Double-component modified molecular sieve with improved hydrothermal stability and production method thereof

Abstract

A method for producing double-component modified molecular sieve comprises adding molecular sieve to an aqueous solution containing phosphorus to form a mixture, allowing the mixture to react at pH of 1-10, temperature of 70-200 C. and pressure of 0.2-1.2 MPa for 10-200 min, and then filtering, drying and baking the resultant to obtain phosphorus-modified molecular sieve, and then adding the phosphorus-modified molecular sieve to an aqueous solution containing silver ions, allowing the phosphorus-modified molecular sieve to react with silver ions at 0-100 C. in dark condition for 30-150 min, and then filtering, drying and baking. The obtained double-component modified molecular sieve contains 88-99 wt % molecular sieve with a ratio of silica to alumina between 15 and 60, 0.5-10 wt % phosphorus (based on oxides) and 0.01-2 wt % silver (based on oxides), all based on dry matter. A catalyst produced from the double-component modified molecular sieve has improved hydrothermal stability and microactivity.

Claims

1. A method for preparing double-component modified molecular sieves with improved hydrothermal stability, wherein, according to said method, the molecular sieve is added to an aqueous solution containing phosphorus and allowed to react at pH of 2-7 at a reaction temperature of 90-160 C. under a reaction pressure of 0.2-0.8 MPa for 10-200 minutes, followed by filtering, drying and calcining, so as to obtain a phosphorus-modified molecular sieve; the phosphorus-modified molecular sieve is added into an aqueous solution containing silver ions and allowed to react at a reaction temperature of 0-100 C. for 30-150 minutes, followed by filtering, drying and calcining, so as to obtain a double-component modified molecular sieve, wherein the molecular sieve is one of ZSM type or type, molecular sieve, and the silica to alumina ratio of the molecular sieve is in the range of 15-60, the weight ratio of the aqueous solution containing silver ions to the molecular sieve is in the range from 3:1 to 7:1, and the aqueous solution containing silver ions has a concentration of 0.01-0.1 mol/L wherein the aqueous solution containing phosphorus is a solution of phosphoric acid, a solution of phosphorous acid, an aqueous solution of a soluble phosphate and/or an aqueous solution of a soluble phosphite, wherein, the soluble phosphate is one or more selected from triammonium phosphate, diammonium hydrogen phosphate, and ammonium dihydrogen phosphate, wherein the aqueous solution containing silver ions is an aqueous solution of silver nitrate, an aqueous solution of silver acetate or both wherein the aqueous solution containing phosphorus has a concentration of 0.05-1.0 mol/L.

Description

DETAILED DESCRIPTION OF THE INVENTION

(1) The analysis methods in each examples and comparative examples are as follows:

(2) 1. The element analysis is measured by X-ray fluorescence spectrometry (XRF), wherein the instrument used is Japanese Rigaku ZSX primus type X-ray fluorescence spectrometer.

(3) 2. The stability is evaluated by the difference between the relative crystallinity (ZSM-5%) before and after hydrothermal aging at 800 C. for 4 h and that at 800 C. for 17 h, wherein the crystallinity is measured on a X-ray diffractomer D/max-3C from Japanese Rigaku Company.

(4) 3. The activity is evaluated on a microreactor apparatus sold by Huayang Company, Beijing. The feedstock oil is light diesel oil from Dagang. The evaluation condition is as follows: the catalyst is treated by 100% water steam at 800 C. for 4 h or 17 h; the load of the catalyst is 5 g; the reaction temperature is 460 C.; the reaction time is 70 s; and the catalyst/oil ratio is 3.2.

Example 1

(5) 9.3 g of (NH.sub.4).sub.2HPO.sub.4 is dissolved in 500 g of distilled water. 100 g of ZSM-5 molecular sieve sample is added to the solution under stirring, and pH value is adjusted to 4. The mixture is stirred and allowed to react at reaction temperature of 100 C. under reaction pressure of 0.2 MPa for 60 min, followed by filtering and drying, and then calcined at 500 C. for 4 h. The molecular sieve sample thus obtained is labeled as PZ-1.

