共查询到20条相似文献,搜索用时 31 毫秒
1.
Syuhei Yamaguchi 《Electrochimica acta》2010,55(26):7745-7750
The photocatalytic reaction in the partial oxidation of α-methylstyrene (α-MS) to acetophenone (AP) was investigated for TiO2 supported on H-ZSM-5 (H-MFI), H-mordenite (H-MOR), and H-Y-type (H-FAU) zeolites. XRD results demonstrated that the anatase was the stable phase of TiO2 supported on zeolites. Photocatalytic activities of supported catalysts decreased in the following order: TiO2/H-MFI >> TiO2/H-MOR > (TiO2) > TiO2/H-FAU >> (blank). TiO2/H-MFI catalyst exhibited the best performance for photocatalytic oxidation of α-MS to AP. The maximal activity was obtained by 25 wt% TiO2/H-ZSM-5. The addition of water to the reaction solvent resulted in significantly lowering the photocatalytic activity for TiO2/H-ZSM-5 catalyst, although its activity for TiO2 and TiO2 + H-ZSM-5 mechanical mixture was little influenced by the amount of water added to reaction solvent. 相似文献
2.
Suphot Phatanasri Piyasan Praserthdam Thana Punsupsawat 《Korean Journal of Chemical Engineering》2000,17(4):414-419
Toluene methylation with methanol was investigated on MFI-type zeolite catalysts containing Fe or Zn within the range of 0-2% by weight as an active component. The catalytic performances were compared on catalysts to which Fe or Zn was introduced by different methods, i.e., ion-exchanged and incorporation methods. The prepared catalysts were characterized by XRD, XRF, BET, FTIR and pyridine adsorption technique on in-situ FTIR. The results showed that the incorporated samples, H-Fe, Al-silicate (Si/Fe=150) and H-Zn, Al-silicate (Si/Zn=150), exhibited catalytic activity and xylene selectivities approximately equivalent to those from the ion-exchanged samples, Fe(0.8)/H-MFI and Zn(1.0)/H-MFI, containing nearly the same amount of Fe or Zn. The higherp-xylene selectivity was achieved with H-Fe, Al-silicate (Si/Fe=150) and H-Zn, Al-silicate (Si/Zn=150) because of Brönsted acid strengths weaker than Fe(0.8)/H-MFI and Zn(1.0)/H-MFI. Therefore, the isomerization ofp-isomer produced primarily was suppressed on the incorporated catalysts better than the ion-exchanged ones. 相似文献
3.
The conversion of methanol to dimethyl ether was carried out over various commercial zeolites and modified H-ZSM-5 catalysts to evaluate their catalytic performance. A series of commercially available zeolite samples were used for vapor-phase dehydration of methanol to DME. Catalyst screening tests were performed in a fixed-bed reactor under the same operating conditions (T = 300 °С, P = 16 barg, WHSV = 3.8 h−1). It was found that all the H-form zeolite catalysts in this study were active and selective for DME synthesis. According to the experimental results MDHC-1 catalyst exhibited the highest activity in dehydration of methanol.After finding the most active catalyst, the H-MFI90 zeolite was modified with Na content varying from 0 to 120 mol%, via wet-impregnation method to further improve its selectivity. All of catalysts were characterized by BET, XRD, NH3-TPD, ICP, TGA, SEM, FT-IR and TPH techniques. It was found that these materials affected activity of MDHC-1 zeolite by changing its acidity. Ultimately, among all the catalysts studied, Na100-modified H-MFI90 zeolite exhibited optimum activity, selectivity and stability at methanol dehydration reaction. 相似文献
4.
Palladium catalysts supported on carbon nanofibers (CNFs) and XC-72 carbon were developed by chemically reducing palladium chloride with ethylene glycol. The morphologies and crystal structure of the Pd/CNF catalyst and Pd/XC-72 catalyst were investigated by TEM and XRD, respectively. The electrocatalytical activity of the catalysts was examined via cyclic voltammetry testing techniques. The performance of the air electrodes was examined by linear polarization methods. Magnesium air fuel cells with Pd/CNF catalyst and Pd/XC-72 catalyst were fabricated and characterized. The results showed that the Pd/CNF catalyst had higher catalytic activity for the oxygen reduction reaction and achieved better performance of the magnesium air fuel cell compared with the Pd/XC-72 catalyst. 相似文献
5.
