CA1039027A - Production of carbon disulfide by reaction of sulfur vapor with hydrocarbon gases - Google Patents

Production of carbon disulfide by reaction of sulfur vapor with hydrocarbon gases

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Publication number
CA1039027A
CA1039027A CA263,208A CA263208A CA1039027A CA 1039027 A CA1039027 A CA 1039027A CA 263208 A CA263208 A CA 263208A CA 1039027 A CA1039027 A CA 1039027A
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hydrocarbon
sulfur
stream
reaction
reactor
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French (fr)
Inventor
Morton Meadow
Sidney Berkowitz
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FMC Corp
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FMC Corp
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Abstract

ABSTRACT OF THE DISCLOSURE

Continuous process for producing carbon disulfide by reaction of sulfur and hydrocarbon gas containing a multi-carbon hydrocarbon having at least three carbon atoms at a pressure in the range of 1.0 to 12 atmospheres. A
stream of sulfur at a temperature of at least 650°C and a stream of the hydrocarbon gas are fed into a reaction zone continuously. The flow conditions and mixing conditions of said gas and vapor streams are such that the hydrocarbon gas becomes substantially completely mixed with the sulphur vapor before the hydrocarbon comes into contact with a wall of the reaction zone. The improvement comprises moving the reaction mixture vertically from the zone of introduction of the hydrocarbon stream, the temperatures and rates of flow of the vapor and gas are such that the calculated mixing temperature thereof is in the range of about 585°to 700°C., preferably about 625° to 675°C.

Description

This invention is concerned with continuous process for producing carbon disulfide by reaction of sulfur and hydrocarbon gas containing a multi-carbon hydrocarbon having at least thr~e carbon atoms at a pressure in the range of 3.5 to 12 atmospheres.
The reaction between hydrocarbons and sulfur to produce carbon disulfid~ is well known and is described for instance in Encyclopedia of Chemical Technology of Kirk-Othmer (second edition) Vol. 4 pages 376-380 (and references cited therein) and in numerous patents, such as U.S. patents 2,568,121; 2,636,810; 2,661,267; 2,708,154;
2,857,250; 2,882,130; 2,882,131; 3,087,788; these are only a few of the many patents on this subject.
To avoid the production of impurities, such as taxs which can clog the reactor and contaminate the product or the re-covered unreacted sulfur, it has been customary to employ methane of high purity and to minimize the content of higher hydrocarbons. It has heretofore been thought that non-catalytic ~, mixing of sulfur vapor and hydrocarbon gas containing substan-tial proportions of higher hydrocarbons causes an undesirable thermal reaction to produce polymerization and condensation products. Thus at page 378 of the above-cited Encyclopedia of Chemical Technology there is described a process comprising "mixing the sulfur vapor and preheated methane streams and passing the mixture through a superheater before it enters the lcatalytic] reaction", with the principal reaction taking pla~e in the presence of a catalyst. In discussing this process, the Encyclopedia states:

"This procedure imposes a top limit on the amounts of other hydrocarbons, such as pro-~ pane or heavier, in the methane feed. If " . . . . . .
:

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present in large amounts, these higher molecular weight hydrocarbons, which are more reactive than methane under these conditions, will reac~ thermally with the sulfur in the superheater to pro-duce polymerization and condensation products..."
There have been teachings in the patent literature ; `
to the effect that certain of the higher hydrocarbons can be reacted non-catalytically with sulfur vapor. One of these, British patent 939,209 describes a process using a hydrocarbon feed containing at least 5 carbon atoms in the molecule, using a reaction temperature of at least 750C, such as 900C or 1000C, at atmospheric pressure. The use of such high reaction temperatures re~uires special temperature-resistant materials of construction. Thus, ordinary stainless steels are known to have a short life at temperatures above say, 750C
in the presence of sulfur compounds. Furthermore ope-ration at atmospheric pressure causes considerable difficulty in the recovery of the products of the reaction ¦;
(as in the step of condensing the carbon disulfide from the reaction mixture) and increases the size of the .;.
reactor required. Another disclosure of a non-catalytic processj--in U.S. patent-3,436,181, employs olefinic or diolefinic hydrocarbons and states that the results are "contrary to what could be expected from the résults of the well-known reaction of sulfur or parafinic hydrocarbons higher than C2 ~ ; see also U.S. patent
3,699,215. Another patent, British 1,173,344, employs a hydrocarbon feed in which propane constitutes at least 50% by weight and illustrates operation at atmospheric pressure.

