Progress in Processes and Catalysts for Dehydrogenation of Cyclohexanol to Cyclohexanone

The dehydrogenation of cyclohexanol to cyclohexanone is a crucial industrial process in the production of caprolactam and adipic acid, both of which serve as important precursors in nylon textiles. This endothermic reaction is constrained by thermodynamic equilibrium and involves a complex reaction network, leading to a heightened focus on catalysts and process design. Copper-based catalysts have been extensively studied and exhibit exceptional low-temperature catalytic performance in cyclohexanol dehydrogenation, with some being commercially used in the industry. This paper specifically concentrates on research advancement concerning active species, reaction mechanisms, factors influencing product selectivity, and the deactivation behaviors of copper-based catalysts. Moreover, a brief introduction to the new processes that break thermodynamic equilibrium via reaction coupling and their corresponding catalysts is summarized here as well. These reviews may off er guidance and potential avenues for further investigations into catalysts and processes for cyclohexanol dehydrogenation.

Selective hydrogenation of phenol to cyclohexanone in water over Pd catalysts supported on Amberlyst-45

A series of Pd catalysts were prepared on different supports（Fe2O3,SiO2,ZnO,MgO,Al2O3,carbon,and Amberlyst-45） and used in the selective hydrogenation of phenol to cyclohexanone in water.The Amberlyst-45 supported Pd catalyst（Pd/A-45） was highly active and selective under mild conditions（40-100 ℃,0.2-1 MPa）,giving a selectivity of cyclohexanone higher than 89%even at complete conversion of phenol.Experiments with different Pd loadings（or different particle sizes） confirmed that the formation of cyclohexanone was a structure sensitive reaction,and Pd particles of12-14 nm on Amberlyst-45 gave better selectivity and stability.

The Effect of Platinum on Stability of the B_2O_3/TiO_2-ZrO_2 Catalyst for Beckmann Rearrangement of Cyclohexanone Oxime

The addition of platinum over the B2O3/TiO2-ZrO2 remarkably enhanced its catalytic stability in the vapor phase Beckmann rearrangement of cyclohexanone oxime under the carder gas of H2. The content of coke deposited on catalyst surface was decreased from 1.92% over the B2O3/TiO2-ZrO2 to 1.14% over the platinum promoted B2O3/TiO2-ZrO2 after reaction of six hours. This result indicates that the platinum added on the B2O3/TiO2-ZrO2 catalyst plays an important role in reducing the coke formation on the catalyst surface.

Solid-Liquid Equilibria of Succinic Acid in Cyclohexanone,Cyclohexanol and Their Mixed Solvents

Solubilities were measured for succinic acid dissolved in cyclohexanone, cyclohexanol and 5 of their mixed solvents at the temperature range from 291. 85 K to 358.37 K using a dynamic method. The solubility data were regressed by λh equation, with,the average absolute relative deviation 3.47%. The binary interaction parameter is 0.306 7 for the mixed solvent of oyolohexanone and cyclohexanol was determined by correlating the experimental solubilities with the modified λh equation. When the binary interaction parameter was determined it can be used to extrapolate the solubilities of succinic acid in mixed solvents of cyclohexanone and cyclohexanol at any proportion.The average absolute relative deviation was 7. 69% by using the modified λh equation to correlate the solubility data, however, the average absolute relative deviation was 8.89% by using NRTL equation to correlate the solubility data. The results show that the accuracy of the modified λh equation is better than that of the NRTL equation for the solubility of succinic acid in the 5 mixed solvents of cyclohexanone and cyclohexanol.

Study on the Performance of Regenerated Catalyst for Ammonoximation of Cyclohexanone

The study on the deactivated catalyst and the regenerated catalyst for the 70 kt/a cyclohexanone ammonoximation commercial test unit had revealed that addition of a proper amount of silicon additive could suppress the solubilization-induced loss of silicon in catalyst while providing protection to the catalyst. Compared to the direct calcination method for catalyst regeneration, adoption of the regeneration method through pretreatment-calcination of catalyst could be more beneficial to the restoration of catalyst channels and enhancement of the performance of the regenerated catalyst, which could be repeatedly regenerated and utilized. The outcome of commercial scale testing of the catalyst had indicated the good performance of the regenerated catalyst, which could be used for four times, resulting in a reduction of the production cost of cyclohexanone-oxime in big chunks.

Catalytic synthesis of cyclohexanone 1,2-propanediol ketal with H_4SiW_(12)O_(40)/PAn

A new environmental friendly catalyst, H_4SiW_(12)O_(40)/PAn was prepared andidentified by means of FT-IR, XRD and TG/DTA. Cyclohexanone 1,2-propanediol ketal was synthesizedfrom cyclohexanone and 1,2-propanediol in the presence of H_4SiW_(12)O_(40)/PAn The factorsinfluencing tlie synthesis were discussed and the best conditions were found out. The optimumconditions are: molar ratio of cyclohexanone to 1,2-propanediol is 1:1.4, the quantity of catalystis equal to 1.0 percent of feed stocks, and the reaction time is 40 min. H_4SiW_(12)O_(40)/PAn is anexcellent catalyst for synthesizing cyclohexanone 1,2-propanediol ketal and its yield can reachover 96.5 percent.

