Process for production of propylene and ethylene by non-catalytic oxycracking of propane or propane-rich C.sub.2 -C.sub.4 paraffins

A process for the production of propylene and ethylene by non-catalytic oxidative conversion of propane by allowing the endothermic hydrocarbon cracking reaction to occur simultaneously with the exothermic hydrocarbons oxidative conversion reactions in an empty tubular reactor is disclosed. The process comprises mixing of oxygen and propane at ambient temperatures, mixing of sulfur compound with steam, admixing the mixture of steam and sulfur compound and the mixture of oxygen and propane and preheating the resulting admixture, passing said mixture through an empty tubular reactor, cooling and separating the components of effluent product gases by known methods and recycling the unconverted reactants, if required.

FIELD OF INVENTION 
This invention relates to a process for the production of propylene and 
ethylene by non-catalytic oxidative cracking of propane or propane-rich 
C.sub.2 -C.sub.4 paraffins. The invention particularly relates to 
production of propylene and ethylene by non-catalytic oxidative conversion 
of propane or propane-rich C.sub.2 -C.sub.4 paraffins in a most energy 
efficient manner by allowing the endothermic hydrocarbon cracking 
reactions to occur simultaneously with the exothermic hydrocarbons 
oxidative conversion reactions in an empty tubular reactor. 
The process of this invention could be used for the production of propylene 
from propane or propane-rich C.sub.2 -C.sub.4 paraffins. 
BACKGROUND OF INVENTION 
Propylene, an important feedstock in the petrochemical industry, is 
produced commercially along with ethylene by the thermal cracking of 
ethane, propane, ethane-propane mixture or naphtha in the presence of 
steam (ref. L. Kniel et al., in Chemical Industries, Vol. 2 "Ethylene: 
Key-stone to the Petrochemical Industry, Marcel Dekkor, Inc., New York, 
1980 and L. F. Albright et al., eds., in Pyrolysis: Theory and Industrial 
Practice, Academic Press, New York, 1983). In the thermal cracking of 
these paraffins, ethylene is produced in larger quantities than propylene. 
The cracking process is highly endothermic and hence highly energy 
intensive and also involves extensive coke formation. Typical results 
given in the above references indicate that at 93% conversion of propane, 
23.7 wt %, 41.4 wt % and 12.9 wt % yield for methane, ethylene and 
propylene, respectively, could be obtained by the thermal cracking of 
propane. The ethylene, propylene and also other olefins produced in the 
cracking process and the unreacted paraffins are separated from the 
product stream by the well-known cryogenic separation method involving 
liquefaction and fractionation of hydrocarbons. 
The process for the production of propylene and ethylene, based on thermal 
cracking of propane or other paraffins have following limitations: (1) 
They are highly endothermic and hence require a large amount of energy for 
the cracking of paraffins. (2) They involve extensive coke deposition 
inside the pyrolysis reactor tubes, thus causing increase in pressure drop 
and hence there are frequent break-downs for removing the coke from the 
pyrolysis reactor tubes. (3) The life of the pyrolysis reactor tubes is 
low because of their high temperature operation; the temperature at 
external surface of the tubes is about 200.degree. C. higher than the 
temperature inside the tubes. 
Catalytic processes based on oxidative dehydrogenation of propane for the 
productions of propylene area also known in the prior art. A number of 
catalysts are known for the oxidative dehydrogenation of propane [ref. JP 
58,153,538 (matushi Electric Ind. Co. Ltd.), 1983; U.S. Pat. No. 
4,472,314, Conner et al., 1984; U.S. Pat. No. 4,547,618 (Mobil Oil Corp.), 
Porbus and Nancy, 1985; U.S. Pat. No. 4,607,129 (Phillips Petroleum Col.), 
Lee and Fu, 1985; U.S. Pat. No. 4,886,928, Imai and Schmidt, 1989; U.S. 
Pat. No. 5,306,858, Salem et al., 1994; JP 08,231,441, Saito et al., 1996 
and DE 19,530,454, Baerns et al., 1997]. In the catalytic oxidative 
propane dehydrogenation processes, the catalyst is deactivated during the 
process due to the loss of active components from the catalyst by 
evaporation at hot spots and/or due to the catalyst sintering. The 
catalysts are also deactivated due to coke deposition on their surface 
during the process. Moreover, since these processes are highly exothermic, 
their operation is hazardous. 
The present energy crisis and/or high energy cost, and also the 
environmental pollution problems have created a great need for developing 
a process for the production of propylene, the demand of which is 
increasing day-by-day, by non-catalytic oxidative cracking of propane or 
propane-rich C.sub.2 -C.sub.4 paraffins to propylene and ethylene with 
high propylene/ethylene mole ratio, which requires little (i.e. much 
smaller than that required for the thermal cracking process) or no 
external energy, operates in a most energy efficient manner and with high 
conversion, selectivity and productivity but without coke formation and 
also has absolutely no hazards (i.e. very safe operation). This invention 
is, therefore, made with the following objects so that most of the 
drawbacks or limitations of the earlier processes could be overcome. 
