I was given a 2-tonne trolley jack some time ago and tried it out under my Ducato-based 'van. Placing it under the jacking points, at full extension it did not even lift the wheels off the ground, and it felt unstable: I think "molly2" said it all. I did think of investing in a bottle jack but I think it would have to be a twin extension jack - very expensive!!
However, for me this is rather academic: since my particular model of 'van lacks capacity to carry a spare wheel I can't envisage a circumstance while I am travelling that would require me to jack up my van. As a precaution, I have filled my tyres with "Airseal" pre-puncture sealant so I can keep moving should I have a puncture - unless as happened a few years ago with an earlier 'van, when some passing **** stuck a screwdriver through the sidewall of one of my front tyres while my 'van was parked on my drive: with the tyre as flat as a pancake I could not then get the jack I had at the time under the jacking point, anyway.