(6) 0.73 g of AgNO.sub.3 is dissolved in 350 g of distilled water. The molecular sieve PZ-1 is added to the silver-containing solution. The mixture is stirred and allowed to react in dark place at reaction temperature of 20 C. for 120 min, followed by filtering and drying, and then calcined at 500 C. for 2 h, so as to obtain a double-component modified molecular sieve APZ-1. Subsequently, kaolin (45%), alumina gel (15%) and APZ-1 (40%) are added into distilled water in the above proportion under slurrying, dried at 120 C. and calcined at 450 C. for 1 h, followed by crushing and screening. The catalyst sample thus obtained is labeled as C-1, from which 20-40 mesh catalyst particles are tested for their activity in the microreactor. Tables 1-3 show the composition of the sample, the crystallinity before and after aging, and the activity of this model catalyst tested in the microreactor.

Example 2

(7) 18.6 g of (NH.sub.4).sub.2HPO.sub.4 is dissolved in 400 g of distilled water. 100 g of ZSM-5 molecular sieve sample is added to the solution under stirring, and pH value is adjusted to 3. The mixture is stirred and allowed to react at reaction temperature of 120 C. under reaction pressure of 0.4 MPa for 120 min, followed by filtering and drying, and then calcined at 550 C. for 4 h. The molecular sieve sample thus obtained is labeled as PZ-2.

(8) 1.46 g of AgNO.sub.3 is dissolved in 350 g of distilled water. The molecular sieve PZ-2 is added to the silver-containing solution. The mixture is stirred and allowed to react in dark place at reaction temperature of 40 C. for 100 min, followed by filtering and drying, and then calcined at 500 C. for 2 h, so as to obtain a double-component modified molecular sieve APZ-2. Subsequently, kaolin (45%), alumina gel (15%) and APZ-2 (40%) are added into distilled water in fixed proportion under slurrying, dried at 120 C. and calcined at 450 C. for 1 h, followed by crushing and screening. The catalyst sample thus obtained is labeled as C-2, from which 20-40 mesh catalyst particles are tested for their activity in the microreactor. Tables 1-3 show the composition of the sample, the crystallinity before and after aging, and the activity of this model catalyst tested in the microreactor.

Example 3

(9) 37.2 g of (NH.sub.4).sub.2HPO.sub.4 is dissolved in 500 g of distilled water. 100 g of ZSM-5 molecular sieve sample is added to the solution under stirring, and pH value is adjusted to 2. The mixture is stirred and allowed to react at reaction temperature of 140 C. under reaction pressure of 1 MPa for 200 min, followed by filtering and drying, and then calcined at 450 C. for 6 h. The molecular sieve sample thus obtained is labeled as PZ-3.

(10) 2.19 g of AgNO.sub.3 is dissolved in 400 g of distilled water. The molecular sieve PZ-3 is added to the silver-containing solution. The mixture is stirred and allowed to react in dark place at reaction temperature of 60 C. for 60 min, followed by filtering and drying, and then calcined at 500 C. for 2 h, so as to obtain a double-component modified molecular sieve APZ-3. Subsequently, kaolin (45%), alumina gel (15%) and APZ-3 (40%) are added into distilled water in fixed proportion under slurrying, dried at 120 C. and calcined at 450 C. for 1 h, followed by crushing and screening. The catalyst sample thus obtained is labeled as C-3, from which 20-40 mesh catalyst particles are tested for their activity in the microreactor. Tables 1-3 show the composition of the sample, the crystallinity before and after aging, and the activity of this model catalyst tested in the microreactor.

