fluoride or 70 kg of sulfuric acid is required to obtain 1 ton of alkylate. Despite the return and regeneration of the used catalysts, the cost of alkylate at 30% is determined by the price of the catalyst. Reducing the requirements for the quality of reagents (in terms of moisture, dienes, sulfur-containing compounds) increases the consumption of hydrogen fluoride to 1 kg per 1 ton of alkylate, and the consumption of sulfuric acid increases to 200 kg / t of alkylate. The toxicity, the correlating effect on equipment materials, the formation of difficult to recycle waste with a global scale of alkylate production exceeding 70 million tons / year, and the high probability of environmental disasters make the use of these catalysts very problematic.

Various acid heterogeneous systems have been proposed as alternative catalysts for the alkylation reaction. Only four of them are brought to the level of demonstration pilot plants. Among them are the developments of Haldor Topsoe, Catalitika, Neste Oy, Konoko, Chemical Research and Licensing, Chevron and UOP. The developments of these firms proposed several technological schemes for the use of heterogeneous catalysts, among them:

1. Known Bronsted acids heterogenized on inorganic carriers of a porous and non-porous nature, as described in European Patents EP 0433954 A1, EP 0542620 A1.

2. Known Lewis acids heterogenized on inorganic crystalline supports with regular porous structure (zeolites) or on polymer supports, both zeolites and organic polymers initially possess the Bronsted acid function, US Pat. No. 3,975,299, 4,384,161, 4992616.

3. Polymer materials containing perfluoroalkylene sulfonic or perfluoroarylene sulfonic groups, their use is described in US Pat. U.S. 3855342, 3862258, 4038213.

4. Solid inorganic crystalline materials with a regular porous structure of certain sizes (zeolites), which simultaneously have the properties of Bronsted and Lewis acids, US Pat. U.S. 4300015, 4992615, 5258569, WO 93 \ 017106, 99 \ 19279.

5. Solid inorganic amorphous materials with an irregular porous structure, modified by the deposition of compounds with the properties of "super acid". According to the well-known definition, “superacid” means a mixture of such compounds that separately possess the properties of Bronsted and Lewis acids with known properties, and their mixture surpasses 100% sulfuric acid in strength. Patent information on the catalytic effect of such systems is represented by Japanese patents: 51-63386, 57-3650, 59-40056, 59-6181, 61-242461; China 1230463, 1362286; US 3251902, 3655813, 4377721, 5491278, 5493067, which together set forth the concept of analogues of our invention, and RF patent 2091360, adopted by us for the prototype of the invention.

All five areas of using heterogeneous catalysts for the production of alkylate require professional expert evaluation on a number of parameters. These parameters of the alkylation process are:

- the conversion of olefins (butenes), K,%, which at the time of completion of the inter-regeneration run of the catalyst should be at least 90%,

- yield of alkylate to the missed butenes, B, wt.%. In real conditions, alkylation includes not only the main reaction of isobutane + butenes → trimethylpentanes, dimethylhexanes (alkylate) alkylate formation (1), but also a side process of butene oligomerization → butene oligomer (2). Therefore, the theoretical yield of reaction products according to equations (1) and (2) is taken equal to 203.6 and 100 wt.%, Respectively. In the presence of superacids, the yield of alkylate increases due to the self-alkylation of isobutane 2 (isobutane) → trimethylpentanes, dimethylhexanes (alkylate) + hydrogen (3) and increases up to 210% or more,

- productivity on alkylate, measured by the mass of alkylate produced by the unit mass (volume) of the catalyst for 1 hour, P, kg _alk \ kg _cat h, kg _alk \ l _cat h,

- the resource (lifetime) of the catalyst, measured by the amount of alkylate obtained from a unit mass (volume) of the catalyst for the inter-regeneration run, P kg _alk \ kg _cat , kg _alk \ l _cat . The duration of the catalyst run in hours is the quotient of dividing the value of P by the value of P.

The operational parameters for the catalysts of all five of the above types are presented in table 1. As follows from the table, the best indicators for the yield of alkylate, productivity and resource of action have a prototype catalyst.

Table 1.
Performance characteristics of heterogeneous catalysts for the production of alkylate in accordance with five concepts of their origin. Indicators Heterogeneous catalysts in accordance with the concept 1,2 3.4 5 Analogs Prototype The conversion of butenes, K,% 98-100 90-100 95-100 94-99 The yield of alkylate, In, wt.% 190-210 180-210 195-200 186-204 Alkylate productivity P, kg _alk \ kg _cat h 2.0-2.1 (1.2-1.3) 0.05-1.0 (0.03-0.6) 0.2-0.3 (0.1-0.24) 0.2-1.7 (0.12-0.99) Resource, P, kg _alk / kg _cat 500-600 (300-360) 3-24
(2-15) 20-50
(14-35) 300-670
(180-400) Life time, h 250-300 40-200 80-250 200-880 Regeneration option No 3 - no, 4 - yes Yes Yes Note: in parentheses are mass-volume indicators, kg / l h, kg / l.

