Skeletal isomerization of n-heptane to clean gasoline can be catalyzed by solid acids such as zeolites, sulfated zirconia, heteropoly compounds, and WO3/ZrO2 and their Pt or Pd-modified catalysts (bifunctional catalysts). The catalytic properties of these catalysts for isomerizations of n-butane and n-pentane are generally reviewed. The activation steps of alkane and factors influencing the activity and selectivity are discussed. Our study on the reaction mechanism for the isomerization of n-butane using 13C-n-butane is interpreted. The bimolecular mechanism is the main contributor on solid acid catalysts (sulfated zirconia and Cs2.5H0.5PW12O40). In contrast, the monomolecular mechanism is predominant over the bifunctional catalysts in the presence of H2. The reaction pathways of n-heptane isomerization are presented and the characteristics of this reaction are discussed. Recent reports and our data for the isomerization of n-heptane are summarized and discussed. Pt-Cs2.5H0.5PW12O40/SiO2 and Pd-H4SiW12O40/SiO2 are comparable to Pt-H-β in selectivity to branched heptanes and the latter heteropoly catalyst has superior activity.
Direct DME synthesis from CO2 and H2 was carried out using hybrid catalysts consisting of a methanol synthesis catalyst (CuO-ZnO-Al2O3-Ga2O3-MgO) and a methanol dehydration catalyst (γ-Al2O3 or ZrO2·Al2O3). The effects of the compositions of the two catalysts on methanol + DME yield, DME selectivity and durability of the hybrid catalysts were investigated. The optimum mixing ratio of the methanol synthesis catalyst to the methanol dehydration catalyst in a hybrid catalyst was 50 : 50 wt%. In the DME direct synthesis from CO2 and H2, the methanol + DME yield and the DME selectivity increased with higher temperature. However, after the methanol yield reached the equilibrium, the methanol + DME yield declined with higher temperature. ZrO2·Al2O3 as a methanol dehydration catalyst had a higher DME synthesis activity than γ-Al2O3. A two-layer structure consisting of an upper layer of methanol synthesis catalyst and a lower layer of a mixture of the methanol synthesis catalyst and the methanol dehydration catalyst was the most effective. The hybrid catalyst with the two-layer structure also showed better durability than catalysts with other structures.
Magnetic flux leakage testing (MFLT) is a reliable inspection method for far-side metal loss type flaws. Corrosion products of ferromagnetic substances are generated in wet environments, so may affect the application of MFLT to real tank bottom floors. This study investigated the influence of corrosion products on MFL signals. Rectangular grooves with various depths and widths were cut in test specimens and filled with various ratios of iron oxides as corrosion products. Magnetic flux leakage density distributions from the grooves were measured with a Hall probe. Analytical models for magnetic leakage field from flaws containing corrosion products were also considered using the three-dimensional finite element method. From the experimental and analytical results, the influence of corrosion products on MFL signals in inspections was discussed.
Photochemical and enzymatic synthesis of formic acid was investigated from HCO3− with formate dehydrogenase (FDH) from Saccharomyces cerevisiae and reduced methylviologen (MV2+) produced by the visible light photosensitization of zinc tetrakis(4-methylpyridyl) porphyrin (ZnTMPyP) in the presence of triethanolamine (TEOA) as an electron donating reagent. Irradiation of a solution containing TEOA, ZnTMPyP, MV2+, NaHCO3 and FDH in potassium phosphate buffer, with visible light resulted in formic acid production and HCO3− consumption. The optimum FDH activity was 20 units and the amount of formic acid and the yield of HCO3− to formic acid after 4 h irradiation were estimated to be 50 μmol·dm−3 and 5.0%, respectively.
