Surface Properties of Rh/AlPO4 Catalyst Providing High Resistance to Sulfur and Phosphorus Poisoning

Catalytic upcycling of waste plastics over nanocellulose derived biochar catalyst for the coupling harvest of hydrogen and liquid fuels

A powerful simple biochar catalyst derived from nanocellulose was applied to the catalytic upcycling of waste plastics into H₂ and liquid fuels for the first time. For the results from model low-density polyethylene (LDPE) pyrolysis, the C₈-C₁₆ aliphatics and monocyclic aromatics were dominant constitutes of the liquid product with the yields ranging from 22 to 68 wt%. At the temperature of 500 °C and biochar to LDPE ratio surpassing 3, the LDPE could be completely degraded into liquid and gas without wax production. A wax yield of 16 wt% was observed at the temperature of 450 °C and biochar to LDPE ratio of 4, which was dramatically lower than that (77 wt%) from the absence of biochar at the temperature of 500 °C. Up to 92 vol% of H₂ was detected in the gaseous product with a yield of 36 wt%. The lower temperatures and higher biochar to LDPE ratios favored increasing the generation of H₂ at the expense of light gas C_nH_m especially CH₄. Moreover, this biochar catalyst was tested effectively to convert the real waste plastics including grocery bags and packaging tray into valuable liquid and H₂-enriched gas.

Plasma-Functionalized Polytetrafluoroethylene Nanoparticles for Improved Wear in Lubricated Contact

Plasma-functionalized polytetrafluoroethylene (PTFE) nanoparticles were employed to evaluate their utility in improving the lubrication property of a group III mineral oil with a significantly low amount of zinc dialkyl dithiophosphate (ZDDP). The particles were coated with two consecutive films; the initial coating contained silica to enhance amorphous glassy tribofilm formation, followed by a methacrylate film to protect the silica coating and enhance dispersibility in the oil. The functionalized nanoparticles were evaluated for their tribological performance using a high-frequency reciprocating rig, in a cylinder-on-flat configuration. The oil formulations containing ZDDP (350 ppm phosphorus level) and the functionalized nanoparticles resulted in dramatic reductions in the friction coefficient and overall wear compared to the samples containing nonfunctionalized PTFE nanoparticles, ZDDP (350 ppm P), and samples devoid of nanoparticles but containing ZDDP with a 700 ppm P treat rate. XPS and XANES spectroscopy were employed to characterize the tribological films formed on the test samples. The samples with functionalized particles and ZDDP clearly exhibited tribofilms with Si- and F-doped polyphosphates of Zn coupled with the presence of ZnS at the metal-tribofilm interface. On the other hand, oils without the functionalized nanoparticles have oxides of Fe and to a lesser extent short-chain phosphates of Zn. The overall results suggest that the synergism between plasma-coated PTFE nanoparticles and ZDDP contributed to the development of protective tribofilms even at reduced amount of phosphorus in the oil. This new method of employing nanoparticles to deliver novel antifriction and antiwear chemistries at the tribological interfaces stands out as a promising approach to further reduce P levels in oils without compromising friction and wear performance.

Rh Nanoparticle Anchoring on Metal Phosphates: Fundamental Aspects and Practical Impacts on Catalysis

Metal phosphates stabilize Rh nanoparticles on their surface via Rh-O-P bonds, in contrast to the Rh-O-M bonds formed on metal oxides (MO_x ). The local structure, electronic structure, and redox properties of Rh nanoparticles anchored on metal phosphates, and their practical impacts on catalysis, are reviewed based on recent publications from the author's research group. Because of the covalency of the Rh-O-P bond, Rh oxide is readily reduced to metallic Rh having a higher catalytic activity, whereas Rh oxide on metal oxide supports is more difficult to reduce with an increase of the anchoring strength. Furthermore, Rh metal shows a higher tolerance to reoxidation when supported on metal phosphates because the Rh-O-P bond is preserved under reducing atmospheres. The electron deficiency of Rh metal is another feature that affects its catalytic properties, and the extent of the electron deficiency can be tuned by replacing the metal in the metal phosphate with one of higher basicity. Further impacts on practical performance (thermal stability, poisoning stability, and lean NO_x purification) in automobile catalyst applications are also described.