混合酸催化葡萄糖合成乙酰丙酸丁酯

探索固体酸混合无机酸、金属硫酸盐、有机酸协同催化葡萄糖醇解合成乙酰丙酸丁酯的反应,选取混合协同催化效果较好的催化剂用于纤维素的醇解,结果表明,添加的金属硫酸盐大部分对葡萄糖的醇解表现出一定的促进作用,有利于产物收率的提高。有机酸、无机酸和金属盐的加入对葡萄糖醇解合成乙酰丙酸丁酯收率影响较小,但在纤维素醇解过程中表现出较大的促进作用,产物收率较高。为纤维生物质资源转化为高附加值化学品提供了一条有效的、环境友好的参考途径。     

纤维素醇解制备乙酰丙酸酯的研究进展

乙酰丙酸酯是一类具有成为新一代生物燃料或者燃料添加剂潜力的高附加值化学品,通过醇解制备乙酰丙酸酯是纤维素资源化利用的重要途径。本文系统地综述了纤维素在酸催化条件下醇解制备乙酰丙酸酯的最新研究进展,重点介绍了在纤维素醇解过程中研究较为活跃的无机酸、固体酸、混合酸和离子液体等几类主要催化剂的催化效果,并总结了这几类催化剂所具有的优势和劣势。同时,着重分析了其醇解机理,特别是Lewis酸和Br?nsted酸在纤维素糖苷键断裂、葡萄糖单元异构化为果糖单元以及果糖单元进一步转化为乙酰丙酸酯等过程中不同的催化作用。并指出目前纤维素醇解制备乙酰丙酸酯过程中仍存在反应条件苛刻、选择性低、反应机理不清甚至相互矛盾等问题。未来研究的主要方向是必须系统地研究纤维素醇解的详细机理,以及在此基础上设计合成催化活性和选择性更高的催化剂。     

三氟甲基磺酸铜催化果糖醇解制备乙酰丙酸甲酯

采用三氟甲基磺酸铜为催化剂催化果糖醇解制备乙酰丙酸甲酯,考察催化剂种类、催化剂用量、反应温度、反应压力和反应时间等对乙酰丙酸甲酯收率的影响。结果表明,在反应压力为2 MPa、果糖0.75 g、甲醇24 g、催化剂用量0.36 g和反应温度120 ℃条件下反应2.0 h,果糖完全被转化,乙酰丙酸甲酯收率达88.1%。     

Al-MCM-41催化葡萄糖醇解制备乙酰丙酸甲酯

采用水热法合成不同铝硅比的固体酸催化剂Al-MCM-41,催化剂的结构和表面酸性质采用N_2物理吸附、X-射线衍射、NH_3程序升温脱附、吡啶-红外技术进行表征,并考察这些催化剂催化葡萄糖醇解制乙酰丙酸甲酯的反应性能。结果表明:催化剂的活性不仅与B酸、L酸的相对质量有关,而且与酸中心的强度有关。在B/L酸比相对接近的情况下,较弱的酸中心有利于乙酰丙酸甲酯收率的提高。Al/Si摩尔比为3的3Al-MCM-41具有最优的生成乙酰丙酸甲酯的活性。当N_2初压2 MPa、反应温度220℃时,0.3 g葡萄糖与24 g甲醇反应6 h,催化剂用量0.15 g,乙酰丙酸甲酯收率为38%。该催化剂经5次循环后,催化活性保持相对稳定。     

固体酸表面B酸和L酸与果糖转化制乳酸甲酯产物分布

制备了γ-Al₂O₃、HZSM-5、SnOPO₄、SnZrOPO₄(1:1)、SO₄^2-/ZrO₂5种不同的固体酸催化剂,采用NH₃程序升温脱附、吡啶原位吸附红外对催化剂进行了表征。考察了固体酸催化果糖在甲醇中转化的催化性能,结果表明,果糖的转化率均高于98%,产物分布与固体酸表面L酸、B酸酸量具有显著的相关性,乳酸甲酯的收率随着L酸量的减少而降低,L酸催化剂γ-Al₂O₃催化,主产物只有乳酸甲酯,收率为24.4%。而L酸位和B酸位共存的固体酸,产物中有乳酸甲酯、乙酰丙酸甲酯,并且乙酰丙酸甲酯的收率随着B酸量的增多而升高。最后考察了典型L酸γ-Al₂O₃及B酸L酸共存的固体酸HZSM-5不同反应时间的产物分布,结合气相-质谱联用对产物定性分析,得出了果糖转化过程L酸位催化和B酸位催化的反应路径。     

