IL24882A - Process for the purification of hydrogen and of mixtures of hydrogen and nitrogen - Google Patents

Description

Process for the of hydrogen and of mixturoa of hydrogen and nitrogen present invention relates to the purification of hydrogen and of mixtures of hydrogen and Various processes used in the chemica industry lead to the formation of gaseous mixtures containing hydrogen carbon monoxide and saturated and unsaturated hydrocarbons which can be advantageously used for the preparation of hydrogen or of mixtures hydrogen and nitrogen suitable in particular for the synthesis of One example is the preparation o acetylene from methane or from other The usual method o working up these gases involves making available the hydrogen from the for example by partial oxidatio with or by catalytic reforming has with effect of converting hydrocarbons predominantly into carbon monoxide and these two processes leave some Subsequently the gaseous mixture subjected to conversion with this stage the carbon reacts with to form carbon dioxide and However this conversion not complete and some carbon monoxide remains in carbon dioxide is for by washing with water or with a solution of alkaline reagent such as monoethanolamlne or potassium Subsequently the hydrogen is separated from the residual carbon monoxide and methane fo example by low temperature fractionation and washing with liquid Nitrogen may be added to the hydrogen to give a stoichiometric mixture suitable for the synthesis of Besides making available the hydrogen content of the the operations of partial oxidation of catalytic reforming also eliminate the unsaturated hydrocarbons present in the which could interfere during the processing Thus the acetylenic hydrocarbons if they are not eliminated particularly in the conversion to the formation of gas black and polymers which reduce the activity of the catalysts used for the During the low temperature fractionation process an acetylenlc hydrocarbon can solidify and consequently obetruct the equipment and can also form some explosive compounds with copper as the fractionation apparatus is partially made with this Also the conjugated double bonded such as diene and cyclopentadiene can in the presence of traces of nitrogen oxides give rise to such as formation of explosive compounds during low temperature processes of catalytic reforming with steam and of thermal or catalytic partial oxidation are particularly sive as regards both the complexit of equipment used and the high which must be The fuel consumption also is particularly high in the reforming and the used in the partial oxidation process is as it often the starting gases are introduced under as it happens in particular when they result from the production of acetylene from methane or other the gases must be pressed for the reforming or partial Oxidation then they must be recompressed for the subsequent with a consequent consumption of It is an object of the present invention to enable hydrogen and mixtures of hydrogen and particularly suitable for the synthesis of to be prepared starting from mixtures of gases containing carbon and possibly also saturated without requiring expensive operations of reforming and partial Another object of the is to avoid the need for decompression and recompression of the gaseous according to the the gaseous starting mixture is subjected to catalytic hydrogenation before being treated for the conversion of carbon monoxide into carbon for the elimination of carbon dioxide and for the elimination of the residual The catalytic hydrogenatio is carried out under conditions appropriate to convert the acetylenic hydrocarbons into ethylenic saturated it is not necessary to take the hydrogenation further than any conjugated bonded such as diene and when ma be and the olefinic hydrocarbons themselves may be so that the mixture after hydrogenation contains hydrocarbons which are all Whatever the process chosen for the fractionation of mixture after removal of carbon it is always possible to obtain mixtures of hydrogen and nitrogen of very high purity or hydrogen completely free from process of the present invention can be applied with particular advantage to gases which have a hydrogen and carbon monoxide content of at least and a hydrocarbon tent no higher than including substantial quantities of acetylene other acetylenic The hydrogenation can be carried out using palladium 5 2 from to It is particularly work at these temperatures they are lower than the temperatures of normally used for the conversion fore it is sufficient to carry out the hydrogenation treatment during the preheating of the gaseous The fact that the hydrogenation can be carried out at any pressure is particularly advantageous when the starting gas is available under After possibly a further pression of the it is possible to carry out the four operations of elimination of carbon dioxide and separation of the hydrocarbons and of the carbon dioxide at the same high By compressing the gas before and before the there with regard to the conventional processes using low whe the gases must be compressed after the a remarkable saving of since the volumetric ratio between the verted gas and the gas to be converted can for in the case of the residue from acetylene production from methane or from other hydrocarbons or mixtures of and depending on the content of carbon ide in the starting gas and in the converted In this case the saving of energy can vary between and the use of a uniformly high pressure for the four stages allows various other advantages to be especially in a single production The preferred pressure is chosen in the range lying between 80 The following examples Illustrate the treatment of residual gases from the production of acetylene from hereinafter referred to residual having the following 60 to from to from to nitrogen from to oxygen from to methane from to ethane from 50 to 70 ppm propane absent ethylene from to by volume propylene from 30 to 40 ppm by volume acetylene from to 300 ppm by volume propadiene from 20 to 30 ppm by volume 1 Residual gas of the composition described above under pressure of about was heated to about and fed through a layer of catalyst at a space velocity dry of about h per m of It was then saturated with water at a temperature of corresponding to a molar monoxide ratio of and to conversion in two the first was conducted at substantially the same space velocity and at about 4 on a catalyst iron and chromium the at substantially the same space velocity and at about on a catalyst of zinc and copper The content of gaseous hydrocarbon after the hydrogenation ethane propane ppm ethylene ppm After the conversion stage the CO content was reduced to and after the to while the composition remained substantially Afte elimination of carbon dioxide by water and the elimination of hydrocarbons and of by low temperature fractionation and washing with liquid it was found possible to obtain on the one hand a stoichiometric mixture of nitrogen and hydrogen of a very high purity and on the other hand a mixture of hydrocarbons and carbon suitable for use as o Example 2 Residual as under a pressure of 7 was heated and fed through a layer of catalyst at space calculated for the dry of abou 8000 per of It was saturated with water at h temperature of 150 corresponding to monoxide molar ratio of and was then subjected to conversion in stages at substantially the same space first stage involved passing mixture at abou over a catalyst of iron and chromium oxides the second Involved passing the products at a temperature of about over a catalyst of zinc and copper The gaseous hydrocarbon conten after ethane ethylene propylen absent absent propane ppm The slight in the propylene content probably reflects partial hydrogenation of the After the first conversion stage the CO content was reduced to and after the second stage to The conversion were worked up as in Example insufficientOCRQuality

