Pyrolysis Vapors Research Articles

Catalytic Upgrading of Plastic Waste of Electric and Electronic Equipment (WEEE) Pyrolysis Vapors over Si–Al Ash Pellets in a Two-Stage Reactor

This study investigated thermal cracking and catalytic upgrading of waste from electric and electronic equipment (WEEE) plastics on a semi-batch reactor coupled to a heated catalyst fixed bed (2-stage vapor cracking). The catalyst used is a Si–Al ash obtained from commercial activated carbon pellets treated with concentrated NaOH solution and calcination. The purpose of the study was to characterize the waste stream through its thermogravimetry analysis and pyrolysis products, study the effect of temperature (350–500 °C) and catalyst quantity (0.0–7.5 %.wt) on yields of reaction products, physical chemical properties, and chemical composition of bio-oil in order to understand and evaluate production of fuels and chemical feedstock by recycling of WEEE plastic through catalytic upgrading. Time-fractioned samples were taken in determined reaction times (15, 30, 45, and 60 min) to study the evolution of cracking reactions during experiment runs through changes to chemical composition (GC/MS). A comparison with other previous work is also presented to show similarities between different feedstocks using the same thermal unit. The results indicate composition of brominated acrylonitrile-butadiene-styrene (ABS), polycarbonate (PC), and high impact polystyrene (HIPS) for the WEEE plastic. The temperature of 350 °C produced better results when considering acid value but presented lower bio-oil yields (38%) and high gas yields (42%). Catalytic upgrading experiments revealed the increased presence of polycyclic aromatic hydrocarbons (PAH) with an increase in viscosity of bio-oil, increase in char yield (from 11% to 24%), and decrease in gas yields (15% to 5%). Chemical composition showed presence of aromatic hydrocarbons such as styrene, methyl-styrene, and diphenyl-propane and nitrogenated compounds such as benzene-butane-nitrile, phenolic compounds, PAHs, and brominated compounds. WEEE plastic pyrolysis is a challenging subject due to contaminant presence and varying composition, and chemical composition evaluation according to reaction time provides interesting insights into the evolution of semi-batch pyrolysis/catalytic upgrading experiments. Standardization and reproducibility of the tool should be conducted to continue the evaluation of pyrolysis and catalytic upgrading of a wide range of feedstocks.

High-purity hydrogen production from real biomass pyrolysis vapors via a chemical looping process

High-purity H2 could be obtained from biomass pyrolysis vapors via chemical looping with Fe–Al–Ni oxides as the oxygen carrier.

Thermochemical behavior of alkali pretreated biomass – a thermogravimetric and Py-GC/FID study

Pyrolysis of pretreated biomass significantly reduces pyrolysis vapor acidity, enabling improved downstream upgrading. Also, increased selectivity for sugars could provide another valuable co-product for bioethanol.

Efficient and stable Ni-supported novel porous Ca-Mg-Al complex oxide catalyst for catalytic pyrolysis of oleic acid into gasoline-kerosene rich production using methanol as a hydrogen donor: Synthesis methods and process optimization

