CN1325160C - Palladium-carrying catalyst using titanium dioxide as carrier for acetylene hydrocarbon selective hydrogenation - Google Patents

Abstract

The present invention provides a preparation method of a catalyst for the catalytic selective hydrogenation of acetylene to prepare ethene by adopting titanium dioxide from various sources as a carrier; good reaction effect can be obtained, and the yield of the ethene can reach 95%. The present invention is characterized in that the catalyst contains 0.01 to 5 wt% of palladium as a main active component, and at least one of alkali metals, alkaline earth metals or transitional metals of the eighth family as a cocatalyst component. The finished product of the titanium dioxide carrier is soaked with a solution containing one or some of the required metallic elements in a stepwise mode or for one time, or the active component and the cocatalyst component are added during the formation process of the titanium dioxide carrier, and then, the mixture is dried, roasted and reduced to obtain the catalyst.

Description

A supported palladium catalyst supported by titanium dioxide as a carrier for the selective hydrogenation of alkynes

The invention is a catalyst for the selective catalytic hydrogenation reaction of alkynes, which belongs to the technical field of catalytic materials, and is characterized in that it contains 0.01 to 5 wt% of active component palladium and main group I, main group II and main group II The auxiliary agent of at least one metal in Group VIII, wherein said auxiliary agent is one or more of metal Na, K, Mg, Ca, Sr, Ba, Fe, Co, Ni, by using one or more The solution of various required metal elements is used to impregnate the finished titanium dioxide carrier step by step or together, or add active components and additives during the formation of the titanium dioxide carrier, followed by drying, roasting and reduction, so that excellent reaction effects can be obtained, and the yield of ethylene can reach Up to 95% or more.

As we all know, the production of olefins, which are the basic organic chemical raw materials in petrochemical industry, is always accompanied by the generation of toxic substances such as alkynes or diolefins that affect the further processing of olefins, so the development of new selective hydrogenation catalysts to remove The research on the required impurities has always been a hot spot in the hydrogenation of carbon two (C ₂ ) fractions to remove alkynes.

At present, most of the industries use group VIII elements as the active components of the reaction, such as palladium, platinum, rhodium, nickel, etc. Among them, the palladium catalyst has attracted extensive attention of many scholars and researchers because of its good reactivity and ethylene selectivity. In terms of additive research, for example, patent EP0689872 uses Ag as a cocatalyst to improve the selectivity of palladium catalyst; US4533779 mentions that Au element is added to Pd/ _Al2O3 , combined with ammonia water to improve the sulfur resistance of the _catalyst ; US5889187 uses Alkali or alkaline earth metals are used to adjust the reaction performance; Chinese patent CN1296880 adds rare earth elements; Dai Wei et al. (CN1279126A) prepared palladium/bismuth bimetallic catalysts. Carrier research aspects such as: the patent CN1361231 proposes to prepare a composite carrier of alumina and titania by chemical method to carry palladium, thereby improving selectivity and service life; Tao Jialin et al. (CN1317367) propose to use ZnO containing additive components as carrier; US6388150 The carrier in it is a fiber with a three-dimensional network structure; other studies involve the use of cordierite, sepiolite or SiO ₂ , diatomite, and honeycomb ceramics. There are also a considerable number of reports in the literature on these aspects, including the treatment of catalysts.

The purpose of the present invention is to further optimize the design of the supported catalyst to improve its catalytic reaction performance and obtain excellent reaction effect, aiming at the current research hotspots in the field of hydrogenation catalyst research. Considering that the interaction between the support, the active component and the auxiliary agent on the supported catalyst plays a key role in the reaction performance, the inventor has adopted a titanium dioxide support that is prone to strong interactions between the support and the metal element, and is improving the performance of the catalyst. The low-temperature reaction effect improves the yield of the target product ethylene at the same time, reaching more than 95%.

