Showing papers by "National Chemical Laboratory published in 1983"
394 citations
TL;DR: The bulk reaction rate is formulated rigorously, namely, in terms of the pair probability, by use of the new formalism, and the Wilemski-Fixman model for diffusion-controlled reactions is analyzed.
215 citations
TL;DR: In this paper, a diffusion equation for gas permeation through microporous media in the Knudsen regime was obtained theoretically, considering the potential energy between a gas molecule and the solid surface of pores.
Abstract: A diffusion equation for gas permeation through microporous media in the Knudsen regime was obtained theoretically, considering the potential energy between a gas molecule and the solid surface of pores. The equation as a function of temperature contains four parameters, all of which have physical meanings. The most significant of these parameters is the effective potential energy e*, by which the gas diffusion equation as a function of temperature is characterized. Permeabilities of He, H2, CO, N2, O2, Ar, and CO2 through a microporous Vycor glass membrane were measured in the temperature range from 300 K to 950 K. The validity of the diffusion equation obtained was verified experimentally and was shown to express well the previous data. For helium in particular, diffusion is almost gas-phase flow, with no adsorbed flow except at very low temperature. However, the diffusion is affected by the interaction energy between the gas molecules and the solid surface in the pores.
94 citations
TL;DR: In this paper, the acidity distribution and catalytic properties of H-ZSM-5 zeolites under different deammoniation conditions (i.e., varying temperature, period, atmosphere and heating rate) have been studied.
72 citations
TL;DR: In this paper, the possibilities of using microporous ceramic membranes for the production of hydrogen from hydrogen sulfide were examined for the direct decomposition of hydrogen and the yield of hydrogen increased by about two times the equilibrium yield calculated for the process without hydrogen removal.
69 citations
TL;DR: In this paper, the authors investigated the relationship between the concentration of surface hydroxyl groups, acidic sites, and the turnover number for the isomerization of ortho-xylene over HZSM5 zeolite.
65 citations
TL;DR: In this paper, a method has been proposed to estimate the rheograms of a polymeric melt at temperatures relevant to its processing conditions with the use of a master curve, knowing the melt flow index and glass transition temperature of the material.
Abstract: A knowledge of the complete flow curve or rheogram of a polymeric melt depicting the variation of the melt viscosity over industrially relevant range of shear rate and temperature is essential in the design of polymer processing equipment, process optimization and trouble-shooting. These data are generated on sophisticated rheometers that are beyond the financial and technical means of most plastics processors. The only flow parameter available to the processor is the melt flow index of the material. In the present work, a method has been proposed to estimate the rheograms of a melt at temperatures relevant to its processing conditions with the use of a master curve, knowing the melt flow index and glass transition temperature of the material. Master curves that coalesce rheograms of different grades at various temperatures have been generated and presented for low density polyethylene, high density polyethylene, polypropylene, polystyrene and styrene-acrylonitrile copolymer.
65 citations
TL;DR: In this article, the relative contributions of catalytic reaction and thermal cracking in the hydrocracking of heavy oil were evaluated in detail, and it was concluded that light oil fractions are formed mainly by thermal cracking and the main role of the catalyst is to supply hydrogen to the heavy oil fraction and prevent its carbonization.
56 citations
TL;DR: Multiple shoots were induced from nodal segments of mature Eucalyptus torelliana F. Muell and E. camaldulensis Dehnh trees on Murashige and Skoog's medium supplemented with Kn, BAP, Cal.Pan and Bio.
Abstract: Multiple shoots were induced from nodal segments of mature Eucalyptus torelliana F. Muell. and E. camaldulensis Dehnh trees on Murashige and Skoog's medium supplemented with Kn, BAP, Cal.Pan and Bio. Incubation in semi-solid media at 15°C with continuous illumination followed by growth in agitated liquid media was essential for shoot induction and development in primary explants of E. camaldulensis. For culture of E. gorelliana, growth in agitated liquid media alone was sufficient. Rooting could be induced in shoot cultures of E. torelliana by treatment with NAA whereas treatment with a mixture of IAA, IBA, IPA and NAA was essential for E. camaldulensis. After auxin treatment, transfer to a charcoal-containing medium was necessary. Rooted plantlets could be successfully transferred to pots and field. By this method it is estimated that about 50,000 plantlets of E. torelliana and 20,000 of E. camaldulensis can be produced, in a year, from a single nodal segment of a mature tree.
