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1.
M.Yu. Sinev O.V. Udalova Y.P. Tulenin L.Ya. Margolis V.P. Vislovskii R.X. Valenzuela V. Cortés Corberán 《Catalysis Letters》2000,69(3-4):203-206
A novel approach for the partial oxidation of propane to acrolein, based on the use of layers of combined catalysts in a single
reactor, provides good yields of acrolein with selectivity above 62%. The results depend strongly on the layer configuration,
and reveal new mechanistic features for the process.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
2.
Photocatalytic oxidation of alkane at a steady rate over alkali-ion-modified vanadium oxide supported on silica 总被引:4,自引:0,他引:4
Tsunehiro Tanaka Tomokazu Ito Sakae Takenaka Takuzo Funabiki Satohiro Yoshida 《Catalysis Today》2000,61(1-4):109-115
Photocatalysts were applied to photocatalytic oxidation of propane in a fixed bed flow reactor. Titanium dioxide exhibited fairly high activity but the deep oxidation was predominant. Silica-supported vanadium oxide (VS) favors the partial oxidation to form propanone and variety of aldehydes and the fast deactivation took place accompanied by reduction of vanadium ions. On the other hand, alkali-ion-modified VS exhibited the highest activity and high selectivity to propanone. The activity was stable because vanadates in alkali-ion-modified VS do not change their structure or are not poisoned by water molecules throughout the reaction. The cleavage of C=C double bond to form aldehydes predominantly proceeded in the case of photo-oxidation of 1-butene over VS while in the case of photo-oxidation of Rb-modified VS, the oxidation of secondary carbon atom to form methyl vinyl ketone is favored. Methyl ethyl ketone was produced at a steady rate over Rb-VS in the photo-oxidation of n-butane. 相似文献
3.
Jinbao Gao Liang Lu Wenjuan Zhou Guohua Gao Mingyuan He 《Journal of Porous Materials》2008,15(2):127-132
Vanadyl Schiff base complexes covalently attached on the surface of MCM-41 have been synthesized by anchoring Schiff base
and subsequent reaction with VO(acac)2. XRD, nitrogen adsorption and desorption, UV-visible spectroscopy and FT-IR show that vanadyl Schiff base complexes were
successfully anchored on the surface of MCM-41 and the mesopore ordering decreased after the anchoring. The so-prepared heterogeneous
catalysts have showed high activity for sulfide oxidation. 相似文献
4.
Ja Hun Kwak Jose E. Herrera Jian Zhi Hu Yong Wang C.H.F. Peden 《Applied Catalysis A: General》2006,300(2):109-119
The morphology of vanadium oxide supported on a titania-modified mesoporous silica (MCM-41), obtained by means of a careful grafting process through atomic layer deposition, was studied using a variety of characterization techniques. The X-ray diffraction (XRD) together with transmission electron microscopy (TEM), 51V nuclear magnetic resonance (51V-NMR), Raman, FTIR and DRS-UV/Vis results showed that the vanadia species are extremely well dispersed onto the surface of the mesoporous support; the dispersion being stable upon thermal treatments up to 400 °C. Studies of the catalytic activity of these materials were performed using the partial oxidation of ethanol as a probe reaction. The results indicate an intrinsic relationship between dispersion, the presence of a TiO2–VOx phase, and catalytic activity for oxidation and dehydration. 相似文献
5.
Catalytic performance of vanadyl pyrophosphate in the partial oxidation of toluene to benzaldehyde 总被引:1,自引:0,他引:1
Vanadyl pyrophosphate catalysts were generated by dehydrating VOHPO4·(1/2)H2O at different temperatures and duration of the dehydration procedure. The as-synthesised materials were characterised by
X-ray diffractometry, FTIR spectroscopy and temperature-programmed reduction. The prolongation of the formation period at
higher temperatures led to improved crystallinity and lower BET surface areas of the vanadyl pyrophosphate specimens and,
additionally, a significantly impeded reducibility of the vanadyl sites was observed. The catalytic performance of the samples
was tested in the partial oxidation of toluene to benzaldehyde. The obtained results revealed an increasing benzaldehyde selectivity
with improved catalyst crystallinity. In situ FTIR and ESR spectroscopy were used to throw more light on the interaction of
the toluene–air feed with the surface of the catalyst.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
6.
