Study into the Specific Surface Area and Pore Space of Carbon Additives for Veba Combi Cracking (VCC)

摘要

This paper presents a comparative study into the specific surface area (BET) and the volume and pore size (BJH) of carbon additives for slurry-phase reactors of the Veba Combi Cracking (VCC) process. The main textural parameters of carbon additives affecting the conversion rate of asphaltene nanoaggregates in the reaction medium of the VCC process were determined. The size of asphaltene nanoaggregates was assessed by laser diffraction in a toluene solution, simulating the reaction mixture. It was shown that the original carbon additive proposed by the VCC technology licensor (USA) and its Russian analogue provide for asphaltene conversion only at the expense of the outer specific surface, since their pore space remains inaccessible due to the small pore size. The treatment of carbon additives with water steam at a temperature of 800°C and heat treatment in nitrogen atmosphere at a temperature of 400°C led to a significant increase in the volume of their pore space and pore diameter, thus facilitating adsorption of asphaltene nanoaggregates on the interstitial surface. Involvement of the pore space of carbon additives into the adsorption of asphaltenes enhances their conversion in the reaction medium of the VCC process.