PROCESS FOR PRODUCING C2 AND C3 HYDROCARBONS
20170349843 · 2017-12-07
Inventors
- Arno Johannes Maria Oprins (Maastricht, NL)
- Andrew P. DAVIES (Cleveland, GB)
- Andrew Mark Ward (Stockton-on-Tees, GB)
- Kae Shin WONG (Geleen, NL)
- Luis ARAMBURO (Geleen, NL)
- Maikel van IERSEL (Den Bosch, NL)
Cpc classification
C10G65/00
CHEMISTRY; METALLURGY
International classification
Abstract
The invention relates to a process for producing C2 and C3 hydrocarbons, comprising a) subjecting a mixed hydrocarbon feedstream to first hydrocracking in the presence of a first hydrocracking catalyst to produce a first hydrocracking product stream; b) separating the first hydrocracking product stream to provide a light hydrocarbon stream comprising C4− hydrocarbons and c) subjecting the light hydrocarbon stream to C4 hydrocracking in the presence of a C4 hydrocracking catalyst to obtain a C4 hydrocracking product stream comprising C2 and C3 hydrocarbons.
Claims
1. A process for producing C2 and C3 hydrocarbons, comprising a) subjecting a mixed hydrocarbon feedstream to first hydrocracking in the presence of a first hydrocracking catalyst to produce a first hydrocracking product stream; b) separating the first hydrocracking product stream to provide a light hydrocarbon stream comprising C4− hydrocarbons and c) subjecting the light hydrocarbon stream to C4 hydrocracking optimized for converting C4 hydrocarbons into C3 hydrocarbons in the presence of a C4 hydrocracking catalyst to obtain a C4 hydrocracking product stream comprising C2 and C3 hydrocarbons.
2. The process according to claim 1, wherein the first hydrocracking is a hydrocracking process suitable for converting a hydrocarbon feed that is relatively rich in naphthenic and paraffinic hydrocarbon compounds to a stream rich in LPG and aromatic hydrocarbons.
3. The process according to claim 1, wherein the first hydrocracking catalyst is a catalyst containing one metal or two or more metals of group VIII, VI B or VII B of the periodic classification of elements deposited on a carrier.
4. The process according to claim 1, wherein the C4 hydrocracking catalyst comprises a mordenite or an erionite.
5. The process according to claim 1, wherein the C4 hydrocracking catalyst consists of a mordenite and an optional binder or comprises sulfided-nickel/H-Erionitel and the C4 hydrocracking is performed under conditions comprising a temperature between 325 and 450° C., a partial hydrogen pressure between 2 and 4 MPa, a molar ratio hydrogen to hydrocarbon feed of 2:1 to 8:1, wherein the number of moles of the hydrocarbon feed is based on the average molecular weight of the hydrocarbon feed and a VVH of 0.5 to 5 h.sup.−1.
6. The process according to claim 1, wherein step b) further provides a heavy hydrocarbon stream comprising C6+ hydrocarbons and the process further comprises the step of d) subjecting the heavy hydrocarbon stream to second hydrocracking in the presence of a second hydrocracking catalyst to produce a second hydrocracking product stream comprising BTX, wherein the second hydrocracking is more severe than the first hydrocracking.
7. The process according to claim 1, wherein the second hydrocracking product stream is substantially free from non-aromatic C6+ hydrocarbons.
8. The process according to claim 1, wherein the second hydrocracking is performed using a hydrocracking catalyst comprising 0.01-1 wt-% hydrogenation metal in relation to the total catalyst weight and a zeolite having a pore size of 5-8 Å and a silica (SiO.sub.2) to alumina (Al.sub.2O.sub.3) molar ratio of 5-200 under conditions comprising a temperature of 300-580° C., a pressure of 0.3-5 MPa gauge and a Weight Hourly Space Velocity (WHSV) of 0.1-15 h.sup.−1.
9. The process according to claim 1, wherein C4− hydrocarbons in the second hydrocracking product stream are separated from the second hydrocarbon product stream and recycled back to the separation of step b) or subjected to the C4 hydrocracking of step c).
10. The process according to claim 1, wherein step b) further involves separating C5 hydrocarbons from the first hydrocracking stream to be recycled back to the first hydrocracking of step a).
11. The process according to claim 1, wherein at least part of the C4 hydrocarbons in the C4 hydrocracking product stream is recycled back to the C4 hydrocracking in step c).
12. The process according to claim 1, wherein the mixed hydrocarbon feedstream comprises a naphtha or a naphtha-like product.
