M. Siebenhofer

Oxidation of glycerol by 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO) in the presence of laccase.

Glycerol has the potential of being a low-cost and extremely versatile building block. However, current transformation strategies such based on noble-metal-catalysts show several disadvantages including catalyst deactivation or negative environmental impacts. In this study glycerol was oxidized by 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO) in the presence of laccase from Trametes hirsuta. Analysis of the reaction production indicated sequential oxidation to glyceraldehyde, glyceric acid and tartronic acid, finally resulting in mesoxalic acid. The number and nature of oxidation products was depended on the concentration of TEMPO used. At lower TEMPO concentrations (<6mM) the major initial reaction product was glyceraldehyde while at higher concentration in addition considerable amounts of glyceric acid were formed. Glycerol oxidation was also shown with laccase immobilised on alumina pellets which increased laccase stability.

Synthesis of lactic acid from dihydroxyacetone: use of alkaline-earth metal hydroxides

By-products from bio-based processes show great potential as renewable feedstock sources. In this context, upgrading the biodiesel by-product glycerol is highly promising. This paper focuses on the production of lactic acid from dihydroxyacetone, which is a primary oxidation product of glycerol, under mild reaction conditions (ambient pressure and temperatures below 90 °C) with alkaline-earth metal hydroxides. Whereas both Ca(OH)2 and Ba(OH)2 effectively catalysed the formation of lactic acid in the liquid phase, lactic acid was not formed with Mg(OH)2 at 25 °C. The final yield was higher with Ca(OH)2 (59%) than with Ba(OH)2 (50%). With Ca(OH)2, increasing reaction temperatures resulted in higher reaction rates. At 85 °C, however, competing side and degradation reactions were dominating, limiting the yield of lactic acid to 36%. We demonstrated that the method can be directly applied to dihydroxyacetone in fermentation broths. This research opens up a new synthesis route for lactic acid from dihydroxyacetone and glycerol, respectively.

Lactic Acid Production as a New Approach for Exploitation of Glycerol

Electrochemical oxidation of glycerol, the principal by-product of biodiesel production, generally leads to multicomponent product mixtures. The aim of this project was to investigate the feasibility of a technical process for electrochemical oxidation of crude glycerol followed by catalytic conversion of the intermediates dihydroxyacetone and glyceraldehyde to lactic acid. Partial electrochemical oxidation of glycerol with diamond coated electrodes was assumed to provide a route for converting glycerol to dihydroxyacetone and glyceraldehyde. Through instant selective conversion of dihydroxyacetone and glyceraldehyde to lactic acid the major disadvantage of electrochemical conversion, cleavage of intermediates, may be limited. Continuous separation of lactic acid from the electrolyte enables acceptable current efficiency as well as yield of products. Reactive extraction with phosphoryl compounds has proven applicable for the isolation of lactic acid from the electrolyte. Based on the results of these investigations a complete process for lactic acid production from glycerol was designed.

Formation of liquid and solid products from liquid phase pyrolysis

The aim of the present work was to improve the C:O ratio in biomass by preserving the lignin macrostructure of lignocellulosic feed. The intention of liquid phase pyrolysis is to liquefy biomass and prepare biomass for further upgrading steps like hydrogenation and deoxygenation. Pyrolysis was carried out in a non-aqueous liquid phase heat carrier. The process was carried out in a semi-batch reaction vessel under isothermal conditions at T=350°C, supported by a quench to stop reactions instantaneously in order to observe formation of solid intermediates. This pyrolysis system enables the observation of liquid and solid product formation. Transformation of biomass into biochar was analyzed by infrared spectroscopy and elemental analysis. Stable lignin structure throughout the whole transformation was confirmed. It was shown that the lignin frame in wood remains without substantial loss, while the major amount of carbohydrates is pyrolyzed during liquid phase pyrolysis at T=350°C.

Hydrocarbon liquid production via the bioCRACK process and catalytic hydroprocessing of the product oil

Continuous hydroprocessing of liquid phase pyrolysis Bio-oil, provided by BDI-BioEnergy International bioCRACK pilot plant at OMV Refinery in Schwechat/Vienna Austria was investigated. These hydroprocessing tests showed promising results using catalytic hydroprocessing strategies developed for unfractionated Bio-oil. A sulfided base metal catalyst (CoMo on Al2O3) was evaluated. The bed of catalyst was operated at 400 °C in a continuous-flow reactor at a pressure of 12.1 MPa with flowing hydrogen. The condensed liquid products were analyzed and found that the hydrocarbon liquid was significantly hydrotreated so that nitrogen and sulfur were below the level of detection (<0.05), while the residual oxygen ranged from 0.7 to 1.2%. The density of the products varied from 0.71 g mL−1 up to 0.79 g mL−1 with a correlated change of the hydrogen to carbon atomic ratio from 2.1 down to 1.9. The product quality remained high throughout the extended tests suggesting minimal loss of catalyst activity through the test. These tests provided the data needed to assess the quality of liquid fuel products obtained from the bioCRACK process as well as the activity of the catalyst for comparison with products obtained from hydrotreated fast pyrolysis Bio-oils from fluidized-bed operation.

