Hi Riccardo,
The BatchPreprocessing script recognizes the XBINNING, BINNING and CCDBINX header keywords (the script only works with square pixels, so Y-axis binning is ignored). Including additional keywords would be very easy (you can do that yourself: just add the required keyword after line 668 of BatchPreprocessing-engine.js). However, the keyword's value must be a single integer literal equal to or greater than one, not an arbitrary string such as '2x2'.