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In accordance with the present invention the higher hydrocarbons, alone or in admixture, can be reacted with sulfur vapor under pressures greater than 3.5 atmospheres (that is, greater than about 37 psig or greater than about 2700 or 3000 mm Hg absolute) to produce carbon disulfide in high yields with very little undesirable by-products by continuously bringing together, in a reaction zone, a stream of sulfur vapor having a temperature of at least 650C (and preferably below about 750C) and a stream 10 - of gas comprising the-higher hydrocarbon. The feed tempera-tures and rates of flow of the sulfur vapor and hydrocarbon gas must also be such that the calculated mixing tempera-ture is in the range of about 585 to 700C, more preferably about 625 to 675C, and the flow conditions and mixing ~;
conditions o~ the sulfur stream and hydrocarbon stream must be such that the hydrocarbon stream becomes substantially completely mixed with sulfur vapor before the hydro-carbon comes into contact with a solid surface in the reaction ~one, such as a heated wall thereof, so that a non-catalytic reaction occurs between substantially all the higher hydrocarbon and sulfur prior to such contact.
In accordance with the process of this invention, the reaction between the higher hydrocarbon and the sul-fur occurs almost instantaneously. Thereafter the mix-ture may be brought into contact with the walls of the reactor, or into contact with packing or other solid surfaces without adverse effect.
In the process a substantially undiluted higher hydrocarbon may be used as the feedstock. In that case extremely high turbulence is needed in order to provide .

~)3~0i~7 the necessary rapid mixing of the components. We have found, for instance, that such turbulence results from feeding the hydrocarbon stream countercurrent to the sulfur stream so that the two streams collide head-on.
A~ can be seen from the Examples below, by this technique we have converted high0r hydrocaxbons, such as liquified petroleum gas (propane-butane mixtures) and pentane, in high yields to carbon disulfide in a residence time of 0.6 second in the reactor; the actual reaction time probably was much less.
As the concentration of higher hydrocarbon in the stream thereof is decreased, a lower degree of agitation is required to bring substantially all its molecules ~`
into reactive contact with the sulfur molecules of the surrounding stream before said hydrocarbon molecules reach the wall of the reactor. For instance when the hydrocarbon stream is primarily methane (which does not itself have a substantial tendency to form by-product tars during its thermal reaction with sulfur) and the concentration of hydrocarbon having more than four carbons in the injected stream is below about 3 mol%
very good results can be obtained, in a reaction tube, by aiming the hydrocarbon stream co-current into the middle of the sulfur vapor stream to form a hydrocarbon I jet which travels within the tube (for example, centrally, - or axially) without coming into contact with the walls of the tube, while the turbulence of the streams helps to mix them and assure that the molecules of higher hydrocarbon react with the sulfur. When, however, the same hydrocarbon jet is aimed slightly to the side (see . . , :
. . :.

103~)27 Example X), significant amounts of undesired polymerization or condensation products, such as tars, are formed. After the initial mixing period, during which substantially all the higher hydrocarbon is xeacted out of contact with the walls, the mixture may be led through further lengths of hot tubes around bends and into contact with various surfaces such as packings; during this further travel, substantially all the methane may be reacted with the sulfur under non-catalytic or catalytic conditions.
10The rapid initial mixing of the two streams may be promoted in various ways. Thus, the tube may have a converging portion at about the point of introduction of ; the hydrocarbon stream so that the sulfur vapor travels the path of a converging cone whose apex lies along the center line of the hydrocarbon stream, the sulfur vapors being forced into the central stream, giving rapid mixing while the mixture is out of contact with the surrounding walls. Other mixing techniques to accomplish this purpose will be apparent to those skilled in the art. Also, the hydrocarbon may be introduced as a plurality of streams (for example, two, three or four co-eurrent streams clustered about the axis of the tube) or as a central annular stream. It is also within the broader scope of the invention to effect the initial mixing by injecting one or more streams of the hydroearbon into a large back-mixing reactor into which a stream of sulfur is also introduced continuously and from which a stream of the reaction mixture is withdrawn continuously, the walls of the back-mixing reactor being spaced a considerable distanee from the hydrocarbon injection ~0;~5~0;~7 points and the contents of that reactor being continuously agitated, as by means of turbulence induced by the mode of introduction of the sulfur vapors; the hack-mixing reactor may be of such volume in relation to the feed volumes and have such mixing therein that the reaction mixture is of substantially uniform composition within the reaction zone, the composition of the mixture into which the feed gases are continuously injected being substantially the same as the composition of the mixture being continuously withdrawn from the reaction zone.
As indicated above, the reaction may be carried out in a tubular reaction chamber through which the hot sulfur vapor is fed and into which the hydrocarbon stream is introduced through an orifice (which may be the out-let end of a hydrocarhon introduction nozzle). In one preferred embodiment, to help keep the hydrocarbon from contact with the walls of the reactor before it has i reacted with the sulfur, the reaction chamber has a ¦ diameter which is more than five tfor example, 6, 10, 15 ! 20 or 20) times the diameter of the hydrocarbon-introduction orifice. Thus, in an arrangement in which the hydrocarbon i is introduced co-current with the sulfur stream, the reaction chamber may be a straight pipe having the afore-said relatively large diameter over a distance (measured axially) of more than 50 (for example, 80, 100, 200 or more) times the diameter of the hydrocarbon-introduction ; orifice. Or, it may be a tube which flares outwardly downstream of the hydrocarbon-introduction orifice. As mentioned above, the higher hydrocarbon reacts very rapidly while any methane in the hydrocarbon feed reacts , more slowly with the sulfur. Thus, when the feed contains methane, the reactor may have à downstream portion for conversion of unreacted methane to carbon disulfide in-cluding a heating section which may be of considerably lesser diameter than the reaction chamber; for example, the initial reaction may be carried out in a large diameter heated tube in a furnace and the reaction mixture may then be led through smaller diameter heated tubes in the same furnace and then to a large diameter packed reactor to carry the methane-sulfur reaction further.
The rapid initial mixing may also be promoted by using a stream of sulfur which moves substantially vertically, as by using a tubular reactor whose walls are substantially vertical rather than horizontal, there-by minimizing the effects of stratification of the streams and consequent contact between unreacted hydrocarbon and the walls of the tube. The sulfur vapor is much denser than the hydrocarbon under the conditions of the reaction and this density difference is accentuated, under the high pressures preferably used in the practice of this invention; that is, increased pressure increases the average molecular weight of the sulfur (more S 8 and S 6 are formed at the expense of S2). The use of a vertically `
moving sulfur stream in itself constitutes another aspect of this invention, and it is within the broader scope of the invention to employ the vertically moving sulfur stream to obtain improved results even under conditions of lower pressure (for example, atmospheric pressure or a pressure of 2 atmospheres) or lower mixing temperature, or both. The sulfur stream may move downward ;..... . . .

