CATEGORY: HYDROTREATING
PATENT
Catalyst
That Can Be Used In Hydrotreatment, Comprising Metals Of Groups Viii And Vib,
And Preparation With Acetic Acid And Dialkyl Succinate C1-C4
United States Patent Application 20130008829
Inventors:
Marchand, Karin (Lyon, FR)
Guichard, Bertrand (Izeaux, FR)
Digne, Mathieu (Lyon, FR)
Rebeilleau, Michael (Harfleur, FR)
Lopez, Sylvie (Lyon, FR)
Hugon, Antoine (Lyon, FR)
Application Number:
13/516411
Publication Date:
01/10/2013
Assignee:
IFP Energies nouvelles (Rueil-Malmalson Cedex, FR)
Total Raffinage Marketing (La Defense, FR)
Abstract:
The
invention relates to a catalyst usable in hydrotreatment processes, which
comprises an alumina-based amorphous support, phosphorus, a C1-C4 dialkyl
succinate, acetic acid and a hydro-dehydrogenizing function comprising at least
one group VIII element and at least one group VIB element, preferably made up
of cobalt and molybdenum, a catalyst whose Raman spectrum comprises the most
intense bands characteristic of the Keggin heteropolyanions (974 and/or 990
cm−1), C1-C4 dialkyl succinate and acetic acid (896 cm−1). Preferably, the
dialkyl succinate concerned is dimethyl succinate and its main band is at 853
cm−1.
The invention also relates to the method of preparing said catalyst,
wherein a catalytic precursor comprising the group VIB and group VIII elements,
in particular the molybdenum-cobalt pair, and phosphorus, introduced by
impregnation, then dried at a temperature below 180° C., is impregnated by the
C1-C4 dialkyl succinate, the acetic acid and the phosphorus compound, if the
latter has not been entirely introduced beforehand, then, after maturation,
dried at a temperature below 180° C. prior to being optionally sulfurized.
The invention also relates to the use of this catalyst in any hydrotreatment process.
FIELD OF THE INVENTION
The invention relates to a catalyst, its method of preparation and its use in
the sphere of hydrotreatments.
Usually, the purpose of a hydrocarbon cut hydrotreatment catalyst is to
eliminate the sulfur or nitrogen compounds contained in such cuts so that a
petroleum product meets the required specifications for example (sulfur
content, aromatics content, etc.) for a given application (car fuel, gasoline
or diesel fuel, heating oil, jet fuel). The goal can also be to pre-treat this
feed so as to eliminate the impurities it contains prior to subjecting it to
various conversion processes in order to modify the physico-chemical properties
thereof, such as, for example, reforming, vacuum distillate hydrocracking,
catalytic cracking, atmospheric or vacuum residue hydroconversion processes.
The composition and the use of hydrotreatment catalysts are particularly well
described in the article by B. S. Clausen, H. T. Topsøe and F. E. Massoth, from
the book Catalysis Science and Technology, Vol. 11 (1996), Springer-Verlag.
After sulfurization, several surface species are present on the support, which
do not all show good performances for the desired reactions. These species are
particularly well described in the publication by Topsøe et al. published in
issue No. 26 of Catalysis Review Science and Engineering of 1984, pp. 395-420.
The tightening of vehicle pollution standards in the European Community
(Official Journal of the European Union, L76, 22 Mar. 2003, Directive
2003/70/CE, pp. L76/10-L76/19) has compelled refiners to considerably reduce
the sulfur content in diesel fuels and gasolines (maximum 10 ppm weight of
sulfur on 1 Jan. 2009, vs. 50 ppm on 1 Jan. 2005). Besides, refiners are
compelled to use feeds that are increasingly refractory to hydrotreatment
processes, on the one hand because crudes are increasingly heavy and therefore
contain more and more impurities and, on the other hand, because of the
increase of conversion processes in refineries. In fact, the latter generate
cuts that are more difficult to hydrotreat than cuts directly resulting from
atmospheric distillation. An example thereof is the diesel cut obtained from
catalytic cracking, also referred to as LCO (Light Cycle Oil) in reference to
its high aromatic compounds content. These cuts are co-treated with the diesel
cut obtained from atmospheric distillation; they require catalysts having
highly improved hydrodesulfurizing and hydrogenizing functions in relation to
conventional catalysts so as to decrease the aromatics content in order to
obtain a density and a cetane number in accordance with specifications.
