Pyrolysis and co-pyrolysis of Laminaria japonica and polypropylene over mesoporous Al-SBA-15 catalyst
© Lee et al.; licensee Springer. 2014
Received: 27 May 2014
Accepted: 27 July 2014
Published: 1 August 2014
The catalytic co-pyrolysis of a seaweed biomass, Laminaria japonica, and a typical polymer material, polypropylene, was studied for the first time. A mesoporous material Al-SBA-15 was used as a catalyst. Pyrolysis experiments were conducted using a fixed-bed reactor and pyrolysis gas chromatography/mass spectrometry (Py-GC/MS). BET surface area, N2 adsorption-desorption isotherms, and NH3 temperature programmed desorption were measured to examine the catalyst characteristics. When only L. japonica was pyrolyzed, catalytic reforming slightly increased the gas yield and decreased the oil yield. The H2O content in bio-oil was increased by catalytic reforming from 42.03 to 50.32 wt% due to the dehydration reaction occurring on the acid sites inside the large pores of Al-SBA-15. Acids, oxygenates, mono-aromatics, poly aromatic hydrocarbons, and phenolics were the main components of the bio-oil obtained from the pyrolysis of L. japonica. Upon catalytic reforming over Al-SBA-15, the main oxygenate species 1,4-anhydro-d-galactitol and 1,5-anhydro-d-manitol were completely removed. When L. japonica was co-pyrolyzed with polypropylene, the H2O content in bio-oil was decreased dramatically (8.93 wt% in the case of catalytic co-pyrolysis), contributing to the improvement of the oil quality. A huge increase in the content of gasoline-range and diesel-range hydrocarbons in bio-oil was the most remarkable change that resulted from the co-pyrolysis with polypropylene, suggesting its potential as a transport fuel. The content of mono-aromatics with high economic value was also increased significantly by catalytic co-pyrolysis.
KeywordsCatalytic co-pyrolysis Laminaria japonica Polypropylene Al-SBA-15
The development of renewable and sustainable energy resources is one of the most urgent tasks that scientists and engineers are facing owing to limited fossil fuel reserves and accelerating global warming. Compared to other renewable energies, such as solar energy, which require relatively long time for research and development, biomass is expected to be capable of replacing fossil fuels with much less efforts. Unlike crude oil, biomass is distributed evenly over the world and its quantity is gigantic, which makes biomass a promising energy source of the future.
Pyrolysis, which is a well-known method to produce energy from biomass, is a thermal conversion process producing a liquid fuel called bio-oil. The bio-oil produced from catalytic pyrolysis of biomass normally exhibit low oxygen content, high heating value, and improved miscibility with petroleum-derived liquid fuels.
While lignocellulosic biomass has widely been used as a feedstock for catalytic pyrolysis, macroalgae, including various seaweeds, are recently receiving significant attention as a new biomass material for energy production. The high photosynthetic efficiency of seaweeds, compared to that of woody land biomass, arouses an anticipation of producing bio-oil more effectively . However, the pyrolysis bio-oil of seaweeds often displays severe instability, requiring catalytic reforming to improve the stability of the oil [1, 2]. The research on the catalytic pyrolysis of macroalgae is still limited, compared to that for land biomass. Application of various catalysts to the pyrolysis of macroalgae needs to be investigated to realize the potential of macroalgae as an energy source.
Mesoporous catalysts can be good candidates for the catalytic pyrolysis of biomass because their large pore size is beneficial for the catalytic cracking of large-molecular-mass species during the pyrolysis process . For instance, a mesoporous catalyst Al-SBA-15 was used in the catalytic pyrolysis of herb residue or miscanthus, leading to the production of valuable components such as phenolics [3, 4].
Organic waste can also be used to produce energy. For example, a substantial amount of plastics are produced, consumed, and discarded. Waste plastics can be used to produce liquid fuel through pyrolysis. The pyrolysis oil produced from plastics is composed mostly of carbon and hydrogen, with only a limited content of oxygen, because plastics are produced from fossil fuels that contain much less oxygen than normal biomass materials. Therefore, if waste plastics are pyrolyzed together with biomass materials, they provide carbon and hydrogen and lower the oxygen content, resulting in an improvement of the oil quality . This co-pyrolysis of biomass and plastics has recently been investigated actively [6–17]. However, the co-pyrolysis of macroalgae and plastics has never been studied yet.
In this study, a representative mesoporous catalyst Al-SBA-15 was applied to the catalytic pyrolysis of Laminaria japonica, a kind of seaweed, for the first time. The co-pyrolysis of polypropylene (PP), which is a representative plastic material, and L. japonica was also investigated for the first time.
