Sigurd Schober - Academia.edu (original) (raw)

Papers by Sigurd Schober

Archivo Digital UPM (Universidad Politécnica de Madrid), Sep 4, 2015

16th European Biomass Conference and Exhibition, 2008

Proceedings of the Virtual 2021 AOCS Annual Meeting & Expo, 2021

Renewable Energy, 2019

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

European Journal of Lipid Science and Technology, 2021

Waste animal fats represent a very attractive feedstock for biodiesel production. Primary fatty a... more Waste animal fats represent a very attractive feedstock for biodiesel production. Primary fatty acid amides (PFAA) are a class or bioactive signaling lipids found in mammalian organisms, as well as several plant families. Waste animal fat coming from rendering plants can obtain up to 2.0% PFAA. After the conversion process they pose a risk in the final biodiesel as they can lead to deposits in storage tanks or plug fuel filters. In this paper, a method for efficient separation and quantification of PFAAs in waste animal fat is presented. The method consists of separation of PFAAs via solid phase extraction (SPE) using cartridges with 60 Å silica as stationary phase. The most effective eluents are determined to be hexane: ethyl acetate followed by chloroform: 2-propanol. The isolated PFAAs are identified and quantified via gas chromatography-flame ionization detector (GC-FID) using nonadecanoic acid amide as an internal standard. The recovery of PFAAs in lard as matrix is determined to be around 100%. Six real samples are analyzed for the content of PFAAs leading to concentrations between 0.04% and 1%. Additionally, the limits of detection and quantification are determined to be 0.002% and 0.005%, respectively. Practical applications: The developed method is an efficient tool for characterization and determination of primary fatty acid amides in animal fat used as starting material for biodiesel production. The developed simple and efficient separation of PFAA via SPE and GC-FID analysis without derivatization can also be applied to other biological fat samples, such as fat tissue, and plasma samples or microbial oils.

European Journal of Lipid Science and Technology, 2018

† This article has been accepted for publication and undergone full peer review but has not been ... more † This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as

Proceedings of the …, 2008

ABSTRACT: As fossil reserves become scarcer and the price for crude oil drastically increases, ne... more ABSTRACT: As fossil reserves become scarcer and the price for crude oil drastically increases, new energy sources have to be explored. The transport sector today mainly depends on liquid fuels and an opportunity to substitute fossil fuels is biofuels. Thus, the European ...

2019 IEEE 20th International Conference on Dielectric Liquids (ICDL), 2019

To determine the reliability of furan compound analysis for insulation-system health prediction, ... more To determine the reliability of furan compound analysis for insulation-system health prediction, the furan level found in oil, paper and pressboard was monitored throughout a large-scale ageing study. Therefore, thermally upgraded and normal Kraft paper as well as transformer pressboard were immersed in 4 different types of insulation liquid (mineral oil, G-t-L oil, synthetic and natural ester) at 3 different ageing temperatures (110, 130 and 150circmathrmC)150^{\circ}\mathrm{C})150circmathrmC) and studied throughout a 56 day ageing setup, resulting in 100 mixed samples and 300 furan analyses. While the evolution of furan compounds in each system was somehow steady, comparisons between different material mixes and temperatures show significant aberrations. For similar stages of wear, standard deviations of 100% and more are detectable for the total furan compound concentration in oil, while deviations in solid insulation materials can be even higher. Due to the complexity and high number of variables, irregular analysis intervals without supporting information seem to be highly arguable for transformer health prediction.