采用负载Rh的泡沫独石整体型催化剂研究了甲烷催化部分氧化过程,考察了外界温度、空速和甲烷与氧气进料比例对反应转化率和选择性的影响,并对过程控制条件和调控参数进行了分析。研究结果表明该过程为毫秒级超短接触过程,反应可以在自热条件下进行,高空速条件下(8×105 h-1),甲烷与氧气进料比(体积比)为1.8,甲烷转过率超过90%,CO选择性接近95%,H2选择性超过90%。外界加热对过程有利,可获得更高的转化率和选择性。 相似文献
7.
Stephen Poulston Martyn V. Twigg Andrew P. Walker 《Applied catalysis. B, Environmental》2009,89(3-4):335-341
The catalytic UV photo-oxidation of NO in the absence and presence of ethane, ethene, propane, propene, and n-butane over TiO2 in the presence of excess oxygen was studied in the temperature range 21–150 °C. It was confirmed in our system that in the absence of hydrocarbon NO was photocatalytically oxidised by oxygen to NO2 over TiO2 and was strongly absorbed. Both NO and hydrocarbon could be simultaneously photo-converted with the conversion varying considerably with both NO and hydrocarbon concentration and the nature of the hydrocarbon. In some instances the presence of NO in the feed gas enhanced hydrocarbon oxidation via reactions involving NO2 that is a powerful oxidant. The extent of this effect depended on the relative strengths of adsorption on TiO2 of the reactants and products. To reduce surface coverage of hydrocarbon most reactions were run at 150 °C, and it was shown that at this temperature NOx adsorbed on titania could be reduced by photogenerated hydrocarbon surface species to N2O and N2 under these conditions. The formation of N2 was confirmed using 15NO with helium as carrier gas. By contrast, at room temperature in the presence of propene NO was converted to NO2. 相似文献
8.
The partial oxidation of methane to synthesis gas has been studied in an isothermal continuous flow reactor operated with
the phases in plug flow, using a silica-supported palladium catalyst. The reaction mechanism involves the sequential combustion
and reforming of methane. The catalyst bed is not uniform in terms of the composition of the palladium phase. The implications
for investigations using a pulse apparatus are discussed. Finally, large palladium crystallites readily grow carbon filaments.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
9.
Vanadia/titania catalysts for gas phase partial toluene oxidation: Spectroscopic characterisation and transient kinetics study 总被引:1,自引:0,他引:1
Formation of vanadia species during the calcination of ball milled mixture of V2O5 with TiO2 was studied by Raman spectroscopy in situ and at ambient conditions. It is found that calcination in air leads to fast (1–3 h) spreading of vanadia over TiO2 followed by a slower process leading to the formation of a monolayer vanadia. The calcinated catalyst showed higher activity during toluene oxidation than the uncalcinated one, but the selectivity towards C7-oxygenated products (benzaldehyde and benzoic acid) remains unchanged. The activity of the catalysts is ascribed to the formation of vanadia species in the monolayer. The details of the parallel–consecutive reaction scheme of toluene oxidation are presented from steady-state and transient kinetics studies. Different oxygen species seem to participate in the deep and partial oxidation of toluene. Coke formation was observed during the reaction presenting an average composition C2nH1.1n. The amount of coke on the catalyst was not dependent on the calcination step and the vanadium content in the catalyst. Coke formation was seen to be responsible for the deactivation of the catalyst. 相似文献
10.
Burcu Selen alayan Ahmet K. Avc Z. lsen
nsan A. Erhan Aksoylu 《Applied Catalysis A: General》2005,280(2):181-188
Indirect partial oxidation (IPOX) of propane was studied over bimetallic 0.2 wt.% Pt–15 wt.% Ni/δ-Al2O3 catalyst in the 623–743 K temperature range. The unreduced and reduced forms of the catalyst were characterized by ESEM–EDAX and X-ray diffraction (XRD). In the IPOX tests, the effects of steam to carbon ratio (S/C), carbon to oxygen ratio (C/O2) and residence time (W/F (gcat h/mol HC)) on the hydrogen production activity, selectivity and product distribution were studied in detail. The effect of temperature program applied (increasing from 623 to 743 K, ITP; decreasing from 743 to 623 K, DTP) during reaction was also tested. The results showed that the Pt–Ni bimetallic system has superior performance characteristics compared to the monometallic catalysts reported in literature. The reason is thought to be the utilization of the catalyst particles as micro heat exchangers during IPOX; the heat generated by Pt sites during exothermic total oxidation (TOX) being readily transferred through the catalyst particles acting as micro heat exchangers to the Ni sites, which promote endothermic steam reforming (SR). The optimal conditions were found as S/C = 3, C/O2 = 2.70 and W/F = 0.51 gcat h/mol HC for IPOX of propane on the basis of high hydrogen productivity and selectivity between 623 and 748 K for the experimental conditions tested. The thermo-neutral points obtained showed the sustainability of reaction in terms of energy. 相似文献
11.
