Mixtures Of N-paraffins Research Articles

Thermal cracking of Al-Dora asphalt for the simultaneous production of light fuel and activated carbon for desulfurization process

Thermal cracking of an Iraqi asphalt, namely Al-Dora asphalt, at multiple temperatures for various durations was first achieved. The main target of this investigation was to produce an upgraded liquid fuel and microporous activated carbon. The thermal pyrolysis of asphalt was carried out in the temperature range of 400–600 °C for different durations (30–150 min) at a 20 °C/min heating rate. The maximum liquid fuel yield (51.55%) was produced at 450 °C for 1 h. This treatment process raised the American Petroleum Institute (API) gravity of the original asphalt from 3.26 to 34.54, while its viscosity was reduced from 422.0 mm2.s−1 to 3.76 mm2.s−1. Analysis of the produced liquid fuel by 1H NMR spectroscopy,13C NMR spectroscopy, and GC-MS disclosed that it was a mixture of n-paraffins (57.05%), isoparaffins (12.68%), and alkenes (30.27%) with a C6 and C19 carbon distribution. The physical and chemical features of the liquid were also determined following ASTM procedures, and the outcomes revealed that the produced liquid fuel had preferable properties to that of the authentic asphalt, suggesting its suitability as an alternative to diesel fuel. The coke produced after thermal pyrolysis of Al-Dora asphalt was successfully converted into active carbon (AC) via the optimized KOH-activation route, and the selected AC was prepared using a 2:1 KOH: coke impregnation ratio at 750 °C for 1 h. The AC was characterized by various techniques, including BET surface area and pore volume, X-ray diffractometry (XRD), field-emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray analysis (EDX), and infrared spectroscopy (FTIR). The total acid and basic surface groups besides the pHPZC of the AC were also determined. The adsorption efficiency of the as-obtained AC was tested in the adsorptive desulfurization process. For this target, dibenzothiophene (DBT) in n-hexane was selected as a model fuel. The AC showed an excellent efficiency of 99.33% for eliminating DBT from a model fuel containing 500 mg/L DBT using 0.35 g of AC at 40 °C for 30 min. Moreover, the removal of S- compounds from commercial gasoline using the AC under typical experimental conditions reached 65.12%. The adsorption of DBT by the produced AC offered an excellent fitting for Freundlich isotherm and the pseudo-2nd-order kinetics model. Finally, the regenerated AC demonstrated its ability to eliminate DBT up to the 6th reuse cycle efficiently.

Modelling of the separation of long-chain normal paraffins from kerosene in a simulated moving bed process: effect of the desorbent

Linear paraffins can be selectively separated from the rest of components of kerosene (branched hydrocarbons, aromatics and naphthenes) by means of liquid phase adsorption on 5A zeolite using the technology of simulated moving bed (SMB). In previous works, the kinetic and equilibrium parameters required for modelling and design of the SMB unit were obtained for pure n-paraffins and n-paraffin mixtures. However, the simulation of the SMB process indicated the presence of n-C5, used as a desorbent, in the separation zone, especially after the feed mixture is introduced. This finding motivated this work, in which n-paraffin mixtures (n-C10, n-C12, n-C14) including n-C5 were studied to address its influence in the process. The kinetic and equilibrium parameters for these mixtures were obtained and included in the model for the simulation of an SMB unit. While mixtures without n-C5 preferentially adsorbed shorter n-paraffins, it was found that including n-C5 in the mixtures reverses the selectivity of the adsorbent. In this case, longer n-paraffins are preferentially adsorbed, matching the trend observed for pure n-paraffins. In addition, n-C5 significantly increases the mobility of n-paraffins, as indicated in their higher mass transfer coefficients. The model was validated by comparing the predicted performance with the reported separation achieved by a commercial SMB unit that separates n-paraffins from hydrotreated kerosene fractions. The predicted separation performance is very similar to that achieved in our previous works, slightly improving the purity (99.6%) of the extract as a trade for a small loss in recovery (95.4%).

Enhancing the objective function used to predict the composition of n-paraffin mixtures from calorimetric curves

An algorithm to predict the composition of n-paraffin mixtures from calorimetry is proposed and applied for two thermodynamic approaches: one considering the formation of solid solutions and the other, known as multisolid phase model, assuming the presence of several independent pure solid phases. This methodology compares modeled calorimetric curves with DSC results through Particle Swarm Optimization. In order to better predict the mixtures compositions an appropriate proposal of the objective function was necessary. The present paper elucidates the process of defining an enhanced objective function aiming to improve the quality of predictions allowing the employment of calorimetric curves without information about sample’s mass. The deviations in calculated compositions are related to a difference of up to 1K in the location of calorimetric peaks for solid solution approach.

