A method for preparing pure isopropanol from carbon dioxide

Abstract

The present invention provides a method for preparing pure isopropanol from carbon dioxide, and the synthesis route is as follows: 1) using a membrane electrode assembly reactor and a nickel single atom-nitrogen doped activated carbon material to electrocatalytically reduce carbon dioxide to pure carbon monoxide; 2) using a solid electrolyte electrolytic cell and a copper gel material to electrocatalytically reduce carbon monoxide to pure acetic acid; 3) using a cerium oxide material to catalyze the acetic acid ketolysis reaction at 300°C and normal pressure to obtain acetone and carbon dioxide, wherein the carbon dioxide can be recycled to step 1 for recycling; 4) using a bipolar membrane membrane electrode assembly reactor and a lattice stretched ruthenium metal nanocatalyst to electrocatalytically reduce pure acetone to pure isopropanol liquid. The present invention proposes a potential solution for the highly selective, mild and green preparation of carbon dioxide to isopropanol by integrating the two-step electrolysis of carbon dioxide, acetic acid ketolysis and acetone electroreduction reactions.

Description

Technical Field

[0001] The invention belongs to the technical field of new energy chemical industry, and relates to a synthetic route for preparing pure isopropanol from carbon dioxide, which couples a multi-step process of two-step electrolysis of carbon dioxide, acetic acid ketonization and acetone electroreduction, and is clean, economical and independent of fossil energy. Background Art

[0002] Due to the heavy dependence and consumption of fossil fuels in the development of human society, on the one hand, excessive carbon dioxide emissions have caused a series of environmental problems such as global warming, and on the other hand, energy shortages have caused it. It is imperative to reduce carbon dioxide emissions and adjust the energy structure. Using clean electricity generated by sustainable energy to convert excess carbon dioxide into high-value-added chemicals is an effective solution to reduce carbon emissions and open up new pathways for chemical synthesis. However, the types of products obtained by carbon dioxide electroreduction are limited, and the manufacture of many important chemical products is heavily dependent on fossil energy and is accompanied by serious carbon emissions. Therefore, it is of far-reaching significance to further utilize the products of carbon dioxide electroreduction to synthesize fossil fuel-derived chemicals.

[0003] Isopropyl alcohol is an important bulk chemical, especially as a raw material for chemical synthesis and an organic solvent. It is widely used with good economic benefits and a huge market share. The preparation process of isopropyl alcohol is mainly based on propylene hydration. The direct hydration method requires a high temperature and high pressure environment, but the one-way conversion rate of the raw materials used to synthesize isopropanol is very low, and the purity of the raw material propylene is very high (99.5%), which greatly limits the expansion of its production scale and increases its dependence on fossil fuel propylene. The additional consumption caused by the purification and concentration process of propylene also makes the cost of this production process extremely high. If the conversion efficiency is to be further improved, more stringent production conditions are required; while the indirect hydration method is to make propylene and sulfuric acid esterify, and the obtained isopropanol sulfate is subsequently hydrolyzed to obtain isopropanol. This process has low requirements for the purity of propylene, a wider range of raw materials, and greatly improves the one-way conversion rate of propylene, which can reduce the refining cost, but requires a large amount of concentrated sulfuric acid. Not only does it have problems in production safety, but the highly corrosive sulfuric acid will also seriously corrode the production equipment. After the hydrolysis of isopropyl ester, a large amount of waste acid with a high concentration will be produced, which cannot be directly discharged into the environment, and the recovery and concentration will also increase the cost. In addition, both synthesis methods are based on propylene and rely on fossil fuels. In summary, to a certain extent, the expansion of the production scale of isopropanol is limited. Acetone hydrogenation reduction (thermal or electrical) can also be used to produce isopropanol, but considering that the current mainstream production method of acetone still relies on fossil fuels (propylene, benzene), we began to explore the possibility of preparing acetone from carbon dioxide. To this end, we combined the two-step electrolysis of CO2 and the ketolysis reaction of acetic acid, designed the electroreduction of carbon dioxide to carbon monoxide, and then further electrochemically reduced to acetic acid or acetate, and finally obtained acetone from acetic acid or acetate through the chemical catalytic process of carboxylic acid ketolysis. The use of the prepared acetone for electrochemical hydrogenation to prepare isopropanol is expected to achieve the synthesis of isopropanol, an important chemical raw material, from carbon dioxide, using clean electricity generated by sustainable energy, without relying on any fossil fuels and petrochemical processes, and relatively mildly. And considering that the synthesis process has many steps, directly synthesizing pure products and reducing separation costs will be beneficial to the improvement of the economic benefits of the overall solution. Summary of the invention

