CATALYST AND PROCESS FOR PRODUCING LIGHT AROMATIC HYDROCARBONS AND LIGHT ALKANES FROM HYDROCARBONACEOUS FEEDSTOCK

Info

Publication number: 20090023968
Type: Application
Filed: Jul 18, 2008
Publication Date: Jan 22, 2009
Applicants: CHINA PETROLEUM & CHEMICAL CORPORATION (Beijing), SHANGHAI RESEARCH INSTITUTE OF PETROCHEMICAL TECHNOLOGY SINOPEC (Shanghai)
Inventors: Deju WANG (Shanghai), Zhongneng LIU (Shanghai), Xueli LI (Shanghai), Minbo HOU (Shanghai), Zheming WANG (Shanghai), Jianqiang WANG (Shanghai)
Application Number: 12/175,835

Abstract

The present invention provides a catalyst comprising metallic Pt and/or Pd supported on a binder-free zeolite for producing light aromatic hydrocarbons and light alkanes from hydrocarbonaceous feedstock, wherein the amount of metallic Pt and/or Pd is of 0.01-0.8 wt %, preferably 0.01-0.5 wt % on the basis of the total weight of the catalyst, and the binder-free zeolite is selected from the group consisting of mordenite, beta zeolite, Y zeolite, ZSM-5, ZSM-11 and composite or cocrystal zeolite thereof. The present invention also provides a process for producing light aromatic hydrocarbons and light alkanes from hydrocarbonaceous feedstock using said catalyst.

Description

Description

TECHNICAL FIELD

The present invention relates to a catalyst as well as the corresponding process for producing light aromatic hydrocarbons and light alkanes from hydrocarbonaceous feedstock.

BACKGROUND ART

Regarding the separation of aromatic hydrocarbons BTX,i.e.benzene, toluene and xylene, from non-aromatic hydrocarbons, some catalytic conversion processes have been developed in the prior art. For example, U.S. Pat. No. 3,729,409 disclosed converting non-aromatic hydrocarbons to lower alkanes by hydrocracking reaction and then separating aromatic hydrocarbons from non-aromatic hydrocarbons through gas-liquid separation; U.S. Pat. No. 5,865,986 and U.S. Pat. No. 6,001,241 disclosed a process for upgrading naphtha fraction, wherein a zeolite-based catalyst is used in some reactors to improve the production of aromatic hydrocarbons; and CN1217892C disclosed a similar process, wherein reformate, pyrolysis gasoline and the like are upgrade to produce LPG and light aromatic hydrocarbons.

The acidic catalyst used in these catalytic conversion processes would deactivate quickly due to coke and/or carbon-deposition, although this can be alleviated by supporting the metals with high hydrogenation activity and the hydrogenation activity of the catalyst also can be adjusted by varying the amount and/or the distribution of the supported metals, however, too high hydrogenation activity on the metallic center may result in side reaction of saturation of aromatic rings. With this regard, U.S. Pat. No. 5,865,986 proposed to adjust the metallic activity with sulfur compounds. Furthermore, U.S. Pat. No. 6,001,241 proposed to use Pb or Bi to control the degree of hydrogenation.

On the other hand, the zeolite molecular sieve powder used for said catalysts are generally manufactured into shaped particles with certain mechanical strengths and shapes, and during this manufacture some binders e.g. oxides such as Al₂O₃, SiO₂, TiO₂and the like as well as clay minerals are needed usually. This is because the shaped catalysts are widely used in industries and have to suffer from various stresses during its use, thus, sufficient mechanical strengths are necessary for ensuring the whole catalytic process to be conducted smoothly, otherwise if the shaped catalysts have poor mechanical strengths, some problems such as the lines being blocked by fine powders, the liquid being distributed unevenly, the pressure drop being increased and the like would be introduced, so as to lead to poor catalytic efficiency, and even a unexpected shut-down in worse case.

However, introduction of binders during shaping the zeolite powders would reduce the concentration of effective components in the zeolite particles, result in reduced effective surface area, thus the adsorption value would be reduced. This is because some binders would enter into part of channels of the zeolite or block part of pores of the zeolite, thus limiting the diffusion, resulting in poor adsorption ability and adsorption selectivity as well as reduced rates of adsorption and desorption, further the reduced activity and selectivity in the catalytic reactions; furthermore, undesired side reactions may be initiated in the presence of binders.

Regarding the above-mentioned disadvantages in connection with the introduction of binders during shaping the zeolite powders, the inventors have tried to develop a process for producing a binder-free zeolite, c.f. CN1915820A, which is incorporated herein by reference. The binder-free zeolite means that the shaped zeolite particles do not comprise inert binders, thus having high concentration of zeolite and large available surface area, furthermore, better properties in adsorption separation and ion exchange as well as better catalytic properties in some reactions are shown.

Based on the above-mentioned finding, the inventors further tried to develop a catalyst using said binder-free zeolite particles as support. Said catalyst has higher catalytic activity and stability and can be used for producing light aromatic hydrocarbons and light alkanes from hydrocarbonaceous feedstock.

SUMMARY OF THE INVENTION

The present invention provides a catalyst for producing light aromatic hydrocarbons and light alkanes from hydrocarbonaceous feedstock, wherein the binder-free zeolite was used to support noble metals as catalytic active components, so the catalyst possesses the advantages such as large acid density, unobstructed pores, moderate hydrogenation activity and the like, thus possessing excellent activity and stability.

