Abstract
In biomass pyrolysis engineering, it is important to develop an industrial catalyst with efficient activity, high selectivity, and a long working life. Dolomite-based porous ceramics were considered in this work. The influence of total corn flour content on the open porosity, compressive strength, and thermal conductivity of dolomite-based porous ceramics was investigated. In order to enhance the catalytic activity, dolomite-based porous ceramics were impregnated with an Al2(SO4)3 solution to load the Al2O3 catalyst. Catalytic fast pyrolysis experiments using corn stalk were conducted with the aforementioned catalyst. The bio-oil yield increased as the open porosity of the dolomite-based porous ceramics increased. The pyrolysis bio-oil yield decreased as the Al2(SO4)3 concentration increased. The phenol content in the bio-oil increased as the Al2O3 load increased. Aluminum oxide not only promoted the formation of phenols in the bio-oil, but it also promoted the conversion of phenols, e.g., 4-ethylphenol and 2, 6-dimethoxy-phenol. The results demonstrated that Al2O3 was beneficial for the formation of phenols during pyrolysis. The results detailing the preparation of Al2O3 loaded dolomite-based porous ceramics can provide a reference for large-scale biomass pyrolysis projects.
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Preparation of Dolomite-based Porous Ceramics with Al2O3-Loading as the Heat Carrier for Biomass Catalytic Pyrolysis
Yaya Liu, Shanjian Liu,* Weidong Liu, Dongmei Bi, and Ning Li
In biomass pyrolysis engineering, it is important to develop an industrial catalyst with efficient activity, high selectivity, and a long working life. Dolomite-based porous ceramics were considered in this work. The influence of total corn flour content on the open porosity, compressive strength, and thermal conductivity of dolomite-based porous ceramics was investigated. In order to enhance the catalytic activity, dolomite-based porous ceramics were impregnated with an Al2(SO4)3 solution to load the Al2O3 catalyst. Catalytic fast pyrolysis experiments using corn stalk were conducted with the aforementioned catalyst. The bio-oil yield increased as the open porosity of the dolomite-based porous ceramics increased. The pyrolysis bio-oil yield decreased as the Al2(SO4)3 concentration increased. The phenol content in the bio-oil increased as the Al2O3 load increased. Aluminum oxide not only promoted the formation of phenols in the bio-oil, but it also promoted the conversion of phenols, e.g., 4-ethylphenol and 2, 6-dimethoxy-phenol. The results demonstrated that Al2O3 was beneficial for the formation of phenols during pyrolysis. The results detailing the preparation of Al2O3 loaded dolomite-based porous ceramics can provide a reference for large-scale biomass pyrolysis projects.
Keywords: Biomass; Bio-oil; Catalyst; Porous ceramics; Aluminum oxide
Contact information: School of Agricultural Engineering and Food Science, Shandong University of Technology, Zibo 255000 China; *Corresponding author: liushanjian08@163.com
INTRODUCTION
The overuse of fossil fuel-based energy has led to environmental pollution, e.g., the greenhouse effect, acid rain, and haze (Rehman et al. 2019). Biomass is a renewable, abundant, and environment-friendly carbon source, which can be used as a substitute for fossil energy to produce various fuels and chemicals (Masnadi et al. 2014). Biomass fast pyrolysis technology is an efficient thermochemical method for converting biomass into power fuels, carbon-based materials, or high value-added chemicals (Sikarwar et al. 2016; Bi et al. 2019). In addition, some chemicals found in the bio-oil are the raw materials used to produce environment-friendly phenolic resin adhesives and bio-asphalt, e.g., furfural, levulinic acid, and 5- hydroxymethylfurfural (Gao et al. 2018; Zhao et al. 2018).
