In several answers in AskPhilosophers, philosophers say that some uttered words express emotions, feelings, sensations and the like (but you always use the word "express"), and that this is not the same as some words saying or stating that such emotion (etc.) occurred. So you make a big difference between expressing and saying (or perhaps stating). For instance, "ouch" expresses pain, while "I am feeling pain" states that such pain exists. Sometimes you say that expressing cannot be true or false, but statements can. It is very difficult for me to understand this difference. I understand that "ouch" is much more immediate than "I am feeling pain", and that "ouch" is slightly humorous, and there may be other differences, but basically these two sentences just say the same thing. They convey the same basic information and both can be used to give a false information. Would you be so kind as to explain me what is the difference between expressing and saying (stating) in cases where what is expressed can be...

A very interesting question touching on complicated territory! Probably the best response I can give is to recommend the SEP article on "Pragmatics," available at this link . I think you'll find it contains lots of information highly relevant to your question.

Is it possible for someone to produce knowledge simply based on reason alone, without any emotion?

I see no reason, in principle, why not. If knowledge were not possible without emotion, then no emotionless computer could achieve knowledge, which would come as a shock to the proponents of artificial intelligence (AI). Nor do I see anything in the concept of knowledge itself that rules out knowledge based on reason alone without any emotional content or associations. I don't mean to say that emotion can't play an essential role in some kinds of knowledge, only that I can't see how emotion would be essential to every kind of knowledge.