Furthermore, the present invention provides a process for producing light aromatic hydrocarbons and light alkanes from hydrocarbonaceous feedstock using said catalyst, which process makes the separation of hydrocarbonaceous feedstock easier and brings higher additional values to heavy aromatic hydrocarbons and non-aromatic hydrocarbons.

Specifically, the present invention provides a catalyst comprising metallic Pt and/or Pd supported on a binder-free zeolite for producing light aromatic hydrocarbons and light alkanes from hydrocarbonaceous feedstock, wherein the amount of metallic Pt and/or Pd is of 0.01-0.8 wt %, preferably 0.01-0.5 wt % on the basis of the total weight of the catalyst, and the binder-free zeolite is selected from the group consisting of mordenite, beta zeolite, Y zeolite, ZSM-5, ZSM-11 and composite or cocrystal zeolite thereof.

According to the catalyst of the present invention, the binder-free zeolite preferably is selected from the group consisting of ZSM-5, mordenite, beta zeolite, ZSM-5/USY composite zeolite, ZSM-5/beta composite zeolite, or ZSM-5/ZSM-11 cocrystal zeolite.

According to the catalyst of the present invention, it may further comprise a promoter selected from the group consisting of Cu, Zn, Sn, Pb, Fe and mixture thereof, preferably from the group consisting of Zn, Sn, Pb and mixture thereof, most preferably Zn, in amount of less than 1 wt %, preferably less than 0.6 wt % on the basis of the total weight of the catalyst.

According to the catalyst of the present invention, wherein the binder-free zeolite has a molar ratio SiO₂/Al₂O₃in range of 10-200, preferably 20-100, and a pore size of about 4-8 Å, preferably 5-7 Å generally.

According to the catalyst of the present invention, the acidic center can be adjusted by varying the molar ratio SiO₂/Al₂O₃of the binder-free zeolite, and the hydrogenation activity can be adjusted by varying the supported amount of Pt and/or Pd as well as the distribution thereof, thus making the acidic center and metallic center of the catalyst match with each other.

Furthermore, when using Pt and Pd in combination as catalytic active metals, the catalyst of the present invention may possess better sulfur resistance without compromising the excellent hydrogenation property, thus it can be adapted to the feedstock comprising sulfur compounds such as pyrolysis gasoline very well. This is because when being used in combination rather than being present separately in the catalyst, some electrical or chemical effects are occurring between Pt and Pd by complex thereof, so that providing excellent hydrogenation and sulfur resistance properties.

The catalyst according to the present invention can be prepared as following: firstly synthesizing Na-type binder-free zeolite, converting the Na-type binder-free zeolite into H-type binder-free zeolite by ion exchange with ammonium salt solution or acid solution such as hydrochloric acid and the like followed by calcination, then supporting Pt and/or Pd as catalytic active metals thereon by ion exchange or impregnation, finally drying the obtained catalyst at a temperature of less than 200° C. and calcining the same at a temperature of 300-600° C.

During the above-mentioned preparation, the precursor of the catalytic active metals can be the aqueous solutions of palladium chloride, palladium nitrate, palladic chloride, palladous chloride, ammonium palladic chloride, ammonium palladous chloride, platinum nitrate, platinum chloride, platinic chloride, platinous chloride, ammonium platonic chloride, ammonium platinous chloride, tetraammineplatinum chloride and mixture thereof; furthermore, a promoter selected from the group consisting of Cu, Zn, Sn, Pb, Fe and mixture thereof can be added in amount of less than 1 wt %, preferably less than 0.6 wt % on the basis of the total weight of the catalyst to adjust the hydrogenation activity of the catalytic active metals.

Furthermore, the present invention provides a process for producing light aromatic hydrocarbons and light alkanes from hydrocarbonaceous feedstock, comprising the following steps:

(a) introducing hydrogen and a hydrocarbonaceous feedstock having boiling point in range of 30-250° C. into at least one reaction zone;

(b) converting the hydrocarbonaceous feedstock to an effluent enriched in light aromatic hydrocarbons of benzene, toluene and xylene and light alkanes in the reaction zone in the presence of the catalyst according to the present invention, wherein of the hydrocarbonaceous feedstock the heavy aromatic hydrocarbons are subjected to hydrodealkylation and/or transalkylation with light aromatic hydrocarbon, the light aromatic hydrocarbons are subjected to isomerization and the non-aromatic hydrocarbons are subjected to hydrocracking reaction; and

(c) recovering the light aromatic hydrocarbons and the light alkanes respectively by passing the effluent through gas-liquid separation and distillation sequentially, and the separated heavy fraction is recycled to the reaction zone for further reaction.

