FR2667587A1 - Ternary molybdenum chalcogenide materials deposited on support - are prepd. as catalysts for oxy-chloration of hydrocarbon cpds., by reducing mixt. of molybdenum an metal using hydrogen@ - Google Patents

Abstract

Chalcogenides (I) of formula MxMO6Se; x = integer of 0-4; M = metal; deposited on a support, are claimed. (A) Prepn. of (I) by (1) inserting M in Mo6Se in presence of current of gas, or (2) reducing mixt. of MoS2 and a metal M, or their precursors, using H2. (B) Prepn. of (I) on support by redn. with H2 of porous support impregnated with MoS2 and M or their precursors, partic. with such support prepd. starting from Ni-Mo-S or Co-Mo-S alloys deposited thereon, opt. as hydrodesulpuration catalyst. USE/ADVANTAGE - Catalyst in oxychloration of hydrocarbons, partic. of ethylene to 1,2-dichloroethane (II) which is then pyrolysed to vinyl chloride, HCl as co-prod. being recycled to oxychloration process. (I) have greater mechancial resistance than conventional oxychloration catalysts (III) (Cu on porous support such as alumina), and give, partic. when mixed with (III), improved conversion and selectivity compared with (III). (Dwg.0/0)

Description

 The present invention relates to oxychlorination catalysts based on ternary chalcogenides of molybdenum. 1,2-Dichloroethane (D 12) is a product produced industrially at a rate of several million tons per year, which by pyrolysis gives vinyl chloride monomer (VCM) and hydrochloric acid (HCl). VCM is polymerized into poly (vinyl chloride) (or PVC) plastic material commonly used. The HCl obtained by pyrolysis is separated from the VCM and is then contacted with ethylene and oxygen in the presence of a catalyst to give D 12, the oxychlorination reaction. This reaction is very general and can be done with most hydrocarbons.

Oxychlorination has been described in numerous patents, in particular in FR 2 063 365, FR 2 260 551 and FR 2 242 143,
FR 2 213 259 and FR 2 125 748. The catalyst consists of a copper salt deposited on powdered alumina.

 A new oxychlorination process has now been found in which the catalyst is a ternary chalcogenide of molybdenum containing copper.

The present invention is therefore a process for the oxychlorination of a hydrocarbon to form a chlorinated hydrocarbon in which the hydrocarbon, an oxygen-containing gas and gaseous hydrochloric acid pass over a feed comprising a ternary chalcogenide of molybdenum containing copper and formula:
Cux Mo6 Ch8 where x is any number between 0 and 4 and Ch represents sulfur, selenium or tellurium.

 These chalcogenides may be pseudo-molecular compounds based on the Mog Ch8 motif which constitutes a host network with a rigid structure, developing intersecting channels in the three dimensions in which Cu cations are housed.

 These pseudo-molecular phases can also be presented as several nested networks: a network of metal atoms (the Mo6 octahedron) inscribed in a pseudo-cubic anionic network of chalcogen ("cube" Ch8), finally a network of tunnels that develop between Mo6 Ch8 patterns.

These tunnels are then occupied by Cu cations that stabilize the structure. These chalcogenides crystallize in the hexagonal-rhombic system.

 These chalcogenides are usually used in the form of powders or granules.

The hydrocarbon may be a mixture of several hydrocarbons chosen from C1 to C7 aliphatic hydrocarbons.
C20, cycloaliphatics up to C12 and aromatics having up to four fused benzene rings as well as their chlorinated substitution derivatives. They can be chosen for example from methane, ethane, propane, ethylene and propylene. the invention is particularly useful for ethylene. The oxygen-containing gas is simply air but can also be used, depleted or enriched with oxygen.

 The purpose of oxychlorination is essentially to use hydrochloric acid as a source of chlorine. The amount of oxygen and of hydrocarbon is thus adjusted to obtain approximately stoichiometrically the chlorinated hydrocarbon while consuming the maximum of HCl and hydrocarbon.

bien qu'on puisse opérer en lit fixe ou en lit fluidisé, on préfère le lit fluidisé.In the case of ethylene the reaction is

although it is possible to operate in a fixed bed or in a fluidized bed, the fluidized bed is preferred.

