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Petroleum Processing Catalysts
Published in Alvin B. Stiles, Theodore A. Koch, Catalyst Manufacture, 2019
Alvin B. Stiles, Theodore A. Koch
Molecular sieves are useful for many catalytic applications, particularly for petroleum processing, but are also finding use as detergents, desiccants, etc. Additionally, in the recent literature many references are made to the replacement of some of the acid sites with copper, manganese, nickel, iron, and other metals, which then can be used for certain other catalytic processing. An effort was made to replace the acid site with zinc and copper to produce methanol, which then, in the presence of the molecular sieve, would be converted to dimethyl ether and subsequently into gasoline fractions. To date, this has not been reported to be a satisfactory system. However, certain replacements of the acid sites by metals that catalyze other operations such as hydrogenation have enjoyed success.
Adsorption Cooling Heat Pumps
Published in Sotirios Karellas, Tryfon C. Roumpedakis, Nikolaos Tzouganatos, Konstantinos Braimakis, Solar Cooling Technologies, 2018
Sotirios Karellas, Tryfon C. Roumpedakis, Nikolaos Tzouganatos, Konstantinos Braimakis
Zeolites: The high regeneration costs of activated carbon have created the need for alternative low cost adsorbents including zeolites. Zeolite is a crystalline aluminosilicate with a three-dimensional framework structure of AlO4 and SiO4 that forms uniformly sized pores at a size of a molecule (Čejka 2007; Kulprathipanja and Wiley 2010). The basic structure of a typical zeolite is presented in Figure 6.2. The pores preferentially adsorb molecules that fit inside the pores and do not adsorb too-large molecules, hence acting as sieves on a molecular sieve. Zeolite crystallization takes place under hydrothermal conditions, from gels containing silica and alumina, in the presence of organic compounds as structure-directing agents (SDA) (Lu and Zhao 2004). There are many factors affecting the formation of zeolites, including source materials, solvent, SDA, gel composition, pH value, and crystallization conditions (Liu and Yu 2016). As of 2016, 232 types of zeolite materials have been identified by the Structure Commission of the International Zeolite Association (Baerlocher and McCusker 2016). The main reasons for the steady increase in the use of zeolites include the large number of commercially available structures, their high structural ability, and safety and environmental considerations (Martínez and Corma 2013).
Industrial Odor Control
Published in Paul N. Cheremisinoff, Air Pollution Control and Design for Industry, 2018
Molecular sieves are synthetic zeolites which can be manufactured with extremely close control of pore size. Therefore, they can be tailored to suit specific applications. In addition to gas drying applications, molecular sieves are used for the separation of gases and vapors on the basis of molecular size and shape. Surface areas range from 350 to 1,000 ft2/ft3.
Methods and synthesis parameters affecting the formation of FAU type zeolite membrane and its separation performance: a review
Published in Journal of Asian Ceramic Societies, 2020
Liyana Salwa Mohd Nazir, Yin Fong Yeong, Thiam Leng Chew
Over the past decades, zeolites have been a subject of interest among scientists and researchers in material science and technology due to their flexibility and adaptability. Many types of zeolites with different structures and compositions are commercially available and used for a number of environmental and industrial applications including ion-exchange [34-36], catalysts [8], adsorbents [31] and membrane separation [6,11,12]. Zeolites are also known to have a well-defined micropores which gives them molecular sieving properties. The term molecular sieves can be defined as the ability of zeolites to adsorb molecules that are smaller than its pores and channels while rejecting molecules that are too large based on the size exclusion phenomenon [37]. This property has shown to be beneficial for adsorption application in industrial gas separation process. Zeolite adsorbent such as zeolite A and X has been used in industrial application for ethanol dehydration, natural gas processing, air purification, CO and H2 adsorbent, hydrocarbon separation, and N2O removal [38].
Modeling of the HCPB Helium Coolant Purification System for EU-DEMO: Process Simulations of Molecular Sieves and NEG Sorbents
Published in Fusion Science and Technology, 2023
Jonas C. Schwenzer, Alessia Santucci, Christian Day
In the ZMS process, a fraction of the coolant stream is extracted after the main coolant compressor and routed over a copper oxide bed, converting the contained hydrogen into water. The stream is then cooled down and passed over a bed of ZMS 4A, where the formed water is adsorbed. The outgoing stream is used to precool the incoming stream in an economizer and then is reintroduced into the coolant upstream of the compressor, using the pressure differential to drive the process. Once saturated, the molecular sieve bed is regenerated by decoupling it from the process, depressurizing to ambient level, and purging it with hot inert gas in counterflow direction. The purge gas is hereby circulated in a closed loop, and a condenser is used to remove the desorbed water.
Dehydration – purification of aqueous ethyl alcohol by adsorption over molecular sieves: continuous operation
Published in Journal of the Chinese Institute of Engineers, 2021
Pooja Sanap, Akash Shetty, Yogesh Mahajan
Gas chromatograph (GC, Model no. 5765, NUCON Make) was used for analysis, as detailed by Sanap, Shetty, and Mahajan (2020). Calibration was done using IPA as internal solvent, with almost 98% accuracy of the results. In order to evaluate the performance of different adsorbents, different experiments were performed. Experiments with a single column were done initially. Each adsorbent is known to adsorb differently (Table 2). Different sieves are used to selectively adsorb different compounds: e.g. water is removed using 3A whereas 4A molecular sieves are used for removing methane, ethane, propane and other lower alkanes (Al-Asheh, Banat, and Al-Lagtah 2004). The adsorption capacity of each sieve is fixed and so a column can only be effectively operated for a fixed time, followed by switch – over to another column. Different experiments were performed with these considerations as mentioned below: Experiments with one columnExperiments with different adsorbents: 3A, 4A and 5A MS, activated charcoal and activated alumina;Experiments by varying the pellet size;Experiments by varying the quantity of adsorbents;Experiments conducted by varying the feed flow rate and