KNITTING OF NOBLE METAL NETS USING IGNOBLE MATERIALS AT THE EDGE, NOBLE METAL NET PRODUCED IN THIS WAY AND A METHOD FOR USING THE NOBLE METAL NET

Abstract

The present invention relates to a method for producing a non-rectangular noble metal net (5) on flat bed knitting machines, comprising the steps of providing noble metal wire or noble metal alloy wire providing combustible yarn knitting a net (5) using noble metal wire or noble metal alloy wire for the reaction zone (7), wherein combustible yam is used for the offcut area (9), which is singed off or otherwise removed after the knitting process.

Claims

1. Method for producing a non-rectangular noble metal net on flat bed knitting machines, having the steps of providing noble metal or noble metal alloy wire providing combustible yarn knitting a net using noble metal or noble metal alloy wire for the reaction zone, characterized in that for the offout area (9), combustible yarn is used that is singed off or otherwise removed after the knitting process.

2. Method according to claim 1, characterized in that a platinum or platinum alloy wire is used as the noble metal or noble metal alloy wire.

3. Method according to claim 2, characterized in that a platinum alloy wire having at least 75% platinum is used as noble metal alloy wire.

4. Method according to claim 1, characterized in that a palladium or palladium alloy wire is used as noble metal or noble metal alloy wire.

5. Method according to claim 4, characterized in that a palladium alloy wire having at least 75% palladium is used as noble metal alloy wire.

6. Method for producing noble metal nets according to claim 1, characterized in that a combustible yarn selected from the group consisting of chemical fibers, plant fibers and animal fibers is used for the area of the offcut zone.

7. Method for producing noble metal nets according to claim 1, characterized in that an ignoble metal wire M ad e of heat resistant steel or a heat-concluding alloy is used for the area of the net fixing zone (8).

8. Net, produced according to claim 1, characterized in that it consists of noble metal or noble metal alloy wire in the area of the reaction zone (7) and of wire made from neat-resistant steel or a heat-conducting alloy in the area of the net fixing zone.

9. Method for catalytic oxidation of ammonia, comprising the steps of installing a net stack, containing nets according to claim 8 into a flow reactor (1) supplying a gas comprising ammonia and oxygen at a temperature in the flow reactor of between 500° C. and 1300° C. and a pressure of between 0.1 MPa and 1.4 MPa.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] FIG. 1 schematically shows the reactor with the net stack installed therein;

[0018] FIG. 2 shows the noble metal net (shown in black-and-white) with the combustible yarn (shown in gray) connected to the noble metal net.

[0019] FIG. 3 shows show the noble metal net (shown in black-and-white) with the combustible yarn (shown in gray) connected to the noble metal net in a different manner.

[0020] FIG. 4 shows the noble metal net after singeing off the combustible yarn.

[0021] FIG. 5 shows, for comparison, a net corresponding to the prior art in which no corresponding wire hoop is visible at the edge.

DETAILED DESCRIPTION

[0022] This object is achieved by a method for producing noble metal nets on flat bed knitting machines, consisting of [0023] providing noble metal or noble metal alloy wire [0024] providing combustible yarn [0025] knitting a net using noble metal or noble metal alloy wire for the reaction zone,

[0026] wherein combustible yarn is used for the offcut area (9), which yarn is singed off or otherwise removed after the knitting process.

[0027] The waste of noble metal net, and thus the costs, are thereby markedly reduced, since the noble metal from the offcut needs only be recycled again and processed into wire before it can be resupplied for use. The product according to the invention differs from the prior art only at the edge, and thus outside of the reaction zone, as will be described below. FIG. 2 and FIG. 3 show the noble metal net (shown in black-and-white) with the combustible yarn (shown in gray) connected via the tuck or stitch of the noble metal net. The terms tuck and stitch are known to the person skilled in the art. After singeing off the combustible yarn, the previously connecting tuck or the stitch remain visible a wire hoop at the edge of the noble metal net (FIG. 4). FIG. 5 shows, for comparison, a net corresponding to the prior art in which no corresponding wire hoop is visible at the edge.

[0028] In a preferred variant, a platinum or platinum alloy wire is used as a noble metal or noble metal alloy wire. For a preferred variant of this embodiment, a platinum alloy wire with at least 75% platinum is used.

[0029] In a further preferred variant, a palladium or palladium alloy wire is used as noble metal or noble metal alloy wire. For a preferred variant of this embodiment, a palladium alloy wire with at least 75% palladium is used.

[0030] In one embodiment variant of this method for producing noble metal nets, a combustible yarn selected from the group consisting of chemical fibers, plant fibers and animal fibers is used for the area of the offcut zone (9).

[0031] Chemical fibers are thereby to be understood as all fibers that are produced by chemical methods; plant fibers are to be understood as all fibers that are produced based on plants; and animal fibers are to be understood as all fibers that are produced based on animals (https://de.wikipedia.org/wiki/Faser, downloaded on 25 Apr. 2019, and G. Schnegelsberg: Handbuch der Faser—Theorie and Systematik der Faser [Manual of fiber—theory and systematics of fiber]. Deutscher Fachverlag, Frankfurt a. M. (1999)).

[0032] In a further embodiment variant of this method for producing noble metal nets, an ignoble metal wire made of heat-resistant steel or a heat-conductive alloy is used outside of the reaction zone (7) for the area of the net fixing zone (8).

[0033] Furthermore, this invention further comprises a net that is produced in accordance with the method according to the invention and that consists, in the area of the reaction zone (7) of noble metal or noble metal alloy wire, and in the area of the net fixing zone (8), of wire made of heat-resistant steel or a heat-conductive alloy.

[0034] A further part of this invention is a method for the catalytic oxidation of ammonia using a net stack that contains catalyst nets according to the invention and is operated in the presence of oxygen at a temperature in a flow reactor of between 500° C. and 1300° C. and a pressure of between 0.1 MPa and 1.4 MPa.

[0035] The invention is described in the following using an example:

EXAMPLE 1

[0036] For a reaction zone having a diameter of 100 cm and a net fixing zone of 5 cm in width, a square net with an edge length of 110 cm must be knitted. to The total area is 12100 cm.sup.2.

[0037] Cotton was used for the offcut zone, which could easily be singed off after the knitting process. A reduction of the noble metal usage by 21% thereby results.

[0038] Furthermore, the noble metal wire in the net fixing zone was replaced by a heat-conducting alloy, Material No. 1.4767. The resulting reduction of the noble metal usage in comparison to the original square net is 14%.

[0039] Legend for FIG. 1 [0040] 1 Flow reactor [0041] 2 Reaction plane [0042] 3 Net stack [0043] 4 Catalyst nets [0044] 5 Gettering and separating nets [0045] 6 Reaction gas [0046] 7 Reaction zone [0047] 8 Net fixing zone [0048] 9 Offcut zone