Calcium Benzoate Research Articles

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The performance of a suite of different carboxylic salts of calcium, have been assessed as dual NOx/SOx reducing agents. The salts studied include, calcium magnesium acetate (CMA), calcium acetate (CA), calcium formate (CF), calcium benzoate (CB), calcium propionate (CP) and magnesium acetate (MA). The primary fuel was propane operating with a primary zone stoichiometry fixed at λ1=1.05 and the reburn zone stoichiometry, λ2, was varied between 1.03 and 0.86. Overall stoichiometry, λ3, was 1.15. CMA was also tested using a US Blend coal as the primary fuel. Experiments were performed in a down-fired pulverised coal furnace operating at an output of 80 kWth. Results showed that CMA and CP were the best dual NOx/SO2 performers followed by CB, CA, MA and CF. Also, the co-injection of urea with the carboxylic salts as an advanced reburning agent was studied. The results showed that real improvements in NO reduction over basic reburning of greater than 70% could be obtained depending to a large extent on the initial effectiveness of the reburn fuel as well as nitrogen stoichiometric ratio within the reburn zone. Decomposition of the carboxylic salts was studied by thermo-gravimetric analysis (TGA) yielding information on the release of organic fractions important as precursors for CHi radical formation. Examination of structural and thermo-chemical properties of the carboxylic salts identified a correlation of NO reduction under reburning conditions with volatile organic content. Calcium magnesium acetate and calcium propionate showed superior SO2 capture ability with reductions greater than 70% at Ca/S above 2, around 20% higher than calcium acetate and calcium formate. Magnesium acetate achieved reductions of less than 10% at Mg/S ratios up to 2.5. There is a clear difference in the potential effectiveness of the sorbents as dual NOx/SO2 reductants, since the organic input for a given Ca input varies according to the composition of the sorbent. Some compromise may have to be made when choosing the correct operating conditions since good reductions in SO2 may not give acceptable NOx reductions. However, the application of advanced reburning under these conditions has been shown here to compensate for low initial NOx reductions by basic reburning.

The Effectiveness of Calcium (Magnesium) Acetate and Calcium Benzoate as NOxReduction Agents in Coal Combustion

Abstract A laboratory study was conducted to assess the effectiveness of the chemicals calcium magnesium acetate (CMA), calcium acetate (CA), and calcium benzoate (CB) in reducing NOx emission from coal-fired furnaces. CMA, which is currently being used as a non-corrosive road deicing salt, has demonstrated exceptional effectiveness in our laboratory as an in-boiler S02 removal agent (Levendis et al., 1993). This is due to the affinity of the calcium and magnesium components of CM A for sulfur; the reaction results in solid sulfate salts. The current investigation explored the role of the organic component of CMA, as well as that in CA and CB, in removing NOx emissions that are typically found in post-flame regions of furnaces burning pulverized coal or residual oil. Bench-scale experiments were conducted at gas temperatures ranging from 450 to 1450°C and oxygen concentrations between 0 to 5%. The residence time was in the order of 4 s, Injection of the CMA reagent at a mass ratio of CMA/NO of 41 (or an equivalent acetate/NO molar ratio of 18) reduced NO, by more than 90% (at 0% O2 and temperatures above 850°C) to 50% (at 5% O2 and 650 to 850°C). At an oxygen concentration of 2%, NOx reduction seemed to be most effective between 1000 and 1350°C with NOx reductions of 70 to 80%. The efficacy of calcium acetate (CA) and calcium benzoate (CB) as NO, reducers was also explored, with CA (CA/NO mass ratio of 41 and acetate/NO molar ratio of 15) being less efficient than CMA at a similar φ with oxygen present but as efficient in 0% oxygen. CB (CB/NO mass ratio of 41 with benzoic acid/NO molar ratio of 9) was as efficient as CMA, regardless of O2 concentration, but at temperatures higher by 200°C

Molecular Interaction between Benzoic Acid and Florite and Complex Formation.

The molecular interaction between benzoic acid and florite R (porous calcium silicate) in solid state was studied by using powder X-ray diffraction analysis, infrared (IR)-spectroscopy, differential sanning calorimetry and thermogravimetric analysis. It was found that the mixing ratio, relative humidity and heating significantly affected the molecular behavior of benzoic acid in the physical mixture. In low mixing ratios (up to 30% benzoic acid), benzoic acid was almost transformed to amorphous calcium benzoate within a few hours after mixing. Storage of the physical mixtures containing benzoic acid in the ratio of 40-60% at high relative humidity, or heating them in sealed ampules, accelerated the rate of transformation of benzoic acid to amorphous calcium benzoate and also allowed the formation of a crystalline complex of the following composition : (C6H5COO)2 Ca·C6H5COOH·H2O. The same complex was successfully prepared using benzoic acid and calcim benzoate trihydrate in a 1 : 1 molar ratio by coprecipitation from an aqueous solution, by mechanical grinding and by heating in sealed ampule at 100°C.

