Kinetic study for the oxidation of cyclohexanol and cyclohexanone with nitric acid to adipic acid

The adipic acid is an important intermediate in the production of nylon, polyurethane and polyester resins. The industrial approach for preparing adipic acid is through the liquid catalytic oxidation of KA oil with nitric acid. In this work, a comprehensive model is developed for this reaction based on the kinetic study conducted in a continuous flow tubular reactor. The kinetic model fits well with the experimental results across the experimental conditions, and the average relative error between the calculated and experimental values is 5.7%. Results show that there was an induction period at the early stage of reaction. Moreover, it is found that at temperature range of 328-358 K, the formation rate of adipic acid strongly dependents on the temperature and nitric acid concentration. The developed model is used to predict the yield of adipic acid at 359-368 K. The work in this study could provide much knowledge for industrial tubular reactor design.     

基于BP神经网络的乳酸脱水制丙烯酸仿真模拟

通过生物质发酵产生的乳酸（2-羟基丙酸）在食品和医药领域具有广泛的商业应用价值,作为可再生资源的生物质乳酸已成为备受关注的化学原料。本文采用BP神经网络对乳酸脱水制丙烯酸的催化过程进行了仿真研究。采用正交实验设计确定实验点,主要考察原料液pH、原料液流速、载气流量和温度4个因素对丙烯酸产率的影响。针对正交实验的缺陷,将正交实验设计和神经网络结合起来,采用基于DOS界面并能方便调节BP神经网络计算的程序包对正交实验结果进行训练,用训练好的网络模拟催化反应体系的动态过程。结果表明,由神经网络仿真模拟出的三维图可以直观地体现各个反应条件对丙烯酸产率的影响,并用穷举法求出最佳反应条件,在该条件下的神经网络模拟产率为27.45%,与实验结果较吻合,相对误差约为－0.4391%。     

硝酸氧化醇酮生产己二酸反应机理和影响因素

硝酸氧化醇酮是极其快速的强放热氧化反应，是一种自由基链式反应，在生成最终产物己二酸之前，要经过一系列中间产物，其中，6-肟基-6-硝基己酸(硝脑酸,NA)和双酮是反应过程中生成的相对稳定和对己二酸收率影响较大的关键中间产物。为提高己二酸收率，应使反应向生成硝脑酸方向进行，促进双酮分解成己二酸，减少副反应。对硝酸氧化醇酮反应机理进行了分析，并通过工业化的试运转，得出反应温度，硝酸投料比和催化剂浓度是影响己二酸收率的关键因素。     

Hydrodynamics study of a fast liquid–liquid oxidation process with in situ gas production in microreactors

Hydrodynamics characteristics of a fast and highly exothermic liquid–liquid oxidation process with in situ gas production in microreactors were studied using a newly developed experimental method. In the adipic acid synthesis through the K/A oil (the mixture of cyclohexanol and cyclohexanone) oxidation with nitric acid, bubble generation modes were divided into four categories. The gas production became more intensive, unstable, even explosive with increasing the oil phase feed rate and the temperature. A novel automatic image processing method was developed to monitor the instantaneous velocity online by tracking the gas–liquid interface. The axial velocity at the same location was unstable due to the changing gas production rate. Furthermore, the actual residence time was obtained easily with being only 36% of the space–time minimally, beneficial for establishing accurate kinetics and mass transfer models with time participation. Finally, an empirical correlation was developed to predict the actual residence time under different conditions.     

金属卟啉催化空气氧化环己烷反应的工艺优化

简单铁、钴、铜、锰四苯基卟啉用于催化空气氧化环己烷联产KA油（环己醇和环己酮）和己二酸的反应，利用正交实验方法考察了锰四苯基卟啉催化下环己烷氧化反应中反应温度、压力、空气流速、时间、催化剂用量对反应转化率和产物选择性的影响，并获得了优化的工艺条件。以醇酮酸（环己醇、环己酮和己二酸）总产率作为评价指数进行极差分析得到温度、空气流速、反应时间、压力、催化剂量的极差值分别为6.17、3.12、2.25、1.81、1.53，表明温度是影响环己烷氧化的关键因素。锰四苯基卟啉催化环己烷空气氧化反应的优化工艺条件为温度150 ℃、压力1.2 MPa、空气流速0.13 m3·h-1、催化剂用量7 mg、反应时间3.5 h。验证实验表明，在上述优化条件下，环己烷转化率达20.0 %，醇酮酸总选择性可达90.0 %，己二酸选择性达到21.0%。     