[0004] In view of this, the technical problem to be solved by the present invention is to provide a method for preparing pure isopropanol from carbon dioxide. The four-step process for synthesizing pure isopropanol by coupling two-step electrolysis of carbon dioxide, ketolysis of carboxylic acid and electroreduction of acetone provided by the present invention realizes the mild, green and clean conversion of carbon dioxide to pure isopropanol, and is expected to be applied to the large-scale production and on-site preparation of isopropanol under the framework of new energy structure, without relying on any fossil energy.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] The process includes two-step electrolysis of carbon dioxide, ketolysis of carboxylic acid and electroreduction of acetone. In order to reduce the separation cost, the intermediate product obtained in each step can be directly used as raw material in the next step. The schematic diagram of the route is shown in the figure. Figure 1 As shown;

[0007] A method for preparing pure isopropanol from carbon dioxide comprises the following steps:

[0008] Step 1: The carbon dioxide electroreduction process, based on the corresponding catalyst, an anion exchange membrane electrode reactor and supporting accessories, realizes the efficient preparation of carbon monoxide at room temperature and pressure, and the purity does not affect the subsequent process;

[0009] Step 2: A process of carbon monoxide electroreduction, characterized in that, based on a corresponding catalyst, a solid electrolyte membrane electrode reactor and supporting accessories, a pure acetic acid aqueous solution is efficiently prepared at room temperature and pressure, and the purity does not affect subsequent processes;

[0010] Step 3: ketolysis of acetic acid or acetate, characterized in that acetone is prepared from pure acetic acid aqueous solution or acetate at a certain temperature and normal pressure based on a corresponding catalyst, a fixed bed reactor and supporting accessories;

[0011] Step 4: The process of preparing pure isopropanol by electro-reduction of acetone is characterized in that, based on the corresponding catalyst, bipolar membrane electrode reactor and supporting accessories, pure isopropanol is prepared from pure acetone without introducing other impurities.

[0012] Furthermore, the anion exchange membrane electrode reactor in step 1 is characterized in that it comprises a cathode membrane, an anion exchange membrane and an anode membrane which are laminated in sequence, and the structural schematic diagram is as shown in Figure 2 As shown;

[0013] The cathode film is composited with a catalyst, characterized in that it includes but is not limited to one or more materials selected from nickel single atom-nitrogen doped activated carbon, iron single atom-nitrogen doped activated carbon, cobalt phthalocyanine molecules, commercial nano zinc oxide, commercial nano gold powder, commercial nano silver powder, etc.;

[0014] The anion exchange membrane is characterized in that it includes one or more of Fumapem FAA-3-50, Sustainion X37-50 RT and Sustainion X37-FA;

[0015] The material of the anode film includes one or more of iridium oxide, ruthenium oxide, nickel foam, metal iridium / ruthenium and iron-nickel layered double metal hydroxide;

[0016] The membrane electrode solid electrolyte battery also includes a cathode housing having a groove and an anode housing having a groove;

[0017] The cathode shell with the groove and the anode shell with the groove are fitted and fixed to form a sealing structure;

[0018] A sealing gasket is provided between the edge of the cathode shell outside the groove and the edge of the anode shell outside the groove;

[0019] The cathode membrane is disposed in a groove of the cathode housing;

[0020] The cathode shell is provided with a carbon dioxide inlet and a carbon dioxide outlet;

[0021] The carbon dioxide outlet is connected to an absorption bottle filled with one or more of potassium hydroxide, sodium hydroxide, lithium hydroxide, and ammonium hydroxide solutions to absorb the incompletely converted carbon dioxide;

[0022] The anode membrane is disposed in a groove of the anode housing;

[0023] The anode shell is provided with an anolyte inlet and an anolyte outlet;

[0024] The anolyte includes one or more of sulfuric acid solution, perchloric acid solution, phosphoric acid, sodium hydroxide and potassium hydroxide.

