Mei Ren,Jun Li,Manhong Huang,Donghui Chen,Xuelian Chen,Qi An,Songmei Sun
The escalating environmental issues resulting from waste plastic necessitate innovative decomposition methods that optimize conversion rates and product selectivity. In this study, we demonstrate that linear low-density polyethylene (LLDPE) can be effectively hydrothermolyzed into C1 − C4 compounds with a selectivity of 100 % in the presence of trace water on H-ZSM-5 catalyst under a relatively low temperature of 220 °C. Water plays a dual role here as both a solvent and a reactant. It was found the density of Brønsted acid sites is crucial for LLDPE decomposition, serving as the primary active centers for cracking LLDPE chains. In-situ EPR studies indicate a synergistic mechanism of free radical and carbenium ion pathways in LLDPE depolymerization. Density Functional Theory (DFT) simulations show that the depolymerization starts with the cleavage of a C–C bond in polyethylene, instigated by a hydrogen radical from the Brønsted acid site, leading to various intermediate stages for the formation of tert -butanol, acetone and acetic acid from two potential pathways. The presence of water is crucial in these pathways, aiding bond breakages and the creation of oxygenated products in the Brønsted acid site. This study represents a substantial leap forward in sustainable methodologies for upcycling plastic waste.
A series of metal-TS-1 zeolite catalysts were designed to selectively catalyze the photo oxidation of furfural to C 4 carboxylic acid derivatives at ambient temperature and pressure. The photocatalytic preparation of malic acid from furfural was realized for the first time. The selective distribution of products could be controlled by adjusting the physical and chemical characteristics of the catalyst. Smaller pore size prevented the further conversion of maleic acid to malic acid; moderate acidity was beneficial for the preparation of malic acid; lower valence band was in favor of maleic acid production while higher valence band tended to form malic acid. The synergistic effect of pore structure, acidity and energy band structure of catalysts affected the product distribution. The yield of maleic acid reached as high as 40% over Fe-TS-1, meanwhile, the yield of malic acid reached as high as 63% over Ni-TS-1. The doping of metal was believed to be an effective procedure to adjust the structure and physicochemical properties of zeolite. Matel-TS-1 zeolite was also expected to be widely used in photocatalytic system to achieve more selective reactions.
危险品化学品经营许可证（带存储）