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The co-pyrolysis of industrial enzymatic hydrolysis of lignin residue with waste plastic to produce bio-oil can increase resource utilization and reduce pollution. However, the high concentration of oxygenated compounds, particularly phenolic compounds, limits the large-scale application of crude bio-oil. Bimetallic-loaded bifunctional catalysts have been prepared by loading different transition metals and Ru onto Nb 2 O 5. We explored their performances in crude co-pyrolysis bio-oil hydrodeoxygenation (HDO). Compared to other transition metals, the selectivities for aromatic hydrocarbons, phenolic compounds, and other oxygenated compounds in the upgraded oil obtained by the catalytic HDO of Ni and Ru bimetallic-loaded Nb 2 O 5 (Ni-Ru@Nb 2 O 5) was the lowest, whereas the aliphatic hydrocarbons selectivity was the highest. The selectivities for other oxygenated compounds, phenolic compounds, and aromatic hydrocarbons in the upgraded oil decreased as the Ni loading increased, whereas the aliphatic hydrocarbons selectivity increased. Ni-Ru@Nb 2 O 5 catalyzed HDO of crude bio-oil showed a maximum selectivity of 86.30 % for hydrocarbons in the upgraded oil at a reaction time of 2 h and a reaction temperature of 280 °C. The degree of deoxygenation of upgraded oil reached 68.87 % under optimal conditions, and the molar ratio of H-to-C was increased from 1.31 (crude bio-oil) to 2.37 (upgraded oil). Ni-Ru@Nb 2 O 5 is an effective catalyst method for the HDO of crude bio-oil. [Display omitted] • Bimetallic-loaded Nb 2 O 5 catalysts were prepared by loading Ru and transition metals. • Hydrodeoxygenation of co-pyrolysis bio-oil was carried out to produce hydrocarbons. • A maximum selectivity of 86.30 % for hydrocarbons was obtained in upgraded oil. • The mechanism of Ni-Ru@Nb 2 O 5 promoting hydrocarbon generation was investigated. [ABSTRACT FROM AUTHOR]

[Display omitted] • Industrial lignin residue was used to prepare MAHs via microwave-assisted pyrolysis. • Co-pyrolysis of lignin residue with PE to increase MAHs content in the product. • Optimal pyrolysis temperature and catalyst addition for co-pyrolysis were defined. • Synergistic mechanism of co-pyrolysis promoting hydrocarbon generation was studied. Enzymatic hydrolysis lignin (EHL), lignosulfonate (LS), alkali lignin (AL), and hydrolysis lignin (HL) residues are mostly burned for heating in industrial production, which greatly wastes resources and pollutes the environment. In this study, we investigated the effects of different temperatures and catalyst-to-biomass mass (C/B) ratios on the relative content of hydrocarbons in the products by microwave-assisted pyrolysis in a fluidized bed. Co and Ni bimetal-loaded molecular sieve with core-shell structure (Co-Ni@H/M) was used as the catalyst. The main component of waste plastic, polyethylene (PE), was pyrolyzed with these four lignin residues to prepare monocyclic aromatic hydrocarbons (MAHs), and the mechanism of synergistic interaction in co-pyrolysis was investigated. It was shown that the maximum liquid phase yield and hydrocarbons relative content were obtained at 550 °C when lignin residues were pyrolyzed alone. Compared with the pyrolysis of lignin residues alone, the liquid phase and gas phase yields of co-pyrolysis were improved, while the solid phase yield decreased. Moreover, the temperature for maximum liquid phase yield and hydrocarbons relative content were reduced to 500 °C. Further exploration of the liquid phase products revealed that the relative contents of hydrocarbons in the four lignin residues and PE (EHL-PE, LS-PE, AL-PE, and HL-PE) co-pyrolysis products at 500 °C were 49.6 %, 33.1 %, 37.7 %, and 43.2 %, respectively, with MAHs as the main components. The results of the effect of different C/B ratios on the distribution of pyrolysis products showed that Co-Ni@H/M promoted the deoxygenation of oxygenated compounds, especially phenolic compounds, and the conversion of aliphatic hydrocarbons into MAHs by cyclization and aromatization. [ABSTRACT FROM AUTHOR]

