RU2205818C1 - Method for preparing isopropanol - Google Patents

Abstract

FIELD: organic chemistry, chemical technology. SUBSTANCE: invention relates to method for preparing isopropanol used as solvent as the parent raw in production of catalysts, chemicals for agriculture, drugs and isopropyl acetate. Method involves liquid-phase catalytic hydrogenation of acetone at temperature 30-130 C under pressure 1.0-2.0 MPa carrying out in two successively arranged reactive zones in film regime with recycle of part of reaction mixture to the first zone and direct-flow feeding reagents to the second zone. In the first zone process is carried out in counter-flow liquid-gas. EFFECT: enhanced output, retained high selectivity of process. 1 tbl, 1 dwg

Description

 The invention relates to organic chemistry, to the field of producing aliphatic compounds having a hydroxyl group, by reduction of an oxygen-containing functional group with hydrogen, and in particular to methods for producing isopropanol by hydrogenation of acetone.

 Isopropanol (isopropyl alcohol) is used as a solvent, and also as a starting material in the production of catalysts, chemicals for agriculture, pharmaceuticals, isopropyl acetate.

 Two main areas of industrial synthesis of isopropanol are known: hydration of propylene [RF patent 2158725, cl. C 07 C 29/04, op. November 20, 2000] and the hydrogenation of acetone [Kirk-Othmer, 3-ed, vol 19, p. 198-215].

 The application of a particular method is mainly determined by the availability of raw materials and the cost of propylene and acetone.

 In industry, gas-phase and liquid-phase technologies for producing isopropanol by hydrogenation of acetone on a stationary catalyst are used. To gas-phase technology relates to a method [ed. St. USSR 1051055, class S 07 S 31/10, op. 10/30/1983].

 Liquid-phase hydrogenation processes are more productive and selective compared to gas-phase ones.

 A known method of liquid-phase hydrogenation of acetone [US patent 5081321, class. C 07 C 029/145; C 07 C 031/10 on. 01/14/1990, EP 379323, class S 07 S 29/145, on. 07/25/1990]. The method consists in the catalytic hydrogenation of liquid-phase acetone with hydrogen gas in a reactor containing a heterogeneous catalyst. Reagents are fed into the upper part of the reactor by a concomitant gas-liquid stream.

The interaction takes place in the range from ambient temperature to 200 ^o C. In an industrial embodiment, the temperature is from 35 to 150 ^o C. A higher temperature promotes the decomposition of acetone, which leads to a decrease in the yield of the target product. The pressure may be from atmospheric to 80 kg / cm ² , preferably from 2 to 50 kg / cm ² . The ratio of gaseous hydrogen and acetone at the input corresponds to 1-10: 1, preferably 1.2-5 mol of hydrogen per 1 mol of acetone.

 Known [application of Japan 3133941, cl. S 07 S 31/10, on. 06/07/1991] a method for producing isopropanol and an apparatus for its implementation, according to which the initial mixture containing acetone is fed into the upper part of the reactor filled with catalyst, where hydrogen is also introduced. Passing through a catalyst bed (for example, Raney nickel), these substances interact to form the target product - isopropanol. The reaction mixture is discharged from the bottom of the reactor and introduced into the separator. Part of the separated liquid is recycled, while the ratio of the recirculated product to the supplied to the synthesis is 1: 1-1: 30. The rest, passing through the degasser and filter, is output. The gaseous products separated in the separator are cooled in a heat exchanger and partially recycled or removed.

 The closest analogue is a method for producing isopropanol by liquid-phase hydrogenation of acetone [patent EP 1070698, cl. S 07 S 29/145, on. 01/24/01; German patent 19933691, class S 07 S 29/145, op. January 18, 2001].

In this method, hydrogenation is carried out in two reactors filled with a catalyst containing nickel. The reaction temperature is from 60 to 140 ^o C, the pressure is from 10 to 50 bar, the ratio of hydrogen: acetone is at least from 1.5: 1 to 1: 1. In both reactors, the reactants are introduced in a passing stream from above, onto the catalyst bed. The first reactor operates with a recycle of the liquid reaction mixture; the second - without recycling. The thermal conditions of the reactors are adiabatic.

