Method of preparing olefins from methanol

Abstract

The present disclosure provides a method of preparing olefins from methanol, in which methanol and phenol-like molecules are used as raw material, which is gasified and then passed into a two-stage fixed-bed catalytic reactor. The raw material reacts with a catalyst A (silica-aluminum molecular sieve) and a catalyst B (silica-aluminum or phosphorus-aluminum molecular sieve) in sequence to produce ethylene.

Claims

1. A method of preparing olefins from methanol, comprising: taking the methanol and phenol molecules as raw materials; gasifying the raw materials and passing into a two-stage fixed-bed catalytic reactor under an anaerobic environment, such that ethylene is generated after a reaction, wherein the reaction lasts for 100 hours; wherein the two-stage fixed-bed catalytic reactor comprises a first constant-temperature zone and a second constant-temperature zone in an order from an inlet to an outlet, wherein the first constant-temperature zone is at a temperature of 300? C. to 400? C., wherein the second constant-temperature zone is at a temperature of 160? C. to 400? C.; placing a catalyst A in the first constant-temperature zone; and placing a catalyst B is placed in the second constant-temperature zone; wherein the catalyst A is a silica-aluminum molecular sieve; wherein the catalyst B is a silica-aluminum molecular sieve or a phosphorus-aluminum molecular sieve; and wherein the phenol molecules represented by a structural formula as listed below: ##STR00004## wherein R.sup.1-R.sup.5 are independently selected from one of H atom, alkyl, alkoxy, phenol hydroxyl, alcohol hydroxyl, ##STR00005## halogen, respectively; and R is selected from one of H atom, hydroxyl, alkoxy, alkyl, and amino.

2. The method according to claim 1, wherein a molar ratio of the methanol to the phenol molecules is 1:1 to 8:1.

3. The method according to claim 1, wherein the first constant-temperature zone is at a temperature of 320? C. to ?360? C.

4. The method according to claim 1, wherein the second constant-temperature zone is at a temperature of 200? C. to ?300? C.

5. The method according to claim 1, wherein further comprising: introducing an inert gas, wherein the inert gas is mixed with the gasified raw materials.

6. The method according to claim 5, wherein the inert gas is one or more of N.sub.2, He, or Ar.

7. The method according to claim 5, wherein a flow rate of the inert gas is 0 mL/min to 100 mL/min.

8. The method according to claim 1, wherein quartz sand is added to the first constant-temperature zone of the two-stage fixed-bed catalytic reactor, and wherein the quartz sand is mixed with the catalyst A.

9. The method according to claim 1, wherein quartz sand is added to the second constant-temperature zone of the two-stage fixed-bed catalytic reactor, and wherein the quartz sand is mixed with the catalyst B.

10. The method according to claim 1, wherein a space velocity of the methanol is 3 kg CH.sub.3OH/(kg cat. A)/h to 200 kg CH.sub.3OH/(kg cat. A)/h.

11. The method according to claim 1, wherein a mass ratio of the catalyst A/catalyst B is 0.1 to 12.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic view of a two-stage fixed-bed catalytic reactor used in the present disclosure and a schematic diagram of a reaction process.

(2) FIG. 2 shows a thermogravimetric diagram of SAPO-34 before and after the reaction in Embodiment 21.

(3) FIG. 3 shows a trend diagram of the reaction in Embodiment 21 as a function of temperature.

(4) FIG. 4 shows a diagram of stability results of the catalytic reaction in Embodiment 21.

(5) FIG. 5 shows a reaction principle of a process for a highly selective preparation of ethylene from methanol according to the present disclosure.

DETAILED DESCRIPTION

(6) The present disclosure is further illustrated below by means of embodiments, but the embodiments do not limit the present disclosure thereby.

(7) Thorough the embodiments, reagents used are analytically pure unless otherwise specified.

