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Summary: Catalytic effects in fast pyrolysis of low‐rank coal and coal tar conversion were investigated in a two‐stage fixed‐bed reactor over HZSM‐5 zeolite and Mg/HZSM‐5. Mg/HZSM‐5 caused the lower total tar yield and the higher non‐condensable gas yield but the fraction of light tar (boiling point below 360°C) increased to allow a slightly higher total yield of light tar. It also exhibited good catalytic activity and increased the species of light tar than HZSM‐5 zeolite. The light tar fraction was increased from 45 to 74.6 wt% than without catalyst (66%) at the pyrolysis temperature of 600°C. Ex‐situ catalytic fast pyrolysis over Mg/HZSM‐5 also lowered the contents of element N and S in the resulting coal tars by 29% and 15% respectively. The corresponding increase in the content of element H and molar ratio of H to C of the resulting coal tars was reported as 17% and 13% respectively. The addition of Mg into HZSM‐5 increased the ability of the catalyst for inhibiting coke deposition. [ABSTRACT FROM AUTHOR]

This study investigated the effects of hydrothermal temperature (HT, 160–240 °C) and residence time (RT, 30–90 min) of hydrothermal carbonization (HTC) on the properties of tobacco stems and their pyrolysis behaviors with catalysts (CaO, HZSM-5). The characterization of hydrothermal products (hydrochars) was carried out by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and 13C superconducting nuclear magnetic resonance (NMR). The pyrolysis experiments of the samples were conducted by pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) and thermogravimetric analyzer coupled to Fourier transform infrared spectroscopy (TG-FTIR). The experimental results showed that with the increase of HT and RT, the fixed carbon content, high heating value, and energy densification of hydrochar were increasing and the crystallinity index increased first and then decreased, and the aromaticity increased continuously. HTC reduced the contents of acetic acid and ketones in the bio-oil and increased the contents of hydrocarbons and 1,6-anhydro-β-d-glucopyranose. When the HT was higher than 180 °C, excessive aromatization of hydrochar affected the yield of chemical compounds in bio-oil. When HT was lower than and equal to 200 °C, the catalyst HZSM-5 and HTC exhibited combined effects of promoting an increase in the production of aromatic hydrocarbons. When HT was higher than 200 °C, the catalytic effects of the double-layer catalysts were better than that of the single-layer catalyst, and CaO and HZSM-5 exhibited synergistic effects that promoted an increase in aromatic hydrocarbon content. [ABSTRACT FROM AUTHOR]

