| 摘要 |
<PICT:0375314/IV/1> Formaldehyde is obtained by passing methane together with oxides of nitrogen and gases which contain a split off oxygen, at temperatures below the ignition point of the mixture, over catalysts consisting of one or more of the elements platinum, tungsten, chromium, copper, silver, nickel, zinc, manganese, or silicon, or oxides thereof. Steam may be employed as a gas splitting off oxygen. When metals are used as catalysts, they may be inserted as resistances in an electric circuit, in the form of wires, gauzes, lamin , or the like. Wire spirals made from alloys containing 56 per cent copper, 31 per cent nickel, and 13 per cent zinc, or containing 88 per cent nickel and 12 per cent chromium are used in examples. In another example a mixture of oxygen and nitrogen oxides is led through an opaque quartz glass tube heated to 620 DEG C. The initial mixture of methane and oxygen may be supplied with nitrogen oxides by a preliminary passage through an electric arc. The process may be carried out by supplying methane or a gas such as coke gas or natural gas containing methane from a container 1 to a mixer 5 through a pipe 4, nitrogen oxides being supplied to the mixer 5 from a container 2, and oxygen being either supplied as air by means of the air pump 3, or introduced into the mixer 5 from a separate container. The reaction takes place in the chamber 6, the necessary temperature being attained either by external heating or by electrically heating the catalysts contained therein. Water vapour produced in the reaction is condensed in the cooler 7 and separated in the receiver 8. The residual gases are led to a washer 9, wherein the formaldehyde still contained therein is dissolved by water sprinkled over cascade or other filling surfaces. The solution is collected in a vessel 10, whence it is returned by a pump 11 to the washer 9 until it contains 20 to 25 per cent formaldehyde. The solution is then led through a three-way cock 12 into a collecting vessel 13. The residual gas may be returned to the reaction chamber 6 or worked up in a second similar plant. The formaldehyde solution from the vessel 13 is brought to a strength of 30 to 40 per cent in a rectifier 14 and is finally collected in a vessel 16. The weaker solution from the rectifier 14 is held in a collector 15, and returned to the washer 9 by way of the vessel 10. According to the Specification as open to inspection under Section 91 (3) (a), the catalysts used comprise one or more elements selected from series 3, 4, 5, 7, and 8 of groups I, II, IV, VI, VII or VIII of the periodic table, or one or more oxides thereof. Magnesium is specifically mentioned. This subject-matter does not appear in the Specification as accepted.
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