Nonoxidative methane activation,coupling, and conversion to ethane,ethylene, and hydrogen over Fe/HZSM‐5, Mo/HZSM‐5, and Fe–Mo/HZSM‐5 catalysts in packed bed reactor

A high abundance of methane and its relatively low price make it an attractive raw feedstock for the production of ethylene, which is in the consumer demand in recent years. Direct catalytic nonoxidative conversion is interesting, because it could be utilized on natural gas well sites. Monometallic and bimetallic Fe and Mo catalysts were prepared for the purpose of the coupling to ethane and ethene. Three supported materials were synthesized with the following loading of metal: 2.5‐wt% Fe, 5.0‐wt% Fe, and 2.5‐wt% Mo on HZSM‐5. Process' chemical reactions were also catalyzed with a constant 2.5‐wt% Mo/HZSM‐5, which had different amounts of Fe, namely, 0.5, 1.0, and 2.5 wt%. Fourier transform infrared (FTIR), N₂ adsorption/desorption, NH₃ temperature‐programmed desorption (TPD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X‐ray diffraction (XRD) were applied for characterization. Coke, accumulated on spent solids, was determined by thermogravimetric analysis (TGA). Activity was evaluated in quartz‐packed bed reactor. All surfaces suffered from deactivation due to carbon formation. The addition of Fe to Mo increased CH₄ reacted. The highest selectivity for alkenes was achieved over 1.0‐wt% Fe to 2.5‐wt% Mo/HZSM‐5. At the peak of performance, the C‐based reactivity was 52% for olefins and 2% for alkanes. Stability was accomplished over 2.5‐wt% Fe/HZSM‐5, where the rate of C₂ synthesis was comparatively stable for 20 hours of the time on stream. The selective C‐basis yield for C₂H₄ and C₂H₆ was 36% and 23%, respectively. The lowest measured quantity of (carbonaceous) by‐products was deposited on 2.5‐wt% Fe/HZSM‐5 after 26 hours. Propylene was detected very limitedly.     

Friction properties of carbon-carbon composites

The friction of composite materials based on carbon-carbon fiber over the counter-pair made from SG-T siliconized graphite is investigated. The friction conditions that appeared in the working period under definite loads are considered. The structure of the wear products is investigated by electron microscopy.     

High-field Josephson magnetic resonance in high-temperature superconductors

The possibility of high-field Josephson magnetic resonance (HFJMR) in high-temperature super-conductors (HTSCs) is theoretically demonstrated. The HFJMR mechanism is related to the Josephson oscillations in intergranular junctions of a polycrystalline HTSC, which are caused by the penetration of Abrikosov vortices into the grains. In fields within H _c1 ≤ H < H _x (where H _c1 is the first critical field and H _x is the field corresponding to vortex separation from pinning centers in the grains), measurements of the microwave absorption spectra of a sample can be used for investigations of the HTSC macrostructure and the properties of vortex matter. In the latter aspect, the HFJMR method is analogous to the SQUID technique.     

Structure and properties of hot stamped magnetic circuits from 50N powder sprayed using nitrogen

Translated from Poroshkovaya Metallurgiya, No.8(320), pp. 69–72, August, 1989.     

Experimental study of turbulent flow in a rotating channel

Results are shown of measurements pertaining to the turbulence of flow in a short channel rotating about its axis.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 24, No. 6, pp. 1103–1108, June, 1973.     

Torsional rigidity of harmonic gear drives

A model is proposed for harmonic gear drives. The model takes into account that harmonic engagement involves multiple pairs and multiple zones and also takes account of the manufacturing and assembly errors, the deformation of the drive components, and the adjustment of the gaps in the engagement under load. By means of the model, harmonic gear drives with high torsional rigidity may be designed.