55 citations
TL;DR: In this paper, the change in Gibbsfree energy (ΔGr) in the solid-solution reaction was calculated from solubility duta for C-S-H in water.
Abstract: Calcium silicate hydrate (C-S-H) can be viewed as a solid solution, 0.833Ca(OH)2.SiO2.0.917H2O-xCa(OH)2, at equilibrium at 30°C. On this basis, the change in Gibbsfree energy (ΔGr) in the solid-solution reaction was calculated from solubility duta for C-S-H in water. The change in ΔGrwith real ratio decreased notably for the higher calcium contents (CaO/Si021.7; ×0.867). Thermochemical values for C-S-H (CaO/SiO2=1.7) were estimated to be ΔH°=-2890 kJ/mol, ΔG°=-2630 kJ/mol, and S°=200 J1/mol.K at 298 K.
48 citations
TL;DR: The high recovery of cellulolytic enzymes indicates that the adsorption of these enzymes on cellulose is not irreversible, and the recovery of enzyme from the insoluble residues is high.
Abstract: Penicillium funiculosum produces a complete cellulase which brings about 97% hydrolysis of cotton and has high beta-glucosidase, xylanase, laminarinase, and lichenase activities. This article deals with the effect of different pretreatments on the hydrolysis of sugarcane bagasse by P. funiculosum enzymes and the recovery of enzyme from the insoluble residues. Enzymic saccharification of bagasse pretreated with hot 1N NaOH followed by neutralization with HCI and steam treated under pressure (7 kg/cm(2)) gave 63 and 59% saccharification, respectively, in 48 h. Hemicellulose is not lost in these pretreatments. With a 30% slurry of steam-treated bagasse, a semisolid mass containing 14% sugar was obtained. A 90% recovery of CMCase, beta-glucosidase, and filter paper activity from the hydrolysates was obtained under the following conditions: (1) maintaining the ratio of enzyme to substrate high by stepwise addition of substrate, (2) brief grinding of the residual substrate with glass powder, and (3) addition of 0.4% Tween-80 to the eluting buffer. The high recovery of cellulolytic enzymes indicates that the adsorption of these enzymes on cellulose is not irreversible.
TL;DR: The conductivity of doped poly(2,6-naphthylene and poly(p-phenylene) is about 10−1 S · cm−1 as mentioned in this paper.
Abstract: Poly(p-phenylene), poly(2,6-naphthylene), poly(2,7-naphthylene), poly(1,5-naphthylene), and poly(1,4-naphthylene) were prepared by nickel-catalyzed polycondensation of Grignard reagents from the corresponding dibromides. The polymers were annealed in vacuo. Doping with SbF5 markedly increase the conductivity of the polymers. Annealed poly(2,6-naphthylene) is the most conductive among the four isomers after SbF5 doping. The conductivity of doped poly(2,6-naphthylene) and poly(p-phenylene) is about 10−1 S · cm−1. Annealed poly(p-phenylene) shows a broad single line ESR signal which changes to a narrow single line upon doping. Superposition of the two signals is observed at the initial stage of doping. Simultaneous conductivity and ESR measurements indicate that the narrow signal is closely related to conductivity.
TL;DR: Two strains of Neurospora crassa have been identified which utilize cellulase and produce extracellular cellulase [see 1.4-(1,3; 1,4)-β- d -glucan 4-glucaneohydrolase, EC 3.2.1.4] and β- d −glucosidase.
TL;DR: In this article, a new phase transition from the Sb(III) into a b.c. phase was found to be stable for a wide range of pressure from 28 GPa to at least 43 GPa.
