What is the maximum temperature of engine bleed air for de-icing the wings?
This is based on aircraft type and manufacturer approved limitations.  Typically it’s limited by temperature or duration of use.  Compressor bleed air is tapped at around 450° F, hotter than a typical household oven.  These high temperatures can begin to significantly affect the yield strength of aluminum alloys typically used in aircraft construction, approaching the design factor said of safety and potentially resulting in a local structural compromise during high load factors, etc.