13. The process according to claim 1, wherein H2 or H2 and C1 hydrocarbon is separated from the first hydrocracking product stream before the separation to provide the light hydrocarbon stream.
14. The process according to claim 1, wherein the amount of methane in the first hydrocracking product stream is at most 5 wt %.
15. The process according to claim 1, wherein the amount of the C5+ hydrocarbons in the light hydrocarbon stream is at most 10 wt % and the amount of the C2-C3 hydrocarbons in the C4 hydrocracking product stream is at least 60 wt %.
16. The process according to claim 8, wherein the temperature is 425-580° C.
17. The process according to claim 12, wherein the mixed hydrocarbon feedstream has a boiling point range of 20-200° C.
Description
PREFERRED EMBODIMENTS
[0087] In some particularly preferred embodiments,
step b) further involves separating C5 from the first hydrocracking stream to be recycled back to the first hydrocracking of step a);
step b) further provides a heavy hydrocarbon stream comprising C6+ and
the heavy hydrocarbon stream obtained by step b) is subjected to second hydrocracking in the presence of a second hydrocracking catalyst to produce a second hydrocracking product stream comprising BTX, wherein the second hydrocracking is more severe than the first hydrocracking.
System
[0088] In a further aspect, the present invention also relates to a process installation suitable for performing the process of the invention, an example of which is illustrated in
[0092] The separation unit (102) may be arranged to provide further a heavy hydrocarbon stream (112) comprising at least C6+.
[0093] The system (100) according to the invention may further comprise
a second hydrocracking unit (103) arranged for performing second hydrocracking of the heavy hydrocarbon stream (112) in the presence of a second hydrocracking catalyst to produce a second hydrocracking product stream (114) comprising BTX.
[0094] The separation unit (102) may be arranged to separate C5 (108) from the C4 hydrocracking stream (106) and the system (100) according to the invention may further be arranged to recycle back at least part of the C5 (108) to the first hydrocracking unit (101).
[0095] The separation unit (102) may use any known technology for the separation of a mixed hydrocarbon stream, for example, gas-liquid separation, distillation or solvent extraction.
[0096] The separation unit (102) may be one fractionating column having outlets for different hydrocarbon streams or a combination of multiple fractionating columns. For example, the separation unit (102) may comprise a fractionating column having respective outlets for the light hydrocarbon stream (107), the C5 hydrocarbon stream (108) and the heavy hydrocarbon stream (112).
[0097] In other embodiments, the separation unit (102) comprises a first column having an outlet for the light hydrocarbon stream (107) and an outlet for the remainder; and a second column having an inlet connected to the outlet for the remainder of the first column, an outlet for the C5 hydrocarbon stream (108) and an outlet for the heavy hydrocarbon stream (112).
[0098] The system according to the invention may further comprise a C4 processing unit arranged for processing C4 e.g. in the C4 hydrocracking product stream or separated out from the separation unit (102). The C4 processing unit may be formed of one or more processing units. For example, the C4 processing unit may be a unit for processing C4 hydrocarbon by isomerization, butane dehydrogenation (non-oxidative and oxidative) or reaction with methanol and reaction with ethanol. The C4 processing unit may also be a combination of units, e.g. a unit for isomerization followed by a unit for reaction with methanol or a unit for reaction with ethanol.
[0099] As shown in
[0100] In this embodiment, the separations are performed such that the light hydrocarbon stream 107 consists of C4−, and the heavy hydrocarbon stream 112 consists of C6+. The separation unit 102 further provides a C5 hydrocarbon stream 108.
[0101] The light hydrocarbon stream 107 of C4− is fed to the C4 hydrocracking unit 115 which produces a C4 hydrocracking stream 116 comprising C2 and C3. C4 may be separated from the C4 hydrocracking stream 116 to be recycled back to the C4 hydrocracking unit 115 (not shown).
[0102] The heavy hydrocarbon stream 112 of C6+ is subjected to the second hydrocracking unit 103, which produces a second hydrocracking product stream 114 comprising BTX. The second hydrocracking product stream 114 is separated into a stream 117 comprising BTX and a stream 111 comprising C4− which is recycled back to the separation unit 102.
[0103] The C5 hydrocarbon stream 108 is recycled back to the first hydrocracking unit 101. Due to the recycling from the separation unit 102 to the first hydrocracking unit 101, the amount of C2-C3 in the final product in the light hydrocarbon stream 107 is increased.
