Thermochemical Characterization

Cardona-Martı́nez, Nelson; Dumesic, James A.

doi:10.1002/9783527610044.hetcat0058

Cited by 4 publications

(2 citation statements)

References 145 publications

(202 reference statements)

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“…As shown in Figure , the NH 3 desorption profile for 4 wt % Rh–ReO x /C (1:0.5) displays a peak with maximum at 498 K. The number of acid sites on 4 wt % Rh–ReO x /C (1:0.5) was 40 μmol g –1 , and number ratio of acid to metal sites was equal to 0.28. Assuming that the standard entropy change of adsorption (Δ S ° ads ) is approximately −150 J K –1 mol –1 , , which corresponds to loss of the gas-phase translational entropy, and that first-order desorption and rapid readsorption occurs, the heat of adsorption of NH 3 (Δ H ° ads ) on 4 wt % Rh–ReO x /C (1:0.5) can be estimated to be −100 kJ mol –1 . In contrast, no discernible NH 3 desorption peaks were observed for monometallic 4 wt % Rh/C and 3.6 wt % Re/C under the conditions employed.…”

Section: Resultsmentioning

confidence: 99%

Selective Hydrogenolysis of Polyols and Cyclic Ethers over Bifunctional Surface Sites on Rhodium–Rhenium Catalysts

et al. 2011

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A ReO(x)-promoted Rh/C catalyst is shown to be selective in the hydrogenolysis of secondary C-O bonds for a broad range of cyclic ethers and polyols, these being important classes of compounds in biomass-derived feedstocks. Experimentally observed reactivity trends, NH(3) temperature-programmed desorption (TPD) profiles, and results from theoretical calculations based on density functional theory (DFT) are consistent with the hypothesis of a bifunctional catalyst that facilitates selective hydrogenolysis of C-O bonds by acid-catalyzed ring-opening and dehydration reactions coupled with metal-catalyzed hydrogenation. The presence of surface acid sites on 4 wt % Rh-ReO(x)/C (1:0.5) was confirmed by NH(3) TPD, and the estimated acid site density and standard enthalpy of NH(3) adsorption were 40 μmol g(-1) and -100 kJ mol(-1), respectively. Results from DFT calculations suggest that hydroxyl groups on rhenium atoms associated with rhodium are acidic, due to the strong binding of oxygen atoms by rhenium, and these groups are likely responsible for proton donation leading to the formation of carbenium ion transition states. Accordingly, the observed reactivity trends are consistent with the stabilization of resulting carbenium ion structures that form upon ring-opening or dehydration. The presence of hydroxyl groups that reside α to carbon in the C-O bond undergoing scission can form oxocarbenium ion intermediates that significantly stabilize the resulting transition states. The mechanistic insights from this work may be extended to provide a general description of a new class of bifunctional heterogeneous catalysts, based on the combination of a highly reducible metal with an oxophilic metal, for the selective C-O hydrogenolysis of biomass-derived feedstocks.

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Section: Resultsmentioning

confidence: 99%

Selective Hydrogenolysis of Polyols and Cyclic Ethers over Bifunctional Surface Sites on Rhodium–Rhenium Catalysts

et al. 2011

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“…The first review presents a survey of theoretical and applied aspects of microcalorimetry to heterogeneous catalysis up to 1992 . The next two reviews focus on applications for the characterization of solid acidity and basicity from 1986 to 2005. , The fourth reviews adsorption microcalorimetric studies of unsupported metals and metal-based catalysts performed up to 1997 …”

Section: Microcalorimetrymentioning

confidence: 99%

A Career in Catalysis: James A. Dumesic

et al. 2021

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After 43 years as a professor in the Chemical and Biological Engineering Department at the University of Wisconsin-Madison, James A. Dumesic retired in 2019. Jim is one of the most influential researchers in the field of heterogeneous catalysis. In this Account, we discuss the scientific discoveries that he made and the intellectual processes that he followed during his illustrious career to steer the field of heterogeneous catalysis into new frontiers. He began his career by fundamentally probing the nature of active sites on heterogeneous catalysts using in situ Mossbauer spectroscopy, electron microscopy, FTIR, and kinetic analysis. This tool kit was used to elucidate the "strong metal support interaction" (SMSI) effect. He developed new microcalorimetric tools to measure the energetics of adsorbates on catalyst surfaces. Jim pioneered microkinetic analysis as a tool to describe heterogeneous reaction kinetics incorporating the essential surface chemistry into kinetic analysis, thereby providing a novel strategy for kinetic assisted catalyst design. Density functional theory (DFT) was combined with FTIR and microcalorimetry to elucidate catalytic surface reactions which were then incorporated into microkinetic models. In the early 2000s, Jim developed the aqueous-phase catalytic processing of biomass-derived oxygenates into fuels and chemicals. This led to the development of new processes to make diesel fuel, jet fuel, gasoline, aromatics, and oxygenated chemicals from renewable resources, several of these technologies are in the process of being commercialized. Jim tailored nanostructured catalytic materials by atomic layer deposition and controlled surface reactions to withstand harsh aqueous-phase biomass processing conditions. He used careful selection and tuning of the solvent composition to achieve substantial control over the activity and selectivity of various biomass upgrading reactions and developed a theory to explain these solvent effects. Underlying these discoveries was a thought process that used fundamental surface chemistry to explain the relationship between the structure, properties, and performance of the catalytic system. Leveraging this thought process across many different reaction classes helped to establish both new tools for catalysis research and to develop new processes for the sustainable production of fuels and chemicals.

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Catalyst Characterization—Heterogeneous

Stavitski

Beale

Weckhuysen

2010

Encyclopedia of Catalysis

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The study of catalysts under in‐situ conditions enables the catalyst scientist to identify and understand the important steps, e.g., the formation of important reaction intermediates and active sites, and stages in a catalyst?s lifetime, such as activation/deactivation. The development of characterization methods as well as the design and construction of appropriate in‐situ cells and reactor probes are inevitable in order to obtain such insight. Both spectroscopic and scattering techniques have been used in attempt to understand quantitative structure/composition‐activity/selectivity relationships in catalysis. Armed with such detailed knowledge about the catalyst, it is then possible for scientists to design, in a more rational way, new and efficient catalysts for sustainable production of bulk and fine chemicals as well as for the removal of harmful compounds in industrial catalytic processes. This chapter provides an overview of the in‐situ characterization techniques available for investigation of catalytic materials. The possibilities and limitations of the methods are discussed and illustrated with numerous case studies.

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Thermochemical Characterization

Abstract: The sections in this article are Introduction Principles of Temperature‐Programmed Desorption Applications of Temperature‐Programmed Desorption Principles of Adsorption Microcalorimetry Applications of Adsorption Microcalorimetry Conclusions

Cited by 4 publications

References 145 publications

Selective Hydrogenolysis of Polyols and Cyclic Ethers over Bifunctional Surface Sites on Rhodium–Rhenium Catalysts

Selective Hydrogenolysis of Polyols and Cyclic Ethers over Bifunctional Surface Sites on Rhodium–Rhenium Catalysts

A Career in Catalysis: James A. Dumesic

Catalyst Characterization—Heterogeneous

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