CN107715876B

CN107715876B - Preparation method and application of catalyst for removing trace phenylacetylene in styrene

Info

Publication number: CN107715876B
Application number: CN201711018765.8A
Authority: CN
Inventors: 肖子辉; 安翠华; 殷康娟; 丁轶
Original assignee: Tianjin University of Technology
Current assignee: Xiao Zihui; Tianjin University of Technology
Priority date: 2017-10-27
Filing date: 2017-10-27
Publication date: 2020-06-09
Anticipated expiration: 2037-10-27
Also published as: CN107715876A

Abstract

The invention discloses a preparation method and application of a catalyst for removing trace phenylacetylene in styrene, belonging to the technical field of material preparation and industrial catalysis. The catalyst mainly solves the problems of limitation of a hydrogenation operation mode and high equipment investment and energy consumption in the prior art, the catalyst takes zinc-titanium hydrotalcite as a carrier, one or more noble metals are loaded as active metals by adopting a photoreduction method, the method is simple, the operation steps are few, high-temperature treatment and pre-reaction treatment are not needed, and the active phase of the catalyst is uniformly dispersed. On the catalyst, trace phenylacetylene in styrene can be efficiently removed at normal pressure and low temperature, the ethylbenzene can be effectively prevented from being generated by excessive hydrogenation, the loss rate of the styrene is reduced, and the catalyst has good reusability and stability. The reaction can be carried out in a batch or semi-batch reactor, and the equipment is simple, the operation is carried out under normal pressure, and the method is safe and low in cost.

Description

Preparation method and application of catalyst for removing trace phenylacetylene in styrene

Technical Field

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

Background

Industrially, styrene is an important monomer of synthetic resin, ion exchange resin, synthetic rubber and the like, and is mainly obtained by ethylbenzene dehydrogenation and extraction from ethylene byproduct carbon eight fraction, but the obtained styrene contains trace phenylacetylene and has the content of about 150-7000 ppm. Because the properties of phenylacetylene and styrene are similar, the phenylacetylene and the styrene can not be effectively separated through extractive distillation, and in addition, the existence of the phenylacetylene poisons a catalyst for styrene polymerization, so that the performance of a styrene polymer is reduced, and the effective removal of trace phenylacetylene in the styrene is particularly important.

At present, selective hydrogenation is an effective way for removing phenylacetylene, however, excessive hydrogenation of phenylacetylene and further hydrogenation of styrene lead to a great increase in the loss rate of styrene, so that the control of selectivity and the reduction of styrene loss are technical difficulties. Patent CN102886267 discloses a catalyst for selectively hydrogenating phenylacetylene in styrene, which can realize complete hydrogenation of phenylacetylene in C8 fraction on the catalyst, and the loss of styrene can also be minimized, but the catalyst component is complex, and needs pretreatment, and in addition, a fixed bed continuous operation, high pressure operation and large equipment investment are adopted. Patent CN102649663 discloses a method for selectively hydrogenating phenylacetylene in the presence of styrene, which also adopts fixed bed continuous operation, and has high reaction pressure, high equipment cost, and low conversion efficiency because the product still contains trace phenylacetylene. Patent CN1852877A discloses a method for reducing phenylacetylene impurities in the presence of styrene monomer, which has the problems of high reaction temperature, low phenylacetylene hydrogenation efficiency (about 70%), high styrene loss rate and short catalyst life. Patent CN1087892A discloses a method and apparatus for purifying phenylacetylene monomer in styrene stream by hydrogenation, which uses a multi-stage catalytic bed reactor to hydrogenate phenylacetylene impurity into styrene, but the catalyst has short service life and high equipment investment. Patent CN101475437A discloses a method for removing phenylacetylene in the presence of styrene, which adopts a two-stage hydrogenation method for removing acetylene, and although the selectivity of the catalyst can be greatly improved, the two-stage hydrogenation will undoubtedly increase the complexity of the process, and the phenylacetylene hydrogenation is still incomplete.

