Characterization of coke on equilibrium, fluid catalytic cracking (FCC) catalysts contaminated with metals was investigated
using temperature-programmed oxidation (TPO). TPO spectra of spent equilibrium catalysts from cracking of sour imported heavy
gas oil (SIHGO) were deconvoluted into four peaks (Peak K, L, M and N). The four peaks were assigned to different types of
coke on the catalyst. Peak L in the TPO spectrum was assigned to the 'contaminant' coke in the vicinity of metals. The amount
of contaminant coke (Peak L) correlates with metal-contaminant concentration. The size of Peak L which is related to amount
of contaminant coke decreased significantly for the spent highly contaminated catalyst pretreated with hydrogen and methane
prior to cracking reactions as compared to the non-pretreated catalysts. Since both hydrogen and methane pretreatment can
reduce oxidation state of the vanadium that present at high concentrations on the equilibrium catalysts the decrease in the
amount of contaminant-coke represented by Peak L was explained by the reduction of the oxidation state of vanadium. Less contaminant
coke was produced after the equilibrium catalysts were pretreated using hydrogen and methane gases since reduced vanadium
has lower dehydrogenation activity compared to oxidized vanadium.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
Tartaric acid is mainly used in food, pharmaceuticals and cosmetics industries. In this study, the waste samples, which contain
tartaric acid, from the wastes of wine and grape juice industries were characterized by using TG, DSC, FTIR and XRD techniques.
HPLC was used to determine tartaric acid content of samples. The decomposition temperatures of waste samples were found to
be relatively higher compared with that of pure tartaric acid. This difference in decomposition temperatures was attributed
to the presence of potassium tartrate since high potassium content was detected with ICP-AES. 相似文献
Type II photoinitiated self‐condensing vinyl polymerization for the preparation of hyperbranched polymers is explored using 2‐hydroxyethyl methacrylate (HEMA) or 2‐(dimethylamino)ethyl methacrylate (DMAEMA), and methyl methacrylate as hydrogen donating inimers and comonomer, respectively, in the presence of benzophenone and camphorquinone under UV and visible light. Upon irradiation at the corresponding wavelength, the excited photoinitiator abstracts hydrogen from HEMA or DMAEMA leading to the formation of initiating radicals. Depending on the concentration of inimers, type of the photoinitiator, and irradiation time, hyperbranched polymers with different branching densities and cross‐linked polymers are formed.
The reliable generation of quasi-homogeneous autoignition inside a combustor fed by a continuous air flow would represent a milestone in realizing pressure gain combustion in gas turbines. In this work, the ignition distribution inside a stratified fuel–air mixture is analyzed. The ability of precise and reproducible injection of a desired fuel profile inside a convecting air flow is verified by applying tunable diode laser absorption spectroscopy in non-reacting measurements. High-speed, static pressure sensors and ionization probes allow for simultaneous detection of the flame and pressure rise at several axial positions in reactive measurements with dimethyl ether as fuel. A second, exchangeable combustion tube enables optical observation of OH* intensity in combination with pressure measurements. Experiments with three arbitrary fuel profiles show a set of ignition distributions that vary in shape, homogeneity, and the number of simultaneous autoignition events. Although the measurements show notable variation, a significant and reproducible influence of the fuel injection on the ignition distribution is observed. Results show that uniform autoignition leads to a coupling of the reaction front with the pressure rise and, therefore, induces a greater aerodynamic constraint than non-uniform ignition distributions, which are dominated by propagating deflagration fronts. 相似文献
Using data envelopment analysis (DEA) in conjunction with stochastic frontier analysis (SFA), the aim of this study was to measure the relative efficiency of quality management (QM) practices in Turkish public and private universities. Based on the extant literature, a set of nine critical QM factors and seven performance indicators for Turkish universities were identified as input and output variables, respectively. SFA confirmed the existence of significant relationships between QM factors and performance indicators. DEA findings indicated that private universities with higher levels of QM efficiency on stakeholder-focus indicators achieved better performance in terms of fulfilling the expectations of their stakeholders. In contrast, public universities were more successful in managing QM practices for a superior teaching and research performance. Finally, after eliminating the managerial discrepancies, no significant structural efficiency difference was found between these two groups of universities through stakeholder-focus model, though some significant variation was noted in both factor-efficiency and total-efficiency models. As for total-efficiency model, we may infer that the structural differences found in favour of public universities for factor-efficiencies are counterbalanced by private universities which tend to focus more on their stakeholders in managing QM applications. 相似文献
We determine the optimal investment strategy in a Black–Scholes financial market to minimize the so-called probability of drawdown, namely, the probability that the value of an investment portfolio reaches some fixed proportion of its maximum value to date. We assume that the portfolio is subject to a payout that is a deterministic function of its value, as might be the case for an endowment fund paying at a specified rate, for example, at a constant rate or at a rate that is proportional to the fund’s value. 相似文献
This study aimed the characterization of the films casted from the aqueous mixtures of the pH induced complexes between silk
fibroin (SF) and hyaluronic acid (HA). The insoluble and transparent films were subjected to scanning electron microscopy
(SEM) analyses to show the morphological changes. Thermal analysis of complex films was determined by a differential scanning
calorimeter (DSC). The changes in the crystalline state were monitored by X-ray diffractometer (XRD) and Fourier transform
infrared spectroscopy (FTIR). It was shown that the complexation between HA and SF was dominantly induced by pH. It was shown
that the complex films comprised mixtures of crystalline and non-crystalline regions. 相似文献