共查询到20条相似文献,搜索用时 15 毫秒
1.
M. A. Ryaskentseva 《Russian Chemical Bulletin》1996,45(8):2015-2017
The 2 % Re/sibunite catalyst is more active than 2 % Re/-Al2O3 and 2 % Re/-Al2O3 catalysts in the dehydrogenation of cyclohexane into benzene (T = 350 °C,w = 0.5 h–1). The substitution of NH4ReO4 by HReO4 in the preparation of the catalyst enhances its activity by a factor of 1.3. Treatment with HNO3 or oxalic acid increases the selectivity by a factor of 1.2 and 1.35, respectively, the overall conversion of cyclohexane being 32–40 %.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 2119–2121, August, 1996. 相似文献
2.
M. O. Kazakov A. V. Lavrenov I. G. Danilova O. B. Belskaya V. K. Duplyakin 《Kinetics and Catalysis》2011,52(4):573-578
The acidic and hydrogenating of Pt/SO42−-ZrO2-Al2O3 samples containing from 18.8 to 67.8 wt % Al2O3 as a support constituent were studied by the IR spectroscopy of adsorbed CO and pyridine, and the model reactions of n-heptane and cyclohexane isomerization on these catalysts were examined. The total catalyst activity in the conversion of
n-heptane decreased with the concentration of Al2O3; this manifested itself in an increase in the temperature of 50% n-heptane conversion from 112 to 266°C and in an increase in the selectivity of isomerization to 94.2%. In this case, the maximum
yield of isoheptanes was 47.1 wt %, which was reached on a sample whose support contained 67.8 wt % Al2O3. A maximum yield (69.6 wt %) and selectivity (93.7%) for methylcyclopentane formation from cyclohexane were also reached
on the above catalyst sample. This can be explained by lower concentrations of Lewis and Br?nsted acid sites in the Pt/SO42−-ZrO2-Al2O3 system, as compared with those in Pt/SO42−-ZrO2. The experimental results allowed us to make a preliminary conclusion that the Pt/SO42−-ZrO2-Al2O3 catalyst whose support contains 67.8 wt % Al2O3 is promising for use in the selective hydroisomerization of benzene-containing gasoline fractions in the thermodynamically
favorable process temperature range of 250–300°C. 相似文献
3.
Xiaohuin Liu Yong Guo Wenjie Xu Yanqin Wang Xueqing Gong Yanglong Guo Yun Guo Guanzhong Lu 《Kinetics and Catalysis》2011,52(6):817-822
The influence of the alumina support on the catalytic activity of Pt/Al2O3 catalysts in aqueous phase reforming of ethylene glycol to hydrogen was studied. The catalysts were prepared by impregnation
of γ-, δ-, and α-alumina with H2PtCl6. The highest rate of hydrogen production (452 μmol min−1 g−1) obtained with the Pt/α-Al2O3 catalyst can be related to the highest extent of dispersion of Pt on α-Al2O3. XPS, TEM-EDX and TPR-H2 measurements showed the absence of chloride-containing surface complexes in the Pt/α-Al2O3 catalyst. However, chloride-containing entities were found on the surface of Pt/γ-Al2O3 and Pr/δ-Al2O3 catalysts. When chloride ions are removed chlorinated Pt species facilitate the sintering of Pt crystallites and in this
way affect the extent of Pt dispersion. Moreover, depending upon the particular crystalline form, alumina atoms have different
coordination and alumina surfaces contain varying amounts of OH groups of different nature which affect the interaction between
Pt and the support. 相似文献
4.