OBJECTS OF THE INVENTION 
1. Accordingly the main object of this invention is to provide process for 
the production of propylene and ethylene, with propylene/ethylene mole 
ratio of at least 0.15, from propane or propane-rich C.sub.2 -C.sub.4 
paraffins by non-catalytic oxidative cracking of propane or propane-rich 
C.sub.2 -C.sub.4 paraffins in the presence of steam, volatile sulfur 
compound and limited oxygen so that the endothermic thermal cracking and 
exothermic oxidative conversion reactions of propane, described later, 
occur simultaneously. 
2. Another important object of this invention is to provide a non-catalytic 
process for the production of propylene and ethylene, with 
propylene/ethylene mole ratio of at least 0.15, from propane or 
propane-rich C.sub.2 -C.sub.4 paraffins, which requires little (i.e. much 
smaller than that required for the thermal cracking process) or no 
external energy and also operates in a most energy efficient manner 
without any hazards (i.e. with a very safe process operation) through 
coupling of the exothermic oxidative hydrocarbon conversion reactions with 
the endothermic hydrocarbon cracking or pyrolysis reactions. 
3. Yet another object of this invention is to be provide process for the 
production of propylene and ethylene, with propylene/ethylene mole ratio 
of at least 0.15, from propane or propane-rich C.sub.2 -C.sub.4 paraffins 
by their simultaneous oxidative conversion and thermal cracking, which 
operates with high conversion, selectivity and productivity without 
deposition of coke on the reactor walls. 
SUMMARY OF THE INVENTION 
This invention provides a non-catalytic process for the production of 
propylene and ethylene, with propylene/ethylene mole ratio of at least 
0.15, by oxidative cracking of propane or propane-rich C.sub.2 -C.sub.4 
paraffins with high conversion, selectivity and productivity, operating in 
most energy efficient and safe manner, in an empty tubular reactor. The 
process comprises of passing continuously a gaseous feed, comprising of 
propane or propane-rich C.sub.2 -C.sub.4 paraffins, oxygen, steam, and 
volatile sulfur compound, preheated at 200.degree.-550.degree. C. through 
an empty tubular reactor at the temperature of 550.degree.-900.degree. C., 
pressure 0.5-5 atm, space velocity 500-50,000 h.sup.-1 and mole ratios of 
O.sub.2 /hydrocarbon, steam/hydrocarbon and sulfur compound/hydrocarbon in 
the feed 0.01-1.0, 0.1-10 and 10.sup.-2 -10.sup.-6, respectively. 
The main finding of this invention is that in the present process, the 
endothermic thermal cracking and exothermic oxidative hydrocarbon 
conversion reactions occur simultaneously and because of this there is a 
coupling of the exothermic and endothermic reactions and thereby the 
process operates in a most energy efficient manner and also without 
formation of hot spots in the reactor, making the process operation safe. 
Another important finding of this invention is that the present process 
requires a little or no external energy and it can be made thermoneutral 
or mildly exothermic or mildly endothermic by manipulating the process 
conditions. Yet another important finding of this invention is that the 
present process operates with high conversion, selectivity and 
productivity, producing propylene and ethylene with propylene/ethylene 
mole ratio of at least 0.15, and moreover there is no coke deposition on 
the reactor walls. Further one more important finding of this invention is 
that because of the addition of volatile sulfur compound in the feed, the 
propane conversion and/or selectivity for olefins is increased.

DETAILED DESCRIPTION OF THE INVENTION 
Accordingly, this invention provides a process for the production of 
propylene and ethylene by non-catalytic oxidative cracking of propane or 
propane-rich-C.sub.2 -C.sub.4 paraffins, which comprises: 
a) mixing of oxygen or O.sub.2 -enriched air and propane or propane-rich 
C.sub.2 -C.sub.4 paraffins at ambient temperature, 
b) mixing of a volatile sulfur compound with steam, 
c) admixing the mixture of steam and volatile sulfur compound and the 
mixture of oxygen or O.sub.2 -enriched air and propane or propane-rich 
C.sub.2 -C.sub.4 paraffins, and preheating the resulting admixture to a 
temperature between about 200.degree. C. to about 550.degree. C., 
d) passing continuously the preheated admixture feed through an empty 
tubular reactor, while maintaining the mole ratio of oxygen to 
hydrocarbon, steam to hydrocarbon and volatile sulfur compound to 
hydrocarbon in said admixture feed between about 0.01 to about 1.0, 
between about 0.1 to about 10, and between about 10.sup.-2 to about 
10.sup.-6, respectively, with a gas hourly space velocity of said 
admixture feed between about 500 h.sup.-1 to about 50,000 h.sup.-1 at a 
reaction temperature between about 620.degree. C. to about 900.degree. C. 
and a pressure between about 0.5 to about 5.0 atm, such that propylene to 
ethylene mole ratio in products is at least 0.15 and there is a coupling 
of exothermic hydrocarbon oxidative conversion and endothermic hydrocarbon 
cracking reactions due to the simultaneous occurrence of these exothermic 
and endothermic reactions, and 
e) cooling and separating the components of effluent product gases by known 
methods and, it required, recycling the unconverted reactants. 
