氧化锆负载Pd-Cu双金属催化剂上山梨醇选择性氢解合成乙二醇和丙二醇

山梨醇和木糖醇等多元醇是可再生生物质转化合成液体燃料和化学品的重要平台分子,其中,可通过选择氢解反应一步制备乙二醇和丙二醇等重要化工原料,有望代替从乙烯和丙烯制备二元醇的传统石油化工工艺.目前文献中多元醇氢解反应主要使用Ru基和Ni基催化剂等,但是不可避免地生成C?C键非选择性断裂的副产物甲烷等.与之相比,非贵金属Cu基催化剂往往具有较优异的选择性,但其活性较低和水热稳定性较差.因此,到目前为止研制具有高活性和选择性、以及良好水热稳定性的Cu基催化剂用于生物质基多元醇氢解反应仍然存在挑战.在本文中,我们采用贵金属修饰的方法提高Cu基催化剂在山梨醇选择氢解反应中的活性和水热稳定性.通过分步浸渍法合成了1%Pd-3%Cu/ZrO2、1%Pt-3%Cu/ZrO2和1%Ru-3%Cu/ZrO2双金属催化剂,并比较了它们在山梨醇氢解反应中的催化性能.在相同的反应条件下,上述催化剂中1%Pd-3%Cu/ZrO2(Cu/Pd =5)具有最优的活性及乙二醇、丙二醇和甘油的总选择性.以固体碱La(OH)3为助剂,1%Pd-3%Cu/ZrO2的山梨醇氢解活性高达20.3 h-1,是单金属1%Pd/ZrO2(8.7 h-1)和3%Cu/ZrO2(6.5 h-1)催化剂活性的2-3倍,也高于含有相同Pd、Cu含量的1%Pd/ZrO2和3%Cu/ZrO2机械混合体系的活性(12.2 h-1).而且, Pd-Cu/ZrO2双金属催化剂对C2-C3低碳多元醇的选择性也明显优于Pd/ZrO2和Cu/ZrO2以及二者的机械混合体系.这些结果说明Pd对Cu/ZrO2的促进作用不仅仅需要Pd与Cu两种金属的共同存在,还需要它们两者之间的相互作用.进一步发现, Pd-Cu/ZrO2双金属催化剂在Cu/Pd比为1.5-10.0的较宽范围内都表现出了较高的反应活性(17.8-20.3 h-1)以及乙二醇、丙二醇和甘油的总选择性(57.3%-62.8%),说明较低含量Pd的存在就能够有效地改善Cu催化剂的催化性能.在493 K和5.0 MPa H2的反应条件下,以1%Pd-3%Cu/ZrO2为催化剂,在山梨醇接近完全转化时,获得了61.7%的乙二醇、丙二醇和甘油的总选择性.同时, Pd的加入还能有效地抑制水热反应条件下Cu粒子的团聚,使得Pd-Cu/ZrO2催化剂在山梨醇氢解反应中具有优良的水热稳定性和循环使用性能.在5次循环实验中1%Pd-3%Cu/ZrO2的活性和选择性基本保持不变; X-射线粉末衍射结果表明,反应后的催化剂上未观察到Cu的特征衍射峰, Cu粒子仍然保持良好的分散状态.而对于没有Pd修饰的单金属3%Cu/ZrO2催化剂,经5次循环使用后山梨醇氢解反应的活性则下降了42%;在循环反应中Cu粒子显著地聚集而长大到~30 nm. CO吸附漫反射红外光谱结果揭示了Cu粒子倾向于在Pd粒子表面沉积,随着Cu/Pd原子比的增大, Cu粒子逐渐稀释并覆盖Pd的表面位点,说明Pd与Cu粒子之间存在紧密的接触.氢气程序升温还原结果表明,可能与氢溢流有关, Pd的加入促进了CuO的还原.然而,不同于Pd/ZrO2和Cu/ZrO2机械混合样品的TPR图谱,其显示PdO和CuO各自的还原峰, Pd-Cu双金属催化剂则只存在一个宽化的还原峰,这说明了Pd-Cu之间结构上的紧密接触使得两种金属之间存在强相互作用,其中可能存在从Pd向Cu的电子转移.综合这些结构和电子效应,可以推测Pd的存在促进了Cu粒子对山梨醇的脱氢能力和不饱和中间体的加氢能力,进而提高了Cu基催化剂在山梨醇氢解反应中的活性及目标产物的选择性.同时Pd-Cu之间的强相互作用和氢溢流效应抑制了Cu粒子在水热反应条件下的聚集,提高了催化剂的稳定性.这些结果和认识有助于指导人们为多元醇氢解和其它生物质基化学品的转化反应设计具有更高效率和水热稳定性的新型Cu基催化剂.     

