(560a) Production of High Quality Bio-Oil Via Fast Co-Pyrolysis (FCP) of Cellulose and Polypropylene

Production
of High Quality Bio-oil via Fast Co-Pyrolysis (FCP) of Cellulose and
Polypropylene

Deepak
Kumar Ojha and R. Vinu

Department
of Chemical Engineering and National Center for Combustion Research and
Development, Indian Institute of Technology Madras, Chennai- 600036, India

Abstract

Fast
pyrolysis has received a great attention for direct conversion of biomass into
liquid fuels and valuable intermediates. The bio-oil produced from the process
has high oxygen content and needs further upgradation to make it usable as a
transportation fuel. Currently this is achieved via catalytic hydrodeoxygenation
which is highly energy and hydrogen intensive. Co-processing of biomass with
polymers is a novel strategy and this is expected to increase the product quality
in terms of H/C ratio and heating value, thus reducing the upgradation cost.
Detailed understanding of these reactions is prerequisite for the technological
development and commercial implementation of the process. Fast co-pyrolysis (FCP)
is thought to proceed via complex network of competing free radical and
concerted reactions such as aldol condensation, retro-Diels-Alder reaction,
β-scission and hydrogen abstraction between biomass and polymer free radicals.

In
this study, fast co-pyrolysis of cellulose and polypropylene (PP) is
investigated. The objectives of this work are two fold: firstly, the effects of
cellulose: PP ratio on the yield of individual products and heating values were
evaluated at different temperatures from 400 to 700 ^oC. Secondly,
the evolution of major functional groups in a short time period of a few
seconds is studied. Fast co-pyrolysis experiments were conducted in a Pyroprobe^®
5200 pyrolyzer (CDS Analytical Inc.) which was interfaced with multidimensional
gas chromatograph/mass spectrometer (2D-GC/MS, Agilent Technologies). For the
real time function group analysis, the Pyroprobe was interfaced with Cary 660 Fourier
transform infrared spectrometer (FT-IR, Agilent Technologies). Table 1 depicts
the yields of major products formed during fast co-pyrolysis of cellulose and
PP of different compositions. Significant difference between calculated and
experimental product yields shows that interactions between cellulose and PP are
manifested in the form of alcohols. Importantly, the alcohols belonged to C10-C15
carbon number range. Specifically, long chain alcohols like (2,4,6-trimethylcyclohexyl) methanol, 2-isopropyl-5-methyl-1-heptanol and 11-methyldodecanol
were obtained in significant amounts when PP content was high (50-75 wt.%) in
the mixture. The heating values of the products were calculated using the empirical
relation of Davenport, and interestingly, the heating values correlated well
with the sum of yields of alcohols, hydrocarbons and monoaromatics. Overall, two
fold improvement in heating value of the condensable products was observed. 
Higher pyrolysis temperature led to the formation of mono and poly aromatic
hydrocarbons. The real time functional group analysis indicated a reduction in
reaction time with an increase in PP content in the feed. The time taken for
the maximum yield of various products corresponded to 10 seconds, while
pyrolysis was complete in less than a minute.

Table 1. Comparison between experimental and calculated
composition of the major products formed in co-pyrolysis of cellulose and PP of
different compositions at 500 ^oC.