 When operating with a catalyst arranged in a fluidized bed, the temperature at which the oxychlorination reaction is carried out is usually between 150 and 450 ° C. Preferably, this temperature is between 200 and 3000 ° C.

 The pressure at which the oxychlorination reaction is carried out is not critical in itself. Usually, one operates with pressures between 1 and 10 atm and preferably with pressures between 1 and 8 atm.

 The fluidization rate of the catalyst compositions is not critical in itself and depends essentially on the particle size of the catalyst and the dimensions of the equipment. Generally, one operates with speeds between 5 and 100 cm / s and preferably between 10 and 50 cm / s.

 Finally, the ratio of the reagents used is the same as that generally used in the previous processes.

Usually, one operates with a slight excess of ethylene with respect to the amount of HCl used. However, the catalytic compositions of the invention also make it possible to work in the vicinity of the stoichiometry, or even in excess of HCl.

 All these operating conditions are known from the prior art.

 The advantage of the invention is that the catalyst is much more mechanically resistant than the oxychlorination catalysts of the prior art, however the performance in hydrocarbon conversion of hydrochloric acid and selectivity to dichloroethane are not good. .

 The Applicant has discovered that if we add to these chalcogenides of known oxychlorination catalysts, we obtain higher performance than known catalysts.

These known catalysts refer to conventional catalysts made of copper deposited on a porous support which may be alumina, that is to say that one operates with a mixture of chalcogenide and conventional catalysts. These are, for example, the catalysts described in patents FR 2 125 748,
FR 2 063 365, FR 2 141 452, EP 57796, EP 62320, EP 119933 and
EP 255156.

 These known catalysts are advantageously substantially alumina-based powders with a particle size of between 20 and 200 d and a surface area of between 90 and 450 m 2 / g and preferably between 30 and 90 μl and between 250 and 400 m 2 / g. These powders are impregnated with copper or a copper salt in an amount of up to 10%, and preferably 3 to 10% by weight of the copper relative to the finished catalyst.

 The Applicant has also discovered that oxychlorination catalysts which are themselves a mixture of an oxychlorination catalyst and a catalytically and chemically inert solid substance can be added to these chalcogenides. That is, one operates with a mixture of a chalcogenide, a conventional oxychlorination catalyst and an inert substance. Oxychlorination catalysts consisting of a mixture of catalyst and an inert substance are described in patent FR 2 242 143.

 By way of example, as a catalytically and chemically inert substance, mention may be made of glass or silica micro-beads, alpha-alumina and, preferably, silica sand which is found in the natural state and whose distribution is granulometric particle size is adapted to the needs of the fixed bed or the fluid bed.

 Advantageously, the size of the inert particles is between 20 and 200.

 The amount of inert substance can vary within wide limits. Advantageously, the amount of inert may represent from 1 to 20 times by weight the amount of catalyst, that is to say of the total chalcogenide and conventional oxychlorination catalyst.

 The Applicant has also discovered that it is possible to add to these chalcogenides non-impregnated catalyst support, that is to say alumina powders containing no copper. These are, for example, powders having a particle size of between 20 and 200 μm and a surface area of between 90 and 450 m 2 / g which have been mentioned previously but which are not impregnated with copper.

In addition to the unpregnated catalyst support, it is also possible to add a catalytically and chemically inert solid substance. This substance was previously defined micro-glass or silica beads, alpha alumina
The oxychlorination process of the invention can therefore be carried out with the following catalytic charges
chalcogenides,
a mixture of chalcoaenides and conventional oxychlorination catalysts and optionally a catalytic and chemically inert substance,
a mixture of chalcogenides and non-impregnated catalyst support and optionally a catalytic and chemically inert substance.

These catalytic fillers can be used in a fixed bed or in a fluidized bed. The preceding chalcogenides, that is to say the chalcogenides Cux Mo6 Ch8, are known (J. Solin
State Chem. 3, 515, 519 (1971), however, the catalytic charges comprising a mixture of chalcogenides and conventional oxychlorination catalysts and optionally a catalytic and chemically inert substance are new.

 The same applies to mixtures of chalcogenides and non-impregnated catalyst support and possibly a catalytic and chemically inert substance.