Example 4

(11) 25.1 g of (NH.sub.4).sub.2HPO.sub.4 is dissolved in 500 g of distilled water. 100 g of ZSM-5 molecular sieve sample is added to the solution under stirring, and pH value is adjusted to 3. The mixture is stirred and allowed to react at reaction temperature of 140 C. under reaction pressure of 0.4 MPa for 200 min, followed by filtering and drying, and then calcined at 550 C. for 4 h. The molecular sieve sample thus obtained is labeled as PZ-4.

(12) 2.19 g of AgAc is dissolved in 400 g of distilled water. The molecular sieve PZ-4 is added to the silver-containing solution. The mixture is stirred and allowed to react in dark place at reaction temperature of 20 C. for 300 min, followed by filtering and drying, and then calcined at 500 C. for 2 h, so as to obtain a double-component modified molecular sieve APZ-4. Subsequently, kaolin (45%), alumina gel (15%) and APZ-4 (40%) are added into distilled water in fixed proportion under slurrying, dried at 120 C. and calcined at 450 C. for 1 h, followed by crushing and screening. The catalyst sample thus obtained is labeled as C-4, from which 20-40 mesh catalyst particles are tested for their activity in the microreactor. Tables 1-3 show the composition of the sample, the crystallinity before and after aging, and the activity of this model catalyst tested in the microreactor.

Example 5

(13) 16.2 g of NH.sub.4H.sub.2PO.sub.4 is dissolved in 250 g of distilled water. 100 g of ZSM-5 molecular sieve sample is added to the solution under stirring, and pH value is adjusted to 2. The mixture is stirred and allowed to react at reaction temperature of 120 C. under reaction pressure of 0.4 MPa for 60 min, followed by filtering and drying, and then calcined at 600 C. for 2 h. The molecular sieve sample thus obtained is labeled as PZ-5.

(14) 1.46 g of AgNO.sub.3 is dissolved in 300 g of distilled water. The molecular sieve PZ-5 is added to the silver-containing solution. The mixture is stirred and allowed to react in dark place at reaction temperature of 20 C. for 200 min, followed by filtering and drying, and then calcined at 500 C. for 2 h, so as to obtain a double-component modified molecular sieve APZ-5. Subsequently, kaolin (45%), alumina gel (15%) and APZ-5 (40%) are added into distilled water in fixed proportion under slurrying, dried at 120 C. and calcined at 450 C. for 1 h, followed by crushing and screening. The catalyst sample thus obtained is labeled as C-5, from which 20-40 mesh catalyst particles are tested for their activity in the microreactor. Tables 1-3 show the composition of the sample, the crystallinity before and after aging, and the activity of this model catalyst tested in the microreactor.

Example 6

(15) 28.2 g of NH.sub.4H.sub.2PO.sub.4 is dissolved in 500 g of distilled water. 100 g of ZSM-5 molecular sieve sample is added to the solution under stirring, and pH value is adjusted to 2. The mixture is stirred and allowed to react at reaction temperature of 130 C. under reaction pressure of 0.6 MPa for 120 min, followed by filtering and drying, and then calcined at 600 C. for 2 h. The molecular sieve sample thus obtained is labeled as PZ-6.

(16) 2.19 g of AgAc is dissolved in 300 g of distilled water. The molecular sieve PZ-6 is added to the silver-containing solution. The mixture is stirred and allowed to react in dark place at reaction temperature of 60 C. for 300 min, followed by filtering and drying, and then calcined at 500 C. for 2 h, so as to obtain a double-component modified molecular sieve APZ-6. Subsequently, kaolin (45%), alumina gel (15%) and APZ-6 (40%) are added into distilled water in fixed proportion under slurrying, dried at 120 C. and calcined at 450 C. for 1 h, followed by crushing and screening. The catalyst sample thus obtained is labeled as C-6, from which 20-40 mesh catalyst particles are tested for their activity in the microreactor. Tables 1-3 show the composition of the sample, the crystallinity before and after aging, and the activity of this model catalyst tested in the microreactor.

