Experimental Study of Ignition of a Gasoline–Air Mixture in a Constant‐Volume Combustion Chamber

The characteristics of flamekernel development in a premixed gasoline–air mixture in a cylindrical constantvolume combustion chamber are measured. The experiments are performed with an initial temperature of 393 K, pressure of 6 bar, and equivalence ratio = 0.8 with the use of various ignition systems and spark plugs. The schlieren pictures of the process are presented, and the measured results for flame velocity, heatrelease rate, and mass fraction of the burnt fuel are analyzed.     

Effect of framework aluminum in proton‐ or copper‐exchanged MFI ferrialuminosilicates on their activity for the reduction of nitric oxide with ammonia

Reduction of NO with ammonia in excess oxygen has been carried out on protonform and Cu²⁺exchanged MFI ferrialuminosilicate. Though HZSM5 showed very low activity, the framework Al in Hferrialuminosilicate greatly enhanced the activity. The framework Al in Cu²⁺exchanged ferrialuminosilicate also enhanced the activity to some extent.     

Postinduction Processes During Thermal Explosion in the Systems “Porous Material–Reactive Gas–Solid Product”

A complete solution of the unsteadystate filtration problem of thermal explosion incorporating the postinduction period is given for the first time. The paper describes a study of the temperaturefield dynamics, poregas pressure, and the degree of condensedphase conversion versus the reactivegas deficiency in a reactive porous material. Focus is on the formation and propagation of frontal regimes of exothermic chemical reactions (their number, direction, and velocity of propagation, degree of condensedphase conversion at the front). The study revealed double selfignition phenomena and combustionwave propagation regimes with incomplete conversion at the front. A surface regime of thermal explosion limited by gas filtration from the outside was considered. The regularities in the dynamics of the exothermic chemical reaction found in the present study allow one to qualitatively control hightemperature synthesis under thermal explosion conditions.     

Some Features of Gas‐Flame Propagation in Narrow Tubes

The dependence of the flamefront curvature on the composition of the mixture in tubes of various diameters is considered. The combustionwave velocities are measured for different fractions of fuel in the mixture. It is shown that the dependence of the burning velocity on the composition of the mixture has two maximums, one of them being related to the transition of the laminar combustion mode to turbulent combustion. Combustion turbulization is caused by flame instability to acoustic oscillations. Variations of the combustionwave shape due to acoustic oscillations are observed.     

Passage of a Bubble‐Detonation Wave into a Chemically Inactive Bubble Medium

Passage of detonation waves from a chemically active bubble medium into a chemically inactive bubble medium is studied experimentally. The structure of incident (detonation) and transmitted (postdetonation) waves is investigated, and the pressures of these waves for different parameters of bubble media are measured. The evolution of postdetonation waves is traced. Decay constants of postdetonation waves are determined. The speeds of propagation of detonation and postdetonation waves are measured. The energydissipation mechanisms for detonation and postdetonation waves in bubble media are analyzed qualitatively.     

Chemistry of Combustion Waves in Substances with a Complicated Structure of Reagent Molecules. 1. Structure of the Front of Rich Isopentane Flame

Results on the structure of the lowtemperature relaxation zone of the front of a laminar Bunsen flame of isoC₅H₁₂ (2methylbutane) under atmospheric pressure are presented. The flame of a premixed mixture isoC₅H₁₂ + O₂ + Ar with a fueltoair equivalence ratio of 1.7 is examined. The mass fluxes, total rates of reactions of matter consumption and expenditure, balance of substances, and profiles of bulk heatrelease rates are calculated on the basis of the experimental concentration and temperature profiles. The results obtained indicate that there is a vast region of lowtemperature conversion of isopentane in the flame front. It is found that only part of the products sampled by the microprobe from different points of the flame front results from transformations in the lowtemperature region, namely, oxygen, isopentane, water, carbon monoxide, propane, methane, and methanol. Ethylene, propylene, hydrogen dioxide, and formaldehyde are present in the lowtemperature zone in insignificant amounts; they are secondary products of conversion of methyl and propyl radicals. It is assumed that the observed feature is a result of the competing interaction of two mechanisms of fuelmixture conversion: selfcatalysis and thermal selfacceleration. Based on the previously suggested mechanism of oxidation pyrolysis by the scheme of intramolecular quadratic destruction, experimentally observed fragmentation of the isopentane molecule is demonstrated. In contrast to npentane, formation of methyl alcohol has been found in isopentane convection products.     