The partial oxidation of crotonaldehyde, furan, crotonic acid and maleic anhydride was carried out over V–Mo–O
x
catalyst in the temperature range 260–360 °C. The dependence of selectivity to main reaction products on the conversion of
crotonaldehyde confirmed the parallel character of furan and maleic anhydride formation. The effect of water vapor on furan
formation was explained by ability of the catalyst to isomerize crotonaldehyde. The reaction scheme of the oxidation of crotonaldehyde
was suggested based on the experimental data. 相似文献
12.
Transient kinetics in the toluene oxidation over V/Ti oxide catalysts prepared by grafting and impregnation have been compared. V4+ cations are supposed to be the sites for the formation of electrophilic oxygen species participating in deep oxidation. Another oxygen species (probably nucleophilic) present on the oxidised catalyst surface are responsible for benzaldehyde formation. Selectivity of 80–100% can be obtained during the initial period of the reaction on the grafted catalysts in the presence of gaseous oxygen and during the interaction of toluene (without O2 in the mixture) with partially reduced catalysts. 相似文献
13.
Previously, it was reported that the direct partial oxidation (DPO) of CH4 with O2 over HZSM-5 catalysts produces C5+ hydrocarbon liquids when the feed contains a propane or propene additive. This work studies additive effects on C5+ production in this system by processing a CH4/C3H8 feed with subsequent removal of the C3 additive and by processing natural gas feed. Results show C5+ production is maintained at constant yields for HZSM-5 catalysts having different zeolitic Al contents after removal of the C3 additive. Mechanistic implications are discussed. Natural gas DPO consistently produced C5+ liquids due to the presence of C2+ components in the feed. While C5+ yields from natural gas DPO are higher than those observed for CH4/C3 feeds, increasing feed O2 concentration, and thus conversion, deleteriously affected C5+ selectivity. 相似文献
14.
S. Han E. A. Kaufman D. J. Martenak R. E. Palermo J. A. Pearson D. E. Walsh 《Catalysis Letters》1994,29(1-2):27-32
Extended studies on Zn-ZSM-5 catalyst for the production of liquid hydrocarbons in the direct partial oxidation (DPO) of CH4 with O2 are reported. Previously, it was reported that metal-containing ZSM-5 catalysts could produce C5+ hydrocarbons from pure CH4/O2 feeds without feed additives. Zn-ZSM-5 produced the highest C5+ yields of the catalysts tested. This work shows that the method of introducing Zn onto the catalyst, ion-exchange versus impregnation, does not significantly alter C5+ yields if low Zn content is maintained ( 0.4–0.5 wt%). Liquid hydrocarbon yields in this system doubled after 8 h on stream while overall C2+ yields increased by over 300%. Mechanistic implications of these findings are discussed. Finally, processing a natural gas feed over Zn-ZSM-5 gave higher C5+ yields over CH4 feed but these yields were not improved over previously published results using HZSM-5. 相似文献
15.
Different Pt and Pd catalysts supported on an activated carbon were prepared by using different metal precursors. Prepared catalysts were pretreated at 400 °C under different atmospheres to decompose the precursor compound and reduce the metal. After pretreatments, the supported catalysts were characterized by H2 chemisorption, X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy to know their metal dispersion, particle size, distribution and oxidation state. Afterwards, the catalysts were tested in methanol partial oxidation with two different O2/CH3OH molar ratios. Results obtained in this reaction were compared with those obtained for methanol decomposition in inert atmosphere. For Pt catalysts, there was an increase in methanol conversion and hydrogen production and a decrease in carbon monoxide production under oxidizing conditions. Both methanol conversion and partial oxidation reactions appear to be sensitive to Pt particle structure in the particle size range studied. Results obtained under oxidizing conditions differed between Pd and Pt catalysts. Finally, catalytic activity in methanol partial oxidation was more affected by Pt than Pd particle size in the size range studied. 相似文献
16.