Droplet ignition of approximately continuous liquid mixtures of n-paraffins and n-alkyl aromatics

This paper presents experiments on the auto ignition of single droplets of liquid mixtures which have a composition such that their distillation behaviour approximates a “continuous” mixture, i.e. one which can be described by a continuous distribution function. A number of such mixtures of both n-paraffins and n-alkyl aromatics were designed by matching their distillation curves to those of equivalent continuous distributions, and single droplet ignition experiments were then performed on them. To correlate the results and gain insight into the mixture ignition process, a continuous mixture droplet ignition model was devised by adding a continuous formulation for a global reaction rate expression to an existing droplet evaporation model. Expressions for rate parameters as functions of the distribution variable (molecular mass) were developed from experiments on pure hydrocarbons. The resulting ignition model was found to reproduce experimental mixture ignition delay times well. The mixtures tested here behave similarly to pure compounds of the same average molecular mass.

Reduced Haematological Indices in Auto-Mechanics and Fuel Attendants in Elele Nigeria

Gasoline is largely a mixture of hydrocarbon and hydrocarbon consists of mixture of n-paraffins, naphthalene, olefins and aromatics. Aromatics is mostly a mixture of benzene, toluene and xylene. Fuel attendants and auto mechanics are exposed to gasoline either by direct contact or inhalation. The effect of this exposure in fuel attendants and auto mechanics is determined using haematological parameters. 35 fuel attendants and 35 auto mechanics were used as test group and compared with 30 apparently healthy individuals of same age range. Some haematological parameters were determined using standard manual methods. RBC, Hb, MCH and MCHC were reduced (p < 0.05) in fuel attendants and auto mechanics when compared with control. Fuel attendants exposed to gasoline fumes beyond 2 years have lower (p < 0.05) PCV, Hb, MCH and MCHC than those exposed for 2 years or less while auto mechanics of over two years had their RBC, Hb, MCH and MCHC significantly lower (p < 0.05) than auto mechanics of two years and below. Auto mechanics and fuel attendants are exposed to gasoline vapour leading to decreased haematological indices. Fuel attendants are more at risk than auto mechanics and could be at risk of developing anaemia over time.

ISOMERIZATION OF PARAFFIN MIXTURES PRODUCED FROM SUNFLOWER OIL

The importance of biofuels becomes more acute, especially in the European Union. Beside them, the bio gas oil is a promising product that is a fuel with high isoparaffin content in the gas oil boiling range, which can be produced by the catalytic hydrogenation of different triglycerides. In this paper the isomerization of different intermediate products obtained over different hydrogenation catalysts and having high n-paraffin content was studied on SAPO-11 catalyst at 300–380 °C temperature, 20–80 bar pressure, 0.5–3.0 h-1 of liquid space velocity and 400 Nm3/m3 of H2/feed ratio. It was found that the oxygen containing intermediate products significantly changed the degree ofisomerization, but the hydrocarbon composition and the aromatic content of the n-paraffin mixtures had no noticeable effect on the conversion. During the experiments excellent quality diesel gas oil blending components were produced with high i-paraffin content and they were practically free of heteroatom content.

Acid natural clinoptilolite: Structural properties against adsorption/separation of n-paraffins

The employment of an acid natural clinoptilolite (AZH-1) in the adsorption and separation of n-paraffins has been evaluated. Natural clinoptilolite, NZ, was the raw material used to prepare the sodium-exchanged clinoptilolite (AZ) starting from which the AZH-1 sample was obtained by acid treatment. The structural stability of the samples after the applied treatments was demonstrated. The nitrogen adsorption experiments indicated that the acid sample has a homogeneous porous distribution and a considerable increase in the micropore volume with respect to NZ and AZ. The employment of the inverse gas chromatography at infinite dilution (IGCID) allowed studying the adsorption and separation of n-paraffin mixtures on AZH-1. It was also confirmed that the diffusion on AZH-1 took place in an unblocked structure through the A channel of ten members with minimal interactions. The IGCID results demonstrated the capacities of the acid Cuban natural zeolite in the adsorption and separation of n-paraffin mixtures.

