Bing Zhong

Synthesis of dimethyl carbonate by transesterification over CaO/carbon composites

A CaO/C composite, a new solid base catalyst, was prepared and served as a convenient and efficient heterogeneous catalyst for synthesis of DMC from methanol and propylene carbonate. Compared with pure CaO, the CaO/C shows the same basic properties and a high performance. In addition, the CaO/C catalyst, which is easily recovered, can be reused with little deactivation, if a suitable particle size is chosen.

A catalyst with high activity and selectivity for the synthesis of C2+-OH: ADM catalyst modified by nickel

For ADM catalyst, Ni was an effective promoter for the activity, in particular C2+-OH selectivity. At a Ni/Mo molar ratio of 0.5, the highest ratio of C2+-OH/C1-OH (8.75) was obtained, which was about 10 times that of ADM catalyst in the absence of Ni (0.87). The modification of Ni showed remarkable structural effects and the great deviation of methanol from the linear A-S-F distribution indicated a different reaction route, which might be caused by the bi-functionality of nickel species, namely, the formation of corresponding precursor of alcohol and the strong ability of CO insertion.

06-P-10 - Formation of double-mesopore silica and its transformatoin into MCM-41

Publisher Summary This chapter discusses the formation of double-mesopore silica and its transformation into MCM-41. The influence of alkali/silica molar ratio in the synthesis of mesoporous molecular sieve materials is studied in a simple synthesis system containing tetraethylorthosilicate, water, alkali, and cetyltrimethylammonium bromide at room temperature. The resulting silicate materials are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and N2 adsorption–desorption isotherms. The results suggest that the formation of different surfactant-silicate aggregation array morphology not only relies on an interaction between silicate ions and the surfactant but also on a proportion of the silicate species to surfactant.

Compositional effects of bimodal mesopore silica synthesized by a base- catalyzed ambient pressure sol-gel processing

Abstract The effects of tetraethylorthosilicate (TEOS) concentration and TEOS/surfactant molar ratio on the synthesis of bimodal mesopore silica (BMS) were studied. It was found that the BMS silica can be synthesized in a wide range of component concentration and its secondary mesopore size is more sensitive to the change of precursor concentration than its primary mesopore size and the secondary mesopore volumes can be up to 2.0 or more times as large as the primary mesopore volumes. The controllability of the bimodal mesopore size distributions, in particular the secondary mesopore size of BMS silica is of great interest to catalysis because they greatly facilitate mass transport to the primary mesopore.

Structural and textural evolution of bimodal mesopore silica xerogels during aging and drying

Abstract The effects of aging and drying conditions on the structural and textural properties of surfactant-templated silica xerogel with bimodal mesopore distribution characteristic (designated as BMS) prepared under base-catalyzed sol-gel process were investigated. It was found that the change of aging and drying conditions would influence not only the size and the packing geometry of surfactant-encapsulated silica primary particles, in turn the textural mesoporosity, but also the polymerization extent of framework pore wall which would determine the framework mesopore properties. Both the lower aging temperature and the higher drying temperature are conducible to the formation of a high-quality BMS silica xerogel. However, over the range studied, aging and drying conditions had no significant effect on the framework mesopore sizes, though the corresponding specific surface areas and pore volumes can, be varied markedly.

Influence of synthesis parameters on the formation and structure of bimodal mesopore silica in a controlled sol-gel process

In the present work, a series of synthesis parameters, including those that may affect the size of surfactant micelles and that may affect the relative rate of hydrolysis and condensation of tetraethyl orthosilicate (TEOS), were judiciously adjusted to study their direct influence on the formation and structure of our previously reported bimodal mesopore silica (designated as BMS). It is found that both the framework and textural mesopores of BMS silica can be tailored over a fairly wide size range, but on the whole the textural mesopore size is more sensitive to the change of the synthesis parameters than that of the framework mesopore size. The change of three synthesis parameters, such as increasing the amount of ethanol, decreasing the chain length of surfactant or increasing the alkali/silica molar ratio, would lead to the mesostructure of the silica obtained to transform from initial BMS into MCM-41.

Catalytic conversion of n-parafins in supercritical phase

Abstract The catalytic conversion of n-paraffins in supercritical phase, including catalytic dehydrogenation of C 10 -C 14 n-paraffins to linear monolefins and Pt reforming of heptane at low temperature, was investigated here. The results indicated that the supercritical catalysis led to the improvement of both conversion of the reactants and selectivity of the main products as well as the reduction of coke formation.

Solvent effects on BMS silica formation in a base-catalyzed sol-gel process

The effects of solvent properties on the formation and structure of bimodal mesopore silica (designated as BMS) are studied in a base-catalyzed sol-gel process. It is found that BMS can be synthesized over a wide range of solvent water content, but a narrow range of cosolvent alkan-1-ols content. Increasing the alkan-1-ols concentration or the carbon atom numbers in the alkan-1-ols molecules used leads to an even rapid hydrolysis and condensation of tetraethoxysilane (TEOS), thus a larger textural mesopore to be formed in the resulting BMS products. However, when an excessive amount of alcohol is added, the synthesis system will transform from the initial gelation (BMS) into a speedy formed deposition (MCM-41).

Studies on immobilization of Co(II)-La(III) schiff base complex in MCM-41

Abstract Immobilization of heteronuclear Co(II)-La(III) salen (denoted as (CoLa)salen ) complex into the pores of MCM-41 matrix was studied and characterized by element analysis, TG-DTA, FTIR and UV-vis. The results showed that the heteronuclear complex may undergo dissociation during immobilization step due to the strong guest/host interaction. Nevertheless, the obtained product(designated as (Co,La)salen/MCM-41) exhibits higher conversion than Cosalen/MCM-41 and Lasalen/MCM-41 and high stability for the oxidation of styrene. In addition, the effects of the reaction time, reaction temperature, and solvent on the catalytic properties of (Co,La)salen/MCM-41 in oxidation of styrene were also investigated.