CN110054547B - Method for preparing ethanol by oxalate hydrogenation under coupled catalysis of integrated catalyst - Google Patents
Method for preparing ethanol by oxalate hydrogenation under coupled catalysis of integrated catalyst Download PDFInfo
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- C07C29/149—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of an oxygen containing functional group of >C=O containing groups, e.g. —COOH of carboxylic acids or derivatives thereof with hydrogen or hydrogen-containing gases
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Abstract
The invention relates to a method for preparing ethanol by oxalic ester hydrogenation under the coupling catalysis of an integrated catalyst, which comprises the following steps: filling the iron-containing catalyst subjected to reduction and carbonization in a first section of a reactor, filling the reduced copper-containing zinc catalyst in a second section of the reactor, and enabling the oxalate solution and hydrogen to be catalyzed by the first section and the second section in sequence to obtain a finished product. In the process, the byproduct of the reaction of the oxalate on the iron-containing catalyst is only methyl acetate, but the methyl acetate can be further converted into ethanol on the copper-zinc catalyst, and the variety and the number of the byproducts are extremely small, so that the selectivity of the byproducts is obviously reduced compared with the selectivity of the byproducts in the prior art, and the selectivity of the ethanol is greatly improved. Under the optimized process conditions, the conversion rate of the oxalate can reach 100%, the selectivity of ethanol can reach 98%, the waste discharge is reduced, and the cost of subsequent separation is greatly reduced. The technology makes the engineering application of the technology of preparing ethanol by high-selectivity hydrogenation of oxalate of synthesis gas possible.
Description
Technical Field
The invention relates to the technical field of ethanol preparation, in particular to a method for preparing ethanol by coupling and catalyzing oxalate through an integrated catalyst and hydrogenating.
Background
Ethanol, commonly known as alcohol, is an important chemical raw material and is widely applied to the fields of food, medicine, chemical industry, national defense and the like. Because the oxygen content of the ethanol reaches 34.7 percent, the ethanol can also be used as a methyl tert-butyl ether (MTBE) substitute to be added into gasoline to obtain ethanol gasoline, so that the gasoline consumption can be reduced, the gasoline can be combusted more fully, and the emission of pollutants such as CO and the like in the combustion can be reduced. The traditional route for ethanol production mainly comprises two routes. One is a petroleum route, in which ethanol is obtained by hydration by using petroleum cracking product ethylene as a raw material. The other is a biological fermentation route, and various sugar-containing agricultural products, agricultural and forestry byproducts and wild plants are used as raw materials, and the disaccharide and the polysaccharide are converted into monosaccharide and further converted into ethanol through hydrolysis and fermentation.
With the rapid development of the automobile industry, the production of bioethanol in China is rapidly developed, and the production of bioethanol in China is currently promoted to the third major fuel ethanol production country and consumer countries in the world. Because of the restriction of national conditions, the large-scale use of sugarcane or corn for producing fuel ethanol is limited, and the ethanol production technology using cellulose as a raw material is not mature. Based on the relatively rich national conditions of coal in China, ethanol preparation from synthesis gas is of wide interest. The reported method for preparing ethanol from synthesis gas mainly uses Rh/SiO2Catalyst at 3-10MPa and 30Reacting at 0 deg.C to obtain organic oxygen-containing compound containing two carbon atoms and mainly including acetaldehyde, ethanol, ethyl acetate and acetic acid, and reacting at Cu/SiO2[JP6259632]、Pd-Fe/SiO2[JP61178940,JP61178942]Or Cu-Zn-Al-Mg-Mo [ CN1122567]And further hydrogenating the acetaldehyde, the ethyl acetate, the acetic acid and other products on the catalysts to convert the acetaldehyde, the ethyl acetate, the acetic acid and other products into the ethanol. The technical process has the defects of harsh conditions, poor catalyst stability, low selectivity and the like, so that large-scale application is not obtained at present.
Chinese patent CN101934228A reports a copper-based catalyst for preparing ethanol by acetate hydrogenation, wherein the carrier is alumina or silica, the auxiliary agent is oxides of elements such as zinc, manganese, chromium, calcium, barium, iron, nickel, magnesium, etc., and the conversion rate of acetate is up to 88%, but the reaction efficiency is low.
CN102327774 reports that a copper-based catalyst is applied to a reaction system for preparing ethanol by acetate hydrogenation, and the preparation method comprises the steps of adding silica sol or soluble aluminum salt into a mixed solution of soluble salt of copper and auxiliary metal soluble salt, stirring uniformly, adding the mixed solution into a solution of a precipitator at 50-95 ℃, and then aging, filtering, washing, drying, roasting, forming and reducing to obtain the catalyst. The highest conversion rate of the prepared catalyst in the acetate hydrogenation reaction is 85%, and the selectivity of ethanol is 91%.