In the process for producing light aromatic hydrocarbons and light alkanes from hydrocarbonaceous feedstock according to the present invention, wherein:

in step (a), the hydrocarbonaceous feedstock is introduced into the reaction zone at a weight hour space velocity of 0.5-10 hr⁻¹, preferably 1-4 hr⁻¹, and the molar ratio of hydrogen to the hydrocarbonaceous feedstock is of 0.5:1-10:1, preferably 2:1-8:1, wherein the hydrocarbonaceous feedstock is selected from the group consisting of reformate, pyrolysis gasoline, naphtha and mixture thereof;

in step (b), the reaction temperature is of 250-600° C., preferably 300-500° C., and the reaction pressure is of 0.5-5.0 MPa, preferably 2.0-4.0 MPa; and

in step (c), passing the effluent through a gas-liquid separator to obtain first overhead stream comprising hydrogen, methane, ethane and LPG and first bottom stream comprising aromatic hydrocarbons as well as residual hydrogen and non-aromatic hydrocarbons, recovering LPG from the first overhead stream; and passing the first bottom stream through a distillation column to obtain second overhead stream comprising residual hydrogen and non-aromatic hydrocarbons and second bottom stream comprising aromatic hydrocarbons, further recovering LPG from the second overhead stream, and recovering aromatic hydrocarbons from the second bottom stream.

In the process for producing light aromatic hydrocarbons and light alkanes from hydrocarbonaceous feedstock according to the present invention, a target product can be obtained by varying the feedstock or the composition of the feedstock, e.g. a feedstock with high concentration of aromatic hydrocarbons such as reformate and pyrolysis gasoline can be used to improve the yield of aromatic hydrocarbons, and a feedstock with high concentration of non-aromatic hydrocarbons such as naphtha can be used to obtain LPG primarily.

In the process for producing light aromatic hydrocarbons and light alkanes from hydrocarbonaceous feedstock according to the present invention, in the presence of the catalyst according to the present invention, benzene, toluene and xylene (BTX), which are important raw organic materials in petrochemical industry, can be obtained through some simultaneous reactions of hydrocracking reaction of non-aromatic hydrocarbons as well as hydrodealkylation, transalkylation and isomerization of aromatic hydrocarbons; at the same time, light alkanes including LPG are produced as by products.

In the process for producing light aromatic hydrocarbons and light alkanes from hydrocarbonaceous feedstock according to the present invention, of the reactions in step (b), hydrocracking reaction is most important because the non-aromatic hydrocarbons in the hydrocarbonaceous feedstock are hydrocracked into light alkanes enriched in LPG, thus the solvent extraction and the like are not necessary for the separation of aromatic hydrocarbons from non-aromatic hydrocarbons; furthermore, hydrodealkylation, transalkylation and isomerization upgrade the aromatic hydrocarbons in the hydrocarbonaceous feedstock, e.g., C₉⁺ aromatic hydrocarbons used as fuel oils can be converted into benzene, toluene and xylene (BTX) through dealkylation, toluene and xylene can be produced through transalkylation between benzene and C₉⁺ aromatic hydrocarbons, and C₈aromatic hydrocarbons can be subjected to isomerization furthermore; on the other hand, some olefinic intermediates such as ethylene and propylene can be produced during hydrocracking and dealkylation, however, they will be hydrogenated to saturation quickly, so the catalyst will not deactivate due to the coke resulted from olefins polymerization and the aromatic hydrocarbons in the product will not degrade due to transalkylation between olefins and light aromatic hydrocarbons.

DETAILED DESCRIPTION OF THE INVENTION

Now the present invention is further described in details by following non-limiting examples.

EXAMPLE 1

A mixture of a solution of tetrapropylammonium hydroxide (TPAOH), tetraethyl orthosilicate (TEOS) and water in molar ratio of (TPA)₂O:5.5TEOS:90H₂O was stirred homogeneously, then aged and refluxed for 3-day at 80° C. to obtain ZSM-5 seed crystal orienting agent. Dosing 180 g white carbon black, 10 g sesbania flour, an aqueous solution of 19.7 g sodium aluminate and 40 g ZSM-5 seed crystal orienting agent, further adding 230 g silica sol(40 wt %) and required amount of water, then kneading and drying to obtain a cylindrical precursor. In a reaction vessel, to which a mixture of 35 g ethylenediamine and 5 g distilled water was pre-added, 150 g cylindrical precursor as above-prepared was placed on a porous stainless steel screen therein, and a vapor-solid phase treatment was carried out at 160° C. for 5-day after sealing the reaction vessel. The product was washed with distilled water and dried, then was calcined at 550° C. in air. The calcined product was demonstrated to be a binder-free ZSM-5 zeolite by XRD characterization and has a molar ratio SiO₂/Al₂O₃of 54.6 and a compressive strength of 50 N/mm as determined. Then the binder-free ZSM-5 zeolite was converted into H-type zeolite through ion exchange with a solution of ammonium nitrate and calcination. Supporting 0.15 wt %Pd and 0.15 wt %Pt on the H-type binder-free ZSM-5 zeolite by impregnation, then calcining at 400° C. for 4-hour to prepare catalyst A.

