This book describes a detailed multi-scale approach integrating nano- (active site), meso- (porous catalyst architecture) and macroscale (reactor) efforts, to address the challenges of producing a better epoxidation catalyst. It contains an in-depth study of the design and synthesis of gold nanoparticles and their application as a catalyst for direct gas phase propylene epoxidation. “Direct” means using only hydrogen and oxygen in one step, which is key for sustainable manufacturing, as opposed to commercialised, more complex production routes requiring multiple steps, or integration with another chemical plant. The insights gained can be used for rational design for stable and selective catalysts for other reactions. It also details the step-by-step process to build an epoxidation reactor system with a focus on safety aspects, which can be used as a guidebook for undergraduate and graduate students in chemical engineering. Beyond heterogeneous catalysis, the new, easily accomplished methodology for synthesising atomically precise nanoparticles is shown to be relevant to electrocatalysis and to healthcare applications, such as anti-microbial surfaces. This book will be of interest to researchers, engineers and experts in the related areas of chemical engineering, chemistry, material science and electrochemistry.