Batch and continuous synthesis of well-defined Pt/Al2O3 catalysts for the dehydrogenation of homocyclic LOHCs

In this work, the controlled synthesis of supported Pt nanoparticles with well-defined nanoparticle sizes from 1.9 to 6.0 nm and their application in the dehydrogenation of cyclic liquid organic hydrogen carrier (LOHC) molecules are demonstrated. For this purpose, a colloidal approach is used in which a stabilized Pt precursor solution is chemically reduced with aqueous solutions of sodium borohydride (NaBH4). In this batch process, an increased pH increases the stability of the reduction solution and thus enhances the control of the size of the resulting Pt nanoparticles. Various synthesis parameters are varied and their effects on the properties of the Pt nanoparticles are studied. Additionally, the nanoparticles were supported on powder Al2O3 support and the general suitability of the catalysts for the dehydrogenation of the LOHC perhydro benzyltoluene (H12-BT) is demonstrated. The transferability of the catalyst synthesis route from powder to shaped supports, as commonly used in LOHC dehydrogenation reactors, is successfully demonstrated. Moreover, a successful upscaling of the synthesis procedure is realized, where larger amounts of catalysts are synthesized without significant deviations in nanoparticle size and catalytic activity. Finally, a continuous synthesis of Pt/Al2O3 catalysts is implemented using a microfluidic reactor. The prepared catalysts from small-scale, large-scale, and continuous syntheses display a comparable Pt-based productivity in the dehydrogenation of H12 BT.