固相反应制备Pt/C催化剂 总被引:1,自引:0,他引:1
利用固相反应法制得具有较高催化活性的Pt/C催化剂,探讨了制备条件对催化剂性能的影响。结果显示:用水作浸渍介质、n(NaOH)/n(H2PtCl6)=6 4、固相还原剂为聚甲醛时,制得的Pt/C催化剂中Pt粒子的平均粒径为3 8nm。线性扫描伏安结果表明:在30℃、扫速为50mV/s时,制得的Pt/C催化剂在c(CH3OH)=0 5mol/L和c(H2SO4)=0 5mol/L混合溶液中,甲醇氧化的峰电流密度为11 3mA/cm2;而同样条件下,E TEK公司商品化的Pt/C催化剂为9 2mA/cm2。 相似文献
6.
Jesús López-Sanz Elena Pérez-Mayoral Dana Procházková Rosa M. Martín-Aranda Antonio J. López-Peinado 《Topics in Catalysis》2010,53(19-20):1430-1437
Catalytic performance of zeolites H-BEA, H-MFI, H-FAU and H-MOR, exhibiting textural differences and with different Brønsted and Lewis acid sites concentration, have been studied in the synthesis of quinolines via Friedländer reaction. H-BEA and H-FAU efficiently promoted the condensation of 2-aminoaryl ketones 3 with ethyl acetoacetate (4a) or acetylacetone (4b) under mild reaction conditions, those being the first examples of zeolites as catalysts for this transformation. While H-FAU showed similar catalytic behaviour than that reported for (Al)SBA-15 affording mixtures of quinolines 5 and quinolones 6, H-BEA mainly led to quinolines 5 in almost total selectivity and good yields. However, H-MFI and H-MOR zeolites afforded quinolones 6 as the major reaction product. Methodology reported here was found to be useful for the synthesis of biologically active compounds with excellent yields avoiding unnecessary purifications protocols and tedious work-up procedures. 相似文献
7.
采用共沉淀法同时制备了PdO/M-Al2O3(M=Ce、Zr、Ce-Zr)和PtO-PdO/M-AlO3催化剂.考察了Pt的加入对PdO/M-Al2O3催化剂的影响,助剂Ce、Zr改性的PtO-PdO/Al2O3催化剂的甲烷催化燃烧反应性能以及催化剂预处理对催化反应性能的影响.结果表明,PtO-PdO/Ce-Al2O3... 相似文献
8.
采用共沉淀法同时制备了PdO/M-Al2O3(M=Ce、Zr、Ce-Zr)和PtO-PdO/M-Al2O3催化剂。考察了Pt的加入对PdO/M-Al2O3催化剂的影响,助剂Ce、Zr改性的PtO-PdO/Al2O3催化剂的甲烷催化燃烧反应性能以及催化剂预处理对催化反应性能的影响。结果表明,PtO-PdO/Ce-Al2O3催化剂的活性最好,其甲烷完全转化温度为475℃,比PdO/Ce-Al2O3催化剂低90℃。另外,用蒸馏水反复洗涤的催化剂相比于未经蒸馏水洗涤的催化剂具有较低的甲烷起燃温度和完全转化温度。 相似文献
9.
Dang-guo Cheng Xinli Zhu Yuheng Ben Fei He Lan Cui Chang-jun Liu 《Catalysis Today》2006,115(1-4):205-210
Ni/Al2O3 catalyst was first treated by argon glow discharge plasma followed by calcination in air. The catalyst prepared this way exhibits an improved low-temperature activity for carbon dioxide reforming of methane, compared to the catalyst prepared without plasma treatment. The catalyst characterization using XRD, chemisorption and TEM analyses show that the plasma treatment followed by calcination thermally induces a generation of specific nickel species on the support. This kind of “plasma” metal species is highly dispersed on the support and can remain stable during reforming reactions. The average size of the “plasma” metal particles is ca. 5 nm. The plasma treatment can also enhance the anti-carbon deposition performance of the catalyst. The formation of carbon species that is responsible for catalyst deactivation can be inhibited. The catalyst stability is therefore improved. 相似文献
10.
