Dehydration of 2,3-butanediol to produce 1,3-butadiene over Sc2O3 catalyst prepared through hydrothermal aging

2021 ◽  
Vol 516 ◽  
pp. 111996
Author(s):  
Kazuki Nakazono ◽  
Ryoji Takahashi ◽  
Yasuhiro Yamada ◽  
Satoshi Sato
Keyword(s):  
Hydrothermal Aging

scholarly journals The Hydrothermal Stability and the Properties of Non- and Strongly-Interacting Rh Species over Rh/γ, θ-Al2O3 Catalysts

Catalysts ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 99
Author(s):  
Guanghao Cheng ◽  
Gurong Shen ◽  
Jun Wang ◽  
Yunhao Wang ◽  
Weibo Zhang ◽  
...  
Keyword(s):  
Activation Energy ◽  
Apparent Activation Energy ◽  
Aging Time ◽  
Reaction Path ◽  
Aging Treatment ◽  
Hydrothermal Stability ◽  
Hydrothermal Aging ◽  
Strongly Interacting

The present work reports the effects of γ-, θ-phase of alumina on the hydrothermal stability and the properties of non- and strongly-interacting Rh species of the Rh/Al2O3 catalysts. Comparing to γ-Al2O3, θ-Al2O3 can not only reduce the amount of occluded Rh but also better stabilize Rh during hydrothermal aging treatment. When the aging time was prolonged to 70 h, all the non-interacting Rh was transformed into strongly-interacting Rh and occluded Rh. The XPS results indicated that non- and strongly-interacting Rh might exist in the form of Rh/Rh3+ and Rh4+, respectively. CO-NO reaction was chosen as a probe reaction to research more information about non- and strongly-interacting Rh. The two Rh species had similar apparent activation energy (Eapp) of 170 kJ/mol, which indicated that non- and strongly-interacting Rh follow the same reaction path. The non-interacting Rh was removed from aged samples by the acid-treated method, and obtained results showed that only 2.5% and 4.0% non-interacting Rh was maintained in aged Rh/γ-Al2O3 and Rh/θ-Al2O3.

scholarly journals Phase evolution and mechanical performance of an ettringite-based binder during hydrothermal aging

2021 ◽  
Vol 143 ◽  
pp. 106403
Author(s):  
Hoang Nguyen ◽  
Valter Carvelli ◽  
Wolfgang Kunther ◽  
Mirja Illikainen ◽  
Paivo Kinnunen
Keyword(s):  
Mechanical Performance ◽  
Phase Evolution ◽  
Hydrothermal Aging

scholarly journals Effect of Accelerated Aging on Some Mechanical Properties and Wear of Different Commercial Dental Resin Composites

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2769
Author(s):  
Jonne Oja ◽  
Lippo Lassila ◽  
Pekka K. Vallittu ◽  
Sufyan Garoushi
Keyword(s):  
Mechanical Properties ◽  
Flexural Strength ◽  
Accelerated Aging ◽  
Wear Depth ◽  
Resin Composites ◽  
Expiration Date ◽  
Dental Resin ◽  
Hydrothermal Aging ◽  
Dental Resin Composites