Jifei Jia Liwu Lin Jianyi Shen Zhusheng Xu Tao Zhang Dongbai Liang Yi Chen 《中国科学B辑(英文版)》1998,41(6):606-615
CO adsorption microcalorimetry was employed in the study of γ-Al2O3-supported Pt, Pt-Sn and Pt-Fe catalysts. The results indicated that the initial differential heat of CO adsorption of the
Pt/γ-Al2O3 catalyst was 125 kJ/mol. As CO coverage increased, the differential heat of adsorption decreased. At higher coverages, the
differential heat of adsorption decreased significantly. 60% of the differential heat of CO adsorption on the Pt/γ-N2O3 catalyst was higher than 100 kJ/mol. No significant effect on the initial differential heat was found after adding Sn and
Fe to the Pt/γ-Al2O3 catalyst. The amount of strong CO adsorption sites decreased, while the portion of CO adsorption sites with differential
heat of 60–110 kJ/mol increased after increasing the Sn or Fe content. This indicates that the surface adsorption energy was
changed by adding Sn or Fe to Pt/γ-N2O3. The distribution of differential heat of CO adsorption on the Pt-Sn(C)/γ-Al2O3 catalyst was broad and homogeneous. Comparison of the dehydrogenation performance of C4 alkanes with the number of CO adsorption sites with differential heat of 60–110 kJ/mol showed a good correlation. These results
indicate that the surface Pt centers with differential heats of 60–110 kJ/mol for CO adsorption possess superior activity
for the dehydrogenation of alkanes.
Project supported by FORD and the National Natural Science Foundation of China (Grant No. 09412302) and the Transcentury Training
Program Foundation for the Talents by The State Education Commission of China. 相似文献
5.
用酸中和法制备了活性γ-Al2O3, 并在其表面负载SO3得到固体酸催化剂SO3/γ-Al2O3, 用XRD, TG-DTA, FT-IR,NMR, NH3-TPD等对其进行了结构和酸性研究. 结果表明: 在SO3/γ-Al2O3的制备过程中形成少量的Al2(SO4)3, 同时SO3与γ-Al2O3表面上的羟基反应, 形成强的Brönsted酸位, 根据1H/27Al 双共振(TRAPDOR)MAS NMR与FT-IR实验结果提出了Brönsted酸结构模型. SO3/γ-Al2O3表面存在两种不同强度的酸中心, 其酸强度大于分子筛HZSM-5, 但弱于传统的固体超强酸 /γ-Al2O3. 相似文献
6.
I. P. S. Kapoor P. Srivastava G. Singh 《Journal of Thermal Analysis and Calorimetry》2008,92(2):553-557
Polyaniline/α-Al2O3 (PANI/α-Al2O3) composites were synthesized by in situ polymerization through ammonium persulfate ((NH4)2S2O8, APS) oxidized aniline using HCl as dopant. XRD and FTIR were used to characterize the PANI/α-Al2O3 composites. The thermal stabilities and glass transition temperature (T
g) of PANI/α-Al2O3 composites were tested using thermogravimetric (TG) method and modulated differential scanning calorimetry (MDSC) technique.
The results of TG showed that the thermal stability of PANI/α-Al2O3 composite increased and then decreased with the increase in α-Al2O3 content. The derivative thermogravimetry (DTG) curves showed one step degradation of PANI when the α-Al2O3 content was lower than 52.5 mass%, and exhibited two steps degradation when the α-Al2O3 content was higher than 63.6 mass%. The MDSC curves showed that the T
g of PANI/α-Al2O3 composites increased and then decreased with the augment of α-Al2O3 for the interaction between PANI chains and the surface of α-Al2O3. 相似文献
7.
0.5%Pt-K/γ-Al2O3 catalysts for the synthesis of o-phenylphenol(OPP) from o-cyclohexenyl-cyclohexanone (dimer) dehydrogenation were prepared by means of a two subsequent impregnation method. The effects of catalyst preparation parameters, such as K promoters, calcination, and reduction conditions, were investigated. The results showed that the addition of K2SO4 to Pt/γ-Al2O3 catalyst notably promoted the selectivity of OPP, and its optimum content was found to be 6% in mass fraction. The higher activity was obtained when Pt/γ-Al2O3 catalyst was calcined in nitrogen atmosphere at 400--500 ℃ and then reduced at the same temperature for 3 h in hydrogen atmosphere. The conversion of the dimer and the selectivity of OPP were always above 99% and 90%, respectively, over 0.5%Pt-6% K2SO4/γ-Al2O3 catalyst during the pilot scale test of 8000 h. 相似文献
8.
