Method of forming a catalyst article on a substrate
The present disclosure relates to a method for forming a catalyst article comprising: (a) forming a slurry having a solids content of up to 50 wt % by mixing together at least the following components a crystalline molecular sieve in an H + or NH 4 + form, an insoluble active metal precursor and an aqueous solvent at a temperature in the range 10 to 35° C.; (b) coating a substrate with the slurry formed in step (a); and (c) calcining the coated substrate formed in step (b) to form a catalyst layer on the substrate. 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 slurry by mixing together at least the following components:
(i) a crystalline molecular sieve in an H + or NH 4 + form;
(ii) an insoluble active metal precursor comprising a metal carbonate;
(iii) an aqueous solvent;
wherein the slurry has a solids content of up to 50 weight % and wherein step (a) is carried out at a temperature in the range 10 to 35° C.;
(b) coating a substrate with the slurry formed in step (a), wherein the slurry is not subjected to further processing steps prior to coating; and
(c) calcining the coated substrate formed in step (b) to form a catalyst layer on the substrate.
2 . The method of claim 1 , wherein in step (a) the components to be mixed together further include (iv) a binder component and/or (v) a rheology modifier.
3 . The method of claim 2 , wherein the binder component is selected from alumina, alumina precursors, aluminium hydroxide, TiO 2 , SiO 2 , ZrO 2 , CeZrO 2 , SnO 2 , aluminophosphate, non-zeolitic aluminosilicate, silica-alumina, clays or mixtures thereof.
4 . The method of claim 2 , wherein the rheology modifier is selected from a polysaccharide, a starch, a cellulose, an alginate, or mixtures thereof.
5 . The method of claim 1 , wherein the relative quantitative proportions of the components used in step (a) are selected such that the catalyst layer formed in step (c) comprises 85 to 92 wt % of metal-loaded molecular sieve and 8 to 15 wt % binder.
6 . 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.
7 . The method of claim 1 , wherein the insoluble active metal precursor is selected from the group consisting of 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, and any mixture of two or more thereof.
8 . The method of claim 1 , wherein the insoluble active metal precursor comprises copper (II) carbonate.
9 . The method of claim 1 , wherein the aqueous solvent is water.
10 . The method of claim 1 , wherein the slurry formed in step (a) has a solids content in the range 30 to 50 wt %.
11 . The method of claim 1 , wherein step (a) is carried out at a temperature in the range 10 to 30° C.
12 . The method of claim 1 , wherein step (b) is carried out at a temperature in the range 10 to 35° C.
13 . The method of claim 1 , wherein the slurry formed in step (a) has a solids content in the range 30 to 48 wt %.
14 . A catalyst article obtained by the method as defined in claim 1 .
15 . The catalyst article of claim 14 , which is catalytically active for SCR.
16 . An exhaust system comprising: a source of nitrogenous reductant and an injector for injecting a nitrogenous reductant into a flowing exhaust gas, wherein the injector is disposed upstream from the catalyst article of claim 15 .
17 . The method of claim 1 , wherein step (a) is carried out at a temperature in the range 18 to 28° C.
18 . The method of claim 1 , wherein step (b) is carried out at a temperature in the range 10 to 30° C.
19 . The method of claim 1 , wherein step (b) is carried out at a temperature in the range 18 to 28° C.
20 . The method of claim 1 , wherein the insoluble active metal precursor comprises a mixture of copper (II) carbonate and cerium carbonate.