Why can't goverments print money to fund their economies? In previous questions I understood that printing money and injecting it in the economy generates inflation because there is a bigger demand for the same offer (please correct me if I'm wrong) so it's not a good idea. After thinking this, a new question arose. Why can't goverments print money to fund the productive sector? In that way, it can get money in circulation while generating more offer so there is no inflation. I can't understand what prevents goverments to do that.
The first thing to be aware of is that money is continuously being created and destroyed through the process of fractional reserve banking (which according to the Bank of England and others is incorrectly explained in most textbooks). Under this system there can be periods in which, in the absence of central bank intervention, there will be a fall in the money supply and deflation. In these periods there would be little risk of inflation if the government printed money for whatever purpose they liked. Indeed some economists have advocated direct money printing instead of QE.

With regard to the idea that creating money for productive purposes causes less inflation because more is produced - I know that this is something that Prof. Richard Werner has emphasised in the past, though I don't have a specific reference for that to hand.