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1.
The chemical reactions and kinetics of the catalytic coupling reaction of carbon monoxide to diethyl oxalate were studied in the presence of hydrogen over a supported palladium catalyst in the gaseous phase at the typical coupling reaction conditions. The experiments were performed in a continuous flow fixed-bed reactor. The results indicated that hydrogen only reacts with ethyl nitrite to form ethanol, and kinetic studies revealed that the rate-determining step is the surface reaction of adsorbed hydrogen and the ethoxy radical (EtO-). A kinetic model is proposed and a comparison of the observed and calculated conversions showed that the rate expressions are of rather high confidence. 相似文献
2.
Carbon monoxide (CO) can be metabolized by a number of microorganisms along with water to produce hydrogen (H2) and carbon dioxide. National Renewable Energy Laboratory researchers have isolated a number of bacteria that perform this
so-called water-gas shift reaction at ambient temperatures. We performed experiments to measure the rate of CO conversion
and H2 production in a trickle-bed reactor (TBR). The liquid recirculation rate and the reactor support material both affected the
mass transfer coefficient, which controls the overall performance of the reactor. A simple reactor model taken from the literature
was used to quantitatively compare the performance of the TBR geometry at two different size scales. Good agreement between
the two reactor scales was obtained. 相似文献
3.
Fandong Meng Genhui Xu Zhenhua Pa DuState Key Laboratory of C Chemical Technology Tianjin University Tianjin China Luoyang Petrochemical Engineering Corporation Luoyang China 《天然气化学杂志》2002,(Z2)
The chemical reactions and kinetics of the catalytic coupling reaction of carbon monoxide to diethyl oxalate were studied in the presence of hydrogen over a supported palladium catalyst in the gaseous phase at the typical coupling reaction conditions. The experiments were performed in a continuous flow fixed-bed reactor. The results indicated that hydrogen only reacts with ethyl nitrite to form ethanol, and kinetic studies revealed that the rate-determining step is the surface reaction of adsorbed hydrogen and the ethoxy radical (EtO-). A kinetic model is proposed and a comparison of the observed and calculated conversions showed that the rate expressions are of rather high confidence. 相似文献
4.
[Bmim]Cl/FeCl3离子液体催化α-生育酚与β-D-五乙酰葡萄糖的糖基化反应 总被引:2,自引:0,他引:2
以[Bmim]Cl/FeCl3(三氯化铁/氯化丁基甲基咪唑)离子液体作为反应介质和催化剂, 考察了离子液体的酸度、反应温度及反应时间对α-生育酚与β-D-五乙酰吡喃型葡萄糖糖基化反应的影响. 结果表明, 离子液体的催化活性与其酸强度密切相关, 离子液体的酸性越强, 其对此糖基化反应催化活性越高. 在FeCl3与[Bmim]Cl物质的量比为2的[Bmim]Cl/FeCl3离子液中, α-生育酚与β-D-五乙酰吡喃型葡萄糖在45 ℃下反应3 h, 可以得到较高的转化率, α-生育酚的转化率最高可达70.2%. 同有机溶剂作为反应介质相比, 反应条件温和, 反应时间短, 室温离子液体具有更好的催化活性, 所得产物与离子液体不溶, 便于分离, 催化体系可循环使用, 且对环境友好. 相似文献
5.
Grethlein A. J. Worden R. M. Jain M. K. Datta R. 《Applied biochemistry and biotechnology》1990,(1):875-884
Continuous, steady-state fermentations using carbon monoxide gas as the sole carbon and energy source have been achieved with
the CO strain ofButyribacterium methylotrophicum. Fermentation pH was found to regulate carbon monoxide metabolism over the pH range of 6.8 to 5.0. Cell growth diminished
at low pH, with washout occurring at pH 5.0. As observed previously in batch culture, lower pH values favored production of
butyrate over acetate. The mechanism responsible for this trend is currently being investigated by quantification of key intracellular
enzyme activities.
