WO2007125004A1

WO2007125004A1 - Method for manufacturing catalysts for catalytic hydrogen chloride oxidation

Info

Publication number: WO2007125004A1
Application number: PCT/EP2007/053297
Authority: WO
Inventors: Olga Schubert; Martin Sesing; Martin Karches; Heiko Urtel; Christian Walsdorff
Original assignee: Basf Aktiengesellschaft
Priority date: 2006-04-26
Filing date: 2007-04-04
Publication date: 2007-11-08

Abstract

Method for manufacturing catalysts containing a) 0.001 to 10 % by weight of at least one metal from the group consisting of ruthenium, copper, and gold, b) 0 to 5 % by weight of one or more alkaline earth metals, c) 0 to 5 % by weight of one or more alkali metals, d) 0 to 10 % by weight of one or more rare earth metals, e) 0 to 10 % by weight of one or more additional metals selected from the group consisting of palladium, platinum, osmium, iridium, silver, and rhenium, based in each case on the total weight of the catalyst, on a substrate, in which the substrate is impregnated with one or more metal salt solutions that contain the active metal(s) and optionally promoter metals a) to e), and the impregnated substrate is dried and calcined, characterized in that the impregnated substrate is calcined at 200 to 600 °C in an acid-containing atmosphere in a fixed-bed or fluidized-bed reactor.

Description

Process for the preparation of catalysts for the catalytic hydrogen chloride oxidation

description

The invention relates to a process for the preparation of catalysts for the catalytic hydrogen chloride oxidation and to a process for the catalytic hydrogen chloride hydrogenation.

In the process of catalytic hydrogen chloride oxidation developed by Deacon in 1868, hydrogen chloride is oxidized with oxygen in an exothermic equilibrium reaction to form chlorine. By converting hydrogen chloride into chlorine, chlorine production can be decoupled from sodium hydroxide production by chloralkali electrolysis. Such decoupling is attractive, as the demand for chlorine worldwide grows faster than the demand for caustic soda. In addition, hydrogen chloride precipitates in large quantities, for example in phosgenation reactions, for example in the preparation of isocyanate, as coproduct.

EP-A 0 743 277 discloses a process for the production of chlorine by catalytic hydrogen chloride oxidation, in which a ruthenium-containing supported catalyst is used. Ruthenium is applied to the support in the form of ruthenium chloride, ruthenium oxychlorides, chloro-ruthenate complexes, ruthenium hydroxide, ruthenium-amine complexes or in the form of further ruthenium complexes. The catalyst may contain as further metals palladium, copper, chromium, vanadium, manganese, alkali, alkaline earth and rare earth metals.

According to GB 1 046,313, in a catalytic hydrogen chloride oxidation process, a catalyst obtained by applying ruthenium (III) chloride to alumina and then calcining at 250 ° C. in air is used.

Usually, gamma-alumina is used as the alumina carrier.

To prepare the catalyst, the oxidic support is impregnated with one or more metal salt solutions containing the active metal or metals and optionally promoter metals, the impregnated support is dried and then calcined. The calcination is usually carried out in an oven, for example a rotary kiln, tray oven or fluidized bed calciner, under oxygen or air. When calcining chloride-containing catalysts, chlorine or hydrogen chloride is released. Because of the corrosive atmosphere, calcination must be carried out in corrosion resistant equipment.

The object of the present invention is to provide a simpler and more economical process for the preparation of catalysts for the catalytic hydrogen chloride oxidation. It is also an object of the present invention to provide a simpler and more economical process for catalytic hydrogen chloride oxidation.

