Stabilization of pyrolysis oils by solvent additions

Fast pyrolysis bio oils (FPBO) can consist of more than 300 substances. Because those liquids are not in thermodynamic equilibrium components tend to react with each other and change their properties (aging). The addition of different solvents like alcohols and carbon dioxide can improve their properties. For the detection of their effectiveness, reliable analytical procedures and methods are required

Sequential hydrothermal processing of sewage sludge to produce low nitrogen biocrude

A hydrothermal pre-treatment has been developed to improve sewage sludge quality or to produce low nitrogen biocrude via hydrothermal liquefaction (HTL) in a subsequent step. The mild hydrothermal pre-treatment (150 °C) step was performed with deionized water, sulfuric acid (0.5 M), or citric acid (0.5 M) to solubilize nitrogen containing compounds in the aqueous supernatant. Downstream, the residual solid material was liquefied with the addition of sodium carbonate via hydrothermal liquefaction (350 °C). The pre-treatment with citric acid transferred up to 66.7 wt. % of nitrogen into the aqueous supernatant, while 62.0 wt. % of carbon was recovered in the solid. Due to the pre-treatment lipids retained in the sewage sludge solid, which increased the favored biocrude yield up to 42.9 wt. % and the quality evaluating value H/Ceff ratio significantly to 1.48. Multi-method characterization of the resulted biocrude samples showed a lower concentration of N-heterocycles, while long-chain aliphatics and free fatty acid are increased

Side-by-Side Comparison of Clean and Biomass-Derived, Impurity-Containing Syngas as Substrate for Acetogenic Fermentation with Clostridium ljungdahlii

Syngas, the product of biomass gasification, can play an important role in moving towards the production of renewable chemical commodities, by using acetogenic bacteria to ferment those gaseous mixtures. Due to the complex and changing nature of biomass, the composition and the impurities present in the final biomass-derived syngas will vary. Because of this, it is important to assess the impact of these factors on the fermentation outcome, in terms of yields, productivity, and product formation and ratio. In this study, Clostridium ljungdahlii was used in a fed-batch fermentation system to analyze the effect of three different biomass-derived syngases, and to compare them to equivalent, clean syngas mixtures. Additionally, four other clean syngas mixtures were used, and the effects on product ratio, productivity, yield, and growth were documented. All biomass-derived syngases were suitable to be used as substrates, without experiencing any complete inhibitory effects. From the obtained results, it is clear that the type of syngas, biomass-derived or clean, had the greatest impact on product formation ratios, with all biomass-derived syngases producing more ethanol, albeit with lesser total productivity

Microwave spectroscopy for pyrolytic bio-slurries

The elemental composition of bio-slurry as intermediate for renewable fuel production in the bioliq® process of the Karlsruhe Institute of Technology, its water content and heating value have to be controlled carefully to regulate the gasification process and to adjust the gasification products. The continuous knowledge of the bioslurry composition is very important for this. Microwave spectroscopic measuring methods in connection with a multivariate data analysis to data evaluation are, however, well suited for solving such measuring tasks. This was the motivation to evaluate the use of microwave spectroscopy techniques for following up the properties of bio-slurry in the bioliq® process. Two different microwave spectroscopic measuring systems were tested in this application. A large number of test measurements was carried out, with good results

Two Steps Upgrading of Beech Wood Fast Pyrolysis Bio-oil with Nickel-based Catalysts