[0025] Furthermore, the preparation condition parameters of step 1 are: a carbon dioxide flow rate of 5 to 100 standard cubic centimeters per minute, a catalyst loading on the electrode of 0.5 to 2 milligrams per square centimeter, a reactor applied voltage of 1.8 to 3.0 volts, and an anode electrolyte flow rate of 30 to 600 milliliters per hour.

[0026] Preferably, the carbon dioxide flow rate is 40 to 60 standard cubic centimeters per minute, the catalyst loading on the electrode is 0.8 to 1.2 milligrams per square centimeter, the reactor applied voltage is 2.4 to 2.6 volts, and the anolyte flow rate is 50 to 100 milliliters per hour.

[0027] Furthermore, the solid electrolyte membrane electrode reactor in step 2 is characterized in that it comprises a cathode membrane, an anion exchange membrane and an anode membrane which are laminated in sequence, and the structural schematic diagram is as shown in Figure 3 As shown:

[0028] including a cathode membrane;

[0029] an anion exchange membrane attached to the cathode membrane;

[0030] A solid electrolyte layer attached to the anion exchange membrane;

[0031] a cation exchange membrane attached to the solid electrolyte layer;

[0032] An anode membrane is attached to the cation exchange membrane.

[0033] Preferably, the use for carbon monoxide electroreduction includes using carbon monoxide electroreduction to prepare liquid acetic acid aqueous solution;

[0034] The cathode film comprises a composite catalyst, including but not limited to one or more of copper gel, copper gel doped with heterogeneous metal atoms, copper nanocubes, copper nanosheets, copper nanowires, copper multilayer spherical shells, carbon materials modified with copper particles, commercial nano copper powder and the like;

[0035] The material of the anion exchange membrane includes one or more of Fumapem FAA-3-50, Sustainion X37-50 RT and Sustainion X37-FA;

[0036] The material of the solid electrolyte layer includes styrene-divinylbenzene copolymer, Cs x H 3−x PW 12 O 40 , ceramics and 10 wt.% H3PO4 / polyvinyl pyrrolidone gel one or more;

[0037] The material of the cation exchange membrane includes one or more of Nafion 115, Nafion 117, Nafion N212 and Nafion 1110;

[0038] The material of the anode film includes one or more of iridium oxide, ruthenium oxide, nickel foam, metal iridium / ruthenium and iron-nickel layered double metal hydroxide;

[0039] The membrane electrode solid electrolyte battery also includes a cathode housing with a groove, a solid electrolyte layer frame and an anode housing with a groove;

[0040] The cathode shell with the groove, the solid electrolyte layer frame and the anode shell with the groove are fitted and fixed to form a sealing structure;

[0041] A sealing gasket is provided between the edge of the cathode housing other than the groove and the frame of the solid electrolyte layer;

[0042] A sealing gasket is provided between the frame of the solid electrolyte layer and the edge of the anode shell other than the groove;

[0043] The cathode membrane is disposed in a groove of the cathode housing;

[0044] The cathode shell is provided with a carbon dioxide inlet and a carbon dioxide outlet;

[0045] The solid electrolyte layer frame is provided with an air inlet and / or a water inlet, and an outlet for formic acid and / or formic acid aqueous solution;

[0046] The anode membrane is disposed in a groove of the anode housing;

[0047] The anode shell is provided with an anolyte inlet and an anolyte outlet;

[0048] The anolyte includes one or more of sulfuric acid solution, perchloric acid solution, phosphoric acid, sodium hydroxide and potassium hydroxide.

[0049] Further, the preparation condition parameters in step 2 are: a carbon monoxide flow rate of 5 to 100 standard cubic centimeters per minute, a catalyst loading on the electrode of 0.5 to 2 milligrams per square centimeter, a reactor voltage of 2.0 to 3.0 volts, a deionized water flow rate of 10 to 60 milliliters per hour for carrying out acetic acid, and an anolyte flow rate of 30 to 600 milliliters per hour;

[0050] Preferably, the carbon monoxide flow rate is 40-60 standard cubic centimeters per minute, the catalyst loading on the electrode is 0.8-1.2 milligrams per square centimeter, the voltage applied to the reactor is 2.7-2.8 volts, the deionized water flow rate carrying out acetic acid is 40-50 milliliters per hour, and the anolyte flow rate is 50-100 milliliters per hour.