The deactivation of catalyst is a significant reason for its limited application during the catalytic fast pyrolysis (CFP) process. To reduce the coke formation, binary compound impregnation (BCI) and chemical liquid deposition (CLD) were used to modify HZSM-5 catalysts. At the same time, the self-designed microwave reactor separated the pyrolysis of bamboo and catalytic upgrading of primary vapor, which made the catalytic effect more thorough. Experimental results indicated that CLD used TiO 2 deposition to cover external acid sites, while BCI by phosphorus-nickel could cover and partly destroy superficial acid sites through two different ways. Within the scope of the loaded amount studied, the yield of aromatic hydrocarbons in the oil phase increased at first and then decreased, while the coke formation reduced continuously. BTX (benzene, toluene and xylene), the most valuable product in bio-oil, drastically increased by 39.1% and 22.6% respectively over the CLD and BCI modified catalysts. Considering the catalytic performance as well as cost, CLD over HZSM-5 has more advantages in the CFP process to upgrade bio-oil. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Graphical abstract A novel hierarchical micro-mesoporous composite molecular sieve is fabricated. The impact of different preparation conditions on the catalyst is investigated. The structure of hierarchical HZSM-5/MCM-41 catalyst is ordered with 2.0 mol/L NaOH solution, 10 wt% mass fraction CTAB solution, 110℃ digestion and crystallization temperature, and 24 h digestion and crystallization duration. The catalyst characterization, inclusive of TEM images and N 2 adsorption-desorption measurement analysis, revealed that the structure of hierarchical micro-mesoporous composite molecular sieve with HZMS-5 zeolite as the core and MCM-41 zeolite as the shell. The catalytic performance of the catalyst on producing hydrocarbons, especially aromatic hydrocarbons, from pyrolysis of RH is estimated in a Py-GC/MS reactor. For products distribution, the peaked relative abundance of hydrocarbons is 54%, and relative abundance of aromatics is 39%, when CFP of RH over catalyst under the appropriate conditions. Under these circumstances, the relative abundance of oxygenates has the lowest value. Abstract In order to promote efficient production of hydrocarbons, catalytic fast pyrolysis (CFP) of rice husk (RH) over catalysts is performed using Py-GC/MS. The catalyst is hierarchical micro-mesoporous composite molecular sieve prepared under different conditions including different concentrations (1.5 mol/L, 2.0 mol/L, 2.5 mol/L, 3.0 mol/L) of NaOH solution, different mass fraction of cetyltrimethylammonium bromide (CTAB) solution, different temperatures (90℃, 100℃, 110℃, 120℃) and durations (12 h, 24 h, 36 h). The fabricated hierarchical catalyst with HZSM-5 structure as the core and MCM-41 structure as the shell is characterized using N 2 adsorption-desorption measurement and transmission electron microscopy. As the experimental results suggest, the highest value of total peak area of all the chemical compounds is obtained at 600℃. The fabricated hierarchical catalyst exhibit pronounced deoxygenation and excellent selectivity of aromatics. The maximum relative abundance of hydrocarbons (54%), maximum relative abundance of aromatics (39%) and value of selectivity of monocyclic aromatics (65%) are obtained by comparison with different hierarchical catalysts. Besides, the catalyzed transformation of large oxygenated compounds into hydrocarbons can be improved as a function of significant activation of hydrocarbon pool. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Catalytic fast co-pyrolysis of bamboo sawdust and waste tire over combined HZSM-5 and MgO was studied. • A tandem reactor with bubbling fluidized bed and fixed bed system was investigated. • An addition of waste tire in bamboo sawdust increased the bio-oil yield and formation of aromatic hydrocarbons. • Sequential mode was effective in the production of aromatic hydrocarbons at higher HZSM-5 proportion. • An additive effect of HZSM-5 and MgO regarding the formation of aromatic hydrocarbons was studied. Abstract Catalytic fast co-pyrolysis (co-CFP) of bamboo sawdust and waste tire over HZSM-5 and MgO was conducted using a tandem pyrolysis and upgrading system which consists of a bubbling fluidized bed and a fixed bed reactor. HZSM-5 mixed and sequential with MgO modes were studied to explore the additive effect for the promotion of aromatic hydrocarbons. Experimental results indicated that co-CFP of bamboo sawdust with waste tire over pure HZSM-5 increased the yields of pyrolysis oil and char, while the gas yield decreased with the increasing of waste tire percentage in the feedstock blends. The product distribution of pyrolysis oil obtained from co-CFP of bamboo sawdust and waste tire over pure HZSM-5 was dominated by aromatic hydrocarbons, and the relative concentration increased from 26.71 to 71.50% as the waste tire percentage elevated from 0 to 60 wt%. Co-CFP of bamboo sawdust and waste tire using HZSM-5 mixed with MgO mode produced a higher yield of pyrolysis oil than the sequential mode when HZSM-5/MgO mass ratio was raised from 1:4 to 1:1. However, the sequential mode was proved to be more effective in the promotion of aromatic hydrocarbons than the mixed mode at a higher HZSM-5 proportion. A positive additive effect for alkylbenzenes was found when the sequential mode was used at varying HZSM-5/MgO mass ratios. Regarding the olefins, C10 olefins were main products, and limonene selectivity increased at first and then decreased with the highest selectivity of 38.87% occurring at HZSM-5/MgO of 2:3 in the mixed mode case. The additive effect of HZSM-5 and MgO indicated that both the mixed and sequential modes inhibited the formation of polycyclic aromatic hydrocarbons with the most significant additive effect obtained at HZSM-5/MgO mass ratio of 1:1 using the mixed mode. [ABSTRACT FROM AUTHOR]

