The best way to search for peer-reviewed journal articles is to use a literature database. Databases index the research articles in journals and have powerful search filtering tools. Most databases also have quality standards that journals need to meet to be included, which limits your chances of encountering predatory publications.
Here are some of the most useful databases to get started with for chemical engineering:
Preprints are early versions of research articles which have not yet been peer-reviewed. Scientists may choose to disseminate their research as preprints before submitting to an academic journal, which can make the research reported very cutting edge, but these reports should be read critically as they have not yet been reviewed by other experts.
You can use the Web of Science Preprint Index to search several different preprint repositories at once.
You can also browse individual preprint repositories related to your research: