Process for producing high grade diesel fuel

Details Process for producing high grade diesel fuel Process for producing high grade diesel fuel

1999-11-23

2002-06-04

Yildirim, Bekir L. (Department: 1764)

Chemistry of hydrocarbon compounds

Saturated compound synthesis

By isomerization

C585S266000, C208S142000

Reexamination Certificate

active

06399845

ABSTRACT:

This application is the national phase under 35 U.S.C. §371 of PCT International Application No. PCT/FI98/00447 which has an International filing date of May 28, 1998 which designated the United States of America.
The present invention relates to chemical industry, especially to petroleum refining. Particularly, the object of the invention is a process for producing high grade middle distillate without substantially altering the distillation range. The product can for instance be used as a diesel fuel.
A low content of sulfur and aromatic compounds, a high cetane number, and an adequate density are among the particular properties of a high grade diesel fuel to be mentioned.
The increasingly strick environmental requirements, in particular regulations limiting the exhaust emissions from the fuels are continuously increasing the demands made on the properties of a high grade fuel. Less polluting diesel fuels are badly needed. Lowering the content of sulfur and aromatic compounds in diesel fuels has an influence on the particle emission from a diesel engine. Further, lowering the amount of aromatic compounds and increasing the cetane number reduce emissions of nitrogen oxides, and a high cetane number seems to reduce the formation of smoke at low temperatures, and particle emissions. In addition, lowering the content of polynuclear aromatic compounds reduces the health hazards associated to diesel exhaust gases. In particular, the emissions from a diesel engine are significant at low temperatures, for instance in wintertime in countries where the temperature remains an extended period of time under 0° C., or even less. Such conditions are very demanding for a diesel engine.
The density of a diesel fuel and accordingly the energy content in a unit volume thereof should remain constant throughout the year to ensure the smooth runnig of the engine to reduce emissions therefrom.
Being heavier, the low temperature properties of a diesel fuel are far more important than those of gasoline. In a cold climate such low temperature properties of a diesel fuel should be good. The diesel fuel must remain liquid in all conditions of use, and it may not form precipitates in the fuel feeding devices. The low temperature properties are evaluated by determining the cloud and pour points, as well as the filterability of the fuel. Favourable low temperature properties of a diesel fuel, and a high cetane number are somewhat contradictory. Normal paraffins have high cetane numbers, but poor low temperature properties. On the other hand, aromatics have superior low temperature properties, but low cetane numbers.
Several liquid hydrocarbon fractions contain relatively high amounts of aromatics. Various methods for reducing the content of aromatic compounds and therefore increasing the cetane number are familiar to those skilled in the art. One of these methods is hydrogenation. In hydrogenation the middle distillate is treated with hydrogen at an elevated pressure in the presence of a hydrogenation catalyst. Hereby the cetane number of the diesel fuel increases. In comparison to the feed, the low temperature properties of the fuel are not essentially changed.
On the other hand, there are processes for selectively cracking off normal paraffins that lead to poor properties at low temperatures. In these processes the catalyst used is normally a zeolite with a suitable pore size. Only normal paraffins with straight chains, or paraffins with moderately branched chains can penetrate into the pores. As examples of such zeolites can be mentioned ZSM-5, ZSM-11, ZSM-12, ZSM-23, and ZSM-35, the use thereof being described in U.S. Pat. Nos. 3,894,938, 4,176,050, 4,181,598, 4,222,855, and 4,229,282. With normal paraffins removed, the low temperature properties of the product are improved, but the cetane number is lowered and the content of aromatic compounds is usually increased. Especially heavy feeds are treated with such a process with which waxy components are desired not only to be removed, but also to be converted to other, more valuable materials. Moreover, this process is applicable to lighter middle distillate feeds, as is disclosed in PCT Patent Publication WO95/10578. The said publication relates to a method for converting a hydrocarbon feed containing waxes, and at least 20% by weight thereof boiling above 343° C., to a middle distillate product with a lower wax content. According to this method the feed is contacted in the presence of hydrogen with a hydrocracking catalyst containing a carrier, at least one hydrogenation metal component selected from the metals of the group(s) VIB and/or VIII of the periodic table of the elements, and a zeolite with a large pore size, the diameter of the pores being between 0.7 and 1.5 nm, and then the hydrocracked product is contacted in the presence of hydrogen with a catalyst for wax removal containing a crystalline molecular sieve with a medium pore size selected from metallosilicates and silicoaluminophosphates. The method comprises both a hydrocracking step and a step for wax removal using respectively a different catalyst.
U.S. Pat. No. 5,149,421 discloses a process for isomerizing a lubricating oil with a catalyst combination containing a silicoaluminophosphate molecular sieve as well as a zeolite catalyst. Further, U.S. Pat. No. 4,689,138 describes a method for wax removal from lubricating oils and from middle distillates. The hydrogenation of aromatic compounds is not discussed in this patent. The catalyst was a SAPO-11 to which the hydrogenating metal was added in an unusual way, namely directly to the crystallization solution of the molecular sieve.
In U.S. Pat. No. 4,859,311 wax is removed from a hydrocarbon feed boiling above 177° C., hereby converting the hydrocarbons at least partially and selectively to non-waxy hydrocarbons with a lower molecular weight. Essentially, also this patent relates to the production of a lubricating oil.
Moreover, there are processes for removing wax from distillates used as starting feed materials, by isomerizing, the waxy paraffins without any substantial cracking, such as described in the patent FI 72 435. Here, the typical feed materials are hydrocarbons boiling above 180° C. (>C
10
). Hereby the low temperature properties of the product are improved in comparison with the feed.
Wax removal is also carried out using, methods in which heavy normal paraffins are removed with a solvent to improve the low temperature properties of the product. Surprisingly, it has now been found that it is possible to produce, by using a single treatment and middle distillates as the feed, a high grade diesel component with superior low temperature properties and a low content of aromatic compounds, without significantly changing the cetane number of the product. An optimal balance between the cetane number, the content of aromatic compounds and the low temperature properties is attained in the diesel fuel by treating these distillates in a specific way.
Accordingly, one object of the present invention is a process for producing from a middle distillate a high grade diesel fuel with superior low temperature properties and a low content of aromatic compounds. Another object of the invention is to provide a process for producing diesel fuel that leaves the cetane number of the product essentially unchanged even though normal paraffins are isomerized to isoparaffins with lower cetane numbers. The cetane features lost with the isomerization of the paraffins are recovered by hydrogenating the aromatics. In addition, the treatment can cause opening of ring structures and minor cracking. Due to this cracking the product may also comprise lighter isopraffins than the feed, these lighter isoparaffins having superior low temperature properties as well as high cetane numbers.
The present invention relates to a process for producing from a hydrocarbon feed as the starting material, especially from a middle distillate a product suitable as a diesel fuel with improved low temperature properties and a low content of aromatic compounds.
The invention is

Affiliated with

Also associated with

Rating

Process for producing high grade diesel fuel does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Process for producing high grade diesel fuel, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for producing high grade diesel fuel will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2947624