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1.
The ruthenium(II) complex fac-[Ru(CO)2(H2O)3(C(O)C2H5)][CF3SO3] dissolved in aqueous tetrabutylammonium hydrogensulfate ([(CH3(CH2)3)4N][HSO4]) or sodium hydrogensulfate (NaHSO4) catalyzes the hydrocarboxylation of ethylene to propionic acid and additionally produces minor amounts of hydrocarbonylation products (diethyl ketone and propanal), under water-gas shift reaction conditions. This system is stable with a selectivity of 90% to propionic acid for high ethylene conversion. A turnover frequency of propionic acid, TOF(C2H5CO2H)/24?h?=?5?×?103 (TOF (C2H5CO2H)?=?([(moles of C2H5CO2H)/(moles of Ru)?×?rt)]?×?24?h) was achieved for Ru?=?7.45?×?10?4?mol, [(CH3(CH2)3)4N][HSO4]?=?80?g (2.36?×?10?2?mol); H2O?=?40?g (2.22?mol); CO?=?C2H4?=?20?g (total pressure?=?88?atm); T?=?150°C by a reaction time (rt) of 2.87?h. The countercation (sodium or tetrabutylammonium), the ruthenium concentration and the hydrogensulfate/H2O ratio of the medium affect the catalytic reaction. A nonlinear dependence on total ruthenium concentration was shown. The data are discussed in terms of a potential catalytic cycle. Formation of propionic acid comes from hydrolysis, and formation of diethyl ketone and propanal comes from hydrogenolysis of the Ru-ketyl and Ru-acyl complexes, respectively.  相似文献   

2.
The objective of the present work was to study the reforming of simulated natural gas via the nonthermal plasma process with the focus on the production of hydrogen and higher hydrocarbons. The reforming of simulated natural gas was conducted in an alternating current (AC) gliding arc reactor under ambient conditions. The feed composition of the simulated natural gas contained a CH4:C2H6:C3H8:CO2 molar ratio of 70:5:5:20. To investigate the effects of all gaseous hydrocarbons and CO2 present in the natural gas, the plasma reactor was operated with different feed compositions: pure CH4, CH4/He, CH4/C2H6/He, CH4/C2H6/C3H8/He and CH4/C2H6/C3H8/CO2. The results showed that the addition of gas components to the feed strongly influenced the reaction performance and the plasma stability. In comparisons among all the studied feed systems, both hydrogen and C2 hydrocarbon yields were found to depend on the feed gas composition in the following order: CH4/C2H6/C3H8/CO2 > CH4/C2H6/C3H8/He > CH4/C2H6/He > CH4/He > CH4. The maximum yields of hydrogen and C2 products of approximately 35% and 42%, respectively, were achieved in the CH4/C2H6/C3H8/CO2 feed system. In terms of energy consumption for producing hydrogen, the feed system of the CH4/C2H6/C3H8/CO2 mixture required the lowest input energy, in the range of 3.58 × 10−18–4.14 × 10−18 W s (22.35–25.82 eV) per molecule of produced hydrogen.  相似文献   

3.
A novel type of plasma reactor having a rotating electrode is proposed for CO2 reforming of methane without catalyst at room temperature and atmospheric pressure. Results indicated that employing rotating ground electrode leads to a stable discharge for any period of time. Effects of feed composition, feed flow rate, applied power and electrodes separation on the carbon dioxide and methane conversions as well as the products selectivity were investigated. Increasing CO2/CH4 molar ratio in the feed favors the reagents conversion and consequently promotes the formation of hydrogen and carbon monoxide. If the target product is hydrogen, it is proposed to operate the reactor at CO2/CH4 = 1 molar ratio and if the target product is carbon monoxide then CO2/CH4 = 3 molar ratio is the preferred option for feed composition. This reactor system has advantages of stable operation and high conversion ability. Also, the obtained syngas with flexible molar ratio of H2 to CO is suitable for vast industrial applications.  相似文献   