[0051] Furthermore, the fixed bed reactor for acetic acid ketolysis described in step 3 includes a feed inlet, a catalyst chamber, a gas outlet and a cold trap, and the schematic diagram of the structure is shown in Figure 4 As shown;

[0052] The ketolysis of acetic acid converts acetic acid into acetone and carbon dioxide at a reaction temperature of 280-350° C., preferably 290-310° C.;

[0053] One or more of argon, nitrogen and helium are introduced into the feed port as carrier gas, and the carrier gas passes through the acetic acid aqueous solution to pass the acetic acid vapor into the catalytic chamber; the carrier gas flow rate is 5 to 30 standard cubic centimeters per minute, preferably 10 to 20 standard cubic centimeters per minute; the mass concentration of the acetic acid aqueous solution is 500 to 3000 ppm, preferably 1500 to 2500 ppm;

[0054] The catalyst bin is filled with catalyst, and the catalyst includes but is not limited to one or more materials selected from commercial nano cerium oxide, commercial nano zirconium oxide, commercial nano aluminum oxide, commercial nano titanium oxide, etc.; the catalyst loading amount is 0.1-0.6 g, preferably 0.2-0.4 g;

[0055] The gas outlet is connected to a cold trap, and an alkaline drying tube is provided in front of the cold trap to absorb the generated carbon dioxide and residual acetic acid vapor. The filling material in the drying tube includes but is not limited to one or more of potassium hydroxide, sodium hydroxide, and lithium hydroxide powder. The absorbed carbon dioxide is recovered and processed together with the carbon dioxide absorbed in step 1;

[0056] The cold trap is used for recovering acetone liquid.

[0057] Furthermore, the bipolar membrane electrode reactor in step 4 includes a cathode membrane, a bipolar membrane and an anode membrane which are sequentially attached, and the schematic diagram of the structure is as follows: Figure 5 As shown;

[0058] The acetone electro-reduction comprises electro-reducing liquid pure acetone to prepare liquid pure isopropanol;

[0059] The cathode film is compounded with a catalyst, including but not limited to one or more of commercial nano-ruthenium powder, commercial nano-ruthenium oxide, lattice-stretched ruthenium catalyst, ruthenium-modified carbon material, etc.;

[0060] The material of the bipolar membrane includes one or more of Fumasep FBM-PK, Aquivion-870-Durion-LMW, Dyneon-725-Durion-LMW and Nafion-1000-Durion-LMW.

[0061] Furthermore, the catalytic material of the anode membrane includes one or more of iridium oxide, ruthenium oxide, nickel foam, metallic iridium, metallic ruthenium and iron-nickel layered double metal hydroxide.

[0062] Furthermore, the membrane electrode assembly also includes a cathode shell with a groove and an anode shell with a groove, and the cathode shell and the anode shell are fitted together to form a sealing structure; the cathode shell is provided with a cathode electrolyte inlet and a cathode electrolyte outlet, and the cathode membrane is arranged in the groove of the cathode shell; the anode shell is provided with an anode electrolyte inlet and an anode electrolyte outlet, and the anode membrane is arranged in the groove of the anode shell.

[0063] Furthermore, a sealing gasket is provided between the edge of the cathode housing outside the groove and the edge of the anode housing outside the groove.

[0064] Furthermore, the cathode electrolyte is acetone, and the acetone is cyclically electrolyzed in the cathode housing to produce pure isopropanol.

[0065] Furthermore, the anolyte includes one or more of a lithium hydroxide solution, a sodium hydroxide solution and a potassium hydroxide solution.