EXAMPLE 2

Mixing 100 g white carbon black, 20 g USY zeolite with a molar ratio SiO₂/Al₂O₃of 16 and 20 g ZSM-5 seed crystal orienting agent from example 1, adding aqueous solution of 26 g Al₂(SO₄)₃.18H₂O to adjust the Si/Al ratio, further adding 150 g silica sol(40 wt %), then kneading and drying to obtain a cylindrical precursor. In a reaction vessel, to which a mixture of 34 g ethylamine and 5 g distilled water was pre-added, 100 g cylindrical precursor as above-prepared was placed on a porous stainless steel screen therein, and a vapor-solid phase treatment was carried out at 180° C. for 5-day after sealing the reaction vessel. The product was washed with distilled water and dried, then was calcined at 550° C. in air. The calcined product was demonstrated to be a binder-free ZSM-5/USY composite zeolite by XRD characterization, ZSM-5 zeolite and USY zeolite therein are at amounts of 91 wt % and 9 wt % respectively as determined through quantitative analysis by XRD, ZSM-5 zeolite therein has a molar ratio SiO₂/Al₂O₃of 68.1 as determined and a determined compressive strength of the calcined product is of 85 N/mm. And it was shown by SEM that ZSM-5 zeolite and USY zeolite are cross-growing in the calcined product. Then the binder-free ZSM-5/USY composite zeolite was converted into H-type zeolite through ion exchange with a solution of ammonium nitrate and calcination. Supporting 0.3 wt %Pd on the H-type binder-free ZSM-5/USY composite zeolite by ion exchange, then calcining at 400° C. for 4-hour to prepare catalyst B.

EXAMPLE 3

Mixing 180 g white carbon black, 140 g beta zeolite with a molar ratio SiO₂/Al₂O₃of 20 and 40 g ZSM-5 seed crystal orienting agent from example 1, adding an aqueous solution of 110 g Al₂(SO₄)₃.18H₂O to adjust the Si/Al ratio, further adding 220 g silica sol(40 wt %), then kneading and drying to obtain a cylindrical precursor. In a reaction vessel, to which a mixture of 40 g ethylamine and 5 g distilled water was pre-added, 100 g cylindrical precursor as above-prepared was placed on a porous stainless steel screen therein, and a vapor-solid phase treatment was carried out at 150° C. for 7-day after sealing the reaction vessel. The product was washed with distilled water and dried, then was calcined at 550° C. in air. The calcined product was demonstrated to be a binder-free ZSM-5/beta composite zeolite by XRD characterization, ZSM-5 zeolite and beta zeolite therein are at amounts of 70.5 wt % and 29.5 wt % respectively as determined through quantitative analysis by XRD, ZSM-5 zeolite therein has a molar ratio SiO₂/Al₂O₃of 26.5 as determined and a determined compressive strength of the calcined product is of 87 N/mm. And it was shown by SEM that ZSM-5 zeolite and beta zeolite are cross-growing in the calcined product. Then the binder-free ZSM-5/beta composite zeolite was converted into H-type zeolite through ion exchange with a solution of ammonium nitrate and calcination. Supporting 0.10 wt %Pd and 0.10 wt %Pt on the H-type binder-free ZSM-5/beta composite zeolite by ion exchange, then calcining at 400° C. for 4-hour to prepare catalyst C.

EXAMPLE 4

Supporting 0.20 wt %Pt and 0.15 wt %Cu on the H-type binder-free ZSM-5 zeolite prepared in example 1 by ion exchange, then calcining at 400° C. for 4-hour to prepare catalyst D.

EXAMPLE 5

Mixing 120 g white carbon black, 5 g sesbania flour, 22.4 g sodium aluminate with an amount of Al₂O₃of 43 wt % and 200 g beta zeolite with a molar ratio SiO₂/Al₂O₃of 30, further adding 300 g silica sol (40 wt %), then kneading and drying to obtain a cylindrical precursor. A mixture of 60 g cylindrical precursor as above-prepared and 83 g solution of tetraethylammonium hydroxide (TEAOH)(13 wt %) was charged into a crystallization vessel to experience a hydrothermal treatment at 145° C. for 4-day therein. The product was washed with distilled water and dried, then was calcined at 550° C. in air. The calcined product was demonstrated to be a binder-free beta zeolite by XRD characterization and has a molar ratio SiO₂/Al₂O₃of 40 and a compressive strength of 58 N/mm as determined. Then the binder-free beta zeolite was converted into H-type zeolite through ion exchange with a solution of ammonium nitrate and calcination. Supporting 0.15 wt %Pd and 0.15 wt %Pt on the H-type binder-free beta zeolite by ion exchange, then calcining at 400° C. for 4-hour to prepare catalyst E.

EXAMPLE 6

Mixing 180 g white carbon black, 12 g sesbania flour, 50 g SiO₂-containing pseudo-boehmite powder (SiO₂O:26 wt %, Al₂O₃:44 wt % and H₂O:30 wt %), 21 g sodium hydroxide, 60 g mordenite with a molar ratio SiO₂/Al₂O₃of 20 and 550 g silica sol(40 wt %), then kneading and drying to obtain a cylindrical precursor. A mixture of 60 g cylindrical precursor as above-prepared and 120 g solution of sodium hydroxide (2.5 wt %) was charged into a crystallization vessel to experience a hydrothermal treatment at 160° C. for 3-day therein. The product was washed with distilled water and dried, then was calcined at 550° C. in air. The calcined product was demonstrated to be a binder-free mordenite zeolite by XRD characterization and has a molar ratio SiO₂/Al₂O₃of 30 and a compressive strength of 65 N/mm as determined. Then the binder-free mordenite was converted into H-type zeolite through ion exchange with a solution of ammonium nitrate and calcination. Supporting 0.15 wt %Pd and 0.15%wtPt on the H-type binder-free mordenite by ion exchange, then calcining at 400° C. for 4-hour to prepare catalyst F.