TL;DR: Haploid plants were induced from anther callus of Annona squamosa Linn with an initial dark period and a high sucrose medium followed by light and lowered sucrose levels and Root tip squashes of the regenerated plantlets revealed the haploid nature of the plantlets.
Abstract: Haploid plants were induced from anther callus of Annona squamosa Linn. (Custard apple) on a Nitsch basal medium supplemented with 6-benzyl-aminopurine and naphthalene acetic acid. When naphthalene acetic acid was replaced by indole-3-acetic acid only multiple shoots were obtained. Pretreatment (chilling, centrifugation, reduced atmospheric pressure etc.) of the flowers was not effective but dissection of the flowers in a suspension of activated charcoal and sucrose was found essential. The anthers required an initial dark period and a high sucrose medium followed by light and lowered sucrose levels. Root tip squashes of the regenerated plantlets revealed the haploid (n = 7) nature of the plantlets.
TL;DR: In this paper, the acid strength distribution and catalytic behavior in the disproportionation of toluene of HZSM-5 zeolites with varying SiO2/Al2O3 ratios and calcined at different temperatures have been studied.
TL;DR: This communication discusses the compatibility of Penicillium funiculosum cellulase with Saccharomyces uvarum cells and the results on the combined hydrolysis and fermentation of cellulose to ethanol using a system of S. u varum cells immobilized in an open pore gelatin matrix described earlier from the same laboratory.
Abstract: This communication discusses the compatibility of Penicillium funiculosum cellulase with Saccharomyces uvarum cells and the results on the combined hydrolysis and fermentation of cellulose to ethanol using a system of S. uvarum cells immobilized in an open pore gelatin matrix described earlier from the same laboratory. (Refs. 10).
TL;DR: In this paper, the effects of chain branching and chain rigidity on the master curve of a resin type have been elucidated with reference to polyacetal and polysulfone, respectively.
Abstract: A method proposed earlier has been extended to estimate complete flow curves or rheograms of engineering plastics. Master curves that are independent of the grade and temperature have been generated and presented for acrylics, polyacetal, nylons, polyethylene terephthalate, polycarbonate and polysulfone. The influence of the various molecular parameters on the viscosity behaviour of polymer melts have been explained rationally. More specifically, the effects of chain branching and of chain rigidity on the master curve of a resin type have been elucidated with reference to polyacetal and polysulfone, respectively. The method presented here can be used effectively by processors of engineering plastics.
TL;DR: In this paper, two simple and rapid gas chromatographic techniques based on adsorption and thermal desorption of pyridine for measuring the acid strength distribution on solid catalysts at temperatures close to those employed in catalytic reactions are described.
TL;DR: In this article, the rate of the reaction between the Mg-23.3%Ni alloy and hydrogen, which was measured by a constant-volume method, was expressed by the equation dn dt = k(P − P eq n where n is the hydrogen-to-magnesium ratio, P is hydrogen pressure, Peq is the equilibrium pressure and k is the rate constant.
Abstract: The kinetics and the time dependence of the reaction between the Mg-23.3%Ni alloy and hydrogen and of the deactivation of the alloy are presented. The Mg-23.3%Ni alloy, which is a eutectic compound of magnesium and Mg2Ni, has the lowest melting point (507 °C) of the MgNi alloys. The rate of the reaction between the Mg-23.3%Ni alloy and hydrogen, which was measured by a constant-volume method, was expressed by the equation dn dt = k(P − P eq n where n is the hydrogen-to-magnesium ratio, P is the hydrogen pressure, Peq is the equilibrium pressure and k is the rate constant. With regard to the temperature dependence of the rate, the relation between In k and 1 T was not linear and hence the activation energy was not obtained. Prior to each run the hydrided alloy was dehydrided in a vacuum and was then pretreated by introducing a specific amount of hydrogen into the system. The reaction rate decreased with the time elapsed after pretreatment. Normal pretreatment together with full hydriding reactivated the alloy to its original level.
TL;DR: The substrate specificity and mode of action of the four pure β- d -glucosidase enzymes from Sclerotium rolfsii were studied and their contribution to cellulolysis is discussed.