Besides, conversion processes such as catalytic cracking or hydrocracking use
catalysts having an acid function, which makes them particularly sensitive to
the presence of nitrogen impurities, and particularly basic nitrogen compounds.
It is therefore necessary to use catalysts for pre-treating these feeds so as
to remove these compounds. These hydrotreatment catalysts also require an
improved hydrogenizing function insofar as the first hydrodenitrogenation stage
is known as a stage of hydrogenation of the aromatic ring adjacent to the C—N
bond.
It is therefore interesting to find means of preparing hydrotreatment catalysts
allowing to obtain new catalysts with improved performances.
BACKGROUND OF THE INVENTION
Adding an organic compound to hydrotreatment catalysts in order to improve
their activity is now well known to the person skilled in the art. Many patents
protect the use of various ranges of organic compounds such as mono-, di- or
polyalcohols, possibly etherized (WO96/41848, WO01/76741, U.S. Pat. No.
4,012,340, U.S. Pat. No. 3,954,673, EP601722). Catalysts modified with C2-C14
monoesters are described in patent applications EP466568 and EP1046424, however
these modifications do not always allow to sufficiently increase the
performances of the catalyst in order to meet the specifications relative to
the sulfur contents of fuels, which have become increasingly restricting for
refiners.
In order to overcome this, patent WO2006/077326 filed by the TOTAL Company
proposes using a catalyst comprising groups VIB and VIII metals, a refractory
oxide as the support and an organic compound, comprising at least 2 carboxylic
ester functions of formula R1-O—CO—R2-CO—O—R1 or R1-CO—O—R2-O—CO—R1 wherein
each R1 independently represents a C1 to C18 alkyl group, a C2 to C18 alkenyl
group, a C6 to C18 aryl group, a C3 to C8 cycloalkyl group, a C7 to C20
alkylaryl or arylalkyl group, or the 2 groups R1 jointly form a C2 to C18
divalent group, and R2 represents a C1 to C18 alkylene group, a C6 to C18
arylene group, a C3 to C7 cycloalkylene group, or a combination thereof, and
the carbon chain of the hydrocarbon groups represented by R1 and R2 can contain
or carry one or more heteroatoms selected from among N, S and O, and each group
R1 and R2 can carry one or more substituents of formula
—C(═O)O—R1 or —O—C(═O)—R1, where R1 has the aforementioned meaning. A preferred
mode uses C1-C4 dialkyl succinate, and in particular dimethyl succinate that is
exemplified. These compounds can be introduced in the presence of a solvent (a
considerable list of solvents is mentioned) or of a carboxylic acid. Among the
about thirty acids notably mentioned, there is acetic acid, which is however
not mentioned among the ten preferred acids. It can be noted already that
citric acid is preferred.
The catalyst preparation method as described in patent WO2006/077326 comprises
maturation and thermal treatment stages that can last up to several days, for
example from 49 days to 115 days, which would greatly limit the production of
these catalysts and would therefore require improvements.
Other patents of the prior art describe an activity gain linked with the
combined use of an organic acid or an alcohol on a hydrotreatment catalyst.
Thus, patent application No.JP1995-136523 filed by KK Japan Energy provides a
solution consisting in:
preparing according to a first preferred mode of the invention a solution
containing a catalyst support, one or more metals from group VI of the periodic
table and from group VIII, an organic acid. According to a second preferred
mode of the invention, this solution also comprises a phosphorus precursor.
carrying out a thermal treatment between 200° C. and 400° C.,
carrying out impregnation of the catalyst obtained above by an organic acid or
an alcohol with a ratio of 0.1 to 2 per mole of metals.
One of the preferred modes of the invention then comprises drying at a
temperature below 200° C., whereas a second preferred mode of the invention
comprises a final thermal treatment at a temperature greater than or equal to
400° C.
It has been observed that these catalysts do not have a sufficient activity to
meet the new environmental standards in the face of the increasingly
hydrogen-poor feeds available to refiners.
