Creating mesopores in ZSM-48 zeolite by alkali treatment: Enhanced catalyst for hydroisomerization of hexadecane

ZSM-48 zeolites with various Si/Al ratios were hydrothermally synthesized in the H;N（CH;）;NH;（HDA）-containing media. The obtained samples were highly crystallized with minor mixed phases as evidenced by X-ray powder diffraction（XRD）. The alkaline treated ZSM-48 zeolites maintained its structure under different concentrations of Na OH aqueous solution. Micropores remained unchanged while mesopores with wide pore size distribution formed after the alkaline treatment. The surface area increased from 228 to 288 m;/g. The Br?nsted acid sites had little alteration while an obvious increase of Lewis acid sites was observed. The hydroisomerization of hexadecane was performed as the model reaction to test the effects of the alkali treatment. The conversion of hexadecane had almost no change, which was attributed to the preservation of the Br?nsted acid sites. While high selectivity to iso-hexadecane with an improved iso to normal ratio of alkanes was due to the mesopore formation and improved diffusivity.

More than Color:Pigments with Thermal Storage Capacity;Processing and Degradation Behavior

A standard ultramarine pigment was used to produce phase change material composites, by adsorbing n-hexadecane paraffin around the pigment surface with the aim of obtaining a pigment providing thermal storage capacity apart from color. Vacuum impregnation method was employed optimizing the process variables to maximize the latent heat of the hexadecane/pigment composite. In addition to the process optimization, the stability of the composite having the maximum latent heat was investigated. The hexadecane/pigment composite providing the highest latent heat has a Latent heat of fusion of 44 J/g (around a 20%wt. hexadecane adsorbed in the pigment). Durability of the material was tested by thermo-diffractometric measurements. The results indicate slow reduction of the area intensity up to 6.5% after the 100 cycles.

Surface passivation and boundary lubrication of self-mated tetrahedral amorphous carbon asperities under extreme tribological conditions

Tetrahedral amorphous carbon coatings have the potential to significantly reduce friction and wear between sliding components.Here,we provide atomistic insights into the evolution of the sliding interface between naked and hydrogen-passivated ta-C sliding partners under dry and lubricated conditions.Using reactive classical atomistic simulations we show that sliding induces a sp3 to sp2 rehybridization and that the shear resistance is reduced by hydrogen-passivation and hexadecane-lubrication-despite our finding that nanoscale hexadecane layers are not always able to separate and protect ta-C counter surfaces during sliding.As asperities deform,carbon atoms within the hexadecane lubricant bind to the ta-C sliding partners resulting in degradation of the hexadecane molecules and in increased material intermixing at the sliding interface.Hydrogen atoms from the passivation layer and from the hexadecane chains continue to be mixed within a sp2 rich sliding interface eventually generating a tribo-layer that resembles an a-C:H type of material.Upon separation of the sliding partners,the tribo-couple splits within the newly formed sp2 rich a-C:H mixed layer with significant material transfer across the sliding partners.This leaves behind a-C:H coated ta-C surfaces with dangling C bonds,linear C chains and hydrocarbon fragments.