Investigation of solar active phenomena requires systematic data of solar cosmic ray outbursts, the identification of sources and study of their impacts on near-Earth space. The description of these phenomena changed and developed during space age according to instrumentation and understanding. Consequently the goal was to have a uniform catalogue of solar proton events covering various years. Initiated by Z. Švestka and P. Simon this data base exists for the years 1955-1996. The catalogue includes solar proton events with E ≥ 10 MeV flux exceeding 1 cm (-2) s (-1) sr (-1) near Earth. Enhancing this catalogue by solar cycle 23 we can now present a comparative analysis of solar activity in cycles 20-23 (period 1955-2009), including energy spectra characteristics of proton fluxes, their connection with X-rays and shock waves. For the first time a study of the maximum energy of the accelerated particles in individual solar proton events will be shown. We will describe the proposed method to determine the maximum energy and present a statistical analysis, based on source parameters and propagation conditions in the heliosphere.