Claims (10)

1. A process for the purification of hydrogen or of mixtures of hydrogen and nitrogen, suitable for the synthesis of ammonia, starting from a gaseous mixture containing hydrogen, carbon monoxide and hydrocarbons, including acetylenic hydrocarbons, in which the mixture is subjected to catalytic hydro-genation and then treated for conversion of carbon monoxide into carbon dioxide, removal of carbon dioxide, and separation of hydrogen optionally with the incorporation therewith of nitrogen.

2. A process according to Claim 1 in which said gaseous mixture has a hydrogen and carbon monoxide content of at least 70 , and a content of saturated and unsaturated hydrocarbons not higher than 30$.

3. · A process according to Claim 2, in which said gaseous mixture comprises residual gases from the synthesis of acetylene from methane or other hydrocarbon.

4. A process according to Claim 1, 2 or 3 in which the hydrogenation is conducted to convert substantially all the into aoetylenic hydrocarbon/ethylenic and/or saturated hydrocarbon.

5. A process according to any preceding claim in which the hydrogenation is carried out with a palladium catalyst supported on alumina.

6. A process according to any preceding claim in which the hydrogenation is carried out at a temperature in the range 100° and 300°C. 24882/2

7. , A process according to the preceding claime in which the hydrogenation is conducted under substantial pressure and this pressure is not substantially reduced until the hydrogen lias been separated.

8. 6* A process according to Claim 7 in which said pressure is between 14 and 80 atmospheres.

9. A process for purifying hydrogen or a mixture thereof with nitrogen, substantially as set forth in either of the foregoing examples*

10., Hydrogen, and mixtures thereof with nitrogen, when purified by a process according to any of Claims 1 to 9·