Soft magnetic composite materials (SMCs)

Catalytic hydrotreatment or hydrodeoxygenation (HDO) has been researched extensively with the crude bio-oil and its model compounds over conventional sulfided Ni(Mo), Co(Mo) catalysts and supported noble metal catalysts. These types of catalysts showed themselves unsuitable for the target HDO process, which resulted in an urgent need to search for a new catalytic system meeting such requirements as low cost, stability against coke formation and leaching of active components due to adverse effect of the acidic medium (bio-oil). In the present work a series of Ni-based catalysts with different stabilizing components has been tested in the hydrodeoxygenation (HDO) of guaiacol (2-methoxyphenol), bio-oil model compound. The process has been carried out in an autoclave at 320 °C and 17 MPa H2. The main products were cyclohexane, 1-methylcyclohexane-1,2-diol, and cyclohexanone. The reaction scheme of guaiacol conversion explaining the formation of main products has been suggested. The catalyst activity was found to rise with an increase in the active component loading and depend on the catalyst preparation method. The most active catalysts in HDO of guaiacol were Ni-based catalysts prepared by a sol–gel method and stabilized with SiO2 and ZrO2. According to TPR, XRD, XPS, and HRTEM, the high activity of these catalysts correlates with the high nickel loading and the high specific area of active component provided by the formation of nickel oxide–silicate species. The effect of temperature on the product distribution and catalyst activity in the target process (HDO) has been investigated as well. The catalysts were shown to be very promising systems for the production of hydrocarbon fuels by the catalytic upgrading of bio-oil.

Ni-based sol–gel catalysts as promising systems for crude bio-oil upgrading: Guaiacol hydrodeoxygenation study

https://www.ou.edu/catalysis/pubs/2011-4.pdf

Conversion of furfural and 2-methylpentanal on Pd/SiO2 and Pd–Cu/SiO2 catalysts

This paper reports on novel Pd–Cu bimetallic catalysts for selective CO2 hydrogenation to methanol. Strong synergistic effect on promoting methanol formation was observed over amorphous silica supported Pd–Cu bimetallic catalysts when the Pd/(Pd + Cu) atomic ratios lied in the range of 0.25–0.34. The methanol formation rate over Pd(0.25)–Cu/SiO2 was two times higher than the simple sum of those over monometallic Cu and Pd catalysts. The Pd–Cu bimetallic catalysts were characterized by X-ray diffraction, transmission electron microscopy, scanning transmission electron microscopy coupled with energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and hydrogen temperature-programmed desorption. Detailed characterization results demonstrated the importance of two well-dispersed Pd–Cu alloy particles (PdCu and PdCu3) for the observed methanol promotion over Pd–Cu bimetallic catalysts. Similar bimetallic promotion was also observed for Pd–Cu catalysts supported on uniform mesoporous MCM-41, SBA-15 and MSU-F. Conversion-selectivity profile of the Pd–Cu/SiO2 catalyst suggested that CO2 was a primary carbon source for methanol synthesis at lower CO2 conversion, and byproduct CO contributed at higher CO2 conversion within the conversion range examined.

Bimetallic Pd–Cu catalysts for selective CO2 hydrogenation to methanol

We report a novel synthesis of nanoparticle Pd-Cu catalysts, containing only trace amounts of Pd, for selective hydrogenation reactions. Pd-Cu nanoparticles were designed based on model single atom alloy (SAA) surfaces, in which individual, isolated Pd atoms act as sites for hydrogen uptake, dissociation, and spillover onto the surrounding Cu surface. Pd-Cu nanoparticles were prepared by addition of trace amounts of Pd (0.18 atomic (at)%) to Cu nanoparticles supported on Al2O3 by galvanic replacement (GR). The catalytic performance of the resulting materials for the partial hydrogenation of phenylacetylene was investigated at ambient temperature in a batch reactor under a head pressure of hydrogen (6.9 bar). The bimetallic Pd-Cu nanoparticles have over an order of magnitude higher activity for phenylacetylene hydrogenation when compared to their monometallic Cu counterpart, while maintaining a high selectivity to styrene over many hours at high conversion. Greater than 94% selectivity to styrene is observed at all times, which is a marked improvement when compared to monometallic Pd catalysts with the same Pd loading, at the same total conversion. X-ray photoelectron spectroscopy and UV-visible spectroscopy measurements confirm the complete uptake and alloying of Pd with Cu by GR. Scanning tunneling microscopy and thermal desorption spectroscopy of model SAA surfaces confirmed the feasibility of hydrogen spillover onto an otherwise inert Cu surface. These model studies addressed a wide range of Pd concentrations related to the bimetallic nanoparticles.

Single atom alloy surface analogs in Pd0.18Cu15 nanoparticles for selective hydrogenation reactions

Alumina-supported palladium-copper catalysts, which promote liquid-phase nitrate reduction, have been prepared according to different impregnation sequences of γ-Al 2 O 3 support and characterized by X-ray photoelectron spectroscopy (XPS), X-ray induced Auger electron spectroscopy (XAES) and temperature-programmed reduction (TPR). Analysis of Pd XPS/XAES spectra reveals that palladium is present on the γ-alumina support in the metallic form. Copper is reduced at lower temperatures in the presence of palladium particles compared to the CuO/γ-Al 2 O 3 sample. Due to the low copper content in catalysts ( σ Cu ≈10 14 atoms cm −2 ), the XPS/XEAS spectral features of reduced copper species are quite different from those of bulk copper. As shown by TPR and XPS/XAES data, formation of highly dispersed Pd-Cu bimetallic clusters is suggested. It was discovered by means of TPR analysis that the catalyst preparation in which the γ-alumina support is impregnated first by copper salt, results in higher formation of the Pd-Cu alloy.

Djordje Mandrino

Papers

XPS and TPR examinations of γ-alumina-supported Pd-Cu catalysts

Characterization of the carbides and the martensite phase in powder-metallurgy high-speed steel

Scanning electron microscopy, X-ray diffraction and thermal analysis study of the TiH2 foaming agent

XPS investigations of tribofilms formed on CrN coatings

Initial oxidation of duplex stainless steel