CN105344341A - Preparation method of solid catalyst used for synthesizing dimethyl carbonate - Google Patents

Abstract

The invention relates to a preparation method of a solid catalyst used for synthesizing dimethyl carbonat. The method comprises the following steps: taking graphene oxide as a carrier and taking magnesium nitrate as an active ingredient precursor, dipping the materials, drying and calcining the materials to obtain the solid catalyst used for synthesizing the dimethyl carbonate by performing ester interchange on ethylene carbonate and methanol. The method operation is simple, the obtained solid catalyst has the advantages of high efficiency and low cost, the filtered solid catalyst enables continuous cycle usage after reaction, has advantages of long service life and no pollution. The catalyst is used for synthesizing the dimethyl carbonate through ester interchange, yield of the dimethyl carbonate can reach as high as 87.1%, and selectivity can reach 99.3%.

Description

A kind of preparation method of the solid catalyst for the synthesis of dimethyl carbonate

Technical field

The present invention relates to the preparation field of solid catalyst, particularly a kind of preparation method of the solid catalyst for the synthesis of dimethyl carbonate.

Background technology

Dimethyl carbonate (DimethylCarbonate, DMC), is a kind of water white liquid during normal temperature, is insoluble in water, but immiscible organic solvent that can be nearly all with alcohol, ether, ketone etc.DMC toxicity is very low, is just classified as non-toxic product by Europe in 1992, and be a kind of environmental protective type chemical raw material meeting modern cleaning procedure requirement, therefore the synthetic technology of DMC receives the extensive attention of domestic and international chemical circles.

The initial production method of DMC is phosgenation, succeed in developing, but the toxicity of phosgene and corrosivity limits the application of this method in 1918, and particularly along with environmental protection is by the raising day by day of whole world attention degree, phosgenation is eliminated.Early 1980s, it is the commercialization of being synthesized DMC technique by methanol oxidation carbonylation of catalyst that gondola EniChem company achieves with CuCl, and this is first technique realizing industrialized non-phosgene synthesis DMC, is also most widely used technique.When the defect of this technique is high conversion, the deactivation phenomenom of catalyst is serious, and therefore its conversion per pass is only 20%.In the nineties in 20th century, the research of DMC synthesis technique obtains and develops rapidly, the technique of Ube to EniChem company methanol oxidation carbonylation synthesis DMC of Japan is improved, conversion ratio almost reaches 100%, this technique achieves industrialization, but this technique take CO as raw material, and CO is a kind of poisonous gas, and the safety problem that therefore CO causes limits the application of this technique.

Texaco company of the U.S. develops first by oxirane and carbon dioxide reaction Formed vinyl acetate, then to produce the technique of DMC through ester exchange with methyl alcohol, and this technique coproduction ethylene glycol, achieved industrialization in 1992.Adopt oxirane and carbon dioxide to be raw material synthesizing ethylene carbonate under catalyst action, then make ethylene carbonate and methyl alcohol carry out ester exchange reaction to obtain dimethyl carbonate and the by-product ethylene glycol dimethyl carbonate industrialized preparing process that to be current domestic employing more.

Ester exchange reaction Synthesis of dimethyl carbonate catalyst system and catalyzing, homogeneous catalytic reaction and heterogeneous catalytic reaction can be divided into again according to catalyst system and catalyzing difference, synthesis DMC mainly passes through homogeneous catalytic reaction system both at home and abroad at present, react catalyst used to have, alkali metal oxide, alkali metal hydroxide, alkali metal alcoholates, alkali carbonate, alkaline metal oxalate, quaternary ammonium halides salt and organic base etc.Although alkali metal oxide, hydroxide, carbonate and oxalates all show good catalytic performance, because its specific area is little, bad dispersibility in reaction system, therefore catalytic efficiency is lower, and catalyst amount is generally larger; Quaternary ammonium salt and organic base are not only expensive, and separation is after the reaction had any problem, and easily causes catalyst loss, not only increases production cost, but also cause product purity to reduce.Industrial is sodium methoxide by ethylene carbonate and methanol-fueled CLC dimethyl carbonate catalyst used, the use of sodium methoxide catalyst, there is many shortcomings, can be summarized as follows: the consumption of (1) catalyst is large, industrial often production 1 ton of dimethyl carbonate, needs sodium methoxide about the 80-110kg of mass percentage 25-30% now; (2) produce a large amount of waste residues after catalyst failure, cause environmental pollution; (3) the precipitation influential system quantity-produced stability of solid in catalysis system, blocking pipe and equipment, have a strong impact on the continuity of production; (4) synthesis technique is complicated, in order to catalyst waste slag is shifted out from reaction mass system, when preventing rectifying, solid waste is separated out, be attached to heat exchanger tube inner wall surface and be attached on filler, desalted water to be added from reactive distillation column tower reactor heavy constituent out and pass into carbon dioxide, to make the inefficacy of remaining catalyst sodium methoxide become NaOH then become inorganic salts sodium carbonate with carbon dioxide reaction, then fall sodium carbonate by metre filter, this makes production technology very complicated; (5) catalyst can not reuse, owing to generating sodium carbonate inorganic salts after catalyst failure, no longer includes catalytic action.

