JPS595522B2 - Tellurium recovery method from tellurium-containing metal oxides - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for efficiently recovering tellurium from a tellurium-containing metal oxide, particularly a tellurium-containing catalyst.

Tellurium-containing metal oxides are used as catalysts for various chemical reactions.

For example, the catalyst made of molybdenum-cobalt-tellurium oxide described in Japanese Patent Publication No. 39-21348;
Catalysts made of molybdenum/zinc/tellurium oxides described in Japanese Patent Publication No. 1-7774, Catalysts made of tellurium/cerium oxides described in Japanese Patent Publication No. 18447/1983, Japanese Patent Publication No. 1983-60
Catalyst consisting of molybdenum/tellurium/manganese/phosphorus oxide described in Japanese Patent Publication No. 46-2804; Catalyst consisting of iron/antimony/(vanadium, molybdenum, tungsten)/tellurium oxide described in Japanese Patent Publication No. 1983-2804; -4
It is known that a catalyst made of molybdenum/iron/tellurium oxides described in Publication No. 23 is effective for oxidizing olefins.

Tellurium is not abundant on Earth and is mostly obtained as a byproduct of copper smelting, making its production relatively inflexible.

Moreover, the price is also expensive. Therefore, when tellurium-containing catalysts are used industrially, tellurium recovery from spent catalysts is an important issue.

Conventionally, this problem has not received much attention because the tellurium content of catalysts used industrially has been small and the absolute amount has been small.

In particular, it has been economically difficult to recover tellurium from catalysts with low tellurium content.

In addition, many tellurium-containing catalysts used in gas-phase catalytic reactions are multi-component as mentioned above, so to recover tellurium from the catalyst, acids and alkalis are used, and the tellurium components are recovered by repeating dissolution and precipitation operations. It required a complicated process to isolate the .

As a result of various studies on industrially advantageous methods for recovering tellurium from tellurium-containing catalysts, the present inventors found that when a tellurium-containing catalyst is brought into contact with a reducing substance at a specific temperature, only the tellurium component sublimes. We discovered that tellurium can be recovered efficiently.

The present invention has been made based on this knowledge.

Tellurium from a tellurium-containing metal oxide catalyst containing at least one element selected from the group consisting of iron, cobalt, nickel, manganese, zinc, copper, cerium, tin, chromium, titanium, bismuth, molybdenum, tungsten, and antimony. To separate and recover the components, the tellurium-containing metal oxide catalyst is heated at a temperature of 450° C. to 1,000° C. in the substantially absence of gaseous oxygen, with a drop of 0/min.
Sublimating the tellurium component by contacting it with at least one gas selected from propylene, butane, butane, hydrogen, ammonia, and carbon monoxide, and then cooling it to a temperature of 400°C or less to precipitate it as metallic tellurium crystals. A tellurium recovery method characterized by:

In the method of the present invention, first, a tellurium-containing metal oxide catalyst is heated and reduced to sublimate the tellurium component in the oxide. At this time, the reducing substances used include propane, propylene, butane, Examples include hydrocarbons such as butene, and reducing gases such as hydrogen, ammonia, and carbon monoxide.

Further, the reducing substance does not need to be a specific one, and can be used in combination as appropriate.

The reduction temperature is preferably 450°C or higher.

At temperatures below 400°C, the reduction rate is extremely slow and is not practical.

Further, when the reduction temperature is raised, the reduction rate increases, but if it is too high, the surface area of the catalyst decreases due to sintering, etc., and the reduction rate conversely decreases.

This upper limit temperature varies depending on the catalyst components, but is approximately 10
Temperatures above 00°C are generally negative.

The reduction treatment time should be longer if the temperature is low, or may be shorter if the temperature is sufficiently high.

Next, the sublimed tellurium component is cooled in a cooling section and precipitated as crystals, but the temperature of the cooling section is preferably about 400° C. or lower.

Then, the precipitated tellurium metal is recovered.

The metal oxide catalyst that can recover tellurium by the method of the present invention may be any metal oxide catalyst that contains tellurium. IJ Examples include oxide catalysts containing at least one element selected from the group consisting of ram, tin, chromium, titanium, bismuth, molybdenum, tungsten and antimony.

In the method of the present invention, mainly only the tellurium component is selectively sublimed from the tellurium-containing metal oxide catalyst.
When the catalyst contains tellurium and antimony, antimony trioxide may sublimate at the same time depending on the conditions, especially when the reduction temperature is high.

However, since the precipitation temperature of the former is lower than that of metallic tellurium and antimony trioxide, each can be recovered separately by utilizing this temperature and precipitating them separately.

Further, in a catalyst system containing tellurium and antimony, the recovery rate of the tellurium component may not be increased depending on the catalyst composition or manufacturing conditions.

The cause is not clear, but it is thought that the catalyst undergoes rapid reduction during reduction, coating the catalyst particles with metal antimony, or forming an alloy, making it difficult for the tellurium component of the catalyst to sublimate. .

Therefore, it is better to avoid reducing treatment at high temperatures of about 800° C. or higher using highly reducing substances.

