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1.
The CH4 chlorination over Y zeolites was investigated to produce CH3Cl in a high yield. Three different catalytic systems based on Y zeolite were tested for enhancement of CH4 conversion and CH3Cl selectivity: (i) HY zeolites in H+-form having various Si/Al ratios, (ii) Pt/HY zeolites supporting Pt metal nanoparticles, (iii) Pt/NaY zeolites in Na+-form supporting Pt metal nanoparticles. The reaction was carried out using the gas mixture of CH4 and Cl2 with the respective flow rates of 15 and 10 mL min−1 at 300–350 °C using a fixed-bed reactor under a continuous gas flow condition (gas hourly space velocity = 3000 mL g−1 h−1). Above the reaction temperature of 300 °C, the CH4 chlorination is spontaneous even in the absence of catalyst, achieving 23.6% of CH4 conversion with 73.4% of CH3Cl selectivity. Under sufficient supplement of thermal energy, Cl2 molecules can be dissociated to two chlorine radicals, which triggered the C-H bond activation of CH4 molecule and thereby various chlorinated methane products (i.e., CH3Cl, CH2Cl2, CHCl3, CCl4) could be produced. When the catalysts were used under the same reaction condition, enhancement in the CH4 conversion was observed. The Pt-free HY zeolite series with varied Si/Al ratios gave around 27% of CH4 conversion, but there was a slight decrease in CH3Cl selectivity with about 64%. Despite the difference in acidity of HY zeolites having different Si/Al ratios, no prominent effect of the Si/Al ratios on the catalytic performance was observed. This suggests that the catalytic contribution of HY zeolites under the present reaction condition is not strong enough to overcome the spontaneous CH4 chlorination. When the Pt/HY zeolite catalysts were used, the CH4 conversion reached further up to 30% but the CH3Cl selectivity decreased to 60%. Such an enhancement of CH4 conversion could be attributed to the strong catalytic activity of HY and Pt/HY zeolite catalysts. However, both catalysts induced the radical cleavage of Cl2 more favorably, which ultimately decreased the CH3Cl selectivity. Such trade-off relationship between CH4 conversion and CH3Cl selectivity can be slightly broken by using Pt/NaY zeolite catalyst that is known to possess Frustrated Lewis Pairs (FLP) that are very useful for ionic cleavage of H2 to H+ and H−. Similarly, in the present work, Pt/NaY(FLP) catalysts enhanced the CH4 conversion while keeping the CH3Cl selectivity as compared to the Pt/HY zeolite catalysts. 相似文献
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3.
Dibenzyltin bis(2‐ethylhexanoate) 1 (4‐Y C6H4CH2)2Sn(OC(O)R1)2 [Y = H, 1a; MeO, 1b; Cl, 1c; Me, 1d; and R1 = MeCH2CH2CH2CH(Et) ] were synthesized either from the reaction of corresponding dibenzyltin dichlorides with silver 2‐ethylhexanoate or from the reaction of dibenzyltin oxides with 2‐ethylhexanoic acid. Compound 1a was further utilized as a catalyst for the reaction of mono‐ and di‐isocyanates [PhNCO, CH3C6H3‐2,4‐(NCO)2 and OCN(CH2)6NCO] with alcohols (primary, secondary, tertiary, cyclohexcyl, alkyl, allyl, benzyl and aryl) leading to the formation of the corresponding urethanes. The catalytic efficiencies of 1 vis‐à‐vis industrially known organotin catalysts have been determined through kinetic studies for the reaction of PhNCO and n‐BuOH at various temperatures. Compounds 1a, 1c and 1d show higher efficiency than dibutyltin bis(2‐ethylhexanoate). FTIR studies further provide mechanistic insights into the catalytic cycle, which comprises pre‐coordination of isocyanate to tin(IV), formation of stannyl carbamate and generation of dibenzyl(alkoxy)carboxylate as the active catalyst. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
4.
An active and reusable heterogeneous Rh(I) organometal catalyst (Rh(I)-PMO-3D) was synthesized by template-directed co-condensation of Rh[PPh2(CH2)2Si(OCH2CH3)3]3Cl and (CH3CH2O)3SiPhSi(OCH2CH3)3. This catalyst displayed bicontinuous cubic Ia3d mesostructure channel, which ensured the high dispersion of Rh(I) active sites and the convenient diffusion of reactant molecules into the pore channels. Meanwhile, the Ph-functionalization could enhance the surface hydrophobicity, which promoted the adsorption of organic reactant molecules on the catalyst, especially in aqueous medium. During water-medium 1,4-conjugate addition reactions, Rh(I)-PMO-3D catalyst exhibits higher catalytic activity than the corresponding homogeneous Rh(I) catalyst and could be used repetitively for more than five times, showing a good potential in industrial applications. 相似文献
5.
