CN107715876B - A kind of preparation method and application of catalyst for removing trace amount of phenylacetylene in styrene - Google Patents

Abstract

The invention discloses a preparation method and application of a catalyst for removing trace phenylacetylene in styrene, and belongs to the technical field of material preparation technology and industrial catalysis. It mainly solves the limitations of the hydrogenation operation mode in the previous technology, as well as the problems of high equipment investment and high energy consumption. The catalyst uses zinc-titanium hydrotalcite as the carrier, and adopts the method of photoreduction to support one or several precious metals as active metals. , This method is simple, has few operation steps, does not need high temperature treatment, does not need reaction pretreatment, and the catalyst active phase is uniformly dispersed. On this type of catalyst, the trace amount of phenylacetylene in styrene can be efficiently removed under normal pressure and low temperature, which can effectively prevent excessive hydrogenation to generate ethylbenzene, reduce the loss rate of styrene, and the catalyst has good reusability and stability. . The reaction can be carried out in a batch or semi-batch reactor with simple equipment, normal pressure operation, safety and low cost.

Description

A kind of preparation method and application of catalyst for removing trace amount of phenylacetylene in styrene

technical field

The invention belongs to the technical fields of material preparation and industrial catalysis, and relates to a preparation method and application of a catalyst for removing trace phenylacetylene in styrene.

Background technique

In industry, styrene is an important monomer for synthetic resins, ion exchange resins and synthetic rubbers. Phenylacetylene, the content is about 150-7000ppm. Because the properties of phenylacetylene and styrene are similar, they cannot be effectively separated by extractive distillation. In addition, the presence of phenylacetylene poisons the catalyst for styrene polymerization and reduces the performance of styrene polymers. Therefore, it is particularly important to effectively remove trace amounts of phenylacetylene in styrene. important.

At present, selective hydrogenation is an effective way to remove phenylacetylene. However, excessive hydrogenation of phenylacetylene and further hydrogenation of styrene lead to a great increase in the loss rate of styrene. Therefore, it is a technical difficulty to control the selectivity and reduce the loss of styrene. . Patent CN102886267 discloses a catalyst for the selective hydrogenation of phenylacetylene in styrene. The phenylacetylene in the C8 fraction on the catalyst can be completely hydrogenated, and the loss of styrene can also be minimized. However, the catalyst composition is complex and requires pretreatment. , In addition, the use of fixed bed continuous operation requires high-pressure operation and large equipment investment. Patent CN102649663 discloses a method for the selective hydrogenation of phenylacetylene in the presence of styrene, which also adopts fixed-bed continuous operation, with high reaction pressure and high equipment cost, and the product still contains a trace amount of phenylacetylene, and the conversion efficiency is low. Patent CN1852877A discloses a method for reducing phenylacetylene impurities in the presence of styrene monomer. The patented technology has high reaction temperature, low hydrogenation efficiency of phenylacetylene (about 70%), high styrene loss rate, and catalyst life. short question. Patent CN1087892A discloses a method and equipment for purifying phenylacetylene monomer in styrene stream by using hydrogenation method. The phenylacetylene impurity is hydrogenated to styrene by means of a multistage catalytic bed reactor, but the catalyst has a short service life, and the equipment Investment is high. Patent CN101475437A discloses a method for removing phenylacetylene in the presence of styrene. The patented technology adopts a two-stage hydrogenation method for removing acetylene. Although the selectivity of the catalyst can be greatly improved, the two-stage hydrogenation undoubtedly increases the complexity of the process. And the hydrogenation of phenylacetylene is still incomplete.

It is not difficult to see that the existing technologies are mostly limited to the continuous operation of the fixed bed and require a certain pressure, so the equipment cost is high, and some technologies have the problem of low conversion efficiency. Compared with continuous operation, batch or semi-batch operation has simple equipment, low cost, and easy operation. However, due to the problem of back-mixing, the product quality is unstable, especially in series reactions. To solve this problem, the catalyst must have long-term product stability, that is, the reaction reaches equilibrium, and the product selectivity does not change with time, so the design of the catalyst is very demanding. Although patent CN103785858A discloses a preparation method of amorphous nanometer rhodium-palladium alloy and its catalytic application, the intermittent operation mode can control the selective reduction of phenylacetylene to generate styrene, but the selectivity of styrene is not high, and does not consider Long-term styrene selectivity. Similarly, the Pd-Au bimetallic catalyst (Phys.Chem.Chem.Phys., 2017, 19, 6164-6168) showed better selectivity than the Pd catalyst, but with the prolongation of time, the selectivity of styrene decreased significantly, The long-term stability is not good, and it is not suitable for intermittent or semi-batch operation in the industry, which will inevitably lead to the problem of poor product stability.

SUMMARY OF THE INVENTION

The object of the present invention is to overcome the above-mentioned problems existing in the prior art, provide a kind of catalyst that efficiently removes trace phenylacetylene in styrene, adopts intermittent or semi-batch operation, realizes the complete removal of phenylacetylene at normal pressure, and controls the amount of styrene amount of loss.

