合成和表征ERI类型的UZM-12热和它们的甲醇-olefin性能
Joo Hyuck Lee1, Min Bum Park, Jun Kyu Lee
1Department of Chemical Engineering and School of Environmental Science and Engineering, POSTECH, Pohang 790-784, Korea.
Journal of the American Chemical Society
|August 26, 2010
概括
合成的UZM-12热石对结构指导剂和金属酸盐敏感. 在H-UZM-12中的纳米晶体性可能会由于焦炭形成而对甲醇-olefin催化产生负面影响.
科学领域:
- 材料科学 材料科学 材料科学
- 催化剂是一种催化剂.
- 纳米技术 纳米技术
背景情况:
- UZM-12是一种高氧化,与石相关.
- 石合成通常使用结构指导剂 (SDA).
- 电荷密度不匹配 (CDM) 方法用于焦化合成.
研究的目的:
- 为了研究UZM-12的合成,使用各种二四次性基离子作为SDA.
- 探索SDA结构和金属子对UZM-12结晶的影响.
- 评估H-UZM-12在甲醇-olefin反应中具有不同晶体体大小的催化性能.
主要方法:
- 使用电荷密度不匹配 (CDM) 方法合成UZM-12.
- 使用 (27) Al MQ MAS NMR进行表征,以确定部位偏好.
- 在甲醇-olefin (MTO) 反应中对H-UZM-12进行催化试验.
主要成果:
- UZM-12结晶非常依赖SDA的基离子结构和金属离子.
- 在UZM-12框架中,优先占据高多重性的地点.
- 纳米晶体H-UZM-12 (≤100nm) 由于焦炭沉积,在MTO反应中表现出降低的活性和稳定性.
结论:
- SDA 和金属离子体的尺寸对于指导UZM-12热酸盐合成至关重要.
- 在MTO反应中,纳米晶体性可能会损害H-UZM-12的催化性能.
- 在小晶体的外部表面积聚焦阻碍了向活性部位的扩散.
相关概念视频
01:13Olefin Metathesis Polymerization: Overview
Recently, the development of olefin metathesis polymerization advanced the field of polymer synthesis. Simply put, the reorganization of substituents on their double bonds between two olefins in the presence of a catalyst is known as the olefin metathesis reaction. The use of metathesis reaction for polymer synthesis is called olefin metathesis polymerization.
Ruthenium-based Grubbs catalyst is the most commonly used catalyst for olefin metathesis polymerization. Grubbs catalyst consists of a...
Ruthenium-based Grubbs catalyst is the most commonly used catalyst for olefin metathesis polymerization. Grubbs catalyst consists of a...
01:33Carboxylic Acids to Methylesters: Alkylation using Diazomethane
Carboxylic acids react with diazomethane in an ether solvent via alkylation at the carboxylate oxygen atom to give methyl esters of the corresponding acid with excellent yields.
02:29Ethers from Alcohols: Alcohol Dehydration and Williamson Ether Synthesis
Overview
Ethers can be prepared from organic compounds by various methods. Some of them are discussed below,
Preparation of Ethers by Alcohol Dehydration
In this method, in the presence of protic acids, alcohol dehydrates to produce alkenes and ethers under different conditions. For example, in the presence of sulphuric acid, dehydration of ethanol at 413 K yields ethoxyethane, whereas it yields ethene at 443 K.
Ethers can be prepared from organic compounds by various methods. Some of them are discussed below,
Preparation of Ethers by Alcohol Dehydration
In this method, in the presence of protic acids, alcohol dehydrates to produce alkenes and ethers under different conditions. For example, in the presence of sulphuric acid, dehydration of ethanol at 413 K yields ethoxyethane, whereas it yields ethene at 443 K.
02:35Ethers from Alkenes: Alcohol Addition and Alkoxymercuration-Demercuration
Overview
Ethers can also be prepared from alkenes through acid-catalyzed addition of alcohols and alkoxymercuration–demercuration.
Preparation of Ethers by Acid-Catalyzed Addition of Alcohol to Alkenes
The acid-catalyzed addition of alcohol to an alkene involves treating the alkene with an excess of alcohol in the presence of an acid catalyst to form an ether under suitable conditions. The hydrogen will add to the less substituted carbon so that the nucleophile can attack the more substituted...
Ethers can also be prepared from alkenes through acid-catalyzed addition of alcohols and alkoxymercuration–demercuration.
Preparation of Ethers by Acid-Catalyzed Addition of Alcohol to Alkenes
The acid-catalyzed addition of alcohol to an alkene involves treating the alkene with an excess of alcohol in the presence of an acid catalyst to form an ether under suitable conditions. The hydrogen will add to the less substituted carbon so that the nucleophile can attack the more substituted...
00:53Olefin Metathesis Polymerization: Acyclic Diene Metathesis (ADMET)
Acyclic diene metathesis polymerization or ADMET polymerization involves cross-metathesis of terminal dienes, such as 1,8-nonadiene, to give linear unsaturated polymer and ethylene. As ADMET is a reversible process, the formed ethylene gas must be removed from the reaction mixture to complete the polymerization process.
Similar to cross-metathesis, ADMET also involves the formation of metallacyclobutane intermediate by [2+2] cycloaddition of one of the double bonds of a terminal diene with...
Similar to cross-metathesis, ADMET also involves the formation of metallacyclobutane intermediate by [2+2] cycloaddition of one of the double bonds of a terminal diene with...
02:43E1 Reaction: Stereochemistry and Regiochemistry
One of the critical aspects of the E1 reaction mechanism, as also observed in E2, is the regiochemistry, with multiple regioisomers obtained as products. In the example discussed, the presence of water as a weak base favors elimination over substitution to generate two alkenes. Given that alkenes’ stability increases with the number of alkyl groups across the double bond, typically, E1 reactions lead to the Zaitsev product, for this is more substituted and stable than the Hofmann product.