It is worth noting that a suitable catalyst can play an important role during the biomass pyrolysis process, i.e., decreasing the activation energy for molecular cracking reactions, or increasing the content of high-value chemicals in the bio-oil (Chen et al. 2017; Iliopoulou et al. 2018; Liu et al. 2019). The catalysts, e.g., molecular sieve, calcined dolomite, limestone, nickel-based catalysts, zinc oxide, and aluminium oxide, have been used for biomass pyrolysis in previous studies. Among them, some rare noble metal catalysts have a higher catalytic activity, e.g., nickel, platinum, palladium, barium, and cerium, but the prices of those catalysts are high. However, coking and carbon deposition readily occur during the pyrolysis process, resulting in the deactivation of these catalysts (Kim et al. 2018; Hernando et al. 2019). In general, natural ore catalysts are not as active as noble metal catalysts during the biomass catalytic pyrolysis. However, these catalysts, e.g., dolomite, limestone, kaolin, and peridot, have the advantages of low cost, abundance in nature, and are resistant to coking during pyrolysis. In addition, calcined activated dolomite or limestone have a lower mechanical strength. They are easily broken and readily form fragments, which will degrade the flow and catalytic performance of catalysts in the reactor (Montoya et al. 2015).
Furthermore, in biomass pyrolysis engineering, the design of the reactor and pyrolysis system also plays a key role in the generation of pyrolysis products; the design can result in the product yields and component distributions in the bio-oil greatly differing from the theoretical results. A novel V-shaped down-tube reactor, which was developed by the author’s research group, has been demonstrated to be suitable for large-scale biomass fast pyrolysis (as shown in Fig.1) (Fu et al. 2017).
Fig. 1. Novel V-shaped down tube reactor for biomass pyrolysis
The pyrolysis reactor employs high-temperature ceramic balls, quartz sand, or metal particles as the heat carrier. Because the pyrolysis reactor does not need a large amount of carrier gas, the organic component concentrations in pyrolysis gases are high, which are easier to collect than bio-oil, causing the economic cost of the operation to be reduced. However, solid ceramic spheres with a large mass and a small specific surface area were used in previous applications, which resulted in a low catalytic capacity. The preparation of porous ceramics based on dolomite as a catalyst carrier was proposed. It is well known that porous ceramics have multiple advantages, i.e., a high mechanical strength, a high temperature resistance, an anti-corrosive character, and a flexible ratio of different raw materials. Porous ceramics are used as catalysts and heat carriers in biomass catalytic pyrolysis reactors. However, the pore size distribution of porous ceramics are primarily macropores, which have the lowest “shape-selective catalysis” capacity for pyrolysis intermediate products and have weak selectivity for most target organic components in the bio-oil (Cui et al. 2016). In order to improve the catalytic reactivity, it has become an important concern to produce bio-oil with specific chemical components and relatively high content via the loading of certain metal ions on the catalyst carrier (Dai et al. 2020).
It should be noted that bio-oil is rich in phenols and can be extracted as a matrix for the synthesis of phenolic resin, which has good potential economic benefits (Mullen and Boateng 2011). In previous studies by the authors, it was found that the acid content decreased, while the ester and phenol content drastically increased when Al2O3 was used as a catalyst during biomass pyrolysis. The Al3+ could promote the formation of hydrocarbons, aromatics, and olefins during the catalytic pyrolysis of biomass (Zhang et al. 2013). Meanwhile, the Al3+ favoured the conversion of hydrocarbons to phenols by reducing the number of acid sites during the biomass pyrolysis process (Lu et al. 2018).
Since alumina is insoluble in water, it is impossible to prepare such a catalyst by impregnating alumina solution. So instead, soluble aluminum sulfate was used as the impregnant, and then the material was sintered to produce alumina and complete the loading of alumina. In this paper, the preparation of dolomite-based porous ceramics (DPCs) loaded with Al2O3 was introduced. The influence of the dolomite to quartz sand ratio, along with the corn flour content, on the physical properties of porous ceramics was analyzed. Furthermore, the yields of the products and the distributions of the primary components in the synthesized bio-oil under different catalytic pyrolysis conditions were studied. This paper proposed a strategy to prepare a novel and economic catalyst which favoured the production of phenols via biomass pyrolysis.