Variable‐temperature IR spectroscopic studies of CO adsorbed on Na‐ZSM‐5 and Na‐Y zeolites

CO interacts with extraframework alkali metal cations (M⁺=) of zeolites to form both M⁺CO and M⁺OC species. By using variabletemperature FTIR spectroscopy, these Cbonded and Obonded species were found to be in a temperaturedependent equilibrium. For the same cation, the difference in interaction energy depends upon the zeolite framework. Thus, for the equilibrium process ZNa⁺=CO ZNa⁺OC, where Z represents the zeolite framework, H ⁰ was found to take the values 3.8 and 2.4 kJ mol^– for CO/NaZSM5 and CO/NaY, respectively. The Cbonded species show always the highest cation–CO interaction energy.     

Convective Regime of Filtration Combustion of Energetic Materials in a Cocurrent Flow of Their Combustion Products

The convective regime of filtration combustion of energetic materials in a cocurrent flow of their combustion products is studied using a model with extremely simplified kinetics and heat transfer, which shows instability of the process. It is shown that the more accurate twotemperature model describes a steadystate regime. In this regime, the gas temperature on the hot boundary of the heating zone is well below the combustion temperature, and the solidphase temperature is well below the temperature proposed in recent studies on this topic. It is pointed out that the twotemperature approach is unjustified and intragranular nonisothermicity must be taken into account for convective regimes. It is shown that the threetemperature model, which takes into account this effect, does not give a stable steadystate solution.     

Quasi‐Homogeneous and Pseudospin Modes of Zirconium‐Wire Combustion in Air

A novel experimental technique is proposed for examining the transition mechanism from quasihomogeneous to heterogeneous combustion — burning of a variablepitch spring. Depending on the pitch of aircombustible zirconium springs, two combustion modes are possible. Quasihomogeneous (layerbylayer) combustion is observed in the case of smallpitch springs; as the spring pitch increases, quasihomogeneous combustion transforms into heterogeneous (pseudospin) combustion. Conditions for the occurrence of various combustion modes, depending on the spring diameter and pitch, are studied.     

Synthesis of nanosized platinum cluster in cubic mesoporous material via a direct introduction method

Platinumclustercontaining cubic mesoporous material (PtMCM48) has been synthesized by direct introduction of chloroplatinic acid during the synthesis of MCM48. In addition, we have also studied the incipient wetness impregnation and ionexchange method to obtain the platinumcontaining cubic mesoporous material. The nature of the platinumMCM48 catalyst has been characterized by different techniques such as XRD, N₂ adsorption, TEM, XPS, and NMR. The catalyst obtained by direct introduction of platinum in the synthesis gel shows higher activity in the hydrogenation of benzene and toluene.     

Model of an Ideal Solid‐Flame Combustion Wave with a Variable Chemical‐Reaction Surface

A model for a combustion wave in condensed mixtures with autoinhibition by a highmelting reaction product is constructed with allowance for a reduction in the particle surface of the highmelting reactant during chemical interaction with the lowmelting reactant. An approximate analytical solution is derived using the method of a semiinfinite reaction zone. The method is validated by qualitative and numerical studies of differential equations. The literature model of the process considered ignores the variation in the particle surface of the highmelting reactant, which leads to neglect of the key characteristics of all chemical reactions — a continuous decrease in the reaction rate during combustion of the reactants.     

Combustion of a Mixture of Aluminum and a Titanium‐Containing Raw Material in the Presence of Additives

A model of the gasphase component of combustion of an aluminum mixture with metal oxides is described. By the example of titanium reduction from its oxide, it is shown that atomic oxygen formed thereby facilitates gasphase oxidation of aluminum and decreases metal yield. The effect of graphite, activated carbon, and diesel fuel on combustionwave velocity and temperature is considered. Two waves (cold and hot ones) are observed in the system titanium oxide–ferric oxide–aluminum–carboncontaining additives. Hydrocarbon additives inhibit the aluminumoxidation reaction by oxygen contained in air in the first wave, and graphite and activated carbon play the same role in the second wave in the titaniumreduction reaction. Experimental confirmation is found for the fact that the action of additives increases the amount of aluminum consumed directly for titanium reduction in the second wave, which enhances exothermality of the process.     

Location of Mn in MnAPO‐11: influence of synthesis from aqueous and non‐aqueous media

MnAPO11 samples were synthesized from aqueous (MnAPO11(A)) and ethylene glycol (MnAPO11(NA)) media. The crystallinity of the samples was more when the synthesis was carried out in ethylene glycol. Chemical and thermogravimetric analyses reveal greater incorporation of Mn in the framework of MnAPO11(NA) than in MnAPO11(A). At least five different types of Mn(II) species are detected in the samples by ESR. The studies suggest that Mn is more homogeneously distributed in MnAPO11(NA) than in MnAPO11(A).     

