Hong Du,Miao Jiang,Xiuyun Ma,Peifang Yan,Z. Conrad Zhang
The rapid consumption of fossil resources and the grim environmental situation encourage the application of renewable and clean energy resources. Conversion of biomass, which is a kind of renewable, CO 2 neutral as well as abundant reserves carbon containing resource, is significantly important. The production of fuels from biomass by means of gasification and Fischer-Tropsch synthesis is one of the most promising routes for industrial applications. The wax-free liquid fuels synthesis directly from H 2 -deficient syngas similar to bio-gas is highly advantageous for reducing investment and operating cost. Thus, the Mn-promoted meso-ZSM-5 supported cobalt catalyst was applied for the production of wax-free liquid fuels by catalytic H 2 -deficient syngas conversion in this study. The performance of the reaction was influenced obviously by Mn content. The cobalt dispersion increased with the addition of Mn, whereas the reduction degree decreased after Mn doping. Then, the balance between the dispersion and reduction degree led to the change in CO uptake followed a volcanic curve. The catalyst with moderate amount of Mn (1 wt%) had the suitable cobalt particle size and the maximum CO uptake. Thus, the highest CO conversion was obtained over Co-1Mn/meso-ZSM-5 catalyst thanks to its maximum exposed active sites. The appropriate amount of Mn addition also resulted in the decreasing of CH 4 selectivity. The highest space time yield of liquid fuels was acquired over the Co-1Mn/meso-ZSM-5 catalyst from H 2 -deficient syngas conversion under the moderate conditions.
Tao He,Yuxin Wang,Pengjie Miao,Jianqing Li,Jinhu Wu,Yunming Fang
Deep hydrogenation of aromatics is an important reaction in modern oil refinery. The key of an aromatic hydrogenation unit is high active, sulfur resistant hydrogenation catalyst. In this paper, the catalytic performance of a newly developed hydrogenation catalyst, platinum supported on mesoporous ZSM-5 (Pt/MZ-5), was tested in naphthalene (model compound of light cycle oil) hydrogenation. Pt/ZSM-5 and Pt/Alumina were used as reference. In some experiments, dibenzothiophene (DBT) was added to test the sulfur tolerance of catalysts. In the absence of DBT, Pt/MZ-5 and Pt/Alumina showed much higher hydrogenation activities and decalin selectivity than Pt/ZSM-5. The selectivity to decalin exceeds 97% over Pt/MZ-5 at temperature range between 523 and 573 K. Furthermore, Pt/MZ-5 shows better sulfur resistance than that of Pt/Alumina. In the presence of 3000 ppm dibenzothiophene, the selectivity of decalin over Pt/MZ-5 was only slightly dropped to 89.4% at 573 K, which is much higher than that of Pt/Al 2 O 3 (51.4%). The excellent catalytic performance and sulfur tolerance of Pt/MZ-5 were attributed to the combination of high acidity and mesoporous structure in MZ-5.
High-efficiency adsorbents are essential for ultradeep desulfurization through selective adsorption, which features low energy consumption without causing secondary pollution. Aluminum oxide is always added as a binder to form physically bound pellets, which weakens the adsorptive desulfurization performance. In this work, a novel micro–mesoporous binderless ZSM-5 (BL-ZSM-5) was successfully prepared through in situ crystallization, which could efficiently remove thiophene from model fuel. Desulfurization ability was investigated by static and fixed bed adsorption. The breakthrough adsorption capacity of thiophene on BL-ZSM-5 reaches 0.38 mg/g, which is twice as high as that of ZSM-5 with alumina binders (Al-ZSM-5). The improvement is attributed to the conversion of alumina into molecular sieves, which could increase the adsorption sites and provide appropriate mesoporous channels for thiophene transfer. The thermal stability of BL-ZSM-5 is superior to that of Al-ZSM-5. The adsorption performance of BL-ZSM-5 is maintained well after 6 cycles of regeneration. The results demonstrate that the attractive prospect of BL-ZSM-5 in highly efficient desulfurization of transport fuels through selective adsorption.
Chenyao Bi,Zhuangzhuang Zhang,Daizong Han,Chengan Wang,Jianbo Zhang,Ming Sun,Qingqing Hao,Huiyong Chen,Xiaoxun Ma
Quality improvement of pyrolysis tar with yield increasing of high value-added components is highly desired for coal utilization. Herein, Ga-impregnated mesoporous ZSM-5 (Ga/MZ5) directed by organosilane surfactant of [3-(trimethoxysilyl) propyl] octadecyldimethylammonium chloride (TPOAC) is used as a catalyst for the catalytic upgrading of coal pyrolysis volatiles. Effective regulation by reduction and reduction/reoxidation promotes a secondary dispersion of gallium species from external surface deposition to micropore permeation. The comprehensive evaluation of catalytic upgrading performance indicates that the designedly regulated gallium species (mainly Ga + , GaH 2 + and GaO + ), feasible balance of Brønsted and Lewis active sites and mesopore diffusion superiority effectively contribute the yield increasing of both light-fraction ( M LF / M Tar ) and target products of BTEXN (benzene, toluene, ethylbenzene, xylene and naphthalene). The optimal catalyst of Ga/MZ5_R/O exhibited the highest value of M LF / M Tar (88 %) and highest yield of BTEXN (31.84 mg.g −1 ), which are 173 and 589 % higher than non-catalytic single pyrolysis and 133 and 280 % higher than those over the conventional Ga-impregnated ZSM-5 (Ga/Z5). Moreover, the possible reaction networks towards high value-added products of BTEXN based on the positive conversion of polycyclic aromatic hydrocarbons (PAHs), phenols, and other oxygen-containing compounds (abbreviated as PPO) is further proposed.
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