Chemistry of hydrocarbon compounds – Product blend – e.g. – composition – etc. – or blending process...
Reexamination Certificate
2001-06-15
2004-12-21
McAvoy, Ellen M. (Department: 1764)
Chemistry of hydrocarbon compounds
Product blend, e.g., composition, etc., or blending process...
C585S002000, C585S003000, C585S004000, C585S013000, C508S110000, C508S561000, C508S584000, C208S014000, C208S019000
Reexamination Certificate
active
06833484
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to methods of inhibiting oxidation in Fischer Tropsch derived products. The present invention also relates to Fischer Tropsch derived products containing an effective amount of a petroleum-derived hydrocarbonaceous product such that the Fischer Tropsch derived product resists oxidation.
BACKGROUND OF THE INVENTION
The majority of combustible fuel used in the world today is derived from crude oil. There are several limitations to using crude oil as a fuel source. Crude oil is in limited supply; it includes aromatic compounds that may be harmful and irritating, and it contains sulfur and nitrogen-containing compounds that can adversely affect the environment, for example, by producing acid rain.
Combustible liquid fuels can also be prepared from natural gas. This preparation involves converting the natural gas, which is mostly methane, to synthesis gas, or syngas, which is a mixture of carbon monoxide and hydrogen. An advantage of using products prepared from syngas is that they do not contain nitrogen and sulfur and generally do not contain aromatic compounds. Accordingly, they have minimal health and environmental impact.
Fischer-Tropsch chemistry is typically used to convert the syngas to a product stream that includes combustible fuel, among other products. These Fischer Tropsch products have very low levels of sulfur, nitrogen, aromatics and cycloparaffins. The Fischer Tropsch derived fuels are considered “green fuels” and are desirable as environmentally friendly.
Although environmentally friendly, these Fischer Tropsch products tend to oxidize relatively rapidly when exposed to air. The rapid oxidation may be due to a lack natural anti-oxidants, such as sulfur compounds. Further, some of the products produced by the Fischer Tropsch process may be waxy, and these products are frequently are shipped at elevated temperature. Shipping at elevated temperatures increases the tendency of Fischer Tropsch products to oxidize.
Various methods have been proposed to protect Fischer Tropsch products from oxidation during shipping and storage. For example, Berlowitz and Simon of Exxon Research and Engineering Company describe in World Patent Application Nos. WO 00/11116A1 and WO 00/11117A1 the blending of a Fischer Tropsch derived diesel fuel with high boiling sulfur containing streams, derived from gas field condensate or hydrotreated streams. Using the approach of Berlowitz and Simon to prevent oxidation adds high-boiling, sulfur-containing compounds to the Fischer Tropsch diesel fuel. Therefore, the products of Berlowitz and Simon contain sulfur, which prevents their use as low-sulfur, environmentally friendly fuels. Another undesirable feature of the products of Berlowitz and Simon is that a significant portion of the sulfur in those products is in the form of mercaptans (RSH). Mercaptans are well known to cause corrosion. Therefore, when shipping or storing products treated according to Berlowitz and Simon, corrosion of the large storage vessels can be a problem. Corrosion damage may lead to the need for eventual replacement of the large, expensive vessels used to ship and store hydrocarbonaceous products.
Various other well-known antioxidants may be used with Fischer Tropsch diesel fuels to prevent oxidation. These well-known antioxidants may include phenolic compounds and diphenylamine compounds. However, these antioxidants can be expensive when used on a large scale and must be transported to the remote site where the Fischer Tropsch diesel fuel is made.
There is a need for hydrocarbonaceous products comprising Fischer Tropsch derived products that are capable of resisting oxidation. There is a need for efficient and economical methods of inhibiting oxidation of Fischer Tropsch derived products.
SUMMARY OF THE INVENTION
The invention relates to hydrocarbonaceous products comprising Fischer Tropsch derived products that are capable of resisting oxidation. One aspect of the present invention is a blended hydrocarbonaceous product comprising: a) a Fischer Tropsch derived product; and b) an effective amount of a petroleum-derived hydrocarbonaceous product such that the blended hydrocarbonaceous product has a final peroxide number of less than 5 ppm, preferably less than 3 ppm, and most preferably less than 1 ppm after 7 days. A preferred Fischer Tropsch product of the present invention has a branching index of less than five, preferably less than four, more preferably less than three.
Another aspect of the present invention is a blended hydrocarbonaceous product comprising: a) a Fischer Tropsch derived product; b) a petroleum-derived hydrocarbonaceous product; and c) an effective amount of an antioxidant selected from the group consisting of phenolic compounds, diphenylamine compounds and combinations thereof, such that the blended hydrocarbonaceous product has a final peroxide number of less than 5 ppm, preferably less than 3 ppm, and most preferably less than 1 ppm after 7 days; and wherein the effective amount of antioxidant in (a) and (b) is less than the amount that would be required in (a) alone. A preferred Fischer Tropsch product of the present invention has a branching index of less than five, preferably less than four, more preferably less than three.
An additional aspect of the present invention is a method of inhibiting oxidation of a Fischer Tropsch product comprising the steps of:
a) synthesizing a Fischer Tropsch product by a Fischer Tropsch process;
b) adding an effective amount of a petroleum-derived hydrocarbonaceous product to the Fischer Tropsch product to provide a blended product having a final peroxide number of less than 5 ppm, preferably less than 3 ppm and most preferably less than 1 ppm after 7 days; and
c) mixing the petroleum-derived hydrocarbonaceous product into the Fischer Tropsch product.
The method may also comprise the step of processing the mixture with hydrogen (i.e., hydrotreating, hydrocracking, and hydroisomerization) to remove at least a portion of sulfur and other impurities that originate from the conventional fuel component after the period in which oxidation is to be prevented.
A further aspect of the present invention is a method of inhibiting oxidation of a Fischer Tropsch product comprising the steps of:
a) synthesizing a Fischer Tropsch product by a Fischer Tropsch process;
b) adding an amount of a petroleum-derived hydrocarbonaceous product which contains sulfur to the Fischer Tropsch product;
c) mixing the petroleum-derived hydrocarbonaceous product into the Fischer Tropsch product to provide a blended product; and
d) processing the blended product with hydrogen to provide a final product with a sulfur content of less than 100 ppm, preferably less than 10 ppm and most preferably less than 1 ppm.
The step of processing the blended product may involve any process that may be used to remove at least a portion of sulfur and other impurities that originate from the petroleum-derived hydrocarbonaceous component, including for example, hydrotreating, hydrocracking, and hydroisomerization. The processing step may be performed after the period in which oxidation is to be prevented and before use of the products.
A further aspect of the present invention is a method of inhibiting oxidation of a Fischer Tropsch product comprising the steps of:
a) synthesizing a Fischer Tropsch product by a Fischer Tropsch process;
b) creating a blended hydrocarbonaceous product by mixing (i) the Fischer Tropsch product, (ii) a petroleum-derived hydrocarbonaceous product, and (iii) an effective amount of an antioxidant selected from the group consisting of phenolic compounds and diphenylamine compounds such that the blended hydrocarbonaceous product has a final peroxide number of less 5 ppm, preferably less than 3 ppm, and most preferably less than 1 ppm after 7 days; and wherein the effective amount of antioxidant in (i) and (ii) is less than the amount that would be required in (i) alone.
The method may also comprise the step of processing the mixture with hydrogen (i.e., hydrotreating, hydrocracking, and
Burns Doane Swecker & Mathis L.L.P.
Chevron U.S.A. Inc.
McAvoy Ellen M.
LandOfFree
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