JP5131624B2 - Paraffin catalytic cracking process - Google Patents

Description

  The present invention relates to a method for catalytic cracking of paraffin (alkane), and more specifically, a light olefin containing a large amount of propylene by catalytic cracking of paraffin using aluminosilicate MCM-68 adjusted with Si / Al as a catalyst. Alkenes).

In order to obtain propylene by catalytic cracking of about C6 paraffin, ZSM-5, beta-type zeolite, mordenite, etc. with various Si / Al adjustments are known as conventional zeolite catalysts (Patent Document 1, etc.) . However, the yield of propylene was limited. Propylene is currently obtained mainly by pyrolysis of light naphtha at about 700-800 ° C. However, in the case of thermal decomposition, ethylene is theoretically easy to produce, and the ethylene selectivity is actually high.
On the other hand, aluminosilicate MCM-68 is a relatively new zeolite synthesized by Mobil in 2000 (Patent Document 2, etc.). This zeolite has a structure in which large pores (12-membered ring pores) and medium pores (10-membered ring pores) intersect three-dimensionally. Since this type of zeolite generally has a large surface area and a large internal space, it is useful as a catalyst in petroleum refining and petrochemical processes, and is expected to be useful as a catalyst using a relatively bulky organic molecule as a substrate. MCM-68 has a Si / Al ratio of 9-12, so it has a relatively high Al content, that is, active sites, and is considered to be an acid catalyst because it is more stable. As a base material for hydrocarbon processing catalysts because of its high activity in reactions involving methane, such as alkylation of aromatic hydrocarbons, transalkylation of alkylaromatic hydrocarbons, isomerization, disproportionation, dealkylation, etc. Expected.
The present inventors have reported that MCM-68 having a Si / Al ratio of about 70 obtained by dealumination of this MCM-68 is effective as a catalyst for biphenyl isopropylation reaction (non-conversion). Patent Document 1).

Patent No. 4048458 Special Table 2002-535227

Micropor. Mesopor. Mater., 116, 216-226 (2008)

If a catalytic cracking method using a solid acid such as aluminosilicate is used, the reaction temperature can be lowered and the propylene selectivity can be improved. If propylene is obtained by catalytic cracking of light naphtha at around 450 to 600 ° C., it is considered that the energy saving effect is very large compared to thermal cracking.
The object of the present invention is to achieve higher propylene selectivity at a lower temperature than ever by catalytically cracking paraffin using MCM-68 having a new zeolite framework that has not been studied at all. .

The present inventors adjusted the Al amount of aluminosilicate MCM-68 and used it as a catalyst for the catalytic cracking reaction of hexane. As a result, the yield of propylene in the cracked product was reduced by the conventional zeolite catalyst (ZSM- And the present invention has been completed.
That is, the present invention is a method for producing a light olefin by catalytic cracking of a paraffin raw material, and using aluminosilicate MCM-68 having a Si / Al ratio of 20 to 150 as a catalyst.
Further, the present invention is a catalyst for catalytic cracking of paraffin comprising aluminosilicate MCM-68 having a Si / Al ratio of 20 to 150.
Furthermore, the present invention provides a step of producing an aluminosilicate MCM-68 having a Si / Al ratio of 8.3 to 15 by crystallization using an organic template, and dealumination of the aluminosilicate MCM-68 to obtain a Si / Al This is a method for producing a catalyst for catalytic cracking of paraffin comprising the step of producing aluminosilicate MCM-68 having a ratio of 20 to 150.

  The aluminosilicate MCM-68, which is the catalyst of the present invention, has an optimized Si / Al ratio as a catalyst for catalytic cracking of paraffin. When used for the catalytic cracking reaction of paraffin, the catalytic activity is high and propylene (C3 =) Selectivity and yield are high.

It is a figure which shows the fixed bed normal pressure flow reaction apparatus used for the catalytic reaction of an Example.

  The aluminosilicate of the present invention has a basic skeleton of MCM-68 and has a Si / Al ratio of 20 to 150, preferably 30 to 80. In a region where the Si / Al ratio is smaller than this, the instantaneous activity at the initial stage of the reaction is high, but the activity is greatly deteriorated by coking (carbon deposition), resulting in a catalyst having low activity. On the other hand, if the Si / Al ratio is too high, the activity as an acid catalyst decreases.

