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8 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Mechanism and Kinetics of Ethanol–Acetaldehyde Conversion to 1,3-Butadiene over Isolated Lewis Acid La Sites in Silanol Nests in Dealuminated Beta Zeolite

Biomass-derived ethanol (EtOH) and acetaldehyde (AcH) conversion to 1,3-butadiene (1,3-BD) is an alternative process for 1,3-BD production. The present investigation reports the preparation and characterization of isolated La sites introduced into the silanol nests in DeAlBEA as well as detailed studies of the mechanism and kinetics for the conversion of an EtOH-AcH mixture to 1,3-BD. La sites supported on DeAlBEA are found to be present as (≡SiO) 2 La-OH groups that are H-bonded with adjacent Si-OH groups, possessing high C-C coupling activity and stability, superior to state-of-the-art Y-DeAlBEA. La sites supported on silica (La-SiO 2 ) with a similar chemical structure but no H-bonding interaction with Si-OH groups were prepared for comparison. Lewis acid La sites promote AcH aldol condensation, and the activity of such sites is nearly identical for both La-DeAlBEA and La-SiO 2 . Further, the rate of C 4 product formation increases by a factor of 4.8 upon addition of EtOH to the feed of AcH over La-DeAlBEA, whereas that over La/SiO 2 remains unchanged. Investigation of the mechanism and kinetics of AcH aldol condensation and EtOH-AcH conversion to 1,3-BD revealed two C-C bond forming pathways-AcH aldol condensation by Lewis acid La sites and direct coupling of EtOH-AcH over H-bonded (≡SiO) 2 La-OH···HO-Si≡ sites. This study provides important information about the role of the local environment of isolated Lewis acid sites and their effects on the direct coupling of EtOH and AcH to form 1,3-BD.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Materials Data on HoSi by Materials Project

HoSi crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. Ho is bonded in a 5-coordinate geometry to seven equivalent Si atoms. There are a spread of Ho–Si bond distances ranging from 2.94–3.12 Å. Si is bonded in a 9-coordinate geometry to seven equivalent Ho and two equivalent Si atoms. Both Si–Si bond lengths are 2.50 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on HoSi by Materials Project

HoSi crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Ho is bonded in a 7-coordinate geometry to seven equivalent Si atoms. There are a spread of Ho–Si bond distances ranging from 2.93–3.15 Å. Si is bonded in a 9-coordinate geometry to seven equivalent Ho and two equivalent Si atoms. Both Si–Si bond lengths are 2.49 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ho5Si3 by Materials Project

Ho5Si3 crystallizes in the hexagonal P6_3/mcm space group. The structure is three-dimensional. there are two inequivalent Ho sites. In the first Ho site, Ho is bonded in a 3-coordinate geometry to five equivalent Si atoms. There are a spread of Ho–Si bond distances ranging from 2.90–3.41 Å. In the second Ho site, Ho is bonded in a 6-coordinate geometry to six equivalent Si atoms. All Ho–Si bond lengths are 3.03 Å. Si is bonded in a 9-coordinate geometry to nine Ho atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on HoSi2 by Materials Project

HoSi2 is hexagonal omega structure structured and crystallizes in the hexagonal P6/mmm space group. The structure is three-dimensional. Ho is bonded to twelve equivalent Si atoms to form a mixture of edge and face-sharing HoSi12 cuboctahedra. All Ho–Si bond lengths are 3.07 Å. Si is bonded in a 9-coordinate geometry to six equivalent Ho and three equivalent Si atoms. All Si–Si bond lengths are 2.36 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ho10Si17 by Materials Project

Ho10Si17 crystallizes in the orthorhombic Imm2 space group. The structure is three-dimensional. there are three inequivalent Ho sites. In the first Ho site, Ho is bonded in a 8-coordinate geometry to ten Si atoms. There are a spread of Ho–Si bond distances ranging from 2.90–3.31 Å. In the second Ho site, Ho is bonded in a 10-coordinate geometry to ten Si atoms. There are a spread of Ho–Si bond distances ranging from 2.90–3.25 Å. In the third Ho site, Ho is bonded in a 8-coordinate geometry to eleven Si atoms. There are a spread of Ho–Si bond distances ranging from 2.93–3.37 Å. There are ten inequivalent Si sites. In the first Si site, Si is bonded in a 9-coordinate geometry to six Ho and three Si atoms. There are one shorter (2.34 Å) and two longer (2.45 Å) Si–Si bond lengths. In the second Si site, Si is bonded in a 8-coordinate geometry to six Ho and two equivalent Si atoms. Both Si–Si bond lengths are 2.39 Å. In the third Si site, Si is bonded in a 8-coordinate geometry to six Ho and two Si atoms. There are one shorter (2.40 Å) and one longer (2.44 Å) Si–Si bond lengths. In the fourth Si site, Si is bonded in a 9-coordinate geometry to six Ho and three Si atoms. There are a spread of Si–Si bond distances ranging from 2.33–2.40 Å. In the fifth Si site, Si is bonded in a 6-coordinate geometry to six Ho and two Si atoms. In the sixth Si site, Si is bonded in a 6-coordinate geometry to six Ho and two Si atoms. The Si–Si bond length is 2.43 Å. In the seventh Si site, Si is bonded in a 9-coordinate geometry to six Ho and three Si atoms. The Si–Si bond length is 2.42 Å. In the eighth Si site, Si is bonded in a 9-coordinate geometry to six Ho and three Si atoms. The Si–Si bond length is 2.40 Å. In the ninth Si site, Si is bonded in a 9-coordinate geometry to six Ho and three Si atoms. In the tenth Si site, Si is bonded in a 8-coordinate geometry to six Ho and two Si atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on HoSi2 by Materials Project

HoSi2 is hexagonal omega structure-like structured and crystallizes in the orthorhombic Imma space group. The structure is three-dimensional. Ho is bonded to twelve Si atoms to form a mixture of edge and face-sharing HoSi12 cuboctahedra. There are a spread of Ho–Si bond distances ranging from 3.04–3.17 Å. There are two inequivalent Si sites. In the first Si site, Si is bonded in a 9-coordinate geometry to six equivalent Ho and three Si atoms. There are two shorter (2.34 Å) and one longer (2.41 Å) Si–Si bond lengths. In the second Si site, Si is bonded in a 9-coordinate geometry to six equivalent Ho and three Si atoms. Both Si–Si bond lengths are 2.34 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on HoSi3 by Materials Project

HoSi3 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. there are two inequivalent Ho sites. In the first Ho site, Ho is bonded in a 12-coordinate geometry to twelve Si atoms. There are a spread of Ho–Si bond distances ranging from 2.99–3.25 Å. In the second Ho site, Ho is bonded in a 12-coordinate geometry to twelve Si atoms. There are four shorter (2.96 Å) and eight longer (3.01 Å) Ho–Si bond lengths. There are two inequivalent Si sites. In the first Si site, Si is bonded in a 9-coordinate geometry to four Ho and five Si atoms. There are one shorter (2.48 Å) and four longer (2.57 Å) Si–Si bond lengths. In the second Si site, Si is bonded in a 9-coordinate geometry to four Ho and five Si atoms. There are one shorter (2.45 Å) and two longer (2.68 Å) Si–Si bond lengths.

36 MATERIALS SCIENCE↗