纤维二糖与葡萄糖催化转化制备乙二醇(英文)

选用纤维二糖作为探针分子,探索纤维素催化转化制备乙二醇过程的反应路径.分别考察了纤维二糖和葡萄糖在双组分催化剂H2WO4和Ru/C下的催化反应活性.结果表明,乙二醇不仅来自于纤维二糖水解产物葡萄糖的逆羟醛缩合作用,同时也可以来自于纤维二糖的直接逆羟醛缩合过程.而且,纤维二糖的直接逆羟醛缩合作用对糖苷键的水解也有一定的促进作用.比较发现,钨基催化剂作用下纤维二糖的逆羟醛缩合反应活性比葡萄糖要低,因此乙醇醛可以缓慢产生并在Ru/C催化剂上迅速加氢生成乙二醇.使得以纤维二糖作为原料比以葡萄糖作为原料时获得更高的乙二醇收率.     

碳酸乙烯酯选择加氢合成甲醇与乙二醇高效稳定Cu/SiO2催化剂研究

CO2作为重要的碳氧资源, 具有来源丰富、价格低廉、安全等突出优点. 近年来, 由于蕴含的巨大利用潜力,CO2间接利用制备基础化学品、能源燃料对于可持续制备大宗化工品中具有重要研究意义, 日益受到研究者和工业界的广泛重视.甲醇与乙二醇是化学工业中的两种重要大宗原料. 甲醇不仅是重要的有机化工原料、清洁环保的液体燃料, 同时也是氢气和能量储存的良好载体. 乙二醇作为一种重要的有机化工原料, 在聚酯等领域具有广泛应用.CO2经碳酸乙烯酯氢解制备甲醇/乙二醇是典型的原子经济反应, 对资源、能源和环境的可持续发展具有重要意义. 需要指出的是,CO2与环氧乙烷环加成制备碳酸乙烯酯已具备成熟的工业化技术. 因此, 该路线研究重点在于发展碳酸乙烯酯选择加氢联产甲醇和乙二醇高效稳定的催化体系. 近年来, 铜基多相催化剂催化碳酸乙烯酯加氢联产甲醇乙二醇得到了广泛重视. 由于铜基催化剂存在活性较低、高温易失活等问题, 开发高效且具有良好稳定性的铜基催化剂是目前碳酸乙烯酯加氢研究重点.本文针对碳酸乙烯酯选择氢解合成甲醇乙二醇新型铜基催化体系构建和构效关系研究, 采用硅溶胶蒸氨法制备高分散 Cu/SiO2过程中引入多羟基β-环糊精修饰催化剂前驱体的合成策略, 并通过惰性气体中煅烧后的积碳有效抑制活性铜物种的团聚, 获得了β-环糊精改性的 Cu/SiO2催化剂. 通过 N2吸脱附、XRD、N2O 滴定、H2-TPR、TEM 和 XPS 等系统表征,发现β-环糊精可有效调控催化剂结构和表面不同价态活性铜物种分布. 碳酸乙烯酯加氢性能评价结果表明引入适量β-环糊精的 5β-25%Cu/SiO2具有较优催化活性, 乙二醇选择性 98.8% 和甲醇选择性 71.6%, 且相应的催化活性可达 1178 mgEC gcat-1h-1. 高活性的原因很可能归因于不同价态 Cu0与 Cu+物种协同催化作用及适宜的 Cu+/(Cu0+Cu+) 比例. 结合密度泛函理论模拟计算, 我们提出了 Cu0促进氢气解离、Cu+吸附活化碳酸乙烯酯分子中酯羰基的反应机理. 催化剂重复使用和表征结果表明, 5β-25%Cu/SiO2具有良好的稳定性, 使用前后铜粒子大小和铜物种分布几乎未发生明显变化. 本文为解决铜基催化剂高温易烧结等难题提供了简单有效的活性铜物种稳定化方法, 并为CO2经碳酸乙烯酯绿色合成甲醇、乙二醇高效稳定铜基催化新体系的构筑提供了有益借鉴.     