葡萄糖氧化制草酸

针对目前国内草酸生产成本高、工艺复杂等缺点,开展了葡萄糖氧化制草酸的工艺研究。以蔗糖、葡萄糖等碳水化合物为原料,在硫酸、硝酸和水的混合物为氧化介质的反应体系中氧化为草酸。在优化工艺条件下:硫酸的浓度为50%,反应温度60～65℃,m(葡萄糖)∶m(硝酸)=1∶3.2,催化剂的加入量为0.05%(以葡萄糖计,m/m),加料时间6h,母液循环使用。每吨葡萄糖可产草酸1.65～1.75t,收率达90%以上。     

A comparative study on the effectiveness of nitrogen or carbon dioxide flushing in preventing oxidation during the heating of oil

Nitrogen and carbon dioxide gases were evaluated for their ability to protect canola oil from oxidation during heating at frying temperatures. Oil samples were heated in a variety of containers of differing dimensions through which the flow of these gases was regulated. Formation of volatile compounds was analyzed by direct capillary gas chromatography, while chemical analyses included peroxide value and thiobarbituric acid. Flushing with either of these gases at a slow flow rate in 53-mm containers stimulated oxidation rather than arresting it. Carbon dioxide, because of its higher solubility in oil and its density, afforded better protection of canola oil samples during heating. Optimal conditions for minimizing oxidation, such as container dimensions, volume of oil and flow rate of gases, are discussed.     

Two-step continuous synthesis of tetraethylthiuram disulfide in microstructured reactors

We present two-step continuous synthesis of tetraethyl thiuram disulfide using microstructured reactors, starting with the formation of N, N-diethyldithiocarbamic acid from carbon disulfide and diethylamine in the first mi- crostructured reactor, and the oxidation of N, N-diethyldithiocarbamic acid by hydrogen peroxide in the second one. We studied the effects of reaction temperature, LHSV and total flow rate on the yield of the product. In the first microstructured reactor assembled with an HPIMM micromixer and a stainless steel capillary as the delay loop, the yield of N, N-diethyldithiocarbamic acid reached 96.3% in the 40 wt% diethylamine ethanol solution under reaction conditions of the CS₂/(C₂H₅)₂NH molar ratio of 1.1: 1, total flow rate of 4 mL/min, LHSV of 42.4 h⁻¹, and reaction temperature of 25 °C. Consequently, the obtained N, N-diethyldithiocarbamic acid solution was reacted with H₂O₂ solution in another microstructured reactor assembled with SIMM-V2 and a PTFE capillary as the delay loop, the yield of the high purity tetraethylthiuram disulfide reached 89.3% under the optimized reaction conditions.     

β-甲基萘合成2-甲基-1,4-萘醌绿色氧化反应工艺

2-甲基-1,4-萘醌(2-MNQ)是K族维生素的重要中间体,广泛应用于医药、农药、饲料添加剂等领域。本工作以2-甲基萘(2-MN)为原料,(NH4)2S2O8为引发剂,用30% H2O2与冰醋酸在硫酸催化下制备过氧乙酸并滴加至反应液中,氧化合成2-甲基-1,4-萘醌(2-MNQ),通过ICIR, GC-MS, LCMS对其结构进行表征,并验证氧化反应机理及中间产物。考察了催化剂、反应温度、反应时间、氧化剂与引发剂用量对产品2-MNQ收率、转化率的影响,采用HPLC (外标法)测定产品2-MNQ的转化率和收率,得到最佳工艺条件为反应温度65℃、反应时间5 h、n(H2O2):n(2-MN)=26:1,此时,2-甲基萘的转化率为99%,产品收率为34%。本工作的创新点是使用原位红外技术验证反应机理和中间过程,即原料2-甲基萘经过氧乙酸氧化,发生环氧化反应生成中间体,之后重排生成2-甲基羟醌,继续氧化生成目标产物2-甲基-1,4-萘醌。该工艺具有简单环保、操作条件温和、原料易得等特点。     

Identification of the reaction network for the synthesis of adipic acid using machine learning coupling with target factor analysis

This study investigated the reaction network of the oxidation of cyclohexanone with nitric acid through machine learning (ML) model coupling with target factor analysis (TFA). Experiments for the synthesis of adipic acid (AA) were carefully designed and carried out in a microreactor system. An artificial neural network (ANN) model was applied and optimized by training on experimental data. To assess the established ANN model, a comparison between the predicted concentrations of the products and those calculated with the power law kinetic model was implemented. TFA was then performed on both the experimental data and the data simulated by ANN for identifying the candidate reactions and finding out the temperature boundaries. Based on the identification results of the reaction network, the kinetic characteristics of this oxidation process under various operational conditions were further researched through the incremental approach and simultaneous approach.     

