U.S. patent application number 10/359191 was filed with the patent office on 2003-09-25 for catalytic system for the production of olefins.
This patent application is currently assigned to SNAMPROGETTI S.p.A.. Invention is credited to Basini, Luca, Guarinoni, Alessandra, Sanfilippo, Domenico.
Application Number | 20030181778 10/359191 |
Document ID | / |
Family ID | 11449116 |
Filed Date | 2003-09-25 |
United States Patent
Application |
20030181778 |
Kind Code |
A1 |
Basini, Luca ; et
al. |
September 25, 2003 |
Catalytic system for the production of olefins
Abstract
Catalytic system for partial oxidation reactions of hydrocarbons
characterized in that it contains: one or more metals belonging to
the 1.sup.st, 2.sup.nd, and 3.sup.rd transition series; one or more
elements of group IIIA, IVA or VA, wherein at least one of said
metals or said elements is in the form of a nitride.
Inventors: |
Basini, Luca; (Milan,
IT) ; Sanfilippo, Domenico; (Paullo, IT) ;
Guarinoni, Alessandra; (Piacenza, IT) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
SNAMPROGETTI S.p.A.
San Donato Milanese
IT
|
Family ID: |
11449116 |
Appl. No.: |
10/359191 |
Filed: |
February 6, 2003 |
Current U.S.
Class: |
585/658 ;
502/200; 585/659; 585/667 |
Current CPC
Class: |
C07C 2523/42 20130101;
C07C 2523/14 20130101; B01J 23/626 20130101; C07C 5/48 20130101;
C07C 11/04 20130101; C07C 11/02 20130101; C07C 2523/652 20130101;
C07C 2527/24 20130101; C07C 2523/62 20130101; C07C 5/48 20130101;
C07C 2523/644 20130101; B01J 23/8926 20130101; B01J 23/62 20130101;
B01J 27/24 20130101; Y02P 20/52 20151101; C07C 5/48 20130101; C07C
2523/89 20130101 |
Class at
Publication: |
585/658 ;
502/200; 585/659; 585/667 |
International
Class: |
B01J 027/24 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 6, 2002 |
IT |
MI2002A 000214 |
Claims
1) A catalytic system for catalytic partial oxidation reactions of
hydrocarbons containing: one or more metals belonging to the
1.sup.st, 2.sup.nd and 3.sup.rd transition series one or more
elements of group IIIA, IVA or Va characterized in that at least
one of said metals or said elements is in the form of a
nitride.
2) The catalytic system according to claim 1, wherein the metal
belonging to the 1.sup.st, 2.sup.nd and 3.sup.rd transition series
is deposited on the nitride or oxy-nitride.
3) The catalytic system according to claim 2, wherein the metal
belonging to the 1.sup.st, 2.sup.nd and 3.sup.rd transition series
deposited on the nitride or oxy-nitride is in a quantity ranging
from 0.05 to 15% by weight.
4) The catalytic system according to claim 1, wherein the element
of group IIIA, IVA or VA is deposited on the nitride or
oxy-nitride.
5) The catalytic system according to claim 4, wherein the element
of group IIIA, IVA or VA deposited on the nitride or oxy-nitride is
in a quantity ranging from 0.05 to 15% by weight.
6) The catalytic system according to claim 1, wherein the metal
belonging to the 1.sup.st, 2.sup.nd and 3.sup.rd transition series
is selected from Pt, Cr, V, Mo, Cu, W, Ru, Zn, Ag, Au, Rh, Mn, Fe,
Co and Ni.
7) The catalytic system according to claim 1, wherein the element
of group IIIA, IVA or VA is selected from Sn, Ga, Pb, Sb, Bi and
Si.
8) The catalytic system according to claims 3 and 5, wherein there
are two or three metals deposited on the nitride or
oxy-nitride.
9) The catalytic system according to claim 8, wherein the two
metals deposited are selected from the combinations Pt--Sn, Pt--Ga
and Pt--Cu.
10) The catalytic system according to claim 8, wherein the three
metals deposited are selected from the combinations Pt--Sn--Cr,
Pt--Sn--Ga and Pt--Sn--Bi and Pt--Sn--Sb.
11) A process for the production of olefins from gaseous paraffinic
hydrocarbons, having from two to 6 carbon atoms, comprising a
partial oxidation of said hydrocarbons with a gas containing
molecular oxygen in the presence of a catalytic system according to
at least one of claims 1 to 10.
12) The process according to claim 11, wherein the partial
oxidation is effected at a temperature ranging from 450 to
1000.degree. C., at a pressure ranging from 1 to 15 Atm and a space
velocity ranging from 5000 to 800000 h.sup.-1.
13) The process according to claim 11, wherein the partial
oxidation is carried out using reactors in which the gas inlet zone
and catalytic zone either have a tubular shape or a sand-glass
shape or a truncated-conical shape.
14) The process according to claim 13, wherein a stream of oxygen,
air or enriched air and a fuel not having the function of directly
producing olefins is sent into the gas inlet zone and a gaseous
stream of paraffinic hydrocarbons is sent into the catalytic
zone.
15) The process according to claim 13, wherein in the
tubular-shaped or sand-glass shaped or truncated-conical shaped
reactor, the catalyst fillings are differentiated so as to have two
or three catalytic beds in series.
16) The process according to claim 15, wherein the catalytic bed
upstream consists of Pt deposited on nitrides or oxy-nitrides and
the catalytic bed downstream consists of Pt, Sn and Ga deposited on
nitrides or oxy-nitrides.
17) The process according to claim 15, wherein the catalytic bed
upstream consists of Pt and Cu deposited on nitrides or
oxy-nitrides and the catalytic bed downstream consists of Pt, Sn
and Ga deposited on nitrides or oxy-nitrides.