The thermal conductivity of alumina nanoparticles dispersed in ethylene glycol

The thermal conductivities of several nanofluids (dispersions of alumina nanoparticles in ethylene glycol) were measured at temperatures ranging from 298 to 411 K using a liquid metal transient hot wire apparatus. Our measurements span the widest range of temperatures that have been investigated to date for any nanofluid. A maximum in the thermal conductivity versus temperature behavior was observed at all mass fractions of nanoparticles, closely following the behavior of the base fluid (ethylene glycol). Our results confirm that additional temperature contributions inherent in Brownian motion models are not necessary to describe the temperature dependence of the thermal conductivity of nanofluids. Our results also show that the effect of mass or volume fraction of nanoparticles on the thermal conductivity of nanofluids can be correlated using the Hamilton and Crosser or Yu and Choi models with one adjustable parameter (the shape factor in the Hamilton and Crosser model, or the ordered liquid layer thickness in the Yu and Choi model).     

Optimization of experimental parameters in single-drop microextraction-gas chromatography-mass spectrometry for the determination of periodate by the Malaprade reaction, and its application to ethylene glycol

The aim of present work was to optimize the experimental parameters in single drop microextraction under solution immersion (SDME) and headspace (HS-SDME) extraction modes for the determination of periodate using guaifenesine [3-(2′-methoxyphenoxy)-1,2-propane diol] and norephedrine (phenylpropanolamine) as new and alternative reagents for the Malaprade reaction. The reactions were complete within 5 min resulting in the formation of 2-(2′-methoxyphenoxy)-acetaldehyde and benzaldehyde, respectively. SDME/HS-SDME of oxidation products with 2 μl of anisole or 1 μl of toluene, respectively, has permitted the determination of periodate at μg l⁻¹ concentration levels. The results indicated that HS-SDME (range 0.01-10 mg l⁻¹, r² = 0.9990; limit of detection 1.55 μg l⁻¹) was more sensitive than SDME (range 0.05-50 mg l⁻¹, r² = 0.9984; limit of detection 3.42 μg l⁻¹), and was inexpensive, rapid and convenient. Tolerance of excess of iodate has permitted the application of this method in the determination of ethylene glycol in motor oil; the average recovery on spiked sample was 98.6% with R.S.D. of 4.2%.     

介质阻挡放电甲醇脱氢偶联一步合成乙二醇反应中氢气的催化作用

利用原位发射光谱表征和在线色谱分析,研究了甲醇介质阻挡放电脱氢偶联一步合成乙二醇反应中氢气的催化作用,考察了放电频率、甲醇和氢气进料量以及反应压力的影响.结果表明,在介质阻挡放电产生的非平衡等离子体中,H2不但能显著提高甲醇转化率,而且能显著提高乙二醇的选择性.在300°C,0.1 MPa,反应器注入功率为11 W,放电频率为12.0 k Hz,甲醇气体进料量为11.1 m L/min,氢气进料量为80–180 m L/min的条件下,甲醇转化率接近30%,乙二醇选择性大于75%.乙二醇收率与激发态氢原子的Hα谱线强度之间存在同增同减关系.由此推测,氢原子是起催化作用的活性氢物种.活性氢物种的生成途径是:基态氢分子通过与电子碰撞变成激发态,激发态氢分子通过第一激发态氢自动解离为基态氢原子.放电反应条件通过影响氢分子解离来影响氢气的催化作用.氢气在非平衡等离子体中显示的催化作用有可能为开辟新的化学合成途径提供重要机遇.     

