Chemistry of hydrocarbon compounds – Saturated compound synthesis – By isomerization
Reexamination Certificate
1999-05-12
2001-05-22
Yildirim, Bekir L. (Department: 1764)
Chemistry of hydrocarbon compounds
Saturated compound synthesis
By isomerization
C585S739000, C585S750000, C208S018000, C208S027000
Reexamination Certificate
active
06235960
ABSTRACT:
The present invention relates to a process for improving the pour point of feeds containing linear and/or slightly branched, long (more than 10 carbon atoms) paraffins, in particular 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 catalyst used comprises at least one zeolite with structure type MTT, TON or FER or any possible combination of these types, at least one hydro-dehydrogenating element, preferably selected from elements from group VIB and group VIII of the periodic table, at least one deposited promoter element which is selected from the group formed by boron, silicon and phosphorous, optionally at least one group VIIA element, and optionally at least one group VIIB element.
The invention also relates to a catalyst as described above but containing silicon as the promoter element and optionally phosphorous and/or boron. The present invention also claims the use of this catalyst for converting hydrocarbons and a process for reducing the pour point.
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 compared 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 kerosine or jet fuel.
High molecular weight paraffins which are linear or very slightly branched which are present in the oils or kerosine 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 zeolite 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 (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.
SUMMARY OF THE INVENTION
In order to overcome these disadvantages, we have concentrated our research on developing catalysts containing at least one zeolite with a structure type MTT, TON, or FER or any possible combination of these types, preferably also containing at least one element selected from elements from group VIB and VIII of the periodic table, boron and/or silicon, optionally phosphorous, and optionally at least one group VIIA element also encouraging isomerization of these compounds.
The present invention proposes a catalytic process for reducing the pour point based on such catalysts.
In a first aspect, the invention provides a process for improving the pour point of a paraffin feed comprising paraffins containing more than 10 carbon atoms, in which the feed to be treated is brought into contact with a catalyst containing at least one zeolite with structure type MTT, TON, or FER or any possible combination of these types, at least one hydro-dehydrogenating element, preferably selected from elements from group VIB and group VIII of the periodic table, at least one deposited promoter element selected from the group formed by boron, silicon and phosporous, optionally at least one group VIIA element, and optionally at least one group VIIB element, at a temperature in the range 170° C. to 500° C., a pressure in the range 1 to 250 bars and at an hourly space velocity in the range 0.05 to 100 h
−1
, in the presence of hydrogen in an amount of 50 to 2000 l/l of feed.
The zeolites comprised in the catalyst of the invention have structure types TON, MTT or FER and are described in the “Atlas of Zeolite Structure Types, W. M. Meier, D. H. Olson and Ch. Baerlocher, 4
th
Revised Edition, 1996, Elsevier.
The catalyst has an activity and dewaxing selectivity (improving the pour point) which is higher than the catalytic formulae based on known MTT, TON and FER zeolites. Without wishing to be bound by a particular theory, it appears that this particularly high activity of the catalysts of the present invention is due to reinforcement of the acidity of the catalyst by the presence of the promoter element, in particular boron and/or silicon, in the matrix which results in the improvement in the properties with respect to catalysts in current use.
The process can advantageously convert a feed with a high pour point to a product with a lower pour point. It can thus be applied to reducing the pour point of gas oils, for example. It can also 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 50 carbon atoms, and advantageously 15 to 40 carbon atoms. Heavy feeds (to produce oils) comprise paraffins essentially containing more than 30 carbon atoms; gas oils generally 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 catalyst of the invention under the conditions described above can produce products with a low pour point in good yields, and oils with a high viscosity index.
DETAILED DESCRIPTION OF THE INVENTION
A zeolite with structure type TON includes the following zeolites: theta, ISI-1, NU-10, KZ-2 and ZSM-22 (described in U.S. Pat. No. 4,810,357). A zeolite with structure type MTT includes ZSM-23 zeolites (described in U.S. Pat. Nos. 4,076,842 and 4,104,141), EU-13, ISI-4, KZ-1 and SSZ-32 (described in U.S. Pat. No. 5,053,373). A zeolite with structure type FER includes the following zeolites which essentially have the same structure: ferrierite, FU-9, NU-23, ZSM-35 (described in U.S. Pat. No. 4,016,245), and ISI-6.
The MTT, TON and FER zeolites used in the catalyst of the invention c
Benazzi Eric
George-Marchal Nathalie
Kasztelan Slavik
Institut Francais du Pe'trole
Millen White Zelano & Branigan P.C.
Yildirim Bekir L.
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