Skip to main content

Nemanja Miletic

University of Kragujevac, Serbia, Food Technology, Faculty of Agronomy in Cacak, Faculty Member

Followers

24

Following

19

Co-authors

2

Public Views

Assistant Professor - Faculty of Agronomy Cacak, University of Kragujevac, Serbia (2016-present)
PostDoc - School of Engineering, University of the Basque Country, Bilbao, Spain (2013-2016)
PhD - Zernike Institute for Advanced Materials, University of Groningen, The Netherlands (2005-2009)
Master degree - Department of Physics, Chemistry and Biology, University of Linkoping, Sweden (2004-2005)
Bachelor degree - Faculty of Technology and Metallurgy, University of Belgrade, Serbia (1998-2005)

less

Interests

Uploads

Papers by Nemanja Miletic

Kinetika ekstrakcije vanilinske kiseline iz semena bundeve

In this sdudy, the extraction of vanillic acid from pumpkin seeds, using the maceration process, ... more In this sdudy, the extraction of vanillic acid from pumpkin seeds, using the maceration process, were investigated. The influence of temperature (25-45oC) and time (10-100 min) on the content of vanillic acid in extracts was confirmed. Based on the experimental results of the extraction of kinetics, a modeling of pumpkin seeds-40% ethanol (v/v) extraction system was performed using hyperbolic model. Also, based on the average values of the RMS, SD and R2, it was found that the hyperbolic model show acceptable agreement.U ovom radu proučena je ekstrakcija vanilinske kiseline iz semena bundeve primenom postupka meceracije. Ispitan je uticaj temperature (25-45oC) i vremena (10-100 min) ekstrakcije na sadržaj vanilinske kiseline u ekstraktima. Na osnovu eksperimentalnih rezultata kinetike ekstrakcije izvešeno je modelovanje ekstrakcionog sistema seme bundeve-40% etanol (v/v) primenom hiperbolnog modela. Takođe, na osnovu srednjih vrednosti RMS, SD i R2 modelovanih i eksperimentalnih vre...

Uticaj Načina Presovanja Na Promene Lešnikovog Ulja Tokom Čuvanja I Senzorna Svojstva Keksa

The changes in the spectrum, peroxide numbers and specific absorbances (at 232 nm and 270 nm) of ... more The changes in the spectrum, peroxide numbers and specific absorbances (at 232 nm and 270 nm) of fresh and storaged oils (4 months at 4 °C) obtained by different hazelnuts pressing were monitored. The results showed reduced viability of the oil obtained from the hazelnut exposed to elevated temperature during conditioning and pressing: changes in the spectrum about 290 nm, a peroxide number close to the legally allowed maximum (7.5 mmolkg-1) and possible presence of secondary oxidation products. Sensory evaluation of biscuits with hazelnut oil showed that the samples belonged to the categories of quality: very good and good. The overall sensory score was highest for biscuits with hazelnut oil pressed in an electric press.

Influence of D and Rec strains of plum pox virus on phenolic profile and antioxidant capacity of fresh plum fruits of ‘Čačanska Lepotica’ cultivar

Spanish Journal of Agricultural Research

Aim of study: To investigate the changes in chemical composition of fresh plum fruits cv. ‘Čačans... more Aim of study: To investigate the changes in chemical composition of fresh plum fruits cv. ‘Čačanska Lepotica’ prompted by the presence of various strains of plum pox virus (PPV). Area of study: Serbia Material and methods: In an experimental orchard of ‘Čačanska Lepotica’ plum cultivar, fruits were picked from virus-free and PPV-infected trees (PPV-D and PPV-Rec strains) in four harvest stages in 2017 and 2018. Fruits were further analyzed on total phenolics, flavonoids, anthocyanins, antioxidant capacity and selected phenolics. Main results: The results indicate that virus infection causes chemical changes to a certain extent, but mostly in initial harvest stages, while the values are equal in later stages. In the last harvest stage, as the most utilizable in commercial purposes, only chlorogenic acid content was affected in 2017, while in 2018 contents of neochlorogenic acid and chrysanthemin were altered by the PPV infection. Total contents of flavonoids and phenolics revealed no...