18) The process according to claim 15, wherein the catalytic bed
upstream consists of Pt and Ni deposited on nitrides or
oxy-nitrides and the catalytic bed downstream consists of Pt, Sn
and Cr deposited on nitrides or oxy-nitrides.
19) The process according to claim 15, wherein the catalytic bed
upstream consists of Pt deposited on nitrides or oxy-nitrides, the
intermediate catalytic bed consists of Pt and Sn deposited on
nitrides or oxy-nitrides, and the catalytic bed downstream consists
of Pt, Sn and Ga deposited on nitrides or oxy-nitrides.
20) The process according to claim 15, wherein the catalytic bed
upstream consists of Pt and Cu deposited on nitrides or
oxy-nitrides, the intermediate catalytic bed consists of Pt, Sn and
Bi deposited on nitrides or oxy-nitrides, and the catalytic bed
downstream consists of Pt, Sn and Ga deposited on nitrides or
oxy-nitrides.
21) The process according to claim 15, wherein the catalytic bed
upstream consists of Pt deposited on nitrides or oxy-nitrides, the
intermediate catalytic bed consists of Pt and Sn deposited on
nitrides or oxy-nitrides, and the catalytic bed downstream consists
of Pt, Sn and Sb deposited on nitrides or oxy-nitrides.
22) The process according to claim 15, wherein the catalytic bed
upstream consists of Pt and Cu deposited on nitrides or
oxy-nitrides, the intermediate catalytic bed consists of Pt, Sn and
Cr deposited on nitrides or oxy-nitrides, and the catalytic bed
downstream consists of Pt, Sn and Ga deposited on nitrides or
oxy-nitrides.
23) The process according to claim 15, wherein the catalytic bed
upstream consists of Pt and Sn deposited on nitrides or
oxy-nitrides, the intermediate catalytic bed consists of Pt and Sn
deposited on nitrides or oxy-nitrides, and the catalytic bed
downstream consists of Pt, Sn and Ga deposited on nitrides or
oxy-nitrides.
24) A process for the production of olefins from gaseous paraffinic
hydrocarbons, having from two to 6 carbon atoms, comprising a
partial oxidation of said hydrocarbons with a gas containing
molecular oxygen in the presence of a catalytic system effected at
a temperature ranging from 450 to 1000.degree. C., at a pressure
ranging from 1 to 15 Atm and at a space velocity ranging from 5000
to 800000 h.sup.-1, using reactors in which the gas inlet zone and
catalytic zone either have a tubular shape or a sand-glass shape or
a truncated-conical shape, characterized in that a stream of
oxygen, air or enriched air and a fuel not having the function of
directly producing olefins is sent into the gas inlet zone and a
gaseous stream of paraffinic hydrocarbons is sent into the
catalytic zone.
25) The process according to claim 14 or 24, wherein the fuel not
having the function of directly producing olefins is selected from
natural gas, synthesis gas, hydrogen or a mixture of hydrogen and
CO.
Description
[0001] The present invention relates to a catalytic system for the
production of olefins by means of a partial oxidation process of
saturated hydrocarbons such as ethane, propane, isobutane and
naphtha. The catalytic system and the reactor solutions described
provide the possibility of effecting the partial oxidation
reactions of saturated hydrocarbons to olefins also with a low
contact time, at a high temperature and high pressure.
[0002] The main reaction on which the process is based is the
following:
C.sub.nH.sub.2n+1--CH.sub.2CH.sub.2--C.sub.mH.sub.2m+1+0.5O.sub.2.fwdarw.C-
.sub.nH.sub.2n+1--CH.dbd.CH--C.sub.mH.sub.2m+1+H.sub.2O [1]
[0003] Olefins have various uses in the production field of
polymers (for example, polyethylene, polypropylene), copolymers
(for example, synthetic rubbers), plastic materials (for example,
vinyl plastics), basic chemical products (for example, ethylene
oxide, propylene oxide, cumene and acrolein) and high-octane
products (for example, methyl tertbutyl ether).
[0004] Olefins are industrially produced by means of non-catalytic
steam cracking processes and fluid bed or mobile bed or fixed bed
catalytic dehydrogenation processes.
[0005] Steam cracking is the most widely-used process for producing
low molecular weight olefins such as ethylene and propylene and can
treat mixed charges of hydrocarbons such as naphtha. Steam cracking
processes can be divided into three zones where the following
operations take place:
[0006] dehydrogenation reactions of hydrocarbons and the formation
of olefins (hot zone)
[0007] compression of the reaction products
[0008] separation of the reaction products (cold zone)
[0009] The chemical reactions in the steam cracking processes are
pyrolysis reactions which are effected at high temperatures by
passing a stream of saturated hydrocarbons and steam inside coiled
tubes inserted in an oven.
[0010] The formation reactions of olefins [2]
C.sub.nH.sub.2n+2.fwdarw.C.sub.nH.sub.2n+H.sub.2 [2]
[0011] are highly endothermic and the process requires in relation
to the charge used, from 1.6 to 2.8 mJ/kg of product.
[0012] The residence times of the gaseous stream of the reagents
inside the tubes typically vary from 0.1 to 0.15 sec. but there are
also technologies which use residence times of a few
milliseconds.
[0013] The inlet temperatures of the tubes range from
500-700.degree. C., whereas those at the outlet are within the
range of 775-950.degree. C.
[0014] The reaction zone of the plants is modular. The modules have
a capacity of about 100,000 tons/year; as a whole world-scale
plants have a capacity which is even higher than 750,000
tons/year.
[0015] The heat necessary for the steam cracking reactions is
produced by burning hydrocarbons; this causes strong emissions of
CO.sub.2 and NO.sub.x which in many countries must be separated
before the fumes are released into the atmosphere.
[0016] Steam cracking also requires the presence of vapour (30-50%
in the feeding) which decreases the partial hydrocarbon pressure
and reduces coke formation reactions.