Similarly, patent WO2005/035691 claims an activation method that schematically
allows to decrease the proportion of crystallized phase of CoMoO4 type
present on the regenerated catalysts comprising groups VIII and VIB metal
oxides, a method comprising contacting the regenerated catalyst with an acid
and an organic additive. Therefore, the citric acid (CA)-polyethylene glycol
(PEG) combination has been used on a regenerated catalyst in many examples.
SUMMARY OF THE INVENTION
The present invention relates to a catalyst and to its preparation method, the
catalyst being usable for hydrotreatment and allowing to improve the catalytic
performances (notably the catalytic activity) in relation to the catalysts of
the prior art. In fact, it has been shown that using the pair made up of C1-C4
dialkyl succinate, in particular dimethyl, and of acetic acid on a dried
catalytic precursor surprisingly leads to a markedly improved catalytic
activity in comparison with each one of the compounds of the pair.
More precisely, the invention relates to a catalyst comprising an alumina-based
amorphous support, phosphorus, at least one C1-C4 dialkyl succinate, acetic
acid and a hydro-dehydrogenizing function comprising at least one group VIII
element and at least one group VIB element, a catalyst whose Raman spectrum
comprises the bands at 990 and/or 974 cm−1 characteristic of at
least one Keggin heteropolyanion, the bands characteristic of said succinate
and the main band at 896 cm−1 characteristic of acetic acid. The
hydro-dehydrogenizing function preferably consists of cobalt and molybdenum. It
can also comprise at least one group VIII element and at least one group VIB
element, except for the hydro-dehydrogenizing function consisting of cobalt and
molybdenum.
The catalyst obtained has a characteristic Raman spectrum grouping together:
1) Bands characteristic of the heteropolyanion(s) of Keggin PXY11O40x−
and/or PY12O40x− type where Y is a group VIB
metal and X is a group VIII metal.
According to Griboval, Blanchard, Payen, Fournier, Dubois in Catalysis Today 45
(1998) 277 FIG. 3e), the main bands of the PCoMo11O40x−
structure are on a dried catalyst at 232, 366, 943, 974 cm−1 and,
according to M. T. Pope “Heteropoly and Isopoly oxometalates”, Springer Verlag,
p 8, these bands are not characteristic of the nature of atom X or Y, but of
the structure of the HPA. The most intense band characteristic of this type of
lacunar Keggin HPA is at 974 cm−1.
According to Griboval, Blanchard, Gengembre, Payen, Fournier, Dubois, Bernard,
Journal of Catalysis 188 (1999) 102, FIG. 1a), the main bands of PMo12O40x−
are in the mass state of the HPA, for example with cobalt as the counterion at
251, 603, 902, 970, 990 cm−1. The most intense band characteristic
of this Keggin HPA is at 990 cm−1. M. T. Pope “Heteropoly and
Isopoly oxometalates”, Springer Verlag, p 8, also teaches us that these bands
are not characteristic of the nature of atom X or Y, but of the structure of
the Keggin HPA, complete, lacunar or substituted.
2) Bands characteristic of the dialkyl succinate(s) used. The Raman spectrum of
the dimethyl succinate is a univocal fingerprint of this molecule. In the 300-1800
cm−1 spectral zone, this spectrum is characterized by the series of
bands as follows (only the most intense bands are recorded, in cm−1):
391, 853 (most intense band), 924, 964, 1739 cm−1. The spectrum of
the diethyl succinate comprises, in the spectral zone considered, the main
bands as follows: 861 (most intense band), 1101, 1117 cm−1.
Similarly, for the dibutyl succinate: 843, 1123, 1303, 1439, 1463 cm−1 and
the diisopropyl succinate: 833, 876, 1149, 1185, 1469 (most intense band), 1733
cm−1.
3) Bands characteristic of acetic acid, with the main ones: 448, 623, 896 cm−1.
The most intense band is 896 cm−1.
The exact position of the bands, their shapes and their relative intensities
can vary to a certain extent depending on the spectrum recording conditions, while
remaining characteristic of this molecule. The Raman spectra of the organic
compounds are besides well documented, either in the Raman spectrum databases
(see for example Spectral Database for Organic Compounds,
http://riodb01.ibase.aist.go.jp/sdbs/cgi-bin/direct_frame_top.cgi), or by the
suppliers of the product (see for example www.sigmaaldrich.com).
