电合成芳香醛反应机理的研究

利用红外光谱（IR）研究了槽外合成对甲氧基苯甲醛和对溴苯甲醛的反应机理，结果证明：在Ce^4＋与对取代甲苯的氧化反应中，苯环上甲基被Ce^4＋氧化的难易受苯环上对位取代基的影响。对甲基苯甲醚先氧化成对甲氧基苯甲醇，再氧化成对甲氧基苯甲醛并最终氧化成对甲氧基苯甲酸，第一个电子传递步骤为控制步骤：对溴甲苯先氧化成对溴苯甲醇，再氧化成对溴苯甲醛，后者为控制步骤。     

槽外法苯甲酸催化甲苯电合成苯甲醛

以苯甲酸作相转移催化剂,Mn3+/Mn2+为媒介,甲苯为原料,采用槽外法电合成苯甲醛。利用正交实验研究了H2SO4浓度、反应温度和苯甲酸用量对苯甲醛生成速率和产率的影响。结果表明,当每升甲苯含8 g苯甲酸、水相H2SO4浓度为51.6%和反应温度85℃时,苯甲醛的收率大于93%。     

TEMPO抑制K_2S_2O_8氧化甲苯生成苯甲醛过程中的过度氧化

采用TEMPO/Cu(OAc)2为催化剂,探究其在抑制苯甲醛过度氧化成苯甲酸方面的能力,考察反应时间、反应温度、催化剂用量等因素对苯甲醛收率的影响。研究结果表明,TEMPO以及TEMPO衍生物在Cu(OAc)2催化下,可以有效地抑制甲苯合成苯甲醛过程中苯甲醛进一步氧化成苯甲酸。优化条件下,甲苯氧化生成苯甲醛的收率高达78%,而且没有苯甲醇和苯甲酸生成。     

无溶剂下钴卟啉/NHPI催化甲苯选择性氧化制备苯甲醛

以钴卟啉/N-羟基邻苯二甲酰亚胺(NHPI)为催化剂，分子氧为氧化剂，在无溶剂的条件下，研究温和条件下催化甲苯选择性氧化制备苯甲醛的工艺。在甲苯0.2 mol、钴卟啉物质的量分数1×10^-4%、NHPI物质的量分数0.25%、70℃、O₂压力2.0 MPa和3 h优化条件下，甲苯转化率为5.5%,苯甲醛、苯甲醇和苯甲酸选择性分别为88.0%、10.2%和0.8%。通过原位红外和电子顺磁共振波谱仪等表征方法，表明该反应机理为典型的自由基反应过程。     

甲苯制备苯甲醛合成工艺的改进

苯甲酸做相转移催化剂,在H2SO4溶液中用MnO2将甲苯氧化成苯甲醛.利用正交实验研究了H2SO4浓度、反应温度和苯甲酸用量对苯甲醛生成速率和收率的影响.结果表明,0.001 13 mol苯甲酸溶解到40 mL 58% H2SO4与10 mL甲苯组成的溶液中,在75 ℃与MnO2反应条件适宜,以MnO2计,苯甲醛收率42%.     

催化合成苯甲醛催化剂研究进展

综述了甲苯气相氧化法、液相氧化法、苯甲醇选择性氧化法、苯甲酸甲酯还原法制备苯甲醛的主催化剂研究进展,并提出了具有开发应用前景的八面体分子筛催化剂体系.     

苯甲醛制备高纯苯甲醇的工艺研究

通过苯甲醛歧化反应制备苯甲醇,由硼氢化钾精制苯甲醇,同时使用气相色谱法对高纯苯甲醇中苯甲醛的含量进行测定,控制苯甲醛在苯甲醇中的含量,以达到提高苯甲醇品质的目的。该研究结论对高纯苯甲醇制备方法的选择提供重要依据。     

苯甲醛清洁生产工艺技术研究进展

介绍了苯甲醛清洁生产工艺的甲苯气相氧化、甲苯液相氧化、苯甲醇氧化、苯甲酸还原法、苯甲酸甲酯还原法、间接电解氧化法及其氧化反应动力学、甲苯三氧化二锰非均相氧化、甲苯超(近)临界流体法、近临界水法等;提出三氧化二锰非均相氧化法和近临界水法具有比较好的工业应用前景。     

