CN1111090C - Dual-component modified zeolite catalyst for aromatizing reaction of hydrocarbons - Google Patents

Abstract

A two-component modified zeolite catalyst for hydrocarbon aromatization, characterized in that the catalyst is ZSM-5 with a Si/Al molar ratio of 20-70, metal Ga and metal La, Ag, Pd, Zn, Any composition in Re, the weight percentage of each component is ZSM-5 46-99.4%, Ga 0.5-2%, any one of La, Ag, Pd, Zn, Re 0.01-2%, binder Alumina 0-50%, the catalyst has good selectivity and is suitable for the aromatization of C ₂ -C ₈ alkanes, with reduced carbon formation, good stability, high conversion rate and long service life.

Description

Two-component Modified Zeolite Catalyst for Hydrocarbon Aromatization

The invention belongs to HZSM-5 catalysts, in particular to a two-component modified zeolite catalyst used for hydrocarbon aromatization.

The Ga/HZSM-5 zeolite prepared by HZSM-5 high-silica zeolite modified by Ga has high reactivity and aromatics selectivity for the direct synthesis of aromatics from low-carbon alkanes such as propane and butane, and has attracted widespread attention. However, like many organic catalytic reactions, there is the problem of catalyst surface coking leading to a decrease in catalyst activity, and frequent regeneration is required, which brings many difficulties to industrial fixed-bed operations. Therefore, improving the anti-coking performance of the catalyst, improving the stability of the catalyst, prolonging the reaction cycle and the service life of the catalyst are the keys to its industrial application. Predecessors have also made a lot of efforts in this regard. CN 1081938A discloses a process for the activation and modification of an aromatization catalyst, which uses water vapor to activate the Zn/HZSM-5 type catalyst at high temperature and is used for the aromatization of pyrolysis gasoline. The life of the catalyst is improved, but the best result is The one-way life is 29 hours, and the article does not mention hydrocarbons with lower carbon numbers. CN 86 108104A and USP 4,636,483 of Universal Corporation of the United States propose to use a composite catalyst to make C ₂ -C ₅ hydrocarbon production achieve good coking resistance, thereby prolonging the service life of the catalyst. The main method is to improve the preparation of the carrier. Silicate zeolite is mixed with phosphorus-containing alumina and dispersed into balls with high-temperature oil. The preparation process is complicated. The Zn-Pt and Ga-Pt modified HZSM-5 and HZSM-11 zeolite catalysts disclosed in Chinese patent CN 1062100A for the aromatization of light hydrocarbons are also limited to higher oilfield light hydrocarbons (C ₄ -C ₉ ) cuts, and the noble metal Pt is used, the catalyst cost is higher. The disclosed Ga/HZSM-5 catalyst of USP4,180,689 and USP4,334,114 is used for the aromatization of C ₃ -C ₁₂ hydrocarbons, and the purpose is to improve the activity and aromatics selectivity of the catalyst, and does not involve the anti-coking property of the catalyst Stability issues.

The purpose of the present invention is to provide a two-component modified zeolite catalyst with strong anti-coking property and good stability, which is used for the aromatization reaction of hydrocarbons.

The purpose of the present invention is achieved by adding a second metal component to Ga/HZSM-5 to adjust the surface acid properties of the catalyst, and at the same time narrow the pores of the molecular sieve to suppress the generation of coking precursors, thereby reducing coking amount, for the purpose of improving stability.

The catalyst of the invention is composed of ZSM-5 with Si/Al molar ratio of 20-70, metal Ga and any one of metals La, Ag, Pd, Zn and Re.

The weight ratio of each component is:

ZSM-5 46-99.4% Ga 0.5-2%

Any of La, Ag, Pd, Zn, Re 0.01-2%

Alumina binder 0-50%

The optimum range of each component weight percent is:

ZSM-5 63-99% Ga 0.8-1.6%

Any of La, Ag, Pd, Zn, Re 0.1-1%

Alumina adhesive 0-35%

The concrete preparation method of catalyst of the present invention is as follows:

(1) Select ZSM-5 molecular sieve raw powder with a Si/Al molar ratio of 20-70, add HCl and heat to reflux, wash until no Cl ^- ions are present, dry, and roast at 600° C. for 4 hours to obtain HZSM-5 powder;

(2) According to the ratio of the catalyst composition, the salt Ga(NO ₃ ) ₃ solution containing the active component Ga is selected, and Ga is loaded on the HZSM-5 by ion exchange or impregnation method, dried and roasted to make Ga/HZSM -5 powder;

(3) Take Ga/HZSM-5, add alumina binder according to the ratio of catalyst composition, use 4% _HNO3 to bond and form, dry, and roast to make Ga/HZSM-5 containing binder;

(4) According to the ratio of the catalyst composition, select a nitrate solution or chloride solution containing any one of La, Ag, Pd, Zn, Re, and introduce it into Ga/HZSM-5 by ion exchange or impregnation. The inventive catalyst is obtained.

