Process for producing alkylated aromatic hydrocarbons from a mixed hydrocarbon feedstream

Abstract

The present invention relates to a process for producing alkylated aromatic hydrocarbons such as ethyl benzene or cumene from a mixed hydrocarbon feedstream comprising subjecting C6 cut separated from said mixed hydrocarbon feedstream to hydrocracking to provide benzene and subjecting said benzene to alkylation.

Claims

1. A process for producing alkylated aromatic hydrocarbons comprising: (a) subjecting a mixed hydrocarbon feedstream to a separation to provide a C6 cut; (b) subjecting the C6 cut to hydrocracking, wherein the hydrocracking comprises contacting the C6 cut with a hydrocracking catalyst comprising a hydrogenation metal and a zeolite under hydrocracking conditions comprising a temperature of 450-580 C., a pressure of 300-5000 kPa gauge, and a Weight Hourly Space Velocity of 0.1-20 h.sup.1 to provide a benzene stream, wherein the benzene stream has a benzene purity of at least 98 wt %; and (c) subjecting the benzene stream to alkylation to provide a product stream rich in alkylated aromatic hydrocarbons.

2. The process according claim 1, wherein step (b) further comprises separating the benzene stream by vapor-liquid separation.

3. The process according to claim 1, wherein the hydrocracking catalyst comprises 0.1-1 wt-% of the hydrogenation metal in relation to the total catalyst weight and the zeolite has a pore size of 5-8 and a silica (SiO.sub.2) to alumina (Al.sub.2O.sub.3) molar ratio of 5-200.

4. The process according to claim 3, wherein the benzene stream comprises less than 1 wt % co-boilers of benzene.

5. The process according to claim 1, wherein the hydrocracking produces a benzene stream comprises less than 1 wt % co-boilers of benzene.

6. The process according to claim 1, wherein the alkylation comprises contacting the benzene stream in the presence of ethylene with an alkylation catalyst under alkylation conditions to produce ethylbenzene, wherein said alkylation catalyst comprises beta zeolite, zeolite Y, ZSM-12, MCM-22 or mordenite and wherein said alkylation conditions comprise a temperature of 120-250 C., a pressure of 1000-5000 kPa, a Weight Hourly Space Velocity (WHSV) of 0.5-20 h.sup.1, and a benzene/ethylene molar ratio of 3-10.

7. The process according to claim 6, wherein the temperature is 150-230 C., the Weight Hourly Space Velocity is 1-10 h.sup.1, and the benzene/ethylene molar ratio is 5-8.

8. The process according to claim 1, wherein the alkylation comprises contacting the benzene stream in the presence of propylene with an alkylation catalyst under alkylation conditions to produce cumene, wherein said alkylation catalyst comprises a zeolite selected from the group consisting of beta zeolite, zeolite Y, ZSM-12, MCM-22 and mordenite and wherein said alkylation conditions comprise a temperature of 120-250 C., a pressure of 1000-5000 kPa, a Weight Hourly Space Velocity (WHSV) of 0.5-20 and a benzene/propylene molar ratio of 3-10.

9. The process according to claim 8, wherein the temperature is 150-230 C., the Weight Hourly Space Velocity is 1-10 h.sup.1, and the benzene/propylene molar ratio is 5-8.

10. The process according to claim 1, wherein the stream rich in alkylated aromatic hydrocarbons is subjected to a separation to provide a monoalkylated aromatic product stream and a stream comprising polyalkylated aromatic product and wherein said polyalkylated aromatic product is recycled to the hydrocracking.

11. The process according to claim 1, wherein the mixed hydrocarbon feedstream comprises reformate.

12. The process according to claim 1, the benzene stream has a benzene purity of greater than 99 wt %.

13. The process according to claim 1, wherein the hydrocracking further produces a C2-3 alkane stream that is subjected to olefins synthesis to provide a C2-3 alkene stream that is subjected to the alkylation as alkylation agent.

14. The process according to claim 13, wherein the C2-3 alkane stream comprises ethane and the olefins synthesis is ethane cracking to provide ethylene.

15. The process according to claim 13, wherein the C2-3 alkane stream comprises propane and the olefins synthesis is propane dehydrogenation to provide propylene.

16. The process according to claim 15, wherein the dehydrogenation comprises contacting the propane with a dehydrogenation catalyst under dehydrogenation conditions to produce propylene.

17. The process according to claim 16, wherein the dehydrogenation catalyst comprises a catalyst support comprising 0.1-1 wt-% hydrogenation metal in relation to the total catalyst weight.