EXAMPLE 7

A mixture of a solution of tetrabutylammonium hydroxide (TBAOH), tetraethyl orthosilicate (TEOS) and water in molar ratio of (TBA)₂O:6.22TEOS:163H₂O was stirred homogeneously, then aged and refluxed at 95° C. for 3-day to obtain ZSM-11 seed crystal orienting agent. Dosing 200 g white carbon black, 12.5 g sesbania flour, 36 g SiO₂-containing pseudo-boehmite powder (SiO₂:26 wt %, Al₂O₃:44 wt % and H₂O:30 wt %) and 51 g ZSM-11 seed crystal orienting agent, adding 20 g aqueous solution of sodium hydroxide, further adding 475 g silica sol(40 wt %), then kneading and drying to obtain a cylindrical precursor. A mixture of 40 g cylindrical precursor as above-prepared and 80 g solution of tetrabutylammonium hydroxide (TBAOH)(8 wt %) was charged into a crystallization vessel to experience a hydrothermal treatment at 160° C. for 3-day therein. The product was washed with distilled water and dried, then was calcined at 550° C. in air. The calcined product was demonstrated to be a binder-free ZSM-11 zeolite by XRD characterization and has a molar ratio SiO₂/Al₂O₃of 43 and a compressive strength of 55 N/mm as determined. Then the binder-free ZSM-11 zeolite was converted into H-type zeolite through ion exchange with a solution of ammonium nitrate and calcination. Supporting 0.15 wt %Pd and 0.15 wt %Pt on the H-type binder-free ZSM-11 zeolite by impregnation, then calcining at 400° C. for 4-hour to prepare catalyst G.

EXAMPLE 8

Mixing 200 g white carbon black and 80 g Na-type ZSM-5 zeolite with a molar ratio SiO₂/Al₂O₃of 60, adding 26 g sodium aluminate with an amount of Al₂O₃of 43 wt % to adjust the Si/Al ratio, further adding 45 g ZSM-5 seed crystal orienting agent from example 1, further adding 410 g silica sol (40 wt %) and 30 g water, then kneading and drying to obtain a cylindrical precursor. In a reaction vessel, to which a mixture of 34 g ethylamine and 5 g distilled water was pre-added, 100 g cylindrical precursor as above-prepared was placed on a porous stainless steel screen therein, and a vapor-solid phase treatment was carried out at 180° C. for 5-day after sealing the reaction vessel. The product was washed with distilled water and dried, then was calcined at 550° C. in air. The calcined product was demonstrated to be a binder-free ZSM-5 zeolite by XRD characterization and has a molar ratio SiO₂/Al₂O₃of 56 and a compressive strength of 11ON/mm as determined. Then the binder-free ZSM-5 zeolite was converted into H-type zeolite through ion exchange with a solution of ammonium nitrate and calcination. Supporting 0.04 wt %Pd and 0.04 wt %Pt on the H-type binder-free ZSM-5 zeolite by ion exchange, then calcining at 430° C. for 4-hour to prepare catalyst H.

EXAMPLE 9

Supporting 0.04 wt %Pt and 0.13 wt %Pb on the H-type binder-free ZSM-5 zeolite prepared in example 8 by ion exchange, then calcining at 400° C. for 4-hour to prepare catalyst 1.

EXAMPLE 10

Supporting 0.01 wt %Pt and 0.03 wt %Sn on the H-type binder-free ZSM-5 zeolite prepared in example 8 by ion exchange, then calcining at 400° C. for 4-hour to prepare catalyst J.

In order to evaluate the properties, testing the above-prepared catalysts A-J in a fixed bed reactor under following conditions:

Composition of the hydrocarbonaceous feedstock ( wt %): <C₆non-aromatic hydrocarbons 3.99, C_6-8non-aromatic hydrocarbons 3.563, C_6-8aromatic hydrocarbons 71.662 (wherein ethylbenzene 5.14 and xylene 9.142), C₉15.471 (wherein indane 2.466), and C10⁺ 5.314 (wherein tetrahydrodicyclopentadiene 4.481); and

Process conditions: hydrogen pressure 3.0 MPa, H₂/oil volume ratio 400, inlet temperature 400° C., and WHSV 2.0-4.0 hr⁻¹.

The results of reaction are shown in table 1.

TABLE 1 Test results on catalysts Catalyst A B C D E F G H I J WHSV/hr⁻¹ 3.7 3.0 3.0 3.0 3.0 2.5 2.0 2.0 2.0 2.0 Distribution <C₆ 14.90 14.31 13.25 13.53 13.98 14.40 15.02 15.50 13.78 13.27 of reaction non-aromatic product hydrocarbons (wt %) C_6-8aromatic 79.48 78.65 75.86 76.08 78.99 79.21 81.92 82.05 82.4 81.0 hydrocarbons C_6-8 0.18 0.095 0.37 0.23 0.27 0.18 0.056 0.051 0.015 0.03 non-aromatic hydrocarbons C₉ 3.50 3.87 4.02 3.45 3.78 3.21 2.95 2.78 2.56 3.56 Ethylbenzene 0.69 1.50 2.80 2.20 3.20 2.9 0.90 0.95 0.80 1.20 Xylene 11.38 11.72 10.58 11.26 12.05 12.10 11.80 11.72 11.50 12.0 Conversion of C_6-8 94.95 97.00 89.62 93.54 92.42 94.95 98.43 98.57 99.6 99.2 non-aromatic hydrocarbons (%) Conversion of C₉(%) 77.38 75.00 74.02 77.70 75.57 79.25 80.93 82.03 83.45 76.99

