Comparison of the thermal behaviour of some fatty esters and related ethers by TGA–DTA analysis

Dufaure, Corinne; Thamrin, Usman; Mouloungui, Zéphirin

doi:10.1016/s0040-6031(99)00177-x

Cited by 14 publications

(8 citation statements)

References 5 publications

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“…Thermal analytical approaches such as thermogravimetric analysis (TGA) and pressurized differential scanning calorimetry (P-DSC) were applied to study the oxidation of derivatives of vegetable oils and fats. − Isothermal and non-isothermal (temperature ramping) P-DSC analyses provided accurate and fast screening of the effects of antioxidants in biodiesel. − Non-isothermal DSC and P-DSC were applied to study the oxidation kinetics of long-chain fatty acids and ethyl esters and determined that increasing degree of unsaturation decreases the activation energy ( E a ). − …”

Section: Introductionmentioning

confidence: 99%

Thermal Oxidation of Biodiesel by Pressurized Differential Scanning Calorimetry: Effects of Heating Ramp Rate

Dunn

2012

Energy Fuels

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Despite its many promising characteristics as an alternative diesel fuel, the oxidative stability of biodiesel during storage is a major concern to fuel producers. Extensive degradation can affect fuel quality with respect to viscosity, acid value, cetane number, and other properties. Fuel standards in the U.S. and Europe include the induction period (IP), which is designed to ensure that good quality is maintained during storage. However, IP is measured at 110 °C to accelerate the formation of radicals and induce the oxidation reaction. This work analyzes the kinetics of thermal oxidation of biodiesel from soybean oil (SME) by non-isothermal pressurized differential scanning calorimetry (P-DSC). SME samples from four different sources were evaluated by P-DSC in static mode (zero purge gas flow) under 2000 kPa pressure. Effects of adding antioxidants to SME were also examined. Heating scans were conducted at various ramp rates (β) to determine the onset temperature (OT) of degradation. The Ozawa–Flynn–Wall analytical method was applied to infer activation energy (E a) and pre-exponential Z-factor to calculate rate constant (k) as a function of temperature. Comparison with literature values showed that E a and Z from static mode P-DSC were reliable with respect to oxidation of uninhibited SME. Similar analysis of data for SME treated with antioxidants suggested the nonoxidative thermal degradation dominated during heating. Thus, static mode P-DSC may not be recommended for analyzing the kinetics of thermal oxidation of SME treated with antioxidants. For uninhibited SME, results from static mode P-DSC indicated that detection of secondary degradation products by an oxidative stability or Rancimat instrument may not be a reliable indicator of the actual IP, with respect to isothermal measurement at 50 °C.

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Section: Introductionmentioning

confidence: 99%

Thermal Oxidation of Biodiesel by Pressurized Differential Scanning Calorimetry: Effects of Heating Ramp Rate

Dunn

2012

Energy Fuels

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“…Although Litwinienko et al [15,27,28] studied the oxidation of saturated and unsaturated fatty acid derivatives quite extensively, their work focussed on the kinetics of the initial stages of oxidation, as opposed to residue formation, and they employed atmospheric pressure DSC at temperatures below 300°C. Dufaure et al [29] used simultaneous TGA/DTA to study the thermo-oxidative decomposition of a series of mono-esters and ethers at temperatures up to 600°C, however their focus was on thermal and thermooxidative stability and not on residue formation. Therefore, our understanding of the high temperature oxidation processes of fatty acid methyl esters, and how these processes lead to the formation of thermally-stable residues, is limited.…”

Section: Introductionmentioning

confidence: 99%

Effect of Alkyl Chain Unsaturation on Methyl Ester Thermo‐Oxidative Decomposition and Residue Formation

Pillar

Ginic‐Markovic

Clarke

et al. 2009

J Americ Oil Chem Soc

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The formation of persistent residues by esters used in sheet metal-working lubricant formulations interferes with metal surface cleanliness and impairs the integrity of subsequent surface coatings. Understanding the thermal decomposition and residue formation properties of esters is therefore crucial to minimising residue formation during furnace-based cleaning and will aid in the improvement of coated metal products such as galvanised steel. The thermo-oxidative decomposition profiles of four different methyl esters were studied by Thermogravimetric Analysis (TGA) and Pressure Differential Scanning Calorimetry (PDSC). Chemical characterisation of residues remaining at different stages during the thermo-oxidative decomposition process was achieved by infrared spectroscopic analysis of TGA residue samples. Relationships between ester alkyl chain unsaturation levels and the amount/chemical nature of residue present at high temperature (500°C) were assessed. In the presence of oxygen, polyunsaturated esters decomposed to leave significantly greater amounts of thermally-stable residue, comprising of metal carboxylate and non-volatile oxygenated compounds, than more saturated esters. Given that the formation of analogous residues by more complex esters used in sheet metal-working lubricants may give rise to metal surface coating defects, the results of this study suggest that polyunsaturated esters should be avoided in lubricant formulations where preventing residue formation is of paramount importance.