In the present invention, the Si / Al ratio (molar ratio) refers to a value quantified using inductively coupled plasma atomic emission spectrum (ICP-AES) analysis. That is, the Si / Al molar ratio calculated from the number of moles of Si and the number of moles of metal calculated from the weight (mg / L) of Al obtained by ICP-AES measurement.
Usually, a silicate having a desired Si / Al molar ratio can be obtained by preparing a calibration curve in advance for the Si / Al molar ratio with respect to conditions such as processing time and temperature and managing the conditions.

The aluminosilicate of the present invention comprises (1) a step of producing MCM-68 having a Si / Al ratio of about 8.3 to 15, and (2) the MCM-68 having a Si / Al ratio of 20 to 150, preferably It can be obtained by a production method comprising a step of performing an acid treatment (dealuminization treatment step) so as to be 30 to 80.
Hereafter, the manufacturing method of the aluminosilicate of this invention is demonstrated in order.
(1) First, MCM-68 (hereinafter also referred to as “Al-MCM-68”) having Si / Al of about 8.3 to 15 is manufactured.
MCM-68 is an aluminosilicate with a structure in which 12-membered and 10-membered channels intersect three-dimensionally. The unit cell (unit cell) is a tetragonal system having a composition of Si _100.6 Al _111.4 O ₂₂₄ . For the MCM-68 structure, the three-letter code of the International Zeolite Association Structure Commission (IZA-SC) is MSE, and has a skeletal topology that is uniquely determined by the atomic coordinates shown in Table 1. There is a straight 12-membered ring channel (diameter 0.67 nm) in the c-axis direction, and two wavy 10-membered ring channels (diameter 0.50-0.55 nm) in the a-axis and b-axis directions. Moreover, it has a cavity (cage) (0.65 × 1.73 nm) accessible only through a 10-membered ring (J. Phys. Chem. B, 2006, 110, 2045-2050).

注）空間群 P4₂/mnm （International Union of Crystallography (IUCr)の定めるNo. 136の空間群）格子定数 a (=b) = 18.286(1) Å, c = 20.208(2) Å

Note) Space group P4 ₂ / mnm (No. 136 space group defined by International Union of Crystallography (IUCr)) Lattice constant a (= b) = 18.286 (1) Å, c = 20.208 (2) Å

Aluminosilicate MCM-68 is represented by the following composition formula.
_{H n Al n Si 112-n} O 224
(In the formula, n represents 7 to 12.)
Si / Al is about 8.3-15.
The X-ray diffraction data includes the following values.
2θ = 6.56 ± 0.10, 6.88 ± 0.10, 8.16 ± 0.10, 8.80 ± 0.10, 9.70 ± 0.10, 19.50 ± 0.10 21.76 ± 0.10, 22.56 ± 0.10, 23.10 ± 0.10

This aluminosilicate MCM-68 can be manufactured as follows.
1. As a template for making MCM-68 (structure directing agent: SDA), N, N in 3 steps from bicyclo [2.2.2] oct-7-ene-2,3: 5,6-tetracarboxylic dianhydride , N ′, N′-Tetraethylbicyclo [2.2.2] oct-7-ene-2,3: 5,6-dipyrrolidinium diiodide is synthesized.
2. The gel obtained by mixing the iodide, colloidal silica, potassium hydroxide, aluminum hydroxide, and water is heated at 160 ° C. for 16 days in an autoclave.
3. The crystals (as-synthesized sample) obtained by filtration are fired at 600 ° C. for 5 hours.

(2) De-Al treatment (acid treatment) stage In this stage, the aluminosilicate MCM-68 is treated with an acid so that the Si / Al (molar ratio) is 20 to 150, preferably 30 to 80.
The acid treatment is performed under the following conditions.
Examples of the acid include nitric acid, hydrochloric acid, and sulfuric acid. The acid is preferably used in an aqueous solution of about 1-6M.
In this aqueous solution, the aluminosilicate MCM-68 is usually heated at about 80 to 100 ° C. for about 24 hours or longer, preferably about 24 to 36 hours.
In order to set Si / Al (molar ratio) to a desired value, knowledge is obtained in advance about the degree of dealumination (Si / Al molar ratio) with respect to conditions such as acid type, concentration, treatment time, and temperature. Control by managing conditions.
The aluminosilicate thus obtained is also referred to as deAl-MCM-68.