(8) Ethylene selectivity and ethylene yield for 100 hours of continuous operation (abbreviated as 100 h ethylene yield) are calculated using the following equations, respectively.

(9) $\begin{array}{cc}{C}_2{H}_4\mathrm{selectivity}\mathrm{in}\mathrm{gas}\mathrm{phase}\mathrm{product}=\frac{2?.Math.C_2{H}_4.Math.}{.Math.x?.Math.\mathrm{products}.Math.}?100\%& \left(1\right)\end{array}$

(10) $\begin{array}{cc}100h{C}_2{H}_4\mathrm{yield}=100?\frac{.Math.C_2{H}_4.Math.}{m_{cat}}& \left(2\right)\end{array}$

(11) where |C.sub.2H.sub.4| represents the number of moles of ethylene in the reaction products per hour; |products| represents the number of moles of each reaction product per hour, m.sub.cat represents the mass of the catalyst, and x is the number of carbon atoms in the gas phase product. For example, for CH.sub.4, x=1; for C.sub.2H.sub.4, x=2.

(12) A catalyst evaluation device involved in the embodiments of the present disclosure includes a liquid chromatograph-mass spectrometer (LC-MS) and an online gas chromatography. During the reaction process, the composition of the gas-phase product in the reactor is monitored and analyzed in real time by the online gas chromatography, while a liquid phase product in the reactor is collected and analyzed by liquid chromatograph-mass spectrometer to obtain information on composition and characteristic parameters of the liquid phase product in the reaction.

(13) The preparation route of the present disclosure is shown below:

(14) ##STR00003##

(15) where R.sup.1-R.sup.5 are independently selected from one of H atom, alkyl, alkoxy, phenol hydroxyl, alcohol hydroxyl, carbonyl, halogen, respectively.

Embodiment 1

(16) Methanol and phenol are mixed according to a molar ratio of 8:1 at a feed rate of 1.0 mL/h. The raw material is gasified and passed into a reaction tube under nitrogen, with a flow rate of nitrogen is 30 mL/min. The catalyst A is NaX molecular sieve at an amount of 50 mg and a bed temperature of 320? C.; the catalyst B is KY molecular sieve at an amount of 150 mg and a bed temperature of 250-290? C. In order to enhance the mass and heat transfer, each of the catalyst A and the catalyst B is mixed with 400 mg of quartz sand with a mesh size of 20-40 mesh when loading. The gas phase product is detected and analyzed by the online gas chromatography, and the liquid phase product is collected and analyzed by the liquid chromatograph-mass spectrometer. The results obtained are shown in Table 1.

Embodiments 2-35

(17) Referring to the method described in Embodiment 1, the experimental parameters adopted in Embodiments 2-35 are slightly different from Embodiment 1, and the specific experimental parameters and reaction properties are shown in Table 1.