Chemical Studies on a Nepalese Panacea - Shilajit (I)

AbstractShilajit is an asphalt-like substance found embedded in rocky sediments in the Himalayas in western Nepal at altitudes between 2500-5000 m. It is popularly used in Nepal as a tonic. Chemical analysis of shilajit revealed that two-thirds by weight of this medicinal material was extractable by warm 50% alcohol. Repeated crystallization of the hydroalcoholic extract has led to the isolation of crystals, which were subsequently identified as calcium benzoate. The antiseptic properties of benzoates may account for the antiseptic effects of shilajit in places where hygiene remains at a low level.

Mechanism of ketonic decarboxylation. Pyrolysis of calcium decanoate

The complex mixtures resulting from pyrolysis of carboxylic acid salts have been analyzed by combined gas chromatography-mass spectrometry with the following results. Pyrolysis of calcium decanoate at 500 produces a homologous series of nonyl ketones, 2-undecanone through 10-nonadecanone ; normal alkanes and monoalkenes of nine carbon atoms or less are also produced. Pyrolysis of calcium decanoate deuterated at C-8, C-9, and C-10 indicates that the smaller alkyl groups in the above ketones originate from the portion of the alkyl chain nearest the carbonyl group. When pyrolyzed in the presence of ferric chloride hexahydrate (a chlorine radical donor), calcium decanoate does not produce ketones but yields only normal alkanes and monoalkenes of nine carbon atoms or less. Calcium benzoate gives benzene and diphenyl ketone upon pyrolysis at 500. The pyrolysate of calcium 2,2-dimethyloctanoate consists of about equal amounts of 2-methyl-l-octene, 2-methyl-2-octene, and 1-hexene. The above data have been interpreted in terms of a free-radical mechanism in which alkyl and acyl radicals act as initiators. hermal decomposition of salts of carboxylic acids T yields symmetrical ketones. For example, calcium acetate when heated to 350 produces acetone and calcium carbonate.lc Mixtures of salts of two different acids pyrolyze to unsymmetrical ketones in varying yields. Thus, a mixture of benzoate and decanoate salts is converted upon pyrolysis to nonyl phenyl ketone in 50% yield.2 In contrast to these straightforward transformations, there are also some anomalous cases which seem to involve a skeletal rearrangement: salts of trimethylacetic acid give a low yield of tert-butyl isobutyl ketone (rather than the expected di-tert-butyl ketone) under certain pyrolysis conditions. In an attempt to study the mechanism of this reaction (known as ketonic decarboxylation), pyrolyses of salt mixtures, one of which is labeled with 13C or 14C in the carbonyl group, were carried out by several authors. The extent of label retention in the resulting unsymmetrical ketone gave an indication of the source of the carbonyl group. Unfortunately, these data and others5-' were not conclusive; nevertheless, they formed the basis for proposing various mechanisms involving carbanions 3 , 4 f 3 5 (see reactions 1 and 2) , carbonium ions4b (see reaction 3), free r a d i c a l ~ ~ ~ > 6 (see reaction 4), and a four-center intermediate' (see reaction 5) . From the variety of mechanisms reported in the literature, it is obvious that the details of this reaction, even after a century of sporadic work, are still not well understood. In most of these investigations, the emphasis has been on the yield and nature of the major product as (1) (a) C. Friedel, Justw Liebigs Ann. Chem., 108, 122 (1858); ( b ) H. Limpricht, ibid., 108, 183 (1858); (c) R. Fittig, ibtd., 110, 17 (1859). (2) C. Granito and H. P. Schultz, J . Org. Chem., 28, 879 (1963). (3) A. L. Miller, N. C. Cook, and F. C . Whitmore, J. Amer. Chem. Soc., 72, 2732 (1950). (4) (a) J. Bell and R. I. Reed, J . Chem. Soc., 1383 (1952); (b) C. C. Lee and J. W. T. Spinks, J . Org. Chem., 18, 1079 (1953); (c) R. I. Reed, J . Chem. Soc., 4423 (1955); (d) V. D. Nefedov, M. A. Toropova, and I. A. Skulskii, Zh. Fir. Khim., 29, 2236 (1955); (e) M. Okubo and R. Goto, Nippon Kagaku Zasshi, 81, 1132 (1960); (f) L. Otvos and L. Noszko, Tetrahedron Lett., 19 (1960). ( 5 ) 0. Neunhoeffer and P. Paschke, Eer. Deut. Chem. Ges. E, 72,919 (1939). (6) W. A. O'Neill and R . I . Reed, J . Chem. Soc., 3911 (1953). (7) (a) R. I. Reed and M. B. Thomley, ibid., 3714 (1957); (b) A. M. Rubinshtein and V. I. Yakerson, Kine?. Katal., 2, 118 (1961). (1) RCOOM R+ COz + M+ R'COOM + RR'COR + MORCH,COOM RCHCOOM + H+ R'COOM + RCHCOOM -t R'CCHCOOM + MOI1 I OR R'CCHCOOM + H+ R'CCH2R + CO, + M' II 0 II I OR