Takashi Fujikawa Hiroshi Kimura Kazuyuki Kiriyama Kazuhiko Hagiwara 《Catalysis Today》2006,111(3-4):188-193
Cosmo Oil has successfully developed a new CoMo HDS catalyst, C-606A, for production of ultra-low sulfur diesel fuels. This catalyst was prepared by an impregnation method using a solution containing Co, Mo, P, and citric acid on a HY-Al2O3. The resulting catalyst air-dried only without calcination. The HDS activity was measured with straight-run light gas oil feedstocks under industrial hydrotreating conditions. C-606A had a three times higher HDS activity compared with the conventional CoMoP/Al2O3 catalyst. Commercial operation with C-606A has successfully demonstrated high performance. This catalyst has superior activity, which enables <10-ppm sulfur content in products in a commercial hydrotreater designed to produce 500-ppm sulfur diesel fuels. 相似文献
11.
采用沉淀法制备了Pt/SO42-/ZrO2-Al2O3 (PtSZA)催化剂,考察了氢氧化锆水凝胶干燥速率、锆盐浓度、铂含量、Al2O3和SO42-添加顺序等制备条件对PtSZA异构化性能,尤其是低温异构化性能的影响,并用XRD和TG对催化剂进行了表征。结果表明,提高水凝胶的干燥速率降低了PtSZA催化剂中的硫含量,大大提高了催化剂中的单斜相,进而导致了催化剂低温失活加速以及高温活性下降。较低或较高的锆盐浓度劣化了PtSZA的低温异构化稳定性,以0.4~0.6mol/L硝酸氧锆制备的催化剂硫含量和四方相氧化锆含量较高,异构化活性相对较好,Al2O3和SO42-添加顺序对PtSZA异构化性能没有明显影响。 相似文献
12.
Ethylene and propylene methylation rates increased linearly with olefin pressure but did not depend on dimethyl ether (DME) pressures on proton-form FER, MFI, MOR, and BEA zeolites at low conversions (<0.2%) and high DME/olefin ratios (30:1) in accordance with a mechanism that involves the zeolite surface being predominantly covered by DME-derived species reacting with olefins. Higher first-order reaction rate constants for both ethylene and propylene methylation were observed over H-BEA and H-MFI compared with H-FER and H-MOR, indicating that olefin methylation reaction cycles involved in the conversion of methanol-to-gasoline over zeolitic acids are propagated to varying extents by different framework materials. Systematically lower activation barriers and higher rate constants were observed for propylene methylation in comparison with ethylene methylation over all frameworks studied, reflecting the increased stability of reaction intermediates and activated complexes with increasing olefin substitution. A binomial distribution of d0/d3/d6 in unreacted DME upon introduction of equimolar protium- and deuterium-form DME under steady-state reaction conditions of ethylene methylation over H-MFI suggests the presence and facile formation of reactive surface-bound methoxide species and the absence of C–H bond cleavage. 相似文献
13.
采用小型固定流化床,研究了MTO副产物C4/C5^+烯烃在DMTO再生催化剂上的催化裂解反应、预积炭情况,以及预积炭后再生催化剂对MTO反应性能的影响。结果表明:C4/C5^+烯烃可作为原料在DMTO再生催化剂上进行催化裂解,生成乙烯、丙烯,增加双烯产量。在此裂解过程中,DMTO再生催化剂发生预积炭,可以提高MTO反应中双烯的初始选择性,缩短反应诱导期,提高双烯收率;同时,可以减小甲醇的生焦率,降低甲醇消耗。DMTO再生催化剂预积炭会影响催化剂寿命,其经C4/C5^+裂解预积炭过程中碳质量分数以3%左右为宜。 相似文献
14.
Three bi-functional catalysts have been prepared by physical mixing of a commercial methanol synthesis catalyst (CuO–ZnO–Al2O3) with three different methanol dehydration catalysts including: H-MFI90, γ-Al2O3 and H-Mordenite in order to investigate the role of interaction effects of dehydration component on characteristic properties and performance of these admixed catalysts. The bi-functional catalysts have been characterized by XRD, N2 adsorption, H2-TPR, NH3-TPD and XRF techniques and tested in a mixed slurry bed reactor at the same operating conditions (T = 240 °C, P = 50 bar, H2/CO = 2, SV = 1100 ml g-cat− 1 h− 1) for 60 h time on stream. Among the examined bi-functional catalysts, the physical mixture of KMT + HMFI-90, which had lower reducing peak temperature (T = 200 °C), higher SCu (39.1 m2 g-cat− 1) and Cu Dispersion (11.6%), showed higher XCO (84 mol%), yield of DME (YDME = 55.5 mol%), DME selectivity (SelectDME = 66.7 mol%) and also good stability over 60 h time on stream as compared to the other catalysts. This could be assigned, from NH3-TPD results, to more middle strength acidic sites of H-MFI90 zeolite (SiO2/Al2O3 = 90, total acid site density = 476 µmol/g-cat) which inhibits detrimental interactions with methanol synthesis catalyst and deep dehydration of methanol. 相似文献
15.
