Microwave-assisted Catalytic Fast Pyrolysis Research Articles

Production of monocyclic aromatic hydrocarbons from microwave co-pyrolysis of polyethylene terephthalate and low-density polyethylene using coconut husk carbon as microwave absorbent

The application of biochar as microwave absorbers in microwave-assisted catalytic fast pyrolysis (MACFP) has been widely studied. It has been reported that coconut husk carbon (CHC) showed good process characteristics and product distribution as microwave absorbers. However, the existing studies did not pay much attention to the reusability of CHC absorbers. In this study, the CHC absorbers prepared from agricultural and forestry wastes were reused in multiple cycles in the MACFP of polyethylene terephthalate (PET) and low-density polyethylene (LDPE). Compared with typical microwave absorbers such as spherical silicon carbide (SiC) and granular activated carbon (GAC), CHC demonstrated favorable process characteristics with relatively high heating rate (29 °C/min) and short heating time (within 12 min). In terms of product properties, the highest liquid yield of 51.67 wt% and the highest content of monocyclic aromatic hydrocarbons (MAHs) of 82.82 % were obtained at the appropriate pyrolysis temperature (550 °C). After five consecutive uses, the CHC bed still produced comparable heating profiles and product distributions, compared to that of SiC. At the same time, a positive synergistic effect between PET and LDPE was observed. The co-feeding of PET and LDPE (50L50P) appropriately increased the liquid yield (42.50 wt% vs 38.75 wt%) and the relative content of MAHs (77.11 % vs 72.96 %) in comparison to their theoretical value. Finally, this study supplies a new strategy for utilizing recycled CHC as a microwave absorber for the treatment of hydrogen-rich and hydrogen-deficient mixed plastic wastes to produce MAHs products, which also reduces waste and realizes energy conversion.

Parametric study of the catalytic fast pyrolysis of rice husk over hierarchical micro-mesoporous composite catalyst in a microwave-heated fluidized bed

To improve the efficiency of the catalyst fast pyrolysis (CFP) of rice husk and the quality of bio-oil, we integrate both microwave heating and fluidized bed reactor methods and build a microwave-heated fluidized bed system. In this study, the liquid yield from the CFP of rice husk in a microwave-heated fluidized bed (55.3 wt.%) is significantly higher than that obtained from a fixed bed (47.6 wt.%). Meanwhile, the relative content of hydrocarbons from microwave assisted catalytic fast pyrolysis (MACFP) of rice husk (RH) over a hierarchical micro-mesoporous composite molecular sieve (HM-2.0 T) is 67.6 % higher than that (51.6 %) of the organic base modified HZSM-5 (HT-2.0) and HZSM-5 (40.2 %) in the microwave-heated fluidized bed system. Furthermore, we focused on the ratio of biomass to catalyst in CFP processing and discover that the increased amount of catalyst promoted the decarbonylation and decarboxylation reactions, producing more hydrocarbon compounds, however, the excessive amount of catalyst does not contribution to higher monocyclic aromatic hydrocarbon selectivity. Besides, the hierarchical micro-mesoporous composite catalyst had strong regeneration ability and reusability. The selectivity of monocyclic aromatics remained high when the regeneration times increase from 1 to 4, which provided possibilities for applications of hierarchical micro-mesoporous composite catalyst in industrial production in the future.

Conversion of soybean soapstock into hydrocarbon fuel by microwave-assisted catalytic fast pyrolysis using MCM-41/HZSM-5 in a downdraft reactor

Microwave-assisted catalytic pyrolysis of biomass is a promising technology to obtain hydrocarbon rich fuel oil. In consideration of this method, HZSM-5 is currently recognized as a catalyst with a good effect. However, given the small pore diameter and easy coking of HZSM-5, the catalytic upgrading of bio-oil is limited to a certain extent. In this study, MCM-41 and HZSM-5 were used for joint catalysis to explore the effect of catalytic temperature, the ratio of two catalysts, and the ratio of soybean soapstock and catalysts on the pyrolysis products. The optimal reaction conditions included the following: catalytic temperature, 400 °C; MCM-41/HZSM-5 ratio, 1:1; feedstock/catalyst ratio, 2:1. The results showed that MCM-41 could effectively alleviate the coking of HZSM-5, and the use of both catalysts reduced the bio-oil yield but effectively improved the selectivity of monocyclic aromatic hydrocarbons in bio-oil, thus increasing the value of bio-oil.