[0066] Further, the preparation condition parameters are: an acetone flow rate of 30 to 90 milliliters per hour, a catalyst loading on the electrode of 0.5 to 2 milligrams per square centimeter, a reactor applied voltage of 2.0 to 6.0 volts, and an anolyte flow rate of 30 to 90 milliliters per hour;

[0067] Preferably, the acetone flow rate is 50-70 ml per hour, the catalyst loading on the electrode is 0.8-1.2 mg per square centimeter, the voltage applied to the reactor is 3.5-4.5 volts, and the anolyte flow rate is 40-60 ml per hour. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] Figure 1 Schematic diagram of the synthesis route for pure isopropanol from carbon dioxide;

[0069] Figure 2 A schematic diagram of the reactor structure for the process of electroreduction of carbon dioxide to produce carbon monoxide;

[0070] Figure 3 Schematic diagram of the reactor structure for preparing pure acetic acid aqueous solution for carbon monoxide electroreduction;

[0071] Figure 4 Schematic diagram of the reactor configuration for preparing acetone by ketonization of acetic acid or acetate;

[0072] Figure 5 Schematic diagram of the reactor structure for the electroreduction of acetone to produce pure isopropanol;

[0073] Figure 6 Faradaic efficiency of carbon monoxide and hydrogen at different potentials for the electroreduction of carbon dioxide to carbon monoxide;

[0074] Figure 7 The partial current of carbon monoxide at different potentials in the preparation of carbon monoxide for the electroreduction of carbon dioxide;

[0075] Figure 8 Faradaic efficiency of pure acetic acid at different potentials in aqueous solution for the electroreduction of carbon monoxide to pure acetic acid;

[0076] Fig. 9 The partial current of pure acetic acid and the mass fraction of pure acetic acid aqueous solution at different potentials in the preparation of pure acetic acid aqueous solution by electroreduction of carbon monoxide;

[0077] Fig.10 The figure shows the comparison of the hydrogen nuclear magnetic resonance spectra of the final isopropanol and the commercially available isopropanol. DETAILED DESCRIPTION

[0078] In order to further illustrate the present invention, a synthetic route design for preparing pure isopropanol from carbon dioxide provided by the present invention is described in detail below in conjunction with examples. However, it should be understood that these examples are implemented on the premise of the technical scheme of the present invention, and detailed implementation methods and specific operation processes are given only to further illustrate the features and advantages of the present invention, rather than to limit the claims of the present invention, and the protection scope of the present invention is not limited to the following examples. Example 1

[0079] The process of producing carbon monoxide by electroreduction of carbon dioxide:

[0080] I. Synthesis of Ni Single Atom-Nitrogen Doped Activated Carbon Nanocatalyst:

[0081] (1) Dissolve commercial carbon black in nitric acid at room temperature with stirring. The mass of carbon black is 1.95 g. The concentration of nitric acid is 9 mol / L and the volume is 100 mL. Ultrasonic treatment is performed for 5 min to evenly disperse the carbon black in the nitric acid solution. The mixed solution is placed in a flask for condensation reflux. The reflux temperature is 80°C and the reaction time is 3 h. The mixture is then cooled to room temperature. The solid material cooled to room temperature is centrifuged at a speed of 9000 rpm for 5 min. The product obtained by centrifugation is ultrasonically washed with a polar solvent for 3 min. The product is then centrifuged at a speed of 9000 rpm for 3 min. The product obtained by centrifugation is ultrasonically washed with a polar solvent for 2 min. The product is vacuum dried at 65°C overnight to obtain activated carbon black.

[0082] (2) The activated carbon black was evenly dispersed in a deionized water solution to obtain a mixed solution A, the mass of the carbon black was 1000 mg, and the volume of the deionized water was 400 mL; nickel nitrate solution was added to the mixed solution A under stirring at room temperature and stirred vigorously to obtain a mixed solution B; the concentration of the nickel nitrate solution was 3.0 mg / mL, the volume of the nickel nitrate solution was 40 mL, and the addition rate was about 15 mL / h by manual slow dripping. The mixed solution B was stirred at room temperature for 8 h, and the stirred material was centrifuged at a speed of 8000 rpm for 5 min. The product obtained by centrifugation was ultrasonically washed with a polar solvent for 1 min, and then continued to be centrifuged at a speed of 8000 rpm for 5 min. The product obtained by centrifugation was ultrasonically washed with a polar solvent for 1 min, and then continued to be centrifuged at a speed of 8000 rpm for 5 min. The product obtained by centrifugation was ultrasonically washed with a polar solvent for 1 min, and then vacuum dried to obtain Ni 2 + -Carbon black powder, Ni 2+-Carbon black powder and urea were uniformly mixed in a mass ratio of 1:10, and the mixed sample was placed in a crucible and put into a tube furnace for high-temperature sintering. The sintering atmosphere was argon with a flow rate of 100 sccm, the sintering temperature was 300°C, and the sintering reaction time was 1 h, thereby obtaining Ni single atom-nitrogen doped activated carbon nanocatalyst.