It is obvious that the prior art is mostly limited to the continuous operation of the fixed bed, and a certain pressure is required, so the equipment cost is high, and part of the technology has the problem of low conversion efficiency. Compared with continuous operation, batch operation or semi-batch operation, the method has the advantages of simple equipment, low cost and easy operation, but the product quality is unstable due to the back mixing problem, and particularly the continuous reaction is obvious. To solve this problem, it is necessary to have a catalyst with long-term product stability, i.e., the reaction reaches equilibrium, the selectivity of the product does not change with time, and thus the design requirement for the catalyst is high. Although patent CN103785858A discloses a preparation method of amorphous nano-rhodium-palladium alloy and its catalytic application, which can control the generation of styrene by selective reduction of phenylacetylene by intermittent operation, the selectivity of styrene is not high and the selectivity of styrene for a long time is not considered. Similarly, the Pd-Au bimetallic catalyst (Phys. chem. Phys.,2017,19,6164-6168) has better selectivity than the Pd catalyst, but the selectivity of styrene is obviously reduced along with the prolonging of time, the long-term stability is not good, the Pd-Au bimetallic catalyst is not suitable for batch or semi-batch operation in industry, and the problem of poor product stability is inevitably caused.

Disclosure of Invention

The invention aims to overcome the problems in the prior art, and provides a catalyst for efficiently removing trace phenylacetylene in styrene, which adopts intermittent or semi-intermittent operation to realize complete removal of phenylacetylene under normal pressure and control the loss of styrene.

The technical scheme of the invention is as follows:

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

(1) selecting a certain amount of metal zinc salt and titanium salt as precursors, and synthesizing a zinc-titanium hydrotalcite carrier by adopting a coprecipitation-hydrothermal method; wherein the hydrothermal temperature is 120-200 ℃; the hydrothermal time is 12-72 h;

(2) mixing the dried carrier with a certain amount of noble metal salt solution, synthesizing the catalyst by adopting a photoreduction method, and carrying out the steps ofDrying to obtain the final loaded noble metal catalyst; wherein the light source intensity is 5-200mW/cm^-2(ii) a The photoreduction time is 10-60 min.

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

The precursor zinc salt and titanium salt in the step (1) are metal nitrate, metal chloride or metal sulfate; the molar ratio of the zinc to the titanium is 1-5: 1; the precipitator is one or more of urea, sodium hydroxide and sodium carbonate; in the step (2), the noble metal salt solution is a chloride or nitrate aqueous solution; the noble metal loading is 0.1-2 wt%. The noble metal is one or two of Pd and Au.

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

The invention has the advantages and beneficial effects that:

the preparation process of the catalyst is simple, the catalyst does not need high-temperature treatment and reaction pretreatment; the phenylacetylene can be completely removed, the limit of continuous operation is broken, intermittent or semi-intermittent operation is adopted, and the equipment cost is low; in addition, the catalyst can control the selectivity of styrene for a long time, greatly reduce the influence caused by back mixing in a batch or a semi-batch process, and is suitable for industrial application.

Drawings

Figure 1 is an XRD pattern of the catalysts obtained in examples 1, 3 and 4.

Detailed Description

Example 1

(1) The amount of the zinc salt is adjusted to prepare the catalysts with different molar ratios of zinc and titanium. Taking 0.6g, or 1.2g, or 3.0g Zn (NO)₃)₂·6H₂O、220μL TiCl₄And 3.0g of urea dissolved in 100mLTransferring the hydrotalcite into a hydrothermal kettle, carrying out hydrothermal treatment at 130 ℃ for 48 hours, and washing and drying to obtain hydrotalcite carriers with different Zn/Ti molar ratios.

(2) 0.1g of hydrotalcite carrier and 8mL of deionized water were added with 82. mu.L (56.4mM) of PdCl₂Mixing the solution with 479 μ L (9.17mM) chloroauric acid solution, stirring, performing photoreduction for 30min at light intensity of 100mW/cm^-2And washing and drying to obtain the supported noble metal catalyst, wherein the supported noble metal is 1.4 wt%, which is shown in Table 1.

TABLE 1

Example 2

Step (1) was the same as in example 1.

(2) 0.1g of hydrotalcite carrier and 8mL of deionized water were added with 165. mu.L (56.4mM) of PdCl₂Stirring the solution uniformly, and carrying out photoreduction treatment for 30min at the light intensity of 100mW/cm^-2And washing and drying to obtain the Pd/ZnTi (2) catalyst with the noble metal loading of 1 wt%.

Example 3

(1) Changing the precursor of the zinc salt to 0.54g ZnCl₂Or 0.64g of ZnSO₄The procedure is as in example 1 except for the zinc salt precursor.

