Delayed Coker Coke Characterization: Correlation between Process Conditions, Coke Composition, and Morphology

Abstract

Delayed coking is the technology most used to upgrade vacuum residue into high-value products, but in this process, secondary reactions produce coke. It is already known that the chemical and physical properties and composition of the feedstock and processing conditions affect coke morphology. Recently, a new type of morphology, called transition coke, has been described, but this morphology should be avoided because it induces operational and safety risks to delayed coking units. Several studies have attempted to understand the complex structure of this type of coke and the factors that control the different final morphologies. Therefore, the purpose of this study is to shed additional insight on the correlation between surface chemical composition and the morphology of delayed coker coke with variables of the process, such as the temperature, pressure, and elemental composition of the feedstock. All of the samples had a surface area between 1 and 4 m 2 /g, showing that the coke lacks porosity. Morphological classification by scanning electron microscopy (SEM) showed transition/associated shot-and spongetype coke. From X-ray photoelectron spectroscopy (XPS), it was possible to identify heteroatoms as N, S, Si, and O on the surface of the samples. Metals were not found on the surface of the solids, despite the fact that atomic absorption (AA) and total reflection X-ray florescence (TXRF) showed elements such as Ni and V in the bulk. Solid-state nuclear magnetic resonance (ssNMR) was used to identify the aromatic and aliphatic regions and to calculate the aromaticity factor ( f a ) and the relationship of peri-to cata-condensed carbons, C peri /C cata , in the aromatic structure of the samples, giving us an idea of the condensation degree, ϕ, of the aromatic moieties. The results of this work allow us to verify that the low metal amount in the samples is related to sponge and transition coke. Thus, it is possible that this fact, in combination with the amounts of nitrogen and sulfur on the surface, could influence the formation of transition coke and that variables, such as the temperature, direct a change in morphology from transition to sponge coke.

Processing Unconventional Oil: Partial Upgrading of Oilsands Bitumen

“…This comparison should be considered qualitative because the coke characterizations reported in Table were from industrial samples and were not accompanied by characterizations of the bitumen feed materials. Nevertheless, similar observations can be found for other oils where the feed and coke from delayed coking were both characterized in the same study …”

“…Nevertheless, similar observations can be found for other oils where the feed and coke from delayed coking were both characterized in the same study. 64 Delayed coking is inherently associated with a yield loss due to the formation of coke and light gases. For Athabasca bitumen, typical coke and gas yields are around 25 and 3 wt %, respectively.…”

Polymer Composites with Carbon Fillers Based on Coal Pitch and Petroleum Pitch Cokes: Structure, Electrical, Thermal, and Mechanical Properties

“…Table 4. The results of FTIR analysis of carbon fillers [49][50][51][52][53][54][55]. It was also found that during grinding the PET coke was broken down into rather irregular solid crumbs, while the CP coke grains disintegrated mainly along carbon planes giving flake-shaped particles (Figure 3).…”

Synthesis of sulfur-doped porous carbon from heavy coker gas oil and its application in CO2 capture

“…Without the S-crosslinker, the carbon yield is only 5 wt%, with a s.a. o10 m 2 g À1 . 23 the complexity of the feed and the crosslinked intermediate presents challenges to derive mechanism. A key analytical breakthrough came from 1H NMR and GPC.…”