Determination of trace ethylene glycol in industrial solvents and lubricants using phenyl boronic acid derivatization and multidimensional gas chromatography

A practical gas chromatographic approach is introduced for the characterization of trace ethylene glycol in industrial solvents and lubricants. The analytical approach employs single step derivatization technique that effectively converts ethylene glycol to the cyclic boronate ester (2-phenyl-1,3,2-dioxaborolane), using phenyl boronic acid as a derivatizing reagent. The separation of the derivatized product was achieved by using multidimensional gas chromatography. Heavy lubricant matrices like engine crankcase oil were back-flushed to improve sample throughput and system cleanliness. Detection and quantitation of 2-phenyl-1,3,2-dioxaborolane was conducted with mass spectrometry in selected ion monitoring mode.     

Dechlorination of poly(vinyl chloride) using NaOH in ethylene glycol under atmospheric pressure

A solution of NaOH dissolved in ethylene glycol (EG) was effective in the dechlorination of poly(vinyl chloride) (PVC) at atmospheric pressure. The degree of dechlorination increased with increasing temperature, reaching a maximum of 97.8% at 190 °C. The dechlorination proceeded under chemical control and exhibited first-order kinetics with an apparent activation energy of 170 kJ mol⁻¹. The apparent rate constant for dechlorination in 1.0 M NaOH/EG was approximately 150 times greater than that in 1.0 M NaOH/H₂O. In addition, dechlorination was faster at atmospheric pressure in NaOH/EG than under high pressure in NaOH/H₂O. The dechlorination reaction occurs via a combination of E2 and S_N2 mechanisms.     

Conformation of ethylene glycol: Isometric group,ab initio study of internal H bonding and ir-matrix spectra of the species CH2OHCH2OH,CD2OHCD2OH and CH2ODCH2OD

The isometric group of a semirigid model of the ethylene glycol molecule with 3 internal degrees of freedom is derived. Results of extensiveab initio computation of the electronic potential function with a Gaussian lobe basis set are presented from which two differentr _e conformations are predicted. Both feature one single internal H bond in which one of the lone electron pairs of the acceptor O atom is involved. Symmetry sets of isometricr _e-conformations and of transition points of the potential function are discussed. Infrared matrix spectra of glycol and 2 deuterated modifications are presented and discussed on the basis of two internally bonded conformations predicted byab initio calculations. Dedicated to Prof. H. Hartmann on the occasion of his 60th birthday.     

Vapor–liquid equilibrium in the system ethane + ethylene glycol

The solubility of ethane in ethylene glycol (EG) has been determined at temperatures in the range 298–398 K at pressures up to 20 MPa. The experimental results were correlated by the Peng–Robinson equation of state, and interaction parameters have been obtained for this system. The parameters in the Krichevsky–Ilinskaya equation were calculated from these interaction parameters.     

Synthesis of 2-methylpyrazine from cyclocondensation of ethylene diamine and propylene glycol over promoted copper catalyst

The 2-methylpyrazine was synthesized by catalytic reaction of ethylene diamine and propylene glycol at 380 ℃. The alumina supported copper catalysts with promoter were prepared by impregnation method, characterized by ICP-AES, BET and TPR. The results demonstrated that the dehydrogenation was improved by addition of chromium promoter. The selectivity of 2-methylpyrazine reached 84.75%, while the conversions of reactants were also enhanced.     