L. japonica and PP
Proximate analyses of L. japonica and PP were conducted using a method suggested in a previous study [1, 2]. L. japonica was shown to consist of moisture (7.7%), volatile matter (53.1%), fixed carbon (11.0%), and ash (28.3%) on a mass basis, whereas most mass (99.8%) was volatiles with only 0.2% of ash in the case of PP. Elemental analyses showed that L. japonica was composed of C (30.6%), H (4.9%), O (62.4%), N (1.5%), and S (0.5%) on a mass basis, whereas PP was composed only of C (85.4%) and H (14.6%).
Synthesis and characterization of the catalyst
Mesoporous Al-SBA-15 was synthesized using a method suggested in a previous study . The characterization of the synthesized catalyst was performed using BET, N2 adsorption-desorption analysis, X-ray diffraction patterns (XRD) and temperature-programmed desorption (TPD) of ammonia. Refer to a previously published report for more detailed analysis procedure [1, 3].
Catalytic pyrolysis and co-pyrolysis using a fixed-bed reactor
A U-type quartz reactor was used to investigate the change in the yields of gas and bio-oil by co-pyrolysis. To make an oxygen-free condition, 50-mL/min nitrogen gas flow was used to purge the reactor for 30 min prior to each experiment. Experiments were conducted with a 5-g L. japonica sample for 1 h at 500°C using 50-mL/min N2 gas as the carrier gas. In the case of co-pyrolysis of L. japonica and waste plastics, a mixture of 2.5-g L. japonica and 2.5-g PP was used for the experiments. In the case of catalytic pyrolysis, a catalyst/feedstock ratio of 1/10 was used. The pyrolysis product oil was collected in two consecutive condensers maintained at −20°C. A Teflon bag (DuPont Co., Wilmington, DE, USA) was installed after the condensers to collect the gaseous species that were not condensed in the condensers owing to their too low boiling points. The H2O content in bio-oil was analyzed using a Karl Fischer Titrator. Refer to previously published papers for more detailed experimental procedures [1, 2, 5].
Catalytic pyrolysis and co-pyrolysis using a pyrolysis gas chromatography/mass spectrometry
For more detailed in situ analysis of pyrolysis product composition, a single-shot pyrolyzer (Py-2020iD, Frontier-Lab Co., Koriyama, Fukushima, Japan) connected directly to GC/MS (called hereafter pyrolysis gas chromatography/mass spectrometry (Py-GC/MS)) was used. The pyrolyzer was maintained at 500°C. When pyrolyzing L. japonica only, 2 mg of L. japonica sample was put in a cup, whereas a mixture of 1 mg of L. japonica sample and 1 mg of PP was put in the cup for co-pyrolysis. When the experiments were performed with catalyst, quartz wool was laid over the cup containing the biomass sample forming an intermediate layer, over which 2 mg of catalyst was placed. The pyrolysis product vapor was upgraded catalytically while passing through the catalyst layer. Each test was conducted three times to check the reproducibility. One can refer to a previous paper [1, 3] for more detailed experimental procedures.
Results and discussion
Characterization of catalyst
Physical properties of catalysts
Average Pore Size (nm)
Catalytic pyrolysis of L. japonica
Yield of gas composition from catalytic pyrolysis of Laminaria japonica
C1 ~ C4
Water contents in bio-oil (wt%)
Catalytic co-pyrolysis of L. japonica
Yield of gas composition from catalytic co-pyrolysis of Laminaria japonica and polypropylene
C1 ~ C4
Water contents in bio-oil (wt%)
The catalytic co-pyrolysis of L. japonica and polypropylene resulted in the production of bio-oil with significantly higher quality compared to the catalytic pyrolysis of L. japonica only or the non-catalytic co-pyrolysis. The water content in the bio-oil produced from the catalytic co-pyrolysis was 8.93 wt%, which was much lower than that for the catalytic pyrolysis of L. japonica only (50.32 wt%). Co-pyrolysis also considerably increased the contents of light hydrocarbons and mono-aromatics that have high economic values. The main hydrocarbon species obtained from the catalytic co-pyrolysis were gasoline-range (C5-C9) and diesel-range (C10-C17) species, whereas non-catalytic co-pyrolysis produced mainly wax species (C17 or larger). The production of these valuable species was attributed to the catalytic conversion of oxygenates, acids, and heavy hydrocarbons occurring on the acid sites inside the large pores of Al-SBA-15.
pyrolysis gas chromatography/mass spectrometry
X-ray diffraction patterns.
This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (2012R1A1B3003394).
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