Abstract: A method of gaseous acid catalysis which finds particular applications in the manufacture of furfural includes the steps of introducing a solid reactant containing one or more hydroxyl groups into a reactor (1); introducing superheated steam from a superheater (2) until the temperature within the reactor (1) is higher than that of the dew points of both water and the catalyst and the reactant is dry. The catalyst is then introduced into the superheated steam by vaporiser (3). Product gas formed is liquified in condenser (4) and the condensate collected in a buffer tank (5). Separation plant isolates the product gas and recovers the acid catalyst, preferably as its azeotrope with water, and recycles it into the vaporiser.

Abstract: Process for the manufacture of furfural wherein a pentosan-containing raw material acidified or not, is heated to a temperature T1 by admitting steam through valve 2 while the valves 3 and 4 are closed. During the very short heating process, the steam condenses, thus increasing the moisture content of the charge. Then, valve 2 is closed and a leak valve 3 is opened so as to produce a steady small flow of product vapor by gradual depressurization. This causes a slow drop in temperature. When a suitably chosen temperature T2 is reached, the leak valve 3 is closed to terminate the first “gradual depressurization”. If at the end of this period no more furfural was obtained, the digestion is completed by opening valve 4 to discharge the residue. If, however, furfural was still obtained, the reactor is reheated and submitted to another “gradual depressurization” period.

Abstract: A process for the production of furfural from lignosulphonate waste liquor which contains pentose is described, the process essentially comprising the maintenance of a boiling condition of the liquor at predetermined pressures for a sufficient time to convert the pentose to furfural and for the furfural produced to be removed without reacting with pentose, lignosulphonate or itself. Hot air or some other gas under pressure or hot mercury may be used to maintain the boiling of the liquor to ensure that the furfural produced transfers from the liquid to the gas phase and is transported from the reactor in the gas stream. Apparatus for carrying out the process includes a columnar reactor (4) with means (8) to control the pressure, an inlet for preheated liquor, an inlet for hot air under pressure at a low level, an outlet for spent liquor and an outlet for the gaseous phase, from which the furfural is recovered.