The template carbonization technique has been developed for synthesizing novel carbon materials. This technique utilizes inorganic substances with openings or pores which are well defined at the nanometer level. This paper describes recent experiments utilizing the nanospace in zeolites for the synthesis of novel porous carbon materials. The effects of zeolite type, carbon precursor, and experimental conditions on the structure and properties of the carbon are described. In particular, focus is put on the preparation of carbons with long-range structural regularity. Unique characteristics of the resultant carbons are discussed in detail.

View full abstract

Field measurement of volatile petroleum hydrocarbon in soil usually precedes the submission of samples for more rigorous analysis in the laboratory. Hand-held photoionization detectors (HHPIDs) are commonly used for field measurements, although there is growing concern about their reliability under field conditions. This concern is accentuated by an increasing tendency to rely on such field measurements alone. Three different case studies, where commercial HHPID field data and the corresponding laboratory data have been made available to us, were critically examined. Disturbingly, there is little correlation between the HHPID readings obtained in the field and the corresponding measurements in the laboratory, with a large number of false positives being recorded. Also, the measurements obtained from the HHPID were invariably much higher than the corresponding laboratory measurements. In an attempt to identify some of the underlying problems that could influence the response of HHPIDs in the field, a series of laboratory experiments was conducted under controlled conditions in order to monitor, by Gas Chromatography with Mass Selective Detection (GCMSD), the linearity and accuracy of HHPID response to spiked BTEX levels (benzene, toluene, ethyl benzene and xylenes) in a variety of matrices under varying moisture content conditions (namely; in pure water, dry sandy loam, dry silt and moist silt). These studies reveal that, under controlled conditions, the HHPID response is linear over a spiked BTEX range of approximately 0-500mg/kg for a variety of matrices. However, the sensitivity (as measured by the slope of the response line) depends very much on the specific combination of conditions, such as the matrix and moisture content. These results suggest that for linearity of response to be established in the field, corrections must be made for variations in moisture content and soil type, and perhaps for other parameters. The slope of the response line could then be used as an "instrument factor" to quantify the level of contaminant from the HHPID response. Several other factors that could influence HHPID readings were also investigated including the HHPID response over time and the effect on response of component interactions in contaminant mixtures. The former investigation shows that there is no statistical difference between HHPID measurements taken up to 1.5h apart from identical spiked samples. The latter study suggests that multiple components in a sample may affect the HHPID response.

View full abstract

Hydrocracking of Arabian heavy vacuum residue was investigated over alumina-supported nickel molybdenum catalyst (Ni-Mo/Al₂O₃), unsupported nickel molybdenum catalyst (Ni-Mo) and unsupported molybdenum catalyst (Mo), under hydrogen at 8MPa (cold charge)and at 410°C, using a swing micro-autoclave of 140ml inner volume. Using Ni-Mo/Al₂O₃, asphaltene (Asp.) was cracked almost completely to yield hexane soluble fraction (HS), increasing with reaction time, to a maximum of 60% at reaction time of 4h. The remaining HS in the reaction had a higher H/C value, much lower sulfur concentration and lower nitrogen concentration compared to the HS in the feedstock. However, ca. 30% of HS remained after 4h reaction, suggesting that the fraction stable against thermal cracking was concentrated. Ni-Mo showed lower activity for Asp, cracking and lower yield of distillable fraction (VD) than Ni-Mo/Al₂O₃. Fresh Ni-Mo showed higher activity for 1-methylnaphthalene hydrogenation than fresh Ni-Mo/Al₂O₃, but spent Ni-Mo showed lower hydrogenation activity than Ni-Mo/Al₂O₃ suggesting that Ni-Mo loses hydrogenation activity fairly rapidly in the above reaction. Using Mo catalyst, comparable yield of VD and higher yield of Asp. were obtained compared to using Ni-Mo/Al₂O₃, and a similar amount of tetrahydrofuran insoluble fraction compared to the thermal reaction.

View full abstract

The catalytic activities of thirteen types of single component metal oxides were measured for the selective catalytic reduction (SCR) of NO with ethene in excess oxygen and related reactions to elucidate the characteristic features of catalyst activity. The related reactions were the oxidation of NO₂ with O₂, the oxidation of C₂H₄ with O₂, the reduction of NO₂ with C₂H₄ in the absence of O₂, and the reduction of NO with C₂H₄ in the absence of O₂. Alumina exhibited the highest activity for SCR, followed by ZrO₂, SNO₂, MgO, CaO, Y₂O₃, and TiO₂; WO₃, Co₃O₄, CuO, Fe₂O₃, ZnO, and SiO₂ showed little activity. The active catalysts including alumina had the characteristic features of high activities for both the oxidation of NO to NO₂ and the reduction of NO₂ with C₂H₄ to form N₂, as well as low activity for the oxidation of C₂H₄ with O₂. Although Co₃O₄, CuO, and Fe₂O₃ showed high activities for the oxidation of NO to NO₂, they were also highly active for the oxidation of C₂H₄ with O₂. Therefore, C₂H₄ was consumed without reduction of NO over these catalysts. The characteristic features for the active catalysts also support the reaction scheme that the SCR proceeds by the successive reactions of the oxidation of NO to NO₂ and the reduction of NO₂ with C₂H₄ to form N₂.

