RU2721906C2 - Method of preparing catalyst for dehydrating methylphenylcarbinol - Google Patents

Abstract

FIELD: chemistry.SUBSTANCE: invention relates to a method of preparing an aluminum oxide catalyst for producing styrene from methylphenylcarbinol (1-phenylethanol) (MPC) at high temperature in the presence of a dehydration catalyst, in which the dehydration catalyst includes molded particles of a catalyst based on aluminum oxide, which are obtained by extrusion on piston presses from pre-molded workpieces from paste with moisture content of 55–60 % at a pressure of not less than 5–15 MPa, and calcination is carried out at temperature of 440–490 °C.EFFECT: technical result consists in improvement of mechanical strength of catalyst while maintaining high conversion and selectivity.1 cl, 1 tbl, 5 ex

Description

The invention relates to the field of technology of catalysts for the dehydration of aromatic alcohols, and in particular to a method for preparing an catalyst based on alumina intended for the production of styrene from methylphenylcarbinol (1-phenylethanol) (MPA) at elevated temperature.

A known method of producing a catalyst for dehydration of MPA, including the operation of modifying active alumina by introducing zeolite to 50.0 wt. % in decationized form. In this case, ferrierite, or mordenite, or erionite, or zeolite of type Y or ZSM are taken as zeolite [Application No. 20011133657/04, C07C 1/24, B01J 21/04, 06/20/2003. Lamberov A.A., Romanova R.G., Egorova S.R. et al. Aromatic alcohol dehydration catalyst]. Modification allows you to adjust the acid-base properties of the catalyst.

The disadvantage of this method is the use in the composition of the catalyst molding paste a significant amount of non-plastic material - zeolite, which leads to extrusion molding to obtain low-strength catalyst granules. Improving the rheological properties by introducing special additives into the molding material can adversely affect the catalytic properties of the catalyst. Known methods for producing active alumina, including plasticization of pseudoboehmite or boehmite mass, molding, drying and calcining granules [Copyright certificates No. 423351, 1001627, 1256379, 1274232] . In order to increase strength, organic and inorganic acids, a solution of ammonia, etc. are used as a plasticizer.

The disadvantages of the known methods are the presence in the composition of the paste based on active alumina plasticizers, the decomposition products of which remain in the composition of the catalyst during its heat treatment, which can adversely affect the catalytic properties. Perhaps for this reason, these sources do not contain data on the catalytic activity in the reaction for the production of styrene from MPA.

The closest set of essential features is the method of producing styrene by dehydration of 1-phenylethanol (methyl phenyl carbinol MFC) on a catalyst in the form of molded particles based on alumina [RF Patent No. 23233198, C07C 1/24, B01J 21/04, 04/27/2008]. The catalyst is prepared by mixing a solid phase (alumina powder or alumina precursor powder and possibly a binder) and water and passing this mixture (paste) through an extruder, followed by calcining the obtained granules. To improve the extrusion process, the paste contains additives, for example, peptizers and flocculants, which contribute to a denser packing of particles in the extrusion paste and retain water. The application of the method allows to reduce the amount of by-products formed and increase the operating time of the catalyst before its regeneration. The mechanical strength of the catalyst particles by crushing along the generatrix does not exceed 1.3-1.4 MPa. After 50 hours of testing the catalyst at 300 ° C, the MPC conversion reaches 99.9% and after 50 hours it decreases to 99.7%. Moreover, the styrene selectivity after 50 hours of testing is 96.5%.

The disadvantage of this method is the low mechanical strength of the granules.

The problem to which the invention is directed, is to increase the mechanical strength of the catalyst while maintaining high conversion and selectivity.

The stated technical problem is achieved in that a method for producing a catalyst for the process of dehydration of methylphenylcarbinol at an elevated temperature in the presence of a dehydration catalyst, in which the dehydration catalyst comprises molded particles of an aluminum oxide catalyst, in which the dehydration catalyst is obtained by extrusion followed by calcination, according to the invention, molded particles are obtained on a piston extruder from pre-pressed pastes with a pressure of 5-15 MPa from pastes with a moisture content of 55-60%, and the molding of the particles is calcined at a temperature of 440-490 ° C.

Distinctive features of the invention is that the extrusion to obtain the formed particles on a piston extruder is carried out from pre-pressed blanks at a pressure of 5-15 MPa with a humidity of 55-60%, and calcination is carried out at a temperature of 440-490 ° C.

The present invention meets the condition of patentability "novelty", since the prior art failed to find a technical solution, the essential features of which would completely coincide with all the features available in the independent claim.

Also, the present invention meets the criteria of the invention of "inventive step", because the prior art could not find a technical solution, the essential features of which ensured the fulfillment of the same technical task to which this invention is directed.

When the paste moisture content is less than 55%, the density of both the raw billet and molded particles and the finished catalyst increases, which affects the catalytic properties of the catalyst. In addition, a decrease in molding moisture - worsens the ductility of the paste, which leads to clogging of the holes of the die, resulting in low-quality particles with low strength. Increasing the moisture content of the paste by more than 60% reduces the density of the crude billet and the finished product, and also the strength of the catalyst.