近临界甲醇中稀硫酸催化葡萄糖醇解反应动力学

为了探索近临界甲醇中稀硫酸催化下生物质醇解一步法制备乙酰丙酸甲酯方法的可行性,本文以葡萄糖为模型物质,系统地测定了葡萄糖初始浓度10～30 mg·mL-1、温度160～190 ℃、硫酸浓度0.01～0.06 mol·L^-1范围内葡萄糖醇解反应中乙酰丙酸甲酯产物生成反应动力学数据。实验结果表明,反应温度对葡萄糖的醇解选择性影响比较显著,提高温度有利于提高乙酰丙酸甲酯的产率。采用一级反应动力学模型对数据进行了拟合,得到主、副反应的活化能分别为107.5 kJ·mol^-1和68.4 kJ·mol^-1;葡萄糖醇解的主、副反应对[H⁺]分别为0.981级、0.953级。研究结果表明近临界甲醇中稀硫酸催化醇解生物质一步法制备乙酰丙酸甲酯是一条很有发展前景的工艺路线。     

微晶纤维素在SnOx/γ-Al_2O_3催化剂上的催化醇解反应研究

以γ-Al2O3为载体,采用浸渍沉淀法,制备了不同SnOx负载量的SnOx/γ-Al2O3催化剂,采用X射线光电子能谱法(XPS)和吡啶吸附红外(Py-IR)光谱法对催化剂活性中心和表面酸性进行了表征,考察了不同载体和SnOx不同负载量的SnOx/γ-Al2O3催化剂对微晶纤维素催化醇解活性和产物分布的影响规律。结果表明,催化剂活性及产物分布与催化剂的表面酸性及SnOx负载量有关,载体表面较强的B酸中心有利于促进微晶纤维素催化醇解生成乙酰丙酸甲酯,而中等强度L酸中心有利于生成乳酸甲酯。以SnOx/γ-Al2O3为催化剂时,催化剂活性和乳酸甲酯生成量随SnOx负载量增加而增加,当Sn的负载量为6.75wt%时,在240℃反应10 h,微晶纤维素的转化率达82%,乳酸甲酯的收率达到28.1%。     

近临界甲醇中NiO催化生物质糖转化制备乳酸甲酯的研究

生物质化学催化制备乳酸甲酯是一条有工业化应用前景的途径。论文在不同来源NiO筛选基础上,开展了近临界甲醇中NiO催化生物质糖转化制备乳酸甲酯的工艺优化,结合催化剂表征,对NiO催化生物质糖转化为乳酸甲酯的机理进行了探索。结果表明,不同来源的NiO对葡萄糖催化转化制备乳酸甲酯反应的影响很大,购自Aladdin的NiO催化效果最好。在较佳工艺条件下,近临界甲醇中NiO催化葡萄糖转化为乳酸甲酯的摩尔收率可达46.2%。同时催化剂重复使用试验表明Aladdin的NiO具有良好的重复使用性能。中等强度的酸性可能是影响乳酸甲酯收率的核心因素,中等强度酸含量越高,乳酸甲酯的摩尔收率就越高。研究工作将促进生物质化学催化制备乳酸甲酯非均相催化体系的开发。     

水热体系下ZrO_2-SiO_2混合氧化物催化纤维素转化

采用共沉淀法合成了混合氧化物Zr O2-Si O2。用XRD,BET,NH3-TPD对其结构性质进行了表征。在水热条件下利用该催化剂催化纤维素转化。考察了n(Zr)/n(Si)、反应时间、反应温度等因素对纤维素转化的影响。结果表明,Zr O2-Si O2混合氧化物具有较高的酸量,n(Zr)/n(Si)=7时催化剂酸量最高,催化效果最优。反应条件为200℃、2.5 MPa N2、5 min时,纤维素转化率达到59.0%,葡萄糖、乳酸、乙酰丙酸、5-HMF的总收率为26.9%。     

介孔分子筛B-SBA-15催化合成柠檬酸三丁酯

采用直接和间接合成法,将硼原子嵌入介孔分子筛SBA-15骨架中,用柠檬酸与正丁醇的酯化反应评价催化剂的催化性能。间接和直接合成法合成的催化剂活性对比结果表明,间接合成法制备催化剂的活性高于直接合成催化剂。重点考察了催化剂中硅硼比、催化剂用量、反应温度和酸醇比等因素对间接合成催化剂酯化反应性能的影响。筛选出B-SBA-15催化剂最佳硅硼摩尔比为30∶1,最佳反应条件：催化剂用量为原料质量的1.5%,反应温度为130 ℃,酸醇摩尔比1∶6。试验结果表明,介孔分子筛催化剂 B-SBA-15具有较高的稳定性,是合成柠檬酸三丁酯较为理想的分子筛催化剂。     