In order to enhance aromatic hydrocarbon production, catalytic fast co-pyrolysis (co-CFP) of corn stover and fusel alcohol is conducted with ZSM-5 catalyst in a fluidized bed reactor. Effects of co-CFP temperature, catalyst loading and mass ratio of fusel alcohol to biomass on aromatic hydrocarbon yields are investigated and the experimental results show that bio-derived aromatic hydrocarbons can be formed through Diels-Alder cycloaddition and catalyst-induced hydrocarbon pool. It is found that co-CFP temperature of 550 °C results in the maximum aromatic hydrocarbon yield and the carbon and hydrogen yields of individual and total aromatic hydrocarbons increase dramatically with an elevated catalyst loading amount. Additionally, an apparent synergy between biomass and fusel alcohol is observed during co-CFP. With the consideration of aromatic hydrocarbon yields in bio-oil, the mass ratio of fusel alcohol to biomass of 1:1 in the blends is the best option. Moreover, isotopic labeling technique is utilized to unearth the origin of carbon and hydrogen in aromatic hydrocarbons, and the results demonstrate that carbon and hydrogen atoms from both feedstocks can coexist in the individual aromatic hydrocarbon and make up the targeted products during co-CFP of the blends. [ABSTRACT FROM AUTHOR]

An integrated modified HZSM-5 was prepared by sodium hydroxide leaching and followed by hydrothermal process in series, and the co-modified zeolites were then used to conduct the catalytic fast pyrolysis of waste cooking oil to investigate whether an enhanced production of aromatics could be obtained. X-ray diffraction, N 2 adsorption–desorption, TEM and NH 3 -TPD were utilized to characterize the modified zeolites. Experimental results indicated that the crystal structure of HZSM-5 was damaged as alkali treatment time was beyond 4 h, and a micro-mesopore hierarchical system was created inside the zeolites. Simultaneously, the strong acid sites decreased with the increment of modification time, while the weak acid sites performed an opposite inclination. The relative yields of aromatics and olefins presented deviation when alkali treatment time exceeded the specific limitation, and a moderate alkali treatment time of 4 h was beneficial for promoting the yield of aromatics. [ABSTRACT FROM AUTHOR]

The effects of hierarchical porous HZSM-5 zeolites on improving the yield of aromatic hydrocarbons during catalytic fast pyrolysis (CFP) of waste cardboard (WCB) were investigated. Desilicated HZSM-5 zeolites were successfully prepared by alkaline treatment using NaOH solution with different concentrations (0.1 M–0.7 M). A Py-GC/MS apparatus was adopted to carry out the CFP experiments. Results showed that under mild alkaline treatment (NaOH concentration ≤ 0.3 M), the micropores and crystallinity of HZSM-5 were preserved, while the mesopores and weak acid sites increased. The desilicated HZSM-5 zeolites increased the total yield of pyrolytic products from WCB. With regard to the product distribution, carbon yield of aromatics increased dramatically, while that of sugars, carbonyl compounds and other oxygenates decreased obviously. Specifically, HZSM-5 treated by 0.3 M NaOH solution (HZ-0.3 M) was proved to be the most effective catalyst, resulting in a 44% increase of carbon yield of aromatics and an 82% increase of carbon yield of BTX (benzene, toluene and xylenes) comparing to the parent HZSM-5. In addition, the amount of coke deposited on HZ-0.3 M decreased by 29% compared to that on the parent HZSM-5. The retained micropores and the created mesopores of desilicated HZSM-5 zeolites contributed to the enhancement of catalytic performance. However, harsh alkaline treatment of HZSM-5 zeolites (NaOH concentration ≥0.5 M) resulted in the grave collapse of zeolitic crystallinity and the obvious loss of micropores. As a result, the catalytic activities of HZSM-5 zeolites had been weakened. [ABSTRACT FROM AUTHOR]