1(~390Z7 or upward and the hydrocarbon stream may be introduced countercurrent or co-current in either case, or may even be introduced into an upwardly or downwardly moving sulfur stream.
~ he mixing temperature can be calculated from the heat contributed by each feed component, assuming adiabatic mixing (no additional heat supplied by, or lost from, the outside during mixing) and no chemical reaction (it may be termed the "adiabatic non-reaction 10- mixing temperature"). At this mixing temperature the sum of the gains and losses in enthalpy by the various feed components in reaching that temperature is zero;
thus, for a two-component mixture the heat gained by one component is equal to the heat lost by the other.
The gain or loss in enthalpy can be readily determined on the basis of published thermodynamic data.
For instance, the enthalpy of propane tin BTU
per pound mol) as a function of temperature ("T", in degrees Kelvin) may be expressed as follows:
-49,409.318-1.739T ~ 6.551 X 10 2T2 -2.254 X 10 gT3;
this formula is based on thermodynamic data given by ~-Kobe et al in a series of articles on the thermochemistry of petrochemicals in Petroleum Refiner January 1949 to July 1958. (It will be apparent that, since the first term, -49,409.318, is not affected by temperature and since the number of mols of propane before and after mixing is the same, this first term has no effect on the calculation). The effect, on the enthalpy, of the change in the partial pressure of propane owing to mixing is negligible and is disregarded since it has no significant :: . , .. .. ~ , .
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~039027 effect on the calculation (the propane behaves essentially as a perfect gas under the conditions of operation).
The calculation of the enthalpy change for the sul-fur requires additional steps, because sulfur exists in various molecular forms, such as S2, S~ and S~ (while other sulfur species exist, disregarding them has no significant effect on the calculation). For S2 the enthalpy ~in BTU per pound mol) is 51,986.842 + 11.698T
+ 4.768 X 10 3T2 -2.338 X 10 6T3; and for S6 it is 39,463.695 + 34.6T + 2.376 X 10 3T~; and for Sa it is 35,065.98 + 45.00T + 3.168 X 10 3T2. See for instance, K.K. Kelly, U.S. Bureau of Mines Bulletin 406.5 (1937).
The distribution (relative proportions) of the various sulfur species depends on the pressure and temperature and can be calculated from ~nown thermodynamic data, such as given by Kelly. Thus the distribution of S mole-cules in the incoming sulfur stream (whose temperature and pressure is known) can be determined by a trial-and-error method (as by repeated iterations on a computer).
That is, a distribution-is assumed and its correctness is checked mathematically by the use of known kinetic constants (given by Kelly) relating to the conversion of one form of sulfur into another; based on those calculations, another assumed distribution is chosen and the process of calculation and choice is continued until the correct value is obtained.
The mixing temperature can be calculated by a double set of trial-and-error computations. That is, a mixing temperature is assumed and, from the known number of mols of substances other than sulfur in th~ feed (for .. . ... .... . . .
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examp~e, propane) and the known weight of sulfur in the feed, one can calculate (by trial and error as described above) the distribution of the various sulfur species in the mixture at that assumed mixing temperature. From this, the changes in enthalpies at the assumed mixing temperature are calculated; based on that calculation a new assumed mixing temperature i5 chosen, a new sulfur distribution is calculated (again by trial and error, as above and the changes in enthalpies at that new assumed mixing temperature are calculated; and the process of calculation and choice is repeated (as by repeated iterations on a computer) until a temperature is found at which the sum of ~he enthalpy changes for the feed components is zero.
While the formulas for enthalpies are given above in terms of BTU per pound mol, the very same formulas may be employed for metric units. That is, in the calculation the units in which the formulas are expressed (whether BTU per pound mole or calories per gram mol) become immaterial.
It is found that the calculated mixing temperature is affected significantly by the pressure; thus, if pro-pane is preheated to 200C and supplied at the rate of 153.3 pounds per hour and sulfur is preheated to 600C
and supplied at the rate of 1823 pounds per hour (stoichiometrically, a 63% excess of sulfur), at atmospheric pressure the calculated mixing temperature is about 574C, at 2 atmospheres pressure it is about 563C, and at 4 atmospheres it is about 549C. The pressure in the reactor is preferably within the range of 3.5 to 12 atmospheres, more preferably about 5 to 10 atmospheres.

