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We have created a self-assembly method to synthesize the mesoporous structure (SBA-15 and MCM-48) in micro-ZSM-5 by a seed induced crystallization. The micro/mesoporous MCM-48@Z5 composite display the complement effect of micro/mesopores structure in the aromatic yield and coke deposits during catalytic fast pyrolysis of lignite towards aromatics, compared to SBA-15@Z5. Impressively, the mesoporous MCM-48 from the epitaxial growth of ZSM-5 crystal achieved the high alkyl-substituted aromatics in the upgraded tar. By contrast, the developed mesopores in SBA-15@Z5 composites presented the low content of aromatics owing to insufficient acidity. Moreover, from the analysis of the coke nature and composition deposited on the spent zeolites, it can be found that the coke species possessed the light species (i.e. , benzene, naphthalene and it's derivatives) and heavy species (i.e. , long-chain aliphatics), similarly to the coke species on ZSM-5. The coke growth strongly depends on the polymerization on the surface area during catalytic fast pyrolysis of lignite towards aromatics, despite more mesopores on catalysts. • Direct conversion of volatiles to aromatics over micro-mesoporous composite zeolite. • Alkyl-aromatics was produced by coupling with pre-cracking of Al-MCM-48 and aromatization of ZSM-5. • A self-assembly method for composite zeolites with a seed induced crystallization was provided. • The coke growth strongly depends on the polymerization on the surface area of zeolite. [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]

Promising technology for the conversion of cellulose to aromatics by catalytic fast pyrolysis (CFP) was investigated using five zeolite catalysts, i.e., 5A, SAPO-34, HY, BETA and HZSM-5. The relationship between the porosity and acidity of different zeolites with product selectivity was studied. The results showed that both the acidity and pore size of the zeolite significantly affected the production of aromatics and coke, especially the bio-oil composition. The bio-oils obtained over 5A or SAPO-34 (small pore<5.5 nm) have relatively high oxygen content. The BTEXN (benzene, toluene, ethylbenzene, xylenes and naphthalene) carbon yields over weak acidic zeolites of HY and BETA are only 6.5% and 9.0%, respectively. Due to the appropriate pore size distribution and acid position, HZSM-5 gave the highest BTEXN carbon yield of 21.1%. Moreover, the coke deposited on the spent zeolites was analyzed by temperature programmed oxidation. Furthermore, three possible mechanisms that the acid sites catalyze vapor towards non-condensable gases, aromatics and coke were also studied. HZSM-5 achieved satisfactory deoxygenation and aromatic production simultaneously, made it a potential catalyst for producing light aromatics from reforming the biomass pyrolytic vapors. Image 1 • The mechanism that the acid sites catalyze vapor was revealed. • The content of BTEXN was significantly enhanced by HZSM-5. • The free radical reaction of catalytic reforming vapors over zeolites was promoted. • Light aromatics formation during CFP of biomass depends significantly on zeolite type. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Me-HZ greatly promoted the generation of H 2 , BTX and NH 3. • CFP of SS over 0.5Ni-HZ presented the highest yield of aromatics. • Nitrogen evolution mechanism during CFP of SS was investigated. • Reaction pathway for CFP of SS over Me-HZ was proposed. Abstract In order to effectively improve the quality of bio-oil from catalytic pyrolysis (CFP) of sewage sludge (SS) and to produce aromatic-rich bio-oil, the evolution mechanisms of nitrogen and formation of aromatics during CFP of SS over metal-loaded HZSM-5 (HZ) were investigated in depth. The results show that the presence of metals caused the slight decrease in oil-C (carbon in bio-oil) yield and the increase in gas yield and total carbon yield of aromatics. Ni-loaded HZ has a better performance than Co-loaded one in improving the carbon yield of aromatics, while the maximum yield of 11.2% was obtained over 0.5Ni-HZ. Metal-loaded HZ promoted the formation of monocyclic aromatics rather than polycyclic aromatics and Ni significantly enhanced the selectivity of benzene. With the addition of Ni and Co, more nitrogen was released as NH 3 or fixed in solids. NH 3 yield increased by raising the metal loading, and the highest NH 3 yield of 36.8% was obtained over 3.0Ni-HZ. Ni and Co promoted the cracking reactions during CFP to generate more H radicals, which have advantages to the ring-opening of N -containing heterocycles in SS to produce aromatics and NH 3. A possible catalytic mechanism of CFP of SS over metal loaded HZ was proposed in this study. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Propose a method for modifying HZSM-5 with leaching agent HF and loading Ni. • The content of BTEXN was significantly enhanced by 1%Ni-0.5 mol/LHF-HZSM-5. • The mechanism of in situ reforming of cellulose vapor over zeolites was revealed. • Light aromatics formation depends on zeolite acidic sites and pore structure. Abstract Pore structure and accessible active sites of HZSM-5 (Z5) are the key factors for its catalysis. The bifunctional hierarchical Z5 were prepared with leaching agent HF and loading Ni, and their performance for catalytic fast pyrolysis (CFP) of cellulose was investigated in a drop tube quartz reactor. Z5 modified with 0.5 mol/L HF (0.5F-Z5) showed excellent light aromatics (LAs) yield, which can be attributed to the enhancement in the small mesopores (2–10 nm) and the decrease of Brønsted acid sites during dealumination. Simultaneously, the loading of a 1 wt% Ni produced more LAs than 0.5F-Z5, due to the improvement in deoxidation/hydrogenation reactions. The highest LAs yield (31.3%) was obtained over 1%Ni-0.5 mol/LHF-Z5, which increased by 44.9% compared to the parent Z5. In addition, the reaction routes over different active centers and acid-catalyzed reactions were analyzed, based upon the composition of bio-oils and catalyst characterization. [ABSTRACT FROM AUTHOR]

