Question

Why are chemical reactions the same at different gravity levels?

Answer 1

to me, a reaction being performed in space will be the same as asking about a reaction being performed in a vacuum. it heterogeneous catalysis , there are many reactions performed through in situ techniques ( real time analysis performed in vacuum) that are comparable to reaction at atmospheric pressure, since in catalysis we are focused on turnover frequency ( onversions per unit time per catalysis site) .
other things to consider would include the design of the reactor system. above, I just described something deliberately performed in a vacuum. you can pressurize a reaction vessel easily in space/ vacuum to replicate atmospheric pressure, and it would be similar. it's everything outside of the reactor that you have to consider.