Calcium-based solid base catalyst and preparation and application thereof
By preparing a calcium-based solid base catalyst, the problems of separation and deactivation of existing catalysts were solved, and the efficient synthesis of cyclic carbonates and alcohol transesterification reaction was achieved. The catalyst has high activity and good stability and is suitable for the industrial synthesis of dialkyl carbonates.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- LANZHOU INSTITUTE OF CHEMICAL PHYSICS CHINESE ACADEMY OF SCIENCES
- Filing Date
- 2024-04-29
- Publication Date
- 2026-04-28
AI Technical Summary
Existing homogeneous catalysts are difficult to separate, while heterogeneous catalysts are prone to deactivation. High reaction temperatures and low catalytic activity are significant factors hindering the efficient conversion of transesterification reactions.
A calcium-based solid base catalyst is prepared through an acid-base neutralization reaction. It utilizes azole organic ligands to activate alcohols and catalyzes the transesterification reaction of cyclic carbonates with alcohols. The reaction conditions are mild and the catalyst has good stability.
The efficient synthesis of dialkyl carbonates at room temperature was achieved using a catalyst with high activity, good stability, and is economical, green, and environmentally friendly.
Smart Images
Figure CN118477689B_ABST
Abstract
Description
Technical Field
[0001] This invention provides a calcium-based solid base catalyst, mainly used for catalyzing the transesterification of cyclic carbonates with alcohols to synthesize dialkyl carbonates, belonging to the field of catalysts and chemical synthesis technology. Background Technology
[0002] Dialkyl carbonates, such as dimethyl carbonate (DMC), diethyl carbonate (DEC), dibutyl carbonate (DBC), and methyl ethyl carbonate (EMC), are important reaction intermediates. Their molecular structures contain carbonyl and alkyl groups, allowing them to be used as carbonylating or alkylating agents in various organic reactions. Furthermore, due to their high dielectric constant, low viscosity, and good solubility in lithium salts, they are widely used in lithium-ion batteries and fuel additives. Currently, reported methods for synthesizing dialkyl carbonates can be mainly classified into the phosgene method, oxidative carbonylation method, and transesterification method. The phosgene method has high production efficiency, but the raw material phosgene is highly toxic, and the generated strong acid HCl severely corrodes equipment; this method has been gradually phased out. The oxidative carbonylation method uses methanol, ethanol, CO, and O2 as main raw materials, but the yield of dialkyl carbonates is too low, and the reaction involves O2, posing safety hazards. The transesterification method for synthesizing dialkyl carbonates has mild reaction conditions, is easy to control, and has low environmental pollution, making it considered the most promising process route currently.
[0003] Transesterification is a process in which an ester reacts with an alcohol / acid / ester (different esters) under acid or base catalysis to form a new ester and a new alcohol / acid / ester. Catalysts are mainly classified as homogeneous and heterogeneous catalysts. Homogeneous catalysts, such as NaOH and NaOCH3, are widely used due to their low cost and excellent catalytic efficiency. However, homogeneous catalysts have disadvantages, such as sensitivity to water, difficulty in separation, and limited stability, leading to complex production processes, high energy consumption, and the generation of large amounts of strongly alkaline solid waste as a byproduct in efforts to improve product quality and purity. To address the separation problem of homogeneous catalysts, some heterogeneous catalysts (CaO, KAlO2 / γ-Al2O3, K-TS-1, MgAl, CeO2, ZnY, etc.) have been designed for this reaction. For example, CaO solid base catalysts have high activity, but their stability is poor; calcium oxide can react with water and DMC in the system to form inactive calcium carbonate (Fuel, 2022, 330, 125696). Feng et al. reported a CaO-ZrO2 composite oxide catalyst for the reaction of propylene carbonate (PC) with methanol, achieving a PC conversion of 55% at 117°C (Catal. Today, 2006, 115, 107–110). Currently, homogeneous catalysts are difficult to separate, heterogeneous catalysts are prone to deactivation, and high reaction temperatures combined with low catalytic activity are significant factors hindering the efficient conversion of transesterification reactions. Therefore, it is necessary to further develop low-cost, high-performance heterogeneous catalysts for the industrial synthesis of dialkyl carbonates. Summary of the Invention
[0004] The purpose of this invention is to disclose a calcium-based solid base catalyst and its preparation method, so as to achieve low-cost preparation of calcium-based catalysts.
[0005] Another objective of this invention is to disclose the application of the above-mentioned calcium-based solid base catalyst in the transesterification of cyclic carbonates with alcohols to prepare dialkyl carbonates, so as to achieve the synthesis of dialkyl carbonates with high catalytic performance.
[0006] I. Preparation of Calcium-Based Solid Base Catalysts
[0007] A method for preparing a calcium-based solid base catalyst involves first dissolving a nitrogen-based azole organic ligand in deionized water, then adding a calcium-based precursor and stirring at room temperature for 8-10 h. The mixture is then filtered to remove insoluble solid impurities, and the filtrate is subjected to reduced pressure at 80-100 °C to remove water, thereby obtaining the calcium-based solid base catalyst.
[0008] The calcium-based precursor is at least one of CaO, Ca(OH)2, Ca2(OH)2CO3, CaCO3, Ca(OAC)2, Ca(NO3)2, and CaCl2.
[0009] The azole organic ligand is one of triazole, aminotriazole, nitrotriazole, and diaminotriazole.
[0010] The mass ratio of the calcium-based precursor to the nitrogen-based organic ligand is 1:(1~4).