 The present invention thus also relates to these catalytic charges.

 These chalcogenides can be prepared according to a method described in J. Solid State Chem. 3515-519 (1971).

 The various constituents in the form of element or sulphide are intimately mixed in an agate mortar and then the powder is pelletized, introduced into a silica tube, sealed under dynamic vacuum (10 -2 mmHg, Argon). The chalcogenide is obtained after heating to about 750 C. To have a pure product it is often useful to carry out several cycles: grinding - pelletizing - annealing. All these operations are done under a controlled atmosphere in a glove box under Argon.

 This process makes it possible to prepare only small quantities. The applicant has found a process that can be used on an industrial scale and which also makes it possible to prepare a whole family of chalcogenides.

 The invention is therefore a process for the preparation of chalcogenides of formula Mx Mo6 S8 in which x is any number between 0 and 4 and M denotes a metal, characterized in that a hydrogen reduction of a mixture is carried out. MoS2 and metal M or their precursors. The metal M may be, for example, an alkali metal, an alkaline earth metal, an element of column 3b of the periodic table of the elements, a lanthanide, an actinide, lead, tin, magnesium, zinc, manganese, cadmium, copper, nickel, iron or cobalt.

We would not go beyond the scope of the invention by using
MoS2 and a precursor of the metal M, the metal M and a precursor of MoS2, a mixture of MoS2, a precursor of MoS2 and a metal M or any combination. The reduction with hydrogen can be carried out simply by bringing the hydrogen into contact with the MoS 2 mixture, M.

It can be operated at any pressure of hydrogen, the temperature is between 450 and 1100 ° C, the precursors of MoS2 and M are products which, under these hydrogenation conditions, give MoS2 or M.The precursor of MoS2 can be for example
(NH4) 2Mo3Sl3 or (NH4) 2MoS4
The precursor of the metal M can be a salt such as a chloride, a sulphide, a nitrate, a sulphate, or an acetate. The proportions of MoS2 and M in the mixture before the hydrogenation are adjusted according to the desired chalcogenide and the particular reactivities of M or its precursor. There may also be mixed precursors, for example Cu (NH4) MoS4.

Depending on the chalcogenide one wants to manufacture, they can be used alone or with other precursors of the metal or MoS2.

 It is not necessary to isolate MoS2 or M before preparing the chalcogenide, that is to say that the reagents MoS2 and M are made in situ, and that the reaction continues towards the chalcogenide.

 The MxMo6S8 chalcogenides have the same structure as the CuxMo6Ch8 chalcogenides mentioned above, that is to say that there is a No6S8 pattern which creates a host network of rigid structure. These chalcogenides crystallize in the hexagonal rhombohedral theme.

 The invention also relates to a process for the preparation of chalcogenides of formula NxHo6S8 in which x is any number between 0 and 4 and M denotes a metal, characterized in that an insertion of the metal M into existing Mo6S8 is carried out in the presence of a stream of gas.

 The metal can be used in the state or one of its salts.

It is sufficient to mix the metal and Mo6S8 preferably each being in a divided state and heat while the reaction mixture is swept with a gas. It is advantageous to use nitrogen. The temperature can be between 220 and 400 C.

The present invention also relates to a chalcogenide of formula MxMo6S8 in which x is any number between
O and 4 and M denotes a metal characterized in that it is deposited on a porous support.

 These chalcogenides are those which have just been mentioned a preparation process. The porous support may be alumina, silica, silico aluminas, graphite, charcoal, TiO 2, ZrO 2, and generally anything that is used as a catalyst support. Mention may be made more particularly of alumina powders with a particle size of between 20 and 200 μm and a surface area of between 90 and 450 m 2 / g, and preferably between 30 and 90 μm and between 250 and 400 m 2 / g.

 The chalcogenides supported with M being copper are useful as oxychlorination catalysts for hydrocarbons.

These supported chalcogenides can be prepared by impregnating the precursor support with MoS2 and metal M, and then reducing with hydrogen. The precursors of
MoS2 and M are those previously mentioned. The precursor can also be prepared in situ in the pores of the support, for example (NH4) 2MoS4 can be prepared by reaction between the para-methylbdate (NH4) 6Mo7024-4H2O in solution in
NH40H with H2S. For example (NH4) 2Mo3S13 can be prepared by reacting (NH4) 6Mo7024-4H20 with ammonium polysulfide.

