Boundary conditions of flow reactor J. F. Wehner and R. H. Wilhelm, Chem. Engng Sci. 6: 89–93, 1956

An analysis is presented of the boundary conditions for a steady state flow-reactor with axial diffusion and first order reaction. Conclusions regarding reactor properties are reached as the result of simultaneous solution of the three differential equations for the reaction section and fore and after sections. Axial diffusion, but no reaction, may occur in the latter two sections.     

Solution of boundary-value problems by orthogonal collocation : J. V. Villadsen and W. E. Stewart, Chem. Engng Sci. 22, 1483–1501, 1967

A standard method for treatment of differential equation models was discovered more or less by chance when applying a quadrature-Galerkin method to solve a simple chemical engineering problem. The method was easy to use and it made manual solution of even complicated problems seem possible.     

On shape factors for irregular particles-I. The steady-state problem. Diffusion and reaction : R. Aris, Chem. Engng Sci. 6: 262–268, 1957

The effectiveness of a catalyst particle with diffusion and first-order reaction is governed by a parameter proportional to the ‘size’ of the particle. If that size is taken to be the ratio of the volume to external surface area, the effectiveness factors for all particle shapes come together asymptotically and are reasonably close together over the whole range.     

The continuous phase heat and mass-transfer properties of dispersions : P. H. Calderbank and M. B. Moo-Young, Chem. Engng Sci. 16: 39–54, 1961

Techniques have been developed for measuring the interfacial area in gas-liquid dispersions. The results have been combined with other published data for heat and masstransfer in liquid-liquid and solid-gas dispersions.     

The diffusion model of longitudinal mixing in beds of finite length. Numerical values H. Brenner, Chem. Engng Sci. 17: 229–243, 1962

Accurate numerical values are tabulated pertaining to the solution of the partial differential equation governing miscible fluid displacement dispersion phenomena in finite beds. Nondimensional results are furnished for the instantaneous exit solute concentration and average solute concentration remaining. Various asymptotic cases are discussed.     

Notes on the diffusion-type model for the longitudinal mixing of fluids in flow : O. Levenspiel and W. K. Smith, Chem. Engng Sci. 6: 227–233, 1957

Turbulence, velocity gradients, and molecular diffusion-all these cause material to move at different speeds in a flowing stream. The overall effect of these factors can be accounted for by a single quantity, a sort of diffusion coefficient. This paper shows how to find this coefficient by a pulse tracer experiment.     

Interfacial areas in agitated gas-liquid contactors K. R. Westerterp, L. L. van Dierendonck and J. A. de Kraa, Chem. Engng Sci. 18: 157–176, 1963

A chemical reaction is used to determine the specific interfacial areas in gas-liquid contactors. Two regions with and without agitation effect are distinguished and separated by a minimum agitation rate. The influence of vessel and agitator geometry on the minimum agitation rate and the specific interfacial area is correlated for different impeller types and for widely varying vessel and agitator sizes.     

The behaviour of porous catalyst particles in view of internal mass and heat diffusion effects : P. B. Weisz and J. S. Hicks, Chem. Engng Sci. 17: 265–275, 1962

The effectiveness of porous catalyst depends on the interplay between the rates of molecular transport (diffusion) and the intrinsic activity (chemical kinetics). This interaction has been analyzed in many past investigations. This paper examines the additional phenomena that can occur when the chemical reactions release or absorb heat. Unusual reaction behaviour can then result.     

Longitudinal diffusion and resistance to mass transfer as causes of nonideality in chromatography : J. J. van Deemter, F. J. Zuiderweg and A. Klinkenberg, Chem. Engng Sci. 5 271–289, 1956

The sharpness of separation in a gas-liquid chromatographic column is effected by longitudinal molecular diffusion, slowness to reach absorption equilibrium, and by flow irregularities in channels and across the column. The total effect of all these causes can be described by a simple equation which can be derived from the rigorous mathematical solution by introducing reasonable simplifying assumptions.     

Studies in Lithium Oxide Systems: XIII, Li,O.Al2O3.2SiO2-Li2O.Al2O3.2GeO2

Complete solid solubility was demonstrated to occur between LiAlGeO₄ and the low temperature form of Li AlSiO₂ (a-eucryptite). Hydrother-mal preparation was necessary for the silicate-rich compositions. Under atmospheric pressure, about 65 mole % LiAlGeO₄ entered the β-eucryβ-tite phase at 1150°C, but solid solutions containing more than 25 mole % LiAlGeO4 exsolved if held at lower temperatures. Directional thermal expansion data were obtained by X-ray diffraction methods on both α- and β-eucryptite and their solid solutions. Substitution of Ge⁴⁺ for Si⁴⁺ produced no significant difference in the thermal expansion coefficients in the α and β phases. An increase in the lattice parameters in the a and c directions took place as expected when Ge⁴⁺ (0.53 A) was substituted for Si⁴⁺ (0.39 A).     

