One-step Hydrothermal Synthesis Of Micro-mesoporous Zeolite By Template Method

Zeolite is one of the most widely used solid catalysts in the industry because of its regular pore structure, high stability and high catalytic activity. With the development of industrialization and petrochemical, people are faced with the treatment of macromolecular substances. Limitation of zeolite molecular sieve is more and more evident. Due to its small pore size and mass transfer resistance, its application of involving macromolecules is limited. Micro-mesoporous zeolite integrate the advantages of mesoporous and microporous, which can solve diffusion limitation of microporous zeolite and the low stability of mesoporous zeolite, so that it has a broader scope of application.The Micro-mesoporous zeolites are usually synthesized by template methods, post synthesis method and rigid template method. These methods are complex, it is difficult to control the synthesis conditions and it is hard to adjust the structure of synthesized Micro-mesoporous zeolites. Thus using amphiphilic template to synthesize micro-mesoporous zeolite with regular and steerable mesopore by one step is considered to be a new direction to synthesize micro-mesoporous zeolite. In this paper, a series of dual-functional surfactants are used as templates to synthesize micro-mesoporous zeolites by hydrothermal synthesis method in one step and the adsorption and catalytic properties of synthesized samples are preliminary studied.A series of rigid bolaform eight-head-group octadic ammonium surfactants(C6-6-6-6-6-O、C6-6-6-6-10-O、C6-6-6-6-12-O) were designed and synthesized in this paper.The eight-head-group octadic ammonium surfactants were used as templatezs to synthesized zeolites(BWS-6, BWS-10, BWS-12) to discuss how the crystallization time, crystallization temperature, silicon source, aluminum source and the length of intermediate hydrophobic carbon chain impact the characteristics of as-synthesized zeolites. The adsorption property and catalytic property of as-synthesized zeolites were also investigated. Results showed that the optimal crystal time is 7 days, the optimal crystal temperature is 150 ℃, the optimal silicon source is TEOS, the optimal aluminum source is Na Al O2. The length of sparse water chain has obvious effect on the structure and character of zeolites. So selecting appropriate length of carbon chain of template is more conducive to prepare zeolites with more excellent properties. In the toluene adsorption test, the adsorption quality of as-synthesized samples were respectively 234.57 cm3/g(BWS-12), and 119.767 cm3/g(BWS-10), and 65.46 cm3/g(BWS-6), they are significantly higher than the adsorption quality of traditional beta(47.24 cm3/g). In the aldolization reaction, the final conversion(81.25%) of formaldehyde catalyzed by BWS-12 is superior to the conversion(57.01%) catalyzed by conventional beta. In the friedel-crafts alkylation reaction, the conversion of phenol catalyzed by BWS-12 are twice as many as the conversion of phenol catalyzed by conventional beta in each period. This work can provide a useful reference for the design and synthesis of dual-function template, which can be used as a single template in one-step hydrothermal synthesis of micro-mesoporous molecular sieves.A series of two, four and six head-group ammonium surfactants were synthesized as templates to synthesize micro-mesoporous molecular sieves ZZM-18, ZZM-22, ZZM-N6, and ZZM-N2 by one-step hydrothermal method to investigate how the number of head-group ammonium and the hydrophobic chain length impact the structure and characteristics of as-synthesized zeolites. Results showed that the chain length and the number of head-group ammonium have obvious effects on the characteristics of as-synthesized zeolites. So selecting appropriate number of head-group ammonium and chain length can synthesize more excellent products. In the toluene adsorption test, the adsorption quality of as-synthesized samples were respectively 186.25 cm3/g(ZZM-22) and 65.04cm3/g(ZZM-N2), they are significantly higher than the adsorption quality of traditional ZSM-5(47.24 cm3/g). In the aldolization reaction, the final conversion(84.72%) of formaldehyde catalyzed by BWS-12 is superior to the conversion(61.76%) catalyzed by conventional beta. In the friedel-crafts alkylation reaction, the conversions of phenol catalyzed by BWS-12 are five times compared with the conversion of phenol catalyzed by conventional ZSM-5 in each period.A four head-group ammonium surfactant containing benzene was designed and synthesized as template synthesize molecular sieve in different proportions by one-step hydrothermal method under the same conditions. This is to investigate the effect of template on the type of as-synthesized molecular sieve in this paper. Results showed that Beta(BZW) and ZSM-5(ZHS) were synthesized by the same template in different proportions. In the toluene adsorption test, the adsorption quality of as-synthesized samples were respectively 141.96 cm3/g(ZHS) and 126.09cm3/g(BZW), they are significantly higher than the adsorption quality of conventional zeolites. In the aldolization reaction, the final conversions of formaldehyde were 79.11% and 83.21%. They were respectively catalyzed by ZHS and BZW, which were superior to the conversions catalyzed by conventional zeolites. In the friedel-crafts alkylation reaction, the conversions of phenol when the reaction time was 6h catalyzed by ZHS and BZW were respectively 48.25% and 61.45%. This can provide a useful reference for the design and synthesis of dual-function template that can be used as a single template in one-step hydrothermal synthesis of micro-mesoporous molecular sieves.