Method for forming a catalyst article
The present disclosure relates to a method for forming a catalyst article comprising: (a) forming a plastic mixture having a solids content of greater than 50% by weight by mixing together a crystalline small pore or medium pore molecular sieve in an H + or NH 4 + form, an insoluble active metal precursor, an inorganic matrix component, an organic auxiliary agent, an aqueous solvent and optionally inorganic fibres; (b) moulding the plastic mixture into a shaped article; and (c) calcining the shaped article to form a solid catalyst body. The present disclosure further relates to a catalyst article, particularly a catalyst article which is suitable for use in the selective catalytic reduction of nitrogen oxides, and to an exhaust system.
1. A method for forming a catalyst article comprising:
(a) forming a plastic mixture by mixing together at least the following components:
(i) a crystalline small pore or medium pore molecular sieve in an H + or NH 4 + form;
(ii) an insoluble active metal precursor;
(iii) an inorganic matrix component;
(iv) an organic auxiliary agent;
(v) an aqueous solvent;
wherein the mixture has a solids content of greater than 50% by weight; wherein the insoluble active metal precursor is selected from the group consisting copper carbonate, manganese carbonate, nickel carbonate, cobalt carbonate, iron carbonate, palladium carbonate, platinum carbonate, cerium carbonate, yttrium carbonate, niobium carbonate, lanthanum carbonate, zinc carbonate, zirconium carbonate, calcium carbonate, magnesium carbonate, manganese hydroxide, nickel hydroxide, cobalt hydroxide, iron hydroxide, palladium hydroxide, platinum hydroxide, cerium hydroxide, yttrium hydroxide, niobium hydroxide, lanthanum hydroxide, zinc hydroxide, zirconium hydroxide, calcium hydroxide, manganesium hydroxide, copper oxalate, calcium oxalate, iron oxalate, manganese oxalate, cobalt oxalate, cerium oxalate, yttrium oxalate, zinc oxalate and any mixture of two or more thereof; and,
wherein step (a) is carried out at a temperature in the range 10 to 35° C.;
(b) moulding the plastic mixture into a shaped article; and
(c) calcining the shaped article to form a solid catalyst body.
2. The method as claimed of claim 1 , wherein in step (a) the components to be mixed together further include: (vi) inorganic fibres.
3. The method of claim 2 wherein, the crystalline molecular sieve is a small pore zeolite having a Framework Type selected from CHA, AEI or AFX, LTA or ERI.
4. The method of claim 2 , wherein the insoluble active metal precursor comprises one or more of copper (II) carbonate, and copper oxalate.
5. The method of claim 2 , wherein the plastic mixture formed in step (a) has a solids content of at least 60 wt %.
6. The method of claim 1 , wherein the relative quantitative proportions of the components used in step (a) are selected such that the solid catalyst body formed in step (c) contains 60 to 85 weight % of metal-loaded molecular sieve, 20 to 40% by weight of matrix component and 0 to 10 wt. % of inorganic fibres.
7. The method of claim 1 , wherein the crystalline molecular sieve is a small pore zeolite having a Framework Type selected from CHA, AEI or AFX, LTA or ERI.
8. The method of claim 1 wherein the insoluble active metal precursor comprises one or more of copper (II) carbonate, copper oxalate.
9. The method of claim 1 wherein the aqueous solvent is water.
10. The method of claim 1 wherein the plastic mixture formed in step (a) has a solids content of at least 60wt %.
11. The method of claim 1 wherein the inorganic matrix component comprises an alumina precursor and/or a clay.
12. The method of claim 1 wherein the organic auxiliary agent comprises at least one of acrylic fibres, a cellulose derivative, organic plasticizers, a lubricant and a water-soluble resin.
13. The method of claim 1 , wherein step (b) is carried out at a temperature in the range 10 to 35° C.
14. The method of claim 1 , wherein the plastic mixture formed in step a) is employed directly in step b) without any additional processing steps.
15. The method of claim 1 , wherein the insoluble active metal precursor comprises copper (II) carbonate.