4.
The [C4H6O] ion of structure [CH2?CHCH?CHOH] (a) is generated by loss of C4H8 from ionized 6,6-dimethyl-2-cyclohexen-1-ol. The heat of formation ΔHf of [CH2?CHCH?CHOH] was estimated to be 736 kJ mol?1. The isomeric ion [CH2?C(OH)CH?CH2] (b) was shown to have ΔHf, ? 761 kJ mol?1, 54 kJ mol?1 less than that of its keto analogue [CH3COCH?CH2]. Ion [CH2?C(OH)CH?CH2] may be generated by loss of C2H4 from ionized hex-1-en-3-one or by loss of C4H8 from ionized 4,4-dimethyl-2-cyclohexen-1-ol. The [C4H6O] ion generated by loss of C2H4 from ionized 2-cyclohexen-1-ol was shown to consist of a mixture of the above enol ions by comparing the metastable ion and collisional activation mass spectra of [CH2?CHCH?CHOH] and [CH2?C(OH)CH?CH2] ions with that of the above daughter ion. It is further concluded that prior to their major fragmentations by loss of CH3˙ and CO, [CH2?CHCH?CHOH]+˙ and [CH2?C(OH)CH?CH2] do not rearrange to their keto counterparts. The metastable ion and collisional activation characteristics of the isomeric allenic [C4H6O] ion [CH2?C?CHCH2OH] are also reported.  相似文献   

5.
An artificial photosynthetic (APS) system consisting of a photoanodic semiconductor that harvests solar photons to split H2O, a Ni‐SNG cathodic catalyst for the dark reaction of CO2 reduction in a CO2‐saturated NaHCO3 solution, and a proton‐conducting membrane enabled syngas production from CO2 and H2O with solar‐to‐syngas energy‐conversion efficiency of up to 13.6 %. The syngas CO/H2 ratio was tunable between 1:2 and 5:1. Integration of the APS system with photovoltaic cells led to an impressive overall quantum efficiency of 6.29 % for syngas production. The largest turnover frequency of 529.5 h?1 was recorded with a photoanodic N‐TiO2 nanorod array for highly stable CO production. The CO‐evolution rate reached a maximum of 154.9 mmol g?1 h?1 in the dark compartment of the APS cell. Scanning electrochemical–atomic force microscopy showed the localization of electrons on the single‐nickel‐atom sites of the Ni‐SNG catalyst, thus confirming that the multielectron reduction of CO2 to CO was kinetically favored.  相似文献   

6.
An artificial photosynthetic (APS) system consisting of a photoanodic semiconductor that harvests solar photons to split H2O, a Ni‐SNG cathodic catalyst for the dark reaction of CO2 reduction in a CO2‐saturated NaHCO3 solution, and a proton‐conducting membrane enabled syngas production from CO2 and H2O with solar‐to‐syngas energy‐conversion efficiency of up to 13.6 %. The syngas CO/H2 ratio was tunable between 1:2 and 5:1. Integration of the APS system with photovoltaic cells led to an impressive overall quantum efficiency of 6.29 % for syngas production. The largest turnover frequency of 529.5 h?1 was recorded with a photoanodic N‐TiO2 nanorod array for highly stable CO production. The CO‐evolution rate reached a maximum of 154.9 mmol g?1 h?1 in the dark compartment of the APS cell. Scanning electrochemical–atomic force microscopy showed the localization of electrons on the single‐nickel‐atom sites of the Ni‐SNG catalyst, thus confirming that the multielectron reduction of CO2 to CO was kinetically favored.  相似文献   

7.
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   

8.
The fragmentations of the acylium ions O?C+? CH2? CH2? CO2CH3 and O?C+? CH2? CH2? COCH3 generated from methyl levulinate are governed extensively by the interaction of the two carbonyl groups. Both species eliminate a molecule of CO unimolecularly and under CID conditions. The results derived from measurements of 13C and 18O labelled precursors, together with kinetic energy release values, have been used to study the mechanisms. In the first of these acylium ions, both carbonyl groups are equivalent; this phenomenon can be the result of a 1,4 methoxy shift. In the second acylium ion, only the oxygen atoms change their positions; this isomerization occurs via the [M? H]+ of γ-valerolactone. Some other fragmentation processes also discussed in relation to 2H labelling are the formation of the [M ? COOCH3] + ion and the loss of HCOOCH3 in the collision-induced dissociation mass spectra of the first acylium ion, and the formation of the [CH3CO]+ ion and the loss of H2O for the second one.  相似文献   

