Biomass conversion process

Abstract

Biomass material is converted into precursors for hydrocarbon transportation fuels by contacting the biomass with liquid superheated water or supercritical water to depolymerize and deoxygenate the biomass into the transportation fuel precursors. Temperatures above 200° C. and preferably above 300° C. are preferred with supercritical water at temperatures above 374° C. and pressures above 22 MPa providing a capability for higher conversion rates.

Description

FIELD OF THE INVENTIONThe present invention relates to a process for the production of transportation fuels by the conversion of biomass.BACKGROUND OF THE INVENTIONPetroleum is currently estimated to account for over 35% of the world's total commercial primary energy consumption. Coal ranks second with 23% and natural gas third with 21%. The use of liquid hydrocarbon fuels on an enormous scale for transportation has led to the depletion of readily accessible petroleum reserves in politically stable regions and this, in turn, has focused attention, economically, technically and politically on the development of alternative sources of liquid transportation fuels. Liquid hydrocarbons are far and away the most convenient energy sources for transportation in view of their high volumetric energy. The energy density of gasoline, for example at about 9 kWh / litre and of road diesel at about 11 kWh / litre, far exceeds that of hydrogen (1.32 kWh / litre at 680 atm, or batteries, 175 Wh / kg. Furthe...

AI Technical Summary

Benefits of technology

We have now devised a process for the conversion of biomass into transportation fuel precursors which does not rely upon gasification and which uses cheap, readily availabl

Problems solved by technology

While direct, carbon-neutral use of biomass as fuel is established, for example, biodiesel, this route is limited because the limited choice of source materials, e.g. vegetable oils.

The major disadvantage of this pathway is that only a fraction of the total carbon in biomass is converted to the final desired liquid fuel.

The conversion of biomass to hydrocarbon transportation fuels by the gasification-liquefaction sequence has, however, certain limitations both technically and economically.

First, the conversion of the biomass to synthesis gas requires large process units, high in capital cost to deal with the enormous volumes of gas generated in the process.

Second, the gas-to-liquid conversion uses catalysts which may, for optimum results, use noble metal components and accordingly be very expensive.

Third, and by no means least is the fact that enormous biological resources are needed to supply current consumption levels.

An approximate estimate for the land area required to support the current oil consumption of about 2 million cubic metres per day by the US transportation sector is of the order of 2.67 million square km which represents 29% of the total US land area, using reasonable assumptions for the efficiency of the conversion process, thus suggesting that large scale production of liquid fuels from such a biomass conversion process is impractical.