Kye Sang Yoo

Synthesis of Ni promoted molybdenum dioxide nanoparticles using solvothermal cracking process for catalytic partial oxidation of n-dodecane

Ni promoted MoO2 nanoparticles were synthesized by combining spray pyrolysis and solvothermal cracking process. First, polycrystalline MoO3 microparticles were prepared by spray pyrolysis at 600 °C. Then nano-sized Ni-MoO2 particles were formed by solvothermal cracking process after adding Ni precursor, which disassembled polycrystalline MoO3 microparticles into crystalline grains by thermal expansion and shattered them into Ni-MoO2 nanoparticles by the subsequent solvothermal polyol reduction process. TPR profiles of Ni-MoO2 nanoparticles presented the decrease of reducibility of MoO2 with addition of Ni promoter. Catalytic partial oxidation of n-dodecane was conducted at various temperatures from 450 °C to 850 °C using Ni-MoO2 nanoparticles and pure MoO2 nanoparticles. H2 yield of all the Ni-MoO2 nanoparticles was higher than that of pure MoO2 nanoparticles at 850 °C. Specially, 7 and 10 mol% Ni-MoO2 nanoparticles showed desirable catalytic performance of ca. 60% of H2 yield. This is mainly attributed to the existence of polymolybdate with addition of Ni and Ni2+ species partly located in the polymolybdate layer without formation of bulk Ni phase.

Rapid solvothermal synthesis of microporous UiO-66 particles for carbon dioxide capture

One of the important metal-organic frameworks known as UiO-66 has received significant attention recently due to its unprecedented chemical and thermal stability, with exceptionally high surface area. We prepared UiO-66 particles by a rapid solvothermal method which took only 30 min at 120 °C to prepare, compared to the previous work which took longer than 12 h. Changing the precursor’s concentration ratio from 0.5 to 1.5 and reaction temperature from 80 °C to 140 °C resulted in the increase of UiO-66 particle size from 30 to 150 nm. The highest surface area of ca. 1,300 m2/g was achieved at concentration ratio of 1 and temperature of 120 °C with bi-modal pore sizes of ca 0.60 nm and 1.25 nm, respectively. The UiO-66 particles with the highest surface area were then employed to capture carbon dioxide from a binary gas mixture. Results from CO2 adsorption capacity measurement using UiO-66 indicate that the adsorbent was capable of capturing 1.3611 mmol/g at pressure of 1.5-1.7 bar and flowrate of 300 cm3/min.

Facile Spray Pyrolysis Synthesis of Various Metal-Doped MoO 2 Microspheres for Catalytic Partial Oxidation of n -Dodecane

AbstractMoO2 microspheres doped with various metal species (Zr, Ti or Co) were simply prepared by means of a one-step ultrasonic spray pyrolysis. The dopant metal species were used as a reducing agent to promote the synthesis of MoO2, which is a metastable phase. The differences in electronegativity and radius between Mo and the dopant metal species influenced the structure and catalytic activity of the resulting MoO2 material. Partial oxidation of n-dodecane, a surrogate of Jet A fuel, was performed to evaluate the catalytic activity of MoO2 spheres doped with Zr, Ti, or Co. Among the produced samples, Co-doped MoO2 microspheres showed the highest H2 and CO yield as well as the highest C12 conversion.Graphical AbstractVarious metal-doped MoO2 microspheres (with Ti, Zr, or Co dopants) were simply prepared by means of a one-step ultrasonic spray pyrolysis, where the dopant metal species were used as a reducing agent to promote the synthesis of MoO2. The differences in electronegativity and radius between Mo and the dopant metal species influenced the structure and catalytic activity for partial oxidation of n-dodecane.