12-Heteropolymolybdates as catalysts for vapor-phase oxidative dehydrogenation of isobutyric acid 2. Group Ib, IIb, IIIb, and VIII metal salts

Akimoto, Masamichi; Shima, Kenji; Ikeda, Hitoshi; Echigoya, Etsuro

doi:10.1016/0021-9517(84)90358-0

Cited by 75 publications

(7 citation statements)

References 14 publications

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“…The oxidizing ability of HPAs in the solid state has been estimated by various methods: rates of reduction of HPAs, ,− and ESR and XPS spectra of reduced HPAs. ,,− It must be considered that the results are affected significantly by the method of reduction as well as the purity of the samples. , Another important reason for the apparent inconsistency in the literature may be the ignorance of the presence of surface- and bulk-type reactions (see below).…”

Section: B Redox Propertiesmentioning

confidence: 99%

Heterogeneous Catalysis

1998

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Section: B Redox Propertiesmentioning

confidence: 99%

Heterogeneous Catalysis

1998

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“…Moreover, it is known that propene formation requires Brønsted acid sites. 39 Based on the above discussion, one may conclude that, the dehydration activity of the catalysts is mainly due to; (i) the Brønsted acidity of the catalysts, aided to a large extent by the water adsorption, which is known to create Brønsted sites; 39 (ii) the flexible nature of the secondary structure of heterocompounds, which allows the polar molecule, e.g. isopropanol, to penetrate the bulk of the solid; 38 and (iii) the existence of the Keggin structure, which has an influence in stabilizing the reaction intermediates.…”

Section: Acidity and Basicity Determinationmentioning

confidence: 99%

Catalytic performance of Brønsted acid sites during esterification of acetic acid with ethyl alcohol over phosphotungestic acid supported on silica

Said¹,

El‐Wahab²,

Alian³

2007

J of Chemical Tech & Biotech

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Different ratios of phosphotungestic acid supported on silica gel were prepared by an impregnation method with PWA loadings ranging from 1 to 30% w/w and calcined at 350 and 500 • C for 4 h in a static air atmosphere. The catalysts were characterized by thermogravimety (TG), differential thermal analysis (DTA), X-ray diffraction, FT-IR spectroscopy and N 2 adsorption measurements. The surface acidity and basicity of the catalyst were investigated by the dehydration-dehydrogenation of isopropanol and the adsorption of pyridine (PY) and 2,6-dimethyl pyridine (DMPY). The gas-phase estrification of acetic acid with ethanol was carried out at 185 • C in a conventional fixed-bed reactor at 1 atm using air as carrier gas. The results clearly revealed that the catalyst containing 10% w/w PWA/SiO 2 is the most active and delivers reaction selectively to ester with 85% yield. The Brønsted acid site resulting from hydroxylation of tungsten oxide plays the main role in the formation of ester. Figure 1 shows TG and DTA curves of the pure silica, pure PWA and PWA supported on silica. It is seen 514 Perspective Perspective 55 Sheinthauer M, Cheung TK, Jentoft RE, Grasselli RK, Gates BC and Knozinger H, Characterization of WO x /ZrO 2 by vibrational spectroscopy and n-Pentane isomerization catalysis. J Catal 180:1-13 (1998). 56 Baertsch CD, Soled SL and Iglesia E, Isotopic and chemical titration of acid sites in tungsten oxide domains supported on zirconia. J Phys Chem B 105:1320-1330 (2001). RESULTS AND DISCUSSION Thermal analysis

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“…Based on the above discussion, one may conclude that, the dehydration activity of the catalysts is mainly due to; (i) the Brønsted acidity of the catalysts, aided to a large extent by the water adsorption, which is known to create Brønsted sites;39 (ii) the flexible nature of the secondary structure of heterocompounds, which allows the polar molecule, e.g. isopropanol, to penetrate the bulk of the solid;38 and (iii) the existence of the Keggin structure, which has an influence in stabilizing the reaction intermediates.…”

Section: Resultsmentioning

confidence: 96%

“…In agreement with such a suggestion; Okuhara et al 38 reported that, on Na x H 3−x PW 12 O 40 , the formation of ethylene from ethyl alcohol requires fission of the CO bond on the Brønsted acid sites. Moreover, it is known that propene formation requires Brønsted acid sites 39…”

Section: Resultsmentioning

confidence: 99%

Introduction to the Special Issue: JTRES 2009

Schoeberl

Higuera-Toledano

2011

Concurrency and Computation

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Java is a very successful language for several application domains: be it desktop applications, large enterprise server applications, web services, or applets for mobile phones. With the Real-Time Specification for Java (RTSJ) and the upcoming definition of a Safety-Critical Java profile, Java enters the domain of soft and hard real-time systems.The The RTSJ is the main standard for real-time systems implemented in Java. Several commercial and research implementations of the RTSJ are available today. However, the optimal implementation of some features of the RTSJ is still an open research questions. The primary goal for asynchronous event handlers (AEH) in the RTSJ is to have a lightweight concurrency mechanism. In the article, Applying Fixed-Priority Preemptive Scheduling with Preemption Threshold to Asynchronous EventHandling in the RTSJ [1], Kim and Wellings propose a scheduling scheme for AEH that minimizes the number of server threads needed. In the article they first define the worst-case scenario that demands the least upper bound of servers for self-suspending and non-self-suspending handlers. Based on the worst-case scenarios, it is proved that the number of servers required to execute a given number of non-self-suspending handlers depends on the number of priority levels, not on the number of handlers. It is also shown that each self-suspending handler is required to have its own server to prevent unbounded priority inversion.The RTSJ supports two kinds of real-time threads: one that can operate on the garbage collected heap and another one that avoids influence by garbage collection by using a region-based memory management. Basanta-Val et al. present in their article, Extending the concurrency model of the Real-Time Specification for Java [2], a more flexible thread model, where the thread can switch between a heap and a non-heap mode. The authors propose a simple extension to the current threading model named RealtimeThread++, in an attempt to introduce more flexibility in the RTSJ concurrency model. The article describes the extension from several points of view: (i) the programmer, identifying scenarios that may benefit from it significantly; (ii) the real-time Java technology perspective, identifying changes required in the current real-time virtual machine to support it; and (iii) the accumulated experience, relating empirical results obtained from a software prototype that supports the extension.The current practice for soft real-time systems in Java is to avoid the cumbersome programming model of scoped memories and, instead, use a real-time garbage collector. Kalibera presents in his article, Replicating , an incremental garbage collector. The realtime collector has to relocate objects in the heap to avoid fragmentation. This is usually achieved via an indirection that has to be followed on every read and write to the heap. Kalibera presents an alternative solution, based on object replication, which does not need any special handling for memory reads, but writes are more expensive: every va...

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12-Heteropolymolybdates as catalysts for vapor-phase oxidative dehydrogenation of isobutyric acid 2. Group Ib, IIb, IIIb, and VIII metal salts

Cited by 75 publications

References 14 publications

Heterogeneous Catalysis

Heterogeneous Catalysis

Catalytic performance of Brønsted acid sites during esterification of acetic acid with ethyl alcohol over phosphotungestic acid supported on silica

Introduction to the Special Issue: JTRES 2009

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