Effect of metal content on the activity and product selectivity of n-decane hydroisomerization over Ni-Pd/HY zeolite

Metal-loaded zeolite catalysts were synthesized and examined in the hydroisomerization of n-decane.Specifically,zeolite Y was impregnated with 0.1 wt%Pd and varying amounts of Ni（0.1-0.5 wt%].The crystallinity of the metal-loaded catalysts was characterized by X-ray diffraction,and the average metal particle size was determined by transmission electron microscopy.The states of Pd and Ni were identified by X-ray photoelectron spectroscopy.Ammonia temperature-programmed desorption analysis revealed the occurrence of ion-exchange of some of the catalyst acid sites with Ni-（2＋）.The reducibility of the HY zeolite-supported Pd,Ni,and Pd-Ni catalysts was studied by temperature-programmed reduction.The hydroisomerization of n-decane over the prepared catalyst was conducted at 200-450℃ under 1 atm.Ni addition of up to 0.3 wt%over 0.1 wt%Pd/HY enhanced the n-decane conversion and isomerization product selectivity.The improved selectivity of the mono- and dibranched isomers suggested the occurrence of a protonated cyclopropane intermediate mechanism.However,further Ni addition above 0.3 wt%considerably reduced the activity and isomerization selectivity.The bimetallic catalysts were more selective toward the formation of dibranched isomers,i.e.,those containing a higher octane number.

Shock tube study of n-decane ignition at low pressures

Ignition delay times for n-decane/O2/Ar mixtures were measured behind reflected shock waves using endwall pressure and CH＊ emission measurements in a heated shock tube. The initial postshock conditions cover pressures of 0.09-0.26 MPa, temperatures of 1 227-1 536 K, and oxygen mole fractions of 3.9%-20.7% with an equivalence ratio of 1.0. The correlation formula of ignition delay dependence on pressure, temperature, and oxygen mole fraction was obtained. The current data are in good agreement with available low-pressure experimental data, and they are then compared with the prediction of a kinetic mechanism. The current measurements extend the kinetic modeling targets for the n-decane combustion at low pressures.

Experimental study of n-decane decomposition with microsecond pulsed discharge plasma

A highly-integrated experimental system for the plasma decomposition of fuels was built.Experiments were conducted in a flow reactor at atmospheric pressure and confirmed that n-decane could be cracked by large-gap dielectric barrier discharge under the excitation of a microsecond-pulse power supply. Alkanes and olefins with a C atom number that is smaller than10 as well as hydrogen were found in the cracked products of n-decane（n-C10 H22）. The combination of preheating and plasma decomposition had strong selectivity for olefins. Under strong discharge conditions, small molecule olefins were found in the products. Moreover, there was a general tendency that small molecule olefins gradually accounted for higher percentage of products at higher temperature and discharge frequency.

SOLUBILITIES OF CARBON DIOXIDE IN MIXTURES OF n-DECANE-n-HEXADECANE AND n-HEPTANE-TOLUENE

Solubilities of CO2 in binary mixtures of n-decane-n-hexadecane and n-heptane-toluenewere measured in a glass apparatus by a synthetic method.Henry’s constants at several temperaturesand solvent compositions were reported.While the Henry’s constants of CO2 in mixtures of decaneand hexadecane can be satisfactorily predicted by a simple linear interpolation,prediction of Henry’sconstants for CO2 in mixtures of heptane and toluene requires excess Gibbs energy of the solvent mix-tures.The standard thermodynamic functions of solution（ΔH0,ΔG0,and ΔS0）were reported.

Experimental investigation on n-decane plasma cracking in an atmospheric-pressure argon environment

In order to solve the problem of the difficulty of igniting and steadily propagating a continuous rotating detonation engine when using liquid hydrocarbon fuel, an experiment was carried out using a dielectric barrier discharge excited by a nanosecond power supply to crack n-decane, the single alternative fuel to aviation kerosene, in a pre-heated argon environment.By changing the voltages and the discharge frequencies, the concentrations of different components as well as a number of different species were acquired.The generating mechanism of olefins and alkanes together with their competition mechanism were acquired.The influence of the voltage on isomer products was also analyzed.The results demonstrate that the bond energy distribution and the species generating condition are the main factors affecting the formation of the products.With the increasing of voltage and discharge frequency, small molecule olefins, large molecular olefins, large molecular alkanes, small molecular alkanes, and hydrogen were detected, and in turn, their concentrations were also increased except for ethylene;what is more, when the voltage was increased over 8.5 kV, the n-butene converted to trans-butene, and the n-pentene converted to isoamylene.

n-Decane hydro-conversion over bi-and tri-metallic Al-HMS catalyst in a mini-reactor

Bi-metallic(Pt–Sn and Sn–Ni) and tri-metallic(Pt–Sn–Ni) catalysts,supported on Al-containing hexagonal mesoporous silica(Al-HMS)(Si/Al = 20) materials,were synthesized.N_2 adsorption–desorption,X-ray diffraction(XRD),Brunauer–Emmett–Teller(BET) test,and temperature programed desorption(NH3-TPD)were used to characterize physicochemical characteristics and textural properties of the Al-HMS catalysts.Catalytic performances on hydro-cracking of n-decane at different reaction conditions were studied in a microreactor.Comparison between Pt–Sn,Sn–Ni and Pt–Sn–Ni catalyst under different hydro-cracking conditions was made.The experimental results indicate that the proper balance between the acid and metal functions is the key in synthesizing a catalyst with a better performance in hydro-cracking.Tri-metallic catalyst exhibits the best catalytic performance in n-decane hydro-cracking than two bi-metallic catalysts.