In this study, a series of cost-effective and eco-friendly Ca-Mg-Al and Ni-modified Ca-Mg-Al catalysts were successfully synthesized with different methods (coprecipitation, impregnation and mechanical mixing method) and applied to catalytic pyrolysis vapor upgrading of oleic acid (OA) to produce gasoline-kerosene rich production using methanol as a hydrogen donor. In addition, the effects of the process parameters (catalyst type, OA to methanol ratio, pyrolysis/catalytic temperature, catalyst loading, feedstock injection volume) on the product yield and selectivity were explored, and the reuse properties and deactivation mechanism were also evaluated. Active Ni species coupled with methanol were more conducive to enhancing the catalyst activity and OA conversion and obviously increased the selectivity toward the gasoline-kerosene product. The impregnation method was favorable for the formation of NiAl2O4 species, and coprecipitation method suppressed the formation of NiAl2O4 species. The enhanced activity and deoxygenation selectivity of the coprecipitation method (NiCaMgAl) at lower pyrolysis temperatures was attributed to the abundant higher specific surface area and pore size, higher active metal oxide (Ni2+) and well-active Ni dispersion with a smaller particle size, as well as the lower acidity and partially oxidized Ni, which suppressed the NiAl2O4 spinel phase formation compared with the Ni/Ca-Mg/Al (impregnation) and Ca-Mg-Al (mixing) catalysts, which was beneficial to the decarbonylation/ decarboxylation reaction and inhibited the hydrocracking reaction of CC. Therefore, 100% conversion, 97.12% hydrocarbon yield, 54.53% gasoline and 58.80% kerosene content over NiCaMgAl catalyst were obtained under optimal conditions (pyrolysis/catalytic temperature = 450/500°C, catalyst loading = 1.5 g, feedstock injection volume = 0.1 ml/min and OA to methanol ratio = 3:1). Moreover, NiCaMgAl catalyst also demonstrated good reusability and hydrothermal stability performance due to the lower amount of coke deposition with a lower graphitized structure, which suppressed sintering.

Ex-situ catalytic fast pyrolysis of wood chips over lamellar MFI zeolite supported nickel catalyst

Lamellar MFI zeolite and lamellar MFI zeolite supported nickel were synthesized and examined for ex-situ catalytic upgrading of the vapors (without using any fluidized gases such as N2 and H2) resulted from fast pyrolysis of wood chips in comparison to its commercial MFI zeolite and its supported nickel counterparts. Pyrolysis tests were carried out using a catalytic augur reactor at atmospheric pressure, while pyrolysis unit was operating at 450 °C and upgrading unit at 420 °C, respectively. The introduction of nickel with a high dispersion over the zeolitic supports caused a significant increase in the products of aromatic compounds. Moreover, the addition of nickel to zeolite supports changed their acidity and decreased the total number of acid sites and the ratio of Brønsted to Lewis acid sites as determined by pyridine-FTIR spectroscopy. The use of lamellar zeolite catalysts increased the efficiency of catalytic cracking of pyrolysis vapors and their modification with nickel helped tuning the Lewis acidity to further increase catalytic cracking which resulted in a higher yield of the low molecular weight aromatics present in the bio-oil.

At-Line Sampling and Characterization of Pyrolytic Vapors from Biomass Feedstock Blends Using SPME-GC/MS-PCA: Influence of Char on Fast Pyrolysis.

Solid-phase microextraction (SPME) coupled with gas chromatography-mass spectrometry (GC-MS) analysis was used for the at-line sampling of pyrolytic vapors produced during the fast pyrolysis of biomass. The pure and binary blends of switchgrass (SWG) and pine harvest residues (PT6) were used as biomass feedstocks. Sequential SPME sampling allowed for monitoring of changes in the pyrolysis vapors as char accumulated in the fluid bed. The relative concentration and composition of the pyrolysis vapors desorbed from the SPME fibers were investigated using GC-MS, and the resulting chromatograms were analyzed using principal component analysis (PCA) to compare the composition of the pyrolysis vapors over the course of the pyrolysis run. The chemical compositions of both carbohydrate and lignin fragments varied as the char builds up in the reactor bed. Fragments derived from cellulose and hemicelluloses included anhydrosugars, furans, and light-oxygenated compounds. Lignin fragments included methoxyphenols, phenolic ketones, aldehydes, and low-molecular-weight aromatics. The composition of the carbohydrate fragments changed more than those of the lignin fragments as the char built up in the fluid bed. This combination of SPME-GC/MS-PCA was a novel, easy, and effective method for measuring the composition and changes in the composition of pyrolysis vapors during the fast pyrolysis process. This work also highlighted the effect of char build-up on the composition of the overall pyrolysis vapors.

