Showing papers on "Silica gel published in 1971"
156 citations
TL;DR: It would be reasonable to conclude that there are many forms of biogenous silica ranging from silica gel to pseudo-opaline silica, and convenient methods can be devised to estimate the easily soluble parts of biogeneous silica.
Abstract: Estimation of the silica balance in the ocean requires clarification of the trend of dissolution of biogenous silica. We used biogenous silica in our experiments to compare silica gel and opal. From the results, convenient methods can be devised to estimate the easily soluble parts of biogenous silica. The soluble parts of diatomaceous silica vary considerably with the different species and the characteristics of organic body matter. X-ray diffraction patterns of the biogenous silica suggests an amorphous silica gel form. All different kinds of diatomaceous silica used show infra-red spectra patterns similar to that of silica gel. In the dissolution trends, there exist differences between recent and ancient silica frustules, the former resembling silica gel, the latter opaline silica. Silicious sponge spicules show characteristics similar to that of opaline silica in respect to dissolution and infra-red spectrum pattern. It would, therefore, be reasonable to conclude that there are many forms of biogenous silica ranging from silica gel to pseudo-opaline silica.
114 citations
TL;DR: In this paper, the absorption spectra of silica gel were measured in order to assign the bands senstive to adsorption at 870 and around 950 cm−1.
Abstract: Infrared absorption spectra of the systems of silica gel - H216O,D216O,H218O, and some organic vapors were measured in order to assign the bands senstive to adsorption at 870 and around 950 cm−1. Deuteration of silica gel caused the absorption decrease at 870 cm−1 and the appearance of a band at 620 cm−1. The band around 950 cm−1 appearing by adsorption not only of water but also of organic vapors showed no shift on deuteration, but shifted toward low frequency side by 25 cm−1 on the substitution of 16O of surface silanol groups with 18O. From these facts the bands at 870, 620 and 950 cm−1 were assgned to Si–OH bending, Si–OD bending and Si–O stretching vibrations of surface silanol groups, respectively. The oxygen atom of silanol groups of silca gel was found to exchange with that of adsorbed water molecules even at room temperature for a sample treated at temperature below 300°C. On the other hand, higher reaction temperature of ca. 200°C was necessary for a sample calcined at 800°C. mechanism of the ox...
96 citations
TL;DR: In this paper, a simple model of adsorption chromatography systems of the type electron donor solvent, silica, is discussed, and the expression for the RM coefficient derived by the application of the law of mass action to the competitive equilibria express quantitatively the effect of the following parameters: mole fraction of electron donate solvent (XS) diluted with an inert solvent, specific surface area of the adsorbent (a), molar volume of the solvent (V S o ), adsorbents weight to solvent volume ratio (WA/VS), and the pKA of the
Abstract: A simple model of adsorption chromatography systems of the type electron donor solvent — silica is discussed. Equations for the RM coefficient derived by the application of the law of mass action to the competitive adsorption equilibria express quantitatively the effect of the following parameters: mole fraction of electron donor solvent (XS) diluted with an inert solvent, specific surface area of the adsorbent (a), molar volume of the solvent (V S o ), adsorbent weight to solvent volume ratio (WA/VS), and the pKA of the basic solute. If certain assumptions are fulfilled, the RM value of the solute should be linearly related to log XS, log a, log V S o , pKA and log (WA/VS). Experimental confirmation of some of these relationships is given. The derivation of the equations is simple so that the model considered can be useful for didactic purposes.
62 citations
Patent•
09 Jun 1971
TL;DR: In this article, a method of improving the surface characteristics of plastics and elastomers is described, which in its preferred aspects includes the steps of forming a bonding or coupling film of an organic silicon compound on the surface of a plastic or elastomeric material and thereafter contacting the film with a compound or a mixture of compounds, or a solution thereof, capable of forming or coating of silica or silica gel thereon, and articles produced in accordance with the method.
Abstract: A method of improving the surface characteristics of plastics and elastomers which in its preferred aspects includes the steps of forming a bonding or coupling film of an organic silicon compound on the surface of a plastic or elastomeric material and thereafter contacting the film with a compound or a mixture of compounds, or a solution thereof, capable of forming a deposit or coating of silica or silica gel thereon, and articles produced in accordance with the method.
58 citations
TL;DR: In this article, a thermodynamic consistency test for adsorption from binary liquid mixtures is derived using the Gibbs equation for adaption, where the mixture pairs A-B, A-C, and B-C on the same adsorbent must be thermodynamically consistent.
Abstract: A thermodynamic consistency test for adsorption from binary liquid mixtures is derived using the Gibbs equation for adsorption. Adsorption data for the liquid mixture pairs A-B, A-C, and B-C on the same adsorbent must be thermodynamically consistent. The consistency test is applied to experimental data for adsorption from the binary liquid mixtures benzene-cyclohexane, benzene-n-heptane and cyclohexane-n-heptane on silica gel at 30°C.