Xiaodong Wang Weicheng Liu Tao Zhang Xiaoying Sun Dongbai Liang Liwu Lin 《Reaction Kinetics and Catalysis Letters》2000,69(2):299-303
A kinetic model presented for the selective reduction of NO with CH4 over an In-Fe2O3/HZSM-5 catalyst by considering the process as a combination of two simultaneous reactions: NO+O2+CH4 (reaction 1) and O2+CH4 (reaction 2). Linear regression calculation was employed to find the kinetic parameters. It was found that although the activation energies of the two reactions were almost identical, the reaction rate constants were dramatically different, namely, k1k2, indicating that the NO+O2+CH4 reaction was more preferable to take place on the In-Fe2O3/HZSM-5 catalyst as compared with the O2+CH4 reaction. 相似文献
6.
Wendy J. Shaw Yongsheng Chen John Linehan Tom Bitterwolf 《Journal of organometallic chemistry》2008,693(12):2111-2118
A recoverable, water soluble, hydrogenation catalyst was synthesized by reacting poly-N-isopropylacrylamide containing a terminal amino group (H2N-CH2CH2-S-pNIPAAm) with [Rh(CO)2Cl]2 in organic solvents to form the square planar rhodium complex (Rh(CO)2Cl(H2N-CH2CH2-S-pNIPAAm)). The catalyst-ligand structure was characterized using in situ multinuclear NMR, XAFS and IR spectroscopic methods. Model complexes containing glycine (H2NCH2COOH), cysteamine (H2NCH2CH2SH) and methionine methyl ester (H2NCH(CH2CH2SCH3)COOCH3) ligands were studied to aid in the interpretation of the coordination sphere of the rhodium catalyst. The spectroscopic data revealed a switch in ligation from the amine bound (Rh-NH2-CH2CH2-S-pNIPAAm) to the thioether bound (Rh-S(-CH2CH2NH2)(-pNIPAAm)) rhodium when the complex was dissolved in water. The evolution of the structure of the rhodium complex dissolved in water was followed by XAFS. The structure changed from the expected monomeric complex to form a rhodium cluster of up to four rhodium atoms containing one SRR′ ligand and one CO ligand per rhodium center. No metallic rhodium was observed during this transformation. The rhodium-rhodium interactions were disrupted when an alkene (3-butenol) was added to the aqueous solution. The kinetics of the hydrogenation reaction were measured using a novel high-pressure flow-through NMR system and the catalyst was found to have a TOF of 3000/Rh/h at 25 °C for the hydrogenation of 3-butenol in water. 相似文献
7.
A. Loustaunau R. Fayolle-Romelaer S. Celerier S. Brunet 《Journal of fluorine chemistry》2011,132(12):1262-1265
The addition of zinc in low amount to chromium based catalyst supported over partially fluorinated alumina has a positive effect for the fluorination reaction of CF3CH2Cl in the presence of dioxygen in order to prevent the catalyst deactivation. However, under these operating conditions, the Deacon reaction by reaction with HCl produced by Cl/F exchanges could be involved. The formation of various by-products was observed corresponding to the addition of HCl or Cl2 into halogenated double bonds. 相似文献
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Pulse reaction showed that Co/Al2O3 catalyst was active for the high-temperature decomposition of CH4 and CO2. CH4 mainly was completely decomposed to give surface carbon, which could be inactivated quickly in the absence of enough O(ad) (arising from dissociation of CO2). CO2 was dissociatively adsorbed on Co(0) sites to give CO(ad) and O(ad), which was a slow step. Further decomposition of CO(ad) happened in the case of CO2 decomposition. 相似文献
10.
Levulinic acid (LA) is an industrially important product that can be catalytically valorized into important value-added chemicals. In this study, hydrothermal conversion of glucose into levulinic acid was attempted using Brønsted acidic ionic liquid catalyst synthesized using 2-phenyl-2-imidazoline, and 2-phenyl-2-imidazoline-based ionic liquid catalyst used in this study was synthesized in the laboratory using different anions (NO3, H2PO4, and Cl) and characterized using 1H NMR, TGA, and FT-IR spectroscopic techniques. The activity trend of the Brønsted acidic ionic liquid catalysts synthesized in the laboratory was found in the following order: [C4SO3HPhim][Cl] > [C4SO3HPhim][NO3] > [C4SO3HPhim][H2PO4]. A maximum 63% yield of the levulinic acid was obtained with 98% glucose conversion at 180 °C and 3 h reaction time using [C4SO3HPhim][Cl] ionic liquid catalyst. The effect of different reaction conditions such as reaction time, temperature, ionic liquid catalyst structures, catalyst amount, and solvents on the LA yield were investigated. Reusability of [C4SO3HPhim][Cl] catalyst up to four cycles was observed. This study demonstrates the potential of the 2-phenyl-2-imidazoline-based ionic liquid for the conversion of glucose into the important platform chemical levulinic acid. 相似文献
11.