Example 7

(17) 16.2 g of H.sub.3PO.sub.4 is dissolved in 200 g of distilled water. 100 g of ZSM-5 molecular sieve sample is added to the solution under stirring, and pH value is adjusted to 2. The mixture is stirred and allowed to react at reaction temperature of 200 C. under reaction pressure of 1.0 MPa for 60 min, followed by filtering and drying, and then calcined at 450 C. for 6 h. The molecular sieve sample thus obtained is labeled as PZ-7.

(18) 1.46 g of AgNO.sub.3 is dissolved in 400 g of distilled water. The molecular sieve PZ-7 is added to the silver-containing solution. The mixture is stirred and allowed to react in dark place at reaction temperature of 40 C. for 240 min, followed by filtering and drying, and then calcined at 500 C. for 2 h, so as to obtain a double-component modified molecular sieve APZ-7. Subsequently, kaolin (45%), alumina gel (15%) and APZ-7 (40%) are added into distilled water in fixed proportion under slurrying, dried at 120 C. and calcined at 450 C. for 1 h, followed by crushing and screening. The catalyst sample thus obtained is labeled as C-7, from which 20-40 mesh catalyst particles are tested for their activity in the microreactor. Tables 1-3 show the composition of the sample, the crystallinity before and after aging, and the activity of this model catalyst tested in the microreactor.

Example 8

(19) 28.2 g of H.sub.3PO.sub.4 is dissolved in 400 g of distilled water. 100 g of ZSM-5 molecular sieve sample is added to the solution under stirring, and pH value is adjusted to 2. The mixture is stirred and allowed to react at reaction temperature of 120 C. under reaction pressure of 0.6 MPa for 200 min, followed by filtering and drying, and then calcined at 600 C. for 2 h. The molecular sieve sample thus obtained is labeled as PZ-8.

(20) 1.09 g of AgAc and 1.07 g of AgNO.sub.3 are dissolved in 400 g of distilled water. The molecular sieve PZ-8 is added to the silver-containing solution. The mixture is stirred and allowed to react in dark place at reaction temperature of 60 C. for 300 min, followed by filtering and drying, and then calcined at 500 C. for 2 h, so as to obtain a double-component modified molecular sieve APZ-8. Subsequently, kaolin (45%), alumina gel (15%) and APZ-8 (40%) are added into distilled water in fixed proportion under slurrying, dried at 120 C. and calcined at 450 C. for 1 h, followed by crushing and screening. The catalyst sample thus obtained is labeled as C-8, from which 20-40 mesh catalyst particles are tested for their activity in the microreactor. Tables 1-3 show the composition of the sample, the crystallinity before and after aging, and the activity of this model catalyst tested in the microreactor.

Example 9

(21) 9.3 g of (NH.sub.4).sub.2HPO.sub.4 is dissolved in 100 g of distilled water. 100 g of molecular sieve sample is added to the solution under stirring, and pH value is adjusted to 4. The mixture is stirred and allowed to react at reaction temperature of 110 C. under reaction pressure of 0.4 MPa for 120 min, followed by filtering and drying, and then calcined at 500 C. for 6 h. The molecular sieve sample thus obtained is labeled as P-1.

(22) 0.73 g of AgNO.sub.3 is dissolved in 300 g of distilled water. The molecular sieve P-1 is added to the silver-containing solution. The mixture is stirred and allowed to react in dark place at reaction temperature of 20 C. for 100 min, followed by filtering and drying, and then calcined at 500 C. for 2 h, so as to obtain a double-component modified molecular sieve A-1. Subsequently, kaolin (45%), alumina gel (15%) and AP-1 (40%) are added into distilled water in fixed proportion under slurrying, dried at 120 C. and calcined at 500 C. for 1 h, followed by crushing and screening. The catalyst sample thus obtained is labeled as C-9, from which 20-40 mesh catalyst particles are tested for their activity in the microreactor. Tables 1-3 show the composition of the sample, the crystallinity before and after aging, and the activity of this model catalyst tested in the microreactor.