The object is achieved by a process for the preparation of catalysts for the catalytic hydrogen chloride oxidation containing

a) 0.001 to 10 wt .-% of ruthenium, copper and / or gold, b) 0 to 5 wt .-% of one or more alkaline earth metals, c) 0 to 5 wt .-% of one or more alkali metals, d) 0 to 10 Wt .-% of one or more rare earth metals, e) 0 to 10 wt .-% of one or more other metals selected from the group consisting of palladium, platinum, osmium, iridium, silver and rhenium,

in each case based on the total weight of the catalyst, on a support in which the support is impregnated with one or more metal salt solutions which comprise the active metal (s) and optionally promoter metals a) to e), the impregnated support is dried and calcined, characterized that calcining the impregnated support at 200 to 600 ° C in an oxygen-containing atmosphere in a fixed bed or fluidized bed reactor.

The object is further achieved by a process for the catalytic oxidation of hydrogen chloride with oxygen to chlorine in a fixed bed or fluidized bed reactor containing containing catalyst particles from a catalyst

in each case based on the total weight of the catalyst, on a carrier in which the carrier is mixed with one or more metal salt solutions which tivmetalle and optionally the promoter metals a) to e), impregnated, the impregnated support dries and calcined the impregnated support at 200 to 600 ° C in an oxygen-containing atmosphere, characterized in that the impregnated support at 200 to 600 ° C in a calcined oxygen-containing atmosphere in the fixed bed or fluidized bed reactor and performs the catalytic hydrogen chloride oxidation on the calcined in the fixed or fluidized bed reactor catalyst.

By carrying out the calcination already in the fixed-bed or fluidized-bed reactor in which the catalytic hydrogen chloride oxidation is subsequently carried out on the calcined catalyst, a separate corrosion-resistant apparatus for carrying out the calcining step is saved. Also eliminates the installation and removal of the catalyst in or out of Calciniervorrichtung (oven). Overall, therefore, a simpler and more economical process is realized.

The catalysts used according to the invention are obtained by impregnation of the support material with aqueous solutions of salts of the metals. The metals other than gold are usually applied to the support as aqueous solutions of their chlorides, oxychlorides or oxides. The shaping of the catalyst can take place after or preferably before the impregnation of the support material. The catalysts used according to the invention are also used as fluidized-bed catalysts in the form of powder having an average particle size of 10-200 μm. As fixed bed catalysts, they are generally used in the form of shaped catalyst bodies.

The copper or ruthenium-supported catalysts can be obtained, for example, by impregnating the support material with aqueous solutions of CuCl ₂ or RuCl ₃ and optionally a promoter for doping, preferably in the form of their chlorides.

Gold-containing catalysts of the present invention can be obtained by applying gold in the form of the aqueous solution of a soluble gold compound, then drying or drying and calcining. Preferably, gold is applied to the support as an aqueous solution of AuCl ₃ or HAuCl ₄ .

The ruthenium, copper and / or gold catalysts of the invention for the catalytic hydrogen chloride oxidation may additionally contain compounds of one or more other noble metals selected from palladium, platinum, osmium, iridium, silver or rhenium. The catalysts may also be doped with one or more further metals. For doping are suitable as promoters Alkali metals such as lithium, sodium, potassium, rubidium and cesium, preferably lithium, sodium and potassium, more preferably potassium, alkaline earth metals such as magnesium, calcium, strontium and barium, preferably magnesium and calcium, more preferably magnesium, rare earth metals such as scandium, yttrium, lanthanum, Cerium, praseodymium and neodymium, preferably scandium, yttrium, lanthanum and cerium, more preferably lanthanum and cerium or mixtures thereof, furthermore titanium, manganese, molybdenum and tin.

In a preferred embodiment, the catalyst is impregnated by impregnation of an oxidic support, for example an aluminum oxide powder or shaped body, with an aqueous ruthenium chloride hydrate solution corresponding to the water absorption of the support, then dried at 100 to 200 ° C., incorporated into the fixed bed reactor or fluidized bed reactor and finally calcined at 200 to 600 ° C, preferably at 300 to 400 ° C, in an oxygen-containing atmosphere, preferably in an air atmosphere, for a period of 1 to 12 hours, preferably 2 to 4 hours in the reactor. Locally, temperature peaks (hot spots) with temperatures above 600 ° C can occur. To avoid the formation of hot spots, the oxygen supply can be controlled. After calcination, ruthenium is generally present essentially as ruthenium (IV) oxide.

