Selective solar wax refining with nanoscale zero-valent iron.

Abstract

Wax refining transforms raw wax into high-grade product by increasing the uniformity of molecular carbon-chain length and removing impurities. Conventional thermochemical approaches face inherent limitations in effectively reducing carbon-chain dispersity (Ð) due to their non-selective C-C scission in feedstock waxes. This mechanistic constraint consequently necessitates energy-intensive downstream processing involving fractional distillation and purification. Here, we demonstrate a selective solar wax refining method that upgrades the raw polyethylene wax by significantly reducing its Ð from 2.5 to 2.0 in one step with a reaction selectivity beyond 80%, enabled by nanoscale zero-valent iron (nZVI) catalyst and sunlight. At the nZVI-wax interface, photons activate C-H bonds to provide hydrogen atoms, while localized hot spots mediate C-C bonds cleavage via hydrogen atom transfer initiated hydrocracking and concurrent evaporative desorption of fragmented wax product, thereby achieving precise control over carbon-chain dispersity. This work exemplifies the potential in precise and efficient solar refinery.