Polyphenolic Profiles of Selected Medicinal Herbs

The total phenolic contents and contents of main individual phenolics in plant extracts of bilber... more The total phenolic contents and contents of main individual phenolics in plant extracts of bilberry, willow gentian, wild raspberry, spearmint and peppermint were determined. The above-ground parts of plants were subjected to the exhaustive extraction with ethanol using Soxhlet apparatus. The total phenolic content for the medicinal herbs, ranged from 2.8 to 15.2 mg GAE/g dm, were as follows: spearmint > peppermint > willow gentian > wild raspberry > bilberry. Using high-performance liquid chromatography, an extremely high content of rosmarinic acid was revealed in peppermint sample (849 mg/100 g dm). The plant of bilberry was characterized by greater amounts of chlorogenic acid, rutin and sinapinic acid (367, 248, and 229 mg/100 g dm, respectively) than the above-ground parts of other analyzed species.

University of Groningen Properties of Immobilized Candida antarctica Lipase B on Highly Macroporous Copolymer Handayani, Nurrahmi; Miletic, Nemanja; Loos, Katja; Achmad, Sadijah; Wahyuningrum, Deana

In spite of their excellent catalytic properties, enzymes should be improved before their impleme... more In spite of their excellent catalytic properties, enzymes should be improved before their implementation both in industrial and laboratorium scales. Immobilization of enzyme is one of the ways to improve their properties. Candida antarctica lipase B (Cal-B) has been reported in numerous publications to be a particularly useful enzyme catalizing in many type of reaction including regioand enantiosynthesis. For this case, cross-linking of immobilized Cal-B with 1,2,7,8 diepoxy octane is one of methods that proved significantly more stable from denaturation by heat, organic solvents, and proteolysis than lyophilized powder or soluble enzymes. More over, the aim of this procedure is to improve the activity and reusability of lipase. Enzyme kinetics test was carried out by transesterification reaction between 4-nitrophenyl acetate (pNPA) and methanol by varying substrate concentrations, and the result is immobilized enzymes follows the Michaelis-Menten models and their activity is match ...

Isolation and Chemical Profile of Thymus Serpyllum L. and Lavandula Angustifolia Mill. Essential Oils

Uticaj Određenih Stresogenih Faktora Na Kvalitet Goveđeg Mesa

Stress inevitably occurs from farm to slaughter in modern cattle breeding. The effects of stress ... more Stress inevitably occurs from farm to slaughter in modern cattle breeding. The effects of stress on behavior, physiological status, and meat quality have been examined by a number of authors. The mechanism of the effects of stress on physiological and biochemical changes and the consequent effects on meat quality attributes are significantly more limited. This review summarizes the primary stress factors that affect animal welfare and cause biochemical changes during the early postmortem period, which reduces the quality of carcasses and their nutritional quality. In order to obtain high quality meat, further studies are needed to uncover the complex mechanisms mentioned above.

Modeling convective thin-layer drying of carrot slices and quality parameters

Thermal Science, 2021

The influence of thin layer convective dehydration parameters on drying kinetics parameters, chem... more The influence of thin layer convective dehydration parameters on drying kinetics parameters, chemical composition, and color parameters of carrot slices were investigated, and corresponding mathematical models were developed. In the carrot slices, convective dehydration process hot air temperature and the sample slice thickness were varied, while measured, calculated, and modeled responses were: time of dehydration, effective moisture diffusivity, the energy of activation, proteins and cellulose contents, lightness, redness, and yellowness. The obtained results showed that varied convective dehydration process parameters statistically significantly affected all investigated responses except activation energy. The most efficient drying model with the minimum thickness (3 mm) and the maximum drying temperature (70?C) had the shortest drying time (231 minutes). This model had the minimum resistance to mass transfer (the minimum effective moisture diffusivity, 2.04 ? 10?08 ? 7.12 ? 10?0...

