Influence of the V + Mo/Al ratio on vanadium and molybdenum speciation and catalytic properties of V–Mo–ZSM-5 prepared by solid-state reaction

V–Mo–ZSM-5 catalysts with various composition prepared by solid-state ion exchange were investigated with respect to their physico-chemical characteristics using chemical analysis, XRD, BET, DRIFT, UV–vis, ²⁷Al MAS-NMR spectroscopy, H₂ TPR and TPD of NH₃. It was found that all the preparations leads to either metal ions sitting at the bridging oxygen of Si–OH–Al or anchored at Si–OH groups or deposited as oxide. These different solids were tested in the selective catalytic reduction of NO_x by ammonia. The main result is that upon addition of small amount of Mo to V–ZSM-5, catalytic performances were enhanced.     

Characterization and catalytic performance of vanadium supported on sulfated Ti-PILC catalysts issued from different Ti-precursors in selective catalytic reduction of nitrogen oxide by ammonia

Vanadium supported on sulfated Ti-pillared clay catalysts (STi-PILCs) issued from different Ti-precursors were investigated for selective catalytic reduction (SCR) of NO by NH₃ in the presence of O₂. The STi-PILCs supports were prepared by hydrolysis of a series of organic or inorganic Ti-precursors; Ti(OCH₃)₄, Ti(OC₂H₅)₄, and TiCl₄ with H₂SO₄, and then modified with vanadium introduced by impregnation method. The unpromoted and promoted vanadium pillared clays were characterized using chemical analysis, N₂-physisorption, NH₃-TPD, H₂-TPR, and tested for SCR of NO by NH₃. It was found that the textural and acidic properties of the STi-PILC materials are influenced by the nature of the Ti-precursor; and the use of Ti-methoxide allows the synthesis of STi-PILC with the highest acidity. The presence of vanadium on STi-PILC supports reduces their surface areas and porous volumes, creates new redox sites, and enhances the reducibility of the sulfate groups leading to better redox properties of the binary V-STi-PILCs. After vanadium addition, the STi-PILC materials issued from Ti(OCH₃)₄, exhibited higher NO reduction activity at high temperature. These results underline the importance of the Ti-precursor for the preparation of the STi-PILC support, and the role of vanadium to increase the redox properties of V-STi-PILC catalyst for the SCR of NO by NH₃.     

Investigation on the effects of laser power and scanning speed on polypropylene diode transmission welds

For mechanical product, tolerance includes Dimensional Tolerance, Form, Profile, Orientation, Location, Runout, and Assembly Mating Tolerance. Generally, the error of part or product is restricted by a kind of tolerance or several kinds of tolerance. In order to analyze error and its stack-up of mechanical product effectively and absolutely, this paper presents an integrated modeling method of unified tolerance representation based on Key Features (KFs) and Graph Theory in order to deal with these types of tolerances simultaneously. The method includes three steps. The first is to build a tolerance-meta model covering KFs, the relationship set of KFs, the type of tolerance, attributes of tolerance, and variational direction of KF. The model of Dimensional Tolerance, Form, Profile, Orientation, Location, and Runout can be built by tolerance-meta model. The second is to build a model of part’s tolerance and Assembly Mating Tolerance based on sum arithmetic of Graph Theory. The third is to build the integrated tolerance model including Dimensional Tolerance, Form, Profile, Orientation, Location, Runout, and Assembly Mating Tolerance. The integrated model is propitious to represent tolerancing experience from engineers. The method is applied successfully to build the integrated tolerance model for a component of aircraft’s fuselage.     

Comparative quality analysis of gluten strength and the relationship with high molecular weight glutenin subunits of 6 Tunisian durum wheat genotypes

Six Tunisian durum wheat genotypes (4 landraces and 2 improved) were evaluated for protein content, gluten strength, rheological characteristics, and HMW-GS patterns using a LabChip system. Variance analysis identified genotypic variation. The landraces Azizi, Mahmoudi, Chili, and Arbi exhibited the highest protein concentrations and gluten contents, and best dough tenacity and extensibility values. The Mahmoudi and Chili varieties had the highest protein contents (17.06 and 17.32% dry mass, respectively). Arbi and Chili had the highest gluten contents (60.88 and 60.59%, respectively). Azizi, Mahmoudi, and Chili were characterized by higher dough tenacity, lower dough extensibility, and a greater alveograph configuration ratio P/L. The high molecular weight glutenin subunits 6+8 (Azizi and Mahmoudi) and 7+15 (Chili), coded by the Glu-B1 locus, improved gluten strength and viscoelastic dough properties. Calculated HMW to LMW-GS ratios were within a narrow range of 0.17–0.29. Some genotypes have potential to be used as parents in breeding programs.     

Direct microwave heating of alumina for different densities: experimental and numerical thermal analysis

Microwave heating of pure alumina is studied experimentally and numerically, in a 2.45 GHz single-mode cavity, for different density levels. Even considering a constant incident power, the results show a complex evolution of the alumina temperature: first a two-step increase, then a maximum, and finally a cooling stage. In addition, a density dependence of the heating efficiency is observed: a more efficient heating occurs for lower densities. Using the effective medium approximation (EMA) to derive the physical data as functions of density, the numerical simulations are in contradiction with the experiments, proving that the EMA approach is not able to correctly predict the imaginary part of the permittivity. Furthermore, the simulations do not accurately describe the first moments of the heating, nor the long-term evolution of the temperature (cooling). We then explain the origin of this discrepancy: the need to adjust the movable stub on the one hand, and to account for heat exchange between the cavity and its surroundings on the other.     

Polyimides based on furanic diamines and aromatic dianhydrides: synthesis,characterization and properties

Novel polyimides containing furan moieties were prepared from the resulting furanic diamine monomers with various aromatic dianhydrides including 1,2,4,5-benzene-tetracarboxylic dianhydride, 3,3′,4,4′-biphenyltetracarboxylic dianhydride, 4,4′-oxydiphthalic anhydride, and hexafluoroisopropylidene 2,2-bis(phthalic anhydride), via a two-step process. The resulting polyimides were characterized by solubility tests, viscosity measurements, FTIR, ¹H NMR spectroscopy, differential scanning calorimetric (DSC), and thermogravimetric analysis (TGA) analysis. The polyimides with inherent viscosities in the range of 0.048–0.095 L/g showed excellent solubility in aprotic amide and organic solvents, such as N,N-dimethylacetamide, N-methyl-2-pyrrolidinone, dimethylformamide and acetone, chloroform, etc. DSC showed glass transition temperatures (T _g) in the range of 116–143 °C. These polymers showed excellent thermal stability up to 390 °C.