Selective synthesis for light olefins from acetone over ZSM-5 zeolites with nano- and macro-crystal sizes
Selective synthesis for light olefins from acetone over ZSM-5 zeolites with nano- and macro-crystal sizes
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DOI：
10.1016/j.apcata.2011.06.029
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发表时间：
2011-08-22
影响因子：
5.5
通讯作者：
Masuda, Takao
中科院分区：
文献类型：
--
作者：
Tago, Teruoki;Konno, Hiroki;Masuda, Takao
研究了在ZSM-5分子筛上丙酮制乙烯、丙烯和异丁烯等低碳烯烃的反应。这些轻质烯烃是由丙酮在沸石的酸位点上通过一系列连续反应生产的，其中烯烃如乙烯和丙烯是通过由丙酮的羟醛缩合产物生产的异丁烯的裂化获得的。分别采用水热法和乳液法制备了大尺寸和纳米尺寸的ZSM-5分子筛，得到的ZSM-5分子筛具有几乎相同的酸性和BET比表面积，与晶粒尺寸无关。从SEM观察，沸石的晶体尺寸为约2000 nm和30-40 nm。将不同晶粒尺寸的沸石用于丙酮合成低碳烯烃反应，考察了晶粒尺寸对催化剂活性和稳定性的影响。与宏观捕获的沸石相比，纳米沸石在长寿命内表现出高活性。然而，由于纳米尺寸的沸石具有大的外表面积，由所产生的轻质烯烃形成芳族化合物的不期望的反应发生在位于外表面附近的酸位点上。为了抑制芳烃的形成，位于沸石外表面附近的酸中心的选择性失活是通过使用二苯基硅烷（DP-硅烷）的硅烷催化裂化（CCS）方法实现的。CCS方法在使位于ZSM-5沸石的外表面附近的酸中心失活方面是有效的。此外，在高丙酮转化率条件下，使用DP-硅烷CCS处理后的纳米尺寸沸石表现出高烯烃和低芳烃产率。(C)2011爱思唯尔有限公司版权所有。
Production of light olefins such as ethylene, propylene and isobutylene from acetone was examined over ZSM-5 zeolites. These light olefins are produced from acetone over the acid sites of the zeolite via a series of consecutive reactions where olefins such as ethylene and propylene are obtained by cracking of isobutylene produced from aldol condensation products of acetone. Macro- and nano-sized ZSM-5 zeolites were prepared by conventional hydrothermal and emulsion methods, respectively, and the ZSM-5 zeolites with nearly the same acidity and BET surface area were obtained regardless of the crystal sizes. From SEM observations, the crystal sizes of the zeolites were approximately 2000 nm and 30-40 nm. These zeolites with different crystal sizes were applied to light olefins synthesis from acetone, and the effect of crystal size on catalytic activity and stability was investigated. As compared with the macro-seized zeolite, the nano-sized zeolite exhibited a high activity over a long lifetime. However, because the nano-sized zeolite possesses a large external surface area, undesirable reactions to form aromatics from the produced light olefins occurred on the acid sites located near the external surface. To inhibit aromatics formation, selective deactivation of the acid sites located near the outer surface of the zeolite was achieved via the catalytic cracking of silane (CCS) method using diphenyl silane (DP-silane). The CCS method was effective in deactivating the acid sites located near the external surface of the ZSM-5 zeolite. Moreover, the nano-size zeolite after the CCS treatment using DP-silane exhibited high olefins and low aromatics yields under high acetone conversion conditions. (C) 2011 Elsevier B.V. All rights reserved.