scholarly journals A study of catalytic actions at solid surfaces. Part VII.— The influence of pressure on the rate of hydrogenation of liquids in presence of Nickel

1921 ◽  
Vol 100 (704) ◽  
pp. 240-252 ◽  
Keyword(s):  
Organic Compounds ◽  
Solid Surfaces ◽  
Experimental Proof ◽  
Wide Range ◽  
Metallic Catalyst ◽  
Atomic Condition ◽  
Determining Factor ◽  
Unsaturated Organic Compound ◽  
Unstable Intermediate ◽  
Absorption Of Hydrogen

In Parts I, II and V of this series we have indicated the reasons which lead us to believe that during the catalytic hydrogenation of liquids the function of the metallic catalyst is to combine with both agents—the unsaturated organic compound and hydrogen—and produce an unstable intermediate complex. The experimental evidence has furthermore impressed upon us the conviction that the determining factor in hydrogenation is the degree of affinity displayed between nickel and the unsaturated compound; whilst we have had ample opportunity to observe the selective nature of the process as exemplified by the widely-varying rates of absorption of hydrogen characteristic of various definite types of organic compounds, we have not been fortunate enough to obtain experimental proof of the mode in which nickel effects the actual introduction of hydrogen to an organic molecule. We have, therefore, directed our attention to the influence of the concentration of hydrogen on the rate of hydrogenation of liquids, and have examined a wide range of unsaturated organic compounds with respect to the rates at which they absorb hydrogen under varying pressures. Existing data on this subject are scanty, but indicate, in the case of the hydrogenation of fatty oils, that the rate of action is simply proportional to the pressure. On the other hand, it has been suggested that the action of nickel is to adsorb the hydrogen (at the same time dissociating it into the atomic condition) and that it is the atomic hydrogen which interacts with the ethylenic linkage; if this were the case the acceleration induced by increasing the gas-pressure should be proportional to the square root of the latter.

scholarly journals A study of catalytic actions at solid surfaces. II.—The transference of hydrogen from saturated to unsaturated organic compounds in the liquid state in presence of metallic nickel

1919 ◽  
Vol 96 (678) ◽  
pp. 322-329 ◽  
Keyword(s):  
Organic Compound ◽  
Organic Compounds ◽  
Liquid State ◽  
Intermediate Compound ◽  
Solid Surfaces ◽  
Metallic Nickel ◽  
Saturated Compound ◽  
Unstable Type ◽  
Unsaturated Organic Compound ◽  
Intermediate System

It has been shown in the first part of this series that hydrogenation in the liquid state at a surface of metallic nickel is to be considered as effected by the temporary union of the unsaturated organic compound and of hydrogen with the nickel, followed by a breakdown of this intermediate system into nickel and the saturated compound. This explanation is a development of the “intermediate compound” theory of catalysis first put forward by De la Rive and differs from the older view mainly in that it postulates an intermediate system of a very loose unstable type, similar to that produced between the natural enzymes, water (or oxygen), and the compounds attacked by the latter, during enzymic catalysis.

scholarly journals Emissions of organic carbon and methane from petroleum and dairy operations in California's San Joaquin Valley

2013 ◽  
Vol 13 (10) ◽  
pp. 28225-28278 ◽  
Author(s):  
D. R. Gentner ◽  
T. B. Ford ◽  
A. Guha ◽  
K. Boulanger ◽  
J. Brioude ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Organic Carbon ◽  
Gas Phase ◽  
Organic Compounds ◽  
Methane Emissions ◽  
San Joaquin Valley ◽  
Motor Vehicles ◽  
Meteorological Model ◽  
Wide Range ◽  
Petroleum Extraction

Abstract. Petroleum and dairy operations are prominent sources of gas-phase organic compounds in California's San Joaquin Valley. Ground site measurements in Bakersfield and aircraft measurements of reactive gas-phase organic compounds were made in this region as part of the CalNex (California Research at the Nexus of Air Quality and Climate Change) project to determine the sources contributing to regional gas-phase organic carbon emissions. Using a combination of near-source and downwind data, we assess the composition and magnitude of emissions from these prominent sources that are relatively understudied compared to motor vehicles We also developed a statistical modeling method with the FLEXPART-WRF transport and meteorological model using ground-based data to assess the spatial distribution of emissions in the San Joaquin Valley. We present evidence for large sources of paraffinic hydrocarbons from petroleum extraction/processing operations and oxygenated compounds from dairy (and other cattle) operations. In addition to the small straight-chain alkanes typically associated with petroleum operations, we observed a wide range of branched and cyclic alkanes that have limited previous in situ measurements or characterization in emissions from petroleum operations. Observed dairy emissions were dominated by ethanol, methanol, and acetic acid, and methane. Dairy operations were responsible for the vast majority of methane emissions in the San Joaquin Valley; observations of methane were well-correlated with non-vehicular ethanol, and multiple assessments of the spatial distribution of emissions in the San Joaquin Valley highlight the dominance of dairy operations for methane emissions. The good agreement of the observed petroleum operations source profile with the measured composition of non-methane hydrocarbons in unrefined natural gas associated with crude oil suggests a fugitive emissions pathway during petroleum extraction, storage, or processing with negligible coincident methane emissions Aircraft observations of emission hotspots from operations at oil wells and dairies are consistent with the statistical source footprint determined via transport modeling and ground-based data. At Bakersfield, petroleum and dairy operations each comprised 22–23% of anthropogenic non-methane organic carbon and were each responsible for ~12% of potential precursors to ozone, but their direct impacts as potential SOA precursors were estimated to be minor. A comparison with the California Air Resources Board emission inventory supports the current relative emission rates of reactive organic gases from these sources in the region.

