UNIFICATION OF PETROLEUM FEEDSTOCKS FOR THE PRODUCTION OF TECHNI

Abroad, the provision of feedstocks for technical carbon is based on two main petroleum refining processes: catalytic cracking (decanted gas oil) and pyrolysis (resins from ethylene production). Typical quality requirements for these feedstocks include I0 parameters [7]. Both feedstocks possess a highly aromatic character (correlation index not less than 120). In the Soviet Union feedstocks for technical carbon are obtained by thermal and catalytic cracking, pyrolysis, extraction, and coking (Table i). Different technical standardization documents (NTD) exist even for feedstocks that are produced by the same process, with similar correlation indexes (for instance, thermal oil and thermal concentrate, gas oils from thermal and catalytic cracking, etc.). Of the 15 parameters used to assess the feedstock quality (Table i) only three (density, correlation index, and water content) are determined almost for every kind of feedstock. Changing to the production of predominantly high-index feedstocks will reduce the number of feedstock components in the production of technical carbon. The selection of the feedstock parameters which determine the quality and yield of the final product, requires special investigations. The most important criterion for the feedstock quality is its degree of aromatization. The yield and quality of tehcnical carbon depend on the carbon content of the feedstock, which is related to the number of aromatic rings in the molecule. Naphthenic and paraffinic hydrocarbons participate in the formation of the soot particles only after various transformations, in particular after dehydrogenation; thus, the yield of carbon black decreases when they are present in the feedstock. Most carbon-black products are polycyclic aromatic hydrocarbons; thus, the production of soot particles and their combination into spatial structures is most intensive when these hydrocarbons are present [8]. Industrial hydrocarbon feedstocks must contain 2.5-3.5 aromatic rings in the average molecule, i.e., the most desirable components of the feedstock are the two-, three-, and four-ring aromatic hydrocarbons. Only in this instance the production of a highly dispersed technical carbon can be guaranteed. Hydrocarbons with more than 3.5 rings have a negative effect on the atomization and evaporation of the feedstock, assist the growth of coke inclusions in the technical carbon, although theoretically the highest rate of formation of soot nuclei should occur at an aromatic ring content of 8-10, which is identical to the ring content in the basic plane of a graphite crystallite of medium size [9].