功能化离子液体催化合成甘油单月桂酸酯

合成了由吡啶、N-甲基咪唑、N-甲基-2-吡咯烷酮提供有机阳离子, 磷钨酸、对甲苯磺酸提供阴离子的6种离子液体。使用NMR、FT-IR和TG对离子液体表征, 并考察它们催化甘油与月桂酸酯化的催化效果。结果表明, 这些离子液体都具有较好的热稳定性, 以1-(丁基-4-磺酸基)-3-甲基咪唑磷钨酸盐离子液体的热稳定性最好。在最佳条件使用离子液体催化甘油与月桂酸反应时, 阴离子的种类对月桂酸的转化率影响较大, 以对甲苯磺酸为阴离子的离子液体催化反应时, 月桂酸转化率较以磷钨酸为阴离子的离子液体的高;1-(丁基-4-磺酸基)-3-甲基咪唑对甲苯磺酸盐离子液体做催化剂时甘油单月桂酸酯的产率最高。催化剂重复使用性方面, 离子液体重复使用5次催化活性没有明显变化。     

Transesterification of vegetable oil to biodiesel fuel using acid catalysts in the presence of dimethyl ether

The immiscibility of methanol and vegetable oil leads to a mass-transfer resistance in the transesterification of vegetable oil. To overcome this problem, dimethyl ether (DME) was used as an environmentally friendly cosolvent to produce a homogeneous solution. Methylesterifications of corn oil in both the presence and the absence of DME were performed using p-toluenesulfonic acid (PTSA), benzenesulfonic acid and sulfuric acid. PTSA showed highest catalytic activity. The yield of FAME reached 97.1% when 4 wt% of PTSA based on the oil weight was used at 80 °C with a reaction time of 2 h in the presence of DME. The obtained biodiesel was composed of methyl palmitate (9.1 wt%), methyl oleate (33.9 wt%), methyl linoleate (53.5 wt%), methyl linolenate (3.0 wt%) and methyl arachidate (0.5 wt%), and it was similar to the biodiesel compositions from corn oil as reported. The effects of concentrations of FFA and water on FAME yields were also investigated. All results suggested that the reaction rate was greatly improved by the addition of DME to the reaction system.     

Purification of Biorefinery Lignin with Alcohols

After hydrothermal pretreatment and enzymatic hydrolysis of wheat straw, a slurry rich in lignin but with a high content of inorganic substances, especially silica, and residual carbohydrates is produced. This slurry was used to develop an ethanol organosolv separation method to produce silica-free lignin fractions. The addition of para toluene sulphonic acid (PTSA) and the use of two alternative long-chain alcohols, oleyl alcohol or nonylphenol, were tested. In every reaction, two lignin fractions were produced and their molecular size and elemental composition were characterized. The yield of each fraction and the change in MWD were studied as a function of temperature and solid to liquid ratio. At 100, 150, and 200°C and with the use of PTSA, high-purity lignin fractions were obtained. After lignin fractionation with nonylphenol, a liquid silica-free product with high lignin content was obtained in yields between 17 and 72%.     

酸掺杂聚苯胺催化马来酸丁酯化及动力学

用对甲苯磺酸作为搀杂剂对水相氧化法合成的盐酸搀杂的聚苯胺(HC l/PANI)进行搀杂,制备了由聚苯胺(PANI)负载对甲苯磺酸的固体酸催化剂(PTSA/PANI)。以PTSA/PANI为催化剂、马来酸酐和正丁醇为原料合成马来酸二丁酯。考察了原料配比、催化剂用量和反应时间等因素对反应的影响以及催化剂的重复使用性能,测定了反应动力学。最佳反应工艺条件为:n(正丁醇)∶n(马来酸酐)=3.33∶1、w(PTSA/PANI)=3.81%、反应温度≤130℃、反应时间3 h。结果表明,在该条件下马来酸酐的转化率为96.23%;催化剂经重复使用5次后,马来酸酐的转化率为90.82%;确定反应级数为二级,表观活化能为41.0 kJ/mol。对甲苯磺酸搀杂聚苯胺催化剂具有催化活性高、稳定性好、容易制备、无环境污染等优点。     

Bifunctional imidazole-PTSA deep eutectic solvent for synthesizing long-chain ester IBIBE in reactive extraction

