Roland Feiner

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.

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.

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.

Lignocellulosic Biofuels: Phase Separation during Catalytic Hydrodeoxygenation of Liquid Phase Pyrolysis Oil

This paper contributes to the understanding of liquid phase pyrolysis (LPP) oil upgrading. The subject of discussion is hydrodeoxygenation (HDO). A three-stage hydrotreatment of liquid phase pyrolysis oil is described. It was found that during the initial heating stage conditions no HDO oil was produced. The HDO oil was formed during the main heating stage. During the initial heating stage, the oxygen content and the average molecular weight remained relatively constant. In the main heating stage the oxygen content decreased from 40 wt.% to 24 wt.% and the average molecular weight also decreases from 630 to 570 g/mol. Finally in the isothermal stage HDO oil was formed, indicated by a drop in oxygen content.