The aim of current in vitro research was to determine the effect of hydrothermal accelerated aging on the mechanical properties and wear of different commercial dental resin composites (RCs). In addition, the effect of expiration date of the composite prior its use was also evaluated. Five commercially available RCs were studied: Conventional RCs (Filtek Supreme XTE, G-aenial Posterior, Denfil, and >3y expired Supreme XTE), bulk-fill RC (Filtek Bulk Fill), and short fiber-reinforced RC (everX Posterior). Three-point flexural test was used for determination of ultimate flexural strength (n = 8). A vickers indenter was used for testing surface microhardness. A wear test was conducted with 15,000 chewing cycles using a dual-axis chewing simulator. Wear pattern was analyzed by a three-dimensional (3D) noncontact optical profilometer. Degree of C=C bond conversion of monomers was determined by FTIR-spectrometry. The specimens were either dry stored for 48 h (37 °C) or boiled (100 °C) for 16 h before testing. Scanning electron microscopy (SEM) was used to evaluate the microstructure of each material. Data were analyzed using ANOVA (p = 0.05). Hydrothermal aging had no significant effects on the surface wear and microhardness of tested RCs (p > 0.05). While flexural strength significantly decreased after aging (p < 0.05), except for G-aenial Posterior, which showed no differences. The lowest average wear depth was found for Filtek Bulk Fill (29 µm) (p < 0.05), while everX Posterior and Denfil showed the highest wear depth values (40, 39 µm) in both conditions. Passing the expiration date for 40 months did not affect the flexural strength and wear of tested RC. SEM demonstrated a significant number of small pits on Denfil’s surface after aging. It was concluded that the effect of accelerated aging may have caused certain weakening of the RC of some brands, whereas no effect was found with one brand of RC. Thus, the accelerated aging appeared to be more dependent on material and tested material property.

Effect of fiber surface modification on water absorption and hydrothermal aging behaviors of GF/pCBT composites

2015 ◽  
Vol 82 ◽  
pp. 84-91 ◽  
Author(s):  
Bin Yang ◽  
Jifeng Zhang ◽  
Limin Zhou ◽  
Mingkun Lu ◽  
Wenyan Liang ◽  
...  
Keyword(s):  
Surface Modification ◽  
Water Absorption ◽  
Fiber Surface ◽  
Hydrothermal Aging

Hydrothermal aging affects the three-dimensional fit and fatigue lifetime of zirconia abutments

2021 ◽  
Vol 124 ◽  
pp. 104832
Author(s):  
Edmara T.P. Bergamo ◽  
Tiago M.B. Campos ◽  
Adolfo C.O. Lopes ◽  
Karina B. Cardoso ◽  
Marcus V.R. Gouvea ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Hydrothermal Aging ◽  
Fatigue Lifetime

scholarly journals Mussel-Inspired Co-Deposition of Polydopamine/Silica Nanoparticles onto Carbon Fiber for Improved Interfacial Strength and Hydrothermal Aging Resistance of Composites

Polymers ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 712 ◽  
Author(s):  
Xuejun Cui ◽  
Lichun Ma ◽  
Guangshun Wu
Keyword(s):  
Carbon Fibers ◽  
Interfacial Strength ◽  
Fiber Surface ◽  
The Novel ◽  
Hydrothermal Aging ◽  
One Pot ◽  
Polar Groups ◽  
Aging Resistance ◽  
Interfacial Compatibility ◽  
Hydrolysis Of

A novel and effective strategy was first proposed for the codeposition of a mussel-inspired nanohybrid coating with excellent wettability onto the surface of carbon fibers (CFs) by simultaneous polymerization of bioinspired dopamine (DA) and hydrolysis of commercial tetraethoxysilane (TEOS) in an eco-friendly one-pot process. Mussel-inspired nanohybrids could be adhered onto the surface of CFs firmly. The novel modification could afford sufficient polar groups and significantly improve fiber surface roughness and energy without decreasing fiber intrinsic strength, which were advantageous to promote interfacial compatibility and wettability between CFs and matrix resin. As a result, the interfacial shear strength of composites increased to 48.21 ± 1.45 MPa compared to that of untreated composites 29.47 ± 0.88 MPa. Meanwhile, the nanohybrid coating increased significantly composites’ hydrothermal aging resistance. The efficient strategy shows a promising and green platform of surface functionalization of CFs for preparing advanced polymer composites arising from broadly mechanical-demanding and energy-saving usages.