At low pH values, direct, steady-state fermentation of carbon monoxide to alcohols has been verified. Of major significance
is the production of butanol from carbon monoxide in pure culture. This newly identified pathway provides a potential mechanism
for direct bioconversion of synthesis gas to butanol. 相似文献
6.
7.
Anton Purnomo Susan Gallardo Leonila Abella Chris Salim Hirofumi Hinode 《Reaction Kinetics and Catalysis Letters》2008,95(2):213-220
The characterization and catalytic activity of a Ni/CeO2/ZrO2 catalyst for methane steam reforming at 600°C were investigated. The addition of ceria increased the surface area and basicity
of the catalysts. The redox reaction capability of the ceria increased the hydrogen yield and carbon monoxide selectivity,
and inhibited carbon formation. 相似文献
8.
pH and temperature play critical roles in multistep enzymatic conversions. In such conversions, the optimal pH for individual
steps differs greatly. In this article, we describe the production of glucoamylase (from Aspergillus oryzae MTCC152 in solid-state fermentation) and glucose isomerase (from Streptomyces griseus NCIM2020 in submerged fermentation), used in industries for producing high-fructose syrup. Optimum pH for glucoamylase was
found to be 5.0. For glucose isomerase, the optimum pH ranged between 7.0 and 8.5, depending on the type of buffer used. Optimum
temperature for glucoamylase and glucose isomerase was 50 and 60°C, respectively. When both the enzymatic conversions were
performed simultaneously at a compromised pH of 6.5, both the enzymes showed lowered activity. We also studied the kinetics
at different pHs, which allows the two-step reaction to take place simultaneously. This was done by separating two steps by
a thin layer of urease. Ammonia generated by the hydrolysis of urea consumed the hydrogen ions, thereby allowing optimal activity
of glucose isomerase at an acidic pH of 5.0. 相似文献
9.
Jinzhang Gao Kanjun Sun Wu Yang Huixian Zhou 《Central European Journal of Chemistry》2005,3(3):502-510
A simple analytical method for the determination of p-nitrobenzene-azo-naphthol was proposed by a sequential perturbation with different amounts of p-nitrobenzene-azo-naphthol on an oscillating chemical system. The method involves a Cu(II)-catalysed oscillating reaction
between hydrogen peroxide and sodium thiocyanate in alkaline medium with the aid of continuous-flow stirred tank reactor (CSTR).
A good linear relationship between the changes, oscillation amplitude or/and period, and the concentration of p-nitrobenzene-azo-naphthol was obtained. The use of analyte pulse perturbation technique provides a possibility of sequential
determination in a same oscillating system, due to a new steady state that reappeared rapidly after each perturbation. The
calibration curve fits a linear equation very well when the concentration of p-nitrobenzene-azo-naphthol ranging from 5.2×10−7 to 3.3×10−3M. Influence of temperature, injection point, flow rate and reactants variables on this system were investigated in detail. 相似文献
10.
Van Ooteghem Suellen A. Beer Stephen K. Yue Paul C. 《Applied biochemistry and biotechnology》2002,98(1-9):177-189
Virtually all members of the order Thermotogales have demonstrated the ability to produce hydrogen; however, some members of this order produce considerably greater quantities
than others. With one representative of this order, Thermotoga neapolitana, we have consistently obtained accumulation of 25–30% hydrogen with 12–15% carbon dioxide as the only other prominent product
in the batch reaction. In contradistinction to information widely disseminated in the literature, we have also found that
most members of this order tolerate and appear to utilize the moderate amounts of oxygen present in the gaseous phase of batch
reactors (6–12%), with no apparent decrease in hydrogen production. Hydrogen accumulation has been widely reported to inhibit
growth of Thermotogales. While this may be true at very high hydrogen tensions, we have observed log phase bacterial morphology (rods) even in the
presence of 25–35% hydrogen concentrations. To maximize hydrogen production and minimize production of hydrogen sulfide, inorganic
sulfur donors are avoided and the cysteine concentration in the medium is increased. We and others have demonstrated that
different members of the order Thermotogales utilize a wide variety of feedstocks, including complex carbohydrates and proteins. Thus, it appears that organisms within
this order have the potential to utilize a variety of organic wastes and to cost-effectively generate hydrogen. 相似文献
11.
