I will rent a 9 passanger van from Paris and drive through Belgium and Germany and return it to France. We will be in Cologne and Frankfurt and I understand you need a green sticker for Environmental restrictions in those cities in Germany. Will my France rental van have those available? We need to drive into the city centers. Will we be able to do this? Also, I understand in 2020 they are adding restrictions to diesel vehicles so should I try to get a non-diesel vehicle for 9 passengers? How do we obtain a sticker for a specific vehicle when we don't know which vehicle we will be driving until we pick it up?
Getting a 9 passenger van might be problematic. The maximum is eight passengers (i.e., 9 persons overall) with a normal driver license in Germany; to my knowledge, it is the same in France. Even if your license covers the transport of 9 passengers, I doubt you could get a 10 seat van from a rental company in France.
A car rented in France will not have the required sticker for German environmental zones (unless you are really lucky). You will have to stop at a repair shop (e.g., ATU chain), technical inspection facility (TÜV, DEKRA) or a car dealer of the respective brand. Just takes a few minutes if within their opening times.
The Diesel situation is a bit unclear at the moment, I might not have the latest information. Maybe someone living in these towns can comment..
The 9 passenger is including the driver-9 people total not 10 and I already have one reserved to pick up in Paris. Do I just give them the papers the rental place gave me for the vehicle and they can issue a sticker right there? How long would that take? where would I find a place?
Are you taking any luggage with you?
where would I find a place?
Assuming that you will enter Germany from Belgium via A44 and A4 the most convenient places may be in Düren halfways between Aachen and Köln. Both the TÜV and the DEKRA offices are near the exit Düren of the A4. Look up Google Maps for either DEKRA Automobil Gmbh Düren or TÜV Rheinland Düren (entering the "ü"'s as "ue" will work). Picking up the sticker will take just a few minutes.
We will be in Cologne and Frankfurt and I understand you need a green
sticker for Environmental restrictions in those cities in Germany.
Correct, also other cities and towns in Germany with low emission zones.
Will my France rental van have those available?
We need to drive into the city centers. Will we be able to do this?
Not permitted without emission class sticker on car. High fines, no exceptions. Tips for Cologne.
Also, I understand in 2020 they are adding restrictions to diesel
vehicles so should I try to get a non-diesel vehicle for 9 passengers?
Do short research if your destinations are affected. Search for "Diesel Fahrverbot" & Köln / Frankfurt. To be sure ask the tourist offices of your destinations.
How do we obtain a sticker for a specific vehicle when we don't know
which vehicle we will be driving until we pick it up?
You can buy them at various places for up to 10 EUR (often cheaper), e.g. at TÜV, Dekra or also specialised retailers such as ATU (find a store). Important: You need to have an original vehicle registration certificate with the car's data - no copy. Also be aware of the opening times.
How long would that take?
As chris-s mentioned, a couple of minutes.
But, what is your plan and why are you renting a car? Paris-Belgium-Cologne-Frankfurt is a trip through some the most densely populated areas of Europe. That means that public transport is excellent, with frequent trains and buses everywhere. In contrast, the motorways in the area are usually busy and very prone to congestion. So I can't help but feeling this is a trip better done by train.