how could scientists know the exact catalyst for every reactions??? THANX sooo much
Believe me, nema, there's no way that we chemists know the best catalyst for every reaction. That would be simply impossible. However, from the type of reaction, the reactants, products, reaction conditions, solvents, etc. and from one's experience and the literature (papers and patents) one can get a good idea for most reactions of the type of catalyst that has worked for similar systems. One then starts off with a catalyst from the literature and modifies or changes it if improvement is needed based on chemical principles that one learns. There are also some theoretical calculations that can be made. Sometimes they work and sometimes they don't :) If it is an industrially important process like the Haber process for making ammonia from nitrogen gas and hydrogen gas, there may be thousands of catalysts which have been tried and evaluated. New minor improvements are being made every day. When a company does find a very good catalyst for an important reaction, often they keep it a trade secret. The good catalyst can make a huge difference in how commercially successful a particular process is. That's a large part of what chemical engineers do. You may never know if you have the best catalyst. The most you can hope for is one that is good enough. So it's a few parts personal knowledge, a few parts literature, a couple of parts theory, a lot of experimentation and often, more than not, a little luck. :)