An innovative process for synthesis of superfine nanostructured Li2TiO3 tritium breeder ceramic pebbles via TBOT hydrolysis – solvothermal method

In this paper, a method combining hydrolysis of tetrabutyl orthotitanate (TBOT) and solvothermal reaction was first used to fabricate nanostructured Li₂TiO₃ tritium breeder ceramic pebbles. Initially, superfine nanostructured Li₂TiO₃ powders were synthesized with average particle size of about 10?nm, according to TEM. The surface area of precursor particles synthesized via this method was found to be 115.85?m²/g by BET analysis, which is much larger than that of the product obtained using traditional methods. The results showed that precursor particles had high sintering activity. XRD pattern revealed that the phase transition temperature for monoclinic phase Li₂TiO₃ prepared by this method was nearly 450?°C, which was the lowest phase transition temperature reported among all wet chemical methods to date. Subsequently, investigation of ceramic sintering demonstrated that Li₂TiO₃ ceramic pebbles with desired nano-crystalline sizes (27.98 ~ 55.03?nm) were obtained by sintering at 500 ~ 600?°C for 4?h. The possible mechanisms were proposed based on the reaction processes of TBOT hydrolysis, solvothermal reaction and sintering.     

Wilson parameters for the system H2, N2, CO,CO2, CH4, H2S,CH3OH,and H2O

Parameters for the Wilson equation have been determined for 24 of the 28 binary pairs in the system: H₂, N₂, CO, CO₂, CH₄, H₂S, CH₃OH, and H₂O. The data for eleven pairs were fit using the symmetric convention, with the remaining pairs satisfying the unsymmetric convention. Coefficients for the missing pairs could be estimated from Henry's Law constants. References have been included for the heat capacities of liquid methanol and carbon dioxide. Heats of mixing were also found in the literature. This information, plus readily available gas heat capacities, provides sufficient information to calculate multicomponent material and energy balances for the columns used in the separation of H₂S and CO₂ by cold methanol absorption.     

THE SYSTEM: Al2O3.SiO2

This paper deals with a study of the equilibrium relations of mixtures of pure alumina and silica at high temperatures. The results are expressed concisely in the form of an equilibrium, diagram and their bearing on ceramic problems is discussed. The principal feature of the diagram is the absence of the compound Al₂O₃.SiO₂, the only compound being 3Al₂O₃.2SiO₂. Crystals of this latter compound occur in all alumina-silica refractories. The optical properties of these crystals have been determined and are compared with those of sillimanite, Al₂O₃.SiO₂, which has hitherto been regarded as the crystalline compound occurring in refractories and clay bodies in general. The behavior of natural sillimanite on heating is discussed.     

Effect of AB5 alloy on Ti0.10Zr0.15V0.35Cr0.10Ni0.30 hydrogen storage alloy

The structure and electrochemical characteristics of melted composite Ti_0.10Zr_0.15V_0.35Cr_0.10Ni_0.30 + x% LaNi₄Al_0.4Mn_0.3Co_0.3 (x = 0, 1, 5) hydrogen storage alloys have been investigated systematically. XRD shows that though the main phase of the matrix alloy remains unchanged after LaNi₄Al_0.4Mn_0.3Co_0.3 alloy is added, a new specimen is formed. The amount of the new specimen increases with increasing x. SEM-EDS analysis indicates that the V-based solid solution phase is mainly composed of V, Cr and Ni; C14 Laves phase is mainly composed of Ni, Zr and V; the new specimen containing La is mainly composed of Zr, V and Ni. The electrochemical measurements suggest that the activation performance, the low temperature discharge ability, the high rate discharge ability and the cyclic stability of composite alloy electrodes increase greatly with the growth of x. The HRD is controlled by the charge-transfer reaction of hydrogen and the hydrogen diffusion in the bulk of the alloy under the present experimental conditions.     

Studies of Silica-Structure Phases: I, GaPO4, GaAsO4, and GaSbO4

In the course of work on all compositions which would probably yield silica-structure phases, a detailed study was made of the A³⁺B⁵⁺O₄-type compounds with gallium as the trivalent element. Two forms of GaPO₄ exist corresponding to quartz and cristobalite; the quartz form has a thermal expansion of the low-quartz type and no stable α-β transition is found in this phase. It inverts stably to the cristobalite form at 933°± 4°C. The cristobalite form melts at 1670°C. and the liquid cannot be made to form a glass. The cristobalite form also has a metastable displacive transition at 616°± 2°C. GaAsO₄ exists only in a form corresponding to the lowquartz structure. It disproportionates into Ga₂O₃ and As₂O₅ at about 1000°C. GaSbO₄ could only be prepared in one form corresponding to the rutile structure. The influence of such phases on SiO₂ was determined by studying a few mixtures in the system SiO₂-GaPO₄. The SiO₂ end member appears to admit about 25% GaPO₄ into solid solution in the cristobalite phase at the highest temperature. Even under hydrothennal conditions, however, equilibrium cannot be easily attained at the lower temperatures in a few hundred hours. The results are presented in a not-impossible diagram for the system GaPO₄-SiO₂.