[0017] In spite of the presence of vapour, periodical decoking
operations of the plants are necessary. The modular nature of the
plants allows these operations to be cyclically effected without
interrupting the production.
[0018] Only 35-50% of the heat produced by the burners is
transferred to the reagent mixture; thermal recovery and vapour
generation systems, however, increase the overall thermal
efficiency of the process.
[0019] In the case of the production of ethylene, the yields vary
from 50 to 60% on a molar basis depending on the charges used.
Starting from ethane, the yields can range from 57-60% on a molar
basis, with conversion values of ethane which can reach 67% and
selectivity values to ethylene which can reach 83%.
[0020] Catalytic dehydrogenation processes are mainly used for the
production of propylene, butenes and pentenes from pure charges of
propane, isobutane, butane and isopentane (F. Buonomo, D.
Sanfilippo, F. Trifiro, Dehydrogenation Reactions in: "Handbook of
Heterogeneous Catalysis", Vol. 5, pages 2140-2151, G. Ertl, H.
Knozinger, J. Weitkamp Eds. VCH Verlagsgesellschaft mbH,
Weinheim).
[0021] Industrial catalytic dehydrogenation processes are mainly
based on three groups of materials consisting of:
[0022] supported noble metals, mainly represented by Pt/Sn
systems,
[0023] supported chromium oxides
[0024] mixed oxides such as molybdenum and vanadium oxides.
[0025] Systems consisting of Pt/Sn and alkaline metals are used in
the Oleflex technology of UOP and the STAR technology of Phillips
(D. H. James, W. M. Castor, Ullmann's Encycl. Ind. Chem. 5.sup.th
Ed. 1994, Vol. 25, pages 329-344).
[0026] Systems based on chromium oxide are used in the Catofin
technology of UCI-ABB Lummus and FBD technology of
Snamprogetti-Yarsintez.
[0027] The reactor solutions used in catalytic dehydrogenation
technologies comprise a reaction step in which the dehydrogenation
of the hydrocarbon takes place, and a regeneration step of the
catalyst consisting of a combustion process of the carbonaceous
residues accumulated in the reaction step.
[0028] More specifically, the reaction solutions used comprise:
[0029] fixed bed adiabatic reactors (Catofin technology of Lummus)
which operate with rapid reaction and regeneration cycles; wherein
the regeneration cycle has the double function of burning the
carbon accumulated during the reaction and supplying the heat for
the subsequent dehydrogenation reactions (F. Trifiro, F. Cavani,
Oxidative Dehydrogenation and Alternative Dehydrogenation Processes
Catalytica Studies Division Mountain View Calif., USA 1993 Study
Number 4192 OD)
[0030] mobile bed adiabatic reactors (Oleflex technology of UOP)
between which the catalyst is moved and heated and finally sent to
a regeneration step in which the carbonaceous residues are burnt
(P. R. Pujado, B. V. Vora Hydroc.Process 1990, 65)
[0031] fixed bed multi-tubular reactors inserted in ovens analogous
to those of steam reforming processes in which various blocks are
used alternatively in reaction and regeneration cycles (STAR
technology of Phillips, R. O. Dunn, G. F. Schuette, F. M.
Brinkmeyer, W. Sund, Proc. De Witt Petrochem. Review Houston 1991,
1)
[0032] fluid bed reactors in which the catalyst circulates
continuously between a regeneration and reaction reactor conveying
the heat necessary for the dehydrogenation (FBD technology of
Snamprogetti-Yarsintez, D. Sanfilippo, F. Buonomo, G. Fusco, M.
Lupieri, I. Miracca Che.Eng.Sci. 1992, 47, 2313).
[0033] The energy requirements of the reactions and necessity for
transferring heat to the reactions are largely responsible for the
investment costs and energy consumption of the "hot" section of
steam cracking technologies and catalytic dehydrogenation
technologies.
[0034] An alternative method to that so far applied for the
production of ethylene consists of partial oxidation reactions,
also called oxidative dehydrogenation [3].
C.sub.nH.sub.2n+2+1/2 O.sub.2.fwdarw.C.sub.nH.sub.2n+H.sub.2O
[3]
[0035] These reactions are moderately exothermic, they have a low
selectivity towards carbonaceous products and can be carried out in
adiabatic reactors.
[0036] This method has been studied in depth, but since 1992 good
yields of olefinic products have not been obtained (F. Trifiro, F.
Cavani, Oxidative Dehydrogenation and Alternative Dehydrogenation
Processes Catalytica Studies Division Mountain View Calif., USA
1993 Study Number 4192 OD).
[0037] In 1992, L. D. Schmidt et Al. at the University of Minnesota
discovered reaction conditions and catalysts which allowed the
production of yields to ethylene comparable to those of steam
cracking processes and to propylene higher than those of catalytic
processes.
[0038] The reactions are carried out with a low contact time
(.apprxeq.10 ms) and produce olefins from mixtures of the
corresponding saturated alkanes and oxygen/air.
[0039] The results obtained are described in numerous articles in
scientific literature (M. Huff, L. D. Schmidt J. Phys. Chem. 1993,
97, 11815; M. Huff and L. D. Schmidt, J.Catal. 1994, 149, 127; C.
Yokoyama S. S. Bharadwaj and L. D. Schmidt, Catalysis Lett. 1996,
38, 181; A. S. Bodke, D. A. Olshki, L. D. Schmidt E. Ranzi, Science
1999, 285, 712; A. S. Bodke, D. Henning, L. D. Schmidt, S. S.
Bharadwaj, J. J. Maj, J. Siddal, J.Catal. 2000, 191, 62).
[0040] Basic studies were followed by studies on technological
applications which generated patents and patent applications. The
University of Minnesota, Dow Chemical Company and BP-Amoco are the
most active organizations in this field.
