Molecular conformation and crystal structure of n-alkanes using multi-scale terrain/funneling optimization

Document Type

Conference Proceeding

Date of Original Version



Waxing of petroleum or hydrocarbon fuels such as home heating and diesel fuels is a costly problem in the petroleum industry. The molecular conformation of n-alkanes and the interplay between molecular conformation and crystal structure in the waxing of petroleum fuels were studied. Typical fuel oils were modeled as pure n-alkanes while fractional coordinates were used to describe crystal structure. A multi-scale global optimization methodology based on the combined use of a terrain method and funneling algorithm was used to find minimum energy molecular conformations of diesel, home heating, and residual fuel oils and low energy crystal structures. The terrain method is used to gather average gradient and average Hessian matrix information at the small length scale while funneling was used to generate structural changes at the large length scale that drive iterates to a global minimum on the potential energy surface. The funneling method used a mixture of average and point-wise derivative information to produce a monotonically decreasing sequence of objective function values and to avoid getting trapped at local minima on the potential energy surface. The calculated molecular conformations comprised of zigzag structure with considerable wrapping at the ends of the molecule and that planar zigzag conformations usually correspond to saddle points. This is an abstract of a paper presented at the AIChE Annual Meeting (Salt Lake City, UT 11/4-9/2007).

Publication Title

2007 AIChE Annual Meeting

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