Catalytic upgrading of cow manure pyrolysis vapors over zeolite/carbon composites prepared from coal gasification fine slag: High quality bio-oil obtaining and mechanism investigation

The resource utilization of solid waste not only reduces the environmental pollution, but also reduces the use of fossil energy. In this study, three low-cost zeolite/carbon composites, including Y-type zeolite/carbon, Beta zeolite/carbon and ZSM-5 zeolite/carbon, were prepared from coal gasification fine slag (CGFS), which were used for catalytic upgrading of pyrolysis vapors of cow manure (CM). The composition and distribution of products from the catalytic pyrolysis of CM over different types composites were explored, and the relationship between catalysts structure and product selectivity was clarified. The results show that different types of catalysts have virous effects on the composition and distribution of products due to different physiochemical structures such as pore size and acid site. Among them, ZSM-5 zeolite/carbon is more conducive to the formation of monocyclic aromatics due to its shape selective catalysis, Beta zeolite/carbon has relatively large pore size and has high selectivity for polycyclic aromatics, and Y-type zeolite/carbon is more conducive to the removal of nitrogen and oxygen-containing compounds. Moreover, vanillin, glucose and valine, which are the main components of lignin, cellulose and protein in CM were selected as model compounds to reveal the reaction mechanism of catalytic upgrading. The results of this study can provide reference and theoretical guidance for the comprehensive utilization of solid waste and the development of low-carbon green industry.

Conversion of low temperature coal tar into high value-added chemicals based on the coupling process of fast pyrolysis and catalytic cracking

To convert the Xinjiang low temperature coal tar (XJ-CT) into high value-added chemicals, the coupling process of fast pyrolysis and catalytic cracking (FP-CC process) is proposed, and the related fundamental data is collected in this research. First, the composition of XJ-CT is analyzed by GC-GC/MS, and the result shows that the relative contents of alkanes, alkenes, aromatics, and the oxygen compound are 13.16%, 4.85%, 48.38%, and 29.29%, respectively. Then, the performance of XJ-CT fast pyrolysis is evaluated under different reaction temperature. The results show that aromatics is predominant among the pyrolysis vapor, whereas the yield of aliphatic products enhances with the increase of temperature. And the aliphatic products are mainly formed from the deep cleavage of long-chain aliphatics and alkyl side chains (alkyl bridge chain) of aromatics. Meanwhile, the relative content of oxygen-containing compounds decrease with the increase of temperature. Furthermore, molecular distributions of the major groups in pyrolysis vapor with different temperatures are summarized to gain insight into the pyrolysis process. Finally, the ZSM-5 (40), ZSM-5 (200), and USY zeolite are used to catalyze the pyrolysis vapor. It is demonstrated that the maximum light olefin yield of 31.79% is obtained over ZSM-5 (40), while converting XJ-CT to liquid fuels can be realized on USY zeolite.

Evolution of Chemical Component and Physical Properties of Datong Long-Flame Coal After Superheated Water Vapor Pyrolysis

ABSTRACT Datong long-flame coal from China was pyrolysis with superheated water vapor at 300°C to 536°C. Chemical and physical changes of long flame coal, including composition, weight loss, pore fracture structure, density, and water absorption were tested, and the qualitative and quantitative relationships among these changes were analyzed. superheated water vapor pyrolysis removes moisture and volatile components from long flame coals and increases the fixed carbon content. After superheated water vapor pyrolysis, the O/C and H/C atomic ratios of long flame coal decreased due to the decomposition of oxygen-containing functional groups and chain aliphatic hydrocarbons. superheated water vapor pyrolysis increased the porosity of long flame coal by material removal and matrix fracture. Material removal occurs throughout the pyrolysis process but matrix fracture occurs only at the initial stage of the conversion of solid organic matter to oil and gas products. The expansion of pore fractures in long flame coal caused a significant decrease in apparent density and an increase in water absorption. Quantitative analysis revealed the forced water absorption of long flame coal was quadratically polynomial with respect to porosity.