The invention provides a method for preparing a novel supported hydrogenation catalyst with titanium dioxide as a carrier, which is characterized in that: based on the catalyst, titanium dioxide from various sources is used as a carrier to carry 0.01 to 5wt.% of the main activity Component palladium and an auxiliary agent of at least one element in the I main group, the II main group and the VIII group, wherein the auxiliary agent is the element Na, K, Mg, Ca, Sr, Ba, Fe, Co, One or more of Ni. The preparation steps include impregnating the finished titanium dioxide step by step or jointly with a salt solution containing one or more required metals, or adding active components and auxiliary agents, drying, calcining and reducing during the formation of the titanium dioxide carrier. The carrier adopts titanium dioxide of anatase, rutile and brookite type from various sources, and the preparation method includes co-precipitation and sol-gel method.

In the present invention, the acetylene hydrogenation reaction is carried out in a constant pressure fixed bed continuous reactor with a temperature control device. The supported palladium is used as a catalyst, and the reaction product is detected by gas chromatography (hydrogen flame FID). The chamber was at 90°C, and the data was recorded by a chromatography workstation N2000.

The present invention is also characterized in that: the raw material gas is a mixed gas of acetylene, hydrogen and nitrogen, the reaction temperature is room temperature to 200°C, preferably 30 to 120°C; the yield of ethylene is over 95%.

The present invention will be further described below in conjunction with embodiment:

Reference example:

Weigh an appropriate amount of 20-40 mesh activated alumina (roasted at 1050°C) as the catalyst carrier, add a certain concentration of palladium chloride solution to the carrier and add an appropriate amount of distilled water to impregnate for 1 hour by wet impregnation method, at 100°C-150°C After drying for 5 hours, bake in a muffle furnace at 500°C for 5 hours, and then reduce it in a hydrogen atmosphere at 300°C to 500°C before use. The activity evaluation device is as above, after the reaction is stabilized at the controlled temperature point, samples are taken for analysis. The activation temperature of the catalyst is about 70°C. After activation, the corresponding acetylene conversion rate and ethylene selectivity are 97.02% and 91.06% respectively after the reaction is stable. The ratio of carbon dihydrocarbons to methane in the reaction product is 1798.

Embodiment one:

Tetrabutyl titanate is used as the titanium source, the appropriate pH value is adjusted with NaOH solution to fully hydrolyze and age the tetrabutyl titanate, and then anatase titanium dioxide powder is obtained by filtration, washing, drying and roasting. Commercial titanium dioxide and the anatase titanium dioxide prepared by the above-mentioned co-precipitation method were respectively used as carriers, and a catalyst containing 0.15% palladium was prepared by using the conventional preparation method of the palladium catalyst used in the reference example. The reaction performance is shown in Table 1.

Table 1 Performance of catalysts on two sources of titanium dioxide carrier

Table 1 Influence of preparation method of TiO ₂ support

TiO ₂ 40℃ 80℃ Conv.% sele.% yield% conv.% sele.% yield% purchase coprecipitation 0.070.71 97.1294.17 0.700.67 86.2086.17 98.0695.51 84.5282.30

catalyst=0.15wt%Pd/TiO ₂ , m=80mg.

The results show that the hydrogenation catalyst adopting the titanium dioxide carrier has a greater improvement than the traditional alumina carrier in terms of acetylene conversion rate and ethylene selectivity. In the reaction investigation, it is observed that the titanium dioxide in the present invention is the same active component as the carrier. The activation temperature of the catalyst with palladium content is 10-15° C. lower than that of the alumina carrier, and the selectivity of the target product remains above 95% before and after activation. The ratio of carbon dihydrocarbons to methane is greater than 4500, that is, the use of titanium dioxide carrier effectively inhibits the cracking reaction.

Embodiment two:

Using the supported catalyst prepared in the reference example and Example 1, the activity evaluation device was as above, the reaction process conditions were changed, and the catalytic performance was investigated under the condition of a severe excess of hydrogen. The supported palladium catalyst can only reach 21% ethylene yield, and under the same temperature, the conversion rate of acetylene is close to 100% on the same content loaded palladium catalyst with titanium dioxide as the carrier, and its target product selectivity has reached 88%. The selectivity of the reaction can reach 91%. It can be seen that under harsh reaction conditions, the reaction performance of the supported palladium catalyst with titania as the carrier is far better than that of the conventional alumina carrier sample.

