Carbon as a support for catalysts—III glassy carbon as a support for iron

As described in the Hucke patent, glassy carbons containing not only open pores of molecular size but also pores in the transitional or macropore range can be produced from appropriate formulations. The formulation always consists of a carbon-yielding monomer, an organic to yield larger pores upon its removal once the monomer has been partially polymerized, and a polymerization catalyst. It may contain a dispersing agent, depending upon the size of the larger pores which is desired. In this study, furfuryl alcohol was the monomer. Great flexibility is shown to exist in the total surface areas of the carbons which can be produced, degree of carbon molecular sieving in the super micropores, and pore volume and pore size in the larger pores following polymerization and carbonization steps. Different ways of adding iron into the mix are explored which also can have pronounced effects on the nature of the porosity in the final carbons. Further modification is shown upon addition of potassium or boron into the mix. Carbons produced are expected to have potential as catalyst supports.     

Mixed oxides as a support for new CoMo catalysts

Interest in bifunctional catalysts, active in reactions such as hydrodesulphurisation (HDS) of hydrocarbon fractions, is growing in the last years. An improvement of CoMo/Al₂O₃ materials can be obtained by the introduction of other oxides during the sol–gel synthesis. This heavily affects the acid–base characteristics of the catalysts, while textural properties are less influenced. The catalytic performances change as well: a relationship between the density of acid sites and HDS activity has been found.     

Disordered mesoporous KIT-1 as a support for hydrodesulfurization catalysts

MoO₃ and NiO were supported on KIT-1, a new disordered mesoporous molecular sieve. MoO₃ is homogeneously dispersed as a monolayer on the support, whereas NiO tends to form small crystallites in the mesoporous channels. KIT-1 supported MoO₃ and/or NiO catalysts exhibit higher catalytic activities for thiophene hydrodesulfurization than similar MCM-41 and NaY zeolite supported catalysts, because the three-dimensional disordered network of short channels in KIT-1 reduces the risk of blockage in the catalysts and facilitates the transport of reactant and product molecules. This revised version was published online in July 2006 with corrections to the Cover Date.     

MFI zeolite as a support for automotive catalysts with reduced Pt sintering

The noble metals used as catalysts in automotive exhaust systems are subject to sintering at extreme temperatures, leading to deterioration of catalytic activity. Zeolite with the MFI (ZSM5) structure is examined as a support for Pt particulate catalysts. The MFI structure is composed of agglomerates of single-crystal zeolite with interstitial mesoporosity. Pt fixed within these mesopores is shown through high-temperature aging tests in air to be highly resistant to sintering due to the mechanical constraints on particle size imparted by the mesoporous structure. The deterioration of catalytic activity after aging is significantly lower than that for comparable γ-alumina supported catalyst.     

Miniemulsion polymers as solid support for transition metal catalysts

A pentadentate salen-type ligand was immobilized in a poly[(styrene)]-co-(butyl acrylate)] matrix by miniemulsion polymerization. The obtained polymer beads revealed a particle size of 50 nm in the dry state by transmission electron microscopy. Dynamic light scattering experiments in methanol and water showed a solvent-dependent average particle size with a mean particle diameter of up to 233 nm in methanol. These results provide valuable insights for the optimization of macromolecular oxidation catalysts and their future use as enzyme-like entities in aqueous media. The particle stability was demonstrated over a wide pH range (3-11) by gel permeation chromatography, and initial results for the metal ion binding ability were obtained.     

Porous carbon as support for iron and ruthenium catalysts

Iron and ruthenium catalysts have been supported on a porous carbon prepared by pyrolysis and activation of the copolymer Saran. For comparison, a graphitized carbon black (V3G) has also been used as support for both metals. The catalysts have been characterized by chemisorption of H₂ and CO₂ at 298 K (373 K in some cases) and by X-ray line broadening. The hydrogen chemisorption on iron catalysts was very low and increased with adsorption temperature, whereas the CO chemisorption results indicate the formation of subcarbonyl species. However, H₂ and CO uptakes led to similar dispersion values for the ruthenium catalysts. The X-ray results were in good agreement with the chemisorption results except in the case of highly dispersed Fe catalysts. The results obtained in the hydrogenation of CO indicate that in the case of Fe catalysts the highest selectivity toward hydrocarbons was given by the catalyst supported on V3G, with large metal particle size which, at the same time, exhibited a lower decrease in activity with reaction time than the other Fe catalysts with smaller average particle size. The olefin/paraffin ratio is very large for the catalyst prepared from Fe(CO)₅.The Ru catalysts are essentially of the methanation type.     

