Muffler device for internal combustion engines

#The present invention relates in general to adsorbent composites and more particularly to methods for coating an aluminum substrate with a layer of solid adsorbent to form adsorbent-substrate composites for use in automobile mufflers.

#There are a variety of solid adsorbents which have been useful in adsorption and catalysis including commonly known materials such as activated carbons, activated clays, silica gel, activated alumina, and crystalline molecular sieves. Of these adsorbents, crystalline molecular sieves such as silicoalumino-phosphates, aluminophosphates and aluminosilicate zeolites have been particularly useful because of their uniform pore size.

#In many instances it is desirable to have the solid adsorbent deposited on a substrate as a coating instead of being contained in particulate form as pellets, beads, or other particles. There are several reasons why solid adsorbent coatings have been used including for example, to improve the catalytic or adsorption properties of the solid adsorbent by improving the surface area to weight ratio, to reduce the amount of solid adsorbent required, to protect the underlying substrate material from a harmful environment, to achieve a particular strength or form, and to perform the particular adsorptive or catalytic function over the entire coated surface of the substrate.

#The present invention provides adsorbent-substrate composites and methods for preparing the composites by coating an aluminum substrate with a layer of solid adsorbent, preferably molecular sieve, and more preferably zeolite. Other aspects of the present invention relate to process for utilizing the adsorbent coatings.

#The aluminum substrates used in the present invention provide structural support for the solid adsorbent layer as well as provide a suitable bonding medium for the solid adsorbent and binder. The substrate may be, for example, aluminum metal, aluminized steel, aluminized ceramic and other similar materials. The substrate may be in various forms including, but not limited to, sheets, foils, tubes, wires, plates, balls, bars, chains, mesh or particles. It is not necessary for the aluminum substrate to be chemically treated or washed with solvent in order to practice the present invention, however the substrate should be relatively free from large amounts of foreign matter such as dirt or grease, which may adversely affect bonding,.

#Virtually any synthetic or naturally occurring solid adsorbent capable of maintaining its physical integrity during the coating process is suitable for use according to the present invention. The selection of the particular solid adsorbent will depend on factors such as its effective pore diameter and the particular end use intended. The term "effective pore diameter" is conventional in the art and is used herein to functionally define the pore size in terms of the size of molecules that can enter the pores rather than actual dimensions which are often difficult to determine as the pores are often irregularly shaped, i.e., non-circular. D. W. Breck, in Zeolite Molecular Sieves, John Wiley and Sons, New York, 1974, at pages 633 to 641, provides a discussion of effective pore diameter which is hereby incorporated by reference.