The reaction kinetics of the selective oxidation of carbon monoxide in the presence of hydrogen on a Pt/carbon support catalyst was studied. It was found that this catalyst exhibited high activity and decreased the concentration of CO in a hydrogen-containing gas from 0.6–1.0 vol % to less than 10 ppm at the inlet concentration ratio O2/CO = 1.0–1.5. A kinetic model of the reaction was proposed to describe quantitatively the experimental results. 相似文献
12.
Beker M. J. Shvinka J. E. Pankova L. M. Laivenieks M. G. Mezhbarde I. N. 《Applied biochemistry and biotechnology》1990,(1):265-274
Two biotechnological systems were developed for sucrose conversion into levan and ethanol withZymomonas mobilis, ensuring a 66.7% transfer of substrate carbon in a batch and 61% carbon transfer in a continuous culture. The effect of
glucose, ethanol, and medium pH on sucrose conversion byZ. mobilis was studied. The addition of ethanol to the fermentation medium, in the final conc. of 100 g/L, uncoupled levan synthesis
from ethanol fermentation. For a continuous culture, the most efficient conversion of substrate carbon into levan was reached
at pH 4.8, giving 64.2 g/L levan, with the levan yield of 0.22 g/g and the productivity of 3.2 g/L/h. 相似文献
13.
The kinetics of the oxidation of five catecholamines viz., dopamine (A), L-dopa (B), methyldopa (C), epinephrine (D) and norepinephrine
(E) by sodium N-chloro-p-toluenesulfonamide or chloramine-T (CAT) in presence of HClO4 was studied at 30±0.1 °C. The five reactions followed identical kinetics with a first-order dependence on [CAT]
o
, fractional-order in [substrate]
o
, and inverse fractional-order in [H+]. Under comparable experimental conditions, the rate of oxidation of catecholamines increases in the order D>E>A>B>C. The
variation of ionic strength of the medium and the addition of p-toluenesulfonamide or halide ions had no significant effect
on the reaction rate. The rate increased with decreasing dielectric constant of the medium. The solvent isotope effect was
studied using D2O. A Michaelis-Menten type mechanism has been suggested to explain the results. Equilibrium and decomposition constants for
CAT-catecholamine complexes have been evaluated. CH3C6H4SO2NHCl of the oxidant has been postulated as the reactive oxidizing species and oxidation products were identified. An isokinetic
relationship is observed with β=361 K, indicating that enthalpy factors control the reaction rate. The mechanism proposed
and the derived rate law are consistent with the observed kinetics. 相似文献
14.
The heat, equilibrium, and kinetics of adsorption of 1-ethoxy-2-propanol vapours on granulated activated carbon were determined simultaneously by a reaction calorimeter SETARAM C80 D at T=298.15 K at various relative vapour pressures (0.1< p/ps<0.8). The adsorption isotherm was correlated by the Freundlich equation. It was observed that the enthalpies of adsorption decrease slightly with increasing of the relative vapour pressure of the adsorptive. The rate of adsorption were calculated from analysis of the heat flux signals and it was found that the mass-transfer coefficient for 1-ethoxy-2-propanol vapours in granulated activated carbon increased with increasing relative vapour pressure of the adsorptive.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
15.
Ion transfer across the toluene|water, toluene–ionic liquid mixture|water and ionic liquid|water boundary generated by electrochemical redox reaction of tert-butylferrocene (tBuFc) was studied with the glassy carbon (GC) electrode partially covered by the organic liquid deposit and immersed in the aqueous electrolyte solution. The electrooxidation of the redox probe in toluene deposit is followed by ejection of newly formed cation into the aqueous solution. The same reaction in the toluene–ionic liquid deposit promotes anion insertion. This pathway is also found at the electrode modified with ionic liquid. 相似文献
16.
