Abstract: Heat is removed from, or supplied to, a vertical pipe of any cross-section, whose internal temperature is above or below the ambient temperature and whose wall temperature must neither exceed nor fall below a predetermined temperature range, by a method in which, in order to maintain the predetermined temperature range, the pipe is provided with a coaxial sheath and gas is passed through the gap between the pipe and the sheath. The invention is particularly directed to maintaining a predetermined temperature range at the outer pipe wall of the vertically oriented, double walled pipes which connect the reaction sections with the collectors in a steam reformer.

Abstract: Methanol is prepared by catalytic conversion of a synthesis gas mixture, containing hydrogen, carbon monoxide, carbon dioxide and/or water, at from 200.degree. to 320.degree. C. and under from 30 to 300 bar in adiabatic and/or isothermal reactions in the presence of a catalyst containing copper and zinc, by a process in which the fresh catalyst is reduced with a hydrogen-containing gas before the start-up of the process, and then the synthesis is started under conventional conditions and is continued until the formation of methanol in the reaction zone has declined substantially, after which the reaction is interrupted and the catalyst is regenerated.

Abstract: A process for the manufacture of ethylene polymers by high pressure polymerization of ethylene, if desired mixed with other compounds copolymerizable with ethylene, and isolation of the reaction product in a multi-stage isolation zone. The molecular weight of the ethylene polymer can be varied by varying the temperature prevailing in the isolation zone. The isolation zone preferably consists of two stages, with a higher pressure prevailing in the first stage than in the second stage.

Abstract: A process for the manufacture of ethylene polymers by homopolymerization and copolymerization of ethylene at pressures of from 500 to 5,000 bars and at from 50.degree. to 450.degree. C, with subsequent isolation of the polymers in high pressure product isolation zones and low pressure product isolation zones. The various parallel product isolation zones are at different temperatures, and the mean product residence times in the zones may be identical or different. Very different products, in amounts which can be chosen according to requirements, and with mutually independent polymer properties, can be obtained using only one high pressure polymerization system.

Abstract: A process for the manufacture of ethylene polymers by high pressure polymerization of ethylene, if desired mixed with other compounds copolymerizable with ethylene, and isolation of the reaction product in a multi-stage isolation zone. The molecular weight of the ethylene polymer can be varied by varying the mean product residence time in the isolation zone. The isolation zone preferably consists of two stages, with a higher pressure prevailing in the first stage than in the second stage.