Processes for producing low acid biomass-derived pyrolysis oils

Abstract

Processes for producing a low acid biomass-derived pyrolysis oil are provided that include pre-treating a biomass-derived pyrolysis oil to form a treated acid-containing biomass-derived pyrolysis oil. The processes also include esterifying the treated acid-containing biomass-derived pyrolysis oil in the presence of supercritical alcohol and a catalyst composition to form the low-acid biomass-derived pyrolysis oil, the catalyst composition comprising a material selected from the group consisting of an unsupported solid acid catalyst, an unsupported solid base catalyst, and a catalytic metal dispersed on a metal oxide support.

Description

FIELD OF THE INVENTION[0001]The present invention generally relates to biofuels and processes for producing biofuels, and more particularly relates to low acid biomass-derived pyrolysis oils and processes for producing the same.DESCRIPTION OF RELATED ART[0002]Biomass-derived pyrolysis oil can be burned directly as fuel for certain boiler and furnace applications, and can also serve as a potential feedstock in the production of biofuels in petroleum refineries or in stand-alone process units. To form biomass-derived pyrolysis oil, solid carbonaceous biomass feedstock, i.e., “biomass”, such as wood waste, agricultural waste, etc., is initially rapidly heated to pyrolysis temperatures of about 300° C. to about 900° C. in the absence of air using a pyrolysis reactor. Under these conditions, solid products, liquid products, and gaseous pyrolysis products are produced. A condensable portion (vapors) of the gaseous pyrolysis products is condensed into biomass-derived pyrolysis oil.[0003]Al...

AI Technical Summary

Benefits of technology

[0006]In an embodiment, by way of example only, a process for producing a low acid biomass-derived pyrolysis oil includes pre-treating a biomass-derived pyrolysis oil to form a treated acid-containing biomass-derived pyrolysis oil and esterifying the treated acid-containing biomass-derived pyrolysis oil in the presence of supercritical alcohol and a catalyst composition to form the low-acid biomass-derived pyrolysis oil, the catalyst composition comprising a material selected from the group consisting of an unsupported solid acid catalyst, an unsupported solid base catalyst, and a catalytic metal dispersed on a metal oxide support. The unsupported solid acid catalyst comprises a material selected from the group consisting of a molecular sieve and a Group V metal oxide. The molecular sieve comprises a material selected from the group consisting of zeolite and MCM 41. The unsupported solid base catalyst comprises a material selected from the group consisting of an alkaline earth metal exchanged molecular sieve, calcium oxide (CaO), magnesium oxide (MgO), and silicon oxide (SiO2). The catalytic metal comprises a metal selected from the group consisting of noble metals, non-noble metals, and combinations thereof the metal oxide support comprises a metal oxide selected from the group consisting of a Group IV metal oxide, a Group V metal oxide, a Group IIIA metal oxide, and combinations thereof.

[0007]In another embodiment, by way of example only, a process for producing a low acid biomass-derived pyrolysis oil includes pre-treating a biomass-derived pyrolysis oil to form a treated acid-containing biomass-derived pyrolysis oil, diluting the treated acid-containing biomass-derived pyrolysis oil with supercritical ethanol to form a solution including at least about 30% ethanol, by weight, and esterifying the treated acid-containing biomass-derived pyrolysis oil included in the solution in the presence of a catalyst composition and in the absence of gas in an upflow reactor to form the low-acid biomass-derived pyrolysis oil, wherein the catalyst composition comprises a noble metal support on a sulfated metal oxide.

Problems solved by technology

Although biomass-derived pyrolysis oil has great potential to replace up to 60% of transportation fuels and to reduce the dependency on conventional petroleum and its environmental impact, unprocessed biomass-derived pyrolysis oil is a complex, highly oxygenated organic liquid having properties that currently limit its utilization as a biofuel.

Specifically, unprocessed biomass-derived pyrolysis oil is generally thermally unstable and acidic (as measured by the total acid number (TAN)), making it corrosive, low in energy density, and susceptible to increased viscosity over time.

The low energy density and poor thermal stability of the biomass-derived pyrolysis oil is attributable in large part to oxygenated hydrocarbons in the oil, which undergo secondary reactions during storage.

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