Basic parameters of the quality of fresh meat of different types of freshwater fish

Acta agriculturae Serbica, 2017

Analysis of the effect of temperature and reaction time on yields, compositions and oil quality in catalytic and non-catalytic lignin solvolysis in a formic acid/water media using experimental design

Bioresource technology, 2017

The catalytic solvolysis of Norway spruce (Picea abies L.) lignin in a formic acid/water media wa... more The catalytic solvolysis of Norway spruce (Picea abies L.) lignin in a formic acid/water media was explored at different temperatures and reaction times (283-397°C and 21-700min, respectively). Non-catalyzed experiments were compared with the effect of three different type of bifunctional catalysts (Pd/Al2O3, Rh/Al2O3 and Ru/Al2O3) and a solid Lewis acid (γ-Al2O3). We demonstrated that surface response methodology (RSM) and principal component analysis (PCA) were an adequate tool to: (i) evaluate the effect of the catalysts, temperature and reaction time in the oil yield, oil quality (H/C and O/C ratios, and Mw) and composition of the oil, (ii) establish the differences and/or similarities between the three bifunctional catalyst and (iii) to determine the role of the noble metal and the alumina support in the reaction system. In addition, the most active catalysts, Ru/Al2O3, and the optimum reaction conditions were determined (i.e. 340°C and 6h).

Regeneration of surface acid-sites via mild oxidation on dehydration catalysts

Catal. Sci. Technol., 2016

This work reports novel experimental evidence for the use of mild oxidation conditions to remove ... more This work reports novel experimental evidence for the use of mild oxidation conditions to remove humin deposits on active xylose dehydration catalysts that showed deactivation. The catalytic regeneration experiments carried out at 70 °C using iron precursors as catalysts and H2O2 as an oxidant show that the catalysts achieve 95% acid site regeneration using the Fenton chemistry.

Macromol. Rapid Commun. 1/2010

Macromolecular Rapid Communications, 2010

Polyphenolic Content and Antioxidant Capacity in Fruits of Plum (Prunus domestica L.) Cultivars “Valjevka” and “Mildora” as Influenced by Air Drying

Journal of Food Quality, 2013

Impact of raspberry leaf blotch emaravirus on red raspberry ‘Willamette’ fruits

Pesticidi i fitomedicina

Raspberry leaf blotch emaravirus (RLBV) has become established in many Serbian raspberry orchards... more Raspberry leaf blotch emaravirus (RLBV) has become established in many Serbian raspberry orchards as the most prevalent virus of raspberries in the country. The aim of this study was to evaluate the impact of RLBV on the red raspberry ?Willamette? variety. A trial was conducted in four raspberry orchards located in Western Serbia. Fruits from RLBVinfected and uninfected canes were analyzed for fruit size (fruit length, width, height, shape, and weight), soluble solids content, pH, titratable acidity, total sugars, and total phenolic and anthocyanin contents. The results of the study confirmed that RLBV significantly decreases fruit size and weight (9.15-27.49%) of ?Willamette? fruits. Soluble solids content was higher in infected fruits (1.55-7.39%), but the increase was not significant. RLBV did not cause significant changes in titratable acidity of raspberry juice, pH or total sugars content. Total phenolic and anthocyanin contents were higher in fruits of RLBV-infected plants in ...

Improved biocatalysts based on Candida antarctica lipase B immobilization

Phenolic content and antioxidant capacity of fruits of plum cv. 'stanley' (Prunus domestica L.) As influenced by maturity stage and on-tree ripening

Australian Journal of Crop Science

Biocatalysis in Polymer Chemistry

ABSTRACT

Phenolic compounds and antioxidant capacity of dried and candied fruits commonly consumed in Serbia

Czech Journal of Food Sciences

One-pot 2-methyltetrahydrofuran production from levulinic acid in green solvents using Ni-Cu/Al2O3 catalysts

