Biomass pyrolysis has been widely explored for its potential to generate a sustainable chemical source capable of producing synthetic fuels and chemicals. Lignocellulosic biomass is the carbon rich, inedible fraction of wood that is comprised of long oxygenated biopolymers, primarily cellulose, hemicellulose and the highly aromatic lignin. High temperature thermal conversion of biomass to bio-oil (pyrolysis oil) occurs on the order of milliseconds and converts long chain biopolymers to a carbon-rich liquid crude. The chemistry of biomass pyrolysis is greatly complicated by significant heat and mass transport challenges. The complex fluid dynamics of the reactive liquid intermediate are examined in situ with high temperature spatiotemporally resolved techniques (T = 450 – 1000 °C, 1 µm, 1 ms), chemical analyses and computational fluid dynamics. Discoveries include the mechanism for aerosol generation during pyrolysis, existence and control of the Leidenfrost effect, and understanding bio-oil microexplosions. Zeolites are widely utilized to catalytically upgrade fuels by cracking, hydrogenation and hydrodeoxegenation as well as having applications in separations, sorption, ion-exchange. While new hierarchical materials are synthesized with transport lengthscales that are increasingly smaller, substantial diffusional transport limitations persist in small particles, often dominating the observed rates. The presence of these transport limitations remains a significant technical challenge. In this work, a mechanistic understanding is developed to describe such limitations. The potential for surface barriers to diffusion are experimentally assessed by Zero Length Chromatography and frequency response methods, and further confirmed by dynamic Monte Carlo simulations.