18. The process according to claim 16, wherein the dehydrogenation conditions comprise a temperature of 450-800 C. and a pressure of ambient to 1000 kPa gauge.

19. The process according to claim 18, wherein the temperature is 540-700 C. and the pressure is 25-500 kPa gauge.

Description

EXAMPLE 1

(1) The main advantage of employing the hydrocracking process step in the process of the present invention is to produce high purity benzene, from a mixed C6 hydrocarbon stream, that is subsequently sent to alkylation unit for EB/cumene production. The results showed below were obtained by combination of laboratory experimentation and flowsheet modelling. The GHC product slate is simulated via a yield estimator that is based on extensive experimental data. The alkylation process step is modelled based on literature data published in Laredo et al. (2009) Applied Catalysis A: General 363, 11-18 and Laredo et al. (2009) Applied Catalysis A: General 363, 19-26.

(2) The composition of reformate C6 cut can vary substantially but essentially consists of C6 paraffins, isoparaffins, benzene and small amount of naphthenes. Table 1 shows examples of reformate C6 cut contents:

(3) TABLE-US-00001 TABLE 1 Examples of reformate C6 heart cut compositions: Component RC6-1 (wt %) RC6-2 (wt %) Benzene 16.5 13.4 Paraffins 21.6 22.7 Naphthenes 4.9 4.6 Iso-paraffins 55.9 58.3

(4) In example 1, RC6-2 is sent to the GHC unit that is operated at a temperature of 475 C., a hydrogen-to-hydrocarbon ratio of 3 and a pressure of 1379 kPa (200 psig) using a hydrocracking catalyst comprising a 1:1 weight ratio physical mixture of Pt/Al.sub.2O.sub.3 and ZSM-5 zeolite as described in Example 1 of WO/2013/182534 A1. The products of hydrocracking unit are divided into liquid aromatics (benzene and toluene) and lights gases (hydrogen, methane, ethane and propane).

(5) A simple reactor model developed previously was used to predict the product slate of GHC unit. The reactor model uses correlations that was statistically obtained from experiments of wide range conditions, see Table 2. The model is capable of estimating the reaction products for a defined reactor feed composition and set of operating conditions.

(6) TABLE-US-00002 TABLE 2 Temperature ( C.) 450 500 525 550 Pressure (psig) 100 200 300 400 WHSV (hr.sup.1) 2 3 4 4

(7) Table 3 shows the product distribution after GHC unit. The high purity benzene produced by GHC is subsequently sent to an alkylation unit loaded with zeolite Beta (220 C., 3100-4800 kPa and benzene-to-olefin ratio of 1), where EB and cumene are produced with approximately 50% conversion (Laredo et al. (2009) loc. cit).

(8) TABLE-US-00003 TABLE 3 Effluent of GHC unit using reformate C6 heart cut as feed: Feed Composition Effluent of GHC unit Component (wt. %) (wt. %) Methane 7.1 Ethane 13.6 Propane 65.1 Benzene 13.4 12.0 Toluene 0.9 1.6 Cumene 0.0 Polyalkylbenzene 0.0 C6 iso-paraffins 58.3 0.6 C6 n-paraffins 22.7 C6 naphthenes 4.6

(9) For Example 1, the effluent of alkylation consists of 99.7% aromatics. Benzene recycle stream can be obtained by simple distillation.

EXAMPLE 2 (COMPARATIVE)

(10) Example 2 is identical to the Example 1 except reformate C6 cut is sent directly to alkylation unit without pre-treated in the GHC unit. At the same alkylation conditions (220 C., 3.1-4.8 MPa and benzene-to-olefin ratio of 1), the following product distribution is predicted for both cases.

(11) TABLE-US-00004 TABLE 4 Comparison of alkylation effluents in Examples 1 and 2: Effluent of Alkylation unit Feed (wt. %) composition Example 1: Example 2: Component (wt. %) GHC + alkylation Direct alkylation Methane Ethane Propane Benzene 13.4 49.3 6.4 Toluene 0.9 0.6 Cumene 38.0 5.5 PAB 11.0 2.8 C6 iso- 58.3 0.2 57 paraffins C6 n- 22.7 21.3 paraffins C6 4.6 0.1 4.1 naphthenes

(12) For Example 2, the effluent of alkylation consists of 15.3% aromatics. Benzene needs to be recovered by extractive distillation or liquid-liquid extraction due to the unconverted C6 naphthenes, iso- and n-paraffin in the effluent.