EXPERIMENTAL
Materials
Corn stalk was selected as the fast pyrolysis biomass material. The feedstock was pulverized and screened with a sieve size of 0.18 to 0.25 mm. The industrial analysis and elemental analysis of the corn stalks are shown in Table 1. The corn stalk was pre-dried in an electric thermostatic drying oven at a temperature of 105 °C for 24 h.
The mineral elements of corn stalk ash were detected via X-ray fluorescence spectrometry (ZSX-100e, Rigaku, Japan), as shown in Table 2. The contents of the three primary components, i.e., cellulose (32.54%), hemicellulose (18.34%), and lignins (22.02%), in the corn stalks were determined using the Van Soest method (Chen et al. 2010).
The Preparation of Dolomite-Based Porous Ceramics (DPCs)
DPCs can be prepared utilizing a variety of different techniques, e.g., the space-holder method, foaming method, polymeric sponge dipping method, and sol-gel method (Sopyan and Kaur 2009; Sopyan et al. 2011; Ghomi et al. 2016; Moghadam et al. 2017). In this paper, DPCs were prepared via the space-holder method due to its simple processing technology. Dolomite (CaO: 30%, MgO: 22%, and CO2: 48%) and quartz sand (SiO2 greater than or equal to 99%) were the aggregates of the porous ceramics. In addition, corn flour and zinc borate were incorporated as the space-holder and flux of the DPCs, respectively.
The mass ratios of the dolomite and quartz sand in the aggregate of the porous ceramics were 30 to 70 and 40 to 60, respectively. The aggregate (dolomite and quartz sand) to space-holder to flux ratio was 25 to 2 to 1. The raw materials were uniformly mixed in a mixer to prepare the slurry. The slurry was rotated in a granulator, and then was sprayed with the flux to prepare the ball blank. A ball blank with diameter of 2 mm was selected to dry in an electrothermal blowing dry box until the water content was less than 15%.
The dried ball blank was placed in a cool shady spot and allowed to dry for 24 h in order to avoid cracking during the sintering of DPCs. The DPCs were sintered in a high-temperature box-type resistance furnace (SX-G08133, Tianjin Zhonghuan Experimental Electric Furnace Co., Ltd, Tianjin, China). The sintering temperature of the porous ceramics could be decreased to 1000 °C when zinc borate (flux) was added to the paste. However, deformation and hot cracking could occur in the porous ceramics when the temperature suddenly drops during the sintering process. Therefore, the water content of the porous ceramic ball embryos was reduced to less than 15% before sintering. In the experiment, porous ceramic ball embryos with a size of 8 mesh to 10 mesh were selected.
Loading of the Al2O3 into the Dolomite-Based Porous Ceramics (DPCs)
In this paper, the DPCs were loaded with Al2O3 via the impregnation-calcination method. The impregnation solution was Al2(SO4)3 at concentrations of 0.3 mol/L, 0.5 mol/L, and 1.0 mol/L. The mixture of the porous ceramic balls and Al2(SO4)3 solution were stirred in a magnetic heating stirrer (WH240-plus, WIGGENS GmbH, Straubenhardt, Germany) at a temperature of 25 °C for 6 h. Then, the porous ceramic balls were dried at a temperature of 110 °C for 4 h. Finally, the DPCs were calcined at a temperature of 850 °C for 2 h at a heating rate of 100 °C/h. The chemical reaction of the Al2(SO4)3 during calcination was Al2(SO4)3 → Al2O3 + 3SO3↑. The resultant formation of the Al2O3 was γ-Al2O3 in the above reaction.
