Catalytic fast pyrolysis of pine sawdust was successfully carried out in VTT's 20 kg h −1 Process Development Unit using a spray dried HZSM-5 catalyst. Approximately 250 kg of partially deoxygenated pyrolysis oil was produced over a period of four days. The catalytically produced pyrolysis oil had an average moisture content of 8.3 wt%, and average carbon and oxygen contents of 72.0 and 21.5 wt% on a dry basis, respectively. Approximately 24% of the original biomass carbon was present in the pyrolysis oil, whereas 14% of carbon was in the form of aqueous side products, which totaled approximately 600 kg. The pyrolysis oil contained a high amount of lignin derived water-insoluble material, as well as 6.4 wt% of aromatic hydrocarbons. The majority of the carbohydrate derived products, i.e. acids, aldehydes, ketones and sugar-type compounds, were found in the aqueous product fraction. While the quality of pyrolysis oil remained quite stable during the four day experiment, distinct changes were observed in the properties and the behavior of the catalyst. Coke formation was heaviest at the beginning of the experiment, and then subsided over time. Catalyst micropore area and volume also decreased during the experiment. This transformation was accompanied by apparent changes in the crystallinity and the structure of the catalyst. Scanning electron microscope images of the catalyst also revealed clear physical damage to the particles. Biomass alkali metals also deposited on the catalyst, and the spent catalyst contained a total of 1.1 wt% of Ca, K, Mg and P after the experiment. A linear correlation was observed between catalyst alkali metal content and acidity, which indicated that biomass alkalis substituted the proton functionalities of the HZSM-5 acid sites. † Electronic supplementary information (ESI) available. See

Fast pyrolysis bio-oil oil is a promising alternative to fossil fuels and is currently entering the heating oil market. However, there is a lack of available information about the phase stability of bio-oil. The water-soluble and water-insoluble compounds in bio-oil can either be in one homogeneous phase or form two individual phases, to which we refer to as phase separation. Phase separation can occur immediately after condensation of the pyrolysis vapors to bio-oil because of certain pyrolysis conditions or type of raw material or after years of aging because of changes in composition caused by repolymerization reactions. We present how the phase separation of bio-oils is related to the chemical composition and show that the probability of phase separation can be predicted with a numerical stability index based on the chemical composition. The chemical composition of the bio-oils studied was characterized using a solvent extraction scheme that describes the composition of bio-oil as a blend of three macro fractions: C 1 −C 6 oxygenated molecules (named co-solvents), water-insoluble molecules, and watersoluble polar molecules (including water but excluding the co-solvents), e.g., anhydrosugars. The results show that the required amount of co-solvent to dissolve both fractions and keep the bio-oil homogeneous varies depending upon the chemical composition. The minimum amount of co-solvent for homogeneous bio-oils was observed to be from 15 to 30 wt %. The correlation between the chemical composition and homogeneity of fresh and aged bio-oils is shown in ternary-phase diagrams. Addition experiments were made with model compounds to cover a larger part of the phase diagram.

The fuel properties of fast pyrolysis bio-oils differ significantly from those of fossil fuels. As transportation fuel, bio-oil is not suitable without upgrading because of its relatively low energy content, high water content, acidity, and poor storage stability. Upgrading of bio-oil has usually been done by treating the whole oil in a reactor. The problem with this treatment is that pyrolysis oil is a mixture of different compound groups, which all need different conditions and catalysts to react in a desirable way. Therefore, an efficient fractionation of bio-oil before upgrading may be a more efficient way of producing liquid fuels than treating the whole oil. In this work, the target was to compare two industrially relevant fractionation concepts. In the first concept, most of the water was removed during liquid recovery by adjusting the scrubber temperature. When the scrubber temperature was increased from 36 to 66 °C, the water content in the bio-oil decreased from 24 to 7 wt %. In the second concept, fast pyrolysis was carried out with wet feedstock. This would reduce the drying cost in the plant. By this means, a spontaneous phase separation was generated after liquid condensation. In the experiments, the moisture content of the raw material was increased up to 25 wt %, but even with this moisture content, the oily bottom phase still contained 22 wt % watersoluble compounds. However, if the target is to produce transportation fuels from bio-oil, fractionation by phase separation is a better concept for dividing the bio-oil into different compound groups.

Fast pyrolysis technology is currently moving forward to commercialization, and demonstration plants are at the commissioning stage.

Metso, UPM, Fortum, and VTT have developed the world’s first integrated bio-oil production concept to provide an alternative to fossil fuels. The consortium has constructed an up to 7 tons/day bio-oil production pilot unit, which uses a bubbling fluidized-bed (BFB) pyrolysis reactor integrated with a conventional fluidized-bed boiler. Proof-of-concept has been carried out; close to 90 tons of bio-oil has been produced from sawdust and forest residues at high availability. Around 40 tons of bio-oil has been combusted in Fortum’s 1.5 MW district heating plant in Masala, Finland, with high efficiency. Flue gas emissions were close to those of heavy fuel oil, at 4% O2, CO emissions ranged from 0 to 10 ppm and NO x emissions ranged from 300 to 400 ppm. Organic compounds were under 5 mg m–3 N–1, and particulate emissions were in the range of 150–200 mg m–3 N–1. No odor emissions occurred. Development of the concept has been supported by experimental work on fast pyrolysis at VTT. This paper presents the recent results from the piloting project covering the whole chain from feedstock processing to bio-oil combustion, including the quality control system with online gas and liquid analyzers. The research supporting the pilot project, from various laboratory-scale units to systematic analytical development, is discussed, and the potential for market introduction of the new technology in forest product industries in western Europe and North America is described.