A. E. Goncharov A. A. Politov N. A. Pankrushina O. I. Lomovskii 《Chemistry of Natural Compounds》2006,42(3):336-339
Extracts of Aconitum septentrionale Koelle roots obtained using chloroform, isopropanol, and ethanol were purified using chloroform and basic γ-Al2O3. Ballast materials were selectively adsorbed by γ-Al2O3, increasing the mass fraction of lappaconitine in the extract. The ethanol extract was purified most. The degree of lappaconitine
extraction by chloroform was unaffected by the presence of γ-Al2O3. However, the mass fraction in the extract and lappaconitine extraction from Aconitum septentrionale were increased more than twice.
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Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 274–276, May–June, 2006. 相似文献
9.
N. B. Shitova V. A. Drozdov P. E. Kolosov M. D. Smolikov 《Reaction Kinetics and Catalysis Letters》2000,41(5):720-728
The formation of Pt/γ-Al2O3 and Pt/C catalysts from platinum carbonyl clusters H2[Pt3(CO)6]n (n = 2, 5) is studied. The strength of interaction between clusters (strong Lewis bases) and the support and the state of platinum
in catalysts are governed by the acceptor strength of the support. The formation of a stable platinum compound with a surface
of γ-Al2O3 (strong Lewis acid) is shown for a Pt/γ-Al2O3 catalyst by the method of radial distribution functions. In a Pt/C catalyst containing the same amount of Pt supported on
a carbon material known to be a weaker acceptor, metallic platinum is formed along with surface-bonded platinum. Proceeding
from the existence of the active phase of catalysts in the form of a surface platinum complex and platinum crystallites, the
properties of catalysts are discussed in the complete oxidation of methane and the dehydrogenation of cyclohexane, as well
as the high dispersity of platinum and its thermal stability 相似文献
10.
The catalytic properties of supported mono- and bimetallic catalysts of the Tc/support, M/support, and M-Tc/support types
(M=Pt, Pd, Rh, Ru, Ni, Re, Co; supports are γ-Al2O3, MgO, SiO2) were investigated in the acetone hydrogenation. The main products of this reaction are isopropyl alcohol and propane. The
catalytic activity in the acetone hydrogenation of the metals studied decreases in the consequence Pt>Tc≈Rh>Pd>Ru >Ni≈Re>Co
(with γ-Al2O3 as the support). The influence of support nature on the catalytic activity was investigated for the Rh−Tc system as an example.
A nonadditive increase in the catalytic activity of Rh−Tc/γ-Al2O3 in comparison with monometallic catalysts was found. The state of the surface of the catalysts was characterized by the UV-VIS
diffuse reflectance spectra.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 414–417, March, 1998. 相似文献
11.
In the reaction of catalytic oxidation of CH4, CO2 with O2 to synthesis gas, carbon-deposition is an important factor for deactivation. By adding different oxides to Ni/Al2O3 catalyst, its resistance to carbon-deposition was improved. The experimental results indicate that the order of resistance
to carbon-deposition is as follows: Ni/CaO-Al2O3>Ni/MgO-Al2O3>Ni/ TiO2-Al2O3 > Ni/CeO2-Al2O3>Ni/La2O3-Al2O3>Ni/Y2O3-Al2O3>Ni/Fe2O3-Al2O3>Ni/Al2O3. The catalysts were characterized by CO2-TPD, O2-TPD and XPS methods. Here the relation between the order of resistance to carbon-deposition and performance of catalyst is
discussed. 相似文献
12.
Guoyi Bai Chenfang Zhang Yuecheng Zhang Haijun Yu Fei He Huisen Ning Ligong Chen 《Reaction Kinetics and Catalysis Letters》2007,90(2):373-380
The racemization of R-(-)-2-amino-1-butanol in a reaction using Co/γ-Al2O3 catalysts and catalysts modified by Mg or Ca was investigated in this paper. Complete racemization was achieved with a yield
of over 83% at using the Mg modified Co/γ-Al2O3 catalyst under optimized reaction conditions of 170°C and 2.5 MPa of H2. The catalysts were thoroughly characterized by XRD, XPS, TPR, SEM and TEM. The addition of Mg and Ca may be advantageous
for dispersing and stabilizing the active species of the Co/γ-Al2O3 catalyst, protecting from sintering, significantly improving its catalytic activity and stability. 相似文献
13.
