PATENT
United States Patent Application 20120138449
Inventors:
Basfar, Ahmed Ali (RIYADH, SA)
Mohamed, Khaled Abdel-aziz (Cairo, EG)
Application Number: 13/371467
Publication Date: 06/07/2012
Assignee: King Abdulaziz City for Science and Technology (KACST) (Riyadh, SA)
Abstract:
FIELD OF THE INVENTION
The present disclosure relates to a method of removing sulfur from crude oil and diesel by ionizing radiation.
BACKGROUND
Recent developments in environmental legislations are inexorably moving us to a world of zero-sulfur emission standards. Global warming is demanding that this problem be addressed and be addressed soon. In the wake of these legislations, especially in the case of gasoline desulphurization, quite a number of novel processes such as catalytic and non-catalytic ones options have been revisited (Brunet S et al. 2005).
Sulfur-containing compounds that are typically present in hydrocarbon fuels include aliphatic molecules such as sulfides, disulfides, and mercaptans as well as aromatic molecules such as thiophene, benzothiophene, dibenzothiophene, and alkyl derivatives such as 4,6-dimethyl-dibenzothiophene. Those later molecules have a higher boiling point than the aliphatic ones and are consequently more abundant in higher boiling fractions.
Conventional hydro-desulfurization (HDS) technology can desulfurize aliphatic and cyclic sulfur-containing organic compounds on an industrial scale, as in most refineries in the world. Aromatic dibenzothiophene (DBT) and especially 4,6-alkyl-substituted DBTs, however, are difficult to convert to H2S due to the sterically hindered nature of these compounds on the catalyst surface (Shiraishi Y et al. 2002).
For this reason, removal of the DBTs by HDS to give the desired low levels of sulfur requires high temperature and H2 pressure conditions and hence a larger reactor as well as an active catalyst is required. From environmental and economic viewpoints, it is desirable to develop a more energy-efficient desulfurization process for production of virtually sulfur-free fuel.
Deep desulfurization processes include selective adsorption, (McKinley S, Angelici R 2003), extraction with ionic liquids (Bosmann L. et al. 2001), oxidative desulfurization (ODS) (Garcia-Gutierrez J et al. 2006) and other processes (Song C et al. 2003). Due to a short reaction time at ambient conditions, high efficiency, and selectivity, ODS combined with extraction is among the most promising processes. In this process, such sulfur-containing species as sulfides, benzothiophene, dibenzothiophene, and alkyl-related derivatives are transformed into the corresponding sulfoxides or sulfones species, which are then removed in a second step.
An extractive distillation process, GT-DeSulph™, has been reported by GTC in 2002. The GT-DeSulph™ utilizes a proprietary aromatics selective solvent, which is effective in extracting thiophenic sulfur species and aromatics, and to a limited extent, mercaptans and sulfides as well (Kumar S and Gentry J 2003).
Consequently, various studies on the oxidative desulphurization (ODS) process have been employed for different oxidizing agents, such as NO2 (Tam P et al. 1990) tert-butyl-hydroxide (Wang E et al. 2003) and H2O2 (Garcia-Gutierrez J et al. 2006). Hydrogen peroxide is commonly used as an oxidizing reagent due to its relatively low price, environmental compatibility, and commercial availability.
H2O2 is effective in the presence a transition-metal based catalyst and in acidic media. Examples of transition-metal-based systems are tungstophosphoric acid (Yazu K et al. 2004) and other transition metal-based oxides (Yu B et al 2006). Some catalytic system was evaluated for the removal of sulfur-containing compounds in diesel (Xiao T et al. 2008).
A combined oxidation and extraction desulfurization process is described by Li C et al. (2004). The catalyst [(C18H37)2N+(CH3)2]3[PW12O40] assembled in emulsion droplets can selectively oxidize the sulfur-containing molecules present in diesel using H2O2 as an oxidant under mild conditions. The catalyst in the emulsion demonstrates high performance (≧96% efficiency of H2O2, is easily recycled, and ˜100% selectivity to sulfones) that makes it possible to achieve the ultra-deep desulfurization (<0.1 ppm sulfur).
In addition, the new oxidation system was tested on a commercial diesel sample supplied by Rabigh refinery in Saudi Arabian Oil Company (Saudi Aramco). The sulfur-containing compounds in the diesel sample were oxidized to their corresponding sulfones, and these were further extracted with methanol. The sulfur concentration was successfully reduced by ODS and then by extraction to more than 92% and 97%, respectively (Al-Shahrani F et al. 2009). The chemical and physical properties of sulfones are much different from those of fuel oil hydrocarbons. Therefore, they can be easily removed by conventional separation such as distillation, solvent extraction, adsorption, and decomposition, (Garcia-Gutierrez J et al. 2006, Yu B et al. 2006).
Extraction of organic sulfur compounds from diesel feed by a variety of extractants, from common polar organic solvents to ionic liquids, is discussed in many reports. It appears that a selective extraction of aromatic sulfur compounds from diesel is not straightforward. This comes from the fact that the polarity of such aromatic sulfide type compounds is too close to that of aromatic hydrocarbon molecules of similar structures without a sulfur atom. The experimental results of liquid extraction of organic solvents indeed demonstrate a poor removal of sulfur compounds from the feed (˜50% at most), and also a high amount of co-extraction of aromatic hydrocarbon molecules, leading to a high loss of feed volume.
