CN104072335A - Method of cellulose catalytic conversion to prepare dihydric alcohol, hexahydric alcohol and gamma-valerolactone - Google Patents

Abstract

The invention relates to the preparation of chemicals by converting cellulose, which uses molecular sieves and metal or metal interstitial compounds as active components, coats metal or metal interstitial compounds in the pores of molecular sieves to prepare bifunctional catalysts, and uses the catalysts for maintenance A method for preparing dibasic alcohols, hexavalent alcohols and gamma-valerolactone by hydrodegrading conversion of ketones. The molecular sieve coated metal or interstitial compound catalyst prepared by the method has the characteristics of small metal or interstitial compound nano particle size, good dispersion, high catalyst activity and selectivity.

Description

A kind of method of catalytic conversion of cellulose to prepare glycol, hexahydric alcohol and gamma-valerolactone

technical field

The invention relates to the preparation of chemicals by converting cellulose, in particular to a method for preparing diols, hexaols and gamma-valerolactones by using molecular sieve-coated metals or metal interstitial compounds to catalyze cellulose hydrogenation degradation conversion.

Background technique

Cellulose is the most abundant biomass resource in nature, and its catalytic conversion to energy chemicals is the focus and focus of academic and industrial research. Glucose, sorbitol, ethylene glycol, synthesis gas, aromatic hydrocarbons, and furan compounds can be obtained by catalytic degradation of cellulose. The above compounds can be derived into more chemicals or commodities, which may become the basis of future chemistry, materials and fuels. Cellulose is polymerized by glucose molecules through β-1,4-glucosidic bonds to form a single chain of cellulose, and then forms a supramolecular stable structure through hydrogen bonds and van der Waals forces between the single chains. This structure makes the hydrolysis activity of cellulose extremely low and difficult to It is directly hydrolyzed to glucose, which is also difficult to be bioutilized.大量的专利报道了提高纤维素水解制葡萄糖效率的方法(CN101974161A、CN101638441B、CN102409113A、CN101733088A、CN101730751A、US4316747、US4316748、US4699124、US4935567、CN101362827A)及相关水解催化剂，如无机液体酸(CN102471694A、CN101525355A)、 Metal halides (CN102066304A), ionic liquids (CN101514375A, CN101402658B, CN102060642A, CN101798603A, CN101289817B), oxide solid acids (CN102417937A, CN102218306A, CN102218306A), etc. In 2005, Dumesic et al. first proposed the idea of using hydroxymethylfuran (HMF) as an intermediate to prepare liquid alkanes from carbohydrates, and (Science 2005, 308, 1446-1450) research on the use of cellulose conversion to prepare chemicals has gradually emerged.将纤维素水解及水解产物转化反应耦合制备糖醇(CN100513371C、CN101428214B、CN101394928A)、呋喃类化合物(CN102050806A)、烷烃燃料(CN101153219、CN101519599A、CN101671571A、US4396786，US7943792B2)、合成气(CN101144021B、CN101537347A、CN1869157A ), levulinic acid (CN101148458A, CN102030646A), and ethylene glycol (CN101648140B, CN101723802A) have been widely reported. The above-mentioned patents mainly involve the combination of an acid catalyst and a catalyst with a hydrogenation function to improve the efficiency of cellulose catalytic conversion. Compared with traditional thermal degradation or enzymatic conversion, catalytic conversion of cellulose has incomparable and significant advantages in many conversion pathways. From the research results of the current literature, the catalyst system for catalytic conversion of cellulose, the combination of solid acid and metal catalyst, is mainly introduced by mechanical mixing, or the metal catalyst is directly supported on the outer surface of the oxide carrier. Dhepe (ChemSusChem, 2012, 5, 751-761) reported the conversion of hemicellulose into C ₅ sugars and furan compounds using molecular sieve catalysts. At present, there is no report that uses cellulose as a raw material and exists in the pores of molecular sieves in the form of coating through metal or metal interstitial compounds. Using this coating catalyst to catalyze the conversion of cellulose to produce chemicals with high efficiency and high selectivity . The catalytic properties of molecular sieves are mainly reflected in the aspect of shape selectivity. It was found that by positioning the metal components in the pores of the molecular sieve, the molecular sieve channels can be used to achieve shape selection for the transition state of the cellulose degradation intermediate. On the other hand, the acid sites in the pores cooperate Participate in the activation and hydrogenation reaction of intermediates, and then realize the catalytic conversion of cellulose with high selectivity and high activity in the pores of molecular sieves.

Contents of the invention

The object of the present invention is to provide a kind of method that molecular sieve coated metal catalyst prepares dibasic alcohol, hexahydric alcohol and gamma-valerolactone in cellulose hydrogenation degradation; It can realize under the reaction condition of hydrothermal hydrogenation, cellulose Catalytic conversion converts with high yield and high selectivity.

In order to achieve the above object, the technical scheme that the present invention takes is:

The invention discloses a method for preparing diol, hexaol and gamma-valerolactone by catalytic conversion of cellulose. The method comprises the steps of placing cellulose in water and reacting under the action of a catalyst to obtain diol, hexaol and gamma-valerolactone.

