GB294759A - Improvements in the manufacture of carbon from carbon monoxide - Google Patents

Abstract

294,759. Cassel Cyanide Co., Ltd., and Ewan, T. July 5, 1927. Carbon is prepared by the catalytic decomposition of carbon monoxide in the presence of massive catalysts. The catalysts employed in the reaction include iron, nickel, cobalt or their oxides, but iron or mild steel in sheet form are preferably used in the process. The steel may be activated by dipping in fused sodium cyanide, washing in water, reducing carefully in carbon monoxide or hydrogen, and prolonged heating at 500-700‹ C. in carbon monoxide, or by repeated oxidation and reduction in carbon monoxide at 600-700‹ C. The carbon is deposited on the catalytic surface and is removed by mechanical scrapers which do not touch the surface. The carbon produced may contain 3-13 per cent of iron when iron is used as catalyst. The scrapers may be arranged to give a thin film with high iron content and rate of deposition or a thick film with the reverse. In one form, the carbon monoxide is brought into contact with the carbon produced at a temperature varying, according to the pressure employed, e.g. at 20-120‹ C. at atmospheric pressure, thus reducing the iron content of the carbon with the addition of iron carbonyl to the gas. The catalytic decomposition which takes place at a higher temperature e.g. 300-600‹ C. may be carried out in an iron tube, or a tube of silica or other non-catalytic material provided with a sheet-iron catalyst. The carbonyl accelerates the reaction and allows it to be conducted at a lower temperature, giving a more finely divided product. The tube has mechanical means for detaching the catalyst and conveying it in counter-current to the gas and for permitting removal of the carbon without admitting air. In a modificatiod, the carbon monoxide is passed directly into the hot zone and iron carbonyl is also added by passing a small proportion of the gas over reduced iron at atmospheric or higher pressure, or by bubbling it through iron carbonyl, or by injecting the carbonyl directly into the zone. Other carbonyls may also be used. By water cooling the inlet pipe, decomposition of the car- 'bonyl before it reaches the catalytic zone is prevented. The carbon may be retained in continuous agitation in the hot zone for about 12 hours to reduce its iron content. The carbon monoxide may contain an indifferent gas. The first Provisional Specification describes the use of carbon monoxide containing nitrogen, and, in that form of the process in which two temperature zones are employed, the removal of iron from the gas from the first zone by heating &c. The gas may be expanded to atmospheric pressure and mixed with further carbon monoxide before or after the removal of the iron.