Example 10

(23) 18.6 g of (NH.sub.4).sub.2HPO.sub.4 is dissolved in 250 g of distilled water. 100 g of molecular sieve sample is added to the solution under stirring, and pH value is adjusted to 3. The mixture is stirred and allowed to react at reaction temperature of 160 C. under reaction pressure of 0.8 MPa for 60 min, followed by filtering and drying, and then calcined at 450 C. for 6 h. The molecular sieve sample thus obtained is labeled as P-2.

(24) 1.46 g of AgNO.sub.3 is dissolved in 300 g of distilled water. The molecular sieve P-2 is added to the silver-containing solution. The mixture is stirred and allowed to react in dark place at reaction temperature of 20 C. for 200 min, followed by filtering and drying, and then calcined at 500 C. for 2 h, so as to obtain a double-component modified molecular sieve AP-2. Subsequently, kaolin (45%), alumina gel (15%) and AP-2 (40%) are added into distilled water in fixed proportion under slurrying, dried at 120 C. and calcined at 500 C. for 1 h, followed by crushing and screening. The catalyst sample thus obtained is labeled as C-10, from which 20-40 mesh catalyst particles are tested for their activity in the microreactor. Tables 1-3 show the composition of the sample, the crystallinity before and after aging, and the activity of this model catalyst tested in the microreactor.

Example 11

(25) 18.6 g of (NH.sub.4).sub.2HPO.sub.4 and 16.2 g of NH.sub.4H.sub.2PO.sub.4 are dissolved in 400 g of distilled water. 100 g of molecular sieve sample is added to the solution under stirring, and pH value is adjusted to 5. The mixture is stirred and allowed to react at reaction temperature of 100 C. under reaction pressure of 0.2 MPa for 180 min, followed by filtering and drying, and then calcined at 600 C. for 2 h. The molecular sieve sample thus obtained is labeled as P-3.

(26) 1.09 g of AgAc and 1.07 g of AgNO.sub.3 are dissolved in 350 g of distilled water. The molecular sieve P-3 is added to the silver-containing solution. The mixture is stirred and allowed to react in dark place at reaction temperature of 20 C. for 90 min, followed by filtering and drying, and then calcined at 500 C. for 2 h, so as to obtain a double-component modified molecular sieve AP-3. Subsequently, kaolin (45%), alumina gel (15%) and AP-3 (40%) are added into distilled water in fixed proportion under slurrying, dried at 120 C. and calcined at 500 C. for 1 h, followed by crushing and screening. The catalyst sample thus obtained is labeled as C-11, from which 20-40 mesh catalyst particles are tested for their activity in the microreactor. Tables 1-3 show the composition of the sample, the crystallinity before and after aging, and the activity of this model catalyst tested in the microreactor.

Comparative Example 1

(27) 18.6 g of (NH.sub.4).sub.2HPO.sub.4 is dissolved in 400 g of distilled water. 100 g of ZSM-5 molecular sieve is added to the solution under stirring, and pH value is adjusted to 3. The mixture is stirred and allowed to react at reaction temperature of 90 C. for 120 min, followed by filtering and drying, and then calcined at 550 C. for 4 h. The molecular sieve sample thus obtained is labeled as PZD-1.

(28) 1.46 g of AgNO.sub.3 is dissolved in 350 g of distilled water. The molecular sieve PZD-1 is added to the silver-containing solution. The mixture is stirred and allowed to react in dark place at reaction temperature of 40 C. for 100 min, followed by filtering and drying, and then calcined at 500 C. for 2 h, so as to obtain a double-component modified molecular sieve APZD-1. Subsequently, kaolin, alumina gel and APZD-1 (40%) are added into distilled water in fixed proportion under slurrying, dried at 120 C. and calcined at 450 C. for 1 h, followed by crushing and screening. The catalyst sample thus obtained is labeled as CD-1, from which 20-40 mesh catalyst particles are tested for their activity in the microreactor. Tables 1-3 show the composition of the sample, the crystallinity before and after aging, and the activity of this model catalyst tested in the microreactor.

