I cant find anything on journal explain about the kinetic reaction beeten FeCl2 + H2SO4
Normally technical questions are off topic on Ask Patents. However I, like you, have often tried to search for more information related to what I found in a patent document so I'm trying to address your question.
Patents (and the cited document is an application, the associated patent is here) are unlike academic publications. If the invention is by an academic researcher then there is every possibility the inventor may publish in a journal after the application is filed. However many, if not most, inventions are not by academics so publication in a technical journal is less likely. Each patent (or application) cites some relevant prior art so you can start your searching with those. Otherwise I would try Google searching with the inventor's name and some applicable keywords. I google searched with the keywords: "Alexander Kehrmann" "ferrous sulfate heptahydrate" and found the following results. A Google Scholar search with the same keywords found only two hits.