Controlling the Phase Stability of Biomass Fast Pyrolysis Bio-oils

Abstract

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.

Modification and regeneration of HZSM-5 catalyst in microwave assisted catalytic fast pyrolysis of mushroom waste

“…Despite some high value-added chemicals are found in the biooil, which includes hydrocarbons, alcohols, furans, phenols and so forth, its application is still limited as a consequence of the high oxygen content, low caloric value, high corrosion behavior and chemical instability [3,4]. Upgrading of biomass derived bio-oil provides an effective and efficient process to attain an energy benefit with a minimum effect on environment [5].…”

Mild Upgrading of Bio‐Crude Pyrolysis Oil: A Concept Based on Bio‐Based Alcohols with Selective Water Adsorption

“…The BcPO is acidic and its storage stability is limited because of the presence of acids and polymerisation reactions of reactive aldehydes with phenolics. Thus, the direct use as transportation fuel, or co‐feeding in conventional oil refineries, has still several barriers to be tackled.…”

“…It contains as ubstantial amounto fw ater and oxygen-containing compounds,w hich impliesal ow heating value as well (estimated at 40-50 %o f that for hydrocarbon fuels). [1] TheB cPO is acidic and its storage stability is limited [1,[5][6][7] because of the presence of acids and polymerisation reactions of reactive aldehydes with phenolics.T hus,t he direct use as transportation fuel, or co-feeding in conventional oil refineries,h as still severalb arriers to be tackled. Therefore, to extend the application prospects,u pgrading of BcPO is crucial.…”

Comparison of fast pyrolysis bio‐oils from straw and miscanthus

“…A correlation between the reaction water and the content of minerals in the biomass can be established. In their investigation, Oasmaa et al concluded that the bio‐oil produced from feedstocks with an ash content below 1.0 wt% typically consists of one phase and above 2 wt% likely separate into two phases . As agricultural residues have higher contents of catalytically active alkali metals compared to forest residues and soft woods, the bio‐oils obtained from them will also have higher water content, and thus a phase separation is to be expected.…”

“…In their investigation, Oasmaa et al concluded that the bio-oil produced from feedstocks with an ash content below 1.0 wt% typically consists of one phase and above 2 wt% likely separate into two phases. 12 As agricultural residues have higher contents of catalytically active alkali metals compared to forest residues and soft woods, 13 the bio-oils obtained from them will also have higher water content, and thus a phase separation is to be expected. This paper investigates the bio-oil production from two different feedstocks: a mixture of barley and wheat straw and miscanthus using an ablative hot surface reactor system.…”