Therefore, the object of the invention is to development and operation simple, product facilitates with catalyst separation, and products obtained therefrom purity is high, the method for catalyst recovery and the good Synthesis of dimethyl carbonate of multiplexing performance.But, up to the present, be that carrier is prepared loaded catalyst Synthesis of dimethyl carbonate and also do not had bibliographical information with graphene oxide.

Summary of the invention

The technical problem to be solved in the present invention is for the catalyst use amount occurred in current ester exchange synthesis DMC process is large and separation and recovery of catalyst is difficult, the problem such as the yield of product DMC is lower, there is provided a kind of simple to operate, product and catalyst separation are conveniently, products obtained therefrom purity is high, the method for catalyst recovery and the good Synthesis of dimethyl carbonate of multiplexing performance.

In order to solve the problem, the invention provides a kind of solid catalyst for the synthesis of DMC and preparation method thereof, high catalytic activity, the high selectivity of solid catalyst in ethylene carbonate and methyl alcohol ester exchange reaction can be realized, and catalyst recovery and recycle simple, reaction cost reduces greatly.

The technical solution adopted for the present invention to solve the technical problems is:

The preparation method of catalyst:

(1) a certain amount of graphene oxide is added in deionized water, graphene oxide be 1:10 ~ 1:20 with the mass ratio of deionized water, ultrasonic disperse 30 ~ 60 minutes under room temperature condition, power 120 ~ 240W;

(2) magnesium nitrate is added in the material of step (1) gained, and at room temperature magnetic agitation 12h, wherein the mass ratio of magnesium nitrate and graphene oxide is 1:10 ~ 1:20;

(3) by step (2) gained material evaporate to dryness in a water bath, transfer in baking oven subsequently and dry, transfer in tube furnace subsequently, under nitrogen atmosphere or argon gas atmosphere, be warming up to 400-450 DEG C, and keep 3h-6h at this temperature, be down to room temperature subsequently.

Wherein carrier graphene oxide is prepared as follows:

In ice-water bath, 5g crystalline flake graphite and 2.5g sodium nitrate are mixed with the concentrated sulfuric acid of 115mL, in stirring, slowly adds 15gKMnO ₄, keep less than 2 DEG C sustained response 1h, transfer them to 35 DEG C of water-bath 30min, progressively add 250mL deionized water, temperature can obviously be observed mixture and become glassy yellow by sepia after rising to 98 DEG C of continuation reaction 1h.Be diluted with water continuously further, and with the H of mass fraction 30% ₂o ₂solution-treated.By above-mentioned solution suction filtration, with 5%HCl solution washing to neutral, filter cake is put into 80 DEG C, baking oven and be fully drying to obtain graphite oxide.Get 0.1g graphite oxide and put into 50mL deionized water, ultrasonic process 1.5h (180W, 60Hz), carries out suction filtration subsequently, filter cake is put into vacuum drying oven 40 DEG C of (10Pa) dry 6h and namely obtains required graphene oxide.

The present invention is carrier with graphene oxide, is that presoma has successfully prepared a kind of graphene oxide-loaded magnesia catalyst with magnesium nitrate.Compared with traditional catalyst carrier molecular sieve or active carbon, graphene oxide is with low cost, is as the ideal material of catalyst carrier.In addition, graphene oxide has the little advantage of resistance to mass tranfer as catalyst carrier because it is only the two-dimensional structure of plane, these be the material such as molecular sieve or active carbon incomparable; In addition, carboxyl functional groups a large amount of on graphene oxide can form coordinate bond with magnesium metal ion, not only make magnesia in dipping process be scattered at carrier surface uniformly, but also can be good at fixing magnesia, thus avoid the loss of active component.The inventive method is simple, and cost is low, and immobilized effective, catalyst activity is high, is a kind of effective ways preparing loaded catalyst, successfully overcomes the drawback of conventional method.

Solid catalyst of the present invention is applied to the ester exchange reaction Synthesis of dimethyl carbonate of ethylene carbonate and methyl alcohol, gets and obtain good effect.In course of reaction, not only catalytic activity is high for catalyst, and recycles through simple filtration and recyclable continuation after the reaction, and the life-span is long, without any pollution, also greatly reduces the preparation cost of catalyst.

Detailed description of the invention

The present invention will be described further with regard to following examples, but it is to be understood that these embodiments are only the use illustrated, and should not be interpreted as restriction of the invention process.

Embodiment 1

Getting 0.2g graphene oxide joins in 2mL deionized water, at room temperature ultrasonic 30 minutes subsequently, ultrasonic power 200W; Again 0.03g magnesium nitrate is added in above-mentioned solution, stirring at room temperature 12h; By gained material evaporate to dryness in 70 DEG C of water-baths, to transfer to subsequently in baking oven and dry 6h under 100 DEG C of conditions; Transfer to subsequently in tube furnace, be warming up to 450 DEG C with the speed of 10 DEG C/min under a nitrogen, and keep 3h at this temperature, be down to room temperature subsequently, obtain catalyst A.

