It is entriely possible that either is the answer because a sentence like that can obviously be understood either way. This is why good writers will always make sure they don't write ambiguous sentences. I think it's A: all these end users will get both chemicals and catalysts. If I wanted to say your B version, I may write "to make chemicals, and to create catalysts for…" or "to create chemicals, and also to make catalysts for…" or even better split it in two sentences like "The remainder is used to make a variety of chemicals. The most common products are catalysts for…" Something along those lines. I'm not a master writer so don't hold me to account for these exact suggestions.

I think it is A. I understand the sentence as: The remainder is used to make {chemicals-&-catalysts} for {chemical plants, petroleum refineries and automobiles}. One reason I think that is that it seems unnatural to give a list of uses for the "catalysts" but not for the "chemicals." I think that for some reason there must be some reason why "catalysts" are not considered to be a "chemical," so the writer feels obliged to name them both. Or, perhaps the writer was bothered by the strange sound of "The remainder is used to make chemicals for chemical plants..."