Abstract Selective cleavage of C O bonds in benzyl phenyl ether (BPE) as a typical lignin α-O-4 ether to produce aromatics is a challenging and attractive topic. Herein, the earth-abundant first-row transition metals, such as Co, Ni and Cu were supported on activated carbon (Co/AC, Ni/AC and Cu/AC) to identify their ability for cleaving C O bond of BPE. Among these catalysts, Ni/AC exhibit highest activity for cleavage of C O bond. The reaction with BPE was carried out at pretty mild condition of 140 °C and 2 MPa H 2 , which is highly selective afforded toluene and phenol as the major products with the optimum yields of 88.5 and 86.5%, respectively. Based on the test, the reaction pathways were proposed. A abundant of dissociated H· atoms on Ni(0) sites forms surface active Ni H species; Ni(0) activates and facilitates cleavage of the C O bond in BPE to form benzyl (C 6 H 5 C·) and phenoxy radicals (C 6 H 5 O·); H· atoms spill from active species Ni H recombined together with C 6 H 5 C· and C 6 H 5 O· forming the products of toluene and phenol, respectively. Graphical abstract Highlights • Ni/AC exhibited high activity and selectivity for cleaving of C O bond in BPE. • The reaction was performed under mild condition of 140 °C and 2 MPa of H 2. • The maximum yields of toluene and phenol reached 88.5 and 86.5%, respectively. • Proposed mechanism of cleavage C O of BPE over Ni/AC under different atmospheres. [ABSTRACT FROM AUTHOR]

To elucidate the catalytic mechanism and nitrogen transfer behavior of sewage sludge (SS) during catalytic fast pyrolysis (CFP), product distributions and nitrogen transformation from SS and amino acids during CFP were investigated on a drop tube quartz reactor at various temperatures and HZSM-5 catalysts. Phenylalanine (Phe), proline (Pro), leucine (Leu) and aspartic acid (Asp) were employed as model compounds with different chemical structures for protein-rich SS to help analyze catalytic cracking behavior of SS. During CFP of SS, the maximum aromatics yield of 16.4% was obtained over HZSM-5 with Si/Al ratio of 25 at 500 °C, and increasing temperature promoted the conversion of nitrogen to NH 3 . Amino acids with aromatic ring or saturated hydrocarbon side chain such as Phe and Leu in SS favored the formation of aromatics and NH 3 . Amino acids of N -ring structure in SS promoted the formation of N -containing heterocyclic compounds, which were prone to coke on catalyst and inhibited the catalytic cracking of SS to produce more aromatics and NH 3 . In addition, excessive Asp of short chain dibasic acid structure in SS was not conducive to the complete thermal decomposition of SS under the optimum pyrolysis condition. A general catalytic mechanism of SS was proposed to provide support for the resource reuse of SS. [ABSTRACT FROM AUTHOR]

