PL159870B1 - The method of production of a catalyst for alkylation with methanol to orthocresol phenol - Google Patents

Abstract

A method of producing a catalyst for the alkylation of phenol with methanol to ortho-cresol, consisting of iron oxide modified with a small addition of other metals, involving the precipitation of components of aqueous solution with excess ammonia, filtering of the precipitate, forming and drying, characterized in that magnetite together with modifying agents is precipitated from equimolar solutions of iron(II) and iron(III) sulphates containing added chromium, silicon, potassium and vanadium in the form of salts.

Description

The present invention relates to a process for the preparation of a catalyst for the alkylation of phenol with methanol to ortho-cresol, the catalyst containing iron oxide modified with small additions of other metals.

The known method of preparing the catalyst for the synthesis of orthocresol consists in the precipitation or co-precipitation of metal salts and their hydroxides from aqueous solutions. For this purpose, usually aqueous solutions of ammonia, sodium hydroxide or carbonate are used. All known methods initially produce iron hydroxide which is then dried and calcined. During these operations, hydrated iron oxide is transformed into hematite a-FezCh. The hematite is then reduced with hydrogen, methanol or a mixture of the reactants, i.e. methanol and phenol. Reduction from cr-Fe2O3 from hematite partially produces magnetite Fe3O4, which is probably the active component of the catalyst. In some cases, the dried mass is calcined and formed into lozenges or extrudates, and then impregnated with solutions of appropriate salts, introducing e.g. All these known methods of producing catalysts require the use of high temperature calcination and activation. Moreover, the obtained catalyst is not stable and is active only at high temperature. The literature knows the method of synthesizing hydrated magnetite Fe3 (O · 4H2O - J.Supniewski - "Inorganic preparation ¹¹ , PWN -1958, page 587. Synthetic magnetite is obtained by precipitation with aqueous ammonia solutions from a mixture of iron and ferrous sulphate solutions. The thus obtained magnetite. it has a coarse structure and is not very active, both when used alone and with metallic additives.

According to the invention, the catalyst preparation method consists in precipitating synthetic magnetite in the presence of chromium, silicon, potassium and vanadium ions. Magnetite and modifiers are precipitated with an excess of ammonia from equimolar solutions of ferrous and ferrous sulphates containing the mentioned additives in the form of salts. The precipitate formed is filtered, formed and dried.

The precipitation of synthetic magnetite in the presence of chromium, silicon, potassium and vanadium ions makes it possible to obtain a product with high activity and selectivity in the alkylation of phenol. The high activity of the catalyst is likely due to the fact that magnetite is present in a highly dispersed state. For this reason, the catalyst does not require thermal treatment and activation or reduction. Moreover, the catalyst is active at the temperature of 553-563K, that is at a temperature 60-80K lower than known catalysts. The time of effective work of the catalyst, with the use of optimal parameters of the alkylation process, is over 2400 hours without the need for regeneration.

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The subject of the invention is illustrated in the following examples.

Example 1 A solution made of 65 g of crystalline ferrous sulfate in 2500 ml of water was mixed with 660 g of an aqueous solution containing 189.4 g of ferric sulfate. 4.45 g of chromium nitrate was added to the solution mixture, and 2.75 g of water glass was gradually introduced. The precipitate was precipitated at room temperature with concentrated aqueous ammonia solution to pH = 8. The precipitate was separated and washed with distilled water until the disappearance of SO4 ² - ions. The compacted mass was formed by extrusion and dried at 343K for 12 hours, then impregnated with 30 ml of a solution containing 0.8 g of KVO3 and dried again at 343K for 14 hours. Thus prepared catalyst had a surface area of 71 m ² / g.

Example II. The catalyst mass was prepared as in Example 1. Potassium metavanadate solution was added in an amount as in Example 1. Dried at 383K for 8 hours, ground and pelleted with 2% graphite. This catalyst, after calcination at the temperature of 523K for 10 hours, had a water absorption of 0.28 cm3 / g.

Example III. The catalyst was prepared as in Example II. 5% graphite was added to the mass during the pelleting. The next step was as in example 2. This catalyst had a crushing strength of 560 0.980665 · 10 ² kPa and an abrasion resistance of 0.8% after 1 hour.

For comparison, a catalyst was made according to Japanese Patent No. 80,129235. From an aqueous solution containing 202 g of ferric nitrate and 4.87 g of zirconium chloride, a precipitate was precipitated with a 25% ammonia solution, maintaining the pH at 7. The precipitate was separated and washed with distilled water until NO3 disappeared. The catalyst in the form of pellets was formed from the dried mass and calcined at the temperature of 723K for 3 hours. In this way, an iron catalyst for the alkylation of phenol with methanol to ortho-cresol with an atomic ratio of Fe: Zr 96: 4 was obtained. Its water absorption was 0.15 cm3 / g, while the crushing strength was 160 0.980665 · 10 ² kPa and abrasion after 1 hour 4.8%.

The catalysts of Examples I, II and III and the comparative catalyst were tested in the process of alkylation of phenol with methanol to ortho-cresol. Experiments lasting many hours were carried out in a reactor operating at atmospheric pressure, at a temperature of 543 to 662K, with a catalyst load of 0.5 V / Vh and a reaction mixture of phenol, methanol and water with a molar ratio of 1: 5: 1. at 559 K, the following yields of ortho-cresol and 2,6-xylenol:

Catalyst according to the example Yield of ortho-cresol in% vol. Yield of 2,6-xylenol 2 vol.% AND 42.1 9.1 II 45.8 7.8 III 44.2 8.1 comparative 25.2 8.0

Comparative and II catalysts, after 350 hours of operation, allowed to obtain 24.3145.6% of ortho-cresol at the temperature of 563K, respectively. However, after 170 hours of operation at the optimum temperature of 623K, the ortho-cresol efficiency in the presence of the comparative catalyst decreased from 37.8 to 32.2%. All the catalysts prepared according to the invention had a significantly higher activity in phenol alkylation at temperatures below 573K than the comparative catalyst. This catalyst only at the temperature of 623K allowed to obtain a similar orthocresol yield (37.8%), but then also 27.8% of 2,6-xylenol was formed. Hence, the yield of ortho-cresol in the presence of this catalyst drops significantly with the passage of time. On the other hand, all catalysts according to the invention, thanks to their operation at low temperature (below 573K), are characterized by constant activity and a very long life.

Department of Publishing of the UP RP. Circulation of 90 copies. Price: PLN 10,000

Claims (1)

Patent claim A method for the preparation of a catalyst for the alkylation of phenol with methanol to ortho-cresol, consisting of iron oxide modified with a small addition of other metals, consisting in precipitating the components with an excess of ammonia from aqueous solutions, filtering the precipitate, forming and drying, characterized in that, from equimolar solutions, ferric sulphates and ferrous materials containing the additions of chromium, silicon, potassium and vanadium in the form of salts, magnetite together with modifiers is precipitated.