Promotional effect of bismuth as dopant in Bi-doped vanadyl pyrophosphate catalysts for selective oxidation of n-butane to maleic anhydride

Bismuth-promoted (1% and 3%) vanadyl pyrophosphate catalysts were prepared by refluxing Bi(NO3)3·5H2O and VOPO4·2H2O in isobutanol. The incorporation of Bi into the catalysts lattice increased the surface area and lowered the overall V oxidation state. Profiles of temperature programmed reduction (TPR) in H2 show a significant shift of the maxima of major reduction peaks to lower temperatures for the Bi-promoted catalysts. A new peak was also observed at the low temperature region for the catalyst with 3% of Bi dopant. The addition of Bi also increased the total amount of oxygen removed from the catalysts. The reduction pattern and reactivity information provide fundamental insight into the catalytic properties of the catalysts. Bi-promoted catalysts were found to be highly active (71% and 81% conversion for 1% and 3% Bi promoted catalysts, respectively, at 703 K), as compared to the unpromoted material (47% conversion). The higher activity of the Bi-promoted catalysts is due to that these catalysts possess highly active and labile lattice oxygen. The better catalytic performance can also be attributed to the larger surface area

Pricing of American call options using regression and numerical integration

Consider the American basket call option in the case where there are N underlying assets, the number of possible exercise times prior to maturity is finite, and the vector of N asset prices is modeled using a Levy process. A numerical method based on regression and numerical integration is proposed to estimate the price of the American option. In the proposed method, we first express the asset prices as nonlinear functions of N uncorrelated standard normal random variables. For a given set of time-t asset prices, we next determine the time-t continuation value by performing a numerical integration along the radial direction in the N-dimensional polar coordinate system for the N uncorrelated standard normal random variables, expressing the integrated value via a regression procedure as a function of the polar angles, and performing a numerical integration over the polar angles. The larger value of the continuation value and the time-t immediate exercise value will then be the option value. The time-t option values over the N-dimensional space may be represented by a quadratic function of the radial distance, with the coefficients of the quadratic function given by second degree polynomials in N-1 polar angles. Partitioning the maturity time T into k* intervals of length Δt, we obtain the time-(k-1)Δt option value from the time-kΔt option values for k= k*, k*-1,…, 1. The time-0 option value is then the price of the American option. It is found that the numerical results for the American option prices based on regression and numerical integration agree well with the simulation results, and exhibit a variation of the prices as we vary the non-normality of the underlying distributions of the assets. To assess the accuracy of the computed price we may use estimated standard error of the computed American option price. The standard error will help us gauge whether the number of selected points along the radial direction and the number of selected polar angles are large enough to achieve the required level of accuracy for the computed American option price

The effect of Bi promoter on vanadium phosphate catalysts synthesized via sesquihydrate route

A series of 1%, 3% and 5% Bi-doped vanadyl pyrophosphate catalysts were prepared via sesquihydrate route (VPOs method). These catalysts were denoted as VPOs-Bi1%, VPOs-Bi3% and VPOs-Bi5%. Bulk and Bi-promoted vanadyl pyrophosphate catalysts prepared via sesquihydrate route exhibited a well-crystallized (VO)2P2O7 phase. Two V5+ phases, i.e. β-VOPO4 and αII-VOPO4 were observed in all Bi-promoted VPO catalysts, which led to an increase in the specific surface area and average oxidation state of vanadium. Bi-promoted VPO catalysts showed six to nine times higher amounts of oxygen evolved than the bulk VPO catalyst in oxygen TPD and a significant shift in the reduction peaks to lower temperatures. Catalytic tests revealed that both activity and selectivity to maleic anhydride increased with the presence of bismuth promoter

A review of Scaphochlamys (Zingiberaceae) from borneo, with description of eleven new species

In the present paper, the genus Scaphochlamys from Borneo is revised. Twenty-four species are recognised, of which 11 are new species: S. durga, S. graveolens, S. hasta, S. lanjakensis, S. lucens, S. nigra, S. multifolia, S. penyamar, S. pseudoreticosa, S. scintillans, and S. uniflora. Scaphochlamys depressa is treated as a synonym to S. argentea. The Bornean species are arranged into six informal groups based on morphological characteristics: Anomala Group, Calcicola Group, Graveolens Group, Limiana Group, Petiolata Group, and Polyphylla Group. The paper includes an overview of morphological characteristics, identification keys to groups and species, and species descriptions. A discussion of the recently recognized generic segregate, Borneocola is included. © 2017 Magnolia Press

Cu-Mn and Cu-Ce supported over agro-based carbons: characteristics and NOx adsorption study

As there is an urgent need for cheaper and sustainable resources for selective catalytic reduction catalyst, this study determined the potential, in terms of the catalyst characteristics and NOx adsorption, of coconut shell (CSAC) and palm kernel shell activated carbons (PSAC) to be used as precursors for the catalyst in a low-temperature flue gas denitrification system. The carbons were impregnated with bimetallic catalysts –copper-manganese (Cu-Mn) and copper-cerium (Cu-Ce) – before calcined at low temperature. The produced coconut shell catalysts (CuMn/CS and CuCe/CS) and palm kernel shell catalysts (CuMn/PS and CuCe/PS) were then characterized using a nitrogen adsorption-desorption test, Fourier-Transform infra-red, x-ray fluorescence, x-ray diffraction and hydrogen temperature-programmed reduction. The removal of NOx was also studied for all catalysts in a fixed-bed reactor. It was found that CuMn/CS gave the highest NOx removal. CuMn/CS had high pore volume, good Cu-Mn crystallinity, highmetal loading and dispersion, high copper reduction activity at the operating temperature, and rich in ketone and amine surface functional groups. It is then concluded that the coconut shell has the potential to be developed as a good SCR catalyst via impregnation with Cu-Mn

Dependence of n-butane activation on active site of vanadium phosphate catalysts

The nature and the role of oxygen species and vanadium oxidation states on the activation of n-butane for selective oxidation to maleic anhydride were investigated. Bi–Fe doped and undoped vanadium phosphate catalysts were used a model catalyst. XRD revealed that Bi–Fe mixture dopants led to formation of αII-VOPO4 phase together with (VO)2P2O7 as a dominant phase when the materials were heated in n-butane/air to form the final catalysts. TPR analysis showed that the reduction behaviour of Bi–Fe doped catalysts was dominated by the reduction peak assigned to the reduction of V5+ species as compared to the undoped catalyst, which gave the reduction of V4+ as the major feature. An excess of the oxygen species (O2−) associated with V5+ in Bi–Fe doped catalysts improved the maleic anhydride selectivity but significantly lowering the rate of n-butane conversion. The reactive pairing of V4+-O− was shown to be the centre for n-butane activation. It is proposed that the availability and appearance of active oxygen species (O−) on the surface of vanadium phosphate catalyst is the rate determining step of the overall reaction