TL;DR: The National Chemical Laboratory for Industry (NCL) model 4 chemical engine has been completed as mentioned in this paper, which is composed of a pair of these containers, two electrical boilers (9 kW), a circulating pump, valves and other components.
Abstract: The National Chemical Laboratory for Industry (NCL) model 4 chemical engine has been completed. This is a type of hydrogen compressor using LaNi5 as the energy conversion medium. The container, consisting of 19 copper tube elements with aluminium inner fins and covered with a stainless steel heat-insulated water jacket, is filled with 18.9 mol of LaNi5. The compressor is composed of a pair of these containers, two electrical boilers (9 kW), a circulating pump, valves and other components. The container is able to absorb 1.3 m3 (at normal temperature and pressure (NTP)) of hydrogen and the time needed for preheating (90 °C) and cooling (27 °C) is less than 3 min. In the present investigation, using this container, the basic operating characteristics such as the hydrogen-absorbing and hydrogen-desorbing ability, the thermal efficiency, the heat transfer coefficient and the reaction velocity have been examined. Because of the circulating hot water (90 °C; 30 1 min−1), the NCL model 4 compressor is able to desorb 360 1 min−1 (NTP) of high pressure (18-12 atm) hydrogen gas continuously in 3 min. However, this is its maximum ability under stable conditions. The overall heat transfer coefficient estimated is about 300–1200 kcal m−2 h−1 °C−1. Using a plunger pump, the NCL model 4 compressor has been combined with a reverse osmosis type of desalination apparatus and a practical test is now under way.
TL;DR: The thermodynamic properties of Zr(FexMn1−x)2 alloy hydrides (x = 0-1) were studied by measuring the equilibrium dissociation pressures.
Abstract: The thermodynamic properties of Zr(FexMn1−x)2 alloy hydrides (x = 0–1) were studied by measuring the equilibrium dissociation pressures. When x is in the range 0–0.8, Zr(FexMn1−x)2 alloys readily occlude hydrogen at pressures below 0.1 MPa at room temperature without requiring any activation. The cyclic stabilities of the present alloys are so good that no irreversible phase separation is observed after numerous hydrogen absorption-desorption cycles. The dissociation pressures of the hydrides increase as the lattice parameters of the alloys decrease. When x = 1 this formula corresponds to ZrFe2 which is essentially inactive to hydrogen. The alloy hydrides show sloping plateaux and this phenomenon is not significantly affected by heating the parent alloys to 1300 K in an argon atmosphere. As the square root of the equilibrium pressure has a linear relationship with the hydrogen concentration, the sloping plateaux observed here are believed to be inherent.
01 Jul 1983
TL;DR: In this paper, three kinds of sodium salts of S-acid were prepared, and the results of potentiometric titration, IR, and 13 C NMR were concluded that the monosodium salt of s-acid (S-1Na) consisted mainly of the neutralizing product of the carboxylic group attached to the 4-positioned carbon of S acid.
Abstract: Penicillium spiculisporum produces 4,5-dicarboxy-4-pentadecanolide (spiculisporic acid, S-acid) efficiently from glucose. Three kinds of sodium salts of S-acid were prepared. As a result of potentiometric titration, IR, and 13 C NMR, it was concluded that the monosodium salt of S-acid (S-1Na) consisted mainly of the neutralizing product of the carboxylic group attached to the 4-positioned carbon of S-acid, the disodium salt of S-acid (S-2Na) corresponded to the neutralizing product of the carboxylic group attached to the 4- and 5-positioned carbons, and the trisodium salt of S-acid (S-3Na) was the saponified product of the lactone group of S-2Na. The micelle formation of these three kinds of S-acid salts was ascertained in water by means of both surface tension and electrical conductance measurements. And, the CMC values were S-1Na, 3.9 × 10 −3 ; S-2Na, 6.1 × 10 −2 ; and S-3Na, 1.7 × 10 −1 mole/liter, respectively. These three salts showed low foaming properties, with S-2Na having the highest foaming property of the three. Further, these showed a dispersing action for hydrophilic pigments, as well as showing both calcium ion sequestration and buffering actions. It will be a future theme to study the connection with the biological function of S-acid from the viewpoint of biosurfactant.