Comparative Example 2

(29) 18.6 g of (NH.sub.4).sub.2HPO.sub.4 is dissolved in 400 g of distilled water. 100 g of ZSM-5 molecular sieve is added to the solution under stirring, and pH value is adjusted to 3. The mixture is stirred and allowed to react at reaction temperature of 20 C. under reaction pressure of 0.4 MPa for 120 min, followed by filtering and drying, and then calcined at 550 C. for 4 h. The molecular sieve sample thus obtained is labeled as PZD-2.

(30) 2.19 g of AgNO.sub.3 is dissolved in 400 g of distilled water. The molecular sieve PZD-2 is added to the silver-containing solution. The mixture is stirred and allowed to react in dark place at reaction temperature of 40 C. for 100 min, followed by filtering and drying, and then calcined at 500 C. for 2 h, so as to obtain a double-component modified molecular sieve APZD-2. Subsequently, kaolin (45%), alumina gel (15%) and APZD-2 (40%) are added into distilled water in fixed proportion under slurrying, dried at 120 C. and calcined at 450 C. for 1 h, followed by crushing and screening. The catalyst sample thus obtained is labeled as CD-2, from which 20-40 mesh catalyst particles are tested for their activity in the microreactor. Tables 1-3 show the composition of the sample, the crystallinity before and after aging, and the activity of this model catalyst tested in the microreactor.

Comparative Example 3

(31) 18.6 g of (NH.sub.4).sub.2HPO.sub.4 and 100 g of ZSM-5 molecular sieve are mechanically mixed until homogeneous and then calcined at 550 C. for 4 h. The molecular sieve sample thus obtained is labeled as PZD-3.

(32) 2.19 g of AgNO.sub.3 is dissolved in 400 g of distilled water. The molecular sieve PZD-3 is added to the silver-containing solution. The mixture is stirred and allowed to react in dark place at reaction temperature of 40 C. for 100 min, followed by filtering and drying, and then calcined at 500 C. for 2 h, so as to obtain a double-component modified molecular sieve APZD-3. Subsequently, kaolin (45%), alumina gel (15%) and APZD-3 (40%) are added into distilled water in fixed proportion under slurrying, dried at 120 C. and calcined at 450 C. for 1 h, followed by crushing and screening. The catalyst sample thus obtained is labeled as CD-3, from which 20-40 mesh catalyst particles are tested for their activity in the microreactor. Tables 1-3 show the composition of the sample, the crystallinity before and after aging, and the activity of this model catalyst tested in the microreactor.

Comparative Example 4

(33) 9.3 g of (NH.sub.4).sub.2HPO.sub.4 is dissolved in 110 g of distilled water. 100 g of ZSM-5 molecular sieve sample is added to the solution and impregnated for 300 min, followed by drying, and then calcined at 500 C. for 4 h. The molecular sieve sample thus obtained is labeled as PZD-4.

(34) 1.46 g of AgNO.sub.3 is dissolved in 350 g of distilled water. The molecular sieve PZD-4 is added to the silver-containing solution. The mixture is stirred and allowed to react in dark place at reaction temperature of 40 C. for 200 min, followed by filtering and drying, and then calcined at 500 C. for 2 h, so as to obtain a double-component modified molecular sieve APZD-4. Subsequently, kaolin (45%), alumina gel (15%) and APZD-4 (40%) are added into distilled water in abovementioned proportion under slurrying, dried at 120 C. and calcined at 450 C. for 1 h, followed by crushing and screening. The catalyst sample thus obtained is labeled as CD-4, from which 20-40 mesh catalyst particles are tested for their activity in the microreactor. Tables 1-3 show the composition of the sample, the crystallinity before and after aging, and the activity of this model catalyst tested in the microreactor.

