CN106866372B - Recycling method of tungsten-based catalyst in preparation of low-carbon alcohol by catalysis of carbohydrate - Google Patents

Abstract

In the reaction of catalytic conversion of sugar compounds to prepare low-carbon alcohols, the tungsten salt solution will be partially or completely dissolved in the reaction solution, resulting in difficulty in recovery. In the present invention, paratungstate with low solubility is used as the tungsten source, and is applied to the reaction of catalytic conversion of sugar compounds to prepare propylene glycol, and the lower alcohol is prepared through a one-step catalytic conversion process. The reacted solution is separated to remove solid substances, concentrated to precipitate paratungstate, filtered and recycled into the reactor to realize the whole process circulation of tungsten. The invention has the advantages of high recovery rate of the tungsten-based catalyst and simple process, and realizes the whole-process utilization of the tungsten catalyst.

Description

Recycling method of tungsten-based catalyst in saccharide compound catalyzed production of lower alcohol

technical field

The invention belongs to the field of catalysis in biomass chemical industry, and particularly relates to the recycling of tungsten salt catalysts, in particular to a method for recovering and using tungsten salts in the catalytic conversion of sugar compounds.

Background technique

Ethylene glycol, propylene glycol and other low-carbon alcohols are important energy liquid fuels, and are also very important polyester synthesis raw materials, for example, for polyethylene terephthalate (PET), polyethylene naphthalate ( PEN), can also be used as antifreeze, lubricant, plasticizer, surfactant, etc., is a wide range of organic chemical raw materials.

At present, the production methods of ethylene glycol and 1,2-propylene glycol mainly include direct hydration method and indirect hydration method of ethylene oxide and propylene oxide. Although various methods are relatively mature in technology, there are still many shortcomings. For example, these methods have problems such as serious environmental pollution and high cost, and are difficult to produce on a large scale. At the same time, due to the rapid rise in the prices of fossil raw materials such as ethylene and propylene, the cost of the above-mentioned production process is also increasing. Therefore, it is of great practical significance to research and develop a low-cost, high-efficiency, and environment-friendly method for the production of low-carbon alcohols by catalytic hydrogenation of biomass.

With the development of agricultural technology, the production of sugar compounds is increasing day by day. The development of the preparation of propylene glycol from sugar compounds can not only reduce the dependence on petroleum resources to a certain extent, but also help to realize the deep processing of agricultural products to produce high value-added chemicals. At present, the technology of making polyols with sugar compounds (Document 1: A new process for producing ethylene glycol, CN200610068869.5 Document 2: A method for producing diols and polyols by cracking sorbitol, CN200510008652.0) There are disadvantages such as complex technical route, high energy consumption and poor product selectivity, which seriously affect the economy of the process.

At present, the conversion of carbohydrates to ethylene glycol by catalytic hydrogenation under hydrothermal conditions has been widely developed, and shows high catalytic selectivity (Document 3: CN 101735014A, a method for preparing ethylene glycol from carbohydrates; document 4: CN 102190562A, a method for preparing ethylene glycol from carbohydrates). The method uses a mixed catalyst composed of a tungsten-based catalyst and a hydrogenation catalyst to catalytically convert cellulose, thereby obtaining 60-75% ethylene glycol and propylene glycol. Similarly, using a two-component catalyst composed of tungsten and hydrogenation metal, under the condition of hydrothermal hydrogenation, high selectivity of sugar-containing compounds such as cellulose and starch can be used to prepare ethylene glycol and propylene glycol (Document 5: a Method for preparing ethylene glycol from polyhydroxy compounds WO2011113281A).

However, during the reaction process, tungsten will be partially or completely dissolved in the solution. After the rectification process, the high boiling point polyol and the tungsten salt are dissolved together, and the two are difficult to separate. In industry, organic matter is generally removed by incineration to obtain tungsten oxide, which is then dissolved in alkali and recovered by ammoniation. The process is extremely complicated, and the recovery efficiency of the product is low (Document 6: Research on the extraction of tungsten from tungsten-containing waste, China Mining Industry, 2008, 17:77-81). In addition, the presence of tungsten salts will make it difficult to utilize the rectification substrate and affect the economy of the entire process.

The tungsten-based catalyst provided by the invention has the advantages of simple operation, easy utilization, etc. The selected tungsten-based catalyst exhibits high catalytic activity in the reaction of catalytic conversion of sugar compounds to prepare lower alcohols, and the subsequent catalyst is easy to recover and recycle. In addition, the tungsten catalyst has the advantages of high recovery efficiency and easy industrialization in the whole reaction process.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a recycling method of a tungsten-based catalyst in the catalytic conversion of sugar compounds to prepare a lower alcohol.

