Comparison of Structural Properties of Pitches Prepared from Petroleum Refinery/Petrochemical Residues using NMR Spectroscopy

CATEGORY: RESIDUES

The Open Petroleum Engineering Journal, 2012, 5, 14-20

Comparison of Structural Properties of Pitches Prepared from Petroleum Refinery/Petrochemical Residues using NMR Spectroscopy

Manoj Srivastava*, Manoj Kumar, U. C. Agrawal and M. O. Garg

manojs@iip.res.in

CSIR - Indian Institute of Petroleum, Dehradun 248 005, India

Abstract:

Several petroleum pitches have been prepared by thermal treatment of various petroleum-derived residues such as clarified oil, aromatic extract and pyrolysis tars. These pitches were characterized physico-chemically (softening point, coking value, QI, & TI) and instrumentally (NMR) and compared. Attempts have been made to correlate physicochemical properties of petroleum residues and pitches with their NMR structural parameters through regression analysis. Studies on high temperature in-situ 1H NMR analysis of pitches have also been carried out. Structural characterization of petroleum residues and pitches is very useful for screening of petroleum residues and optimization of process variables for tailoring pitch properties for different end-use applications.

INTRODUCTION

Today, petroleum refining industry is facing unprecedented challenges like declining crude quality and more severe product specifications. One main challenge before petroleum refiners/petrochemical producers is the effective utilization of petroleum residues produced during various petroleum refinery/petrochemical processes. Generally, these residues are used as blending streams for fuel oils but the market of fuel oil is shrinking. To fetch substantial money out of these low value petroleum residues, one way is to convert these petroleum residues into pitch. Pitch is a widely used precursor for making many low volume but high cost ‘industrial’ and ‘advanced’ carbon materials [1]. Pitch is generally prepared by thermal treatment of petroleum/coal derived residues. The inherent complexity of petroleum residues increases the pitch complexity many more times. The properties of pitch are largely dependent on feed properties, thermal treatment temperature, residence time, pressure and additives used. The proper selection of these variables leads to formation of desired quality of pitches. The feed stock constituents and their reactivity greatly influence the properties of pitch. The knowledge of structural composition of isotropic pitch is also important for their conversion into mesophase pitch and thereafter production of various carbon materials namely needle coke, carbon fibers, meso carbon micro beads (MCMB) etc. NMR spectroscopy [2] is one of the powerful tools for structural characterization of feed stocks as well as pitches. It helps to quantify the different kinds of carbon and hydrogen atoms depending on their location and bonding within the molecules.

In the present study, various petroleum-derived residues were characterized and converted into pitches. The main objective of this work is to carry out a detailed study to correlate physico-chemical properties of feed stocks and pitches. High temperature in-situ NMR studies were also carried out to examine the mesophase formation behaviour in various isotropic pitches at high temperature. This will help to have a better understanding for selection of feed stocks for making ‘mesophase pitches’.

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