NHPI/Co(Salen)复合催化液相氧化甲苯的工艺考察

为了开发甲苯液相氧化的新催化体系,寻求合适的反应条件提高甲苯选择性氧化生成苯甲醛、苯甲醇的选择性。以分子氧为氧源,在无溶剂条件下,采用N-羟基邻苯二甲酰亚胺(NHPI)与双水杨醛缩乙二胺合钴配合物(Co(Salen))复合催化甲苯液相氧化反应。详细考察了NHPI单独催化以及NHPI与Co(Salen)复合催化过程中NHPI用量、Co(Salen)用量、反应温度、反应时间和氧压对甲苯选择性氧化反应的影响。结果表明:在甲苯0.22 mol,NHPI的摩尔分数2%,Co(Salen)的摩尔分数0.02%,氧压1.60 MPa,110℃的条件下反应2 h,甲苯转化率达到13.6%,苯甲醛选择性32.7%,苯甲醇选择性10.8%,苯甲醛、醇、酸总选择性达97.7%,该反应条件为较佳的工艺条件。     

苯甲酸类化合物的绿色合成

在钨酸钠、磺基水杨酸和十六烷基三甲基溴化铵催化下,以苯甲醛类化合物为原料,用30%过氧化氢作为氧化剂,合成了苯甲酸类化合物。研究了反应时间、过氧化氢用量和催化剂对苯甲醛氧化合成苯甲酸反应产率的影响,给出了绿色合成苯甲酸类化合物方法,得到了六个苯甲酸类化合物。     

锰卟啉-醋酸钴复合催化体系对甲苯氧气氧化的催化作用

研究了在无溶剂体系中,对氯四苯基锰卟啉［T(p-Cl)PPMnCl］和醋酸钴［Co(OAc)2］复合催化下,空气氧化甲苯制苯甲醛、苯甲醇和苯甲酸的新工艺。实验发现,T(p-Cl)PPMnCl/Co(OAc)2为复合催化剂时比单独使用T(p-Cl)PPMnCl 或Co(OAc)2时有更高的甲苯转化率和苯甲醛、苯甲醇、苯甲酸的收率,表现出明显的复合催化作用。研究表明,反应温度、反应时间和催化剂比例对T(p-Cl)PPMnCl/Co(OAc)2的复合催化效果有影响。     

苯甲酸工艺的节能减排以及连续化工艺的开发

文章针对传统苯甲酸生产工艺中产生的乏汽开发了乏汽回收技术,将低热蒸汽有效用于中和、干燥工段的加热,实现了节能减排的目的。在间歇操作的基础上,开发了甲苯连续催化氧化工艺。当离心多孔气体分布器的转速为550 r/min时,苯甲酸的收率可达50%。混合液体经过连续精馏不仅可得到苯甲酸,而且还可得到附加值很高的苯甲醇、苯甲醛以及苯甲酸苄酯。     

Aerial oxidation of substituted aromatic hydrocarbons catalyzed by Co/Mn/Br− in water-dioxane medium

Aerial oxidation of substituted aryl aromatic hydrocarbons were carried out using Co/Mn/Br⁻ catalyst system in water-dioxane medium in the range 14–56 bar air and temperature 383–423 K. The combination of optimum catalyst concentration of salts Co(OAc)₂, Mn(OAc)₂ and NaBr (1:3:10 molar ratio) in water-dioxane (1:2 mole ratio) is found catalyze aerial oxidation of substituted aryl aromatic to give corresponding oxygenated products. Under the optimized conditions, p-cymene gave p-isopropyl benzaldehyde (33.1%), p-isopropylbenzyl alcohol (54.7%) and p-isopropyl benzoic acid (3.3%), respectively, at p-cymene conversion 40.2%. Similarly, oxidation of p-methoxy toluene gave p-methoxy benzaldehyde (87.4%), benzyl alcohol (5.5%), and p-methoxy benzoic acid (6%), while oxidation of p-tert-butyl toluene yielded p-tert-butyl benzaldehyde (87%), p-tert-butyl benzyl alcohol (5.7%) and p-tert-butyl benzoic acid (6.1%), at conversions 16.4% and 36.1%, respectively. It is found that Co/Mn/Br⁻catalyst system in water-dioxane medium is effective in the aerial oxidation of substituted aromatic hydrocarbons to get corresponding alcohol and aldehydes in greater yields.     

超临界二氧化碳中的甲苯选择性氧化反应

考察了甲苯选择性氧化反应中反应物及产物在超临界二氧化碳中的溶解性质。结果表明,甲苯在超临界二氧化碳中的溶解度较大,在反应条件下能与二氧化碳形成均相;苯甲醇、苯甲醛和苯甲酸在超临界二氧化碳中的溶解度随着物质极性的增强而降低。利用不同产物的溶解性差异,可实现超临界二氧化碳中甲苯的选择性氧化。同时考察了超临界二氧化碳中甲苯选择性氧化反应过程中,反应时间、反应压力、反应温度以及n(甲苯)/n(氧气)对反应选择性的影响。     

甲苯液相催化氧化过程模拟与优化

Liquid-phase oxidation of toluene with air has become the main technology for producing benzoic acid in a reactor at present. Based on the kinetic model of the toluene oxidation process obtained from laboratory and mass balance of key component, a novel model is established to simulate the industrial toluene oxidation process, in which the effects of benzaldehyde and benzyl alcohol are considered and the kinetic parameters are revised by industrial data. The simulation results show that the error of benzoic acid yield is within 3.5%. Based on the simulation model, to maximize the benzoic acid yield, an optimization model is proposed to optimize the operating parameters, including toluene feed-in mass flux and temperature. The optimization result indicates that on the allowable operating conditions the maximum benzoic acid yield obtained with the reaction temperature at 167.2 C an the mass flux at 104.1 t·h^- 1 is greater than the current one, which can be used to guide industrial reactor s operation.     