Catalytic fast pyrolysis of sawdust was investigated over HZSM-5 zeolites (SiO 2 /Al 2 O 3 = 25, 50 and 80) in a drop tube quartz reactor for production of green aromatics and olefins. The effects of temperature, weight hourly space velocity (WHSV), SiO 2 /Al 2 O 3 ratio and atmosphere on yield and selectivity of aromatics were investigated. The results show that almost all small organic oxygen species in initial volatiles were converted into gaseous hydrocarbons and aromatics after in situ catalysis of HZSM-5. HZSM-5 whose SiO 2 /Al 2 O 3 is 25 exhibited the best performance with the aromatics yield of 21.8% on carbon basis at 500 °C. However, HZSM-5 can act as cracking and aromatization catalyst, but not as an agent to promote hydrogenation. The ESI-MS revealed the most abundant macromolecular compounds in initial volatiles were O 1 O 27 species with 0–20 double bond equivalent (DBE) values and 5–40 carbon numbers, while the macromolecules were O 1 O 9 species with 2–12 DBE and 10–25 carbon numbers after upgrading. Furthermore, the formation of coke on catalysts was influenced by the properties of HZSM-5 and experimental conditions. Image 1 • In situ catalytic reforming of volatiles from sawdust fast pyrolysis. • Renewable olefins and aromatics were produced directly using HZSM-5. • The yield and selectivity of aromatics can be adjusted. • The macromolecular substances in bio-oils was significantly changed. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The commercial HZSM-5 zeolites were modified by alkaline solutions and tested for the catalytic fast pyrolysis of lignin. • The modification of the catalyst samples improves the performances of lignin catalytic pyrolysis. • Different performances of various kinds of alkalies were compared. • Catalyst treated with 0.3 M NaOH was the optimal choice. Abstract The application of hierarchical HZSM-5 zeolite catalysts in the catalytic fast pyrolysis (CFP) of lignin was investigated using a pyrolyzer coupled with gas chromatography-mass spectrometry (Py-GC–MS). A series of modified HZSM-5 zeolites were prepared by the post-treatment desilication of commercial HZSM-5 zeolite with varying concentrations of sodium hydroxide (NaOH) solutions (0.1 – 0.5 mol/L) and the following solutions: 0.3 mol/L of sodium aluminate (NaAlO 2), 0.3 mol/L of sodium carbonate (Na 2 CO 3), and 0.3 mol/L of tetrapropylammonium hydroxide (TPAOH). The catalyst samples were characterized by XRD, XRF, TEM, N 2 adsorption–desorption, and NH 3 -TPD techniques. The crystallinity, the SiO 2 /Al 2 O 3 , the morphology, the pore properties, and the density of acid sites of the HZSM-5 zeolites were changed after alkali treatment. The alkali treatment improved the catalytic performance of HZSM-5 zeolite for cracking bulky oxygenates released from lignin (such as guaiacol, syringol, and their derivatives from the pyrolysis of lignin) to produce aromatic hydrocarbons. The HZSM-5 zeolite treated with 0.3 mol/L NaOH was the optimal choice for the catalytic fast pyrolysis of lignin for producing aromatic hydrocarbons. [ABSTRACT FROM AUTHOR]

Thermal and catalytic fast pyrolysis of Prosopis juliflora (P.juliflora) , fractions namely wood, seed pods, leaves and their mixtures (wood: seeds: leaves at 80:10:10, and seeds: leaves at 50:50) were investigated. Fast pyrolysis tests were performed in a py-GC/MS to study the product distribution at 450, 500 and 550 °C. Further catalytic tests at 500 °C, used HZSM-5, 1 wt% Ni-HZSM-5 and 5 wt% Ni-HZSM-5, and the wood fraction as feedstock. For all the non-catalytic thermal tests, significant proportions of acids, ketones, aldehydes, sugars, alcohols, phenols, nitrogenous compounds (NITs) and other oxygenates were observed. Out of the three Prosopis fractions studied, the wood at 500 °C yielded the highest amount of ketones, aldehydes and phenolics (78.67%), whilst the mixture (wood: seeds: leaves at 80:10:10), yielded 83.04%. This suggests that Prosopis feedstock can be processed as a mixture thus eliminating the need for pre-separation. The catalytic tests were completed at 500 °C with catalyst: biomass ratios (C/B) of 3:1, 6:1 and 9:1. The use of zeolite-based catalysts, improved the product distribution by forming aromatic hydrocarbons (monocyclic) and polycyclic aromatic hydrocarbons (PAHs) thus reducing the proportion of oxygenates detected in the thermal tests. The addition of nickel to the zeolite catalyst (9:1 C/B ratio; 5 wt% Ni-HZSM-5), resulted in aromatics and polyaromatic hydrocarbons (PAHs) yields of 60.28% and 27.50%, respectively. Overall, the tests using Ni-loaded zeolites showed selectivity towards aromatics, as higher proportions were obtained when compared to PAHs. Our results correlated the influence of specific components in the individual fractions of Prosopis (wood, seeds, and leaves) on the pyrolysis products. We established the potential of using an invasive plant to yield aromatics, which are main components for biofuels production, thus proposing a sustainable pathway to manage its spread and to yield a high-value product. • Prosopis invasive plant can be converted to aromatics (biodiesel precursors). • Fast pyrolysis of Prosopis leaves, seeds, wood, and their mixtures was evaluated. • Ash and fixed carbon considerably varied in Prosopis individual fractions. • Thermal and catalytic fast pyrolysis (CFP) of Prosopis can yield aromatics. • CFP of Prosopis wood and 5 wt%Ni-HZSM-5 catalyst yielded 60.3% of aromatics. [ABSTRACT FROM AUTHOR]

