Hydrogenolysis of n-Hexadecane on iron and its inhibition by carbon monoxide

The hydrogenolysis of normal hexadecane was studied over iron at 325° and 355°C. As expected with iron catalysts, the main product was methane, but the selectivities for intermediate alkanes were moderately large, probably due to the length of the carbon chain. Furthermore, gas chromatography—mass spectrometry analysis of the heavier products indicated the presence of alkylbenzenes, alkenes and branched alkanes which accounted for about 20 mole % of the C₉–C₁₃ hydrocarbons. When 5.7 mole % of carbon monoxide was added to the feed, hydrogenolysis reactions were inhibited and products similar to those in the Fischer—Tropsch synthesis were found. Therefore, CO acts like a poison for the hydrogenolysis of hydrocarbons.     

The kinetics of the reduction of iron oxide by carbon monoxide mixed with carbon dioxide

Results are reported for the repeated reduction of iron oxide particles, 300–425 μm diameter, by a mixture of CO, CO₂, and N₂ in a fluidized bed of 20 mm internal diameter. The conclusions were as follows: (1) Reduction of either Fe₂O₃ to Fe₃O₄ or of Fe₃O₄ to Fe_0.947O is first‐order in CO. (2) With the particle sizes used, the rates of the reduction reactions are controlled by intrinsic chemical kinetics. Activation energies and pre‐exponential factors are reported. (3) The first cycle gave anomalous results, but (a) the rate of reduction of Fe₂O₃ to Fe₃O₄ remained constant over cycles 2–10; (b) the rate of reduction of Fe₃O₄ to Fe_0.947O declined by 60–85% over cycles 2–10. (4) The rates of reduction declined with solids conversion down to zero at 80% conversion. The rates were incorporated into a conventional model of a fixed bed, which was used to predict, satisfactorily, the reduction behavior of iron oxide. © 2009 American Institute of Chemical Engineers AIChE J, 2010     

Mechanistic investigations of single-walled carbon nanotube synthesis by ferrocene vapor decomposition in carbon monoxide

The single-walled carbon nanotubes (SWCNTs) were synthesized by the carbon monoxide disproportionation reaction on Fe catalyst particles formed by ferrocene vapor decomposition in a laminar flow aerosol (floating catalyst) reactor. On the basis of in situ sampling of the product collected at different locations in the reactor, kinetics of the SWCNT growth and catalyst particle crystallinity were studied. Catalyst particles captured before SWCNT nucleation as well as inactive particles were determined to have cementite (Fe₃C) phase, while particles with γ- and α-Fe phases were found to be embedded in the SCWNTs. The growth rate in the temperature range from 804 to 915 °C was respectively varied from 0.67 to 2.7 μm/s. The growth rate constant can be described by an Arrhenius dependence with an activation energy of E_a = 1.39 eV, which was attributed to the carbon diffusion in solid iron particles. CNT growth termination was explained by solid-liquid phase transition in the catalyst particles. A high temperature gradient in the reactor was found to not have any effect on the diameter during the SWCNT growth and as a result on the chirality of the growing SWCNTs.     

Diesel fuel from thermal decomposition of soybean oil

Soybean oil was thermally decomposed and distilled in air or in nitrogen sparge with standard ASTM distillation apparatus. GC-MS analysis showed that approximately 75% of the products were made up of alkanes, alkenes, aromatics and carboxylic acids with carbon numbers ranging from 4 to more than 20. Fuel properties of the pyrolyzed materials were characterized and compared with those of the parent oil. The pyrolyzates had lower viscosities and higher cetane numbers than the parent vegetable oil. Thermally decomposed soybean oil shows promise as alternative fuel for the direct-injection diesel engine. Presented at the AOCS meeting in New Orleans, LA, in May 1987. Address all correspondence to Marvin O. Bagby, NRRC, ARS/USDA, 1815 N. University St., Peoria, IL 61604. Deceased.     

过氧钨配合物催化过氧化氢制备环氧大豆油的研究

研究了无溶剂和石油醚作溶剂时,30%过氧化氢存在下过氧钨配合物催化大豆油进行相转移的环氧化,并考察了溶剂、反应时间和催化剂等因素对产物的影响。结果显示石油醚作溶剂,1,2 磷钨酸吡啶盐(CWP)作催化剂,60℃反应6h,环氧值为6.4%,碘值为4.4mg/100mg,达到最佳效果。     

Removal of phosphorus and iron by commercial degumming of soybean oil

Samples of crude and water-degummed soybean oils were obtained from five commercial processors. period of at least 2 weeks between samples. The crude and degummed oils were analyzed for iron and phosphorus content. Phosphorus removal within each processing plant was consistent, but between plants removal varied from a low of 79% to a high of 95%. Removal of iron compounds during commercial degumming varied from a low of 14% to a high of 57%. Significance of these results in steam-refining operations are discussed. Presented in part at the AOCS meeting, New York, May 1977.     