Competitive Adsorption of C20−C36 Linear Paraffins on the Amorphous Microporous Silica−Alumina ERS-8 in Vapor Phase and Liquid Phase

Adsorption of C20−C36 linear paraffins on the amorphous microporous silica−alumina ERS-8 was studied at vapor phase and liquid phase conditions. Henry adsorption constants and low coverage adsorption enthalpies were determined using the pulse chromatographic method at temperatures between 90 and 370 °C in gas phase. The low coverage adsorption enthalpy increases linearly with carbon number with 5.5 kJ/mol per additional methyl group. Competitive adsorption in liquid and dense vapor phase conditions was studied by performing column breakthrough experiments with various binary C20−C36 n-paraffin mixtures diluted in short chain length alkane solvents or undiluted as bulk mixture, at temperatures ranging from 25 to 300 °C and pressures from 3 to 110 bar. Both the adsorption capacity and the selectivity are strongly temperature and pressure dependent. At low temperature and high pressure, all n-paraffins are adsorbed equally and no separation is possible. With increasing temperature and decreasing pressure, the density of the bulk phase decreases, and a transition from a pure liquid paraffin stream to a dense vapor stream occurs. In such conditions, longer n-paraffins are adsorbed preferentially compared to the shorter n-paraffins. The selectivity increases with increasing difference in chain length between the adsorbing n-paraffins.

Catalytic upgrading of higher 1-alkenes from polyethylene thermal cracking by modified Wacker oxidation

The economic success of feedstock recycling procedures for plastic wastes is increasingly demanding the conversion of the starting residue into more valuable chemicals. Thermal cracking of polyethylenes leads to the preparation of equimolar mixtures of n-paraffins and 1-alkenes within the C2–C100 range. These 1-olefins can be catalytically upgraded by selective oxidation processes to more valuable products (e.g., ketones and fatty acids) with different uses such as polar waxes, cetane improvers, varnishes, and printer inks. The results obtained on oxidation in a modified Wacker system of a model 1-olefin (1-dodecene) as well as of a distillate cut (C10–C25) of the product from the thermal cracking of urban polyethylene waste are described.

Modeling of Fischer–Tropsch products hydrocracking

The hydrocracking behavior of a C 4 –C 70 mixture of n-paraffins on a platinum/amorphous silica–alumina catalyst has been analyzed. The influence on the system behavior of operating conditions, i.e. pressure, temperature, H 2 /feed ratio and stream velocity, has been investigated by means of experimental data from a bench scale reactor, the last aim being the derivation of a proper model for the reaction system. Because of the high number of species involved, a model which takes into account pseudocomponents (lumped model) corresponding to the cuts of interest for the refinery has been considered. The obtained results show good agreement with experimental data.

Spectroscopic study of rotation-crystalline modifications of mixtures of n-paraffins C 22–C 24

The binary solid mixtures of n-paraffins, C 22–C 24, with different molar ratios of 96:4, 3:1, 2:1, 1:4, 1:5, and 1:10 have been studied by FTIR spectroscopy, X-ray diffraction and differential scanning calorimetry (DSC). Temperature-dependent studies of Davydov splitting value, Δ ν 1,2, of in-phase CH 2 rocking vibrations have been shown to allow the determination of Δ T rot temperature intervals, where rotation-crystalline states, characterized by different types of molecular motion, exist. The comparison of the ΔT rot values obtained by FTIR and DSC methods with the corresponding temperature-dependent X-ray powder diffraction data has shown their good agreement.

Real-time inferencing of solid–liquid phase equilibria in solution polymerization of polyethylene

An algorithm for the real-time prediction of multi-component solid–liquid equilibrium (SLE) in a polyethylene (PE) process flowsheet has been attempted. While most of the available literature assumes the polymer to possess a single average molecular weight and lump the entire polymer as a single component, the present work proposes to consider a polydispersed multi-component fraction, characterized by the pseudo-component approach. The SLE model has been used to study the effects of monomer and polymer polydispersity in solution polymerization process. At first, it has been validated on the solubility data of n-alkanes in n-hexane, polyethylene in M-xylene and on wax precipitation from a mixture of n-paraffins. The SLE model is based on perturbed chain SAFT (PC–SAFT) equation of state (EOS). An algorithm for the real-time prediction of SLE phase boundaries in solution polymerization has been subsequently presented. A simulation experiment on the polyethylene flowsheet highlighted the potential of real-time inferencing for industrial applications.