The deAl-MCM-68 obtained at this stage is represented by the following composition formula.
H _4n-3m Al _m Si _112-n O ₂₂₄
(In the formula, m represents 0 to 0.74, and n represents 7 to 12.)
The X-ray diffraction data includes the following values.
2θ = 6.56 ± 0.10, 6.86 ± 0.10, 8.16 ± 0.10, 8.80 ± 0.10, 9.68 ± 0.10, 19.48 ± 0.10 21.76 ± 0.10, 22.66 ± 0.10, 23.18 ± 0.10

The catalytic cracking of industrial paraffin is usually carried out as follows.
A catalyst layer (0.1 g to 10 kg) held in a reaction tube (inner diameter 4 mm to 400 mm, length 100 mm to 10 m) is heated to 400 to 600 ° C., and paraffin or naphtha is circulated in the gas phase together with an inert gas. The contact time (W / F) during the catalytic reaction is usually adjusted to be in the range of ^{1 to} 100 g-catalyst h (mol) ⁻¹ .

The following examples illustrate the invention but are not intended to limit the invention.
In this example, Si / Ti and Si / Al were determined by a calibration curve method (aqueous solution mode) using an inductively coupled plasma atomic emission spectrometer (ICP-8000E manufactured by Shimadzu Corporation).

Example 1
(1) Synthesis of aluminosilicate Prior to the synthesis of aluminosilicate, N, N, N ', N'-tetraethylbicyclo [structure-directing agent (SDA) for crystallization of Al-MCM-68 2.2.2] oct-7-ene-2,3: 5,6-dipyrrolidinium diiodide (TEBOP ²⁺ (I ⁻ ) ₂ ) was prepared according to a previous report (Patent Document 2).
Next, hydrothermal synthesis of Al-MCM-68 was performed using this SDA. Specifically, first, colloidal silica (DuPont, LUDOX (registered trademark) HS-40, SiO ₂ : 40 wt%) is put into a container made of fluororesin (PFA) having an internal volume of 180 mL, 6.01 g (40 mmol, SiO ₂ ). Then, 312 mg (4.0 mmol) of Al (OH) ₃ (Pfaltz & Bauer) was dissolved and stirred for 10 minutes. Then KOH (8mol / L, 6.047mmol / g) a (Wako) was added, and stirred for 30 min and finally the structure directing agent ^{SDA (TEBOP 2+ (I -)} 2) 2.23 g (4.0 mmol) was added 3 hours Stir. The gel composition ratio was SiO ₂ −0.1 TEBOP ²⁺ (I ⁻ ) ₂ −0.375 KOH-0.1 Al (OH) ₃ -30 H ₂ O. The prepared gel was transferred to a 125 mL autoclave and left in an oven at 160 ° C. for 16 days. The obtained product was centrifuged and then dried in an oven at 80 ° C. to obtain 2.55 g of white powder (Al-MCM-68 (as-synthesized)).

(2) Preparation of aluminosilicate catalyst The obtained Al-MCM-68 was calcined in a muffle furnace at 600 ° C. for 10 hours to remove SDA contained in the aluminosilicate. At this time, the heating rate was set to 1 to 2 ° C./min. The solid sample after firing was confirmed to retain the MSE structure by powder X-ray diffraction.
Al-MCM-68 after firing was appropriately dealuminated by nitric acid treatment. Specifically, 45 mL of 0.5-2.0 M nitric acid aqueous solution was put into a 100-mL eggplant flask, and 1.5 g of baked Al-MCM-68 was added thereto, followed by stirring for 2 hours in an air atmosphere and under reflux conditions. . After the nitric acid treatment, filtration and washing with distilled water were performed, and then the collected solid was dried at 100 ° C. overnight. It was confirmed that the solid sample after the nitric acid treatment also retained the MSE structure by powder X-ray diffraction. Nitrogen treatment yielded moderately dealuminated Al-MCM-68 (deAl-MCM-68, Si / Al ratio = 51, 74 and 156).

