PHASE STABILITY OF LOW-TEMPERATURE AMORPHOUS CONDENSATES OF WATER AND WATER–GAS MIXTURES

Recent studies have shown that appropriate levels of alkali promotion can significantly improve the rate of low-temperature water gas shift (LT-WGS) on a range of catalysts. At sufficient loadings, the alkali metal can weaken the formate C–H bond and promote formate dehydrogenation, which is the proposed rate determining step in the formate associative mechanism. In a continuation of these studies, the effect of Rb promotion on Pt/ZrO2 is examined herein. Pt/ZrO2 catalysts were prepared with several different Rb loadings and characterized using temperature programmed reduction mass spectrometry (TPR-MS), temperature programmed desorption (TPD), diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), an X-ray absorption near edge spectroscopy (XANES) difference procedure, extended X-ray absorption fine structure spectroscopy (EXAFS) fitting, TPR-EXAFS/XANES, and reactor testing. At loadings of 2.79% Rb or higher, a significant shift was seen in the formate ν(CH) band. The results showed that a Rb loading of 4.65%, significantly improves the rate of formate decomposition in the presence of steam via weakening the formate C–H bond. However, excessive rubidium loading led to the increase in stability of a second intermediate, carbonate and inhibited hydrogen transfer reactions on Pt through surface blocking and accelerated agglomeration during catalyst activation. Optimal catalytic performance was achieved with loadings in the range of 0.55–0.93% Rb, where the catalyst maintained high activity and exhibited higher stability in comparison with the unpromoted catalyst.

Download Full-text

Fast oxygen ion migration in Cu–In–oxide bulk and its utilization for effective CO2 conversion at lower temperature

Chemical Science ◽

10.1039/d0sc05340f ◽

2021 ◽

Author(s):

Jun-Ichiro Makiura ◽

Takuma Higo ◽

Yutaro Kurosawa ◽

Kota Murakami ◽

Shuhei Ogo ◽

...

Keyword(s):

Low Temperature ◽

Water Gas Shift ◽

Chemical Looping ◽

Co2 Conversion ◽

Ion Migration ◽

Oxygen Ion ◽

Reverse Water Gas Shift ◽

Oxygen Ion Migration ◽

Lower Temperature ◽

Water Gas

Efficient activation of CO2 at low temperature was achieved by reverse water–gas shift via chemical looping (RWGS-CL) by virtue of fast oxygen ion migration in a Cu–In structured oxide, even at lower temperatures.

Download Full-text

Preparation, Characterization, and Activity of Pd/PSS-Modified Membranes in the Low Temperature Dry Reforming of Methane with and without Addition of Extra Steam

Membranes ◽

10.3390/membranes11070518 ◽

2021 ◽

Vol 11 (7) ◽

pp. 518

Author(s):

Cecilia Mateos-Pedrero ◽

Miguel A. Soria ◽

Antonio Guerrero-Ruíz ◽

Inmaculada Rodríguez-Ramos

Keyword(s):

Low Temperature ◽

Flow Reactor ◽

Dry Reforming ◽

Dry Reforming Of Methane ◽

Porous Stainless Steel ◽

Pd Membrane ◽

Continuous Flow Reactor ◽

Oxidation In Air ◽

H2 Yield ◽

Water Gas

The external surface of a commercial porous stainless steel (PSS) was modified by either oxidation in air at varying temperatures (600, 700, and 800 °C) or coating with different oxides (SiO2, Al2O3, and ZrO2). Among them, PSS-ZrO2 appears as the most suitable carrier for the synthesis of the Pd membrane. A composite Pd membrane supported on the PSS-ZrO2 substrate was prepared by the electroless plating deposition method. Supported Ru catalysts were first evaluated for the low-temperature methane dry reforming (DRM) reaction in a continuous flow reactor (CR). Ru/ZrO2-La2O3 catalyst was found to be active and stable, so it was used in a membrane reactor (MR), which enhances the methane conversions above the equilibrium values. The influence of adding H2O to the feed of DRM was investigated over a Ru/ZrO2-La2O3 catalyst in the MR. Activity results are compared with those measured in a CR. The addition of H2O into the feed favors other reactions such as Water-Gas Shift (RWGS) and Steam Reforming (SR), which occur together with DRM, resulting in a dramatic decrease of CO2 conversion and CO production, but a marked increase of H2 yield.

Download Full-text

Characteristics of Low Temperature Degradation Free ZTA for Artificial Joint

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.631.18 ◽

2014 ◽

Vol 631 ◽

pp. 18-22 ◽

Cited By ~ 2

Author(s):

Junji Ikeda ◽

Takayuki Murakami ◽

Takayoshi Shimozono ◽

Reiji Watanabe ◽

Mikio Iwamoto ◽

...

Keyword(s):

Low Temperature ◽

Phase Stability ◽

Mechanical Characteristics ◽

Bending Strength ◽

Accelerated Aging ◽

Ceramic Materials ◽

Wear Property ◽

Artificial Joint ◽

Four Point Bending ◽

Bearing Materials

Low temperature degradation free Zirconia toughened alumina (ZTA) has been developed. It is reported that ZTA has higher mechanical strength compared to alumina due to the stress induced transformation and spontaneously transformation of zirconia phase on some ZTA have been occurred. For achieving the higher reliability of artificial joint prosthesis alternative to alumina and other ceramic materials, it is necessary to improve and validate the both mechanical characteristics and phase stability at the same time. We evaluated that microstructure, mechanical characteristics and phase stability of newly developed ZTA (BIOCERAM®AZUL). It was confirmed that four-point bending strength and weibull modulus were extreamly high, and ZTA has higher reliability. There were no significant changes and deterioration in four-point bending strength, crystal structure and wear property with and without accelerated aging test. Newly developed ZTA not only with high mechanical characteristics but also with phase stability could be quite useful as bearing materials in artificial joints for longer clinical use.

Download Full-text