China
Africa
Explore chapters and articles related to this topic
Feedstock Chemistry in the Refinery
Published in James G. Speight, Refinery Feedstocks, 2020
Dehydrogenation is essentially the removal of hydrogen from the parent molecule. For example, at 550°C (1,025°F) n-butane loses hydrogen to produce butene-1 and butene-2. The development of selective catalysts, such as chromic oxide (chromia, Cr2O3) on alumina (Al2O3) has rendered the dehydrogenation of paraffins to olefins particularly effective, and the formation of higher-molecular-weight material is minimized. The extent of dehydrogenation (vis-à-vis carbon–carbon bond scission) during the thermal cracking of crude oil varies with the starting material and operating conditions, but because of its practical importance, methods have been found to increase the extent of dehydrogenation and, in some cases, to render it almost the only reaction.
Feedstock Preparation
Published in James G. Speight, Handbook of Petrochemical Processes, 2019
Dehydrogenation is essentially the removal of hydrogen from the parent molecule. For example, at 550°C (1,025°F) n-butane loses hydrogen to produce butene-1 and butene-2 The development of selective catalysts, such as chromic oxide (chromia, Cr2O3) on alumina (Al2O3) has rendered the dehydrogenation of paraffin derivatives to olefin derivatives particularly effective, and the formation of higher molecular weight material is minimized. The extent of dehydrogenation (vis-à-vis carbon-carbon bond scission) during the thermal cracking of petroleum varies with the starting material and operating conditions, but because of its practical importance, methods have been found to increase the extent of dehydrogenation and, in some cases, to render it almost is the only reaction.
A review of sulfur extended asphalt modifiers: Feasibility and limitations
Published in Gianluca Dell’Acqua, Fred Wegman, Transport Infrastructure and Systems, 2017
S.E. Zoorob, C. Sangiorgi, S. Eskandersefat
At temperatures above 130°C the sulfur ring molecules suffer partial decomposition and polymerize in to long diradical chains. When sulfur is blended with bitumen at high temperature these sulfur radicals react with some components of bitumen provoking two competitive reactions. These radicals may either extract hydrogen from hydrocarbon molecules with subsequent hydrogen sulfide formation by means of dehydrogenation reactions, or can be incorporated to bitumen structure as carbon-sulfur bonds by means of addition reactions. Which of these two reactions is predominant depends on temperature, sulfur content and heating rate. Generally, the dehydrogenation reactions predominate at temperatures above 150°C (Masegosa et al. 2012).
Performance evaluation of PEM fuel cell-chemical heat pump-absorption refrigerator hybrid system
Published in International Journal of Ambient Energy, 2022
Emin Açıkkalp, Mohammad H. Ahmadi
CHP system is an alternative way of utilising the low-temperature heat source or waste heat; and thus, the renewable energy, including solar and geothermal energy, can be utilised. In contrast to conventional steam-compressed heat pumps, they do not involve mechanical compression generally. In this study, an i-propanol-acetone-hydrogen CHP was chosen. It can provide heat to the environment at 150–200°C, and the operating pressure is about 1 or 2 bars. The operational process of the CHP originates from the dehydrogenation of methanol, ethanol or n-butanol and hydrogenation of formaldehyde, acetaldehyde or butyraldehyde, respectively. In these systems, the dehydrogenation reaction takes place at low-temperature (70–100°C) and requires thermal energy; while the hydrogenation reaction is carried out at high-temperature (150–200°C) as an exothermic reaction. The alcohol produced by the hydrogenation reaction of aldehyde or ketone and hydrogen is recycled for dehydrogenation reaction. Part of low-level thermal energy is upgraded to high-level energy, and the rest is removed by condenser at ambient temperature. No mechanical energy is necessary as a driving force (Karaca, Kıncay, and Bolat 2002).
Comparative analysis of catalyst operation in the process of higher paraffins dehydrogenation at different technological modes using mathematical model
Published in Petroleum Science and Technology, 2018
Evgeniya V. Frantsina, Emiliya D. Ivanchina, Elena N. Ivashkina, Nataliya S. Belinskaya, Kseniya O. Fefelova
The process of higher paraffins (С9–С14) dehydrogenation to the corresponding olefins is widespread in the oil refining and petrochemical industry for the production of and is a key stage in the production of linear alkylbenzenes - the main components of synthetic detergents (Castañeda, Muñoz, & Ancheyta 2014; Jones & Pujado 2006; Leprine 2001; Olah 2002; Sunggyu 2005). The main purpose of the dehydrogenation process is to obtain normal olefins by dehydrogenating the paraffins of kerosene fraction (С9–С14) in the production of synthetic detergents (Rana et al. 2007; Sanfilippo & Miracca 2006). The process conversion is 8-10% with selectivity in terms of olefins equal to 90%. Deactivation of platinum catalysts of higher paraffins (C9–C14) dehydrogenation process is one of the major problems of modern oil refining and leads to an increase in production costs and, as a consequence, overall production costs (Buyanov & Pakhomov 2001; Frantsina et al. 2015; Froment 2008; Makaryan & Savchenko 2009; Tailleur & Davila 2008; Zaripov, Nazarov, & Ponikarov 2013). The most common reason for the deactivation of platinum catalysts is blocking of active platinum metal sites by coke, leading to the loss of catalyst activity in the target reaction (He 2009; Jiang et al. 2015; Niknaddaf et al. 2013; Vafajoo et al. 2014). Therefore, it is important to develop ways to reduce and slow down the processes of coke formation in high-temperature processing of hydrocarbon feedstock, as well as to develop methods for controlling the process of catalyst deactivation under industrial conditions (Bayat 2017; Belinskaya et al. 2016, 2017; Padmavathi et al. 2005).
Thermal stress stability of hydrocarbon fuels under supercritical environments
Published in Chemical Engineering Communications, 2023
Sundaraiah Konda, Madhavaiah Nalabala, Srikanta Dinda
Pyrolytic deposits or amorphous coke formation generally occur as a result of polymerization and polycondensation reactions. Generally, dehydrogenation and polycondensation reactions occur above 450 °C. The probable mechanism of amorphous coke formation is shown in Equations (16–18). The Diels–Alder reaction is also a potential route for the formation of pyrolytic coke.