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Steam Gasification and Reforming Technologies
Published in Yatish T. Shah, Water for Energy and Fuel Production, 2014
This reaction follows a number of steps that involve the dehydrogenation of ethanol to form acetaldehyde, which in turn decomposes to produce methane and carbon monoxide. Further reforming of methane and water–gas shift reaction leads to the formation of hydrogen. Since ethanol has high hydrogen content, the process produces a significant amount of hydrogen. There are, however, side reactions such as dehydration and decomposition of ethanol which produce methane, diethyl ether, and acetic acid that reduce the production of hydrogen. These side reactions can be minimized by the use of selective catalysts. In addition, the formation of large amounts of carbon monoxide reduces the hydrogen yield and it also requires complex gas cleanup process. Overall, ethanol is still one of the best raw materials for steam reforming to produce hydrogen.
Flow Synthesis: A Better Way to Conjugated Polymers?
Published in John R. Reynolds, Barry C. Thompson, Terje A. Skotheim, Conjugated Polymers, 2019
James H. Bannock, Martin J. Heeney, John C. de Mello
We turn now to the use of flow chemistry for the synthesis of conjugated polymers—a use that is motivated by the need for better production methods that are capable of yielding high quality materials in the quantities required for industrial application. The difficulty of synthesizing conjugated polymers in the multi-kilogram quantities needed for large-scale commercialization has been highlighted in numerous recent publications, [40–46] many of which have pointed to the need for new quality-assured production methods that can offer greatly improved batch to batch reproducibility. Factors such as molecular weight distributions, chemical defects in the conjugated backbone, end-group species, and impurity levels are known to change significantly between individual batches, leading to substantial variations in rheology, processability, and optoelectronic performance for nominally identical materials [47]. This is a particular issue when attempting to increase production from the small sub-gram quantities used in research and development to the kilogram-scale batches needed for industrial application. Increased reaction volumes typically lead to diminished mixing efficiencies and poorer heat management [48], causing spatial variations in both chemical composition and temperature. These variations affect the local reaction kinetics and lead to the emergence of unwanted side reaction pathways that can detrimentally influence the final product. Intensive optimization of reaction conditions is required for each reactor scale, and, even then, unavoidable reductions in materials quality or yield frequently occur [49]. As we discuss below, flow chemistry provides a promising solution to many of these issues.
Methane Conversions
Published in Saeed Sahebdelfar, Maryam Takht Ravanchi, Ashok Kumar Nadda, 1 Chemistry, 2022
Saeed Sahebdelfar, Maryam Takht Ravanchi, Ashok Kumar Nadda
Thermodynamic equilibrium calculations show that coke and hydrogen are the main products and practically no benzene is formed (Moghimpour Bijani et al., 2012). Consequently, the side reactions should be kinetically controlled by using an appropriate catalyst. Under coke free conditions, for instance, the equilibrium conversion of methane is only about 12% with 50% selectivity to benzene and 50% selectivity to naphthalene at 700°C (Wang et al., 1997). By using the appropriate (shape selective) catalyst, the selectivity of benzene can be increased at the expense of that of naphthalene and other more bulky aromatics.
The continued development of multilayered and compositionally modulated electrodeposits
Published in Transactions of the IMF, 2022
Particularly in the case of multiple layers requiring a crisp profile, it is clear that the need for uniform thickness, composition and morphology of deposits, demands adequate control of electrocrystallisation during nucleation and growth, including pretreatment, together with an appropriate local reaction environment at the cathode. Such control over reaction environment includes appropriate attention to aspects of electrochemical engineering to: (e) minimise side reactions,(f) achieve uniform electrode potential, current density and concentration profiles over the cathode surface,(g) ensure well-defined electrolyte flow to and from the cathode.(h) Such considerations mean that further attention to classical electrode and cell designs is justified, particularly the rotating cylinder electrode58,59 and controlled flow rectangular channel cells.60,61