Asphaltenes dispersion

D. Miller, A. Vollmer, M. Feustel, and P. Klug. Synergistic mixtures of phosphoric acid esters and carboxylic acid derivatives as asphaltene dispersants (Synergistische Mischungen von Phosphorsaureestem mit Carbonsaurederivaten als Asphalten-Dispergatoren). Patent EP 967361, 1999. 

W. K. Stephenson and M. Kaplan. Asphaltene dispersants-inhibitors. Patent CA 2029465, 1991. 

Manek, M.B., Asphaltene Dispersants as Demulsification Aids in Proc. SPE International Symposium on Oilfield Chemistry, Society of Petroleum Engineers Richardson,... 

This problem occurs primarily in treating heavy crude oils and light asphaltic crude oils produced by miscible flooding. The addition of an asphaltene dispersant to the crude oil to prevent accumulation of insoluble asphaltenes may resolve this problem. 

The selection of asphaltene dispersant chemistry and dosages requires careful consideration. Most asphaltene dispersants are either light aromatic compounds with polar groups (e.g., cresylic acid) or highly water-dispersible or water-soluble surfactants. These materials will prevent insolubility of asphaltenes, but they also tend to adversely affect the dehydration of emulsions and to increase oil-in-water concentrations. 

Successful selection of asphaltene dispersant chemistries and dosages will provide reductions in interface pads, emulsion-breaker consumption, and oil-in-water concentrations and provide oil-free inorganic solids. 

If one cannot diffuse the asphaltenes to the catalyst, why not diffuse the catalyst to the asphaltenes Dispersed catalysts also can be continuously added in sufficiently low enough amounts (i.e., 100 ppm) to consider them throwaway catalysts with the carbonaceous by-product. However, economics usually dictate some form of catalyst recycle to minimize catalyst cost. Nevertheless, by designing the reactor to maximize the solubility of the converted asphaltenes, the conversion of vacuum resids to gas and volatile liquids can be above 95% with greater than 85% volatile liquids. However, the last 5-10% conversion may not be worth the cost of hydrogen and reactor volume to produce hydrocarbon gases and very aromatic liquids from this incremental conversion. The answer depends on the value and use of the unconverted carbonaceous liquid by-product. 

Nonhydrocarbon Solvents, Although an asphaltene fraction can be removed from petroleum by using a wide variety of hydrocarbon liquids (14), the use of nonhydrocarbon solvents as deasphalting media and their influence on asphaltene dispersibility and compatibility has also been investigated. Dispersibility of asphaltenes in petroleum is suggested to be conveniently related to the surface tension of the system components (8, 20, 21, 22, 23). Obviously, asphaltene dispersion and compatibility is complex and is dependent on several factors and varies markedly with the character of the added liquid. 

Solubility and Incompatibility. Asphaltenes are, in fact, insoluble in the oil fraction (3, 4) and the likelihood that asphaltene dispersion is mainly attributable to the resins is possible. 

Figure 10. An early model of the physical structure of petroleum showed the asphaltenes dispersed and peptized by resin species.

Thus, asphaltene dispersibility and compatibility in the liquid medium is an important factor in process control (105) and needs to be addressed at some stage of the operation. The consequences of not doing so can be costly. 

It is well recognized that these emulsions are stabilized by means of an interplay between different heavy components, organic and inorganic particles, respectively. Heavy components cover asphaltenes, resins, etc. In a depressurized anhydrous crude oil the asphaltenes are normally in a particulate form. The role of the resins (and lighter polar components) is to stabilize the asphaltene dispersion (suspension) by adsorption mechanisms. Owing to this strong interaction the asphaltene particles are prevented... 

Bitumens are colloid systems, as are crude oils, and consist of the two colloidal components, petroleum resins and asphaltenes, dispersed in a dispersion medium. To investigate the composition of the system, a colloid precipitation according to Neumann [4-10] is carried out. The chemical nature of the bitumen and its components were determined by element analysis, where the atomic ratio H/C includes an indicator of the aromacity. Further characterization is performed by measuring the average relative particle mass (mean of the molecular weight M) by vapor pressure osmometry. 

Asphaltene dispersed in the asphalt can form micelles, supeimicelles, and even giant supermicelles or liquid crystals, depending on the content of asphaltene and resins. All units exist in the asphiit systems but their distributions are different. The micelles and supeimicelles are predominantly sol type asphalts liquid crystal are predominantly gel type asphalts and giant supermicelles are predominantly sol-gel types. For different types of asphalt, the physical and chemical properties are different and, therefore, their uses and applications will differ. 

The solubility of asphaltene in the solvent with different polarity has been demonstrated by other researchers. According to the polarity of asphaltene and that of various solvents, the degree of asphaltene dispersion is various. The asphaltene size distributions in the different solutions will vary from each other. Using the derived Kord law, the relationship between the size distribution of asphaltene particles and solvent characteristics are established. 

Bitumen blowing is an oxidation operation by the in the air. It is designed to increase asphaltene dispersion in bitumen. The gases are scrubbed in a hot soft water countercurrent and the resulting water constitutes a remarkably stable chemical emulsion (2000 to 8000 mg r ) which can be broken only by severe coagulation or by acidification. 

Asphalt is a black, sticky, viscous Uquid that is obtained from crude petroleum. It comprises almost entirely a form of tar called bitumen. The structure of asphalt is actually a colloidal suspensitm, with small particulates called asphaltenes dispersed through the petroleum matrix. More environmentally friendly aqueous-based asphalt emulsions are currently being used for road repair appUcatitms. 

Asphaltenes stabilize the crude oil emulsion by different modes of action. When asphaltenes disperse on the interface, the film formed at a water/ crude oil interface behaves as a skin whose rigidity can be shown by the formation of crinkles at interface when contracting the droplet to a smaller drop size ( ). They can also aggregate with resin molecules on the interfaces and prevent droplet coalescence by steric interaction (Figure 11). Some authors suggest that asphaltenes stabilize the emulsion by formation of hydrogen bonding between asphaltenes and water molecules (79-so)... 

Prevention or inhibition of organic deposition is far more effective than removal. Commercially available inhibitor treatment products (wax crystal modifiers, and asphaltene dispersants or inhibitors) are available. Selection should be based on careful laboratory evaluation and testing with appropriately preserved produced crude oil samples. 

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