Abstract:The poet Percy Bysshe Shelley (1792-1822) followed advances in the sciences with enthusiasm. This essay sketches the biographical details and historical context of Shelley's interest in science, and shows how past and present literary criticism has interpreted the influence of science on Shelley's poetry.
“…One of the most difficult classes of sulfur compounds to process using HDS is the dibenzothiophenes (Figure ), which are found mainly in diesel fuel. To reduce the amount of pollution from diesel fuel combustion, the United States has mandated a reduction in sulfur levels from the current average of 500 ppm to 15 ppm starting in 2006. 1a, Europe has a similar plan in place with a goal of 2008. 3a, The removal of dibenzothiophenes from diesel fuels is necessary in order to meet these low sulfur requirements. 1 Numbering schemes for dibenzothiophene (DBT) and benzothiophene (BT).…”
The complexes [CpRu(CO)2(μ2-η1(S):η6-DBT)RuCp‘]2+ (Cp‘ = η5-C5H5 (3), η5-C5Me5 (4)) were
synthesized and shown by X-ray crystallography to contain a bridging dibenzothiophene
ligand that is coordinated to {CpRu(CO)2}+ through the sulfur atom and to {Cp‘Ru}+ through
an arene ring (η6). Kinetic studies of the displacement of the [Cp*Ru(η6-DBT)]+ moiety in 4
by P(OPh)3 show that the η6-coordinated {Cp*Ru}+ group weakens the Ru−S bond, as
compared to that in [CpRu(CO)2(η1(S)-DBT)]+, and greatly increases the rate of DBT
dissociation.
“…One of the most difficult classes of sulfur compounds to process using HDS is the dibenzothiophenes (Figure ), which are found mainly in diesel fuel. To reduce the amount of pollution from diesel fuel combustion, the United States has mandated a reduction in sulfur levels from the current average of 500 ppm to 15 ppm starting in 2006. 1a, Europe has a similar plan in place with a goal of 2008. 3a, The removal of dibenzothiophenes from diesel fuels is necessary in order to meet these low sulfur requirements. 1 Numbering schemes for dibenzothiophene (DBT) and benzothiophene (BT).…”
The complexes [CpRu(CO)2(μ2-η1(S):η6-DBT)RuCp‘]2+ (Cp‘ = η5-C5H5 (3), η5-C5Me5 (4)) were
synthesized and shown by X-ray crystallography to contain a bridging dibenzothiophene
ligand that is coordinated to {CpRu(CO)2}+ through the sulfur atom and to {Cp‘Ru}+ through
an arene ring (η6). Kinetic studies of the displacement of the [Cp*Ru(η6-DBT)]+ moiety in 4
by P(OPh)3 show that the η6-coordinated {Cp*Ru}+ group weakens the Ru−S bond, as
compared to that in [CpRu(CO)2(η1(S)-DBT)]+, and greatly increases the rate of DBT
dissociation.
“…The removal of sulfur from transportation fuels is an important aspect of the effort to reduce pollution of the atmosphere by sulfur oxides . Currently, sulfur content in gasoline is limited to 400 ppm (0.04 wt %), but the EPA has recently introduced new restrictions that will reduce this level gradually to 25 ppm (0.0025 wt %) by the year 2006 . This ambitious agenda will require the rapid development of new technologies in order to achieve such a large reduction in sulfur content in a short period of time.…”
In an effort to demonstrate that Ru(NH3)5(H2O)2+ can be used to remove dibenzothiophene
from hydrotreated petroleum feedstocks, this metal complex was reacted with a variety of
thiophenes (Th*), including dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-Me2DBT) to give complexes of the type Ru(NH3)5(Th*)2+. This ability of Ru(NH3)5(H2O)2+ to bind to
thiophenes has been used in an extraction process in which a solution of Ru(NH3)5(H2O)2+ in
70% DMF and 30% H2O is contacted with a simulated petroleum feedstock (45% toluene/55%
hexanes) containing 400 ppm of DBT. One extraction removes 50% of the DBT from the feedstock
phase as Ru(NH3)5(DBT)2+, which is present in the DMF/H2O phase. Five successive extractions
reduce the amount of DBT in the simulated feedstock from 400 to 25 ppm. The Ru(NH3)5(H2O)2+
extractant can be regenerated from the Ru(NH3)5(DBT)2+ either by air-oxidation followed by H2-reduction or by displacement of the DBT by adding H2O to the DMF/H2O phase. Extraction of
4,6-Me2DBT from the simulated feedstock using Ru(NH3)5(H2O)2+ in 70% N,N-dimethylacetamide
and 30% H2O was less successful as the 4,6-Me2DBT concentration was only reduced from 400
to 340 ppm.
“…1 Currently, sulfur content in diesel fuel is limited in the U.S. to 500 ppm (0.05% by weight) and 400 ppm (0.04% by weight) in gasoline; but the EPA has recently introduced new restrictions that will reduce this level gradually to 15 ppm (0.0015% by weight) in diesel fuel and to 30 ppm (0.0030% by weight) in gasoline by 2006. 2 While most of the sulfur is now removed from petroleum-based feedstocks by hydrotreating, 3 hindered dibenzothiophenes with alkyl groups in the 4 and 6 positions are removed only if the hydrotreating process is operated under extreme and costly conditions. 4 Since these 4,6-R 2 DBT compounds constitute the bulk of the remaining sulfur compounds in diesel fuel, new approaches to deep desulfurization are required.…”
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