(18) TABLE-US-00001 TABLE 1 Summary of experimental parameters and reaction properties of the Embodiments Molar 100 h Type of ratio of Catalyst A Catalyst B ethylene phenol- methanol Temper- Temper- Ethylene yield Emb. like to phenol- Amount ature Amount ature Selectivity (mmol No. molecule like molecule Type (mg) (? C.) Type (mg) (? C.) (%) C.sub.2H.sub.4 g.sup.?1 cat) 1 Phenol 8 NaX 50 320 KY 150 290 97.3 221.1 2 Phenol 8 NaX 50 320 KX 150 360 96.3 113.6 3 Phenol 8 NaX 50 320 K-beta 150 360 96.5 107.5 4 Phenol 8 NaX 50 320 HY 150 360 59.6 141.2 5 Phenol 8 NaX 50 320 SAPO-34 150 160 99.7 52.7 6 Phenol 8 NaX 50 320 SAPO-34 150 200 99.3 155.8 7 Phenol 8 NaX 50 320 SAPO-34 150 230 99.4 196.5 8 Phenol 8 NaX 50 320 AlPO-18 150 400 99.1 189.7 9 Phenol 8 NaX 50 320 SAPO-18 150 230 99.6 294.8 10 Phenol 8 NaX 50 320 SAPO-11 150 230 99.3 79.8 11 Phenol 8 NaX 50 320 SAPO-14 150 230 99.4 70.6 12 Phenol 8 NaX 50 320 SSZ-13 150 350 99.8 503.6 13 Phenol 8 NaX 50 320 ZSM-5 150 230 99.2 273.3 14 Phenol 8 NaX 50 320 chaba 150 300 99.3 168.9 15 Phenol 8 NaY 50 360 SAPO-34 150 230 99.2 175.0 16 Phenol 8 Na- 50 400 SAPO-34 150 230 98.7 61.4 beta 17 Phenol 8 ?- 50 400 SAPO-34 150 230 98.7 138.2 Al.sub.2O.sub.3 18 Phenol 8 MgO 50 400 SAPO-34 150 230 98.7 9.2 19 Phenol 6 NaX 50 300 SAPO-34 150 230 99.3 162.7 20 Phenol 4 NaX 50 340 SAPO-34 150 230 99.7 168.9 21 Phenol 3 NaX 50 360 SAPO-34 150 230 99.5 208.8 22 Phenol 2 NaX 50 380 SAPO-34 150 230 98.9 129.0 23 Phenol 1 NaX 50 400 SAPO-34 150 230 98.9 101.3 24 Cresol 3 NaX 50 360 SAPO-34 150 230 99.6 531.2 25 Ethyl- 3 NaX 50 360 SAPO-34 150 230 99.9 525.1 phenol 26 Propyl- 3 NaX 50 360 SAPO-34 150 230 98.7 496.4 phenol 27 4-Methoxyphenol 3 NaX 50 360 SAPO-34 150 230 99.4 551.8 28 4- 3 NaX 50 360 SAPO-34 150 230 99.4 531.3 Ethoxyphenol 29 Hydroquinone 3 NaX 50 360 SAPO-34 150 230 98.7 215.8 30 4-(Hydroxy 3 NaX 50 360 SAPO-34 150 230 99.4 426.8 methyl)phenol 31 4- 3 NaX 50 360 SAPO-34 150 230 99.4 196.8 Hydroxyacetophenone 32 4-Hydroxybenzoic 3 NaX 50 360 SAPO-34 150 230 99.4 451.4 acid 33 Methyl 4- 3 NaX 50 360 SAPO-34 150 230 99.4 186.2 hydroxybenzoate 34 4-Bromophenol 3 NaX 50 360 SAPO-34 150 230 99.4 104.2 35 4-Chlorophenol 3 NaX 50 360 SAPO-34 150 230 99.4 96.8

(19) The process described in the present disclosure has a good stability and can be operated continuously for more than 100 h. A little coke is formed in catalyst during the reaction. In contrast, the conventional methanol-to-olefin (MTO) process is prone to coke deposition, the catalyst runs continuously for less than 10 h, and after a period of operation, the catalyst must be regenerated by air combustion to remove the coke before it can continue to be used. In the 100 h stability tests of Embodiments 1-38, the catalytic performance is maintained, and the 100 h ethylene yield, which is the amount of ethylene produced per gram of catalyst over the 100 h stable life cycle of the catalyst, is up to 551.8 mmol C.sub.2H.sub.4 g.sup.?1 cat, which is higher than the amount of ethylene produced on conventional MTO catalysts (150-250 mmol C.sub.2H.sub.4 g.sup.?1 cat) per gram of catalyst produced over a stable life cycle (10 h) (Ref: ?lvaro-Mu?oz, T., M?rquez-?lvarez, C., Sastre, E. Applied Catalysis A: General. 472, 72-79 (2014). Tian, P., Wei, Y., Ye, M., Liu, Z. ACS Catalysis. 5(3), 1922-1938 (2015).).