Resonance dynamical intermolecular interaction in the crystals of pure and binary mixture n-paraffins

In the present paper, we report temperature dependent FTIR spectra studies of Davydov splitting value for CH 2 rocking vibrations of pure crystalline n-paraffins C n H 2 n+2 ( n is the number of carbon atoms) and some isomorphically substituted binary mixtures of n-paraffins C 22H 46:C 24H 50. Temperature dependencies of Davydov splitting value have been shown to be characterized by the amount of irregularities (sharp decreasing), which corresponds to the phase transitions into the high-temperature (hexagonal) state for pure n-paraffins or different rotator crystalline states for the mixtures. Statistic and dynamic models have been proposed, which provides an adequate description of the observed effect. In the framework of these models, two different mechanisms are responsible for the temperature behavior of the vibrational mode splitting value. Besides the thermal expansion of crystals at heating, the quenching of vibrational excitons on the orientational defects of different nature takes place, accompanied with the breakage of the crystal lattice translational symmetry. The creation of such defects is resulted from the excitation of librational and rotational molecular degrees of freedom at the crystal polymorphic transitions into different rotary crystalline states. The manifestation of the resonance dynamical intermolecular interaction in the spectra of intramolecular vibrations in these crystals has been theoretically analyzed in terms of stochastic equations, taking into consideration the above mentioned phase transition. We have obtained the explicit expression for the theoretically predicted dependence of Davydov splitting value on temperature. The absorption bands, corresponding to Davydov splitting components, have been shown to approach rapidly each other at the transition to the high-temperature (hexagonal) phase. Computer simulation of such dependence has been performed for some aliphatic compounds. Good agreement between the experimental and computer simulation results has been obtained. The theoretical approach developed in the present paper for the resonance dynamical intermolecular interaction near such transitions from the three-dimensional to one-dimensional phase of crystalline n-paraffins has a general character and can be applied to the description of some specific features observed in the vibrational spectra of rotary crystals.

Dynamics of molecules and phase transitions in the crystals of pure and binary mixtures of n-paraffins

In the present paper, we report on temperature dependent FT-IR spectra studies of the value of Davydov splitting for CH 2 rocking vibrations of pure crystalline n-paraffins C n H 2 n+2 (with odd number n of carbon atoms) and some isomorphic substituted binary mixtures of n-paraffins C 22/C 24. It was shown that the temperature dependencies of Davydov splitting value are characterized by the number of irregularities (sharp decreasing), which correspond to phase transitions into the high-temperature (hexagonal) state for pure n-paraffins or different rotator crystalline states for the mixtures. A statistic and dynamic model is proposed which provides adequate description of the observed effect. In the framework of this model, two different mechanisms are responsible for the temperature behavior of the splitting value of vibrational modes. In addition to thermal expansion of crystals under heating, the damping of vibrational excitons on orientational defects of different nature takes place breaking the translational symmetry of the crystal lattice. Genesis of such defects is connected with excitation of librational and molecular rotational degrees of freedom at the crystal polymorphic transitions into different rotator crystalline states. Theoretical analysis of the effect of resonance dynamical intermolecular interaction on the spectra of intramolecular vibrations of the crystals was performed in terms of stochastic equations with account for mentioned phase transitions. Computer simulation of such dependence was performed for pure n-paraffin compounds. Good agreement between the experimental and computer simulation results was obtained.

Radiation-Chemical Behavior of TBP in Hydrocarbon and Chlorohydrocarbon Diluents under Conditions of Reprocessing of Spent Fuel from Nuclear Power Plants

Experiments were performed for comparative assessment of the effect of ionizing radiation on the service characteristics of 30% TBP solutions in various diluents: hexachlorobutadiene (HCBD), mixtures of n-paraffins (RED diluent), and fraction of naphthenic hydrocarbons (RZh diluent). The following main parameters were chosen for comparative assessment of the quality of irradiated extractant solutions: composition and behavior of diluent radiolysis products, effect of diluents on the TBP radiolysis, and aggregative stability of emulsions in the main operations of the extraction cycle. The service life of the extraction mixtures was estimated from variation of the above parameters with the irradiation dose. Principles for choosing solvents with increased service life under irradiation were substantiated.

Hydrocracking and isomerization of n-paraffin mixtures and a hydrotreated gasoil on Pt/ZSM-22: confirmation of pore mouth and key–lock catalysis in liquid phase

A mixture of n-paraffins as well as a hydrotreated gasoil were hydrocracked over a Pt/ZSM-22 and a Pt/USY zeolite catalyst in a three phase reactor with complete internal mixing operated under industrially relevant conditions. The distribution of the isomerization products obtained from the n-paraffin mixture and the hydrotreated gasoil on Pt/ZSM-22 shows that pore-mouth and key–lock catalysis are operative, although the selective formation of branching at the end of the carbon chain is less pronounced. Ethylbranching is suppressed in liquid as well as vapor phase conditions. The cracked products obtained on Pt/ZSM-22 for both feedstocks contain a high amount of linear paraffins in comparison to the amount observed for hydrocracking on Pt/USY. This indicates that similar to vapor phase operations, the scission of the bond in the β position of the positively charged secondary carbon atom towards a new secondary carbenium ion (s,s β-scission) is also the dominant cracking mechanism for operations in liquid phase. The differences between vapor and liquid phase operations of Pt/ZSM-22 are attributed to differences in the adsorption modes of the molecules.