Microwave-assisted catalytic fast pyrolysis of rice husk over a hierarchical HZSM-5/MCM-41 catalyst prepared by organic base alkaline solutions

This paper reports the results obtained for microwave-assisted catalytic fast pyrolysis (MACFP) of rice husk. The MACFP process employed a hierarchical catalyst prepared via a combination of organic alkali treatment (TPAOH) and the generation of an external layer of MCM-41-type mesoporous channels. We propose this catalyst which is used for the first time for pyrolysis of lignocellulosic biomass, as a tool to reduce coke agglomeration and increase hydrocarbon yields. Our results indicate that during catalyst preparation the mass fraction of cetyltrimethylammonium bromide (CTAB) has a direct effect on the content of MCM-41 formed on top of the HZSM-5 core. For MACFP, we hypothesize that the small molecules generated from thermal decomposition of rice husk react further to form aromatic and aliphatic hydrocarbons by decarbonylation, decarboxylation, oligomerization and aromatization. The highest hydrocarbon yield (60.5%) was obtained for a catalyst modified by a 2.0 mol/L TPAOH solution, with 10 wt% of CTAB (template for producing MCM-41), as well as with digestion and crystallization at 110 °C for 24 h. In addition, the highest liquid yield (47.6 wt%) was obtained at 550 °C. The relative content of hydrocarbons goes through a maximum of 60.5% with CTAB mass fraction which was higher than values obtained with MCM-41 (3.2%) and HZSM-5 (36.0%). Characterization and catalytic testing results suggest that the digestion temperature plays a more important role in the catalyst synthesis than the crystallization temperature. High digestion temperature (120 °C) decreases the overall hydrocarbon selectivity from 60.5% (110 °C) to 39.2%. The relative content of oxygenates reached the lowest value of 35.9% at the digestion and crystallization temperature of 110 °C. The synergistic effect of the MCM-41 shell and the HZSM-5 core promotes the catalytic activity, leading to outstanding deoxygenation capabilities and excellent selectivity to BTEX (52.7%).

Microwave-Assisted Catalytic Fast Pyrolysis of Biomass for Hydrocarbon Production with Physically Mixed MCM-41 and ZSM-5

To delve into the law of hydrocarbon production in microwave-assisted catalytic fast pyrolysis (MACFP) of corn straw, physical mixed Mesoporous Crystalline Material-41 (MCM-41) and Zeolite Socony Mobile-5 (ZSM-5) catalyst prototypes were exploited in this study. Besides, the effects exerted by temperature of reaction and MCM-41/ZSM-5 mass ratio were explored. As revealed from the results, carbon outputs of hydrocarbons rose initially as the temperature of MACFP rose and reached the maximal data at 550 °C; subsequently, it declined as reaction temperature rose. Moreover, the MCM-41/ZSM-5 mass ratio of 1:2 was second-to-none for hydrocarbon formation in the course of biomass MACFP. It was reported that adding MCM-41 can hinder coke formation on ZSM-5. Furthermore, MCM-41/ZSM-5 mixture exhibited more significant catalytic activity than ZSM-5/MCM-41 composite, demonstrating that hydrocarbon producing process can be stimulated by a simple physical MCM-41 and ZSM-5 catalysts mixture instead of synthesizing complex hierarchically-structured ZSM-5/MCM-41 composite.