ChemSusChem, 2015

The one-pot hydrogenation of levulinic acid to 2-methyltetrahydrofuran (MTHF) was performed using... more The one-pot hydrogenation of levulinic acid to 2-methyltetrahydrofuran (MTHF) was performed using a series of Ni-Cu/Al2 O3 catalysts in green solvents, such as water and biomass-derived alcohols. Ni/Al2 O3 provided the highest activity, whereas Cu/Al2 O3 was the most selective, reaching a 75 % MTHF yield at 250 °C after 24 h reaction time. Synergetic effects were observed when bimetallic Ni-Cu/Al2 O3 catalysts were used, reaching a 56 % MTHF yield in 5 h at 250 °C for the optimum Ni/Cu ratio. Remarkably, these high yields were obtained using non-noble metal-based catalysts and 2-propanol as the solvent. The catalytic activity and selectivity results are correlated to temperature programmed reduction (TPR), XRD, and STEM characterization data, identifying the role associated with mixed Ni-Cu particles in addition to monometallic Cu and Ni.

Simultaneous catalytic de-polymerization and hydrodeoxygenation of lignin in water/formic acid media with Rh/Al2O3, Ru/Al2O3 and Pd/Al2O3 as bifunctional catalysts

Journal of Analytical and Applied Pyrolysis, 2015

ABSTRACT The catalytic solvolysis of 3 lignins of different sources in a formic acid/water media ... more ABSTRACT The catalytic solvolysis of 3 lignins of different sources in a formic acid/water media using bifunctional Ru/Al2O3, Rh/Al2O3, Pd/Al2O3 catalysts was explored in a batch set-up at different temperatures and reaction times (340 °C-380 °C and 2-6 hours respectively). Blank experiments using only gamma-alumina as catalysts and non-catalyzed experiments were also performed and compared with the supported catalysts results. All the supported catalysts significantly improved the oil yields on a lignin basis, with yields up to 91.5 wt% using the Ru catalyst. The main components phenol, cresol, guaiacol, methylguaiacol, catechol, ethylcatechol, syringol and o-vanillin are found in different concentrations depending on the catalytic system. The stable Lewis acidity in the alumina support has been found to be active in terms of de-polymerization of lignin, leading to lower average molecular weight oils. In addition, it was found that alumina plays a significant role in the re-polymerization mechanism of the monomers. The effect of the type of lignin on the final oil and solid yields was also established, demonstrating that lignins produced by basic pretreatment of biomass do not show significant increase in oil yield when catalysts on an acid support like alumina are used. The interpretation is that acid conditions are needed for efficient de-polymerisation of the lignin.

Kinetika ekstrakcije vanilinske kiseline iz semena bundeve

In this sdudy, the extraction of vanillic acid from pumpkin seeds, using the maceration process, ... more In this sdudy, the extraction of vanillic acid from pumpkin seeds, using the maceration process, were investigated. The influence of temperature (25-45oC) and time (10-100 min) on the content of vanillic acid in extracts was confirmed. Based on the experimental results of the extraction of kinetics, a modeling of pumpkin seeds-40% ethanol (v/v) extraction system was performed using hyperbolic model. Also, based on the average values of the RMS, SD and R2, it was found that the hyperbolic model show acceptable agreement.U ovom radu proučena je ekstrakcija vanilinske kiseline iz semena bundeve primenom postupka meceracije. Ispitan je uticaj temperature (25-45oC) i vremena (10-100 min) ekstrakcije na sadržaj vanilinske kiseline u ekstraktima. Na osnovu eksperimentalnih rezultata kinetike ekstrakcije izvešeno je modelovanje ekstrakcionog sistema seme bundeve-40% etanol (v/v) primenom hiperbolnog modela. Takođe, na osnovu srednjih vrednosti RMS, SD i R2 modelovanih i eksperimentalnih vre...