All other catalysts have no prospects for implementation either on environmental or on technical and economic indicators. The prototype authors declared the presence of high performance of the proposed catalysts by the method of their synthesis, characterized in that at the first stage of preparation of the catalyst it is necessary to synthesize a carrier matrix, and then at the second stage apply the active component with a particle size of not more than 1-50 nm. It was also stated that the catalyst can be repeatedly regenerated after deactivation by washing with organic solvents without or with an additional supply of hydrogen during washing.

The disadvantage of the prototype is a low resource of action and a moderately low yield of alkylate for the olefin taken in the reaction, especially after several regenerations.

The objective of the invention is the creation of an environmentally friendly method for producing gasoline alkylate in the presence of a heterogeneous super-acid catalyst that conducts the alkylation reaction of isobutane with butenes.

The basis of the solution of the technical problem lies in increasing the operational properties of a heterogeneous catalyst, which is expressed both in increasing the catalyst resource and in increasing the resistance to regeneration, and the initial properties of the catalyst are reproduced, unlike the prototype, many times. Improving the properties of the catalyst compared to the prototype is achieved due to a certain ratio of active components that are formed not in two but in one stage, and the active components interact with each other at the level of particles having nanoscale sizes, i.e. at the molecular level.

Contrary to the assertion of the authors of the prototype about the beneficial effect on the catalyst resource of additives in the feedstock of the reaction product, the alkylate, we found that this additive significantly reduces the catalyst resource. In reality, only adding aromatic hydrocarbons to the feedstock actually increases the catalyst resource. In practice, we recommend adding up to 5% of the mass to the feedstock. aromatic hydrocarbons in the form of reformate or catalysis from the process of aromatization of the BTX fraction (benzene, toluene, xylene). In the proposed method of alkylation, the catalyst is regenerated by washing it with a reformate in a hydrogen atmosphere. Reform after use is applied as intended.

A solid heterogeneous catalyst for producing gasoline alkylate by contacting a liquid mixture of isobutane and a butane-butene fraction with this catalyst is a solid porous superacid based on metal silicates, zirconium, hafnium or mixtures thereof, promoted with salts of doubly or triply charged metal cations with doubly charged anions, and has the general formula

(EO ₂ .a SiO ₂ ) .b (M _c * X _d ),

where E = Zr, Hf or mixtures thereof,

a = 17-34

b = 0.5

with c = 1 and d = 1,

M = Ni ²⁺ , Zn ²⁺ and ZrO ²⁺

X = SO ₄ ^2- , ZrF ₆ ^2- ,

and a = 17-34, b = 0.1666 with c = 2 and b = 3,

M = Sc ³⁺ Y ³⁺ , Ga ³⁺ ,

X = SO ₄ ^2- ,

moreover, the coefficients a and b can deviate relative to the indicated values up or down by 20% for coefficient a and by 5% for coefficient b.

The process is carried out at a temperature of 348-375 K, a pressure of 1.7-2.5 MPa and a feed rate of the raw material mixture of 6.4-8.5 g / ml _cat h. A mixture of isobutane and butenes with a molar ratio of from 10 to fifteen.

To increase the duration of the catalyst, 0.6-1.0 wt.% Of aromatic hydrocarbons are additionally introduced into the initial raw material mixture in the form of industrial reformate or catalysis from the aromatization process of BTX lower paraffins (benzene-toluene-xylene mixture).

The restoration of the activity of a deactivated solid heterogeneous catalyst is carried out by replacing the feedstock with a reformate supplied with a space velocity of 2-3 h ^-1 at a temperature of 403-423 K for 4-6 h and additionally saturated with hydrogen under a pressure of 5 MPa.

3 catalyst samples were synthesized. The first is in the conditions of the prototype, the rest - according to our technique.

Example 1. The catalyst K 1 according to the prototype was synthesized from a 20% sol of silicic acid, taken in an amount corresponding to the content of 81.0 g of silicon dioxide. The sol was mixed with a solution of zirconyl nitrate, taken in an amount containing 10.96 g of a two-water salt. After heating and stirring to a homogeneous mass, the resulting gel is dried to constant mass and ground into powder. The powder was placed in 200 ml of a solution containing 0.17 g of platinum in the form of H ₂ (PtCl ₆ ) 6 H ₂ O, as well as 13.78 g of the zinc salt of zirconylsulfuric acid in terms of anhydrous. After evaporation to dryness, the catalyst composition has a composition, wt.%:

SiO ₂ 81.0 ZrO ₂ 5.05 Pt 0.17 ZnZrO (SO ₄ ) ₂ 13.78.