[0083] According to detection, the mass fraction of nickel in the nickel single atom-nitrogen doped activated carbon nanocatalyst obtained in this example is 1.0 wt.%.

[0084] II. Electrocatalytic reduction of carbon dioxide to carbon monoxide over nickel single atom-nitrogen doped activated carbon nanocatalysts: Reference Figure 2 As shown, a carbon gas diffusion layer loaded with nickel single atom-nitrogen doped activated carbon nanocatalyst is used as the cathode, and the catalyst loading on the electrode is 1 mg per square centimeter. In the membrane electrode assembly reactor, an anion exchange membrane is closely attached to the catalyst surface; iridium oxide loaded on carbon paper is used as the anode, which is closely attached to the other side of the anion exchange membrane. Silicone gaskets are added on both sides to ensure sealing, and titanium plates are added as current collectors. The carbon dioxide electroreduction performance test is carried out in the membrane electrode assembly using pure carbon dioxide as the raw gas. During the test, the carbon dioxide flow rate is maintained at 50 sccm, and the anode potassium hydroxide electrolyte flow rate is maintained at 60 mL / h. The test adopts a constant potential method. The reaction gas phase products are detected by gas chromatography, and the liquid phase products are detected by nuclear magnetic resonance hydrogen spectrum. The coulomb amount corresponding to the product concentration is calculated, and the catalytic selectivity, activity and other data are obtained based on the total coulomb amount recorded by the electrochemical workstation. The Faraday efficiency of each product at different potentials is shown in the following figure. Figure 6 As shown, the carbon dioxide bias current measured at different potentials is as follows Figure 7 shown. Example 2

[0085] Process for preparing pure acetic acid by electroreduction of carbon monoxide:

[0086] I. Synthesis of copper gel nanocatalyst: 500 mg of hydrated cupric chloride and 120 mg of lead nitrate were dissolved in 3 ml of isopropanol at room temperature. After the solid was completely dissolved, 3 ml of propylene oxide was added to the mixture for ultrasonic dispersion. Then 0.3 ml of deionized water was added to the mixture for dispersion and then aged at room temperature for 12 h. After aging, the supernatant was removed and the solid product was vacuum dried at 80 °C for 12 h.

[0087] II. Electrocatalytic reduction of carbon monoxide to pure acetic acid using copper gel nanocatalysts: Reference Figure 3As shown, a carbon gas diffusion layer loaded with a copper gel nanocatalyst is used as a working electrode, the catalyst loading on the electrode is 1 mg / cm2, and the gas flow rate is 50 standard cubic centimeters per minute. In a membrane electrode solid electrolyte battery, a carbon gas diffusion layer loaded with the above copper-based single-atom alloy catalyst is used as a working electrode, and an anion exchange membrane is closely attached to the catalyst surface; iridium oxide is used as a counter electrode, and a cation exchange membrane is closely attached to the counter electrode surface, and a solid electrolyte is filled between the anion exchange membrane and the cation exchange membrane for electrical conduction. The principle of the device is: when carbon monoxide is reduced, the acetate anions generated at the cathode move to the middle solid electrolyte channel through the anion exchange membrane under the drive of the electric field. At the same time, the protons generated by water oxidation on the anode side can pass through the cation membrane to compensate for the charge. Since the solid electrolyte used is a proton conductor, the acetic acid product can be formed by ion recombination at the interface between the solid electrolyte and the anion membrane, and diffused out through liquid deionized water.

[0088] In the actual reaction, deionized water at a flow rate of 50 ml / h was introduced into the solid electrolyte layer to collect acetic acid generated during the carbon monoxide electroreduction process.