The calcination of the catalyst and the catalytic hydrogen chloride oxidation can be carried out in a fluidized bed reactor. The fluidized bed contains the catalyst as a fluidized granulate. The individual granules may each consist of catalyst material or contain the catalyst material on its surface. In a preferred embodiment, the catalyst comprises the metal components on an oxidic support. Alumina, for example γ-aluminum oxide or δ-aluminum oxide, zirconium oxide or titanium oxide or mixtures of these oxides can be used as oxidic support. The oxidic supports are preferably used in powder form with an average particle diameter of 30 to 150 μm, more preferably 40 to 100 μm and in particular 50 to 80 μm. The fine fraction having a particle size <20 μm is preferably less than 40% by weight, more preferably less than 30% by weight and in particular less than 20% by weight.

When using the fluidized bed reactor for the oxidation of hydrogen chloride to chlorine, for. For example, the catalysts based on ruthenium known from GB 1, 046,313, DE-A 197 48 299 or DE-A 197 34 412 can be used. Furthermore, the catalysts described in DE-A 102 44 996 based on gold, containing on a support 0.001 to 30 wt .-% gold, 0 to 3 wt .-% of one or more alkaline earth metals, 0 to 3 wt. % of one or more alkali metals, 0 to 10% by weight of one or more rare earth metals and 0 to 10% by weight of one or more other metals selected from the group consisting of ruthenium, Palladium, osmium, iridium, silver, copper and rhenium, each based on the total weight of the catalyst.

In one embodiment, the catalyst is impregnated by impregnation of a γ-alumina powder with an aqueous ruthenium chloride hydrate solution corresponding to the water absorption of the carrier, then dried at 100 to 200 ° C and finally at 200 to 600 ° C, for example about 400 ° C. , calcined under air atmosphere in the fluidized bed reactor. The ruthenium content of the catalyst is preferably 1 to 5 wt .-%, in particular 1, 5 to 3 wt .-%.

The calcination of the catalyst and the catalytic hydrogen chloride oxidation can be carried out in a fixed bed reactor. As a fixed bed reactor, a tube bundle reactor is preferably used. The fixed bed contains the catalyst as a bed of shaped catalyst bodies or catalyst split. Suitable shaped catalyst bodies are any desired forms, preference being given to tablets, rings, cylinders, stars, wagon wheels or spheres, particular preference being given to rings, cylinders or star strands. Suitable oxidic supports are alumina, for example gamma-alumina or δ-alumina, zirconia or titania or mixtures of these oxides. Another suitable carrier material is alpha-alumina, optionally in admixture with other carrier materials such as graphite, silicon dioxide, titanium dioxide and / or zirconium dioxide. Alpha alumina can be prepared by heating gamma alumina to temperatures in excess of 1000 ° C.

The present invention also provides a process for the catalytic oxidation of hydrogen chloride with oxygen to chlorine on the catalyst which has been calcined according to the invention.

For this purpose, a hydrogen chloride stream and an oxygen-containing stream are fed into the fixed bed or fluidized bed reactor and hydrogen chloride is partially oxidized to chlorine in the presence of the previously calcined catalyst to give a product gas stream containing chlorine, unreacted oxygen, unreacted hydrogen chloride and water vapor. The hydrogen chloride stream, which may originate from an isocyanate-producing plant, may contain impurities such as phosgene and carbon monoxide.

Typical reaction temperatures are between 150 and 500 ° C, usual reaction pressures are between 1 and 25 bar, for example 4 bar. Preferably, the reaction temperature is> 300 ° C, more preferably between 350 ° C and 400 ° C. Furthermore, it is expedient to use oxygen in superstoichiometric amounts. For example, a 1, 5 to 4-fold excess of oxygen is customary. There no Selectivity losses are to be feared, it may be economically advantageous to work at relatively high pressures and, accordingly, with respect to normal pressure longer residence times.