COMPARATIVE EXAMPLES 1-2

Using silica and alumina as binders, shaping raw H-type ZSM-5 zeolite powder with a molar ratio SiO₂/Al₂O₃of 60, drying and then calcining at 550° C. for 4-hour to prepare a shaped H-type ZSM-5 zeolite comprising 28.6 wt % of silica as binder and a shaped H-type ZSM-5 zeolite comprising 34.4 wt % of alumina as binder respectively. Supporting 0.04 wt %Pt and 0.13 wt %Pb on both of the above-prepared H-type ZSM-5 zeolites by impregnation, and then calcining at 450° C. for 4-hour to prepare catalysts R and S.

In order to evaluate the properties, testing the above-prepared catalysts R-S in a fixed bed reactor, wherein the feedstocks and the process conditions being same as that in example 9.

The results of reaction are shown in table 2.

TABLE 2 Test results on catalysts Catalyst R S Distribution <C₆non-aromatic 11.22 13.83 of reaction hydrocarbons product C_6-8aromatic hydrocarbons 74.82 75.02 (wt %) C_6-8non-aromatic 0.27 0.18 hydrocarbons C₉ 8.37 6.89 Ethylbenzene 4.12 3.6 Xylene 9.32 9.18 Conversion of C_6-8non-aromatic 92.42 94.95 hydrocarbons (%) Conversion of C₉(%) 45.90 55.46

As can be seen from the data in tables 1-2, under the same process conditions, compared with the catalysts based on zeolite comprising binders in the prior art, the catalyst based on binder-free zeolite according to the present invention shows much better activities for hydrodealkylation and cracking reaction, specifically, the conversion of C₉is much higher.

EXAMPLE 11

Supporting 0.04 wt %Pt and 0.13 wt %Sn on the H-type binder-free ZSM-5 zeolite prepared in example 1 by ion exchange, then calcining at 450° C. for 4-hour to prepare catalyst K.

EXAMPLE 12

Supporting 0.5 wt %Pd on the H-type binder-free ZSM-5 zeolite prepared in example 1 by ion exchange, then calcining at 450° C. for 4-hour to prepare catalyst L.

EXAMPLE 13

Supporting 0.04 wt %Pd and 0.04 wt %Pt on the H-type binder-free ZSM-5 zeolite prepared in example 1 by ion exchange, then calcining at 450° C. for 4-hour to prepare catalyst M.

In order to evaluate the properties, testing the above-prepared catalysts K-M in a fixed bed reactor under following conditions:

Composition of the hydrocarbonaceous feedstock ( wt %): <C₆non-aromatic hydrocarbons 2.33, C_6-8non-aromatic hydrocarbons 2.393, C_6-8aromatic hydrocarbons 76.578 (wherein ethylbenzene 6.748 and xylene 8.884), C₉12.49 (wherein indane 3.425), C₁₀⁺ 6.206 (wherein tetrahydrodicyclopentadiene 3.318), bromine value 14.00 g Br₂/100 g of the feedstock, and sulfur concentration 105 ppm; and

Process conditions: hydrogen pressure 3.0 MPa, H₂/oil volume ratio 500, inlet temperature 350-370° C., and WHSV 2.0-5.0 hr⁻¹.

The results of reaction are shown in table 3. The data show that a better conversion of C₉can be obtained with the catalyst according to the present invention, even though the feedstock comprises sulfur and unsaturated components.

TABLE 3 Test results on catalysts Catalyst K L M Inlet temperature ° C. 350 370 370 WHSV/hr⁻¹ 4.2 2.1 2.1 Distribution <C₆non-aromatic 10.14 8.93 9.59 of reaction hydrocarbons product C_6-8aromatic hydrocarbons 84.21 81.12 82.78 (wt %) C_6-8non-aromatic 0 0.12 0 hydrocarbons C₉ 2.78 3.98 2.98 Ethylbenzene 1.88 2.51 1.68 Xylene 9.69 8.96 9.07 Conversion of C_6-8non-aromatic 100 94.98 100 hydrocarbons (%) Conversion of C₉(%) 77.74 68.13 76.14

EXAMPLE 14

Supporting 0.05 wt %Pt and 0.08 wt %Zn on the H-type binder-free ZSM-5 zeolite prepared in example 8 by ion exchange, then calcining at 400° C. for 4-hour to prepare catalyst N.

EXAMPLE 15

A mixture of 40 g cylindrical precursor prepared in example 7 and 80 g solution comprising 5 wt % of tetrabutylammonium hydroxide (TBAOH) and 3 wt % of tetrapropylammonium hydroxide(TPAOH) was charged into a crystallization vessel to experience a hydrothermal treatment at 170° C. for 3-day therein. The product was washed with distilled water and dried, then was calcined at 550° C. in air. The calcined product was demonstrated to be a binder-free ZSM-5/ZSM-11 cocrystal zeolite by XRD characterization and has a molar ratio SiO₂/Al₂O₃of 42.9 and a compressive strength of 62 N/mm as determined. Then the binder-free ZSM-5/ZSM-11 cocrystal zeolite was converted into H-type zeolite through ion exchange with a solution of ammonium nitrate and calcination. Supporting 0.05 wt %Pt and 0.08 wt %Zn on the H-type binder-free ZSM-5/ZSM-11 cocrystal zeolite by impregnation, then calcining at 400° C. for 4-hour to prepare catalyst O.