The treatment of biomass-derived fast pyrolysis vapors with solid acid catalysts (in particular HZSM-5 zeolite) improves the quality of liquid bio-oils. However, due to the highly reactive nature of the oxygenates, the catalysts deactivate rapidly due to coking. Within this study, the deactivation and product yields using steam-treated phosphorus-modified HZSM-5/γ-Al2O3 and bare γ-Al2O3 was studied with analytical Py-GC. While at a fixed catalyst temperature of 450 °C, a rapid breakthrough of oxygenates was observed with increased biomass feeding, this breakthrough was delayed and slower at higher catalyst temperatures (600 °C). Nevertheless, at all (constant) temperatures, there was a continuous decrease in the yield of oxygen-free hydrocarbons with increased biomass feeding. Raising the reaction temperature during the vapor treatment could successfully compensate for the loss in activity and allowed a more stable production of oxygen-free hydrocarbons. Since more biomass could be fed over the same amount of catalyst while maintaining good deoxygenation performance, this strategy reduces the frequency of regeneration in parallel fixed bed applications and provides a more stable product yield. The approach appears particularly interesting for catalysts that are robust under hydrothermal conditions and warrants further investigations at larger scales for the collection and analysis of liquid bio-oil.

Graphical abstract Highlights • A tandem bubbling fluidized bed/fixed bed reactor was used for CFP of bamboo sawdust. • Effect of pyrolytic/catalyst temperature on bio-oil yield and distributions was studied. • Ex-situ enhanced the formation of alkylphenols using base metal oxides as catalysts. • Mixed CaO with HZSM-5 mode facilitated the content of aromatic hydrocarbons in bio-oil. • Synergistic effect between base catalysts and HZSM-5 was revealed. Abstract Catalytic fast pyrolysis of bamboo sawdust was conducted by a tandem bubbling fluidized bed/fixed bed reactor. Effect of pyrolysis and catalyst temperatures on product yield was studied. In addition, synergistic effect of HZSM-5 and base catalysts (including CaO, MgO, and SrO) for the promotion of aromatic hydrocarbons was revealed. Experimental results illustrated that both pyrolytic and catalytic reactor temperatures played pivotal roles in the yield of bio-oil, and the optimal pyrolysis and catalytic reactor temperatures were 550 °C and 500 °C, respectively. Ex-situ catalytic trial decreased the yield of bio-oil compared to in-situ run, while it facilitated the formation of phenol and alkylphenols. Mixed catalytic upgrading modes exhibited more significant aromatization and deoxygenation activities than sequential ones. In particular, ex-situ run using CaO mixed with HZSM-5 increased the concentration of aromatic hydrocarbons to 31.34%, which was ∼11.48% higher than that derived from CaO and HZSM-5 sequentially processed mode. The dominated products in alkylphenols were cresol isomers and ethylphenols, and compared to sequential cases, mixed catalytic upgrading trials promoted the relative selectivity of phenol. Synergistic effect of base catalysts and HZSM-5 contributed to the production of monocyclic aromatic hydrocarbons, and CaO mixed with HZSM-5 mode showed the most prominent synergistic effect for the enhanced relative selectivity to xylenes and toluene. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A tandem catalytic bed (TCB) was developed in an analytical pyrolyzer. • CeO 2 was effective in deoxygenating from acids, aldehydes and methoxy phenols. • The TCB of CeO 2 and HZSM-5 enhanced hydrocarbon yield to utmost 85%. • An effective H/C ratio of 0.7 was optimum for producing hydrocarbons in the TCB. • Mechanisms on co-pyrolysis of corn stover and LDPE in the TCB were discussed. Abstract The excessive oxygen content in biomass obstructs the production of high-quality bio-oils. In this work, we developed a tandem catalytic bed (TCB) of CeO 2 and HZSM-5 in an analytical pyrolyzer to enhance the hydrocarbon production from co-pyrolysis of corn stover (CS) and LDPE. Results indicated that CeO 2 could remove oxygen from acids, aldehydes and methoxy phenols, producing a maximum yield of hydrocarbons of 85% and highest selectivity of monocyclic aromatics of 73% in the TCB. The addition of LDPE exhibited a near-complete elimination of oxygenates, leaving hydrocarbons as the overwhelming products. With increasing LDPE proportion, the yield of aliphatics and the selectivity of BTX kept increasing. An optimum H/C eff of 0.7 was superior to that reported in literature. Mechanisms consisting of deoxygenation, Diels-Alder reactions, hydrocarbon pool and hydrogen transfer reactions were discussed extensively. Our findings provide an efficient method to produce high-quality biofuels from renewable biomass resources. [ABSTRACT FROM AUTHOR]