Uticaj Načina Presovanja Na Promene Lešnikovog Ulja Tokom Čuvanja I Senzorna Svojstva Keksa

The changes in the spectrum, peroxide numbers and specific absorbances (at 232 nm and 270 nm) of ... more The changes in the spectrum, peroxide numbers and specific absorbances (at 232 nm and 270 nm) of fresh and storaged oils (4 months at 4 °C) obtained by different hazelnuts pressing were monitored. The results showed reduced viability of the oil obtained from the hazelnut exposed to elevated temperature during conditioning and pressing: changes in the spectrum about 290 nm, a peroxide number close to the legally allowed maximum (7.5 mmolkg-1) and possible presence of secondary oxidation products. Sensory evaluation of biscuits with hazelnut oil showed that the samples belonged to the categories of quality: very good and good. The overall sensory score was highest for biscuits with hazelnut oil pressed in an electric press.

Influence of D and Rec strains of plum pox virus on phenolic profile and antioxidant capacity of fresh plum fruits of ‘Čačanska Lepotica’ cultivar

Spanish Journal of Agricultural Research

Aim of study: To investigate the changes in chemical composition of fresh plum fruits cv. ‘Čačans... more Aim of study: To investigate the changes in chemical composition of fresh plum fruits cv. ‘Čačanska Lepotica’ prompted by the presence of various strains of plum pox virus (PPV). Area of study: Serbia Material and methods: In an experimental orchard of ‘Čačanska Lepotica’ plum cultivar, fruits were picked from virus-free and PPV-infected trees (PPV-D and PPV-Rec strains) in four harvest stages in 2017 and 2018. Fruits were further analyzed on total phenolics, flavonoids, anthocyanins, antioxidant capacity and selected phenolics. Main results: The results indicate that virus infection causes chemical changes to a certain extent, but mostly in initial harvest stages, while the values are equal in later stages. In the last harvest stage, as the most utilizable in commercial purposes, only chlorogenic acid content was affected in 2017, while in 2018 contents of neochlorogenic acid and chrysanthemin were altered by the PPV infection. Total contents of flavonoids and phenolics revealed no...

Polyphenolic Profiles of Selected Medicinal Herbs

The total phenolic contents and contents of main individual phenolics in plant extracts of bilber... more The total phenolic contents and contents of main individual phenolics in plant extracts of bilberry, willow gentian, wild raspberry, spearmint and peppermint were determined. The above-ground parts of plants were subjected to the exhaustive extraction with ethanol using Soxhlet apparatus. The total phenolic content for the medicinal herbs, ranged from 2.8 to 15.2 mg GAE/g dm, were as follows: spearmint > peppermint > willow gentian > wild raspberry > bilberry. Using high-performance liquid chromatography, an extremely high content of rosmarinic acid was revealed in peppermint sample (849 mg/100 g dm). The plant of bilberry was characterized by greater amounts of chlorogenic acid, rutin and sinapinic acid (367, 248, and 229 mg/100 g dm, respectively) than the above-ground parts of other analyzed species.

University of Groningen Properties of Immobilized Candida antarctica Lipase B on Highly Macroporous Copolymer Handayani, Nurrahmi; Miletic, Nemanja; Loos, Katja; Achmad, Sadijah; Wahyuningrum, Deana

In spite of their excellent catalytic properties, enzymes should be improved before their impleme... more In spite of their excellent catalytic properties, enzymes should be improved before their implementation both in industrial and laboratorium scales. Immobilization of enzyme is one of the ways to improve their properties. Candida antarctica lipase B (Cal-B) has been reported in numerous publications to be a particularly useful enzyme catalizing in many type of reaction including regioand enantiosynthesis. For this case, cross-linking of immobilized Cal-B with 1,2,7,8 diepoxy octane is one of methods that proved significantly more stable from denaturation by heat, organic solvents, and proteolysis than lyophilized powder or soluble enzymes. More over, the aim of this procedure is to improve the activity and reusability of lipase. Enzyme kinetics test was carried out by transesterification reaction between 4-nitrophenyl acetate (pNPA) and methanol by varying substrate concentrations, and the result is immobilized enzymes follows the Michaelis-Menten models and their activity is match ...