HZSM-5 was modified via alkaline treatment and wet impregnation method which loading transition metals (Co, Mo–Co and Ni–Co). The performance of catalysts for the catalytic fast pyrolysis of lignite was tested in a drop tube reactor at 600 °C. In comparison to non-catalytic experiment, the chemical composition of upgrading tar was obviously simplified, which mainly contains light aromatics such as benzene, toluene, ethylbenzene, xylene and naphthalene (BTEXN). The yield of BTEXN was significantly increased from 12.9 to 26.4 mg/g when Ni/Co-H-5 was used. Meanwhile, the Ni/Co-H-5 treated by NaOH solution achieved considerable deoxygenation performance (86.6%) than other ones. The addition of bimetallic Mo–Co or Ni–Co significantly enhanced the BTEXN selectivity of HZSM-5. Ni promoted H 2 formation in gaseous product and caused the decrease of naphthalenes yield. Whereas the yields of toluene and o -xylene increased after the pyrolysis vapors pass through Mo/Co-H-5. The zeolite treated by NaOH solution (AT-HZSM-5) favors the generation of aromatics and phenolics, conversely naphthalene derivatives. Moreover, AT-Mo/Co-H-5 and AT-Ni/Co-H-5 inhibited the coke formation. A catalytic pathway was also proposed to describe the diffusion process of pyrolysis vapors on the active site of catalyst. [ABSTRACT FROM AUTHOR]

This work is aimed to study in situ upgrading of Shengli lignite pyrolysis vapors over different metal-loaded HZSM-5 in a drop tube reactor. Co/HZSM-5, Mo/HZSM-5 and Ni/HZSM-5 (5.0 wt%) were prepared by wet impregnation and characterized by N 2 adsorption-desorption analyzer, X-ray diffraction, transmission electron microscope, Fourier transform infrared spectrometer and temperature programmed desorption of ammonia. The effects of temperature and catalyst on product yields and tar properties were investigated. The results show that the optimal temperature for liquid product was 600 °C and aromatics can be directly produced from solid lignite by catalytic fast pyrolysis over metal-loaded HZSM-5 under such mild condition. Due to the participation of metal and acid sites, the bifunctional metal-loaded HZSM-5 showed comparable catalytic activity for deoxygenation reaction in the valorization of oxygen content below 7.1%. The introduction of metal causes the increase of aromatics and the decrease of organic oxygen species in upgraded tar remarkably. Among the catalysts, Ni/HZSM-5 exhibited the best performance for production of high quality tars with highest aromatics content of 94.2% (area%), which can be used as a potential candidate for catalytic upgrading of pyrolysis oil. [ABSTRACT FROM AUTHOR]

[Display omitted] • Hierarchical Ga/Al HZSM-5 exhibits high BTEXN yield at 600 °C. • Ga and HZSM-5 presented a strong synergy during the formation of aromatics. • Ga/Al HZSM-5 keep high stability during 6th cycle reactions. • Multifunctional catalysts promote the formation of H 2 by dehydrogenation. HZSM-5 was hydrothermally synthesized by Ga substitution to regulate the texture properties for light aromatics such as benzene, toluene, ethylbenzene, xylenes and naphthalene (BTEXN) during the lignite volatiles catalytic upgrading process. High BTEXN yield was obtained over xGa/H5(A) (added NaOH in crystallization) and the value increased with raising the amount of Ga incorporation when the Ga content was<1.26 g. 1.26 Ga/H5(A) (1.26 g Ga(NO 3) 3) displayed the highest yield of BTEXN (29.3 mg/g-daf coal) since Ga species and acidic protons promoted the aromatization process. However, excessive Ga brought a negative effect on the production of aromatics due to the weakened synergistic effect between Ga species and acid sites of H5. Additionally, 1.26 Ga/H5(A) with the interconnected meso -micropores and moderate acidity distribution exhibited excellent reaction stability during the 6 cycle experiments. xGa/H5(A) provided a potential prospect for enhancing the BTEXN formation during catalytic upgrading of lignite pyrolysis volatiles. [ABSTRACT FROM AUTHOR]