2020 IEEE 3rd International Conference on Dielectrics (ICD), 2020

To determine the long-term persistence of stabilizing additives in thermally upgraded Kraft paper... more To determine the long-term persistence of stabilizing additives in thermally upgraded Kraft paper insulation material under operation conditions, the nitrogen migration from the solid material into the encircling insulation material was monitored as part of a large-scale ageing study. Therefore, thermally upgraded as well as normal Kraft paper, combined with pressboard, copper and sheet metal in representative amounts and ratios, was immersed in different types of insulation liquids (mineral oil, G-t-L oil, synthetic as well as natural ester). A continuous 56-day ageing experiment under oxygen-free conditions at elevated temperatures (130 and 150°C) was conducted, with a continuous sampling interval of 2 weeks. The nitrogen concentration of the embedding insulation liquids stayed constant for every insulation liquid aged with natural Kraft paper material, whereas a clear increase of nitrogen levels could be observed over time as soon as thermally upgraded Kraft paper was immersed into the insulation liquids. For prolonged ageing periods at 150°C the measured nitrogen levels in the insulation liquid could rise by as much as 120 ppm, corresponding to nearly 0.3% of dry insulation paper mass, indicating a significant loss of nitrogen-rich stabilizing agents into the corresponding insulation liquid just within weeks of ageing.

Research and Technology Development (RTD) cooperation between Europe and Latin America in the fie... more Research and Technology Development (RTD) cooperation between Europe and Latin America in the field of biofuels is seen as important contribution to the development of a future more sustainable transport sector worldwide. Several LA countries have large potential for the production of biofuels which may be untapped through increased RTD cooperation with European research institutes and industries. The project BioTop (Biofuels Assessment on Technical Opportunities and Research Needs for Latin America), supported by the European Commission in the Seventh Framework Programme for Research and Technological Development (FP7), aimed to foster collaboration between European and Latin American stakeholders in the production of biofuels by identifying priority RTD needs and opportunities and to increase awareness among European and Latin American stakeholders about technical opportunities and the large potential of biofuel production in LA. Research and technology roadmaps have been elaborated to present a set of RTD needs on the following biofuels conversion technologies: 1st generation bioethanol, 2nd generation bioethanol, pure plant oil (PPO) and biodiesel, biomethane, Biomass-to-Liquids (BtL) fuels, and biorefineries. In addition, synthesised country-specific roadmaps have been developed for Argentina, Brazil, Chile, Mexico, and Colombia. These roadmaps illustrate short-, medium-and long-term developments and research gaps in order to support the production of biofuels in Latin America and to identify priority areas for (public and private) RTD efforts. Thereby, the roadmaps include proposed RTD timeframes and highlight specific research topics in order to close knowledge gaps that hinder an effective development path of biofuel technologies in Latin America.

2020 IEEE 3rd International Conference on Dielectrics (ICD), 2020

Insulation liquids perform a vital role in protecting power equipment, such as transformers, from... more Insulation liquids perform a vital role in protecting power equipment, such as transformers, from thermal, electrical and environmental stress. Considering the poor fire-safety properties and low biodegradability of mineral oil as the leading kind of insulation liquid, alternative insulation liquids are of high interest for their implementation in power equipment. In this experiment we aimed to simulate the processes occurring in faulty power equipment by ageing four different kinds of insulation liquids (mineral oil, GTL-insulation liquid, synthetic ester and natural ester) under laboratory conditions. The use of optimized analytical routine methods has allowed us to monitor as well as quantify volatile acid and polymer formations upon ageing of insulation liquids. The ageing process under aerated conditions has led to the formation of formic, acetic and propionic acid, especially in natural ester, alongside notable polymerization effects. All other types of insulation liquids showed significantly lower amounts of volatile acids. Per contra, the experiments conducted under oxygen-free conditions resulted in minimal volatile acid and polymer build-ups in all four insulation liquids.

