Applied Catalysis A, General (v.313, #1)
Editorial Board (CO2).
Statistical design and modeling of the process of methane partial oxidation using V-MCM-41 catalysts and the prediction of the formaldehyde production by Guoan Du; Yanhui Yang; Wei Qiu; Sangyun Lim; Lisa Pfefferle; Gary L. Haller (1-13).
As a simplified approach to optimize the production of formaldehyde from partial oxidation of methane, this paper illustrates the application of statistical multivariate analysis and prediction through a multi-regression model, as well as the optimization of the processing parameters in the complex reaction process. This approach is advantageous, especially when experimental evaluation and optimization of a process is time consuming and expensive. By carrying out a finite number of experiments, statistical modeling in this work shows reasonable good prediction ability in terms of methane conversion, formaldehyde selectivity, and space time yield (STYHCHO). Moreover, not only are the synergistic effects between reaction parameters revealed, but also a comprehensive understanding of the whole production process over variation of the all reaction parameters (within the phase space represented by the experimental grid) are allowed.
Keywords: Design of experiment; Multiple regression model; Regression; V-MCM-41; Partial oxidation of methane;
The regenerative effect of catalyst fluidization under methanation conditions by M.C. Seemann; T.J. Schildhauer; S.M.A. Biollaz; S. Stucki; A. Wokaun (14-21).
The regenerative effect of fluidization on catalysts in methanation reactors was shown by in situ measurements of the axial gas phase concentration profiles. The profiles prove strong carbon exchange processes between the catalyst and the gas phase. These exchange processes structure the bed into three zones: carbon deposition, predominantly by CO dissociation, at the inlet; predominant gasification of solid carbon species from the catalyst in the following zone, and predominant carbon deposition by methane dissociation in the upper part of the bed. By analyzing the carbon-balance, locally up to 20% excess carbon was found in the gas phase, mainly in form of methane. The excess methane decomposes again, forming less reactive carbon with a slow rate. Due to an intensive catalyst mixing, the build-up of unreactive carbon can be prevented by regeneration in the middle zone of the reactor. As these processes are influenced by the particle movement, conclusions about regions of up- and down-flow of the catalyst particles can be drawn.
Keywords: Bubbling fluidized bed; Methanation; Carbon deposition; Internal regeneration;
Partial oxidation of methanol for hydrogen production over carbon nanotubes supported Cu-Zn catalysts by I. Eswaramoorthi; V. Sundaramurthy; A.K. Dalai (22-34).
Carbon nanotubes (CNTs) were used as support to Cu-Zn catalysts and tested their feasibility for hydrogen production from partial oxidation of methanol. The CNTs were synthesized by CVD method using acetylene as carbon source over anodic aluminum oxide template. The structural characteristics of CNTs were analysed by SEM, TEM, XRD, Raman spectroscopy and TGA. Using these CNTs as support, Cu-Zn catalysts with varying metal loading were prepared by co-precipitation method. The reducibility of the catalysts was tested with H2-TPR. N2 adsorption and CO chemisorption were used to monitor the surface area and total CO uptake of catalysts, respectively. The metal particle size of Cu-Zn/CNTs catalysts were measured from XRD and TEM. The nature of copper species and acidity were analysed by DRIFT study of CO adsorption and pyridine adsorption method, respectively. The deposition of Cu on CNTs surface resulted in creation of strong Lewis acid sites. The methanol conversion rate and H2 selectivity are increased from 0.066 to 0.11 mol/h/g cat and 57 to 70.6%, respectively, when increasing Cu loading from 5 to 12 wt% at 260 °C and further increase shows a fall in activity. The enhanced activity of 12 wt% Cu-9 wt% Zn/CNTs is due to the improved metal dispersion, narrow particle size distribution and almost complete reduction of Cu particles. The XRD analysis of spent catalyst indicates that during the POM reaction, the active Cu0 species is slowly converted into CuO, which is responsible for fall in activity.
Keywords: Carbon nanotubes; H2 production; Cu-Zn catalysts; Partial oxidation of methanol;
Passivation of vanadium in an equilibrium FCC catalyst at short contact-times by E. Tangstad; T. Myrstad; E.M. Myhrvold; I.M. Dahl; M. Stöcker; A. Andersen (35-40).
