Deliverables Reaction mechanisms for aqueous pyrolysis of lignin The result is a description of the chemical pathways followed by both lignin units and cutin analogues during aqueous pyrolysis. The reactions identified include: Demethylation, dehydroxylation, beta - oxygen -4 bond cleavage, alpha bond cleavage, methylation and char formation. Cutin analogues did not break down under non-degassed conditions in the temperature regime under study. Decarboxylation and carbon-carbon bond cracking occurs under degassed conditions both in the presence and absence of water. These processes have been tracked as a function of temperature, heating time, oxygen content, water content aqueous equilibrium pressure and loading of lignin or cutin units. The loss of oxygen from lignin and cutin units is the first step in the thermal conversion of biomass to hydrocarbons in the fluid fuel range. The reaction mechanisms of simple organic compounds, which can as models for lignin and cutin in hot aqueous systems, have been investigated. The products formed from thermolysis of these compounds have been identified between 150 and 350 degrees Celsius for time periods between 0 and 180 hours. Trace amounts of the aromatic hydrocarbon benzene were observed upon thermolysis of lignin monomers, however, the main liquid phase products are composed of methoxyphenols, phenols and catechols. Pyrolysis product yields from the lignin monomeric units follow essentially first-order kinetics. Direct demethoxylation of methoxyphenols is not a major reaction pathway. In contrast the thermal demethoxylation of aromatic methoxy groups occurs via demethylation and dehydroxylation reactions. The influence of water and molecular oxygen were examined. Closed system micro-scale pyrolysis of 2-methoxyphenol in the presence of molecular oxygen yielded low amounts of phenol as well as benzoic acid and increased coke formation. This confirmed that pyrolysis should be conducted in the absence of oxygen. The primary reaction during thermolysis of lignin dimeric units and selected biomass types (namely thermo-mechanical pulp (TMP), beech wood and fungus-decayed beech wood) was the homolysis of the beta-oxygen-4 link. Heating of both model dimers and TMP at temperatures equal to and greater than 270 degrees Celsius yielded small amounts of water, this could arise from dehydroxylation of alkyl side chains or in the case of biomass from dehydroxylation of carbohydrates. The main secondary reactions during the thermolysis of model dimers and biomass were dehydroxylation as well as demethylation of aromatic methoxyl groups. In contrast thermolysis of lignin dimers did not yield polyaromatic moieties. Comparison of the liquid phase in-volatile reaction products for lignin monomers and dimers with biomass suggested that the methoxyphenol compounds are excellent analogues for lignin. Fungal degradation of biomass could be a useful pre-treatment step in that it can be used to control the pyrolysis product composition. Thermodynamic calculations for aqueous pyrolysis and energy and mass balances for two biomass types The result consists of calculated relationships based on thermodynamic properties of simple compounds that representat critcal molecular types for the conversion process. The energy and mass balances are based on models using thermodynamic data of specific compounds that represent major constituents in the biomass and products. The results show how temperature, pressure and water-to-carbon ratio influence the stability of the selected representative compounds, the hydrocarbon hexane, acetic acid, solid carbon, and the gas phase hydrogen, carbon dioxide and carbon monoxide. Excess water promotes hydrocarbon stability relative to coke and carbon dioxide. Hydrogen is a stable product under a wide range of conditions, while acetic acid and carbon are not thermodynamically stable. The mass and energy balances are based on experimental data, and combining specific data for gas phase products and representative single compounds for the more complex products. The experimental conditions used in the target systems show a positive or neutral energy balance. Comparable data for hydrous systems are very scarce, and especially energy balances have been considered uncertain. Catalogue of results from aqueous pyrolysis of different biomass types The result summarises the mapping of product compositions as a function of experimental variables for aqueous pyrolysis of a number of biomass and waste types. The results can be used to evaluate the potential for valorisation of different wet biomass and organic waste types, and provide a basis for designing further experiments and reactor systems. The result is a practical description of the relationship between different biomass staring materials and product spectra, and describes the conditions of aqueous pyrolysis that are optional for each combination of raw material and products. The biomass types included in the catalogue are a clean woody biomass and waste from pulping, three kinds of sewage sludge, sludge from a beer brewery, residues form alginate production and Miscanthus (energy crop) biomass. The experimental conditions include temperature, duration, amount of water present, loading of biomass and addition of homogenous and heterogenous catalysts. Products include light and heavy oils, gas exploitable as fuel gas, exploitable aqueous products (especially acetic acid) and coke. The catalogue includes tables of yields and optimised models for prediction of yields as a function of experimental conditions. Corresponding data are available only to a limited degree, for some of the biomass types. Comparable analytical data for product composition has not before been published for most of the systems investigated. Searching for OpenAIRE data... There was an error trying to search data from OpenAIRE No results available
