Synthesis and characterization of niobium-promoted cobalt/iron catalysts supported on carbon nanotubes for the hydrogenation of carbon monoxide

Bimetallic Co /Fe catalysts supported on carbon nanotubes( CNTs) were prepared,and niobium( Nb) was added as promoter to the 70 Co ∶30Fe /CNT catalyst. The physicochemical properties of the catalysts were characterized,and the catalytic performances were analyzed at the same operation conditions( H_2 ∶CO( volume ratio) = 2 ∶1,p = 1 MPa,and t = 260 ℃) in a tubular fixed-bed microreactor system. The addition of Nb to the bimetallic catalyst decreases the average size of the oxide nanoparticles and improves the reducibility of the bimetallic catalyst. Evaluation of the catalyst performance in a Fischer-Tropsch reaction shows that the catalyst results in high selectivity to methane,and the selectivity to C_(5+) increased slightly in the bimetallic catalyst unlike that in the monometallic catalysts. The addition of 1% Nb to the bimetallic catalyst increases CO conversion and selectivity to C_(5+). Meanwhile,a decrease in methane selectivity is observed.

Effect of ethanedioic acid functionalization on Ni/Al_2O_3 catalytic hydrodeoxygenation and isomerization of octadec-9-enoic acid into biofuel: kinetics and Arrhenius parameters

The effect of ethanedioic acid（Ed A） functionalization on Al2O3 supported Ni catalyst was studied on the hydrodeoxygenation（HDO）, isomerization, kinetics and Arrhenius parameters of octadec-9-enoic acid（OA） into biofuel in this report. This was achieved via synthesis of two catalysts; the first, nickel alumina catalyst（Ni/Al2O3） was via the incorporation of inorganic Ni precursor into Al2O3; the second was via the incorporation nickel oxalate（Ni Ox） prepared by functionalization of Ni with Ed A into Al2O3 to obtain organometallic Ni Ox/Al2O3 catalyst. Their characterization results showed that Ni species present in Ni/Al2O3 and Ni Ox/Al2O3 were 8.2% and 9.3%, respectively according to the energy dispersive X-ray result. Ni Ox/Al2O3 has comparably higher Ni content due to the Ed A functionalization which also increases its acidity and guarantees high Ni dispersion with weaker metal-support-interaction leading to highly reducible Ni as seen in the X-ray diffraction, X-ray photoelectron spectroscopy, TPR and Raman spectroscopy results. Their activities tested on the HDO of OA showed that Ni Ox/Al2O3 did not only display the best catalytic and reusability abilities, but it also possesses isomerization ability due to its increased acidity. The Ni Ox/Al2O3 also has the highest rate constants evaluated using pseudo-first-order kinetics,but the least activation energy of 176 k J/mol in the biofuel formation step compared to 244 k J/mol evaluated when using Ni/Al2O3. The result is promising for future feasibility studies toward commercialization of catalytic HDO of OA into useful biofuel using organometallic catalysts.

Long-Term Release of Iron-Cyanide Complexes from the Soils of a Manufactured Gas Plant Site

Iron-cyanide (Fe-CN) complexes have been detected at Manufactured Gas Plant sites (MGP) worldwide. The risk of groundwater contamination depends mainly on the dissolution of ferric ferrocyanide. In order to design effective remediation strategies, it is relevant to understand the contaminant’s fate and transport in soil, and to quantify and mathematically model a release rate. The release of iron-cyanide complexes from four contaminated soils, originating from the former MGP in Cottbus, has been studied by using a column experiment. Results indicated that long-term cyanide (CN) release is governed by two phases: one readily dissolved and one strongly fixed. Different isotherm and kinetic equations were used to investigate the driving mechanisms for the ferric ferrocyanide release. Applying the isotherm equations assumed an approach by which two phases were separate in time, whereas the multiple first order equation considered simultaneous occurrence of both cyanide pools. Results indicated varying CN release rates according to the phase and soil. According to isotherm and kinetic models, the long-term iron cyanide release from the MGP soils is a complex phenomenon driven by various mechanisms parallely involving desorption, diffusion and transport processes. Phase I (rapid release) is presumably mainly constrained by the transport process of readily dissolved iron-cyanide complexes combined with desorption of CN bound to reactive heterogeneous surfaces that are in direct contact with the aqueous phase (outer-sphere complexation). Phase II (limited rate) is presumably driven by the diffusion controlled processes involving dissolution of precipitated ferric ferrocyanide from the mineral or inner-sphere complexation of ferricyanides. CN release rates in phase I and II were mainly influenced by the pH, organic matter (OM) and the total CN content. The cyanide release rates increased with increasing pH, decreased with low initial CN concentration and were retarded by the increase in OM content.