Preparation Parameters of the Dolomite-Based Porous Ceramics (DPCs)
In the reactor, the DPCs interacted with the biomass powder and reactor walls to achieve heat exchange with the biomass powder as well as catalyze the formation of pyrolysis gas during biomass pyrolysis. The porosity, bulk density, compressive strength, thermal shock resistance, thermal expansion coefficient, and thermal conductivity of the DPCs could influence the heat exchange and the catalytic activity of the catalyst.
Open Porosity and Bulk Density
The porosity of the porous ceramics consists of open porosity and closed porosity (Zou and Malzbender 2016). In this study, the DPCs were used as heat carriers and catalysts during biomass pyrolysis. Hence, the open porosity (Pa) of the DPCs was measured, as shown in Eq. 1,
(1)
as well as the bulk density (ρ), as shown in Eq. 2,
(2)
where m1, m2, and m3 are the dried mass of DPCs (g), the mass of the saturated of DPCs in the air (g), and the mass of the saturated DPCs in the water (g), respectively.
Compressive Strength, Thermal Shock Resistance, Thermal Expansion Coefficient, and Thermal Conductivity
A simple cylinder with a diameter of 20 mm and height of 20 mm was utilized to measure the compressive strength of the DPCs. The thermal shock resistance of the DPCs was measured using simple cuboids with dimensions of 120 mm × 20 mm × 10 mm. The thermal shock resistances of the DPCs were obtained at temperatures of 25, 400, and 600 °C using a thermal shock resistance tester (KRZ-S01, Guangzhou Key Instrument Co., Ltd., Guangzhou, China). Generally speaking, the thermal expansion coefficient decreased as the thermal stability increased (Roy et al. 1989). The test sample for measuring the thermal expansion coefficient (α) was a cylindrical porous ceramic with a diameter of 150 mm and height of 10 mm, and was calculated using Eq., 3,
(3)
where t0, t, L0, and Lt are the initial temperature (°C), the final temperature (°C), the length of sample at t0 (mm), and the length at t (mm), respectively.
The thermal conductivity of the DPCs is drastically affected by the heat transfer between the biomass powder and the porous ceramic balls, the biomass powder, and the pyrolysis gas in the pyrolysis reactor. The thermal conductivity sample had a diameter of 120 mm and height of 5 mm. The thermal conductivity of the DPCs was measured with a thermal conductivity tester (THQDC-1, Xi’an Xiaxi Electronic Technology Co., Ltd., Xi’an Xi’an, China) via the steady state method.
Catalytic Pyrolysis Using Dolomite-Based Porous Ceramics (DPCs)
The catalytic fast pyrolysis of corn stalks was conducted using a thermostatic horizontal tube furnace reactor (SK-G06123K-3-655, Tianjin Zhonghuan Experimental Electric Furnace Co., Ltd., Tianjin, China). The experimental system consisted of a thermostatic horizontal tube furnace reactor and a condensation unit. First, nitrogen at a rate of 30 L/h was introduced into the experimental system for 5 min to create an oxygen-free environment. Then, the corn stalk and catalyst were mixed at a mass ratio of 1 to 5. The pyrolysis temperature was 475 °C and the pyrolysis reaction holding time was 10 min. Once the temperature of the furnace reached 475 °C, the porcelain boat serving the biomass and catalyst was quickly pushed into the reactor. The pyrolysis gas was condensed in a low-temperature thermostatic bath to obtain the bio-oil. The temperature of the condensation unit was -10 °C.
RESULTS AND DISCUSSION
The Effect of the Corn Flour Content on the Catalyst Properties
The influence of the corn flour content on the open porosity, bulk density, compressive strength, thermal shock resistance, thermal expansion coefficient, and thermal conductivity of the DPCs are shown in Fig. 2. The mass ratio of dolomite to quartz sand was 3 to 7. The mass ratio of corn flour to aggregate (dolomite and quartz sand) was 6%, 8%, 10%, and 12%, respectively.