Modeling of soybean oil bed extraction with supercritical carbon dioxide

Dry-milled soybeans are extracted with supercritical carbon dioxide at pressures 270 to 375 atm, temperature 50 to 70‡C, solvent flow rates 0.025 to 0016 cm/sec as a linear velocity in the bed-at supercritical state, and three types of soybean particle size in the range 0.05 to 0.2828 cm. Under these conditions, extraction rates of soybean oil from solid substrates in a fixed bed (1.1 mm I.D. x 200 mm Height) have been determined. The extraction rates were constant during the initial extraction period where the film resistance controls the rates, and then, the rales shifted to time-dependent diffusion controlling mass transfer mode. To correlate these features, mass transfer calculations were carried our for the constant rate period and the subsequent unsteady mass transfer rate period, respectively.     

Sensing and identification of carbon monoxide using carbon films fabricated by methane arc discharge decomposition technique

Carbonaceous materials have recently received attention in electronic applications and measurement systems. In this work, we demonstrate the electrical behavior of carbon films fabricated by methane arc discharge decomposition technique. The current-voltage (I-V) characteristics of carbon films are investigated in the presence and absence of gas. The experiment reveals that the current passing through the carbon films increases when the concentration of CO₂ gas is increased from 200 to 800 ppm. This phenomenon which is a result of conductance changes can be employed in sensing applications such as gas sensors.     

Selective decomposition of isobutylaldehyde to propene,carbon monoxide and hydrogen

Supported palladium modified with sodium sulphide was an excellent catalyst for the selective decomposition of iso-butylaldehyde (IBA) to its feed stocks, propene and oxo gas. The catalyst gave about 90% conversion and 99% propene selectivity at 350°C and under atmospheric pressure. The sulphide ion suppressed propene hydrogenation and promoted CO desorption from the catalyst.     

超临界CO_2萃取大豆油的实验研究

采用超临界CO2 萃取技术进行了大豆油的萃取实验。在压力为 2 0～ 30MPa、温度为 30 8～ 32 3K的范围内 ,考察了萃取压力、萃取温度、流体流量和物料预处理方式等条件对出油率的影响。在本文实验范围内 ,大豆油的最佳萃取工艺条件为 :压力 30MPa ,温度 313K ,物料状态为约 0 .4mm厚的大豆片。流体流量只影响萃取速率 ,而不影响最终的出油率     

Production of carbon monoxide and hydrogen by methanol decomposition over nickel dispersed on porous glass

The methanol decomposition to carbon monoxide and hydrogen is catalyzed at 200°C over nickel supported on porous glasses of which major pore diameters are 4, 19, and 45 nm. The catalyst in which the crystallite size of nickel is close to the pore diameter of 19 nm is the most active while in other samples the crystallite size is significantly different from the pore diameter, suggesting that the reaction over nickel particles is enhanced in the pore of which size is close to that of the particles.     

Lipase-catalyzed glycerolysis of soybean oil in supercritical carbon dioxide

The transesterification of soybean oil with glycerol, 1,2-propanediol, and methanol by an immobilized lipase in flowing supercritical carbon dioxide for the synthesis of monoglycerides is described. A lipase from Candida antarctica was used to catalyze the reaction of soybean oil with glycerol, 1,2-propanediol, ethylene glycol, and methanol. Reactions were performed in supercritical carbon dioxide at a density of 0.72 g/L and at a flow rate of 6 μL/min (expanded gas). The substrates were added at flows ranging from 2.5 to 100 μL/min. Monoglycerides were obtained at up to 87 wt%, and fatty acid methyl esters at nearly 100 wt%. The reactivity of the alcohols paralleled the solubility of the substrate in liquid carbon dioxide. Glycerol has the slowest reaction rate, only 2% of that of methanol.     

Thermo-catalytic decomposition of waste lubricating oil over carbon catalyst

The thermo-catalytic decomposition of waste lubricating oil over a carbon catalyst was investigated in an I.D. of 14.5mm and length of 640mm quartz tube reactor. The carbon catalysts were activated carbon and rubber grade carbon blacks. The decomposition products of waste lubricating oil were hydrogen, methane, and ethylene in a gas phase, carbon in a solid phase and naphthalene in a liquid phase occurring within the temperature ranges of 700 °C-850 °C. The thermo-catalytic decomposition showed higher hydrogen yield and lower methane yield than that of a non-catalytic decomposition. The carbon black catalyst showed higher hydrogen yield than the activated carbon catalyst and maintained constant catalytic activity for hydrogen production, while activated carbon catalyst showed a deactivation in catalytic activity for hydrogen production. As the operating temperature increased from 700 °C to 800 °C, the hydrogen yield increased and was particularly higher with carbon black catalyst than activated carbon. As a result, carbon black catalyst was found to be an effective catalyst for the decomposition of waste lubricating oil into valuable chemicals such as hydrogen and methane.     