In the process of the present invention, the preferred reaction temperature 
is between about 635.degree. C. and about 800.degree. C.; the preferred 
pressure ranges from about 1 atm to about 3 atm; the preferred mole ratio 
of O.sub.2 to hydrocarbon, steam to hydrocarbon and volatile sulfur 
compound to hydrocarbon in the feed ranges from about 0.05 to about 0.5, 
about 0.3 to about 3.0 and about 10.sup.-3 to about 10.sup.-5, 
respectively; and the preferred gas hourly space velocity of the feed 
ranges from about 1000 h.sup.-1 to about 20,000 h.sup.-1. The preferred 
volatile sulfur compound in the feed is thiophene. 
In the process of the present invention, the products formed are propylene, 
ethylene, methane, ethane, hydrogen, carbon monoxide, carbon dioxide and 
water and C.sub.4+ hydrocarbons. The gaseous product stream comprises of 
ethylene, propylene, C.sub.4+ hydrocarbons, methane, ethane, H.sub.2, CO, 
CO.sub.2, H.sub.2 O and unconverted propane and oxygen or air components. 
The feed used in the process of the present invention comprises of propane 
or propane-rich C.sub.2 -C.sub.4 paraffins, oxygen or O.sub.2 -enriched 
air, steam and volatile sulfur compound. The hydrocarbon components of the 
feed and oxygen are reactants but steam is a feed diluent and acts as an 
indirect reactant for the gasification of the carbon or coke formed in the 
process under oxygen deficient conditions or by thermal cracking or 
pyrolysis of hydrocarbons. The presence of steam in the feed has two 
beneficial effects: one, the formation of coke and tar-like product in the 
process are avoided and second, the severity of the exothermic hydrocarbon 
oxidation reactions is reduced due to the feed dilution. The steam in the 
product stream can be easily separated simply by its condensation. The 
oxygen in the feed plays following important roles in the process. Because 
of the presence of O.sub.2 in the feed, not only the total conversion of 
propane but also its conversion purely by its thermal cracking is much 
higher than that observed in the absence of O.sub.2. Further, because of 
the oxidation of coke precursors (i.e. hydrogen deficient or highly 
unsaturated hydrocarbon species formed in the conversion of the propane or 
propane-rich C.sub.2 -C.sub.4 paraffins) by the oxygen, the coke formation 
in the process of this invention is avoided. The volatile sulfur compound 
in the feed plays two significant roles: (1) its passivates the inner 
walls surface of the tubular reactor by deactivating the coke forming 
sites present on the reactor inner walls through sulfidation and (2) its 
presence in the feed causes a significant increase in the conversion 
and/or selectivity for olefins. The preheating of the feed gases can be 
effected by exchanging heat between the hot reactor effluent product gas 
stream and the feed gases by known prior art methods. 
Following non-catalytic exothermic and endothermic reactions occur in the 
process of present invention. 
Exothermic reactions 
a) Oxidative dehydrogenation of propane or propane rich C.sub.2 -C.sub.4 
paraffins: 
EQU C.sub.3 H.sub.8 +0.5O.sub.2 .fwdarw.C.sub.3 H.sub.6 +H.sub.2 O+28.3 
kcal.mol.sup.-1 (at 700.degree. C.) (1) 
EQU C.sub.n H.sub.2n+2 +0.5O.sub.2 .fwdarw.C.sub.n H.sub.2n +H.sub.2 O+heat(2) 
(when n=2-4) 
b) Combustion of propane or propane rich C.sub.2 -C.sub.4 paraffins, which 
are highly exothermic reactions: 
EQU C.sub.3 H.sub.8 +5O.sub.2 .fwdarw.3CO.sub.2 +4H.sub.2 O+489.0 
kcal.mol.sup.-1 (at 700.degree. C.) (3) 
EQU C.sub.3 H.sub.8 +3.5O.sub.2 .fwdarw.3CO+4H.sub.2 O+286.4 kcal.mol.sup.-1 
(at 700.degree. C.) (4) 
EQU C.sub.2 -C.sub.4 paraffins+oxygen.fwdarw.CO, CO.sub.2 and H.sub.2 O+heat(5) 
C) Oxidation of hydrogen to water, which is also highly exothermic: 
EQU H.sub.2 +0.5O.sub.2 .fwdarw.H.sub.2 O+59.4 kcal.mol.sup.-1 (6) 
Endothermic reactions 
Thermal cracking or pyrolysis of propane or propane-rich C.sub.2 -C.sub.4 
paraffins: 
EQU C.sub.3 H.sub.8 .fwdarw.C.sub.3 H.sub.6 +H.sub.2 -30.9 kcal.mol.sup.-1 (at 
700.degree. C.) (7) 
EQU C.sub.3 H.sub.8 .fwdarw.C.sub.2 H.sub.4 +CH.sub.4 -18.7 kcal.mol.sup.-1 (at 
700.degree. C.) (8) 
EQU C.sub.2 -C.sub.4 paraffins.fwdarw.C.sub.2 H.sub.4, C.sub.3 H.sub.6, 
C.sub.4+ hydrocarbons, CH.sub.4 and H.sub.2 -heat (9) 
In the process of the present invention, since the above exothermic and 
endothermic reactions are occurring simultaneously, the heat produced in 
the exothermic reactions is used instantly for the endothermic reactions, 
thus making the process operation most energy efficient and safe. Since 
the thermal hydrocarbon cracking reactions have high activation energy, 
their reaction rate increases very fast with the increase in the 
temperature. The coupling of the exothermic and endothermic reactions, as 
described above, leads to an establishment of a sort of a buffer action 
for the reaction temperature in the process thus restricting the 
temperature rise and, therefore, an occurrence of run-away reaction 
condition during the operation of the process is totally eliminated. 