Considering a series of issues facing the application of catalysts in large scale catalytic fast pyrolysis systems, a novel composite catalyst of ZSM-5 coatings on SiC foam supports was developed and tested for ex-situ catalytic upgrading of the pyrolytic vapors. Different configurations of catalysts placement were compared and the results showed the composite catalyst could significantly improve the bio-oil quality without significantly reducing the yield. The effect of catalyst to biomass ratio on the product yields and bio-oil composition was studied and the results showed that increasing catalyst to biomass ratio could improve the quality of bio-oil at the cost of its yield. In addition, the composite catalyst can maintain its activity until a catalyst to biomass ratio of 1/10, outperforming ZSM-5 in other configurations reported in literature. Furthermore, the composite catalysts could be regenerated and reused while well preserving its material properties and catalytic activity after seven reaction-regeneration cycles. [ABSTRACT FROM AUTHOR]

The hierarchical HZSM-5 and Hβ zeolites were prepared by alkaline post-treatment methods adopting Na2CO3, TMAOH/NaOH mixture, and NaOH as desilication sources, respectively. More mesopores are produced over two kinds of zeolites, while the micropores portion is well preserved. The mesopores formed in hierarchical Hβ zeolites were directly related to the basicity of the alkaline solution, indicating that Hβ zeolite is more sensitive to the alkaline post-treatment. The hierarchical HZSM-5 and Hβ zeolites are more active than the parent one for catalytic fast pyrolysis (CFP) of Kraft lignin. Hierarchical zeolites retained the function of acid catalysis, while additionally creating larger mesopores to ensure the entry of bulkier reactant molecules. The increase of the condensable volatiles yield can be attributed to the improvement of the mass transfer performance, which correlates well with the change of mesoporous surface area. In particular, the condensable volatiles yield for the optimized hierarchical Hβ reached approximately two times that of the parent Hβ zeolites. In contrast to the parent HZSM-5, the optimized hierarchical HZSM-5 zeolite significantly reduced the selectivity of oxygenates from 27.2% to 3.3%. [ABSTRACT FROM AUTHOR]

Catalytic fast pyrolysis (CFP) bio-oils with different organic oxygen contents (4–18 wt%) were prepared in a bench-scale dual fluidized bed reactor system by ex situ CFP of southern pine over HZSM-5, and the oils were subsequently hydrotreated over a sulfided CoMo catalyst at 170 bar. The goal was to determine the impact of the CFP oil oxygen content on hydrotreating requirements. The CFP oils with higher oxygen contents included a variety of oxygenates (phenols, methoxyphenols, carbonyls, anhydrosugars) whereas oxygenates in the 4 wt% oxygen oil were almost exclusively phenols. Phenols were the most recalcitrant oxygenates during hydrotreating as well, and the hydrotreated oils consisted mainly of aromatic and partially saturated ring hydrocarbons. The temperature required to produce oil with <1% oxygen was approximately 350 °C for the CFP oil with the lowest oxygen content whereas temperatures around 400 °C were required for the other CFP oils. The carbon efficiency during hydrotreating slightly decreased as the CFP oil oxygen content increased but remained above 90% in all cases, and the carbon efficiency for the integrated process was dominated by the efficiency of the CFP process. A preliminary technoeconomic evaluation suggested that with the current zeolite-based CFP catalysts, it is economically beneficial to preserve carbon during CFP, at the expense of higher oxygen contents in the CFP oil. [ABSTRACT FROM AUTHOR]

