Coke removal from deactivated Co–Ni steam reforming catalyst using different gasifying agents: An analysis of the gas–solid reaction kinetics

The reactivity of various gases, namely; O₂, air, CO₂, H₂ and N₂, with carbon deposited on alumina-supported Co–Ni catalyst during propane reforming in a fluidized bed reactor at 773–973 K using relatively low feed steam:carbon ratio (0.8–1.5) has been investigated in a thermogravimetric analysis unit. Analysis of the transient solid weight loss revealed that carbon removal mechanism is dependent on the type of gasifying agent. Carbon gasification kinetics using O₂ and air followed the Avrami-Erofeev (A2) model while data for both CO₂ and H₂ were captured by the geometrical (contracting area, R2) model. However, carbon gasification with inert N₂ proceeded at much slower rate (about 10 times lower than air) and was adequately fitted by the one-dimensional diffusion (D1) model. Specific reaction rates from these phenomenological models were also linearly correlated with the catalyst carbon content with reactivity coefficient of the gasifying agent decreasing in the order, O₂ > air > CO₂ > H₂ > N₂. In order to minimize energy consumption during catalyst regeneration, reduce greenhouse gas emissions and reduce catalyst sintering, it would be desirable to employ a mixture of air and CO₂ as the carbon gasifying agent to take advantage of the coupled exothermic (air oxidation) and endothermic (reverse Boudouard reaction involving CO₂ and carbon) nature taking place during the carbon removal operation.     

Molecular species analysis of phosphoglycerides from the ripe roes of cod (Gadus morhua)

Molecular species of the 3,5-dinitrobenzoyl derivatives of phosphatidylcholine (PC), phosphatidylethanolamine (PE) and phosphatidylinositol (PI) were quantitated by UV detection at 254 nm after reversed-phase HPLC using solvent systems modified from Takamuraet al. (Lipids 21, 356–361, 1986). Three isocratic solvent systems were used and a total of 39 different molecular species detected. Four species, 16∶0/20∶5, 18∶1/20∶5, 16∶0/22∶6 and 18∶1/22∶6 contributed 67.2% and 61.8% of PC and PE respectively but only 23.0% of PI. In PI the most important species was 18∶0/20∶4 at 36.7% but this species only constituted 0.7% in each of PC and PE. Small amounts of dipolyunsaturated species were also found in PC and PE. Molecular species are abbreviated as follows: e.g., 16∶0/20∶5 PC is 1-palmitoyl-2-eicosapentaenoyl-sn-glycero-3-phosphocholine.     

Enhanced Bioavailability of Eicosapentaenoic Acid from Fish Oil After Encapsulation Within Plant Spore Exines as Microcapsules

Benefits of eicosapentaenoic acid (EPA) can be enhanced by raising their bioavailability through microencapsulation. Pollen can be emptied to form hollow shells, known as exines, and then used to encapsulate material, such as oils in a dry powder form. Six healthy volunteers ingested 4.6 g of fish oil containing 20% EPA in the form of ethyl ester first alone and then as 1:1 microencapsulated powder of exines and fish oil. Serum bioavailability of EPA was measured by area under curve (AUC_0–24). The mean AUC_0–24 of EPA from ethyl ester with exine (M = 19.7, SD = 4.3) was significantly higher than ethyl ester without exines (M = 2, SD = 1.4, p < 0.01).The bioavailability of EPA is enhanced by encapsulation by pollen exines.     

A density functional theory study of hydrogen recombination and hydrogen-deuterium exchange on Ga/H-ZSM-5

Density functional theory calculations have been carried out to determine the thermodynamic stability of various Ga species in gallium-exchanged ZSM-5, the thermodynamics of H₂ adsorption, and the most favorable pathway for H₂/D₂ exchange. The portion of the zeolite associated with Ga was represented by a cluster containing 7, 21, or 33 atoms. The B3LYP hybrid method was used to account for the effects of electron exchange and correlation. The most likely form of Ga expected in freshly exchanged and calcined ZSM-5 is ZGa(OH)₂. H₂ reduction of this species is projected to produce ZGa(H)(OH) and ZGa(H)₂. While the thermodynamics of H₂ desorption from ZGa(H)₂ are favorable, the process is projected to be slow because of a high activation barrier. The most favorable pathway for H₂/D₂ exchange over ZGa(H)₂ proceeds via Z(D)(Ga(H)₂(D)) as an intermediate. Similar calculations have been carried out for H₂/D₂ exchange over H-ZSM-5. This revised version was published online in June 2006 with corrections to the Cover Date.     

Semiclosed-Cell Mullite Foams: Preparation and Macro- and Micromechanical Characterization

The preparation and characterization of the properties of mullite ceramic foams suitable for diesel exhaust filtration systems are described. Two foams of different cell sizes, 32 and 61 ppi (pores per inch), were prepared from slurries by the replication process with polyurethane sponges as the templates. The microstructure and the dependence of the porosity and the mechanical properties on the preparation and resulting foam cell size and normalized density are discussed. In addition the micro- and macromechanical properties have been characterized using instrumented indentation techniques; with sharp (Berkovich) and small spherical-tipped indenters the hardness and modulus of the dense strut materials have been measured. The macroproperties have been measured with a large sapphire indenter, ∼5 mm radius using a load partial-unloading technique. The latter enables the modulus and the contact pressure versus penetration to be measured. These values are compared with traditional bulk measurements for crushing strength and elastic modulus. The results are discussed in terms of available theoretical treatments of the indentation of brittle porous materials.     

