Method of preparing a plate-like support bearing catalytically a

Details Method of preparing a plate-like support bearing catalytically a Method of preparing a plate-like support bearing catalytically a

1990-01-18

1991-02-19

Shine, W. J.

Catalyst, solid sorbent, or support therefor: product or process

Miscellaneous

502527, B01J 3200, B01J 3502

Patent

active

049944304

DESCRIPTION:

BRIEF SUMMARY
The invention relates to a method of preparing a plate-like support bearing catalytically active compounds, including the degreasing or etching of an embossed, solid-surfaced or grid-like metal base structure followed by the application of a vitreous enamel coating thereto.
Many different methods are known for producing plate-like supports bearing catalytically active compounds. With the aim of achieving a continuous, low-cost production it has already been proposed to feed sheet metal for the metal base structure continuously from a coil, to provide it with spaced cuts in a certain pattern running the width of the band, i.e., transversely of the direction of transport, to make the band an expanded metal plate material by stretching it in the feed direction, i.e., the direction of transport of the band, and to degrease it. Then a molten metal is sprayed onto the surface of the degreased expanded-metal band for the purpose of applying a catalytically active substance onto the rough surface thus formed. Between leaf-like protective layers, an embossing was then performed step by step to form ribs in the direction of feed or movement of the expanded metal band, and finally the expanded metal plate provided with the catalytically active compounds was trimmed to size after removal of the protective layers (DE-PS 32 08 634). Catalyst plates of this kind offer the advantage of low-cost coating independently of any special shaping of the catalyst support. These plate-like supports bearing catalytically active compounds have been proposed for use as catalyst plates for the removal of nitrogen from exhaust gases.
In the removal of nitrogen from exhausts from boilers, special attention must be paid to the danger of poisoning the catalytically active surfaces of the metal support by impurities contained in the exhaust gases. Knowledge gained in this regard indicates that the danger of poisoning increases with the duration of the contact between the catalyst poisons and the catalytically active surfaces. One possibility is to dispose the supports of catalytically active surfaces in rotating regenerative heat exchangers in place of the heat-exchanging storage masses in order to expose the supports of the catalytically active compounds alternately to the stream of a pure gas, e.g., the purified gas, and to that of the gas that is to be cleaned. The purifying apparatus that have been developed and proven for these rotating regenerative heat exchangers can then continuously remove catalyst poisons deposited onto the catalytically active surfaces. Purification systems of this kind, however, place considerable stress on the catalytically active surfaces and threaten them with destruction by blasting them with the jets of the cleaning medium, especially air or superheated steam.
The invention is addressed to the problem of providing plate-like supports, regardless of their particular shape, with a firmly adherent coating of catalytically active compounds, and especially of achieving at the same time a coating that is uniform over the entire surface.
Setting out from a method of the kind described above, the method of the invention is characterized by the fact that a vitreous enamel forming a low-porosity bottom layer and a rough top layer of high resistance to acid is applied to the metal base structure, and is fired on this surface as a ground coat, and furthermore that the base structure covered with the ground coat after firing is first wetted with a catalyst slip liquefying under the influence of shear forces and formed of a powder of catalytically active compounds, a binding agent and water as well as wetting agents in some cases, by immersing it into a stirred bath of catalyst slip, and the wetted base structure is removed again from the bath while the stirring of the slip is sustained, and it is then delivered to a drying operation. During their immersion in the stirred slip, which is rendered fluid by the action of shear forces, the plates or grids, regardless of their particular configuration, such as multiple textur

REFERENCES:
patent: 4771026 (1988-09-01), Kainer et al.
patent: 4847234 (1989-07-01), Hums

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