CN107011150B

CN107011150B - Method for preparing gluconic acid/gluconate and hydrogen by catalytic dehydrogenation of glucose under mild condition

Info

Publication number: CN107011150B
Application number: CN201710316481.0A
Authority: CN
Inventors: 梁长海; 刘佳鑫; 李闯
Original assignee: Dalian University of Technology
Current assignee: Dalian University of Technology
Priority date: 2017-05-08
Filing date: 2017-05-08
Publication date: 2020-09-11
Anticipated expiration: 2037-05-08
Also published as: CN107011150A

Abstract

The invention discloses a method for preparing gluconic acid/gluconate and hydrogen by catalytic dehydrogenation of glucose under mild conditions, and belongs to the technical field of biomass catalytic conversion. The invention provides a new way for preparing high value-added chemicals by catalytic dehydrogenation and oxidation of glucose, which takes a supported metal catalyst as a catalyst and directly converts the glucose into gluconic acid/salt and hydrogen through catalytic dehydrogenation and oxidation at room temperature and normal pressure. The yield of the hydrogen prepared by the method can reach more than 89mo 1%. The reaction condition is mild, oxidant, light and electricity are not needed, and high temperature and high pressure conditions are not needed. The catalyst has excellent catalytic performance, long service life, high economic benefit and wide industrial application foreground.

Description

Method for preparing gluconic acid/gluconate and hydrogen by catalytic dehydrogenation of glucose under mild condition

Technical Field

The invention belongs to the technical field of biomass catalytic conversion, and relates to a novel method for preparing gluconic acid/salt and hydrogen by using glucose as a raw material.

Background

With the increasing exhaustion of fossil energy and the aggravation of greenhouse effect, the exploration and development of the utilization of renewable energy sources are imminent. In the exploration of a plurality of unconventional energy sources, the conversion of biomass can not only relieve the bottleneck caused by the shortage of fossil energy sources, but also alleviate the environmental problems caused by fossil resources. The development, conversion and utilization of biomass energy has been the subject of a great deal of research over the last decade. Glucose is a representative basic structural unit and model compound of biomass, and is an important monosaccharide substance which is distributed most widely in nature. Glucose is used as a research object to research the transformation mechanism and characteristics of the glucose, and has great significance on the utilization of biomass resources. The conversion of glucose into high value-added products through the dehydrogenation oxidation path of the glucose has very important practical significance.

The gluconic acid/salt is used in the field of medicine and has the function of regulating the acid-base balance of the body. The corrosion inhibitor is used for food additives, water quality stabilizers and the like, has the function of coordination effect, is suitable for phosphorus, silicon, tungsten, nitrite and other components, has obvious corrosion inhibition effect, and the corrosion inhibition rate of the corrosion inhibitor is increased along with the rise of temperature. Gluconic acid/salt has strong complexing ability to calcium, magnesium and iron salt and to Fe³⁺Has good chelating effect. The sodium gluconate is used as the corrosion and scale inhibitor of the circulating cooling water, has obvious effect and has the advantage of no pollution. Based on the advantages, the gluconic acid/salt is used for the glass bottle cleaning agent, and can obviously improve the problems that the conventional cleaning agent has weak detergency, trace residual phosphate and the like are harmful to edible safety, washing water is polluted, and the like. Hydrogen is an ideal energy source in the future, and has the following characteristics: (1) the mass energy density of hydrogen is high. The mass energy density of hydrogen is the highest of all fuels, except nuclear fuels. (2) Hydrogen is the cleanest energy source. the product of the combustion process is only water, and there is no greenhouse gas, nitrogen oxide gas, etc. discharged when the fossil energy such as coal is burnt. (3) The storability of hydrogen is better, compares traditional electric energy and heat energy, and hydrogen can store on a large scale. Because the hydrogen has the advantages, the reasonable preparation of the hydrogen as an energy source becomes one of the research hotspots at home and abroad. Aiming at the problem of producing high value-added chemicals by catalytic conversion of glucose, a nano noble metal catalyst is successfully developed for the dehydrogenation and oxidation reaction of glucose, and two high value-added products are generated under the conditions of normal temperature and normal pressure: gluconic acid/salt and hydrogen. Wherein, the gluconic acid/salt is a liquid phase product, and the hydrogen is a gas phase product, which can be directly separated, thereby avoiding the energy consumption of separation.