Manipulating microstructure and mechanical properties of CuO doped 3Y-TZP nano-ceramics using spark-plasma sintering

Nano-powder composites of 3Y-TZP doped with 8 mol% CuO were processed by spark-plasma sintering (SPS). A 96% dense composite ceramic with an average grain size of 70 nm was obtained by applying the SPS process at 1100 °C and 100 MPa for 1 min. In contrast to normal, pressureless, sintering during SPS reactions between CuO and 3Y-TZP were suppressed, the CuO phase was reduced to metallic Cu, while the 3Y-TZP phase remained almost purely tetragonal. Annealing after SPS results in grain growth and tetragonal to monoclinic zirconia phase transformation. The grain size and monoclinic zirconia phase content are strongly dependent on the annealing temperature. By combining the processing techniques studied in this work, including traditional pressureless sintering, properties of the composite ceramic can be tuned via manipulation of microstructure. Tuning the mechanical properties of dense 8 mol% CuO doped 3Y-TZP composite ceramic by utilising different processing techniques is given as an example.     

Selective solid-phase extraction of rare earth elements by the chemically modified Amberlite XAD-4 resin with azacrown ether

A selective solid-phase extraction procedure using chemically modified Amberlite XAD-4 with monoaza dibenzo 18-crown-6 ether was investigated for the preconcentration and separation of La(III), Nd(III) and Sm(III) in synthetic solution. Before loading samples on synthesized adsorbent adjust pH 4.5 by suitable buffer solution. The adsorbed rare earth elements were eluted by 2 M hydrochloric acid. Various parameters like preconcentration, breakthrough capacity, flow rate were investigated. The limits of detection (n = 5) and limits of quantification (n = 5) for La(III), Nd(III) and Sm(III) were founded 3.9, 4.2 and 7.4 μg L^?1 and 13, 15 and 26 μg L^?1, respectively. The eluted metal ions were determined by ICP-AES.     

Enhanced nanofluidization by alternating electric fields

We show experimental results on a proposed technique to enhance the fluidization of nanoparticle beds. This technique consists of the application of an alternating electric field to the nanofluidized bed. Three different field configurations have been tested: co‐flow field, cross‐flow field, and variable field configurations. Nanoparticle agglomerates are naturally charged by contact and tribo charging mechanisms and therefore are agitated by the action of the externally applied field, which enhance fluidization. According to our observations, the best results are obtained for the variable field configuration. In this configuration, the electric field strength is higher at the bottom of the bed, whereas it is almost negligible at the free surface. Thus, the larger agglomerates, which tend to sink at the bottom of the bed due to stratification, and usually impede uniform fluidization, are strongly agitated. It is thought that the strong agitation of the bigger agglomerates that usually sink to the bottom of the bed contributes to further homogenize the distribution of the gas flow within the bed by destabilizing the development of gas channels close to the gas distributor. On the other hand, the smaller agglomerates at the vicinity of the free surface are just weakly excited. Consequently, fluidization is greatly enhanced, whereas at the same time excessive elutriation is avoided. It is demonstrated that this technique is even suitable to achieve highly expanded fluidization of unsieved nanopowder samples even though the fluidization state returns to be heterogeneous upon the electric field being turned off. © 2009 American Institute of Chemical Engineers AIChE J, 2010     

The phase behavior and the Flory-Huggins interaction parameter of blends containing amorphous poly(resorcinol phthalate-block-carbonate), poly(bisphenol-A carbonate) and poly(ethylene terephthalate)

The phase behavior of the blends of poly(ethylene terephthalate) (PET) and poly(Resorcinol Phthalate-block-Carbonate) (RPC) and the blends of PET and poly(Bisphenol-A Carbonate) (PC) was investigated by dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), and transmission electron microscopy (TEM). Blends of high molecular weight PET and RPC copolymer with 20 mol% resorcinol phthalate (RPC20) showed two glass transition temperatures in DMA and DSC but the cold crystallization rate of PET phase was substantially lowered as compared to neat PET, indicating partial miscibility at all compositions. The RPC20 with M_w = 31,500 g/mol formed miscible blends with PET when PET has weight-average molecular weight <9500 g/mol. The Flory-Huggins interaction parameter between PET and RPC20 was calculated to be 0.029 ± 0.003 by using the Flory-Huggins equation at critical composition and molecular weight. PC with M_w = 30,000 g/mol formed miscible blends with PET only when PET had molecular weight <2800 g/mol, indicating PC/PET blends were much less miscible than RPC20/PET blends. Group contribution methods agreed well with the experimental results obtained both in the present study and a previous study [1], predicting that the addition of a resorcinol phthalate block to a PC backbone should increase the miscibility of PC and PET.