Synthesis of Light Olefins from Oxygenated Organic Compounds over Metallosilicates with MFI and MTW-type Zeolite Structures
Synthesis of Light Olefins from Oxygenated Organic Compounds over Metallosilicates with MFI and MTW-type Zeolite Structures
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DOI：
10.1627/jpi.60.277
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发表时间：
2017-11
影响因子：
1
通讯作者：
Y. Nakasaka;T. Tago;T. Masuda
中科院分区：
文献类型：
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作者：
Y. Nakasaka;T. Tago;T. Masuda
乙烯、丙烯、丁烯等轻烯烃是石油化工行业必不可少的原料化学品，对这些轻烯烃的需求逐年持续增长。大多数轻烯烃是由石脑油蒸汽裂解生产的，但其生产成分不可控，副产品有丙烯和丁烯。此外，石脑油的蒸汽裂解发生在高温下，因此消耗了大量的能量。因此，在温和的反应条件下控制生产轻质烯烃的工艺是非常可取的。沸石是一种具有三维连接框架结构的铝硅酸盐晶体，具有强酸性、高比表面积和接近碳氢化合物分子大小的规则孔隙等重要特性。此外，沸石在高温条件下是稳定的，因此在工业过程中得到广泛应用。广泛研究了沸石催化剂上以石脑油（1)~10)、甲醇（11）~16）、乙醇（17）和丙酮（18）~20)为原料制备轻烯烃的反应机理（21）~30)。轻烯烃是反应的中间产物，因此选择性生产需要抑制由轻烯烃生成芳烃和焦炭的连续反应。此外，沸石的孔径与轻烯烃和芳烃的分子尺寸接近，因此酸位反应速率和分子在孔内的扩散速度与分子在孔内的停留时间有关，对这些不良反应的进行有很大的影响。另外，还制备了旨在削弱酸位的交换沸石，成功地从丙酮中选择性地合成了异丁烯。Al在沸石骨架中被其他三价元素（如B、Ga、Fe和Zr）（如LTA、MFI、MTW和MOR）同构取代31)、32)形成金属硅酸盐可以改变沸石的酸性。例如，在具有mfi型沸石结构的硅酸铁上，甲醇制烯烃反应对芳烃的选择性较低（33），34)。在沸石上的催化反应中，由于活性位点位于沸石孔的表面，原料必须从散装流体中扩散到沸石孔内。日本石油学院学报，60,(6),277-287 （2017）
Light olefins such as ethylene, propylene and butenes are essential raw chemicals in the petrochemical industry, and demand for these light olefins continues to increase year by year. Most light olefins are produced by steam cracking of naphtha, but the output composition is uncontrollable and propylene and butenes are present as by-products. In addition, steam cracking of naphtha occurs at high temperature so consumes a large amount of energy. Therefore, processes to obtain controlled production of light olefins under mild reaction conditions are very desirable. Zeolites are crystalline aluminosilicates with threedimensionally connected framework structures and have important properties such as strong acidity, high surface area, and regular pores with sizes close to the molecular size of hydrocarbons. In addition, zeolites are stable under high temperature conditions, so are widely used in industrial processes. Production of light olefins from various sources such as naphtha1)~10), methanol11)~16), ethanol17) and acetone18)~20) over zeolite catalysts has been investigated extensively, and the reaction mechanisms over zeolite have also been evaluated21)~30). Light olefins are intermediate products of the reaction, so suppression of consecutive reactions forming aromatics and coke from light olefins is required for selective production. Furthermore, the pore size of zeolites is close to the molecular size of light olefins and aromatics, so the reaction rates on acid sites and diffusion velocities of molecules inside the pores, which are related to the residence time of molecules inside the pores, strongly affect the progress of such undesirable reactions. P r ev ious ly, s i l y l a t ed18),19) o r a l ka l i -me ta l i on exchanged20) zeolites were prepared intended to weaken the acid sites, which succeeded in producing isobutylene selectively from acetone. Isomorphous substitution of Al by other trivalent elements (e.g., B, Ga, Fe and Zr) in the zeolite framework31),32), such as LTA, MFI, MTW and MOR, to form metallosilicates can modify the acidity of zeolites. For example, the methanol to olefins reaction over ferrisilicate with MFI-type zeolite structure showed low selectivity for aromatics33),34). In the catalytic reaction over zeolite, the feedstock must diffuse inside the zeolite pores from the bulk fluid because the active sites are located on the surfaces of the zeolite pores. The product molecules formed on 277 Journal of the Japan Petroleum Institute, 60, (6), 277-287 (2017)