Dimethyl ether (DME) was synthesized from methane through a two-step process, in which CH3Br was prepared from the oxidative bromination reaction of methane in the presence of HBr and oxygen over a Rh-SiO2 catalyst and then, in the second step, CH3Br was hydrolyzed to DME over a silica supported metal chloride catalyst. 12 mol%ZnCl2/SiO2 catalyst was found to be the most active, but it deactivated because of Cl− losing. 相似文献
12.
Heinrich Hahn Wolfgang Meindl Kurt Utvary 《Monatshefte für Chemie / Chemical Monthly》1985,116(2):157-166
Photochemical chlorination of (CH3NPF3)2 yields ClCH2(NPF3)2CH3(I) and ClCH2(NPF3)2CH2Cl (II). By reaction with organometallics unsymmetric N-substituted hexafluorodiazadiphosphetidines are synthesized. Depending on the nucleophilic strength of the used organometallic the chlorine atom of the N-CH2Cl group can be selectively substituted versus an organic substituent without side-reaction at the phosphorus atom. 相似文献
13.
Kazem Karami Mahzad Rahimi Mohammad Dinari 《Journal of the Iranian Chemical Society》2018,15(2):281-291
In this work, the phosphorus ylide, [PPh3CHC(O)CH2Cl], was reacted with AgNO3 to give the [Ag{C(H)PPh3C(O)CH2Cl}2]+NO3 ? as the product. Then, it was supported on the modified montmorillonite nanoclay to prepare a new catalyst for the reduction reaction. The structure and morphology of the nanoclay catalyst were characterized by FT-IR, X-ray powder diffraction, scanning electron microscopy, energy-dispersive X-ray analysis and transmission electron microscopy techniques; also, the content of silver was obtained by inductively coupled plasma analyzer. This composition was exploited to study its catalytic activity in the reduction in aromatic nitro compounds; it displayed the high catalytic activity. Factors such as catalyst amount, solvent, temperature and reaction time were all systematically investigated to elucidate their effects on the yield of catalytic reduction in nitroarenes. This catalytic system exhibited high activity toward aromatic nitro compounds under mild conditions. The catalyst was reused five times without any significant loss in its catalytic activity. 相似文献
14.
Jiayun Li Jiajian Peng Ying Bai Yingqian Hu Huayu Qiu Guoqiao Lai 《Phosphorus, sulfur, and silicon and the related elements》2013,188(2):484-490
Ionic liquid–modified silica has been prepared by a “one-pot” reaction of activated silica, 3-chloropropyltriethoxysilane, and alkylimidazole or pyridine. It was found that the catalytic activity and β-adduct selectivity of the supported catalyst Rh(PPh3)3Cl/ionic-liquid–modified-SiO2 for the hydrosilylation reaction of alkenes with triethoxysilane was significantly improved. Furthermore, the catalyst system could be recovered easily. 相似文献
15.
Ryszard Grzybek 《Reaction Kinetics and Catalysis Letters》1996,58(2):315-322
The catalyst precursor preparedin situ from rhodium dimer [Rh(cod)Cl]2 and a new water-soluble phosphine Ph2PCH2CH2CONHC(CH3)2CH2SO3H (in Li+ salt form) has been found to act as an effective olefin hydrogenation catalyst. Catalytic hydrogenation reactions have been tested in either two phase: aqueous catalyst/insoluble olefin or methanolic catalyst/olefin systems. The observed reaction rates were higher for terminal than for internal olefins. 1-Hexene in methanolic solution has been hydrogenated with a turnover frequency of about 8000 h–1. This system has also been applied in the form of a supported aqueous phase catalyst. 相似文献
16.
Jia-xu Zhang Ze-sheng Li Jing-yao Liu Chia-chung Sun 《Theoretical chemistry accounts》2007,117(4):579-586
The radical–molecule reaction mechanism of CH2Cl with NO2 has been explored theoretically at the B3LYP/6–311G(d,p) and MC–QCISD (single-point) levels of theory. Our results indicate that the title reaction proceeds mostly through singlet
pathways, less go through triplet pathways. The initial association between CH2Cl and NO2 is found to be the carbon-to-nitrogen attack forming the adduct a H2ClCNO2 with no barrier, followed by isomerization to b
1
H2ClCONO-trans which can easily convert to b
2
H2ClCONO-cis. Subsequently, the most feasible pathway is the C–Cl and O–N bonds cleavage along with the N–Cl bond formation of b (b
1
, b
2
) leading to product P
1
CH2O + ClNO, which can further dissociate to give P
5
CH2O + Cl + NO. The second competitive pathway is the 1,3-H-shift associated with O–N bond rupture of b
1
to form P
2
CHClO + HNO. Because the intermediates and transition states involved in the above two favorable channels all lie below the
reactants, the CH2Cl+NO2 reaction is expected to be rapid, as is confirmed by experiment. The present results can lead us to understand deeply the
mechanism of the title reaction and may be helpful for further experimental investigation of the reaction. 相似文献
17.