Embodiment three:

Adopt the palladium catalyst conventional preparation method that reference example is used, prepare respectively the active component palladium content (wt.%) of catalyzer overall weight to be 0.02%, 0.05%, 0.08%, 0.15%, 1.0%, 2.0%, 3.0% % of seven titanium dioxide-supported metal catalysts. The activity evaluation device is the same as that of the reference example, and the reaction temperature is 80°C. The specific reaction results are shown in Table 2.

The impact of palladium content on the reaction performance on the titania carrier of table 2

Table 2 Influence of palladium content on TiO ₂

Pd content wt% conv.% sele.% yield% 0.020.050.080.151.002.003.00 0.0723.1077.9786.2099.0598.9299.60 100.078.7497.0998.0696.7894.2183.03 0.0718.1975.7084.5295.8693.2082.70

T=80℃, catalyst=Pd/TiO ₂ , m=80mg.

The result shows that along with the increase of the palladium content, the catalyst activity increases successively, and the activation temperature decreases thereupon, and when the palladium content is less than 0.15%, the activity of the sample jumps greatly, and the acetylene conversion jumps from 0.07% to 86.2%, but due to the catalyst The active site will not change significantly as the amount of palladium continues to increase. The activity of the palladium content increases from 0.15% to 3.00%. %. For selectivity, the selectivity of each sample is almost equal when the sample with less palladium content reaches the optimal conversion rate, all around 95%, and the green oil generation difference of the catalyst after activation is not very large; but palladium content When gradually increasing, the selectivity will decrease with the increase of activity. As the palladium content increases, the yield of the target product presents a peak shape, and its maximum value appears at the sample point where the palladium content is 1% based on the overall weight of the catalyst.

Embodiment four:

Similar to Example 2, according to the wet impregnation method, an appropriate amount of additive salt solution is added while impregnating the active component palladium salt, followed by drying, roasting, and reduction to prepare a titanium dioxide-supported palladium-based catalyst containing an additive. The overall weight of the catalyst is The active component palladium content of the meter is kept at 0.15%. The activity evaluation device is the same as before. The reaction results are shown in Table 3.

Table 3 The role of promoters on titanium dioxide-supported palladium-based catalysts

Table 3 Role of different promoter on the performance

Catalyst (Pd0.15%) Conv.(%) Sele.(%) Yield(%) Ratio of C ₂ H ₄ /C ₂ H ₆  PdPd-FePd-NaPd-Mg 47.6376.8982.7882.42 96.3494.4395.6597.37 45.8972.6179.1780.25 26.3216.9521.9737.02

T=60℃, t=30min, Support=TiO ₂ , Pd/promoter=1:1

From the results, it can be seen that the titanium dioxide-supported bimetallic catalyst added with transition metals, alkalis and alkaline earth metals has a significantly higher activity than the sample without additives at a lower reaction temperature while maintaining a high selectivity of 95%. improvement, thereby greatly increasing the yield of the target product.

Claims (5)

1. a selective acetylene hydrocarbon hydrogenation is the carried palladium catalyst of carrier in order to titanium dioxide, it is characterized in that this catalyst contains the auxiliary agent of at least a element in 0.01% to 5wt% main active component palladium and I main group, II main group and the group VIII, wherein said auxiliary agent is one or more among element Na, K, Mg, Ca, Sr, Ba, Fe, Co, the Ni, and the mol ratio of auxiliary element and palladium is an auxiliary agent: palladium=1: 1.

2. selection hydrogenation catalyst as claimed in claim 1 is characterized in that the carrier of loaded catalyst adopts the titanium dioxide in various sources, comprises the titanium dioxide of anatase, rutile and the brookite type of coprecipitation, Prepared by Sol Gel Method.

3. selection hydrogenation catalyst as claimed in claim 1 is characterized in that active component palladium content is 0.03 to 1.0wt.%.

4. selection hydrogenation catalyst as claimed in claim 1 is characterized in that preparation process is a palladium salt solution impregnation finished product titanium dioxide, or adds the salting liquid of active component and auxiliary element, drying, roasting, reduction then in the titania support forming process.

5. selection hydrogenation catalyst as claimed in claim 1 is characterized in that being applicable to the acetylene catalysis selective hydrogenation reaction in the mixed atmosphere, and reaction temperature is from room temperature～200 ℃.