For comparison, Al-MCM-68 without dealumination was also prepared. Ammonium ion exchange was performed to remove K cations present at the ion exchange site of Al-MCM-68 after firing. Specifically, after dissolving 3.0 g of ammonium nitrate (NH ₄ NO ₃ ) in 75 g of distilled water in a 250 mL-PP bottle, add 1.5 g of baked Al-MCM-68 and heat at 80 ° C for 24 hours. did. After heating, the solid sample was collected by filtration. After the ion exchange and filtration operations were repeated three times, the solid sample was dried to obtain ammonium-type Al-MCM-68. Thereafter, baking was performed at 550 ° C. for 6 hours in a muffle furnace to obtain proton type Al-MCM-68. It was confirmed that the solid sample after ion exchange and firing also retained the MSE structure by powder X-ray diffraction. The Si / Al ratio of proton-type Al-MCM-68 is 13, which is almost unchanged from the Si / Al ratio of 12 of the original Al-MCM-68, and it is considered that dealumination has hardly occurred. .

(3) Catalytic reactor Prior to the catalytic reaction, powdered aluminosilicate was molded and sized. Specifically, 1 to 2 g of aluminosilicate powder was packed in a tablet molding machine with an inner diameter of 20 mm, and then press molded at 0.4 MPa with a hydraulic press to obtain pellets with a diameter of 20 mm. The pellets were appropriately pulverized on a sieve and sized to 500 to 600 μm and used as a catalyst.
The catalytic reaction in this example was performed using a fixed bed normal pressure flow reactor. A schematic diagram of the apparatus is shown in FIG. Hexane as a reactant was supplied from a syringe using a syringe pump and introduced into a methane (5%)-helium mixed gas as a carrier gas. Hexane supplied from the syringe pump was evaporated into gas because it was introduced into the preheated vaporization chamber, and this gas was accompanied by the carrier gas. A stainless steel pipe with an inner diameter of 2 mm was used for the gas line of the reactor, and the condensation of vaporized hexane was prevented by heating from the outside to an appropriate temperature with a heater.
The reaction tube used was a quartz tube having an inner diameter of 8 mm, packed with 100 mg of the aluminosilicate catalyst previously sized, and the catalyst layer was held in the center of the reaction tube with quartz wool. As a pretreatment for the reaction, the temperature was raised to 650 ° C. at a rate of temperature increase of about 7 ° C./min under air flow, and kept in this atmosphere for 1 hour. Then, after switching to helium circulation, the reaction tube temperature was lowered to 450 ° C. at 5 ° C./min. After confirming that it was stable at 450 ° C., a methane-helium mixed gas accompanied by hexane was supplied to the catalyst layer to start the catalytic reaction. By switching the hexagonal valve at a predetermined time during the reaction, the reaction products accumulated in the sampling loop are introduced into the gas chromatograph, separated by a capillary column, and each product / unreacted product is detected by a hydrogen flame detector (FID). The reaction product was qualitatively and quantitatively determined. After a predetermined time (70 minutes), the supply of hexane to the catalyst layer was stopped and the helium flow was switched to. Thereafter, when the temperature was stabilized by heating to 500 ° C. at 1 to 2 ° C./min, hexane was supplied again to carry out the catalytic reaction. The same operation was continued at 550 and 600 ° C. The W / F during the catalytic reaction was 12.1 g-catalyst h (mol-hexane) ^-1 at any reaction temperature. After stopping the catalytic reaction at 600 ° C., it was allowed to cool naturally under helium flow.

(4) Results Table 2 shows the results of hexane cracking with each aluminosilicate catalyst. The selectivity for each product was determined on a carbon basis (in terms of carbon atoms). The propylene yield (C ₃ = yield) was determined by the conversion rate × selectivity to propylene (C ₃ =). The numbers in parentheses in the aluminosilicate notation represent the Si / Al ratio (atomic ratio).
In addition, reaction temperature is measured between the heater installed so that the quartz reaction tube of a fixed bed normal pressure flow reaction apparatus may be heated from the outside, and the reaction tube.