scholarly journals Mapping Asian anthropogenic emissions of non-methane volatile organic compounds to multiple chemical mechanisms

2013 ◽  
Vol 13 (12) ◽  
pp. 32649-32701 ◽  
Author(s):  
M. Li ◽  
Q. Zhang ◽  
D. G. Streets ◽  
K. B. He ◽  
Y. F. Cheng ◽  
...  
Keyword(s):  
Volatile Organic Compounds ◽  
Organic Compounds ◽  
Individual Species ◽  
Chemical Mechanisms ◽  
Mixing Ratios ◽  
Wide Range ◽  
Oxygenated Volatile Organic Compounds ◽  
Volatile Organic ◽  
Species Mapping ◽  
Multiple Chemical

Abstract. An accurate speciation mapping of non-methane volatile organic compounds (NMVOC) emissions has an important impact on the performance of chemical transport models (CTMs) in simulating ozone mixing ratios and secondary organic aerosols. In this work, we developed an improved speciation framework to generate model-ready anthropogenic Asian NMVOC emissions for various gas-phase chemical mechanisms commonly used in CTMs by using an explicit assignment approach and updated NMVOC profiles, based on the total NMVOC emissions in the INTEX-B Asian inventory for the year 2006. NMVOC profiles were selected and aggregated from a wide range of new measurements and the SPECIATE database. To reduce potential uncertainty from individual measurements, composite profiles were developed by grouping and averaging source profiles from the same category. The fractions of oxygenated volatile organic compounds (OVOC) were corrected during the compositing process for those profiles which used improper sampling and analyzing methods. Emissions of individual species were then lumped into species in different chemical mechanisms used in CTMs by applying mechanism-dependent species mapping tables, which overcomes the weakness of inaccurate mapping in previous studies. Gridded emissions for eight chemical mechanisms are developed at 30 min × 30 min resolution using various spatial proxies and are provided through the website: http://mic.greenresource.cn/intex-b2006. Emission estimates for individual NMVOC species differ between one and three orders of magnitude for some species when different sets of profiles are used, indicating that source profile is the most important source of uncertainties of individual species emissions. However, those differences are diminished in lumped species as a result of the lumping in the chemical mechanisms.

A mixed contact model for an immersed collision between two solid surfaces

2008 ◽  
Vol 366 (1873) ◽  
pp. 2205-2218 ◽  
Author(s):  
Fu-Ling Yang ◽  
Melany L Hunt
Keyword(s):  
Surface Deformation ◽  
Elastohydrodynamic Lubrication ◽  
Solid Particles ◽  
Solid Surfaces ◽  
Additional Energy ◽  
Collision Model ◽  
Dry Granular Flow ◽  
Wide Range ◽  
The Impact ◽  
Surrounding Liquid

Experimental evidence shows that the presence of an ambient liquid can greatly modify the collision process between two solid surfaces. Interactions between the solid surfaces and the surrounding liquid result in energy dissipation at the particle level, which leads to solid–liquid mixture rheology deviating from dry granular flow behaviour. The present work investigates how the surrounding liquid modifies the impact and rebound of solid spheres. Existing collision models use elastohydrodynamic lubrication (EHL) theory to address the surface deformation under the developing lubrication pressure, thereby coupling the motion of the liquid and solid. With EHL theory, idealized smooth particles are made to rebound from a lubrication film. Modified EHL models, however, allow particles to rebound from mutual contacts of surface asperities, assuming negligible liquid effects. In this work, a new contact mechanism, ‘mixed contact’, is formulated, which considers the interplay between the asperities and the interstitial liquid as part of a hybrid rebound scheme. A recovery factor is further proposed to characterize the additional energy loss due to asperity–liquid interactions. The resulting collision model is evaluated through comparisons with experimental data, exhibiting a better performance than the existing models. In addition to the three non-dimensional numbers that result from the EHL analysis—the wet coefficient of restitution, the particle Stokes number and the elasticity parameter—a fourth parameter is introduced to correlate particle impact momentum to the EHL deformation impulse. This generalized collision model covers a wide range of impact conditions and could be employed in numerical codes to simulate the bulk motion of solid particles with non-negligible liquid effects.

scholarly journals Comparison of OH reactivity measurements in the atmospheric simulation chamber SAPHIR