Fig. 2. The effect of corn flour content on the physical properties of the DPCs: (a) porosity, (b) bulk density, (c) compressive strength, (d) thermal expansion coefficient, (e) thermal conductivity, and (f) thermal shock resistance
The results showed that the open porosity of the DPCs linearly increased as the corn flour content increased. When the corn flour content was increased from 6% to 12%, the open porosity increased two-fold (Fig. 2a). The bulk density of the DPCs markedly decreased as the corn flour content increased. The bulk density decreased from 0.8296 to 0.7299 g/cm3 when the corn flour content increased from 6% to 8% (Fig. 2b). The reason for this phenomenon was that when the corn flour content increased, the pore volume in the porous ceramics increased, thereby decreasing their bulk density. The compressive strength of the DPCs linearly decreased as the corn flour content increased. When the corn flour content increased by 2%, the compressive strength decreased by 70%. The reason for this phenomenon was that the open porosity of the DPCs was higher and the quantity of pores and voids was higher. Meanwhile, the strength of the framework in the DPCs became weaker. Thus, the compressive strength of the porous ceramics decreased as the open porosity increased (Fig. 2c). The thermal expansion coefficient of the porous ceramics did not drastically change as the corn flour content increased (Fig. 2d). The thermal conductivity of the porous ceramics decreased as the corn flour content increased. The thermal conductivity decreased by 33.4% when the corn flour content increased from 8% to 12% (Fig. 2e). The thermal shock resistance of the DPCs decreased as the corn flour content and the temperature increased (Fig. 2f).
The open porosity and compressive strength of the DPCs were high when used as a catalyst and a hot carrier during the biomass pyrolysis process. Therefore, the optimal corn flour content of the DPCs was judged to be 8%.
The Effect of the Dolomite to Quartz Sand Ratio on the Catalyst Properties
Table 3 presents the DPCs properties at different ratios of dolomite and quartz sand (30 to 70 and 40 to 60). A comparison between calcined dolomite and the DPCs clearly showed that the compressive strength was drastically improved. The reason for this phenomenon was that the CO2 content in the dolomite was thermally decomposed, which causes the ceramic aggregate to lose weight and leave multiple irregular pores. In addition, the open porosity in sample 2 was higher than the open porosity of sample 1. Therefore, the optimum ratio of dolomite and quartz sand was 40 to 60.
The specific surface area and pore volume were detected via a mercury porosimeter (PoreMaster 33, Quantachrome Instruments, Boynton Beach, FL) with a ratio of dolomite to quartz sand of 40 to 60 in the DPCs. The specific surface area and pore volume of the DPCs were 0.4328 m2/g, and 0.4329 cc/g, respectively.
Dolomite-Based Porous Ceramics (DPCs) Loaded with Al2O3
The loading content of Al2O3 crystals attached to the surface of the DPCs increased as the Al2(SO4)3 solution concentration increased. The Al2O3 crystals were uniformly dispersed on the DPCs. The loading quantity of Al2O3 on the DPCs was detected using an X-ray fluorescence analyzer (XRF) (XS100e 5700, RIKAGU, Tokyo, Japan), and the ratio of dolomite to quartz sand was 40 to 60 (Fig. 3).
Fig. 3. The loading quantity of Al2O3 on the DPCs
The results showed that the loading quantity of Al2O3 was 2.58%, 3.17%, and 4.05% when impregnated with 0.3, 0.5, and 1 mol/L of Al2(SO4)3, respectively. Therefore, it could be seen that loading Al2O3 onto the DPCs via the impregnation method was effective.
Dolomite-Based Porous Ceramics (DPCs) Loaded with Al2O3 for the Pyrolysis of Biomass
The collected bio-oil was analyzed via a GC/MS (Agilent 6890/5973, Agilent Technologies Inc., Santa Clara, CA) equipped with a Rtx-5 capillary column (30 m × 0.25 mm × 0.25 µm). The carrier gas was He with high purity (greater than 99.99%). The split ratio was 30 to 1, the injection volume was 0.2 µL, and the gasification temperature was 280 °C. The temperature procedure was set to increase from room temperature to 240 °C at a heating rate of 5 °C/min, and then held at 240 °C for 5 min. The ionization mode was EI and the electron bombardment energy was 70 eV. The temperature of the ion source and the interface were set at 240 and 250 °C, respectively. The non-condensable bio-gas was analyzed using an infrared gas analyzer (3100, Wuhan Sifang Photoelectric Technology Co., Ltd., Wuhan, China).