CN101941887A adopts silicon oxide or aluminum oxide as carrier, copper as active component, Zn, Mn, Cr, Ca, Ba and other metals or metal oxides as auxiliary agent to prepare the copper-based catalyst, the selectivity in the acetic ester hydrogenation reaction can reach 99% to the maximum, and the conversion rate can reach 92% to the maximum.
CN101411990 discloses a preparation method of a copper-silicon catalyst for preparing ethylene glycol by oxalate hydrogenation, which is to add 600-1200m specific surface area into a copper-ammonia complex2The catalyst is prepared by filtering, washing, drying, roasting and reducing the mesoporous silica molecular sieve powder per gram.
CN102350358A discloses a preparation method and application of a copper-based catalyst for preparing ethanol by oxalate hydrogenation, wherein zirconia and silica are used as composite carriers, copper is used as an active component, metals such as Mg, Ca, Ba, Mn and the like or metal oxides are used as auxiliaries to prepare the copper-based catalyst, the conversion rate of oxalic acid vinegar in the preparation of ethanol by oxalate hydrogenation reaches 100%, and the selectivity of ethanol reaches 85%.
CN102649745A and CN102649744A disclose a technical scheme of contacting oxalic acid vinegar as a raw material with a copper-containing catalyst in a fluidized bed reactor to generate an effluent containing glycolic acid vinegar, so as to improve the selectivity of glycolic acid vinegar.
Theories and experiments prove that the catalytic system and the process have the problems of more side reactions and low selectivity of the product ethanol.
Disclosure of Invention
The invention aims to provide a process for preparing ethanol by coupling and catalyzing oxalate hydrogenation by using an integrated catalyst, which finally converts reactant oxalate into ethanol by using a two-stage catalyst containing two active components. The oxalate is first converted in a first stage iron containing catalyst and the product is then further hydrogenated to ethanol in a second stage copper containing zinc catalyst. The process can effectively inhibit main side reactions, reduce the selectivity of three-carbon alcohol, four-carbon alcohol and acetate, and thus effectively improve the selectivity of ethanol. The integrated catalyst which takes iron carbide as an active component, silicon dioxide as a carrier and copper zinc as an active component is adopted to realize artificial regulation and control of a reaction route, so that high ethanol selectivity is obtained. Under the optimized process conditions, the conversion rate of the oxalate can reach 100%, the highest selectivity of ethanol can reach 98%, the waste discharge is reduced, and the cost of subsequent separation is greatly reduced.
The technical scheme adopted by the invention is as follows:
a method for preparing ethanol by oxalate hydrogenation through coupling catalysis of an integrated catalyst is characterized by comprising the following steps: the method comprises the following steps: filling an iron-containing catalyst in a first section of a reactor, filling a copper-containing zinc catalyst in a second section of the reactor, and enabling an oxalate solution and hydrogen to sequentially react through catalyst bed layers of the first section and the second section to generate a finished product stream containing ethanol; the iron-containing catalyst is iron carbide loaded on a carbon carrier; the copper-zinc-containing catalyst takes silicon dioxide as a carrier and takes copper zinc as an active substance.
The active component of the iron-containing catalyst is iron carbide, mesoporous carbon is used as a carrier, the carrier accounts for 60-90% of the mass of the catalyst, and the active component accounts for 10-40% of the mass of the catalyst;
the copper-zinc-containing catalyst takes silicon dioxide as a carrier and copper zinc as an active substance, the carrier silicon dioxide accounts for 50-80% of the mass of the catalyst, the active component copper accounts for 15-40% of the mass of the catalyst, and the active component zinc accounts for 2-15% of the mass of the catalyst.
Before filling, the iron-containing catalyst is firstly reduced in a hydrogen atmosphere, and then carbonized in a hydrogen-methanol atmosphere; the temperature of reduction in the hydrogen atmosphere is 250-400 ℃, and the temperature of carbonization of the catalyst is 180-300 ℃.
And before the copper-zinc-containing catalyst is filled, reducing in a hydrogen atmosphere, wherein the reduction temperature in the hydrogen atmosphere is 250-400 ℃.
And filling the reduced and carbonized iron-containing catalyst and the reduced copper-zinc catalyst into the fixed bed tubular reactor in a manner that the iron-containing catalyst is close to the inlet end of the raw material stream and the copper-zinc-containing catalyst is close to the outlet end of the product stream.
Furthermore, the molar hydrogen-ester ratio of the oxalate solution is 40-300; the total mass space velocity of the oxalate feeding is 0.2-2.0h-1。
Furthermore, the total pressure of the reaction system is 1.0-4.0MPa, and the reaction temperature is 180-300 ℃.
Furthermore, the preparation method of the iron-containing catalyst comprises the following steps:
the method includes the steps that mesoporous carbon with certain granularity is dried in advance, and the water absorption capacity of the mesoporous carbon per unit mass is measured;
weighing a certain mass of ferric nitrate, adding deionized water according to the measured water absorption capacity for dissolving, then dripping the obtained solution into a carrier weighed according to the load capacity, and ultrasonically stirring for a period of time;
drying the mixture obtained in the step II at 40-120 ℃, and then roasting for 4-10h at 350-450 ℃ in an inert atmosphere;
fourthly, after tabletting and screening, the iron-containing catalyst precursor obtained in the step three is loaded into a reactor, the iron-containing catalyst precursor is reduced under the conditions that the hydrogen pressure is 0.1-5MPa and the temperature is 250-400 ℃, the temperature is adjusted after reduction, and hydrogen and methanol mixed gas is introduced to carry out carbonization on the iron-containing catalyst.