A. Goifman J. Gun F. Gelman I. Ekeltchik O. Lev J. Donner H. Brnick E. Worch 《Applied catalysis. B, Environmental》2006,63(3-4):296-304
A new catalyst based on the formation of carbon supported “CoN4” structures by heat treatment of Co(CH3COO)2 and imidazole impregnated carbon black is introduced. The performance of the new catalyst is compared to the performance of other catalysts including activated carbon powder, granular activated carbon, and pyrolysed cobalt(II) mesotetra-4-methoxyphenylporphyrin. The optimized form of the new catalyst outperforms all these catalysts. The underlying concept is borrowed from fuel cell technology, which uses electrocatalysts that activate triplet dioxygen and facilitate its reduction. The same concept is used to reduce oxygen by hydrogen sulfide. In electrochemistry oxygen reduction is carried out by heterogeneous electron transfer, whereas in dehydrosulfurization the reduced sulfur moieties serve as the electron donors. We postulate that the reason for the improved performance of the new catalyst compared to pyrolysed carbon supported cobalt porphyrin, which is also a Me–N4 type catalyst, stems from the ability to load a larger amount of cobalt chelates rather than from a change of oxidation mechanism. 相似文献
16.
采用共沉淀法制备了不同La含量改性Cu/Zn/Al的催化剂,通过热重分析(TG/DTG)、X射线衍射(XRD)、比表面积测定(BET)、H2程序升温还原(H2-TPR)等表征手段对改性催化剂进行评价,分析结果表明,La助剂能够促进活性组分在载体表面的分散,很好地维持了催化剂的孔结构,适量助剂La的添加可促进CuO、ZnO两相间相互融合,增加活性中心的分散度,使CuO更加易于还原,但过多的La含量会使催化剂的性能发生改变,导致催化剂的活性降低。在超临界甲醇中使用La改性Cu/Zn/Al催化剂催化液化微晶纤维素,发现添加少量的La可有效地提高催化液化效果,相较于为添加助剂的Cu/Zn/Al催化剂,MCC转化率与醇类收率都得到了明显的提高。通过GC-MS分析,可以得到液化产物主要有醇类、酯类、酮类、醛类、烷烃等物质,添加助剂后提高了醇类产物的选择性。设置单因素实验,可知改性后Cu1.2Zn4.8Al1.9La0.1催化剂的最佳反应条件为:反应温度320℃,反应时间75min,催化剂用量75%。 相似文献
17.
Makoto Toba Yasuo Miki Takashi Matsui Masaru Harada Yuji Yoshimura 《Applied catalysis. B, Environmental》2007,70(1-4):542-547
To achieve selective hydrodesulfurization (HDS) of fluid catalytic-cracked (FCC) gasoline for producing sulfur-free gasoline (S < 10 ppm), the reactivity of various olefins contained in FCC gasoline on CoMoP/Al2O3 sulfide catalysts was investigated. Isomerization of the CC double bond from the terminal position to an internal position was observed. The steric hindrance around the CC double bond suppresses the reactivity of olefin hydrogenation. The sulfidation temperature of the catalyst has a major influence on olefin hydrogenation active sites. Addition of the appropriate amount of cobalt (Co/Mo ratio approximately 0.6) contributes to the suppression of olefin hydrogenation at high reaction temperature (260 °C). From the comparison of catalytic performance and characterization of our CoMoP/Al2O3 catalyst with an analogous commercial catalyst, it is suggested that the hydrogenation of olefins depends not only on the state of the Mo CUS but also on the steric effects of both olefin structure and MoS2 crystalline structure. 相似文献
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Development of novel Ru catalyst of preferential CO oxidation for residential polymer electrolyte fuel cell systems 总被引:2,自引:0,他引:2
CO preferential oxidation on a novel Ru catalyst greatly improved in activity and selectivity over a wide temperature range by the pre-treatment of H2 reduction was characterized. The high performance was obtained by increasing the population of surface Ru(0) which improved O2 activation at low temperatures. Methanation of CO on the catalyst can also contribute to the final CO clean-up from ca. 100 to <1 ppm at low temperatures where the influence of CO2 methanation can be ignored. 相似文献