From Table 2, the conversion rate decreases as the Si / Al ratio increases, and in particular, deAl-MCM-68 (156) is lower than deAl-MCM-68 (51).
Also, if the Si / Al ratio is low (13), the selectivity to propylene (C ₃ =) is low. In Al-MCM-68 (13) that was not dealuminated, a significant decrease in activity occurred, and at a reaction temperature of 600 ° C., it was below the cracking activity at a lower reaction temperature. deAl-MCM-68 (51) showed high propylene selectivity regardless of the reaction temperature, and no significant deactivation occurred. Specifically, with deAl-MCM-68 (51), propylene selectivity exceeding 45% was obtained over a wide range from 450 ° C to 600 ° C and after 65 minutes from the start of the reaction.
When the reaction temperature is 600 ° C. and the Si / Al ratio is 50 to 80, the propylene yield is 30% or more, which is preferable for producing a light olefin (alkene) containing a large amount of propylene by catalytic cracking of paraffin. I can say that.

deAl-MCM-68(51)及びdeAl-MCM-68(156)は、温度によらず、クラッキング活性はほとんど低下せず、炭素析出量も非常に少なかった。しかし、Al-MCM-68(13)の炭素析出量は非常に多いことから、Ｓｉ／Ａｌ比が２０未満では激しい炭素析出が起こり、触媒としては好ましくないといえる。 Next, the carbon deposition amount of the aluminosilicate catalyst recovered after the reaction was determined.
Using the catalyst, the reaction temperature was set to 450 ° C., 500 ° C., 550 ° C., and 600 ° C. for 70 minutes in this order, followed by cooling in a helium stream, and then the catalyst was recovered at room temperature. The recovered catalyst was measured for the weight loss value with a differential thermal and thermogravimetric analyzer (TG-DTA). Of the weight loss values, the weight loss up to 150-800 ° C. was considered as the carbon deposited on the catalyst burned, and the amount of precipitated carbon was estimated by weight (WA). On the other hand, the catalyst which is an inorganic substance is considered that oxidation and combustion do not occur at all during this measurement, and the catalyst itself is obtained by subtracting the weight (WC) reduced to 800 ° C. from the sample weight (WB) before the measurement. It was estimated as the derived weight (WD (= WB-WC)). The amount of carbon deposition was calculated as a percentage by (WA / WD). It is thought that when carbon deposition occurs, the activity is reduced. The results are shown in Table 3.

In deAl-MCM-68 (51) and deAl-MCM-68 (156), the cracking activity was hardly lowered and the amount of carbon deposited was very small regardless of the temperature. However, since the carbon deposition amount of Al-MCM-68 (13) is very large, if the Si / Al ratio is less than 20, severe carbon deposition occurs, which is not preferable as a catalyst.

Claims (9)

A method for producing a light olefin comprising catalytic cracking of a paraffin raw material, wherein aluminosilicate MCM-68 having a Si / Al ratio of 20 to 150 is used as a catalyst. The method according to claim 1, wherein the Si / Al ratio is 30-80. The process according to claim 1 or 2, wherein the reaction temperature is 450 to 600 ° C. The method according to any one of claims 1 to 3, wherein the paraffin raw material contains C5-C8 hydrocarbons. The method according to claim 4, wherein the paraffin raw material is naphtha. A catalyst for catalytic cracking of paraffin comprising aluminosilicate MCM-68 having a Si / Al ratio of 20 to 150. The catalyst according to claim 6, wherein the Si / Al ratio is 30-80. The step of producing an aluminosilicate MCM-68 having an Si / Al ratio of 8.3 to 15 by crystallization using an organic template, and dealumination of the aluminosilicate MCM-68 to obtain an Si / Al ratio of 20 to 150 A process for producing a catalyst for catalytic cracking of paraffin comprising the step of producing aluminosilicate MCM-68. The method according to claim 8, wherein an aluminosilicate MCM-68 having a Si / Al ratio of 30 to 80 is produced in the dealumination step.

Images