In order to determine the bio-oil (Yo), bio-char (Yc), and non-condensable bio-gas (Yg) yields, the respective results were calculated according to Eqs. 4, 5, and 6,
(4)
(5)
(6)
where mo, mc, and M are mass of bio-oil (g), the mass of bio-char (g), and the mass of corn stalk (g), respectively.
The catalytic pyrolysis of corn stalk was conducted using the DPCs loaded with Al2O3 as the catalyst. The experimental design is shown in Table 4. The effects of the dolomite to quartz sand ratio, as well as if the DPCs were loaded with Al2O3, on the pyrolysis products and the distribution of the bio-oil were analyzed.
Fig. 4. The yields of the pyrolysis products from corn stalk
Figure 4 presents the yields of the pyrolysis products from corn stalk. The bio-oil yields increased as the ratio of dolomite to quartz sand increased. The bio-oil yields increased by 5.9% (Run 2), and 16.5% (Run 3) when compared with the non-catalytic pyrolysis process (Run 1). Compared with Run 1, the bio-char yields in Run 2 and Run 3 were reduced by 18.50% and 39.13%, respectively. Dolomite promoted the cracking of macromolecular organics during the biomass pyrolysis, which caused a reduction in total bio-char yield. The non-condensable bio-gas yield increased as the dolomite mass increased. A comparative analysis between Run 3 and Runs 4, 5, and 6 clearly showed that the bio-oil yield decreased when the DPCs were loaded with Al2O3. The addition of alumina additives may promote the conversion of other substances into phenolic substances. It maybe breaks the bonds of the big molecules, so the coke, small molecular e.g. CO2, CH4, CO, and other non-condensable gases increased, and the output of bio-oil was reduced. The non-condensable bio-gas yields increased by 39.57% (Run 4), 27.87% (Run 5), and 27.93% (Run 6) when compared with Run 1.
Fig. 5. Content and distribution of the components in the bio-oil
Figure 5 illustrates the chemical compounds and their distributions in the bio-oil synthesized from corn stalk. Compared with the non-catalytic pyrolysis process (Run 1), the formic acid hydrazide, methyl acetate, and 3-(2-hydroxyphenyl)-2-propenoic acid contents in the bio-oil from Run 3 decreased by 14.7%, 26.4%, and 11.3%, respectively. Meanwhile, the 3-furaldehyde and 2-methoxy-4-vinylphenol contents increased by 1.7%, and 2.0%, respectively. In order to study the influence of Al2O3 on the compound contents in the bio-oil, the data obtained from Runs 3 through 6 were analyzed. The formic acid hydrazide, methyl acetate, and 3-furaldehyde contents increased when Al2O3 was loaded on the DPCs. The formic acid hydrazide, methyl acetate, and 3-furaldehyde content increased as the Al2O3 loading quantity increased. The 3-(2-hydroxyphenyl)-2-propenoic acid, and 2-methoxy-4-vinylphenol contents decreased as the Al2O3 loading quantity increased.
There were more than 400 chemical compounds in the pyrolysis bio-oil derived from corn stalk (Li et al. 2017). It was difficult to detect all the components in the bio-oil. The primary components in the bio-oil and their respective relative contents were detected via GC/MS and only peak areas greater than 1% were analyzed in detail.
The primary components in the bio-oil derived from Runs 1, 3, 4, 5, and 6 consisted of alcohols, ketones, phenols, acids, and aldehydes (Fig. 6).