Conversion of pyrolysis vapors derived from non-biodegradable waste plastics (PET) into valuable fuels using nickel-impregnated HZSM5-70 catalysts

Recycling waste plastics into pyrolytic fuels is a highly promising energy-saving approach. The improvement and enhancement of the resulting fuel quality from heavy oil-derived-waste plastics pyrolysis is in high demand. We performed catalytic reforming of heavy oils-derived polyethylene terephthalate (PET) pyrolysis to simultaneously improve the quality of oils into valuable fuels (gasoline-range hydrocarbon) and reduce the oxygenated compounds. Nickel-impregnated HZSM5-70 catalysts were prepared by the wet-impregnation method. The catalytic process was carried out in a catalytic tubular reactor at a constant feeding rate of 2.5 mL/h. In particular, various processing factors were examined by varying the impregnation loading of nickel (2–10 wt%), catalyst mass (1–5 wt%), and process temperature (400–500 °C). Increasing any of the three process parameters resulted in a relatively similar decrease in the quantity of liquid products and an improvement in the quality of reformed products. The best quality of reformed oils were obtained at 5 % catalyst loading and 10 % nickel loading on the catalyst at 450 °C. FT-IR analyses show that raising process parameters has a substantial influence on increasing aliphatic and aromatic hydrocarbon content, while lowering the quantity of undesired products (acids, alcohols, and ketones) in the oils. GC–MS analysis results confirmed that the relative content/area of liquid products predominantly contains gasoline-range hydrocarbons (C5-C12), with a total of 33.39 % on blank-run. The hydrocarbons (C5-C12) production from HZSM5-70 and NiO/HZSM5-70 was greatly enhanced to 66.48 % and 85.05 %, repectively, while the oxygenated compounds, including alcohols, acids, and ketones were reduced from 39.38 to 10.75 % (total area). In comparison to HZSM5-70, the NiO/HZSM5-70 catalyst performs more effectively, retaining its catalytic activity after five cycles (∼3 % decrease). Thus, the NiO/HZSM5-70 exhibits high catalytic performance and reusability.

Enhancing high selectivity production of light aromatics from in-situ catalytic upgrading of cellulose pyrolysis vapors by regulating hierarchical core-shell ZSM-5@MCM-41

The catalytic upgrading of cellulose pyrolysis vapors is one of the effective methods to realize its high value utilization. Tuning the pore structure and acid sites of ZSM-5 (Z5) is a necessary strategy to develop effective catalysts for the production of light aromatics and the inhibition of carbon formation. In this study, a core-shell structure ZSM-5 @MCM-41 was developed and used for the first time in catalytic fast pyrolysis (CFP) of cellulose to prepare light aromatic hydrocarbons. The successful synthesis of the hierarchical core-shell ZSM-5 @MCM-41 was confirmed by nitrogen physisorption, X-ray diffraction (XRD), and transmission electron microscope (TEM) analysis. In aromatic hydrocarbon production, 1.0SH-Z5 @ M41 (1.0 mol/L, ZSM-5 @MCM-41) has the highest relative content of 98.76%. The relative content of BTEX (benzene, toluene, ethylbenzene, and xylene) is up to 89.83%, which is 2.39 times that of traditional microporous Z5. The quadratic polynomials were developed to correlate the Brønsted-to-Lewis acid site strength ratio (BLR) and mesopore-to-micropore volume ratio (MMR) with the relative content of BTEX. The mechanism of in-situ catalytic upgrading of cellulose pyrolysis vapor over ZSM-5 @MCM-41 was revealed. Due to high selectivities and low coke formation, ZSM-5 @MCM-41 offers an improved option for making monocyclic aromatics from cellulosic biomass.

