Process for the preparation of a C2 -C4 paraffin dehydrogenation catalyst

Claim 2

A process for dehydrogenating C 2 -C 4 paraffins, characterized in that it comprises contacting said paraffins under dehydrogenation conditions with a dehydrogenation catalyst prepared by using impregnation liquors in which the platinum and/or tin compound occurs in the form of a halogen-containing compound as follows: (a) impregnating an alumina carrier with an aqueous solution of a tin compound; (b) calcining the composition; (c) impregnating the composition with an aqueous solution of a platinum compound; (d) reducing the composition; (e) removing at least part of the halogen ions, which were introduced into the composition by using a halogen-containing platinum compound and/or tin compound in steps (a) and/or (c), by treating the composition with a non-acidic aqueous solution comprising NH 4 + ions to provide a final catalyst containing less than 0.1% w of halogen; and (f) impregnating the composition with a non-acidic aqueous solution of an alkali metal compound.

Claim 3

A process as claimed in claim 1, characterized in that the dehydrogenation is applied to C 3 and/or C 4 paraffins.

Claim 4

A process as claimed in claim 1, characterized in that the catalyst is subjected to a hydrotreatment at an elevated temperature before being contacted with the feed.

Claim 5

A process as claimed in claim 2, characterized in that hydrogen is added to the feed.

Claim 6

A process as claimed in claim 2, characterized in that it is carried out at a temperature of 400°-650° C., a pressure of 0.1-10 bar and a space velocity of 1-20 kg.kg -1 .h -1 .

Claim 7

A process as claimed in claim 5, characterized in that it is carried out at a temperature of 500°-600° C., a pressure of 0.5-3 bar and a space velocity of 2-10 kg.kg -1 .h -1 .

Claim 8

A process for the preparation of an aromatic C 5 + hydrocarbon mixture from C 2 -C 4 paraffins, characterized in that it is carried out in two stages, in which process the paraffins are dehydrogenated in the first stage according to a process as described in claim 1 and in which the reaction product from the first stage is aromatized in the second stage by contact under aromatizing conditions with a crystalline metal silicate as catalyst, which crystalline metal silicate after one hour's calcination in air at 500° C. has the following properties: (a) thermally stable up to a temperature of at least 600° C.; (b) an X-ray powder diffraction pattern in which the strongest lines are the four lines mentioned in Table A: TABLE A ______________________________________ d(Å) ______________________________________ 11.1 ± 0.2 10.0 ± 0.2 3.84 ± 0.07 3.72 ± 0.06 ______________________________________ (c) in the formula which represents the composition of the silicate expressed in moles of the oxides and which in addition to SiO 2 includes one or more oxides of a trivalent metal A chosen from the group formed by aluminum, iron, gallium and chromium, the SiO 2 /A 2 O 3 molar ratio is higher than 10.

Claim 9

A process as claimed in claim 7, characterized in that the crystalline metal silicate includes both iron and aluminum.

Claim 10

A process as claimed in claim 8, characterized in that the second stage is carried out at a temperature of 200°-500° C., a pressure of 0.1-20 bar and a space velocity of 0.5-10 kg.kg -1 .h -1 .

Claim 11

A process as claimed in claim 9, characterized in that the second stage is carried out at a temperature of 300°-450° C., a pressure of 0.5-10 bar and a space velocity of 1-5 kg.kg -1 .h -1 .

Claim 12

A process as claimed in claim 10, characterized in that at least part of the C 4 - product from the second stage is recycled to the first stage.