Furthermore, the preparation method of the iron-containing catalyst may further include the steps of:
the method comprises the steps of weighing ferric nitrate, adding the ferric nitrate into water for dissolving, and heating the obtained solution;
adding a sodium carbonate solution into an iron nitrate solution until the pH value is 6.5-7.5, aging the obtained product for 2-4h, filtering and washing;
drying the filter cake obtained in the step II for 6-12h, grinding after drying, and roasting in a muffle furnace at the temperature of 350-450 ℃ for 4-10h to obtain an iron-containing catalyst precursor;
fourthly, tabletting and screening the iron-containing catalyst precursor obtained in the step three, then loading the iron-containing catalyst precursor into a reactor, reducing the iron-containing catalyst precursor under the conditions that the hydrogen pressure is 0.1-5MPa and the temperature is 400 ℃, adjusting the temperature after reduction, and introducing mixed gas of hydrogen and methanol with the molar ratio of 1/20 to carbonize the iron-containing catalyst for 12-48h at the carbonization temperature of 240-300 ℃.
Furthermore, the preparation method of the copper-zinc-containing catalyst comprises the following steps:
the method comprises the steps of weighing copper nitrate and zinc nitrate, and dissolving the copper nitrate and the zinc nitrate with water to obtain a solution A;
weighing tetraethoxysilane and dissolving the tetraethoxysilane in ethanol to obtain a solution B;
mixing the solution A with the solution B to obtain a solution C;
fourthly, ammonium carbonate is weighed and dissolved in water to obtain a solution D;
mixing the solution C and the solution D, and filtering and washing after aging;
sixthly, roasting the filter cake obtained in the step I after vacuum drying;
and sixthly, tabletting and screening the product obtained in the step VI, then putting the product into a reactor, and reducing the product after adjusting the pressure in the reactor.
The solvent in the oxalate solution is either ethanol or methanol, or both.
The method for preparing ethanol by oxalate hydrogenation through coupling catalysis of the integrated catalyst is characterized by comprising the following steps: the final product of the reaction mainly comprises ethanol and methyl acetate, the sum of the yields of the ethanol and the methyl acetate reaches more than 99%, and the yield of the ethanol reaches more than 96%.
The invention has the advantages and positive effects that:
the invention applies a strategy of catalyzing oxalate hydrogenation to prepare ethanol by coupling reaction, adopts a two-stage integrated catalyst containing two active components, firstly converts oxalate on an iron-containing catalyst, and then further hydrogenates the product of the oxalate on a copper-zinc catalyst to obtain the target product ethanol. In the process, the byproduct of the reaction of the oxalate on the iron carbide catalyst is only methyl acetate, but the methyl acetate can be further converted on the copper-zinc catalyst, and the types and the quantity of the byproducts are extremely small, so that the byproduct selectivity is obviously reduced compared with the byproduct selectivity of the existing process, and the selectivity of ethanol is greatly improved. Under the optimized process conditions, the conversion rate of the oxalate can reach 100%, the yield of the ethanol can reach 98%, the waste discharge is reduced, and the cost of subsequent separation is greatly reduced.
Drawings
FIG. 1 is a process flow diagram of the present invention;
FIG. 2 is a schematic of two-stage catalyst loading.
In fig. 1: 1-pressure reducing valve, 2-mass flowmeter, 3-high pressure constant flow pump, 4-vaporization chamber, 5-reactor, 6-gas-liquid separator and 7-back pressure valve.
In fig. 2: 1-feed stream, 2, 4, 6-inert material, 3-iron carbide catalyst, 5-copper zinc catalyst, 7-product stream.
Detailed Description
The present invention is further illustrated by the following examples, but is not limited to these examples. The experimental methods not specified in the examples are generally commercially available according to the conventional conditions and the conditions described in the manual, or according to the general-purpose equipment, materials, reagents and the like used under the conditions recommended by the manufacturer, unless otherwise specified.
A method for preparing ethanol by oxalate hydrogenation through coupling catalysis of integrated catalyst is disclosed, as shown in figures 1 and 2, the innovation of the invention is as follows: the method comprises the following steps: and filling the iron-containing catalyst 3 in a first section of a reactor 5, filling the copper-containing zinc catalyst 5 in a second section of the reactor, and enabling the oxalate solution 1 and hydrogen to be catalyzed by the first section and the second section in sequence to obtain a finished product 7.
In this embodiment, inert materials 2, 4, and 6 such as quartz sand or quartz wool are filled in the raw material stream inlet 1, between the two catalysts, and in the product stream outlet 7 of the reactor, respectively.
