Cobalt-zeolite catalysts for the synthesis of hydrocarbons from CO and H2

Catalysts prepared by mechanical mixing of high-silica zeolite ZSM-5 with cobalt oxide Co₃O₄, basic cobaltous carbonate, and cobaltous carbonate were studied. The nature of the cobalt compound introduced into the mixture affects the catalytic and physicochemical properties of the catalyst. The presence of Co₃O₄ in the sample (introduced as oxide or obtained by thermal decomposition of the carbonate) is favorable to the formation of aromatic compounds from CO and H₂. The use of cobaltous carbonates for the preparation of catalysts results in development of the porous structure of the catalyst. During preparation of samples, the mechanical treatment partially destroys the zeolite framework of the support.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1070–1073, June, 1995.     

Metallosilicates as supports of Co catalysts for the synthesis of liquid hydrocarbons from CO and H2

The effect of the nature of the silicate support on the activity and selectivity of 10%. Co/M silicate catalysts (where M=Cu, Zn, Ce, Ti, Hf, La, Al, Zr, Co, Mg) in the synthesis of hydrocarbons from CO and H₂ has been established. Co and Zr catalysts have been shown to provide the highest catalytic efficiency. The yield of liquid hydrocarbons in their presence exceeds 120 g m^–3.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 480–482, March, 1993.     

Scientific principles of synthesis of liquid hydrocarbons from CO and H2 in the presence of cobalt catalysts (review)

The effect of the nature of the support, method of preparation and preliminary treatment of the catalyst (temperature of reduction and heat treatment with air) on the synthesis of liquid hydrocarbons from CO and H₂ in the presence of Co catalysts was examined in the present review. The effect of the composition of the starting gas mixture on the occurrence of the process and composition of products formed was demonstrated. Some features of genesis of Co catalysts in different stages of their preparation and the effect of gaseous additives on synthesis were determined. Generalizations were made concerning the features of formation of Co catalysts.Review of data from the research awarded the Academy of Sciences N. D. Zelinskii Prize in chemical sciences for 1990.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2681–2698, December, 1991.     

The synthesis of hydrocarbons from CO and H2 over well-characterized supported PtFe catalysts

A combination of Mössbauer spectroscopy, chemisorption measurements and kinetic studies of the synthesis of hydrocarbons from CO and H₂ has been employed to investigate alumina-supported Fe, Pt and PtFe catalysts. Three different chemical states of Fe have been identified in the reduced catalysts: ferrous ions, ferromagnetic Fe metal and PtFe bimetallic clusters. The relative amounts of these species depend upon the Pt:Fe ratio and the total metal loading.At low concentrations (0.1%) iron was not reduced by hydrogen beyond the ferrous state at 773 K, and the ferrous ions had no catalytic activity in the synthesis reaction. However, catalysts containing 1.75 wt.% Pt and varying amounts of Fe showed marked differences. The addition of this amount of platinum to iron on alumina led to the formation of PtFe clusters on reduction. At high Pt:Fe ratios (∼5) all of the iron combined with platinum to form clusters. The iron in the PtFe clusters was catalytically inert in the CO/H₂ synthesis reaction and the clusters exhibited essentially the catalytic behaviour of platinum. At low Pt:Fe ratios (0.1) ferromagnetic iron metal, in addition to Fe²⁺ ions and PtFe clusters, was produced. The ferromagnetic iron dominated the activity and selectivity pattern of the catalyst because of the higher specific activity of the iron compared to Pt or PtFe clusters.The inert behavior of the iron in PtFe clusters is attributed to a decrease in the electron density on the iron as indicated by the Mössbauer isomer shift. The direction of electron transfer is opposite to that proposed for alkalimetal-promoted Fe catalysts on which the production of higher molecular weight species and the activity was enhanced.Finally, this investigation shows that bimetallic alloys with stoichio-metries identical to the metal loading are not necessarily formed in reduced supported catalysts.     

CO2 enhanced carbon nanotube synthesis from pyrolysis of hydrocarbons

We report on the role of CO(2) in improving carbon nanotube yield and crystallinity from catalytic chemical vapor deposition of hydrocarbons.     

Synthesis of hydrocarbons from CO and H2 using Co-mixed-oxide catalysts

Conclusions The use of binary carriers made of oxides of silicon and Mg, Be, Zr, and Mn for Co catalysts for synthesis of liquid hydrocarbons from CO and H₂ leads to an increase in their activity and selectivity in comparison with individual oxides, and also to an increase in the catalyzate of the isoparaffin content and that of hydrocarbons of the C₁₁-C₁₈ fraction.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimcheskaya, No. 11, pp. 2474–2477, November, 1988.The authors express their gratitude to A. A. Vedenyapin for performing differential thermal analysis.     

Co-electrolysis of CO2 and H2O: From electrode reactions to cell-level development

The electroreduction of CO₂ into value-added products (e.g. CO) constitutes an excellent means of decreasing this greenhouse gas emissions, but limited efforts have been devoted to the implementation of this reaction within the so-called co-electrolysis cells operating at process-relevant currents >> 100 mA·cm_geom^?2. Reaching such performances shall require a combination of gas-fed reactants and the corresponding diffusion electrodes, along with ion-exchange membranes and ionomers that set the operative pH at the cells' cathode and anode. The latter constitutes a key design parameter that must be combined with the need to minimize the crossover of reaction products and/or (bi)carbonate anions from the cathode to the anode, whereby their reoxidation to carbon dioxide leads to a decrease in the device's net CO₂ consumption.     