[0089] See also Figure 7 , Figure 7 The invention discloses the Faraday efficiency of acetic acid at different potentials in producing pure acetic acid by a membrane electrode solid electrolyte battery containing a copper gel nanocatalyst.

[0090] See also Figure 8 , Figure 8 The invention discloses the partial current of acetic acid at different potentials and the mass fraction of the obtained acetic acid aqueous solution when a membrane electrode solid electrolyte battery containing copper gel nanocatalyst produces pure acetic acid.

[0091] like Figure 7 and 8 As shown in the figure, the flow rate of deionized water into the solid electrolyte during the reaction was 50 ml / h, and the selectivity of pure acetic acid remained above 40% when the total current exceeded 200 mA. The concentration of acetic acid collected at a current of 250 mA exceeded 2500 ppm. Example 3

[0092] Process for preparing acetone by ketolysis of acetic acid:

[0093] Reference Figure 40.2 g of commercial cerium oxide catalyst was ground and pressed into tablets, which were loaded into a fixed bed reactor for ketonization reaction at 300 °C. Ar was used as a carrier gas at a flow rate of 20 sccm. through a container filled with 2000 ppm acetic acid aqueous solution, bringing acetic acid vapor into the reactor, while taking acetone vapor and by-product carbon dioxide out of the reactor. A basic drying tube was connected to the tail to absorb carbon dioxide, water vapor and incompletely converted acetic acid. The liquid was collected in a cold trap and quantified by hydrogen nuclear magnetic resonance spectroscopy. Example 4

[0094] Process for preparing pure isopropanol by electroreduction of acetone:

[0095] I. Preparation of lattice stretched ruthenium metal nanocatalysts:

[0096] Step 1: Add 70 mg of ruthenium dioxide and 5 mL of n-hexane into a three-necked flask at room temperature, and reflux at 65 °C for 1 h under nitrogen protection to obtain a mixed solution;

[0097] Step 2: Add 4 mL of 2 mol / L n-butyl lithium in n-hexane solution to the mixed solution obtained in step 1, reflux at 65°C for 2 h, wash twice with n-hexane, wash twice with anhydrous ethanol, take the precipitate, and obtain a lithium-intercalated ruthenium precursor;

[0098] Step 3: Mix the lithium-intercalated ruthenium precursor obtained in step 2 with 50 mL of deionized water at room temperature, perform ultrasonic treatment at room temperature for 1 hour under nitrogen protection, centrifuge, remove the supernatant, wash with deionized water 3 times, and dry in a vacuum oven at 30°C for 12 h to obtain a lattice-stretched ruthenium metal nanocatalyst.

[0099] II. Electroreduction of acetone to pure isopropanol over lattice-stretched ruthenium metal nanocatalysts:

[0100] Reference Figure 5 , the acetone electrocatalytic reduction was carried out, the catalyst loading on the electrode was 1 mg / cm2, acetone was used as the cathode electrolyte, 1 mol / L potassium hydroxide solution was used as the anode electrolyte, and the electrolyte circulation flow rate was maintained at 60 mL / h during the test; the constant potential method was used for the test, and the added full cell potential was -4 V. The liquid phase product was micro-sampled and detected by nuclear magnetic resonance hydrogen spectrum. Fig.10 As shown, the purity of the obtained isopropanol is comparable to that of commercially available isopropanol (99.7 wt.%). According to the ratio of the peak areas in the hydrogen nuclear magnetic resonance spectrum and the purity of commercially available isopropanol, the purity of the obtained isopropanol can be calculated to be 99 wt.%.

[0101] The above is a detailed introduction to the synthetic route design for preparing pure isopropanol from carbon dioxide provided by the present invention. The principle and implementation mode of the present invention are described in detail using specific examples herein. The description of the above embodiments is only used to help understand the method and core idea of ​​the present invention, including the best mode, and also enables any technician in the field to practice the present invention, including manufacturing and using any device or system, and implementing any combined method. It should be pointed out that for ordinary technicians in the technical field, without departing from the principle of the present invention, the present invention can also be improved and modified in several ways, and these improvements and modifications also fall within the scope of protection of the claims of the present invention. The scope of patent protection of the present invention is defined by the claims, and may include other embodiments that can be thought of by those skilled in the art. If these other embodiments have structural elements that are not different from the textual expression of the claims, or if they include equivalent structural elements that are not substantially different from the textual expression of the claims, then these other embodiments should also be included in the scope of the claims.