The methods for producing high value-added chemicals by converting glucose have some defects:

chinese patent, publication No.: CN103570772A introduces a method for preparing high value-added chemicals by glucose photocatalysis. Namely rutile phase TiO loaded with noble metal₂Is a photocatalyst, and glucose is directly converted into arabinose, erythrose and hydrogen by a photocatalytic dehydrogenation oxidation way at room temperature. The product contains by-product formic acidSeparated and the main product yield is low.

Chinese patent, publication No.: CN102971074A, which describes a method for producing glucaric acid by catalyzing glucose with a platinum-gold bimetallic catalyst. A platinum-gold bimetallic catalyst prepared using an impregnation process converts glucose to glucaric acid at high temperature and pressure. The reaction conditions are harsh, and the product selectivity is low.

Chinese patent, publication No.: CN106337067A introduces a method for producing sodium gluconate by enzymatic fermentation. This patent is an oxidation of glucose to gluconic acid/salt under mild conditions with catalase and glucose oxidase as catalysts. But has the problems that the separation of the product and the catalyst is difficult, a large amount of waste water is generated after the reaction, and the environment is polluted.

Chinese patent, publication No.: CN103436910A introduces an electrocatalyst for oxidation of glucose and a preparation method thereof. Preparing pure phase Cu₄V_2.15O_9.38Has excellent electrocatalytic performance of glucose oxidation. But the energy consumption is large and the process is complicated.

Chinese patent, publication No.: CN102259024A, discloses a nano-gold catalyst for glucose oxidation and a preparation method and a use method thereof. The patent uses a nano gold catalyst to generate sodium gluconate under the conditions of 60 ℃, pH 9.5 and oxygen flow 39 mL/min. The problems of single product and serious oxygen waste exist.

Disclosure of Invention

The invention discloses a method for preparing a high value-added chemical by dehydrogenating and oxidizing glucose, belonging to the technical field of biomass catalytic conversion. The invention aims to provide a new way for generating high value-added chemicals by catalyzing glucose, namely, glucose is dehydrogenated and oxidized to generate equimolar gluconic acid/salt and hydrogen.

The technical scheme of the invention is as follows:

a method for preparing gluconic acid/gluconate and hydrogen by catalytic dehydrogenation of glucose under mild conditions comprises the following steps:

under the conditions of no oxygen and alkalinity, the supported metal catalyst reacts in water-alcohol solvent at normal temperature and pressure, and glucose is converted into gluconic acid/salt and hydrogen with equal molar quantity through dehydrogenation and oxidation.

The water-alcohol solvent is water-methanol, water-ethanol, water-propanol or water-butanol solution, wherein the volume fraction of the alcohol is 20-95%;

the concentration of the glucose is 1-20 wt%;

the molar ratio of the supported metal catalyst to the glucose is 0.01-0.2.

The anaerobic condition is a vacuum pumping method or inert gas is used for removing air in the reactor, and the inert gas is nitrogen, helium or argon.

The alkaline condition is that alkali metal hydroxide or alkaline earth metal hydroxide is added into the solution to control the pH of the solution to be 13 or solid alkali carrier is used to provide alkaline site required by reaction.

The supported metal catalyst is one or two metal alloys of platinum and iridium, and the metal supporting amount is 1.0-10.0 wt% of the carrier.

The preparation steps of the supported metal catalyst are as follows:

adding the carrier into a noble metal precursor solution, reducing the noble metal by adopting a reducing agent, and carrying out aftertreatment: comprises solid-liquid separation, washing with deionized water until no Cl is formed^-Drying and roasting the solid matter; the drying temperature is 60-200 ℃, and the drying time is 0.5-100 hours; the roasting temperature is 200 ℃ and 700 ℃; the roasting time is 3-20 hours; the roasting of the catalyst is performed in a muffle furnace or a tubular furnace, the roasting atmosphere is selected from nitrogen, helium, hydrogen, air or oxygen, and the gas flow is 10 mL/min-80 mL/min.

The noble metal precursor is one or the mixture of more than two of noble metal nitrate, chloride, acetate and hydrochloride.

The support refers to carbon supports such as activated carbon, graphene and carbon nanotubes or metal oxides such as cerium oxide and magnesium oxide.

The reducing agent is one or a mixture of more than two of urea, glycol, sodium borohydride and hydrazine hydrate.

The invention has the beneficial effects that:

1. the method takes glucose as a raw material to prepare the gluconic acid/salt and the hydrogen with high added values, has high atom utilization rate, can directly separate products to avoid separation energy consumption, and is different from the current path of conversion from glucose in documents.