In addition, in such cases, oxidize the treated catalyst,
By performing reduction again, and repeating this further as necessary, it is possible to improve the recovery rate of the tellurium component from the catalyst.

In this case, the oxidation temperature is preferably 600°C or higher.

According to the method of the present invention, the tellurium component in the tellurium-containing metal oxide catalyst can be very effectively recovered as metal tellurium.

Moreover, the recovered metal tellurium has a high purity and can be used as a raw material for the catalyst again without any special purification.

In addition, the tellurium recovery rate is high. Therefore, when it is desired to recover the tellurium component from the tellurium-containing waste catalyst, it can be carried out very advantageously from an industrial perspective.

Hereinafter, the configuration and effects of the present invention will be specifically explained using Examples, but the present invention is not limited only to these Examples.

Example 1 Consisting of iron, antimony, tungsten, tellurium, oxygen and silica, iron: 8.5% by weight, antimony: 46.2% by weight, tungsten: 0.7% by weight, tellurium: 1.1% by weight
50 g of a catalyst (10-200 micron fluidized catalyst) containing 20 mm in diameter was packed into a quartz tube with a diameter of 20 mm.

A reducing gas consisting of 30 parts per volume of pump and the remainder nitrogen was passed through this at a flow rate of 15 e per hour, and the temperature was gradually raised.

It was treated at 500°C for 3 hours. The outlet of the quartz tube was air-cooled so that the temperature gradually decreased.

Antimony trioxide (partially containing metallic antimony) is precipitated in the high-temperature part of the quartz tube outlet, and in the lower-temperature part (approximately 400°C or less) it is shaped like a needle with a metallic luster. Crystals precipitated.

After purging with nitrogen, the blackened catalyst was taken out, calcined in air at 600°C for 15 hours, and then analyzed with fluorescent X-rays.

Tellurium was 0.01% by weight. Antimony also decreased slightly.

Further, it was confirmed by fluorescent X-ray analysis that the precipitated needle crystals with metallic luster were metallic tellurium.

The amount recovered was 0.5g, and the tellurium recovery rate was 9.
I was in charge 4.

The recovered tellurium has a purity of over 98% and is of a quality that can be used as a catalyst raw material as is.

A scanning micrograph of the recovered tellurium is shown in the figure.

Example 2 Composed of molybdenum, tellurium, manganese, phosphorus and oxygen, molybdenum 37.8% by weight, tellurium 16.8% by weight
Catalyst 34I (20 to 40 mesh) containing 8°7% by weight of manganese and 4.9% by weight of phosphorus was charged into the same apparatus as in Example 1.

Ammonia-nitrogen mixed gas (ammonia 30% by volume) was used as the reducing gas, and the treatment was carried out at 480°C for 15 hours.

The tellurium recovery rate was 89.6%.

In addition, the purity of the recovered tellurium was 99 or higher.

Example 3 Consisting of nickel, cerium, tellurium, molybdenum, oxygen and silica, nickel 0.9% by weight, cerium 3.
3% by weight, tellurium 4.0% by weight, molybdenum 9. [Catalyst (20 to 40 mesh) containing a weight factor was
It was filled into the same equipment.

A mixed gas of propylene and nitrogen (propylene 10% by volume) was used as the reducing gas, and the treatment was carried out at 450°C for 14 hours.

The tellurium recovery rate was 91%.

In addition, the purity of the recovered tellurium is 99 or higher.

Example 4 A catalyst (20~ 40 mesh) was charged into the same apparatus as in Example 1.

A mixed gas consisting of 30 volumes of isobutane and the balance nitrogen was introduced into the mixture, and the temperature was raised.

Reduction was performed at 550°C for 3 hours.

Observation of the outlet of the reaction tube showed no increase in the amount of tellurium precipitated, so the reduction was stopped and the recovery rate was determined from the weight of the recovered tellurium, which was 30%.

Air was introduced into the reduction catalyst and calcined at 700°C for 4 hours.
Oxidized.

When this was reduced again at 500°C, tellurium was observed to be deposited in the area below about 400°C at the outlet of the reaction tube.

Reduction was continued for 3 hours.

As a result, the total recovery rate of tellurium was 78 fO.

Moreover, the purity of this recovered tellurium was 97% or more.

[Brief explanation of the drawing]

The figure is a scanning electron micrograph of tellurium recovered in Example 1. The needle-like crystals are tellurium metal.

Claims (1)

[Claims] 1. A tellurium-containing metal oxide catalyst containing tellurium and at least one element selected from the group consisting of iron, cobalt, nickel, manganese, zinc, copper, cerium, tin, chromium, titanium, bismuth, molybdenum, tungsten, and antimony. In separating and recovering the tellurium component, the tellurium-containing metal oxide catalyst is heated to propane, propylene, butane, butene, and hydrogen at a temperature of 450°C to 1,000°C in the substantially absence of gaseous oxygen. Tellurium recovery characterized by sublimating the tellurium component by contacting it with at least one gas selected from ammonia and carbon monoxide, and then cooling it to a temperature of 400°C or less to precipitate it as metallic tellurium crystals. Law.