Congratulations to Dr. Adrian Hergesell on a successful PhD defense, during which he defended his PhD thesis, supervised by Prof. Bert Weckhuysen and Dr. Ina Vollmer.

In his PhD thesis, Adrian investigated the mechano-chemical depolymerization of polyolefins, abundant but chemically inert plastic waste, using ambient ball milling as a low-temperature alternative to conventional pyrolysis.

A central contribution was the development of surface-activated mechano-catalysts (SAM catalysts): catalytically functionalized grinding spheres whose paramagnetic surface species interact with radical intermediates generated during milling, boosting small hydrocarbon yields to up to 45% C₁–C₁₀ from polypropylene within one hour. Adrian also showed that reactivity is governed by the magnitude of applied impact forces rather than total kinetic energy input, a finding he rationalized using an adapted form of the Zhurkov equation.

Further work demonstrated that milling with common crystalline materials, such as sand (which generates reactive surface radicals upon fracture), can increase hydrocarbon yields by a factor of 25. Finally, Adrian showed that zeolite catalysts, though initially active, rapidly deactivate under milling conditions due to structural collapse, and that immobilizing zeolite species on roughened grinding spheres produces a second class of protected SAM catalysts.

Adrian’s full thesis can be read here.