~39~
The reactor walls may be of any suitable corrosion-resistant construction material such as steel containing significant proportions of chromium and/or nickel. Such commonly available materials as stainless steels, such as those containing about 20% nickel, about 25% chromium and about 0.2 to 0.4~ carbon, may be employed. The temperature of the reactor walls is preferably below about 750C, and above 550C or 600C, such as about 650 to 700C.
As indicated previously the reaction of sulfur with the higher hydrocarbons takes place very quickly in the process of this invention. The reaction mixture may then be quenched and treated to recover sulfur and carbon disulfide in conventional manner. The reaction mixture may be also maintained at a relatively high temperature (for example, in the range of about 550 to 700.C, such as about 600 to about 650C) for relatively long periods before quenching; this is particularly useful for mixtures containing substantial proportions of the more slowly reacting methane, in order to cause the methane to be converted substantially completely to carbon disulfide, and for this purpose additional reaction zones (such as described by Porter U.S. patent 3,087,788) may be used.
The counter-current mixing in itself constitutes another aspect of this invention and it is within the broader scope of the invention to employ the counter-current mixing procedure to obtain improved results even under conditions of lower pressure (for example, atmospheric pressure or a pressure of 2 atmospheres) .

103~0Z-f or lower mixing temperature, or both.
As will be seen from the following Example6, the proportion and type of the multi-carbon hydrocarbon may vary widely. It may constitute 100% of the hydrocarbon feed stream or a much smaller fraction. For instance the hydrocarbon feed stream may be methane containing as little as about 0.3 mol % of hydrocarbons having three or more carbon atoms or as little as 0.04 mol ~
of hydrocarbons having four or more carbon atoms, or it may be methane containing over 1~ of hydrocarbons having four or more carbon atoms. The higher hydrocarbons may be saturated aliphatic hydrocarbons, but (as indicated below) they may be cycloaliphatic or even aromatic, and olefinic compounds may also be present. Generally the average number of carbons of the multi-carbon hydro-carbons will be less than 8 and the content of hydro-carbons having nine carbon atoms or higher will be well below 10 mol %.
For best results the sulfur is fed to the reactor at a rate in excess of that stoichiometrically needed for the formation of CS 2 by reaction with the particular hydrocarbon feedstock. This excess is preferably well above 1%, more preferably at least 10%. With higher concentrations of the higher hydrocarbons in the feed-stock, it is preferable to use greater excesses of sulfur, such as excesses of about 20-300% more preferably about 30-200%.
As indicated in the Examples, the hydrocarbon stream may be fed into admixture with the sulfur stream through a single circular openin~ or orifice. It is also within ;, " ' ~ . ' , - . ~: , 1~)3902~
the broader scope of the invention to feed it th~ough orifices of other shapes, such as rectangular or annular, as well as through a plurality of orifices which ma~ all be located at the same stage of the sulfur flow or (but not necess~rily) located at different stages thereof, that is, a second orifice being situated downstream of the first one. The hydrocarbon feed is preferably at a temperature below that at which significant thermal cracking occurs for its hydrocarbons of at least three carbon atoms (it is believed, however, that su~h cracking occurs when the hydrocarbons come into contact with the hot sulfur vapors, with the sulfur acting as a cracking initiator in process). Thus, the temperature of the hydrocarbon feed is preferably below about 500C, such as below about 450C, for example, about 425, 400 or much lower, such as room temperature. It is, however, within the broader scope of the invention, although less desirable, to preheat the hydrocarbon to a temperature at which cracking does occur.
The following Examples are given to illustrate this invention further. In the Examples the volumes ¦ given represent, in accordance with standard practice, the volume calculated to standard conditions (STP) of a temperature of 0C and an absolute pressure of 760 mm Hg. Residence times are given in seconds and are ! equal to 3600 divided by "space velocity" (S.V.~ expressed in hours ; S.V. is the quotient of the total volume (in liters) of reactants at STP (with sulfur calculated as S2) per hour, divided by the reactor volume ~in liters).

,. ~, : ~ , 10390~7 EXAMPLE I
In this Example a narrow stream of propane heated to 425C is injected countercurrent concentrically into a much wider stream of sulfur preheated to 700C to react substantially adiabatically at a pressure of about 40 psig, that is, 2.8 kg/cm2 gauge. The flow xates are so controlled that the amount of sulfur is about 34% in excess of that required for the stoichiometric reaction with the propane to form carbon disulfide. The reaction 10, is effected in a short reactor, the residence time therein being 0.61 second, and the reaction mixture is then immediately quenched, first in a vessel at 140C
(thereby condensing the sulfur in the reaction mixture).
The non condensed gases, including carbon disulfide, then pass through a pressure-regulator (set to provide a back pressure of 3.7 atmospheres, that is, 40 psig or 2.8 kg/cm2 gauge) from which the gases are passed to a condenser at 0C and undex pressure to condense carbon disulfide; non-condensed gases are vented at atmospheric pressure. The propane lS injected through a 0.318 cm diameter circular orifice into the stream of sulfur flowing in a circular pipe having an internal diameter of a 2.09 cm.
The calculated mixing temperature is about 675C.
Il The propane is converted substantially quantita-I tively (over 99%) and analysis of the condensed carbon -disulfide indicates that it has a purity of 99.89%, about 0.02% of henzene, about 0.09% of thiophene and no toluene. The condensed sulfur contains only traces of carbonaceous material.