Co-pyrolysis of beech wood and polyamide-6: Impact of plastic concentration and wood/plastic synergistic effects

Biomass residues and waste can be converted into bioliquids by pyrolysis, which can contribute to both the production of renewable fuels and the recycling of waste. In this paper, the catalytic co-pyrolysis of mixtures of beech wood (BW) and polyamide-6 (PA6) in different ratios was investigated to assess the effect of PA6 concentration on the properties of bio-oils and on the catalyst performances in upgrading the bio-oils. The catalytic treatment was applied to the pyrolysis vapors that were driven across a H-ZSM-5 catalyst bed before their condensation into liquid products. Increasing the PA6 concentration in the BW+PA6 blends led to an increase in the average molar mass of bio-oils and to an increase in their N-content. Caprolactam and 5-cyano-1-pentene were the main products derived from PA6 pyrolysis, and their ratio also changed with the PA6 concentration. The production of fully deoxygenated compounds was strongly reduced in the presence of PA6, as the result of catalyst deactivation, also evidenced by the increase in sugars and decrease in furans concentrations. The amount of coke deposited on the catalyst decreased as the PA6 concentration increased, but this coke contained more nitrogen. Synergistic effects in the BW+PA6 pyrolysis were evidenced by the positive or negative deviation of different parameters (mass of gas, liquid, solid products, mass of coke on the catalyst, C, N, O composition of bio-oils) from a simple arithmetic combination of the same parameters for pure BW or pure PA6 weighted by their concentrations, in particular the N-content in the bio-oils was much higher than expected.

Thermal maturity and chemical structure evolution of lump long-flame coal during superheated water vapor–based in situ pyrolysis

Oil and gas products can be successfully obtained from low-rank coal using superheated water vapor in situ pyrolysis technology, and investigating the pyrolysis properties of coal during this process is crucial. Herein, the in situ pyrolysis of lump long flame coal with superheated water vapor using a proprietary superheated water vapor pyrolysis system was simulated. The vitrinite reflectance (Ro) and functional groups of coal samples were analyzed using a microscope photometry and Fourier transform infrared spectroscopy. Moreover, the relationship between the chemical structural parameters and vitrinite reflectance during different thermal maturation processes was examined. The results indicate that the vitrinite reflectance increased from 1.01% for raw coal to 2.2% at 550 °C as the pyrolysis temperature increased. The ranges of the critical temperature for the removal of aliphatic structures, C–O, CO, –OH, and aromatic structures from the coal were 271°C-506 °C, 333°C-550 °C, 220°C-550 °C, RT–333 °C, and 333°C-550 °C, respectively. As Ro increased, the aromaticity and condensation both increased linearly and then decreased; the CH2/CH3 ratio first decreased and then increased; the C-factor exhibited negative exponential reduction. Artificial thermal maturation was more effective than natural thermal maturation in promoting the evolution of the aliphatic structure but less effective in promoting the condensation of aromatic rings. Both types of thermal maturation have the same effect on the evolution of aromaticity and C-factor.

Coupling effect of pyrolysis temperature and condensing temperature on the enrichment of high value-added phenolic compounds in bio-oil from pyrolysis of crop straw

Pyrolysis experiments were performed using cotton straw and corn straw as raw materials at 723 and 773 K. The variations in condensation efficiency, moisture, and content of important components in bio-oil condensed from pyrolysis vapors were investigated in a water-bath condensation temperature of 313–363 K. The condensing efficiency, moisture, and content of important components of bio-oil increased with increased pyrolysis temperature. The single pyrolysis temperature provided limited control over the quality of bio-oil. The variation in condensing temperature affected the condensing of pyrolysis vapors. As the condensing temperature increased, the moisture in bio-oil was reduced by 200%, and the maximum content of the important components was elevated. The phenol content of the target bio-oil increased by 340.40%. For guaiacol and its derivatives, the relationship between condensing temperature and their content was analyzed using a polynomial fitting function to explore the phase-transition patterns.

