摘要: In order to improve the tar quality by decreasing the heavy tar content and ensuring high tar yield, in-situ catalytic upgrading of tar from the integrated process of coal pyrolysis coupled with steam reforming of methane was conducted over carbon (KD-9) based Ni catalyst. The results show that at 650 °C, the tar yield of CP-SRM over 5Ni/KD-9 is 24.4%, which is a little lower than that of without catalyst, while the light tar yield (i.e.,18.9%) is 1.4 times higher than that of without catalyst, and the content of C2, C3 and C4 alkyl used as a substitute for benzene significantly increases tar yields by 0.5, 0.6 and 4.0 times, respectively. The content of phenols and naphthalenes in tar also increases dramatically after upgrading. Isotope tracer approach combined with the mass spectra of typical components was employed in exploring the mechanism of the upgrading process. The results show that 5Ni/KD-9 catalyzes coal tar cracking and SRM at the same time. Small free radicals such as ·CHx, ·H and ·OH generated by SRM can combine with free radicals from tar cracking, thus avoiding excessive cracking of tar.
摘要: H-[B,Al]-ZSM-5 zeolites were synthesized with glucose as assistant template to catalyze methanol converting toward propylene. The superior catalytic performance in terms of the propylene selectivity and the activity longevity was related to high ratio of weak acid to strong acid for favorable production of propylene and to high mesoporosity for improved diffusion of reactants and prevention from fast coking. More framework Al siting in the straight or sinusoidal channels of the MFI zeolite could also enhance the propylene/ethylene ratio due to the promotional effect on propylene formation. Low weak acid density was conducive to the production of high propylene/ethylene ratio. With the B/Al ratio of 2 and the (Al2+B2)/Si ratio of 0.01, HZ5-G-2B was applied in the methanol to propylene reaction at CH3OH/H2O (1∶1.2) WHSV of 1.8 h−1 and 480 °C. Propylene selectivity of 51.6%, the ${\rm{C}}_{{2-4}}^ {=} $ selectivity of 83.7% and complete conversion of methanol were achieved. The propylene/ethylene ratio was 2. The catalytic activity kept stable for 580 h.
摘要: The dehydrogenation performance of vanadyl catalysts was closely related to the form of surface vanadyl species. To enhance the vanadium dispersion, phosphorus was adopted to modify V-MCM-41 catalysts by using organic vanadium and phosphorus precursors. The influence of phosphorus introduction to the mesoporous structure and vanadyl species were investigated by various characterization techniques. The results showed that the catalysts could maintain ordered hexagonal mesoporous structures though the specific surface area slowly decreased along with the increase of phosphorus content. Both the reducibility and dispersion of the surface vanadyl species were improved. The proportion of polymerized vanadyl species obviously decreased due to the presence of phosphorus species. The propane dehydrogenation reaction results showed that both the catalytic performance and the catalyst stability were improved. Both the maximum surface vanadyl site density and optimum propane dehydrogenation performance were obtained over the sample with Si/P molar ratio of 30.
摘要: Recently, a new carbon nitride (C3N5) photocatalyst has attracted much attention due to its excellent light harvesting and unique 2D structure. However, high recombination rates of electron-hole pairs of bulk C3N5 serious affect the photocatalytic performance. Herein, nickel oxide (NiO) modified C3N5p-n junctions photocatalyst was synthesized by a facile hydrothermal method. Results indicated that the 9-Ni/C3N5 nanosheet photocatalyst showed excellent hydrogen production efficiency under visible light. The hydrogen production rate reached 357 μmol/(g·h), which was 107-fold higher than that of pristine C3N5. The high catalytic performace was attributed to the 9-Ni/C3N5p-n junctions which could efficiently promote photogenerated electron-hole pair separation and thus promote the hydrogen evolution reaction.
