Process for producing gasoline with an improved octane number

Details Process for producing gasoline with an improved octane number Process for producing gasoline with an improved octane number

2000-10-02

2002-08-20

Griffin, Walter D. (Department: 1764)

Mineral oils: processes and products

Chemical conversion of hydrocarbons

Plural serial stages of chemical conversion

C208S066000

Reexamination Certificate

active

06436278

ABSTRACT:

The present invention relates to an improved process for producing gasoline with an improved octane number from hydrocarbon-containing feeds, preferably from hydrocarbon-containing feeds from the Fischer-Tropsch process, with optional simultaneous production of middle distillates (gas oils, kerosine) of very high quality (i.e., with a low pour point and a high cetane index for gas oils) and of oils.
PRIOR ART
The application of increased environmental constraints means that gasoline can no longer contain lead, this is in force in the United States and Japan and is in course of being generalised in Europe. Initially, aromatic constituents, the principal constituents of reformed gasoline, and isoparaffins produced by aliphatic alkylation or isomerisation of light gasolines, compensated for the loss of octane number resulting from removing lead from gasolines.
Subsequently, oxygen-containing compounds such as methyl tertiobutyl ether (MTBE) or ethyl tertiobutyl ether (ETBE) were introduced into gasoline. More recently, the known toxicity of compounds such as aromatic compounds, in particular benzene, olefins and sulphur-containing compounds, and the desire to reduce the vapour pressure of gasoline, have resulted in the production of reformulated gasoline in the United States. As an example, the maximum amounts of olefins, aromatic compounds and benzene in gasoline distributed in California in 1996 were respectively 6% by volume, 25% by volume and 1% by volume. In Europe, the specifications are less severe, however a similar reduction in the maximum amounts of benzene, aromatic compounds and olefins in produced and marketed gasolines are anticipated.
Gasoline pools comprise a number of components. The major components are reformulated gasolines, which normally comprise between 60% and 80% by volume of aromatic compounds, and FCC gasolines which typically contain 35% by volume of aromatic compounds but provide the majority of olefinic and sulphur-containing compounds present in the gasoline pools. The other components can be alkylates, with no aromatic or olefinic compounds, isomerised if at all, or non isomerised light gasolines, which contain no unsaturated compounds, oxygen-containing compounds such as MTBE, and butanes.
Provided that the aromatic compound content is not reduced below 35-40% by volume, the contribution of reformates to the gasoline pool remains high, typically 40% by volume. In contrast, an increased restriction to the maximum admissible amount of aromatic compounds to 20-25% by volume would cause a reduction in the use of reforming, and as a result the need to upgrade cuts composed of paraffins which are slightly or not isomerised, if at all, and with boiling points which correspond those of a gasoline cut, by routes other than reforming.
To this end, the production of multibranched isomers from slightly branched paraffins (contained in the gasoline cuts) instead of the production of toluene and xylenes, for example from naphthas, appears to be an extremely promising route. This forms the reasoning behind the search for high performance catalytic systems for isomerising paraffins (also known as hydroisomerisation when carried out in the presence of hydrogen), and more generally gasoline cuts, and for the search for processes allowing selective recycling of low octane number compounds, namely straight chain and monobranched paraffins, to the isomerisation step (hydroisomerisation step).
Adsorption and permeation separation techniques are particularly suitable for separating straight chain, monobranched and multibranched paraffins.
Conventional adsorption separation processes can be based on carrying out PSA (pressure swing adsorption), TSA (temperature swing adsorption), chromatographic (elution or simulated counter-current chromatography, for example) type processes. They can also be based on a combination of these implementations. The common factor in all of those processes is that a liquid or gaseous mixture is brought into contact with a fixed bed of adsorbent to eliminate certain constituents of the mixture which may be adsorbed. Desorption may be carried out in different ways.
The common characteristic of PSA type processes is regeneration of the bed by depressurisation and in some cases by low pressure flushing. PSA type processes have been described in U.S. Pat. No. 3,430,418 by Wagner or in the more general work by Yang (“Gas separation by adsorption processes”, Butterworth, US, 1987).
TSA processes, which use temperature as the driving force for desorption, are the first processes to have been developed for adsorption. The bed to be regenerated is heated by circulating a pre-heated gas in an open or closed loop in the reverse direction to that of the adsorption step. Numerous variations of schemes (“Gas separation by adsorption processes”, Butterworth, US, 1987) are used depending on local constraints and the nature of the gas employed.
Gas or liquid chromatography is a highly effective separation technique since it employs a very large number of theoretical plates (Ind. Eng. Chem. Prod. Res. Develop., 1979, 18, 263). It can thus employ relatively low adsorption selectivities and difficult separations can be carried out. Such processes are in fierce competition with continuous simulated moving bed or simulated counter current processes, which have been developed to a sophisticated degree in the petroleum industry. The use of such adsorption processes in the field of gasoline production is well known. However, such processes are always applied to the light C
5
-C
6
fraction with the aim of improving the octane number.
Permeation separation techniques have the advantage over adsorption separation techniques of being continuous and as a result of being relatively simple to carry out. Further, they are recognised for their modular nature and compactness. About ten years ago, they took their place beside gas adsorption and separation techniques, for example for recovering hydrogen from refinery gases, decarbonising natural gasoline and producing inerting nitrogen (“Handbook of Industrial Membranes”, Elsevier Science Publishers, UK, 1995).
Regarding catalytic paraffin isomerisation systems, a compromise can be reached between isomerisation proper and acid cracking or hydrogenolysis, which produce light C
1
-C
4
hydrocarbons and which drop the global yields. Thus the more branched the paraffin, the easier it isomerises, but the greater its propensity for cracking. This justifies the search for more selective catalysts and for processes arranged so as to supply different isomerisation sections with streams which are rich in straight chain paraffins or monobranched paraffins.
AIM OF THE INVENTION
The Applicant has directed its research towards developing an improved process for producing gasolines with an improved octane number, generally accompanied by the production of middle distillates with a high cetane index and the production of very high quality oils (the oils obtained have a high viscosity index (VI), low volatility, good UV stability and a low pour point) from petroleum cuts, preferably from hydrocarbon-containing feeds from the Fischer-Tropsch process, or feeds from hydrocracking vacuum distillates, that is to say, hydrocracking residues in general.
The invention describes a process for producing gasoline with an improved octane number from a hydrocarbon-containing feed, comprising the following successive steps:
(a) converting the feed with simultaneous hydroisomerisation of the paraffins of the feed, said feed having a sulphur content of less than 1000 ppm by weight, a nitrogen content of less than 200 ppm by weight, a metals content of less than 50 ppm by weight, an oxygen content of at most 0.2% by weight, said step being carried out at a temperature of 200-500° C., at a pressure of 5-25 MPa, with a space velocity of 0.1-5 h
−1
, in the presence of hydrogen, and in the presence of a catalyst containing at least one noble metal deposited on an amorphous acidic support and separating at least one gasoline cut and at least one residue conta

Affiliated with

Also associated with

Rating

Process for producing gasoline with an improved octane number 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 gasoline with an improved octane number, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for producing gasoline with an improved octane number will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2879207