The paper describes transesterification of oil by methanol with use of cosolvents such as ethyl acetate, tetrahydrofuran, hexane, acetone and diethyl ether at catalyst homogeneous (potassium hydroxide) and heterogeneous (mixed oxides). The cosolvents dissolve oil and methanol to form a single (homogeneous) phase, which increases the reaction rate. Therefore, the biodiesel production will be environmentally friendly because less energy is consumed, which increases sustainability. The whole binodal curve of ternary plots of oil, methanol and cosolvent was determined to find the molar ratio, in which the reaction mixture forms a single phase. The ethyl acetate and tetrahydrofuran have relatively small heterogeneous region, because of the similarity of their electric dipole moment with methanol. After transesterification, the detailed analysis of ester and also glycerol phase was carried out. For homogeneous catalyst, the highest esters content in the ester phase was achieved with tetrahydrofuran. For heterogeneous catalyst, the ester content was lower with cosolvent than without cosolvent, probably due to dilution of reaction components by cosolvent or bonding of cosolvent to the active sites of the catalyst.
- MeSH
- Biofuels * MeSH
- Esterification MeSH
- Esters * MeSH
- Catalysis MeSH
- Methanol MeSH
- Plant Oils MeSH
- Publication type
- Journal Article MeSH
Photocatalytic degradation of pharmaceuticals (hydrocortisone, estradiol, and verapamil) and personal care product additives (parabens-methyl, ethyl, and propyl derivatives) was investigated in the homogeneous phase (with ferric ions as the catalyst) and on TiO2. Ferric ions in concentrations corresponding to concentrations in natural water bodies were shown to be a significant accelerator of the degradation in homogeneous reaction mixtures. In heterogeneous photocatalytic reactions on TiO2, lower reaction rates, but mineralisation to higher extents, were observed.
- MeSH
- Estradiol chemistry MeSH
- Photolysis radiation effects MeSH
- Hydrocortisone chemistry MeSH
- Catalysis MeSH
- Pharmaceutical Preparations chemistry MeSH
- Parabens chemistry MeSH
- Spectrophotometry, Ultraviolet MeSH
- Titanium chemistry MeSH
- Ultraviolet Rays * MeSH
- Verapamil chemistry MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
... 200 -- Not all carboxylic acid derivatives are equally reactive 205 Acid catalysts increase the reactivity ... ... and reactions in transition metal complexes 1073 -- Palladium is the most widely used metal in homogeneous ... ... Asymmetric formation of carbon-carbon bonds 1126 -- Asymmetric aldol reactions 1129 -- Enzymes as catalysts ...
Second edition xxv, 1234 stran : ilustrace ; 28 cm
- Conspectus
- Organická chemie
- NML Fields
- chemie, klinická chemie
- NML Publication type
- učebnice vysokých škol
The effects of phase separation temperatures (5-90°C) on losses of higher fatty acid (C(16) and C(18)) ethyl esters in the glycerol phase were investigated. Losses of ethyl esters produced from ethanolysis of rapeseed oil were 30-60% higher when NaOH rather than KOH was used as homogeneous catalyst. The losses decreased with an increase in separation temperature, resulting in an increase in the yield of the ester phase. The concentration of impurities (e.g. alkali metals, free glycerol and glycerides) in the ester phase increased with increasing separation temperature due reversible transesterification and reciprocal solubility of the compounds. Carbonates formed during neutralization of the catalysts are also transesterification catalysts and they cause reverse reaction. The ethyl ester bound in the glycerol phase during NaOH-mediated catalysis can be extracted by heating the separated glycerol phase to 60-90°C. The ester yield is increasing with increasing separation temperature, however with decreasing quality.
Uveden postup při současné identifikaci a kvantifikaci a amfetaminu a metamfetaminu v lidských vlasech. Metoda zahrnuje promytí vlasů (postupně destilovaná voda teploty asi 50 'C, 0,1M kyselina chlorovodíková, destilovaná voda do neutrální reakce, metanol), usušení na vzduchu, homogenizaci rozstříháním (1 - 2 mm délky), alkalickou hydrolýzu (20 mg vlasů, 1 ml IM hydroxidu sodného, 55 °C, 120 min.), neutralizaci IM kyselinou chlorovodíkovou na pH = 7, extraktivní benzoylaci s 2,3,4,5,6-pentafluorobenzoylchloridem (0,3 ml IM hydroxidu sodného, 4 ml cyklohexanu, 30 lil cyklohexylaminu v cyklohexanu koncentrace 20 ng/μl - vnitřní standard, 50 μl vodného roztoku trietylaminhydrochloridu koncentrace 100 mg/ml - katalyzátor reakce a 10 μl derivatizačního cinidla 2,3,4,5,6-pentafluorobenzoylchloridu ředění 1:10, třepáni 5 min. v ruce a 10 min. ponechani v klidu), odstředění (5 min., 3000 ot./min.), odebrání 2 ml cyklohexanové vrstvy, její odpaření při 40 °C v dusíkové atmosféře a naředění 100 μl cyklohexanu. Derivatizovaný extrakt byl podroben analýze metodou GC-MS. Uvedený postup byl použit k segmentační analýze vlasů dvou osob dlouhodobě zneužívajících metamfetamin. Nalezené koncentrace se pohybovaly v rozmezi U,99 - 5,25 mg/kg metamfetaminu a 0,13 - 0,73 mg/kg amfetaminu.
The authors present a procedure of concurrent identification and quantification of amphetamine and metamphetamine in human hair. The method involves rinsing of the hair (distilled water 55 °C, 0.1 M hydrochloric acid, distilled water to neutral reaction , methanol) drying in air, homogenization by cutting (1-2 mm long), alkaline hydrolysis (20 mg hair, 1 ml IM sodium hydroxide, 55 "C, 120 min.), neutralization with 1 M hydrochloric acid to pH=7, extracting benzoylation with 2,3,4,5,6-pentafluorobenzoyl chloride (0.3 ml 1 M sodium hydroxide, 4 ml cyclohexane, 30 ul cyclohexylamine in cyclohexane of a concentration of 20 ng/ul - internal standard, 50 ul aqueous ^oiution of triethylamine hydrochloride concentration of 100 mg/ml - reaction catalyst and 10 ul of derivation agent 2,3,4,5,6-pentafluorobenzoyl chloride dilution 1:10 , shaking for 5 mins. by hand and leaving to stand for 10 mins.), centrifugation (5 mins., 3000 rotations/min.), collection of 2 ml cyclohexane layer, its evaporation at 40 *C in nitrogen atmosphere and dilution with 100 ul cyclohexane.The derivated exctract was subjected to analysis by the GC-MS method. The procedure was used for segmentation analysis of hair of two subjects abusing metamphetamine for prolonged periods. The revealed concentrations varied within the range of 0.99-5.25 mg/kg metamphetamine and 0.13-0.73 mgAcg amphetamine.
- MeSH
- Amphetamine analysis MeSH
- Chromatography, Gas methods instrumentation MeSH
- Humans MeSH
- Sequence Analysis methods MeSH
- Forensic Medicine MeSH
- Spectrometry, Mass, Secondary Ion MeSH
- Hair MeSH
- Check Tag
- Humans MeSH
- Publication type
- Review MeSH
... Origins of Enantiomeric Homogeneity in Nature 209 6.5. ... ... Enantioselective Reactions with Chiral Nonracemic Catalysts 947 d. ...
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