Mineral oils: processes and products – Chemical conversion of hydrocarbons – Cracking
Reexamination Certificate
2001-07-23
2004-05-18
Griffin, Walter D. (Department: 1764)
Mineral oils: processes and products
Chemical conversion of hydrocarbons
Cracking
C208S108000, C208S111010, C208S111150, C208S111100, C208S111200, C208S111300, C208S111250
Reexamination Certificate
active
06736959
ABSTRACT:
The present invention concerns a process for improving the pour point of feeds containing straight chain and/or slightly branched, long chain (more than 10 carbon atoms) paraffins, in particular to provide good yields on converting feeds with high pour points into at least one cut with a low pour point and a high viscosity index.
High quality lubricants are of fundamental importance to the proper operation of modern machines, automobiles and trucks. However, the quantity of paraffins originating directly from untreated crude oil with properties that are suitable for use in good lubricants is very low with respect to the increasing demand in this sector.
Heavy oil fractions containing large amounts of straight chain or slightly branched paraffins must be treated in order to obtain good quality oil bases in the best possible yields, employing an operation that aims to eliminate the straight chain or slightly branched paraffins from feeds which are then used as base stock, or as kerosene or jet fuel.
High molecular weight paraffins that are straight chain or very slightly branched and are present in the oils or kerosene or jet fuel lead to high pour points and thus to coagulation for low temperature applications. In order to reduce the pour points, such straight chain paraffins that are not or are only slightly branched must be completely or partially eliminated.
That operation can be carried out by extracting with solvents such as propane or methyl ethyl ketone, termed dewaxing, with propane or methyl ethyl ketone (MEK). However, such techniques are expensive, lengthy and not always easy to carry out.
A further technique is catalytic treatment; zeolites are among the most widely used catalysts because of their form selectivity.
Zeolite based catalysts such as ZSM-5, ZSM-11, ZSM-12, ZSM-22, ZSM-23, ZSM-35 and ZSM-38 have been described for their use in such processes.
The Applicant has directed its research towards developing alternative processes for improving the pour point of feeds, using different catalysts.
SUMMARY OF THE INVENTION
The invention concerns a process for improving the pour point of a feed comprising paraffins containing more than 10 carbon atoms, in which the feed is brought into contact with a catalyst comprising at least one dioctahedral 2:1 phyllosilicate and at least one hydrodehydrogenation element, in general in the metallic form.
Preferably, the phyllosilicate contains fluorine; it has been synthesised in a fluoride medium in the presence of HF and/or a further source of fluoride anions.
Advantageously, the interplanar spacing is at least 20×10
−10
m (2 nm) and preferably, the space between the phyllosilicate sheets comprises pillars based on at least one oxide of elements from groups IVB, VB, VIB, VIII, IB, IIB, IIA, IVA or any combination of these oxides, preferably selected from the group formed by SiO
2
, Al
2
O
3
, TiO
2
, ZrO
2
and V
2
O
5
, or any combination of the latter.
The process can advantageously convert a feed with a high pour point to a mixture (for example oil) with a lower pour point and, in the case of oil, a high viscosity index. It can also be applied to reducing the pour point of gas oils, for example.
The feed is composed, inter alia, of straight chain and/or slightly branched paraffins containing at least 10 carbon atoms, preferably 15 to 50 carbon atoms, and advantageously 15 to 40 carbon atoms.
The catalyst comprises at least one hydrodehydrogenation element, for example at least one group VIII metal (Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, Pt) or a combination of at least one group VIII (non noble) metal or compound and at least one group VIB metal or compound, and the reaction is carried out under conditions which will be described below.
Advantageously, the catalyst also contains a matrix.
The use of a dioctahedral 2:1 phyllosilicate, preferably synthesised in a fluoride medium in the presence of the acid HF and/or a further source of fluoride anions, wherein the interplanar spacing is at least 20×10
−10
m (2 nm) and comprising pillars based on at least one oxide of elements from groups IVB, VB, VIB, VIII, IB, IIB, IIA and IVA or any combination of these oxides, preferably selected from the group formed by SiO
2
, Al
2
O
3
, TiO
2
, ZrO
2
and V
2
O
5
, or any combination of these latter, and at least one group VIII element can result in good yields of products with a low pour point and a high viscosity index.
The interplanar spacing d
001
of the dioctahedral 2:1 phyllosilicates (preferably previously to prepared in a fluoride medium in the presence of the acid HF and/or another source of fluoride ions), preferably bridged by employing the process described above, is at least 20×10
−10
m, preferably at least 26.5×10
−10
m, more preferably more than 28×10
−10
m and still more preferably at least 30×10
−10
m or even 33×10
−10
m. Said interplanar spacing is generally 60×10
−10
m or less, preferably 50×10
−10
m or less. Said interplanar spacing, represented by d
001
, represents the sum of the thickness of a sheet plus the space between the sheets. This value can be obtained directly using a conventional orientated powder X ray diffraction method.
Dioctahedral 2:1 phyllosilicates are minerals that are formed by layers of elementary sheets. Although the chemical bonds between the elements of the phyllosilicate structure are ionocovalent, they will be assumed to be ionic, to simplify the description.
From a representation where the O
2−
ions are in a plane in contact with each other, it is possible to produce a plane with a hexagonal cavity, termed the hexagonal plane, by withdrawing alternate O
2−
ions from alternate rows of O
2−
ions.
The structure of a phyllite can be simply represented by arrangements of hexagonal planes of O
2−
ions and compact planes of O
2−
and OH
−
ions. The OH
−
ions fill the cavities in the hexagonal planes of O
2−
ions.
Superimposing two compact planes sandwiched by hexagonal planes defines an octahedral layer (O) between two tetrahedral layers (T) giving the sheet the denomination TOT.
Such an arrangement, also termed 2:1, defines a plane of octahedral cavities located in the octahedral layer between two planes of tetrahedral cavities, one in each tetrahedral layer. Each tetrahedron has one O
2−
ion in common with the octahedral layer and each of the three other O
2−
ions is shared with another tetrahedron in the same tetrahedral layer.
The crystalline lattice is thus constituted by 6 octahedral cavities each having 4 tetrahedral cavities either side. In the case of a phyllite constituted by the elements Si, Al, O, H, such an arrangement corresponds to the ideal formula Si
8
(Al
4
∘
2
)O
20
(OH)
4
. The tetrahedral cavities contain the element silicon, and the octahedral cavities contain the element aluminium but in this case one octahedral cavity in three is empty (∘). Such an assembly is electrically neutral. Usually, the half-cell is used, with formula
Si
4
(Al
2
∘)O
10
(OH)
2
The tetrahedral element silicon can be substituted by trivalent elements such as aluminium or gallium or iron (Fe
3+
). Similarly, the octahedral element aluminium can be substituted by:
the trivalent elements cited above, or a mixture of those elements;
divalent elements such as (Mg).
These substitutions endow the structure with a negative charge. This necessitates the existence of exchangeable compensating cations located in the space between the sheets. The thickness of the space between the sheets depends on the nature of the compensating cations and their hydration. That space is also capable of accepting other chemical species such as water, amines, salts, alcohols, bases, etc.
The existence of —OH groups causes thermal instability due to a dehydroxylation reaction with equation: 2-OH→—O—+H
2
O. In this respect, the introduction of the element fluorine into the structure during synthesis in place of the O—H
Benazzi Eric
Marchal-George Nathalie
Griffin Walter D.
Institut Francais du Pe'trole
Millen White Zelano & Branigan P.C.
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