Preferably, the catalytic hydrogen chloride oxidation is carried out in the same fixed bed or fluidized bed reactor in which the catalyst has previously been calcined. The hydrogen chloride oxidation can be carried out in one or more stages.

The catalyst bed of the fixed bed reactor or the catalyst fluidized bed may contain, in addition to the catalyst according to the invention, further suitable catalysts or additional inert material.

In the isothermal or approximately isothermal mode of operation, it is also possible to use a plurality of reactors with additional intermediate cooling, for example 2 to 10, preferably 2 to 6, more preferably 2 to 5, in particular 2 to 3 reactors connected in series. The oxygen can be added either completely together with the hydrogen chloride before the first reactor or distributed over the various reactors. This series connection of individual reactors can also be combined in one apparatus.

An embodiment of the fixed-bed method consists in using a structured catalyst bed in which the catalyst activity increases in the direction of flow. Such structuring of the catalyst bed can be carried out by different impregnation of the catalyst support with active material or by different dilution of the catalyst bed with an inert material. As an inert material, for example, rings, cylinders or balls of titanium dioxide, zirconium dioxide or mixtures thereof, alumina, steatite, ceramic, glass, graphite or stainless steel can be used. The inert material preferably has similar external dimensions as the shaped catalyst bodies.

The conversion of hydrogen chloride in a single pass can be limited to 15 to 90%, preferably 40 to 85%. Unreacted hydrogen chloride can be partially or completely recycled to the catalytic hydrogen chloride oxidation after separation. The volume ratio of hydrogen chloride to oxygen at the reactor inlet is generally between 1: 1 and 20: 1, preferably between 1, 5: 1 and 8: 1, more preferably between 1, 5: 1 and 5: 1.

From the product gas stream obtained in the catalytic hydrogen chloride oxidation, the chlorine formed can subsequently be separated off in a customary manner. The separation usually comprises several stages, namely the separation and if appropriate, recycling of unreacted hydrogen chloride from the product gas stream of the catalytic hydrogen chloride oxidation, drying of the resulting, consisting essentially of chlorine and oxygen residual gas stream and the separation of chlorine from the dried stream.

Claims

claims

1. A process for the preparation of catalysts containing

a) 0.001 to 10 wt .-% of at least one metal selected from the group consisting of ruthenium, copper and gold, b) 0 to 5 wt .-% of one or more alkaline earth metals, c) 0 to 5 wt .-% of one or more alkali metals , d) 0 to 10 wt .-% of one or more rare earth metals, e) 0 to 10 wt .-% of one or more other metals selected from

Group consisting of palladium, platinum, osmium, iridium, silver and rhenium,

2. Catalyst according to claim 1, characterized in that the active metal is ruthenium.

3. The method according to claim 1 or 2, characterized in that the carrier is an aluminum oxide.

4. A process for the catalytic oxidation of hydrogen chloride with oxygen to chlorine in a fixed bed or fluidized bed reactor containing catalyst particles comprising a catalyst

a) 0.001 to 10 wt .-% of at least one metal selected from the group consisting of ruthenium, copper and gold, b) 0 to 5 wt .-% of one or more alkaline earth metals, c) 0 to 5 wt .-% of one or more alkali metals , d) 0 to 10% by weight of one or more rare earth metals, e) 0 to 10% by weight of one or more further metals selected from the group consisting of palladium, platinum, osmium, iridium, silver and rhenium, in each case based on the total weight of the catalyst, on a support in which the support is impregnated with one or more metal salt solutions which comprise the active metal (s) and optionally the promoter metals a) to e), the impregnated support is dried and the impregnated support is dried. calcined at 200 to 600 ° C in an oxygen-containing atmosphere, characterized in that calcining the impregnated support at 200 to 600 ° C in an oxygen-containing atmosphere in the fixed bed or fluidized bed reactor and the catalytic hydrogen chloride oxidation at the in the Fest- or fluidized bed reactor calcined catalyst.