57 citations
TL;DR: In this paper, the partial oxidation of ethylene to ethylene oxide was studied using silver deposited on aluminas or silicas with moderate to high surface area, and very high activity and good selectivity were obtained with a catalyst having silver particles 30-70 A in diameter.
56 citations
TL;DR: In this article, dense adsorbed layers of polyethylene glycols of different molecular weights on graphitised carbon black and of polyarylate Ph-1 on macroporous silica gel were prepared.
55 citations
TL;DR: When trypsin is incorporated into a polymerizing silicic acid sol, the resulting silica xerogel shows tryptic activity which is not removed by washing, and the same immobilizedtrypsin preparation showed no proteolytic activity to casein.
53 citations
TL;DR: The procedure involves addition of a labeled internal standard, [3H]digoxin, extraction with methylene chloride and preliminary purification on a florisil column followed by thin-layer chromatography on silica gel.
47 citations
TL;DR: In this article, the elimination reactions of halopropanes and halocarbons on solid acids and bases, including a series of metal sulfates supported by silica gel, were studied at 300°C by means of the pulse technique in order to clarify the mechanism of catalytic dehydrohalogenation.
Abstract: The elimination reactions of haloethanes and halopropanes on solid acids and bases, including a series of metal sulfates supported by silica gel, were studied at 300°C by means of the pulse technique in order to clarify the mechanism of the catalytic dehydrohalogenation. The trans-1,2-dichloroethylene/cis-1,2-dichloroethylene (trans-1,2/cis-1,2) selectivities from 1,1,2-trichloroethanes as well as the activities of the metal sulfates supported by silica gel were well correlated with the electronegativities of the metal ions. Generally speaking, the rates of the dehydrochlorination from chloroalkanes were nearly equal to those of the dehydrobromination from bromoalkanes on the solid acids, but the latter were larger than the former on solid bases. The reactivities of the alkylhalides on solid acids and bases were examined from the electronic view-point, and we tried to correlate them with some reactivity indexes. A kinetic isotope effect with regard to hydrogen was observed on solid bases, but not on solid...
TL;DR: In this article, the authors measured the lifetime of opositronium in silica gel adsorbed with various amounts of water, n−hexane, or nitromethane.
Abstract: The lifetimes of o‐positronium in silica gel adsorbed with various amounts of water, n‐hexane, or nitromethane were measured. The fraction of o‐positronium escaping the condensed phase can be related to the specific area and the pore volume of the silica gel. The mean life of o‐positronium in the pores is found to be very sensitive to the surface properties of silica gel. The formation of free radicals on the surface of silica and the reactions between these free radicals and o‐positronium are suggested as the explanations.
TL;DR: Several organophosphorus pesticides were also identified in the waters by the technique described, the persistence of which in the environment had not previously been suspected.
TL;DR: In this paper, thin-layer chromatography on silica gel is proposed as a method for assigning the relative configurations of diastereomeric pairs of compounds of the above type.
TL;DR: It is advisable to employ an independent means of stopping phospholipase A reactions prior to product separation in chromatographic systems after silica gel stimulates the hydrolysis of aqueous lecithin suspensions by phosphorus A.
TL;DR: The chromatographic behavior of some minor components of natural lipids was studied using layers of magnesium oxide and of commercial adsorbents containing magnesium oxide to afford means for the detection of unusual lipids in natural materials, and their isolation.
TL;DR: The present data are consistent with an addition product whose bridging group is a new chroman ring and does not reduce Emmerie-Engel reagent prior to treatment with concentrated hydriodic acid, nor do the ether-extractable products after such treatment.
Abstract: There is evidence that an addition compound of oxidizeddl-alpha-tocopherol and linoleic acid is formed when the components are absorbed in mixed monolayer on silica gel at a molecular ratio of 1∶20, and subjected to heating in air at 80C. A relatively nonpolar tocopheryl quinone is also formed in smaller amounts. These are the major tocopherol oxidation products isolated in this system and do not correspond to any known to the authors. The addition compound has about the same mobility as linoleic acid in most thin layer chromatography (TLC) and chromatographic systems, but can be isolated by successive chromatography on silica and gel filtration on Sephadex LH-20. It yields a single spot in TLC in several systems. The elemental analysis is reproducible and consistent with a simple addition compound of linoleic acid and bivalently oxidized tocopherol. The compound has a carboxyl group which can be esterified. The ester has about the same TLC mobility as methyl linoleate. The molecular weight of the ester is 722.6. The UV spectrum shows a single peak, 2
max
ETOH
=3000 A, E=4.74. The IR spectrum shows a very strong chroman ether band at 9.12 μ, a strong methyl band at 7.24 μ and carboxyl but no hydroxyl absorption. The NMR spectrum shows, in contrast to that of tocopherol, a reduction in aromatic methyl protons, a carboxyl proteon exchangeable with deuterium oxide, but no hydroxy proton. The compound does not reduce Emmerie-Engel reagent prior to treatment with concentrated hydriodic acid, nor do the ether-extractable products after such treatment. The present data are consistent with an addition product whose bridging group is a new chroman ring.