Because of the coupling of the exothermic and endothermic reactions 
occurring simultaneously, the process of this invention can be made mildly 
exothermic, thermoneutral or mildly endothermic by manipulating the 
process conditions. 
The process can be operated in an empty non-adiabatic tubular reactor, 
containing single or multiple parallel coiled tubes, without any serious 
problems for removing heat from the reactor, when the process is mildly 
exothermic or providing energy to the reactor, when the process is mildly 
endothermic, thus requiring no or little (i.e. much smaller than that 
required for the thermal cracking process) external energy, respectively. 
The present invention is described with respect to the following examples 
illustrating the process of this invention for the simultaneous exothermic 
oxidative conversion of propane or propane-rich C.sub.2 -C.sub.4 paraffins 
and endothermic thermal cracking of propane or propane-rich C.sub.2 
-C.sub.4 paraffins in a most safe and energy efficient manner. These 
examples are provided for illustrative purposes only and are not to be 
construed as limitations on the invention. 
Definition of terms used in the examples 
Total conversion of reactant (%)=percent of the reactant converted to all 
the products. Conversion of a reactant to a particular product=percent of 
the reactant converted to the particular product. 
Selectivity for a particular product (%)=100.times.[Conversion of reactant 
to the product (%)]/[Total conversion of reactant (%)]. 
Gas: hourly space velocity, GHSV=Volume of gaseous reactant mixture, 
measured at 0.degree. C. and 1 atm pressure, passed through an unit volume 
of reactor per hour. 
All the ratios of reactants or products are mole ratios. 
The net heat of reactions, .DELTA.H.sub.r, in the overall process is 
defined as follows: 
Net heat of reactions, .DELTA.H.sub.4 =[H.sub.f ].sub.products =[H.sub.f 
].sub.reactants. 
Wherein, [H.sub.f ].sub.products and [H.sub.f ].sub.reactants are the heat 
of formation of products and reactants, respectively. The negative value 
of the net heat of reactions indicates that the overall process is 
exothermic and the positive value of the heat of reactions indicates that 
overall process is endothermic. 
EXAMPLE 1 
This example illustrates the process of this invention for the production 
of propylene and ethylene by non-catalytic oxidative cracking of propane 
in the presence of oxygen, steam and thiophene. 
The process is carried out in a continuous flow empty tubular reactor 
having internal diameter of 7.0 mm and a volume of 5.2 cm.sup.3, by mixing 
oxygen with propane at room temperature, mixing thiophene vapors with 
steam, admixing the steam-thiophene mixture and oxygen-propane mixture, 
preheating the admixture and then passing continuously the preheated 
admixture through the reactor at the reaction conditions given below. The 
reactor was kept in an electrically heated tubular furnace. The reaction 
temperature was measured by a Chromel-Alumel thermocouple located axially 
in the center of the reactor. The reactor effluent gases were quenched and 
cooled at about 0.degree. C. to condense the water from them, using a 
coiled condenser immersed in ice-water slurry, and then analyzed for the 
products and unconverted reactants by an on-line gas chromatograph. 
Reaction conditions 
______________________________________ 
Feed A mixture of propane, oxygen, 
steam and thiophene 
Feed preheating temperature 500.degree. C. 
O.sub.2 /propane mole ratio in feed 0.25 
H.sub.2 O/hydrocarbon mole ratio in feed 0.5 
Thiophene/propane mole ratio feed 10.sup.-4 
Gas hourly space velocity (GHSV) 3000 h.sup.-1 
Pressure 1.1 atm. 