Densities and viscosities of binary mixtures of n-decane + 1-pentanol,+1-hexanol,+1-heptanol at temperatures from 293.15 to 363.15 K and atmospheric pressure

Densities(ρ) and dynamic viscosities(η) for three binary mixtures of n-decane with 1-pentanol,1-hexanol and1-heptanol are presented at temperatures from 293.15 to 363.15 K and atmospheric pressure over the entire composition range.The density and viscosity are measured using a vibrating tube densimeter and a cylindrical Couette type rotating viscometer,respectively.Excess molar volumes(V^E),viscosity deviations(△η) and excess Gibbs energy of activation of viscous flow(△G^(*E)) are calculated from the experimental measurements.Intermolecular and structural interactions are indicated by the sign and magnitude of these properties.Partial molar volumes and infinity dilution molar partial volumes are also calculated for each binary system.These results are correlated using Redlich-Kister type equations.

Numerical investigation of pyrolysis effects on heat transfer characteristics and flow resistance of n-decane under supercritical pressure

Pyrolysis of hydrocarbon fuel plays an important role in the regenerative cooling process. In this article, a Two-Dimensional（2D） numerical model is proposed to investigate the pyrolysis effects on the heat transfer characteristics and flow resistance of n-decane under supercritical pressure. The one-step global pyrolytic reaction mechanism consisting of 19 species is adopted to simulate the pyrolysis process of n-decane. The thermophysical and transport properties of the fluid mixture are computed and incorporated into the numerical model for simulation. Comparisons between the current predictions and the open published experimental data are carried out and good agreement is achieved. In order to better understand the complicated physicochemical process, further investigations on the turbulent flow and heat transfer coupled with pyrolysis in a tube have been performed under various operating conditions. The results indicate that the pyrolysis intensively takes place in the high fluid temperature region. The occurrence of the heat transfer deterioration would lead to increasing n-decane conversion at the beginning of the heated section. It is found that the pyrolysis could improve the heat transfer deterioration and promote the heat transfer enhancement. Meanwhile, pyrolysis gives rise to an abrupt increase of flow resistance. The mechanisms of the physicochemical phenomena are also analyzed in a systematic manner, which would be very helpful in the development of the regenerative cooling technology.

An Improved Heat Transfer Correlation for Supercritical Aviation Kerosene Flowing Upward and Downward in Vertical Tubes

Correlations are crucial to the design of cooling channels employed in regenerative cooling systems for scramjets.In this paper,correlations for the aviation kerosene flowing upward and downward in vertical tubes are studied and discussed.Four existing correlations are assessed against the available experimental data.To further improve the prediction accuracy of the heat transfer behaviors of the supercritical aviation kerosene,a new dimensionless parameter(Qi)relevant to the heat flux is proposed and introduced into the construction of a new correlation.Verification shows that the new correlation is more accurate than existing correlations.

A Simplified Chemical Reaction Mechanism for Surrogate Fuel of Aviation Kerosene

n-Decane was chosen as a one-component surrogate fuel to investigate the combustion performance ofRocket Propellant-3（RP-3） aviation kerosene. Sensitivity analysis and the reaction-path mlalysis method were used tosimplify the detailed reaction mechanism of n-decane, and a simplified mechanism including 36 species and 62 ele-mentary reaction steps was obtained. Moreover, 38-step elementary reaction investigated in the reference was simu-lated in the paper. Numlerical simulation method was conducted for both the 62-step and the 38-step reaction me-chanisms using pre-evaporation combustion models. Simultaneously Bunsen bunter for the combustion of premixed,pre-evaporated RP-3 aviation kerosene was designed to verify the simplified mechanism, and the temperature and gascomponent concentrations in the axial and radial directions at different heights were measured. The experimental re-sults revealed that the reaction temperature and the CO2 concentration increased first and then decreased across thea：,：ial positions, but on the contrary for the O2 concentration. The temperature and the O2 concentration distributionsof experimental results are in good agreement with that of numerical simulation results for the 62-step simplifiedreactions, and the CO2 concentration distribution is in general agreement with the numerical data. But the 38-stepsimplified reactions can only predict the change trend for the important parameters which are mentioned above.Through the contrastive analysis for these two kinds of simplified reactions, the 62-step reactions can more accuratelysimulate the combustion characteristics of RP-3 kerosene. Aud n-decane can be used as a one-component surrogatefuel for RP-3 aviation kerosene.

Dynamic Characteristics of Hydrocarbon Fuel within the Channel at Supercrit- ical and Pyrolysis Condition

Regenerative cooling with fuel as the coolant is used in the scramjet engine. In order to grasp the dynamic cha- racteristics of engine fuel supply processes, this article studies the dynamic characteristics of hydrocarbon fuel within the channel. A one-dimensional dynamic model was proved, the thermal energy storage effect, fuel volume effect and chemical dynamic effect have been considered in the model, the ordinary differential equations were solved using a 4th order Rungc-Kutta method. The precision of the model was validated by three groups of expe- rimental data. The effects of input signal, working condition, tube size on the dynamic characteristics of pressure, flow rate, temperature have been simulated. It is found that cracking reaction increased the compressibility of the fuel pyrolysis mixture and lead to longer responding time of outlet flow. The responding time of outlet flow can reach 3s when tube is 5m long which will greatly influence the control performance of the engine thrust system. Meanwhile, when the inlet flow rate appears the step change, the inlet pressure leads to overshoot, the overshoot can reach as much as 100%, such highly transient impulse will result in detrimental effect on fucl pump.