2. The reaction conditions in the invention are room temperature and normal pressure, no oxidant is needed, and light or electricity is introduced.

3. The supported metal catalyst which is easy to separate is used, so that the pollution to products is avoided and the product can be recycled.

Detailed Description

To further illustrate the present invention, the following examples are set forth without limiting the scope of the invention as defined by the various appended claims.

Example 1: dissolving chloroplatinic acid and urea in an aqueous solution, wherein the concentration of the chloroplatinic acid is 0.4g/L and the concentration of the urea is 0.08mol/L, adjusting the pH value of the solution to be more than the isoelectric point of a carrier, adding carrier modified activated carbon into the solution, controlling the reaction temperature to be 95 ℃ and the reaction time to be 24 hours, and filtering and washing until the catalyst is free of Cl^-Drying at 100 ℃ for 12h, roasting at 400 ℃ for 2h in an argon atmosphere with the flow of 30mL/min argon, roasting at 300 ℃ for 2h in a hydrogen-argon mixed atmosphere with the flow of 20mL/min argon and the flow of 10mL/min hydrogen to form Pt/AC, wherein the Pt loading is 4%.

Example 2: dissolving chloroplatinic acid and urea in an aqueous solution, wherein the concentration of the chloroplatinic acid is 0.4g/L, the concentration of the urea is 0.08mol/L, adjusting the pH value of the solution to be more than the isoelectric point of a carrier, adding the carrier graphene oxide into the solution, controlling the reaction temperature to be 95 ℃, reacting for 24 hours, filtering and washing until the catalyst is free of Cl^-Drying at 100 ℃ for 12h, roasting at 400 ℃ for 2h in an argon atmosphere with the flow of 30mL/min argon, roasting at 300 ℃ for 2h in a hydrogen-argon mixed atmosphere with the flow of 20mL/min argon and the flow of 10mL/min hydrogen to form Pt/Gr, wherein the Pt loading is 4%.

Example 3: dissolving chloroplatinic acid and urea in water solution, the concentration of chloroplatinic acid is 0.4g/L and the concentration of urea is 0.08mol/L, regulating the pH value of the solution to be more than the isoelectric point of a carrier, adding the carrier modified carbon nano tube into the solution, controlling the reaction temperature to be 95 ℃, and reactingThe time is 24 hours, and the catalyst is filtered and washed until no Cl exists^-Drying at 100 ℃ for 12h, roasting at 400 ℃ for 2h in an argon atmosphere with the flow of 30mL/min argon, roasting at 300 ℃ for 2h in a hydrogen-argon mixed atmosphere with the flow of 20mL/min argon and the flow of 10mL/min hydrogen to form Pt/CNTs with the Pt loading of 4%.

Example 4: dissolving chloroplatinic acid and urea in an aqueous solution, wherein the concentration of the chloroplatinic acid is 0.4g/L and the concentration of the urea is 0.08mol/L, adjusting the pH value of the solution to be more than the isoelectric point of a carrier, adding the carrier cerium oxide into the solution, controlling the reaction temperature to be 95 ℃, reacting for 24 hours, filtering and washing until the catalyst is free of Cl^-Drying at 100 ℃ for 12h, roasting at 400 ℃ for 2h in an argon atmosphere with the argon flow rate of 30mL/min, roasting at 300 ℃ for 2h in a hydrogen-argon mixed atmosphere with the argon flow rate of 20mL/min and the hydrogen flow rate of 10mL/min to form Pt/CeO₂The Pt loading was 4%.

Example 5: dissolving chloroplatinic acid and urea in an aqueous solution, wherein the concentration of the chloroplatinic acid is 0.4g/L and the concentration of the urea is 0.08mol/L, adjusting the pH value of the solution to be more than the isoelectric point of a carrier, adding the carrier magnesium oxide into the solution, controlling the reaction temperature to be 95 ℃, reacting for 24 hours, filtering and washing until the catalyst is free of Cl^-Drying at 100 ℃ for 12h, roasting at 400 ℃ for 2h in an argon atmosphere with the flow of 30mL/min argon, roasting at 300 ℃ for 2h in a hydrogen-argon mixed atmosphere with the flow of 20mL/min argon and the flow of 10mL/min hydrogen to form Pt/MgO, wherein the Pt loading is 4%.