Reaction temperature 800.degree. C. 
The results obtained at the above reaction conditions are as follows. 
No coke deposition is observed in the process. 
Conversion of propane (%) 
79.1 
Conversion of oxygen (%) 93.5 
Selectivity (%) for 
Propylene 21.8 
Ethylene 42.4 
Methane 19.6 
Ethane 2.3 
C.sub.4+ hydrocarbons 5.6 
Carbon monoxide 7.5 
Carbon dioxide 0.8 
C.sub.3 H.sub.6 /C.sub.2 H.sub.4 ratio in products 
0.34 
Net heat of reaction (.DELTA.H.sub.r) (kcal.mol.sup.-1) -11.6 
______________________________________ 
The net heat of reaction is small with --ve sign, indicating that the 
overall process is mildly exothermic. It also indicates that no external 
energy is required for the process. 
EXAMPLES 2-27 
These examples illustrate the process of the present invention for the 
production of propylene and ethylene by non-catalytic oxidative cracking 
of propane in the presence of oxygen, steam and different volatile sulfur 
compounds at different process conditions. The process is carried out in 
the reactor and by the procedure same as that described in Example 1. The 
process performance was evaluated at following process conditions. 
______________________________________ 
Feed A mixtures of propane, 
oxygen, steam and volatile 
sulfur compound 
Volatile sulfur compound Thiophene, CS.sub.2 or 
dimethyl sulfide (DMS) 
Feed preheating temperature 300.degree. or 500.degree. C. 
O.sub.2 /propane mole ratio in feed varied from 0.06 to 0.5 
Steam/propane mole ratio in feed varied from 0.4 to 2.5 
Sulfur compound/propane mole varied form 10.sup.-3 to 10.sup.-5 
ratio in feed 
Gas hourly space velocity (GHSV) varied from 1170 to 7150 h.sup.-1 
Pressure 0.95-1.1 atm 
Reaction temperature varied from 600.degree.-800.degree. C. 
______________________________________ 
The results obtained at different process conditions are given in Tables 
1-6. There was no coke deposition on the reactor walls. 
This example also illustrates that the net heat of reactions in the process 
of this invention is quite small; it is with positive or negative sign, 
indicating that the process at the corresponding reaction conditions is 
mildly endothermic or mildly exothermic, respectively. This example also 
illustrates that the process of this invention occurs in a most energy 
efficient and safe manner and also the process can be made mildly 
exothermic, near thermoneutral or mildly endothermic by manipulating the 
process conditions, particularly the reaction temperature and the O.sub.2 
/hydrocarbon mole ratio in the feed. This example further illustrates that 
for the process of present invention, either there is no requirement of 
external energy, particularly when the net heat of reaction, 
.DELTA.H.sub.r is negative (i.e. when the present process is mildly 
exothermic) or there is a requirement of much lower energy than that 
required for the thermal cracking of propane: C.sub.1 H.sub.x 
.fwdarw.C.sub.3 H.sub.6 +H.sub.2, which is highly endothermic with a heat 
of radiation, .DELTA.H.sub.4 =+39.93 kcal.mol.sup.-1 (at 727.degree. C.). 
The external energy required in the process of process invention is much 
lower than that required for the propane thermal cracking process and 
hence there is a large energy saving. 
EXAMPLE 28 
This example illustrates that in the presence of limited O.sub.2 in the 
feed of the process of present invention, not only the total conversion of 
propane but also the conversion of propane purely by its thermal cracking 
is much higher than that observed in the absence of O.sub.2. The propane 
conversion reactions in the presence of O.sub.2 and in the absence of 
O.sub.2 were carried out in the reactor and by the procedure similar to 
that described in Example 1. Results showing the influence of the presence 
of O.sub.2 in feed at different concentrations (O.sub.2 /C.sub.3 H.sub.8 
mole ratio=0-0.5) on the total conversion of propane and its conversion 
purely by thermal cracking at different temperatures 
(635.degree.-800.degree. C.) are presented in Table 7. Because of the 
presence of O.sub.2, not only the total conversion of propane but also its 
conversion purely by thermal cracking is much higher that that observed in 
the absence of O.sub.2. Both the total conversion of propane and its 
conversion by thermal cracking alone are increased markedly with 
increasing the concentration of O.sub.2 relative to propane at all the 
temperatures. 
TABLE 1 
______________________________________ 
Results of the oxycracking of propane at different temperatures 
Example 2 
Example 3 
Example 4 
Example 5 
______________________________________ 
Process conditions 
Reaction temp. (.degree.C.) 620 635 715 810 
O.sub.2 /C.sub.3 H.sub.8 mole ratio 0.5 0.5 0.5 0.5 
Steam/C.sub.3 H.sub.8 mole ratio 0.5 0.5 0.5 0.5 
Thiophene/C.sub.3 H.sub.8 mole 10.sup.-4 10.sup.-4 10.sup.-4 10.sup.31 
4 
ratio 
GHSV (h.sup.-1) 3000 3000 3000 3000 
Pressure (atm) 0.95 0.95 0.95 0.95 
Feed preheating 500 500 500 500 
temp. (.degree.C.) 
