Mineral oils: processes and products – Chemical conversion of hydrocarbons – Cracking
Reexamination Certificate
2000-08-09
2002-02-26
Griffin, Walter D. (Department: 1764)
Mineral oils: processes and products
Chemical conversion of hydrocarbons
Cracking
C208S111300, C208S111350, C208S136000, C208S137000, C208S138000, C208S027000, C585S739000
Reexamination Certificate
active
06350370
ABSTRACT:
The present invention concerns a process for improving the pour point of feeds containing linear and/or slightly branched, long (more than 10 carbon atoms) paraffins, to provide good yields on converting feeds with high pour points to at least one cut with a low pour point and a high viscosity index for oil bases.
The present invention also concerns a NU-85 zeolite from which a portion of the elements Al, Fe, Ga or B has been removed, for example dealuminated, a catalyst containing that zeolite, its use in converting hydrocarbons, and a process for reducing the pour point using that catalyst.
PRIOR ART
High quality lubricants are fundamentally important for the proper operation of modern machines, automobiles and trucks. However, the quantity of paraffins originating directly from untreated crude oil with properties which 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 linear or slightly branched paraffins must be treated in order to obtain good quality oil bases in the best possible yields, using an operation which aims to eliminate the linear or slightly branched paraffins from feeds which are then used as base stock, or as kerosene or jet fuel.
High molecular weight paraffins which are linear or very slightly branched which are present in the oils or kerosene or jet fuel result in high pour points and thus in coagulation for low temperature applications. In order to reduce the pour points, such linear paraffins which are not or are only slightly branched must be completely or partially eliminated.
This 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 selective cracking of the longest linear paraffin chains to form compounds with a lower molecular weight, part of which can be eliminated by distillation.
Because of their form selectivity, zeolites are among the most widely used catalysts. The idea underlying their use is that zeolitic structures exist which have pore openings which allow long linear or very slightly branched paraffins to enter their micropores but which exclude branched paraffins, naphthenes and aromatic compounds. This phenomenon leads to selective cracking of linear or very slightly branched paraffins.
Zeolite based catalysts with intermediate pore sizes such as ZSM5, ZSM-11, ZSM-12, ZSM-22, ZSM-23, ZSM-35 and ZSM-38 have been described for their use in such processes.
The present invention proposes a pour point reduction process based on NU-85 zeolite.
Further, processes using some of such zeolites (ZSM-5, ZSM-11, ZSM-12, ZSM-22, ZSM-23, ZSM-35 and ZSM-38) can produce oils by cracking feeds containing less than 50% by weight of linear or linear or very slightly branched paraffins. However, for feeds containing higher quantities of these compounds, it has become apparent that cracking them leads to the formation of large quantities of products with lower molecular weights such as butane, propane, ethane and methane, which considerably reduces the yield of desired products.
In order to overcome these disadvantages, we have concentrated our research on developing catalysts based on NU-85 zeolites which also encourage isomerisation of such compounds.
AIM OF THE INVENTION
The invention provides a process for improving the pour point of a paraffinic feed comprising paraffins containing more than 10 carbon atoms, in which process the feed to be treated is brought into contact with a catalyst based on NU-15 zeolite and at least one hydro-dehydrogenating element, at a temperature which is in the range 170° C. to 500° C., a pressure in the range 1 to 250 bar and an hourly space velocity in the range 0.05 to 100 h
−1
, in the presence of hydrogen in a proportion of 50 to 2000 l/l of feed.
NU-85 in its hydrogen form, termed H-NU-85, obtained by calcining and/or ion exchanging as synthesised NU-85, used in the process of the invention, to and its synthesis are described in European patent EP-A2 0 462 745. This NU-85 is a hybrid of EU-1 and NU-87 zeolites.
The composition of this NU-85 zeolite, expressed as its anhydrous form, in terms of molar ratios of the oxides, has the following formula:
100
×O
2
: 10 or less Y
2
O
3
: 20 or less R
2
O
where R represents one or more cations with valency n, X represents silicon and/or germanium, Y represents one or more of the following: aluminium, iron, gallium, boron, titanium, vanadium, zirconium, molybdenum, arsenic, antimony, chromium or manganese, preferably Al, Fe, Ga, B (elements T).
This NU-85 zeolite comprises crystals with an X ray diffraction diagram which has the characteristic lines of EU-1- and NU-87 zeolites and these peaks have between them a continuity and are characteristic of a continuous crystalline framework.
In its as synthesised state, i.e., prepared by synthesis, this NU-85 zeolite also comprises network images (obtained using a transmission electron microscope) which, in the orientation producing 20±0.2 Å fringes for EU-1-zeolite, exhibits intermediate fringes of 12.5±0.2 Å in association with those fringes of 20±0.2 Å, and/or an X ray diffraction diagram containing the lines shown in the following table:
Relative
d (Å)
intensity
11.15 ± 0.20
m
10.30 ± 0.20
w
6.89 ± 0.12
w
4.66 ± 0.10
m
4.31 ± 0.10
vs
4.00 ± 0.08
s to vs
3.86 ± 0.08
w to m
3.71 ± 0.07
m
3.42 ± 0.07
w to m
3.37 ± 0.06
w to m
3.26 ± 0.06
s to vs
3.16 ± 0.06
w
3.10 ± 0.06
w
2.96 ± 0.05
w
2.71 ± 0.05
w
w (weak) corresponds to a value of less than 20, m (medium) corresponds to a value in the range 20 to 40, s (strong) corresponds to a valuc of over 40 and below 60, vs (very strong) corresponds to a value of over 60.
The term “NU-85 zeolite” encompasses a family of products in which the NU-87 and EU-1 contents can vary substantially depending on the conditions selected to synthesis the NU-85 zeolite. Thus, and as is well known to the skilled person, the intensity of these lines can vary depending on the form of the zeolite, without raising doubts as to whether that zeolite belongs to the NU-85 family.
The process can advantageously convert a feed with a high pour point to a product with a lower pour point. It can be applied to reducing the pour point of gas oils, for example. It can also be used to convert heavier feeds to oils with a high viscosity index.
Among others, the feed is composed of linear and/or slightly branched paraffins containing at least 10 carbon atoms, preferably 15 to 20 carbon atoms, and advantageously 15 to 40 carbon atoms. Heavy feeds (to produce oils) contain paraffins essentially containing more than 30 carbon atoms; gas oils contain paraffins containing 10-30 carbon atoms.
The isomerised products present in the final products may contain about 65% to 80% of single-branched products and about 20% to 35% of multi-branched products. The term “single-branched products” means linear paraffins comprising a single methyl group, and the term “two-branched products” means linear paraffins containing 2 methyl groups which are not carried by the same carbon atom. Thus “multi-branched” paraffins can be defined by extension.
Further, the catalyst comprises at least one hydro-dehydrogenating function, for example a group VIII metal (noble or non-noble) or a combination of at least one group VIII (non noble) metal or compound and at least one group VI metal or compound, and the reaction is carried out under conditions which will be described below.
Using the NU-85 zeolite of the invention under the conditions described above can produce products with a low pour point in good yields, with a high viscosity index for oils.
DETAILED DESCRIPTION OF THE INVENTION
NU-85 zeolite has an Si/T atomic ratio in the range 5 to 600 and in particular in the range
Benazzi Eric
Billon Alain
Briot Patrick
George-Marchal Nathalie
Gueret Christophe
Griffin Walter D.
Institut Francais du Pe'trole
Millen White Zelano & Branigan P.C.
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