GB691360A - Improvements in and relating to the production of ethanol - Google Patents

Abstract

<PICT:0691360/IV (b)/1> Ethanol is obtained by the direct catalytic hydration of ethylene by reacting ethylene and water at 250 DEG to 350 DEG C. and at a pressure of 200 to 500 atmospheres over a solid hydration catalyst consisting of the blue oxide of tungsten, using a feed rate of water in the range from 0.05 to 3.0 litres per hour per litre of catalyst bulk space and a feed rate of ethylene such as to maintain the total reaction pressure constant by compensating for any loss of ethylene from the reaction zone, and removing only the liquid phase from the reaction zone. The pressure on the liquid leaving the reaction zone may be reduced in stages down to atmospheric pressure and the liquid may be taken to a heat-exchanger where it may serve to preheat the water or the water and the ethylene to be reacted. The liquid may then be passed to a still where the ethanol is recovered as an azeotrope with water and this azeotrope may be subjected to further azeotropic distillation, e.g. with benzene to recover substantially pure ethanol whilst the water withdrawn from the still may be recycled to the reaction zone. The catalyst is preferably one of the unsupported type in the form of pellets and may be prepared from tungstic acid as described in example 2 of Specification 622,937, and this form of catalyst is employed in the examples given in which the process is carried out at 300 atmospheres pressure at temperatures of 300 DEG , 320 DEG and 345 DEG C. respectively, using a feed rate of 1 litre of water per hour per litre of bulk space occupied by the catalyst and in an example in which the process is carried out at 300 DEG C. and 300 atmospheres pressure with various water feed rates. The process may be effected in the plant illustrated in the Figure, wherein 1 is a converter containing a catalyst charge 2, ethylene being introduced via a compressor system 3 of one or more stages whilst water is introduced by way of compressor pump 4. The ethylene and water are both compressed to the desired pressure, e.g. 300 atmospheres and are then passed countercurrently to the liquid withdrawn from the bottom of converter 1 and exchange heat with the liquid. The water and ethylene then pass through a preheater 6 where they are raised to the operating temperature, e.g. to 300 DEG C. and the mixture then passes to the converter 1. The pressure is kept constant by regulating the flow of ethylene into the converter by means of a valve on the ethylene inlet line. The liquid from the converter then passes through the heat exchanger 5 as stated into catch pot 8 where some of the dissolved ethylene flashes off and may be recycled to compressor 3. The pressure is finally let down to atmospheric by valve 10 and the liquid then enters a still 11 heated by a steam coil. An azeotropic water-ethanol mixture is passed through a condenser 13 to catchpot 15 where a small quantity of ethylene flashes off and may be recycled. Water leaving the bottom of still 11 may also be recycled to the process via pipe 17.