 The objective of the invention is to increase the productivity of the process while maintaining its high selectivity.

The essence of the invention lies in the fact that isopropanol is obtained by liquid-phase hydrogenation of acetone, which is carried out at a temperature of 50-130 ^o C and a pressure of 1.0-2.0 MPa, in two reaction zones (reactors) filled with a catalyst in a film mode. The first zone (reactor) operates with the recycling of the liquid reaction mixture, the second without recycling. Hydrogen is sequentially supplied to the first zone (or to the first reactor) under the catalyst bed in countercurrent with the liquid phase, and then to the second zone (second reactor) - in a downstream flow with liquid from top to bottom. The thermal conditions in both reactors are adiabatic. The heat of the chemical reaction in the first reactor is removed in a heat exchanger mounted on the recycle line. In the first zone (reactor), the degree of conversion of acetone is 75-85%, after the second zone, the degree of conversion of acetone can be 99% or more.

 The hydrogenation process according to the proposed method is carried out in a reactor unit, including 2 reactors, however, it can be structurally carried out in one reactor, divided into two reaction zones. The first zone, like the first reactor, must have a circulation circuit and operate in a liquid-gas countercurrent mode, and the second zone - without recycle of the reaction mixture, with passing reactants.

 The proposed method for supplying hydrogen, as shown by comparative experiments, turned out to be more efficient: with the same contact load on the catalyst, the conversion of acetone in the first reactor and, accordingly, in the entire reactor unit was higher than in the direct-flow circuit.

 Our studies have allowed us to find an explanation for this effect.

When working in a countercurrent scheme, fresh hydrogen, coming into contact with a liquid reaction mixture heated to T _o , is saturated to its equilibrium by vapors. The temperature of the liquid reaction mixture decreases in accordance with the return of the heat of evaporation. As hydrogen is consumed in a chemical reaction, the vapors of the reaction mixture condense along the height of the catalyst bed, increasing the temperature of the liquid phase. As a result, hydrogenation in a countercurrent reactor (or zone) takes place at a higher temperature level than in a once-through reactor.

 The counterflow also has a positive effect on the process due to the fact that, together with isopropanol vapors, unreacted acetone vapors are transferred from the reactor outlet to the inlet side, which reduces its concentration in the reaction mixture entering the second reactor inlet, thereby increasing the total degree of acetone conversion in the reactor unit .

 A quantitative assessment of the effect of the counterflow was carried out at the installation (drawing), which included reactor 1 with circulation of the reaction mixture with a diameter of 50 mm, a height of 1.8 m, filled with 3.5 l of catalyst, and a reactor 2 that did not have a circulation loop, with a diameter of 50 mm and a height 0.8 m with 1.4 l of catalyst. Hydrogen is supplied to the reactor 1 countercurrently, in the second - direct flow.

The following examples in the table illustrate the effectiveness of the invention. In all examples, the temperature at the inlet to each reactor was equal to 50 ^o C, the circulation ratio K = Q rec / Q max was 4.3-4.6, the adiabatic heating in both reactors was 80 ^o C.

 Hydrogenation was carried out at pressures of 10 and 20 MPa, on two types of catalysts - Raney nickel and nickel-chromium. The size of the granules of the Ni-Raney catalyst is 4-5 mm, the tablets of the Ni-Cr catalyst d = 5 mm, L = 4 mm.

 In all examples of the table, the selectivity of acetone hydrogenation was 100% (the concentration of by-products was determined with an accuracy of 50 ppm).

Thus, the main distinguishing feature of the present invention from the prototype method is the process with the supply of gas and liquid phases, including part of the recycled reaction mixture, into the first reactor in countercurrent flow, and in the second - in direct flow, carrying out the process at a temperature of 50-130 ^o C and pressure 1-2 MPa.

Claims (1)

The method of producing isopropanol by liquid-phase catalytic hydrogenation of acetone, carried out in two successive reaction zones in a film mode with recycle of a part of the reaction mixture to the first zone and direct-flow supply of reagents to the second zone, characterized in that the reaction is carried out at a temperature of 50-130 ^o C and pressure 1 , 0-2.0 MPa, moreover, in the first zone, the process is carried out in a liquid-gas countercurrent.

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