2017 ◽  
Author(s):  
Hendrik Fuchs ◽  
Anna Novelli ◽  
Michael Rolletter ◽  
Andreas Hofzumahaus ◽  
Eva Y. Pfannerstill ◽  
...  
Keyword(s):  
Water Vapor ◽  
Organic Compounds ◽  
Limit Of Detection ◽  
Measurement Techniques ◽  
Oh Radical ◽  
Atmospheric Measurements ◽  
Radical Reactivity ◽  
Wide Range ◽  
Chemical Conditions ◽  
Simulation Chamber

Abstract. Hydroxyl (OH) radical reactivity (kOH) has been measured for 18 years with different measurement techniques. In order to compare the performances of instruments deployed in the field, two campaigns were conducted performing experiments in the atmospheric simulation chamber SAPHIR at Forschungszentrum Jülich in October 2015 and April 2016. Chemical conditions were chosen either to be representative of the atmosphere or to test potential limitations of instruments. All types of instruments that are currently used for atmospheric measurements took part in one of the two campaigns. The results of these campaigns demonstrate that OH reactivity can be accurately measured for a wide range of atmospherically relevant chemical conditions (e.g. water vapor, nitrogen oxides, various organic compounds) by all instruments. The precision of the measurements (limit of detection

Tin-Mediated Radical Cyclization Reactions

2021 ◽  
Vol 25 ◽  
Author(s):  
Saima malik ◽  
Aditya G. Lavekar ◽  
Bimal Krishna Banik
Keyword(s):  
Organic Compounds ◽  
Organic Synthesis ◽  
Biological Significance ◽  
Radical Cyclization ◽  
Organic Reactions ◽  
Cyclization Reactions ◽  
Complex Molecules ◽  
Radical Chemistry ◽  
Wide Range

: The radical was first come into existence in 1900 by Gomberg, where the triphenylmethane radical was explored. Thus, even to date, two centuries have seen radical chemistry as the methodology of preference in organic synthesis. Due to the fascinating nature of the radical-mediated cyclization reactions, it always caught the eye of organic chemists for the synthesis of novel organic compounds with diverse stereochemistry. Moreover, the development of radical methods further proves beneficial for the synthesis by providing atom- and step-economical methods to complex molecules. Among these, where radical chemistry has been employed, the use of tin-based radical annulation is the most common and widely used field for the synthesis of a wide range of organic reactions with medicinal importance. In this review, we compiled recent tin-mediated radical cyclization reactions toward the synthesis of molecules of biological significance.

scholarly journals Effects of gas–wall interactions on measurements of semivolatile compounds and small polar molecules

2019 ◽  
Vol 12 (6) ◽  
pp. 3137-3149 ◽  
Author(s):  
Xiaoxi Liu ◽  
Benjamin Deming ◽  
Demetrios Pagonis ◽  
Douglas A. Day ◽  
Brett B. Palm ◽  
...  
Keyword(s):  
Organic Compounds ◽  
Transmission Efficiency ◽  
Polar Molecules ◽  
Ionization Mass ◽  
Atmospheric Measurements ◽  
Wide Range ◽  
Teflon Tubing ◽  
Gas Interactions

Abstract. Recent work has quantified the delay times in measurements of volatile organic compounds (VOCs) caused by the partitioning between the gas phase and the surfaces of the inlet tubing and instrument itself. In this study we quantify wall partitioning effects on time responses and transmission of multifunctional, semivolatile, and intermediate-volatility organic compounds (S/IVOCs) with saturation concentrations (C∗) between 100 and 104 µg m−3. The instrument delays of several chemical ionization mass spectrometer (CIMS) instruments increase with decreasing C∗, ranging from seconds to tens of minutes, except for the NO3- CIMS where it is always on the order of seconds. Six different tubing materials were tested. Teflon, including PFA, FEP, and conductive PFA, performs better than metals and Nafion in terms of both delay time and transmission efficiency. Analogous to instrument responses, tubing delays increase as C∗ decreases, from less than a minute to >100 min. The delays caused by Teflon tubing vs. C∗ can be modeled using the simple chromatography model of Pagonis et al. (2017). The model can be used to estimate the equivalent absorbing mass concentration (Cw) of each material, and to estimate delays under different flow rates and tubing dimensions. We also include time delay measurements from a series of small polar organic and inorganic analytes in PFA tubing measured by CIMS. Small polar molecules behave differently than larger organic ones, with their delays being predicted by their Henry's law constants instead of their C∗, suggesting the dominance of partitioning to small amounts of water on sampling surfaces as a result of their polarity and acidity properties. PFA tubing has the best performance for gas-only sampling, while conductive PFA appears very promising for sampling S/IVOCs and particles simultaneously. The observed delays and low transmission both affect the quality of gas quantification, especially when no direct calibration is available. Improvements in sampling and instrument response are needed for fast atmospheric measurements of a wide range of S/IVOCs (e.g., by aircraft or for eddy covariance). These methods and results are also useful for more general characterization of surface–gas interactions.

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