Natural Zeolite Catalysts for the Integrated Cracking, Waterless Extraction and Upgrading of Oilsands Bitumen

Natural Zeolite Catalysts for the Integrated Cracking, Waterless Extraction and Upgrading of Oilsands Bitumen

Junaid, Abu (2011)

Department of Chemical and Materials Engineering

Abstract: 

Canadian oilsands bitumen represents one of the largest petroleum reserves in the world.  Extraction of that resource raises significant environmental, operational and quality-related challenges. Current extraction processes are water intensive.  They generate high volume tailings ponds that are challenging to treat. The bitumen has higher concentrations of heteroatoms and heavy metals than those found in typical crude oil.  A large portion of the material consists of high boiling point fractions. Severe upgrading techniques are required to convert this bitumen to synthetic crude oil prior to refining.

The multi-step processing operations that address these issues are capital intensive, with substantial operational and maintenance costs. Inexpensive, globally abundant natural zeolites including chabazites and clinoptilolites offer an alternate approach. These minerals have platy morphology and high external surface areas that can accommodate large molecules such as asphaltenes for cracking. Analytical and surface sensitive techniques show that both raw and ion-exchanged forms of these minerals have higher acid strengths and/or acid site densities than the commercial petroleum cracking catalyst zeolite Y. Interestingly, the addition of small amounts of water creates acid sites on untreated chabazite and clinoptilolite surfaces by hydrolysis, eliminating the need for ion-exchange to achieve acidification. Because of these extraordinary features, natural zeolite catalysts can crack oilsands bitumen at temperatures much below typical thermal cracking conditions, lowering viscosities and average molecular weights while adsorbing undesirable heteroatoms (nitrogen, sulfur) and heavy metals (vanadium, nickel). The reactions convert up to ~81% of the heavy residue fraction in a stirred batch system at relatively low severity conditions, and produce very high total liquid yields (≤96%), significant amounts of which are residue-free (≤71%). High conversion of the asphaltenes results in liquid products that are almost entirely extractable from the sand matrix using light hydrocarbons (pentane and hexane). Based on these findings, we envision a low severity, integrated extraction and upgrading process for oilsands bitumen that uses self-acidified natural zeolites, is waterless and environmentally friendly, requires fewer steps and improves pipeline transportation. As more energy efficient alternatives, natural zeolites can also be used to upgrade pre-extracted or in situ bitumen.

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