Looking for some advice on removing a hydraulic cylinder.

Weird kneeling swivel chair with a totally blown strut. Unlike other chair cylinders I have seen this looks like there is a welded sleeve in the frame and the cylinder is press fit in? I can’t seem to get it to spin clamping the pipe end in a vice. Given that the strut is no longer under pressure would it be alright to apply heat to the sleeve? Or is there a better way I should be going about this.