Post-Column On-Line HPLC Measurement of Reaction Rates by using an Open--Closed Derivatizing System

1991 ◽  
Vol 29 (9) ◽  
pp. 377-381 ◽  
Author(s):  
M. D. Luque de Castro ◽  
J. M. Fernandez-Romero
Keyword(s):  
Reaction Rates ◽  
On Line ◽  
Hplc Measurement

New DRIFTS Cell Design for the Simultaneous Acquisition of IR Spectra and Kinetic Data Using On-Line Product Analysis

2001 ◽  
Vol 55 (11) ◽  
pp. 1537-1543 ◽  
Author(s):  
M. M. Schubert ◽  
T. P. Häring ◽  
G. Bräth ◽  
H. A. Gasteiger ◽  
R. J. Behm
Keyword(s):  
Co Oxidation ◽  
Gas Flow ◽  
Reaction Rates ◽  
Gas Analysis ◽  
Cell Design ◽  
Product Analysis ◽  
Kinetic Measurements ◽  
On Line ◽  
Improved Performance ◽  
Diffuse Reflectance Infrared

A new design for a DRIFTS (diffuse reflectance infrared Fourier transform spectrometry) cell for in situ studies in heterogeneous catalysis is presented, which allows for improved reaction control (i.e., gas flow, temperature, minimized background conversion) and for precise kinetic measurements via on-line gas analysis by a tandem-arranged gas chromatograph. Specifically, the very low background activity of the cell itself for CO and H2 oxidation makes it possible to study the preferential CO oxidation in H2-rich gases (PROX) at relevant reaction temperatures (150–350 °C) and reactant concentrations (≤1 kPa CO and O2). Comparison with results obtained in a quartz tube reactor shows excellent agreement with the reaction rates obtained in the DRIFTS cell. The improved performance of the new DRIFTS cell design is demonstrated by examining the influence of CO2 on the PROX reaction over a Au/Fe2O3 catalyst. The addition of CO2 to idealized reformate (varying CO and O2 partial pressures, 75 kPa H2, balance N2) significantly reduces both the CO oxidation rate and the selectivity of the PROX reaction on Au/α-Fe2O3 and strongly affects the frequency of the C–O stretch vibration of adsorbed CO due to CO2 coadsorption.

scholarly journals On-line estimation of the reaction rates from sampled measurements in bioreactors

2016 ◽  
Vol 49 (7) ◽  
pp. 1205-1210 ◽  
Author(s):  
I. Bouraoui ◽  
M. Farza ◽  
T. Menard ◽  
R. Ben Abdennour ◽  
M. M’Saad
Keyword(s):  
Reaction Rates ◽  
On Line ◽  
Sampled Measurements

On-line HPLC-measurement and control of substrate in a continuously operated biological tank reactor

1988 ◽  
Vol 3 (4) ◽  
pp. 151-157 ◽  
Author(s):  
J. Meschke ◽  
H. Bennemann ◽  
H. Herbst ◽  
S. Dormeier ◽  
D. C. Hempel
Keyword(s):  
Tank Reactor ◽  
On Line ◽  
And Control ◽  
Measurement And Control ◽  
Hplc Measurement

scholarly journals LES study of the impact of moist thermals on the oxidative capacity of the atmosphere in southern West Africa

2017 ◽  
Author(s):  
Fabien Brosse ◽  
Maud Leriche ◽  
Céline Mari ◽  
Fleur Couvreux
Keyword(s):  
Turbulent Mixing ◽  
Reaction Rate ◽  
Reaction Rates ◽  
Oxidative Capacity ◽  
Detailed Chemistry ◽  
Substantial Modification ◽  
Large Eddy ◽  
On Line ◽  
The Mean ◽  
The Impact

Abstract. The hydroxyl radical (OH) is a highly reactive specie and plays a key role in the oxidative capacity of the atmosphere. The total OH reactivity, corresponding to the inverse of OH lifetime, may have a significant fraction non-attributable to commonly measured compounds. The turbulence-driven segregation of OH and its reactants can cause substantial modification of averaged reaction rates, and thus of the total OH reactivity, when compared to a perfectly mixed assumption. We study the impact of turbulent mixing on the OH reactivity with Large-Eddy Simulations from the Meso-NH model coupled on-line with a detailed chemistry mechanism in two contrasted regimes. Our findings show that the non-mixing of isoprene (resp. aldehydes) and OH leads to 30 % decrease (resp. 16 % increase) of the mean reaction rate at the top of the boundary layer and consequently to 9 % decrease (resp. 5 % increase) of the OH total reactivity in a biogenic (resp. anthropogenic) environment. Moreover, the total OH reactivity is highest inside thermals in both cases.

