Oxidative Desulfurization Process

Abstract

Disclosed is a process which reduces the sulfur and/or nitrogen content of a distillate feedstock to produce a refinery transportation fuel or blending components for refinery transportation fuel, by contacting the feedstock with an oxygen-containing gas in an 5 oxidation/adsorption zone at oxidation conditions in the presence of an oxidation catalyst comprising a titanium-containing composition whereby the sulfur species are converted to sulfones and/or sulfoxides which are adsorbed onto the titanium-containing composition.

Description

FIELD OF THE INVENTION[0001]The present invention relates to fuels for transportation which are derived from natural petroleum, particularly processes for the production of components for refinery blending of transportation fuels which are liquid at ambient conditions. More specifically, it relates to a process for making such fuels which includes oxidation of a petroleum distillate in order to oxidize nitrogen and / or sulfur-containing organic impurities therein, by contacting the petroleum distillate with an oxygen-containing gas at oxidation conditions in the presence of a heterogeneous catalyst.BACKGROUND OF THE INVENTION[0002]It is well known that internal combustion engines have revolutionized transportation following their invention during the last decades of the 19th century. While others, including Benz and Gottleib Wilhelm Daimler, invented and developed engines using electric ignition of fuel such as gasoline, Rudolf C. K. Diesel invented and built the diesel engine which ...

AI Technical Summary

Benefits of technology

[0039]The process of the present invention involves reducing the sulfur content of a distillate feedstock containing sulfur-containing organic impurities to produce a refinery transportation fuel or blending components for refinery transportation fuel, by contacting the feedstock with an oxygen-containing gas in an oxidation / adsorption zone at oxidation conditions in the presence of a heterogeneous oxidation catalyst comprising a titanium-containing composition whereby the sulfur-containing compounds are converted to sulfones and / or sulfoxides a portion of which are subsequently adsorbed on to the titanium-containing composition. A fuel or blending component having a reduced sulfur content is then recovered from the oxidation zone. The sulfones and / or sulfoxide can be further removed from the catalyst for further processing whereby the catalyst is regenerated for reuse in the process.

Problems solved by technology

Modern high performance diesel engines demand ever more advanced specification of fuel compositions, but cost remains an important consideration.

Sulfur-containing organic compounds in fuels continue to be a major source of environmental pollution.

Even in newer, high performance diesel engines combustion of conventional fuel produces smoke in the exhaust.

However, most such compounds have high vapor pressure and / or are nearly insoluble in diesel fuel, and they have poor ignition quality, as indicated by their cetane numbers.

Diesel fuels of low lubricity may cause excessive wear of fuel pumps, injectors and other moving parts which come in contact with the fuel under high pressures.

Thus refiners are faced with the challenge of reducing the sulfur levels in fuels and in particular diesel fuel within the timeframes prescribed by the regulatory authorities.

First, the conventional three-way catalyst (TWC) catalyst is ineffective in removing NOx emissions from diesel engines, and second, the need for particulate control is significantly higher than with the gasoline engine.

Several exhaust treatment technologies are emerging for control of Diesel engine emissions, and in all sectors the level of sulfur in the fuel affects efficiency of the technology.

Furthermore, in the context of catalytic control of Diesel emissions, high fuel sulfur also creates a secondary problem of particulate emission, due to catalytic oxidation of sulfur and reaction with water to form a sulfate mist.

The combustion process leaves tiny particles of carbon behind and leads to significantly higher particulate emissions than are present in gasoline engines.

However, significant quantities of unburned hydrocarbon are adsorbed on the carbon particulate.

While an increase in combustion temperature can reduce particulate emissions, this leads to an increase in NOx emission by the well-known Zeldovitch mechanism.

Furthermore, NOx trap systems are extremely sensitive to fuel sulfur and available evidence suggests that they would need sulfur levels below 10 ppm to remain active.

Conventional hydrodesulfurization (HDS) catalysts can be used to remove a major portion of the sulfur from petroleum distillates for the blending of refinery transportation fuels, but they are not efficient for removing sulfur from compounds where the sulfur atom is sterically hindered as in multi-ring aromatic sulfur compounds.

Using conventional hydrodesulfurization catalysts at high temperatures would cause yield loss, faster catalyst coking, and product quality deterioration (e.g., color).

Using high pressure requires a large capital outlay.

Such methods have proven to be of only limited utility since only a rather low degree of desulfurization is achieved.

In addition, substantial loss of valuable products may result due to cracking and / or coke formation during the practice of these methods.

However, to obtain this low sulfur level only about 85 percent of the distillate feedstream is recovered as a low sulfur distillate fuel product.

Therefore it is not prudent to extract an inordinate amount of the aromatics.

The use of sulfuric acid as an oxidizing acid is problematic in that corrosion is a concern when water is present and hydrocarbons can be sulfonated when a little water is present.

Formic acid is relatively more expensive than acetic acid.

These expensive alloys would have to be used in the solvent recovery section and storage vessels.

It is believed this undesirable phase can be formed due to the poor lipophilicity of formic acid.

Therefore at lower temperatures, formic acid cannot maintain in solution some of the extracted sulfones.

Images