High-pressure phase equilibrium in multicomponent hydrocarbon systems using the MFLG model

The Mean-Field Lattice-Gas model (MFLG) is applied to the description of phase equilibria in systems containing a supercritical fluid and long-chain hydrocarbons. It is shown that two of the four model-parameters for a pure substance depend on the chain length of a hydrocarbon. If the other two parameters are chosen as temperature dependent, they can be kept constant for different hydrocarbons. Both, subcritical VLE-data and supercritical PvT-data of these substances are than described in good quality. The use of an identical set of binary parameters for methane- n-alkanes provides satisfactory results for different binary and ternary mixtures of n-paraffins and supercritical methane. Even for multicomponent n-paraffin systems the dew-point temperature as well as the composition in the coexisting phases can be predicted in good agreement with experimental data. Thus, using the described procedure, the number of parameters needed for phase-equilibrium calculations could be reduced significantly.

Solubility of synthesis and product gases in a Fischer-Tropsch SASOL wax

In This paper, solubility of hydrogen, carbon monoxide, methane, carbon dioxide, ethane, and ethylene is reported at five pressures from 10 to 50 atm and at temperatures from 200 to 300 [degrees]C in a Fischer--Tropsch SASOL wax which is primarily a mixture of n-paraffins. The experimental solubility is compared with Huang et al.'s correlation.

Evaluation of the simplified perturbed hard chain theory (SPHCT) for prediction of phase behavior of n-paraffins and mixtures of n-paraffins with ethane

The ability of the simplified perturbed hard chain theory (SPHCT) equation of state (EOS) to represent the phase behavior of both pure n-paraffins and mixtures of ethane + n-paraffins has been evaluated. The SPHCT EOS predicts reasonably well the vapor pressures and saturated liquid densities of n-paraffins extending from methane to n-C 64 (average absolute deviations, AAD, of 4% and 7%, respectively). Less accurate predictions, however, are obtained from the SPHCT at temperatures near the triple and the critical points. In general, comparable predictions of phase compositions are obtained from the SPHCT and the Soave (SRK) EOS for ethane + n-paraffin binary systems. For the heavier paraffins (n-C 20 and heavier), however, the SPHCT EOS produces better results. Accurate representation of the experimental data (root mean square error (RMSE within 1 bar for bubble point pressures) requires the use of an interaction parameter for ethane with each n-paraffin. Optimum binary interaction parameters for ethane with n-paraffin solvents extending from C 3 to n-C 44 are presented for the two equations. Simple generalized correlations have been developed for the SPHCT and SRK EOS input variables ( T *, v * and c for SPHCT; and T c, P c, and w for SRK). Using such correlations, a signle parameter ( C ij ) produces useful predictions for ethane in the complete n-paraffin series (RMSE of 1.5 bar for bubble point pressures) including the heaviest members of the series.

Improvement in coal liquefaction solvent quality by dewaxing

Recycle oils from the Integrated Two-Stage Liquefaction (ITSL), H-Coal and Solvent Refined Coal (SRC) processes were dewaxed by variants of commercial dewaxing processes—the ketone and the urea adduction techniques — yielding up to 47 wt % ‘wax’. Feed oils and product fractions were characterized by elemental analysis, 1H n.m.r. and gas chromatography. The clean waxes were nearly pure mixtures of n-paraffins. The dewaxed oils were substantially better coal liquefaction solvents than the original (non-dewaxed) oils in batch liquefaction tests. For example, in one case, dewaxing improved the conversion of a bituminous coal to tetrahydrofuran-solubles under standard reaction conditions from 71 wt% (dafb) with the original oil to 87 wt % (dafb). These data provide a direct indication of the inimical effect of paraffinic components on solvent quality. The impact of solvent quality is particularly relevant to liquefaction processes in which thermal reactions proceed in a recycle solvent. In addition, the results indicate the technical feasibility of dewaxing coal liquefaction recycle oils by commercially available technology to improve solvent quality and to produce a useful by-product. Dewaxing could be applied in any liquefaction process that uses a deasphalted (preferably distillate) recycle stream.