Catalyst of the present invention has following advantage compared with prior art:

1. Because the catalyst of the present invention is by adding the second metal component in Ga/HZSM-5, the surface acid properties of the catalyst are adjusted, and at the same time, because the second metal component enters the Ga/HZSM-5 molecular sieve channel, the molecular sieve channel is different The degree becomes narrower, the effective pore size becomes smaller, the formation of coking precursors is inhibited, the amount of coking of the catalyst is reduced, and the stability of the catalyst is improved.

2. This catalyst is suitable for the aromatization reaction of C ₂ -C ₃ alkanes, especially C ₃ -C ₆ alkanes, with high conversion rate, good selectivity of aromatics, long single-pass life of the catalyst, and stable regeneration activity for multiple times.

3. The catalyst of the present invention does not contain noble metal Pt, and the preparation process is simple, and the catalyst cost is low.

Example 1

Take 40g of ZSM-5 molecular sieve raw powder with a Si/Al ratio of 56, add 240ml of 1N HCl, heat and reflux for 1h, wash the slurry 4 times until there is no Cl ^- ion, drain, put in an oven at 120°C overnight, and bake in a muffle furnace at 600°C After 4h, HZSM-5 powder was obtained. Add 20g of HZSM-5 powder, add 100ml of deionized water and 100ml of Ga(NO ₃ ) ₃ solution with a concentration of 0.0198gGa/ml, heat to reflux for 4h, let it stand for 10h to balance, filter, wash with hot water for 3 times, filter the cake under infrared light It was dried at 120°C overnight in an oven, and baked in a muffle furnace at 540°C for 4 hours to obtain Ga/HZSM-5 powder with a Ga content of 1.6wt.%. Tablet, crush, sieve, take 20-40 mesh particles as catalyst, record as catalyst A.

Example 2

Weigh 0.0394g of AgNO ₃ (AR), dissolve it in 5ml of deionized water, take 5g of the catalyst A in Example 1, impregnate it, let it stand for 10h, dry it under an infrared lamp, put it in an oven at 120°C overnight, and put it in a muffle furnace at 540°C Calcined at ℃ for 4h to obtain Ga/HZSM-5 with Ag content of 0.5wt.%. Denote it as Catalyst B.

Example 3

Take 10g of Ga/HZSM-5 powder in Example 1, add 0.0Tg of alumina and 4% HNO ₃ 6ml to bond and form, dry at 120°C overnight, and bake at 540°C for 4h to obtain Ga/HZSM-5 containing binder. Get 5g20-40 purpose Ga/HZSM-5 and use concentration to be 1mgPd/ml _PdCl2 solution 4.5ml, replace the _AgNO3 solution in Example 2, other steps are identical with Example 2, make the Ga/HZSM-5 of Pd content 0.1%. HZSM-5. Denote it as Catalyst C.

Example 4

Take 80g of ZSM-5 molecular sieve raw powder with a Si/Al ratio of 56, add 480ml of 1N HCl, heat and reflux for 1h, wash the slurry 4 times until there is no Cl ^- ion, drain, put in an oven at 120°C overnight, and bake in a muffle furnace at 600°C After 4h, HZSM-5 powder was obtained. Add 50g of HZSM-5 powder, add 370ml of deionized water and 29ml of Ga(NO ₃ ) ₃ solution with a concentration of 0.0397gGa/ml, heat to reflux for 4h, let it stand for 20h to balance, filter, wash with hot water for 3 times, and put the filter cake in the infrared lamp Dry it under the oven, put it in an oven at 120°C overnight, put it into a muffle furnace and bake it at 540°C for 4 hours to get Ga/HZSM-5 powder. Add 20g of Ga/HZSM-5 powder, add 10g of alumina, mix evenly, bond with 4% HNO ₃ 19ml, extrude into strips, dry under infrared lamp, put in oven at 120°C overnight, put into muffle furnace and bake at 540°C for 4h, The Ga content is 1.0 wt.%. Crushing and sieving, take 20-40 mesh particles as catalyst, record as catalyst D.

Example 5

Catalyst D5g in Example 4, add concentration is 22.25mg Zn/ml Zn(NO ₃ ) ₂ solution 2.25ml and deionized water 6.8ml, impregnate, let stand for 10h, dry under infrared lamp, 120 ℃ overnight in oven , put into muffle furnace and bake at 540°C for 4h to obtain Ga/HZSM-5 with Zn content of 0.5%. Denote it as Catalyst E.

