JPS638342A - Production of aromatic hydrocarbon from lower paraffinic hydrocarbon - Google Patents

Abstract

PURPOSE:To obtain an aromatic hydrocarbon in high selectivity, by treating a lower paraffinic hydrocarbon in the presence of a zinc silicate catalyst or a platinum-carrying zinc silicate catalyst in a specific temperature range. CONSTITUTION:A lower paraffinic hydrocarbon is treated in the presence of a zinc silicate catalyst or a zinc silicate catalyst carrying 0.25-1.5wt% platinum (molar ratio of Si/Zn is 20-400 in both the cases) at 300-700 deg.C to give an aromatic hydrocarbon. The zinc silicate catalyst is prepared by adding an aqueous solution containing metallic salt shown by the formula Zn(NO3)2.6H2O, a nitrogen-containing organic cation, an inorganic acid and an ion adjustor and an aqueous solution of silicate to an aqueous solution containing the ion adjustor, the nitrogen-containing cation, the inorganic acid and an alkali hydroxide in such a way that the pH is 9-11 to form gel, separating the gel form the mother liquor, grinding the gel mixture, combining the gel with the mother liquor and subjecting to hydrothermal synthesis.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a process for producing aromatic hydrocarbons from lower paraffinic hydrocarbons.

More particularly, the present invention relates to a process for converting lower paraffinic hydrocarbons having 5 or fewer carbon atoms, such as ethane, propane, butane, pentane, and mixtures thereof, into aromatic hydrocarbons.

Conventional technology ZSM-5 catalyst with shape selectivity function (Mopil Oil Co., Ltd.) A method for obtaining aromatic hydrocarbons with high selectivity from lower paraffin thread hydrocarbons using a platinum-supported catalyst with K dehydrogenation function has been reported. has been done.

Previously, the present applicant and the same applicant discovered that a platinum-supported gallium silicate catalyst exhibits excellent performance in the selective conversion of lower paraffins to aromatic hydrocarbons, and filed a patent application (Japanese Patent Application No. 60-218103).

However, since gallium is expensive, there is a need to develop a catalyst to replace it for practical use. Therefore, in the present invention, we focused on Zn, which showed excellent effects in the ion exchange type H-ZSM-5 catalyst, synthesized a Zn-silicate catalyst, and synthesized a zinc silicate catalyst (8i/Zn%
The present invention was achieved by discovering that a platinum-supported zinc silicate catalyst (Si/Zn molar ratio 20-400) exhibits excellent selectivity in the production of aromatic hydrocarbons from lower paraffinic hydrocarbons. did.

The conversion reaction from lower paraffinic hydrocarbons (C2-C5 hydrocarbons) to aromatic hydrocarbons, which the invention attempts to solve, is first carried out by lower paraffinic hydrocarbons (e.g. propane) using a dehydration catalyst (e.g. platinum).
is dehydrogenated to an olefinic hydrocarbon (for example, propene), and then propene molecules are polymerized at the acid site of the zinc silicate catalyst to form a polymeric olefin 11, and then aromatic hydrocarbons are produced. At this time, the main reaction products are limited to methane, ethane, and aromatic hydrocarbons, but it is necessary to suppress the production of hydrocarbons having 1 and 2 carbon atoms.

In addition, in the case of Zn-silicate, the conversion activity is low (kana), so in order to improve the conversion activity, platinum-supported Z
A propane conversion reaction is carried out using an n-silicate catalyst,
An effect of increasing activity was observed.

Means for Solving the Problems The present invention uses C2-C3 lower paraffinic hydrocarbons with the following composition (mol%): Si/Zn 20-4 0 0 0 H-/5in20.3-1.0 I-1, 0/5i0230-100 h+alkali metal 0.05-0.15Nacl/H2
Zinc silicate catalyst of the formula 00,01-0,06 (wherein R is a quaternary alkylammonium cation, alkali gold MU sodium or potassium) or zinc supported with 0.25 to 1.5% by weight of platinum. This invention relates to a process for producing aromatic hydrocarbons from lower paraffin thread hydrocarbons in the presence of a silicate catalyst at a reaction temperature of 300 to 700°C. Below Zn-
A silicate catalyst) and a platinum-supported zinc silicate catalyst (referred to as a Pt-supported Zn silicate catalyst) were produced as follows.

