Can I use an 11 watt bulb in a desk lamp that says "CFL max 9 watts"?
The power consumption permitted by the fixture is 9 watts; the bulb that you've selected is 11 watts. You've exceeded the permitted wattage, even if it is by a very small margin.

Is it safe? Most of the max wattage specifications by manufacturers are conservative, so you would probably be fine. But why exceed a stated limit? I would suggest considering a smaller wattage bulb for that fixture, or a fixture that supports the bulb wattage that you've selected.