TL;DR: In this article, carboxy-polybutadienes and hydroxy polybutadiene were separated using stepwise elution from silica gel. Recoveries in the 95-100% range have been achieved.
Abstract: Separations of carboxy-polybutadienes and hydroxy-polybutadienes according to functionality have been effected using stepwise elution from silica gel. Recoveries in the 95–100% range have been achieved. Subjection of the fractions obtained from the silica gel separation to analysis via gel-permeation chromatography and infrared or near-infrared spectroscopy yields not only functionality distribution data, but also provides the relationship between molecular weight distribution and functional type. Analytical techniques and interpretation of data are discussed.
Patent•
06 Jan 1971TL;DR: In this article, the authors describe the use of a HEAT SINK between a double bed of SILICA gels and a MOLECULAR SIEVE to prevent water poisoning.
Abstract: IN THE PROCESS WHEREIN NITROGEN OXIDES ARE RECOVERED FROM STACK GAS STREAMS CONTAINING WATER VAPOR BY SELECTIVE ADSORPTION USING A DUAL BED OF SILICA GEL AND MOLECULAR SIEVES, THE FORMATION OF CORROSICE AQUEOUS NITRIC ACID IN THE ADSORBENT BED DURING REGENERATION THEREOF IS PREVENTED BY THE USE OF A HEAT SINK INTERPOSED BETWEEN THE SILICA GEL AND THE MOLECULAR SIEVE. THE HEAT SINK SERVES TO PREVENT PREMATURE DESORPTION OF WATER FROM THE SILICA GEL BED AND THE CONTACT OF LIQUID WATER WITH DESORBED NO2.
TL;DR: In this article, the surface areas of supported catalytic metals (e.g., platinum on silica gel) can be rapidly determined by measuring evolution of chemisorbed hydrogen in a flowing hydrogen-argon mixture that contains 1 mole % hydrogen.
TL;DR: The authors showed that 1-Methyl-1,2-epoxycycloheptane, 2α, 3α-epoxypinane and 3α, 4α-empoxycarane undergo typical carbonium ion rearrangements in contact with active silica gel, while Humulene epoxide-II and caryophyllene oxide did not undergo any transformation under these conditions.
TL;DR: The methyl radicals produced on silica-gel surfaces by photolysis of methyl iodide or methane have been investigated by ESR as discussed by the authors, and the adsorption sites for these radicals were estimated to be siloxane groups.
Abstract: The methyl radicals produced on silica-gel surfaces by the photolysis of methyl iodide or methane have been investigated by ESR. When the silica gel is preheated at high temperatures (above ca. 300°C), two methyl radicals which have abnormally small hfs constants are trapped on the surfaces. In the case of the photolysis of methyl iodide, these two radicals disappear by continuing uv-irradiation, and instead an ordinary type of methyl radical is produced. The former two radicals have nearly isotropic g-values, and these values are approximately equal to that of a free electron and are considered to have a non-planar structure. The adsorption sites for these radicals were estimated to be siloxane groups. On the other hand, when the silica gel is preheated at low temperatures (below ca. 300°C) the methyl radicals produced have hfs constants of the same magnitude as that of the ordinary type of methyl radical, but each proton line of the radicals is accompanied by four satellite lines. The outer satellite li...
TL;DR: In this article, the surface properties of silica-alumina-combinations differ in many ways from those of either silica or of alumina, as such, three different procedures for preparing the silicaaluminas may be mentioned, viz., (a) adsorption (chemisorption) of aluminium hydroxide on a wet silica surface, (b) precipitation of aluminum hydroxides on a wet silica gel, (c) co-gelling of a silica acid-and an aluminium salt solution.
Abstract: Since Eugene Houdry discovered some clays to be excellent catalysts for the “cracking” of heavy oils, the surface properties of silica-alumina combinations have been studied in various places and from various angles. The surface properties of silica-alumina-combinations differ in many ways from those of silica or of alumina, as such. Three different procedures for preparing the silica-aluminas may be mentioned, viz., (a) adsorption (chemisorption) of aluminium hydroxide on a wet silica surface, (b) precipitation of aluminium hydroxide on a wet silica gel, (c) co-gelling of a silica acid-and an aluminium salt solution. The influence of the alumina adsorption on the specific surface area, as measured with the B.E.T.-method and with the lauric acid method will be discussed. An attempt is made to give a picture of the binding of aluminium hydroxide on the silica, which leads to three possibilities, depending on the relative amount of both constituents. One of these possibilities leads to preparations with an acid character.
Journal Article•
TL;DR: The laser Raman spectra of styrene adsorbed on 18-30 mesh Chromatographic grade silica gel, Cab-o-sil, and Aerosil 380 are described in this article.