Cobalt‐catalyzed amination of 1,3‐cyclohexanediol and 2,4‐pentanediol in supercritical ammonia

The onestep procedure of amination of bifunctional secondary alcohols to diamines has been investigated in a continuous fixedbed reactor. Application of supercritical NH₃ as a solvent and reactant suppressed catalyst deactivation and improved selectivities to amino alcohol intermediates, whereas selectivities to diamines remained poor (8–10%). The main reason for the low diamine selectivity of 1,3dihydroxy compounds is water elimination leading to undesired monofunctional products via ,unsaturated alcohol, ketone or amine intermediates. This side reaction does not occur with 1,4dihydroxy compounds which afford high aminol and diamine selectivities under similar conditions. Amination of secondary diols with ammonia was found to be faster, but less selective than that of the corresponding primary 1,3propanediol.     

Vapor‐phase synthesis of acetophenone in benzene acylation over CeHZSM‐5(30) zeolite

The benzene acylation was carried out with acetic anhydride as an acylating agent in vapor phase over HZSM5, Si/Al =30 and 280, HY and Ce, Vmodified HZSM5(30) zeolite catalysts at atmospheric pressure. The yield of acylated product acetophenone was found to be 82.1 wt% with 95.0% selectivity at 86.4 wt% conversion of acetic anhydride over Cemodified HZSM5(30) where Brønsted acidic sites are active for this reaction.     

Analysis of the Thermal Explosion in Systems Porous Reagent–Active Gas–Solid Product

The specific features of dynamics of the thermal explosion in systems porous reagent–active gas–solid product under conditions where the heattransfer and masstransfer regions are separated from the ambient medium are considered. In addition to the competition of heat release and heat removal, the process of initiation of exothermal chemical interaction in these systems under normal pressures depends significantly on conditions of filtration transport of the gaseous reagent. The induction and postinduction periods of the thermal explosion are studied. The theoretical analysis of thermalexplosion issues is supplemented by an experimental study of the process for the porous titanium–nitrogen–titanium nitride system.     

Experimental Investigation and Numerical Simulation of an Expanding Multifront Detonation Wave

Results of experimental investigations of an expanding multifront detonation wave are presented. Two stages of spontaneous formation of new disturbances and transverse waves on the expanding detonationwave front are observed. The main mechanisms of reinitiation of detonation waves are discussed. Twodimensional numerical simulation of the dynamics of a multifront detonation wave in a linearly expanding channel is performed. The effect of spontaneous formation of new disturbances and new transverse waves is confirmed by computations, and the main mechanism of multiplication of transverse waves is the instability of detonationwavefront elements at the stage they cease to be in the overdriven state and are attenuated during expansion.     

Fabrication and characterization of the Ag‐based high‐technology model nanocluster catalyst for ethylene epoxidation manufactured by electron beam lithography

Nanocluster catalysis is an area where greater fundamental knowledge is needed to understand the behavior of aggregates of metal atoms in determining product selectivity of chemical reactions. While catalysis is practiced industrially with economic success there is still a great need to eliminate wasteful sidereactions which hurt overall yields. Here we report on fabrication of a Agbased hightechnology model nanocluster catalyst by using electron beam lithography (EBL) designed for systematic studies of the ethylene epoxidation reaction. The catalyst is made of a square array of cylindershaped Ag nanoclusters that are 200 Å in diameter, deposited on a four inch silicon wafer, precovered with a 100 Å thick film of alumina. The height of the particles and interparticle distance can vary, and were chosen to be 150–300 and 1000 Å, respectively. The high technology catalyst was characterized by Xray photoelectron spectroscopy (XPS), highresolution transmission electron microscopy (TEM), scanning electron microscopy (SEM), and atomic force microscopy (AFM). The thermal stability of Ag nanoclusters in vacuo was investigated.     

Shock‐Induced Polarization of Materials

A new computational method of calculating signals of shockinduced electric polarization of materials is proposed and used to analyze previous experimental results on the shockinduced electric polarization of Plexiglas. Experimental results on the shockinduced electric polarization of granite are presented.     

Gasless Combustion of Ti–Al Bimetallic Multilayer Nanofoils

Ti–Al multilayer foils were produced magnetron vacuum deposition. The microstructure period varied in the range of 5–110 nm, the number of layers was 150–4700, and the total thickness of a multilayer foil reached 15–20 m. The gasless combustion of the foils was studied. Steadystate and pulsating combustion regimes were revealed; combustion temperatures were determined for both regimes. It was shown that the most probable mechanism of the selfpropagating reaction is the diffusion of Al in Ti at a temperature close to the temperature of the transition.