An improved process and apparatus for the selective reaction of terpenes (including mono-, sesqui-, di-terpenes, and others in the terpene family), alpha-olefin oligomers (OOA's), and related olefins to their respective dimeric product in high purity using heterogeneous acid catalyst concurrent with full utilization of energy created in the process. Embodiments of the invention carry out a unique and highly efficient dimerization of terpenes, alpha-olefin oligomers (OOA's), and olefins using cost effective catalysts and low cost equipment that are ideally suited for commercialization of jet/turbine and diesel biofuel processes producing fuels with high flashpoints and superb cold flow properties.