Mineral oils: processes and products – Chemical conversion of hydrocarbons – Plural serial stages of chemical conversion
Reexamination Certificate
2000-03-01
2002-01-15
Preisch, Nadine (Department: 1764)
Mineral oils: processes and products
Chemical conversion of hydrocarbons
Plural serial stages of chemical conversion
C208S016000, C208S133000, C208S062000, C208S092000, C585S734000, C585S738000, C585S014000
Reexamination Certificate
active
06338791
ABSTRACT:
The invention relates to a process for producing a high octane number gasoline pool comprising at least 2% by weight, preferably at least 3% by weight, and more preferably at least 4.5% by weight, of C7 di-branched paraffins, i.e., di-branched paraffins containing 7 carbon atoms. As a preferred example, such a gasoline pool can be obtained by incorporating into said pool a gasoline stock from hydro-isomerisation of a feed constituted by a C5-C8 cut or any cut between C5 and C8, i.e., a cut comprising hydrocarbons containing 5 to 8 carbon atoms, such as C5-C8, C6-C8, C7-C8, C7, C8, etc . . . This invention is an improvement over conventional refining schemes as it proposes upgrading light C5 to C8 cuts comprising paraffinic, naphthenic, aromatic and olefinic hydrocarbons, by hydro-isomerisation and recycling of low octane number paraffins, i.e., straight-chain and mono-branched paraffins. Hydro-isomerisation of light C5 to C8 cuts can be carried out in the gas, liquid or mixed liquid-gas phase in one or more reactors where the catalyst is used in a fixed bed. Normal and mono-branched paraffins can be recycled in the liquid or gas phase using a separation process involving adsorption or permeation using respectively one or more adsorbents, or one or more permeation steps.
In one version of the process, the process comprises at least one hydro-isomerisation section and at least one separation section. The hydro-isomerisation section comprises at least one reactor. The separation section (composed of one or more units) produces two streams, a first stream rich in di- and tri-branched paraffins, and possibly in naphthenes and aromatic compounds, which constitutes a high octane number gasoline stock and which is sent to the gasoline pool, and a second stream which is rich in straight-chain and mono-branched paraffins and which is recycled to the inlet to the hydro-isomerisation section. When separating by adsorption, this version of the process, optimised for feeds containing more than 12 mole %, preferably more than 15 mole % of C7+ (i.e., hydrocarbons containing at least 7 carbon atoms) uses an adsorbable eluent to completely or at least partially regenerate the adsorbent.
In a second version of the process, the process comprises at least two hydro-isomerisation section and at least one separation section. The separation section (composed of one or more units) produces three streams: a first stream which is rich in di- and tri-branched paraffins, and possibly in naphthenes and aromatics which constitutes a high octane number gasoline stock and is sent to the gasoline pool, a second stream which is rich in straight-chain paraffins which is recycled to the inlet of the first hydro-isomerisation section, and a third stream which is rich in mono-branched paraffins which is recycled to the inlet of the second section. Two implementations of this version of the process are preferred: in the first, all of the effluent from the first hydro-isomerisation section traverses the second section, and in the second the effluents from the hydro-isomerisation sections are sent to the separation section or sections.
Carrying out the process enables:
the amount of total aromatic compounds in a conventional gasoline pool to be reduced by 3% to 12% by weight, depending on the composition of the pool and in particular depending on the reformed gasoline fraction and the hydro-isomerisation gasoline introduced;
the amount of benzene in the gasoline pool to be significantly reduced;
the severity of the operation of the associated catalytic reforming units to be reduced.
PRIOR ART
Increasing environmental constraints have resulted in the removal of lead compounds from gasolines, effectively in the United States and Japan and becoming general in Europe. Aromatic compounds, the main constituents of reformed gasolines, and isoparaffins produced by aliphatic alkylation or isomerisation of light gasolines initially compensated for the octane number loss resulting from removing lead from gasoline. Subsequently, oxygen-containing compounds such as methyl tertiobutyl ether (MTBE) or ethyl tertiobutyl ether (ETBE) were introduced into the gasolines. More recently, the known toxicity of compounds such as aromatic compounds, in particular benzene, olefins and sulphur-containing compounds, as well as the desire to reduce the vapour pressure of the gasolines, led the United States to produce reformulated gasolines. 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. Regulations are less severe in Europe, but nevertheless there is a clear tendency to reduce the maximum benzene, aromatic compound and olefin amounts in gasoline which is produced and sold to a similar level.
Gasoline pools contain a plurality of components. The major components are reformed gasoline, which normally comprises 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 neither aromatic compounds nor olefinic compounds, light gasolines which may or may not be isomerised, 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 gasoline pools remains high, typically 40% by volume. In contrast, increased severity as regards the maximum admissible amount of aromatic compounds to 20-25% by volume will result in a reduction in the use of reforming, and as a result the need to upgrade C7-C10 straight run cuts by routes other than reforming.
Thus the production of multi-branched isomers from low-branched heptanes and octanes contained in naphthas, instead of producing toluene and xylenes from those compounds, appears to be an extremely promising route. This justifies the search for high performance catalytic systems for isomerising heptanes (also termed hydro-isomerisation when carried out in the presence of hydrogen), octanes and more generally C5-C8 cuts and intermediate cuts, and the search for processes for selectively recycling low octane number compounds which are straight-chain and mono-branched paraffins to the isomerisation (hydro-isomerisation) step. Regarding the catalytic systems, a compromise has to be found between isomerisation proper and acid cracking or hydrogenolysis, which produces light C1-C4 hydrocarbons which drop the overall yields. Thus the more branched the paraffin, the more easily it isomerises but also the greater is its tendency to crack. This justifies the search for more selective catalysts, and for processes which are arranged to supply different hydro-isomerisation sections with streams which are rich in straight-chain or mono-branched paraffins. The catalytic systems described in the literature use bifunctional catalysts such as Pt/zeolite b (Martens et al., J. Catal., 1995, 159, 323), Pt/SAPO-5 or Pt/SAPO-11 (Campelo et al., J. Chem. Soc., Faraday Trans., 1995, 91, 1551), massive or SiC supported mono-functional oxycarbide catalysts (Ledoux et al., Ind. Eng. Chem. Res., 1994, 33, 1957), mono-functional acid systems such as chlorinated aluminas (Travers et al, Rev. Inst. Fr. Petr., 1991, 46, 89), sulphated zirconias (Iglesia et al., J. Catal., 1993, 144, 238) or some heteropolyacids (Vedrine et al., Catal. Lett., 1995, 34, 223).
Adsorption and permeation separation techniques are particularly suitable for separating straight-chain, mono- and multi-branched paraffins. Processes for separation by conventional adsorption can be based on PSA (pressure swing adsorption), TSA (temperature swing adsorption), chromatography (elution chromatography or simulated counter-current chromatography, for example). They can also result from a combination of the above. Such processes all involve bringing a liquid or gaseous mixtur
Clause Olivier
Durand Jean-Pierre
Hotier Gerard
Jullian Sophie
Ragil Karine
Institut Francais du Pe'trole
Millen White Zelano & Branigan P.C.
Preisch Nadine
LandOfFree
High octane number gasolines and their production using a... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with High octane number gasolines and their production using a..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and High octane number gasolines and their production using a... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2873262