Firstly, I was asked to described what I know about the company (e.g. what are they doing). Then I was asked about what I know about a certain chemical process (related to what are they producing). Then a problem was posed by the interviewer, and I was asked how can I optimised the process (e.g. by varying the reaction temperature or amount of catalyst) and the consequences of doing so (e.g. possible increase in unwanted by-products).