Before loading the iron-containing catalyst, firstly reduction is carried out in hydrogen atmosphere, and then catalyst carbonization is carried out in hydrogen and methanol atmosphere. The temperature of reduction in the hydrogen atmosphere is 250-400 ℃, and the temperature of catalyst carbonization is 180-300 ℃.
Before the copper-zinc-containing catalyst is filled, the reduction is carried out in a hydrogen atmosphere, and the reduction temperature in the hydrogen atmosphere is 250-400 ℃.
The molar hydrogen-ester ratio of the oxalate solution is 40-300; the total mass space velocity of the oxalate feeding is 0.2-2.0h-1. The more preferable scheme is as follows: the molar hydrogen ester ratio of the oxalate solution is 160-200; the total mass space velocity of the oxalate feeding is 0.2-1.0h-1。
The stream exiting the iron-containing catalyst contains either or both methyl acetate or ethanol, and also methanol. The stream coming out of the copper-zinc containing catalyst contains products such as methanol, ethanol and traces of methyl acetate.
The oxalate is either dimethyl oxalate or diethyl oxalate or both. The solvent in the oxalate solution is any one or both of ethanol and methanol.
The specific catalytic process is as follows:
fully reducing and carbonizing the prepared and weighed iron-containing catalyst precursor, fully reducing the copper-zinc catalyst, filling the iron-containing catalyst close to the inlet end of the raw material stream, and filling the copper-zinc-containing catalyst close to the outlet end of the product stream into a fixed bed tubular reactor 5, wherein the two sections of catalysts are isolated by inert materials such as quartz sand, quartz wool and the like so as to avoid the reaction of the raw materials at the interface of the two catalysts.
Adjusting the reaction furnace to a reaction temperature, setting hydrogen and raw material flow to reach a specified hydrogen-ester ratio and a specified mass airspeed as required, preheating and vaporizing an oxalate-containing stream, then feeding the oxalate-containing stream into a reactor to contact with a first section of catalyst for reaction under a hydrogen atmosphere, contacting a generated product stream with a second section of catalyst for further hydrogenation reaction to generate an ethanol-containing stream, feeding the product stream into a gas-liquid separator 6 for condensation gas-liquid separation to obtain a liquid-phase product stream and a non-condensable gas stream, and emptying 7 or recycling the non-condensable gas stream.
The active component of the iron-containing catalyst is iron carbide, mesoporous carbon is used as a carrier, the carrier accounts for 60-90% of the mass of the catalyst, and the active component accounts for 10-40% of the mass of the catalyst; the copper-zinc-containing catalyst takes silicon dioxide as a carrier and copper zinc as an active substance, the carrier silicon dioxide accounts for 50-80% of the mass of the catalyst, the active component copper accounts for 15-40% of the mass of the catalyst, and the active component zinc accounts for 2-15% of the mass of the catalyst.
The preparation method of the iron-containing catalyst comprises the following steps:
the method includes the steps that mesoporous carbon with certain granularity is dried in advance, and the water absorption capacity of the mesoporous carbon per unit mass is measured;
weighing a certain mass of ferric nitrate, adding deionized water according to the measured water absorption capacity for dissolving, then dripping the obtained solution into a carrier weighed according to the load capacity, and ultrasonically stirring for a period of time;
drying the mixture obtained in the step II at 40-120 ℃ for 6-12h, and then roasting at 350-450 ℃ in an inert atmosphere for 4-10 h;
fourthly, after tabletting and screening, the iron-containing catalyst precursor obtained in the step three is loaded into a reactor, the iron-containing catalyst precursor is reduced under the conditions that the hydrogen pressure is 0.1-5MPa and the temperature is 250-400 ℃, the temperature is adjusted after reduction, and hydrogen and methanol mixed gas is introduced to carry out carbonization on the iron-containing catalyst.
The preparation method of the iron-containing catalyst (control) may further include the steps of:
weighing ferric nitrate, adding deionized water for dissolving, and heating the obtained solution to 70 ℃ in a water bath while stirring;
dripping a sodium carbonate solution into an iron nitrate solution under continuous stirring until the pH value reaches about 6.5-7.5, aging the obtained product for 2-4h, and then filtering and washing;
fourthly, tabletting and screening the product obtained in the step three, then loading the product into a reactor, tabletting and screening the prepared powder, then loading the powder into the reactor, adjusting the pressure in the reactor to 1.0-4.0MPa, adjusting the hydrogen flow to 80-120mL/min, heating to 380 ℃ plus material, carrying out on-line reduction on the catalyst precursor for 4-6 h;
drying the filter cake obtained in the step II for 6-12h, grinding after drying, and roasting in a muffle furnace at the temperature of 350-450 ℃ for 4-10h to obtain an iron-containing catalyst precursor;
fourthly, tabletting and screening the iron-containing catalyst precursor obtained in the step three, then loading the iron-containing catalyst precursor into a reactor, reducing the iron-containing catalyst precursor under the conditions that the hydrogen pressure is 0.1-5MPa and the temperature is 400 ℃, adjusting the temperature after reduction, and introducing mixed gas of hydrogen and methanol with the molar ratio of 1/20 to carbonize the iron-containing catalyst for 12-48h at the carbonization temperature of 240-300 ℃.