生物柴油副产物粗甘油催化氧化脱水制备丙烯酸

用生物柴油副产物粗甘油催化氧化脱水制丙烯酸,该过程耦合了甘油脱水制丙烯醛和丙烯醛选择性氧化制备丙烯酸两步反应。结果表明,在甘油脱水反应中,使用Cs3PW12O40, P-ZSM-5和Co0.5H2PO4/SiO2等固体酸催化剂,可得到较高的丙烯醛收率(最高86.9%)。利用上述催化剂和MoVW基氧化催化剂,在脱水/氧化双催化剂床层构型反应器中,以甘油为原料合成丙烯酸的收率达50%~80%,直接加入粗甘油可获得相似的丙烯酸收率。     

丁二烯和醋酸电化学合成山梨酸

正交实验表明 ,在醋酸 醋酐体系中 ,Mn2 + 电解氧化生成Mn3 + 的最佳工艺为 :电解时间 1h ,电解温度 90℃ ,电流密度 5mA/cm2 ,电解液 (2 0 0mL)组成 :5 70gMn(OAc) 2 ·4H2 O +2 0 .0gKOAc+醋酸与醋酸酐的混合物 ,V(HOAc)∶V(Ac2 O) =3∶1,电流效率为 75 %。稳态极化曲线和RDE实验表明 ,在石墨电极上 ,Mn2 + 阳极氧化的电极反应控制步骤为扩散 电荷传递混合控制。通过Mn3 + 氧化有丁二烯存在的醋酸 醋酐体系 ,合成山梨酸的前体乙酰氧基己烯酸 (AA) ,丁二烯的浓度为 0 2 5～ 1.0 0mol/L ,温度控制在 90℃ ,反应 5h ,得到AA。用盐酸可将AA进一步水解生成山梨酸 ,反应温度为 90℃ ,反应 5～ 6h ,产率超过 80 % (对AA而言 )。     

Kinetics of Sulfite Oxidation in the Simultaneous Desulfurization and Denitrification of the Oxidation‐Absorption Process

The kinetics of sulfite oxidation in the simultaneous desulfurization and denitrification of the oxidation‐absorption process was investigated with a bubbling apparatus under the conditions of varying pH, sulfite concentration, nitrite concentration, temperature, and air flow. The results indicate that the oxidation of sulfite is promoted dramatically by mixing with nitrite, due to the decline of the apparent energy of activation and the initiation of nitric dioxide decomposition by nitrite. An increase of the nitrite concentration, the air flow, the reaction temperature, or the pH supports the decomposition of nitrite and the production of nitric dioxide, thus leading to an enhancement of the sulfite oxidation rate. A kinetic model is established according to the experimental results. A satisfactory agreement between the calculated and the experimental values is obtained.     

丙烯酸改性腰果酚聚醚稠油破乳剂的合成与应用性能研究

以腰果酚聚氧乙烯醚(BGF-10)和丙烯酸(AA)为原料，通过直接酯化的方法在对苯二酚为阻聚剂，对甲苯磺酸催化作用下，合成了丙烯酸腰果酚聚醚酯(BGFAA)，探究了反应物物料比n(AA):n(BGF-10)、反应温度、反应时间、催化剂用量、阻聚剂用量对酯化率的影响，并在此基础上采用响应面优化法对酯化反应工艺条件进行了优化。得出合成BGFAA的最佳工艺条件为：在反应温度127℃、反应时间5.2h、n(AA):n(BGF-10)=1.6:1、阻聚剂用量0.6%(占反应物总质量)、催化剂用量5%(同上)时，酯化率高达93.23%，结构经红外光谱和核磁共振进行了表征确认；在偶氮二异丁腈引发作用下将自制BGFAA和丙烯酸（AA）引发聚合制备了新型稠油破乳剂(BGFAA)n，并以脱水率和脱出污水含油吸光度为指标研究了其对陈庄稠油w/o乳液的破乳脱水性能，当破乳温度为60℃、破乳时间为2.5h、破乳剂用量500mg/mL时，脱水率高达86.8%、脱出污水含油吸光度为1.05，表明(BGFAA)n在稠油乳液中具有脱水率高、脱出污水含油低水质清澈的优势。     

Enzymatic acidolysis of an arachidonic acid single-cell oil with capric acid

Incorporation of capric acid (CA) into arachidonic acid (AA) single-cell oil, using five commercial lipases, indicated that lipase PS-30 from Pseudomonas sp. was most effective. The optimal conditions included an oil-to-CA mole ratio of 1∶3, a temperature of 45°C, incubation time of 24 h, 4% lipase from Pseudomonas sp., and a 2% (w/w) water content. Examination of positional distribution of FA on the glycerol backbone of modified AA single-cell oil with CA showed that 89.7% of CA was concentrated in the sn-1,3 positions of the TAG molecules. AA was mainly located at the sn-2 position of the modified AA single-cell oil. Enzymatically modified AA single-cell oil had a higher conjugated dienes (CD) value than its unmodified counterpart. TBARS values of both modified and unmodified AA single-cell oils increased progressively during the entire storage period, but no significant difference existed between TBARS values of both oils. Thus, enzymatically modified oil was more susceptible to oxidation than its unmodified counterpart, when considering both CD and TBARS values. Removal of natural antioxidants during oil modification might play a significant role in rapid oxidative deterioration of enzymatically modified oils. This possibility was confirmed when starting materials were subjected to the same reaction process in the absence of any enzyme, as the resultant oil was indeed significantly less stable than the control oil.     