Catalytic fast pyrolysis is one of the most promising and prevailing technologies for the improvement of bio-oil quality. In this contribution, catalytic fast co-pyrolysis of mushroom waste and waste oil over HZSM-5 zeolite catalyst was conducted to promote the production of aromatics using pyrolysis-gas chromatography/mass spectrometry. The effects of pyrolysis temperature and waste oil to mushroom waste mass ratio on the pyrolytic product distribution were investigated and analyzed. The results showed that with temperature increasing, the relative contents of hydrocarbons increased at first and then decreased, and 600 °C was an optimum temperature as the maximum yield of hydrocarbons could be reached. Besides, the waste oil to mushroom waste mass ratio was of great significance in the catalytic fast co-pyrolysis process, and the total relative contents of hydrocarbons increased with the increasing of waste oil to mushroom waste ratio. On the other hand, a significant synergistic effect between waste oil and mushroom waste was studied during catalytic fast co-pyrolysis, which played an effective role in promoting the production of aromatics remarkably. Catalytic fast co-pyrolysis of waste oil and mushroom waste made a significant contribution to the practical utilization of biomass pyrolysis and provided an effective and efficient way to promote the upgrading of bio-oil. [ABSTRACT FROM AUTHOR]

Pyrolysis of waste tire with HY, HZSM-5 (HZ) and purified attapulgite (PA) catalysts to produce valuable aromatic hydrocarbons has been carried out in a Pyrolyzer- Gas Chromatograph/Mass Spectrum (Py-GC/MS) reactor. Likewise, d -limonene and polybutadiene rubber (BR), which played important roles in the pyrolysis process of waste tire, has also been pyrolyzed in the Py-GC/MS reactor with these catalysts. Based on the product distribution, the catalytic pyrolysis mechanisms of d -limonene were proposed, while those of BR were extended. With these mechanisms, the catalytic pyrolysis characteristics of waste tire could be explained reasonably. Results showed that HY promoted a dramatic increase of aromatics from pyrolysis of d -limonene and BR, leading to the considerable growth of aromatics in the degraded products of waste tire. The shape selectivity of HZ to mono-cyclic aromatics performed effectively in the pyrolysis of BR, yet it exhibited a weak performance in the pyrolysis of d -limonene. As a result, upon the catalytic pyrolysis of waste tire, HZ was inferior to HY in the aromatization ability. However, the selectivity of HZ to BTXE (benzene, toluene, xylene and ethylbenzene) was superior to that of HY. PA performed a weaker catalytic ability in promoting the production of aromatics during the pyrolysis of d -limonene, BR and waste tire. [ABSTRACT FROM AUTHOR]