Technical scheme of the present invention:

A preparation method for removing the catalyst of trace phenylacetylene in styrene, comprises the following steps:

(1) Select a certain amount of metal zinc salt and titanium salt as precursors, and synthesize a zinc-titanium hydrotalcite carrier by a co-precipitation-hydrothermal method; wherein, the hydrothermal temperature is 120-200°C; the hydrothermal time is 12-72h ;

(2) after the carrier after drying is mixed with a certain amount of precious metal salt solution, adopt the method of photoreduction to synthesize catalyst, obtain the precious metal catalyst of final load after drying; Wherein, the intensity of light source is 5-200mW/cm ^-2 ; The photoreduction time is 10-60min.

The synthesized catalyst is used for the reaction of removing trace phenylacetylene in styrene, and the batch or semi-batch operation mode is adopted.

The precursor zinc salt and titanium salt in the above-mentioned steps (1) are metal nitrate, metal chloride, or metal sulfate; the zinc and titanium molar ratio used is 1-5:1; the precipitating agent is urea, and the hydroxide Sodium, one or more of sodium carbonate; the precious metal salt solution in step (2) is chloride salt or nitrate aqueous solution; the precious metal loading amount is 0.1wt%-2wt%. The precious metal is one or both of Pd and Au.

The invention also provides an application of the catalyst prepared by the above method, which is used for the reaction of removing trace phenylacetylene in styrene; the reaction adopts batch or semi-batch operation and normal pressure reaction; the reaction conditions are: substrate styrene The molar content of phenylacetylene is 0.1%-10%; the molar ratio of noble metal and substrate (mixture of phenylacetylene and styrene) in the supported catalyst is 1:2000-1:8000; the reaction temperature is 20-80°C; the reaction Time 5-240min.

The advantages and beneficial effects of the present invention are:

The catalyst preparation process is simple, the catalyst does not require high temperature treatment, and does not require pre-reaction treatment; it can completely remove phenylacetylene, which breaks the limitation of continuous operation, and adopts intermittent or semi-batch operation, and the equipment cost is low; in addition, the catalyst can control the selection of styrene for a long time. It can greatly reduce the impact caused by backmixing in batch or semi-batch, and is suitable for industrial applications.

Description of drawings

FIG. 1 is the XRD patterns of the catalysts obtained in Examples 1, 3 and 4. FIG.

Detailed ways

Example 1

(1) The amount of zinc salt was adjusted to prepare catalysts with different molar ratios of zinc to titanium. Dissolve 0.6g, or 1.2g, or 3.0g of Zn(NO ₃ ) ₂ ·6H ₂ O, 220 μL of TiCl ₄ and 3.0 g of urea in 100 mL of deionized water, transfer it into a hydrothermal kettle, hydrothermally treat it at 130°C for 48 hours, wash and dry Then, hydrotalcite supports with different Zn/Ti molar ratios were obtained.

(2) Take 0.1 g of hydrotalcite carrier and 8 mL of deionized water, add 82 μL (56.4 mM) PdCl ₂ solution and 479 μL (9.17 mM) chloroauric acid solution, stir evenly, photoreduce for 30 min, and the light intensity is 100 mW/cm ^-2 , washed and dried to obtain the supported precious metal catalyst, and the precious metal loading amount was 1.4 wt%, as shown in Table 1.

Table 1

Example 2

Step (1) is the same as in Example 1.

(2) Take 0.1 g of hydrotalcite carrier, 8 mL of deionized water, add 165 μL (56.4 mM) PdCl solution, stir evenly, photoreduce for 30 min, light intensity is 100 mW/cm ^-2 , wash and dry to obtain Pd/ZnTi ( ₂ ) catalyst with a precious metal loading of 1 wt%.

Example 3

(1) Change the zinc salt precursor, take 0.54g ZnCl ₂ or 0.64g ZnSO ₄ as the zinc salt precursor, and the remaining steps are the same as those in Example 1.

Step (2) is with embodiment 1, and the catalyst of preparation is shown in Table 2.

Table 2

Example 4

(1) Dissolve 1.2 g Zn(NO ₃ ) ₂ ·6H ₂ O, 220 μL TiCl ₄ and 3.0 g urea in 100 mL deionized water, transfer them into a hydrothermal kettle, and investigate the effects of different hydrothermal temperatures and times on the hydrotalcite carrier.

Step (2) is the same as in Example 1, and the prepared catalyst is shown in Table 3.

table 3

Example 5

Step (1) is the same as in Example 1.

(2) Take 0.1 g of hydrotalcite carrier and 8 mL of deionized water, add 82 μL (56.4 mM) PdCl ₂ solution and 479 μL (9.17 mM) chloroauric acid solution, stir evenly, and investigate the effect of photoreduction treatment time and light intensity on the supported precious metal catalyst. The prepared catalysts are shown in Table 4.