Annealing at temperatures less than 440 ° C does not provide sufficient particle strength, and as a result, the mass fraction of dust and fines in the finished product increases. Annealing at temperatures above 490 ° C does not give an increase in strength, but at the same time, energy costs increase, and catalyst characteristics deteriorate.

Pre-pressing of the workpieces at a pressure of 5-15 MPa allows the formation of a plastic paste with properties that ensure the production of particles by extrusion on piston presses with a uniform structure and high strength. Without preliminary pressing of the blanks, the formation of a homogeneous structure of the moldable paste is not ensured. The use of a screw extruder, which has greater productivity compared to piston extruders, entails liquefying the paste due to the mechanical action of the screw blades and makes it impossible to obtain high-quality catalyst particles.

The method is illustrated by the following examples:

Example No. 1. The feedstock is aluminum monohydroxide (manufactured by Industrial Catalysts CJSC), a predominantly pseudoboehmite structure with impurities of aluminum trihydroxide with a moisture content of 70.5% is dried to a molding moisture content of 60%. The paste is pressed in a hydraulic press at a pressure of 5 MPa to obtain blanks. The blanks are placed in a piston press and the catalyst particles are extruded in the form of cylinders with a diameter of 5.5 mm, dried in air, dried at a temperature of about 80 ° C to a residual moisture content of not more than 1%, and calcined at a temperature of 440 ° C. The mechanical crushing strength of the catalyst along the generatrix was 1.8 MPa, the MPC conversion at a temperature of 300 ° С after 50 hours of testing was 99.8%, after 120 hours - 99.7%, the selectivity for styrene after 50 hours was 96.5% .

Example No. 2. The feedstock is aluminum monohydroxide (manufactured by Angarsk Plant of Catalysts and Organic Synthesis OJSC), a predominantly pseudoboehmite structure with impurities of aluminum trihydrate with a moisture content of 65% is dried to a molding moisture of 55%. The paste is pressed in a hydraulic press at a pressure of 15 MPa to obtain blanks. The blanks are placed in a piston press and the catalyst particles are extruded in the form of cylinders with a diameter of 6.0 mm, dried in air, dried at a temperature of about 80 ° C to a residual moisture content of not more than 1% and calcined at a temperature of 490 ° C. The mechanical crushing strength of the catalyst along the generatrix was 2.1 MPa, the MPC conversion at a temperature of 300 ° С after 50 hours of testing reaches 99.9%, after 120 hours - 99.8, the selectivity for styrene after 50 hours is -96.6%.

Example No. 3. The experiments were carried out as in example No. 1, but the paste was dried to a molding moisture content of 57%. The paste was pressed on a hydraulic press at a pressure of 8 MPa to obtain blanks. The extruded catalyst particles were calcined at a temperature of 490 ° C. The mechanical strength of the catalyst for crushing along the generatrix of 1.9 MPa, the conversion of MPC at a temperature of 300 ° C after 50 hours of testing is 99, .8%, after 120 hours - 99.7%, the selectivity for styrene after 50 hours is 96.5% .

Example No. 4. The experiments were carried out as in example No. 1, but the paste was dried to a molding moisture content of 51%. The extruded catalyst particles were calcined at a temperature of 500 ° C. The mechanical crushing strength of the catalyst along the generatrix was 1.2 MPa, the MPC conversion at a temperature of 300 ° C after 50 hours was 99.5%, the conversion after 120 hours was 99.4%, and the selectivity after 50 hours was 96.2%.

Example No. 5. The experiments were carried out as in example No. 1, but the paste was dried to a molding moisture content of 64%. The extruded catalyst particles were calcined at a temperature of 420 ° C. The mechanical crushing strength of the catalyst along the generatrix was 13 MPa, the MPC conversion at a temperature of 300 ° С after 50 hours was 99.6%, after 120 hours - 99.5%, the selectivity after 50 hours - 96.4%.

The mechanical crushing strength of the samples along the generatrix was measured using an IPG-1 extensometer (pellet strength tester) in an air atmosphere at room temperature from a sample size of 10 pcs.

The crushing force was related to the cross-sectional area of the catalyst particle. To obtain data on the conversion and selectivity of catalyst samples, a flow-through laboratory type apparatus was used; measurements were performed at atmospheric pressure, a temperature of 300 ° С, and a feed space velocity of 1.5 h ^-1 . Raw materials contained 80.5 wt. % methylphenylcarbinol (IFC) (1-phenylethanol), 11.3 wt. % methylphenylketone and 2% water, the rest is impurities. The composition of the reaction products was determined by chromatographic method. The conversion and selectivity of the catalyst were calculated after 50 hours of testing. Additionally, the conversion rate was also determined after 120 hours of testing. The test results are shown in table 1.

As can be seen from table 1, the application of the claimed method in comparison with the known solution allows to increase the strength of the catalyst by 30-60%, while maintaining high values of conversion and selectivity of the catalyst.

Claims (1)

A method of preparing a catalyst for the dehydration of methyl phenylcarbinol at an elevated temperature in the presence of a dehydration catalyst, in which the dehydration catalyst comprises molded alumina-based catalyst particles, characterized in that the catalyst particles are extruded from piston presses from pre-pressed pastes from a humidity of 55-60 % at a pressure of 5-15 MPa and calcination is carried out at a temperature of 440-490 ° C.