Conversion (%) of 
Propane 12.5 72.0 79.4 91.7 
Oxygen 14.0 86.8 93.8 97.9 
Selectivity (%) for 
Propylene 58.3 26.2 20.1 13.8 
Ethylene 28.9 38.2 40.5 44.0 
Methane 4.2 14.3 16.6 19.7 
Ethane 2.9 2.8 2.3 2.3 
C.sub.4+ hydrocarbons 5.5 5.1 5.5 4.7 
Carbon monoxide 2.0 12.6 13.6 14.5 
Carbon dioxide 0.9 0.7 0.9 1.1 
C.sub.3 H.sub.6 C.sub.2 H.sub.4 mole 1.35 0.46 0.33 0.21 
ratio in products 
Net heat of reaction -33.5 -33.4 -32.7 -27.5 
.DELTA.H.sub.r (kcal.mol.sup.-1) 
______________________________________ 
TABLE 2 
______________________________________ 
Results of the oxycracking of propane at 800.degree. C. 
for different O.sub.2 /C.sub.3 H.sub.8 ratios 
Example 6 
Example 7 
Example 8 
Example 9 
______________________________________ 
Process conditions 
Reaction temp. (.degree.C.) 800 800 800 800 
O.sub.2 /C.sub.3 H.sub.8 0.0 0.5 0.13 0.06 
mole ratio 
Steam/C.sub.3 H.sub.8 0.5 0.5 0.5 0.5 
mole ratio 
Thiophene/C.sub.3 H.sub.8 10.sup.-4 10.sup.-4 10.sup.-4 10.sup.-4 
mole ratio 
GHSV (h.sup.-1) 3000 3000 3000 3000 
Pressure (atm) 1.0 1.1 1.0 1.1 
Feed preheating 500 500 500 500 
temp. (.degree.C.) 
Conversion (%) of 
Propane 53.9 91.7 68.6 61.8 
Oxygen 97.9 95.4 94.8 
Selectivity (%) for 
Propylene 29.3 13.3 25.4 27.2 
Ethylene 41.9 44.0 42.2 42.1 
Methane 20.4 19.7 19.7 19.7 
Ethane 2.0 2.3 2.4 2.3 
C.sub.4+ hydrocarbons 5.7 4.7 6.3 6.4 
Carbon monoxide 0.5 14.5 3.4 1.8 
Carbon dioxide 0.1 1.1 0.5 0.4 
C.sub.3 H.sub.6 /C.sub.2 H.sub.4 0.47 0.21 0.40 0.43 
mole ratio in 
products 
Net heat of reaction -- -30.4 +9.4 +12.1 
.DELTA.H.sub.r (kcal.mol.sup.-1) 
______________________________________ 
TABLE 3 
______________________________________ 
Results of the oxycracking of propane at 
635.degree. C. for different O.sub.2 /C.sub.3 H.sub.8 ratios 
Example 10 
Example 11 
Example 12 
______________________________________ 
Process conditions 
Reaction temp. (.degree.C.) 635 635 635 
O.sub.2 /C.sub.3 H.sub.8 mole ratio 0.0 0.25 0.10 
Steam/C.sub.3 H.sub.8 mole ratio 0.5 0.5 0.5 
Thiophene/C.sub.3 H.sub.8 mole ratio 10.sup.-4 10.sup.-4 10.sup.-4 
QHSV (h.sup.-1) 3000 3000 3000 
Pressure (atm) 1.0 1.0 1.0 
Feed preheating temp. (.degree.C.) 300 300 300 
Conversion (%) of 
Propane 0.8 47.8 22.8 
Oxygen -- 91.9 94.1 
Selectivity (%) for 
Propylene 1.0 31.5 30.7 
Ethylene 65.9 36.7 38.7 
Methane 33.1 13.3 15.1 
Ethane -- 2.3 2:2 
C.sub.4+ hydrocarbons -- 7.5 8.1 
Carbon monoxide -- 8.3 4.6 
Carbon dioxide -- 0.4 0.4 
C.sub.3 H.sub.6 /C.sub.2 H.sub.4 mole ratio 0.01 0.58 0.53 
in products 
______________________________________ 
TABLE 4 
______________________________________ 
Results of the oxycracking of propane at 635.degree. C. 
for different steam/C.sub.3 H.sub.8 ratios 
Example Example Example 
Example 
13 14 15 16 
______________________________________ 
Process conditions 
Reaction temp. (.degree. C.) 635 635 635 635 
O.sub.2 /C.sub.3 H.sub.8 0.5 0.5 0.5 0.5 
mole ratio 
Steam/C.sub.3 H.sub.8 0.4 1.13 1.6 2.5 
mole ratio 
Thiophene/C.sub.3 H.sub.8 10.sup.-4 10.sup.-4 10.sup.-4 10.sup.-4 
mole ratio 
GHSV (h.sup.-1) 3000 3000 3000 3000 
Pressure (atm) 1.0 1.0 1.0 0.95 
Feed preheating 500 500 500 500 
temp. (.degree.C.) 
