Mineral oils: processes and products – Chemical conversion of hydrocarbons – Cracking
Reexamination Certificate
1998-06-24
2004-05-11
Griffin, Walter D. (Department: 1764)
Mineral oils: processes and products
Chemical conversion of hydrocarbons
Cracking
C208S027000, C208S111300, C208S111350, C585S739000
Reexamination Certificate
active
06733658
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 EU-1 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.
BACKGROUND OF THE INVENTION
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 ZSM-5, ZSM-11, ZSM-12, ZSM-22, ZSM-23, ZSM-35 and ZSM-38 have been described for their use in such processes.
Processes using such zeolites 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 which also encourage isomerisation of such compounds.
SUMMARY 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 EU-1 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.
EU-1 zeolite in its hydrogen form, termed H-EU-1, obtained by calcining and/or ion exchanging as synthesized EU-1, used in the process of the invention, and its synthesis are described in European patent EP-B1 0 042 226. That zeolite has the following molar composition: 0.5 to 1.5 R
2
O: T
2
O
3
: at least 10 XO
2
: 0 to 100 H
2
O, where R is a monovalent cation or 1
of a cation with valency n, X is silicon and/or germanium, T is Al, Fe, Ga or B and the water is water of hydration which adds to the initial water present when R is H. This EU-1 zeolite is characterized by the following X ray diffraction table:
X ray diffraction table for zeolite in the form Na—H—EU-1, i.e., partially in its hydrogen form and containing sodium.
Dhkl (Å)
I/I
0
11.11 ± 0.15
vs
10.03 ± 0.15
vs
9.78 ± 0.15
w
7.62 ± 0.15
w
6.84 ± 0.10
m
6.21 ± 0.10
vw
5.73 ± 0.10
w
4.87 ± 0.08
vw
4.60 ± 0.08
vs
4.30 ± 0.08
vs
3.97 ± 0.06
vs
3.77 ± 0.06
s
3.71 ± 0.04
w
3.63 ± 0.04
vw
3.42 ± 0.04
m
3.33 ± 0.04
m
3.27 ± 0.04
s
3.23 ± 0.04
m
3.15 ± 0.04
w
3.07 ± 0.04
w
2.93 ± 0.04
w
2.69 ± 0.04
w
2.63 ± 0.04
vw
2.57 ± 0.04
vw
2.51 ± 0.03
w
2.45 ± 0.03
vw
2.41 ± 0.03
vw
2.32 ± 0.02
vw
2.29 ± 0.02
vw
2.11 ± 0.02
vw
I/I
0
represents the relative intensities of peaks graduated on the following scale:
w = weak (I/I
0
in the range 0 to 20);
m = medium (I/I
0
in the range 20 to 40);
s = strong (I/I
0
in the range 40 to 60);
vs = very strong (I/I
0
in the range 60 to 100).
EU-1 zeolite with structure type EUO, used in the present invention has a one-dimensional microporous network with pore openings delimited by 10 T atoms (tetrahedral atoms: Si, Al, Ga, Fe . . . ), with a pore diameter of 4.1×5.7 Å. This structure is described in “The Atlas of Zeolite Structure Types”, by W. M. Meier, D. H. Olson and Ch. Baerlocher, Fourth Edition, 1996. This zeolite also has wide lateral pockets along its principal channels with pore openings delimited by 10 T atoms (tetrahedral atoms: Si, Al, Oa, Fe . . . ) with dimensions of about 6.8×5.8 Å.
The term “pore opening of 10 or 12 tetrahedral atoms (T)” means pores constituted by 10 or 12 sides.
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.
Among others, the feed is composed of linear and/or slightly branched paraffins containing at least 10 carbon atoms, preferably 15 to 50 carbon atoms, and advantageously 15 to 40 carbon atoms. Heavy feeds contain paraffins essentially containing more than 30 carbon atoms and produce base stock; gas oils are lighter and contain paraffins containing 10-30 carbon atoms.
The isomerised 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 EU-1 zeolite of the invention under the conditions described above can produce products with a low pour point and oils with a high viscosity index, in good yields.
DETAILED DESCRIPTION OF THE INVENTION
EU-1 zeolite has an Si/T atomic ratio in the range 5 to 600 and in particular in the range 10 to 300.
The global Si/T ratio of the zeolite and the chemical composition of the samples are determined by X ray fluorescence and atomic absorption.
The EU-1 zeolite used in the process of the invention can be obtained with the d
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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