Research aims for cleaner crude from Canadian tar sands
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Energy Quarterly
Research aims for cleaner crude from Canadian tar sands By Melissae Fellet Feature Editor Manuel Ramos
D
emand for gasoline and other automotive fuels in emerging markets is expected to be met by growth in oil production from North America. Proven Canadian oil reserves are the third largest in the world, and the majority of those deposits are tar sands in Alberta. Tar sands contain a heavy oil, called bitumen, that is found mixed with clay and water. The viscosity and chemical composition of bitumen makes it difficult to extract, transport, and refine. Technological improvements have made its production economically feasible, though this comes at an environmental cost. In US refineries, processing crude from the oil sands produces more greenhouse gases than the typical crude. Researchers and companies are working to reduce the environmental impact of bitumen production by engineering new catalysts to efficiently clean the dirty crude. They are also working to convert waste from bitumen refining into materials for renewable energy.
Light crude oil from countries in the Middle East flows freely at room temperature because it mainly contains short hydrocarbons that are easily converted to fuel. Bitumen, in contrast, is a mixture of long hydrocarbons and large aromatics that creates a material resembling cold molasses. Producers can recover this crude by directly mining it. In deeper formations, they inject hot steam into tar sands, melting the bitumen so it can be pumped to the surface. Generating the steam involves burning natural gas to boil water, which is one source of emissions during bitumen production. Canadian oil companies are looking for new extraction methods that use less steam. Suncor, based in Alberta, and Imperial Oil, based in Calgary, are pilot testing methods of bitumen recovery by injecting solvents such as propane or butane instead of steam. Less heat is needed inside the reservoir because the solvents also thin the bitumen. Separating and recovering the solvents at the surface are keys to the economic viability of the process. Another energy-intensive step of bitumen production is processing, or upgrading, the crude once it reaches the surface. The goal of this step is to generate a material suitable for further refining into lighter fuel hydrocarbons. Some bitumen is upgraded by dilution with lighter oil or natural gas condensate, reducing the viscosity of the crude so it can flow through pipes to a refinery. Another form of upgrading occurs in the field. The crude is treated with heat, hydrogen, and supported metal catalysts to chemically alter the heaviest fraction of bitumen. The goal of field upgrading with catalysts is to crack long hydrocarbons into small components; remove contaminants like sulfur, nitrogen, and heavy metals; and produce a material similar to diluted bitumen. Typical upgrading catalysts are made from cobalt, nickel, and molybdenum. Several properties of bitumen can reduce the lifetime of the catalysts. The large molecules in bitumen clog pores, leading
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