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Catalytic Upgrading of Heavy Compounds from Bio-OilPDF
  • Introduction
  • Experimental
  • Results
  • Conclusions

Introduction & Motivation

In the past decade, interest has grown in the use of biomass as a renewable source of fuel and organic chemicals by using fast or flash pyrolysis to produce bio-oils. Bio-oils consist of a large number of chemical compounds. Bio-oil composition depends on the biomass source, but typically includes chemicals with carbonyl, carboxyl, and hydroxyl functional groups.

The oxygen content of bio-oils prevents utilization as transportation fuel since the high oxygen content of bio-oils causes high viscosity, poor thermal and chemical stability, corrosivity and immiscibility with hydrocarbon fuels. Therefore, bio-oils must be upgraded. One proposed upgrading method is catalytic deoxygenation.

In this study, the deoxygenation of m-cresol was investigated over supported Ga catalysts. m-cresol itself is undesirable in gasoline, but is a potential source of high-octane toluene.

Objective & Approach

1. To develop novel catalytic processes for upgrading of heavy compounds from bio-oils

2. To understand the effects on activity and selectivity of catalyst Ga content and gas phase composition.

3. To understand the reaction mechanism of m-cresol conversion over Ga modified HBeta catalysts


Catalyst preparation

Ga supported HBeta zeolite (1-6 wt% Ga) was prepared by impregnation of the HBeta support with Ga(NO3)3. All the samples were then activated in air at 550 oC for 4 hours.

Catalyst testing

Catalytic testing of m-cresol conversion was performed with a continuous fixed bed reactor. The products were periodically collected and analyzed by online gas chromatography (GC). The preferred reaction conditions used in the experiments were as follows: temperature, 400-550 oC; total pressure, 1 atm; carrier gas, H2, He; W/F, 2-22 h.

TPD after m-cresol conversion

The evolution of surface intermediates during reaction of m-cresol over modified 3%Ga/HBeta catalysts was followed by TPD. After the m-cresol conversion at 400 oC under H2, the sample was cooled down in a flow of He to 150 oC. TPD measurements were made from 150 to 900 oC with a heating rate of 10 oC/min using H2 as the carrier gas.

Effect of W/F

Reaction condition:
Catalyst = 3%Ga/HBeta, W/F = 2-22 h, Reaction temperature = 400 oC, Carrier gas = H2, Pressure = 1 atm.

Effect of H2

Reaction condition: Catalyst = 3%Ga/HBeta, W/F = 6 h, Reaction temperature = 450 oC, Carrier gas = H2,, He, Pressure = 1 atm.effect of H2


Effect of Ga content

Reaction condition : Catalyst = Ga/HBeta, W/F = 6 h, Reaction temperature = 400, 450 oC, Carrier gas = H2, Pressure = 1 atm.table

Proposed reaction mechanism


The hydrodeoxygenation (HDO) of m-cresol over Ga/HBeta was studied. Products include toluene (indicative of C–OH bond hydrogenolysis), phenol, light hydrocarbons (presumably methane and C2-C4 compounds), bicyclic hydrocarbons and oxygenated hydrocarbons, benzene, and xylene. Gallium improves the toluene yield compared to the HBeta catalyst. The formation of the various products can be explained by a “surface pool” of adsorbed intermediates.