Hydrogenation process

A continuous process for the catalytic hydrogenation of an unsaturated organic compound to a hydrogenation product thereof which comprises:

• providing a catalytic hydrogenation zone comprising first, second and third catalytic stages connected in series, each containing a charge of a hydrogenation catalyst;
• supplying to the first catalytic stage, at a first preselected rate and at a temperature at least as high as the threshold temperature for the hydrogenation reaction, a first vaporous feed stream comprising excess hydrogen and the unsaturated organic compound;
• allowing catalytic hydrogenation to occur substantially adiabatically in the first catalytic stage;
• recovering from the first catalytic stage a vaporous first product stream containing hydrogenation product and excess hydrogen;
• vaporising in the first product stream a preselected amount of further unsaturated organic compound to form a second vaporous feed stream;
• supplying the second vaporous feed stream to the second catalytic stage at a second preselected rate and at a temperature at least as high as the threshold temperature for the hydrogenation reaction, the preselected amount being so chosen in relation to the volume of the catalyst charge in the second catalytic stage and to the second preselected rate that, upon allowing hydrogenation to occur substantially adiabatically in the second catalytic stage, the product mixture recovered therefrom still contains a minor amount of chemically unsaturated material;
• allowing hydrogenation to occur substantially adiabatically in the second catalytic stage;
• recovering from the second catalytic stage a vaporous second product mixture containing hydrogenation product, a minor amount of chemically unsaturated material and excess hydrogen;
• cooling the vaporous second product mixture;
• supplying a third feed stream comprising cooled second product mixture to the third catalytic stage at a temperature at least as high as the threshold temperature for the hydrogenation reaction;
• allowing hydrogenation of the minor amount of chemically unsaturated material in the second product mixture to occur substantially to completion in the third catalytic stage;
• and
• recovering from the third catalytic stage a third product mixture that contains hydrogenation product and excess hydrogen and that is substantially free from chemically unsaturated material.

A continuous process for the catalytic hydrogenation of an aldehyde which may contain one or more unsaturated carbon-carbon bonds to a corresponding alcohol which comprises:

• providing a catalytic hydrogenation zone comprising n catalytic stages in series, where n is an integer of at least 3, each catalytic stage containing a charge of a solid hydrogenation catalyst effective for catalytic hydrogenation of aldehydes;
• supplying to the first catalytic stage a first vaporous mixture comprising excess hydrogenation and the aldehyde at a first temperature which is equal to, or is in excess of, the threshold temperature for the hydrogenation reaction;
• allowing catalytic hydrogenation to occur substantially adiabatically in each catalytic stage up to and including the (n-1)th catalytic stage, thereby to effect hydrogenation to corresponding alcohol of aldehyde supplied to that stage;
• vaporising further aldehyde in the vaporous product mixture from the, or from each, mth catalytic stage in the series, where m is an integer equal to or less then (n-2), to form a corresponding vaporous feed mixture for supply to the corresponding (m+1)th catalytic stage in the series;
• supplying resulting vaporous feed mixture to the corresponding (m+1)th catalytic stage at a temperature which is equal to, or is an excess of, the threshold temperature for the hydrogenation reaction;
• controlling the rate of supply of, and the composition of, the corresponding vaporous feed stream to the (n-1)th catalytic stage in relation to the volume of catalyst therein so that, under the substantially adiabatic conditions prevailing in the (n-1)th catalytic stage, the product mixture recovered therefrom still contains a minor amount of chemically unsaturated material;
• recovering from the (n-1)th catalytic stage a vaporous product mixture containing product alcohol, a minor amount of chemically unsaturated material, and excess hydrogen;
• cooling the product mixture from the (n-1)th catalytic stage;
• supplying cooled product mixture form the (n-1)th catalytic stage to the nth catalytic stage at the temperature which is equal to, or in excess of, the threshold temperature for the hydrogenation reaction;
• allowing hydrogenation to proceed substantially to completion in the nth catalytic stage;
• and
• recovering from the nth catalytic stage a final vaporous product mixture that contains the corresponding product alcohol and that is substantially free from chemically unsaturated material.