Urea dewaxing of the 230?350�C cut of Ust'-Balyk petroleum in a stationary bed of crystalline urea

1972 ◽  
Vol 8 (7) ◽  
pp. 499-501
Author(s):  
K. P. Kukanova ◽  
A. G. Sardanashvili ◽  
V. A. Matishev
Keyword(s):  
Urea Dewaxing ◽  
Crystalline Urea

Adsorption ofn-Paraffin Wax from Isooctane Solution on Crystalline Urea

1994 ◽  
Vol 29 (7) ◽  
pp. 897-906 ◽  
Author(s):  
Neguib M. Hassan ◽  
Rasheed S. Al-Ameeri ◽  
Fathi A. Oweysi
Keyword(s):  
Paraffin Wax ◽  
Crystalline Urea

Electron-density-based calculations of intermolecular energy: case of urea

1999 ◽  
Vol 55 (5) ◽  
pp. 821-827 ◽  
Author(s):  
Kyrill Yu. Suponitsky ◽  
Vladimir G. Tsirelson ◽  
Dirk Feil
Keyword(s):  
Interaction Energy ◽  
Electron Density ◽  
Theoretical Data ◽  
Multipole Moments ◽  
Intermolecular Interaction Energy ◽  
Hartree Fock ◽  
Intermolecular Energy ◽  
Crystalline Urea ◽  
To Come ◽  
Experimental Values

The intermolecular interaction energy in crystalline urea has been calculated both from diffraction data and from the Hartree–Fock crystalline electron-density distribution, using a modified atom–atom approximation scheme. The electrostatic part of this energy has been calculated from the atomic multipole moments, obtained by adjustment of the multipole model to experimental X-ray and to theoretical Hartree–Fock structure amplitudes. To obtain the induction energy, multipole moments were calculated from structure amplitudes for the crystalline electron density and from those that refer to the electron density of a superposition of isolated molecules. This worked well for the calculation of the interaction energy from Hartree–Fock data (6% difference from the sublimation-energy value), but not for the interaction energy from experimental data, where the moments of the superposition have to come from Hartree–Fock calculations: the two sets of multipole moments are far too different. The uncertainty of the phases of the structure amplitudes, combined with systematic errors in the theoretical data and noise in the experimental values, may account for the discrepancies. The nature of the different contributions to intermolecular interactions for urea is examined.

Use of hydrocyclones in urea dewaxing

1977 ◽  
Vol 13 (6) ◽  
pp. 395-396
Author(s):  
A. G. Martynenko ◽  
M. S. Karamyshev ◽  
P. G. Igonin ◽  
Yu. A. Korzhov ◽  
V. A. Vaidukov
Keyword(s):  
Urea Dewaxing

The effect of urea on the utilization of ground, pelleted roughage by penned sheep: I. Food intake, live-weight change and wool growth

1969 ◽  
Vol 72 (2) ◽  
pp. 251-259 ◽  
Author(s):  
J. B. Coombe ◽  
G. K. Preston
Keyword(s):  
Weight Loss ◽  
Food Intake ◽  
Weight Change ◽  
Live Weight ◽  
Basal Diet ◽  
Experimental Period ◽  
Mineral Supplement ◽  
Wool Growth ◽  
Crystalline Urea ◽  
Oat Straw

SUMMARYIndividually-penned adult Merino wethers were fed for 16 weeks on a basal diet of ground, pelleted oat straw or Phalaris straw. Urea was supplied either in a salt-urea block containing 30% urea, or as crystalline urea incorporated into the pellets. A commercial mineral supplement was given during the first 8 weeks, but this was replaced with a laboratory-prepared mineral mix during the second 8 weeks.Urea supplementation significantly reduced live-weight loss. Over the 16 weeks control sheep lost a mean of 14·5 kg, and supplemented sheep 8·7 kg body weight. Most of this response to urea occurred during the second half of the experimental period.Food intakes of all sheep increased over the first 2 weeks and then fell. In the unsupplemented groups, levels of intake then remained fairly low, whereas in the sheep fed urea food intakes rose over the final 6 weeks of the experiment. There was a significant linear regression of live-weight change on food intake only with the urea-fed sheep. Intakes of urea-N from the blocks were extremely variable between individual sheep and between periods within sheep; in most cases, however, they appeared to be adequate, as this type of supplementation gave results similar to those obtained by mixing urea throughout the roughage.There was no significant effect of urea on total wool growth during the experimental period, although wool growth in the supplemented shepp showed a rise towards the end of the experiment. Wool growth in any 4-weekly period was closely related to food intake and live-weight change during that period.

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