Effects of ethanol on the in situ synthesized Cu/SiO_2 catalyst:Texture,structure,and the catalytic performance in hydrogenation dimethyl oxalate to ethylene glycol

The Cu/SiO₂ catalysts were in situ synthesized by the hydrolysis of tetraethyl orthosilicate（TEOS） in one phase solution using ethanol as co-solvent or TEOS/H₂O two phases solution,followed by the precipitation of copper on SiO₂ by ammonia evaporation. In the hydrogenation of dimethyl oxalate,the catalyst prepared by one phase hydrolysis exhibited higher activity and ethylene glycol（EG） selectivity at lower temperature than that of two phases due to its larger BET surface area and multimodal pore distribution.At 488-503 K,the catalyst prepared in one phase solution with water/ethanol（W/E） volume ratio of 3:1 exhibited 90- 95%EG selectivity,while catalyst prepared by two phase hydrolysis reached 90%EG selectivity only at 498-503 K.     

Simultaneous determination of diethylene glycol and propylene glycol in pharmaceutical products by HPLC after precolumn derivatization with p-toluenesulfonyl isocyanate

A simple and reliable HPLC method was developed for the simultaneous quantitative analysis of diethylene glycol (DEG) and propylene glycol (PG) in pharmaceutical products by precolumn derivatization. The derivatization reagent p-toluenesulfonyl isocyanate (TSIC, 10 microL, 20% in ACN v/v) was added to 100 microL of the sample, and then 10 muL of water was added. The resulting derivatives were separated using a C(18)analytical column and a mobile phase composed of 0.01 M KH(2)PO(4)buffer (adjusted to pH 2.5 with phosphoric acid) and ACN (47:53 v/v) at 1 mL/min and 25 degrees C. For detection, UV light at 227 nm was used. The derivatization conditions including reaction time, temperature, and concentration of TSIC were optimized. The calibration curves were linear from 0.062 to 18.6 microg/mL (r(2)= 0.9999) and from 0.071 to 21.3 microg/mL (r(2) = 0.9999) for DEG and PG, respectively. The RSD values of intra- and interday assays were all below 4% for DEG and PG. The proposed method was then successfully applied to analyze two Armillarisin A injection samples and two spiked syrup samples.     

Ab initio study of the conformational equilibrium of ethylene glycol

Summary The conformational equilibrium of ethylene glycol (CH₂OHCH₂OH) has been examined by performing geometry optimizations at the 6-31G*, MP2/6-31G* and 6-31G** levels. Final energies have been calculated at the MP3 level with the optimized geometries. The two most stable conformers are atGg andgGg but it is verified that the inclusion of electronic correlations reduces their energy difference of 0.6 kcal/mol at the HF level to less than 0.2 kcal/mol. The possible coexistence of the two most stable conformers is in agreement with some previous studies of Frei et al. For thetXg conformer a detailed analysis of the intramolecular potential as a function of rotation around the C-C bond is also reported.     

Extraction and determination of morphine in compound liquorice using an aqueous two-phase system of poly(ethylene glycol)/K2HPO4 coupled with HPLC

An aqueous two-phase system (ATPS) of poly(ethylene glycol) (PEG)/K₂HPO₄ coupled with high performance liquid chromatography (HPLC) method was developed for the separation and determination of morphine in compound liquorice. Morphine and its analogs were used as model compounds to investigate influence of various factors on extraction behaviors of ATPS, such as the types and concentrations of salts, PEG molecular mass, temperature and pH. It was observed that the types of salt had much influence on extraction efficiencies of morphine and its analogs. The results indicated that hydrophobic force cooperating with hydrogen bond interaction between analytes and phases played important role in extraction process. In the optimal system of containing 0.5 g PEG2000 and 1.5 g K₂HPO₄, the recoveries of the spiked standards for the analytes were all 91.7-100.3% with relative standard deviation of 1.0-3.0%. Morphine in compound liquorice was determined by the proposed method and the results were consistent with those of LC-MS method. Compared with conventional liquid-liquid extraction or solid-phase extraction, this extraction method can be completed in one operation and is low-cost. Since the entire extraction process is organic solvent-free, this new technique is environmental friendly.     