Conversion (%) of 
Propane 70.8 74.8 73.1 62.7 
Oxygen 91.1 90.1 86.5 79.6 
Selectivity (%) for 
Propylene 24.9 25.4 28.1 28.9 
Ethylene 38.3 38.0 35.5 36.4 
Methane 14.0 14.0 12.3 11.7 
Ethane 2.5 2.6 2.4 2.3 
C.sub.4+ hydrocarbons 7.4 10.2 9.1 5.2 
Carbon monoxide 12.3 13.0 12.1 14.7 
Carbon dioxide 0.6 0.8 0.5 0.7 
C.sub.3 H.sub.6 /C.sub.2 H.sub.4 0.44 0.45 0.53 0.53 
mole ratio in products 
______________________________________ 
TABLE 5 
______________________________________ 
Results of thc oxycracking of propane at 635.degree. C. 
for different space velocities 
Example 17 18 19 20 21 
______________________________________ 
Process conditions 
Reaction temp. (.degree.C.) 635 635 635 635 635 
O.sub.2 /C.sub.3 H.sub.8 mole ratio 0.5 0.5 0.5 0.5 0.5 
Steam/C.sub.3 H.sub.8 mole ratio 0.5 0.5 0.5 0.5 0.5 
Thiophene/C.sub.3 H.sub.8 mole ratio 10.sup.-4 10.sup.-4 10.sup.-4 
10.sup.-4 10.sup.-4 
GHSV (h.sup.-1) 1170 2355 3530 4730 7150 
Pressure (atm) 0.95 1.0 1.05 1.0 1.1 
Feed preheating temp. (.degree.C.) 500 500 500 500 500 
Conversion (%) of 
Propane 88.1 88.2 88.5 75.5 23.7 
Oxygen 98.7 98.6 96.1 84.5 36.4 
Selectivity (%) for 
Propylene 27.1 22.9 21.3 27.1 35.9 
Ethylene 38.0 41.2 41.1 41.2 40.1 
Methane 16.1 14.4 15.4 14.2 11.9 
Ethane 2.9 3.9 2.6 1.6 1.6 
C.sub.4+ hydrocarbons 3.5 3.2 3.1 2.3 4.8 
Carbon monoxide 10.8 12.6 13.8 10.1 2.2 
Carbon dioxide 1.7 1.8 2.8 1.6 1.4 
C.sub.3 H.sub.6 /C.sub.2 H.sub.4 0.48 0.37 0.35 0.44 0.60 
mole ratio in products 
______________________________________ 
TABLE 6 
______________________________________ 
Results of the oxycracking of propane at 635.degree. C. 
for different sulfur compound additives in the feed 
Example 22 23 24 25 26 27 
______________________________________ 
Process 
conditions 
Reaction temp. 635 635 635 635 635 635 
(.degree.C.) 
O.sub.2 /C.sub.3 H.sub.8 0.5 0.5 0.5 0.5 0.5 0.5 
mole ratio 
Steam/C.sub.3 H.sub.8 0.5 0.5 0.5 0.5 0.5 0.5 
mole ratio 
Sulfur Thio- Thio- Thio- Thio- CS.sub.2 DMS 
compound phene phene phene phEne 
additive 
Sulfur 0.0 1 .times. 1 .times. 1 .times. 1 .times. 1 .times. 
compound 10.sup.-5 10.sup.-4 10.sup.-4 10.sup.-4 10.sup.-4 
C.sub.3 H.sub.8 
mole ratio 
GHSV (h.sup.-1) 3000 3000 3000 3000 3000 3000 
Pressure (atm) 1.0 1.0 1.0 1.0 1.0 i.0 
Feed preheat- 500 500 500 500 500 500 
ing temp. (.degree.C.) 
