Submitted to: Industrial and Engineering Chemistry Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 28, 2011
Publication Date: October 28, 2011
Citation: Mihalcik, D.J., Boateng, A.A., Mullen, C.A., Goldberg, N.M. 2011. Packed-bed catalytic cracking of oak derived pyrolytic vapors. Industrial and Engineering Chemistry Research. 50:13304-13312.
Interpretive Summary: The rapid heating of biomass in the absence of oxygen, or fast pyrolysis, allows for decomposition into its constituent parts. Typically, the products of fast pyrolysis of biomass are composed of non-condensable gases (CO, CO2, etc.), charcoal, and condensable gases. The condensable gas fraction is recovered by condensation and the resulting liquid, or bio-oil, contains a wide variety of compounds, the majority of which are high-oxygen compounds. With the goal of using this liquid fraction as a fuel, the high oxygen content must be lowered so as to increase its effectiveness. Naturally occurring, zeolite catalysts may be applied to the fast pyrolysis of biomass to alter the product composition, in this case, to decrease the oxygen content of the condensable gas fraction which would lead to a low-oxygen containing bio-oil. This experiment was performed on the ARS pyrolysis unit to determine optimum location to place the zeolite catalyst for maximum production of energy-rich compounds. Because the pyrolysis system has five major collection points, the vapor stream can be easily fractionated. This allows for the study of the effects of varying the composition of the vapor stream that is exposed to the catalyst. The extent of oxygen removal from the pyrolysis products was determined to be location specific and depended upon temperature and relative concentrations of water, oxygenates, and residual solids, in the approach vapor. This information will be useful to those producing and refining bio-oil into fuels and chemicals on a larger scale.
Catalytic upgrading of pyrolysis vapors derived from oak was carried out using a fixed-bed catalytic column at 425 deg C. The vapors were drawn by splitting a fraction from the full stream of vapors produced at 500 deg C in a 5 kg/hr bench-scale fast pyrolysis reactor system downstream the cyclone separator. The placement of the fixed-bed column was varied within the condenser train to determine the effect of temperature, residual water, solids and oxygenated components of the approach vapor stream on the upgraded product quality. The upgraded liquid was collected by an immediate contact with a dry-ice acetone bath complimented by a secondary collection system comprising a methanol spray condenser. Quantitative GC/MS analysis of the recovered liquid showed a substantial decrease of oxygen containing species with a significant increase in carbon-rich (=C6) aromatic hydrocarbons. The extent of deoxygenation was location specific and depended upon temperature and relative concentrations of water, oxygenates, and residual solids, in the approach vapor. The study provides the engineering practicality to catalytic vapor upgrading and offers the necessary data for the design and optimization of a full-stream upgrading of pyrolysis oils via in-situ vapor cracking.