The preparation method of the copper-zinc-containing catalyst comprises the following steps:
the method comprises the steps of weighing copper nitrate and zinc nitrate, and dissolving with deionized water to obtain a solution A;
weighing ethyl orthosilicate according to a set mass fraction of silicon dioxide, and dissolving the ethyl orthosilicate in ethanol to obtain a solution B;
mixing the solution A and the solution B, and stirring until the solution A and the solution B are not layered to obtain a solution C;
fourthly, weighing ammonium carbonate and dissolving the ammonium carbonate into deionized water to obtain a solution D;
simultaneously dropwise adding the solution C and the solution D, keeping the pH value of the liquid to be 7.0-7.5, aging at 80 ℃ for 18-24 hours, and finally filtering and washing;
sixthly, drying the filter cake obtained in the step I under vacuum at 80 ℃ for 6-12h, and roasting at 400-450 ℃ for 4-6 h;
and sixthly, tabletting and screening the catalyst powder which is obtained by the step VI and is loaded on the silicon oxide, then loading the catalyst powder into a reactor, adjusting the pressure in the reactor to 1.0-4.0MPa, and reducing for 4-6h at the temperature of 380 ℃ under 300 ℃.
Example 1
1.443g of ferric nitrate and 0.8g of fully dried mesoporous carbon support were weighed. Preparing ferric nitrate water solution, dripping into the carrier, and stirring for 10-30 min. The mixture was dried at 50 ℃ for 12 h. The resulting product was dried, ground, and calcined at 400 ℃ in an inert atmosphere, thereby obtaining an iron-containing catalyst precursor. The precursor is subjected to hydrogen reduction at 380 ℃ and carbonization with hydrogen-methanol mixed gas at 260 ℃ for reaction.
According to the following steps of 9: copper nitrate and zinc nitrate are weighed according to the proportion of 1 and dissolved in deionized water to obtain a solution A. Weighing tetraethoxysilane according to the set loading amount of 30 percent, and mixing the tetraethoxysilane with the equal volume of the absolute ethyl alcohol to obtain a solution B. And pouring the solution A into the solution B, and stirring until the solution A is not layered to obtain a solution C. 0.25mol/L ammonium carbonate solution D is prepared. And (3) simultaneously dropwise adding the solution C and the solution D in a water bath at 80 ℃, and keeping the pH value of the liquid in the flask equal to 7.5. Then aged at 80 ℃ for 18 hours. Filtered and washed thoroughly and the filter cake is dried at 120 ℃ for 12 h. Roasting in a muffle furnace at 400 ℃, thereby obtaining the copper-zinc-containing catalyst precursor. The precursor is reduced by hydrogen at 300 ℃ for reaction.
Weighing 0.04g of copper-zinc-containing catalyst and 0.1g of iron-containing catalyst, filling the iron-containing catalyst fully carbonized in advance and the copper-zinc catalyst fully reduced in advance into a reaction tube, wherein the two sections of catalysts are isolated by inert materials such as quartz sand, quartz wool and the like according to the filling sequence in a mode that the iron-containing catalyst is close to the inlet end of a raw material stream and the copper-zinc-containing catalyst is close to the outlet end of a product stream. Switching the feeding of a high-pressure constant flow pump into a dimethyl oxalate methanol solution with the mass fraction of 20%, and setting the liquid phase flow to ensure that the mass airspeed of the dimethyl oxalate is 0.8h-1The hydrogen-ester ratio was 180, samples were taken 2 hours apart and the product composition was analyzed by gas chromatography using a FID detector, and the conversion of dimethyl oxalate and the selectivity for ethanol were calculated. The reaction results are shown in Table 1.
Example 2
Except that the liquid mass space velocity is 1.2h-1Otherwise, the reaction conditions were the same as in example 1, and the reaction results are shown in Table 1.
Example 3
Except that the liquid mass space velocity is 1.6h-1In addition, other conditions are the same as those of the practiceThe same as in example 1, the reaction results are shown in Table 1.
Example 4
Except that the liquid mass space velocity is 2.0h-1Otherwise, the reaction conditions were the same as in example 1, and the reaction results are shown in Table 1.
Comparative example 1
Preparing 0.5mol/L sodium carbonate solution. 200mL of ferric nitrate solution was prepared and heated to 70 ℃. The resulting sodium carbonate solution was dropped into the iron nitrate solution while stirring until the pH reached 7. The resulting product was aged at pH 7 for 2 h. The excess ions are then filtered off. The precipitate was dried at 100 ℃ for 12 h. The resulting product was dried, ground and calcined in a muffle furnace at 400 ℃ to thereby obtain an iron-containing catalyst precursor. The precursor is reduced by hydrogen at 380 ℃, and then carbonized by hydrogen-methanol mixed gas at 260 ℃.
