CZ303642B6 - Process for preparing pellets from silicate and aluminosilicate mesoporous molecular sieves - Google Patents

Abstract

The invented process for preparing pellets from silicate and aluminosilicate mesoporous molecular sieves by molding without the use of additives is characterized in that a mesoporous molecular sieve is pressed to pellets using pressing pressure in the range of 0.7 MPa to 50 MPa.

Description

Process for preparing pellets of silicate and aluminosilicate mesoporous molecular sieves

Technical field

The present invention relates to a novel process for the preparation of pellets from silicate and aluminosilicate mesoporous molecular sieves without the use of additives, to a process for their regeneration, and to pellets prepared by said processes.

BACKGROUND OF THE INVENTION

Mesoporous molecular sieves were first synthesized in 1992 [J. S. Beck, J.C. Vartuli, W.J. Roth, Μ. E. Leonowicz, C. T. Kresge, K. D. Schmitt, C. T. W. Chu, D. H. Olson,

E. W. Sheppard, S. B. McCullen, J. B. Higgins, J. L. Schlenker, J, Am. Chem. Soc. 114 (1992) 10834]. These materials, characterized by a high specific surface area and narrow pore size distribution, can be prepared with a selected pore size in the range of 0.5 to 30 nm. They are used as sorption materials, catalysts and supports of catalytically active systems.

A disadvantage is that the powdered material cannot be directly used for industrial applications and therefore extrudates or pellets are prepared from mesoporous molecular sieves. A mixture of mesoporous molecular sieves with a binder (for example alumina or bentonite) and optionally also a plasticizer (for example methylcellulose) is used to prepare the extrudates. The admixture of these additives causes a deterioration of the textural properties of the material. The extrudates have a lower specific surface area and a lower pore volume compared to the starting mesoporous molecular sieve. In the case of aluminosilicate mesoporous molecular sieves, the surface acidity of the material also decreases.

Only one case of pellet preparation from mesoporous molecular sieves without the use of additives has been found in the literature [J. J. Chiu, D. J. Pine, S.T. Bishop, B.F. Chmelka, J. Catal. 221 (2004) 400]. High pressure (120 MPa) was used for pellet preparation, the disadvantage of which is that it causes the mesoporous structure of the material to collapse. The textiles and structural properties of the prepared pellets were not investigated in this paper.

SUMMARY OF THE INVENTION

These drawbacks are eliminated by the process of preparing pellets from silicate and aluminosilicate mesoporous molecular sieves without the use of additives, which is based on the fact that the mesoporous molecular sieve is pressed into pellets using pressing pressures in the range of 0.7 MPa to

4,7 MPa.

After the catalytic reaction, the isolated pellets can then advantageously be regenerated by heating them in air at 500 ° C,

The nitrogen adsorption isotherms and the diffractograms of the pellets prepared from the mesoporous molecular sieve of the SBA-15 type indicate that the mesoporous structure of the material remains during pellet preparation. The pellets prepared at a compression pressure of 0.7 MPa show the same micropore volume and the same mesopore diameter as the material used for their preparation, the specific surface area of the mesopores decreased by 8%.

The pellets prepared from the aluminosilicate mesoporous molecular sieve type AI-SBA-15 having a Si / Al molar ratio of 122 using a pressure of 0.7 MPa were used as a heterogeneous catalyst for the alkylation of toluene with benzyl alcohol in a batch reactor.

Stirred with inert gas at 110 ° C. It has been verified that the pellets are sufficiently mechanically stable and retain their structural integrity during the reaction.

In recovering the pellets used, the pellets are isolated after the catalytic reaction, air dried at room temperature and then heated in air at 500 ° C, for example for 60 min with a temperature increase of 10 ° C / min. The regenerated pellets exhibit 68% of the original activity and comparable selectivity in the alkylation of toluene with benzyl alcohol.

DETAILED DESCRIPTION OF THE INVENTION

Example 1

Preparation of pellets from silicate mesoporous molecular sieve type SBA-15.

A dry mesoporous molecular sieve of type SBA-15 with a mesopore diameter of 7.0 nm, a micropore volume of 0.200 cm ³ / g and a specific mesopore surface of 475 m ² / g was compressed at room temperature without addition of binder or plasticizer. 5 mm and a height of 0.5 mm using a compression pressure of 0.7 MPa. The prepared pellets had a mesopore diameter of 7.0 nm, a micropore volume of 0.203 cm ³ / g and a mesopore specific surface area of 439 m ² / g.

Example 2

Preparation of Al-SBA-15 type aluminosilicate mesoporous molecular sieve pellets and their use in catalytic reaction.

Dry mesoporous molecular sieve of SBA-15 type with a mesopore diameter of 5.0 nm, a micropore volume of 0.175 cmVg, a specific mesopore surface of 568 m ² / g and a Si / Al molar ratio of 122 was pressed without addition of binder or plasticizer at room temperature equipment for cylindrical pellets with a diameter of 0.5 mm and a height of 0.5 mm using a compression pressure

4,7 MPa.

The pellets prepared as described above were used as a heterogeneous catalyst of FriedelCrafts alkylation of toluene with benzyl alcohol. Pellets with a total weight of 0.0964 g were activated in air at 500 ° C for 30 min with a temperature increase of 10 ° C / min. After activation, the pellets were placed in a 100 ml three-necked distillation flask equipped with a capillary for nitrogen stirring. 5.7 ml of toluene (Lach-Ner) was added, the flask was sealed and immersed in a thermostated bath at 110 ° C. To the nitrogen stirred reaction mixture was added 0.235 mL of benzyl alcohol (Aldrich) and samples of the reaction mixture were sampled at specified time intervals and analyzed by gas chromatography. Besides dibenzyl (toluene and p-benzyltoluene as the main products, dibenzyl ether and a small amount of mbenzyltoluene were also found.

The benzyl alcohol C conversion and selectivity to o-benzyltoluene and t -benzyltoluene S were calculated according to the following formulas:

(’= + A7.V + ri />) / (ns + H /> + f1 \ f + H / g

S = nC (n _} > 4 V V + / /) / where // _s , n _t ., (I), are the substance amounts of benzyl alcohol (n _s ), o-benzyltoluene and // -benzyltoluene (W / 4, N - benzyltoluene (// _t ) and dibenzyl ether -

The found conversion of benzyl alcohol after 60 min reaction was C - 28% with selectivity to obenzyltoluene and p-benzyltoluene 5 = 46%.

Example 3

Regeneration of used pellets The AESBA-15 pellets after the reaction of Example 2 were air dried after separation of the reaction and then reactivated at 500 ° C for 60 min with a temperature increase of 10 ° C / min (color change from white to brown). After cooling, the pellets were used in a new toluene alkylation reaction with benzyl alcohol. The found conversion of benzyl alcohol after 60 min reaction was C = 19% with selectivity to o-benzyltoluene and p-benzyltoluene 5 = 41% (for definition of symbols see example 2).

Industrial applicability

The disclosed processes for the preparation of pellets from silicate and aluminosilicate mesoporous 20 molecular sieves find application in the preparation of pellets useful as sorption materials, catalysts and carriers of catalytically active systems.

Claims (1)

PATENT CLAIMS A process for the preparation of pellets from silicate and aluminosilicate mesoporous molecular sieves by compression without the use of additives, characterized in that the mesoporous molecular sieve is compressed into pellets using pressures ranging from 0.7 MPa to 4.7 MPa.