TECHNICAL FIELD

This disclosure relates to quantifying organic and inorganic sulfur in petroleum material.

BACKGROUND

Sulfur is the third most abundant element in petroleum, occurring in certain heavy oils at concentrations of over 12 weight percent (wt %). Reserves of low sulfur crude oils are depleting worldwide, necessitating the identification of reservoirs of crude oils with high sulfur content. The abundance of sulfur species in hydrocarbon products causes corrosion to infrastructure, health exposure risks, and higher operational and production costs. As a result, environmental regulatory agencies in the world continue to promulgate more stringent regulations towards sulfur emission from fuels and sulfur gases emanating from oil and gas industries.

Methods employed in the petroleum industry to quantify sulfur typically include bulk sample analysis via oxidation, combustion, and other chemical reactions that yield erroneous results caused by masking and matrix effects of other compounds in the samples. In addition, reproducibility and precision of these methods are impractical for quantifying specific sulfur species expected to affect both upstream and downstream operations. Thus, these methods have limited use in hydrocarbon industries for proper characterization and quantification of sulfur content in petroleum products.

SUMMARY

This disclosure describes sequential extraction and quantification of inorganic and organic sulfur species in petroleum materials.

In a general aspect, quantifying an amount of sulfur in a sample having inorganic sulfur components and organic sulfur components includes extracting inorganic sulfur components from the sample to yield extracted organic sulfur components and a residual sample, and reducing the sulfur in the extracted inorganic sulfur components to yield a first quantity of hydrogen sulfide. Organic sulfur components are extracted from the residual sample to yield extracted organic sulfur components, and the sulfur in the extracted organic sulfur components is reduced to yield a second quantity of hydrogen sulfide. The amount of the sulfur in the first quantity of hydrogen sulfide and the second quantity of hydrogen sulfide is quantified.

Implementations of the general aspect may include one or more of the following features.

The sample may include a solid, a liquid, or a mixture thereof.

In some implementations, extracting the inorganic sulfur components from the sample includes sequentially extracting acid volatile sulfur components, pyritic sulfur components, elemental sulfur components, and sulfated sulfur components from the sample.

In some implementations, extracting the inorganic sulfur components from the sample to yield the extracted inorganic sulfur components and the residual sample includes extracting acid volatile sulfur components from the sample to yield extracted acid volatile sulfur components and a first intermediate residual sample, and reducing the sulfur in the extracted inorganic sulfur components to yield the first quantity of hydrogen sulfide includes reducing the sulfur in the extracted volatile sulfur components to yield a first intermediate quantity of hydrogen sulfide. The acid volatile sulfur components typically include at least one of hydrogen sulfide, (H2S), bisulfide (HS−), disulfide (S2−), and iron sulfide (FeS). In some cases, extracting the acid volatile sulfur components from the sample includes contacting the sample with hydrochloric acid.

In some implementations, extracting the inorganic sulfur components from the sample to yield the extracted inorganic sulfur components and the residual sample includes extracting pyritic sulfur components from the first intermediate residual sample to yield extracted pyritic sulfur components and a second intermediate residual sample, and reducing the sulfur in the inorganic sulfur components to yield the first quantity of hydrogen sulfide and the residual sample includes reducing the sulfur in the extracted pyritic sulfur components to yield a second intermediate quantity of hydrogen sulfide. The pyritic sulfur components typically include iron disulfide (FeS2). In some cases, extracting the pyritic sulfur components from the first intermediate residual example includes contacting the first intermediate residual sample with chromium reduction acid distillation mixed solvents.

In some implementations, extracting the inorganic sulfur components from the sample to yield the inorganic sulfur components and the residual sample includes extracting elemental sulfur components from the second intermediate residual sample to yield extrated elemental sulfur components and a third intermediate residual sample, and reducing the sulfur in the inorganic sulfur components to yield the first quantity of hydrogen sulfide includes reducing the sulfur in the extracted elemental sulfur components to yield a third intermediate quantity of hydrogen sulfide. The elemental sulfur components typically include at least one of octasulfur (S8) and zero-valent sulfur. In some cases, extracting the elemental sulfur components from the second intermediate residual sample includes contacting the second intermediate residual sample with a mixture of chloroform and methanol.

In some implementations, extracting the inorganic sulfur components from the sample to yield extracted inorganic sulfur components and the residual sample includes extracting sulfated sulfur components from the third intermediate residual sample to yield extracted sulfated sulfur components and a fourth intermediate residual sample, and reducing the sulfur in the extracted inorganic sulfur components to yield the first quantity of hydrogen sulfide includes reducing the sulfur in the extracted sulfated sulfur components to yield a fourth intermediate quantity of hydrogen sulfide. The sulfated sulfur components typically include SO42−. In some cases, extracting the sulfated sulfur components includes forming a sulfate precipitate, and reducing the sulfur in the extracted sulfated sulfur components to yield a fourth intermediate quantity of hydrogen sulfide includes reducing the sulfate in the sulfate precipitate to yield elemental sulfur, and reducing the elemental sulfur.

In some implementations, extracting the organic sulfur components from the residual sample includes sequentially extracting bitumen sulfur components and kerogen sulfur components from the residual sample.

In some implementations, extracting the organic sulfur components from the residual sample to yield extracted organic sulfur components includes extracting bitumen sulfur components from the residual sample, and reducing the sulfur in the extracted organic sulfur components to yield the second quantity of hydrogen sulfide includes reducing the sulfur in the extracted bitumen sulfur components to yield a fifth intermediate quantity of hydrogen sulfide and a fifth intermediate residual sample. In some cases, extracting the bitumen sulfur components from the fifth intermediate residual sample includes extracting the bitumen sulfur components from the fifth intermediate residual sample with an azeotropic mixture of dichloromethane and methanol, and reducing the sulfur in the extracted bitumen sulfur components via a Raney nickel desulfurization process.

In some implementations, extracting the organic sulfur components from the residual sample to yield the extracted organic sulfur components includes extracting kerogen sulfur components from the fifth intermediate residual sample to yield the extracted kerogen sulfur components, and reducing the sulfur in the extracted organic sulfur components to yield the second quantity of hydrogen sulfide includes reducing the sulfur in the extracted kerogen sulfur components to yield a sixth intermediate quantity of hydrogen sulfide. Reducing the sulfur in the extracted kerogen sulfur components typically includes using a modified Raney nickel and bayerite as a reducing agent.

In some implementations, quantifying the amount of sulfur in the first quantity of hydrogen sulfide includes contacting the first quantity of hydrogen sulfide with a zinc acetate buffer solution to yield zinc sulfide, and quantifying the amount of sulfide in the zinc sulfide. Quantifying the amount of sulfide in the zinc sulfide typically includes a colorimetric determination.

Methods described in this disclosure provide an accurate, robust, and comprehensive approach for sulfur analysis in petroleum materials. These methods are suitable for commercial implementation and allow efficient assessment of the composition and amount of sulfur species in a wide variety of sulfur-bearing petroleum materials, including sulfur components that are likely to be resistant to hydrodesulfurization processes during production and refinery processes. This quantification provides detailed information regarding availability, partitioning, and extent of sulfur distribution in petroleum products, and can be used to pinpoint targets in exploration, production, and refinery processes.

The details of one or more implementations of the subject matter described in this specification are set forth in the accompanying drawings and the following description. Other features, aspects, and advantages of the subject matter will become apparent from the description, the drawings, and the claims.