[0041] In WO-96/13475 assigned to the University of Minnesota, the
production reactions of olefins with a low contact time are
effected using platinum compounds supported on ceramic foamy
monoliths consisting of oxides selected from those of Al, Zr, Ca,
Mg, Hf and/or Ti.
[0042] U.S. Pat. No. 5,639,929 of the University of Minnesota
claims a partial oxidation process of hydrocarbons to mono-olefins
effected in a fluidized bed using a catalyst selected from Pt, Rh,
Ni and Pt--Au deposited on a carrier in the form of
particulate.
[0043] U.S. Pat. No. 5,905,180 of the University of Minnesota
claims a partial oxidation process for the production of
mono-olefins from paraffins with a catalyst consisting of Pt and Sn
deposited on a foamy ceramic carrier.
[0044] In U.S. Pat. No. 6,072,097 of the University of Minnesota,
the production reactions of mono-olefins are obtained with
catalysts consisting of Pt and Sn or Pt and Cu supported on a foamy
ceramic monolith.
[0045] WO-00/14035 of Dow Chemical Company claims a catalytic
partial oxidation process for the production of olefins effected by
putting paraffins, oxygen and hydrogen in contact with each other.
The patent also claims the possibility of carrying out the
reactions in a fluid bed reactor.
[0046] WO-00/14180 of Dow Chemical Company claims a partial
oxidation process of hydrocarbons with an autothermal process in
the presence of a catalyst comprising at least one metallic
promoter supported on a fibrous monolithic carrier in which the
presence of hydrogen together with oxygen and hydrocarbon is
recommended. The patent also claims a method for regenerating the
catalyst during the reaction conditions
[0047] WO-00/37399 of BP Chemical Ltd. claims a production and
separation process of olefins by means of the partial oxidation of
hydrocarbons comprising a partial oxidation passage of hydrocarbons
and a separation step by means of an interaction with a solution of
a metallic salt capable of selectively absorbing the olefins.
[0048] WO-00/14036 of BP Chemical Ltd. claims a catalytic process
for the production of olefins by means of the partial oxidation of
hydrocarbons carried out in various steps. In a first step,
combustion reactions are effected which do not completely use up
the oxygen; in a second step with a second catalyst, the combustion
products and the non-reacted oxygen are interacted with the other
saturated hydrocarbon causing the total consumption of the oxygen
and olefins.
[0049] Finally, WO-00/15587 of BP Chemical Ltd. claims a catalytic
process for the production of olefins and synthesis gas by means of
the partial oxidation of hydrocarbons.
[0050] In short, the documents of scientific literature and patents
mentioned above describe oxidative dehydrogenation processes
carried out with a low contact time both in fluid bed reactors and
fixed bed reactors. The catalysts described mainly contain Pt and a
second metal such as Sn or Cu deposited on a ceramic carrier such
as a foamy monolith. The patents also describe the possibility of
effecting the oxidative dehydrogenation of mixtures of hydrocarbon
reagents, oxygen and hydrogen. The latter gas allows an improvement
in the selectivities of the reactions reducing the contributions of
oxidations to CO, CO.sub.2 and H.sub.2O.
[0051] The use of premixed streams of hydrocarbons, oxygen and
hydrogen however creates problems relating to safety particularly
when the premixed streams are within flammability and explosivity
curves (as in the case of the mixtures described in the documents
of literature mentioned above).
[0052] Furthermore, due to the high reagent flows, the catalytic
beds must be filled and have such dimensions as to allow low
pressure drops, with the consequent use, in most of the experiments
described in literature, of fluid beds or catalytic beds consisting
of monoliths.
[0053] The great increase in temperature and the increase in the
number of reaction moles [2] may be a further cause of a pressure
drop inside the catalytic bed. The pressure drop can be limited by
an increase in the total pressure, but this increase favours
radicalic reactions in gaseous phase which form by-products with a
high C/H ratio and in particular carbonaceous residues which
deactivate the catalysts.
[0054] Finally, strong changes in temperature and high reaction
temperatures can increase the fragility of the ceramic monoliths
and ceramic pellets making them crumble and can also cause a loss
in active metals such as Pt and Sn.
[0055] A catalytic system has now been found, which has an
exceptional thermal, chemical and mechanical stability and provides
the possibility of carrying out partial oxidation reactions of
saturated hydrocarbons to olefins also with a low contact time, at
a high temperature and high pressure.
[0056] The catalytic system, object of the present invention, for
catalytic partial oxidation reactions of hydrocarbons is
characterized in that it contains:
[0057] one or more metals belonging to the 1.sup.st, 2.sup.nd and
3.sup.rd transition series, preferably selected from Pt, Cr, V, Mo,
W, Cu, Ru, Zn, Ag, Au, Rh, Mn, Fe, Co and Ni;
[0058] one or more elements of group IIIA, IVA or VA, preferably
selected from Sn, Ga, Pb, Sb, Bi, Si,
[0059] wherein at least one of said metals or said elements is in
the form of a nitride.
[0060] With the definite presence of at least one nitride, the
metal (or metals) belonging to the 1.sup.st, 2.sup.nd or 3.sup.rd
transition series can be in the catalytic system in the form of a
nitride (as counter-ion of the nitride or oxy-nitride) and/or
deposited, in a quantity preferably ranging from 0.05 to 15% by
weight, with respect to the nitride or oxy-nitride, whereas the
element (or elements) of group IIIA, IVA or VA can be in the
catalytic system in the form of a nitride (as counter-ion of the
nitride or oxy-nitride) and/or deposited, in a quantity preferably
ranging from 0.05 to 15% by weight, with respect to the nitride or
oxy-nitride.
