排序方式: 共有11条查询结果,搜索用时 31 毫秒
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Ron C. Runnebaum Tarit Nimmanwudipong Ryan R. Limbo David E. Block Bruce C. Gates 《Catalysis Letters》2012,142(1):7-15
Abstract
The conversion of 4-methylanisole, a prototypical bio-oil compound, was catalyzed by Pt/Al2O3, Pt/SiO2-Al2O3, or HY zeolite at 573 K and atmospheric pressure. More than a dozen products were formed with each catalyst, the most abundant being 4-methylphenol, 2,4-dimethylphenol, and 2,4,6-trimethylphenol; toluene was also a major product when the catalyst was supported platinum with H2 as a co-reactant. 4-Methylphenol was the only methylphenol isomer formed in significant yields, which indicates that migration of the methyl group on the aromatic ring is not significant under the selected reaction conditions. The data determine approximate reaction networks including reactions forming 4-methylphenol, 2,4-dimethylphenol, and toluene as primary products. The kinetically significant reaction classes were transalkylation, observed with all three catalysts, and hydrogenolysis (including hydrodeoxygenation) and hydrogenation, observed only with the platinum-containing catalysts operating in the presence of H2. Data such as those reported here provide a starting point for predicting the conversion of whole bio-oils for removal of oxygen and upgrading of fuel properties. 相似文献4.
Sirima Somboonthanakij Okorn Mekasuwandumrong Joongjai Panpranot Tarit Nimmanwudtipong Reto Strobel Sotiris E. Pratsinis Piyasan Praserthdam 《Catalysis Letters》2007,119(3-4):346-352
In this study, Pd/SiO2 catalysts with 0.5–10 wt.% Pd loadings were prepared by one-step flame spray pyrolysis (FSP) and characterized by N2 physisorption, X-ray diffraction (XRD), transmission electron microscopy (TEM), CO chemisorption, and X-ray photoelectron
spectroscopy (XPS). The average cluster/particles size of Pd as revealed by TEM were ca. 0.5–3 nm. The turnover frequencies (TOFs) of the flame-made catalysts decreased from 66.2 to 4.3 per s as Pd loading increased
from 0.5 to 10 wt.%, suggesting that the catalytic activity was dependent on Pd particle/cluster size. However, there were
no appreciable influences on 1-heptene selectivity. The flame-made Pd/SiO2 showed better properties than the conventional prepared catalysts. Their advantages are not only the presence of large pores
that facilitates diffusion of the reactants and products, but also the high-catalytic activity of as-synthesized catalysts
so that further pretreatment is not necessary. 相似文献
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Arsenic and other elements in hair, nails, and skin-scales of arsenic victims in West Bengal, India 总被引:3,自引:0,他引:3
Samanta G Sharma R Roychowdhury T Chakraborti D 《The Science of the total environment》2004,326(1-3):33-47
For the first time, biological tissues (hair, nails, and skin-scales) of arsenic victims from an arsenic affected area of West Bengal (WB), India were analyzed for trace elements. Analysis was carried out by inductively coupled plasma-mass spectrometry (ICP-MS) for 10 elements (As, Se, Hg, Zn, Pb, Ni, Cd, Mn, Cu, and Fe). A microwave digester was used for digestion of the tissue samples. To validate the method, certified reference materials--human hair (GBW 07601) and bovine muscle (CRM 8414)--were analyzed for all elements. The W test was used to study the normal/log normal distribution for each element in the tissue samples. For hair (n=44) and nails (n=33), all elements show log-normal distribution. For skin-scale samples (n=11), data are not sufficient to provide the information about the trend. Geometric mean, standard error, and range for each element were presented and compared with literature values for other populations. This study reveals the higher levels of toxic elements As, Mn, Pb, and Ni in the tissue samples compared with available values in the literature. The elevated levels of