Yields Of Other Products Research Articles

Gypsum Seeding to Prevent Scaling

Eutectic freeze crystallization (EFC) is a novel separation technique that can be applied to treat brine solutions such as reverse osmosis retentates. These are often a mixture of different inorganic solutes. The treatment of calcium sulphate-rich brines using EFC often results in gypsum crystallization before any other species. This results in gypsum scaling on the cooled surfaces of the crystallizer, which is undesirable as it retards heat transfer rates and hence reduces the yield of other products. The aim of this study was to investigate and understand gypsum crystallization and gypsum scaling in the presence of gypsum seeds. Synthetic brine solutions were used in this research because they allowed an in-depth understanding of the gypsum bulk crystallization process and scaling tendency without the complexity of industrial brines. A cooled, U-shaped stainless-steel tube suspended in the saturated solution was employed as the scaling surface. This was because a tube-shaped surface enabled the introduction of a constant temperature cold surface in the saturated solution and most industrial EFC crystallizers are constructed from stainless steel. Gypsum seeding was effective in decreasing the mass of scale formed on the heat transfer surface. The most effective seed loading was 0.25 g/L, which reduced scale growth rate by 43%. Importantly, this seed loading is six times the theoretical critical seed loading. The seeding strategy also increased the gypsum crystallization kinetics in the bulk solution, which resulted in an increase in the mass of gypsum product. These findings are relevant for the operability and control of EFC processes, which suffer from scaling problems. By using an appropriate seeding strategy, two problems can be alleviated. Firstly, scaling on the heat transfer surface is minimised and, secondly, seeding increases the crystallization kinetics in the bulk solution, which is advantageous for product yield and recovery. It was also recommended that the use of silica as a seed material to prevent gypsum scaling should be investigated in future studies.

Enhanced yields of furfural and other products by simultaneous solvent extraction during thermochemical treatment of cellulosic biomass

Furfural derived from pentose sugars is one of the key reactive intermediates for production of hydrocarbons from cellulosic biomass for use as drop-in fuels. Simultaneous extraction into a solvent immiscible in water can substantially enhance furfural yields by removing it from the aqueous environment where the yield would otherwise be limited by its rapid degradation to chars and other carbon rich compounds that are loosely termed humins. Thus, in this study, the effectiveness of the organic solvent methyl isobutyl ketone (MIBK) in improving furfural yields from maple wood was determined for reactions of 5 wt% solids in 0.1 M sulfuric or hydrochloric acid at 170 °C over a range of reaction times. For comparison, pure xylose, glucose, and Avicel cellulose were also reacted under the same conditions. Various process configurations based on simultaneous hydrolysis and dehydration were compared to acid hydrolysis followed by dehydration to furfural with and without simultaneous extraction. Without MIBK extraction, the maximum furfural yields were less than 65% when maple wood was reacted for about 40–45 min with either sulfuric or hydrochloric acid. However, the yield increased significantly to about 85.3% when MIBK extraction was employed in combination with sulfuric acid catalysis for 50 min, while combining MIBK extraction with hydrochloric acid catalysis only increased the yield to ∼67.0%. Simultaneous extraction with MIBK also improved yields of other products such as 5-HMF and levulinic acid, compared to results from the acids alone.

Alkalibacterium thalassium sp. nov., Alkalibacterium pelagium sp. nov., Alkalibacterium putridalgicola sp. nov. and Alkalibacterium kapii sp. nov., slightly halophilic and alkaliphilic marine lactic acid bacteria isolated from marine organisms and salted foods collected in Japan and Thailand