Isolation and Chemical Profile of Thymus Serpyllum L. and Lavandula Angustifolia Mill. Essential Oils

Uticaj Određenih Stresogenih Faktora Na Kvalitet Goveđeg Mesa

Stress inevitably occurs from farm to slaughter in modern cattle breeding. The effects of stress ... more Stress inevitably occurs from farm to slaughter in modern cattle breeding. The effects of stress on behavior, physiological status, and meat quality have been examined by a number of authors. The mechanism of the effects of stress on physiological and biochemical changes and the consequent effects on meat quality attributes are significantly more limited. This review summarizes the primary stress factors that affect animal welfare and cause biochemical changes during the early postmortem period, which reduces the quality of carcasses and their nutritional quality. In order to obtain high quality meat, further studies are needed to uncover the complex mechanisms mentioned above.

Modeling convective thin-layer drying of carrot slices and quality parameters

Thermal Science, 2021

The influence of thin layer convective dehydration parameters on drying kinetics parameters, chem... more The influence of thin layer convective dehydration parameters on drying kinetics parameters, chemical composition, and color parameters of carrot slices were investigated, and corresponding mathematical models were developed. In the carrot slices, convective dehydration process hot air temperature and the sample slice thickness were varied, while measured, calculated, and modeled responses were: time of dehydration, effective moisture diffusivity, the energy of activation, proteins and cellulose contents, lightness, redness, and yellowness. The obtained results showed that varied convective dehydration process parameters statistically significantly affected all investigated responses except activation energy. The most efficient drying model with the minimum thickness (3 mm) and the maximum drying temperature (70?C) had the shortest drying time (231 minutes). This model had the minimum resistance to mass transfer (the minimum effective moisture diffusivity, 2.04 ? 10?08 ? 7.12 ? 10?0...

Basic parameters of the quality of fresh meat of different types of freshwater fish

Acta agriculturae Serbica, 2017

Analysis of the effect of temperature and reaction time on yields, compositions and oil quality in catalytic and non-catalytic lignin solvolysis in a formic acid/water media using experimental design

Bioresource technology, 2017

The catalytic solvolysis of Norway spruce (Picea abies L.) lignin in a formic acid/water media wa... more The catalytic solvolysis of Norway spruce (Picea abies L.) lignin in a formic acid/water media was explored at different temperatures and reaction times (283-397°C and 21-700min, respectively). Non-catalyzed experiments were compared with the effect of three different type of bifunctional catalysts (Pd/Al2O3, Rh/Al2O3 and Ru/Al2O3) and a solid Lewis acid (γ-Al2O3). We demonstrated that surface response methodology (RSM) and principal component analysis (PCA) were an adequate tool to: (i) evaluate the effect of the catalysts, temperature and reaction time in the oil yield, oil quality (H/C and O/C ratios, and Mw) and composition of the oil, (ii) establish the differences and/or similarities between the three bifunctional catalyst and (iii) to determine the role of the noble metal and the alumina support in the reaction system. In addition, the most active catalysts, Ru/Al2O3, and the optimum reaction conditions were determined (i.e. 340°C and 6h).

Regeneration of surface acid-sites via mild oxidation on dehydration catalysts

Catal. Sci. Technol., 2016

This work reports novel experimental evidence for the use of mild oxidation conditions to remove ... more This work reports novel experimental evidence for the use of mild oxidation conditions to remove humin deposits on active xylose dehydration catalysts that showed deactivation. The catalytic regeneration experiments carried out at 70 °C using iron precursors as catalysts and H2O2 as an oxidant show that the catalysts achieve 95% acid site regeneration using the Fenton chemistry.

Macromol. Rapid Commun. 1/2010

Macromolecular Rapid Communications, 2010

Polyphenolic Content and Antioxidant Capacity in Fruits of Plum (Prunus domestica L.) Cultivars “Valjevka” and “Mildora” as Influenced by Air Drying

