Xuefeng Bai

Synthesis of microscale and nanoscale ZSM-5 zeolites: effect of particle size and acidity of Zn modified ZSM-5 zeolites on aromatization performance

Microscale and nanoscale HZSM-5 zeolites, MZ5 and NZ5, have been successfully synthesized by using a template-free and an in situ seed-induced method, respectively; the synthesized zeolites were then modified by Zn impregnation to obtain Zn-modified catalysts, Zn/MZ5 and Zn/NZ5. Various techniques, including XRD, SEM, 27Al MAS NMR, N2 adsorption, H2-TPR, XPS, NH3-TPD, Py-IR and TG/DTA, were used in the characterization of the catalysts, and their catalytic performance in the aromatization of 1-hexene was investigated to correlate the particle size, acidity and catalytic behavior. Compared to MZ5, the NZ5 sample exhibited better catalytic stability due to its smaller particle size and weaker acid strength. Both Zn-modified catalysts showed increased BTX yield because of the smaller B/L ratio and newly formed stronger Lewis acid sites provided by the [ZnOZn]2+ species, which effectively facilitated the dehydrogenation process in the aromatization. The highest BTX yield of 57.93 wt% was obtained for the Zn/NZ5 sample.

Pyrolysis of Lignocellulosic Biomass from Northeast China

The pyrolytic decomposition study of four species of lignocellulosic biomass (pine, poplar, bass and birch) from the Northeast China was carried out by thermogravimetric analysis (TGA) under the temperature range from 30 to 800 ℃ in the N2 atmosphere at four heating rates (β) of 10,20,40 and 60 ℃/min. The non-isothermal weight loss process of the above biomass samples was mainly composed of dehydration, rapid weight loss and slow weight loss, with the main pyrolysis reaction occurring in the temperature scope of 211~432 ℃. The temperature for the initialization of volatiles (Ts) and peak weight loss temperature（Tp）were between 211~273 ℃and 348~395 ℃, respectively. Peak weight loss rate (Rp) was in the scope of 340~2759μg﹒min-1. The apparent activation energy (E) and pre-exponential factor (A) were between 36.83~57.30 kJ/mol and 1.0×102 ~2.5×103 min-1, respectively. It was shown that Ts, Tp and R p got higher with the increase of β，Tp and Rp being positively proportional to β and almost exhibiting linearity. It can be concluded from the results that the reaction mechanism and process of biomass pyrolysis can be changed by the alteration of β.

Bio-synthesis of palladium nanocubes and their electrocatalytic properties

The bio-synthesis of palladium nanocubes (PdNCs) was realised using pine needle extract as the reducing agent and cetyl trimethyl ammonium bromide as the capping agent. As an eco-friendly and readily available biomass, pine needle extract avoided the use of highly polluting chemical reducing agents. The growth process of PdNCs was analysed using ultraviolet-vis and Fourier transform infrared spectroscopy. Flavonoids, esters, terpenoids and polyhydric alcohols, which contain reductive groups, were mainly responsible for the transition of Pd2+ ions to PdNCs. The morphology and structure of PdNCs were characterised using transmission electron microscopy (TEM), high-resolution TEM, selected area electron diffraction and X-ray diffraction. It was indicated that the as-prepared PdNCs displayed a relatively high purity and good crystallinity with a face-centred cubic structure and exhibited sizes ranging from 6.11 to 29.51 nm with an average particle size of 11.18 nm. In the methanol electro-oxidation reaction, the PdNCs enclosed by {100} facets exhibited superior electro-catalytic activity to commercial Pd/C, which was rarely reported in other bio-synthesis processes for Pd catalysts. Meanwhile, the PdNCs showed excellent anti-poisoning ability and long-term stability. This study reveals the possibility of preparing shape-controlled PdNCs with a specific structure and excellent electro-catalytic activity.