Comparative Example 5

(35) 18.6 g of NH.sub.4H.sub.2PO.sub.4 is dissolved in 400 g of distilled water. 100 g of molecular sieve sample is added to the solution under stirring, and pH value is adjusted to 2. The mixture is stirred and allowed to react at reaction temperature of 50 C. for 60 min, followed by filtering and drying, and then calcined at 600 C. for 2 h. The molecular sieve sample thus obtained is labeled as PD-1.

(36) 2.19 g of AgNO.sub.3 is dissolved in 350 g of distilled water. The molecular sieve PD-1 is added to the silver-containing solution. The mixture is stirred and allowed to react in dark place at reaction temperature of 40 C. for 100 min, followed by filtering and drying, and then calcined at 500 C. for 2 h, so as to obtain a double-component modified molecular sieve APD-1. Subsequently, kaolin (45%), alumina gel (15%) and APD-1 (40%) are added into distilled water in fixed proportion under slurrying, dried at 120 C. and calcined at 500 C. for 1 h, followed by crushing and screening. The catalyst sample thus obtained is labeled as CD-5, from which 20-40 mesh catalyst particles are tested for their activity in the microreactor. Tables 1-3 show the composition of the sample, the crystallinity before and after aging, and the activity of this model catalyst tested in the microreactor.

Comparative Example 6

(37) 18.6 g of (NH.sub.4).sub.2HPO.sub.4 is dissolved in 400 g of distilled water. 100 g of ZSM-5 molecular sieve sample is added to the solution under stirring and then 10 ml solution containing 1.46 g of AgNO.sub.3 is added, and pH value is adjusted to 3. The mixture is stirred and allowed to react at reaction temperature of 120 C. under reaction pressure of 0.4 MPa for 120 min, followed by filtering and drying, and then calcined at 550 C. for 4 h. The molecular sieve sample thus obtained is labeled as APZD-5.

(38) Subsequently, kaolin (45%), alumina gel (15%) and APZD-5 (40%) are added into distilled water in fixed proportion under slurrying, dried at 120 C. and calcined at 450 C. for 1 h, followed by crushing and screening. The catalyst sample thus obtained is labeled as CD-6, from which 20-40 mesh catalyst particles are tested for their activity in the microreactor. Tables 1-3 show the composition of the sample, the crystallinity before and after aging, and the activity of this model catalyst tested in the microreactor.

INDUSTRIAL UTILITY

(39) The present invention provides the optimal modified molecular sieve that is obtained by the modification method in accordance with the present invention: said molecular sieve contains, based on dry basis, 88-99 wt % of a molecular sieve with a silica to alumina ratio of 15-60, 0.5-10 wt % of phosphorus based on oxide and 0.01-2 wt % of silver based on oxide.

(40) It can be seen according to the data in Table 1 and 2 that the molecular sieves modified by the modification method of Examples 1-11 have higher relative crystallinity than the molecular sieves modified by other methods after 17 h of hydrothermal treatment. Meanwhile, it can also be seen according to the data in Table 3 that the molecular sieve model catalysts modified by the modification method of Examples 1-11 have higher activity in the microreactor than the molecular sieve catalysts modified by other methods.

(41) TABLE-US-00001 TABLE 1 Hydrothermal stability of phosphorus-modified molecular sieves Relative Crystallinity (%) Before After 17 h of *Crystallinity hydrothermal hydrothermal reservation Sample Ref. P.sub.2O.sub.5 (wt %) treatment treatment (%) PZ-1 1.9 93 79 84.9 PZ-2 2.4 91 80 87.9 PZ-3 3.2 90 82 91.1 PZ-4 2.8 91 82 90.1 PZ-5 2.5 91 83 91.2 PZ-6 2.9 90 83 92.2 PZ-7 2.4 91 82 90.1 PZ-8 2.8 92 81 88.0 P-1 1.6 95 86 90.5 P-2 2.0 94 88 93.6 P-3 2.6 92 87 94.6 PZD-1 1.5 92 78 84.8 PZD-2 1.0 92 77 83.7 PZD-3 9.7 84 69 82.1 PZD-4 4.8 87 70 80.4 PD-1 1.0 96 80 83.3 *Crystallinity reservation = relative crystallinity after hydrothermal treatment/relative crystallinity before hydrothermal treatment 100%