Experimental and kinetic analysis of hydrothermal aging effects on ammonia adsorption capacity over a commercial Cu-zeolite selective catalytic reduction catalyst

2018 ◽  
Vol 233 (12) ◽  
pp. 3030-3042
Author(s):  
Tae Joong Wang ◽  
In Hyuk Im
Keyword(s):  
Adsorption Capacity ◽  
Selective Catalytic Reduction ◽  
Catalytic Reduction ◽  
Adsorption Site ◽  
Selective Catalytic Reduction Catalyst ◽  
Aging Effects ◽  
Hydrothermal Aging ◽  
Ammonia Adsorption ◽  
Fresh Catalyst ◽  
Reduction Catalysts

Ammonia/urea selective catalytic reduction is an efficient technology to control NOx emission from diesel engines. One of its critical challenges is the performance degradation of selective catalytic reduction catalysts due to the hydrothermal aging experienced in real-world operations during the lifetime. In this study, hydrothermal aging effects on the reduction of ammonia adsorption capacity over a commercial Cu-zeolite selective catalytic reduction catalyst were investigated under actual engine exhaust conditions. Ammonia adsorption site densities of the selective catalytic reduction catalysts aged at two different temperatures of 750°C and 850°C for 25 h with 10% H2O were experimentally measured and compared to that of fresh catalyst on a dynamometer test bench with a heavy-duty diesel engine. The test results revealed that hydrothermal aging significantly decreased the ammonia adsorption capacity of the current commercial Cu-zeolite selective catalytic reduction catalyst. Hydrothermal treatment at 750°C reduced the ammonia adsorption site to 62.5% level of that of fresh catalyst, while hydrothermal treatment at 850°C lowered the adsorption site to 37.0% level of that of fresh catalyst. Also, in this study, numerical simulation and kinetic analysis were carried out to quantify the impact of hydrothermal aging on the reduction of ammonia adsorption capacity by introducing an aging coefficient. The kinetic parameter calibrations based on actual diesel engine tests with a commercial monolith Cu-zeolite selective catalytic reduction catalyst provided a highly realistic kinetic parameter set of ammonia adsorption/desorption and enabled a mathematical description of hydrothermal aging effect.

scholarly journals Pd/FER vs Pd/SSZ-13 Passive NOx Adsorbers: Adsorbate-controlled Location of Atomically Dispersed Pd(II) in FER Determines High Activity and Stability

2020 ◽  
Author(s):  
Konstantin Khivantsev ◽  
Xinyi Wei ◽  
Libor Kovarik ◽  
Nicholas R. Jaegers ◽  
Eric D. Walter ◽  
...  
Keyword(s):  
Low Temperature ◽  
Beneficial Effect ◽  
Hot Spots ◽  
Release Behavior ◽  
Hydrothermal Aging ◽  
Practical Applications ◽  
Systematic Exploration ◽  
No Release ◽  
Co Concentration ◽  
Very High

<p>Pd-loaded FER and SSZ-13 zeolites as low-temperature passive NOx adsorbers (PNA) are compared under practically relevant conditions. Vehicle cold-start exposes the material to CO under a range of concentrations, necessitating a systematic exploration of the effect of CO on the performance of isolated Pd ions for PNA. NO release temperature of both adsorbers decreases gradually with the increase of CO concentration from a few hundred to a few thousand ppm. This beneficial effect results from local nano-“hot spots” formation during CO oxidation. Dissimilar to Pd/SSZ-13, increasing the CO concentration above ~1,000 ppm improves the NOx storage significantly for Pd/FER, attributed to the presence of a Pd ions in FER γ-site that is shielded from NO<sub>x</sub>. CO mobilizes this Pd atom to the NO<sub>x</sub> accessible position where it becomes active for PNA. This behavior explains the very high resistance of Pd/FER to hydrothermal aging: Pd/FER materials survive hydrothermal aging at 800⁰C in 10% H<sub>2</sub>O vapor for 16 hours with no deterioration in NOx uptake/release behavior. Thus, by allocating Pd ions to the specific microporous pockets in FER, we have produced very hydrothermally stable and active PNA materials with immediate practical applications.<br></p>

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