TL;DR: In this paper, an altered free volume state model has been proposed to interpret transport phenomena in diverse media within a unified framework and its specific application to the interpretation and correlation of data on diffusion in polymer solutions, protein solutions, polymeric gels and blends of polymeric melts has been elaborated.
TL;DR: In this article, the integrated intensities of CH3Cl and CD3Cl molecules have been measured by the pressure broadening technique, and the intensity analysis has been carried out to determine the correct signs of (∂p/∂Qi) for A1 and (−+−) for E species.
Abstract: The integrated intensities of the fundamental bands of CH3Cl and CD3Cl molecules have been measured by the pressure broadening technique. The Coriolis intensity perturbation between ν3 and ν6 bands of CD3Cl has been analysed to determine the sign to be negative. The intensity analysis has been carried out to determine the correct signs of (∂p/∂Qi). The resulting signs are (−++) for A1 and (−+−) for E species. The (∂p/∂SjR) values as well as the atomic polar tensors have been obtained.
TL;DR: In this paper, a method based on the melt flow index rather than the conventional zero shear viscosity is suggested to estimate the activation energy for viscous flow of polymer melts.
Abstract: A method based on the melt flow index rather than the conventional zero shear viscosity is suggested to estimate the activation energy for viscous flow of polymer melts. The method is particularly attractive due to its simplicity and because all the conditions for its derivation fit rather well within the validity range of applicability of the Arrheniustype equation relating viscosity and temperature. Values of activation energy for viscous flow using the suggested technique are calculated for a number of polymers falling within the olefinic, styrenic, cellulosic, and engineering thermoplastic groups.
TL;DR: In this paper, the effects on the pressure-temperature-composition relations of changing x, y and z were studied with the aim of obtaining hydriding alloys suitable for thermal energy conversion systems operating under relatively high temperature conditions (120-200°C).
Abstract: Quaternary alloys with the formula Ti1−xZrx(Fe1−yMny)z were investigated with the aim of obtaining hydriding alloys suitable for thermal energy conversion systems operating under relatively high temperature conditions (120–200°C) The effects on the pressure-temperature-composition relations of changing x, y and z were studied Ti05Zr05(Fe02Mn08)15 hydride had a very low hysteresis (hysteresis factor, 0955) and a high hydrogen capacity ( [H] [M] = 114 (20 wt%) ) at temperatures above 100°C
TL;DR: In this article, an effective method is proposed to generate the melt flow curves of polymer waste from knowledge of its melt flow index, which can be obtained by plotting the available viscosity data in terms of modified functions based on the Melt Flow Index.
TL;DR: In this paper, a unifying approach is proposed that coalesces the flow curves of filled systems of a polymer at various temperatures into a master curve that is independent of the filler parameters.
Abstract: Polymers filled with extending fillers, such as calcium carbonate or talc, or with reinforcing fillers, such as glass fibers or mica, are increasingly being used in a number of applications. The addition of fillers to a polymer changes the melt rheological behavior of the polymer. A knowledge of the viscosity vs. shear-rate flow curves of the filled system at various temperatures and as a function of filler parameters (such as filler type, shape, and amount) is necessary for process design, optimization, and trouble shooting. The generation of such rheological data is ezpensive and cumbersome in view of the broad range of fillers and the large numbers of filler parameters. In the present article, a unifying approach is proposed that coalesces the flow curves of filled systems of a polymer at various temperatures into a master curve that is independent of the filler parameters. An effective methods is presented to estimate the rheograms of filled systems with the use of a master curve, characteristic of a genetic resin type, knowing the melt-flow index and glass-transition temperature of the system. Master curves have been reported for filled system of low-density polyethylene, high-density polyethylene, poly-propylene polystyrene, nylons, poly(ethylene terephthalate), and polycarbonate.