Depends on size of tyres and weight of van. I have approx 1600kg van with 195x14 tyres and recommended cold tyre pressure is 45psi. My compliance plate on the draw bar confirms this. I have sometimes increased that to 50psi prior to an extended holiday as we are usually fully loaded then. Others will probably mention the 5psi variation from cold to warm tyres after driving 50-100km. 45 is a good starting point.
Depends on the specific tyres and what the van weighs.
More information required.
What is the load/pressure information printed on the tyre and what is the ACTUAL weight on the van wheels?