Ex-situ and in-situ catalytic fast pyrolysis (CFP) of biomass over HZSM-5 were compared in a two-stage fluidized-bed/fixed-bed combination reactor. Ex-situ CFP gave a similar carbon yield of aromatics + olefins (∼20%) with in-situ CFP but produced much more olefins (10.3% vs. 5.8%) and less char + coke (42.7% vs. 48.4%). The effects of weight hourly space velocity (WHSV), carrier gas flow rate, pyrolysis temperature and catalysis temperature on product distribution in ex-situ CFP were further studied. The maximum carbon yield of aromatics + olefins (21.7%) was obtained at pyrolysis temperature of 550 °C and catalysis temperature of 600 °C with the highest carrier gas flow rate (1.2 L/min) and WHSV of 1.33 h −1 . Obviously less coke was generated at higher pyrolysis temperature. When catalysis temperature increased to 700 °C, ethylene and benzene carbon selectivities boosted to 79.4% and 60.5%, respectively. [ABSTRACT FROM AUTHOR]

In this study, production of bio-oil and biochar from soapstock via microwave-assisted co-catalytic fast pyrolysis combining the advantages of in-situ and ex-situ catalysis was performed. The effects of catalyst and pyrolysis temperature on product fractional yields and bio-oil chemical compositions were investigated. From the perspective of bio-oil yield, the optimal pyrolysis temperature was 550 °C. The use of catalysts reduced the water content, and the addition of bentonite increased the bio-oil yield. Up to 84.16 wt.% selectivity of hydrocarbons in the bio-oil was obtained in the co-catalytic process. In addition, the co-catalytic process can reduce the proportion of oxygenates in the bio-oil to 15.84 wt.% and eliminate the N-containing compounds completely. The addition of bentonite enhanced the BET surface area of bio-char. In addition, the bio-char removal efficiency of Cd 2+ from soapstock pyrolysis in presence of bentonite was 27.4 wt.% higher than without bentonite. [ABSTRACT FROM AUTHOR]

The hierarchical HZSM-5 and Hβ zeolites were prepared by alkaline post-treatment methods adopting Na2CO3, TMAOH/NaOH mixture, and NaOH as desilication sources, respectively. More mesopores are produced over two kinds of zeolites, while the micropores portion is well preserved. The mesopores formed in hierarchical Hβ zeolites were directly related to the basicity of the alkaline solution, indicating that Hβ zeolite is more sensitive to the alkaline post-treatment. The hierarchical HZSM-5 and Hβ zeolites are more active than the parent one for catalytic fast pyrolysis (CFP) of Kraft lignin. Hierarchical zeolites retained the function of acid catalysis, while additionally creating larger mesopores to ensure the entry of bulkier reactant molecules. The increase of the condensable volatiles yield can be attributed to the improvement of the mass transfer performance, which correlates well with the change of mesoporous surface area. In particular, the condensable volatiles yield for the optimized hierarchical Hβ reached approximately two times that of the parent Hβ zeolites. In contrast to the parent HZSM-5, the optimized hierarchical HZSM-5 zeolite significantly reduced the selectivity of oxygenates from 27.2% to 3.3%.