Table 4

Example 6

Step (1) is the same as in Example 1, wherein the precipitating agent urea is replaced with sodium hydroxide or sodium carbonate, and the influence of the precipitating agent is investigated.

Step (2) is the same as in Example 1, and the prepared catalyst is shown in Table 5.

table 5

Example 7

Step (1) is the same as in Example 1.

( ₂ ) get hydrotalcite carrier 0.1g, deionized water 8mL, add a certain amount of PdCl solution and auric acid solution, Pd/Au mol ratio is 1, investigate the influence of precious metal loading, and all the other steps are with embodiment 1, The prepared catalysts are shown in Table 6.

Table 6

Example 8

Step (1) is the same as in Example 1.

( ₂ ) get hydrotalcite carrier 0.1g, deionized water 8mL, add a certain amount of PdCl solution and chloroauric acid solution, adjust the Pd/Au mol ratio, the remaining steps are the same as in Example 1, and the prepared catalyst is shown in Table 7.

Table 7

Embodiment 9, application

Dissolve 0.03 mmol of phenylacetylene and 2.97 mmol of styrene in 10 mL of ethanol, the molar content of phenylacetylene in styrene is 1%, and the molar ratio of precious metal to substrate is 1:6500, add different catalysts prepared, and react under hydrogen atmosphere The temperature was 70 °C, and the influence of different catalysts on the reaction was investigated. The results are shown in Table 8-1 and Table 8-2.

Table 8-1

Table 8-2

Embodiment 10. Application

Dissolve 0.03 mmol phenylacetylene and 2.97 mmol styrene in 10 mL of ethanol, the molar content of phenylacetylene in styrene is 1%, add Pd5-Au5/ZnTi(2) catalyst, adjust the molar ratio of noble metal to substrate, hydrogen The reaction temperature under the atmosphere was 70°C, and the results are shown in Table 9.

Table 9

Embodiment 11. Application

Dissolve 0.3 mmol of phenylacetylene and 2.7 mmol of styrene in 10 mL of ethanol, the molar content of phenylacetylene in styrene is 10%, add Pd5-Au5/ZnTi(2) catalyst, and the molar ratio of noble metal to substrate is 1:6500 , under a hydrogen atmosphere, the reaction temperature is 70 ℃, the reaction time is 10min, the phenylacetylene is completely converted, and the styrene loss rate is 0.1%;

Embodiment 12. Application

Dissolve 0.03 mmol of phenylacetylene and 2.97 mmol of styrene in 10 mL of ethanol, the molar content of phenylacetylene in styrene is 1%, the molar ratio of noble metal to substrate is 1:6500, Pd5-Au5/ZnTi(2) catalyst, The reaction was carried out under a hydrogen atmosphere, and the influence of the reaction temperature was investigated. The reaction results are shown in Table 10.

Table 10

Embodiment 13. Application

Dissolve 0.3 mmol of phenylacetylene and 2.7 mmol of styrene in 10 mL of ethanol, the molar content of phenylacetylene in styrene is 10%, add the Pd5-Au5/ZnTi(2) catalyst after 5 cycles, the moles of noble metal and substrate The ratio is 1:6500, the reaction temperature is 70°C under a hydrogen atmosphere, and the reaction time is 10 minutes. The phenylacetylene is completely converted, and the styrene loss rate is 0.1%;

Claims (3)

1. A preparation method of a catalyst for removing trace phenylacetylene in styrene is characterized by comprising the following steps:

(1) synthesizing a zinc-titanium hydrotalcite carrier by taking a metal zinc salt and a titanium salt as precursors by adopting a coprecipitation-hydrothermal method; the precursor zinc salt and titanium salt are metal nitrate, metal chloride or metal sulfate; the molar ratio of the zinc to the titanium is 1-5: 1; the precipitator is urea;

(2) mixing the dried carrier and the noble metal salt solution, synthesizing a catalyst by adopting a photoreduction method, and drying to obtain a final supported noble metal catalyst; the noble metal salt solution is a chloride or nitrate aqueous solution; the noble metal is Pd and Au which are used simultaneously, and the molar ratio of the Pd to the Au is 1: 1; the noble metal loading amount is 0.1-2 wt%; the light source intensity is 100-200 mW/cm^-2。

2. The method for preparing a catalyst for removing trace phenylacetylene in styrene according to claim 1, wherein: the hydrothermal temperature in the step (1) is 120-200 ℃; the hydrothermal time is 12-72 h; the photoreduction time is 10-60 min.

3. Use of a catalyst prepared by the process of claim 1, wherein: the reaction is used for removing trace phenylacetylene in styrene; the reaction adopts intermittent or semi-intermittent operation and normal pressure reaction; wherein, the molar content of phenylacetylene in the substrate styrene is 0.1-10%; the molar ratio of the noble metal in the supported catalyst to the substrate, namely the mixture of phenylacetylene and styrene, is 1:2000-1: 8000; the reaction temperature is 20-80 ℃; the reaction time is 5-240 min.

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