Catalytic composition and process using it for the alkylation of aromatic hydrocarbons with alcohols, or mixtures of alcohols and olefins

Abstract

The invention relates to a new catalytic composition for the alkylation of aromatic compounds with alcohols, or mixtures of alcohols and corresponding olefins, wherein said composition comprises a zeolite of the MTW type and is characterized in that it contains one or more alkaline metals in a total quantity which is less than or equal to 0.02% by weight. The use of said catalyst in the alkylation of aromatic compounds with alcohols, in particular benzene with isopropanol or ethanol, allows the formation, as by-product, of the aldehyde or ketone corresponding to the alcohol used, to be minimized: the formation of reaction by-products of said aldehydes or ketones having a boiling point very close to that of polyalkylation products, is therefore significantly reduced. This provides a considerable advantage in the subsequent transalkylation step for the recovery of said polyalkylates by transformation into the corresponding monoalkylates.

Claims

1. A process for the alkylation of an aromatic hydrocarbon with an aliphatic alcohol having 1-8 carbon atoms, or with a mixture of the aliphatic alcohol having 1-8 carbon atoms and a corresponding olefin, which comprises effecting said alkylation in the presence of a catalytic composition comprising: a zeolite of the MTW type, 5 to 40 ppm of sodium ions, and 5 to 80 ppm of potassium ions, wherein: the SiO.sub.2/Al.sub.2O.sub.3 molar ratio in said zeolite is 20-95, and the total amount of alkaline metals, including sodium ions and potassium ions, in the catalytic composition is lower than or equal to 0.015% by weight with respect to the total weight of the catalytic composition.

2. The process according to claim 1, wherein the zeolite is ZSM-12.

3. The process according to claim 1, wherein said catalytic composition further comprises a binder.

4. The process according to claim 1, wherein said catalytic composition comprises said MTW zeolite in acid form wherein the cationic sites present in its structure are occupied by Na.sup.+ and K.sup.+ ions and the remaining cationic sites are occupied by H.sup.+ ions.

5. The process according to claim 4, wherein the zeolite is a ZSM-12 zeolite, having, in its calcined and anhydrous form, a molar composition of the oxides corresponding to the following formula:
1.0?0.4 M.sub.2O.Al.sub.2O.sub.3.20-500 SiO.sub.2.zH.sub.2O, wherein z ranges from 0 to 60, M is H.sup.+ and Na.sup.+ and K.sup.+ ions, in a total amount lower than 0.015% by weight with respect to the total weight of the catalytic composition.

6. The process according to claim 3, wherein said catalytic composition is in the form of a pellet having a diameter ranging from 1.5 to 5 mm and a length ranging from 1 to 50 mm, with a hardness higher than or equal to 8 kg.

7. The process according to claim 3, wherein said catalytic composition has an extrazeolitic porosity not lower than 0.4 ml/g, wherein said extrazeolitic porosity is for at least 30% characterized by pores having a diameter greater than 100 ?.

8. The process according to claim 1, wherein the aromatic hydrocarbon is benzene or toluene.

9. The process according to claim 1, wherein the aliphatic alcohol is ethanol or iso-propanol.

10. The process according to claim 1, carried out in gas phase, mixed phase or liquid phase.

11. The process according to claim 10, carried out under reaction conditions corresponding to a complete gas phase of the reagents.

12. The process according to claim 1, carried out under trickle-flow conditions.

13. The process according to claim 1, wherein the aromatic hydrocarbon is benzene, the aliphatic alcohol is isopropanol, the alkylation product is cumene and said process further comprises: oxidizing the cumene thus obtained to cumyl-hydroperoxide; treating the cumyl-hydroperoxide with acids to obtain a mixture of phenol and acetone; hydrogenating the acetone to isopropanol which is recycled to the alkylation.

14. The process according to claim 1, wherein the process comprises the alkylation of the aromatic hydrocarbon with the aliphatic alcohol having 1-8 carbon atoms, and not with the mixture of the aliphatic alcohol having 1-8 carbon atoms and the corresponding olefin.

15. The process according to claim 1, wherein the process comprises the alkylation of the aromatic hydrocarbon with the mixture of the aliphatic alcohol having 1-8 carbon atoms and the corresponding olefin.

16. The process according to claim 1, wherein the catalytic composition comprises 5 to 30 ppm of said sodium ions and 5 to 30 ppm of said potassium ions.

17. The process according to claim 1, wherein the aliphatic alcohol having 1-8 carbon atoms is selected from ethyl alcohol, iso-propyl alcohol, n-propyl alcohol, n-butyl alcohol, iso-butyl alcohol, sec-butyl alcohol, and t-butyl alcohol.

Description

EXAMPLE 1 (ACCORDING TO THE INVENTION)

(1) 150 g of ZSM-12 ZD06047 zeolite powder (Zeolyst) having a SiO.sub.2/Al.sub.2O.sub.3 molar ratio equal to 65, containing 0.01% by weight of Na and 0.03% by weight of K, are subjected to ion exchange for 1 hour at 60? C. with a solution obtained by dissolving 150 g of ammonium acetate in 1,800 ml of water.

(2) The product thus obtained is washed 3 times with 1.5 liters of water, and subsequently dried at 120? C. for at least 2 hours, obtaining a dried product.

(3) After drying, the zeolite powder is calcined at 580? C. for 4 hours.

(4) 122.3 g of ZSM-12 zeolite obtained from the calcination and 132 g of pseudo-bohemite Versal V200 are dry mixed for 4 hours in an Erweka planetary mixer. 190 ml of aqueous solution of acetic acid at 5% are subsequently fed, slowly and under stirring, for 4 hours.