In order to evaluate the properties, testing the above-prepared catalysts N-O in a fixed bed reactor by running for 1000-hour continuously under following conditions:

Composition of the hydrocarbonaceous feedstock (wt %): <C₆non-aromatic hydrocarbons 0.144, C_6-8non-aromatic hydrocarbons 2.985, C_6-8aromatic hydrocarbons 52.098 (wherein ethylbenzene 8.145 and xylene 9.892), C₉30.069 (wherein indane 8.084), and C₁₀⁺ 14.704 (wherein tetrahydrodicyclopentadiene 3.408); and

Process conditions: hydrogen pressure 3.0 MPa, H₂/oil volume ratio 500, inlet temperature 380° C., and WHSV 2.1 hr⁻¹.

The results of reaction after running for 1000-hour are shown in table 4.

TABLE 4 Test results on catalysts Catalyst N O Distribution of <C₆non-aromatic hydrocarbons 18.56 20.43 reaction C_6-8aromatic hydrocarbons 71.30 72.54 product C_6-8non-aromatic hydrocarbons 0.26 0.10 (wt %) C₉ 4.17 2.73 Ethylbenzene 0.42 0.36 Xylene 17.17 10.02 Conversion of C_6-8non-aromatic hydrocarbons 91.29 96.65 (%) Conversion of C₉(%) 86.13 90.92

As can be seen from the data in table 4, as to the catalyst according to the present invention, when Zn being used as the promoter, a higher conversion of C₉can be obtained, and when ZSM-5/ZSM-11 cocrystal zeolite being used, the conversion of C₉can be improved furthermore.

EXAMPLE 16

Supporting 0.35 wt %Pd and 0.60 wt %Zn on the H-type binder-free ZSM-5 zeolite prepared in example 8 by ion exchange, then calcining at 400° C. for 4-hour to prepare catalyst P.

In order to evaluate the properties, testing catalyst P in a fixed bed reactor under following conditions:

Composition of the hydrocarbonaceous feedstock (wt %): C_6-8aromatic hydrocarbons 11.552 (wherein ethylbenzene 2.367 and xylene 9.185), C₉66.203 (wherein indane 17.154), and C₁₀⁺ 22.245 (wherein tetrahydrodicyclopentadiene 15.155); and

Process conditions: hydrogen pressure 3.0 MPa, H₂/oil volume ratio 800, inlet temperature 380° C., and WHSV 2.0 hr⁻¹.

The results of reaction are shown in table 5.

EXAMPLE 17

Supporting 0.04 wt %Pt, 0.12 wt %Pd and 0.20 wt %Zn on the H-type binder-free ZSM-5 zeolite prepared in example 8 by ion exchange, then calcining at 400° C. for 4-hour to prepare catalyst Q.

In order to evaluate the properties, testing catalyst Q in a fixed bed reactor under following conditions:

Composition of the hydrocarbonaceous feedstock (wt %): C_6-8aromatic hydrocarbons 11.704 (wherein ethylbenzene 2.121 and xylene 9.031), C₉62.627 (wherein indane 16.546), and C₁₀⁺ 25.669 (wherein tetrahydrodicyclopentadiene 16.702); and

Process conditions: hydrogen pressure 3.0 MPa, H₂/oil volume ratio 800, inlet temperature 380° C., and WHSV 2.0 hr⁻¹.

The results of reaction are shown in table 5.

TABLE 5 Test results on catalysts Catalyst P Q distribution <C₆non-aromatic 33.938 38.404 of reaction hydrocarbons product C_6-8aromatic hydrocarbons 56.875 54.904 (wt %) C_6-8non-aromatic 0 0 hydrocarbons C₉ 3.977 4.318 C₁₀⁺ 5.21 2.374 Ethylbenzene 0.675 0.205 Xylene 14.029 16.306 Indane 0.058 0 Tetrahydrodicyclopentadiene 0.257 0.206 Conversion of C₉(%) 93.99 93.10

EXAMPLE 18

In order to evaluate the properties, testing catalyst N prepared in example 14 in a fixed bed reactor by running for 1500-hour continuously, wherein the feedstock and the process conditions being same as that in example 17.

The results of reaction at different time points during running for 1500-hour are shown in table 6.

TABLE 6 Test results on catalysts Time of running/hr 384 826 1450 distribution <C₆non-aromatic 26.012 25.859 30.23 of reaction hydrocarbons product C_6-8aromatic hydrocarbons 58.495 57.196 57.006 (wt %) C_6-8non-aromatic 0 0 0 hydrocarbons C₉ 7.249 7.575 6.594 C₁₀⁺ 8.244 9.370 6.170 Ethylbenzene 0.228 0.164 0.143 Xylene 16.657 17.061 17.554 Indane 0.182 0.183 0.075 Tetrahydro- 4.293 5.077 2.917 dicyclopentadiene Conversion of C₉(%) 88.42 87.90 89.47

As can be seen from the data in tables 5-6, the catalyst according to the present invention can achieve better conversion and stability, even though the feedstock comprises heavy aromatic hydrocarbons at higher amounts.

