Guozhu Liu

Direct preparation of [(CH3)3NC16H33]4Mo8O26 and its catalytic performance in oxidative desulfurization

The catalyst [(CH3)3NC16H33]4Mo8O26 has been synthesized by a direct precipitation method under room conditions from commercially available (NH4)6Mo7O24·4H2O and (CH3)3NC16H33Cl, avoiding the use of any toxic organic solvents. The catalyst was employed in oxidative desulfurization using H2O2 as an oxidant under mild conditions. High dibenzothiophene (DBT) removal (99.4%) was achieved after an adsorption process to remove the residual DBT sulfone (DBTO2), and the catalyst could be used for at least nine cycles without a noticeable decrease in activity. Leaching of Mo species was found to be negligible during the reaction. Moreover, it was found that the sulfur removal remained unchanged, decreased slightly or dramatically in the presence of 10 wt% n-octene, para-xylene or naphthalene, respectively, which was attributed to the different solubilities of DBTO2 in these solvents. The reaction system was further applied for the desulfurization of a kerosene-range jet fuel and a diesel fuel. After oxidation and extraction, 86.4% and 93.2% sulfur removals were derived for the diesel fuel and jet fuel, respectively.

Oxidation of refractory sulfur compounds with molecular oxygen over a Ce-Mo-O catalyst

A Ce–Mo–O catalyst prepared by a simple sol–gel method was proved to be highly active for aerobic oxidative desulfurization. Almost complete conversions of dibenzothiophene and 4,6-dimethyldibenzothiophene were achieved without any additional sacrificial agent at 100 °C and atmospheric pressure, and the conversion of benzothiophene could reach 97%. Reusability of the catalyst was also conducted, and >99% conversions could be achieved in three consecutive runs. As supported by carefully-designed control experiments, oxygen was activated by Ce species in the catalyst first, forming some reactive oxygen species, which oxidized DBT into DBTO2 with the assistance of Mo species. Furthermore, selective quenching experiments indicated the generation of superoxide species during the reaction.

Catalytic cracking of n -pentane over CLD modified HZSM-5 zeolites

With the intrinsic MFI structure well-preserved, HZSM-5 zeolite was controllably surface-modified via a CLD (chemical liquid deposition) strategy and wrapped by tailorable porous SiO2 or TiO2 overlayers. It was found that the CLD-modified catalysts brought about a (maximum 46%) promotion of catalytic activity using the catalytic cracking of n-pentane as a model reaction at 500 °C, attributed to the enhanced sorption process caused by the porous overlayer. In addition, TiO2-CLD modified zeolites exhibited a better catalytic cracking performance compared with SiO2 that was probably due to the extra Lewis acid sites generated by TiO2.

Different roles of CNTs in hierarchical HZSM-5 synthesis with hydrothermal and steam-assisted crystallization

Hierarchical HZSM-5 zeolites with uniform mesopore distribution were synthesized by hydrothermal synthesis (HTS) and steam-assisted crystallization (SAC) methods using multi-walled carbon nanotubes (CNTs) as hard templates. Compared with the HTS method, the SAC method favored the utilization of CNTs because of lower phase separation degree. It was also found that the crystallization process of HZSM-5 was slowed down after the addition of CNTs in the HTS method, while was accelerated in the SAC method. Furthermore, after the addition of CNTs, the hierarchical samples prepared by the HTS method showed lower Si/Al ratios and higher acid amounts while slight changes in the acid properties were observed for those prepared by SAC method. The synthesized hierarchical HZSM-5 zeolites using the SAC method exhibit similar catalytic activities but better stabilities in the catalytic cracking of n-decane than the HTS samples as a result of the presence of more mesopores.

Synthesis of Highly Crystalline Beta/MCM-41 Composites by Controllable Assembly of Tailorable Nano Proto-Zeolitic Building Blocks

Hierarchical Beta/MCM-41 composites have been synthesized by kinetically controlling the assembly process of nano-building blocks around hexadecyl trimethyl ammonium bromide (CTAB) micelles. Composites with different microzeolitic–mesoporous properties were prepared from three typical beta zeolite precursors. Without disturbing the intrinsic acidity of the zeolites, the obtained composites exhibited improved catalytic performance in n-decane cracking.Graphical Abstract

Pd -Pt /HZSM -5 Coating Catalyst for Supercritical Cracking and dehydrogenation of Endothermic Fuel

A bifunctional coating catalysts involved HZSM -5 supported Pd and Pt is prepared and used in order to improve the cooling capacity of fuels as w ell as the ignition performance . To overcome the disadvantage that most of the Pd and Pt particles were masked in the inner bulk of the coating, in this work we load Pd and Pt on the surface of HZSM -5 coating by electroless plating technology. The coating catalyst as prepared is characterized by scanning electron microscopy (SEM), X -ra y diffraction (XRD), X -ray photoelectron spectroscopy (XPS). The characterization s show that the surface is flat without flaws, and metallic Pd and Pt particles are uniformly dispersed on the coating surface . A t ests are carried out under supercritical con ditions in c oated -wall tube reactor to test the activity of various catalysts in terms of heat sink, conversion, hydrogen selectivity in the gaseous products. The results show that Pt -Pd/HZSM -5 catalysts prepared by the gas -aided fluid displacement and ele ctroless plating technologies, have a better activity for cracking and dehydrogenation of model endothermic fuel in contrast with bare tube . Nomenclature

Thermal oxidative stabilities of endothermic fuel model compounds with pressure different scanning calorimeter

Thermal -oxidative stabilities of hydrocarbons in the jet fuels were studied using pressure different scanning calorimeter (PDSC) . Apparent active energies of thermal oxidative reaction for twelve hydrocarbon s were reported with Flynn -Wall -Ozaw method. It is concluded that the PDSC is a rapid and reliable technique to characterize the thermal oxidative stability of jet fuel and to evaluate performance of fuel additives.