Effect of alkali-treated HZSM-5 zeolite on the production of aromatic hydrocarbons from microwave assisted catalytic fast pyrolysis (MACFP) of rice husk

We performed microwave-assisted catalytic fast pyrolysis (MACFP) of rice husk (RH) over an alkali-treated HZSM-5 zeolite, for production of hydrocarbons. The treatment consisted in the modification of the HZSM-5 by the organic base tetrapropylammonium hydroxide (TPAOH) solution at several concentrations. We characterized the resulting catalysts by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), N2 adsorption-desorption, and temperature-programmed sorption of ammonia (NH3-TPD). The results suggest that the TPAOH treatment generated mesoporous structures in the HZSM-5, while preserving its microporous structure and crystallinity. We obtained the highest yield (45.9%) of hydrocarbons from MACFP of rice husk (RH) at 550 °C. As the TPAOH concentration increases, the relative content of BTEX hydrocarbons (benzene, toluene, ethylbenzene, and xylene) reaches a maximum value of 22.9% at 2.0 mol/L. A comparison of results obtained over the organic base TPAOH (HZSM-5 modified by 2.0 mol/L TPAOH solution) with those obtained over an inorganic base (HZSM-5 modified by 2.0 mol/L NaOH solution) shows a 4.3% increase in the relative content of monocyclic aromatic hydrocarbons for the TPAOH. In addition, the TPAOH-treated catalyst shows excellent selectivity of BTEX (58.5%), which is higher than the selectivity obtained with the parent HZSM-5 (51.2%) and NaOH-treated HZSM-5 (53.9%). The TPAOH-modified HZSM-5 catalyst effectively reduced coke formation by 4.6% compared to MACFP over the parent HZSM-5, most likely because TPAOH decreases the concentration of strong acidic sites on the outer surface of the catalyst, creating a mesoporous structure while retaining the weak acidic sites on the HZSM-5 inner surface. The new catalyst generated in this work contains a moderate amount of mesopores structures, which allows for effective upgrading of pyrolysis vapors while simultaneously reducing coke formation, thereby addressing a significant problem in the development of the catalytic fast pyrolysis process.

Microwave-assisted catalytic fast pyrolysis coupled with microwave-absorbent of soapstock for bio-oil in a downdraft reactor

Microwave-assisted pyrolysis of biomass with HZSM-5 coupled with SiC as microwave-absorbent in a downdraft reactor is a promising method for obtaining hydrocarbon-rich bio-oil. The hydrocarbon content limits the economic and commercial viability of the bio-oil produced by pyrolysis. In this study, the effects of catalytic temperature, feedstock-to-catalyst ratio, and WHSV on the yield and composition of bio-oil are studied. In addition, this study compared the influence of downdraft reaction and updraft reaction on the yield and composition of bio-oil. Furthermore, the stability of the catalyst is studied. Catalytic temperature and feedstock-to-catalyst ratio played pivotal roles in the yield and composition of bio-oil. WHSV has minimal influence on the bio-oil yield and composition within the scope of our research. Furthermore, the optimal catalytic temperature, feedstock-to-catalyst ratio and WHSV were 400 °C, 2:1, and 72 h−1, respectively. The results illustrated that the downdraft coupled with the microwave-absorbent was conducive to the formation of aromatic hydrocarbons. The HZSM-5 performed well in five replicate experimental cycles under optimal conditions in terms of bio-oil yield and aromatic hydrocarbon yield.

Bio-oil production from sequential two-step microwave-assisted catalytic fast pyrolysis of water hyacinth using Ce-doped γ-Al2O3/ZrO2 composite mesoporous catalyst

A sequential two-step microwave-assisted catalytic fast pyrolysis (MACFP) of water hyacinth for hydrocarbon-rich bio-oil production is studied. This newly developed technique is characterized by microwave-assisted fast pyrolysis followed by catalytic upgrading using an additional catalyst packed bed, and it thus achieves the independent control of pyrolysis and catalytic upgrading. On the other hand, in order to minimize coke formation and promote hydrocarbon production in sequential two-step MACFP of water hyacinth, Ce-doped γ-Al2O3/ZrO2 composite mesoporous catalyst (CAZ) is synthesized and used in this study. The effects of catalyst type, pyrolysis temperature, catalytic upgrading temperature and catalyst reusability on product distribution and chemical compositions in bio-oil are investigated. The results demonstrate that water hyacinth is a good biomass candidate for fuel demand, and CAZ can facilitate the hydrocarbon fuel production in bio-oil and exhibits an excellent catalyst reusability. Meanwhile, it is found that the optimal temperatures for water hyacinth pyrolysis and pyrolytic vapor upgrading are 650 °C and 450 °C, respectively.