In the method, the catalyst is at least one of Pd, Pt, Ru, Rh, Ir, Ni, Cu, Ni ₂ P and RuP coated with molecular sieves, and the weight content of the coated substance accounts for 1-20% of the catalyst .

The catalyst adopts one of metal ion and silica-alumina sol hydrothermal synthesis, molecular sieve ion exchange method and impregnation method, the molecular sieve is preferably ZSM-5, Y and BETA molecular sieve, and the metal ion is preferably Ru ³⁺ , Pd ²⁺ , Pt ^{2 +} and Ni ²⁺ .

In the method, the mass ratio of water to cellulose is 5:1 to 100:1, the mass ratio of cellulose to catalyst is 1:1 to 20:1, the reaction pressure is 3 to 6MPa, and the reaction time is 30min ～12h, the reaction temperature is 150～250℃.

The method of the invention controls the structure of the cellulose hydrolyzate under the hydrothermal condition and at the same time utilizes the hydrogenation performance of the shape-selective system metal of the molecular sieve to selectively catalyze the conversion of the hydrolyzed intermediate product. The method of the present invention does not need to add an acid catalyst for cellulose hydrolysis and a metal catalyst for hydrogenation, and only needs to directly use the acidity of the molecular sieve itself and the hydrogenation performance of the coated metal, and the catalyst is easy to recycle; the method of the present invention has low equipment requirements , small investment, easy to industrialize. In the method of the invention, the conversion rate of cellulose can reach 100%, and the yields of dihydric alcohol, hexyl alcohol and gamma-valerolactone can respectively reach 65%, 71% and 72%.

Further detailed description will be given below through specific examples.

Detailed ways

Example 1

Preparation of molecular sieve-coated metal catalysts by hydrothermal synthesis: Pt(NH ₃ ) ₄ (NO ₃ ) ₂ , water glass, sodium metaaluminate, sodium hydroxide, and deionized water were formulated into nPt:nSiO ₂ :nAl ₂ O ₃ : nNa ₂ O : nH ₂ O = 0.51 : 70 : 1 : 12 : 2400 silica-alumina sol, placed in a crystallization kettle, and crystallized at 160° C. for 3 days. The obtained sample was washed with deionized water to neutrality, and then dried in an oven at 120°C for 12 hours, then the catalyst precursor was subjected to NH ₄ Cl exchange treatment, and the obtained catalyst was exchanged in H ₂ atmosphere, and the temperature was raised to 400 at a rate of 2°C/min. ℃ reduction for 3 hours to obtain a Pt/ZSM-5 catalyst, the Pt metal accounted for 1% of the weight of the catalyst. The used Pt(NH ₃ ) ₄ (NO ₃ ) ₂ was replaced by Ru(NH ₃ ) ₆ Cl ₃ to obtain a Ru/ZSM-5 catalyst, and Ru metal accounted for 5% by weight of the catalyst. . Catalyst coating success with 1-hexene (0.5nm, smaller than ZSM-5 pore size 0.55nm) and 2,4,4-trimethyl-1-pentene (0.7nm, larger than ZSM-5 pore size) Verification of competitive hydrogenation reaction: the reaction conditions are 20 mg catalyst, 7 kPa 1-hexene and 7 kPa 2,4,4-trimethyl-1-pentene, 100 ° C, 0.4 kPa H ₂ , mass space velocity of olefins 20 h ^-1 , The conversions of 1-hexene and 2,4,4-trimethyl-1-pentene on Pt/ZSM-5 were 99% and 0.8%, respectively, and the conversions of 1-hexene and 2,4 , the conversions of 4-trimethyl-1-pentene were 98% and 1.2%, respectively, proving that most of the Pt and Ru metals were encapsulated inside the ZSM-5 channels.

Example 2:

Synthesis of molecular sieve-coated metal catalysts by ion exchange: 5.0g NaY and 0.02mol/LPd(NH ₃ ) ₄ (NO ₃ ) ₂ solution were ion-exchanged at 80°C for 4 hours, the obtained samples were filtered, washed with water, and then placed at 120°C After oven drying for 12 hours, the catalyst precursor was subjected to NH ₄ Cl exchange treatment, and the exchanged catalyst was heated to 500 °C for 3 hours at a rate of 2 °C/min in an H ₂ atmosphere, and then the obtained sample was subjected to NH ₄ Cl exchange treatment, exchanged The obtained catalyst was reduced in N ₂ atmosphere at a rate of 2°C/min to 500°C for 3h to obtain a Pd/Y catalyst, and Pt metal accounted for 2% of the weight of the catalyst. A Pt/ZSM-5 catalyst was obtained. Replace 0.02mol/L Pd(NH ₃ ) ₄ (NO ₃ ) ₂ solution with 0.01mol/LPd(NH ₃ ) ₄ (NO ₃ ) ₂ and Ni(NH ₃ ) ₆ Cl ₂ solution to obtain Pd-Ni/Y catalyst. The success of catalyst coating was verified by the competitive hydrogenation reaction of benzene (0.5nm, smaller than the pore size of Y molecular sieve 0.7nm) and 1,3,5-triisopropylbenzene (0.85nm, larger than the pore size of Y molecular sieve). The reaction conditions are 10mg catalyst, 7kPa benzene and 7kPa 1,3,5-triisopropylbenzene, 100℃, 96kPa H ₂ , mass space velocity of olefins 50h ^-1 , benzene and 1,3,5-triisopropylbenzene on Pd/Y The conversions of triisopropylbenzene were 96% and 32%, respectively, and the conversions of benzene and 1,3,5-triisopropylbenzene on Pd-Ni/Y were 99.5% and 4.5%, respectively, proving that most of the Pd And Pd-Ni metal is coated in the Y molecular sieve channel.