Comparative study of Cu/ZnO catalysts derived from different precursors as a function of aging

Structural modifications of Cu/ZnO catalysts for methanol steam reforming (MSR) as a function of precipitate aging in catalysts preparation process has been investigated comparatively. Freshly precipitated Cu,Zn-hydroxycarbonate (HC) and Cu,Zn-hydroxynitrate (HN) were aged in their mother liquor for a period of 120 min followed by washing, drying, calcination and reduction. Pronounced effect of aging was found for aged HC precipitates while no significant effect of aging was observed for aged HN solids. The bulk structure of the Cu/ZnO catalysts was investigated by means of TG/MS, in situ XRD and ⁶³Cu NMR. The increase in the activity of the catalysts prepared by HC aging did not correlate linearly with the specific Cu surface area but coincides with an increase in the microstrain in the copper clusters presumably because of the improved interface between Cu and ZnO. Meanwhile, aging of HN precipitates results in large, separated and less strained Cu and ZnO particles with an inferior catalytic activity. Finally, both aged Cu/ZnO catalysts revealed smaller copper crystallite size compared to unaged samples.     

Novel Fe/MnK‐CNTs nanocomposites as catalysts for direct production of lower olefins from syngas

Novel Fe/MnK‐CNTs nanocomposites are developed as catalysts for direct production of lower olefins from syngas, delivering a high iron time yield of 337.2 μmol_CO· ·s^?1 with 51.3%C selectivity toward C₂?C₄ olefins under the optimal reaction conditions (270°C, 2.0 MPa, 30,000 mL h^?1 ). These catalysts are optimized by varying calcination temperature from 150 to 400°C. Multiple techniques including transmission electron microscopy, Elemental mapping, X‐ray diffraction, X‐ray photoelectron spectroscopy, H₂‐temperature‐programmed reduction, and Raman were employed to reveal the relationship between the catalyst nature and unique catalytic behavior. In particular, the resultant catalyst from the calcination temperature of 220°C exhibits the highest selectivity of C₂?C₄ olefins as well as good stability, which are enabled by the trade‐off among the effects of iron particle sizes, promoters, metal‐support interaction and support surface chemistry. Moreover, influences of reaction temperature, reaction pressure and space velocity are also investigated. © 2016 American Institute of Chemical Engineers AIChE J, 63: 154–161, 2017     

Graphitic mesoporous carbon as a support of promoted Rh catalysts for hydrogenation of carbon monoxide to ethanol

Graphitic mesoporous carbon (GMC), prepared through high-temperature graphitization of soft-templated amorphous mesoporous carbon (AMC), was used as the support for Mn, Li, and Fe triple-promoted Rh catalysts for CO hydrogenation to ethanol. The use of GMC results in C₂H₅OH selectivity and formation rate comparable to nonporous SiO₂ support along with a significant inhibition on the formation of undesired CH₄ and light hydrocarbons at the expense of appreciable amounts of CO₂ produced. The better catalytic performance of promoted-Rh/GMC than those supported on other carbon allotropes (AMC and non-porous graphitic carbon black) seems to be associated with the specific graphitic structure and mesoporosity of GMC. The surface modification of GMC by wet oxidation leads to considerable increases in C₂H₅OH selectivity and formation rate. The modified GMC as a support shows substantially greater CO₂-free selectivity for C₂H₅OH than the SiO₂.     

Oxidized carbon as a support of copper oxide catalysts for methanol decomposition to hydrogen and carbon monoxide

Copper oxide supported on oxidized activated carbon is investigated as a catalyst for methanol decomposition to H₂ and CO. The influence of the medium of the precursor deposition on the state of the active phase is observed. The role of the chemical nature of the support in the formation of catalytic active complex is discussed.     

The search for new solid acid catalysts: systems derived from phosphatoantimonates

A series of potassium phosphatoantimonates (KSbP₂O₈, KSb₂PO₈, K₂SbPO₆ and K₃Sb₃P₂O₁₄) crystallizing in a variety of structures (one-, two- and three- dimensionally extended) has been converted to the protonic form and tested for catalytic efficiency in the dehydration of methanol. The predominant product in all cases is dimethyl ether, and the most active is the layered acid HSbP₂O₈ which reaches its maximum activity at a temperature of about 350 °C.     

制浆造纸厂富铁污泥中Fe3+的电化学还原研究

采用电化学法将制浆造纸厂废水Fe^nton氧化产生的难处理富铁污泥中的Fe^3+还原为Fe^2+,以便于其再利用。研究表明,以不锈钢为阴极材料可较大幅度降低Fe^3+还原的过电位;当Fe^3+质量浓度为2000 mg/L时无需辅助电解质,在极水比为0.48 cm^2/mL,电流密度为0.65 mA/cm^2的条件下反应2 h,Fe^2+再生率可达60.1%,电流效率为92.1%。将酸处理后的富铁污泥溶液在上述条件下还原3 h,Fe^2+再生率达68.8%,电流效率近100%。电化学法是富铁污泥中Fe^3+再利用的可行方法。     