Biofuel production from distillers dried grains with solubles (DDGS) co-fed with waste agricultural plastic mulching films via microwave-assisted catalytic fast pyrolysis using microwave absorbent and hierarchical ZSM-5/MCM-41 catalyst

Microwave-assisted catalytic fast co-pyrolysis (co-MACFP) of distillers dried grains with solubles (DDGS) and waste agricultural plastic mulching films (WAPMFs) with SiC as microwave absorbent and hierarchical ZSM-5/MCM-41 as catalyst are implemented in a microwave-induced reactor. MCM-41 mesoporous structure is formed in hierarchical ZSM-5/MCM-41 catalyst as the outer shell layer coupled with ZSM-5 as the inside core. Experimental results show that the use of both microwave absorbent and hierarchical ZSM-5/MCM-41 catalyst significantly increase the carbon yield of hydrocarbons in bio-oil. The influence of co-MACFP temperature and the mass ratio of WAPMFs to DDGS (W/D ratio) on product distribution and hydrocarbon composition is investigated. The total liquid yield and total hydrocarbon carbon yield in bio-oil first increase with the augment of temperature from 500 to 650 °C, and then decrease when temperature continues to rise. Besides, a higher W/D ratio can favor bio-oil production and retard coke formation, and a significant synergy between DDGS and WAPMFs is observed during co-MACFP. Additionally, from the perspective of hydrocarbon carbon yield in bio-oil, W/D ratio of 1.0 is the best option.

Conversion of poultry litter into bio-oil by microwave-assisted catalytic fast pyrolysis using microwave absorbent and hierarchical ZSM-5/MCM-41 catalyst

In order to minimize coke formation during microwave-assisted catalytic fast pyrolysis (MACFP) of poultry litter for bio-oil production, hierarchical ZSM-5/MCM-41 catalyst samples are synthesized and employed in this work, and the effect of NaOH concentration used during catalyst preparation on MACFP of poultry litter is investigated. The catalyst characterization results demonstrate that MCM-41 mesoporous structure is formed in hierarchical ZSM-5/MCM-41 catalyst as the outer shell layer coupled with ZSM-5 as the inside core. For product distribution, when the NaOH concentration increases from 1.5 to 3.0 mol/L, the coke yield decreases, the oil fraction yield first decreases and then increases, and the yields of water and gas first increase and then decrease. For chemical compositions in oil fraction, the relative contents of aliphatic hydrocarbons, aromatic hydrocarbons and oxygen-containing aromatic compounds first increase and then decrease, whereas the relative content of oxygen-containing aliphatic compounds first decrease and then increase.

Microwave-assisted catalytic fast co-pyrolysis of Ageratina adenophora and kerogen with CaO and ZSM-5

Microwave-assisted catalytic fast pyrolysis (MACFP) of Ageratina adenophora, kerogen and their mixtures with CaO and ZSM-5 catalysts are implemented in a microwave-induced reactor. The effects of reaction temperature and CaO/ZSM-5 mass ratio on pyrolysis product yields and selectivities of MACFP of pure Ageratina adenophora and kerogen are investigated. A maximum carbon yield of petrochemicals (aromatics+C2-C4 olefins+C5 compounds) from Ageratina adenophora of 21.9% is obtained at a temperature of 550°C and CaO/ZSM-5 mass ratio of 1:3. A maximum petrochemical yield from kerogen of 54.8% is obtained at a temperature of 650°C and CaO/ZSM-5 mass ratio of 1:3. Likewise, the MACFP of Ageratina adenophora and kerogen mixtures is conducted and the effects of reaction temperature and overall effective hydrogen index (EHI) of feedstock are studied. The highest carbon yield of petrochemicals from Ageratina adenophora and kerogen mixtures is gained at a temperature of 600°C. Additionally, it is observed that co-feeding Ageratina adenophora with kerogen can facilitate hydrocarbon production and thus show a postive synergy. The carbon yield of petrochemicals from co-feeding is higher than running these two feedstocks under their respective optimal reaction temperatures when EHI is at the range of 0.4–1.0. Besides, coke formation can be inhibited during catalytic co-feeding pyrolysis. These findings from this study pave a new route for biorefinery industries to produce developed products from Ageratina adenophora and kerogen through microwave-induced technologies.