Reduction of nitrogen oxides by carbon monoxide over an iron oxide catalyst under dynamic conditions

The reduction of NO and N₂O by CO over a silica-supported iron oxide catalyst was investigated by the transient response method, with different initial oxidation states of the catalyst, i.e. completely reduced (Fe₃O₄), or oxidised (Fe₂O₃). The influence of CO pre-adsorption was also studied. From the material balance on the gas phase species, it was shown that the composition of the catalyst changes during relaxation to steady-state. The degree of reduction of the catalyst at steady-state could thus be estimated. During the transient period, CO was shown to inhibit N₂O as well as NO reductions by adsorption on reduced sites. The activity of the reduced catalyst was found to be substantially higher as compared to the oxidised catalyst for both reactions. On this basis, it was attempted to keep the catalyst in a reduced state by periodically reducing it with CO. As a result, a significant increase in the performance of the reactor with respect to steady-state operation could be achieved for N₂O reduction by CO. Finally, the dynamic behaviour of the N₂O–CO and NO–CO reactions made it possible to evidence reaction steps, the occurrence of which could not be shown during our previous investigations on the separate interactions of the reactants with the catalyst.     

Gold and iron supported on Y-type zeolite for carbon monoxide oxidation

Gold and iron supported on Y-type zeolite for carbon monoxide oxidation have been studied. They were prepared by ion exchange of gold(III) compounds with Y-type zeolite, iron-impregnated Y-type zeolite, or iron-exchanged Y-type zeolite in a chloroauric acid solution. The as-prepared gold/Y sample possessed high activity for carbon monoxide oxidation, but it gradually and irreversibly deactivated during the reaction. The deactivation was attributed to the transformation of some gold ions to gold metal. The activities of as-prepared gold/iron/Y samples were poor when compared with that of gold/Y, but their activities were markedly promoted by a high-temperature reduction treatment at 570°C. This is ascribed to the fact that the reduced gold/iron/Y catalyst could catch and release oxygen at low temperature.     

Investigation into sulfur release in reductive decomposition of calcium sulfate oxygen carrier by hydrogen and carbon monoxide

Chemical looping combustion (CLC) is a promising technology with the inherent property of separating CO₂ from flue gas. For calcium sulfate (CaSO₄) oxygen carrier, the inhibition of the produced sulfurous gases in the reduction of CaSO₄, including sulfur dioxide (SO₂), hydrogen sulfide (H₂S) and carbonyl sulfide (COS), is the key for a CLC system. In this paper, the sensitivities of reacting temperature, oxygen ratio number (defined in this paper) and the mole fraction of both carbon monoxide (CO) and hydrogen(H₂) in the syngas to the sum of the amounts of released SO₂, H₂S and COS are discussed respectively. Thermo-gravimetric analysis (TGA) tests demonstrated that the amount of the produced sulfurous gases is greatly dependent on the partial pressure of H₂ or CO in the reduction of CaSO₄. When the partial pressure of H₂ or CO is higher than 40 kPa, the production of sulfurous gases, indicating the deterioration of the recyclability of CaSO₄, can be prevented completely even if the reacting temperature is as high as 1000 °C. A new kind of CaSO₄/CaCO₃ oxygen carrier is prepared using a mechanical mixing method. The addition of CaCO₃ nanoparticles largely improves the recyclability of the oxygen carrier in comparison with the fresh CaSO₄ oxygen carrier, without CaCO₃ nanoparticles, in a multi-cycle TGA test.     

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 effect of particle size on nitric oxide decomposition and reaction with carbon monoxide on palladium catalysts

The effect of palladium particle size on its catalytic activity was investigated by the decomposition of chemisorbed nitric oxide and the reaction of nitric oxide with carbon monoxide in flow conditions. Palladium particles (30–500 Å) were prepared on silica thin films (100 Å) which were supported on a Mo(110) surface. The reactivity of the supported palladium varied with the metal particle size. On large palladium particles, nitric oxide (NO) reacts to form nitrous oxide (N₂O), dinitrogen (N₂) and atomic oxygen during temperature-programmed reaction, whereas on small particles (< 50 Å), nitrous oxide is not formed. Similarly, reactions of NO with CO on large particles, in flow conditions produce N₂O, N₂ and CO₂, whereas N₂O is not produced on small particles. In addition, more extensive NO decomposition is observed on the smaller particles.