The traditional production of long-chain organic esters like isobutyl isobutyrate (BIBE) suffers from severe problems due to the homogenous catalyst in process and complex system thermodynamics. In this work, an innovative bifunctional deep eutectic solvent (DES) is introduced, playing as both reaction catalyst and extraction solvent, to intensify the esterification process. The DES was formed by imidazole (Im) and p-toluenesulfonic acid (PTSA), which was for the first time found acid–base tunable, represented by weak basic DES [3Im:PTSA] and strong acidic DES [Im:2PTSA]. The formation mechanisms of [3Im:PTSA] and [Im:2PTSA] were illustrated by Fourier-transform infrared spectroscopy (FTIR) and COnductor-like Screening MOdel for Real Solvent (COSMO-RS) combined with the Im-PTSA phase diagram. The dual functions of the acidic [Im:2PTSA] in reactive extraction were evaluated by σ-potential analysis and esterification experiments. The high conversion, easy product separation, and good solvent reusability confirm the excellent catalytic and solvent effect of [Im:2PTSA]. © 2018 American Institute of Chemical Engineers AIChE J, 65: 675–683, 2019     

Hydrolysis of mechanically pre-treated cellulose catalyzed by solid acid SO_4~(2-)-TiO_2 in water–ethanol solvent

An efficient catalyst SO_4~(2-)-TiO_2(ST) from industrial metatitanic acid has been successfully prepared to catalyze hydrolysis of ball-milling cellulose. The results show that the highest catalytic efficiency is obtained for ST calcined at 450 °C(ST-450) with the yield of 21.8% glucose, 13.0% 5-HMF and 4.2% furfural at 200 °C for30 min. The ball milling of cellulose and solid acid catalyst significantly enhances the cellulose hydrolysis. The high Lewis to Br?nsted acid sites ratio for ST-450 induced by bidentate ligands between SO_4~(2-)and TiO_2 benefits high organics yield, and high total acid sites contribute to the high cellulose conversion. The large pore volume of0.29 cm~3·g~(-1) and appropriate pore size of 7.35 nm of ST-450 also contribute to the high performance. High reaction temperature over 200 °C exhibits negative effect on glucose and 5-HMF yield due to undesired side reactions, while furfural product is stable in the reaction system. The bidentate ligands between SO_4~(2-)and TiO_2 are considered as active acid sites for cellulose hydrolysis in water–ethanol solvents.     

Conversion of carbohydrate biomass to methyl levulinate with Al2(SO4)3 as a simple,cheap and efficient catalyst

Al₂(SO₄)₃ was developed as a simple and efficient catalyst for the synthesis of methyl levulinate (MLE) from carbohydrate biomass including fructose, glucose, mannose, sucrose, cellobiose, starch, and cellulose. The maximum MLE yield of 64% from glucose could be obtained at 160 °C for 150 min. Important roles of Al^3 + and Brønsted acid sites generated by the hydrolysis/methanolysis of Al^3 + were elucidated. The reaction process was revealed using in situ real-time attenuated total reflection infrared spectroscopy. Al₂(SO₄)₃ can be regenerated easily and reused at least four times without the loss of activity.     

微波诱导PTSA催化酯化合成没食子酸正丁酯

采用微波辐射技术,以对甲苯磺酸（ＰＴＳＡ）作催化剂,没食子酸和正丁醇直接酯化合成没食子酸正丁酯。最佳反应条件为：没食子酸１９．３ｍｍｏｌ,催化剂０．５ｇ,二者的摩尔比是１∶０１３５,正丁醇２０ｍｌ,微波功率５２５Ｗ,辐射时间２０ｍｉｎ,酯化产率为８７９％。该条件下的反应速度是酶促反应速度的５４倍。     

微波辐射对甲苯磺酸催化合成柠檬酸三丁酯

在微波辐射下 ,以对甲苯磺酸作催化剂 ,柠檬酸和正丁醇直接酯化生成柠檬酸三丁酯。优惠反应条件为 :柠檬酸 5 0 g ,催化剂 0 3 g ,正丁醇 2 0ml,微波功率中高火 ,辐射时间 3 0min ,酯化收率为 91 2 %。该条件下的反应速度是常规加热法反应速度的 6倍。     

离子液体催化合成乙酸丙酯的研究

用微波方法制备了[bmim]PTSA离子液体,应用于催化合成乙酸丙酯反应中,分析了离子液体的催化活性,研究了影响酯化反应的各种因素。结果表明：离子液体[bmim]PTSA是该酯化反应良好溶剂和催化剂,离子液体用量15mL,醇酸摩尔比1．5：1．0,反应时间2．0h,酯化率达94．2％。离子液体易分离回收,可重复使用。