Enhanced activity of NiZrBEA catalyst for upgrading of biomass pyrolysis vapors to H2-rich gas

The main objective of these studies was development of competitive catalyst for the upgrading of biomass pyrolysis vapors to H2-rich gas. The performed experiments were devoted to determination of the effect of incorporation of zirconium into the structure of BEA zeolite on the performance of NiBEA in the mentioned process. Moreover, the most important parameters responsible for the increased activity of NiZrBEA catalyst in comparison to nickel supported on parent zeolite have been identified. The activity of synthesized catalysts was tested in two step fixed bed quartz reactor. Firstly, cellulose or pine were heated to the 500 °C in order to decompose lignocellulosic feedstock. Then, formed pyrolysis vapors were directed through catalyst bed (700 °C) where their upgrading took place. The obtained results revealed that an introduction of zirconium in the structure of BEA zeolite allowed for the increase in the efficiency of Ni catalyst in the formation of H2-rich gas. It was related to the increase in pore volume of the synthesized materials, formation of smaller nickel oxide crystallites and creation of the catalysts with moderate acidity.

Research on the reaction mechanism and modification distance of oil shale during high-temperature water vapor pyrolysis

When oil shale is pyrolyzed with high-temperature water vapor as a heat carrier fluid, the water vapor will participate in the pyrolysis reaction of organic matter, to change the release characteristics of oil and gas products. Based on the self-designed long reaction system of oil shale pyrolysis by injecting water vapor, this paper deeply studies the quantitative law of water vapor temperature and reaction distance on oil upgrading, compares the quality of shale oil using different pyrolysis methods, and reveals the mechanism of upgrading of oil shale pyrolysis by injecting water vapor. The change of heteroatom and light component contents of shale oil can indicate the change in shale oil quality. The relationship between the two indexes and the reaction distance follows the Boltzmann distribution, and the relationship is called the modification distance. When the injection temperature is 450 °C, the modification distance of shale oil is 1400 mm. When the injection temperature reaches 500 °C, the modification distance extends to 2600 mm. Moreover, when the temperature of the water vapor is low, the reaction intensity is low, the upgrading level is low, and the modification distance is short. However, when the temperature of the water vapor is high, the shale oil's rapid hydro-upgrading distance increases, and the upgrading degree is also enhanced. To make oil shale fully pyrolyzed and form shale oil with good quality, the injection temperature should be at least 500 °C. In that case, the reaction distance of 2600 mm is the threshold distance of oil upgrading. The light component content in the shale oil obtained by the pyrolysis of oil shale with water vapor can be two times that obtained by direct distillation and three times that of crude oil.

Improving Fuel Properties and Hydrocarbon Content from Residual Fat Pyrolysis Vapors over Activated Red Mud Pellets in Two-Stage Reactor: Optimization of Reaction Time and Catalyst Content

Catalytic upgrading of vapors from pyrolysis of triglycerides materials is a promising approach to achieve better conversions of hydrocarbons and production of liquid biofuels. Catalytic cracking often shows incomplete conversion due to distillation of initial reaction products and the addition of a second catalytic reactor, whereas pyrolytic vapors are made in contact to a solid catalyst was applied to improve the physical-chemical properties and quality of bio-oil. This work investigated the effect of catalyst content and reaction time by catalytic upgrading from pyrolysis vapors of residual fat at 450 °C and 1.0 atmosphere, on the yields of reaction products, physicochemical properties (density, kinematic viscosity, refractive index, and acid value), and chemical composition of organic liquid products (OLP), over a catalyst fixed bed reactor, in semi pilot scale. Pellets of red mud chemically activated with 1.0 M HCl were used as catalysts. The thermal catalytic cracking of residual fat show OLP yields from 54.4 to 84.88 (wt.%), aqueous phase yields between 2.21 and 2.80 (wt.%), solid phase yields (coke) between 1.30 and 8.60 (wt.%), and gas yields from 11.61 to 34.22 (wt.%). The yields of OLP increases with catalyst content while those of aqueous, gaseous and solid phase decreases. For all experiments, the density, kinematic viscosity, and acid value of OLP decreases with reaction time. The GC-MS of liquid reaction products identified the presence of hydrocarbons and oxygenates. In addition, the hydrocarbon content in OLP increases with reaction time, while those of oxygenates decrease, reaching concentrations of hydrocarbons up to 95.35% (area.). The best results for the physicochemical properties and the maximum hydrocarbon content in OLP were obtained at 450 °C and 1.0 atmosphere, using a catalyst fixed bed reactor, with 5.0% (wt.) red mud pellets activated with 1.0 M HCl as catalyst.