We describe 10 new strains of marine lactic acid bacteria isolated from decaying marine algae, decaying seagrass, raw fish, salted fish and salted and fermented shrimp paste ('ka-pi') collected from a temperate area of Japan and Thailand. The isolates are Gram-positive and non-sporulating. They have motility with peritrichous flagella depending on the strains. They lack catalase and quinones. Under anaerobic conditions, lactate yields were 64-93 % of the glucose consumed; residual products were formate, acetate and ethanol with a molar ratio of approximately 2 : 1 : 1. The pH of the fermentation medium markedly affected the product composition; at higher pH, the yield of lactate decreased (15-48 % at pH 9.0) and yields of other products increased, retaining the molar ratio. Under aerobic conditions, acetate and lactate were produced from carbohydrates and related compounds. The isolates were slightly halophilic, highly halotolerant and alkaliphilic. The optimum NaCl concentration for growth ranged between 0.5 and 4.0 % (w/v), depending on the strain, with a growth range of between 0 and 17-21 % (11 % for one isolate). The optimum pH for growth ranged between 8.0 and 9.5, with a growth range of 6.0-11.0, depending on the strains. Comparative sequence analysis of the 16S rRNA genes revealed that the isolates occupied three phylogenetic positions within the genus Alkalibacterium, showing 97.1-99.8 % similarity to Alkalibacterium indicireducens. DNA-DNA hybridization values (<46 %) among the 10 isolates and phylogenetically related taxa resulted in the identification of four genomic species (designated groups GS1-GS4). The G+C contents of the DNA were 41.7 mol% (group GS1), 42.2 mol% (group GS2), 41.0-43.0 mol% (group GS3) and 38.4-39.4 mol% (group GS4). The cell-wall peptidoglycan was type A4beta, Orn-d-Asp, for three genomic species (groups GS1, GS2 and GS3), and type A4beta, Orn-d-Glu, for the remaining species (group GS4). The major components of cellular fatty acids were C(16 : 0), C(16 : 1)omega9c and C(18 : 1)omega9c (oleic acid). On the bases of phenotypic characteristics, genetic distinctiveness and phylogenetic affiliations, the four genomic species, groups GS1, GS2, GS3 and GS4, were classified as four novel species within the genus Alkalibacterium, for which the names Alkalibacterium thalassium sp. nov., Alkalibacterium pelagium sp. nov., Alkalibacterium putridalgicola sp. nov. and Alkalibacterium kapii sp. nov., respectively, are proposed. The respective type strains are T117-1-2(T) (=DSM 19181(T)=NBRC 103241(T)=NRIC 0718(T)), T143-1-1(T) (=DSM 19183(T)=NBRC 103242(T)=NRIC 0719(T)), T129-2-1(T) (=DSM 19182(T)=NBRC 103243(T)=NRIC 0720(T)) and T22-1-2(T) (=DSM 19180(T)=NBRC 103247(T)=NRIC 0724(T)).

Kinetic Study of n-Butane Isomerization over Pt−H-Mordenite

The kinetics of n-butane isomerization over bifunctional Pt−H-mordenite was studied by varying reactant partial pressure and temperature. The main products were isobutane, propane, and pentanes. Yields of other products, especially methane, ethane, ethene, and propene, were very low, which suggests that protolytic cracking and hydrogenolysis were present only to a minor extent. Especially the protolytic cracking was inhibited, since after introduction of Pt into H-mordenite all strong Bronsted acid sites disappeared and the total density of acid sites decreased. The reaction rate showed complex dependence on the reactant partial pressure, suggesting that two reaction mechanisms on the acid sites, i.e., monomolecular or bimolecular, for isobutane formation are present and the prevailing mechanism depends on the reaction conditions. Three kinetic models were developed based on the current understanding of the reaction mechanisms including hydrogenation and dehydrogenation steps on the metal sites, skeletal ...

Ethylation of benzene with ethanol over substituted large pore aluminophosphate-based molecular sieves

Abstract Ethylation of benzene with ethanol in the vapour phase was studied over AlPO4-5, MAPO-5, ZAPO-5 and MnAPO-5. The products were ethylbenzene (EB), 1,4-diethylbenzene (PDEB), 1,3-diethylbenzene (MDEB) and polyalkyl benzenes (1,2,4- and 1,3,5-triethylbenzene, and 1,2,4,5-tetraethylbenzene). MnAPO-5 was found to be more active than the other catalysts. Maximum conversion (47%) was noted at 400 °C over MnAPO-5. Although isomorphic substitution in MnAPO-5 is nearly the same as in MAPO-5 and ZAPO-5, the increment in conversion was attributed to the presence of unpaired electrons in the d-subshell of manganese. The selectivity of the products was found to decrease with stream but the selectivity to EB showed an increase after 2 h of stream. MnAPO-5 registered nearly 14% yield of EB and 17% yield of DEB, whereas the yield of other products was found to be 16% at maximum conversion.

