Basell Polyolefine Gmbh

Basf Aktiengesellschaft

Walter Schicketanz

Kaspar Evertz

Klaus Berhalter

Volker Schumacher

Gerhard Siebert

Manfred Sandk&uuml;hler

Gerard Duc

A process for preparing polyethylene from 'feed ethylene' comprises: a) a hydrogenation stage in which 'feed ethylene' containing impurities or secondary components such as acetylene and ethane is reacted with hydrogen to remove the acetylene by catalytic hydrogenation to form ethylene and part of the ethylene is converted into ethane, and b) a polymerization stage in which the ethylene leaving stage a) is reacted in the gas phase in a fluidized-bed reactor to form polyethylene, where the fluidizing gas used comprises, on entering the reactor, ethene and from 20 to 70% by volume of ethane, based on the total volume of the fluidizing gas, possibly together with further components, where, in a), ethylene is converted in a targeted manner into ethane in addition to the ethane already present in the &#x201c;feed ethylene&#x201d; so that the concentration specified in b) results. An apparatus for carrying out the process is also provided. In the process claimed, ethane is used to increase the heat capacity of the fluidizing gas used.

Optimization of heat removal in a gas-phase fluidized-bed process

Polyolefins, preferably polyethylene, are prepared in a continuous gas-phase polymerization process in which the fluid monomeric component, preferably ethylene, and, optionally, one or more comonomers is/are polymerized in the polymerization zone of a fluidized-bed reactor in the presence of one or more catalysts, optionally with the addition of various auxiliaries, under reaction conditions where the fluidizing gas is circulated to remove the heat of polymerization or reaction and the polymerization product is taken from the circuit and the corresponding amount of monomer and, optionally, comonomers and optionally further auxiliaries are fed in, wherein the fluidizing gas discharged from the fluidized-bed reactor is cooled by means of a direct cooling apparatus in which the coolant is brought into direct contact with the fluidizing gas and heated coolant is passed to at least one further cooling stage in order to cool it and is, after cooling, wholly or partly returned to the direct cooling apparatus and/or heated or cooled coolant is wholly or partly returned to the reactor.

Gas-phase polymerization with direct cooling

In a process for preparing oxides of nitrogen having a low degree of oxidation by catalytic oxidation of ammonia, ammonia mixed with air and water vapor is oxidized over an oxidation catalyst.

Preparation of oxides of nitrogen having a low degree of oxidation

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Frankenthal, Germany

Walter Schicketanz