Samir K. Konar

Fast one-phase oil-rich processes for the preparation of vegetable oil methyl esters

Abstract A re-evaluation of kinetic data shows that the methoxide base-catalyzed methanolysis of soybean oil at 40°C (6:1 methanol:oil molar ratio) to form methyl esters proceeds approximately 15 times more slowly than butanolysis at 30°C. This is interpreted to be the result of a two-phase reaction in which methanolysis occurs only in the methanol phase. Low oil concentration in methanol causes the slow reaction rate; a slow dissolving rate of the oil in the methanol causes an initiation period. Intermediate mono- and diglycerides preferentially remain in the methanol, and react further, thus explaining the deviation from second-order kinetics. The same explanations apply for hydroxide ion catalyzed methanolysis. At the 6:1 methanol:oil molar ratio the addition of a cosolvent, such as 1.25 volumes of tetrahydrofuran (THF) per volume of methanol, produces an oil-dominant one-phase system in which methanolysis speeds up dramatically and occurs as fast as butanolysis. The critical separation of the glycerol-rich phase still occurs and does so faster than in the cosolvent-free system. For THF, recycle of solvent is simplified because of the similar boiling points of THF (67°C) and methanol (65°C). Possible explanations for the abnormal slowing of the methanolysis reactions are presented in terms of (1) lower rate constants for mono- and diglyceride reactions due to the formation of cyclic intermediates, (2) a fall in the polarity of the reaction mixture due to either methanol depletion or mixing of the oil, methanol and cosolvent, and (3) depletion of hydroxide ion when this is present.

Fuels and chemicals from sewage sludge: 1. The solvent extraction and composition of a lipid from a raw sewage sludge

Abstract With the objective of producing a low-nitrogen and low-sulphur-containing substrate for pyrolysis to liquids, the lipid fraction of a dried raw Atlanta sludge was extracted with both chloroform and toluene. Although the solvents proved equally good for extraction of lipids, toluene is preferred because the pyrolysis of any residual chloroform in the extractive could present environmental problems. In Soxhlet extraction warm solvent removed about 12 wt% lipid whereas extraction by contact with boiling solvent gave 17–18 wt% lipid. Soxhlet extraction of the sludge resulted in 99.5% rejection of nitrogen and 94% rejection of sulphur. Boiling extraction rejected 99% nitrogen and 84% sulphur. The Soxhlet extract contained 10–13% oxygen whereas boiling extraction gave a lipid containing 14–16% oxygen. On a moisture-free basis, the recovered lipid, 91%, from the separation of the toluene extract was comprised of 65% free fatty acids, 7% glyceride fatty acids and 28% unsaponifiable material. The unsaponifiable matter had a distribution of alkanes ranging from C9 to C16, n-nonane and n-pentadecane being the major hydrocarbons present. The free fatty acid esters and the glyceride fatty acid esters had a distribution of fatty acids ranging from C12 to C18. Palmitic, stearic and oleic acids appeared to be the major fatty acids present. These results are significant for the catalytic thermal liquefaction of sewage sludge lipids for the production of fuel and chemical feedstocks.

Fuels and chemicals from sewage sludge: 3. Hydrocarbon liquids from the catalytic pyrolysis of sewage sludge lipids over activated alumina

Toluene-extracted lipids (obtained by extraction with boiling toluene) from a dried raw Atlanta sewage sludge were pyrolysed over activated alumina at 450 °C and atmospheric pressure. Pyrolysis yielded low-viscosity liquids (10.7–67.5 wt%), non-condensable gases (12.1–15.6 wt%), semi-solids (only at higher weight-hourly space velocity) and water. The liquid products were hydrocarbon mixtures which contained predominantly alkanes. Infrared spectra, as well as proton-decoupled 13C nuclear magnetic resonance, confirmed the absence of carbonyl groups in the pyrolysed liquid products; showing that even the carboxylic acids, the major component of the separated lipid fraction, did not survive the pyrolysis reaction. Gas chromatography of the liquid products showed a uniform hydrocarbon distribution across the C6–C20 mass range. Non-condensable gases consisted of carbon dioxide, carbon monoxide, methane, ethane, ethene and C3–C5 compounds. This process resulted in rejection of both nitrogen and sulfur. The lipid extract only contained 1 wt% of the nitrogen and 16 wt% of the sulfur in the sludge. But these elements were reduced by a further 84% in the liquid product with respect to the lipid. The pyrolysed liquid contained 0.08 wt% nitrogen and 0.22 wt% sulfur. This liquid has a great potential to be used as diesel fuel, heating fuel and chemical feedstocks.