金属卟啉催化的甲苯氧化及工艺优化

Catalytic activities of a series of metalloporphyrin complexes in selective aerobic oxidation of toluene were investigated.The effects of different central metal ions in metalloporphyrins[T（p-Cl）PPMCl（M=Fe,Co,Mn,Cu）] on the reaction course had been examined and it was found that T（p-Cl）PPCu presented the highest catalytic activity in the reaction.The reaction conditions of toluene oxidation were optimized by using orthogonal experiment design.Five relevant factors were investigated：temperature,air pressure,catalyst loading,air flow rate and reaction time.The effects of the five factors on both toluene conversion and total yield of benzaldehyde and benzyl alcohol were discussed.The research results showed that the reaction temperature was the most significant factor influencing toluene oxidation.On the basis of the margin analysis,the optimum conditions for the toluene conversion and the total yield of benzaldehyde and benzyl alcohol respectively were achieved,under which the toluene conversion was up to 14.67%and the total yield of benzaldehyde and benzyl alcohol reached 5.89%.     

有机锡催化合成乙酸苄酯新工艺研究

以新型不同类型的有机锡化合物为催化剂,对乙酸苄酯的酯化反应进行了研究,重点考察了不同类型的有机锡催化剂的催化效果、催化剂用量、反应温度、反应时间、酸醇摩尔比和带水剂等因素对乙酸苄酯产率的影响。实验结果表明,Ph3SnCl对合成乙酸苄酯有着良好的催化活性,当催化剂用量为苯甲醇和乙酸总质量1．5％,乙酸和苯甲醇的摩尔比为2．5：1,甲苯为10mU与苯甲醇的摩尔比为0．60）,温度110℃,反应150min后,乙酸苄酯产率可达98．4％．且催化剂重复使用5次仍保持较高活性。     

Relationship between the formation of surface species and catalyst deactivation during the gas-phase photocatalytic oxidation of toluene

Various partial oxidation products were identified on the surface of TiO₂ and an 8% SiO₂–TiO₂ binary catalyst used for the photocatalytic oxidation of gas-phase toluene. Using in situ FTIR spectroscopy, benzaldehyde and benzoic acid were identified on the surface of the deactivated photocatalysts. Additional GC/MS analysis of methanol-extracted surface species confirmed the presence of benzaldehyde and benzoic acid and detected small concentrations of benzyl alcohol. Apparently, benzaldehyde is the main partial oxidation product that is further oxidized to benzoic acid. Benzoic acid is strongly adsorbed on the surface of the catalyst. There seems to be a correlation between the accumulation of benzoic acid on the surface and catalyst deactivation. The presence of gas-phase water in the reactive mixture seems to retard the formation of benzoic acid.

The SiO₂–TiO₂ photocatalyst is more active and appears to deactivate slower than TiO₂. This binary oxide is photocatalytically active even in the absence of gas-phase oxygen. It also seems to have a higher toluene adsorption capacity than TiO₂. The acidity of the different oxides was examined using FTIR spectroscopy of adsorbed pyridine. The results indicate that no pure metal oxide displays Brønsted acidity but when SiO₂ is cofumed with TiO₂, Brønsted acidity of intermediate strength is generated. The generation of new surface sites may be responsible for the increased activity. The mechanism of this promotion effect is not clearly understood and further studies are required to elucidate it.     

Electrooxidation of benzyl alcohol and benzaldehyde on a nickel oxy-hydroxide electrode in a filter-press type cell

The electrooxidation of benzyl alcohol and benzaldehyde in alkaline medium was carried out in a filter-press type cell on a nickel oxy-hydroxide electrode under different experimental conditions. An overpotential occurs in the presence of organic molecules in the solution shifting oxygen evolution towards higher potentials. The results obtained were conclusive that benzyl alcohol and benzaldehyde electrooxidation on NiOOH layers yielded benzoic acid as the main final reaction product. Chromatographic analysis of the bulk solution showed that the electrocatalytic oxidation of harmful molecules was carried out until the formation of acid compounds (benzoic acid) as an ultimate stage, suggesting that a Ni anode can be used successfully for waste remediation.