(20) Embodiments 1-14 illustrate the effect of the type of the catalyst B on the reaction temperature, ethylene selectivity, and 100 h ethylene yield, when the catalyst A is fixed to NaX molecular sieve, the reaction temperature is fixed to 320? C., and the molecular catalyst is phenol. As can be seen from the table, the catalyst B may be one or a mixture of Y-type, X-type, AIPO, SAPO, SSZ, ZSM, chabazite, and more preferably SAPO-type molecular sieves. The best 100 h ethylene yield is achieved when the catalyst B is SAPO-34 and SAPO-18 molecular sieves. During the preparation process, when the catalyst B is selected from KY, KX, AIPO, SAPO, SSZ, ZSM, and chabazite molecular sieves, the ethylene selectivity can all be greater than 95%, while when the catalyst B is selected with the HY molecular sieve, the ethylene selectivity is only 60-70%.

(21) Embodiments 7, 15-18 illustrate the effect of the type of the catalyst A on the reaction temperature, ethylene selectivity, and 100 h ethylene yield, when the catalyst B is fixed to SAPO-34 molecular sieve, the reaction temperature of the catalyst B is fixed to 230? C., and the molecular catalyst is fixed to phenol. As can be seen from the table, the catalyst A may be one or a mixture of X-type, Y-type, and ?-type molecular sieves. The best 100 h ethylene yield is achieved when the catalyst A is NaX molecular sieve. During the preparation process, the 100 h ethylene yield is only 9.21 mmol C.sub.2H.sub.4 g.sup.?1 cat when the catalyst A is MgO.

(22) Embodiments 7, 19-23 illustrate the effect of the molar ratio of methanol to phenol-like molecules on the reaction temperature, the 100 h ethylene yield, and the ethylene selectivity, preferably 8:1-1:1, more preferably 3:1. During the testing process, optimization of the molar ratio of methanol to phenol-like molecules resulted in the modulation of the 100 h ethylene yields, with the highest 100 h ethylene yields up to 208.79 mmol C.sub.2H.sub.4 g.sup.?1 cat.

(23) Taking Embodiment 21 as an example, the thermogravimetric curves of SAPO-34 before and after the reaction are shown in FIG. 2, and there is a little coke formed on the surface of the catalyst B after 100 h of reaction of SAPO-34, which proves the good catalytic stability of the reaction in the present disclosure; the trend of the reaction as a function of temperature is shown in FIG. 3, and the 100 h ethylene yield increases with the rise of the reaction temperature; when the reaction temperature is 230? C., the 100 h ethylene yield is achieved as 208.79 mmol C.sub.2H.sub.4 g.sup.?1 cat and the ethylene selectivity is >99%; the catalytic stability performance is shown in FIG. 4, there is no significant decrease in the reaction performance within 100 h, which further indicates that the reaction process of the present disclosure has good catalytic stability.

(24) Embodiments 21, 24-35 illustrate the effect of the type of phenol-like molecule on the ethylene selectivity and 100 h ethylene yield. The substituents may include one or more of H atoms, alkyl groups, alkoxy groups, phenol hydroxyl groups, alcohol hydroxyl groups, carbonyl groups, and halogens. The ethylene selectivity is each greater than 98%, and the 100 h ethylene yield is up to 551.79 mmol C.sub.2H.sub.4 g.sup.?1 cat when the phenol-like molecule is a methoxy phenol.

