Lian-Xin Dai

Catalytic application of mesoporous molecular sieves to vapor‐phase Beckmann rearrangement of cyclohexanone oxime

The vapor‐phase Beckmann rearrangement of cyclohexanone oxime to ɛ‐caprolactam catalyzed by mesoporous molecular sieves was studied. The proton‐form mesoporous molecular sieves, H‐MCM‐41 and H‐FSM‐16, exhibited extremely high activity, selectivity and stability for ɛ‐caprolactam formation when 1‐hexanol was used as diluent. The weak acid sites and/or surface silanol groups of mesoporous molecular sieves play an important role in the selective ɛ‐caprolactam formation.

Vapour phase Beckmann rearrangement of cyclohexanone oxime catalysed by H? zeolite

when hexan-1-ol was used as the diluent in the vapour phase Beckmann rearrangement of cyclohexanone oxime, Hβ zeolite gave 100% conversion of the oxime with Iµ-caprolactam selective close to 96%.

Highly selective vapor phase Beckmann rearrangement over H-USY zeolites

Abstract The vapor Beckmann rearrangement of cyclohexanone oxime to e-caprolactam catalyzed by H-USY with different SiO2/Al2O3 ratios was studied. The catalytic performance of H-USY zeolites for the highly selective formation of e-caprolactam was greatly improved by adjusting the SiO2/Al2O3 ratio and by using an appropriate diluent. It has been found that H-USY catalysts with SiO2/Al2O3 ratios of 27 and 62 exhibited excellent catalytic activity, selectivity and stability when 1-hexanol was used as diluent. The NH3-TPD results indicate that an appropriate amount of relatively weak acid sites of H-USY zeolites are effective for highly selective Beckmann rearrangement. The interaction of alcohols with H-USY zeolites has been investigated by FT-IR to explain the improving effect of 1-hexanol.

Catalytic application of Mo-incorporated SBA-1 mesoporous molecular sieves to partial oxidation of methane

Abstract Mo-incorporated SBA-1 mesoporous molecular sieves have been synthesized under acidic conditions using cetyltriethylammonium bromide as a surfactant and used as catalysts for partial oxidation of methane with oxygen as an oxidant. In the partial oxidation of methane the catalytic performance of Mo–SBA-1 materials directly synthesized from the Mo-containing gel were superior to those of Mo-impregnated pure siliceous SBA-1 and amorphous silica.

Development of advanced zeolite catalysts for the vapor phase Beckmann rearrangement of cyclohexanone oxime

Abstract The vapor phase Beckmann rearrangement of cyclohexanone oxime to e-caprolactam catalyzed by various zeolites was studied. The catalytic performance was greatly affected by both the zeolite structure and diluent solvent. When 1-hexanol was used in place of benzene, the catalytic performance of all catalysts except silicalite-1 was greatly improved. In particular, the selectivity and stability of H-LTL and H-OFF-ERI zeolites remarkably increased; both catalysts exhibited ca. 100% oxime conversion and e-caprolactam selectivity of >95% for 6 h.

Selective oxidation of methane in CH4–O2–NO2 over MoO3

Selective oxidation of methane in CH4–O2–NO2 was examined using MoO3 catalyst at atmospheric pressure. The selective oxidation was enhanced with addition of NO2 to the reaction system of CH4 and O2, in analogy with the gas-phase reaction. The initiation reaction was assured to take place between CH4 and NO2. The presence of MoO3 catalyst increased CH2O selectivity and decreased CH3OH selectivity, compared with those for the gas-phase reaction in CH4–O2–NO2. Based on variations in reaction of selectivities at several reaction conditions, it could be explained/concluded that formaldehyde was a main product on the MoO3 catalyst and methanol was formed through gas-phase reactions.

Reforming of hexane with Pt/zeolite catalysts

Aromatization and isomerization of n- hexane catalyzed by Pt/zeolite were investigated. For Pt/K- β and Pt/K-mordenite as well as for Pt/K-L, the addition of KCl resulted in an increase in selectivity for benzene formation accompanied with a decrease in selectivity for hydroisomerization. A parallelism was found between changes in the benzene selectivity with the KCl addition and in the terminal cracking index. The treatment of Pt/K-FSM-16 with K2CO3 resulted in a decrease in cracking products and an increase in benzene selectivity. At 523 K, Pt/H- FSM-16 catalyst showed high selectivity for methylcyclopentane and cyclohexane. At 623 K, it showed high and durable isomerization activity.

Partial oxidation of methane catalyzed by mo-incorporated SBA-1

The incorporation of Mo into the SBA-1 phase possessing a three-dimensional pore system has been studied under various acidic conditions using tetraethyl orthosilicate and hexadecyltriethylammonium cation. By adjusting pH, Mo was effectively incorporated into the SBA-1 phase. Mo-SBA-1 was active in the partial oxidation of methane to yield 5.2% of formaldehyde with 61% selectivity.

Enhancement effects of methanol on the reactivity for methane partial oxidation in the gas phase reaction of CH4–O2–NO2

The partial oxidation of methane in the gas phase reaction of CH4–O2–NO2 was enhanced with the addition of a small amount of methanol; the selectivity of methanol at the same level of CH4 conversion was enhanced in the presence of methanol which showed this effect exclusively in the presence of NO2.