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To investigate the molecular composition of soluble organic species in Baiyinhua lignite (BL) and their evolution profiles during pyrolysis, BL was firstly pyrolyzed in a fixed-bed reactor, affording gaseous products, tars and chars, then BL and its chars were thermally dissolved in supercritical methanol affording soluble portions (SPs). The composition and structural characteristics of the SPs and tars were analyzed with a gas chromatograph/mass spectrometer. The results indicate that most of the soluble organic species can be released from BL below 500 °C during pyrolysis. Abundant soluble long-chain aliphatic hydrocarbons and carboxylic acids wrap around the aromatic nucleus in BL. According to the difference between the composition and structural characteristics of the SPs and tars, the evolution profiles of the soluble organic species from BL pyrolysis were discussed in detail. [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]

Thermochemical conversion of crops straw is receiving renewed attention, due to the energy and material recovery that can be achieved. However, it still lacks the kinetic background which is of great importance for a successful design of thermochemical process. In this work, pyrolysis test for soybean straw was performed in a non-isothermal thermogravimetric analysis (TGA) in order to determine the thermal degradation behavior. Pyrolysis experiments were carried out under inert conditions and operated at different heating rates (5, 10, 20, and 30 K/min). Three different kinetic models, iso-conversional Kissinger–Akahira–Sunose (KAS), Ozawa–Flynn–Wall (OFW) models, and Coats–Redfern method were applied on TGA data of soybean straw to calculate the kinetic parameters including activation energy, pre-exponential factor, and reaction order. The activation energy values were 154.15 and 156.22 kJ/mol based on KAS and OFW models, respectively. Simulation of the soybean straw thermal decomposition using the obtained kinetic parameters and comparison with experimental data are in good agreement. [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]

• Sulfated HZSM-5 zeolite was prepared by dealumination, realumination and sulfation. • The introduced extra-framework Al affected the textural-acid properties of catalysts. • Sulfation of catalyst after re-introduced extra-framework Al enhanced LAs production. • The highest LAs and lowest coke yield were produced over SO 4 2−/DHZ5-A. Sulfated HZSM-5 zeolite prepared by dealumination, realumination and sulfation was used as the active mesoporous materials to promote the formation of light aromatics during catalytic reforming of volatiles from Shengli lignite pyrolysis. The results show that HCl-dealumination significantly increased the total pore volume (especially mesopores) and average pore size while reducing acid strength and amount of acid sites. The incorporation of the extra-framework Al species to HZSM-5 combined with SO 4 2− to form superacidic surface sulfate complex exhibited an increase in the yield of light aromatics and a decrease in the yield of coke in comparison with that of original HZSM-5. Among the modified catalysts, SO 4 2−/DHZ5-A (introduced the calcined Al 2 O 3 after HCl-dealumination and modified with (NH 4) 2 SO 4) with the acidity enhancement by sulfation obtained the maximum light aromatics yield of 27.3 mg/g and the lowest coke yield of 2.7%. The relationship between the physic-chemical properties of catalysts and the product distribution was proposed to understand the formation of light aromatics. [ABSTRACT FROM AUTHOR]