Pyrolysis of polypropylene in the presence of oxygen

The polypropylene (PP) was coated on porous α-alumina particles and then pyrolyzed in a flow of helium or a mixture of helium–oxygen at atmospheric pressure. The mass release from PP was dramatically enhanced in the presence of oxygen at temperatures in the range of 200–300°C. The temperature for the 50% mass release was ca. 250°C at an oxygen partial pressure ( P O 2 ) of 16.7 kPa and was lowered by 190°C as compared with a system which contained no oxygen. When P O 2 was higher than 4.2 kPa, the mass release rate obeyed first-order kinetics with respect to P O 2 , and the activation energy was calculated and found to be 65–75 kJ/mol. The activation energy was considerably lower than that for pyrolysis in the absence of oxygen (230 kJ/mol) and agreed well with the value for formation of peroxides on tertiary carbons. When the pyrolysis was conducted at 250°C under P O 2 =16.7 kPa, the carbon-based yield of volatiles exceeded 90%, and the yields of CS 2-soluble oil and wax were 76% and 6.0%, respectively. The carbon-based yields of other products were: Acetone, 2.5%; methanol, 1.5%; CO, 3.0%; CO 2, 2.2% and solid residue; 10%. Proton NMR (nuclear magnetic resonance) analysis showed that the CS 2-soluble oil possessed an elemental composition of C 100H 187O 11. The average number of carbon atoms per molecule of the oil was approximately 10, and –CH 2–OH, –C(CH 3)CO and CH 2 were typical end groups. Their formation is explained by the decomposition of peroxides formed on tertiary carbons.

The in Vitro Metabolism of 17-Hydroxyprogesterone by Ovaries of the Goldfish, Carassius auratus, Is Affected by Substrate Concentration

Ovaries of mature goldfish ( Carassius auratus) were incubated with 17-[ 3H]hydroxyprogesterone and 0, 0.01, 0.1, 1, 10, and 100 μg/ml 17-hydroxyprogesterone (17P). The major products were quantified after separation by thin-layer and high-performance chromatography. The results show that substrate concentration markedly affects the pattern of metabolites. Glucuronides and sulfates decreased from 7.2 ± 2.0 and 28.5 ± 4.4% of recovered radioactivity, respectively, in the absence of added 17P to insignificant yields at 10 μg/ml 17P. 7α-Tetrols were the major products (36-52%) with 0-1 μg/ml substrate, but at 10 and 100 μg/ml 17,20α-dihydroxy-4-pregnen-3-one (17,20αP) was the major metabolite and there were low yields of other products. 11-Deoxycortisol was produced in significant amounts only at low substrate concentrations. The results support the hypothesis that 5α-reduced-7α-hydroxylated metabolites are formed by enzymes of high activity but low capacity and serve to limit secretion of 17,20αP and its 20β epimer to the period of maximum GtH stimulation.

Radiolytic oxidation of propane: Computer modeling of the reaction scheme

The oxidation of gaseous propane under gamma radiolysis was studied at 100 torr pressure and 25°C, at oxygen pressures from 1 to 15 torr. Major oxygen-containing products and their G-values with 10% added oxygen are as follows: acetone, 0.98; i-propyl alcohol, 0.86; propionaldehyde, 0.43; n-propyl alcohol, 0.11; acrolein, 0.14; and allyl alcohol, 0.038. Minor products include i-butyl alcohol, t-amyl alcohol, n-butyl alcohol, n-amyl alcohol, and i-amyl alcohol. Small yields of i-hexyl alcohol and n-hexyl alcohol were also observed. There was no apparent difference in the G-values at pressures of 50, 100 and 150 torr. When the oxygen concentration was decreased below 5%, the yields of acetone, i-propyl alcohol, and n-propyl alcohol increased, the propionaldehyde yield decreased, and the yields of other products remained constant. The formation of major oxygen-containing products was explained on the basis that the alkyl radicals combine with molecular oxygen to give peroxyl radicals; the peroxyl radicals react with one another to give alkoxyl radicals, which in turn react with one another to form carbonyl compounds and alcohols. The reaction scheme for the formation of major products was examined using computer modeling based on a mechanism involving 28 reactions. Yields could be brought into agreement with the data within experimental error in nearly all cases.

Analysis of the reduction of nitroxides by flavin mononucleotide

This article describes a simle method to prepare hydroxylamines from nitroxides by photo-activated flavin mononucleotide. The half-time of reduction varied from 2 to 38.4 s for a series of nitroxides. For most nitroxides short exposures to light (min) were sufficient to produce significant amounts of hydroxylamine; longer periods of exposure increased the yields of other products. Proxyl (2,2,5-trimethyl-5-alkylpyrrolidine- N-oxy) nitroxides were unsually reactive with a much higher yield of products which could not be reoxidized by ferricyanide to the nitroxides. Optimum conditions for reversible reduction depend on the nitroxide and the amounts of other reducible substances such as oxygen and ferricyanide that may be present.