An equilibrium FCC (ECAT) sample containing 2800 ppm vanadium and 2500 ppm nickel was characterized by ESR and ESCA, and tested in a microactivity test (MAT) to study the effect of reductive pretreatments at elevated temperatures. From ESR and ESCA studies, it is found that the vanadium of the ECAT sample consists of V4+ converting to a considerable part of V3+ after a treatment with 5% H2 in N2 between 650 and 750 °C. Approximately, 40% of the vanadium exists as V3+ after such a treatment at 700–750 °C. The reductive procedure led to an increase in the gasoline yield and a reduction in the coke yield in MAT when processing an atmospheric residue from the North Sea at 524 °C. It is shown that it is sufficient with a reduction/passivation time as short as 3 min in hydrogen at 689 °C to obtain a significant effect on the gasoline and coke yields. The results indicate that the main part of the observed reduction occurs in the outer layer of the particle at such short reduction times.
Keywords: FCC; Vanadium; Metals passivation; Resid cracking; MAT; ESR; ESCA;
Synthesis of silver nanoshell-coated cationic polystyrene beads: A solid phase catalyst for the reduction of 4-nitrophenol by Subhra Jana; Sujit Kumar Ghosh; Sudip Nath; Surojit Pande; Snigdhamayee Praharaj; Sudipa Panigrahi; Soumen Basu; Takeshi Endo; Tarasankar Pal (41-48).
Silver nanoshell-coated cationic polystyrene beads have been synthesized at room temperature through immobilization of specific silver precursor ions, followed by wet chemical reduction. The electrostatic field force has been taken into consideration for the immobilization of precursor ions onto the resin beads. The as-synthesized particles were characterized by XRD, XPS, SEM, TEM, EDX, and FTIR studies and have been exploited as a solid phase catalyst for the reduction of 4-nitrophenol in the presence of sodium borohydride. The detailed kinetics of the reduction process was monitored under varied experimental conditions. At the end of the reaction, the catalyst particles remain active. They can thus be separated from the product, 4-aminophenol, and can be recycled a number of times after the quantitative reduction of 4-nitrophenol. The activity of the solid catalyst particles has also been examined to promote the reduction of other nitrophenols, e.g., 2-, 3-nitrophenol. The synthesis of the solid catalyst particles, their applications and detailed kinetic aspects of the reduction of 4-nitrophenol have been reported.
Keywords: Silver nanocomposites; Resin; Nitrophenols; Catalysis; Kinetics;
A novel amorphous alloy Ru–La–B/ZrO2 catalyst with high activity and selectivity for benzene selective hydrogenation by Shouchang Liu; Zhongyi Liu; Zheng Wang; Shuhui Zhao; Yongmei Wu (49-57).
A novel amorphous alloy Ru–La–B/ZrO2 catalyst with high activity and good selectivity to cyclohexene was prepared by a chemical reduction method. Various characterizations on the catalyst were carried out by means of XRD, TEM-SAED, XPS, ICP-AES, PSD and N2-physisorption. The performance of the catalysts was examined under pilot conditions. The results showed that the bulk composition of the catalyst was Ru18.14La0.08B18.86/ZrO2, that almost all ruthenium species existed in the elemental state, and that La existed in the La3+ state. The most probable pore diameter is about 32 nm, and the most probable particle size was ca. 5 μm. The performance and stability of the Ru–La–B/ZrO2 catalyst is superior to that of the Ru–B/ZrO2 due to the promoting effect of La. The slurry comprising zirconia and zinc sulfate is very important for benzene selective hydrogenation over the Ru–La–B/ZrO2 catalysts in order to obtain high yield to cyclohexene. Under the pilot conditions, the performance of the Ru–La–B/ZrO2 catalysts can be improved by changing the pH value of the slurry and by adding zirconia into the slurry.
Keywords: Ru–La–B/ZrO2 amorphous catalyst; Benzene selective hydrogenation; Cyclohexene; Lanthanum;
Catalytically active species in Ni-based catalytic systems for low-temperature methanol synthesis probed by in situ ATR/FTIR in combination with reaction kinetics by Seiichi Ohyama (58-62).