To achieve the above object, the technical scheme adopted in the present invention is:

A method for recycling a tungsten-based catalyst in the reaction of catalyzing conversion of carbohydrate compounds to prepare low-carbon alcohols, characterized in that:

The saccharide compound is used as the reaction raw material, and the catalytic hydrogenation reaction is carried out in water in a reaction kettle or a fixed bed. The catalyst used is a composite catalyst, including that catalyst A is Ru/C or skeleton Ni is a solid catalyst, and catalyst B is paratungstic acid. The salt is filled with hydrogen in the reaction, the pressure is 3-15Mpa, the reaction temperature is 120-310 ° C, the mass concentration of the carbohydrate compound is 1-60%, and the mass space velocity is 0.1-10h ^-1 ;

The reaction product is filtered and separated to obtain a liquid product, and after concentration, paratungstate is precipitated, and the liquid product is separated again for rectification;

Paratungstate is precipitated after concentration, the concentration temperature is 30-120°C, the water content in the solution after concentration is less than 10%, the crystallization temperature is -10-50°C, and the crystallization time is 0.5-24h.

The carbohydrate compound is one or more of starch, cellulose, hemicellulose, sucrose, glucose, fructose, fructan, xylose, and soluble xylo-oligosaccharide.

The reaction conditions are: the reaction temperature is 180-300°C, the pressure is 3-12Mpa, the mass concentration of the saccharide compound is 10-50%, and the mass space velocity is 1-8h ^-1 , or the mass of the saccharide compound in the reactor is 10-50%. The ratio to the total mass of the catalyst is 1-50.

The main substances after the reaction product is filtered, separated and concentrated are ethylene glycol, propylene glycol, butylene glycol, glycerol, mannitol, sorbitol, sorbitan, C6-C18 polyol, and the mass concentration of paratungstate is 1-50 %.

In the crystallization process, a trace amount of ammonium paratungstate can be added as a crystal nucleating agent, and the added amount is less than 0.01% of the mass of the tungsten salt in the liquid product.

Preferred crystallization conditions: the crystallization temperature is -10-30°C, the water content is 0.1-3%, and the crystallization time is 0.5-10h.

The proportion of the tungsten salt recovered in a single time exceeds 90%, and the purity is higher than 95%. The recovered tungsten salt has the same reactivity in the conversion of sugar compounds, and can be recycled for many times.

The precipitation rate of paratungstate exceeds 93%; the recovered paratungstate can be recycled for more than 10 times.

The present invention has the following advantages:

1. The tungsten catalyst does not require complicated treatment procedures and can be directly recycled.

2. Using sugar compounds in biomass as raw materials, it has the advantage of reproducibility and meets the requirements of sustainable development.

3. The economy of the whole process is improved, and it has a good prospect of industrial application.

The present invention will be described in detail below through specific embodiments, but these embodiments do not limit the content of the present invention.

Detailed ways

Example 1

Reaction experiment: 1.0g Ru/C catalyst and 50ml of water were added to a 300ml reaction kettle. After replacing the gas with nitrogen three times, the temperature was programmed to 220°C. At this time, 40wt% of sugar compounds and 1wt% of ammonium paratungstate were pumped. Into the reactor, take the liquid at the same time, the mass space velocity is 2. During the reaction, the product was taken out, separated on a high-performance liquid chromatography calcium-type ion-exchange column and detected with a differential refractive index detector. Products such as propylene glycol, ethylene glycol and glycerol are calculated in the product yield. This reaction can be carried out in a fixed bed, the operation is similar, the sugar solution, space velocity and reaction temperature can be adjusted.

Operating conditions and substrate amounts can be adjusted as desired.

Example 2

Catalyst recovery cycle test:

The reaction solution of Example 1 was separated by filtration from the solid catalyst to obtain a polyol solution containing ammonium paratungstate, concentrated at 80°C, crystallized when the water content was less than 5%, and the crystallization temperature was 0°C, and 0.01 g of ammonium paratungstate crystal seed was added, The crystallization time was 3h, and ammonium paratungstate was precipitated and filtered.

Example 3

After the product is filtered and concentrated, the recovery efficiency of the tungsten-based catalyst under different moisture content conditions is shown in Table 1. The reaction conditions are the same as those in Example 1, and the recovery conditions are the same as those in Example 2.

Table 1 Recovery rate of tungsten salt under different water contents (reaction conditions: 220°C, mass space velocity 1, sugar concentration 10%, tungsten salt is ammonium paratungstate; concentrated at 80°C, crystallization temperature is 0°C, 0.1 g ammonium paratungstate crystal is added species, the crystallization time is 3h)

As shown in Table 1, the moisture content has a great influence on the precipitation of tungsten salts. Among them, the recovery rate of tungsten salt has exceeded 96% when the moisture content is lower than 3%.