Fig. 6. Alcohol, ketone, phenol, acid, and aldehyde contents in the bio-oil
The results showed that the ketone and acid content in Run 3 were decreased by 7.5% and 14.7%, respectively, when compared to Run 1. The alcohol and phenol content in the bio-oil increased when Al2O3 was loaded on DPCs. The alcohol content increased while the phenol content decreased as the Al2O3 loading quantity increased. Therefore, the addition of Al2O3 can improve the cracking of macromolecules, which causes the formation of alcohols and phenols in the bio-oil during pyrolysis. The ketone content gradually decreased as the Al2O3-loading ratio increased. A comparison between Run 1 and Runs 4, 5, and 6 showed that the ketone content in the bio-oil decreased by 14.0%, 25.1%, and 30.5%, respectively. The ketone content in Runs 4, 5, and 6 decreased by 6.9%, 19.0%, and 24.9%, when compared to the ketone content in Run 3. This phenomenon indicated that both dolomite and Al2O3 promoted the decarbonylation reaction effectively, causing the removal of oxygen elements in some oxygen-containing functional groups. The phenol content in the bio-oil decreased as the Al2O3 loading quantity increased. The Al2O3 load had a complex effect on the production of phenols in the bio-oil. It not only promoted the formation of phenols, but also promoted the conversion of phenols, e.g., 4-ethylphenol, 4-allyl-2, 6-dimethoxyphenol, 2-methoxy-4-vinylphenol, and 2, 6- dimethoxy-phenol. The acid content in the bio-oil drastically decreased when Al2O3 was loaded on the DPCs. The acid content in the bio-oil decreased by 18.8%, 25.8%, 44.4%, and 4.8%, 12.9%, and 34.6% when compared with the acid content in Run 1 and Run 3, respectively. Therefore, both dolomite and Al2O3 promoted the conversion of acids, which caused a reduction in bio-oil acid value.
CONCLUSIONS
- The preparation of dolomite-based porous ceramics (DPCs) loaded with Al3+ via the space-holder method was proposed for biomass pyrolysis. The open porosity of the DPCs increased from 34.2% to 68% when the corn flour content was increased from 6% to 12%. The authors suggest that the optimal corn flour content of DPCs is 8%. This would cause the DPCs to have a higher thermal conductivity, higher compressive strength, and larger open porosity.
- The catalytic pyrolysis of corn stalks was performed in a horizontal tube furnace reactor. The bio-oil yields increased as the dolomite content in the DPCs increased. Compared with non-catalytic pyrolysis (Run 1), the bio-oil yields increased by 5.9% (Run 2), and 16.5% (Run 3), respectively. Compared with using DPCs without the addition of a Al2(SO4)3 solution as the catalyst (Run 3), the bio-oil yield decreased when the DPCs were loaded with Al2O3.
- Compared with non-catalytic pyrolysis (Run 1), the formic acid hydrazide, methyl acetate, and 3-(2-hydroxyphenyl)-2-propenoic acid content in the bio-oil synthesized from corn stalk pyrolysis with DPCs (Run 3) decreased by 14.7%, 26.4% and 11.3%, respectively. The 3-(2-hydroxyphenyl)-2-propenoic acid and 2-methoxy-4vinylphenol content decreased as the Al2O3 loading quantity increased. The ketone content in the bio-oil decreased by 14.0% (Run 4), 25.1% (Run 5), and 30.5% (Run 6) when compared to Run 1. The acid content in the bio-oil was drastically reduced when Al2O3 was loaded on the porous ceramics.
ACKNOWLEDGEMENTS
This work received funding from the National Key Research and Development Program of China (2019YFD1100602), the National Natural Science Foundation of China (51606113), and the SDUT & Zhoucun City Integration Development Project (2020ZCXCZH09).
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Article submitted: March 21, 2021; Peer review completed: May 9, 2021; Revised version received and accepted: May 18, 2021; Published: June 1, 2021.
DOI: 10.15376/biores.16.3.5234-5247