Electrocatalytic selective oxidation of ethylene glycol: A concise review of catalyst development and reaction mechanism with comparison to thermocatalytic oxidation process

As an important water and seawater degradable plastic monomer, glycolic acid can be synthesized by selective oxidation of ethylene glycol. This review recapitulates recent advances in electrocatalytic ethylene glycol oxidation reaction (EGOR) from the aspects of catalytic performance and reaction mechanism. For catalytic performance evaluation, target product yield and space-time yield are correlated and analyzed for electrocatalytic and thermocatalytic EGOR systems. To elucidate the rationale behind the electrocatalytic selective oxidation of ethylene glycol, previous works using in situ Fourier transform infrared spectroscopy, online differential electrochemical mass spectrometry, ion chromatography, and theoretical calculations to investigate EGOR are systematically reviewed. Finally, the advantages of electrocatalytic EGOR are summarized by comparing electrocatalytic and thermocatalytic processes.     

高效液相色谱法测定药品中的乙二醇二乙醚二胺四乙酸

建立了高效液相色谱分析方法用来测定药品中乙二醇二乙醚二胺四乙酸(EGTA)含量,通过检测EGTA与Cu²⁺的配合物EGTA-Cu来检测EGTA。采用Ultimate-AQ C18色谱柱(250 mm×4.6 mm, 5 μm),流动相为乙腈-四丁基氢氧化铵水溶液(质量分数约0.3%四丁基氢氧化铵水溶液,醋酸调pH 6.50)-醋酸钠溶液(35 mmol/L醋酸钠,醋酸调pH 6.50)(20:20:60, v/v/v),检测波长为245 nm,流速为1.50 mL/min,柱温为40 ℃,进样量为100 μL。结果表明,EGTA质量浓度在0.10~15.00 mg/L范围内线性关系良好(R=0.9998);以信噪比(S/N)为3及10确定检出限和定量限,分别为0.05 mg/L和0.17 mg/L;样品加标平均回收率为98.34%~99.03%, RSD为1.08%~3.33%(n=9)。该方法操作简便,具有分离度好、灵敏度高、重复性好、回收率高等特点,适合药品中EGTA含量的检测,为EGTA检测提供了一种有效的检测方法。     

Gas chromatography with mass spectrometry for the quantification of ethylene glycol ethers in different household cleaning products

A rapid and simple procedure is reported for the determination of six ethylene glycol ethers in cleaning products and detergents using gas chromatography with mass spectrometry. The analytes were extracted from 2.0 g samples in acetonitrile (3 mL) and the extract was submitted to a clean‐up step by QuEChERS method, using a mixture containing 0.3 g magnesium sulfate, 0.15 g primary/secondary amine, and 0.05 g C₁₈. The clean acetonitrile extract (1 μL) was injected into the chromatographic system. No matrix effect was observed, so the quantification of the samples was carried out against external standards. Detection limits were in the range 3.0–27 ng/g for the six ethylene glycol ethers. The recoveries obtained, using the optimized procedure, were in the 89.4–118% range, with relative standard deviations lower than 14%. Twenty‐three different household cleaning products, including glass cleaner, degreaser, floor, softeners, and clothes and dishwashing detergents, were analyzed. Large interindividual variations were observed between samples and compounds.     

Ethylene glycol aluminum as a novel catalyst for the synthesis of poly(ethylene terephthalate)

Ethylene glycol aluminum was prepared efficiently and characterized by FT-IR and NMR.It exhibited higher catalytic activity and had profitable effect than titanium glycolate and ethylene glycol antimony for the synthesis of poly(ethylene terephthalate) (PET).It was only used as polycondensation catalyst because it was sensitive to water.For this catalyst,the degree of esterification of the theoretical amount of water was produced up to 95%at 260℃,while the intrinsic viscosity and content of terminal carboxyl groups of the corresponding PET polyester,polymerized at 280℃,70 Pa for 39 min,was 0.87 dL/g and 23.0μmol/g,respectively. Ethylene glycol aluminum was a promising catalyst for the synthesis of PET polyester.