CO,CO2, CH4 and H2O sensing by polymer covered interdigitated electrode structures

A gas sensor based on polymer-covered interdigitated electrodes is described and some preliminary results for CO, CO₂, CH₄ and H₂O are presented. It is known that the permittivity and conductivity of a polymer such as polyphenylacetylene (PPA) changes slightly upon absorption of gases. To measure this sensitivity, interdigitated electrode structures were fabricated with an area of 1.2×1.6 mm² and electrode widths and distances of 10 μm; the structures were covered with 0.77 μm PPA. Measurements were performed at room temperature for frequencies between 100 Hz and 100 kHz and pressures between 0 and 20 mmHg.     

新型微孔钨磷多金属氧酸盐(C2N2H10)2[H2P2W18O62]·8H2O的水热合成和电化学性质

采用水热法并以乙二胺为模板剂合成了具有微孔结构的钨磷多金属氧酸盐(C2N2H10)2[H2P2W18O62].8H2O.通过元素分析、等离子发射光谱、X射线单晶衍射等进行了结构表征,并用电化学方法对标题化合物的电化学性质进行了研究.     

Synthesis of hydrocarbons from CO and H2 on supported nickel-palladium catalysts

The use of an Ni-Pd/Al₂O₃ catalyst in the synthesis of C₁-C₄ hydrocarbons from CO and H₂ permits us to increase the selectivity and total yield of these products by a factor of 1.5–2.0 relative to the corresponding nickel and palladium catalysts. The optimal temperatures and CO/H₂ ratios for obtaining hydrocarbons were determined. A structure was proposed for the active sites of the bimetallic catalyst.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1689–1691, July, 1991.     

A vibrational analysis of the (X2O)2(g) (X=H,D, T) isotopomeric species

Harmonic vibrational analysis is carried out for the water dimer (¹H or natural isotopic mixture) and its²D and³T isotopomers in the gas phase, using the recently designed flexible potential energy functions. The results represent the most complete and reliable theoretical evaluation of the vibrational frequencies, directly applicable to various observation interpretations. The complete data set can also be useful for a more general isotopomeric reasoning.     

Two mixed-valence vanadium(III,IV) phosphonoacetates with 16-ring channels: H2(DABCO)[V(IV)O(H2O)V(III)(OH)(O3PCH2CO2)2].2.5H2O and H2(PIP)[V(IVO)(H2O)V(III)(OH)(O3PCH2CO2)2].2.5H2O

Two isostructural mixed-valence vanadium phosphonoacetates H2(DABCO)[V(IV)O(H2O)V(III)(OH)(O3PCH2CO2)2].2.5H2O (1) and H2(PIP)[V(IV)O(H2O)V(III)(OH)(O3PCH2CO2)2].2.5H2O (2) have been synthesized. They crystallize in the orthorhombic space group Pnna with a = 7.0479(10) A, b = 15.307(2) A, and c = 17.537(3) A for 1 and a = 7.0465(9) A, b = 15.646(2) A, and c = 17.396(2) A for 2. X-ray single-crystal diffraction reveals that 1 and 2 have a three-dimensional open framework featuring 16-ring ellipsoid channels that are filled with doubly protonated 1,4-diazabicyclo[2,2,2]octanium/piperazinium cations and water molecules. According to the classification in metal-organic frameworks, 1 and 2 contain infinite (-O-V-)(infinity) chains that are cross-linked by "metalloligand" [VO(H2O)(O3PCH2CO2)2](4-) into a 3-D net of the sra topology. The temperature dependence of the magnetic susceptibility of 1 shows that the chi(m)T value in the range of 60-320 K is constant of 1.105 cm3 K mol(-1)/V2 unit, and upon further cooling, the chi(m)T value rapidly increases to 1.81 cm3 K mol(-1) at 2 K. The corresponding effective magnetic moment (mu(eff))/V2 unit varies from 2.97 mu(B) at 320 K to 3.80 mu(B) at 2 K. The magnetic data in the range of 2-320 K follow the Curie-Weiss law with C = 1.074 cm3 K mol(-1) and Theta= -1.34 K.     

An essential role of CO2 and H2O during single-walled CNT synthesis from carbon monoxide

Single-walled carbon nanotubes (CNTs) were synthesized from carbon monoxide and iron catalyst nanoparticles by two different aerosol methods. The catalyst particles were produced by physical vapor nucleation using a resistively heated iron wire (hot wire generator) and by thermal decomposition of ferrocene vapor. The essential role of etching agents (CO₂ and H₂O) in the CNT formation process was demonstrated. An addition of small amounts of CO₂ and H₂O vapor in the reactor resulted in an increase in CNT length. Also, the CO₂ introduction was found to decrease the minimum temperature for CNT synthesis from 890 °C to below 600 °C.