9.
The effects of separate C2H4/O2 feed and C2H4 feed position on the ethylene epoxidation reaction in an AC cylindrical dielectric barrier discharge reactor were investigated. The highest EO selectivity of 34?% and EO yield of 7.5?%, as well as the lowest power consumption of 1.72?×?10?16 Ws/molecule of EO produced, were obtained at a C2H4 feed position of 0.25, an O2/C2H4 feed molar ratio of 1/4, an applied voltage of 13?kV, an input frequency of 550?Hz, and a total feed flow rate of 75?cm3/min. The results demonstrated, for the first time, that the separate feed of C2H4 and O2 could provide better ethylene epoxidation performance in terms of higher EO selectivity and yield, and lower power consumption, as compared to the mixed feed. All undesired reactions including C2H4 cracking, dehydrogenation, oxidation, and coupling reactions are lowered by the ethylene separate feed because of a decrease in opportunity of ethylene molecules to be activated by generated electrons.  相似文献   

10.
A factorial experimental design was combined with response surface methodology(RSM) to opti-mize the catalyzed CO2 consumption by coke deposition and syngas production during the dry re-forming of CH4. The CH4 /CO2 feed ratio and the reaction temperature were chosen as the variables, and the selected responses were CH4 and CO2 conversion, the H2 /CO ratio, and coke deposition. The optimal reaction conditions were found to be a CH4 /CO2 feed ratio of approximately 3 at 700 °C, producing a large quantity of coke and realizing high CO2 conversion. Furthermore, Raman results showed that the CH4 /CO2 ratio and reaction temperature affect the system's response, particularly the characteristics of the coke produced, which indicates the formation of carbon nanotubes and amorphous carbon.  相似文献   

11.
Abstract

Cobalt(III) complexes of the type [Co(en)2(chel)]X.nH2O where en = ethylenediamine, chel = phthalato = C6H4CO2)2? 2, maleato = (O2CCH = CHCO2)2?, succinato = (O2CCH2CH2CO2)2?, homophthalato = (O2CC6H4(CH2)CO2)2?, citraconato = (O2CC(CH3) = CHCO2)2?, itaconato = (CH2 = C(CO2)CH2CO2)2?, X = NO? 3, Br?, (O2CC6H4CO2H)?, (O2CHC = CHCO2H)?, (O2C(CH2)2CO2H)?, (O2CC6H4(CH2)CO2H)?, (O2CHC = C(CH2)-CO2H)?, and (O2C-CH2?C(= CH2)-CO2H)?, [Co(en)2(malonato)]X.2H2O (where malonato = (O2CCH2CO2)2?, X = Cl?, Br?, and NO? 3) and [Co(en)2CO3]Cl.2H2O have been investigated for their bacterial activity against Escherichia coli B growing on EMB agar and in minimal glucose media both in lag and log phases. Among the most active are where chel = phthalato and homophthalato. The effects are distinct from those known for compounds of Pt, e.g., cis?[Pt(NH3)2Cl2] and rhodium, e.g., trans?[Rh(C5H5N)4,Cl2].6H2O. Antagonisms are reported.  相似文献   

12.
The ability to capture, store, and use CO2 is important for remediating greenhouse‐gas emissions and combatting global warming. Herein, Au nanoparticles (Au‐NPs) are synthesized for effective electrochemical CO2 reduction and syngas production, using polyethylenimine (PEI) as a ligand molecule. The PEI‐assisted synthesis provides uniformly sized 3‐nm Au NPs, whereas larger irregularly shaped NPs are formed in the absence of PEI in the synthesis solution. The Au‐NPs synthesized with PEI (PEI?Au/C, average PEI Mw=2000) exhibit improved CO2 reduction activities compared to Au‐NPs formed in the absence of PEI (bare Au NPs/C). PEI?Au/C displays a 34 % higher activity toward CO2 reduction than bare Au NPs/C; for example, PEI?Au/C exhibits a CO partial current density (jCO) of 28.6 mA cm?2 at ?1.13 VRHE, while the value for bare Au NPs/C is 21.7 mA cm?2; the enhanced jCO is mainly due to the larger surface area of PEI?Au/C. Furthermore, the PEI?Au/C electrode exhibits stable performance over 64 h, with an hourly current degradation rate of 0.25 %. The developed PEI?Au/C is employed in a CO2‐reduction device coupled with an IrO2 water‐oxidation catalyst and a proton‐conducting perfluorinated membrane to form a PEI?Au/C|Nafion|IrO2 membrane‐electrode assembly. The device using PEI?Au/C as the CO2‐reduction catalyst exhibits a jCO of 4.47 mA/cm2 at 2.0 Vcell. Importantly, the resulted PEI?Au/C is appropriate for efficient syngas production with a CO ratio of around 30–50 %.  相似文献   