Example 6: dissolving chloroiridic acid and urea in an aqueous solution, wherein the concentration of chloroiridic acid is 0.4g/L, the concentration of urea is 0.08mol/L, adjusting the pH value of the solution to be more than the isoelectric point of a carrier, adding the carrier modified carbon nano tube into the solution, controlling the reaction temperature to be 95 ℃ and the reaction time to be 24 hours, and filtering and washing until the catalyst is free of Cl^-Drying at 100 ℃ for 12h, roasting at 400 ℃ for 2h in an argon atmosphere, roasting at 300 ℃ for 2h in a hydrogen-argon mixed atmosphere, roasting at 20mL/min in an argon flow and 10mL/min in a hydrogen flow to form Ir/CNTs, wherein the Ir supporting capacity is 4%.

Example 7: dissolving chloroplatinic acid, chloroiridic acid and urea in an aqueous solution, wherein the concentration of the chloroplatinic acid is 0.2g/L, the concentration of the chloroiridic acid is 0.2g/L and the concentration of the urea is0.08mol/L, adjusting the pH value of the solution to be more than the isoelectric point of the carrier, adding the carrier modified carbon nano tube into the solution, controlling the reaction temperature to be 95 ℃ and the reaction time to be 24 hours, and filtering and washing until the catalyst is free of Cl^-Drying at 100 ℃ for 12h, roasting at 400 ℃ for 2h in an argon atmosphere with the flow of 30mL/min argon, roasting at 300 ℃ for 2h in a hydrogen-argon mixed atmosphere with the flow of 20mL/min argon and the flow of 10mL/min hydrogen to form Pt-Ir/CNTs with the Pt-Ir loading of 4%.

Example 8: the catalysts prepared in examples 1-5 were used to catalyze the dehydro-oxidation of aqueous glucose solution to examine the effect of different carriers on the yield of product hydrogen. Firstly, 0.4324g of glucose is dissolved in 40mL of water-ethanol solution, the volume fraction of water is 40%, 0.7405g of KOH is added, the gas in a reactor is replaced by Ar atmosphere, the reaction temperature is 30 ℃, the reaction pressure is normal pressure, and dehydrogenation oxidation catalysts are Pt/AC, Pt/Gr, Pt/CNTs and Pt/CeO₂And Pt/MgO, collecting the product gas, analyzing by using a gas chromatograph, wherein the detector is a thermal conductivity detector, the chromatographic column is TDX-01, the gas chromatograph shows the generation of hydrogen, and the reaction result is shown in Table 1.

Example 9: investigating the influence of the loading capacity on the yield of the product hydrogen, dissolving chloroplatinic acid and urea in an aqueous solution, wherein the concentration of the chloroplatinic acid is 0.1g/L, 0.2g/L, 0.3g/L, 0.4g/L, 0.5g/L, 0.6g/L, 0.7g/L, 0.8g/L, 0.9g/L,1.0g/L, the concentration of the urea is 0.08mol/L, adjusting the pH value of the solution to be more than the isoelectric point of a carrier, adding the carrier modified carbon nano tube into the solution, controlling the reaction temperature to be 95 ℃ and the reaction time to be 24h, and filtering and washing the solution until the catalyst has no Cl^-Drying at 100 ℃ for 12h, roasting at 400 ℃ for 2h in an argon atmosphere, roasting at 300 ℃ for 2h in a hydrogen-argon mixed atmosphere, roasting at 20mL/min in an argon flow and 10mL/min in a hydrogen flow to form the nano Pt catalyst, wherein the Pt loading is 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt% and 10 wt%. The particle size of Pt is 1.5nm-1.6 nm. The prepared nano Pt catalyst is used for the dehydrogenation oxidation reaction of glucose, firstly 0.4324g of glucose is dissolved in 40mL of water-ethanol solution, the volume fraction of water is 40%, 0.7405g of KOH is added, the gas in the reactor is replaced by Ar atmosphere, the reaction temperature is 30 ℃, and the reaction pressure isThe force was atmospheric, the product gas was collected and analyzed using gas chromatography, the detector was a thermal conductivity detector, the chromatographic column was TDX-01, the gas chromatography showed the production of hydrogen, and the reaction results are shown in table 2.

Example 10: the catalysts prepared in example 3, example 6 and example 7 were used for the catalytic dehydrogenation of aqueous glucose oxydation, examining the effect of different active components on the yield of hydrogen product. Firstly, 0.4324g of glucose is dissolved in 40mL of water-ethanol solution, the volume fraction of water is 40%, 0.7405g of KOH is added, the gas in the reactor is replaced by Ar atmosphere, the reaction temperature is 30 ℃, the reaction pressure is normal pressure, the product gas is collected and analyzed by gas chromatography, the detector is a thermal conductivity detector, a chromatographic column is TDX-01, the gas chromatography shows the generation of hydrogen, and the reaction result is shown in Table 3.