Wen Zhu Bi Chen Qu Xiao Lan Chen Sheng Kai Wei Ling Bo Qu Shu Yun Liu Kai Sun Yu Fen Zhao 《Tetrahedron》2018,74(15):1908-1917
Two practical and simple synthetic methodologies towards various heterobenzyl halides were developed. A series of 2-halomethylquinolines were readily prepared by the one-pot reaction of 2-methylquinolines with CuX (X?=?I, Br, Cl) and TBHP in CH3CN. A large variety of heterobenzyl iodides, including 2-iodomethylquinolines, 2-iodomethylquinoxalines, 2-iodiomethylbenzooxazole, and 2-iodiomethylbenzothiazole, were efficiently synthesized by one-pot reaction of 2-methylheterocycles with iodine in the presence of CuSO4·5H2O in CH3CN. 相似文献
18.
在固定床反应器上考察了原粒度(1~3mm)CeO2助Co/SiO2催化剂的费托反应性能,提出了催化剂失活的机理,并采用程序升温还原、X射线衍射和X射线光电子能谱对催化剂进行了表征.结果表明,在1.5MPa,488K和400h-1条件下进行的300h稳定性实验中,原粒度CeO2助Co/SiO2催化剂上的CO平均转化率达到41%,液态烃选择性达到85%,液态烃中C10 烃的质量含量占88%以上.反应器出口的催化剂中有少量的CoO和Co2SiO4生成.催化剂的失活过程受动力学控制而非热力学控制,催化剂的失活机理为:高分散的纳米Co离子在反应器出口高水蒸气压力的作用下,以CoO为中间物种,与水合SiO2作用生成Co2SiO4,即Co H2O→CoO H2,SiO2 H2O→OSi(OH)2,2CoO OSi(OH)2→Co2SiO4 H2O. 相似文献
19.
Yusuke Fuji Kazuya Watanabe Kyung‐Youl Baek Tsuyoshi Ando Masami Kamigaito Mitsuo Sawamoto 《Journal of polymer science. Part A, Polymer chemistry》2002,40(12):2055-2065
A hydrophilic ruthenium complex with ionic phosphine ligands { 1 : RuCl2[P(3‐C6H4SO3Na)(C6H5)2]2} induced controlled radical polymerization of 2‐hydroxyethyl methacrylate (HEMA) in methanol under homogeneous conditions; the initiator was a chloride (R‐Cl) such as CHCl2COPh. The number‐average molecular weights of poly(HEMA) increased in direct proportion to monomer conversion, and the molecular weight distributions were relatively narrow (Mw/Mn = 1.4–1.7). A similar living radical polymerization was possible with (MMA)2‐Cl [(CH3)2C(CO2CH3)CH2C(CH3)(CO2CH3)Cl] as an initiator coupled with amine additives such as n‐Bu3N. In a similar homogeneous system in methanol, methyl methacrylate (MMA) could also be polymerized in living fashion with the R‐Cl/ 1 initiating system. Especially for such hydrophobic polymers, the water‐soluble ruthenium catalyst was readily removed from the polymers by simple washing with an aqueous dilute acid. This system can be applied to the direct synthesis of amphiphilic random and block copolymers of HEMA and MMA. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2055–2065, 2002 相似文献
20.
Shengfu Ji Jian Yang Cigang Xu Jiaxin Wang Jinzhen Xue 《Reaction Kinetics and Catalysis Letters》2006,89(2):209-217
Summary Temperature-programmed desorption (TPD) of CH4, C2H6, C2H4, and CO and temperature-programmed pulse surface reactions (TPSR) of CH4, C2H6, C2H4, CO, and CO/H2 over a Co/MWNTs catalyst have been investigated. The TPD results indicated that CH4 and C2H6 mainly exist as physisorbed species on the Co/MWNTs catalyst surface, whilst C2H4 and CO exist as both physisorbed and chemisorbed species. The TPSR results indicated that CH4 and C2H6 do not undergo reaction between room temperature and 450oC. Pulsed C2H4 can be transformed into CH4 at 400 oC whilst pulsed CO can be transformed into CO2 at 100 or 150oC. In gaseous mixtures of CO and H2 containing excess CO, the products of pulsed reaction were CH3CHO and CH3OH. When the ratio of CO and H2 was 1:2, pulsed CO and H2 were transformed into CH3CHO, CH3OH and CH4. In H2 gas flow, pulsed CO was transformed into a mixture of CH3CHO and CH4 between 200 and 250oC and was transformed into CH4 only above 250oC. 相似文献