N-paraffin Waxes Research Articles

Pt/Al-SBA-15 catalysts for hydrocracking of C21–C34n-paraffin mixture into gasoline and diesel fractions

In this study, a Pt-loaded mesoporous aluminosilicate (Pt/Al-SBA-15) was optimized as a catalyst for the hydrocracking of Fischer–Tropsch waxes, for which n-paraffin wax in the C21–34 range was used as a model reactant. Pt/Al-SBA-15 was more active than a Pt-loaded microporous zeolite (Pt/β-zeolite) in producing gasoline-range products from n-paraffin wax. Hydrocracking over Pt/Al-SBA-15 occurs via a bifunctional mechanism, the activity of which was correlated closely with the density (concentration) of strong acid sites and total exposed Pt surface area. The reaction was more noticeably promoted at the Brønsted acid sites, rather than at the Lewis acid sites, of Al-SBA-15. The highest gasoline yield (72.8%) was achieved with the catalyst comprised of 0.5wt.% Pt and Al-SBA-15 with Si/Al molar ratio of 14.5.

Surface Structuring of Wax in Complex Media

AbstractInvestigators over the past 16 years have considered the nature of surface structuring, referred to as bee structures, in bituminous asphalt, commonly identified by atomic force microscopy. Recently it has been suggested that the interaction between nonpolar molecules present in asphalt, including n-paraffin waxes, are responsible for these surface microstructures. Several research groups now tend to agree that the interactions between crystallizing n-paraffin waxes and the remaining nonwax asphalt molecules are responsible for much of the structuring, including bee-structures. To date, a plausible mechanism to explain the physicochemical manifestation of this type of surface structuring in asphalts has yet to be offered. In this paper a theory is presented that explains the physicochemical nature of surface structuring in asphalts and asphalt fractions based on investigations of simpler material systems reported in the literature pertaining to paraffin and polymer crystallization. Experimental re...

Bioinspired hierarchical superhydrophobic structures formed by n-paraffin waxes of varying chain lengths

Nature demonstrates beautiful examples of superhydrophobic surfaces, which always exhibit hierarchical roughness. We demonstrate a simple biomimetic route to the formation of hierarchical roughness on paraffin wax surfaces by the successive deposition of waxes of increasing molecular weight (Mw). By means of this procedure the lower Mw waxes grow larger crystals, forming higher micro-roughness, the subsequently deposited higher Mw waxes produce lower submicron/nano-roughness, and the overall result is roughness of a higher hierarchical order. We show that, compared to unary wax crystal surfaces, these hierarchical structures have the advantage of increased surface stability expressed by the ability to maintain smaller drops in the Cassie-state, as well as the ability to support liquids having lower surface tensions with contact angles exceeding 150°.

The Properties of Oil–Wax Gels With Changing Lattice Structure of Wax Crystal

The objective of this study was to investigate the relationship between the lattice structure of ceresin wax and different wax mixtures and the glossiness of oil–wax gels. Recently, visual factors such as the glossiness of skin are generally known as the words to express the beauty. The mechanism of glossiness has been suggested to understand the changes that occur in the lattice structure of the wax crystal when they are forming gels and also the effects of the nature of solvent. The present work investigates the relation between the lattice structure of the wax crystal and the glossiness of oil–wax gels obtained from ceresin and microcrystalline wax as well as of the gels formed by different waxes in solvent. The addition of branched wax to ceresin tended to form loose lattice structure of wax crystal, resulting in the high glossiness of oil–wax gels. However, the addition of n-paraffin wax to ceresin tended to form dense lattice structure of the wax crystal, leading to the low glossiness of oil–wax gels. The rheological transition behavior was also discussed as a function of the ratio of wax to ceresin.

Experimental evaluation on natural convection heat transfer of microencapsulated phase change materials slurry in a rectangular heat storage tank

The main purpose of this experiment is to evaluate natural convection heat transfer characteristics of microencapsulated PCM (phase change material) slurry (MPCMS) during phase change process in a rectangular heat storage tank heated from the bottom and cooled at the top. The microencapsulated PCM is several material compositions of n-paraffin waxes (mainly nonadecane) as the core materials, outside a layer of a melamine resin wrapped. In the present study, its slurry is used mixing with water. And the specific heat capacity with latent heat shows a peak value at the temperature of about T=31°C. We investigate the influences of the phase change process of the MPCMS on natural convection heat transfer. The experimental results indicate that phase change process of the MPCMS promote natural convection heat transfer. The local maximum heat transfer enhancement occurs at approximately TH=34°C corresponding to the heated plate temperature. With high mass concentration Cm, the onset of natural convection gets easier for the MPCMS. The temperature gradient is larger near top plate and bottom plate of a rectangular heat storage tank. Heat transfer coefficient increases with the phase change of the PCM. And it summarizes that the phase change process of the PCM promote the occurrence of natural convection.

Physical Property and Thermal Physical Property of Microencapsulated Phase Change Material Slurry

Microencapsulated phase change material (PCM) slurry is a kind of novel heat transfer fluid called latent functionally thermal fluid. Unlike conventional (sensible) materials, when the PCM reach the temperature at which they begin phase change (its melting point), they absorb large amounts of heat with little or no temperature change. Due to this, the heat transfer ability and energy transport ability can be obviously improved. Therefore, they have many potentially important applications in some fields such as energy storage, thermal conditioning of buildings, waste heat recovery, off peak power utilization, heat pump systems, space applications. In present study, the core materials are encapsulated with membrane of synthetic material. And the core materials are composed of several kinds of n-paraffin waxes (mainly nonadecane) and the membrane is a type of melamine resin. The range of diameter of the PCM particles is distributed from 0 μm to 4.5 μm, and its average diameter is 0.74 μm. The thickness of melamine resin is about 11nm. The melting point of the PCM is about 304K. Physical properties, such as density, diameter and its distribution of microencapsulated PCM slurry are investigated. Meanwhile, the thermal physical property, apparent specific heat, is determined by a Differential Scanning Calorimeter (DSC). Also, the influence of mass concentration has been discussed.

