Gasoline particulate filter

1. A particulate filter for use in an emission treatment system of a gasoline engine, the filter having an inlet side and an outlet side, wherein at least the inlet side is loaded with a synthetic ash: wherein the synthetic ash comprises one or more of: aluminum oxide, zinc oxide, zinc carbonate, calcium oxide, calcium carbonate, cerium zirconium (mixed) oxide, zirconium oxide, cerium oxide and hydrated alumina; and where the synthetic ash is free of sulphur oxides, phosphorus, magnesium, manganese, and lead.

2. The particulate filter of claim 1 , wherein the particulate filter is a wall-flow filter.

3. The particulate filter of claim 1 , wherein the synthetic ash comprises one or more of zinc oxide, zinc carbonate, calcium oxide, calcium carbonate and zirconium oxide.

4. The particulate filter of claim 1 , wherein the synthetic ash is devoid of platinum group metal-containing catalytic material.

5. The particulate filter of claim 1 , wherein the filter comprises from 20 to 30 g/L.

6. The particulate filter of claim 1 , wherein the filter comprises a porous body comprising a plurality of pores, and further comprising one or more catalytic washcoats within at least a portion of the plurality of pores, wherein the one or more washcoats include a TWC washcoat.

7. The particulate filter of claim 1 , wherein the particulate filter is uncanned.

8. An emission treatment system comprising the particulate filter of claim 1 , wherein the inlet side of the particulate filter is arranged to be upstream of the outlet side.

9. A method of producing a particulate filter for use in an emission treatment system of a gasoline engine, the method comprising:

providing a filter having an inlet side and an outlet side; and

loading at least the inlet side with a synthetic ash,

wherein the synthetic ash comprises one or more of: aluminium oxide, zinc oxide, zinc carbonate, calcium oxide, calcium carbonate, cerium zirconium (mixed oxide, zirconium oxide, cerium oxide and hydrated alumina; and

wherein the synthetic ash is free of sulphur oxides, phosphorus, magnesium manganese and lead.

10. The method according to claim 9 , wherein the method further comprises canning the synthetic ash-loaded filter.

11. The method according to claim 9 , wherein the synthetic ash is loaded in the form of a particulate having a D90 of less than 1 μm.

12. The method according to claim 9 , wherein loading at least the inlet side with the synthetic ash comprises:

contacting the inlet side with the synthetic ash; and

providing a gaseous flow from the inlet side to the outlet side and/or a vacuum from the outlet side to compact the synthetic ash against the filter.

13. The method of claim 12 , wherein the inlet side is contacted with the synthetic ash in the form of either a gaseous suspension or a liquid suspension.

14. The method of claim 9 , further comprising calcining the loaded synthetic ash.