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“…26 Técnicas automáticas incluem medida da estabilidade do óleo (OSI), Teste em Rancimat ® e análise termogravimétrica (TGA). 27 Técnicas analíticas térmicas, tais como TGA, equipamentos de calorimetria diferencial convencional (DSC) e pressurizado (P-DSC), têm sido aplicadas em análises de oxidação de derivados de petróleo e lubrificantes sintéticos, 28 lubrificantes biodegradáveis, 29 óleo de turbina de avião e polímeros, 30,31 bem como resinas de madeira. Estes estudos geralmente mostram que a P-DSC tem a vantagem de aumentar o número total de moles de oxigênio presente na célula, permitindo a aceleração da reação a baixas temperaturas.…”

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Avaliação da estabilidade oxidativa de biodiesel de óleo de girassol com antioxidantes

Ferrari¹,

Souza²

2009

Quím. Nova

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Recebido em 30/1/08; aceito em 15/7/08; publicado na web em 5/12/08 EVALUATION OF OXIDATION STABILITY OF SUNFLOWER OIL BIODIESEL WITH ANTIOXIDANTS. Biodiesel can contain unsaturated fatty acids, which are susceptible to oxidation, being able to change into polymerized compounds. In this work biodiesel was characterized according to physical-chemistry parameters and the antioxidant activity of butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT) and tert-butylhydroquinone (TBHQ) added to biofuel was analyzed. Biodiesel was submitted to accelerate oxidation in the Schaal oven test, and peroxide value was analyzed.The absorptivity values at 232 nm and 270 nm and oxidative stability in Rancimat ® were determined. It was observed that TBHQ presented superior antioxidant activity than BHT and BHA. Keywords: energy; peroxidation; lipid oxidation. introdUçãoDentre os complexos com grandes potenciais de crescimento está inserido aquele relacionado com a exploração do girassol. Isso porque, a priori, pode-se inferir que no Brasil a produção, o processamento e o consumo da oleaginosa, bem como dos seus principais derivados (óleo e farelo) estão muito abaixo do potencial.1 O girassol é uma cultura que apresenta características desejáveis sob o ponto de vista agronômico, como ciclo curto, elevada qualidade e bom rendimento em óleo, 2 que fazem dela uma boa opção aos produtores brasileiros.Os desafios que o girassol enfrenta no Brasil são basicamente três: oferecer aos produtores uma cultura alternativa que, em caráter complementar, possibilite uma segunda colheita, sobre a mesma área e mesmo ano agrícola; oferecer mais uma matéria-prima oleaginosa às indústrias de processamento de outros grãos, reduzindo sua ociosidade e, finalmente, oferecer ao mercado um óleo comestível de alto valor nutritivo.3 Junta-se a esses desafios a alternativa atual da produção de energia, já que o óleo de girassol pode ser utilizado como matéria-prima para produção de biodiesel. 1 O biodiesel não polui o meio ambiente e também traz vantagens econômicas, pois sua produção e o cultivo de matérias-primas contribuirão para a criação de milhares de novos empregos na agricultura familiar, principalmente nas regiões mais pobres do Brasil. 4 Biodiesel pode ser obtido de fontes renováveis, como óleos vegetais, através de processo de transesterificação, 5,6 no qual ocorre a conversão de triglicerídeos em ésteres de ácidos graxos.7 A maior parte do biodiesel produzido no mundo deriva dos óleos de soja e canola, 8 porém, segundo Parente, 9 todos os óleos vegetais podem ser transformados em biodiesel. Dentre estes, o óleo de girassol destaca-se por suas excelentes características físico-químicas, cuja produção da oleaginosa está entre as maiores culturas do mundo, 10 apresentando viabilidade técnico-ambiental na produção de biocombustíveis. 11O perfil de ácidos graxos dos óleos e gorduras favorece o desenvolvimento da rancidez oxidativa devido à quantidade de ácidos graxos insaturados, principalmente os ácidos oléico (C18:1), linoléico (C18:2) e l...

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Comparison of the thermal behaviour of some fatty esters and related ethers by TGA–DTA analysis

Cited by 14 publications

References 5 publications

Thermal Oxidation of Biodiesel by Pressurized Differential Scanning Calorimetry: Effects of Heating Ramp Rate

Thermal Oxidation of Biodiesel by Pressurized Differential Scanning Calorimetry: Effects of Heating Ramp Rate

Effect of Alkyl Chain Unsaturation on Methyl Ester Thermo‐Oxidative Decomposition and Residue Formation

Avaliação da estabilidade oxidativa de biodiesel de óleo de girassol com antioxidantes

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