Step (2) the same as in example 1, the catalysts prepared are shown in Table 2.

TABLE 2

Example 4

(1) 1.2g of Zn (NO) was taken₃)₂·6H₂O、220μLTiCl₄And 3.0g of urea is dissolved in 100mL of deionized water, the mixture is transferred into a hydrothermal kettle, and the influence of different hydrothermal temperatures and time on the hydrotalcite carrier is examined.

Step (2) the same as in example 1, the catalysts prepared are shown in Table 3.

TABLE 3

Example 5

Step (1) was the same as in example 1.

(2) 0.1g of hydrotalcite carrier and 8mL of deionized water were added with 82. mu.L (56.4mM) of PdCl₂The solution and 479. mu.L (9.17mM) of chloroauric acid solution were stirred uniformly, and the influence of the photoreduction treatment time and light intensity on the supported noble metal catalyst was examined, and the catalysts prepared are shown in Table 4.

TABLE 4

Example 6

Step (1) the same as in example 1, wherein the precipitant urea was replaced with sodium hydroxide or sodium carbonate, and the influence of the precipitant was examined.

Step (2) the same as in example 1, the catalysts prepared are shown in Table 5.

TABLE 5

Example 7

Step (1) was the same as in example 1.

(2) 0.1g of hydrotalcite carrier and 8mL of deionized water are added with a certain amount of PdCl₂The solution and chloroauric acid solution were mixed at a Pd/Au molar ratio of 1, and the influence of the noble metal loading was examined, and the procedure was the same as in example 1, and the catalysts prepared are shown in Table 6.

TABLE 6

Example 8

Step (1) was the same as in example 1.

(2) 0.1g of hydrotalcite carrier and 8mL of deionized water are added with a certain amount of PdCl₂The Pd/Au molar ratio was adjusted by mixing the solution with the chloroauric acid solution, and the rest of the procedure was the same as in example 1, and the catalysts prepared are shown in Table7。

TABLE 7

Example 9 application

0.03mmol of phenylacetylene and 2.97mmol of styrene are dissolved in 10mL of ethanol, the molar content of the phenylacetylene in the styrene is 1%, the molar ratio of the noble metal to the substrate is 1:6500, the prepared different catalysts are added, the reaction temperature is 70 ℃ in a hydrogen atmosphere, the influence of the different catalysts on the reaction is examined, and the results are shown in a table 8-1 and a table 8-2.

TABLE 8-1

TABLE 8-2

Example 10 application

0.03mmol of phenylacetylene and 2.97mmol of styrene are dissolved in 10mL of ethanol, the molar content of the phenylacetylene in the styrene is 1%, a Pd5-Au5/ZnTi (2) catalyst is added, the molar ratio of the noble metal to the substrate is adjusted, the reaction temperature is 70 ℃ in a hydrogen atmosphere, and the results are shown in Table 9.

TABLE 9

Example 11, application

Dissolving 0.3mmol of phenylacetylene and 2.7mmol of styrene in 10mL of ethanol, wherein the molar content of the phenylacetylene in the styrene is 10%, adding a Pd5-Au5/ZnTi (2) catalyst, wherein the molar ratio of noble metal to a substrate is 1:6500, the reaction temperature is 70 ℃ under a hydrogen atmosphere, the reaction time is 10min, the phenylacetylene is completely converted, and the loss rate of the styrene is 0.1%; the reaction time is 120min, the phenylacetylene loss rate is 2.3 percent, the reaction time is 240min, and the phenylacetylene loss rate is 2.3 percent.

Example 12 application

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

Watch 10

Example 13, application

Dissolving 0.3mmol of phenylacetylene and 2.7mmol of styrene in 10mL of ethanol, wherein the molar content of the phenylacetylene in the styrene is 10%, adding a Pd5-Au5/ZnTi (2) catalyst which is cycled for 5 times, wherein the molar ratio of noble metal to a substrate is 1:6500, the reaction temperature is 70 ℃ under a hydrogen atmosphere, the reaction time is 10min, the phenylacetylene is completely converted, and the loss rate of the styrene is 0.1%; the reaction time is 120min, the phenylacetylene loss rate is 2.2 percent, the reaction time is 240min, and the phenylacetylene loss rate is 2.2 percent.

Claims

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.