PROCESS FOR PRODUCING BENZENE AND LPG2

Abstract

The invention is directed to a process for producing benzene and LPG comprising the steps of: (a) reacting a source feed stream comprising monoaromatic compounds of formula (I), wherein R1-R5 are the same or different and are chosen from hydrogen or a linear alkyl group of 1-10 carbon atoms, and methanol in an alkylation reactor comprising a basic catalyst to obtain an alkylation product stream and subsequently (b) contacting the alkylation product stream in the presence of hydrogen in a hydrocracking reactor with 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 (SiO2) to alumina (Al2O3) molar ratio of 5-200 to produce a hydrocracking product stream comprising benzene and LPG under process conditions including a temperature of 425-580° C., a pressure of 300-5000 kPa gauge and a Weight Hourly Space Velocity of 0.1-15 h.sup.−1.

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Claims

1. A process for producing benzene and LPG comprising the steps of: (a) reacting a source feed stream comprising monoaromatic compounds of formula (I), ##STR00003## wherein R1-R5 are the same or different and are chosen from hydrogen or a linear alkyl group of 1-10 carbon atoms, and methanol in an alkylation reactor comprising a basic catalyst to obtain an alkylation product stream and subsequently (b) contacting the alkylation product stream in the presence of hydrogen in a hydrocracking reactor with 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 (SiO2) to alumina (Al2O3) molar ratio of 5-200 to produce a hydrocracking product stream comprising benzene and LPG under process conditions including a temperature of 425-580° C., a pressure of 300-5000 kPa gauge and a Weight Hourly Space Velocity of 0.1-15 .sup.−1.

2. The process according to claim 1, wherein step (b) involves further feeding in the hydrocracking reactor a second feed stream comprising C5-C12 hydrocarbons.

3. The process according to claim 1, wherein the monoaromatic compounds comprise toluene, xylene and/or 1,3,5-trimethyl benzene.

4. The process according to claim 1, wherein the source feed stream comprises C5-C12 hydrocarbons.

5. The process according to claim 1, wherein the second feed stream comprises pyrolysis gasoline, straight run naphtha, light coker naphtha and coke oven light oil or mixtures thereof.

6. The process according to claim 1, further comprising the step of separating the hydrocracking product stream into benzene, LPG and optionally a stream comprising alkyl monoaromatic compounds.

7. The process according to claim 6, wherein the source feed stream comprises the stream comprising the alkyl monoaromatic compounds separated from the hydrocracking product stream and fed back to the alkylation reactor.

8. The process according to claim 1, wherein the alkylation reactor comprises an X or Y zeolite catalyst modified with B, P, Na, K, Cs or Rb or mixtures thereof.

9. The process according to claim 1, wherein in the alkylation reactor the ratio between methanol and the monoaromatic compound is between 1:1 and 1:20.

10. The process according to claim 1, wherein the temperature in the alkylation reactor is between 100 and 1000° C.

11. The process according to claim 1, wherein the temperature in the alkylation reactor is between 350 and 440° C.

12. The process according to claim 1, wherein the process is carried out in a system in which an inlet of the alkylation reactor is heated by an outlet of the hydrocracking reactor.

13. The process according to claim 4, wherein the source feed stream comprises pyrolysis gasoline, straight run naphtha, light coker naphtha and coke oven light oil or mixtures thereof

Description

EXPERIMENT 1

[0060] A feed stream of xylene was fed to an alkylation reactor having an alkylation catalyst comprising Cs-13X zeolite molecular sieve and Cobaltborate. Methanol was also fed to the reactor. The molar ratio between xylene to methanol was 60% to 40%. The temperatures for the reaction are mentioned in Table 1. The pressure was 1 atm and WHSV was 4-5 h.sup.−1.

[0061] The proportions of the obtained compounds are summarized in Table 1 (in wt %).

TABLE-US-00001 TABLE 1 Ethyl Methyl Ethyl Temp methyl Diethyl vinyl vinyl Divinyl (° C.) benzene benzene benzene benzene benzene Naphthalene Xylene Methanol 400 10-20 5-10 5-10 5-10 2-5 — 50-55 15-20 430 10-20 5-10 5-10 5-10 2-5 — 45-50 10-15 450 10-20 5-10 — 5-10 2-5 2-5 45-50 10-15

[0062] When the reaction temperature was 450° C., some portion of naphthalene was formed, which is not desirable. Hence, the reaction temperature is preferably below 450° C., for example at most 440° C.

[0063] About 10-15% of xylene in the feed stream was alkylated to result in various compounds mentioned in Table 1. The methyl groups of xylene were converted into ethyl group or vinyl group, or remained as methyl group.

[0064] Alkylation product streams were thus obtained enriched in monoaromatic compounds having ethyl group or vinyl group instead of methyl group. The alkylation product stream can be subjected to a hydrocracking step as defined in step (b) of the process of the invention.

[0065] Diethyl benzene, ethyl vinyl benzene and divinyl benzene will be converted into benzene in the subsequent hydrocracking step. Hence, it can be concluded that xylene which would not be converted into benzene by hydrocracking can increase benzene yield by first subjecting it to alkylation.

[0066] Ethyl methyl benzene and methyl vinyl benzene will be converted into toluene. If toluene is fed back to the alkylation reactor, some of the toluene will be converted into ethylbenzene. Ethylbenzene will be converted into benzene by subsequent hydrocracking.