The safe and efficient utilization of waste medical masks has attracted worldwide attention. Fast pyrolysis with the catalysis of zeolites can provide a promising route for the production of value-added aromatic hydrocarbons from waste medical masks. Herein, HZSM-5 was employed and modified by metal loading (Ga, Mo) and alkali treatment for the ex-situ catalytic pyrolysis of mask filters. The non-catalytic pyrolysis of mask filters only led to a low yield of aromatics. When HZSM-5 catalysts were employed, the liquid long-chain olefins, cycloalkanes, and alcohols, as well as gaseous light hydrocarbons were mainly converted into aromatics. According to the micro-scale pyrolysis experiments, the alkali treatment as well as Ga and Mo loading further promoted the generation of aromatics, with aromatic yields of 52.8 wt%, 54.1 wt%, and 46.3 wt%, respectively. For alkali treatment, the NaOH concentration of 0.3 mol/L was most effective for aromatic production, due to the moderate change in the pore size. For metal loading, Ga loading had better performance than Mo loading because the former resulted in a higher specific surface area while the two modified catalysts possessed similar acid activity. When the two modification methods were combined, the yields of aromatics increased to 56.7 wt% and 60.3 wt% under the catalysis of Mo/Na-HZSM-5 and Ga/Na-HZSM-5. Based on the lab-scale experiments, the aromatic yield could reach 63.0 wt% with the catalysis of Ga/Na-HZSM-5, accompanied by a high selectivity of 87.6% for monocyclic aromatic hydrocarbons (MAHs). In summary, both MAHs and polycyclic aromatic hydrocarbons (PAHs) were promoted with these catalyst modification methods by expanding the mesopore size and adjusting acid site distribution, with greater promotion on the formation of MAHs. [Display omitted] • Waste medical mask was converted into aromatics via catalytic fast pyrolysis. • Alkali treatment and metal loading were used to modify HZSM-5. • The two modification methods had a concerted promotion on aromatic production. • The maximal yield of aromatics was 60.3 wt% with a MAHs selectivity of 89.1%. [ABSTRACT FROM AUTHOR]

[Display omitted] • Catalytic bio-oils appeared in 3 phases – heavy, light and aqueous fractions. • Mass and energy yields of bio-oils were enhanced by hydrothermal treatment. • Maximum organic liquid yield of 11.4 wt% with 3 wt% oxygen content was achieved. • The liquid contained 6.7 wt% heavy oil and 4.7 wt% light oil. • Irreversible catalyst deactivation was observed when applying high B/C ratio. Catalytic fast pyrolysis (CFP) of biomass has high potential for producing deoxygenated bio-oil in one single process. HZSM-5 is a widely used catalyst for this purpose and various parameters have already been extensively investigated on this catalytic material. Limited studies were performed on the effect of low-temperature hydrothermal treatment of the catalyst with none being applied in ex-situ CFP in a lab-scale pyrolysis unit. The current paper therefore reports the investigation of HZSM-5 characteristics and activities when hydrothermally treated by steam at 550 °C for 5 h. The treatment modified the catalyst in a positive way that can increase 30% of the non-aqueous catalytic bio-oil yield. A maximum organic liquid yield of 11.4 wt% was achieved with 6.7 wt% being heavy fraction and 4.7 wt% being light fraction. These heavy and light bio-oils had very low oxygen contents of 4.3 and 1.6 wt%, respectively. This is equivalent to 93% oxygen removal compared to its corresponding non-catalytic bio-oil. Based on the elemental, FTIR, and GC/MS analyses, the hydrothermal treatment slightly increased the bio-oil oxygen content. Characterization of the catalysts reveal irreversible catalyst deactivation by dealumination. The severity of the deactivation increased continuously with higher amount of biomass being fed to the process. However, the catalyst deoxygenation ability was still acceptable for producing partially-deoxygenated bio-oil even after applying the biomass-to-catalyst ratio of 20.5. [ABSTRACT FROM AUTHOR]