An in situ ATR/FTIR technique was employed to probe the transformation of the nickel precursor in a catalyst composed of Ni(OCOCH3)2 and CH3OK for low-temperature methanol synthesis in a liquid medium. Homogeneous nickel species, Ni(CO)4 and a hydridocarbonylnickel anion ([HNi(CO)3]− and/or [HNi2(CO)6]−) were simultaneously derived from Ni(OCOCH3)2 during the reaction. Reaction kinetics in combination with in situ FTIR observation revealed that the ratio of the reaction rate between the catalysts with different nickel precursors, i.e. Ni(OCOCH3)2/CH3OK and Ni(CO)4/CH3OK, agreed with the ratio of the infrared absorption assigned to the nickel anion. This supports the proposed reaction scheme in which methanol is formed through methyl formate and the nickel anion catalyzes the rate-determining hydrogenation step of methyl formate.
Keywords: Low-temperature methanol synthesis; In situ ATR/FTIR; Nickel precursor; Hydridocarbonylnickel anion; Reaction kinetics;
Increasing olefins by H2 and CH4 addition to the catalytic partial oxidation of n-octane by G.J. Panuccio; L.D. Schmidt (63-73).
The catalytic partial oxidation (CPO) of n-octane over Rh and Pt-coated α-Al2O3 catalysts at approximately 5 ms contact times is examined with H2 and CH4 addition to the reactor feed. The aim is to preferentially oxidize H2 or CH4 and allow more octane to react in the gas phase to form high value chemicals such as ethylene and other olefins. The addition of H2 increases olefin selectivities on both 80 and 45 ppi foams coated with Rh or Pt, and the highest increase in olefin selectivity occurs at H2/O2 = 3/1 on Pt-coated 45 ppi catalysts. In this case, the selectivity to ethylene increases from a maximum of 38 to 51%, and total olefin selectivity increases from 75 to 83% without a decrease in octane conversion. The effect of adding CH4 is heavily dependent on the catalyst metal and average pore size of the support structure. On Pt catalysts and 45 ppi Rh-coated catalysts, the addition of methane can increase olefin selectivities by several percent. However, on 80 ppi Rh-coated foams, adding methane actually suppresses the formation of olefins and increases selectivity to H2 and CO.
Keywords: Catalytic partial oxidation; Olefins; Rhodium; Platinum; Octane; Sacrificial fuel;
The gas phase n-propyl-tert-butyl ether synthesis by Piotr M. Słomkiewicz (74-85).
The kinetics of the synthesis of n-propyl-tert-butyl ether from isobutene and 1-propanol on sulfonated Amberlyst 15 copolymer in gas phase was investigated. The Langmuir–Hinshelwood equations were adjusted to the results of the kinetic experiment using the values of the adsorption equilibrium constants of the reactants from the adsorption measurements separately taken. Also, the equilibrium constants of the synthesis of ether from separate measurements were determined. The presence of both the effect of the maximum rate shift of the synthesis of n-propyl-tert-butyl ether with an increase in 1-propanol partial pressure and the effect of changing the order of the reaction in relation to 1-propanol, from the negative into the zero one with an increase in temperature, was found. The effects were accounted for by the change of the ratios of adsorption equilibrium constants of isobutene and 1-propanol depending on temperature.
Keywords: 1-Propanol; Isobutene; n-Propyl-tert-butyl ether; Langmuir–Hinshelwood kinetics; Amberlyst 15;
Development of TiO2/Ti wire-mesh honeycomb for catalytic combustion of ethyl acetate in air by Kyung Shik Yang; Guido Mul; Jin Seong Choi; Jacob A. Moulijn; Jong Shik Chung (86-93).
Wire-mesh sheets coated with Ti particles were developed by using an electrophoretic deposition (EPD) method. They were thermally treated at various working conditions for enhancing the coating strength. The Ti layer was suitably porous and showed a good adherence to the wire surface, due to partial sintering of Ti particles after thermal treatment at 900 °C. Then additional calcination at 600 °C resulted in the formation of a thin TiO2 layer (∼3 μm) on the outer surface of the Ti layer. After making Pt/TiO2/Ti-coated wire-mesh honeycombs (WMH) successfully, they were applied in catalytic combustion of ethyl acetate in air. The activity was much higher than that of a ceramic honeycomb containing a similar catalyst composition, especially in the high temperature ranges. This is explained by the difference in external mass transfer rate between the two modules. TiO2/Ti-WMH had several additional advantages: (i) the active catalyst platinum could be directly impregnated, since TiO2 could be used as a catalyst support. This reduces the manufacturing process with one-step, viz., support washcoating. (ii) Since there is no additional washcoat, it can be expected that the possibility of catalyst loss during the operation becomes very low. (iii) A rapid thermal response due to the small heat capacity.
