Search

A novel catalyst was prepared by loading nickel on Shenli lignite char via ion-exchange. The results show that the nickel crystallite size (NCS) and specific surface area (SSA) of the catalyst significantly depended on solution pH and carbonization temperature. The catalyst prepared in pH 11 at 650 °C reached the maximum SSA of 236.3 m 2 /g and the nickel particles dispersed quite well in the catalyst with a NCS of 5.6 nm. The catalyst was used for corncob volatiles reforming in a two-stage fixed-bed reactor to study the effects of temperature, steam, and space velocity on gas yields and carbon distributions. It effectively improved tar decomposition at 650 °C under inert atmosphere and produced a tar-free syngas in a yield of 43.9 mmol/g, which is higher than that over a commercial Ni/Al 2 O 3 . The increase of the NCS during catalytic reforming above 650 °C leads to the catalyst deactivation for tar decomposition. The study revealed the possibility of using Ni/char as a potential catalyst for low-temperature gasification of biomass. [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]

• 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]