Adsorption/reaction energetics measured by microcalorimetry and correlated with reactivity on supported catalysts: A review

The formations and transformations of the chemical bonds of reactants and intermediates on cata- lyst surfaces occur in conjunction with the evolution of heat during catalytic reactions. Measure- ment of this evolved heat is helpful in terms of understanding the nature of the interactions be- tween the catalyst and the adsorbed species, and provides insights into the reactivity of the catalyst. Although various techniques have previously been applied to assessments of evolved heat, direct measurements using a Tian-Calvet microcalorimeter are currently the most reliable method for this purpose. In this review, we summarize the relationship between the adsorption/reaction energetics determined by microcalorimetry and the reactivities of supported catalysts, and examine the im- portant role of microcalorimetry in understanding catalytic performance from the energetic point of view.

Effects of Dispersed Mo-Fe Catalysts on Catalytic Hydrothermal Conversion of Residue

Replacement of precious single metal catalysts with cost-effective,highly-dispersed composite catalysts for catalytic hydrothermal conversion of residue holds tremendous promise for the residue upgrading technologies.Organic metals were added to the feed as the oil-soluble precursors,and were transformed into the catalytic active phases in this work.Physical properties and structures of the composite catalysts had been investigated by X-ray fluorescence spectroscopy,X-ray photoelectron spectroscopy,X-ray diffraction,scanning electron microscopy and transmission electron microscopy.The composite catalysts were found to be highly efficient in the catalytic hydrothermal conversion of both the model compound and the residue.Increased metal dispersion and synergistic effects of two metals played indispensable roles in such catalytic system.Results showed that under the test conditions specified in the article,the catalyst had the best catalytic performance when the mass ratio of molybdenum to iron was 1.5.

Characterization and Catalytic Properties of a Rapidly Quenched Ni-RE-P-Al Catalyst

A Ni-RE-P-Al catalyst prepared by alkaline extraction of a rapidly quenched Ni-RE-P-Al alloy was characterized by means of ICP, BET, XRD, XPS and TEM. The results show that the rapidly quenched Ni-RE-P-Al alloy contained less crystalline Al_3Ni than Al-Ni alloy. After alkaline extraction, most of Al in the Ni-RE-P-Al alloy was leached out and the resulted Ni-RE-P-Al catalyst presented a sponge structure similar to Raney Ni. Although crystalline Ni is the major phase in the Ni-RE-P-Al catalyst and Raney Ni, amorphous Ni-P phase has been detected in the Ni-RE-P-Al catalyst. Studies on catalytic hydrogenation of toluene, phenyl ethylene, acetylene benzene, nitrobenzene, cyclohexanone and adiponitrile in liquid phase showed that the activity and selectivity of this Ni-RE-P-Al catalyst are superior to those of Raney Ni, especially at low temperatures. The amorphous phase is considered to be responsible for its superior catalytic properties.

PREPARATION OF ULTRAFINE PARTICLE IRON-CARBONIDE CATALYST AND CHARACTERIZATION OF ITS CATALYTICAL BEHAVIOR

Studies on ultrafine particle catalyst have attracted many researchers' attention by its large surface area,higher activity and selectivity.Based on the mechanism of α-Fe and Fe_xC_y as the catalytical active species this paper reports for the first time the preparation method of Fe_3C ultrafine parti- cle catalyst,from highly dispersed amorphous Fe powder and free carbon.The Fe powder and free car- bon,prepared by laser pyrolysis technique,was then treated by washing and heating at high tempera- ture protected with N_2.The catalyst prepared under different experimental conditions was characterazed by means of XRD,electronic diffraction and TEM.It shows that the crystlline grain size is in a range of 1-4nm and composed of Fe_3C and α-Fe.It has been found that the ultrafine particle iron-carbonide catalyst exhibited much higher activity and selectivity to light olefins.At the standard atmosphere and 380℃ reaction temperature,the conversion of CO reached a maximum of 80%.

Property and Activity of Molybdates Dispersed on Silica Obtained from Various Synthetic Procedures

The synthesis and characterization of several dispersed molybdena catalysts on silica support (MoO3-SiO2) prepared from a variety of precursors (Mo(VI)-acetylacetonate, oxo-peroxo Mo-species, hydrated ammonium heptamolybdate) and preparation methods (deposition of the Mo-phase on finite SiO2 support by aqueous and methanol impregnations, by adsorption, by oxo-peroxo route-like, and by one-step synthesis of MoO3-SiO2 system with molecular precursors) are presented. The molybdena concentration on silica was comprised in a large interval (1.5 - 14 wt%) depending on the preparation method which governed the Mo-loading on silica. Convenient comparisons among samples at similar Mo-concentration have been made discussing the morphologic-structural (XRD, XPS, UV-vis-DRS, and N2-adsorption) and physicochemical (TG-DTG, TPR, and n-butylamine-TPD) sample properties. Polymeric octahedral polymolybdate aggregates predominated in the samples prepared by aqueous and methanol impregnations, which were at high Mo-concentration. On the contrary, isolated Mo(VI) species in distorted Td symmetry predominated in the sample prepared by adsorption which was at very low Mo-concentration. The sample acidity was composed of a weak acidy site population, associated with the silica support, and a strong acid site population associated with the Mo-dispersed phase. Oxidation tests of formaldehyde, an oxygen-containing VOC (Volatile Organic Compound), were performed to determine the prevalent redox or acidic function of the Mo-species at the surface of the catalysts.

Demystifying the catalysis in lithium–sulfur batteries:Characterizationmethods and techniques

Lithium–sulfur(Li-S)batteries are promising next-generation energy storage systems with ultrahigh energy density.However,the intrinsic sluggish“solid–liquid–solid”reaction between S8 and Li2S causes unavoidable shuttling of polysulfides,severely limiting the practical energy density and cycling performance.Recently,the catalysis process has been introduced for the sulfur redox reaction to accelerate the conversion of polysulfides,providing a positive remedy for the polysulfides shuttling.Nevertheless,in-depth understanding of the catalyst evaluation criteria and catalytic mechanism still lies in the“black box”,and precise characterization technique is the key to unlock this puzzle.In this review,we provide a comprehensive overview of characterization techniques on the catalyst in Li-S batteries from two aspects of catalytic performance and catalytic mechanism,highlighting their significance and calling for more efforts to develop precise and fast techniques for Li-S catalysis.Moreover,we envision the future development of characterization for better understanding the catalysis toward practical Li-S battery.

Catalytic applications of nano β-PbO in Paal-Knorr reaction

Several 2,5-dimethyl-N-substituted pyrroles were prepared by the condensation of different substituted anilines with 2,5- hexanedione using nano lead oxide as an efficient and recyclable catalyst.All the synthesized compounds are confirmed through IR, ~1H NMR,^（13）C NMR and mass spectral data.Nano lead oxide β-PbO（P85） was prepared by dissolving lead acetate dihydrate in 1- propanol at a pH 9.0 under stirring at 85℃.The structural study and surface morphology of the lead oxide（PbO） were characterized using X-ray diffraction（XRD）,Scanning electron microscopy（SEM） and the functional groups of the PbO sample were investigated using infrared spectrophotometer.