Crystal structures and voids in diesel waxes

Diesel waxes containing n-alkanes in the range it = 9-30 show only two type s of X-ray diffraction pattern. When indexed these are seen to belong to th e orthorhombic space groups Bb2(1)m and Fmmm; they are isostructural with t wo binary phases, one phase having n = 24 and 26 and the other it = 22 and 24. We designate these the low-disorder (LD) and high-disorder (HD) phases, respectively. From the long spacings shown in the XRD patterns, it is poss ible to calculate the percentage of void space present in the wax crystals. It is found that the larger the spread of it values in the wax composition (i.e. the larger the variance in chain length), the greater the tendency t o crystallize in the HD form and the more extensive the voids.