Observation of nitriles formed in the oxidative dehydrogenation of carboxylic acids over metal-oxygen cluster catalysts

McGarvey, G.B.; Moffat, J.B.

doi:10.1007/bf00764735

Cited by 13 publications

(11 citation statements)

References 13 publications

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“…Earlier work has shown that the ammonium salts have higher surface areas than the potassium salts. (11,12) The surface areas decreased with increasing calcination temperature, as previously reported, (13) and, with the exception of K 3 PMo 12 O 40 which had a surface area of 30 m 2 g À1 after heating at 753 K, reached negligible values at 693 K.…”

Section: Chaptersupporting

confidence: 80%

Stability

2002

Metal-Oxygen Clusters

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A large number of publications have reported studies of the thermal stability of heteropoly oxometalates as part of investigations of other aspects of these materials. Although these reports may have been discussed elsewhere in this monograph where relevant, they have also been included here. The present discussion of thermal stability is, for convenience, restricted to unsupported heteropoly oxometalates with that pertaining to the supported materials included in the section on the properties of the latter. A cautionary note should be added here. The results from studies of stability are dependent not only on the method employed for such evaluations, but in addition are frequently dependent on the conditions under which the experiment was performed.One of the earliest studies of the stability of the heteropoly acids employed differential thermal analysis and X-ray diffraction. (1) With each of the four acids examined, an endotherm and an exotherm are observed at 300 C or less and 340 C or more, respectively (Table 5.1). The low-temperature endotherm is attributed to the removal of water whereas the high-temperature exotherm signals the decomposition of the anion. The authors note that metatungstic acid H 8 [W 12 O 40 ]ÁxH 2 O decomposes at 50 C. When the void in the center of the [W 12 O 40 ] 8À anion is occupied by Si 4 or P 5 , the decomposition temperature increases by approximately 400 or 500 C, respectively. The presence of a positively charged species reduces the effect of thermal vibrations and thus of decomposition.Thermogravimetric analyses of H 3 XW 12 O 40 with X being zinc, iron, cobalt, boron, silicon, or phosphorus, their potassium salts, and their ether-addition compounds have been reported. (2) With the ®rst three acids, three peaks were observed whereas only two were obtained with the latter three acids (Table 5.2). The third peak was attributed to decomposition of the anion. 42CHAPTER 5 STABILITY 43

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Section: Chaptersupporting

confidence: 80%

Stability

2002

Metal-Oxygen Clusters

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“…The positive charge around the silica gel interfered with the adsorption of Cs + on AMP-SG. On the other hand, zeta potentials of alginate The change of lattice constants accompanying ion exchange reactions in AWP is slightly smaller than that of AMP 23,24) .…”

Section: Resultsmentioning

confidence: 89%

Adsorption Behavior of Cesium on Hybrid Microcapsules in Spent Fuel Solution

Onishi

Koyama

Mimura

2020

J.I.E.

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Hybrid microcapsules (H-MCs) are being developed for the column separation of Cs from high-level radioactive liquid waste (HLLW). In this paper, adsorption behavior of H-MCs has been evaluated by a batch method in single-element solution and a spent fuel solution prepared from irradiated MOX fuel. The spent fuel solution contain FPs and minor actinide (MAs), not containing U and Pu. Distribution coefficients (K d ) of various metal ion including Cs were determined for three types of H-MCs (AMP-SG (silica gel enclosing ammonium molybdophosphate), AMP-ALG (calcium alginate gel enclosing ammonium molybdophosphate) and AWP-ALG (calcium alginate gel enclosing ammonium tungstophosphate)) in the spent fuel solution.The three types of H-MCs exhibited higher K d s for Cs than those for the other elements in spent fuel solution. The difference of K d for the specific element (Cs) and the other elements was larger than one order of magnitude. Therefore, chromatographic separation of Cs in the spent fuel solution using a column packed with H-MCs will be achieved. It was the similar tendency between the spent fuel solution and the single-element solution that the K d value for Cs of AWP-ALG was the largest among those of three gels. Thus, the mechanism of adsorption of Cs onto these H-MCs would not be changed in the presence of FPs and MAs. Therefore, these types of H-MCs can be effective for separation of Cs in the spent fuel solutions.

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“…[10][11][12][13][14] Esterification of methacrylic acid (MAA) from light hydrocarbons (ethylene, propylene, and isobutane) to MMA is a promising approach to supplant current ACH technology with an option with a lower environmental impact. [1,[15][16][17][18][19][20] Ethylene and carbon monoxide react in the presence of water to form propionaldehyde, propionic acid, methyl propionate, and methacrolein (MAC) as intermediates. Multiple steps, high investment costs, and intermediates are obstacles to commercialization.…”

Section: Introductionmentioning

confidence: 99%

Oxidation kinetics of 2‐methyl‐1,3‐propanediol to methacrylic acid in a fluidized bed reactor

et al. 2020

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Methacrylic acid (MAA) is a specialty monomer for poly methyl methacrylate (PMMA). Partial oxidation of 2‐methyl‐1,3‐propanediol (2MDPO) to MAA is an alternative to commercial technology with fewer process steps, less cost and toxic feedstocks, and longer catalyst lifetime. Here, we evaluated the effect of 2MPDO and oxygen concentrations, reaction temperature, and contact time on product selectivity and 2MPDO conversion over VOCu0.5/Cs(NH4)2PMo12O40. Higher temperature increases selectivity and conversion; MAA selectivity reached 46% at 69% 2MPDO conversion. Higher 2MPDO to O2 ratio favours higher MAA selectivity due to methacrolein (intermediate) oxidation to MAA (a higher ratio favours consecutive oxidation) or lower combustion of MAA to COx. Shorter contact times decrease MAA selectivity. The Mars van Krevelen model characterizes the experimental data better than both the Langmuir‐Hinshelwood or Eley‐Rideal models; The reaction sequence involves both direct and indirect reactions in which 2MPDO reacts to methacrolein (MAC) as an intermediate and then it oxidizes to MAA (indirect) and/or 2MPDO directly oxidizes to MAA but the indirect reaction rate to MAA is 50 times faster than the direct reaction rate. The reaction is first order with respect 2MPDO and oxygen, and the rate‐limiting step is 2MPDO activation on oxidized sites.

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Observation of nitriles formed in the oxidative dehydrogenation of carboxylic acids over metal-oxygen cluster catalysts

Cited by 13 publications

References 13 publications

Stability

Stability

Adsorption Behavior of Cesium on Hybrid Microcapsules in Spent Fuel Solution

Oxidation kinetics of 2‐methyl‐1,3‐propanediol to methacrylic acid in a fluidized bed reactor

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