[0061] Some nitrides of transition metals have intrinsic catalytic
properties, others can be used as carriers of metallic species with
catalytic properties such as, for example, bimetallic or
trimetallic systems (i.e. where there are two or three metals
deposited on the nitride or on the oxy-nitride) preferably selected
from the combinations Pt--Sn, Pt--Ga and Pt--Cu and the
combinations Pt--Sn--Cr, Pt--Sn--Ga, Pt--Sn--Bi and Pt--Sn--Sb,
respectively.
[0062] In particular, the following nitrides can be metioned,
consisting of:
[0063] AlN, Co.sub.3N, Cr.sub.2N, Fe.sub.4N, Mn.sub.4N, MoN, TiN,
WN, VN, Si.sub.3N.sub.4 (for example described in: F. K. Van Dijen,
A. Kerbr, U. Voigt, W. Pfeiffer, M. Schulze, in "Key Engineering
Materials" Vols. 89-91, M. J. Hofmann P. F. Becher and G. Petzow
Eds. TransTech. 1994, pages 19-28; H. Lange, G. Wotting H. Winter,
Angew. Chem. 1991, 103, 1606)
[0064] Si--N--B systems or Si--B--N--C systems such as
Si.sub.3B.sub.3N.sub.7 and SiBN.sub.3C (H. P. Baldus and M. Jansen,
Angew. Chem. Int. Ed. Engl. 1997, 36, 328)
[0065] systems consisting of layers of aluminum nitrides deposited
on oxide carriers by means of atomic layer epitaxy or chemical
vapour deposition (M. E. Bartram, T. A. Michalske, J. W. Rogers, T.
M. Mayer Chem. Mater. 1991, 3, 353; M. E. Bartram, T. A.
Michalscke, J. W. Rogers, R. T. Paine, Chem. Mater., 1993, 5, 1424;
C. Soto, V. Boiadjiev, W. T. Tysoe, Chem. Mater. 1996, 8, 2359)
[0066] oxy-nitride systems described in P. W. Lednor and R-de
Ruter, J.Chem.Soc. Chem. Comm. 1991, 1625
[0067] The above materials are representative but non-limiting of
the group of nitrides which can be used, as the only limitations
relate to stability under the reaction conditions.
[0068] The above systems in fact have proved to have considerable
resistance to the thermal and mechanical stress which is produced
during the start up reactions and shutdown of the reactions and
also have a high thermal stability under the reaction conditions
particularly at temperatures higher than 1000.degree. C.
[0069] The nitrides AlN, Co.sub.3N, Cr.sub.2N, Fe.sub.4N,
Mn.sub.4N, MoN, Si.sub.3N.sub.4, TiN, WN, VN, can be prepared for
example by means of the reactions [4-7] (as described in The
Chemistry of Transition Metal Carbides and Nitrides, S. T. Oyama
Ed., Blackie Academic Professional, Glasgow, 1996).
M.sub.xO+C+1/2 N.sub.2.fwdarw.M.sub.xN+CO [4]
M+NH.sub.3.fwdarw.MN+3/2 H.sub.2 [5]
M.sub.xO+NH.sub.3.fwdarw.M.sub.xN+H.sub.2O+1/2 O.sub.2 [6]
M.sub.xCl+N.sub.2/H.sub.2.fwdarw.M.sub.xN+HCl [7]
[0070] wherein M=Al, Cr, Ti, V, Mo, Mn, Co, Fe, W
[0071] Bimetallic nitrides containing transition metals of groups
VIB and VIII can be prepared according to reaction [8] as described
in EP 1036592; C. J. H. Jacobsen, Chem. Comm. 2000, 1057
M'.sub.xM".sub.yO.sub.z+H.sub.2+NH.sub.3.fwdarw.M'.sub.xM".sub.yN+H.sub.2O
[8]
[0072] Whereas Si--N--B systems or Si--B--N--C systems such as
Si.sub.3B.sub.3N.sub.7 and SiBN.sub.3C are prepared as described in
P. Baldus, M. Jansen, D. Sporn, Science 1999, 285, 699 according to
the reactions:
Si(CH.sub.3).sub.3--NH--Si(CH.sub.3).sub.3+SiCl.sub.4.fwdarw.Si(CH.sub.3).-
sub.3--NH--SiCl.sub.3+Cl--Si--(CH.sub.3) [9]
Si(CH.sub.3).sub.3--NH--SiCl.sub.3+BCl.sub.3.fwdarw.BCl.sub.2--NH--SiCl.su-
b.3+Cl--Si--(CH.sub.3) [10] 1
[0073] Systems consisting of layers of aluminum nitrides deposited
on oxide carriers (for example Al.sub.2O.sub.3) can, on the other
hand, be obtained by means of consecutive adsorptions of aluminum
alkyls (for example Al(CH.sub.3).sub.3) and ammonia on oxide
surfaces so as to obtain the reaction [13] with a method described
for example in: A. Dabrowski "Adsorption and its application in
industry and environmental protection, Studies in Surf. Sci. and
Catalysis 1999, 120A, 715; C. Soto, V. Bojadjiev, W. T. Tysoe Chem.
Mater. 1996, 8, 2359.
Al(CH.sub.3).sub.3+NH.sub.3.fwdarw.AlN+3CH.sub.4 [13]
[0074] A further object of the present invention relates to a
process for the production of olefins from gaseous paraffinic
hydrocarbons, having from two to six carbon atoms, comprising a
partial oxidation of said hydrocarbons with a gas containing
molecular oxygen in the presence of the catalytic system specified
above.
[0075] The partial oxidation is preferably effected at a
temperature ranging from 450 to 1000.degree. C., at a pressure
ranging from 1 to 15 Atm and a space velocity ranging from 5000 to
800000 h.sup.-1.
[0076] It has also been found that the process described above
using the catalytic system according to the invention can give
excellent results when it is carried out using tubular reactors in
which the gas inlet zone and catalytic zone have a tubular shape,
or reactors with a varying diameter in the gas distribution
direction, in which the gas inlet zone and catalytic zone have a
sand-glass or truncated-conical shape (see IT-MI96A000690).
