Upgrading

methods

Treatment condition/ requirement

Reaction mechanism /process description

Technique Feasibility

Pros.

Cons.

Hydrotreating

/hydrofining

Mild conditions, (~500°C /low pressure) chemical needed: H2/CO, catalyst (e. g., CoMo, HDS, NiMo, HZSM-5)

Hydrogenation without simultaneous cracking (eliminating N, O and S as

NH3, H2O and H2S)

Cheaper route,

Commercialized

already

high coking (8­25%) and poor quality of fuels obtained

Hydro-cracking

/hydrogenolysis

/catalytic

cracking

Severe conditions, (>350 °C, 100~2000 Psi), chemical needed: H2/CO or H2 donor solvents, catalyst (e. g., Ni/Al2O3-TiO2)

Hydrogenation with simultaneous cracking Destructive(resulting in low molecular product)

Makes large quantities of light products

Need

complicated equipment, excess cost, catalyst deactivation, reactor clogging

Supercritical fluid

Mild conditions, organic solvents needed such as alcohol, acetone, ethyl acetate, glycerol

Promotes the reaction by its unique transport properties: gas-like diffusivity and liquid-like density, thus dissolved materials not soluble in either liquid or gaseous phase of solvent

Higher oil yield, better fuel quality (lower oxygen content, lower viscosity)

Solvent is expensive

Solvent addition (direct add solvent or esterification of

thethe oil with

alcohol and acid catalysts

Mild conditions, polar solvents needed such as water, methanol, ethanol, and furfural

Reduces oil viscosity by three mechanisms: (1) physical dilution (2) molecular dilution or by changing the oil microstructure; (3) chemical reactions like esterification and acetalization

The most practical approach

(simplicity, the low cost of some solvents and their beneficial effects on the oil properties)

Mechanisms

involved in adding solvent are not quite understand yet

Emulsification

/Emulsions

Mild conditions, need surfactant (e. g. CANMET)

Combines with diesel directly. Bio-oil is miscible with diesel fuels with the aid of surfactants

Simple, less corrosive

Requires high energy for production

Steam Reforming

Kgh

temperature(800-900 °C), need catalyst (e. g. Ni)

Catalytic steam reforming + water-gas shift

Produces H2 as a clean energy resource

Complicated, requires steady, dependable, fully developed reactors

Chemical extracted from the bio-oils

Mild conditions

Solvent extraction, distillation, or chemical modification

Extract valuable chemicals

Low cost separation and refining techniques still needed