According to the weight ratio of 9: copper nitrate and zinc nitrate are weighed according to the proportion of 1 and dissolved in deionized water to obtain a solution A. Weighing tetraethoxysilane according to the set loading amount of 30 percent, and mixing the tetraethoxysilane with the equal volume of the absolute ethyl alcohol to obtain a solution B. And pouring the solution A into the solution B, and stirring until the solution A is not layered to obtain a solution C. 0.25mol/L ammonium carbonate solution D is prepared. And (3) simultaneously dropwise adding the solution C and the solution D in a water bath at 80 ℃, and keeping the pH value of the liquid in the flask equal to 7.5. Then aged at 80 ℃ for 18 hours. Filtered and washed thoroughly and the filter cake is dried at 120 ℃ for 12 h. And (4) roasting at 400 ℃ in a muffle furnace to obtain the copper-containing zinc catalyst precursor. The precursor is reduced by hydrogen at 380 ℃ for reaction.
Weighing 0.2g of copper-zinc-containing catalyst and 0.5g of iron-containing catalyst, filling the iron-containing catalyst fully carbonized in advance and the copper-zinc catalyst fully reduced in advance into a reaction tube, wherein the two sections of catalysts are isolated by inert materials such as quartz sand, quartz wool and the like according to the filling sequence in a mode that the iron-containing catalyst is close to the inlet end of a raw material stream and the copper-zinc-containing catalyst is close to the outlet end of a product stream. Switching the feeding of a high-pressure constant flow pump into a dimethyl oxalate methanol solution with the mass fraction of 20%, setting the flow of a liquid phase to ensure that the mass airspeed of dimethyl oxalate is 0.2h-1Sampling at 2-hour intervals, analyzing the product composition by gas chromatography using FID detector, and calculating to obtain oxalic acid bisMethyl ester conversion and ethanol selectivity. The reaction results are shown in Table 1.
Comparative example 2
Except that the liquid mass space velocity is 0.4h-1Otherwise, the reaction conditions were the same as in example 1, and the reaction results are shown in Table 1.
Comparative example 3
Except that the liquid mass space velocity is 0.6h-1Otherwise, the reaction conditions were the same as in example 1, and the reaction results are shown in Table 1.
Comparative example 4
Except that the liquid mass space velocity is 0.8h-1Otherwise, the reaction conditions were the same as in example 1, and the reaction results are shown in Table 1.
Comparative example 5
Preparing 0.5mol/L sodium carbonate solution. 200mL of ferric nitrate solution was prepared and heated to 70 ℃. The resulting sodium carbonate solution was dropped into the iron nitrate solution while stirring until the pH reached 7.5. The resulting product was aged at pH 7 for 2 h. The excess ions are then filtered off. The precipitate was dried at 100 ℃ for 12 h. The resulting product was dried, ground and calcined in a muffle furnace at 400 ℃ to thereby obtain an iron-containing catalyst precursor. The precursor is subjected to hydrogen reduction at 380 ℃ and carbonization with hydrogen-methanol mixed gas at 260 ℃ for reaction.
The prepared catalyst precursor is tableted and sieved into 40-60 meshes, then 0.7g of iron-containing catalyst is weighed and filled in a tubular reactor, and reduction is carried out in a hydrogen atmosphere at 380 ℃, the gas flow is controlled at 100mL/min, and the reduction time is 4 hours. After the reduction was completed, the reactor temperature was adjusted to 260 ℃ and the hydrogen-methanol molar ratio was adjusted to 1/20, and methanol was mixed with hydrogen after preheating and vaporization, and the iron-containing catalyst was carbonized in this atmosphere for 24 hours. After carbonization is finished, the feeding of the high-pressure constant flow pump is switched into dimethyl oxalate methanol solution with the mass fraction of 20%, and the liquid phase flow is set to ensure that the mass airspeed of dimethyl oxalate is 0.8h-1The hydrogen-ester ratio was 180, samples were taken 2 hours apart and the product composition was analyzed by gas chromatography using a FID detector, and the conversion of dimethyl oxalate and the selectivity for ethanol were calculated. The reaction results are shown in Table 1.
Comparative example 6
According to the weight ratio of 9: copper nitrate and zinc nitrate are weighed according to the proportion of 1 and dissolved in deionized water to obtain a solution A. Weighing tetraethoxysilane according to the set loading amount of 30 percent, and mixing the tetraethoxysilane with the equal volume of the absolute ethyl alcohol to obtain a solution B. And pouring the solution A into the solution B, and stirring until the solution A is not layered to obtain a solution C. 0.25mol/L ammonium carbonate solution D is prepared. And (3) simultaneously dropwise adding the solution C and the solution D in a water bath at 80 ℃, and keeping the pH value of the liquid in the flask equal to 7.5. Then aged at 80 ℃ for 18 hours. Filtered and washed thoroughly and the filter cake is dried at 120 ℃ for 12 h. Roasting in a muffle furnace at 400 ℃, thereby obtaining the copper-zinc-containing catalyst precursor. The precursor is reduced by hydrogen at 380 ℃ for reaction.