[0077] These reactors with a varying diameter give the possibility
of accelerating/decelerating the gaseous streams of the reagents
and products.
[0078] This allows a reduction in the pressure drops as a result of
the increase in temperature and volume caused by the reactions and
also a reduction in the transmission of the reaction heat to the
premixed reagent streams.
[0079] These characteristics are particularly advantageous if the
reactions for the production of olefins are carried out at
super-atmospheric pressures.
[0080] The possibility of effecting dehydrogenation reactions at
super-atmospheric pressures is a great advantage with respect to
the known technologies as it reduces the costs and consumption
relating to the compression of the mixture of products before
entering the separation cycle.
[0081] As far as the reactor design is concerned, the gas inlet
zone and catalytic zone can either have a tubular shape, a
sand-glass shape or a truncated-conical shape: the geometry is
defined so as to maintain the surface rate values above the flame
speed and contact times lower than the ignition delay in the zone
prior to the catalytic bed and allow expansion of the product
mixture, thus avoiding pressure drops, after the reactions have
been activated.
[0082] The functions of the reagent gas inlet and distribution zone
are therefore:
[0083] to act as a barrier for the spreading of the radicalic
reactions towards the feeding inlet, by the acceleration of the
fluid and also by the presence of inert surfaces, capable of
capturing the radicals
[0084] to uniformly distribute the fluid on the inlet area in the
catalytic bed (FIG. 1A),
[0085] whereas the functions of the catalytic bed are:
[0086] to activate oxidation reactions with mixtures which move at
a high linear rate
[0087] to follow the expansion of the fluid due to the increase in
the number of moles and temperature without causing high pressure
drops
[0088] to maintain a surface rate in the whole of the bed which is
higher than the critical value for producing flames and carbon
black.
[0089] A further object of the present invention relates to a
process carried out using reactors in which the inlet zone and
catalytic zone have a tubular shape or a sand-glass shape or a
truncated-conical shape, with the particular characteristic of
sending into the gas inlet zone a stream of oxygen, air or enriched
air and a fuel, not having the function of directly producing
olefins, preferably selected from natural gas, synthesis gas,
hydrogen or a mixture of hydrogen and CO, and in the catalytic zone
a gaseous stream of paraffinic hydrocarbons.
[0090] This process carried out by feeding two types of fuel in
different points can also be used with different catalysts from
those claimed in the present patent application.
[0091] As already mentioned, the gas increases in volume due to the
increase in temperature and stoichiometry of the reactions and is
overheated by temperature values ranging from 80 to 600.degree. C.,
preferably 100-400.degree. C., in the distribution zone and ranging
from 600 to 1300.degree. C., preferably from 700 to 950.degree. C.
in the reaction zone.
[0092] The differential filling of the catalytic bed with particles
having an increasing diameter along the gas distribution direction
can also be used to reduce pressure drops.
[0093] One of the solutions adopted therefore consists of a filling
of catalyst particles with an increasing diameter along the gas
distribution direction.
[0094] A further innovative aspect relates to the possibility of
using not only various geometries but also different catalysts in
different reaction zones.
[0095] In particular, in reactors having a tubular or sandglass or
truncated-conical shape, the catalyst fillings are differentiated
so as to preferably have two or three catalytic beds in series.
[0096] In the case of two catalytic beds in series it is preferable
to use catalytic systems consisting of:
[0097] Pt deposited on nitrides or on oxy-nitrides in the bed
upstream and Pt and Sn deposited on nitrides or oxy-nitrides in the
bed downstream;
[0098] Pt and Cu deposited on nitrides or on oxy-nitrides in the
bed upstream and Pt, Sn and Ga deposited on nitrides or
oxy-nitrides in the bed downstream;
[0099] Pt and Ni deposited on nitrides or on oxy-nitrides in the
bed upstream and Pt, Sn and Cr deposited on nitrides or
oxy-nitrides in the bed downstream.
[0100] In the case of three catalytic beds in series, it is
preferable to use catalytic systems consisting of:
[0101] Pt deposited on nitrides or on oxy-nitrides in the bed
upstream, Pt and Sn deposited on nitrides or oxy-nitrides in the
intermediate bed and Pt, Sn and Ga deposited on nitrides or
oxy-nitrides in the bed downstream;
[0102] Pt and Cu deposited on nitrides or on oxy-nitrides in the
bed upstream, Pt, Sn and Bi deposited on nitrides or oxy-nitrides
in the intermediate bed and Pt, Sn and Ga deposited on nitrides or
oxy-nitrides in the bed downstream;
[0103] Pt deposited on nitrides or on oxy-nitrides in the bed
upstream, Pt and Sn deposited on nitrides or oxy-nitrides in the
intermediate bed and Pt, Sn and Sb deposited on nitrides or
oxy-nitrides in the bed downstream;
[0104] Pt and Cu deposited on nitrides or on oxy-nitrides in the
bed upstream, Pt, Sn and Cr deposited on nitrides or oxy-nitrides
in the intermediate bed and Pt, Sn and Ga deposited on nitrides or
oxy-nitrides in the bed downstream;
[0105] Pt and Ni deposited on nitrides or on oxy-nitrides in the
bed upstream, Pt and Sn deposited on nitrides or oxy-nitrides in
the intermediate bed and Pt, Sn and Ga deposited on nitrides or
oxy-nitrides in the bed downstream.
[0106] The differentiated use of catalysts with different intrinsic
activity characteristics allows selective combustion reactions to
be effected in the zone downstream of the distribution zone and
selective dehydrogenation reactions to olefins to be effected in
the subsequent zone.
[0107] Two preferred embodiments of the reactors which can be used
are provided hereunder with the help of FIGS. 1A, 1B and 1C.