In this article, we propose beetle-killed lodgepole pine (BKLP) as a feedstock for fast pyrolysis due to its low moisture and high energy content. To the best of our knowledge, no previous studies on fast pyrolysis of beetle-killed trees have been reported. Samples of healthy lodgepole pine and three decay-stage BKLPs were used as feedstock to investigate the effects of the decay stage on the performance of both non-catalytic and catalytic fast pyrolysis using a Py–GC/MS. Compared to the healthy tree, BKLPs were found to have slightly more extractives and less lignin. The decay stage, however, did not affect the product yield and selectivity for both non-catalytic and catalytic fast pyrolysis. A variety of oxygenated compounds were produced in non-catalytic fast pyrolysis, but most of those were converted into aromatic hydrocarbons in the presence of HZSM-5. For non-catalytic fast pyrolysis, the yield of char decreased from 22 wt.% to 11 wt.% as the pyrolysis temperature increased from 450 °C to 650 °C. The average HHV of volatile compounds was found to be around 26 MJ/kg. For the catalytic fast pyrolysis, the yield of hydrocarbons was as high as 40 wt.%, and the yield of char was as low as 5 wt.%. The average HHV of volatiles was found to be about 41 MJ/kg, which is close to the HHV of commercial gasoline and diesel (∼46 MJ/kg). A high yield of toluene (11 wt.%) and xylenes (9 wt.%) was also observed in the catalytic fast pyrolysis process. Our work suggests that beetle-killed trees are a good feedstock for fast pyrolysis, because the bio-oil derived from the trees that have been dead for four years showed the same quality as that from the healthy trees. [ABSTRACT FROM AUTHOR]

Integration of biomass pretreatment with pyrolysis offers an opportunity to improve end-product quality and conversion efficiency. In this study, sugar maple ( Acer saccharum ) was subjected to both hot-water extraction (HWE) at 160 °C (at residence times of 0.5 h, 1.0 h, and 2.0 h) and electron beam (EB) irradiation at a dose of 1000 kGy. Pyrolysis studies were then conducted on all the treated samples at 550 °C using a bench scale pyroprobe-gas chromatography–mass spectrometry (Py-GC/MS). The HWE samples were selected for further evaluation in catalytic pyrolysis using HZSM-5 catalysts for the production of aromatic hydrocarbons. Analysis of the hot-water treated sample at 160 °C for 2 h showed that HWE increased the volatile mater and decreased the fixed carbon and ash contents; also the glucan content increased by 24% and the xylan decreased by 54%. Derivative thermogravimetry (DTG) analysis indicated that EB irradiation reduced the crystallinity of the sugar based polymers while HWE solubilized the hemicellulose fraction. The pyrolysis results showed that EB irradiation increased the formation of furanic aldehydes (furfural and 5-hydroxymethylfurfural (5-HMF)) and decreased hydroxyacetaldehyde (HAA) and levoglucosan (LG). By contrast, HWE increased the yield of LG, HAA, 5-HMF and furfural; but, decreased the yields of acetic acid (HAc), hydroxyacetone, and other ketones. For the HWE-2 h sample, LG formation increased from 4.45 wt.% to 11.57 wt.% and HAc decreased from 4.87 wt.% to 2.40 wt.%. Catalytic pyrolysis of HWE samples with HZSM-5 zeolite showed that the carbon yields of monoaromatic hydrocarbons increased. HWE treatment at 160 °C for 2 h increased the yield of benzene by 46%, toluene by 35% and xylene by 26%. Pyrolysis-TGA also indicated that HWE decreased the formation of char/coke. Overall, the reduction in the formation of acids and ketones caused by HWE suggest that it could be used to improve bio-oil quality in non-catalytic pyrolysis whilst the increase in the yield of monoaromatic hydrocarbons indicate that HWE could be used to enhance the carbon efficiency in catalytic pyrolysis. [ABSTRACT FROM AUTHOR]

Catalytic fast pyrolysis (CFP) of Kraft lignins with HZSM-5 zeolite for producing aromatics was investigated using analytical pyrolysis methods. Two Kraft lignins were fast pyrolyzed in the absence and presence of HZSM-5 in a Curie-point pyrolyzer. Without the catalyst, fast pyrolysis of lignin predominantly produced phenols and guaiacols that were derived from the subunits of lignin. However, the presence of HZSM-5 changed the product distribution dramatically. As the SiO/AlO ratio of HZSM-5 decreased from 200 to 25 and the catalyst-to-lignin ratio increased from 1 to 20, the lignin-derived oxygenates progressively decreased to trace and the aromatics increased substantially. The aromatic yield increased considerably as the pyrolysis temperature increased from 500°C to 650°C, but then decreased with yet further increase of pyrolysis temperature. Under optimal reaction conditions, the aromatic yields were 2.0 wt.% and 5.2 wt.% for the two lignins that had effective hydrogen indexes of 0.08 and 0.35. [ABSTRACT FROM AUTHOR]

