@phdthesis{oai:mie-u.repo.nii.ac.jp:00014725,
 author = {Matsuura, Shinya and 松浦, 真也},
 month = {Mar},
 note = {application/pdf, With the recent fluctuations in crude oil prices, the spread of COVID-19, and the growing environmental orientation based on the concept of the sustainable development goals (SDGs), the demand for oil and the situation surrounding oil itself are changing drastically. In this period of social transition, the overall demand for oil is on a downward trend, but it is expected to increase in some regions such as developing countries, and refining technology that can meet the demand more efficiently is important for sustainable use of oil resources. In particular, the catalytic cracking process using catalysts can increase the yield of useful fractions by cracking the residual oil (such as atmospheric residue and vacuum gas oil (VGO)) after extracting useful fractions such as liquefied petroleum gas, gasoline, and kerosene from crude oil. In recent years, this process has also been widely studied as a technology for obtaining fuel oil from waste plastics and other materials. In this process, there is a need for a catalyst that can crack the reactants more efficiently.
First, in order to prepare catalysts with mesopores, the gel skeletal reinforcement (GSR) method using a hexamethyldisiloxane (HS)-acetic anhydride (AA) silylating agent, which has been applied only to silica matrices, was applied to alumina and titania matrices. As a result, in the case of alumina, a high temperature peak in the range of 400-600 ℃ was observed in NH3 desorption, confirming the introduction of a new acid point. In the case of titania, no transition of the anatase phase to the rutile phase was observed, confirming the improvement of thermal stability. Therefore, alumina and titania matrices with novel physical properties could be prepared by the GSR method. These were used to prepare the mixed catalysts with β-zeolite. The catalytic cracking of n-dodecane was carried out to evaluate the reactivity of the prepared mixed catalysts. The mixed catalyst with alumina matrix showed improved conversion and gasoline selectivity compared to the mixed catalyst with β-zeolite single or with alumina matrix without GSR applied.
Second, in order to prepare zeolite-containing two-layered catalysts (ZC2L) with large mesopores with more uniformly dispersed zeolites, zeolite-containing gels were prepared by the sol-gel method using tetraethyl orthosilicate, and the GSR method of HS-AA system was applied. The zeolites used were ZSM-5, Y and β, which are commonly used in catalytic cracking process. As a result of XRD measurement and nitrogen adsorption / desorption measurement of these catalysts, while maintaining the crystal structure peculiar to zeolite, it has a maximum pore volume of 5 cm3/g and pore diameter of 50 nm or more. Thus, it was confirmed that the micropores of each zeolite and the large mesopores derived from GSR silica were combined. In the catalytic cracking of n-dodecane using these catalysts, the ZC2L catalyst with ZSM-5 improved the conversion by more than 30 % compared with zeolite single, even though the zeolite content was 26 wt%, indicating the improvement of cracking activity. In the case of ZC2L catalysts with β and Y, the multi-branch/single-branch hydrocarbon ratio (m/s) and the olefin/paraffin ratio (O/P) in the gasoline fraction increased by 1.5-2 times. The increase in the mesopore diameter affected the O/P and the conversion, and the micropore size of the zeolite affected the iso-/n- ratio (iso-/n-) in the gasoline fraction.
Third, catalytic pyrolysis of low-density polyethylene was carried out to evaluate the applicability of ZC2L catalysts to feeds with different geometries. A Curie point pyrolyzer was used as the reaction apparatus to compare the catalyst performance in a simple and rapid manner. The results showed that the ZC2L catalyst using ZSM-5 zeolite showed high selectivity for aromatic compounds such as toluene and p-xylene. The product selectivity of the ZC2L catalysts was influenced by the type of zeolite used, i.e., the size of the micropores. All ZC2L catalysts showed high conversion despite the small amount of zeolite used due to their hierarchical structure.
Fourth, the effect of the structure on the catalytic cracking of VGO, a bulky reactant, and the acid properties were evaluated using a catalyst with a three-layered structure developed from the ZC2L catalyst. As a result, three-layered catalysts that maintains the crystal structure of the HY zeolite used as well as the structure of the two-layered catalyst, and also has larger mesopores were able to fabricate. The BET surface area, BJH pore volume, and mesopore diameter of the three-layered catalyst were 716 m2/g, 1.44 cm3/g, and 10.6 nm, respectively. As a result of catalytic cracking of VGO using the fabricated two-and three-layered catalysts, the O/P, iso-/n-, m/s and RON value in gasoline were greatly improved compared with those of zeolite single and kaolin mixed catalyst. They also showed high activity, be suggested that the activity was largely related to the mesopore volume and the acidity of the catalyst.
In summary, various zeolite-containing hierarchical catalysts were prepared by sol-gel method and GSR method. The catalytic activity of the prepared zeolite-containing hierarchical catalysts was clarified by characterization of them and catalytic cracking of various hydrocarbons using them. Although those catalysts contained less zeolite as the main active catalyst, the product selectivity of zeolite in the catalytic cracking reaction was enhanced by the formation of new active sites and the enhancement of cracking activity by the hierarchical structure., 本文/Division of Material Science Graduate School of Engineering Mie University, 133p},
 school = {三重大学},
 title = {Studies on Preparation and Catalytic Cracking Reactivity of Novel Zeolite-Containing Hierarchical Catalysts},
 year = {2022},
 yomi = {マツウラ, シンヤ}
}