Quality of Distillates From Recycle Coking Mohamed Shakir Japanwala Department of Chemical & Materials Eng., University of Alberta

Typical Upgrading Scheme Hydrogen Plant Hydrocracking Cokers Hydrotreaters Treated Naphtha and Gas Oils Synthetic Crude Oil Storage and Blending Bitumen

Coking Process Recycle Stream Feed Coke Liquid Products Coking Reactor

Project Objectives How reactive are the recycled materials to further cracking and coke formation? What are the characteristics of the cracked products? How do the products affect hydrotreating catalysts?

Experimental Plan Vacuum Distillation 1st Stage2nd Stage3rd Stage Vacuum Distillation ReactorReactor Reactor Residue 2 Residue 1 Residue 3 Distillate 1 CokeCoke Coke Distillate 2 Distillate 3 GasGas GasFeed

Experimental Apparatus Nitrogen in Acetone Dry Ice Molten Salt Bath Quartz Tube Reactor U-Tube Reactor Temperature o c Nitrogen Flowrate L/min (NTP) Reactor Volume - 60 mL

Cumulative Product Yields

Characterisation Analytical methods –NMR functional group analysis –Elemental analysis (C, H, N, S) –Average molecular weight –Micro carbon residue (MCR) –Simulated distillation by gas chromatography –High performance liquid chromatography (HPLC)

Hypothetical Hydrocarbon Molecule 1Aromatic Bridgehead C Protonated Aromatic C 3Methyl Group on Aromatic C 5CHAIN : CH 2 that are atleast  from aromatic or terminal methyl or atleast  to cycloparaffin or branch point 4Naphthenic CH 2 6Terminal Chain Methyl's

Structural Changes Constant chain length. Naphthenic carbon decreases. Aromatic carbon increases.

Structural Parameters-Resid

Aromatic Carbon - Mass Balance

Undesirable Constituents of Distillate Nitrogen compounds are known to act as catalyst poison. PAHs contribute to increased coke formation. Bitumen derived gas oil vs conventional gas oil –Higher Sulphur and Nitrogen Content –Higher Aromaticity –Higher MCR

Distillate Nitrogen Content

Structural Parameters-Distillate

UV Absorption Spectra (282nm) Diaromatic Tetraaromatic

Distillate MCR

Distillate Quality Weight % Nitrogen increases MCR content increases Aromaticity increases PAHs increase

Coke Quality on Recycle Coke quality improves. Recycle stream excellent source to make good quality coke!

Implications of Research - Ideal Coker Coke Maximize Distillate Yield Bitumen Feed PAHs Heteroatoms Metals Coking Reactor

Implications of Research The distillate quality rapidly deteriorates upon recycle coking. –A large amount of aromatic carbon is in the form of polycyclic aromatics in the recycle stream. –There is an increase in the weight % nitrogen.

Implications of Research Recycle Stream Feed Coke Distillate Coking Reactor

What Next? Is the lower quality worth the higher yield?