Various types of mono- and bi-metallic modified HZSM-5 catalysts such as Mo-, Fe-, Zn-, Cu-, Mo–Fe-, Mo–Zn-, and Mo–Cu-modified HZSM-5 were prepared via impregnation and were characterized by scanning electron microscope (SEM), inductively coupled plasma atomic emission spectrometry (ICP-AES), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) and pyridine adsorption infrared spectroscopy (Py-IR) analysis. Online catalytic upgrading of Arundo donax pyrolysis vapors was performed using modified zeolite catalysts in a two-stage fixed bed reactor to investigate the catalytic performance. Results showed that loading of Mo, Fe, Zn and Cu were well-dispersed, the channels and acidity of zeolites were modified. Impregnation of HZSM-5 with metals resulted in relatively lower yield of oxygenates and nitrogen-containing compounds in bio-oil as compared to the reference condition without catalyst. Moreover, the addition of metals significantly favored the catalytic selectivity towards aromatics especially monocyclic aromatic hydrocarbons (MAHs). Mo-M/HZSM-5 catalysts was the best catalyst and exhibited the optimal de-oxygenation potential (from 62.66% to 18.03%), denitrification (from 6.53% to 0.43%) and produced maximum MAHs content approximately 28.77%. Among the bimetallic modified zeolite catalysts, Mo–Zn/HZSM-5 exhibited strong catalytic effect in oxygen-free aromatization of the mixed pyrolysis vapors containing methane and propane. In the presence of Mo–Zn/HZSM-5 catalyst, the content of oxygen in bio-oil decreased from 36.07 wt% to 15.05 wt%, and the calorific value reached a maximum value of 34.12 MJ kg−1. Mo–Zn/HZSM-5 has been identified as a superior catalyst for improving the value of Arundo donax pyrolysis to make bio-oil. • Mono and bimetallic loaded HZSM-5 was used for Arundo donax CFP in two-stage system. • Aromatization performance and MAH S selectivity was obviously improved through CFP. • Mo–Zn/HZSM-5 optimally improved the pyrolysis of Arundo donax to make bio-oil. • Co-doping of Mo and Zn on HZSM-5 enhanced the aromatization of CH 4 and propane. [ABSTRACT FROM AUTHOR]

The treatment of biomass-derived fast pyrolysis vapors with solid acid catalysts (in particular HZSM-5 zeolite) improves the quality of liquid bio-oils. However, due to the highly reactive nature of the oxygenates, the catalysts deactivate rapidly due to coking. Within this study, the deactivation and product yields using steam-treated phosphorus-modified HZSM-5/γ-Al2O3 and bare γ-Al2O3 was studied with analytical Py-GC. While at a fixed catalyst temperature of 450 °C, a rapid breakthrough of oxygenates was observed with increased biomass feeding, this breakthrough was delayed and slower at higher catalyst temperatures (600 °C). Nevertheless, at all (constant) temperatures, there was a continuous decrease in the yield of oxygen-free hydrocarbons with increased biomass feeding. Raising the reaction temperature during the vapor treatment could successfully compensate for the loss in activity and allowed a more stable production of oxygen-free hydrocarbons. Since more biomass could be fed over the same amount of catalyst while maintaining good deoxygenation performance, this strategy reduces the frequency of regeneration in parallel fixed bed applications and provides a more stable product yield. The approach appears particularly interesting for catalysts that are robust under hydrothermal conditions and warrants further investigations at larger scales for the collection and analysis of liquid bio-oil. [ABSTRACT FROM AUTHOR]