(42) TABLE-US-00002 TABLE 2 Hydrothermal stability of double-component modified molecular sieves Relative Crystallinity (%) Ag.sub.2O Before After 17 h of *Crystallinity Sample P.sub.2O.sub.5 (wt hydrothermal hydrothermal reservation Ref. (wt %) %) treatment treatment (%) APZ-1 1.8 0.4 92 82 89.1 APZ-2 2.2 0.8 91 84 92.3 APZ-3 2.8 1.1 88 83 94.3 APZ-4 2.5 0.6 91 84 92.3 APZ-5 2.1 0.7 92 85 92.4 APZ-6 2.6 1.0 89 84 94.4 APZ-7 2.0 0.7 90 84 93.3 APZ-8 2.5 0.9 88 81 92.0 AP-1 1.6 0.3 93 88 94.6 AP-2 1.9 0.7 91 87 95.6 AP-3 2.5 0.9 88 84 95.5 APZD-1 0.2 0.8 97 81 83.5 APZD-2 0.3 1.3 94 78 83.0 APZD-3 9.7 1.4 82 65 79.3 APZD-4 0.2 0.9 95 80 84.2 APZD-5 0.4 0.9 95 79 83.2 APD-1 0.3 1.2 96 82 85.4 *Crystallinity reservation = relative crystallinity after hydrothermal treatment/relative crystallinity before hydrothermal treatment 100%

(43) TABLE-US-00003 TABLE 3 Activity performance of modified molecular sieve model catalysts in the microreactor Activity performance Activity performance Sample (%, 4 h of hydrothermal (%, 17 h of hydrothermal Ref. aging at 800 C.) aging at 800 C.) C-1 42 41 C-2 42 41 C-3 44 42 C-4 43 42 C-5 42 40 C-6 46 44 C-7 43 41 C-8 43 40 C-9 46 44 C-10 47 46 C-11 46 46 CD-1 35 29 CD-2 34 28 CD-3 35 28 CD-4 36 30 CD-5 25 24

(44) According to the above research, it has been found that the introduction of phosphorus inhibits the dealuminification of the ZSM-5 zeolite framework under hydrothermal condition and significantly improves the reservation of acid on the zeolite, so as to increase the catalytic activity and selectivity thereof. Meanwhile, in order to further substantially increase the hydrothermal stability of the molecular sieve and adjust the surface acidity of the zeolite at the same time, it is necessary to introduce the second modifying element for its modification. When the silver ion, a transition metal, is introduced into the ZSM-5 molecular sieve, its oxidation effect facilitates the formation of carbocations, which results in improved reactivity by enabling the reaction to be initiated more readily. Because the adsorption of olefins to silver is relatively weak with respect to other transition metals, the hydrogen transfer reactions may be reduced, which is favorable to increase the olefin yields. Moreover, silver can accept or donate electrons during the reaction as the transition metal and produce free radicals, which further crack into olefins, that is, its oxidation-reduction effect enables the reaction to proceed according to free radical reaction mechanism, and thus the yields of light olefins may be increased.

(45) The advantage of the present invention lies in the fact that this method is able to prevent the phosphorus constituent from being heavily washed away when the phosphorus-modified molecular sieve is modified by ion exchange with transition metals, and the double-component modified molecular sieve obtained by such modification and the model catalyst thereof have excellent hydrothermal stability and catalytic activity.