Production of ketones from sewage sludge over zirconia-supporting iron oxide catalysts in a steam atmosphere

Recovering useful hydrocarbons from sewage sludge using zirconia-supporting iron oxide catalysts was investigated. Zirconia has activity for decomposing water molecules to generate active oxygen and hydrogen species. These oxygen species spill over to the surface of iron oxide and react with hydrocarbons to produce oxygen-containing organic chemicals such as acetone. Thus, zirconia-supporting iron oxide catalyst has two kinds of active sites on zirconia and on iron oxide. Sewage sludge was hydrothermally liquefied at 573 K in advance, yielding black water containing various hydrocarbons, to enhance the contact of reactant molecules with the catalysts. It was found that the hydrocarbons in the black water converted well to a mixture containing primarily acetone without any carbonaceous residue over zirconia-supporting iron oxide catalysts under the conditions of one atmospheric pressure and superheating steam atmosphere. Furthermore, it was confirmed that acetone was produced continuously from the sewage-derived black water over the catalysts using a bench scale flow reactor.     

Hydroconversion of resids with dispersed molybdenum catalysts derived from phosphomolybdates

Phosphomolybdic acid (PMA) and cobalt, nickel and potassium phosphomolybdates have been found very active catalyst precursors for the conversion of coal- and petroleum-derived resids when they are impregnated onto coal and Al₂O₃. They are mostly stable up to 400–450°C in the presence of He and H₂, but significant change in stability occurs in the presence of H₂S, transforming these materials into an active form of catalyst. Their solubility in water provides highly dispersed catalysts in the reaction media. PMA and these bimetallic materials were tested at the concentration of 15, 150 and 1500 mg Mo per kg feed for reaction times of 30 and 90 min, and compared to a commercial NiMo/Al₂O₃ catalyst (AKZO-60). In the 30 min reactions, increasing Mo concentration did not provide a significant improvement in resid conversions compared to the non-catalyzed case. However, in the 90 min reactions, improvements were observed in conversion of coal and Mayan resids to distillate boiling below 525°C. The results indicate that thermal reactions play an important role in the 30 min reactions, and catalytic reactions resulting in increased resid conversions become more important in the 90-min reactions. Higher conversions with nickel phosphomolybdate supported on Al₂O₃ were observed with Mayan resid compared with coal resid. Nickel phosphomolybdate has been found to have promising catalytic activity for hydroconversion processes.     

用于低碳混合醇合成的Fe/CuZnSi催化剂研究

采用沉淀-浸渍方法制备了Fe/CuZnSi催化剂,发现在浸渍Fe过程中生成FeZn2 Cu3 O6.5晶体,它在焙烧过程中分解形成CuO晶体,有利于Cu和Fe相互均匀分布,提高催化剂的CO加氢反应活性,CO转化率主要决定于催化剂中的Fe含量,催化剂中的Cu与Zn质量相等时,液态产物中的醇含量明显增加,C2+醇约占总醇质量的50％.     

Alumina-silica binary mixed oxide used as support of catalysts for hydrotreating of Maya heavy crude

Alumina-silica binary mixed oxide support is used to prepare catalysts for hydrotreating of Maya heavy crude. Support is prepared by urea hydrolysis. Sequential incipient wetness and co-impregnation techniques are employed for preparation of catalysts. Ammonium heptamolybdenum is used as precursor of MoO₃. Catalysts are characterized by X-ray diffraction (XRD), temperature-programmed reduction (TPR) and the pore size distribution. Hydrodemetallation (HDM), hydrodesulfurization (HDS), hydrodenitrogenation (HDN), and asphaltene conversion (HDAsp) reactions are studied on these catalysts. One reference catalyst is also taken for comparison. Coke and metals depositions on spent catalysts are measured. The catalyst deactivation rate is also studied. The X-ray diffraction (XRD) results reveal that molybdenum atoms are well dispersed into CoMo catalyst, whereas MoO₃ crystalline phases are found in PCoMo and PNiMo catalysts. TPR reduction profiles are different for different catalysts. The laboratory made catalyst is reduced at one temperature, whereas the reference catalyst shows two reduction profiles. The reference catalyst shows the highest activities among four catalysts. The highest HDM and HDAsp activities of the reference catalyst may be due to its bigger pore diameter. The presence of TiO₂ in the reference catalyst enhances HDS and HDN activities. The CoMo catalyst shows higher activities than those of PCoMo and PNiMo catalysts. The presence of crystalline MoO₃ causes for lower activities of catalysts PCoMo and PNiMo.     

A novel superimposed porous copper/carbon film derived from polymer matrix as catalyst support for metal-air battery

Journal of Porous Materials - Catalyst support of air cathode requires stable structure and high specific surface area, due to the unique semi open structure of metal-air battery. Herein, we...