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103gOZ7 More specifically, the reactor is a vertical 45.6 cm long section of stainless steel pipel specifically Schedule 4~, 3/4 inch IPS pipe, into which a hydrocarbon-introduction tube having an outside diameter of 0.63S
cm pr~jects from the side. The end of that tube is closed and the upstream side of the tube, adjacent the closed end, is machined to form a smooth flat upstream face arranged perpendicular to the flow path of the sulfur through the larger pipe; into that face the 0.318 cm diameter orifice is drilled. There is a bend in the pipe (through which the hot sulfur vapor is supplied) upstream of the vertical reaction section (in which the hydrocarbon-introduction tube is situated); the bend is about 30 cm upstream of the hydrocarbon-introduction orifice. The reactor is situated in a ~urnace, whose temperature is about 700C. The sulfur and propane are fed to the reactor (from storage vessels maintained at pressures of about 100 psig, through suitable preheaters and flow Icontrol devices) at rates of 760 g per hour of sulfur ¦20 and 39.8 liters (at STP) per hour of propane. (The terms "upstream" and "downstream" are used with reference to the direction of flow of the sulfur and of the resulting reaction mixture which is downwaxd in the Example).
EXAMPLE II
Example I is repeated, using a mixture of propane and H2S in a 1:2 volumetric ratio in place of the pure propane; in this case the sulfur excess with respect to stoichiometry is 300~.
The calculated mixing temperature is about 690C.
Here agin there is a substantially quantitative con-;

, .. ~ - .
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''''~ " , ' ' '' ~ ' ~.03~027 version of propane. Analysis of the condensed carbon di-sulfide indicates that it is over 99.99~ pure, contains about 0.0055~ benzene, 0.0002% thiophene and no tolueneO The con-densed sulfur is bright yellow with no trace of tars.
Specifically the feed rates are 760 g per hour of sulfur, 13.3 liters (at STP) per hour of propane and 26.6 liters (at STP) per hour of H2S.
EXAMPLE III
Example I is repeated, using a mixture of n-hexane and H2S in a 1:3 volumetric ratio in place of pure propane (in this case the sulfur excess with respect to stoichio-metry is 100~), a residence time of 0.58 second, a sulfur preheat temperature of 650C a preheat temperature of the hexane-H2S feed to 200C.
The calculated mixing temperature is about 620C.
Conversion of hydrocarbon to carbon disulfide is 97 per cent. Subsequent inspection of the reactor shows no evidence of carbonaceous impurities. Analysis of the con-densed carbon disulfide indicates that it contains some 3.66%
of benzene, 0.35% of thiophene and 0.002% of toluene. The condensed sulfur appears clear and bright.
The subsequent inspection of the reactor also shows a considerable accumulation of scale ~owing to the effects ~ -of a large number of previous runs at various conditions).
It is believed that the level of impurities in the carbon disulfide is largely due to the surface effect because of this scale accumulation. It is preferable to operate with a smooth surfaced reactor. However, even with this scaly reactor the walls are free of carbon deposits after the run.
EXAMPLE IV

.. . . . .
' 103~V;~7 Example I is repeated, using an LPG mixture (made up largely of butanes and propane, as described below) in place of the pure propane, with a sulfur excess of 150~ with re-spect to stoichiometry, a residence time of 0.58 second, a sulfur preheat temperature of 700C and a hydrocarbon preheat temperature of 200C.
The calculated mixing temperature is about 685C.
Conversion of hydrocàrbon to carbon disulfide is 99.8%.
Analysis of the condensed carbon disulfide indicates that -it contains 0.0834% benzene, 0.0425% thiophene, 0.0003%
toluene and no higher molecular weight constituents. The condensed sulfur appears clear and bright.
The LPG mixture (Phillips LPG Mixture No. 31) has the following composition (in which all numbers are mol percents):
ethane 0.01, propane 36.94, isobutane 16.11, n-butane 44.83, n-pentane 0.01, isopentane 2.04, transbutene-2 0.02, cis-butene-2 0.01, isopropylfluoride 0.03.
ExAMæLE V
Example I is repeated, using n-butane in place of the pure propane, with a sulfur excess of 100% with respect to stoichiometry, a residence time of 0.58 second, a sulfur preheat temperature of 700C. and a hydrocarbon preheat temperature of 200C.
The calculated mixing temperature is about 675C.
Conversion of hydrocarbon to carbon disulfide is 99.8 percent. Analysis of the condensed carbon disulfide in- ;
dicates that it contains 0.0246% benzene, 0.1~ thiophene, 0.002~ toluene and 0.002% higher molecular weight con-stituents. The condensed sulfur appears clear and bright.
EXAMPLE VI