[0108] With reference to FIG. 1A (in which the geometrical
characteristics of the gas inlet and distribution zone and
catalytic zone are schematized), the .alpha. values range from
0.degree..ltoreq..alpha..ltor- eq.89.degree.. The value of the
angle .alpha. and distance L are selected so as to:
[0109] allow the expansion of the reaction gas avoiding pressure
drops inside the catalytic bed and consequently prevent the
spreading of flames countercurrent;
[0110] leave the catalytic zone with a complete conversion of the
oxygen molecules.
[0111] FIG. 1B schematizes a reactor with a varying diameter in the
direction of the gas distribution and a tubular reactor.
[0112] In both reactors there is an inlet zone (A) of premixed
reagents and three catalytic zones (R1, R2 and R3) with
differentiated fillings (CAT1, CAT2 and CAT3).
[0113] In FIG. 1C a reactor with a varying diameter in the
direction of the gas distribution and a tubular reactor are
schematized.
[0114] In both reactors there is a first inlet zone (A) of premixed
reagents containing oxygen or air or enriched air (O1) and a fuel
(F1) which can consist of natural gas or hydrogen or synthesis gas
or any other fuel which does not have the function of directly
producing olefins.
[0115] The combustion of this mixture is effected in a first
reaction zone (R1) and has the function of producing the heat and
reagents which favour dehydrogenation reactions, in a second
reaction zone (R2), of a second hydrocarbon reagent (F2) which can
consist of ethane, propane, butane or a liquid hydrocarbon such as
naphtha or any other reagent which must be transformed into an
olefinic compound.
[0116] Three different types of catalysts (CAT1, CAT2, CAT3) are
used in different zones of the two reactors.
EXAMPLE 1
[0117] (Comparative)
[0118] The catalytic materials were tested in a quartz tubular
reactor, with an internal diameter equal to 15 mm.
[0119] Fragments of monolith (upstream) and a ceramic monolithic
foam (downstream) for a thermal shield for the catalytic bed; the
monolith is welded to the reactor by means of ceramic paper in
order to avoid the by-pass of the reagent gases and also acts as a
support for the catalyst.
[0120] The reactor was positioned in an oven, with the double
objective of preheating the reagents and reducing the loss in heat
of the system.
[0121] Two thermocouples, at the beginning and at the end of the
catalytic bed, co-axially positioned with respect to the
distribution direction of the reagents/products, allowed the
temperature of the gases at the inlet and outlet of the catalytic
bed to be monitored.
[0122] The tests were carried out at a pressure slightly higher
than the atmospheric value (1.3-1.5 bars), feeding ethane, nitrogen
(15% v/v of reagent gases), oxygen and hydrogen.
[0123] The ethane/oxygen (C.sub.2H.sub.6/O.sub.2) and
hydrogen/oxygen (H.sub.2/O.sub.2 ratios were varied so as to obtain
a correlation between the operating conditions and reactivity. The
space velocity (GHSV, expressed in NL/kg/h) was maintained at
40.000 to 600.000.
[0124] The mixture of products was analyzed via gaschromatography;
an online paramagnetic detector also allowed the possible presence
of oxygen in the outgoing stream to be monitored and also
facilitated the start-up/shutdown operations.
[0125] In this first example (comparative) the reactor was charged
with a catalyst (indicated with the abbreviation PS7AL2 in Table 1)
in which the carrier consisted of .alpha.-alumina pellets (more or
less spherically shaped, with a particle diameter--d.sub.p--equal
to 1.2 mm). A commercial hydrochloric solution of Pt salts
(H.sub.2PtCl.sub.6) and Sn salts (SnCl.sub.2.4H.sub.2O), was
dripped onto the carrier, so as to give a weight percentage of Pt
equal to 2 and an atomic ratio Sn:Pt equal to 7:1.
[0126] The operating conditions and results of the tests are
summarized in Table 1; Examples 1A-D, ordered according to an
increasing selectivity to ethylene, relate to different
ethane/oxygen, hydrogen/oxygen ratios and space velocities: each
condition was tested for at least 100 h.
EXAMPLE 2
[0127] A group of catalytic materials object of the present
invention was tested in the same experimental apparatus and under
analogous operating conditions to those described in Example 1
(comparative).
[0128] These materials are based on Pt and Sn (atomic ratio 1:7, 2%
by weight of platinum) and were obtained with the same experimental
procedure described in Example 1 using, instead of alumina, pellets
of Si.sub.3N.sub.4 (d.sub.p=1.5 mm).
[0129] The abbreviations PS7SN1, PS7SN3 and PS7SN4 refer to the
same catalyst, obtained in different batches.
[0130] The analytic method used is the same as that described in
Example 1 (Comparative).
[0131] The operating conditions and results of the tests are
summarized in Table 2; examples 2A-F, ordered according to an
increasing selectivity to ethylene, relate to different
ethane/oxygen, hydrogen/oxygen ratios and space velocities: each
condition was tested for at least 100 h.
EXAMPLE 3
[0132] The catalytic materials already described in Example 2 were
alternatively tested in a quartz reactor consisting of a
distribution zone and a catalytic zone, both conical (sand-glass
configuration). The distribution zone has an inlet diameter of 15
mm and a height of 10 mm. The catalytic zone has an inlet diameter
of 4 mm, a height of 18 mm and an outlet diameter of 20 mm.
[0133] The catalytic pellets were positioned between two zones
filled with ceramic material acting as a thermal shield.
[0134] Two thermocouples, positioned longitudinally at the inlet
and outlet of the catalytic bed, monitored the temperature of the
gases at the inlet and outlet.
[0135] Also in this case, the reactor was positioned in an oven,
with the double objective of preheating the reagents and reducing
the loss of heat of the system.
[0136] The tests were carried out at a slightly higher pressure
than atmospheric value (1.3-1.5 bars).