Conversion 
(%) of 
Propane 70.8 76.2 77.1 75.7 7101 78.6 
Oxygen 91.1 91.4 91.9 91.0 92.3 91.1 
Selectivity 
(%) for 
Propylene 24.9 23.8 26.2 23.6 25.2 21.6 
Ethylene 38.3 39.4 38.2 38.2 40.1 44.0 
Methane 14.0 14.6 14.0 14.5 14.0 14.5 
Ethane 2.5 2.8 2.9 2.7 2.9 2.5 
C.sub.4+ hydro- 7.4 6.3 5.6 6.5 6.7 6.8 
carbons 
Carbon 12.3 12.5 12.4 13.3 12.5 13.8 
monoxide 
Carbon 0.6 0.6 0.7 0.6 0.6 0.7 
dioxide 
C.sub.3 H.sub.6 /C.sub.2 H.sub.4 0.44 0.40 0.46 0.41 0.42 0.33 
mole ratio in 
products 
______________________________________ 
TABLE 7 
______________________________________ 
Total conversion of propane and its conversion purely by thermal 
cracking at different temperatures and concentrations of O.sub.2 
(relative to propane) in the feed. Reaction conditions: steam/C.sub.3 
H.sub.8 
and thiophene/C.sub.3 H.sub.8 ratios in feed = 0.5 and 
1 .times. 10.sup.-4, respectively and GHSV = 3000 h.sup.-1 
and feed preheating temperature = 500.degree. C. 
O.sub.2 /C.sub.3 H.sub.8 
Propane conversion (%) 
Temp. (.degree.C.) 
ratio Total Thermal cracking 
______________________________________ 
635 0.00 0.8 0.8 
0.06 15.1 7.0 
0.13 23.4 6.3 
0.25 47.0 27.4 
0.50 72.0 42.4 
660 0.00 1.6 1.6 
0.50 74.7 49.0 
715 0.00 7.5 7.5 
0.50 74.7 56.6 
800 0.00 53.9 53.9 
0.06 61.8 59.0 
0.13 68.6 62.2 
0.25 79.2 72.6 
0.50 91.7 77.4 
______________________________________ 
The main advantages of this invention or major improvement achieved by this 
invention over the earlier processes for the production of propylene from 
propane or C.sub.2 -C.sub.4 paraffins are as follows 
1. In the process of this invention, because of the simultaneous occurrence 
of the endothermic hydrocarbon cracking reactions and the exothermic 
oxidative hydocarbon conversion reactions, the heat produced in the 
exothermic reactions is used instantly in the endothermic reactions and 
there is a coupling of the exothermic reactions with the endothermic ones. 
This has imparted following outstanding features to the process of the 
present invention: 
a) The process is operated in a most energy efficient manner with large 
energy saving, achieving high conversion of paraffins with high 
selectivity for propylene and ethylene, with propylene/ethylene mole ratio 
of at least 0.15, and also the process is operated at higher space 
velocity at lower contact time, thus increasing the productivity or 
space-time-yield of propylene and other olefins. 
b) The process is operated in a very safe manner with no possibility of 
reaction run-away conditions. 
c) The process can be made mildly exothermic, near thermoneutral or mildly 
endothermic by manipulating the process conditions. 
d) The process can be operated in a non-adiabatic empty tubular-reactor 
without any serious problems for removing heat from the reactor, when the 
process is mildly exothermic or for providing energy to the reactor, when 
the process if mildly endothermic, thus requiring no or much smaller 
external energy than that required for the thermal cracking process. 
e) Because of the presence of oxygen, not only the rate of total conversion 
of propane but also the rate of thermal cracking of propane, which is 
occurring simultaneously with the oxidative conversion of propane is 
increased, hence the process is operated at low contact time and thereby 
the productivity of propylene and ethylene in the process of this 
invention is higher than that in the earlier thermal cracking process 
operating in the absence of oxygen and also propylene and ethylene are 
produced with propylene/ethylene mole ratio of at least 0.15. 
2. Because of the presence of oxygen in the feed, there is no coke 
deposition on the reactor walls in the process of this invention. Whereas, 
in the earlier thermal cracking process, there is an extensive coke 
deposition in the pyrolysis reactor tubes, causing increase in pressure 
drop across the reactor and ultimately process breakdown for the coke 
removal. Also because of coke deposition, the life of the reactor tubes in 
the thermal cracking process is low. These limitations of the earlier 
thermal cracking process are also overcome in the process of present 
invention. 
3. The process of this invention has also number of advantages over the 
earlier process based on the catalytic oxidative dehydrogenation of 
propane to propylene. 
a) The process of this invention does not involve a use of catalyst and 
therefore there are no problems of catalyst deactivation due to sintering 
or loss of active components or coke deposition. The process operating 
cost is also reduced, as no catalyst is required. 
b) The process of this invention can be made thermoneutral, mildly 
exothermic or mildly endothermic by controlling the simultaneously 
occurring exothermic oxidative conversion and endothermic thermal cracking 
reactions; hence the process occur in a most energy efficient and safe 
manner and the operation of process is simple. Whereas the catalytic 
dehydrogenation is highly exothermic and hence it is a hazardous process; 
it is not safe to operate. 
c) The reactor design, process operation control for the catalytic 
oxidative dehydrogenation process are much more complicated because of its 
hazardous nature and catalyst deactivation and heat and mass transfer 
problems in the catalytic process, as compared to the non-catalytic 
process of this invention.