Carbon, distribution

It is also possible to extrapolate the carbon distribution to the gasoline range on the one hand and to the residne on the other hand. A high value of %Ca at 500°C (930°F) boiling point nsnally indicates a high content of asphaltenes in the residne, whereas a high valne of %Cnp at a 500°C (930°F) boiling point nsnally indicates a waxy residne. 

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Shell Higher Olefins Process (SHOP). In the Shell ethylene oligomerization process (7), a nickel ligand catalyst is dissolved in a solvent such as 1,4-butanediol (Eig. 4). Ethylene is oligomerized on the catalyst to form a-olefins. Because a-olefins have low solubiUty in the solvent, they form a second Hquid phase. Once formed, olefins can have Htfle further reaction because most of them are no longer in contact with the catalyst. Three continuously stirred reactors operate at ca 120°C and ca 14 MPa (140 atm). Reactor conditions and catalyst addition rates allow Shell to vary the carbon distribution. 

The n-d-M correlation is an ASTM (D-3238) method that uses refractive index (n), density (d), average molecular weight (MW), and sulfur (S) to estimate the percentage of total carbon distribution in the aromatic ring structure (% C ), naphthenic ring structure (Cj,), and paraffin chains (% Cp). Both refractive index and density are either measured or estimated at 20°C (68°F). Appendix 4 shows formulas used to calculate carbon distribution. Note that the n-d-M method calculates, for example, the percent of carbon in the aromatic ring... 

G. Johansson, Carbon distribution in grass (Festuca pratensis L.) during regrowth after cutting-utilization of. stored and newly a.ssimilated carbon. Plant Soil I5I I (1993). 

A. A. Meharg and K. Killham, Carbon distribution within the plant and rhizosphere for Lolium perenne subjected to anaerobic soil conditions. Soil Biol. Biochem. 22 643 (1990). 

G. Johansson, Below-ground carbon distribution in barley Hordeum vulgare L.) with and without nitrogen fertilization. Plant Soil 144 95 (1992). 

Propylene, ammonia, steam and air are fed to a vapour-phase catalytic reactor (item A). The feedstream composition (molar per cent) is propylene 7 ammonia 8 steam 20 air 65. A fixed-bed reactor is employed using a molybdenum-based catalyst at a temperature of 450°C, a pressure of 3 bar absolute, and a residence time of 4 seconds. Based upon a pure propylene feed, the carbon distribution by weight in the product from the reactor is ... 

Table 1. Structural carbon distribution (%) of the humic acids extracted from soil horizons, adopted from Xing (2001). The distribution was calculated from solid state 13C Cross-Polarization Magic-Angle-Spinning (CP/MAS) NMR spectra. Chemical shift assignment for carbon functional groups alkyl 0-50 ppm O-alkyl 50-117 ppm aromatic 107-165 ppm.

Carbon-13 magnetic resonance (CMR) can play a useful role. Since carbon magnetic resonance deals with analyzing the carbon distribution types, the obvious structural parameter to be determined is the aromaticity, fa Direct determination from the various types of carbon environments is one of the better methods for the determination of aromaticity. Thus, through a combination of proton and carbon magnetic resonance techniques, refinements can be made on the structural parameters, and for the solid-state high-resolution carbon magnetic resonance technique, additional structural parameters can be obtained. 

Figure 4 Activation energy for conversion to toluene solubles vs. protonated aliphatic carbon for Argonne Premium Coal sample bank bituminous coals. Data on carbon distribution from Dr. Ronald L. Pugmire, University of Utah.

Standard Test Method for Calculation of Carbon Distribution and Structural Group Analysis of Petroleum Oils by the n-d-M Method. ASTM D3238-95 (2005). 

C/12C ratio in natural vanillin is smaller than that observed in synthetic vanillin. The same effect applies to glucose, whose isotopic carbon distribution varies depending on the biological cycle of the plant. 

Figure 1. Carbon abundance as a function of mass for both components of a close binary system at the onset of mass transfer. The region from Mx=0 to Mr=Mgi=8.1 Mo corresponds to the originally less massive component (gainer), whereas the carbon distribution of the loser is plotted from 8.1 Mo (surface) to 17.1 M (center). The first occurrence of hydrogen depleted layers (Xat<0.7) and the end of the Roche Lobe Overflow are indicated.

Figure 11. Effect of pressure on organic carbon distribution in products and mineral carbonate decomposition...

Very commonly, however, the sample of interest is not a pure compound, but is a complex mixture such as a coal liquid. As a result, a specific structure determination for each molecular type is not practical, although it is possible to determine an average chemical structure. Features which may be determined include the hydrogen distribution between saturate, benzylic, olefinic, and aromatic sites. The carbon distribution is usually split into saturate, heterosubstituted saturate, aromatic + olefinic, carboxyl, and carbonyl types. More details are possible, but depend greatly on the nature of the sample, and what information is desired. 

Nowhere is the contribution of spectroscopic studies more emphatic than in application to the delineation of structural types in the heavier feedstocks. This has been necessary because of the unknown nature of these feedstocks by refiners. One particular example is the n.d.M. method (ASTM D-3238) which is designed for the carbon distribution and structural group analysis of petroleum oils. Later investigators have taken structural group analysis several steps further than the n.d.M. method. 

Combine a spatula of carbon powder with a spatula of sulfur powder. A physical change will occur. There is a change in the sulfur and carbon distribution and an apparent color change, but the sulfur and carbon remain. No new substance is formed. 

ID 13C NMR N/A Can provide a quantitative overview as to the carbon distribution. In the case of NOM, often 2D NMR is central to the interpretation of the ID NMR, which often contains considerable overlap. For quantitative data, the recycle delay (dl) should be >5 x T1 for the slowest relaxing component in the sample and inverse gated decoupling should be carried out, to prevent the transfer of XH NOE to the BC nuclei. 

Kogel-Knabner, I., and Ziegler, F. (1993). Carbon distribution in different compartments of forest soils. Geoderma 56,515-525. 

Wan, J., Tyliszczak, T., and Tokunaga, T. K. (2007). Organic carbon distribution, speciation, and elemental correlation within soil microaggregates Apphcation of STXM and NEXAFS spectroscopy. Geochim. Cosmochim. Acta 71, 5439-5449. 

The quantitative nature of this assumption has been studied in our laboratory on a set of six different coals ranging in rank from lignite to anthracite. The average correction factor for nonprotonated aromatic carbons is 6%. See M. A. Wilson, L. B. Alemany, W. R. Woolfenden, R. J. Pugmire, P. H. Given, D. M. Grant, and J. Karas, "Carbon Distribution in Coals and Coal Macerals as Determined by CP/MAS 13C NMR Studies", submitted for publication. 

Results from both analyses were combined to give carbon distribution in the range 0-10 by several hydrocarbon types namely iso, normal and cyclo paraffins, iso, normal, and cyclo olefins, and mono-ring aromatics. For convenience these groups are abbreviated to IP, NP, CP, IO, NO, CO, and AR respectively, and suffixed by the relevant carbon number i.e. IP-5 equates to total C5 iso-paraffins. 

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