[Display omitted] • Synthetic hollow ZSM-5 (HSZ5) possess higher selectivity for toluene and m/p-xylene. • None-modifier catalysts keep high stability after 7 cycle reactions. • 11HSZ5 exhibits hierarchical meso -microporesity to rich BTEXN at 600 °C. • xHSZ5 show low coke resistance during lignite pyrolysis. Light aromatics could be produced by catalytic fast pyrolysis (CFP) of lignite over HZSM-5 with shape selectivity and accessible active sites. However, the catalytic reactivity in the center crystal has not been fully exploited. In this work, the different hollow hierarchical porosity-tunable ZSM-5 were synthesized using polyethylene glycol as a soft template by a steam-assisted crystallization process. Compared with commercial HZSM-5, the synthesized HZSM-5 exhibited higher selectivity for alkylbenzene (toluene and m/p-xylene) with the yield of 9.91 mg/g (7.31 mg/g over commercial HZSM-5). The hollow HZSM-5 with pore-size fine-tuning were favorable to control the tiny different intermediates for shape-selective of benzene and alkylbenzene in CFP. In addition, the unmodified synthetic hollow catalysts also kept highly stability after seven cycle experiments due to the enhancement of molecules diffusion in crystal center, especially the alkylbenzene yield was sustained at approximately 7.38 mg/g during cycle experiments. The work provides a great prospect to promote the formation of alkyl aromatics in CFP. [ABSTRACT FROM AUTHOR]

• Ga-Sn/AT 0.2 H5 exhibits hierarchical meso-microporesity to rich BTEXN at 600 °C. • Ga and Sn exhibited a strong synergy during the formation of aromatics. • Ga-Sn/AT 0.2 H5 keep high stability after 6 cycle reactions. • Multifunctional catalysts promote the formation of H 2 by dehydrogenation. A multifunctional catalyst of Ga-Sn anchored on hierarchical HZSM‑5 (Sn-Ga/AT 0.2 H5) was investigated in catalytic reforming of lignite pyrolysis volatile. A strong synergy was observed between Ga and Sn for the production of aromatics. The addition of Ga into AT 0.2 H5 remarkably promoted the selectivity of aromatics including benzene, toluene, ethylbenzene, xylene and naphthalene (BTEXN) compared to pure HZSM-5 (H5). The BTEXN yields increased to 24.1 mg/g over monometallic 5%Ga/AT 0.2 H5, in which the benzene yield was attained to 14.8 mg/g. With the introduction of Sn, the yield of aromatics was further improved to 25.1 mg/g. An explanation of this scenario was that introduced active metals could enhance the transformation of cyclic intermediates into aromatics and H5 support with an appropriate concentration of the acid sites provided acidic protons for aromatization. Additionally, the bimetallic Sn-Ga/AT 0.2 H5 exhibited higher stability with the yield of BTEXN maintained over 22 mg/g after three recycle experiments, which offered an efficient strategy to prolong the catalyst lifetime. [ABSTRACT FROM AUTHOR]