Journal of Food Quality, 2013

Impact of raspberry leaf blotch emaravirus on red raspberry ‘Willamette’ fruits

Pesticidi i fitomedicina

Raspberry leaf blotch emaravirus (RLBV) has become established in many Serbian raspberry orchards... more Raspberry leaf blotch emaravirus (RLBV) has become established in many Serbian raspberry orchards as the most prevalent virus of raspberries in the country. The aim of this study was to evaluate the impact of RLBV on the red raspberry ?Willamette? variety. A trial was conducted in four raspberry orchards located in Western Serbia. Fruits from RLBVinfected and uninfected canes were analyzed for fruit size (fruit length, width, height, shape, and weight), soluble solids content, pH, titratable acidity, total sugars, and total phenolic and anthocyanin contents. The results of the study confirmed that RLBV significantly decreases fruit size and weight (9.15-27.49%) of ?Willamette? fruits. Soluble solids content was higher in infected fruits (1.55-7.39%), but the increase was not significant. RLBV did not cause significant changes in titratable acidity of raspberry juice, pH or total sugars content. Total phenolic and anthocyanin contents were higher in fruits of RLBV-infected plants in ...

Improved biocatalysts based on Candida antarctica lipase B immobilization

Phenolic content and antioxidant capacity of fruits of plum cv. 'stanley' (Prunus domestica L.) As influenced by maturity stage and on-tree ripening

Australian Journal of Crop Science

Biocatalysis in Polymer Chemistry

ABSTRACT

Phenolic compounds and antioxidant capacity of dried and candied fruits commonly consumed in Serbia

Czech Journal of Food Sciences

One-pot 2-methyltetrahydrofuran production from levulinic acid in green solvents using Ni-Cu/Al2O3 catalysts

ChemSusChem, 2015

The one-pot hydrogenation of levulinic acid to 2-methyltetrahydrofuran (MTHF) was performed using... more The one-pot hydrogenation of levulinic acid to 2-methyltetrahydrofuran (MTHF) was performed using a series of Ni-Cu/Al2 O3 catalysts in green solvents, such as water and biomass-derived alcohols. Ni/Al2 O3 provided the highest activity, whereas Cu/Al2 O3 was the most selective, reaching a 75 % MTHF yield at 250 °C after 24 h reaction time. Synergetic effects were observed when bimetallic Ni-Cu/Al2 O3 catalysts were used, reaching a 56 % MTHF yield in 5 h at 250 °C for the optimum Ni/Cu ratio. Remarkably, these high yields were obtained using non-noble metal-based catalysts and 2-propanol as the solvent. The catalytic activity and selectivity results are correlated to temperature programmed reduction (TPR), XRD, and STEM characterization data, identifying the role associated with mixed Ni-Cu particles in addition to monometallic Cu and Ni.

Simultaneous catalytic de-polymerization and hydrodeoxygenation of lignin in water/formic acid media with Rh/Al2O3, Ru/Al2O3 and Pd/Al2O3 as bifunctional catalysts

Journal of Analytical and Applied Pyrolysis, 2015

ABSTRACT The catalytic solvolysis of 3 lignins of different sources in a formic acid/water media ... more ABSTRACT The catalytic solvolysis of 3 lignins of different sources in a formic acid/water media using bifunctional Ru/Al2O3, Rh/Al2O3, Pd/Al2O3 catalysts was explored in a batch set-up at different temperatures and reaction times (340 °C-380 °C and 2-6 hours respectively). Blank experiments using only gamma-alumina as catalysts and non-catalyzed experiments were also performed and compared with the supported catalysts results. All the supported catalysts significantly improved the oil yields on a lignin basis, with yields up to 91.5 wt% using the Ru catalyst. The main components phenol, cresol, guaiacol, methylguaiacol, catechol, ethylcatechol, syringol and o-vanillin are found in different concentrations depending on the catalytic system. The stable Lewis acidity in the alumina support has been found to be active in terms of de-polymerization of lignin, leading to lower average molecular weight oils. In addition, it was found that alumina plays a significant role in the re-polymerization mechanism of the monomers. The effect of the type of lignin on the final oil and solid yields was also established, demonstrating that lignins produced by basic pretreatment of biomass do not show significant increase in oil yield when catalysts on an acid support like alumina are used. The interpretation is that acid conditions are needed for efficient de-polymerisation of the lignin.