Embodiment 36

(25) Referring to the method described in Embodiment 21, methanol is mixed with phenol at a molar ratio of 3:1 at a feed rate of 1.0 mL/h. The raw material is gasified and passed into the reaction tube under nitrogen, varying the flow rate of nitrogen to 100, 80, 60, 40, 30, 20, 0 mL/min. The catalyst A is NaX molecular sieve at an amount of 50 mg and a bed temperature of 360? C. The catalyst B is SAPO-34 molecular sieve at an amount of 150 mg and a bed temperature of 230? C. To enhance the mass and heat transfer, each of the catalyst A and the catalyst B is mixed with 400 mg of quartz sand with a mesh size of 20-40 mesh when loading. The gas phase product is detected and analyzed by the online gas chromatography, and the liquid phase product is collected and analyzed by the liquid chromatograph-mass spectrometer. With the gradual decrease of nitrogen flow rate from 100 to 0 mL/min, the ethylene selectivity in the gas phase product is greater than 99%. The 100 h ethylene yield shows an increasing and then decreasing trend with the decrease of nitrogen flow rate. When the nitrogen flow rate is 30 mL/min, the 100 h ethylene yield reaches the highest value of 208.8 mmol C.sub.2H.sub.4 g.sup.?1 cat. When the nitrogen flow rate is 100 mL/min, the 100 h ethylene yield is 83.31 mmol C.sub.2H.sub.4 g.sup.?1 cat. When the nitrogen flow rate is 0 mL/min, the 100 h ethylene yield is 98.06 mmol C.sub.2H.sub.4 g.sup.?1 cat.

Embodiment 37

(26) Referring to the method described in Embodiment 21, methanol is mixed with phenol at a molar ratio of 3:1, varying the feed rate with the methanol space velocity of 3, 6, 9, 40, 80, 120, 160, 200 kg CH.sub.3OH/(kg cat. A)/h, and the nitrogen flow rate is 30 mL/min. The raw material is gasified and passed into the reaction tube under nitrogen. The catalyst A is NaX molecular sieve at an amount of 50 mg at a bed temperature of 360? C., and the catalyst B is SAPO-34 molecular sieve at an amount of 150 mg at a bed temperature of 230? C. To enhance the mass and heat transfer, each of the catalyst A and the catalyst B is mixed with 400 mg of quartz sand with a mesh size of 20-40 mesh when loading. The gas phase product is detected and analyzed by the online gas chromatography, and the liquid phase product is collected and analyzed by the liquid chromatograph-mass spectrometer. It is found that the ethylene selectivity in the gas phase product is greater than 99% with the gradual increase of methanol space velocity from 3 to 200 kg CH.sub.3OH/(kg cat. A)/h. The 100 h ethylene yield shows an increasing and then decreasing trend with the increase of methanol space velocity. When the methanol space velocity is 24 kg CH.sub.3OH/(kg cat. A)/h, the 100 h ethylene yield reaches the highest value of 201.2 mmol C.sub.2H.sub.4 g.sup.?1 cat. When the methanol space velocity is 3 kg CH.sub.3OH/(kg cat. A)/h, the 100 h ethylene yield is 181.3 mmol C.sub.2H.sub.4 g.sup.?1 cat. When the methanol space velocity is 200 kg CH.sub.3OH/(kg cat. A)/h, the 100 h ethylene yield is 109.8 mmol C.sub.2H.sub.4 g.sup.?1 cat.

Embodiment 38

(27) Referring to the method described in Embodiment 21, methanol is mixed with phenol at a molar ratio of 3:1 at a feed rate of 1.0 mL/h and a nitrogen flow rate of 30 mL/min. The raw material is gasified and passed into the reaction tube under nitrogen. The catalyst A is NaX molecular sieve at a bed temperature of 360? C., and the catalyst B is SAPO-34 molecular sieve at a bed temperature of 230? C., varying the catalyst A/B mass ratio of 0.1, 0.33, 1, 3, 6, 9, 12. To enhance the mass and heat transfer, each of the catalyst A and the catalyst B is mixed with 400 mg of quartz sand with a mesh size of 20-40 mesh when loading. The gas phase product is detected and analyzed by the online gas chromatography, and the liquid phase product is collected and analyzed by the liquid chromatograph-mass spectrometer. It is found that the ethylene selectivity in the gas phase product is greater than 99% with the gradual increase of the catalyst A/B mass ratio from 0.1 to 12, and the 100 h ethylene yield shows an increasing and then decreasing trend with the increase of the catalyst A/B mass ratio. When the catalyst A/B mass ratio is 0.1, the 100 h ethylene yield reaches the highest value of 208.8 mmol C.sub.2H.sub.4 g.sup.?1 cat. When the catalyst A/B mass ratio is 0.33, the 100 h ethylene yield is 133.1 mmol C.sub.2H.sub.4 g.sup.?1 cat. When the catalyst A/B mass ratio is 12, the 100 h ethylene yield is 118.3 mmol C.sub.2H.sub.4 g.sup.?1 cat.