[0011] Synthesis mechanism of calcium-based solid base catalysts: The synthesis of the catalyst is based on acid-base neutralization reaction. Taking the reaction of calcium hydroxide and aminotriazole as an example, the reaction formula is as follows:
[0012]
[0013] II. Preparation of Dialkyl Carbonate
[0014] Dialkyl carbonate was prepared by transesterification of cyclic carbonate and alcohol using the above-mentioned calcium-based catalyst, wherein the molar ratio of cyclic carbonate to alcohol was 1:4 to 1:12, the reaction temperature was 20 to 120°C, the reaction time was 5 to 120 min, and the amount of catalyst used was 0.05 wt% to 5 wt% of the mass of cyclic carbonate.
[0015] The cyclic carbonate is one of ethylene carbonate and propylene carbonate.
[0016] The alcohol is one of methanol, ethanol, propanol, and butanol.
[0017] The dialkyl carbonate is one of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, dibutyl carbonate, methyl ethyl carbonate, and methyl butyl carbonate.
[0018] Compared with the prior art, the present invention has the following beneficial effects:
[0019] This invention uses a calcium-based solid base as a catalyst in the preparation of dialkyl carbonate. The catalyst is prepared by simple acid-base neutralization. The catalyst has moderate alkalinity, and the aminotriazole ion can activate methanol, allowing the reaction to proceed at room temperature. The yield of dimethyl carbonate can reach 72% after 5 minutes of reaction. It has the advantages of high activity, low dosage, and good stability. It is economical, green, and environmentally friendly. Attached Figure Description
[0020] Figure 1 The infrared spectrum of calcium aminotriazole (CaATZ) in Example 2 of this invention is shown.
[0021] Figure 2 The XRD patterns of calcium aminotriazole salt (CaATZ) in Example 2 of the present invention and after five reuses (CaATZ-reused) are shown. Detailed Implementation
[0022] The present invention will be further explained and described below with reference to specific embodiments.
[0023] Example 1
[0024] Preparation of calcium triazole catalyst (CaTZ): Weigh 1.4 g of triazole and add it to a 250 ml beaker. Add 80 ml of deionized water and stir to dissolve at room temperature. Add 0.74 g of Ca(OH)2 and stir at room temperature for 8 h. Filter and remove water from the filtrate under reduced pressure at 80 ºC to obtain the CaTZ catalyst.
[0025] Example 2
[0026] Preparation of calcium aminotriazole catalyst (CaATZ): 1.68 g of aminotriazole was weighed and added to a 250 ml beaker, 80 ml of deionized water was added, and the mixture was stirred and dissolved at room temperature. 0.74 g of Ca(OH)2 was added and the mixture was stirred at room temperature for 8 h. The mixture was filtered, and the filtrate was dehydrated under reduced pressure at 80 °C to obtain the CaATZ catalyst.
[0027] Example 3
[0028] Preparation of the catalyst calcium nitrotriazole (CaNTZ): Weigh 1.64 g Ca(NO3)2 and add it to a 250 ml beaker. Add 80 ml of deionized water and stir to dissolve at room temperature. Add 0.8 g NaOH and stir at room temperature for 2 h. A white precipitate is formed. Filter the precipitate, wash it, and add it to 80 ml of nitrotriazole solution (2.2 g of nitrotriazole solution dissolved in 80 ml of water). Stir at room temperature for 8 h and remove water under reduced pressure at 80 ºC to obtain the CaNTZ catalyst.
[0029] The catalysts prepared in Examples 1-3 above were evaluated for their activity in the transesterification of ethylene carbonate (EC) with methanol, ethanol, and butanol to prepare dimethyl carbonate, diethyl carbonate, and dibutyl carbonate, respectively. The results are shown in Table 1.
[0030] Table 1. Activity evaluation of catalysts under different reaction conditions
[0031]
[0032] Table 1 shows that the calcium-based catalyst exhibits high catalytic activity for the transesterification of ethylene carbonate and methanol to synthesize dimethyl carbonate. At 25°C for 5 min, the conversion rate of ethylene carbonate reaches 73%, and the selectivity of the product dimethyl carbonate is 99% (Reaction Evaluation 3). Extending the reaction time to 30 min, the conversion rate of ethylene carbonate can reach 90% (Reaction Evaluation 4), and the catalyst can be reused without changing its activity (Reaction Evaluation 11). In addition, the calcium-based catalyst also shows good versatility in the transesterification of ethylene carbonate with ethanol and butanol to prepare diethyl carbonate (Reaction Evaluation 8) and dibutyl carbonate (Reaction Evaluation 9).
Claims
1. The application of a calcium-based solid base catalyst in the transesterification reaction of cyclic carbonates with alcohols to prepare dialkyl carbonates, characterized in that, The preparation of the calcium-based solid base catalyst includes: first dissolving a nitrogen azole organic ligand in deionized water, then adding a calcium-based precursor and stirring at room temperature for 8-10 h, filtering to remove insoluble solid impurities, and removing water from the filtrate under reduced pressure at 80-100℃ to obtain the calcium-based solid base catalyst. The azole organic ligand is one of triazole, aminotriazole, nitrotriazole, and diaminotriazole; The calcium-based precursor is at least one of CaO and Ca(OH)2.
2. The application as described in claim 1, characterized in that, The mass ratio of the calcium-based precursor to the nitrogen-based organic ligand is 1:1 to 1:
4.
3. The application as described in claim 1, characterized in that: The amount of the calcium-based solid base catalyst used is 0.5% to 5% of the mass of the cyclic carbonate.