Shengjun Huang

Production of propene from 1-butene metathesis reaction on tungsten based heterogeneous catalysts

Abstract A new propene production route from 1-butene metathesis has been developed on heterogeneous 10WO 3 /Al 2 O 3 -HY catalysts with different HY contents. It is found that the catalysts play bi-functionally first for the isomerization of 1-butene to 2-butene and then for the cross-metathesis between 1-butene and 2-butene to propene and 2-pentene. The combination of HY zeolite and Al 2 O 3 is prerequisite for the production of propene. The propene yield keeps increasing with the HY content in the range of 10–70 wt%, where 10WO 3 /Al 2 O 3 -70HY exhibits the highest propene yield. The MS-H 2 -TPR and MS-O 2 -TPO characterizations indicate that the increase of HY content in the catalysts weakens the interaction between W species and supports, whereas enhance the probability of coking on the metal species and acid sites.

Synthesis of C2+-oxygenated compounds directly from syngas

Abstract Vapor Phase synthesis of C2+-oxygenated compounds from synthesis gas was carried out on a bench-scale apparatus. A Rh-Mn/Sio2 catalyst showed an enhanced performance in terms of product selectivity anddurability.

A Facile Top‐Down Protocol for Postsynthesis Modification of Hierarchical Aluminum‐Rich MFI Zeolites

High aluminum content constitutes a major hurdle for the postsynthesis modification of hierarchical zeolites. A facile protocol comprising fluorination and sequential alkaline treatment is presented for the postsynthesis modification of hierarchical Al-rich MFI zeolites. By virtue of this protocol, uniform intracrystalline mesoporosity is introduced in an Al-rich MFI zeolite (Si/Al = 14.3). The obtained hierarchical zeolites exhibit a significant mesopore size distribution, centered around 6 nm, and show improved conversions in catalytic cracking of bulky aromatic molecules. The fundamental implications of the fluorination-alkaline treatment protocol are related to the formation of F-bearing tetrahedral aluminum species in the antecedent fluorination step, which alleviates the resistance of Al sites to the alkaline medium and causes Al-F complexation for regulated hydrolysis of the Al species during the alkaline treatment process. This top-down protocol and the derived mechanistic understandings are expected to be applied in the synthesis of hierarchical Al-rich zeolites with other framework topologies.

Intrinsic Catalytic Role of Mesoporous Silica in Preferential Oxidation of Carbon Monoxide in Excess Hydrogen

We have studied the intrinsic catalytic role of MCM-41 mesoporous silica in preferential oxidation of CO in excess H(2) (PROX). Two types of MCM-41 supports (MCM-41A and MCM-41B) were obtained from the same pristine as-synthesized materials by using different procedures for surfactant removal: one-step calcination or two-step extraction-calcination. Although two kinds of Pt catalysts prepared from the MCM-41 supports exhibit high similarity in apparent physicochemical parameters such as Pt morphology, particle-size distribution, electronic states, support architecture, and pore-size distribution, they show a dramatic difference in catalytic activity (ca. 100 % versus 10 % CO conversions at 298 K). This feature motivated us to investigate the catalytic role of MCM-41 in the PROX reaction. By means of infrared experiments with the isotope tracer technique, it was revealed that the reactive microenvironment at the interface between Pt and the MCM-41A support is the origin of the high activity. On the highly active Pt/MCM-41A catalyst, interfacial silanols play a decisive role in the ignition of CO oxidation, and gaseous O(2) and H(2) are dissociated on CO-free Pt sites created by the interfacial reaction. The dissociated oxygen and hydrogen are proposed to sustain the catalytic cycle in the form of regenerated silanols on the support, which is catalyzed by the Pt surface in the presence of H(2).

Properties of metal species in square-shape mesopores of KSW-2-based silica

Properties arising from 2-D orthorhombic mesoporous silica (KSW-2) were investigated for each structural feature: (1) periodicity in silicate framework and (2) square-shape mesopore. Titanium species were grafted onto the periodic silica walls of KSW-2-based mesoporous silica through silylation with octylmethyldichlorosilane in the presence of organotitanium compounds with cyclopentadienyl ligands. The surface TiO4 units formed after calcination at 550 °C showed a higher activity in the oxidation of cyclohexene with peroxides than those onto FSM-16 and MCM-41 grafted in the same manner, indicating that (1) the periodicity in the framework influenced the catalytic activity due to the heteroatoms fixed at the silicate surfaces. The synthesis of metallic Pt species inside square-shape mesopores of KSW-2-based silica was conducted by reduction of impregnated H2PtCl6. Considering the morphology of metallic Pt species formed through wet H2 and UV reduction, it is considered that (2) the square-shape mesopore is useful for suppressing the sintering of metallic Pt species.

Bridging Dealumination and Desilication for the Synthesis of Hierarchical MFI Zeolites

The rational design of zeolite-based catalysts calls for flexible tailoring of porosity and acidity beyond micropore dimension. To date, dealumination has been applied extensively as an industrial technology for the tailoring of zeolite in micropore dimension, whereas desilication has separately shown its potentials in the creation of mesoporosities. The free coupling of dealumination with desilication will bridge the tailoring at micro/mesopore dimensions; however, such coupling has been prevailingly confirmed as an impossible mission. In this work, a consecutive dealumination-desilication process enables the introduction of uniform intracrystalline mesopores (4-6 nm) into the microporous Al-rich zeolites. The decisive impacts of steaming step have been firstly discovered. These findings revitalize the functions of dealumination in porosity tailoring, and stimulate the pursuit of new methods for the tailoring of industrially relevant Al-rich zeolites.