Patent GB-364023-A (GB)
Title: Improvements in or relating to the manufacture of aliphatic aldehydes
IPC: C07C45/00
Filed: 1930-09-25
Abstract: Aliphatic aldehydes are obtained by subjecting one or more gaseous saturated hydrocarbons in admixture with carbon dioxide or gases containing carbon dioxide to the action of a silent, brush, arc, or glow discharge between electrodes supplied with alternating current of a frequency up to about 1000 cycles. Formaldehyde and/or acetaldehyde may be thus produced by the treatment of mixtures of methane and carbon dioxide.  The use of equimolecular proportions or excess of carbon dioxide suppresses the formation of higher aldehydes, while excess of hydrocarbon and also the use of high current strengths favours the production thereof.  The reaction may be carried out at ordinary temperatures, or at elevated temperatures, for example between 100 and 500 DEG  C. or higher, by heating the reaction vessel and/or preheating the gases.  Ordinary, increased, or reduced pressures may be employed.  Catalysts such as silica or siliceous materials, preferably of high specific surface, may be present. The process may be carried out in apparatus comprising electrodes each separated from the reactive gases by a wall of a dielectric such as glass, the electrodes being, if desired, immersed in water or other liquid containing an ionizing solute such as sulphuric acid.  Alternatively the gas mixture may be passed through a tube fitted with a central electrode and surrounded by a jacket containing a liquid such as water which acts as the other electrode. Other forms of apparatus in which the gases are in contact with both electrodes may be used, the process being in these cases preferably worked under reduced pressure.  In such cases the gases may be passed radially across the discharge, in the same direction as the discharge, or may travel in the same general direction as the discharge on entering, but leave in a radial direction thereto.  The discharge may be produced by means of an induction coil, a hightension transformer supplied with low frequency of about 25 to 1000 cycles, or a high-tension alternator of 50 to 100 or more cycles.  Voltages of 10000 to 100,000 or higher may be employed. According to an example, a mixture of methane and carbon dioxide is passed through a glass tube having a concentric electrode of chromium nickel steel supported by projections from the wall thereof, and surrounded by a jacket containing water acidulated with sulphuric acid as the other electrode.  The electrodes are connected to the secondary of a transformer supplied with alternating current of 50 to 100 cycles, the tension of the secondary being 16000 volts.  The exit gases are washed to separate the mixture of formaldehyde and acetaldehyde formed, and are recirculated with the addition of fresh methane and carbon dioxide.ALSO:Aliphatic aldehydes are obtained by subjecting one or more gaseous saturated hydrocarbons in admixture with carbon dioxide or gases containing carbon dioxide to the action of a silent, brush, arc, or glow discharge between electrodes supplied with alternating current of a frequency up to about 1000 cycles. Formaldehyde and/or acetaldehyde may be thus produced by the treatment of mixtures of methane and carbon dioxide.  The use of equimolecular proportions or excess of carbon dioxide suppresses the formation of higher aldehydes, while excess of hydrocarbon and also the use of high current strengths favours the production thereof. The reaction may be carried out at ordinary temperatures, or at elevated temperatures, for example, between 100 DEG  and 500 DEG  C. or higher, by heating the reaction vessel and/or preheating the gases.  Ordinary, increased, or reduced pressures may be employed. Catalysts such as silica or siliceous materials, preferably of high specific surface, may be present.  The process may be carried out in apparatus comprising electrodes each separated from the reaction gases by a wall of a dielectric such as glass, the electrodes being, if desired, immersed in water or other liquid containing an ionizing solute such as sulphuric acid. Alternatively the gas mixture may be passed through a tube fitted with a central electrode and surrounded by a jacket containing a liquid such as water which acts as the other electrode.  Other forms of apparatus in which the gases are in contact with both electrodes may be used, the process being in these cases preferably worked under reduced pressure.  In such cases the gases may be passed radially across the discharge, in the same direction as the discharge, or may travel in the same general direction as the discharge on entering, but leave in a radial direction thereto.  The discharge may be produced by means of an induction coil, a high-tension transformer supplied with low frequency of about 25 to 1000 cycles, or a high-tension alternator of 50 to 100 or more cycles.  Voltages of 10000 to 100,000 or higher may be employed.  According to an example, a mixture of methane and carbon dioxide is passed through a glass tube having a concentric electrode of chromium nickel steel supported by projections from the wall thereof, and surrounded by a jacket containing water acidulated with sulphuric acid as the other electrode.  The electrodes are connected to the secondary of a transformer supplied with alternating current of 50 to 100 cycles, the tension of the secondary being 16000 volts.  The exit gases are washed to separate the mixture of formaldehyde and acetaldehyde formed, and are recirculated with the addition of fresh methane and carbon dioxide.