European Journal of Lipid Science and Technology, 2018

Established analytic methods for the quantification of phorbol esters (PE), which are some toxic ... more Established analytic methods for the quantification of phorbol esters (PE), which are some toxic components in Jatropha curcas L., include HPLC with UV-detection with the commercially available phorbol myristate acetate (PMA) as internal standard or HPLC coupled with MS detection with an external calibration, mostly also with PMA. The differences in the fatty acid side chains and connection to the base structure of PMA compared to PE leads to different UV absorption and MS ionization effects and cause problems for exact quantitative measurements. In this paper, a method is presented which combines both detection types and shows differences between both results. For this purpose, an extraction routine is performed on a PE-containing seed oil to get a PE standard in high purity, which was used for a standard addition method on two real J. curcas oil samples, derived from Ghana and Mexico. Furthermore, a detection window of AE10 ppm for the high accurate ToF-MS detection is set to eliminate isobaric interferences from co-eluting material. Method evaluation of inter-and intra-day variance as well as the recovery rate are performed and determined. With this method a limit of detection of 62 ng mL À1 (UV) and 11 ng mL À1 (MS) can be achieved. Practical Applications: Due to the good biological and technical properties of Jatropha curcas L., its seed oil seems perfect for the application as biodiesel feedstock. The toxicity on the other hand could cause problems when converting side products from the oil production to products of higher value. With the here described method an accurate and precise analysis procedure for the quantification of the toxic compounds namely, phorbol esters, could be applied for toxicity studies or routine checks in industry which is converting plant material from J. curcas, so that no toxic material is used for example as animal feed.

Journal of the American Oil Chemists' Society, 2021

Catalysts, 2019

Lignocellulose-based biorefineries are considered to play a crucial role in reducing fossil-fuel ... more Lignocellulose-based biorefineries are considered to play a crucial role in reducing fossil-fuel dependency. As of now, the fractionation is still the most difficult step of the whole process. The objective of this study is to investigate the potential of a base-catalyzed organosolv process as a fractionation technique for European larch sawdust. A solvent system comprising methanol, water, sodium hydroxide as catalyst, and anthraquinone as co-catalyst is tested. The influence of three independent process variables, temperature (443–446 K), catalyst loading (20–30% w/w), and alcohol-to-water ratio (30–70% v/v), is studied. The process conditions were determined using a fractional factorial experiment. One star point (443 K, 30% v/v MeOH, 30% w/w NaOH) resulted in the most promising results, with a cellulose recovery of 89%, delignification efficiency of 91%, pure lignin yield of 82%, residual carbohydrate content of 2.98% w/w, and an ash content of 1.24% w/w. The isolated lignin fra...

Archivo Digital UPM (Universidad Politécnica de Madrid), Sep 4, 2015

16th European Biomass Conference and Exhibition, 2008

Proceedings of the Virtual 2021 AOCS Annual Meeting & Expo, 2021

Renewable Energy, 2019

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

European Journal of Lipid Science and Technology, 2021

Waste animal fats represent a very attractive feedstock for biodiesel production. Primary fatty a... more Waste animal fats represent a very attractive feedstock for biodiesel production. Primary fatty acid amides (PFAA) are a class or bioactive signaling lipids found in mammalian organisms, as well as several plant families. Waste animal fat coming from rendering plants can obtain up to 2.0% PFAA. After the conversion process they pose a risk in the final biodiesel as they can lead to deposits in storage tanks or plug fuel filters. In this paper, a method for efficient separation and quantification of PFAAs in waste animal fat is presented. The method consists of separation of PFAAs via solid phase extraction (SPE) using cartridges with 60 Å silica as stationary phase. The most effective eluents are determined to be hexane: ethyl acetate followed by chloroform: 2-propanol. The isolated PFAAs are identified and quantified via gas chromatography-flame ionization detector (GC-FID) using nonadecanoic acid amide as an internal standard. The recovery of PFAAs in lard as matrix is determined to be around 100%. Six real samples are analyzed for the content of PFAAs leading to concentrations between 0.04% and 1%. Additionally, the limits of detection and quantification are determined to be 0.002% and 0.005%, respectively. Practical applications: The developed method is an efficient tool for characterization and determination of primary fatty acid amides in animal fat used as starting material for biodiesel production. The developed simple and efficient separation of PFAA via SPE and GC-FID analysis without derivatization can also be applied to other biological fat samples, such as fat tissue, and plasma samples or microbial oils.