After tabletting the composition by dry pressing, the K 1 catalyst was heated in a muffle furnace to a maximum temperature of 600 ° C and kept under these conditions for 3 hours. The hot catalyst was hermetically sealed.

Example 2. 206.0 g of tetramethoxy- or 281.0 g of tetraethoxysilane are hydrolyzed with 560 ml of distilled water, acidified with nitric acid to pH = 1. The temperature during hydrolysis is not higher than 30 ° C. After obtaining a clear solution, a solution of 21.1 g of zirconyl nitrate dihydrate and 11.8 g of zinc sulfate heptahydrate in a minimum volume of water is added to it with stirring. A clear solution is sprayed in the flame of an air-propane burner, collecting the finished catalyst powder in a cyclone. The powder is impregnated with a platinum compound, as in Example 1, dried and tableted. Calcined as described above. Catalyst K 2 is obtained.

Example 3. 215.0 g of freshly distilled in a vacuum methylate or 271.0 g of zirconium ethylate are dissolved in 2600.0 g in tetramethoxy or 3560.0 g of tetraethoxysilane, 80.8 g of zinc ethylate and 90 g of dimethyl sulfate are added. The resulting solution, after stirring, is pumped into the central nozzle of the atomizer, coaxially surrounded by a nozzle of a larger diameter. Overheated to 200 ° C water vapor is supplied through this nozzle. The ratio of water vapor / organic solution is not less than 10 by weight. The finely dispersed powder is collected in a cyclone, dried at a temperature of 150-200 ° C for 5 hours, 0.17 wt.% Platinum is applied, tabletted and calcined, as described above. Catalyst K 3 is obtained.

The catalysts according to the invention after heat treatment at 600 ° C have the same composition corresponding to the formula

(ZrO ₂ 17.12 SiO ₂ ) 0.52 ZnSO ₄ +1.1 10 ^-2 Pt

They are tested by placing in a heated metal flow reactor. The feed was an isobutane mixture with an industrial butane-butene hydrocarbon fraction with an isobutane / butene molar ratio of 10.3. The feed rate of 6.4 g / ml _cat h, pressure 1.7 MPa, temperature 348 K. The comparison results of all three catalysts are presented in table 2. Regeneration was carried out by pumping reformate saturated with hydrogen under a pressure of 5 MPa through a deactivated catalyst. The volumetric feed rate of reformate is 2-3 h ^-1 , the temperature is 403-423 K.

The duration of the regeneration is 4-6 hours.

Table 2.
The results of comparing the experimental characteristics of the catalysts during the alkylation of isobutane with butenes (10.3 mol / mol), 348 K, 1.7 MPa. Supply of raw materials 6.4 g / ml _cat h (designations - see table 1). Indicators Catalysts According to the prototype Proposed Development K1 K2 K3 K,% 95-97 95-99 96-100 In,% of the mass. 195-202 195-210 195-215 P, g / ml _cat h 0.93 0.94 0.94 Continuous work hours 380 490 550 Continuous operation time after the 5th regeneration, h 250 490 550 K,% 80-85 95-97 95-97 In,% of the mass. 160-172 195-205 195-210

Example 4. The catalyst K 3 to demonstrate the management of its resources is tested during the alkylation of isobutane with butenes containing a reformate additive. The remaining conditions are as in Table 2. The feed rate of 6.45 g / ml _cat h, with 0.05 g / ml _cat h accounted for by reform. An alkylate productivity of 0.98-0.99 g / ml _cat h is obtained for 800 hours. The proportion of reformate in the obtained alkylate is 5% of the mass. and does not significantly affect the marketability of the product.

Example 5. In order to confirm the effectiveness of catalysts with the claimed range of chemical composition, a sample is synthesized for which the coefficient a in the general formula is 34.0. For this, the amount of tetramethoxy or tetraethoxy zirconium indicated in Example 3 (215.0 or 271.0 g, respectively) is dissolved in 5170.0 g of tetramethoxy or 7070.0 g of tetraethoxysilane. The amount of zinc ethylate and dimethyl sulfate is left unchanged, and the addition of platinum is doubled. Obtained from the sample of example 3, the catalyst K 4 is tested under the conditions listed in the heading of table 2. In this case, the following indicators are achieved: K = 95-99%, B = 195-204 wt.%, P = 0.94 g / ml _cat h, continuous operation time 500 hours. From the analysis of analogues of our invention it follows that the value of the coefficient b in the general formula of the proposed catalyst is rigidly set by the optimal molar ratio EO ₂ : doubly charged anion, which is 2 with a magnitude of 5% of the named value.