Common products from gamma-radiolysis and ultraviolet photolysis of metronidazole

u.v. Photolysis of metronidazole in aqueous solution at pH 7.0 results in rearrangement through an imino-ketone to an oxadiazole. These compounds were also found following γ-radiolysis of metronidazole, being about 10% of the products. Saturation of the solution with nitrous oxide caused a slight increase in the yield of imino-ketone in radiolysis. Conversely, the imino-ketone was not detected on addition of sodium formate or propan-2-ol to the radiolysis, but an increased yield of other products was observed. It is suggested that formation of the imino-ketone and oxadiazole in both photolysis and radiolysis occurs via processes which do not involve the nitro radical anion as first transient species.

Reaction of methanol with Cu(111) and Cu(111) + O(ads)

The reactive chemistry of methanol on the Cu(111) surface, both with and without preadsorbed oxygen atoms, is investigated between 190 and 700 K. The clean Cu(111) surface is inert, and molecularly absorbed methanol, the only stable surface species identified on this surface, desorbs at about 210 K. Various trends are examined as a function of oxygen coverage, from the clean surface to the saturation oxygen coverage (approximately 0.45 O atom/Cu atom). The capacity of the surface to adsorb methanol (190 K), and the formaldehyde yield (∼ 400–450 K) are both maximized when the oxygen coverage is about 0.26 O atom/Cu atom. Trends in the yield of other products, and the temperature for decomposition of the stable methoxy intermediate are examined. Also, the rate of methoxy decomposition is limited by CH bond breaking as evidenced by a deuterium kinetic isotope effect (CH versus CD). A minor decomposition path for methanol on O + Cu(111) involves CO 2 formation, probably via a formate surface intermediate. Preadsorbed oxygen serves as an acceptor of the methanol hydroxyl hydrogen, enabling facile methanol conversion to methoxy at low oxygen coverage for T ⩾ 190K. However. at high oxygen coverage ( θ ⪆ 0.26 O atom/Cu atom) oxygen inhibits surface reactivitv. A two-dimensional model which defines three types of surface sites is used to explain the general trend of methanol reactivity as a function of oxygen coverage.

The use of microorganisms in organic synthesis. II. Microbiological asymmetric reduction of 2-methyl-3-oxosuccinates.

In order to synthesize four optically active methyl 2-methylmalates (10-13), microbiological asymmetric reduction of the corresponding dimethyl 2-methyl-3-oxosuccinate (9) was carried out. The β-keto diester 9 was found to be reduced by fermenting baker's yeast (Saccharomyces cerevisiae) and Candida albicans to afford a mixture of the (2R, 3R)-isomer 10 and the (2S, 3R)-isomer 11. Although the optical purity of 10 produced by Candida albicans was reasonably high (95% e.e.), optical yields of other products were unexpectedly low. However, identification of the four possible isomers 14-17 was found to be easily carried out by means of nuclear magnetic resonance spectroscopy.

Implications of ion-molecule reactions observed in silane for recoil silicon atom studies

Ion-molecule reaction sequences in silane, producing tertiary product ions, are reported. A mechanism is presented by which trisilane can be producted from Si+ ions in recoil silicon studies. It is also reported that Si+ ions can be efficiently neutralized by charge exchange with triethylamine. Preliminary studies indicate that the addition of triethylamine to recoil silicon experiments results in a decrease in the absolute yield of trisilane without affecting the yields of other products. In addition, information obtained from ion-molecule studies in silane is applied to radiolysis studies of silane. A mechanism is presented by which higher homologues are produced by hydride ion transfer.

Gamma-Radiolysis of Aqueous Boric Acid Solution

The γ-radiolysis of aqueous boric acid solutions of relatively high concentration has been studied. Boric acid significantly promotes hydrogen formation up to 10−7 mol/ml but does not increase oxygen and hydrogen peroxide to any appreciable extent. Since boric acid reacts at a relatively slow rate with species formed by the primary process of water radiolysis, when an effective scavenger for e − aq—the precursor of H2—such as NO− 3 is present, boric acid has no effects upon the total yield of H2 in the range of concentrations studied. However, the yields of other products of the radiolysis—H2O2 and NO− 2—are significantly reduced at high concentrations of boric acid when NO− 3 is present. These results are explained by established reaction schemes for the radiolysis of aqueous solution. Based upon the behavior of NO− 2 from nitrate solutions, it is suggested that NO− 2 reacts with H3BO3 or H2BO3 radicals, the plausible reaction product from the reaction H3BO3+OH →; H2O+H2BO3.