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Example I is repeated, using n-pentane (practical grade) in place of the pure propane, with a sulfur excess of 504 with respect to stoichiometry, a residence time of 0.58 second, a sulfur preheat temperature of about 630-650C, hydrocarbon preheat temperature of 200C., an orifice of 0.16 cm diameter, and a pressuxe of 4.4 atmospheres (60 psig or 4.22 kg/cm2 gauge) in the reactor.
The calculated mixing temperature is about 605C.
Conversion of hydrocarbon to carbon disulfide is 99 percent. Analysis of the condensed carbon disulfide in-dicates that it contains 0.35% benzene, 0.68% thiophene, 0.0008% toluene and 0.0011~ higher molecular weight con-stituents. The condensed sulfur appears clear and bright.
ExAMæLE VII
Example I is repeated, using an aliphatic petroleum naphtha (containing heptane, methylcyclohexane and toluene as principal constituents) in place of the pure propane, I with a sulfur excess of 100% with respect to stoichiometry, ¦ a residence time of 1.35 seconds, a sulfur preheat tempera-i 20 ture of 650C and a hydrocarbon preheat temperature of -200C. In this case, however, the hydrocarbon-introduction tube is positioned with its flat face (and orifice) facing downstream, so that the flow of hydrocarbon is co-current with the sulfur.
The calculated mixing temperature is about 620C.
Conversion of hydrocarbon to carbon disulfide is 94 percent. Analysis of the condensed carbon disulfide in-dicates that it contains 5.44~ benzene, 0.19% thiophene, no toluene and 0.0002% higher molecular weight constituents.
The condensed sulfur appears clear and bright.

.

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The approximate composition of the naphtha in mol per-cent is: 2-methylhexane 0.3; 2,3-dimethylpentane plus 1,1-dimethylcyclopentane 0.2; trans-1,3-dimethylcyclopentane 1.0; cis-1,3-dimethylcyclopentane 0.6; trans-1,2-dimethyl-' cyclopentane 0.5; isooctane 1.5; n-heptane 25.0; cis-1,2-dimethylcyclopenta~e 1.9; methylcyclohexane 44.3; ethyl-cyclopentane 0.2; 2,5-dimethylhexane 2.3; 3,3-dimethylpent-ane 1.2; toluene 10.2;'2,3,4-trimethylpentane 2.9; 1,1,2-trimethylcyclopentane 0.7; others 7.2.
EXAMPLE VIII
Example I is repeated, except for the following: the reactor is made up of four 61 cm long parallel sections (of the same 3/4 inch IPS, Schedule 40, stainless steel pipe) each of which is joined to its neighbor by a return elbow of the same stainless steel so that the reaction mixture flows successively through the four sections in a sinuous path. The preheated sulfur passes directly into this reactor, while the hydrocarbon is introduced concentrically intp the stream of sulfur (at a point 2.5 cm downstream of the inlet , of the reactor) through the,open end of a feed tube having an internal diameter of 0.683 cm. The reactor is kept in an ~ :
electric furnace and the temperature measured at the internal ' wall of the reactor at a point 16 cm downstream of the reactor i inlet is 650C. The hydrocarbon is a natural gas of the following molar composition: 89.78% methane, 4.18% ethane, 1.7% propane, 2.2% butanes, 2.04% nitrogen and 0.1% water.
The sulfur is preheated to 650C. and the hydrocarbon to 400C..
The sulfur excess i6 15% with respect to stoichiometry, the residence time is about 15 seconds and the reactor pressure is 80 psig.

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103902~
The calculated mixing tempexature i~ about 590C.
Conversion to carbon disulfide is near quantitative.
Analysis of the condensed carbon disulfide indicates that it has a purity of 99.99 + %, containing only 0.0045-0.0075%
benzene and thiophene as trace impurities.
After operating continuously for more than 110 hours, there is no plugging of the tubes of the reactor and no car-bon or tar formation. The condensed sulfur is clear, bright yellow and free of tars. ,~
In this Example, the rates of supply of sulfur and -' hydrocarbon are 357 g,per hour and 50 liters (at STP) per hour, respectively. ', The next two examples illustrate the wall effect on tube fouling and by product formation. ' '~
EXAMPLE IX ~ ' The reactor of Example VIII is utilized with the same -~
natural gas, but introducing that gas through a specially ' designed venturi to obtain instant mixing of the hydrocarbon and sulfur, with a sulfur preheat temperature of 700C, a hydrocarbon preheat temperature of 400C, a sulfur excess of 5~, a measured reactor temperature of 700C, a residence time ',' of 11 seconds, and a pressure of about 6~5 atmospheres (80 psig). " ,' The calculated mixing temperature is about 640C.
The conversion rate of the natural gas is quantitative and the carbon ,disulfide has a purity of 99.99 + % with less than 0.0012% benzene and thiophene as trace impurities. There is no evidence of tar formation in the recovered sulfur.
In this Example the rates of supply of sulfur and hydro-30 carbon are 578 g per hour and 88.3 liters (at STP) per hour, ,~ -20-.

:.
,., '':, ' ' . .