The latter itself being prepared by the action of H2S with a solution of NH40H and sulfur (Chem Ber 112, 778-780).
1979).

 These supported chalcogenides can also be prepared starting from a product already deposited on a porous support but not in the form of chalcogenides.

 For example, it is possible to use an existing hydrodesulfurization catalyst such as a Ni-Mo.S or Co-Mo-S alloy deposited on alumina. It is then sufficient, for example, to sulphurize it and then carry out the reduction with hydrogen.

 The following examples were carried out at the CNRS in the laboratory of solid and inorganic molecular chemistry at the University of Rennes (France), and in the laboratories of the ATOCHEM Company.

EXAMPLE 1 - SYNTHESIS Cu2 5Mo6S8 IN TUBE SEALED
We blend
2.5 Cu + 4 MoS2 + 2 Mo
We pellet the powders. It is introduced into a sealed silica tube under dynamic vacuum (10'2 mmHg pressure). Annealed at 800 C for 70 hours. The powder obtained has an X-ray diffraction pattern. The product crystallizes in the hexagonal rhombohedral system.

Mesh parameter in the hexagonal system: a = 9.6
C = 10.2 A (MoS2 may remain as impurity).

EXAMPLE 2 - SYNTHESIS Cu2Mo6S8 BY HYDROGEN REDUCTION
0.4107 g (NH4) 2MoS4 + 0.0901 g CuCl2, 2H20
Mix, grind the powders in an agate mortar and put in a nacelle of silica. Reduction in a horizontal oven at 700 ° C for 89 hours, with a flow rate
H2 # 1.5 ml / s identification by RX: hexagonal mesh parameter: a = 9.60 A c = 10.22 A (if MoS2 remains, the reaction is not complete, continue the reduction).

MoS2 identified by RX diffraction pattern
ASTM No. 6-0097
and
n 9-312
EXAMPLE 3 - SYBPHESE CUxMO6S8 / E2 3
(Chalcogenide deposited on a porous support)
1 - Precursor imprinting
0.4107 g (NH4) 2MoS4 is dissolved in 6.5 ml concentrated ammonia and 12 g Al2O3 are added. It is left for 24 hours in a desiccator filled with P2O5 and under vacuum.

In a horizontal oven, H2 for 8 minutes, the time to raise the oven temperature from ambient to 400 C, flow
H2 # 0.5 ml / s = product A.

0.0901 g CuCl 2 2H 2 O is dissolved in 8 ml of
NH40HCC and product A is added. 75 hours are left in a desiccator filled with P2O5 and under vacuum. We proceed to the reduction of totality under H2 # 1.5 ml / s for 89 hours, in a horizontal oven. Some pellets are taken. They are placed in a dynamic vacuum sealed silica tube and annealed for 24 hours at 900.degree.

2 - Hentamolsbdate routes 2 different processes
1) Airway
1.5 g (NH4) 6MO7024.4H2O and 1.36 g Cu (NO3) 2.3H2O are dissolved in 5 ml of concentrated ammonia. 10 g of Al 2 O 3 are added and the mixture is left in the ambient air for 1 h 30. The mixture is heated in air at 120 ° C. for 2 hours. Calcination under air at 350 ° C. for 2 hours. Calcination under air at 500 ° C. for 2 hours over a fraction of 10 granules (mass <1 g). Sulfurization with H2S at 4000C for 30 minutes. H2 & num reduction; 1.5 ml / s for 49 hours. Identification by
EXAFS:: Threshold K of the Mo of a mixture CUxHo6S8 and MoS2 the value of x is not known but x> 2.

2) Pathway (H2, N2)
1.5 g (NH4) 6Mo7O24.4H2O and 1.36 g Cu (NO3) 2.3H2O are dissolved in 5 ml NH40HCC. 10 g of
A1203 in granules and left in ambient air for 1 hour 30 minutes.