Gamma-Radiolysis of Aqueous Boric Acid Solution

The γ-radiolysis of aqueous boric acid solutions of relatively high concentration has been studied. Boric acid significantly promotes hydrogen formation up to 10−7 mol/ml but does not increase oxygen and hydrogen peroxide to any appreciable extent. Since boric acid reacts at a relatively slow rate with species formed by the primary process of water radiolysis, when an effective scavenger for e − aq—the precursor of H2—such as NO− 3 is present, boric acid has no effects upon the total yield of H2 in the range of concentrations studied. However, the yields of other products of the radiolysis—H2O2 and NO− 2—are significantly reduced at high concentrations of boric acid when NO− 3 is present. These results are explained by established reaction schemes for the radiolysis of aqueous solution. Based upon the behavior of NO− 2 from nitrate solutions, it is suggested that NO− 2 reacts with H3BO3 or H2BO3 radicals, the plausible reaction product from the reaction H3BO3+OH →; H2O+H2BO3.

Radiolysis of methylcyclopentane. II. Effects of benzene and 1,3-cyclohexadiene in the liquid phase

The inhibiting effects of benzene and of 1,3-cyclohexadiene (CHD) on the formation of hydrogen during the radiolysis of methylcyclopentane (MCP) have been analyzed according to the nonhomogeneous kinetics of charge scavenging. The results are consistent with the following suggestions: CHD is an efficient scavenger of electrons; benzene is not an efficient scavenger of electrons but it may scavenge positive ions. These reactions offer alternatives to the hydrogen atom scavenging mechanism that has often been postulated in the past. They can decrease the hydrogen yield from MCP by 20 g units (based upon the energy absorbed only in MCP). In addition to the above scavenging mechanisms, which occur at relatively low solute concentrations (~ 1 mole %), benzene and CHD can each take part in a less efficient hydrogen inhibition reaction that can decrease g(H2) by another 1.6 units. This confirms the earlier suggestion (J. Chem. Phys. 33, 71 (I960)) that two different, inhibitable hydrogen forming processes occur during the radiolysis of saturated hydrocarbons.The yields of other products are also reported.

γ-Radiolysis of cyclohexane with electron scavengers. II. Solid cyclohexane at 77 °K

The γ-radiolysis of homogeneous solid solutions of SF6 and N2O in cyclohexane has been examined at 77 °K. With SF6, yields of the major products, hydrogen, bicyclohexyl, and cyclohexene, were all reduced, and no large yields of other products were observed. Thus, since SF6 reduces hydrogen yields by capturing electrons, combination of the SF6 anion and cyclohexane cation does not lead to bond breaking. Experimental evidence suggests that the ratio of disproportionation to combination of cyclohexyl radicals in solid cyclohexane at ~ 186 °K is 0.3 ± 0.2.With N2O, hydrogen yields are decreased to 3.5 G units, but large yields of cyclohexene, bicyclohexyl, and cyclohexanol (4.7, 2.0, and 1.0 G units respectively) are produced. Thus combination of O− and the cyclohexane cation leads to a great deal of bond breaking. The yields are explained by a mechanism similar to Dyne's mechanism for the radiolysis of hydrocarbons. It was, however, necessary to assume that excited states of cyclohexane formed directly behave differently from those formed by electron–cation combination.

Perfluoroalkyl derivatives of nitrogen. Part XXV. The reactions of tristrifluoromethylhydroxylamine and mercuric bistrifluoromethylamide with unsaturated systems

Tristrifluoromethylhydroxylamine reacts with perfluorocyclobutene, on irradiation, to give the 1:1 adduct perfluoro-(1-dimethylamino-2-methoxycyclobutane), and lower yields of other products including perfluoro-(1,2-bisdimethylaminocyclobutane), perfluoro-(2,2′-dimethoxybicyclobutyl), and perfluoro-(2-dimethylamino-2′-methoxybicyclobutyl). Reaction with perfluorobut-2-ene is more complex. Perfluoro-2-azapropene gives low yields of the two isomeric 1:1 adducts perfluoro-(2,3-dimethyl-5-oxa-2,3-diazahexane) and perfluoro-(3,5-dimethyl-2-oxa-3,5-diazahexane).Irradiation of mercuric bistrifluoromethylamide gives perfluorodimethylamine, tetrakistrifluoromethylhydrazine, perfluoro-2-azapropene, and perfluoro-(2,3,5-trimethyl-2,3,5-triazahexane). Photolysis in the presence of perfluorocyclobutene gives perfluoro-(1,2-bisdimethylaminocyclobutane), tetrakistrifluoromethylhydrazine, and smaller amounts of perfluorodimethylamine and perfluoro-2-azapropene.