Catalytic reforming of polyethylene pyrolysis vapors to naphtha range hydrocarbons with low aromatic content over a high silica ZSM-5 zeolite

In this study, the microwave-assisted pyrolysis coupled with ex-situ catalytic reforming of polyethylene for naphtha range hydrocarbons, with low aromatic content, was investigated. Experimental results revealed that ZSM-5 zeolites with low SiO2/Al2O3 ratios led to high aromatic selectivity, while an extremely high SiO2/Al2O3 ratio significantly reduced the aromatic selectivity. The high selectivity of C5-C12 hydrocarbons (98.9 %) with low selectivity of C5-C12 aromatics (28.5 %) was obtained over a high silica ZSM-5 zeolite at a pyrolysis temperature of 500 °C, catalytic cracking temperature of 460 °C, and a weight hourly space velocity of 7 h−1. The liquid oil produced was mainly composed of C5-C12 olefins that can be easily converted into paraffin-rich naphtha by hydrogenation or hydrogen transfer reactions as the feedstock for new plastic manufacturing. 8 cycles of regeneration-reaction cycles were carried out successfully with little change on the product distribution, showing the great potential for continuous production of low-aromatic liquid oil. Catalyst characterization showed that the catalyst deactivation was primarily caused by coke deposition (approximately 16.0 wt%) on the surface of the catalysts, and oxidative regeneration was able to recover most of the pore structure and acidity of the zeolite by effectively removing coke. This study provides a better understanding for the plastic-to-naphtha process and even for scale-up studies.

Enhanced production of monocyclic aromatic hydrocarbons by catalytic pyrolysis of rape straw in a cascade dual-catalyst system of modified red mud and HZSM-5

Catalytic pyrolysis of rape straw was carried out on a dual-catalyst system to produce benzene, toluene, xylene (BTX), realized by promoted cracking of large-molecule pyrolysis vapor over red mud (RM) and followed by selectively catalytic conversion over HZSM-5. With the pyrolysis temperature of 550 °C and the catalyst/biomass mass ratio of 2:1, the yield of BTX in bio-oil reached the maximum of 10.27 wt%. The coking resistance of HZSM-5 in the cascade catalytic system was obviously better than pure HZSM-5. The pretreatment of RM by calcination and acid washing was also performed. The unstable components of RM like cancrinite were decomposed during the calcination. Besides, the content of active metal oxides in RM after acid washing increased by removing Na2O and CaO. Its specific surface area was promoted, due to the new micropores caused by the dispersion of dissolved metal oxides. RM treated with 3 mol/L hydrochloric acid presented the highest specific surface area of 55.24 m2/g while the maximized yield of BTX of 12.91 wt%. Therefore, the dual-catalyst system might be an effective method to dispose and high valued use of rape straw and RM as solid wastes with significant environmental impact to promote carbon neutrality.

Performance of expanded perlite as granular bed filtration media: Effect on coal pyrolytic products

Granular bed filtration is considered one of the most promising engineering solutions to the dust removal from high temperature coal pyrolytic vapors. Expanded perlite as filtration media was studied in a lab-scale fixed bed reactor to understand its effect on pyrolysis products. Factors including filtration temperature, filtration time, dust accumulation and regeneration effect were investigated. The results show that there is around 12.9 % reduction in tar yield even under an optimized temperature of 550 °C after filtration bed. Dust accumulation would further promote tar cracking reactions. Coke deposition on the perlite increases with filtration time, which causes further reduction in tar yield. The redox cycle between filtration and regeneration significantly alters the properties of perlite. It is found that carbon deposition on perlite is alleviated in the initial cycles due to the formation of potassium carbonate. And the extent of tar cracking becomes weak. With the cycle numbers further increasing, the situation is inversed. Characterization techniques such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA) were applied to explore the mechanisms behind the findings. Potassium and transition metals such as iron contained in perlite may make significant contributions.