M. A. Ryashentseva 《Chemistry of Heterocyclic Compounds》2006,42(8):1018-1020
In the presence of Pd-and Cr-containing catalysts applied to γ-Al2O3 or sibunite 4,5,6,7-tetrahydroindole is converted into indole. Indole was obtained in quantitative yield on sulfided 0.15–0.5%
Pd/γ-Al2O3 catalyst at 360°C and on catalysts containing 5% Cr2O3, 5% La2O3 (or 5% polirit), 1% K2O/89% γ-Al2O3 at 475–480°C.
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Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1176–1178, August, 2006. 相似文献
14.
A. T. Teleshev V. V. Morozova E. E. Nifant'ev A. V. Kucherov 《Russian Chemical Bulletin》1998,47(10):1980-1982
Complete transligation of (AcO)4Rh2 with 4-ethyl-2,6,7-trioxa-1-phosphabicyclo[2.2.2]octane was conducted in the solid phase on λ-Al2O3. The reduction of Rh11 to RhI on λ-Al2O3 at 130°C under the actionof the above-mentioned bicyclic phosphite is accompanied by the oxidation of the acetate anion to
the acetoxyl radical. The oxidation products were detected by IR and ESR spectroscopy. 2,6-Di-tert-butyl-4-methylphenol was used as a “spin trap” to identify stable secondary radical cations.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2036–2038, October, 1998. 相似文献
15.
Luděk Kalu?a Miroslav Zdra?il Zdeněk Vít 《Reaction Kinetics and Catalysis Letters》2009,97(2):307-313
NiO-MoO3/γ-Al2O3 catalysts were prepared by the reaction of γ-Al2O3 extrudates with an aqueous slurry of MoO3, followed by the reaction of the MoO3/γ-Al2O3 catalyst with an aqueous slurry of NiO, Ni(OH)2, NiCO3·2Ni(OH)2·xH2O, or 2NiCO3·3Ni(OH)2·4H2O and by subsequent drying. The NiO deposition was examined with electron probe microanalysis. The deposited Ni efficiently
increased the activity in benzothiophene hydrodesulfurization. 相似文献
16.
Moo-Jin Kim Soo-Hyun Chang Jung-Sik Choi Wha-Seung Ahn 《Reaction Kinetics and Catalysis Letters》2004,82(1):27-32
Partial oxidation of n-heptane to syngas at 400–450°C was investigated over Rh and Rh-Ni based catalysts. The Rh/-Al2O3 catalyst exhibited much better catalytic activity than the Rh-Ni/-Al2O3 catalyst. A combination of the Rh-based catalyst with the WGS reaction catalyst (Fe3O4—Cr2O3) increases the hydrogen selectivity but has no distinct effect on shifting the balance of the partial oxidation of n-heptane.This revised version was published online in December 2005 with corrections to the Cover Date. 相似文献
17.
El-Sayed A. El-Sharkawy 《Monatshefte für Chemie / Chemical Monthly》2006,137(12):1487-1498
Summary. The textural characteristics, including surface area, mean pore diameters, and total pore volume of Cr2O3–CuO/Al2O3 solid catalysts were determined from the low temperature adsorption of N2 at 77 K. The structural properties were investigated using XRD. The surface acidity of calcined samples was determined using
two comparable methods, including the non-aqueous titration of acidic groups with n-butylamine and dehydration/dehydrogenation activity of cyclohexanol.
XRD patterns assigned a crystalline CuO and γ-Al2O3 for 723 K calcinations products of lower Cr2O3 content. The gradual increase of calcinations temperature promoted the crystallinity of Cr2O3 and resulted in solid–solid interaction of CuO and Cr2O3 forming CuCr2O4. The textural parameters varied with both calcinations temperature and catalyst composition. The surface acid density (DAS)
increased with the increase of chromia content up to 0.132 mole% Cr2O3, while the rise of calcinations temperature led to a decrease of surface acidity.
The dehydration/dehydrogenation of cyclohexanol as well as n-butylamine titration succeeded in characterizing of surface acidity.