The control of particle sizes and pores of the K 1-K 3 catalysts obtained in three different ways using an electron microscope shows that the size of the primary particles of these catalysts is in the range of 3-80 (instead of the stated 1-50 nm), 2-50 and 1-40 nm and the average pore radius is 30-100, 80-300 and 100-1000 nm for the catalysts K 1, K 2 and K 3, respectively. Note that in our proposed catalyst development for the process of producing gasoline-alkylate, the key point is the use of catalyst precursors in the form of true solutions. In such solutions, the molecules of the catalyst precursors exist in the form of particles of nanoscale size. The size of solid heterogeneous particles obtained from these solutions of catalysts also does not go beyond nanoscale, which is fundamentally emphasized in this text and in the description text.

Examples 6-18 are made according to the conditions of example 2 and with the amount of silicon dioxide indicated in this example equal to 1.3488 mol of any of the tetraalkoxysilanes mentioned in example 2. Other components, their number are indicated in the examples with the next serial number.

Example 6. Catalyst K 6 was prepared under the conditions of Example 2. Instead of zirconyl nitrate, hafnium nitrate was used in an amount of 27.7 g of a two-water salt. The content of palladium, introduced in the form of ammonium tetrachloropalladate, 0.2 wt.%.

Example 7. Catalyst K 7 was prepared under the conditions of Example 2 from 22.4 g of a two-water salt of zirconyl nitrate - hafnyl (80-20 at%, respectively). The catalyst contains 0.2 wt.% Palladium.

Example 8. Catalyst K 8 instead of zinc sulfate contains zirconyl sulfate prepared by dissolving 10.5 g of two-water zirconyl nitrate in 80 ml of a 0.5 M aqueous solution of sulfuric acid.

Example 9. The catalyst K 9 instead of zinc sulfate was prepared using 10.4 g of nickel sulfate hexahydrate.

Example 10. Catalyst K 10 was prepared using 11.7 g of zinc nitrate hexahydrate as a zinc source. The nitrate is dissolved in a fluoride solution obtained by dissolving 10.5 g of zirconyl nitrate dihydrate in 100 ml of a 2.6 M aqueous hydrogen fluoride solution.

Example 11. In the same manner as described in example 9, 11.5 g of nickel nitrate hexahydrate was dissolved in a fluoride solution. Catalyst K 11 is obtained.

Catalysts K 12-K 18 were obtained under the conditions of Example 2. Instead of zinc or nickel sulfates, aqueous scandium, yttrium and gallium sulfates were used.

All catalysts are characterized in table 3.4 indicators, the interpretation of which is given in table 1.

Claims (7)

1. A solid heterogeneous catalyst for producing gasoline-alkylate by contacting a liquid mixture of isobutane and butane-butene fraction with this catalyst, which is a solid porous superacid based on zirconium, hafnium metal silicates or mixtures thereof, promoted with salts of doubly or triply charged metal cations with doubly charged anions having the general formula (EO ₂ · a SiO ₂ ) · b (M _c X _d ), where E = Zr, Hf or mixtures thereof, a = 17-34, b = 0.5 with c = 1 and d = 1, M = Ni ²⁺ , Zn ²⁺ and ZrO ²⁺ , X = SO ₄ ^2- , ZrF ₆ ^2- ; b = 0.1666 with c = 2 and d = 3, M = Sc ³⁺ , Y ³⁺ , Ga ³⁺ , X = SO ₄ ^2- , moreover, the coefficients a and b can deviate relative to the indicated values up or down by 20% for coefficient a and by 5% for coefficient b. 2. The catalyst according to claim 1, characterized in that it is obtained in one stage, and the active components interact with each other at the level of particles having nanoscale sizes. 3. The catalyst according to claim 1, characterized in that it further comprises not more than 0.5 wt.% Platinum group metals, such as platinum, palladium or mixtures thereof. 4. A method of producing a high-octane component of gasoline-alkylate automobile fuel by alkylating isobutane with an industrial butane-butene fraction in the presence of a catalyst according to one of claims 1 to 3 at a temperature of 348 to 375 K, a pressure of 1.7 to 2.5 MPa, molar the ratio of isobutane / butenes from 10 to 15, with a volumetric feed rate of 6.4 to 8.5 g / ml cat · h, and subsequent possible regeneration of the specified catalyst. 5. The method according to claim 4, characterized in that 0.6-1.0 wt.% Of aromatic hydrocarbons are additionally introduced into the butane-butene fraction in the form of industrial reformate or catalysis from the aromatization process of the BTX fraction (benzene-toluene-xylene mixture) . 6. The method according to claim 4, characterized in that the regeneration of the catalyst is carried out by rinsing it with BTK reformate or catalysis, at a volumetric feed rate of reformate or catalysis of 2-3 h ^-1 , a temperature of 403-423 K for 4-6 hours in the atmosphere hydrogen. 7. The method according to claim 6, characterized in that the regeneration of the catalyst is carried out at a hydrogen pressure of 5 MPa.