these toxic metals in the tissues may be due to exposure of these elements through drinking water and food. The correlations of Mn and Ni with other essential elements, e.g. Fe, Cu, Zn, suggest that Mn and Ni may substitute for those elements in hair, nails, and skin-scales. However, correlation represents the relation between two elements only and does not take into consideration of the presence of other elements. Principle component analysis was applied to explain the behavior among the elements present in hair and nails. This study reveals that in the arsenic-affected areas of WB, the concentrations of other toxic elements in drinking water and foodstuff should be monitored to evaluate the arsenic poisoning. 相似文献
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Tarit Nimmanwudipong Ron C. Runnebaum Susan E. Ebeler David E. Block Bruce C. Gates 《Catalysis Letters》2012,142(2):151-160
Abstract
The conversion of eugenol (4-allyl-2-methoxyphenol), a compound derived from the lignin in woody biomass, was catalyzed by HY zeolite at 573 K and atmospheric pressure. The main products were isoeugenol and guaiacol, formed by isomerization and by deallylation, respectively. Substituted guaiacols with saturated side-chains (4-methylguaiacol, 4-ethylguaiacol, and 4-propylguaiacol) were also formed, by hydrogen transfer and alkylation reactions. The pseudo-first-order rate constant for the overall disappearance of eugenol was found to be 12.4 L (g of catalyst)/h. When the catalyst was Pt/γ-Al2O3 used in the presence of H2, significant hydrogenation of the propenyl side-chain took place, accompanied by isomerization, and hydrodeoxygenation. Under similar operating conditions, the reaction catalyzed by Pt/γ-Al2O3 in the presence of H2 gave a higher eugenol conversion (X = 0.70) than the reaction catalyzed by HY zeolite (X = 0.11), primarily because of the dominant hydrogenation observed with the former catalyst. In the absence of H2 as a co-reactant, the acidic γ-Al2O3 support in Pt/γ-Al2O3 evidently catalyzed all the classes of reactions catalyzed by HY zeolite. 相似文献8.
Catalytic Reactions of Guaiacol: Reaction Network and Evidence of Oxygen Removal in Reactions with Hydrogen 总被引:1,自引:0,他引:1
Tarit Nimmanwudipong Ron C. Runnebaum David E. Block Bruce C. Gates 《Catalysis Letters》2011,141(6):779-783
Abstract
The conversion of guaiacol, a prototypical compound representative of lignin-derived pyrolysis bio-oils, was catalyzed by Pt/Al2O3 in the presence of H2 at 573 K. The conversion took place with a high selectivity for aromatic carbon–oxygen bond cleavage relative to the accompanying methyl group transfer reactions. This oxygen removal was not observed in the absence of H2 as a co-reactant. Products that were formed by methyl-group transfer match those produced in the conversion catalyzed by zeolite HY, which was not active for oxygen removal reactions. 相似文献9.
Tarit Nimmanwudipong Ron C. Runnebaum Kevin Tay David E. Block Bruce C. Gates 《Catalysis Letters》2011,141(8):1072-1078
Abstract
The conversion of cyclohexanone, often identified as an intermediate in the conversion of lignin-derived compounds, was catalyzed by Pt/γ-Al2O3 in the presence of H2 at 573 K. Dehydrogenation was a kinetically significant reaction, indicated by a high selectivity for phenol. Oxygen-removal reactions are indicated by products including benzene, cyclohexene, and cyclohexene. Bimolecular reactions involving cyclohexanone and/or products of its conversion led to the formation of bicyclic C12 compounds, with 2-cyclohexylcyclohexan-1-one and 2-phenylphenol being the most abundant. Increasing the H2 partial pressure led to increased oxygen removal and faster formation of monocyclic and bicyclic hydrocarbons. At temperatures higher than 573 K, dehydrogenation became the dominant reaction class. 相似文献10.
Ron C. Runnebaum Tarit Nimmanwudipong David E. Block Bruce C. Gates 《Catalysis Letters》2011,141(6):817-820