Example 4

The catalyst recovery results under different crystallization conditions, the reaction conditions are the same as in Example 1 (Table 2).

Table 2. Under different crystallization conditions, the catalyst recovery results of the catalytic conversion of glucose to prepare low-carbon alcohols (reaction conditions: 220 ° C, mass space velocity is 1, sugar concentration is 10%, tungsten salt is ammonium paratungstate, water content is 3%)

As shown in Table 2, the reaction conditions can also significantly change the recovery efficiency of the catalyst. When the reaction conditions are optimized to crystallization at 0 °C, when 0.02 g of seed crystals are added and crystallization is performed for 24 hours, the recovery rate of ammonium paratungstate reaches 99%.

Example 5

Circulation of ammonium paratungstate after crystallization and regeneration, the reaction conditions are the same as those of Example 1 (Table 3). During the circulation process, fresh ammonium paratungstate is added each time, and the additional amount is 2% of the initial catalyst amount.

Table 3. Recycling results of ammonium paratungstate in the catalytic conversion of glucose to prepare low-carbon alcohols (reaction conditions: 220°C, mass space velocity 1, sugar concentration 10%, catalyst Ru/C+ recovery of ammonium paratungstate)

As shown in Table 3, the recovered ammonium paratungstate still has the same catalytic activity, and even after 20 cycles, the yield of ethylene glycol still reaches 60%.

Comparative Example

The method adopted in the present invention is compared with other methods, and the reaction conditions are the same as in Example 1

Table 4. Comparison of cycle effect between this catalyst and other catalysts

As shown in Table 4, compared with other tungsten catalyst recycling methods, the tungsten catalyst recycling method of the present invention has the advantages of high tungsten recovery rate, low catalyst usage, high catalytic activity, simple catalyst recycling process, and no sacrifice of high-boiling alcohols. and other advantages, it has high application value.

Claims (8)

1. The recycling method of the tungsten-based catalyst in the preparation of low-carbon alcohol by the catalysis of carbohydrate is characterized in that:

the saccharide compound is used as reaction material, and the catalytic hydrogenation reaction is performed in water in a reaction kettle or a fixed bed by using the catalyst as composite catalyst, including Ru/C as catalyst A or Ni as skeletonOne or two of solid catalysts, wherein the catalyst B is paratungstate, hydrogen is filled in the reaction, the pressure is 3-15Mpa, and the reaction temperature is 120-310-^oC, the mass concentration of the saccharide compounds is 1-60%, and the mass space velocity is 0.1-10h^-1；

Filtering and separating the reaction product to obtain a liquid product, concentrating and crystallizing to separate out paratungstate, wherein the concentration temperature is 30-120 DEG^oC, the water content in the concentrated solution is less than 10 percent, and the crystallization temperature is-10-50 percent^oC, the crystallization time is 0.5-24h, and the recovered paratungstate can be recycled;

separating again to obtain pure paratungstate and polyalcohol solution,

the main substances of the reaction product after filtration, separation and concentration are ethylene glycol, propylene glycol, butanediol, glycerol, mannitol, sorbitol, sorbitan and polyhydric alcohol of C6-C18, and the mass concentration of the paratungstate is 1-50%.

2. The method of claim 1, wherein:

the saccharide compound is one or more of starch, cellulose, hemicellulose, sucrose, glucose, fructose, levan, xylose and soluble xylooligosaccharide.

3. The method of claim 1, wherein:

the paratungstate is one or more than two of ammonium paratungstate, sodium paratungstate and potassium paratungstate.

4. The method of claim 1, wherein:

the reaction conditions are as follows: the reaction temperature is 180 ℃ and 300 ℃, the pressure is 3-12Mpa, the mass concentration of the carbohydrate is 10-50 percent, and the mass space velocity is 1-8h^-1Alternatively, the ratio of the mass of the saccharide compound to the total mass of the catalyst in the reactor is 1 to 50.

5. The method of claim 1, wherein:

trace ammonium paratungstate can be added as a crystal nucleating agent in the crystallization process of the reaction product, and the addition amount is less than 0.1 percent of the mass of the tungsten salt in the liquid product.

6. The method of claim 1, wherein:

the preferred crystallization conditions are: the crystallization temperature is-10-30 deg.C^oC, the water content is 0.1-3%, and the crystallization time is 0.5-10 h.

7. The method of claim 1, wherein:

the proportion of the tungsten salt recovered in a single time exceeds 90 percent, the purity is higher than 95 percent, the reaction activity of the recovered tungsten salt in the conversion of the carbohydrate is unchanged, and the tungsten salt can be recycled for multiple times.

8. The method of claim 1 or 7, wherein: the separation rate of paratungstate exceeds 93 percent; the recovered paratungstate can be recycled for more than 10 times.