Asphaltenes Mesophase

Effects of Sulfur and Metals on Mesophase Formation in Coal Liquid Asphaltene and Petroleum Pitch... 

The effect of elemental sulfur and organic sulfur compounds and organometallics on the mesophase microstructure was investigated. Elemental and organic sulfur coiqtounds and organometallic compounds were added to Catalytic Incorporated coal liquid asphaltene and A240 petroleum pitch. 

The properties of manufactured graphites are determined by the microstructure of the carbonaceous mesophase which is formed during pyrolysis, usually between the temperatures of 370 C and 500°C. The characteristics of the final product can be measured in a qualitative way by examination of the mesophase micro-structure. Several coal liquid asphaltene and petroleum pitch samples have been screened in this way to determine their suitability as precursors for graphite materials. The physical and chemical properties of the mesophase formed from the samples and their pyrolyses residues were studied(1). It was found that the phenolic oxygen present either in the precursor or by addition during heat treatment suppresses mesophase formation by crosslinking and preventing the development of fluidity(2J>... 

Figure 2. Micrographs of pyrolyiei residues of Catalytic Incorporated (Cat. Ino.) coal liquid. Cat, Ino. asphaltene and the effect of elemental sulfur on mesophase formation in Cat. Ino. asphaltene.

Dibenzothiophene(DBT) was added to Cat. Inc. asphaltene to determine the effect of sulfur when added as an organic molecule. Table III shows the amount in weight percent of DBT that was added to obtain the desired weight percent of sulfur. For 8Z by weight organic sulfur the sample contains almost half DBT. When DBT is pyrolyzed alone to 460 C the pyrolysis yield is zero. As shown in Figure 4 the DBT sulfur has no effect on the microstructure of the pyrolysis residues. It is difficult to tell if this is because most of the DBT vaporizes before mesophase... 

Figure 4. The effect of organic sulfur on mesophase formation in Cat. Inc. asphaltene.

The effect of organometallics at 1600 ppm and 800 ppm on the pyrolysis residues of the Cat. Inc. asphaltene are shown in Figure 5 and Table IV. The additives used were mentioned in the experimental part. Table IV shows that organic Hi and V inhibit mesophase formation because they promote dehydrogenation and condensation reactions to a greater extent than the other listed additives. Pyrolysis yields are increased because of increased... 

In crude oil and water systems asphaltenes are adsorbed at the water-oil interface and flocculate yielding a three-dimensional structured film (as Mesophase C) (43). Such structured films at the W/0 interface were verified by Sif-fert et al. (44). They separated oil, water, and a sticky mass between sheets in asphaltene particles for fliis black mass. These regularly stacked lamellar structures have close similarity to surfactant liquid crystals. 

Precursor Pitch. The precursor material is a mesophase pitch, characterized by a high percentage of asphaltene. Table 8.5 shows the approximate composition of three common mesophase compounds. 

The thermal chemistry of heavy oils and bitumen is extremely complicated because of wide variations in chemical compositions. The most refractory components in petroleum feedstocks are asphaltenes, which contribute the most to coke formation dining thermal cracking. Next to asphaltenes, resins and large aromatics also contribute to coke. To investigate the effect of these three heavy oil components on the mesophase induction period, Athabasca bitumen fractions containing varying amounts of asphaltenes (obtained by supercritical fluid extraction) and Venezuelan heavy... 

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