Keywords: Wire-mesh; Monolith; Electrophoretic deposition; Catalytic combustion; Honeycomb catalyst module; Ethyl acetate;
Active-iron-promoted hydrodehalogenation of organic halides by Y. Moglie; F. Alonso; C. Vitale; M. Yus; G. Radivoy (94-100).
Under very mild reaction conditions, the active-iron-based reducing system composed of FeCl2·4H2O, an excess of lithium powder and a catalytic amount (5 mol%) of 4,4′-di-tert-butylbiphenyl (DTBB) as electron carrier, efficiently performed the hydrodehalogenation of alkyl and aryl halides in tetrahydrofuran at room temperature. The reaction of a series of alkyl and aryl chlorides, bromides, and iodides with this reducing combination led to the formation of the corresponding products resulting from a halogen/hydrogen exchange. Interestingly, the reducing system was efficient in the hydrodehalogenation of aryl fluorides and polychlorinated aromatics. The use of deuterium oxide instead of water in the iron salt allowed the preparation of the corresponding deuterated products. A reaction mechanism has been proposed on the basis of different experiments.
Keywords: Active-iron; Hydrodehalogenation; Organic halides; Polychlorinated aromatics;
Selective synthesis of di-tert-butylperoxide catalyzed by highly active microporous H-beta zeolite by Suman K. Jana; Masamitsu Nakamura; Tsuyoshi Kugita; Seitaro Namba (101-105).
Liquid phase di-tert-butylperoxide synthesis from the condensation reaction between tert-butyl alcohol and tert-butylhydroperoxide over microporous H-beta zeolites, having Si/Al molar ratios ranging from 11.5 to 120, has been investigated. With increasing Al content or in other words the acidity of H-beta zeolite, the catalytic activity is increased and passes through maxima; however, the selectivity for di-tert-butylperoxide is decreased initially to a small extent and then maintain almost the same level. Among the different Al-containing beta zeolites, the catalyst with a Si/Al molar ratio of 40 shows the best performance in the above condensation reaction. Additionally, when compared with other commonly used heterogeneous acidic microporous zeolites (H-ZSM-5, H-mordenite, H-Y, H-MCM-22) and mesoporous solids (Al–MCM-41, Al:SBA-15) having similar Si/Al ratios but different pore structures, the catalytic activity of the H-beta zeolite in the di-tert-butylperoxide synthesis process is found to be much higher.
Keywords: Di-tert-butylperoxide; tert-Butyl alcohol; tert-Butylhydroperoxide; H-beta zeolite;
Oxidation of cyclooctane over metalloporphyrin-exchanged Al,Si-mesoporous molecular sieves of HMS (MMS) type by L. Matachowski; K. Pamin; J. Połtowicz; E.M. Serwicka; W. Jones; R. Mokaya (106-111).
Me(TMPyP) metalloporphyrin catalysts (Me = Mn, Fe, Co) supported on aluminated MMS (HMS) mesoporous silicas were investigated in the liquid phase oxidation of cyclooctane with molecular oxygen (as air) without the use of sacrificial co-reductant. Catalytic activity was shown to depend on the the metalloporphyrin surface density, the pore size of the support and the nature of the metal centre in Me(TMPyP). Increase in metalloporphyrin loading above a certain optimum value resulted in reduction of the catalyst activity attributed to the lessening of site isolation effect. Cyclooctanone and small amounts of cyclooctanol were the only products of the reaction. The enhanced selectivity to cyclooctanone (over 90%) was assigned to steric effect imposed by the mesoporous silica supports. The supported metalloporphyrin catalyst could be reused without any significant loss of its activity.
Keywords: Metalloporphyrins; Mesoporous molecular sieves; Hydrocarbon oxidation; Cyclooctane;
Corrigendum to: “Structural and catalytic aspects of sol–gel derived copper manganese oxides as low-temperature CO oxidation catalyst” [Appl. Catal. A: Gen. 302 (2006) 257–263]. by M. Krämer; T. Schmidt; K. Stöwe; F. Müller; H. Natter; W.F. Maier (112).