Sorbent compositions and desulfurization method using same

Abstract

The disclosed sorbents are for adsorbing sulfur compounds, particularly sulfur-containing aromatic compounds, from liquid hydrocarbon fuels such as gasoline, cracked gasoline, diesel, high sulfur liquid fossil fuels, ultra-low sulfur fuel (ULSF) in fuel cell applications, and mixtures thereof. The sorbent compositions comprise one or more silicates having one or more metal nitrates admixed together. The one or more metal nitrates include iron (II) or (III), zinc (II), cadmium (II) and mercury (II) nitrate. The method of preparing and using the sorbents is also provided.

Description

FIELD OF THE INVENTION [0001] This invention relates generally to pollution control. More specifically, this invention relates to sorbent compositions, their preparation and use for substantially reducing the amount of sulfur compounds in liquid hydrocarbon fuels. BACKGROUND OF THE INVENTION [0002] Sulfur compounds in liquid hydrocarbon fuels have been linked to serious human health and environmental problems. For example, sulfur is a well known poison for catalytic converters in motor vehicles and the resulting SOX in exhaust gas is a major contributor to air pollution. Emissions from poisoned catalytic converters may contain high levels of combusted hydrocarbons, oxides of nitrogen and / or carbon monoxide which, when catalyzed by sunlight, form ground level ozone, referred to as smog. Consequently, rigorous efforts are currently underway in both European countries as well as in the United States of America1,2 to reduce the sulfur content in liquid hydrocarbon fuels from the current...

AI Technical Summary

Benefits of technology

[0010] The present invention is concerned with sorbent compositions, a method of making sorbent compositions, and a method of using the sorbent compositions for the substantial removal of sulfur-compounds from liquid hydrocarbon fuels, particularly sulfur-containing aromatic compounds. As used herein, “liquid hydrocarbon fuels” means gasoline, cracked gasoline, diesel fuel, high sulfur liquid fossil fuel and ultra-low sulfur fuel (ULSF) in fuel cell applications and mixtures thereof. The sorbent composition generally comprises one or more silicates with oxidative metal nitrates on the surface of the one or more silicates. The one or more silicates may be natural or synthetic. The one or more silicates may be selected from the group consisting of clays such as montmorillonite, laumonite, bentonite, Mica, vermiculite and kaolinite, and from silica gels, natural and synthetic molecular sieves, zeolites, and activated alumina. The particle size of the preferred silicates used ranges from about 10 to about 100 micrometers, preferably about 50 micrometers. The active metal nitrates are selected from the group consisting of Fe(NO3)2, Fe(NO3)3, Cd(NO3)2 and Hg(NO3)2 and mixtures thereof.

[0011] The preparation comprises the step of admixing the metal nitrate(s) and the one or more silicates by suspending, grinding or otherwise contacting the metal nitrate(s) with the silicate(s) particles to produce the powdered solid sorbent for use in the desulfurization method.

[0012] The desulfurization method generally comprises the step of contacting the sorbent composition described herein or the components thereof with a sulfur-containing liquid hydrocarbon fuel such as transportation fuels to thereby produce a low or ultra low sulfur fuel and a sulfurized sorbent.

[0013] When the sorbent composition or components thereof are contacted with the sulfur-containing liquid hydrocarbon fuel in the desulfurization zone, sulfur compounds, particularly sulfur-containing aromatic thiophene, benzothiophene and dibenzothiophene and their alkylated derivatives present in the sulfur-containing hydrocarbon fuel are substantially removed from such fuel to produce low sulfur fuel of 15-30 ppm. If the transportation fuel has already undergone treatment by hydrosulfurization, the sulfur compounds will be further reduced by this process to produce ultra low sulfur diesel (ULSD) of less than 15 ppm sulfur and ultra low sulfur gasoline (ULSG) of less than 30 ppm sulfur.

[0014] Other features and advantages of the present invention will become apparent from the following more detailed description, taken in conjunction with the accompanying drawing which illustrates, by way of example, the principles of the invention.

Problems solved by technology

Sulfur compounds in liquid hydrocarbon fuels have been linked to serious human health and environmental problems.

For example, sulfur is a well known poison for catalytic converters in motor vehicles and the resulting SOX in exhaust gas is a major contributor to air pollution.

Consequently, deep desulfurization is becoming a great challenge for environmental chemists, the petroleum refining industry, and others.

In agriculture, diesel fuels more than two-thirds of all farm equipment in the United States, because diesel engines can perform demanding work.

No other fuel can currently match diesel in its ability to move freight economically.

HDS is highly efficient in removing thiols, sulfides, and disulfides but is less effective for refractory sulfur-containing aromatic thiophene, benzothiophene and dibenzothiophene and their alkylated derivatives as depicted in FIG. 1, especially those containing functional groups that hinder the ring sulfur atoms (i.e., 4,6-dimethyl-dibenzothiophene).

The difficulty in their removal may be due to their aromaticity (stability and inactivity) and the steric hindrance.

For diesel fuel, it is very difficult for the current hydrotreating technology to reduce the sulfur content to less than 50 ppmw, because the remaining sulfur compounds in current diesel fuel with 500 ppmw total sulfur level are mostly the refractory sulfur compounds which are difficult to remove.

Consequently, the sulfur content in gasoline cannot be reduced to less than 30 ppmw by current hydrotreating processes.

The major problem for deep desulfurization of hydrocarbon fuels is that the current hydrotreating technology results in high hydrogen consumption and significant reduction of octane number due to olefin saturation.

Other approaches used to generate low sulfur fuels include costly biodesulfurization using bacteria that removes sulfur as a water soluble sulfate salt.

None of these approaches has been entirely satisfactory.

The limitation of the π-complexation-based sorbents is lack of selectivity, because other olefinic and aromatic hydrocarbons in liquid transportation fuel can also be absorbed via π-complexation, thereby causing difficulty in maintaining a fairly good octane and cetane number.

Clayfen is unstable, decomposes rapidly with the evolution of gas.

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