E. N. Deryagina N. A. Korchevin N. V. Russavskaya E. N. Sukhomazova E. P. Levanova 《Russian Chemical Bulletin》1996,45(1):140-143
Gas-phase thermolysis of xanthic acid esters and their reaction with acetylene at 250–600°C have been studied for the first time. The direction of the thermolysis is determined by the nature of the substituents at the oxygen and sulfur atoms. The main products of the thermolysis are gaseous hydrocarbons, carbon monoxide and hydrogen sulfide. The yields of liquid products of the thermolysis and of the reactions with acetylene are 4–46%. The role of thiyl radicals in thiophene molecule formation and reaction routes to carbon disulfide, dithiocarbonates, and stilbene are discussed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 150–153, January, 1996. 相似文献
17.
M. M. Ghoneim R. M. Issa R. A. Mahmoud 《Monatshefte für Chemie / Chemical Monthly》1981,112(3):293-299
The polarographic reduction of phenol red, chlorophenol red and bromophenol red has been investigated in buffered aqueous solutions and alcohol-water water mixtures over a widepH range (2–12). The results show that the three depolarizers are reduced through two irreversible one-electron waves of equal heights at allpH values. The two waves represent the reduction of the triphenylmethane carbon centre. The nature of the waves and the kinetics of the electrode reaction are discussed.
Elektroreduktion von Phenolrot, Chlorphenolrot und Bromphenolrot an der Quecksilbertropfelektrode
Zusammenfassung Die polarographischen Reduktionen wurden in gepufferten wäßrigen Lösungen und in Alkohol—Wasser-Mischungen über einen weitenpH-Bereich (2–12) durchgeführt. Es zeigte sich, daß in allen drei Fällen die Reduktion über zwei irreversible Ein-Elektron-Wellen gleicher Höhen bei allenpH-Werten vor sich ging. Die Kinetik der Elektrodenreaktion wird diskutiert.相似文献
18.
A. D. Kirilin A. A. Dokuchaev I. N. Menchaikina E. V. Semenova N. B. Sokova E. A. Chernyshev 《Russian Chemical Bulletin》1996,45(9):2192-2195
The reaction of hydrosilanes with carbon dioxide and secondary amines or silylamines was studied for the first time. The dependence of the composition and the structure of the products obtained on the nature of the reagents and on the reaction conditions was found. The hydrosilane-carbon dioxide system, unknown previously, can be used as anN-siloxycarbonylating reagent in the synthesis ofO-silylurethanes. A scheme for the formation ofO-silylurethanes was proposed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 2309–2312, September, 1996. 相似文献
19.
Zsófia Kádár Truus De Vrije Miriam A. W. Budde Zsolt Szengyel Kati Réczey Pieternel A. M. Claassen 《Applied biochemistry and biotechnology》2003,107(1-3):557-566
The main objective of this study was to develop a system for the production of “renewable” hydrogen. Paper sludge is a solid
industrial waste yielding mainly cellulose, which can be used, after hydrolysis, as a feedstock in anaerobic fermentation
by (hyper)thermophilic organisms, such as Thermotoga elfii and Caldicellulosiruptor saccharolyticus. Tests on different medium compositions showed that both bacteria were able to produce hydrogen from paper sludge hydrolysate,
but the amount of produced hydrogen and the requirement for other components differed. Hydrogen production by T. elfii strongly depended on the presence of yeast extract and salts. By contrast, C. saccharolyticus was less dependent on medium components but seemed to be inhibited by a component present in the sludge hydrolysate. Utilization
of xylose was preferred over glucose by C. saccharolyticus. 相似文献
20.
T. V. Kokochashvili Z. G. Dzotsenidze 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2007,81(2):309-311
It was demonstrated experimentally that, during the oxidation of hydrogen and carbon monoxide under stationary conditions (i.e., below the first ignition limit), the state of the reaction vessel surface experiences reversible changes, which, in turn, influence the kinetics of the gas-phase process. It was concluded that the reaction of molecular oxygen with hydrogen adatoms plays an important role in chain reactions below the first ignition limit. 相似文献