THE RESPONSE TO 14 MEV NEUTRONS OF SOME CHEMICAL DOSIMETER SYSTEMS

The response to 14 Mev neutrons of 10−3 M ferrous sulphate −0.4 M H2SO4, 10−4 M ceric sulphate −0.4 M H2SO4, 10−3 M calcium benzoate, and 10−1 M terephthalic acid −4 × 10−4 M NaOH solutions has been investigated. G values as follows:G(Fe III) = 10.5 ± 0.2, G(Ce III) = 3.13 ± 0.06, G(salicylic acid) = 0.316 ± 0.006, and G(hydroxyterephthalic acid) = 0.474 ± 0.007. These results are compared with those obtained when the same solutions are irradiated with Co60 γ-rays. Although the response to 14 Mev neutrons is only about one half the response of Co60 γ-radiation, the calcium benzoate and the terephthalic acid systems can measure doses as low as 20 and 2 rads, respectively.

A Redetermination of the Salicylic Acid Yield in the Aqueous Calcium Benzoate Dosimeter

G(salicylic acid) or G(Sal) has been determined for 10-3M and 1-4 M aqueous calcium benzoate solutions irradiated with Co60 - rays, 250-Kvcp x rays, 100-Kvcp x rays, and 50-Kvcp x rays. The G(Sal) values for Co60 rays of 0.655 (10-3 M) and 0.595 (10-4 M) are about 6% lower than previously determined values. Possible sources of error in the measurements have been examined and discussed. For the measurement of low doses (16 rads), the use of chromic acid for cleaning irradiation vessels has been shown to yield irreproducible results.

THE RADIOLYSIS OF AQUEOUS CALCIUM BENZOATE AND BENZOIC ACID SOLUTIONS1

Fluorometric techniques were utilized to determine the yields of o-, m-, p-hydroxybemzoic acids and phenol formed and the yield of benzoate ion (G/sub -Bz/ ) consumed in irradiated aerated aqueous calcium benzoate solutions. For 6 x l0/ sup -4/M solutions irradiated with Co/sup 60/ gamma rays, G/sub ortho/ = 0.67, G/ sub meta/ = 0.37 and G/sub para/ 0.37. Similar o: m: p ratios but slightly lower absolute yields were obtained at higher dose rates using 3 Mev x rays. For Co/ sup 60/ gamma -irradiated calcium benzoate solutions G/sub -Bz/ was 2.05 (10/sup -4/M); and G/sub phOH/ was 0.05 (10/sup -3/ M). Initial hydrogen peroxide yields in Co/sup 60/ gamma irradiated solutions were 2.55, 2.35, and 2.30 in 5 x 10/sup -3/M calcium benzoate, 10/sup -2/M benzoic acid, and 5 x l0/sup -4/ calcium benzoate solutions, respectively. Phenyl benzoate. biphenyl, and 4- biphenylcarboxylic acid, if formed, were formed in small yield. For lO-/sup -3/M benzoic acid solutions (in 0.36M H/sub 2/SO/sub 4/) irradiated with 300 kev peak x rays- G/sub CO2/ was 0.68(aerated), O.4(degassed); and G/sub H2/ was 0.6(degassed). The results are discussed in terms of the free radical theory of radiation chemistry. (auth)

THE AQUEOUS BENZOATE SYSTEM AS A SENSITIVE DOSIMETER FOR IONIZING RADIATIONS

The aqueous benzoate system, as typified by 6 × 10−4 M calcium benzoate, meets many of the requirements for a sensitive chemical dosimeter. The concentration of salicylic acid, determined spectrophotofluorometrically, increases linearly with radiation dose in the range 5 to 5000 rads and is independent of temperature from 15 to 45 °C, of energy from 160 kev to 3 Mev, and of dose rate from 4 to about 1000 rads/minute. The decrease in sensitivity with increasing dose rate from 1000 to 85,000 rads/minute is reported.

THE PYROLYSIS OF CALCIUM SALTS OF CARBOXYLIC ACIDS

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