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Alcohol synthesis from carbon-monoxide and hydrogen over molybdenum-disulfide based catalysts.

Record Type:	Language materials, manuscript : Monograph/item
Title/Author:	Alcohol synthesis from carbon-monoxide and hydrogen over molybdenum-disulfide based catalysts./
Author:	Santiesteban, Jose Guadalupe.
Description:	1 online resource (272 pages)
Notes:	Source: Dissertations Abstracts International, Volume: 51-06, Section: B.
Contained By:	Dissertations Abstracts International51-06B.
Subject:	Chemistry. -
Online resource:	click for full text (PQDT)
ISBN:	9798207813530

Alcohol synthesis from carbon-monoxide and hydrogen over molybdenum-disulfide based catalysts.
Santiesteban, Jose Guadalupe.

Alcohol synthesis from carbon-monoxide and hydrogen over molybdenum-disulfide based catalysts. - 1 online resource (272 pages)

Source: Dissertations Abstracts International, Volume: 51-06, Section: B.

Thesis (Ph.D.)--Lehigh University, 1989.

Includes bibliographical references

The synthesis of linear C1-C4 alcohols from synthesis gas (CO + H2) over alkali-promoted MoS2-based catalysts has been studied. A large doping level of alkali was essential for the formation of alcohols rather than hydrocarbons over these catalysts. The indispensable presence of the alkali salt promoter for alcohol synthesis was due to the bifunctionality of the catalyst in which the alkali activates CO and MoS2 activates H2. Injection of 13C-labeled CH3OH into the synthesis gas stream over alkali-promoted MoS2-based catalysts and analysis by 13C NMR spectroscopy of the condensable products, accompanied by mass spectrometric analysis of light gaseous products, demonstrated that the alcohol chain growth occurred via a classical CO insertion mechanism, and that methane is a secondary product that is formed from an alkyl moiety generated from a C1-oxygenated precursor. The addition of cobalt to the alkali-doped MoS2 catalyst greatly enhanced the rate of the C1→C2 growth step so that ethanol became the dominant product. The alkali-doped MoS2 catalysts prior to and after attaining their working state were fully characterized by XPS, XRD, STEM, and surface area measurements. Electron microscopy results indicated that the MoS2 portion of the catalyst consists of a semicrystalline hexagonal structure with regular lattice spacings (d(002) = 6.15 A) that indicate no intercalation of the alkali. The cesium salt in the best catalysts (10-20 wt% CsOOCH) is distributed as ≈200 A diameter particles and also as a fine surface dispersion. The cesium particle agglomeration results from the low surface energy of MoS2 and is the cause of the large levels of cesium required for the optimal functioning of the catalyst. Pretreatment (400°C, 2% H2/N2, 1 h) of the catalysts induces not only reduction of surface species such as Mo(VI) and SO4² detected on the fresh catalysts, but also dispersion of the cesium on the MoS2 surface. The oxidation states of S and Mo in the tested catalysts correspond to those of MoS2, i.e. Mo(IV) and S²-. XPS intensity equations were derived from geometrical models of the catalyst surface to determine the degree of dispersion and/or segregation of Cs on the MoS2 surface.

Electronic reproduction.
Ann Arbor, Mich. :
ProQuest,
2024

Mode of access: World Wide Web

ISBN: 9798207813530Subjects--Topical Terms:

593913
Chemistry.
Subjects--Index Terms:

Molybdenum silicideIndex Terms--Genre/Form:

554714
Electronic books.

Alcohol synthesis from carbon-monoxide and hydrogen over molybdenum-disulfide based catalysts.
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520 $a The synthesis of linear C1-C4 alcohols from synthesis gas (CO + H2) over alkali-promoted MoS2-based catalysts has been studied. A large doping level of alkali was essential for the formation of alcohols rather than hydrocarbons over these catalysts. The indispensable presence of the alkali salt promoter for alcohol synthesis was due to the bifunctionality of the catalyst in which the alkali activates CO and MoS2 activates H2. Injection of 13C-labeled CH3OH into the synthesis gas stream over alkali-promoted MoS2-based catalysts and analysis by 13C NMR spectroscopy of the condensable products, accompanied by mass spectrometric analysis of light gaseous products, demonstrated that the alcohol chain growth occurred via a classical CO insertion mechanism, and that methane is a secondary product that is formed from an alkyl moiety generated from a C1-oxygenated precursor. The addition of cobalt to the alkali-doped MoS2 catalyst greatly enhanced the rate of the C1→C2 growth step so that ethanol became the dominant product. The alkali-doped MoS2 catalysts prior to and after attaining their working state were fully characterized by XPS, XRD, STEM, and surface area measurements. Electron microscopy results indicated that the MoS2 portion of the catalyst consists of a semicrystalline hexagonal structure with regular lattice spacings (d(002) = 6.15 A) that indicate no intercalation of the alkali. The cesium salt in the best catalysts (10-20 wt% CsOOCH) is distributed as ≈200 A diameter particles and also as a fine surface dispersion. The cesium particle agglomeration results from the low surface energy of MoS2 and is the cause of the large levels of cesium required for the optimal functioning of the catalyst. Pretreatment (400°C, 2% H2/N2, 1 h) of the catalysts induces not only reduction of surface species such as Mo(VI) and SO4² detected on the fresh catalysts, but also dispersion of the cesium on the MoS2 surface. The oxidation states of S and Mo in the tested catalysts correspond to those of MoS2, i.e. Mo(IV) and S²-. XPS intensity equations were derived from geometrical models of the catalyst surface to determine the degree of dispersion and/or segregation of Cs on the MoS2 surface.
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