Die oxidation von butadienstyrolkautschuk und daraus gewonnenem vulkanisat mit salpetersäure

The interaction between butadiene-styrene-rubber Bulex-1500 (a commercial product containing 25 to 30% of styrene links) and a vulcanisate based on it and nitric acid was studied. It was established that a measurable yield of several reaction products may be obtained: Butadiene-styrene-rubber yields oxidized rubber, polyfunctional oligomer, and oxalic acid; the vulcanisate yields oxidized vulcanisate, polyfunctional oligomer, and oxalic acid. The effect of the conditions of oxidation (particle size, time, temperature) on the yield of the reaction products was studied. The conditions needed to obtain optimum yield of a given reaction product were determined. The influence of the styrene links from the molecule of butadienestyrene-rubber on the yield was studied and a comparison with butadiene rubber was made. It was established that oxalic acid is a product of a number of oxidation-decomposition processes in nitric acid medium, and a scheme of its formation was suggested. It was proved that oxidation-decomposition processes and nitration occur simultaneously. It was suggested that the interaction of nitric acid with butadienestyrene-rubber and its vulcanisate may be used to utilize waste products obtained from them.     

Electrolytic oxidation of Ce(III) in nitric acid and sulfuric acid media using a flow type cell

The electrochemical oxidation behavior of Ce(III) in nitric acid and sulfuric acid media with various concentrations and compositions were investigated by cyclic voltammetry (CV) and potentiostatic electrolysis. In nitric acid media, the peak potential separation for the redox reactions of the Ce(III)/Ce(IV) couple shifted to base side with the increasing concentration of nitric acid from 1 to 6 M. The kinetics of the Ce(III)/Ce(IV) couple is rapid in high concentration nitric acid. The formal potential is independent of both proton and nitrate concentrations while the standard rate constant increases with added protons but is independent of nitrate concentration. Constant-potential electrolysis also shows that a high proton concentration is electrochemically favorable for the electron transfer of the Ce(III)/Ce(IV) couple and for a high Ce(IV) yield in nitric acid media. The current efficiency was ca. 75% for the oxidation process of Ce(III) at 298 K. A Ce(IV) yield of ca. 80% was achieved for the electrolysis of 100 mM Ce(III) in 6 M HNO₃ solution. In sulfuric acid media, the peak potential separation for the redox reactions of the Ce(III)/Ce(IV) couple shifted to noble side with rising concentration of sulfuric acid from 0.1 to 2 M and then shifted to base side with further increase in the concentration. A Ce(IV) yield of ca. 95% was achieved for the potentiostatic electrolysis of 100 mM Ce(III) in 3 M H₂SO₄ solution.     

丙烯酸双环戊二烯酯的合成

以丙烯酸(AA)和双环戊二烯(DCPD)为主要原料,合成了丙烯酸双环戊二烯酯(DCPA)。采用单因素试验法探讨了催化剂含量、单体配比、反应温度和反应时间等对DCPA收率的影响,从中优选出合成DCPA的最佳工艺条件。结果表明:以磷钨酸为催化剂,并且当反应温度为70℃、反应时间为10 h、n(AA)∶n(DCPD)=1.2∶1和w(磷钨酸)=2.0%时,DCPA的收率(52.41%)相对最高。     

硝酸氧化仲辛醇液液非均相反应过程热危险性分析

利用反应量热仪器RC1分析半间歇操作下的硝酸氧化仲辛醇的反应放热过程,通过不同的反应温度、搅拌速率、加料时间等反应条件的变化,研究氧化反应过程中放热速率情况和热转化速率的变化趋势,推导出反应失控条件下的绝热温升和所能到达的最大温度等参数。分析结果表明:在室温下该反应就可以进行,随着反应温度的升高,反应放热速率加大;搅拌速率对非均相反应的影响明显;随着加料时间的延长,放热速率减慢,但会延长反应时间;综合分析判定其反应热失控,危险属于中度危险。     

硝酸氧化环己酮合成己二酸的实验研究

硝酸氧化环己酮是反应速度既快又复杂的氧化反应。为提高己二酸的收率及实验的安全性,本实验对反应的温度、硝酸的浓度、原料的配比及催化剂的用量等进行了实验分析。通过实验,确定了对提高己二酸的收率的反应条件。该实验操作方法简单、安全、产率高、可操作性强。