Fuels and chemicals from sewage sludge: 2. The production of alkanes and alkenes by the pyrolysis of triglycerides over activated alumina

Abstract Triolein, canola oil, trilaurin and coconut oil were pyrolysed over activated alumina at 450°C and atmospheric pressure. The liquid products were hydrocarbon mixtures which contained both alkanes and alkenes. I.r. spectra confirmed the absence of carbonyl groups in all the pyrolysed products. Decoupled 13 C n.m.r. supported this as well as showing the presence of thermodynamically unfavourable terminal double bonds. These were probably formed by a gamma hydrogen transfer mechanism in which the glycerol moiety together with the ester carbonyl group was lost. There were 14.3, 17.1, 10.1 and 13.4 carbon atoms per double bond, respectively in the liquid products of tiolein, canola oil, trilaurin and coconut oil pyrolysis. Gas chromatography showed some cracking of the hydrocarbon chains with a preference for C6 and C7 products from triolein and canola oil pyrolysis and C9 and C11 products from trilaurin and coconut oil pyrolysis, but otherwise a uniform distribution across the C6 to C16 mass range. These results are significant for the pyrolysis of the lipid fraction which can be isolated by the solvent extraction of sewage sludge, as well as to the pyrolysis of wastes from food processing industries.

Phase diagrams for oil/methanol/ether mixtures

One-phase transmethylations of vegetable oils with methanol to form methyl esters occur considerably faster than conventional two-phase reactions. Addition of simple ethers is an efficient method for producing a single phase. Ternary phase diagrams have been determined at 23°C for oil/methanol/ether mixtures; these are useful when applying the one-phase method across a wide range of conditions. Soybean, canola, palm, and coconut oils were used in combination with five ethers, namely, tetrahydrofuran (THF), 1,4-dioxane (DO), diethyl ether (DE), diisopropyl ether (DI), andtert-butyl methyl ether (TBM). All five ethers can produce miscibility for all methanol/oil compositions. The ether/methanol volumetric ratios required for miscibility at a methanol/soybean or canola oil volumetric ratio of 0.20 (5.4 molar ratio) at 23°C are: THF, 1.15; DO, 1.60; DE, 1.38 DI, 1.57; and TBM, 1.57. For THF, this results in one-phase mixtures that contain 65 vol% oil. Soybean and canola oil form identical diagrams. Palm oil requires slightly less ether at the lower methanol concentrations, but coconut oil requires considerably less across the whole concentration range. Acid-catalyzed reactions, when performed at the boiling point of the most volatile component, require less ether than predicted from the diagrams.

Development and characterization of flexible epoxy foam with reactive liquid rubber and starch

Flexible foams are prepared using carboxyl-terminated butadiene-acrylonitrile rubber (CTBN), diglycidyl ether of bisphenol A epoxy resin and a chemical blowing agent. Central composite design experiments are conducted to investigate the influences of three independent variables, i.e., the ratio of CTBN to epoxy resin, the amounts of curing agent (dicyandiamide) and blowing agent (azodicarbonamide), on the foam performances. After that, epoxy foams are also characterized for mechanical properties to explore the effects of the aforesaid ratio, accelerator type, starch and foaming methods. SEM analysis is used to evaluate the changes in cell characterizations.