P. Mar cot A. Fakche B. Kellali G. Mabilon P. Prigent J. Barbier 《Applied catalysis. B, Environmental》1994,3(4):283-294
The oxidation of propane and propene was investigated on palladium and platinum supported catalysts. Catalyst intrinsic activities, evaluated by light-off temperatures in slightly oxidizing reactant mixture (5% excess oxygen), show an optimum particle size which maximizes the catalytic activity for a given metal loading. On catalysts prepared from chloride containing precursor salts, chloride poisons the metallic activity whatever the particle size. Moreover, reaction isotherms under varying oxygen levels point out that the effect of chloride is more detrimental under oxidizing conditions. After successive oxidation cycles, this poisoning effect disappears as a consequence of the removal of chloride from the catalyst surface by water produced during propane and propene combustion. On the other hand, addition of relatively large quantities of water (equivalent to the content of the exhaust gas) inhibits the oxidation of hydrocarbon. Poisoning effects of chloride and water are explained by a decreasing active surface for the reactions under consideration. 相似文献
17.
Step-response studies of propylene partial oxidation with oxygen over a hydrophobic Pd/SDB catalyst were conducted at 1000 kPa and 185°C in a fixed-bed reactor. CO2 was found to be the only oxidation product when the feed contained only propylene and oxygen. CO2 formation was significantly suppressed by addition of steam to the feed, and this addition leads to the formation of partial oxidation products: acrolein and acrylic acid. A competitive reaction mechanism involving water molecules is proposed to explain the significant influence of steam concentration on the rate of propylene oxidation and product selectivity. 相似文献
18.
本文阐述了甲烷部分氧化过程中的积碳原因和积碳危害,并从析碳反应的机理上讲述了从5个方面如何预防这种危害。 相似文献
19.
Partial oxidation of methane to syngas at atmospheric pressure and 750°C was examined over Ni/MgO, Ni/CaO and Ni/CeO2 catalysts with nickel loading of 13 wt%. All catalysts had similar high conversion of methane and high selectivity to syngas,
which nearly approached the values predicted by thermodynamic equilibrium. However, only Ni/MgO showed high resistance to
carbon deposition under thermodynamically severe conditions (CH4/O2 = 2.5, a higher CH4 to O2 ratio than the stoichiometric ratio). Its catalytic activity remained stable during 100 h of reaction, with no detectable
carbon deposition. The oxidation of carbon deposited from pure CH4 decomposition and from pure CO disproportionation was investigated by in situ TPO-MS study which showed that both were effectively
inhibited over Ni/MgO. In addition, the catalysts were characterized by TPR, XRD and XPS. It was revealed that the excellent
performance of Ni/MgO resulted from the formation of an ideal solid solution between NiO and MgO.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
20.
Partial oxidation of toluene to benzaldehyde and benzoic acid over model vanadia/titania catalysts: role of vanadia species 总被引:1,自引:0,他引:1
Pure and K-doped vanadia/titania prepared by different methods have been studied in order to elucidate the role of vanadia species (monomeric, polymeric, bulk) in catalytic toluene partial oxidation. The ratio of different vanadia species was controlled by treating the catalysts in diluted HNO3, which removes bulk vanadia and polymeric vanadia species, but not the monomeric ones, as was shown by FT-Raman spectroscopy and TPR in H2. Monolayer vanadia species (monomeric and polymeric) are responsible for the catalytic activity and selectivity to benzaldehyde and benzoic acid independently on the catalyst preparation method. Bulk V2O5 and TiO2 are considerably less active. Therefore, an increase of the vanadium concentration in the samples above the monolayer coverage results in a decrease of the specific rate in toluene oxidation due to the partial blockage of active monolayer species by bulk crystalline V2O5. Potassium diminishes the catalyst acidity resulting in a decrease of the total rate of toluene oxidation and suppression of deactivation. Deactivation due to coking is probably related to the Brønsted acid sites associated with the bridging oxygen in the polymeric species and bulk V2O5. Doping by K diminishes the amount of active monolayer vanadia leading to the formation of non-active K-doped monomeric vanadia species and KVO3. 相似文献