scholarly journals Effects of crystal size on methanol to hydrocarbon conversion over single crystals of ZSM-5 studied by synchrotron infrared microspectroscopy

2020 ◽  
Vol 22 (34) ◽  
pp. 18849-18859
Author(s):  
Ivalina B. Minova ◽  
Santhosh K. Matam ◽  
Alex Greenaway ◽  
C. Richard A. Catlow ◽  
Mark D. Frogley ◽  
...  
Keyword(s):  
Induction Period ◽  
Single Crystals ◽  
Crystal Size ◽  
Hydrocarbon Conversion ◽  
Infrared Microspectroscopy ◽  
Hydrocarbon Pool ◽  
Methanol To Hydrocarbon ◽  
Increasing Temperature

The induction period for alkene formation from methanol in single crystals of HZSM-5 decreases with decreasing crystal size and increasing temperature and hydrocarbon pool species are formed almost instantaneously at higher temperatures.

scholarly journals Structural and thermoelectric properties of the Pr2Zr2O7 compound

2019 ◽  
pp. 4-9
Author(s):  
Adolfo Quiroz-Rodríguez ◽  
Cesia Guarneros-Aguilar ◽  
Ricardo Agustin-Serrano
Keyword(s):  
Electron Microscopy ◽  
Thermal Conductivity ◽  
Thermoelectric Properties ◽  
Crystal Size ◽  
Ambient Pressure ◽  
X Ray Diffraction ◽  
X Ray ◽  
Increasing Temperature ◽  
Thermal Stability Of ◽  
Scanning Electron

In this research, it is presented a detailed study of the structural and thermoelectric properties of the pyrochlore zirconium Pr2Zr2O7 compound prepared by solid-state reaction (SSR) in air at ambient pressure. The synthesized sample was characterized using powder X-ray diffraction. The thermal stability of the thermoelectric compound (TE) Pr2Zr2O7 was tested by thermogravimetric analysis (TGA) and differential thermal analysis (DTA). Scanning electron microscopy shows that the crystal size varies between 0.69 and 2.81μm. Electrical conductivity (\sigma) of the sample calcined at 1400 °C presented values increase irregularly with the increasing temperature from 0.001 to 0.018 S cm-1 as expected in a semiconductor material. The thermal conductivity is lower than 0.44 - 775 W m-1 K-1 which is quite anomalous in comparison with the thermal conductivity of other oxides.

Plastic Deformation of Mo(Si,Al)2 Single Crystals with the C40 Structure

1996 ◽  
Vol 460 ◽  
Author(s):  
M. Moriwaki ◽  
K. Ito ◽  
H. Inui ◽  
M. Yamaguchi
Keyword(s):  
Single Crystals ◽  
Deformation Behavior ◽  
Basal Slip ◽  
Room Temperature ◽  
Slip Systems ◽  
Temperature Range ◽  
Al Content ◽  
Partial Dislocations ◽  
Increasing Temperature ◽  
Critical Resolved Shear Stress

ABSTRACTThe deformation behavior of single crystals of Mo(Si,Al)2 with the C40 structure has been studied as a function of crystal orientation and Al content in the temperature range from room temperature to 1500°C in compression. Plastic flow is possible only above 1100°C for orientations where slip along <1120> on (0001) is operative and no other slip systems are observed over whole temperature range investigated. The critical resolved shear stress for basal slip decreases rapidly with increasing temperature and the Schmid law is valid. Basal slip appears to occur through a synchroshear mechanism, in which a-dislocations (b=1/3<1120>) dissociate into two synchro-partial dislocations with the identical Burgers vector(b*1/6<1120>) and each synchro-partial further dissociates into two partials on two adjacent planes.

A computational study of methanol-to-hydrocarbon conversion — Towards the design of a low-barrier process

2010 ◽  
Vol 88 (8) ◽  
pp. 866-876 ◽  
Author(s):  
Bun Chan ◽  
Leo Radom
Keyword(s):  
Quantum Chemistry ◽  
Computational Study ◽  
Carbon Pool ◽  
Low Energy ◽  
Zeolite Catalysts ◽  
Hydrocarbon Conversion ◽  
Aromatic Carbon ◽  
Computational Quantum Chemistry ◽  
Methanol To Hydrocarbon ◽  
Computational Quantum

Computational quantum chemistry has been employed to examine the production of ethylene with methanol-to-hydrocarbon (MTH) processes via a carbon pool mechanism. We find that the M05-2X functional performs well for the types of reactions that are involved. The methylation reactions of the aromatic cocatalyst are the most energy-demanding steps in the process. For the subsequent production of C2H4, we have identified a low-energy pathway that involves multiple methyl shifts, followed by concerted deprotonation and C2H4 elimination. The substitutions of the Al and Si atoms in the participating Si–OH–Al moiety of zeolite catalysts with Ga and Ge do not lead to lower barriers for the methylation reactions, nor does the use of a more electron-rich aromatic cocatalyst. However, we find that the use of two cocatalysts, a nucleophile and an aromatic carbon pool, can provide an overall low-energy pathway for the MTH process.

scholarly journals Yield Stress Anomaly in B2 FeAl

1996 ◽  
Vol 460 ◽  
Author(s):  
K. Yoshimi ◽  
S. Hanada ◽  
M. H. Yoo
Keyword(s):  
Single Crystals ◽  
Yield Stress ◽  
Rate Sensitivity ◽  
Recovery Process ◽  
Peak Temperature ◽  
Positive Temperature ◽  
Slip Vector ◽  
Temperature Range ◽  
Tension And Compression ◽  
Increasing Temperature

ABSTRACTOur studies on yield stress anomaly of B2 FeAI single crystals are reviewed in this paper. A positive temperature dependence of yield stress, so-called “yield stress anomaly”, is observed in B2 FeAI in which excess vacancies are fully annealed out. Associated with the anomaly, characteristic asymmetry is found between tension and compression. While the strain-rate sensitivity is almost zero in the temperature range of the yield stress anomaly, the stress relaxation becomes significant with increasing temperature, indicating that a recovery process is thermally activated. It is ascertained by the two-surface trace analysis that slip transition from <111> direction at intermediate temperature to <100> at high temperature occurs around the peak temperature. Even at the peak temperature, in addition, operative slip vector for yielding is confirmed to be predominantly <111> by TEM. Also, it is observed that <111>-type superdislocations are frequently climb-dissociated in the temperature range of the anomaly. APB formation on {111} plane is energetically favorable, which is in agreement with the Flinn's calculation for the B2 superlattice that APB energy on {111} plane is lower than that on {110} plane. Such an anisotropy of APB energy would offer specific driving force for the climb dissociation on <111> superdislocations. On the basis of the observed results, the anomalous strengthening behavior of B2 FeAI single crystals is discussed.

Silicate ionic liquid synthesis of zeolite merlinoite: Crystal size control from crystalline nanoaggregates to micron-sized single-crystals

2014 ◽  
Vol 198 ◽  
pp. 35-44 ◽  
Author(s):  
Mohamed Haouas ◽  
Louwanda Lakiss ◽  
Charlotte Martineau ◽  
Jaafar El Fallah ◽  
Valentin Valtchev ◽  
...  
Keyword(s):  
Ionic Liquid ◽  
Single Crystals ◽  
Crystal Size ◽  
Size Control
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