Linear Mono-Olefines by Thermal Deoxygenation of Lipids Over Alumina

When lipids, in the form of triglycerides and fatty acids, are passed over a suitably demoisturized activated alumina catalyst at 450°C and a weight-hourly space velocity of approximately 0.5, high yields of deoxygenated liquids, containing mostly linear mono-olefines, are obtained. Fatty acids are intermediates in one of the two major pathways by which triglycerides are deoxygenated, the other pathway being the direct production of olefines having three less carbon atoms than the triglyceride side chains. The fatty acids are converted to symmetrical ketones, which then form methyl ketones and mono-olefines, presumably by a γ-hydrogen transfer mechanism. The methyl ketones can 1) reduce to alcohols, which then dehydrate to olefines, and 2) oxidize to carboxylic acids, probably via isomerization to aldehydes. The reduction and oxidation are likely coupled because the alumina does not have reductive or oxidizing properties. The new fatty acids ultimately yield mono-olefines which possess one more carbon atom than the original methyl ketones. Catalyst deactivation appears to be caused mainly by the deoxygenation of the methyl ketones. This can be overcome by a simple strategy designed to maintain the balance of acidic sites and/or provide some required hydrogen atoms. The results are relevant to the utilization of waste fats and oils, possibly as detergent precursors, as well as to the biogenesis of petroleum.

Liquid Hydrocarbons from the Extraction and Catalytic Pyrolysis of Sewage Sludge

The lipid fraction of a dried raw Atlanta sludge was extracted with both chloroform and toluene. Although the solvents are equally good for extraction, toluene is preferred because the pyrolysis of any residual chloroform in the extractives could present environmental problems such as the formation of dioxin and other chlorinated organics. Toluene-extracted lipids were then pyrolysed over activated alumina at 450°C and atmospheric pressure. Pyrolysis yielded low-viscosity liquids (68–75 wt%), non-condensable gases, small amounts of solids, and water. The liquid products were hydrocarbon mixtures which contained predominantly alkanes. Infrared spectra as well as 13C nuclear magnetic resonance confirmed the absence of carbonyl groups in the pyrolysed liquid products and therefore showed that even the carboxylic acids of the separated lipid fraction did not survive the pyrolysis reaction. Gas chromatography of the liquid products showed a uniform hydrocarbon chain length distribution across the C7 to C17 mass range. Non-condensable gases consisted of carbon monoxide, carbon dioxide, methane, and C2 to C5 compounds. Carbon dioxide was the major component contributing up to 41–70 wt% of the total gases. Whereas the extraction removed 99% nitrogen the pyrolysis rejected very little (0–38%). The pyrolysis, however, did reject as much as 62% of the sulphur. The results are very significant because in direct sewage sludge pyrolysis long chain carboxylic acids survive, resulting in high-viscosity oils.

Alkanes and Alkenes from the Pyrolysis of Triglycerides over Activated Alumina

Pyrolysis of unsaturated triglycerides (triolein and canola oil) and saturated triglycerides (trilaurin and coconut oil) over activated alumina at 450°C and at atmospheric pressure, produced liquid hydrocarbon mixtures which contained both alkanes and alkenes. Infrared spectra confirmed the absence of carbonyl groups in all the pyrolyzed products. Decoupled i3C nuclear magnetic resonance supported this as well as showing the presence of thermodynamically unfavourable terminal double bonds. The latter were presumably formed by a gamma hydrogen transfer mechanism in which the glycerol moiety together with the ester carbonyl group was lost. Catalytic hydrogenation indicated that there were 14.3, 17.1, 10.1, and 13.4 carbon atoms per double bond, respectively in the liquid products of triolein, canola oil, trilaurin, and coconut oil pyrolysis. Gas chromatography of the liquid products showed some cracking of the hydrocarbon chains with a preference for C6 and C7 products from triolein and canola oil pyrolysis and C9 and C 11 products from trilaurin and coconut oil pyrolysis, but otherwise a uniform distribution across the C6 to C16 mass range. Gas chromatography of the gaseous products from all four substrates indicated the presence of carbon dioxide, carbon monoxide, methane, ethane, ethene, and C3 to C5 compounds. These results have implications for the pyrolysis of the lipid fraction which can be isolated by the solvent extraction of sewage sludge, as well as for the pyrolysis of wastes from food processing industries.