Asphaltene reacted

Reaction with Aluminum Chloride. Asphaltene reacts readily with AlCl3 even at temperatures well below 100° C. The characteristics of the product, mainly in terms of solubility, are strongly influenced by the reaction medium (Table I). Asphaltene treated with AlCl3 in benzene remains fully soluble, while when the remaining solvents are used as a reaction medium the solubility drops to a mere 10%-20%. 

The effect of solvent on the solubility of the product can be explained on the basis of the general mechanism of a typical Friedel-Crafts reaction. Thus, asphaltene reacts with AlCl3 to form intermediate carbonium ions, which then undergo electrophilic substitution. If substitution occurs within the asphaltene molecule new bonds are formed and, depending on the size of initial fragments, the molecule may grow bigger and, thus, less soluble. 

The presence of hydrogen changes the nature of the products, especially the coke yield by preventing the buildup of precursors that are incompatible in the liquid medium and form coke. But precisely how asphaltenes react with the catalysts is open to much more speculation. 

The use of a catalytic process for the conversion of high-asphaltene feedstocks adds another dimension to asphaltene science. Asphaltenes will interact with catalysts, especially acidic support catalysts through the basic nitrogen, just as they will interact with adsorbents. The means by which they do so is another issue, but evidence is available for interaction at a single functional group in which the remainder of the asphaltene molecule remains in the liquid phase. As a less desirable option, the asphaltene reacts with the catalyst at several points of contact, causing a more massive lay-down of coke on the catalyst surface (104). 

Klein et al. " investigated the pyrolysis kinetics of resids, isolated asphaltenes and maltenes from Hondo, Arabian heavy, Arabian light, and Maya oils. At 400°C and 425°C, isolated asphaltenes reacted selectively to form maltenes. At higher temperatures (450°C), asphaltenes reacted... 

Nevertheless, the development of general kinetic data for the hydrodesulfurization of different feedstocks is complicated by the presence of a large number of sulfur compounds each of which may react at a different rate because of structural differences as well as differences in molecular weight. This may be reflected in the appearance of a complicated kinetic picture for hydrodesulfurization in which the kinetics is not, apparently, first order (Scott and Bridge, 1971). The overall desulfurization reaction may be satisfied by a second-order kinetic expression when it can, in fact, also be considered as two competing first-order reactions. These reactions are (1) the removal of nonasphaltene sulfur and (2) the removal of asphaltene sulfur. It is the sum of these reactions that gives the second-order kinetic relationship. 

When catalytic processes are employed, complex molecules (such as those that may be found in the original asphaltene fraction) or those that are formed during the process, are not sufficiently mobile. They are also too strongly adsorbed by the catalyst to be saturated by the hydrogenation component and, hence, continue to react and eventually degrade to coke. These deposits deactivate the catalyst sites and eventually interfere with the hydroprocess. 

While asphalt itself consists of a complex colloidal dispersion of resins and asphaltenes in oils, introduction of liquid elemental sulfur, which on cooling congeals into finely dispersed crystalline sulfur particles and in part reacts with the asphalt, necessarily complicates the rheology of such a SA binder. Differences and changes with SA binder preparation, curing time, temperature etc. must be expected and may be demonstrated by viscosity characteristics. 

Samples of each of the coal derived materials were reacted separately in the presence of several catalysts in a 70 ml batch autoclave using a 1 1 slurry of tetralinrmaterial at 425 C with an initial hydrogen pressure of 6 MPa for 1 hour at reaction temperature. The products from these reactions were separated into oils, asphaltenes, preasphaltene and THF insolubles. 

In either case, in order to explain the molecular size shift and disappearance of the large molecules, we modified the model in two ways. First the molecular diameter of the asphaltene molecules are reduced by an amount directly proportional to their molecular volumes. Secondly, the disappearance of the large molecular-sized vanadium is treated as a non-catalytic first order reaction with a rate constant directly proportional to molecular volume. The vanadium which reacts thermally deposits... 

Whatever the composition of the component molecules, association into larger species is certain. Variations in molecular weight between ca 3000 [15] and 150,000 [16] have been reported, as have asphaltene sizes of60-90A [16]-again considered to be an over-estimate [7,8]. In the context of hydroprocessing it is obviously the size of the entity than actually reacts on the catalyst rather than the absolute size of the molecule or conglomerate that is important. 

The toluene-soluble products from each reacted kerogen were subjected to SARA analysis (saturates, aromatics, resins, asphaltenes) (22). The B toluene solubles gave almost 91% asphaltenes. The C kerogen toluene solubles were almost 81% asphaltenes. The C toluene solubles were more difficult to handle 14.5% of the material was unrecovered from the chromatographic column. 

Application of this model to a residuum desulfurization gave a linear relationship. However, it is difficult to accept the desulfurization reaction as a reaction that requires the interaction of two sulfur-containing molecules (as dictated by the second-order kinetics). To accommodate this anomaly, it has been suggested that, as there are many different types of sulfur compounds in residua and each may react at a different rate, the differences in reaction rates offered a reasonable explanation for the apparent second-order behavior. For example, an investigation of the hydrodesulfurization of an Arabian light-atmospheric residuum showed that the overall reaction could not be adequately represented by a first-order relationship. However, the reaction could be represented as the sum of two competing first-order reactions and the rates of desulfurization of the two fractions (the oil fraction and the asphaltene fraction) could be well represented as an overall second-order reaction. 

In this model, there are four common features that apply to resid conversion and these features are 1) an induction period prior to coke formation 2) a maximum concentration of asphaltenes in the reacting liquid 3) a decrease in the asphaltene concentration that parallels the decrease in heptane-soluble material and 4) the high reactivity of the unconverted asphaltenes. Thus, the model can be represented as ... 

In aLkaline flooding, the injected aUcali reacts with the saponifiable components in the reservoir crude oil. These saponifiable components are described as petroleum acids (naphthenic acids). Naphthenic acid is the name for an unspecific mixture of several cyclopentyl and cyclohexyl carboxylic acids with molecular weight of 120 to well over 700. The main fractions are carboxylic acids (Shuler et al., 1989). Other fractions conld be carboxyphenols (Seifert, 1975), porphyrins (Dnnning et al., 1953), and asphaltene (Pasquarelli and Wasan, 1979). The naphtha fraction of the crnde oil raffination is oxidized and yields naphthenic acid. The composition differs with the crude oil composition and the conditions dnring raffination and oxidation (Rndzinski et al., 2002). 

This means that cracking of the paraffinic periphery (reaction (9.1)) is the only reaction that can cause the reduction of the molecular weight of asphaltenes at this temperature level. In other words, during polycondensation of asphaltenes at 425°C, it is not only the aromatic cores of native asphaltenes that react. Asphaltenes with paraffinic chains also undergo a reaction (reaction (9.3)). 

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