Present address: Chemistry Department, College of Science, King Faisal University, Al-Hofuf 31982, Saudi Arabia 相似文献
18.
P. A. Korovchenko R. A. Gazarov A. Yu. Stakheev L. M. Kustov 《Russian Chemical Bulletin》1999,48(7):1261-1265
The influence of redox treatments on the state of palladium in the K6[SiW11PdO39]·11H2O/γ-Al2O3 system was investigated by diffuse-reflectance IR (DRIFT) spectroscopy using CO as a probe molecule. The K6[SiW11PdO39]·11H2O heteropoly-compound (HPC) and starting γ-Al2O3 support were studied for comparison. It was shown that palladium is present in HPC mainly in the form of Pd2+ ions. Treatment of HPC in an H2 flow results in complete reduction of palladium to Pd0. The HPC is unstable in redox cycles at temperatures above 373 K. When the HPC was supported on alumina, the Keggin units
were stabilized on the support surface and Pd+ formed in the oxidized sample. The supported K6[SiW11PdO39]·11H2O/γ-Al2O3 catalyst displays higher thermal stability and does not decompose during redox treatments at temperatures up to 723 K.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya. No. 7, pp. 1271–1275. July, 1999. 相似文献
19.
Zhang HuaiYing Liu QingFen Li YuGuang Li WangLiang Xiong XiaoChao Xing JianMin Liu HuiZhou 《中国科学B辑(英文版)》2008,51(1):69-77
In-situ coupling of adsorptive desulfurization and biodesulfurization is a new desulfurization technology for fossil oil. It has
the merits of high-selectivity of biodesulfurization and high-rate of adsorptive desulfurization. It is carried out by assembling
nano-adsorbents onto surfaces of microbial cells. In this work, In-situ coupling desulfurization technology of widely used desulfurization adsorbents of γ-Al2O3, Na-Y molecular sieves, and active carbon with Pseudomonas delafieldii R-8 were studied. Results show that Na-Y molecular sieves restrain the activity of R-8 cells and active carbon cannot desorb
the substrate dibenzothiophene (DBT). Thus, they are not applicable to in-situ coupling desulfurization technology. Gamma-Al2O3 can adsorb DBT from oil phase quickly, and then desorb it and transfer it to R-8 cells for biodegradation, thus increasing
desulfurization rate. It is also found that nano-sized γ-Al2O3 increases desulfurization rate more than regular-sized γ-Al2O3. Therefore, nano-γ-Al2O3 is regarded as the better adsorbent for this in-situ coupling desulfurization technology.
Supported by National Basic Research Program of China (Grant No: 2006CB202507) and National High-tech R&D Program (Grant No:
2006AA02Z209) 相似文献
20.
Changlun Chen Di Xu Xiaoli Tan Xiangke Wang 《Journal of Radioanalytical and Nuclear Chemistry》2007,273(1):227-233
The fate and transport of toxic metal ions and radionuclides in the environment is generally controlled by sorption reactions.
The extent of sorption of divalent metal cations is controlled by a number of factors including cosorbing or complexing. In
this work, the effects of pH, humic acid HA/Co(II) addition orders, ionic strength, concentration of HA, and foreign cations
on the Co(II) sorption on γ-Al2O3 in the presence of HA were investigated. The sorption isotherms of Co(II) on γ-Al2O3 in the absence and presence HA were also studied and described by using S-type sorption model. The experimental results showed
that the Co(II) sorption is strongly dependent on the pH values, concentration of HA, but independent of HA/Co(II) addition
orders, ionic strength, and foreign cations in the presence of HA under our experimental conditions. The results also indicated
that HA enhanced the Co(II) sorption at low pH, but reduced the Co(II) sorption at high pH. It was hypothesized that the significantly
positive influence of HA at low pH on the Co(II) sorption on γ-Al2O3 was attributed to strong surface binding of HA on γ-Al2O3 and subsequently the formation of ternary surface complexes such as ≡S-OOC-R-(COO−)
x
Co2−x
. Chemi-complexation may be the main mechanism of the Co(II) sorption on γ-Al2O3 in the presence of HA. 相似文献