(5) The paste thus obtained is extruded into pellets having a diameter of 2 mm and a length of 10 mm, which are left to age for 2 days in the atmosphere.

(6) At the end of the aging, the pellets are calcined at 580? C. for 4 hours.

(7) An extruded catalyst is obtained, with about 55% of active phase, containing: Na=23 ppm K=5 ppm

(8) The extruded catalyst has the following characteristics: Hardness=11.8 kg Poured density=0.59 g/cc Pore volume (mercury intrusion)=0.47 cc/g Pellet density=1.16 g/cc Surface area (BET)=281 m.sup.2/g

(9) A fraction equal to 59% of the extrazeolitic porosity has pores having a diameter higher than 100 ?.

EXAMPLE 2 (ACCORDING TO THE INVENTION)

(10) 150 g of the same ZSM-12 ZD06047 zeolite (Zeolyst) used in Example 1 are subjected to ion exchange for 1 hour at 60? C. with a solution obtained by dissolving 150 g of Ammonium Acetate in 1,800 ml of water.

(11) The product thus obtained is washed 3 times with 1.5 liters of water, and subsequently dried at 120? C. for at least 2 hours.

(12) 134 g of ZSM-12 zeolite obtained after drying and 145 g of pseudo-bohemite Versal V200 are dry mixed for 4 hours in an Erweka planetary mixer.

(13) 205 ml of aqueous solution of acetic acid at 5% are subsequently fed, slowly and under stirring, for 4 hours.

(14) The paste thus obtained is extruded into pellets having a diameter of 2 mm and a length of 10 mm, which are left to age for 2 days in the atmosphere.

(15) At the end of the aging, the pellets are calcined at 580? C. for 4 hours.

(16) An extruded catalyst is obtained, with about 55% of active phase, containing: Na=28 ppm K=10 ppm

(17) The extruded catalyst has the following characteristics: Hardness=12.8 kg Poured density=0.62 g/cc Pore volume (mercury intrusion)=0.43 cc/g Pellet density=1.25 g/cc Surface area (BET)=280 m.sup.2/g

(18) A fraction equal to 56% of the extrazeolitic porosity has pores having a diameter higher than 100 ?.

EXAMPLE 3 (COMPARATIVE)

(19) 150 g of powder of the same ZSM-12 ZD06047 zeolite (Zeolyst) used in Example 1 and 162 g of pseudo-bohemite Versal V200 are dry mixed for 4 hours in an Erweka planetary mixer.

(20) 200 ml of aqueous solution of acetic acid at 5% are subsequently fed, slowly and under stirring, for 4 hours.

(21) The paste thus obtained is extruded into pellets having a diameter of 2 mm, which are left to age for 2 days in the atmosphere.

(22) At the end of the aging, the pellets are calcined at 580? C. for 4 hours.

(23) An extruded catalyst is obtained, with about 55% of active phase, containing: Na=80 ppm K=140 ppm

(24) The extruded catalyst has the following characteristics: Hardness=9.1 kg Poured density=0.52 g/cc Pore volume (mercury intrusion)=0.54 cc/g Pellet density=1.01 g/cc Surface area (BET)=278 m.sup.2/g

(25) A fraction equal to 64% of the extrazeolitic porosity has pores having a diameter higher than 100 ?.

EXAMPLE 4CATALYTIC TEST

(26) An alkylation test of benzene is carried out with isopropyl alcohol using the experimental device described hereunder.

(27) The experimental device is composed of tanks for the reagents: benzene and isopropyl alcohol, feeding pumps of the reagents to the reactor, preheating unit of the reagents, steel reactor positioned inside an electric heating oven, regulation loop of the temperature inside the reactor, regulation loop of the pressure inside the reactor, cooling of the reactor effluent and collection system of the liquid and gaseous products.

(28) In particular, the reactor consists of a cylindrical steel tube with a mechanical seal system and diameter equal to about 2 cm. Along the major axis of the reactor, there is a thermowell having a diameter equal to 1 mm in which there is a thermocouple free to slide along the major axis of the reactor.

(29) The catalyst of Example 1 is charged into the reactor. A quantity of inert material is charged above and below the catalytic bed in order to complete it.

(30) The benzene and isopropanol (IPA) reagents are fed to the reactorpreheated and premixed in a specific mixerwith up-flow.

(31) The reaction products are analyzed via gaschromatography. The reaction conditions under which the test is carried out, are the following: Reaction temperature: 195? C. Reaction pressure: 5 bar WHSV: 2 hours.sup.?1 [Benzene]/[IPA] in the feed: 3.2 moles/moles

(32) The total concentration of water present in the complete conversion system of the isopropyl alcohol reagent is equal to about 5%.

(33) The selectivity during the whole test proves to be equal to 83.6% for the selectivity [Cum]/[IPA] (cumene with respect to the total IPA converted) and 99.0% for the selectivity [Ar]/[IPA] (cumene+diisopropylbenzene+triisopropylbenzene with respect to the total IPA converted).

(34) The specific production of acetone proves to be equal to 0.74 Kg per ton of cumene.

EXAMPLE 5COMPARATIVE TEST

(35) Example 4 is repeated using the catalyst of Example 3.

(36) The same experimental device used in Example 3 is adopted, under the same operating conditions.

(37) The selectivity during the whole test proves to be equal to 82.1% for the selectivity [Cum]/[IPA] and 98.7% for the selectivity [Ar]/[IPA]. In particular, the specific production of acetone proves to be equal to 2.58 Kg per ton of cumene, consequently over three times higher with respect to that obtained in Example 4 in which a catalyst according to the invention is used.