Claims

1. A catalyst comprising metallic Pt and/or Pd supported on a binder-free zeolite for producing light aromatic hydrocarbons and light alkanes from hydrocarbonaceous feedstock, wherein the amount of metallic Pt and/or Pd is of 0.01-0.8 wt %, preferably 0.01-0.5 wt % on the basis of the total weight of the catalyst, and the binder-free zeolite is selected from the group consisting of mordenite, beta zeolite, Y zeolite, ZSM-5, ZSM-11 and composite or cocrystal zeolite thereof.

2. The catalyst according to claim 1, wherein the binder-free zeolite is ZSM-5, mordenite, beta zeolite, ZSM-5/USY composite zeolite, ZSM-5/beta composite zeolite, or ZSM-5/ZSM-11 cocrystal zeolite.

3. The catalyst according to claim 1, further comprising a promoter selected from the group consisting of Cu, Zn, Sn, Pb, Fe and mixture thereof in amount of less than 1 wt %, preferably less than 0.6 wt % on the basis of the total weight of the catalyst.

4. The catalyst according to claim 3, wherein the promoter is selected from the group consisting of Zn, Sn, Pb and mixture thereof.

5. The catalyst according to claim 4, wherein the promoter is Zn.

6. The catalyst according to claim 1, wherein the binder-free zeolite has a molar ratio SiO2/Al2O3 in range of 10-200, preferably 20-100.

7. The catalyst according to claim 2, further comprising a promoter selected from the group consisting of Cu, Zn, Sn, Pb, Fe and mixture thereof in amount of less than 1 wt %, preferably less than 0.6 wt % on the basis of the total weight of the catalyst.

8. The catalyst according to claim 7, wherein the promoter is Zn.

9. The catalyst according to claim 8, wherein the binder-free zeolite has a molar ratio SiO2/Al2O3 in range of 10-200, preferably 20-100.

10. A process for producing light aromatic hydrocarbons and light alkanes from hydrocarbonaceous feedstock, comprising the following steps:

(a) introducing hydrogen and a hydrocarbonaceous feedstock having boiling point in range of 30-250° C. into at least one reaction zone;

(b) converting the hydrocarbonaceous feedstock to an effluent enriched in light aromatic hydrocarbons of benzene, toluene and xylene and light alkanes in the reaction zone in the presence of the catalyst according to any one of claims 1 to 9, wherein of the hydrocarbonaceous feedstock the heavy aromatic hydrocarbons are subjected to hydrodealkylation and/or transalkylation with light aromatic hydrocarbon, the light aromatic hydrocarbons are subjected to isomerization and the non-aromatic hydrocarbons are subjected to hydrocracking reaction; and

(c) recovering the light aromatic hydrocarbons and the light alkanes respectively by passing the effluent through gas-liquid separation and distillation sequentially, and the separated heavy fraction is recycled to the reaction zone for further reaction.

11. The process according to claim 10, wherein in step (a) the hydrocarbonaceous feedstock is introduced into the reaction zone at a weight hour space velocity of 0.5-10 hr−1, preferably 1-4 hr−1, and the molar ratio of hydrogen to the hydrocarbonaceous feedstock is of 0.5:1-10:1, preferably 2:1-8:1.

12. The process according to claim 10, wherein in step (b) the reaction temperature is of 250-600° C., preferably 300-500° C., and the reaction pressure is of 0.5-5.0 MPa, preferably 2.0-4.0 MPa.

13. The process according to claim 10, wherein the hydrocarbonaceous feedstock is selected from the group consisting of reformate, pyrolysis gasoline, naphtha and mixture thereof.

14. The process according to claim 10, wherein in step (c) passing the effluent through a gas-liquid separator to obtain first overhead stream comprising hydrogen, methane, ethane and LPG and first bottom stream comprising aromatic hydrocarbons as well as residual hydrogen and non-aromatic hydrocarbons, recovering LPG from the first overhead stream; and passing the first bottom stream through a distillation column to obtain second overhead stream comprising residual hydrogen and non-aromatic hydrocarbons and second bottom stream comprising aromatic hydrocarbons, further recovering LPG from the second overhead stream, and recovering aromatic hydrocarbons from the second bottom stream.

15. The process according to claim 11, wherein in step (b) the reaction temperature is of 250-600° C., preferably 300-500° C., and the reaction pressure is of 0.5-5.0 MPa, preferably 2.0-4.0 MPa

16. The process according to claim 11, wherein the hydrocarbonaceous feedstock is selected from the group consisting of reformate, pyrolysis gasoline, naphtha and mixture thereof.

17. The process according to claim 11, wherein in step (c) passing the effluent through a gas-liquid separator to obtain first overhead stream comprising hydrogen, methane, ethane and LPG and first bottom stream comprising aromatic hydrocarbons as well as residual hydrogen and non-aromatic hydrocarbons, recovering LPG from the first overhead stream; and passing the first bottom stream through a distillation column to obtain second overhead stream comprising residual hydrogen and non-aromatic hydrocarbons and second bottom stream comprising aromatic hydrocarbons, further recovering LPG from the second overhead stream, and recovering aromatic hydrocarbons from the second bottom stream.