Embodiment 2

Getting 0.2g graphene oxide joins in 2mL deionized water, at room temperature ultrasonic 60 minutes subsequently, ultrasonic power 120W; Again 0.03g magnesium nitrate is added in above-mentioned solution, stirring at room temperature 12h; By gained material evaporate to dryness in 70 DEG C of water-baths, to transfer to subsequently in baking oven and dry 6h under 100 DEG C of conditions; Transfer to subsequently in tube furnace, be warming up to 450 DEG C with the speed of 10 DEG C/min under a nitrogen, and keep 3h at this temperature, be down to room temperature subsequently, obtain catalyst B.

Embodiment 3

Getting 0.2g graphene oxide joins in 4mL deionized water, at room temperature ultrasonic 60 minutes subsequently, ultrasonic power 240W; Again 0.04g magnesium nitrate is added in above-mentioned solution, stirring at room temperature 12h; By gained material evaporate to dryness in 70 DEG C of water-baths, to transfer to subsequently in baking oven and dry 6h under 100 DEG C of conditions; Transfer to subsequently in tube furnace, be warming up to 450 DEG C with the speed of 10 DEG C/min under a nitrogen, and keep 3h at this temperature, be down to room temperature subsequently, obtain catalyst C.

Embodiment 4

Getting 0.2g graphene oxide joins in 4mL deionized water, at room temperature ultrasonic 60 minutes subsequently, ultrasonic power 240W; Again 0.02g magnesium nitrate is added in above-mentioned solution, stirring at room temperature 12h; By gained material evaporate to dryness in 70 DEG C of water-baths, to transfer to subsequently in baking oven and dry 6h under 100 DEG C of conditions; Transfer to subsequently in tube furnace, be warming up to 450 DEG C with the speed of 10 DEG C/min under a nitrogen, and keep 3h at this temperature, be down to room temperature subsequently, obtain catalyst D.

Comparative example 1

This comparative example take graphene oxide as catalyst, is designated as catalyst E.

Above-mentioned catalyst is respectively used to the reaction of ethylene carbonate and methyl alcohol, reaction condition is:

The mol ratio of ethylene carbonate and methyl alcohol is 1:10, and the consumption of catalyst is 1% of ethylene carbonate quality, and reaction temperature is 70 DEG C, and the reaction time is 4h.

Product adopts gas chromatographic analysis, and the condition of chromatography is: OV-101 capillary chromatographic column, vaporizer and detector temperature 250 DEG C, 80 ~ 180 DEG C of temperature programmings of column oven temperature, and determine the yield of product and selective, concrete outcome is as shown in table 1.

The catalytic activity of table 1 catalyst

Catalyst	Dimethyl carbonate selective (%)	Dimethyl carbonate yield (%)
			A	98.7	79.3
B	99.1	81.1
			C	99.3	87.1
D	98.2	75.2
			E	99.5	2.4

As can be seen from Table 1, by catalyst application of the present invention in ester exchange reaction, catalyst all has higher activity.

Adopt the method for filtering by the catalyst recovery in reactant liquor, reuse after drying, catalyst C in the ester exchange reaction of ethylene carbonate and methyl alcohol to reuse result as shown in table 2.

The repetition experimental result of table 2 catalyst

Cycle-index	Dimethyl carbonate selective (%)	Dimethyl carbonate yield (%)
			1	99.3	87.1
2	99.1	87.0
			3	98.8	86.9

As can be seen from Table 2, this catalyst is after three times are recycled, and the selective and yield of dimethyl carbonate is basicly stable, illustrates that this catalyst can reuse and not reduce its catalytic activity, has good effect.

With above-mentioned according to desirable embodiment of the present invention for enlightenment, by above-mentioned description, relevant staff in the scope not departing from this invention technological thought, can carry out various change and amendment completely.The technical scope of this invention is not limited to the content on description, must determine its technical scope according to right.

Claims (2)

1., for the synthesis of a preparation method for the solid catalyst of dimethyl carbonate, it is characterized in that the method is is carrier with graphene oxide, take magnesium nitrate as presoma, by dipping, dry, the method for roasting by MgO-Supported on graphene oxide.

2. the preparation method of a kind of solid catalyst for the synthesis of dimethyl carbonate according to claim 1, is characterized in that what the method was specifically carried out according to following step:

(1) a certain amount of graphene oxide is added in deionized water, graphene oxide be 1:10 ~ 1:20 with the mass ratio of deionized water, ultrasonic disperse 30 ~ 60 minutes under room temperature condition, power 120 ~ 240W;

(2) magnesium nitrate is added in the material of step (1) gained, and at room temperature magnetic agitation 12h, wherein the mass ratio of magnesium nitrate and graphene oxide is 1:10 ~ 1:20;

(3) by step (2) gained material evaporate to dryness in a water bath, transfer in baking oven subsequently and dry, transfer in tube furnace subsequently, under nitrogen atmosphere or argon gas atmosphere, be warming up to 400 ~ 450 DEG C, and keep 3h ~ 6h at this temperature, be down to room temperature subsequently.