Enzymatic hydrolysis lignin (EHL) is produced in large quantities during the fermentation of lignocellulosic biomass to produce ethanol, resulting in environmental pollution and resource waste. HZSM-5/MCM-41 core–shell zeolites (H/M) loaded with transition metal Mn, Fe, Co, Ni, Cu, and Zn at different loading levels (2, 4, 6, 8, and 10 wt%) were prepared as catalysts. Py-GC/MS was employed to investigate their effects on the selectivity for and relative abundance of monocyclic aromatic hydrocarbons (MAHs) in the catalytic pyrolysis products of EHL. On this basis, bimetal-loaded H/M catalysts were constructed, namely Fe-Zn@H/M, Fe-Co@H/M, Fe-Ni@H/M, Co-Zn@H/M, Co-Ni@H/M, and Zn-Ni@H/M. Co-Ni@H/M increased the selectivity for and relative abundance of MAHs by 11.68% and 28.01%, respectively, compared with the H/M catalyst. Moreover, Co-Ni@H/M induced a further increase in the selectivity for and abundance of MAHs compared with the corresponding monometal-loaded catalysts. The characterization results indicated that bimetallic Co and Ni loading were uniformly dispersed on the catalyst surface and did not change the structure of the parent catalyst but affected the pore characteristics and acidic site distribution of the catalyst. Further analysis of the pyrolysis products suggested that bimetallic Co and Ni loading enhanced the dealkylation capacity of the catalyst for furans, aldehydes and phenol derivatives. Oligomerization, cyclization and aromatization of short alkyl chains were promoted in the MAHs by Co-Ni@H/M. Meanwhile, bimetallic Co and Ni loading inhibited the polymerization of phenols and other oxygen-containing compounds by promoting dehydration, decarboxylation and decarbonylation, which indirectly reduced the formation of coke. [Display omitted] • Enzymatic hydrolysis lignin was used to prepare MAHs via catalytic fast pyrolysis. • Six bimetal-loaded catalysts by transition metal modification were constructed. • The highest selectivity of MAHs was obtained under Co-Ni@H/M. • The synergistic effects of Co and Ni during catalytic pyrolysis was investigated. [ABSTRACT FROM AUTHOR]

In this study, catalytic fast co-pyrolysis (co-CFP) of corn stalk and food waste (FW) was carried out to produce aromatics using quantitative pyrolysis–gas chromatography/mass spectrometry (Py–GC/MS), and ZSM-5 zeolite in the hydrogen form was employed as the catalyst. Co-CFP temperature and a parameter called hydrogen to carbon effective ratio (H/C eff ratio) were examined for their effects on the relative content of aromatics. Experimental results showed that co-CFP temperature of 600 °C was optimal for the formation of aromatics and other organic pyrolysis products. Besides, H/C eff ratio had an important influence on product distribution. The yield of total organic pyrolysis products and relative content of aromatics increased non-linearly with increasing H/C eff ratio. There was an apparent synergistic effect between corn stalk and FW during co-CFP process, which promoted the production of aromatics significantly. Co-CFP of biomass and FW was an effective method to produce aromatics and other petrochemicals. [ABSTRACT FROM AUTHOR]

In order to promote efficient production of aromatic hydrocarbons, catalytic co-pyrolysis of corn stalk and high density polyethylene (HDPE) over HZSM-5 zeolite catalyst was performed using quantitative Py–GC/MS. For the catalytic fast pyrolysis (CFP) of HDPE, the relative content of aromatic hydrocarbons tended to increase at first and then decreased gradually. For the catalytic co-pyrolysis (co-CFP) of biomass and HDPE, the effects of co-CFP temperature and mass ratio of biomass to HDPE (biomass/HDPE ratio) on the relative content and economic potential of aromatic hydrocarbons were investigated, and the experimental results showed that the highest relative content of aromatic hydrocarbons was obtained at the temperature of 500–600 °C, whereas 700 °C was optimal when the yield of total organic pyrolysis products was taken into account. In addition, the relative contents and value index (VI) of target products remained virtually constant when the biomass/HDPE ratio was >1:1, but then increased with decreasing biomass/HDPE ratio when this mass ratio was <1:1. The hydrogen to carbon effective ratio ( H / C eff ratio) of feedstock should be adjusted to be >1.0 so that high relative contents and VI of aromatic hydrocarbons could be achieved. [ABSTRACT FROM AUTHOR]

• The CHP of lignocellulosic biomass was carried out over a hierarchical catalyst. • The products of CFP and CHP of rice husk are compared. • CHP of rice husk (RH) over hierarchical catalyst led to a high hydrocarbons content. • The optimum conditions for the CHP of RH were 400 °C and 35 bar. In this study, we compare the products of catalytic fast pyrolysis (CFP) and catalytic hydropyrolysis (CHP) of rice husk over an HZSM-5-based hierarchical catalyst. The results suggest that the addition of hydrogen inhibits polycondensation reactions, leading to a reduction of 2.3 wt% in coke yield at 400 °C and 35 bar. The presence of hydrogen increases the relative content of hydrocarbons in both liquid and gas products, with a more significant increase in CH 4 and C 2 –C 3 yield in the gas, suggesting that hydrodeoxygenation, decarbonylation, and decarboxylation reactions are promoted. Alkali-treatment of the HZSM-5 improves the catalytic activity and coking resistance of the catalyst. The addition of an extra external MCM-41 layer to the alkali-treated HZSM-5 further improves the catalytic activity, resulting in a relative hydrocarbon content of 48.9%, which is higher than that obtained with the alkali-treated HZSM-5 and pristine HZSM-5. We also report the effect of pressure on the products. As the pressure increases from 1 to 35 bar, the relative content of hydrocarbons increases from 39.9 to 48.9%, while the coke yield decreases from 3.4 to 1.9 wt%, and CH 4 and C 2 –C 3 yields decrease from 10.3 wt% and 5.1 wt% to 14.2 wt% and 6.7 wt%, respectively. As the temperature increases from 300 to 400 °C, the relative content of hydrocarbons increases from 38.2% to 48.9%. Both CH 4 and C 2 –C 3 yields reach the highest values of 14.2 wt% and 6.7 wt% at 400 °C and 35 bar. [ABSTRACT FROM AUTHOR]

