Browsing by Author "Zheng, Weiqing"
Now showing 1 - 4 of 4
Results Per Page
Sort Options
Item Activation of Molecular Oxygen for Alcohol Oxidation over Vanadium Carbon Catalysts Synthesized via the Heterogeneous Ligand Strategy(ACS Catalysis, 2022-12-16) Zhao, Li; Yang, Piaoping; Shi, Song; Zhu, Guozhi; Feng, Xiao; Zheng, Weiqing; Vlachos, Dionisios G.; Xu, JieActivation of molecular oxygen to realize selective oxidation is challenging. We employ a heterogeneous ligand method to prepare a vanadium carbon catalyst (V–C catalyst) of high efficiency in alcohol oxidation via oxygen activation. Principal component analysis revealed that the chemisorbed oxygen and pentavalent vanadium oxide are crucial in catalyst performance. Isotopic labeling, electron paramagnetic resonance, and control experiments confirmed that the V–C catalyst activates molecular oxygen to singlet oxygen or its analogue and carries out the reaction. A kinetic study and in situ React-IR spectra illustrated that the main reaction route is the O2 activation to 1O2 or its analogue and oxidizes the substrate through C–H bond activation. We demonstrate the efficiency of the V–C catalyst in selectively oxidizing the hydroxyl group in other substrates, including benzyl alcohols, methyl lactate, and ethyl lactate biomass-based alcohols. This will guide the development of highly active nonprecious metal catalysts for activating O2 for aerobic oxidation.Item Catalytic Hydrodeoxygenation of High Carbon Furylmethanes to Renewable Jet-fuel Ranged Alkanes over a Rhenium Modified Iridium Catalyst(Wiley-Blackwell, 2017-07-07) Saha, Basudeb; Liu, Sibao; Dutta, Saikat; Zheng, Weiqing; Gould, Nicholas S.; Cheng, Ziwei; Xu, Bingjun; Vlachos, Dionisios G.; Sibao Liu, Saikat Dutta, Weiqing Zheng, Nicholas S. Gould, Ziwei Cheng, Bingjun Xu, Basudeb Saha, and Dionisios G. Vlachos; Saha, Basudeb; Liu, Sibao; Dutta, Saikat; Zheng, Weiqing; Gould, Nicholas S.; Cheng, Ziwei; Xu, Bingjun; Vlachos, Dionisios G.Renewable jet-fuel ranged alkanes are synthesized by hydrodeoxygenation of lignocellulose derived high carbon furylmethanes over ReOx modified Ir/SiO2 catalysts under mild reaction conditions. Ir-ReOx/SiO2 with a Re/Ir molar ratio of 2 exhibits the best performance, achieving a combined alkanes yield of 82-99% from C12-C15 furylmethanes. Catalyst can be regenerated in three consecutive cycles with only ~12% loss in the combined alkanes yield. Mechanistically, the furan moieties of furylmethanes undergo simultaneous ring saturation and ring opening to form a mixture of complex oxygenates consisting of saturated furan rings, mono-keto groups, and mono-hydroxy groups. Then, these oxygenates undergo a cascade of hydrogenolysis reactions to alkanes. The high yield of Ir-ReOx/SiO2 arises from a synergy between Ir and ReOx. The acidic sites of partially reduced ReOx activate the C-O bonds of the saturated furans and alcoholic groups, while the Ir sites are responsible for hydrogenation with H2.Item Dynamic Electrification of Dry Reforming of Methane with In Situ Catalyst Regeneration(ACS Energy Letters, 2023-02-10) Yu, Kewei; Wang, Cong; Zheng, Weiqing; Vlachos, Dionisios G.We report the design and performance of a rapid pulse Joule heating (RPH) reactor with an in situ Raman spectrometer for highly endothermic, reversible reactions. We demonstrate it for methane dry reforming over a bimetallic PtNi/SiO2 catalyst that shows better performance than its monometallic counterparts. The catalyst temperature ramp rate can reach ∼14000 °C/s, mainly owing to the low thermal mass and resistivity of the heating element. Joule heating elements afford temperatures unachievable by conventional technology to enhance performance and more than double the energy efficiency. Dynamic electrification can increase syngas productivity and rate. Extensive characterizations suggest that pulse heating creates an in situ catalyst regeneration strategy that suppresses coke formation, sintering, and phase segregation, resulting in improved catalyst stability, under many conditions. Potentially driven by renewable electricity, the RPH can provide superb process advantages for high-temperature endothermic reactions and lead to negative carbon emissions.Item Plasma-Enabled Ligand Removal for Improved Catalysis: Furfural Conversion on Pd/SiO2(ACS Nano, 2023-11-14) Nguyen, Darien K.; Vargheese,Vibin; Liao, Vinson; Dimitrakellis, Panagiotis; Sourav, Sagar; Zheng, Weiqing; Vlachos, Dionisios G.A nonthermal, atmospheric He/O2 plasma (NTAP) successfully removed polyvinylpyrrolidone (PVP) from Pd cubic nanoparticles supported on SiO2 quickly and controllably. Transmission electron microscopy (TEM) revealed that the shape and size of Pd nanoparticles remain intact during plasma treatment, unlike mild calcination, which causes sintering and polycrystallinity. Using Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS), we demonstrate the quantitative estimation of the PVP plasma removal rate and control of the nanoparticle synthesis. First-principles calculations of the XPS and CO FTIR spectra elucidate electron transfer from the ligand to the metal and allow for estimates of ligand coverages. Reactivity testing indicated that PVP surface crowding inhibits furfural conversion but does not alter furfural selectivity. Overall, the data demonstrate NTAP as a more efficient method than traditional calcination for organic ligand removal in nanoparticle synthesis.