13.
In this study, a Pd catalyst was prepared with promoters such as CeO2, BaO and SrO in a washcoated form on a metallic monolith for autothermal reforming of methane to syngas for the Fischer-Tropsch synthesis. A reactor was installed with an electric heater in the form of the metallic monolith as a start-up device instead of a burner with which stable and fast start-ups (within 4 min) were achieved. Gas hourly space velocity and O2/CH4 governed, methane conversion, while H2O/CH4 controlled H2/CO ratio. A methane conversion of approx. 96%, H2+CO selectivity of approx. 85%, and H2/CO of approx. 2.6 were obtained under the conditions of gas hourly space velocity (GHSV) at 103000 h?1, O2/CH4=0.7 and H2O/CH4=0.35.  相似文献   

14.
The electrochemical CO2 reduction reaction (CO2RR) to yield synthesis gas (syngas, CO and H2) has been considered as a promising method to realize the net reduction in CO2 emission. However, it is challenging to balance the CO2RR activity and the CO/H2 ratio. To address this issue, nitrogen‐doped carbon supported single‐atom catalysts are designed as electrocatalysts to produce syngas from CO2RR. While Co and Ni single‐atom catalysts are selective in producing H2 and CO, respectively, electrocatalysts containing both Co and Ni show a high syngas evolution (total current >74 mA cm?2) with CO/H2 ratios (0.23–2.26) that are suitable for typical downstream thermochemical reactions. Density functional theory calculations provide insights into the key intermediates on Co and Ni single‐atom configurations for the H2 and CO evolution. The results present a useful case on how non‐precious transition metal species can maintain high CO2RR activity with tunable CO/H2 ratios.  相似文献   

15.
Low-input high-diversity (LIHD) mixtures of native grassland perennials were subjected to a supercritical treatment process with the aim of obtaining hydrogen-rich gases. The process was studied based on the following treatment variables: reaction temperature (374 °C to 575 °C, corresponding to a pressure range of 22.1 to 40 MPa), residence time (10 to 30 min), biomass content in the feed, and catalysts (0% to 4% NaOH and solid alkali CaO–ZrO2). The gaseous phase produced from gasification of LIHD primarily consisted of hydrogen (H2), with a mixture of carbon monoxide (CO), methane (CH4), and carbon dioxide (CO2). The statistical significance of treatment variables was evaluated using analysis of variance (ANOVA). It showed that at the level of P?<?0.05, temperature, catalysts, and biomass content in the feed significantly affected gas yields, while residence time was not significant.  相似文献   

16.
In this research, the reforming of simulated natural gas containing a high CO2 content under AC non-thermal gliding arc discharge with partial oxidation was conducted at ambient temperature and atmospheric pressure, with specific regards to the concept of the direct utilization of natural gas. This work aimed at investigating the effects of applied voltage and input frequency, as well as the effect of adding oxygen on the reaction performance and discharge stability in the reforming of the simulated natural gas having a CH4:C2H6:C3H8:CO2 molar ratio of 70:5:5:20. The results showed marked increases in both CH4 conversion and product yield with increasing applied voltage and decreasing input frequency. The selectivities for H2, C2H6, C2H4, C4H10, and CO were observed to be enhanced at a higher applied voltage and at a lower frequency, whereas the selectivity for C2H2 showed an opposite trend. The use of oxygen was found to provide a great enhancement of the plasma reforming of the simulated natural gas. For the combined plasma and partial oxidation in the reforming of CO2-containing natural gas, air was found to be superior to pure oxygen in terms of reactant conversions, product selectivities, and specific energy consumption. The optimum conditions were found to be a hydrocarbons-to-oxygen feed molar ratio of 2/1 using air as an oxygen source, an applied voltage of 17.5 kV, and a frequency of 300 Hz, in providing the highest CH4 conversion and synthesis gas selectivity, as well as extremely low specific energy consumption. The energy consumption was as low as 2.73 × 10−18 W s (17.02 eV) per molecule of converted reactant and 2.49 × 10−18 W s (16.60 eV) per molecule of produced hydrogen.  相似文献   