European Journal of Lipid Science and Technology, 2018

† This article has been accepted for publication and undergone full peer review but has not been ... more † This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as

Proceedings of the …, 2008

ABSTRACT: As fossil reserves become scarcer and the price for crude oil drastically increases, ne... more ABSTRACT: As fossil reserves become scarcer and the price for crude oil drastically increases, new energy sources have to be explored. The transport sector today mainly depends on liquid fuels and an opportunity to substitute fossil fuels is biofuels. Thus, the European ...

2019 IEEE 20th International Conference on Dielectric Liquids (ICDL), 2019

To determine the reliability of furan compound analysis for insulation-system health prediction, ... more To determine the reliability of furan compound analysis for insulation-system health prediction, the furan level found in oil, paper and pressboard was monitored throughout a large-scale ageing study. Therefore, thermally upgraded and normal Kraft paper as well as transformer pressboard were immersed in 4 different types of insulation liquid (mineral oil, G-t-L oil, synthetic and natural ester) at 3 different ageing temperatures (110, 130 and 150circmathrmC)150^{\circ}\mathrm{C})150circmathrmC) and studied throughout a 56 day ageing setup, resulting in 100 mixed samples and 300 furan analyses. While the evolution of furan compounds in each system was somehow steady, comparisons between different material mixes and temperatures show significant aberrations. For similar stages of wear, standard deviations of 100% and more are detectable for the total furan compound concentration in oil, while deviations in solid insulation materials can be even higher. Due to the complexity and high number of variables, irregular analysis intervals without supporting information seem to be highly arguable for transformer health prediction.

2020 IEEE 3rd International Conference on Dielectrics (ICD), 2020

To determine the long-term persistence of stabilizing additives in thermally upgraded Kraft paper... more To determine the long-term persistence of stabilizing additives in thermally upgraded Kraft paper insulation material under operation conditions, the nitrogen migration from the solid material into the encircling insulation material was monitored as part of a large-scale ageing study. Therefore, thermally upgraded as well as normal Kraft paper, combined with pressboard, copper and sheet metal in representative amounts and ratios, was immersed in different types of insulation liquids (mineral oil, G-t-L oil, synthetic as well as natural ester). A continuous 56-day ageing experiment under oxygen-free conditions at elevated temperatures (130 and 150°C) was conducted, with a continuous sampling interval of 2 weeks. The nitrogen concentration of the embedding insulation liquids stayed constant for every insulation liquid aged with natural Kraft paper material, whereas a clear increase of nitrogen levels could be observed over time as soon as thermally upgraded Kraft paper was immersed into the insulation liquids. For prolonged ageing periods at 150°C the measured nitrogen levels in the insulation liquid could rise by as much as 120 ppm, corresponding to nearly 0.3% of dry insulation paper mass, indicating a significant loss of nitrogen-rich stabilizing agents into the corresponding insulation liquid just within weeks of ageing.

Research and Technology Development (RTD) cooperation between Europe and Latin America in the fie... more Research and Technology Development (RTD) cooperation between Europe and Latin America in the field of biofuels is seen as important contribution to the development of a future more sustainable transport sector worldwide. Several LA countries have large potential for the production of biofuels which may be untapped through increased RTD cooperation with European research institutes and industries. The project BioTop (Biofuels Assessment on Technical Opportunities and Research Needs for Latin America), supported by the European Commission in the Seventh Framework Programme for Research and Technological Development (FP7), aimed to foster collaboration between European and Latin American stakeholders in the production of biofuels by identifying priority RTD needs and opportunities and to increase awareness among European and Latin American stakeholders about technical opportunities and the large potential of biofuel production in LA. Research and technology roadmaps have been elaborated to present a set of RTD needs on the following biofuels conversion technologies: 1st generation bioethanol, 2nd generation bioethanol, pure plant oil (PPO) and biodiesel, biomethane, Biomass-to-Liquids (BtL) fuels, and biorefineries. In addition, synthesised country-specific roadmaps have been developed for Argentina, Brazil, Chile, Mexico, and Colombia. These roadmaps illustrate short-, medium-and long-term developments and research gaps in order to support the production of biofuels in Latin America and to identify priority areas for (public and private) RTD efforts. Thereby, the roadmaps include proposed RTD timeframes and highlight specific research topics in order to close knowledge gaps that hinder an effective development path of biofuel technologies in Latin America.