The Raman spectra are obtained with a dispersive Raman type spectrometer
equipped with an ionized argon laser (514 nm). The laser beam is focussed on the
sample by means of a microscope equipped with a ×50 long working distance
objective. The power of the laser at the level of the sample is of the order of
1 mW. The Raman signal emitted by the sample is collected by the same objective
and dispersed by means of a 1800 rpm network, then collected by a CCD detector.
The spectral resolution obtained is of the order of 0.5 cm−1. The
spectral zone recorded ranges between 300 and 1800 cm−1. The
acquisition time is set at 120 s for each Raman spectrum recorded.
Preferably, the dialkyl succinate used is dimethyl succinate, and the catalyst
has in its spectrum the main Raman bands at 990 and/or 974 cm−1 characteristic
of the Keggin heteropolyanion(s), 853 cm−1 characteristic of
dimethyl succinate and 896 cm−1 characteristic of acetic acid.
Preferably, the catalyst of the invention comprises a support consisting of
alumina or silica-alumina.
The catalyst according to the invention can also comprise boron and/or fluorine
and/or silicon.
A method of preparing the catalyst according to the invention is also
described. It comprises at least one stage of impregnation of a catalytic
precursor dried at a temperature below 180° C., containing at least phosphorus
and a hydro-dehydrogenizing function, as well as an amorphous support, by an
impregnation solution comprising the combination of acetic acid and C1-C4
dialkyl succinate, followed by a stage of maturation of said impregnated
catalytic precursor, then a drying stage at a temperature below 180° C.,
without subsequent calcination stage (thermal treatment in air). The catalyst
obtained is preferably subjected to a sulfurization stage.
The hydro-dehydrogenizing function comprises at least one group VIII element
and at least one group VIB element. Preferably, the hydro-dehydrogenizing
function consists of cobalt and molybdenum.
The simple and fast preparation method, with unit stages that do not exceed
some hours, thus allows to obtain a higher productivity on the industrial scale
than the methods of the prior art.
More precisely, the method of preparing a hydrotreatment catalyst according to
the invention comprises the successive stages as follows, which will be
detailed below:
a) at least one stage of impregnation of an alumina-based amorphous support by
at least one solution containing the elements of the hydro-dehydrogenizing
function and phosphorus. The product obtained is referred to as “catalytic
precursor”,
b) drying at a temperature below 180° C. without subsequent calcination. The
product obtained is referred to as “dried catalytic precursor”,
c) at least one stage of impregnation by an impregnation solution comprising at
least one C1-C4 dialkyl succinate, acetic acid and at least one phosphorus
compound, if the latter has not been entirely introduced in stage a). The
product obtained is referred to as “impregnated dried catalytic precursor”,
d) a maturation stage,
e) a drying stage at a temperature below 180° C., without subsequent
calcination stage. The product obtained is referred to as “catalyst”.
Preferably, the product obtained at the end of stage e) is subjected to a
sulfurization stage f).
As described below, the method according to the invention is preferably carried
out with the following modes, alone or in combination: the support consists of
alumina or silica-alumina; all of the hydrogenizing function is introduced in
stage a); all of the phosphorus is introduced in stage a); the dialkyl
succinate is dimethyl succinate; stage c) is carried out in the absence of
solvent; stage d) is carried out at a temperature ranging from 17° C. to 50°
C.; stage e) is carried out at a temperature ranging between 80° C. and 160° C.
More preferably, the method according to the invention comprises the successive
stages as follows:
a) at least one stage of dry impregnation of said support by a solution
containing all of the elements of the hydro-dehydrogenizing function and all of
the phosphorus,
b) drying at a temperature ranging between 75° C. and 130° C. without
subsequent calcination,
c) at least one stage of dry impregnation by an impregnation solution
comprising dimethyl succinate and acetic acid,
d) a maturation stage at 17° C.-50° C.,
e) a drying stage, preferably under nitrogen, at a temperature ranging between
80° C. and 160° C., without subsequent calcination stage.
The catalytic precursor containing the hydro-dehydrogenizing function and an
alumina-based amorphous support, as well as its preparation mode, are described
below.
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