Fast microwave-assisted catalytic co-pyrolysis of straw stalk and soapstock for bio-oil production

This study investigated the microwave-assisted catalytic fast pyrolysis (MACFP) of straw stalk and soapstock with HZSM-5 as a catalyst. The effects of pyrolysis temperature, catalyst:feed ratio, and straw stalk:soapstock ratio on bio-oil yield and composition were discussed. Results showed that temperature greatly influenced the yield and product distribution of bio-oil. The maximum bio-oil yield and highest proportion of aromatic hydrocarbons were obtained at 550°C. Adding HZSM-5 decreased bio-oil yield but improved bio-oil quality. Co-feeding straw stalk and soapstock can improved the proportion of aromatic and aliphatic compounds. The optimal range of straw stalk:soapstock ratio was 1:1 to 1:2. Moreover, biochar is rich in various essential elements and can be used as good soil amendment.

Microwave-assisted catalytic fast pyrolysis of spent edible mushroom substrate for bio-oil production using surface modified zeolite catalyst

In order to minimize coke yield and improve hydrocarbon production during microwave-assisted catalytic fast pyrolysis of spent edible mushroom substrate, ZSM-5 zeolite catalyst is modified with pre-coking treatment, chemical vapor deposition of SiO2, and ethylene diamine tetraacetie acid (EDTA) chemical modification method, respectively (labeled PC-ZSM-5, SiO2-ZSM-5 and EDTA-ZSM-5). Experimental results show that all the modification methods result in a loss of external acid sites of ZSM-5. Among the three modified catalysts, the maximum oil fraction yield and the minimum coke yield are obtained with SiO2-ZSM-5. The relative content of hydrocarbons in oil fraction increases in the following order: SiO2-ZSM-5>EDTA-ZSM-5>PC-ZSM-5>original ZSM-5. Moreover, SiO2-ZSM-5 shows the highest relative contents of toluene and xylene, whereas original ZSM-5 produces the lowest ones. Besides, the selectivity of benzene in aromatics follows the order of original ZSM-5>EDTA-ZSM-5>PC-ZSM-5>SiO2-ZSM-5, while the selectivity of toluene+xylene presents the opposite trend.

Modification and regeneration of HZSM-5 catalyst in microwave assisted catalytic fast pyrolysis of mushroom waste

In this contribution, HZSM-5 zeolites were modified by ethylene diamine tetraacetic acid (EDTA) to selectively eliminate the strong external acid sites, and the modified catalysts were then used to conduct the microwave assisted catalytic fast pyrolysis (MACFP) of mushroom waste (MW). Experiment results showed that the modification of HZSM-5 with EDTA had no significant effect on topological structure, and the surface area and total acid sites decreased while the pore volume increased within the modification time regions. Among the modified catalysts, an EDTA treatment for 2h (labeled as 2H-Z5) performed prominent promise for removing oxygenated chemicals and promoting the aromatic species as well as inhibiting the formation of coke. Simultaneously, the effects of various regeneration steps for deactivated 2H-Z5 catalysts on products distribution were studied, and the highest relative content of hydrocarbons (19.9%) and the lowest coke yield (3.48%) could be obtained under the third regeneration cycle condition.

Microwave-assisted catalytic fast pyrolysis of biomass for bio-oil production using chemical vapor deposition modified HZSM-5 catalyst

Chemical vapor deposition with tetra-ethyl-orthosilicate as the modifier was applied to deposit the external acid sites of HZSM-5, and the modified HZSM-5 samples were used for the microwave-assisted catalytic fast pyrolysis (MACFP) of biomass for bio-oil production. The experimental results showed that the external acid sites of HZSM-5 decreased significantly when SiO2 deposited amount increased from 0% to 5.9%. For product distribution, the coke yield decreased, the oil fraction yield decreased at first and then increased, and the yields of water and gas first increased and then decreased over the range of SiO2 deposited amount studied. For chemical compositions in oil fraction, the relative contents of aliphatic hydrocarbons, aromatic hydrocarbons and oxygen-containing aromatic compounds first increased to maximum values and then decreased, while the relative content of oxygen-containing aliphatic compounds first decreased and then increased with increasing SiO2 deposited amount.