Comparative Example 1

(28) This comparative example is carried out with reference to the reaction parameters of Embodiment 21, and differs from Embodiment 21 in that no catalyst B is added. The gas and liquid phase products are detected by chromatography, showing that the main product is anisole and that ethylene is not present. This result indicates that the primary role of the catalyst A is to catalyze the reaction between methanol and phenol to produce anisole molecules. Highly selective ethylene-production from methanol cannot be achieved with only the catalyst A and the molecular catalyst, namely, the phenol-like molecules.

Comparative Example 2

(29) Anisole is used as the raw material, the feed rate is 1 mL/h, and the raw material is gasified and passed into the reaction tube driven by nitrogen, with a nitrogen flow rate of 30 mL/min. The catalyst is SAPO-34 molecular sieve at an amount of 150 mg. To enhance the mass transfer and heat transfer, the catalyst is loaded with 400 mg of quartz sand mixed with a mesh size of 20-40 mesh when loading. During the test, the bed temperature is in a range of 160-230? C. The gas phase product is detected and analyzed by the online gas chromatography, and the liquid phase product is collected and analyzed by the liquid chromatograph-mass spectrometer. It is found that the main product of anisole decomposition is ethylene and phenol, the ethylene selectivity in the gas-phase product is >98%, and the phenol selectivity in the liquid phase product is >91%; the 100 h ethylene yield increases with the increase of temperature. The 100 h ethylene yield is 62.7 mmol C.sub.2H.sub.4 g.sup.?1 cat at 160? C., and 218.8 mmol C.sub.2H.sub.4 g.sup.?1 cat at 230? C. This result suggests that the main role of the catalyst B is to catalyze the decomposition of anisole into phenol and ethylene.

Comparative Example 3

(30) This comparative example is carried out according to the reaction parameters of Embodiment 21, and differs from Embodiment 21 in that no catalyst A is added. The gas and liquid phase products are detected by chromatography, showing that no ethylene is produced, even at a reaction temperature of 230? C.

Comparative Example 4

(31) This comparative example is carried out according to the reaction parameters of Embodiment 21, and differs from Embodiment 21 in that no phenol is added n. The gas and liquid phase products are detected by chromatography, showing that even if the reaction temperature of the catalyst B is 230? C., the methanol as raw material is hardly reacted, and no ethylene is produced in the gas phase.

(32) As can be seen from the synthesis of Embodiment 21 and Comparative Examples 1-4, the molecular catalyst, the catalyst A, and the catalyst B are indispensable in the methanol-to-ethylene process proposed in the present disclosure. The synergistic effect between them is the key to ensure the high selective conversion of methanol to ethylene. The specific reaction process is shown in FIG. 5, where methanol reacts with the phenol-like molecules to generate anisole-like molecules under the action of the catalyst A. Subsequently, the anisole-like molecules decompose to generate the phenol-like molecules and ethylene under the action of the catalyst B, where the phenol-like molecules participate in the reaction, but the quantity thereof before and after the reaction does not change significantly, and thus the phenol-like molecules act as the molecular catalyst. And as can be seen from Embodiments 1-38, factors such as the types of catalysts A and B, the reaction temperature, and the ratio of phenol-like molecules to methanol affect the catalytic reaction performance.