• Mesoporous alkali metal oxide CeO 2 /γ-Al 2 O 3 was synthesized and used as catalyst. • Synthesized CeO 2 /γ-Al 2 O 3 and HZSM-5 were employed to form a dual catalytic stage. • Catalytic fast co-pyrolysis of bamboo sawdust and PE using a dual catalytic stage was conducted. • Catalyst to biomass ratio played a crucial role in the formation of hydrocarbon intermediates. • The additive effect of mono-aromatic hydrocarbons was favored with the increase of PE percentage. Fast co-pyrolysis of bamboo sawdust and waste plastic (linear low-density polyethylene, LLDPE) over a dual catalytic stage of synthesized CeO 2 /γ-Al 2 O 3 and HZSM-5 was conducted to enhance aromatic hydrocarbons production. Experimental results indicated that the catalyst to biomass (C/B) mass ratio played a determining role in the formation of hydrocarbon intermediates and a C/B mass ratio of 4 facilitated the production of aromatic hydrocarbons. Dual catalytic fast co-pyrolysis of bamboo sawdust and LLDPE using synthesized CeO 2 /γ-Al 2 O 3 and HZSM-5 increased the concentration of aromatic hydrocarbons and a CeO 2 /γ-Al 2 O 3 to HZSM-5 mass ratio of 1:3 maximized the target products. The content of aromatic hydrocarbons was increased at first and then decreased as the LLDPE percentage was elevated from 20% to 100% during the dual catalytic fast co-pyrolysis process, with the highest concentration obtained at 75% LLDPE percentage. In addition, the additive effect of monocyclic aromatic hydrocarbons was enhanced with the increasing of LLDPE percentage in the feedstock blends, and higher LLDPE proportion favored the production of xylenes, ethylbenzene, and alkylbenzenes as the additive effects were significantly promoted. [ABSTRACT FROM AUTHOR]

• Catalytic conversion of bisphenol A polycarbonate over HZSM-5 was conducted. • A 5-fold increase of aromatic hydrocarbons was attained in HZSM-5 (38) catalyzed run. • A reaction temperature of 700 °C led to a maximum content of aromatic hydrocarbons. • Co-pyrolysis of polycarbonate with PS produced more monocyclic aromatic hydrocarbons. • The additive effect of monocyclic aromatic hydrocarbons was maximized at 70 % PC percentage. Thermochemical conversion of plastic wastes is a promising approach to produce alternative energy-based fuels. Herein, we conducted catalytic fast co-pyrolysis of polycarbonate (PC) and polystyrene (PS) to generate aromatic hydrocarbons using HZSM-5 (Zeolite Socony Mobil-5, hydrogen, Aluminosilicate) as a catalyst. The results indicated that employing HZSM-5 in the catalytic conversion of PC facilitated the synthesis of aromatic hydrocarbons in comparison to the non-catalytic run. A competitive reaction between aromatic hydrocarbons and aromatic oxygenates was observed within the studied temperature region, and catalytic degradation temperature of 700 °C maximized the competing reaction towards the formation of targeted aromatic hydrocarbons at the expense of phenolic products. Catalyst type also played a vital role in the catalytic decomposition of PC wastes, and HZSM-5 with different Si/Al molar ratios produced more aromatic hydrocarbons than HY (Zeolite Y, hydrogen, Faujasite). Regarding the effect of Si/Al molar ration in HZSM-5 on the distribution of monocyclic aromatic hydrocarbons (MAHs), a Si/Al molar ratio of 38 maximized benzene formation with an advanced factor of 5.1. Catalytic fast co-pyrolysis of PC with hydrogen-rich plastic wastes including polypropylene (PP), polyethylene (PE), and polystyrene (PS) favored the production of MAHs, and PS was the most effective hydrogen donor with a ∼2.5-fold increase. The additive effect of MAHs increased at first and then decreased when the PC percentage was elevated from 30 % to 90 %, achieving the maximum value of 32.4 % at 70 % PC. [ABSTRACT FROM AUTHOR]