17.
Reactions of one or two equiv. of cyclohexyl isocyanide in THF at room temperature with Mo?Mo triply bonded complexes [Mo(CO)2(η5‐C5H4R)]2 (R=COCH3, CO2CH3) gave the isocyanide coordinated Mo? Mo singly bonded complexes with functionally substituted cyclopentadienyl ligands, [Mo(CO)2(η5‐C5H4R)]2(μη2‐CNC6H11) ( 1a , R=COCH3; 1b , R=CO2CH3) and [Mo(CO)2(η5‐C5H4R)(CNC6H11)]2 ( 2a , R=COCH3; 2b , R=CO2CH3), respectively. Complexes 1a , 1b and 2a , 2b could be more conveniently prepared by thermal decarbonylation of Mo? Mo singly bonded complexes [Mo(CO)3(η5‐C5H4R)]2 (R=COCH3, CO2CH3) in toluene at reflux, followed by treatment of the resulting Mo?Mo triply bonded complexes [Mo(CO)2(η5‐C5H4R)]2 (R=COCH3, CO2CH3) in situ with cyclohexyl isocyanide. While 1a , 1b and 2a , 2b were characterized by elemental analysis and spectroscopy, 1b was further characterized by X‐ray crystallography.  相似文献   

18.
Removing CO2 from crude syngas via physical adsorption is an effective method to yield eligible syngas. However, the bottleneck in trapping ppm-level CO2 and improving CO purity at higher working temperatures are major challenges. Here we report a thermoresponsive metal–organic framework ( 1 a-apz ), assembled by rigid Mg2(dobdc) ( 1 a ) and aminopyrazine (apz), which not only affords an ultra-high CO2 capacity (145.0/197.6 cm3 g−1 (0.01/0.1 bar) at 298 K) but also produces ultra-pure CO (purity ≥99.99 %) at a practical ambient temperature (TA). Several characterization results, including variable-temperature tests, in situ high-resolution synchrotron X-ray diffraction (HR-SXRD), and simulations, explicitly unravel that the excellent property is attributed to the induced-fit-identification in 1 a-apz that comprises self-adaption of apz, multiple binding sites, and complementary electrostatic potential (ESP). Breakthrough tests suggest that 1 a-apz can remove CO2 from 1/99 CO2/CO mixtures at practical 348 K, yielding 70.5 L kg−1 of CO with ultra-high purity of ≥99.99 %. The excellent separation performance is also revealed by separating crude syngas that contains quinary mixtures of H2/N2/CH4/CO/CO2 (46/18.3/2.4/32.3/1, v/v/v/v/v).  相似文献   

19.
Partial oxidation of methane(POM) co-fed with CO2 to syngas in a novel catalytic BaCo0.6Fe0.2Ta0.2O3-δ oxygen permeable membrane reactor was successfully reported.Adding CO2 to the partial oxidation of methane reaction not only alters the ratio of CO/H2,but also increases the oxygen permeation flux and CH4 conversion.Around 96%CH4 conversion with more than 93%CO2 conversion and 100%CO selectivity is achieved,which shows an excellent reaction performance.A steady oxygen permeation flux of 15 mL/(cm2 min) is obtained during the 100-h operation,which shows good stability as well.  相似文献   

20.
Syngas (CO/H2) is a feedstock for the production of a variety of valuable chemicals and liquid fuels, and CO2 electrochemical reduction to syngas is very promising. However, the production of syngas with high efficiency is difficult. Herein, we show that defective indium selenide synthesized by an electrosynthesis method on carbon paper (γ‐In2Se3/CP) is an extremely efficient electrocatalyst for this reaction. CO and H2 were the only products and the CO/H2 ratio could be tuned in a wide range by changing the applied potential or the composition of the electrolyte. In particular, using nanoflower‐like γ‐In2Se3/CP (F‐γ‐In2Se3/CP) as the electrode, the current density could be as high as 90.1 mA cm?2 at a CO/H2 ratio of 1:1. In addition, the Faradaic efficiency of CO could reach 96.5 % with a current density of 55.3 mA cm?2 at a very low overpotential of 220 mV. The outstanding electrocatalytic performance of F‐γ‐In2Se3/CP can be attributed to its defect‐rich 3D structure and good contact with the CP substrate.  相似文献   

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