Hi bobkate
Recirculating extractors generally move less air than ducted ones. They also clog filters up quicker and the more they clog the more the flow rate drops. You will definitely need to replace filters and clean the metal grills regularly to keep it as close to its max airflow as possible.
My concern with a recirculating extractor that high up is that:
a) it doesn’t move enough air to do its job effectively at that height;
b) at that height a good proportion of the air it’s pulling will not be the most moisture/fatty laden air (much of this air will dissipate into the room as a result of both the flow rate and the distance between the hob and the extractor).
I’d consider a downdraft extractor especially if you’re having a deep enough island (or can make it deeper). For the same flow rate it should perform a lot better as it’s a lot closer to the hob and therefore to the air you want to be pulling. As a result it should “capture” much more of this air before it dissipates throughout the room. You’ll still need to be regularly checking it’s filters though.
It’s not immediately clear what your floor/subfloor is...but if you could duct a downdraft extractor it would be much better (although care to ensure that the ducting run itself doesn’t create a condensation trap (trapping moisture and fat)).
I hope that helps!