SEM analysis of the change in the reaction rates with deposit structures in the copper-iron cementation system

1978 ◽  
Vol 36 (1) ◽  
pp. 456-457
Author(s):  
V. Annamalai ◽  
L.E. Murr
Keyword(s):  
Structural Characteristics ◽  
Secondary Electron Emission ◽  
Copper Deposit ◽  
Reaction Rates ◽  
Sem Analysis ◽  
Experimental Conditions ◽  
Major Drawback ◽  
Emission Mode ◽  
Scrap Iron ◽  
Image Position

Economical recovery of copper metal from leach liquors has been carried out by the simple process of cementing copper onto a suitable substrate metal, such as scrap-iron, since the 16th century. The process has, however, a major drawback of consuming more iron than stoichiometrically needed by the reaction.Therefore, many research groups started looking into the process more closely. Though it is accepted that the structural characteristics of the resultant copper deposit cause changes in reaction rates for various experimental conditions, not many systems have been systematically investigated. This paper examines the deposit structures and the kinetic data, and explains the correlations between them.A simple cementation cell along with rotating discs of pure iron (99.9%) were employed in this study to obtain the kinetic results The resultant copper deposits were studied in a Hitachi Perkin-Elmer HHS-2R scanning electron microscope operated at 25kV in the secondary electron emission mode.

The on-line use of histogram data for high-speed correction and alignment of electron microscope images

1984 ◽  
Vol 42 ◽  
pp. 556-557
Author(s):  
William Krakow
Keyword(s):  
Power Spectrum ◽  
High Speed ◽  
Direct Memory Access ◽  
Digital Television ◽  
Contrast Transfer Function ◽  
The Past ◽  
High Resolution Tem ◽  
On Line ◽  
Correction Of Astigmatism ◽  
The Fourier Transform

In the past few years on-line digital television frame store devices coupled to computers have been employed to attempt to measure the microscope parameters of defocus and astigmatism. The ultimate goal of such tasks is to fully adjust the operating parameters of the microscope and obtain an optimum image for viewing in terms of its information content. The initial approach to this problem, for high resolution TEM imaging, was to obtain the power spectrum from the Fourier transform of an image, find the contrast transfer function oscillation maxima, and subsequently correct the image. This technique requires a fast computer, a direct memory access device and even an array processor to accomplish these tasks on limited size arrays in a few seconds per image. It is not clear that the power spectrum could be used for more than defocus correction since the correction of astigmatism is a formidable problem of pattern recognition.

Image registration with a computer driven S.T.E.M.

1978 ◽  
Vol 36 (1) ◽  
pp. 98-99
Author(s):  
A.M.H. Schepman ◽  
J.A.P. van der Voort ◽  
J.E. Mellema
Keyword(s):  
Spot Size ◽  
Scanning Transmission Electron Microscope ◽  
Small Computer ◽  
Structural Studies ◽  
Area Of Interest ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Specimen Area ◽  
On Line ◽  
Minimum Distances

A Scanning Transmission Electron Microscope (STEM) was coupled to a small computer. The system (see Fig. 1) has been built using a Philips EM400, equipped with a scanning attachment and a DEC PDP11/34 computer with 34K memory. The gun (Fig. 2) consists of a continuously renewed tip of radius 0.2 to 0.4 μm of a tungsten wire heated just below its melting point by a focussed laser beam (1). On-line operation procedures were developped aiming at the reduction of the amount of radiation of the specimen area of interest, while selecting the various imaging parameters and upon registration of the information content. Whereas the theoretical limiting spot size is 0.75 nm (2), routine resolution checks showed minimum distances in the order 1.2 to 1.5 nm between corresponding intensity maxima in successive scans. This value is sufficient for structural studies of regular biological material to test the performance of STEM over high resolution CTEM.

Design and calibration of an IVEM for general 3-dimensional imaging of non-diffracting materials

1992 ◽  
Vol 50 (2) ◽  
pp. 1040-1041
Author(s):  
Neil Rowlands ◽  
Jeff Price ◽  
Michael Kersker ◽  
Seichi Suzuki ◽  
Steve Young ◽  
...  
Keyword(s):  
3D Imaging ◽  
Tomographic Reconstruction ◽  
Three Dimensional ◽  
3 Dimensional ◽  
3D Microstructure ◽  
Image Translation ◽  
Digital Correlation ◽  
On Line ◽  
Mechanical Stage ◽  
Projection Angle

Three-dimensional (3D) microstructure visualization on the electron microscope requires that the sample be tilted to different positions to collect a series of projections. This tilting should be performed rapidly for on-line stereo viewing and precisely for off-line tomographic reconstruction. Usually a projection series is collected using mechanical stage tilt alone. The stereo pairs must be viewed off-line and the 60 to 120 tomographic projections must be aligned with fiduciary markers or digital correlation methods. The delay in viewing stereo pairs and the alignment problems in tomographic reconstruction could be eliminated or improved by tilting the beam if such tilt could be accomplished without image translation.A microscope capable of beam tilt with simultaneous image shift to eliminate tilt-induced translation has been investigated for 3D imaging of thick (1 μm) biologic specimens. By tilting the beam above and through the specimen and bringing it back below the specimen, a brightfield image with a projection angle corresponding to the beam tilt angle can be recorded (Fig. 1a).

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