The following composition (mol%) Si/Zn 20-400 0H/5in20.3-1.0 H2i0230-100 NaCl + alkali metal 0.05-0.15 Nacl/H
Metal salt CZn (No. 200,010,06) having the composition represented by ,)2・
6H20], a nitrogen-containing organic cation (tetrapropylammonium bromide), an inorganic acid (H2S04), preferably an ion regulator (Nac)) as liquid A,
Silicate aqueous solution (water glass No. 3: 5i0228.9%
, Na209.3%) as liquid B, and an ion regulator (Na209.3%) as liquid B.
p) Preferably, an aqueous solution containing a nitrogen-containing organic cation, an inorganic acid, and an alkali hydroxide is used as liquid C, and the rate of addition of liquids A and B to liquid C is adjusted so that the pH becomes 9-11. After gel formation, the mother liquor was centrifuged, and the gel mixture was fragmented, and the gel and mother liquor were combined and subjected to hydrothermal synthesis under the following conditions.

Initially heated to 160°C while stirring in a hydrothermal table or autoclave.
The temperature was increased to 210'c in 90 minutes, then 210'c in 250 minutes.
The temperature was increased linearly at -2. The gel mixture obtained after hydrothermal synthesis was washed several times with distilled water, dried, and calcined at 540° C. for 3.5 hours to obtain Na-type Zn-silica.

Next, after calcination, 80℃ with IN・Nu4NOj aqueous solution,
The time immersion operation was performed several times to perform ion exchange treatment.

After further washing with distilled water several times, 520-540℃, 3.5
It was calcined in an air stream for an hour to form an H-type Zn-silicate.

The gel fragmentation step is the most important step in the above hydrothermal synthesis reaction.

(2) Pt-supported Zn silicate catalyst Zinc silicate catalyst prepared by the above method (Si/Zn-20-400
) was used as a carrier, and platinum was supported on it by an ion exchange method using tetraammine platinum salt [:Pt(N)(,)4c12') water at a predetermined concentration].

Platinum supported zinc silicate catalyst (8i/Zn 20-40
Regarding 0), when the amount of platinum supported is 0.25% by weight or less, the conversion rate is small, while when the amount of platinum supported is 1.5% by weight or more, the decomposition reaction becomes the main reaction, and the selectivity for aromatic hydrocarbons is small. Become. The preferred range is 0.5 to 1.0% (by weight).

Si/ of Zn-silicate measured by atomic absorption spectrometry
Table 1 shows the results of Zn ratio and S11AJ ratio.

Table 1: Si/Zn and Si/AJ molar ratio measured by atomic absorption spectrometry; charge ratio of Zn and S of synthesized H-type Zn-silicate
The i/Zn ratios were exactly the same. However, the water glass used as a raw material has latent AJ atoms, and its M atoms are also incorporated into the crystal lattice, but the kl amount, 8i/A
The L ratio was not constant, and no compatibility with the Si/Zn ratio was observed.

2) The BET surface area value of Zn-silicate is Si/Zn ratio 20.40.1
175.313,34 per gram of catalyst in the order of 00,400
It was 9,375i.

3) XRD measurement of Zn silicate The X-ray diffraction image of the synthesized Zn-silicate was published in Rigakuden 2g.
Geiger -f tex -2013K Ni-
Filtered Cuk a 11 with 2θ from f to 7
It was determined in the range of 0° (deg).

The first XRD diffraction image of the four synthesized Zn-silicates
Shown in the figure. Diffraction image of silicate containing Zn
M 5 O case ic 8.18, 10.1
9°16.36, 20.79, 24.29 and 2
A characteristic peak was observed at 4.64 (deg), and no diffraction image attributed to zinc oxide was observed.

This suggests that the Zn oxide is dispersed within the crystal in an extremely fine state, probably incorporated into the crystal lattice, and that the Zn-silicate has the pentasil-type pore structure of ZSM-5. it is conceivable that.

4) TP of Zn-silicate thermal decomposition behavior adsorbent
The D results are shown in Figure 2.

Atomic absorption analysis results in Table 1 and adsorbed sugar in Figure 2.

When comparing the TPD results with 8i/Zn ratio is 817A.
Catalysts with Si/Zn-100 and 400, which had a larger J ratio, i.e., those with more AJ than Zn, had a high temperature peak, whereas the Si/Zn ratio was smaller than 8i/) J ratio, 81/ 7Jn -20, 40, i.e.
~Myosu High temperature peaks were not observed in those containing a large amount of Zn, and only low temperature peaks were present. Also, the T of H-ZSM-5
In the PD measurement, a high temperature peak existed around 350°C, and this high temperature peak was due to strong solid acidic points originating from M.