Example 6

Same as Example 5, except that the AgNO _solution 1ml, 5ml, and 8ml with a concentration of 5.0mg Ag/ml are added respectively with 7ml, 3ml, and 0ml of deionized water to replace the solution in Example 5, and the obtained Ag content is 0.1 %, 0.5%, 0.8% of Ga/HZSM-5. Record as catalysts F, G, H.

Catalytic reaction:

Fig. 1 is a graph showing the change of propane conversion rate over time on catalysts A, B, and C.

Fig. 2 is a comparison chart of catalysts D and G in n-hexane aromatization.

Fig. 3 is a curve diagram of aromatization performance of raffinate oil on catalyst D and catalyst G.

The aromatization reaction is carried out in a continuous flow integration reactor at normal pressure, the inner diameter of the stainless steel tubular reactor is 10mm, and the catalyst loading is 1-2g. The product was analyzed online by GC-9A gas chromatograph, using argon (Ar) as the carrier gas, and the low-carbon hydrocarbon and aromatic products were analyzed by Porapak Qs and 0V-101 column respectively, detected by hydrogen flame (FID), and the ratio of hydrogen to carbon (H ₂ /CH ₄ ) was analyzed by the Porapak Qs column of the SC-01 chromatograph, detected by thermal conductivity (TCD), and after renormalization, the product distribution was calculated and expressed in weight percent (wt.%).

Catalysts A, B, and C use propane as raw material. Figure 1 shows their aromatization performance at a reaction temperature of 550°C and a weight hourly space velocity (WHSV) of 4.0h ^-1 . It can be seen that after the second component is added to Ga/HZSM-5, the catalyst propane conversion activity is significantly improved and the stability is improved. Catalyst C showed high conversion activity and good catalytic stability.

Catalysts D, E, F, G, and H use n-hexane and raffinate as raw materials. The fresh catalyst must undergo redox pretreatment before reaction, that is, 600° _C.H2 reduction for 1 hour, 550°C air oxidation for 1 hour, and then react. Raw materials enter the reaction system through the micro liquid flow pump. Table 1 shows the reactivity and stability when n-hexane is used as raw material, the reaction temperature is 550°C, and the weight hourly space velocity (WHSV) is 1.0h ^-1 . It can be seen that the stability of the catalyst added with Zn and Ag is obviously improved, and the catalyst G, GaAg(0.5%)/HZSM-5, shows the best activity and stability. At 550°C, WHSV=0.5h ^-1 , compared the aromatization performance of Catalysts D and G using n-hexane and raffinate (catalyst reformed raffinate provided by Fushun Petroleum Plant) as raw materials, see Fig. 2 and 3. The composition of the raffinate oil is shown in Table 2, and its conversion rate is defined as the conversion percentage of C5, C6 and C7. Catalyst D, when the reagent n-hexane is used as raw material, the 80h average liquid yield is 61.2%, the aromatics yield is 59.3%, the _H2 yield is 3.9%, and the fuel gas is 34.9%; when the catalytic reforming raffinate is used as the raw material, the 70h average Liquid yield 60,2%, aromatics yield 54.6%, H ₂ yield 2.8%, fuel gas 37.0%. Catalyst G, when the reagent n-hexane is used as the raw material, the average liquid product yield is 69.6%, the aromatics yield is 68.4%, the _H2 yield is 4.7%, and the fuel gas is 25.67% in 80 hours; when the catalytic reforming residual oil is used as the raw material, the 70h The average liquid product yield is 64.1%, of which aromatics yield is 55.7%, H ₂ is 2.9%, and fuel gas is 33.0%.

Table 1. Aromatization performance of n-hexane over catalyst (550°C, 1.0h ^-1 ) catalyst D. E. f G h Conversion rate% initial 100 100 100 100 100 30h 94.92 95.31 100 99.91 95.04 Aromatics yield% initial 65.65 62.68 66.27 65.70 60.01 30h 37.45 47.37 47.88 51.50 49.94

Table 2 Basic physicochemical properties of catalytic reforming raffinate Boiling range/℃ Density/g.ml ^-1 composition/% C5 C6 C7 66-99 0.67 5.9 75.7 18.4

Claims (2)

1. A two-component modified zeolite catalyst for hydrocarbon aromatization is characterized in that the catalyst is ZSM-5 of 20-70 by Si/Al mol ratio, metal Ga and metal La, Ag, Pd, Either composition in Zn, Re, the weight percent of each component is: ZSM-5 46-99.4% Ga 0.5-2% Any one of Ag, Pd, Zn, 0.01-2% Alumina binder 0-50%. 2. a kind of hydrocarbon aromatization reaction component modified zeolite catalyst as claimed in claim 1, it is characterized in that the weight percentage of each component of catalyzer is: ZSM-5 63-99% Ga 0.8-1.6% Any one of Ag, Pd, Zn, 0.1-1% Alumina binder 0-35%.

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