Example 3:

Synthesis of molecular sieve-coated metal phosphide catalysts by impregnation method: nickel nitrate and hypophosphorous acid were formulated as a 0.1mol/L nickel salt solution with a molar ratio of 1:4, 5.0g NaY was placed in the mixed solution, and the Impregnated and stirred for 6h, then evaporated to dryness at 100°C. After the obtained sample was dried in an oven at 120°C for 12 hours, the sample was placed in an _H2 atmosphere, and the temperature was raised to 400°C at a rate of ₅ °C/min for reduction for ₃ hours. In the process, the temperature was raised to 400°C at a rate of 2°C/min and reduced for 3 hours to obtain a Ni ₂ P/Y catalyst, and Ni ₂ P accounted for 20% of the weight of the catalyst. The nickel nitrate solution used was replaced by Ru(NH ₃ ) ₆ (NO ₃ ) ₃ solution to obtain a RuP/Y catalyst, and RuP accounted for 5% of the weight of the catalyst. The success of the catalyst coating was verified by the competitive hydrogenation reaction of benzene and 1,3,5-triisopropylbenzene. The reaction conditions are 10mg catalyst, 7kPa benzene and 7kPa 1,3,5-triisopropylbenzene, 100°C, 96kPa H ₂ , olefin mass space velocity 50h ^-1 , benzene and 1,3 on Ni ₂ P/Y, The conversions of 5-triisopropylbenzene were 72% and 0.2%, respectively, and the conversions of benzene and 1,3,5-triisopropylbenzene on RuP/Y were 99.5% and 4.5%, respectively, proving that most Ni ₂ P and RuP metals are coated in the channels of Y molecular sieves.

Example 4:

Cellulose catalytic conversion experiment: Add 0.5g cellulose, 0.025g catalyst and 25mL water into a 100mL reactor, react at 800rpm, 3MPa H ₂ , and 250°C for 30min. The yield of liquid product was calculated as (product weight)/(cellulose weight)×100%. In the product yield, only the target product diols (including ethylene glycol and propylene glycol) and hexahydric alcohols (including sorbitol and mannitol) are calculated, and other liquid products include glycerol, butylene glycol, ethanol, propanol, unknown Components and gas products (CO, CH ₄ , C ₂ H _{6 ,} etc.) have not been calculated for their yields.

Example 5:

Add 0.5g cellulose, 0.5g Ni ₂ P/Y, RuP/Y or Ru/ZSM-5 catalyst and 50mL water into a 100mL reactor, react at 800rpm, 6MPa H ₂ , 200℃ for 6h.

Add 2g of cellulose, 1g of Pd/Y or Pd-Ni/Y catalyst and 10mL of water into a 50mL reactor, and react at 800rpm, 4MPa of H ₂ at 150°C for 12h.

Add 2g of cellulose, 1g of Pt/ZSM-5 catalyst and 10mL of water into a 50mL reactor, and react for 6h at 800rpm, 6MPa of H ₂ at 200°C.

Embodiment 6:

Add 0.5g cellulose, 0.5g Pd/Y or Pd-Ni/Y catalyst and 50mL water into a 100mL reactor, react at 150°C for 30min at 800rpm, then feed 6MPa of H ₂ and react at 150°C 6h.

Claims (4)

1. A method for preparing dibasic alcohol, hexavalent alcohol and gamma-valerolactone by catalytic conversion of cellulose is to place cellulose in water and react under the action of a catalyst to obtain dibasic alcohol, hexavalent alcohol and gamma-valerolactone ester. 2. according to the described method of claim 1, it is characterized in that: catalyzer is at least one in molecular sieve coating Pd, Pt, Ru, Rh, Ir, Ni, Cu, Ni ₂ P and RuP, is coated material weight The content accounts for 1-20% of the catalyst. 3. according to the described catalyst of claim 2, it is characterized in that: catalyst preparation adopts a kind of in hydrothermal synthesis method, ion exchange method or impregnation method, used molecular sieve preferred ZSM-5, Y and BETA molecular sieve, preferred Ru of metal ion ³⁺ , Pd ²⁺ , Pt ²⁺ and Ni ²⁺ . 4. according to the described method of claim 1, it is characterized in that: in the described reaction, the mass ratio of water and cellulose is 5: 1～100: 1, and the mass ratio of cellulose and catalyst is 1: 1～20: 1 , the reaction pressure is 3-6MPa, the reaction time is 10min-12h, and the reaction temperature is 150-250°C.