From the above, M is important for generating acid sites in catalysts with a high Si/Zn ratio, but Zn is important in catalysts with a low Si/Zn ratio. In other words, the strength of the generated acid site (Zn) is M
It was found that the acid site is weaker than that of the acid site.

The properties of Zn-silicate are Ga-silicate and H
-It is thought that the properties are different from ZSM-5.

EXAMPLES Next, the present invention will be explained with reference to examples, but the present invention is not limited thereto.

Example 1 The catalyst prepared as described above (specific gravity: 0.905) was compressed into tablets, crushed into 10 to 20 meshes, and then the catalyst was
．． The reaction was carried out using a normal pressure flow reactor in which a reaction tube with an inner diameter of 8Wx was filled with No. 59. Propane2 as raw material gas
The reaction was carried out using 0 VOI%, 80 vO1% nitrogen, gas hourly space velocity (GH8V) 2000 hr-', and reaction temperature 300°C to 700°C at normal pressure.

The reaction products were analyzed by gas chromatography.

The columns used were MS-5ASvZ-10 and Oyohi Silicon 0VIOI.

The effect of Zn-containing Zn-silicate on propane conversion is shown in Tables 3 to 6 and FIG.

From Figure 3, the reaction temperature is 500℃, 550℃, 600℃,
The propane conversion rate increased as the temperature increased to 650°C.

Further, at each reaction temperature, as the Zn content increases, the conversion rate also increases once, but when the Zn content increases beyond a certain level, the conversion rate decreases inversely by VC.

FIG. 4 shows the influence of the Zn content of Zn silicate on the selectivity of the reaction product (reaction temperature: 600° C.).

From FIG. 4, the aromatic selectivity increased as the propylene selectivity decreased, and conversely, the propylene selectivity increased as the aromatic selectivity decreased, and a clear correlation was observed between the two.

Furthermore, as the Zn content increases to 0.26, 1.04, 2.53, and 4.88 (wt%), the amount of propylene produced also increases to 9.5, 13.1, 13.6, and 20.
2 (C-wt%), it is thought that aromatization occurs from propane to propylene in this reaction due to the dehydrogenation ability of Zn. However, the Zn content was 4.88 wt% (Si/Zn, 20)
At °C, more propylene was produced than the dehydrogenation ability of Zn, but less aromatics were produced.

In addition, in Si, /Zn-2Q, which has a high Zn content, the BET surface area is as small as 175 (m'/l), and when the Zn content increases, the process from propane to propylene is accelerated due to the dehydrogenation ability of Zn, but the catalyst The crystallinity of propylene deteriorates, making it difficult for the process of converting propylene to aromatics to progress], and the conversion rate is thought to decrease.

From Figure 3, as the reaction temperature increases, less Zn
It can be seen that a high conversion rate can be obtained depending on the content. This is consistent with the fact that the process of producing propylene from propane is an endothermic reaction.

From Figures 3 and 4, in this reaction, Zn content, catalyst crystal form, and reaction temperature are important factors for conversion rate and selectivity.
% (Si/Zn -60) is the optimum condition, the conversion rate is 8zO
%, aromatic selectivity was 50.9%, indicating a high aromatization ability.

Table 4 Catalyst Si/Zn -40 [Fees C, H, -20%/N2. SV -2000h-
'Table 5 Catalyst 8i/Zn-100 Example 2 Pt (q FfZn silicate catalyst (5
Example 1 was carried out in the same manner as in Example 1, except that IAn molar ratio 20-400) was used.

As a catalyst, a Q, 5 wt %, Pt supported Zn silicate catalyst (Si/Zn-40, 100) was used.

The resulting Pt-supported H-ZMS-5 catalyst, Pt-supported Ga
- Comparison with the case of silicate catalyst is shown in Table 2.

Furthermore, the conversion rate, aromatic yield, and aromatic selectivity are shown in Tables 7 and 8.

Zn silicate catalyst (8i/Zn-40, reaction temperature 6
00°C), the conversion rate was 64.2% and the aromatic yield was 28.
0%, aromatic selectivity 43.5%; Ga silicate catalyst (
Si/Ga -40, reaction temperature 600°C) conversion rate 25.9%, aromatic yield 9.8%, aromatic selectivity 37.
It was 9%.