The use of a very different type of extractant, namely ionic liquid, is reported by the group of Wasserscheid. An ionic liquid is a non-volatile organic liquid salt, which potentially can extract sulfur and also organic nitrogen compounds in fuels by its polarity. Eber J et al. (2004) gives a good recent overview on the desulfurization with different types of ionic liquids, particularly on the most promising water-stable and less costly (i.e., 1-n-butyl-3 methylimidazolium octylsulfate) type. Given the poor extraction of alkylthiols and sulfides, the formation of liquid-clathrates and p-p interaction is assumed to be the main driving force for extraction.
Interestingly, it is reported that the extraction of 4-methyl DBT and 4,6-dimethyl DBT proceed almost as efficiently as that of DBT. Furthermore, nitrogen compounds are found to be more efficiently extracted than sulfur compounds. The problems of the ionic liquid process are the limited extraction efficiency of sulfur compounds, cross-solubility of hydrocarbons and the regeneration of expensive ionic liquid compounds. With respect to the extraction efficiency, they have, for instance, proposed a 10 steps extraction to reduce sulfur content of 300 towards <10 ppmw (Jess A et al. 2003). Zaykina R. et al. discussed the use of radiation method for demercaptanization and/or desulfurization of oil products (Crude and Fuel oils) in 2002. It was proposed that improved desulfurization involves two stages: radiation pre-processing, followed by the standard procedure for extraction of deeply oxidized sulfuric compounds. During the first stage, no desulfurization of the overall product is observed. It results in strong oxidation of sulfur species reducing their chemical aggressiveness and enhancing their removal potential in stage 2. In addition, it causes moderate sulfur redistribution in the overall product leading to partial desulfurization of light fractions. The high level of sulfur oxidation is proposed to be a result of the double activation of oxidation processes by both radiation activation of the feedstock and activation from atmospheric air. The ozone-containing air, excited by energetic electron bombardment, appears to play the role of an oxidizer. In this disclosure, no experimental details were discussed. Accordingly, the reliability of this work is questionable.
An efficient and highly practical novel desulfurization device capable of executing the depth desulfurization was reported by Ayukawa Y., Ono M. (2003). A high-energy beam irradiating desulfurization device for a petroleum product or a petroleum semi-manufactured product, comprising a catalyst liquid-liquid contact part for contacting a metal compound solution as a catalyst and the petroleum product or the petroleum semi-manufactured product, a high-energy beam irradiating part, and a sulfide collecting part for separating and collecting sulfide of the metal produced by the high-energy beam irradiation, is provided.
A process for desulfurizing a petroleum oil containing sulfur comprises subjecting the oil to high-energy ionizing radiation from an atomic pile whereby a substantial proportion of the sulfur is converted to a less stable form and then contacting the liquid oil product with an adsorbent or solvent which selectively removes the less stable sulfur. A detailed method was followed to desulfurize the oil and about 50% conversion (cracking plus polymerization) took place with each oil (Esso Research, Engineering Company, 1960). There is a need for alternative green technology based approaches over the conventional desulfurization of crude oil and diesel.
SUMMARY
The disclosure describes a method and a process of desulfurizing crude oil and diesel. More particularly it describes desulpurization of Arabian heavy crude oil (AH) and straight run diesel (SRD) using irradiation.
In one embodiment, a sulfur compound present in the AH and SRD is chemically modified to obtain a chemically active AH and SRD for irradiation. In one embodiment, a method to remove sulfur during extraction is to first oxidize sulfur compounds in AH and SRD by adding oxidants prior to extraction and/or irradiation. In another embodiment, after oxidization of the sulfur compounds present in AH and SRD an extraction method using solvents may be performed prior to irradiation. This oxidation/extraction method is performed to increase the polarity of the sulfur compounds present in the AH and SRD, which increases the partition coefficient of the sulfur molecules in the solvent. In another embodiment a cocktail of solvents i.e. a combination of various solvents may be used for extraction prior to irradiation.
In another embodiment, the chemically active AH and SRD are irratiated using a specific absorbed dose. The specific absorbed dose may be between 50-200 kGy. In another embodiment, a process or a method for removing total sulfur in Arabian heavy (AH) crude oils (≅3 mass %) and straight-run diesel (SRD)(≅1.41 mass %) by ionizing radiation is performed. In another embodiment, AH and SRD are exposed to absorbed doses from 50 to 200 kGy to remove the sulfur.
According to another embodiment, the removal of total sulfur is done in the presence of oxidizer (H2O2 and H2O2/CH3COOH). In another embodiment, the process of Advanced Oxidation Processes AOPs, which involve oxidation of sulfur species by .OH radical and other oxidizing radicals, such as radiolysis by gamma-rays provides novel process to remove and/or decrease the total sulfur content. In an another embodiment, ionizing radiation from electron beam accelerators or gamma ray sources is used as a process for oxidation removal of sulfur compounds.
In addition, in another embodiment, sulfur removal from crude oil (AH and others) and SRD was achieved by combining gamma-irradiation with other physical/chemical processes (i.e. Liquid/Liquid extraction and oxidation) which produced considerable reduction of total sulfur in AH and SRD.
In one embodiment, sulfur reduction level are measured as a result of irradiation of crude oil and straigh-run diesel. In another embodiment, a process of removing sulfur from crude oil (eg. AH) and straigh-run diesel by subjecting them to radiation to improve quality and environmental safety may be considered.
According to one embodiment, crude oil is irradiated and level of total sulfur contents are measured. In another embodiment, straigh-run diesel is irradiated and level of total sulfur contents are measured.
The methods and processes disclosed herein may be implemented in any means for achieving various aspects, and may be executed manually or automated using a computer. Other features will be apparent from the accompanying drawings and from the detailed description that follows.
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