A new perspective on polyethylene-promoted lignin pyrolysis with mass transfer and radical explanation

Co-pyrolysis of lignin and waste plastics,for example polyethylene(PE),has been studied,but related reports are basically on condition optimizations.This study revealed a new perspective on PE-promoted lignin pyrolysis to phenolic monomers with mass transfer and radical explanation.Lignin and PE were first pyrolyzed individually to identify pyrolysis characteristics,pyrolytic products,as well as the suitable copyrolysis temperature.Then,co-pyrolysis of blended lignin/PE with various ratios was investigated.Yields of lignin products reached the maximum under lignin/PE ratio of 1:1,but blended approach always inhibited the production of lignin phenols.This resulted from the poor mass transfer and interactions between lignin and PE,in which PE pyrolysates could easily escape from the particle gaps.While in layered approach,PE pyrolysates had to pass through the lignin layer which contributed to the good interactions with lignin pyrolysis intermediates,thus the yields of lignin-derived products were significantly improved.Interactions between lignin and PE(or their pyrolysates)were mainly radical quenching reactions,and X-ray photoelectron spectrum(XPS)and electron paramagnetic resonance(EPR)of pyrolytic chars were conducted to verify these interactions controlled by mass transfer.The percentage of C]C(sp^(2))and concentration of organic stable radicals in layered lignin/PE char were both the lowest compared with those in blended lignin/PE and lignin char,indicating the stabilization of lignin-derived radicals by PE pyrolysates.Moreover,the spin concentration of radicals in the char from layered char/PE was lower than that in lignin char,which further affirmed the quenching of radicals by PE in the layered co-pyrolysis mode.

Modulate the superficial structure of La_(2)Ce_(2)O_(7) catalyst with anchoring CuO_(x) species for the selective catalytic oxidation of NH_(3)

Air contamination caused by the ammonia slip phenomenon has gradually captured the researcher’s extensive attention.An effective strategy for controlling fugitive NH_(2)is critical to improving the air quality and living environment.In the present work,CuO_(x)/La_(2)Ce_(2)O_(7)composite as a potential candidate catalyst is synthesized through the electrostatic adsorption method for the selective catalytic oxidation(SCO_(2))of NH_(2)to N.The 5%Cu Ox/La_(2)Ce_(2)O_(7)exhibits the best catalytic activity(T=243℃)and ammonia conversion efficiency.The improvement of performance is mainly attributed to the superficial connection of[Ce-O-Cu],which enhances the capturing ability of ammonia molecule and accelerates the dissociating efficiency of N–H bonding for Nevolution,simultaneously.This work provides a facile method to synthesis pyrochlore-like composite catalyst of NH_(2)-SCO_(2) for solving the problem of ammonia slip pollution in the future.

Facile synthesis of defected TiO_(2-x)(B) nanosheet/graphene oxide hybrids with high photocatalytic H_(2) activity

TiO_(2)(B) nanosheets/GO(graphene oxide) hybrids are considered to be outstanding performance photocatalysts for high efficiency of H_(2) evolution. However, they still suffer severe challenges during the synthetic processes, such as a large amount of the capping agents adhering on the surface and easy occurrence of aggregation. To figure out these obstacles, Ar plasma treatment as a modified method in this study not only enable the TiO_(2)(B) nanosheets distributed uniformly on the GO sheets but also engineer defects within TiO_(2)(B) nanosheets to significantly improve the photocatalytic activity for the water splitting. The hydrogen evolution rate of the TiO_(2)-x(B)/GO sheets is 1.4 times higher compared with that of original TiO_(2)(B)/GO sheets without Ar plasma treatment. The improved photocatalytic properties were owing to the synergetic effects of oxygen vacancies and the heterojunction between GO and TiO_(2)(B), which can promote the visible light utilization and accelerate separation and transportation of photogenerated electron-holes. This study can provide a facile pathway to prepare the two-dimensional hybrid photocatalysts with high photocatalytic H_(2) activity.