From the above results, it was found that the Zn silicate catalyst is an effective catalyst for aromatizing lower paraffinic hydrocarbons (propane).

However, as shown in Table 2, the H-ZSM-5 catalyst supporting Q and 5 wt% pt shows a high conversion rate of 91.8% at 500°C, whereas the conversion activity of the Zn-silicate catalyst is low. Therefore, a conversion reaction was carried out using a Zn-silicate catalyst of Si/Zn 100 and a 0.5 wt % Pt-supported silicate catalyst. The results are shown in FIG.

The reaction conditions were C, H, 20% (volume), N2 80% (volume), and SV-2000h-'.

From Figure 5, in the case of Pt-supported Zn silicate catalyst, Zn
-Reaction temperature 400-650℃ compared to silicate catalyst
The conversion rate (propane) increased, and the effect of supporting PT was clearly observed.

When the reaction temperature was 550°C, the Pt-supporting effect was large and the conversion rate increased from 26.8% to 51.6%.

0, '5 wt% Pt supported Zn-silicate catalyst (Si
Figure 6 shows the changes over time in the propane conversion rate and the selectivity of the produced hydrocarbons at 600°C using Zn100).

From FIG. 6, it was found that the decrease in propane conversion was smaller than the decrease in selectivity.

The pt-supported Ga-silicate catalyst (Si/
Ga-21) shows higher aromatic ability than the Pt-supported Zn-silicate catalyst, but the catalytic activity significantly deteriorates over time, with initial activity of 80.0% and 54.0% after 25 hours. ing.

On the other hand, the initial activity of the pt-supported Zn silicate catalyst was 866.
The conversion activity remained high at 70.0% after 26 hours, indicating that the Pt-supported Zn-silicate catalyst had a longer catalyst life than the Pt-supported Ga-silicate catalyst.

In addition, catalyst regeneration is performed using oxygen gas (5,07%02/I-
■e, flow rate 35.6 m 17 minutes), 550°C,
It was easily accomplished by baking for about 2 hours. The amount of coke precipitated was also small. This is the P supported during coke firing.
This is thought to be due to the fact that t acts as a combustion catalyst and the reaction temperature can be lowered due to the Pt supporting effect, resulting in a decrease in the amount of coke deposited.

Effects of the Invention (1) The Zn-silicate catalyst has a superior ability to aromatize lower paraffin hydrocarbons than the Ga-silicate catalyst and the H-Z SM-5 catalyst.

(2) The Pt-supported Zn silicate catalyst had better conversion rate, aromatic yield, and aromatic selectivity than the Zn silicate catalyst, and the pt-supporting effect was observed.

Table 7 Catalyst 0.5 wt % Pt/(S i/ Z
n -40) m8 table flAIjA 0.5wt%Pt
/(Si/Zn-1on)

[Brief explanation of the drawing]

Figure 1 is an X-ray diffraction graph of various catalysts. Figure 2 is a graph showing the thermal decomposition behavior of a Zn-silicate catalyst. Figure 3 is a graph showing the Zn content (w) of a Zn-silicate catalyst.
Graph showing the relationship between propane conversion rate (%) and propane conversion rate (%): Figure 4 shows the relationship between Zn content (w
t%) and reaction product selectivity (wt%): Figure 5 is a graph showing the relationship between reaction temperature (°C) and propane conversion rate (support) in a PT-supported Zn-silicate catalyst. : FIG. 6 is a graph showing the relationship between elapsed time (hr) and propane conversion rate in a Pt-supported Zn-silicate catalyst. Agent Masao Miyake (and 1 other person) Section I 2θ (deq,) Figure 2 Temperature (0C) Selectivity (wt%) Propane conversion rate (0 mm) Propane conversion rate (%) Selectivity (wt) %) Propane conversion rate ('/,)

Claims (1)

[Claims] Lower paraffinic hydrocarbons are treated with zinc silicate catalyst (S
i/Zn molar ratio 20-400) or 0.25 to 1
．． 5 wt% platinum supported zinc silicate catalyst (Si/Zn
A process for producing aromatic hydrocarbons from lower paraffinic hydrocarbons, characterized in that the process is carried out at a reaction temperature of 300°C to 700°C in the presence of a molar ratio of 20-400).