Claims

1. A method for preparing pure isopropanol from carbon dioxide, characterized in that: The preparation of pure isopropanol is achieved by using carbon dioxide and water as raw materials. The preparation process includes four steps: electro-reduction of carbon dioxide to carbon monoxide, electro-reduction of carbon monoxide to prepare pure acetic acid aqueous solution or acetate, ketonization of acetic acid to prepare acetone, and electro-reduction of acetone to prepare pure isopropanol. Step 1: Carbon dioxide electroreduction is achieved by using an anion exchange membrane electrode reactor and its accessories, as well as the corresponding catalyst, at the cathode, under normal temperature and pressure conditions, with a carbon dioxide flow rate of 5 to 100 standard cubic centimeters per minute, a catalyst loading of 0.5 to 2 milligrams per square centimeter, a reactor voltage of 1.8 to 3.0 volts, an anolyte flow rate of 30 to 600 milliliters per hour, and purity that does not affect subsequent processes; Step 2, carbon monoxide electroreduction is achieved by solid electrolyte membrane electrode reactor and supporting accessories, as well as the corresponding catalyst, to achieve efficient preparation of pure acetic acid aqueous solution at room temperature and pressure. During the reaction, the carbon monoxide flow rate is 5-100 standard cubic centimeters per minute, the catalyst loading on the electrode is 0.5-2 milligrams per square centimeter, the reactor voltage is 2.0-3.0 volts, the deionized water flow rate of acetic acid is 10-60 milliliters per hour, the anolyte flow rate is 30-600 milliliters per hour, and the purity does not affect the subsequent process; Step 3, acetic acid ketonization to prepare acetone, through a fixed bed reactor and supporting accessories, and the corresponding catalyst, at 300 degrees Celsius, atmospheric pressure to achieve the preparation of acetone from pure acetic acid aqueous solution or acetate, the amount of catalyst used in the reaction is 0.1 to 0.6 grams, loaded in a fixed bed reactor, the reaction temperature is 280 to 350 degrees Celsius, the carrier gas flow rate is 5 to 30 standard cubic centimeters per minute, and the mass concentration of the acetic acid aqueous solution through which the carrier gas passes is 500 to 3000 ppm; Step 4: Acetone electroreduction is achieved by using a bipolar membrane electrode reactor and supporting accessories, as well as corresponding catalysts, to prepare pure isopropanol from pure acetone without introducing other impurities. During the reaction, the acetone flow rate is 30-90 ml per hour, the catalyst loading on the electrode is 0.5-2 mg per square centimeter, the reactor applied voltage is 2.0-6.0 volts, and the anolyte flow rate is 30-90 ml per hour.

2. A method for preparing pure isopropanol from carbon dioxide according to claim 1, characterized in that: The catalyst of step 1 includes, but is not limited to, one or more of nickel single atom-nitrogen doped activated carbon, nickel single atom-nitrogen doped activated carbon, cobalt phthalocyanine molecules, commercial nano zinc oxide, commercial nano gold powder, and commercial nano silver powder.

3. A method for preparing pure isopropanol from carbon dioxide according to claim 1, characterized in that: The catalyst of step 2 includes, but is not limited to, one or more of copper gel, copper gel doped with heterogeneous metal atoms, copper nanocubes, copper nanosheets, copper nanowires, copper multilayer spherical shells, carbon materials modified with copper particles, and commercial nano copper powder.

4. A method for preparing pure isopropanol from carbon dioxide according to claim 1, characterized in that: The catalyst in step three includes, but is not limited to, one or more of commercial nano-cerium oxide, commercial nano-zirconium oxide, commercial nano-aluminum oxide, and commercial nano-titanium oxide.

5. A method for preparing pure isopropanol from carbon dioxide according to claim 1, characterized in that: As a part of the route of producing pure isopropanol from carbon dioxide, the catalyst of step four includes but is not limited to one or more of commercial nano-ruthenium powder, commercial nano-ruthenium oxide, lattice-stretched ruthenium catalyst, ruthenium-modified carbon material and the like.

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