• Recycling benzene and ethylbenzene was explored by CFP of plastics over zeolites. • Polystyrene wastes favored the formation of targeted aromatic hydrocarbons. • USY zeolites was proved to be effective in the production of ethylbenzene. • A Si/Al mole ratio of 5.3 in USY maximized the concentration of targets. • Catalyst to PS ratio was optimized at 1.5 to produce benzene and ethylbenzene. Recovering waste plastics by catalytic fast pyrolysis to selectively generate aromatic hydrocarbons is a promising approach to dispose of solid wastes. In the present work, catalytic conversion of polystyrene over ultra-stable Y zeolites (USY) was conducted to directionally produce benzene and ethylbenzene. Experimental results indicated that catalyst type considerably affected the distribution of aromatic hydrocarbons, and USY with high surface area (734 m2/g), large pore size (5.6 nm), and an abundant amount of strong acid sites (1.21 mmol/g) exhibited the most effective shape selectivity for ethylbenzene and benzene generation as the yield enhanced rate reached 401.8% and 61.1%, respectively. Plastic type also played a vital role in the formation of desirable aromatic hydrocarbons, and polystyrene was more beneficial to the production of ethylbenzene as a 54-fold increase was obtained compared to polycarbonate in the catalytic degradation process. Concerning reaction conditions to maximize the formation of benzene and ethylbenzene in the catalytic decomposition of polystyrene, the catalyst/feedstock mass ratio, Si/Al mole ratio in USY, and catalytic conversion temperature could be optimized at 1.5, 5.3, and 650 °C, respectively. [ABSTRACT FROM AUTHOR]

• Catalytic conversion of rubber wastes over zeolites was conducted to produce aromatics. • A pyrolysis temperature of 750 °C was effective to the formation of aromatics. • USY zeolites shows robust catalytic performance for the production of targeted aromatics. • HY was more favorable to the generation of alkylbenzenes in the catalytic conversion of rubber wastes. • USY zeolites with SiO 2 /Al 2 O 3 mole ratio of 5.3 increased the content of aromatics to the most extent. Catalytic conversion of rubber wastes to produce an alternative fuel resource is a promising approach to dispose of solid wastes and address environmental issues. In this study, catalytic fast pyrolysis (CFP) of rubber wastes over acidic zeolites was conducted, and the effect of SiO 2 /Al 2 O 3 mole ratio of USY zeolites on the formation of aromatic hydrocarbons was explored. Experimental results indicated that alkenes and aromatic hydrocarbons were the main pyrolytic products obtained from fast pyrolysis of rubber wastes, and the pyrolysis temperature played a vital role in the formation of aromatics with the highest concentration achieved at 750 °C. Moreover, catalyst types also affected the catalytic degradation of rubber wastes since limonene was completely decomposed in the presence of zeolites. Compared to SAPO-34, zeolites with higher external surface area, stronger Brønsted acid sites, and larger pore size, including USY, HY, and Hβ, were more effective in the production of aromatic hydrocarbons with the highest content obtained from USY catalyzed run. Given the observed effect of SiO 2 /Al 2 O 3 mole ratio of USY zeolites on the formation of aromatic hydrocarbons during the CFP of rubber wastes, USY with low SiO 2 /Al 2 O 3 ratio of 5.3 was more beneficial to the generation of aromatic hydrocarbons, while that with higher SiO 2 /Al 2 O 3 mole ratio (11.5) facilitated the formation of alkenes. Simultaneously, the product distribution of aromatic hydrocarbons obtained from CFP of rubber wastes over USY zeolites was dominated by xylenes, alkylbenzenes, and toluene, and USY with SiO 2 /Al 2 O 3 mole ratio of 5.3 was more active in the production of toluene and xylenes. [ABSTRACT FROM AUTHOR]