[0137] The analysis section is the same as that described in
Example 1.
[0138] The gases fed in Examples 3A and 3B were ethane, nitrogen
(percentage equal to 15% v/v approx.), oxygen and hydrogen. In
Example 3C (carried out at a very low space velocity and with a
greater volume of catalyst), a mixture of hydrogen and carbon
monoxide was fed, in addition to ethane and oxygen.
[0139] The tests were carried out with the same batch of catalyst
(PS7SN1) already defined in Example 2.
[0140] The operating conditions and results of the tests are
summarized in Table 3; examples 3A-3B were obtained with the same
ethane/oxygen ratio, and with different hydrogen/oxygen ratios and
space velocities, whereas example 3C, in which a mixture of CO and
hydrogen was fed, relates to a different ethane/oxygen ratio and
much lower space velocities: each condition was tested for at least
100 h.
1 TABLE 1 Example 1A Example 1B Example 1C Example 1D Catalyst
PS7AL2 PS7AL2 PS7AL2 PS7AL2 Reactor geometry tubular tubular
tubular tubular Operating conditions T.sub.out (.degree. C.) 828
787 771 768 p (bar) 1.319 1.22 1.21 1.23 GHSV (NL/kg/h) 603.600
389.300 380.600 402.400 C.sub.2H.sub.6/O.sub.2 2.08 2.27 2.38 2.48
H.sub.2/O.sub.2 2.185 2.000 2.000 2.000 Performance Conversion
C.sub.2H.sub.6 68.7% 64.0% 61.3% 59.0% Conversion O.sub.2 100% 100%
100% 100% Selectivity C.sub.2H.sub.4 79.9% 80.5% 81.3% 81.9%
Selectivity CO 7.0% 6.8% 6.3% 6.0% Selectivity CO.sub.2 1.8% 2.6%
2.2% 2.2% Selectivity CH.sub.4 5.5% 5.3% 4.8% 4.7% Selectivity
C.sub.2H.sub.2 1.5% 1.6% 1.3% 1.2% Selectivity C.sub.3 1.6% 1.4%
1.5% 1.4% Selectivity C.sub.4> 2.7% 1.8% 2.6% 2.6% Tot.
selectivity 100.0% 100.0% 100.0% 100.0%
[0141]
2 TABLE 2 Ex. 2A Ex. 2B Ex. 2C Ex. 2D Ex. 2E Ex. 2F Catalyst PS7SN4
PS7SN1 PS7SN3 PS7SN4 PS7SN3 PS7SN3 Reactor geometry tubular tubular
tubular tubular tubular tubular Operating conditions T.sub.out
(.degree. C.) 874 878 837 822 818 804 p (bar) 1.21 1.46 1.34 1.24
1.34 1.32 GHSV (NL/kg/h) 424.000 493.000 538.000 424.000 543.000
535.000 C.sub.2H.sub.6/O.sub.2 2.50 2.08 2.50 3.33 2.84 3.21
H.sub.2/O.sub.2 2.50 1.04 2.00 3.33 2.5 2.82 Performance Conversion
C.sub.2H.sub.6 60.4% 73.4% 65.2% 31.9% 49.1% 39.3% Conversion
O.sub.2 2100% 100% 100% 100% 100% 100% Selectivity C.sub.2H.sub.4
80.4% 82.1% 83.4% 84.3% 86.0% 89.0% Selectivity CO 9.4% 8.5% 5.6%
5.8% 4.3% 2.9% Selectivity CO.sub.2 0.7% 0.4% 0.3% 0.4% 0.3% 0.2%
Selectivity CH.sub.4 5.5% 6.5% 4.8% 3.9% 4.2% 3.3% Selectivity
C.sub.2H.sub.2 1.1% 0.9% 1.3% 0.2% 0.7% 0.6% Stelectivity C.sub.3
1.9% 0.6% 1.6% 2.3% 1.7% 1.2% Selectivity C.sub.4> 1.0% 1.0%
3.0% 3.1% 2.8% 2.8% Tot. selectivity 100.0% 100.0% 100.0% 100.0%
100.0% 100.0%
[0142]
3 TABLE 3 Example 3A Example 3B Example 3C Catalyst PS7SN1 PS7SN1
Catalyst Reactor Geometry conical conical Reactor Geometry conical
Operating conditions Operating conditions T.sub.out (.degree. C.)
933 944 T.sub.out (.degree. C.) 755 P (bars) 1.43 1.38 P (bars) 1.3
GHSV (NL/kg/h) 552,000 475,000 GHSV (NL/kg/h) 42.300 O.sub.2/C
3.205 3.205 O.sub.2/C 0.25 H.sub.2/O.sub.2 2.00 1.00 (CO +
H.sub.2O)/O.sub.2 2.50 Performance Performance Conversion
C.sub.2H.sub.6 35.2% 34.4% Conversion C.sub.2H.sub.6 50.6%
Conversion O.sub.2 100% 100% Conversion O.sub.2 100% Selectivity
C.sub.2H.sub.4 85.5% 81.9% Selectivity C.sub.2H.sub.4 84.4%
Selectivity CO 5.7% 8.3% Selectivity CO 0.0% Selectivity CO.sub.2
0.3% 1.0% Selectivity CO.sub.2 6.7% Selectivity CH.sub.4 4.8% 5.1%
Selectivity CH.sub.4 4.3% Selectivity C.sub.2H.sub.2 1.0% 1.4%
Selectivity C.sub.2H.sub.2 1.0% Selectivity C.sub.3 1.7% 1.6%
Selectivity C.sub.3 31.4% Selectivity C.sub.4> 1.0% 0.7%
Selectivity C.sub.4> 2.2% Tot. Selectivity 100.0% 100.0% Tot.
Selectivity 100.0%
* * * * *