The prepared catalyst precursor is pressed and sieved into 40-60 meshes, then 0.7g of copper-containing zinc catalyst is weighed and filled in a tubular reactor to be reduced in hydrogen atmosphere at 380 ℃, the gas flow is controlled at 100mL/min, and the reduction time is 4 hours. After the reduction is finished, the temperature of the reactor is adjusted to 260 ℃, the feeding of the high-pressure constant flow pump is switched into dimethyl oxalate methanol solution with the mass fraction of 20%, and the liquid phase flow is set to ensure that the mass airspeed of the dimethyl oxalate is 0.8h-1The hydrogen-ester ratio was 180, samples were taken 2 hours apart and the product composition was analyzed by gas chromatography using a FID detector, and the conversion of dimethyl oxalate and the selectivity for ethanol were calculated. The reaction results are shown in Table 1.
Comparative example 7
Preparing 0.5mol/L sodium carbonate solution. 200mL of ferric nitrate solution was prepared and heated to 70 ℃. The sodium carbonate solution obtained was dropped into the iron nitrate solution while stirring until the pH reached 7. The resulting product was aged at pH 7 for 2 h. The excess ions are then filtered off. The precipitate was dried at 100 ℃ for 12 h. The resulting product was dried, ground and calcined in a muffle furnace at 400 ℃ to thereby obtain an iron-containing catalyst precursor. The precursor is subjected to hydrogen reduction at 380 ℃ and carbonization with hydrogen-methanol mixed gas at 260 ℃ for reaction.
According to the weight ratio of 9: weighing copper nitrate and zinc nitrate according to the proportion of 1, and dissolving the copper nitrate and the zinc nitrate in deionized water to obtain a solution A. Weighing tetraethoxysilane according to the set loading amount of 30 percent, and mixing the tetraethoxysilane with the equal volume of the absolute ethyl alcohol to obtain a solution B. And pouring the solution A into the solution B, and stirring until the solution A is not layered to obtain a solution C. 0.25mol/L ammonium carbonate solution D is prepared. And (3) simultaneously dropwise adding the solution C and the solution D in a water bath at 80 ℃, and keeping the pH value of the liquid in the flask equal to 7.5. Then aged at 80 ℃ for 18 hours. Filtered and washed thoroughly and the filter cake is dried at 120 ℃ for 12 h. And (4) roasting at 400 ℃ in a muffle furnace to obtain the copper-containing zinc catalyst precursor. The precursor is reduced by hydrogen at 380 ℃ for reaction.
Then weighing 0.2g of copper-zinc-containing catalyst and 0.5g of iron-containing catalyst, filling the iron-containing catalyst fully carbonized in advance and the copper-zinc catalyst fully reduced in advance into a reaction tube, wherein the two sections of catalysts are isolated by inert materials such as quartz sand, quartz wool and the like according to the filling sequence in a mode that the copper-zinc-containing catalyst is close to the inlet end of a raw material stream and the iron-containing catalyst is close to the outlet end of a product stream. Switching the feeding of a high-pressure constant flow pump into a dimethyl oxalate methanol solution with the mass fraction of 20%, and setting the liquid phase flow to ensure that the mass airspeed of the dimethyl oxalate is 0.8h-1The hydrogen-ester ratio was 180, samples were taken 2 hours apart and the product composition was analyzed by gas chromatography using a FID detector, and the conversion of dimethyl oxalate and the selectivity for ethanol were calculated. The reaction results are shown in Table 1.
Table 1: the reaction result of preparing ethanol by oxalate hydrogenation is as follows:
from the results of the above examples, it can be seen that the integrated catalyst of the present invention can obtain ethanol selectivity up to 98%, which is much higher than that of Fe alone5C2Catalyst or CuZnO-SiO2The selectivity to ethanol obtained over the catalyst was only 78% and 51% for both catalysts given the same reaction conditions. Moreover, the selectivity and the yield of the ethanol obtained by the technology of the invention are far higher than the published literature data of ethanol preparation from synthesis gas by oxalate hydrogenation.
Claims (11)
1. A method for preparing ethanol by oxalate hydrogenation through coupling catalysis of an integrated catalyst is characterized by comprising the following steps: the method comprises the following steps: filling an iron-containing catalyst subjected to reduction and carbonization processes in a first section of a reactor, filling a copper-containing zinc catalyst subjected to reduction processes in a second section of the reactor, and enabling an oxalate solution and hydrogen to sequentially react through catalyst bed layers of the first section and the second section to generate a finished product stream containing ethanol; the iron-containing catalyst is iron carbide loaded on a carbon carrier; the copper-zinc-containing catalyst takes silicon dioxide as a carrier and copper zinc as an active substance;
the active component of the iron-containing catalyst is iron carbide, mesoporous carbon is used as a carrier, the carrier accounts for 60-90% of the mass of the catalyst, and the active component accounts for 10-40% of the mass of the catalyst.