Example 11: evaluation of catalyst recycle. The 4 wt% nano Pt catalyst obtained in example 3 after 4h of reaction was centrifuged and vacuum dried for recovery. 0.4324g of glucose is dissolved in 40mL of water-ethanol solution, the volume fraction of water is 40%, 0.7405g of KOH is added, the gas in the reactor is replaced by Ar atmosphere, the reaction temperature is 30 ℃, the reaction pressure is normal pressure, the product gas is collected and analyzed by gas chromatography, the detector is a thermal conductivity detector, the chromatographic column is TDX-01, and the gas chromatography shows the generation of hydrogen. The catalyst was recycled 5 times and the reaction results are shown in table 4.

TABLE 1 Effect of different carriers on the yield of product Hydrogen

Carrier	Hydrogen yield (mol%)
		AC	81
Gr	87
		CNTs	89
CeO₂	84
		MgO	80

TABLE 2 Effect of loading on product Hydrogen yield

Carrying capacity (wt%)	Hydrogen yield (mol%)
		1	0.18
2	7.5
		3	39
4	68
		5	89
6	91
		7	92
8	92
		9	91
10	92

TABLE 3 influence of different active components on the yield of hydrogen

Active component	Hydrogen yield (mol%)
		Pt	89
Ir	21
		Pt-Ir	95

Table 4 catalyst stability testing

The method for catalytic conversion of glucose can be used for preparing gluconic acid/salt and hydrogen, the yield of the hydrogen can reach more than 89 mol%, and products are respectively gas and liquid which can be directly separated, so that the energy consumption for separation is avoided. The product gluconic acid/salt is an important intermediate of medicine and chemical raw materials, and hydrogen is an ideal clean energy source in the future. Compared with the prior art (selective oxidation, selective hydrogenolysis, dehydration reaction and the like), the method has the advantages of simple reaction process, mild reaction condition, no need of oxidant or light and electricity, and reaction at room temperature and normal pressure. The catalyst can be reused for many times.

Claims

1. A method for preparing gluconic acid/gluconate and hydrogen by catalytic dehydrogenation of glucose under mild conditions is characterized by comprising the following steps:

under the anaerobic and alkaline conditions, the supported metal catalyst reacts in a water-alcohol solvent at normal temperature and normal pressure, and glucose is converted into gluconic acid/salt and hydrogen with equal molar quantity through dehydrogenation and oxidation;

the concentration of the glucose is 1-20 wt%;

the molar ratio of the supported metal catalyst to the glucose is 0.01-0.2;

the alkaline condition is that alkali metal hydroxide or alkaline earth metal hydroxide is added into the solution to control the pH of the solution to be 13 or a solid alkali carrier is used for providing an alkaline site required by the reaction;

the supported metal catalyst is an alloy of two metals, namely platinum and iridium, and the metal supporting amount is 1.0-10.0 wt% of the carrier.

2. The method according to claim 1, wherein the water-alcohol solvent is a water-methanol, water-ethanol, water-propanol or water-butanol solution, wherein the volume fraction of the alcohol is 20-95%.

3. The method as claimed in claim 1 or 2, wherein the oxygen-free condition is a vacuum method or an inert gas excluding air in the reactor, and the inert gas is nitrogen, helium or argon.

4. The method of claim 3, wherein the supported metal catalyst is prepared by the steps of:

adding the carrier into a noble metal precursor solution, reducing the noble metal by adopting a reducing agent, and carrying out aftertreatment: solid-liquid separation, washing with deionized water until no Cl^-Drying and roasting the solid matter; the drying temperature is 60-200 ℃, and the drying time is 0.5-100 hours; the roasting temperature is 200 ℃ and 700 ℃; the roasting time is 3-20 hours.

5. The method of claim 4 wherein the noble metal precursor is one or a mixture of two or more of the nitrates, chlorides, acetates, and hydrochlorides of noble metals.

6. The method of claim 4 or 5, wherein the support is a carbon support.

7. The method according to claim 6, wherein the reducing agent is one or more of urea, ethylene glycol, sodium borohydride and hydrazine hydrate.

8. The method of claim 7, wherein the calcination process of the supported metal catalyst is performed in a muffle furnace or a tube furnace, the calcination atmosphere is selected from nitrogen, helium, hydrogen, air or oxygen, and the gas flow rate is 10mL/min to 80 mL/min.