Nitrogen sweep at 120 ° C. for 3 hours. Hydrogen for 16 hours at 200 ° C. then for 2 hours at 240 ° C. then 67 hours at 245 ° C. Nitrogen at 500 ° C. for 24 hours.

 On a fraction of 10 granules (~ 500 mg).

H2S Sulphurization at 400OC for 30 minutes. Reduction under
H2 &num; 1.5 ml / s for 49 or 89 hours. Identification by
EXAFS: Threshold K of Mo of a mixture CUxHo6S8 and MoS2.

 EXAFS measurements at the K threshold of the Mo result from comparisons between the impregnated products described above and crystallized powders, reference Cu4Mo6S8 and MoS2 (syntheses in sealed tube).

 We carried out the measurements on the reference compounds because there is no library on Cu4Mo6S8 in EXAFS at the K threshold of Mo. There are biblio references for MoS2.

EXAMPLE 4
The oxychlorination tests are carried out in the following equipment. The reactor is a vertical glass tube charged with catalyst. It is fed with gas at the bottom allowing its fluidization. Thermocouples placed in a glass sheath in the middle of the reactor follow the evolution of the temperature both in time and according to the height in the catalyst bed. At the outlet of the reactor, the gases pass on a slaughter column which, by washing with distilled water, recovers all the HC1 which has not reacted. The latter is found in a separatory funnel. The remainder of the gas then passes successively through a water cooler, a brine condenser (t = -5 ° C.) where the solvents recovered in another separating funnel are condensed, and then sample blisters. for the dosages of the remaining gases are scanned before reaching a volumetric meter whose measurement gives the gas flow output. The temperature reading at this level is used to evaluate the correction required to return to TPN conditions (normal temperature and pressure). The atmospheric pressure is read on a mercury manometer.

So there are three different types of samples that lead to the results after analysis
an aqueous solution of HCl
condensed solvents, of which D 12 is
- Exit gases: CO, CO2, D12, and unreacted reagents: C2H4, air.

 A) a conventional 357 m 2 / g surface alumina catalyst, 53 μm average diameter, 33 cm 3/100 g porous volume impregnated with copper chloride and an inert substance which is silica of average diameter. 50 μm and ranging from 20 to 300 μm; with b) a catalyst formed of a chalcogenide Cu2 5No6S8, alumina and an inert substance (silica). Alumina and silica have the same characteristics as in the case of the absence of copper.

 The results are shown in Table 1.

TABLE 1
Overnight conditions:
- power supply: C2H4 4.4 Nl / h
AIR 16.2 Nl / h
HC1 8.6 Nl / h
- reactor diameter 20 mm

<tb><SEP> Cu2 <SEP> 5Mo658 <SEP> 4.25 <SEP> g <SEP> alumina <SEP> with <SEP> copper <SEP> 9.70 <SEP> g
<tb><SEP> A1203 <SEP> 6.00 <SEP> g <SEP> SiO2 <SEP> 23.60 <SEP> g
<tb><SEP> SiO2 <SEP> 22.60 <SEP> g <SEP> conventional <SEP> catalyst
<tb> Quantity <SEP> Cu <SEP> 0.68 <SEP> 0.58
<tb><SEP> (g)
<tb> T <SEP>("C)<SEP> 230 <SEP> 240
<tb> Rate <SEP> of
<tb> conversion <SEP> of <SEP> 78.5 <SEP> 72.3
<tb> C2H4 <SEP>
<tb> Selectivity <SEP> 99.2 <SEP> 99.1
<tb> in <SEP> D <SEP> 12
<Tb>
The catalytic charge of the invention proves better conversion and selectivity (the selectivity expresses the converted C2H4 fraction that has been converted to
D 12).

EXAMPLE 5 - OXYCHLORATZON
Flow rates used at the reactor inlet
air: 12.2 Nl / h C2H4: 4.4 Nl / h HC1: 8.6 Nl / h for 1.2 g of copper for 59 g of catalytic charge tested in total (Cu included), except test 2.