The association behaviors of asphaltene (heptane insoluble fraction) and maltene (heptane soluble fraction) fractionated from Iranian Light (IL) vacuum residue were investigated by measuring the surface tensions of their solutions in quinoline, 1-methylnaphthalene (1-MN), and toluene. Both asphaltene and maltene showed surface activity in quinoline. On the other hand, the surface tension of asphaltene little changed with concentration in 1-MN or toluene. In most systems, some small discontinuities could be observed on the surface tension-log concentration plots, suggesting that stepwise association of asphaltene and maltene components proceeds with increasing concentration.
Heavy residual products in petroleum refineries are a useful source of hydrocarbons, so are a potential substrate for producing middle distillates by hydrocracking technology to increase the supply of transportation fuels. This study used highly refractory furfural extract of lube oil containing 96.0 vol% aromatics with 4.63 wt% S, and 0.15 wt% N with a pour point of +30°C to produce middle distillates through catalytic hydrothermal cracking. The effect of various parameters such as temperature, hydrogen partial pressure, residence time and amount of catalyst were studied with 250 g feed and 25 g nickel-loaded catalyst of 20 : 80 ratio of silica-alumina (A) and molecular sieves 13X (Z) as cracking site and nickel metal serves as hydrogenation site. The maximum yield of middle distillates was 26.4 wt% at temperature 400°C, pressure 10.0 MPa, initial hydrogen partial pressure 9.0 MPa, and residence time 15 min.
Illegal gas oils, prepared by mixing fuel oils with sulfuric acid, were analyzed by spectrofluorophotometry and gas chromatography mass spectrometry (GCMS). The spectrofluorophotometric studies showed that both the excitation wavelength and emission wavelength at the maximum fluorescent peak of the illegal gas oils were blue-shifted to similar wavelengths to those of gas oils. The illegal gas oils could be discriminated by the contour plots of the three-dimensional fluorescent spectra and the peak shapes of the excitation and emission spectra. The GCMS analysis showed that aromatic compounds were removed from the fuel oil with increasing mixing time with H2SO4. The mixing treatment with H2SO4 could not effectively remove non-condensed polycyclic aromatic compounds such as alkyl benzene and biphenyl from the fuel oil in contrast to the condensed polycyclic aromatic compounds such as naphthalene and phenanthrene. As a result, the fuel oil was transformed to illegal gas oil containing abundant saturated hydrocarbons. Although fuel oil moderately mixed with 95% H2SO4 (1 : 1) for 3 min closely resembled the component of gas oil, the modified fuel oil could be discriminated from gas oil by the peak intensity ratios of the molecular ion of 1,2,4-trimethylbenzene to the ion of pentadecane. Accordingly, spectrofluorophotometry and GCMS analyses were very useful for the discrimination of illegal gas oils prepared by mixing fuel oils with H2SO4.
Miscible displacement experiments were performed to study recovery efficiency by gravity drainage in Asmari fractured cores. We used vertically mounted 0.0381 m diameter fractured and non-fractured cores. Kerosene was used as the oil (displaced fluid) and heptane as the displacing fluid. Effects of the fracture, displacement rate and matrix-fracture mass transfer on the oil recovery were studied. Experimental results showed that for displacement rates below the critical flow rate, a significant amount of the displacing fluid flows from fracture to the matrix and a significant amount of the matrix oil flows from matrix to fracture. Thus, for displacement rates below critical flow rate, miscible injection in fractured porous media could be very efficient.
Determining the feasibility of miscible displacement process to increase oil recovery from Iranian naturally fractured reservoirs is the subject of this study. For that purpose, miscible displacement experiments including liquefied petroleum gas (LPG) injection were carried out under reservoir conditions on composite cores, consisting of reservoir fractured core plugs of the chosen rock type. Results of experimental studies indicated that LPG miscible flooding could maximize oil recovery. In this paper, results of the Iranian fractured core flooding experiments are presented.
A thin palladium membrane can be produced on a stainless steel porous support modified with cerium hydroxide. The membrane with the thickness of 8 μm, prepared by electroless plating, is almost defect-free, and the hydrogen permeation is as high as that with palladium membranes supported on porous ceramics.