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Crude Oil Refining—Part 2
Published in Hussein K. Abdel-Aal, Economic Analysis of Oil and Gas Engineering Operations, 2021
Catalytic hydrotreating is used to remove about 90% of contaminants such as nitrogen, sulfur, oxygen, and metals from liquid petroleum fractions. These contaminants can have detrimental effects on the equipment and the quality of the finished product. Hydrotreating for sulfur or nitrogen removal is called hydrodesulfurization (HDS) or hydrodenitrogenation (HDN), respectively. World capacity for all types of hydrotreating currently stands at about 45.7 million b/d. Hydrotreating is used to pretreat catalytic reformer feeds, saturate aromatics in naphtha, desulfurize kerosene/jet, diesel, distillate aromatics saturation, and to pretreat catalytic cracker feeds. Hydrotreating processes differ depending upon the feedstock available and catalysts used. Mild hydrotreating is used to remove sulfur and saturate olefins. More severe hydrotreating removes nitrogen, additional sulfur, and saturates aromatics. In a typical catalytic hydrotreater, the feedstock is mixed with hydrogen, preheated in a fired heater (315–425°C) and then charged under pressure (up to 68 atm) through a fixed-bed catalytic reactor. In the reactor, sulfur and nitrogen compounds in the feed are converted into H2S and NH3. Hydrotreating catalysts contain cobalt or molybdenum oxides supported on alumina and less often nickel and tungsten.
Synthetic Crude Processing
Published in Sonil Nanda, Prakash Kumar Sarangi, Dai-Viet N. Vo, Fuel Processing and Energy Utilization, 2019
Rachita Rana, Sonil Nanda, Ajay K. Dalai, Janusz A. Kozinski, John Adjaye
The removal of sulfur in the form of H2S is termed as hydrodesulfurization (HDS). Figure 12.4 shows some of the common sulfur compounds found in the feed such as thiophenes, benzothiophenes, and dibenzothiophenes. The reaction mechanism for HDS is shown in Figure 12.5. As presented in Figure 12.5, the HDS process can follow two pathways—hydrogenation or hydrogenolysis—which leads to the removal of sulfur from the aromatic structure in the form of hydrogen sulfide. Thus, organo-sulfur compounds react with hydrogen and the polluting sulfur gas is liberated in the form of hydrogen sulphide, thus making the product comply with the clean environmental norms. It is seen that organo-nitrogen compounds tend to deactivate the hydrotreating catalyst. Hence, hydrodenitrogenation (HDN) is used to remove such unwanted hetero-compounds of nitrogen in the form of ammonia.
Adsorption of Aromatic N-Heterocyclic Compounds from Liquid Fossil Fuels
Published in Alexander Samokhvalov, Adsorption on Mesoporous Metal-Organic Frameworks in Solution for Clean Energy, Environment, and Healthcare, 2017
In the industrial-scale commercial processes for the removal of nitrogen-containing organic compounds from refinery streams, catalytic hydrodenitrogenation (HDN) is conducted at an elevated temperature and pressure (Rodríguez and Ancheyta 2004), simultaneously with catalytic hydrodesulfurization (HDS). Aromatic N-heterocyclic compounds are known to adversely affect the performance of HDS (Murti et al. 2003). Specifically, methyl-substituted CBZs such as 1,8-dimethylcarbazole are known to be highly refractory in both HDN and HDS (Shin et al. 2001). Yet another difficulty accompanying catalytic HDS and HDN of refinery streams is undesired catalytic hydrogenation of aromatic hydrocarbons. This side reaction of hydrogenation causes an undesired decrease in the octane number (ON) of the obtained gasoline and an unnecessary consumption of hydrogen.
A potential material for removal of nitrogen compounds in petroleum and petrochemical derivates
Published in Chemical Engineering Communications, 2021
Matheus Antoniel Félix de Carvalho, Deborah Victória Alves Aguiar, Boniek Gontijo Vaz, Maria Eugênia de Oliveira Ferreira, Laiane Alves de Andrade, Indianara Conceição Ostroski
In refineries, the reactions of hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) occur simultaneously to reduce the presence of sulfur and nitrogen compounds in the final products. Basic nitrogen compounds, even in small amounts, cause a considerable inhibitory effect on HDS reactions, due to the fact that they strongly adsorb to the active sites of acid catalysts, reducing the efficiency of sulfur compounds’ removal (García-Gutiérrez et al. 2014; Salazar et al. 2019). The basic nitrogen compounds can still react with the carboxylic acids present in the oil fraction. The organic salts formed can cause incrustations in the process equipment and ducts (Davis 2007). Beltramone et al. (2008) observed the influence of nitrogen compounds in the inhibition of the hydrodesulfurization reaction, using a commercial catalyst. It was found that the inhibitory effect increased in the following order: indoline > indole > tetrahydroquinoline > quinoline. Despite being a very severe process, HDN reactions are not sufficient to eliminate all nitrogenous contaminants present in the oil fractions. For this reason, researchers have been studying new removal techniques, of which it stands out processes oxidation (Bhadra et al. 2019), extraction (Salleh et al. 2018), and adsorption (Ferreira et al. 2019).
Emerging role of organic acids in leaching of valuable metals from refinery-spent hydroprocessing catalysts, and potential techno-economic challenges: A review
Published in Critical Reviews in Environmental Science and Technology, 2021
Ashish Pathak, Mari Vinoba, Richa Kothari
Extensive information about hydroprocessing catalysts, their properties, and deactivation mechanisms have already been provided in the literature (Ancheyta, Rana, & Furimsky, 2005; Marafi et al., 2017). Therefore, for this article, a summary will only be given about fresh hydroprocessing catalysts and their transformation into the spent catalyst. Typically, hydroprocessing operations such as hydrodesulfurization (HDS) or hydrodenitrogenation (HDN) are conducted with a sulfided catalyst. The Mo-containing supported catalysts, promoted either by Co (CoMo/Al2O3) or Ni (NiMo/Al2O3) are being used widely by refiners for hydroprocessing. The y-Al2O3 is widely used as a support due to its excellent textural properties, and low cost (Ancheyta et al., 2005). The fresh hydroprocessing catalysts are in oxide form, and they are converted to active sulfide form (using sulfidation) prior to use in hydroprocessing (Robinson & Dolbear, 2017). The fresh hydroprocessing catalyst comes in different sizes and shapes (spherical, pellets, cylinder, trilobe, tetralobe) which are important criteria for the selection of a hydroprocessing catalyst (Macias & Ancheyta, 2004). The smaller size of the catalyst particle is useful in minimizing the diffusion effects, whereas large-diameter alleviates the pressure drop across the reactor. Besides physical properties, the active metal content and composition, type of support, and support properties are important chemical properties that affect the catalyst performance and life span (Anchyeta, 2016). In addition, the mechanical strength of the fresh catalyst is also vital for the stability of the catalyst in the reactor. The fuel specifications (sulfur content, API gravity, etc.) from different regions also play an important role in the selection of a particular catalyst for hydroprocessing. This is because crude oils vary in physical properties and composition because of the varied geological nature of the source, depth of well, and pressure (Marafi et al., 2019).