Liquefaction of pyrolysis derived biochar: a new step towards biofuel from renewable resources

There are several ways to produce the renewable resource biochar, such as pyrolysis or hydrothermal carbonization. Technologies for the conversion of biochar to biofuels could contribute to suffice the growing demand for fuel. Liquid-phase pyrolysis produces about 40 wt% of biochar. Direct liquefaction of biochar is a conceivable way of producing biofuels but has not been considered yet. Direct liquefaction of biochar is carried out in a 450 ml batch reactor at the temperature of 425 °C using tetralin as a hydrogen donor solvent. Several experiments were conducted to investigate the influence of an initial heating and an isothermal stage on the conversion of biochar to biofuel. The isothermal stage was investigated at two pressure levels. Reaction time was limited to 30 min. Biochar conversion of 84% and an oil yield of 72% were observed.

Biofuels from liquid phase pyrolysis oil: a two-step hydrodeoxygenation (HDO) process

New biomass utilization technologies and concepts are needed to suffice future increasing energy demand. This paper contributes to the understanding of liquid phase pyrolysis (LPP) oil upgrading, which significantly differs from fast pyrolysis (FP) oil upgrading processes. A two-step hydrodeoxygenation (HDO) process was established to convert the LPP oil into a biofuel with diesel fuel-like properties. In the first HDO step (250 °C, 85 bar), the bulk of the water and most of the highly-oxygenated water-soluble carbonaceous constituents were removed, to lower hydrogen consumption in the second HDO step. In addition, the highly reactive compounds were stabilized in the first step. In the second HDO step (400 °C, 150/170 bar), the product specification was improved. This paper shows a proof-of-principle for a two-step HDO process for converting LPP oil to a diesel-like biofuel.

Recovery of Formic Acid and Acetic Acid from Waste Water Using Reactive Distillation

Processing of biobased feedstock materials may lead to formation of multicomponent azeotropic mixtures. Reactive separations provide an opportunity to circumvent azeotropes by changing the substance properties through chemical reactions. Exemplarily several effluents from black liquor processing contain aqueous mixtures of low molecular weight fatty acids such as formic acid and acetic acid. These mixtures form inseparable azeotropes. Separation of the system formic acid–acetic acid–water by esterification with methanol was investigated. Reactive distillation experiments in batch and continuous mode confirmed complete removal of formic acid in a first step. Acetic acid may then be isolated by distillation or by reactive distillation.

Chemical loop systems for biochar liquefaction: hydrogenation of Naphthalene

Liquefaction of biochar from liquid-phase pyrolysis was carried out in the solvent Tetralin. Tetralin is able to act as hydrogen donor during liquefaction of biochar and is itself rearranged into Naphthalene. Naphthalene must be re-hydrogenated to Tetralin to allow for further use in the liquefaction reaction (chemical loop system). Therefore Naphthalene hydrogenation was investigated, applying a full factorial design of experiments approach. The yield of Tetralin was chosen as response variable, while two-level-factors for temperature (150 °C and 200 °C), pressure (20 bar and 50 bar) and Raney-Nickel catalyst load (5 wt% and 10 wt%) were selected. The Design of Experiments approach showed a rising influence of all three factors in the order: temperature < pressure < catalyst load. The reaction kinetics of the hydrogenation of Naphthalene to Tetralin and Decalin was then investigated at 150 °C and 200 °C. The reaction proceeds stepwise and not in consecutive steps. In a first step Naphthalene reacts selectively with 96% yield to Tetralin, while the reaction of Tetralin to Decalin does not start until all Naphthalene is consumed. The rate-constant of the reaction of Naphthalene to Tetralin is one magnitude higher than that for the reaction of Naphthalene to Decalin. This is in agreement with the findings from the design of experiments approach. The results of these investigations indicate that the chemical-loop system Naphthalene–Tetralin is suitable for usage in the liquefaction of biochar.

SOLID/LIQUID EXTRACTION OF ZINC FROM EAF-DUST

The solid/liquid extraction of nonferrous heavy metals was investigated. This process may be of technical importance in the upgrading of dust from steel mills and from electrical arc furnaces (EAF-dust). Extraction was carried out with aqueous acetic acid. Objectives of the project were the evaluation of partition data and the investigation of extraction kinetics. The extraction efficiency of the substances in question is in general accordance with the high solubilities of acetates in water. Solubility is negatively affected by excess acetic acid. The dissolution rate of heavy metals of oxidation number (II) is high and can be modeled with a first-order rate law. The results show that acetic acid is an appropriate extractant for separating zinc and lead from oxidic solid feed material.