This chapter reviews the relevant technology to give the reader a historical perspective in terms of the technology development including the process chemistry and catalysts. A statistical analysis of the issued patents on the corresponding technology catalysts in terms of number, year, continental origin, and applicant category, as well as a statistical analysis for the main technical topics are defined specifically according to each catalyst type separately. The statistics are a good indicator of the flow of information among refineries, catalyst manufacturing companies, Research and Development institutes, and universities. Almost all the patents of catalyst manufacturers are individual applications, without collaborations with other applicant categories. However, a technical survey conducted in this study comprises the aim of giving an opinion as a general guideline for the developments in the field of refinery catalysts. Almost all the patents of catalyst manufacturers are individual applications, without collaborations with other applicant categories.