The introduction of mesopores increased the production of aromatics compared to ZSM-5 catalyst indicating that forming aromatics were mainly determined by diffusion limitation over hierarchical ZSM-5. The deactivation of catalysts in MTA was attributed the formation of insoluble coke. [Display omitted] • Mesopores ZSM-5 promoted forming aromatics, which contradicted with DFT calculation. • Forming aromatics was determined by diffusion limitation over hierarchical ZSM-5. • The deactivation of ZSM-5 zeolites was attributed the formation of insoluble coke. A comparative study on the effects of SiO 2 modification and mesoporous structures on catalytic performances over ZSM-5 zeolites in MTA conversion both theoretically and experimentally was done. Experimental results showed that hierarchical pores increased the production of aromatics. However, DFT calculation proved that energy barriers for producing aromatics over mesoporous ZSM-5 were larger than that of parent ZSM-5 due to decreasing acid strength after alkali treatment which significantly influenced rate-determining step. Furthermore, diffusion behaviors of toluene were studied by Molecular Dynamics. Larger pores led to the improvement of diffusion behaviors over hierarchical ZSM-5 owing to the decrease of collision frequency between molecules. Therefore, the formation of aromatics was mainly determined by diffusion limitation over hierarchical ZSM-5. The lowest BTX selectivity was obtained over SiO 2 deposited mesoporous ZSM-5 due to decreasing acid strength and blockage of pore mouth. Additionally, the deactivation of ZSM-5 serial catalysts in MTA was attributed the formation of insoluble coke. Moreover, the introduction of mesopores and silylation on external surface alleviated the deactivation of catalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] • Direct conversion of volatiles to aromatics over Zn@MCM-41&ZSM-5 tandem catalysis. • High aromatics yield was achieved coupling with cracking and aromatization. • Lifetime of ZSM-5 was prolonged for tandem catalysis system. • The presence of Zn@MCM-41 would pre-catalyze macromolecules into small molecules. Direct conversion of lignite into light aromatics via catalytic fast pyrolysis is a great challenge because of severe catalyst deactivation and low aromatics yield. The tandem catalysis (1Zn@MCM-41 and ZSM-5) system was employed to promote the conversion of thermally-derived volatiles of lignite into aromatics at 600 °C. The mesoporous Zn-incorporated MCM-41 (xZn@MCM-41) with different doping amount of Zn was prepared with a one-pot hydrothermal procedure. The structure and the dispersion of Zn species of 1Zn@MCM-41 were systematically studied with XRD, SEM, BET, NH 3 -TPD and so on. The presence of 1Zn@MCM-41 significantly expands the lifetime of the microporous ZSM-5. Meanwhile, the yield of aromatics, especially benzene, is also increased to some extent. The content of the long-chain hydrocarbons and the phenolic compounds are decreased significantly after being cracked by the mesoporous 1Zn@MCM-41. More small molecules are able to contact with the active sites located in the micropores of ZSM-5 with the presence of Zn@MCM-41. In addition, the ZSM-5 in the tandem catalysts system presents an excellent stability. Therefore, this meso -microporous tandem catalysis system promotes the preferential cracking of macromolecular compounds, the cracked small molecules generated from which then contact with ZSM-5 to produce aromatics. This work provides a new perspective for the gradient catalyzing lignite-derived volatiles over a tandem catalysis system. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Ni@Fe/NC shows good activity and selectivity for cleaving C-O bond in lignin. • NiFe alloy is formed in the catalyst which plays a crucial role in hydrogenolysis. • Aromatics especially guaiacols are dominant products from hydrogenolysis of lignin. • Possible reaction pathways based on hydrogenolysis of BPE and lignin were proposed. The utilization of lignin to produce high value-added chemicals is conducive to alleviating the fossil energy crisis. Herein, Ni nanoparticles supported on iron/nitrogen co-doped carbon was prepared by co-pyrolysis and solvothermal reduction method for catalytic hydrogenolysis (CH) of dealkaline lignin and its model compounds. The catalysts were prepared under different calcination temperature, N/C ratio and Ni loading, and the optimal catalyst was Ni 10% @Fe/NC 0.33 – 800 (calcination temperature: 800 °C, N/C ratio: 0.33, Ni loading: 10%) based the on the CH of benzyl phenyl ether (BPE). Ni 10% @Fe/NC 0.33 – 800 showed good catalytic performance on the selective cleavage of C-O bond of lignin and its model compounds. The BPE conversion reached up to 97.7% over Ni 10% @Fe/NC 0.33 – 800 under mild conditions (230 °C, 1 MPa H 2 , and 0.5 h) with toluene and cyclohexanol as major products. Catalyst characterizations suggest that N content affects the formation of NiFe alloy and the synergistic effect between Ni and Fe plays an important role in CH of BPE. Moreover, Ni 10% @Fe/NC 0.33 – 800 could promote the cleavage of C-O bonds in dealkaline lignin through CH and hence enhance producing aromatics such as phenols, aromatic ethers, and aromatic esters, among which phenols are the main aromatics with guaiacols predominant. [ABSTRACT FROM AUTHOR]

A new route for upgrading coal tar to aromatics was investigated. o -Cresol as model compound was investigated the coupling reaction of coal tar with methanol. ZSM-5 zeolite by 0.3 mol L−1 NaOH treatment showed the best catalytic performances due to higher Brønsted acid sites and larger mesopores. Compared with cresol as sole reactants, mixing methanol significantly promoted the production of aromatics and restrained coke deposition through methylation and hydrogen transfer. Higher yield of aromatics was obtained with increasing methanol/cresol molar ratio, indicating that more aromatic hydrocarbons were produced via providing methyl groups rather than active hydrogen from methanol. Moreover, the types of aromatic hydrocarbons could be tuned by alkylation of methylbenzene with methanol. Main products were toluene, xylene and trimethylbenzene due to the effect of steric hindrance of larger molecules of polymethylbenzene. • A new route for upgrading coal tar coupling with methanol to aromatic hydrocarbons under atmosphere pressure was proposed. • More aromatic hydrocarbons were produced via providing methyl groups rather than active hydrogen from methanol. • The type of aromatic hydrocarbons could be tuned by alkylation of methylbenzene with methanol. • The main products were toluene, xylene and trimethylbenzene. [ABSTRACT FROM AUTHOR]