Homogeneous bed of catalyst and a process for transforming...

Details Homogeneous bed of catalyst and a process for transforming... Homogeneous bed of catalyst and a process for transforming...

2000-02-11

2003-01-28

Yildirim, Bekir L. (Department: 1764)

Mineral oils: processes and products

Chemical conversion of hydrocarbons

Reforming

C585S407000, C585S434000, C585S442000, C585S444000, C585S445000, C502S230000, C502S227000, C502S228000, C502S231000

Reexamination Certificate

active

06511593

ABSTRACT:

The present invention relates to a homogeneous bed and catalyst particles with improved bimetallic and bifunctional effects, the catalyst particles having reduced local composition fluctuations, resulting in much improved catalytic performances, in particular as regards activity and gasoline yields. Such a bed is termed “homogeneous on a micronic scale”. Such particles can even be termed “homogeneous on a nanometric scale”. The invention also relates to a process for transforming hydrocarbons into aromatic compounds using that catalyst, such as a gasoline reforming process and a process for producing aromatic compounds.
Catalysts for gasoline reforming and/or for aromatic compound production are well known. They generally contain a matrix, at least one noble metal from the platinum family, at least one halogen and at least one promoter metal, also known as an additional metal.
Of the promoter metals, tin in particular is used for regenerative processes and rhenium is used for fixed bed processes.
Catalysts for gasoline reforming and/or for aromatic compound production are bifunctional catalysts having two functions which are essential for producing the correct performances: a hydro-dehydrogenating function which dehydrogenates naphthenes and hydrogenates coke precursors, and an acid function which isomerises the naphthenes and paraffins and cyclises long paraffins. The hydro-dehydrogenating function can be provided by an oxide such as molybdenum oxide MoO
3
, chromium oxide Cr
2
O
3
or gallium oxide Ga
2
O
3
, or by a metal from column 10 (Ni, Pd, Pt). Metals, in particular platinum, are known to be much more active than oxide phases for hydro-dehydrogenating reactions, and for this reason metallic catalysts have replaced supported oxide catalysts when reforming gasoline and/or producing aromatic compounds. However, metals such as Ni, and to a lesser extent palladium and platinum, also exhibit a hydrogenolysing activity, to the detriment of the desired gasoline yields when reforming gasoline and/or when producing aromatic compounds. This hydrogenolysing activity can be substantially reduced, and thus the catalyst selectivity can be increased, by adding a second metal such as tin. Further, adding a second metal such as iridium or rhenium increases the hydrogenating properties of the platinum, encouraging hydrogenation of coke precursors and thus increasing the catalyst stability. These various reasons have encouraged the success of bimetallic catalysts over first generation monometallic catalysts. More recently, trimetallic catalysts have been introduced, which retain the increased stability of bimetallic catalysts while increasing the gasoline selectivities of such catalysts.
Selectivity can be increased by various means. In the prior art, U.S. Pat. No. 5,128,300 recommends, for catalyst extrudates, a homogeneous distribution of tin with a local composition fluctuation of no better than 25% about the average tin content, that being 0.1-2% by weight of the catalyst.
We have discovered, and this constitutes the subject matter of the present invention, that catalyst performances could be substantially improved not only by limiting the variation of a single element, but by controlling the relative fluctuations of the ratio of the concentrations (compositions) of noble metal (platinum) to the additional metal and/or of the concentrations (compositions) of noble metal (platinum) to the halogen. Thus homogeneity of the bimetallic noble metal—additional metal effect and/or the bifunctional noble metal-acid effect is obtained in the particle bed which improves the overall performances of the process in which this catalyst is used.
More precisely, the invention is concerned with a catalyst comprising at least one amorphous matrix, at least one noble metal, at least one additional metal M and at least one halogen, and in which, for one catalyst particle, C
Pt
is the local concentration of noble metal, C
M
is the local concentration of additional metal M, and C
x
is the local concentration of halogen, in which catalyst in the form of a homogeneous catalyst particle bed the local dispersion of the value of C
Pt
/C
M
or C
Pt
/C
x
is termed homogeneous, which corresponds to at least 70% of the values C
Pt
/C
M
or C
Pt
/C
x
for the catalyst particle bed deviating by a maximum of 30% from the local average ratio.
The amorphous catalyst matrix is generally a refractory oxide such as magnesium, titanium or zirconium oxide, alumina or silica, used alone or mixed together. The preferred support contains alumina or it is alumina.
For gasoline reforming reactions and/or aromatic compound production reactions, the preferred matrix is alumina, and advantageously the specific surface area is 50-600 m
2
/g, preferably 150-400 m
2
/g.
The catalyst also contains at least one noble metal from the platinum family (Pt, Pd, Rh, Ir), preferably platinum. The catalyst can advantageously contain a noble metal (such as Pt) and also iridium.
The additional metal M is selected from the group formed by tin, germanium, lead, gallium, indium, thallium, rhenium, manganese, chromium, molybdenum and tungsten. In the case of processes for reforming gasoline and/or for producing regenerative aromatic compounds in a moving bed, the preferred metal is tin, and very advantageously it is associated with platinum (catalysts containing Pt, Sn) and more advantageously, the catalyst further contains tungsten (catalysts containing Pt, Sn, W).
In fixed bed processes, the preferred metal is rhenium; very advantageously it is combined with platinum (catalysts containing Pt, Re); more advantageously still, the catalyst contains indium (catalysts containing Pt, Re, In); further, tungsten can be present (catalysts containing Pt, Re, W or Pt, Re, In, W).
The halogen is selected from the group formed by fluorine, chlorine, bromine and iodine. Chlorine is preferred.
The catalyst generally contains 0.01% to 2% by weight of a noble metal, 0.1% to 15% of a halogen and 0.005% to 10% of an additional metal. Preferably, the catalyst also contains at most 2% of additional metal M, and very advantageously better than 0.1% of that metal. Under these preferred conditions, the catalyst will perform better due to the optimised bimetallic effect.
It should also be noted that the catalyst used in gasoline reforming and/or aromatic compound production processes preferably contains practically no alkali.
The catalyst is in the form of a bed in the form of particles which may be beads, extrudates, three-lobed particles or any other routinely used form.
C
Pt
is the local concentration of noble metal (expressed in % by weight) (the noble metal not necessarily being platinum), C
M
is the local concentration (by weight) of the additional metal and C
x
is the local concentration (by weight) of halogen.
The concentrations can also be expressed in atomic %, as the relative fluctuations will be the same.
The overall composition of the catalyst can be determined by X ray fluorescence carried out on the powdered catalyst or by atomic absorption after acid attack of the catalyst.
In contrast to the overall composition of the catalyst, the local composition on the micronic scale can be measured using an electronic microprobe and can if necessary be complemented by STEM (scanning transmission electron microscopy). This measurement can be made by determining the platinum and additional metal contents in some zones of a few cubic microns along the diameter of a catalyst particle, termed the measurement units. This measurement enables the macroscopic distribution of the metals inside the particles to be determined.
The analyses are carried out using a JEOL JXA8800 electronic microprobe (preferred apparatus) or if necessary using a CAMEBAX type Microbeam, each provided with four wavelength dispersion spectrometers. The acquisition parameters were as follows: acceleration voltage 20 kV, current 30 nA, Pt M&agr;, Sn L&agr;, Cl K&agr; lines, and count time 20 s or 40 s depending on the level of concentration. The particles (in the figures they were beads) were coat

Affiliated with

Also associated with

Rating

Homogeneous bed of catalyst and a process for transforming... does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Homogeneous bed of catalyst and a process for transforming..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Homogeneous bed of catalyst and a process for transforming... will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3004897