Experiment on heat storage characteristic of microencapsulated phase change material slurry

Heat storage experiment by natural convection in rectangular enclosures heated from bottom has been conducted with fluid slurry composed of microencapsulated phase change material (PCM). The microencapsulated PCM is prepared by in-situ polymerization method, where the core materials are composed of several kinds of n-paraffin waxes (mainly nonadecane) and the membrane is a type of melamine resin. Its slurry mixed with water is used in this study, and shows a peak value in the specific heat capacity with latent heat at the temperature of about T=31 °C. The influences of the phase change material on heat storage and the heat transfer process, as well as effects of PCM mass concentration C m on the microcapsule slurry, temperature of heat storage T H and a horizontal enclosure height H are also investigated. Transient heat transfer coefficient α, heat storage capacity Q and completion time of heat storage t c are discussed.

Paraffin Polydispersity Facilitates Mechanical Gelation

Incipient wax−oil gel deposits form in crude oil transport pipelines when long-chain n-paraffins precipitate at the cold interior surface of the pipe wall. The kinetics of paraffin gel formation was studied using model fluids consisting of monodisperse and polydisperse n-paraffin components dissolved in petroleum mineral oil. Classical homogeneous nucleation theory was applied to investigate the supersaturation conditions necessary for crystal formation. Differential scanning calorimetry was used to monitor paraffin crystallization rates and to provide solid-phase fraction measurements. Gelation occurs when growing n-paraffin crystals interlock and form a volume-spanning crystal network which entrains the remaining liquid oil among the crystals. Paraffin wax−oil gels exhibit a mechanical response to an imposed oscillatory stress, which is characterized by the elastic storage modulus G‘ being greater in magnitude than the viscous loss modulus, G‘ ‘. Low-temperature rheological gels can form from model fluids with n-paraffin contents as low as 0.5 wt %. Images of wax−oil gel morphologies were obtained using a cross-polarized microscope fitted with a z-drive and indicated crystal lengths of ∼10−20 μm. A microstructural gelation model based on percolation theory was introduced to provide predictions of gel formation conditions among randomly oriented paraffin crystals. The structural model provides correlations of crystal morphologies and solid fractions at the percolation threshold condition. Comparison of the initial wax contents required for gelation of monodisperse and polydisperse n-paraffin wax indicates that sharp crystal edges and ordered crystal faces hinder the paraffin crystal−crystal “anchoring” interactions which result in mechanical gelation.

Inhibition of the Changes in Dielectric Properties Caused by the Oxidation of Hydrocarbons

The additive effects of multicomponent hydrogen-donating hydrocarbons derived from petroleum (HHAP) on the changes in the dielectric properties caused by the oxidation of hydrocarbons were tested compared with conventional antioxidants, and the following results were obtained: (1) The addition of HHAP to LDPE did not affect the dissipation factor, in contrast to the changes caused by the conventional hindered phenolic and bisphenolic antioxidants. (2) During the oxidation of n-paraffin wax at 160 °C in air, the changes in dissipation factor caused by the oxidation were sufficiently inhibited by the addition of HHAP (1 and 2 wt %). (3) The results of the chemical analyses, including IR, acid value, and oxygen content, were well consistent with the dissipation factor. These outcomes are attributable to the high radical-scavenging ability and the pure hydrocarbon constitution of HHAP, which has no functional groups that contain heteroatoms.

Adsorption ofn-Paraffin Wax from Isooctane Solution on Crystalline Urea

ABSTRACT Equilibrium isotherms and kinetics of adsorption of n-paraffin wax from isooctane solution on crystalline urea were obtained at 50 and 70°C and at 50, 70, and 90°C, respectively. The equilibrium data were correlated according to the Polanyi potential theory, which provided a single characteristic curve of the experimental data at two temperatures. The batch kinetic data suggest that the adsorption of n-paraffin wax on crystalline urea is diffusion controlled. Effective diffusion coefficients derived from fractional uptake versus time were in the order of 10−14 to 10−13 cm2/s. The apparent activation energies of diffusion decreased with increasing uptake, as expected.

Correlation of synthesis gas solubility in n-paraffin solvents and Fischer—Tropsch waxes

A correlation of the solubility of Fischer—Tropsch synthesis and product gases in heavy n-paraffin waxes is obtained with the Lacombe—Sanchez equation of state (EOS). The EOS parameters for pure n-paraffins are developed and correlated as functions of carbon number. Interaction parameters with the n-paraffins are determined from solubility data and expressed as functions of carbon number of the n-paraffin solvent for the gases hydrogen, carbon monoxide, methane, carbon dioxide, ethylene and ethane.

Infrared spectra of chlorinated petroleum fractions

AbstractThe infrared spectra of several chlorinated petroleum fractions are reported. Although the spectra of chlorinated branched and linear fractions are different in the 600–800 cm−1 region, it is very difficult to detect less than 15% of the toxic chlorinated kerosene in mixtures with chlorinated n‐paraffin waxes.

Crystal-Growth Poisoning of n-Paraffin Wax By Polymeric Additives and its Relevance to Polymer Crystallization Mechanisms

Crystal-Growth Poisoning of n-Paraffin Wax By Polymeric Additives and its Relevance to Polymer Crystallization Mechanisms