Definitions
XG conversion rate of C2H4
HCl conversion rate
ZG conversion rate of 2
List of tests
1 A1203: 12.0 g 2 Cu2 5Mo6S8: 63.9 g
sio2: 39.6 g
Cu2 5Mo6S8: 7.4 g
4 Al2O3: 51.6 g 6 Same as 4
Cu2.5Mo6S8: 7.4 g
A1203: 29.0 g
CuCl2 / Al2O3: 30.0 g
(4% Cu)
16 A1203: 55.8 g
CuCl22H2O: 3.2 g
The alumina impregnated or not with copper (Al 2 O 3) used in the above tests is identical to that of Example 4. It is the same for silica.

TABLE 2

<tb><SEP> Temp. <SEP> time <SEP> XG <SEP> YG <SEP> ZG <SEP> makes <SEP> rende- <SEP> selec
<tb> test <SEP> time <SEP> (C) <SEP> of <SEP> SE <SEP>% <SEP>% <SEP>% <SEP> ment <SEP> ment <SEP> tivity
<tb><SEP> day (s) <SEP> CO + C02 <SEP> C1 + C2 <SEP> D12
<tb><SEP> 1 <SEP> 4:25 <SEP> 249 <SEP> 4.5 <SEP> 88.3 <SEP> 64.9 <SEP> 78.6 <SEP> 0.7 <SEP> 1.7 <SEP> 97.3
<tb><SEP> 2 <SEP> 0:15 <SEP> 264 <SEP> 4.8 <SEP> 3.1 <SEP> 2.1 <SEP> 17.1 <SEP> 1.7 <SEP> 0.3 <SEP> 36.0
<tb><SEP> 4 <SEP> 4:00 <SEP> 216 <SEP> 5.9 <SEP> 32.2 <SEP> 42.8 <SEP> 26.1 <SEP> 0.8 <SEP> 3.1 <SEP> 87.9
<tb><SEP> 6 <SEP> 4:00 <SEP> 249 <SEP> 5.6 <SEP> 54.4 <SEP> 46.5 <SEP> 64.2 <SEP> 8.5 <SEP> 5.0 <SEP> 75.2
<tb><SEP> 16 <SEP> 4:00 <SEP> 241 <SEP> 5.8 <SEP> 26.6 <SEP> 16.9 <SEP> 11.3 <SEP> 0.4 <SEP> 13.5 <SEP> 47.8
<Tb>
C1 and C2 denote C1 and C2 chlorine products other than D 12.

EXAMPLE 6
Synthesis CuxMo6S8 by insertion into Mo6S8 under nitrogen. The synthesis of Mo6S8 is described in Rev. Chim. Min. 21, 509 (1984).

 We inserted copper in Mo6S8 under nitrogen at a temperature greater than or equal to 200 C. The starting copper may be metallic, or in the form of copper chlorides.

The reagents are in stoichiometric proportions
Mo: Cu = 6: x.

EXAMPLE 7
Synthesis CuxMo6S8 / Al2O3 from existing catalyst type: MoO3, NiO / Al2O3 (Mo: 9% -Ni + Mo: 12%) A1203 large area.

Process
500 mg sulfonation with 15% H2 / H2S at 400 ° C for 4 hours.

 The reduction is then carried out under H2 at 800 ° C. for 66 hours (flow rate H2 different or equal to 1 ml / s). The product is identified by its RX diffraction pattern after vacuum sealed tube annealing at 900 ° C for 24 hours.

Claims (5)

 1. Chalcogenides of formula MxMo6S8 in which x is any number between 0 and 4 and M denotes a metal, characterized in that it is deposited on a porous support.  2. Process for the preparation of chalcogenides according to claim 1, characterized in that a hydrogen reduction of the porous support impregnated with MoS2 and M or their precursors.  3. Method according to claim 2, characterized in that the preparation of the precursor impregnated support is made from Ni-Mo-S or Co-Mo-S alloys deposited on a porous support, the assembly may be already a hydrodesulfurization catalyst.  4. Process for the preparation of chalcogenides of formula MxMo6S8 in which x is any number between 0 and 4 and M denotes a metal, characterized in that an insertion of the metal M into existing Mo6S8 is carried out in the presence of a gas stream. .  5. Process for the preparation of chalcogenides of formula MxMo6S8 in which x is any number between 0 and 4 and M denotes a metal, characterized in that a reduction is carried out with hydrogen of a mixture of MoS2 and metal M or their precursors.