In the manufacturing of formaldehyde from methanol, there are so-called an oxidation method of using air in excess and so-called a dehydrogenation method of using insufficient air. In the manufacturing of formaldehde by the latter method of using methanol in excess in the presence of a single metal catalyst, the author has investigated on the reaction conditions, the method of suppressing the side reaction, the catalyst, and the diameter of reaction furnace, etc.in order to study a possibility of using a single reaction furnace of large size without mixing of water in methanol.This first report deals with the reaction conditions.The result indicated that a standard ratio of air/CH3OH should be taken the value of 0.834 l air/g CH3OH from equilibrium theory and its optimum value was found to be 0.80-0.95 l/g CH3OH from the experimental result. Nearly 100% of reaction rate was obtained with the reaction temperature at 700°C and the standard ratio of 0.834 l air/g CH3OH, but the optimnin temperature of reaction was indicated to be in the range of 580-680°C as there was the problem of side reaction.Also, a caution was necessary for side reaction, especially the formation of carbon monoxide, by noting the temperature of gas after passing through the catalyst layer as well as the temperature of catalyst layer.The space velocity up to the maximum of 80×104 has been experimented.It was indicated that the space velocity had not much influence on the rate of reaction of methanol and the formation of carbon dioxide, but there was a remarkable effect on the formation of carbon monoxide and it was increased with an increase of space velocity.Also, the formation of carbon monoxide was increased by increasing the rate of gaseous flow in spite of the space velocity was kept constant.
The process of supressing the side reactions (formations of carboa dioxide, carbon monoxide, formic acid, etc.) in the manufacture of formaldehyde have been investigated. At first, the change in composition of reacted gas by the distance from outlet after passing through the catalyst layer has been investigated.It was found that the formation of carbon monoxide was mainly caused by the treatment after passing through the catalyst layer, while the formation of carbon dioxide was mainly caused during the process of reaction in the catalyst layer.The next problem was to investigate the process of suppressing the side reaction by an addition of steam into the gaseous raw material, by an external cooling of the gaseous outlet pipe after passing through the catalyst layer, and by a direct cooling of the gas with the spraying of cooling fluid after passing through the catalyst layer.It was found that the most suitable method of suppressing the side reaction, from the standpoint of its effectiveness and operation, was to supply a direct spraying of cooling fluid on the bottom of catalyst floor.By this procedure of using the space velocity at 30×104, 70% of reaction rate and 87% of the theoretical yield as an aim, 73% of reaction rate and 94% of theoretical yield were obtained. The formation of formic acid has been investigated.This was related much on the formation of carbon monoxide and it was found that the formation of formic acid could be decreased by taking a procedure of decreasing the formation of carbon monoxide.