2020 IEEE 3rd International Conference on Dielectrics (ICD), 2020

Insulation liquids perform a vital role in protecting power equipment, such as transformers, from... more Insulation liquids perform a vital role in protecting power equipment, such as transformers, from thermal, electrical and environmental stress. Considering the poor fire-safety properties and low biodegradability of mineral oil as the leading kind of insulation liquid, alternative insulation liquids are of high interest for their implementation in power equipment. In this experiment we aimed to simulate the processes occurring in faulty power equipment by ageing four different kinds of insulation liquids (mineral oil, GTL-insulation liquid, synthetic ester and natural ester) under laboratory conditions. The use of optimized analytical routine methods has allowed us to monitor as well as quantify volatile acid and polymer formations upon ageing of insulation liquids. The ageing process under aerated conditions has led to the formation of formic, acetic and propionic acid, especially in natural ester, alongside notable polymerization effects. All other types of insulation liquids showed significantly lower amounts of volatile acids. Per contra, the experiments conducted under oxygen-free conditions resulted in minimal volatile acid and polymer build-ups in all four insulation liquids.

European Journal of Lipid Science and Technology, 2018

Established analytic methods for the quantification of phorbol esters (PE), which are some toxic ... more Established analytic methods for the quantification of phorbol esters (PE), which are some toxic components in Jatropha curcas L., include HPLC with UV-detection with the commercially available phorbol myristate acetate (PMA) as internal standard or HPLC coupled with MS detection with an external calibration, mostly also with PMA. The differences in the fatty acid side chains and connection to the base structure of PMA compared to PE leads to different UV absorption and MS ionization effects and cause problems for exact quantitative measurements. In this paper, a method is presented which combines both detection types and shows differences between both results. For this purpose, an extraction routine is performed on a PE-containing seed oil to get a PE standard in high purity, which was used for a standard addition method on two real J. curcas oil samples, derived from Ghana and Mexico. Furthermore, a detection window of AE10 ppm for the high accurate ToF-MS detection is set to eliminate isobaric interferences from co-eluting material. Method evaluation of inter-and intra-day variance as well as the recovery rate are performed and determined. With this method a limit of detection of 62 ng mL À1 (UV) and 11 ng mL À1 (MS) can be achieved. Practical Applications: Due to the good biological and technical properties of Jatropha curcas L., its seed oil seems perfect for the application as biodiesel feedstock. The toxicity on the other hand could cause problems when converting side products from the oil production to products of higher value. With the here described method an accurate and precise analysis procedure for the quantification of the toxic compounds namely, phorbol esters, could be applied for toxicity studies or routine checks in industry which is converting plant material from J. curcas, so that no toxic material is used for example as animal feed.

Journal of the American Oil Chemists' Society, 2021

Catalysts, 2019

Lignocellulose-based biorefineries are considered to play a crucial role in reducing fossil-fuel ... more Lignocellulose-based biorefineries are considered to play a crucial role in reducing fossil-fuel dependency. As of now, the fractionation is still the most difficult step of the whole process. The objective of this study is to investigate the potential of a base-catalyzed organosolv process as a fractionation technique for European larch sawdust. A solvent system comprising methanol, water, sodium hydroxide as catalyst, and anthraquinone as co-catalyst is tested. The influence of three independent process variables, temperature (443–446 K), catalyst loading (20–30% w/w), and alcohol-to-water ratio (30–70% v/v), is studied. The process conditions were determined using a fractional factorial experiment. One star point (443 K, 30% v/v MeOH, 30% w/w NaOH) resulted in the most promising results, with a cellulose recovery of 89%, delignification efficiency of 91%, pure lignin yield of 82%, residual carbohydrate content of 2.98% w/w, and an ash content of 1.24% w/w. The isolated lignin fra...