16)3~02~

respectively.
EXAMPLE X
The reactor of Example VIII is utilized with the same natural gas, with a sulfur preheat temperature of 700C, a hydrocarbon preheat temperature of 400C, a sulfur excess of 5%, a measured reactor temperature of 700C, a residence time of 11 seconds, and a pressure of 6.5 atmospheres (80 psig or 5.53 Kg/cm2 gauge). Unlike Example VIII, in this Example the central hydrocarbon inlet tube is tilted noticeably (at an angle greater than 10 to the axis of the reactor pipe) so that the hydrocarbon is directed in-itially somewhat toward the wall of the reactor pipe. In contrast to Example IX (using similar conditions of tempera-ture, pressure, flow rates, residence time, and so forth) the conversion rate of the natural gas is only 97%, the carbon disulfide contains in excess of 0.1% of thiophene and benzene, and there is substantial evidence of tars and fouling in the reactor tubes and in the recovered sulfur.
EXAMPLE XI
(A) The reactor of Example VIII is utilized with the same natural gas, a sulfur preheat temperature of 600C, a hydrocarbon preheat temperature of 400C, 30~ excess sul-fur with respect to stoichiometry, residence time of 11 seconds, measured reactor temperature of 650C, reactor pressure ao psig (about 6.5 atmospheres or 5.63 Kg/cm2 gauge).
The rates of supply of sulfur and hydrocarbon are 611 g per hour and 75.5 liters (STP) per hour, respectively.
The calculated mixing temperature is 560C.
The conversion of hydrocarbon is 92.3%, the condensed - , . . -.
: :..... , .. ~

103~027 carbon disulfide contains 0.0122% thiophene and benzene, and there is evidence of fouling of the reactor.
(B) The Example is repeated, e~cept that the sulfur preheat temperature is 650C. This gives a calculated mix-ing temperature of 605~C. The conversion of hydrocarbon is quantitative, the condensed carbon disulfide is 99.99~ pure, with 0.0036% thiophene and benzene and there is no evidence of tarring or fouling of the reactor.
EXAMPLE XII

.
Example I is repeated, using a mixture of 1 mol of propane and 3 mols of propylene in place of the pure pro-pane, with a sulfur excess of 112% with respect to stoi-chiometry, a residence time of 0.61 seconds, a sulfur pre-heat temperature of 700C and a hydrocarbon preheat tem-perature of 415C and a hydrocarbon-introduction orifice having a diameter of 0.102 cm.
The calculated mixing temperature is about 680C.
Conversion of hydrocarbon is over 99%. Analysis of condensed carbon disulfide indicates that it contains 0.0466% benzene, 0.0118% thiophene, no toluene.
EXAMPLE XIII
Example I is repeated, using methane in place of the pure propane, with a sulfur excess of 150% with re-spect to stoichiometry, a residence time of 0.59 second, a sulfur preheat temperature of 700C and a hydrocarbon preheat temperature of 415C.
The calculated mixing temperature is about 680C.
Conversion of hydrocarbon is about 91%. Analysis of the condensed carbon disulfide indicates that it contains 0.003% benzene, 0.004~ thiophene, no toluene.

.

, .
. . .

~0390Z7 EXAMPLE XIV
In this Example, apparatus similar to that de-scribed in Example VIII is used; sulfur is introduced continuously into a pipe in a furnace and, at a point on the pipe at which the sulfur has become vaporized and preheated the desired predetermined temperature, the preheated hydrocarb~n is introduced continuously through a concentrically located tube to react with the sulfur in the heated pipe. The internal diameter of the pipe is 14.288 cm and the internal diameter of the hydrocarbon feed tube is 3.18 cm (its external diameter is 4.288 cm).
The hydrocarbon feed is natural gas having the following analysis (by mol %): methane 96.73, ethane 2.28, propane Q.32, isobutane 0.02, butane 0.01, isopentane 0.01, n-pentane 0.01, hexane less than 0.01, other hydrocarbons 0.01, nitrogen 0.23, C02 0.37. The inlet pressure is `~
about 7.8 atmospheres (about 100 psig or 7.03 Kg/cm gauge), the sulfur is preheated to 650C, the hydrocarbon feed is preheated to 400C, the excess sulfur with re-spect to stoichiometry is 15%. The sulfur and hydrocarbon enter.the reaction zone at linear velocities of 6.48 and 116 meters per second, respectively (calculated on the basis of their feed rates and cross-sectional areas;
for sulfur the area is that of the annular space around the hydrocarbon feed tube). The calculated mixing tempera-ture is on the order of 600C. The mixture travels through a straight length of the same pipe for about 9.1 meters, then around a bend and through more of the same type of pipe in the furnace, then (its temperature being about 630-650C) enters a packed reactor chamber, then passes ;`

.

- . - . .