Upgrading of fast pyrolysis bio-oil through catalyst hydrotreatment has been suggested as a complementary step to produce oil with improved properties. The upgrading reduces the oxygen and water concentration at the same time that allows the carbon recovery in the bio-oil. Reactive compounds are stabilized and organic acids are mostly concentrated in the aqueous phase formed after the reaction. Due to the high activity and low cost, nickel-based catalysts are promising for production of upgraded oils. Although almost half of the oxygen is removed with a single step upgrading, deeper hydrodeoxygenation is required in order to obtain organic liquids miscible with petroleum-derived products. It can be achieved by sequential hydrotreatment with specific catalysts in each of the steps. Hence, in the present work a beech wood fast pyrolysis bio-oil was upgraded in two steps applying two nickel-based catalysts. A catalyst with higher hydrodeoxygenation activity (Ni/SiO2, 7.9 wt.%) was used in the first step, whereas a catalyst with higher hydrogenation activity (Ni-Cr/SiO2, 30 wt.% metallic nickel, 26 wt.% NiO, 15 wt.% of Cr2O3 and 1.5 wt.% of graphite in diatomaceous earth support 27 wt.%) was employed in the second step. The reactions were conducted in a batch autoclave at 325 ºC and 80 bar of H2. The bio-oil initially hydrotreated with a Ni/SiO2 catalyst prepared by wet impregnation showed a reduction of 44.85 % of the oxygen content and 77.8 % less water in comparison to the initial bio-oil. Carbon, on the other hand increased from 59.9 wt.%, dry basis to 72.9 wt.%, dry basis, respectively. After the second upgrading reaction with Ni-Cr/SiO2, the oxygen concentration was further reduced to 11.6 wt.%, reducing 64.8 % of the original oxygen concentration, and reducing around 90 % of the water content. Additionally, most of the organic compounds were concentrated in the upgraded oil, as the aqueous phase after the second upgrading step was composed by 97 % of water. Such improvement was reflected in the high carbon concentration in the upgraded oil ([C] = 78.6 wt.%), in the HHV (36.9 MJ/Kg), 90.1 % higher in comparison to the original beech wood fast-pyrolysis bio-oil and in the hydrocarbons identified in the two-steps upgraded oil. Hence, the two steps hydrotreatment with adequate catalyst seems to be a promising upgrading process in order to obtain fast pyrolysis oil with improved properties. Please click Additional Files below to see the full abstract

Sequential Extraction and Characterization of Nitrogen Compounds after Hydrothermal Liquefaction of Sewage Sludge

Organic solid wastes such as sewage sludge are potential feedstocks for the production of drop-in biofuels. Hydrothermal liquefaction (HTL) is a process that converts the wet sewage sludge into an organic biocrude. To fulfill industrial fuel standards, the considerable heteroatom content of the biocrude needs to be lowered by downstream processes. Nitrogen (N) contained in several compounds poses a challenge and yet, the complex chemical composition of HTL-biocrude samples has hindered detailed analysis and understanding. In particular, N-containing aromatic substances appear very persistent in biocrude. In the present work, two alkaline (NaHCO$_{3}$ and NaOH) and one acidic (HCL) aqueous solutions were subsequently applied to extract and recover polar N-containing compounds from the biocrude matrix with an N-content of 3.8 wt %. Gas chromatography–mass spectrometry, atmospheric pressure chemical ionization in positive mode, and Fourier transform ion cyclotron resonance mass spectrometry were applied for their characterization and results show that a large share of N-compounds with an aromatic, pyridinic structure was found in the acidic extracted fraction with an N-content of 9.5 wt %. Aliphatic N-compounds were less affected by the separation and ended in the residual fraction. N-compounds with multiple oxygen functionalizations are enriched in the alkaline extracted fractions. This showed that N-compounds with an aromatic structure are strongly affected by polar groups and can potentially be extracted by downstream processes with appropriate solvents

Metal oxide-doped activated carbons from bakery waste and coffee grounds for application in supercapacitors

The functionalization of sustainable carbon materials and their application in energy storage systems attract more and more relevancy. Bakery waste and spent coffee grounds were chosen as abundant organic residues and found to be suitable starting materials for hydrothermal carbonization and a subsequent chemical activation obtaining carbon contents of > 88%. In situ doping of the hydrochars during carbonization has proven to be a successful method for insertion of Fe2O3-, Fe3O4- and MnO2-Nanoparticles into the carbon matrix, supported by XRD analysis and SEM images. Chemical activation with K2CO3 led to iron contents up to 18% of iron and around 8% of manganese, respectively, in the corresponding activated carbon. Electrochemical characterization revealed overall higher specific capacitance for activated carbons derived from spent coffee grounds, with a highest of 87F*g-1. In contrast, the highest specific capacitance measured for activated carbons originated from bakery waste was 40,3F*g-1