2. The method for preparing ethanol by coupling and catalyzing oxalate through hydrogenation by using an integrated catalyst according to claim 1, wherein the method comprises the following steps: the copper-zinc-containing catalyst takes silicon dioxide as a carrier and copper zinc as an active substance, the carrier silicon dioxide accounts for 50-80% of the mass of the catalyst, the active component copper accounts for 15-40% of the mass of the catalyst, and the active component zinc accounts for 2-15% of the mass of the catalyst.
3. The method for preparing ethanol by coupling and catalyzing oxalate through hydrogenation by using an integrated catalyst according to claim 1, wherein the method comprises the following steps: before filling the iron-containing catalyst, firstly reducing in a hydrogen atmosphere, and then carbonizing the catalyst in a hydrogen-methanol atmosphere; the temperature of reduction in the hydrogen atmosphere is 250-400 ℃, and the temperature of carbonization of the catalyst is 180-300 ℃.
4. The method for preparing ethanol by coupling and catalyzing oxalate hydrogenation by using an integrated catalyst according to claim 1 or 3, wherein: before the copper-zinc-containing catalyst is filled, the reduction is carried out in a hydrogen atmosphere, and the reduction temperature in the hydrogen atmosphere is 250-400 ℃.
5. The method for preparing ethanol by coupling and catalyzing oxalate through hydrogenation by using an integrated catalyst according to claim 1, wherein the method comprises the following steps: the reduced and carbonized iron-containing catalyst and the reduced copper-zinc catalyst are filled into a fixed bed tubular reactor in a manner that the iron-containing catalyst is close to the inlet end of the raw material stream and the copper-zinc-containing catalyst is close to the outlet end of the product stream.
6. The method for preparing ethanol by coupling and catalyzing oxalate through hydrogenation by using integrated catalyst according to claim 1, wherein the method comprises the following steps: the molar hydrogen-ester ratio of the oxalate solution is 40-300; the total mass space velocity of the oxalate feeding is 0.2-2.0h-1。
7. The method for preparing ethanol by coupling and catalyzing oxalate through hydrogenation by using an integrated catalyst according to claim 1, wherein the method comprises the following steps: the reaction pressure is 1.0-4.0 MPa; the reaction temperature is 180-300 ℃.
8. The method for preparing ethanol by coupling and catalyzing oxalate hydrogenation by using an integrated catalyst as claimed in claim 1, wherein: the preparation method of the iron-containing catalyst comprises the following steps:
the method includes the steps that mesoporous carbon with certain granularity is dried in advance, and the water absorption capacity of the mesoporous carbon per unit mass is measured;
weighing a certain mass of ferric nitrate, adding deionized water according to the measured water absorption capacity for dissolving, then dripping the obtained solution into a carrier weighed according to the load capacity, and ultrasonically stirring for a period of time;
drying the mixture obtained in the step II at 40-120 ℃, and then roasting for 4-10h at 350-450 ℃ in an inert atmosphere;
fourthly, after tabletting and screening, the iron-containing catalyst precursor obtained in the step three is loaded into a reactor, the iron-containing catalyst precursor is reduced under the conditions that the hydrogen pressure is 0.1-5MPa and the temperature is 250-400 ℃, the temperature is adjusted after reduction, and hydrogen and methanol mixed gas is introduced to carry out carbonization on the iron-containing catalyst.
9. The method for preparing ethanol by coupling and catalyzing oxalate hydrogenation by using an integrated catalyst as claimed in claim 1, wherein: the preparation method of the copper-zinc-containing catalyst comprises the following steps:
the method comprises the steps of weighing copper nitrate and zinc nitrate, and dissolving the copper nitrate and the zinc nitrate with water to obtain a solution A;
weighing tetraethoxysilane, and dissolving in ethanol to obtain a solution B;
mixing the solution A with the solution B to obtain a solution C;
fourthly, ammonium carbonate is weighed and dissolved in water to obtain a solution D;
mixing the solution C and the solution D, and filtering and washing after aging;
sixthly, roasting the filter cake obtained in the step I after vacuum drying;
and sixthly, tabletting and screening the product obtained in the step VI, then putting the product into a reactor, and reducing the product after adjusting the pressure in the reactor.
10. The method for preparing ethanol by coupling and catalyzing oxalate hydrogenation by using an integrated catalyst as claimed in claim 1, wherein: the solvent in the oxalate solution is any one or both of ethanol and methanol.
11. The method for preparing ethanol by coupling and catalyzing oxalate hydrogenation by using an integrated catalyst as claimed in claim 1, wherein: the final product of the reaction mainly comprises ethanol and methyl acetate, the sum of the yields of the ethanol and the methyl acetate reaches more than 99%, and the yield of the ethanol reaches more than 96%.
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