103~02~
through more heated pipe in the furnace to reheat it to about 630-650C and then through a second packed reactor chamber containing silica gel particles, the total residence time of the mixture being about 34 seconds, after which sulfur and carbon disulfide are successively condensed from the mixture in conventional manner. Carbon disulfide is produced in very high yield and at Yery high purity, having especially low benzene content.
EXAMPLE XV
Repeat Example XIV using a hydrocarbon feed tube whose outlet has an internal diameter of 1.4 cm, all other conditions being the same (except for the hydro-carbon linear velocity which is of course higher, since the same amount of hydrocarbon is fed through a smaller opening).
EXAMPLE XVI
Repeat Example XIV using a reactor whose 9.1 meter length (upstream of the first bend encountered by the mix-ture) has a diameter of--20-cm,--all-other--¢onditions-being 20 the same (except for the sulfur linear velocity which is of course lower, since the same amount of sulfur is fed through a larger pipe). -In Examples III, IV, V, VI, VIIt XII, and XIII the sulfur feed rates in grams per hour are 760, 850, 83~, 855, 760, 840 and 760, respectively, and the hydrocarbon -feed rates (in grams per hour unless indicated otherwise) are 53.4 hexane, 47.2 LPG, 58 butane, 80.2 pentane, 53.8 naphtha, 7.5 liters (STP) propane and 22.4 liters (STP) propylene per hour, 54 liters ~STP) methane per hour.
30 In these Examples, simple calculation shows that the linear . , , - .
" .

~0~0;27 velocity of the hydrocarbon stream emerging from the orifice is considerably greater than the linear velocity of the sulfur stream; thus for Example VI the pentane linear velocity is well over twice the sulfur linear velocity, specifically about 30.9 cm par second vs about 6.7 cm per second.
Reference is made here to Canadian patent No. 1,011,533 of Meadow, Berkowitz and Manganaro entitled "Production of Carbon Disulphide from Sulfur Vapours and a Gaseous Hydrocarbon".
That patent disclcses the use of converging sulfur stream.
The venturi mentioned in Example IX above is that shown in Fig. 1 of said patent, in which the sulfur vapor is introduced through the pipe of circular cross section, in an annular stream around the coaxial hydrocarbon feed tube (also of circular cross section) having a chamfered outlet end. To -form the sulfur vapor stream into a converging conical stream, there is a venturi insert which fits securely within the otherwise uniform pipe and which has an inwardly converging portion, a throat and an outwardly converging (or pressure recovery) section. The sulfur vapor stream is thus forced through a narrow gap around the chamfered outlet end of the hydrocarbon feed tube, thus greatly increasing in velocity (bernoulli's principle) as it approaches the hydrocarbon stream. This increase in velocity increases the "force ratio"
of the outer (sulfur) stream to the inner (hydrocarbon) stream forcing the sulfur stream into penetrating contact with the hydrocarbon stream and increases the interpenetration and mixing of ,. . ~ . . , . - , . -.,, -: -10390Z'~ ~
the two streams. The force ratio is defined as Movo ~`
MLVL
where Mo and ML are the mass rates of flow of the ~`
outer and inner streams respectively and VO and V~ are the respective linear velocities of said streams. The force ratio in Example IX is in the neighborhood of 10.

....

... . . .. . . ..

Claims (8)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:
1. Process for producing carbon bisulfide by the reaction of sulfur and a hydrocarbon in gaseous state containing a multi-carbon hydrocarbon having at least three carbon atoms, at a pressure in the range of 1.0 atmospheres to 12 atmospheres, in which a hydrocarbon stream is introduced into a stream of sulfur having a temperature of at least 650°C
in a reactor to form a hot reaction mixture whereby to react said sulfur and hydrocarbon to form carbon bisulfide in said reactor, said reactor having solid walls, the flow conditions and mixing conditions of the sulfur stream and hydrocarbon stream being such that a non-catalytic reaction occurs between substantially all the hydrocarbon and sulfur before the hydrocarbon comes into contact with a solid surface in the reaction zone, wherein the improvement comprises moving said reaction mixture vertically from the zone of introduction of said hydrocarbon stream, the temperatures and rates of flow of said sulfur and said hydrocarbon being such that the calculated mixing temperature thereof is in the range of about 585° to 700°C.
2. Process as in claim 1 in which said reactor comprises a duct having substantially vertical walls and through which a stream of sulfur vapor moves substantially vertically, the stream of hydrocarbon being introduced into the sulfur vapor at a point spaced from said walls.
3. Process as in claim 2 in which said hydrocarbon is principally saturated multicarbon hydrocarbon having at least 3 carbon atoms and the average number of carbon atoms in the hydrocarbon is less than 8.
4. Process as in claim 1, 2 or 3 wherein the reaction is conducted at a pressure of at least 3.5 atmospheres.
5. Process as in claim 1, 2 or 3 wherein the reaction is conducted at a pressure within the range of 3.5 to 12 atmospheres.
6. Process as in claim 1, 2 or 3 wherein the mixing temperature is in the range of about 625 to 675°C.
7. Process as in claim 1, 2 or 3 wherein the mixing temperature is in the range of about 625 to 675°C and the pressure is up to about 12 atmospheres.
8. Process as in claim 1, 2 or 3 wherein the stream of sulphur has a temperature below about 750°C.
CA263,208A 1973-04-30 1976-10-13 Production of carbon disulfide by reaction of sulfur vapor with hydrocarbon gases Expired CA1039027A (en)

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US355991A US3927185A (en) 1973-04-30 1973-04-30 Process for producing carbon disulfide
CA197,162A CA1013117A (en) 1973-04-30 1974-04-09 Production of carbon disulfide by reaction of sulfur vapor with hydrocarbon gases

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