View full abstract

The hydrodesulfurization reaction with two kinds of atmospheric residues was carried out over three kinds of catalysts with different mean pore diameters to obtain catalysts with different deposited amounts of coke and metal on their surfaces. Elemental analysis and physical properties were carried out to elucidate the effects of coke and metal depositions on catalyst deactivation at an early stage of the reaction.
Coke density (ρ_c) and metal density (ρ_m) calculated from the mean pore diameter determined by mercury porosimetry were independent of the kind of catalyst used, and operation time, were 1.25 and 2.50g/cm³, respectively.
These results indicate that the effect on the decrease in pore volume of coke deposition was almost double to that of the metal deposition. Furthermore, accumulative thicknesses of coke (λ_c) and metal (λ_m) on the pore of the catalyst were calculated from decrease in pore diameter, based on the assumption that the pore was simply composed of uniform cylinder. Accumulative thicknesses were different with different kinds of catalyst used and they decreased more, the smaller the surface areas. The initial deactivation constant (α₁) was directly related to the accumulative thickness of coke and metal.
Moreover, it was found that the effect of the coke deposition accumulative thickness on reduction of pore diameter was almost triple to that of metal deposition. The catalyst deactivation on the SOR (start of run) in the hydrodesulfurization reaction was mainly responsible for the deposition of coke on the catalyst.

View full abstract

Measurements of remaining hydrodesulfurization activity and physical properties of 5 catalysts with different coke and metal contents after using them year operation in commercial hydrodesulfurization operation were carried out to elucidate the interactive effect of coke and metal depositions on catalyst deactivation. The properties of the deposited coke on the used catalysts were also examined. Hydrodesulfurization of an atmospheric residue was performed over a new catalyst in the same manner as used one for of the coke properties.
The physical properties, such as surface area, pore volume and mean pore diameter, and the remaining activity were correlated with the volume of deposits (coke and metal) calculated from the specific volume of coke and metal.
Since the C/H ratio of deposited coke was directly proportional to the coke content, it was considered that the coke was formed from the same coke precursor that had gradually condensed and/or dehydrogenated. The coke content on the catalyst decreased with the content of the metal. At the same time, the decreasing in the aliphatic hydrocarbons in the coke was faster than that in the aromatic hydrocarbons. The remained catalytic activity of the commercially used catalysts decreased linearly with the content of the deposits.
From these results, it was considered that the removal of coke with the deposition of metal had partly contributed the decreased catalyst deactivation by coke deposition during the MOR after fast deactivation during the SOR. The depositions of coke and metal on the hydrodesulfurization catalyst were mutually interacted to affect the catalyst deactivation.

View full abstract

Catalytic performance of nickel-loaded zeolite-based supports for CO₂ reforming of methane was investigated. Among the three zeolites (H-Y, H-mordenite, and Na-mordenite), H-mordenite was the best support for the reaction, probably due to its thermal stability. The initial activity of Ni/H-mordenite (Ni/HM) was higher than that of conventional Ni/alumina catalyst (Ni/Al₂O₃), whereas deactivation of the former was slightly faster. A physical mixture of alumina and zeolite was a more effective support than zeolite. The resulting Ni/H-mordenite-alumina catalyst (Ni/HM-Al₂O₃) showed the highest performance among the catalysts tested. Under the conditions of atmospheric pressure of CO₂/CH₄/He stream (20/20/40ml/min)at 750°C, the initial CO₂ conversion was 95% and this value was maintained for more than 20h. The catalytic performance of Ni/HM-Al₂O₃ was higher than that of Ni/Al₂O₃.

View full abstract

The synthesis of 2-oxazolidinone from β-amino alcohol by chemical fixation of carbon dioxide under supercritical conditions using N, N'-dicyclohexylcarbodiimide (DCC) was developed. Even though in non-solvent conditions, 2-oxazolidinone was synthesized with a maximum yield of 96.7% at the critical pressure.

View full abstract

A microbial fungus, Cunninghamella elegans var. echinulata, oxidized not only benzothiophene but also methyl-, ethyl-, and diethyl-benzothiophene to give sulfoxide compounds, and some of them could not be converted by previous reported biodesulfurizing bacteria.

View full abstract

In order to clarify the effect of the structure of liquid hydrocarbons and cetane improvers on the ignition improvement of LPG, the ignition qualities of LPG with liquid hydrocarbons and cetane improvers were investigated. Regarding the hydrocarbons of same carbon number, the straightchained paraffin showed a good ignition quality. A cetane improver that releases a long straightchained alkyl radical and many radicals had better ignition improvement.

View full abstract