Engineering topics

Ouyang, Xiaoying

Publications and source records attributed to Ouyang, Xiaoying.

4 records

DOE OSTI2018

SSZ-70 Borosilicate Delamination Without Sonication: Effect of Framework Topology on Olefin Epoxidation Catalysis

Here, we report a scalable delamination procedure for a SSZ-70-framework layered-zeolite precursor, which for the first time does not involve either sonication or long-chain surfactants. Our approach instead relies on the mild heating of layered zeolite precursor B-SSZ-70(P) in an aqueous solution containing Zn(NO 3 ) 2 and tetrabutylammonium fluoride. Powder X-ray diffraction data are consistent with a loss of long-range order along the z-direction, while 29 Si MAS NMR spectroscopy demonstrates preservation of the zeolite framework crystallinity during delamination. The resulting delaminated material, DZ-2, possesses 1.4-fold higher external surface area relative to the nondelaminated three-dimensional zeolite B-SSZ-70, based on N2 physisorption data at 77 K. DZ-2 was functionalized with cationic Ti heteroatoms to synthesize Ti-DZ-2 via exchange with framework B. Ti-DZ-2 contains isolated titanium centers in its crystalline framework, as shown by UV-Vis spectroscopy. The generality of the synthetic delamination approach and catalyst synthesis is demonstrated with the synthesis of delaminated material DZ-3, which is derived from layered zeolite precursor ERB-1(P) with MWW framework topology. Upon catalytic testing for the epoxidation of 1-octene with ethylbenzene hydroperoxide as oxidant, under harsh tail-end conditions that deactivate amorphous Ti-silica-based catalysts, Ti-DZ-2 exhibits the highest per-Ti-site activity, selectivity, and stability for 1-octene epoxidation of all catalysts investigated. This testing includes the prior benchmark delaminated zeolite catalyst in this area, Ti-UCB-4, which possesses similar external surface area to Ti-DZ-2 but requires sonication and long-chain surfactants for its synthesis. The synthesis of DZ-2 is the first example of an economical delamination of layered zeolite precursor SSZ-70(P) and opens up new doors to the development of delaminated zeolites as commercial catalysts.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2017

Ligand-modified metal clusters for gas separation and purification

Provided is an organic ligand-bound metal surface that selects one gaseous species over another. The species can be closely sized molecular species having less than 1 Angstrom difference in kinetic diameter. In one embodiment, the species comprise carbon monoxide and ethylene. Such organic ligand-bound metal surfaces can be successfully used in gas phase separations or purifications, sensing, and in catalysis.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2014

Role of Delamination in Zeolite-Catalyzed Aromatic Alkylation: UCB-3 versus 3-D Al-SSZ-70

Delaminated zeolite UCB-3 exhibits 2.4-fold greater catalytic activity relative to its three-dimensional (3D) zeolite counterpart, Al-SSZ-70, and 2.0-fold greater activity (per catalyst mass) when compared with industrial catalyst MCM-22, for the alkylation of toluene with propylene at 523 K. The former increase is nearly equal to the observed relative increase in external surface area and acid sites upon delamination. However, at 423 K for the same reaction, UCB-3 exhibits a 3.5-fold greater catalytic activity relative to 3D Al-SSZ-70. The higher relative rate enhancement for the delaminated material at lower temperature can be elucidated on the basis of increased contributions from internal acid sites. Evidence of possible contributions from such acid sites is obtained by performing catalysis after silanation treatment, which demonstrates that although virtually all catalysis in MCM-22 occurs on the external surface, catalysis also occurs on internal sites for 3D Al-SSZ-70. The additional observed enhancement at low temperatures can therefore be rationalized by greater access to internal active sites as a result of sheet breakage during delamination. Such breakage leads to shorter characteristic internal diffusion paths and was visualized using TEM comparisons of UCB-3 and 3D Al-SSZ-70.

aromatic alkylation↗

DOE OSTI2010

La[subscript 4]LiAuO[subscript 8] and La[subscript 2]BaPdO[subscript 5]: Comparing Two Highly Stable d[superscript 8] Square-Planar Oxides

La{sub 4}LiAuO{sub 8} and La{sub 2}BaPdO{sub 5}, two previously known oxides, are presented as model compounds for examining the role of isolated and immobilized Au{sup 3+} and Pd{sup 2+} ions in heterogeneous catalysis. Structural characterization, stability, surface composition, and electronic structure of these compounds are presented. These are examined in studies ranging from synchrotron X-ray scattering, including pair distribution function (PDF) and maximum entropy method (MEM) analysis, to density functional calculations of the electronic structures. The exceptional stability displayed by these compounds as verified by thermogravimetric analysis can be attributed to the presence of covalent Au-O and Pd-O interactions revealed in MEM studies, which suggests a criterion for stabilizing these highly oxophobic transition metals in oxide environments. Catalytic testing of the two compounds as heterogeneous catalysts in the oxidation of CO to CO{sub 2} are presented. La{sub 2}BaPdO{sub 5} appears to be an effective catalyst for CO oxidation, despite the low surface area of the oxide being used. This is the first time that a fully ordered (rather than doped) Pd{sup 2+} oxide had been used to catalyze CO oxidation. La{sub 4}LiAuO{sub 8} on the other hand, is much less effective at catalyzing CO oxidation. Differences in the reactivities of the two compounds are discussed with respect to differences in their density functional electronic structures.

43 PARTICLE ACCELERATORS↗