KNITTING OF PRECIOUS METAL NETWORKS AND A METHOD USING SAME

Abstract

The invention relates to a method for producing large stainless steel meshes on flatbed knitting machines, comprising the steps of providing stainless steel wire and knitting a stainless steel mesh, characterized in that one stainless steel mesh each is knitted on the front and the rear needle bed of the flatbed knitting machine at the same time, and these two stainless steel meshes are linked to each other on one side by connecting stitches.

Claims

1. Method for producing precious-metal gauzes on flat-bed knitting machines, comprising the steps of providing precious-metal wire knitting a precious-metal gauze characterized in that a precious-metal gauze is knitted simultaneously on the front (8) and rear (9) needle beds of the flat-bed knitting machine, and these two precious-metal gauzes are connected at one side by connecting knit meshes.

2. Method according to claim 1, characterized in that the precious-metal gauze which is knitted on the front needle bed (8) is knitted from wire of the same composition as the precious-metal gauze which is knitted on the rear needle bed (9),

3. Method according to claim 1, characterized in that both precious-metal gauzes are knitted in the form of a semicircle, which are then connected at the straight edges so that the product comprises a round precious-metal gauze.

4. Method according to claim 1, characterized in that the wire used consists of platinum or a platinum alloy.

5. Method according to claim 4, characterized in that the wire consists of platinum alloy having at least 75 wt. % platinum.

6. Method according to claim 1, characterized in that the wire used consists of palladium or a palladium alloy.

7. Method according to claim 6, characterized in that the wire consists of palladium alloy having at least 75 wt. % palladium.

8. Method for the catalytic oxidation of ammonia, comprising the steps of providing precious-metal gauzes produced according to claim 1 installing in a flow reactor (1) a gauze stack (3) comprising said precious-metal gauzes (4) supplying a gas (6) comprising ammonia and oxygen at a temperature in the flow reactor (1) between 500° C. and 1300° C. and a pressure between 0.1 MPa and 1.4 MPa.

Description

EXAMPLE

[0028] A precious-metal gauze having a width of 2.3 m is knitted in each case on the front and rear knitting beds on a flat-bed knitting machine (Stoll, CMS type), having a knitted bed width of approximately 2.4 m (96 inches) and is connected at one side by a corresponding thread guide. This produces a precious-metal gauze, which is 4.6 m wide and any length.

[0029] By using the method according to the invention, precious-metal gauzes, which are free of weld seams, can thus be knitted up to a width that corresponds to twice the width of the knitting bed.

Comparative Example

[0030] On a flat-bed knitting machine having a knitted bed width of approximately 2.4 m (96 inches) a precious-metal gauze having a width of 2.3 m is in each case knitted on the front and rear knitted beds.

[0031] The two precious-metal gauzes are then connected to one another at one side by welding in order to be able to produce a precious-metal gauze having a precious-metal gauze diameter of 4.6 m.

[0032] The example according to the invention and the comparative example result in a precious-metal gauze of the same diameter, but the comparative example requires a further production step (welding). In contrast to the example according to the invention, the product in the comparative example also has a weld seam which runs transversely across the reaction zone and, due to its structure, reduces gas permeability and thus negatively influences the catalytic effect. In addition, it constitutes a mechanical weak point which can lead to material defects, in particular when the precious-metal gauze is being changed.

[0033] Legend for FIG. 1:

[0034] 1 Flow reactor

[0035] 2 Reaction plane

[0036] 3 Gauze stack

[0037] 4 Precious-metal gauzes

[0038] 5 Getter and separating gauzes

[0039] 6 Reaction gas

[0040] 7 Minimum gauze diameter

[0041] Legend for FIG. 2:

[0042] 8 Front needle bed

[0043] 9 Rear needle bed

[0044] 10 Needles

[0045] 11 Knitted product

[0046] 12 Casting-off web edge