EXAMPLES
Example 1
[0104] A feed consisting of n-pentane was subjected to hydrocracking in order to determine the influence of hydrocracking conditions to the product compositions. The experiments were carried out in a 12 mm reactor, wherein the catalyst bed was located in the isothermal zone of the reactor heater. The catalyst used was a mixture of 2 grams of Pt on alumina (Pt-loading of 0.75 wt %) and H-ZSM-5 (SiO.sub.2/Al.sub.2O.sub.3=80).
[0105] The feed stream was fed to the reactor. The feed stream enters a vaporizer section prior to the reactor where it is vaporized at 280° C. and mixed with hydrogen gas. The conditions used throughout these experiments were: WHSV=1/hr, pressure was 1379 kPa (200 psig) and the molar ratio H.sub.2/hydrocarbons was 3. The temperature of the isothermal zone of the reactor was varied between 375 and 450° C. The effluent of the reactor was sampled in the gas phase to an online gas chromatograph. Product analyses were carried out once per hour.
TABLE-US-00001 TABLE 1 Compositions of hydrocracking product effluent Component 375° C. 400° C. 425° C. 450° C. Methane (wt %) 0.5 1.1 2.2 3.9 Ethane (wt %) 3.3 7.2 12.7 19.4 Propane (wt %) 16.3 24.4 32.8 39.7 Butanes (wt %) 16.9 19.8 20.8 19.0 i-Pentane (wt %) 11.9 13.8 13.4 9.6 n-Pentane (wt %) 49.0 32.3 17.3 7.2 C6+ (wt %) 2.1 1.4 0.8 1.2 Selectivity (—) 98.7 98 96.8 95.3
[0106] The compositions of the product effluent at different reactor temperatures are provided in Table 1. The selectivity was defined as (100%−(amount of methane formed/amount of C5 converted)). The amount of C5 converted is defined as (total amount−(i-pentane and n-pentane)). By comparing the results in Table 1, it was observed that when the reactor temperature is decreased, the overall selectivity is increased during hydrocracking. It is anticipated that a similar trend will be observed when a feed consisting of butanes is subjected to hydrocracking (based on experiments using different carbon number paraffin feeds and conversions and production rates obtained using naphtha type feeds).
[0107] It can therefore be concluded that a higher selectivity can be achieved by operating at a lower temperature.
Example 2
[0108] A feed consisting of a normal paraffin was subjected to hydrocracking in order to determine the influence of hydrocarbon chain length to the extent of conversion. The experiments were carried out in a 12 mm reactor, wherein the catalyst bed was located in the isothermal zone of the reactor heater. The catalyst used was a mixture of 2 grams of Pt on alumina (Pt-loading of 0.75 wt %) and H-ZSM-5 (SiO.sub.2/Al.sub.2O.sub.3=80).
[0109] The feed stream was fed to the reactor. The feed stream enters a vaporizer section prior to the reactor where it is vaporized at 280° C. and mixed with hydrogen gas. The conditions used throughout these experiments were: WHSV=1/hr, pressure was 1379 kPa (200 psig) and the molar ratio H.sub.2/hydrocarbons was 3. The temperature of the isothermal zone of the reactor was varied between 300 and 500° C. The effluent of the reactor was sampled in the gas phase to an online gas chromatograph. Product analyses were carried out once per hour.
TABLE-US-00002 TABLE 2 Single-pass conversion of normal paraffins Feed component 300° C. 350° C. 375° C. 400° C. 425° C. 450° C. 500° C. n-Pentane 51.03 67.74 82.70 92.82 n-Hexane 92.76 96.35 98.20 98.96 99.67 n-Heptane 92.76 99.10 99.51 99.73 99.90 99.98 100 n-Octane 99.89 100
[0110] The conversion level at different reactor temperatures is provided in Table 2. The conversion level was defined as ((n-paraffin effluent concentration in wt %−100)/100). By comparing the results in Table 2, it was observed that when the chain length of the normal paraffin is reduced, the extent of conversion is reduced at a similar temperature. Alternatively, increased reaction temperatures are required to achieve sufficient conversion levels for normal paraffins with shorter chain length. By interpolation of the data presented in Table 2, the temperature required to achieve 80% conversion could be estimated for n-pentane, n-hexane and n-octane. The estimated reaction temperatures are depicted in
[0111] As illustrated by Example 1, the feed components that are to be exposed to these higher temperatures should be minimized to achieve high selectivities. This could be achieved by sending the butanes and pentanes to a dedicated hydrocracker optimized for converting C4 to C3 instead of subjecting them to second hydrocracking having severe conditions.