Phenol hydrogenation to cyclohexanone over palladium nanoparticles loaded on charming activated carbon adjusted by facile heat treatment

Selective phenol hydrogenation is a green approach to produce cyclohexanone.It still remains a big challenge to prepare efficient supports of the catalysts for the phenol hydrogenation via a simple and cost-effective approach.Herein,a facile approach was developed,i.e.,direct calcination of activated carbon(AC)under argon at high temperature,to improve its structure and surface properties.The modified AC materials were supported with Pd nanoparticles(NPs)to fabricate the Pd/C catalysts.The as-prepared Pd/C600 catalyst exhibits superior catalytic performance in the phenol hydrogenation,and its turnover frequency(TOF)value is 199.2 h^-1,1.31 times to that of Pd/C-raw.The Pd/C600 catalyst presents both better hydrophobicity and more structural defects,contributing to the improved dispersibility in the reaction solution(phenol-cyclohexane),the better Pd dispersion and the smaller Pd size,which result in the enhancement of the catalytic performance.Furthermore,the as-prepared Pd/C600 catalyst shows a good recyclability.

Towards the selectivity distinction of phenol hydrogenation on noble metal catalysts

Selective hydrogenation of phenol to cyclohexanone is intriguing in chemical industry.Though a few catalysts with promising performances have been developed in recent years,the basic principle for catalyst design is still missing owing to the unclear catalytic mechanism.This work tries to unravel the mechanism of phenol hydro-genation and the reasons causing the selectivity discrepancy on noble metal catalysts under mild conditions.Results show that different reaction pathways always firstly converge to the formation of cyclohexanone under mild conditions.The selectivity discrepancy mainly depends on the activity for cyclohexanone sequential hy-drogenation,in which two factors are found to be responsible,i.e.the hydrogenation energy barrier and the competitive chemisorption between phenol and cyclohexanone,if the specific co-catalyzing effect of H 2 O on Ru is not considered.Based on the above results,a quantitative descriptor,E b(one/pl)/E a,in which E a can be further correlated to the d band center of the noble metal catalyst,is proposed by the first time to roughly evaluate and predict the selectivity to cyclohexanone for catalyst screening.

环己酮制备实验的改进

“环己酮的制备”是化学、化工专业大学有机化学实验中的一个代表性实验。实验以环己醇为原料,经重铬酸或次氯酸钠氧化得到环己酮,这会造成重金属铬对环境的污染或次氯酸钠分解产生的氯气对实验者的刺激和毒害。以双氧水为氧化剂,对环境友好。通过催化剂、缓冲剂及温度等条件对环己酮合成影响的试验研究,发现以Fe^(3+)为催化剂,NaH_(2)PO_(4)为缓冲剂,在回流条件下H_(2)O_(2)氧化环己醇制备环己酮的产率约为60%。

过氧化氢/环己酮氧化法合成ε-己内酯催化剂研究进展

ε-己内酯是一种重要的有机中间体,也是合成生物可降解材料聚己内酯、高性能材料聚氨酯等重要聚合物的单体,具有非常广阔的应用前景。在目前已报道的合成方法中,以环己酮为原料,采用过氧化氢氧化法合成ε-己内酯是一种新型的绿色合成方法。在此方法中,由于过氧化氢的活性较低,高效催化剂的引入至关重要。从均相催化剂和非均相催化剂两个角度,综述了使用过氧化氢氧化法合成ε-己内酯的研究进展,通过实例,对比分析不同催化剂的优势和劣势,指出了杂多酸负载多相化策略不仅保留了杂多酸催化剂活性高、选择性好的优点,同时解决了催化剂的分离问题,是一种发展前景较好的催化剂。最后总结了ε-己内酯的应用市场及产业化开发的现状,并展望了在未来研究者们应重点关注的问题。

环己烯制环己醇工艺水合催化剂研究进展

综述了环己烯制环己醇工业生产工艺中所用到的矿物质酸均相催化剂、离子交换树脂、沸石催化剂等三种不同类型的水合催化剂的研究进展,并从结构特点、合成方法与影响因素等方面详细介绍了工艺常用的催化剂ZSM-5分子筛,以期为提高水合工艺催化剂性能和工业生产环己醇收率,阐明分子筛反应机理和开发新型分子筛催化剂提供参考。

高性能环己酮催化剂工业应用实验研究

以10万t/a环己酮装置为例,探讨了目前我国环己酮装置的发展概况,对环己酮生产过程中碳耗进行了分析,通过分析总结出了目前环己酮装置低碳工艺路线的开发主要为高性能的苯部分加氢催化剂技术的开发。结合生产实际研究了高性能苯部分加氢催化剂在工业装置的应用,总结了其应用的规律,并初步归纳了调整的经验。

One-pot conversion of cyclohexanol to ε-caprolactam using a multifunctional Na_2WO_4-acidic ionic liquid catalytic system

Na2WO4‐acidic ionic liquid was used as a simple, ecofriendly, recyclable and efficient catalytic system for the one‐pot conversion of cyclohexanol to ε‐caprolactam. The effect of the structure of the ionic liquid on the catalytic activity of this system was investigated, and the results revealed that sulfonic acid‐functionalized ionic liquids with HSO4? as an anion gave the best results. The highly efficient performance of this catalyst system was attributed to the phase‐transfer behavior of the cation of the ionic liquid, the improved coordination of the substrate to bisperoxotungstate duringthe oxidation reaction, and the stabilization of the intermediate formed during the Beckmann rearrangement.

Ni-Ce/N-rGO催化剂的表征及其催化苯酚加氢制备环己酮的性能

以鳞片石墨、尿素为原料,采用水热法制备了氮掺杂还原氧化石墨烯(N-rGO)载体,然后采用浸渍法制备了不同碱性组分改性的Ni/N-rGO催化剂,将其用于苯酚选择性加氢制备环己酮的反应。并通过N_(2)吸附-脱附、XRD、FT-IR、SEM和EDS等手段对Ni/N-rGO催化剂进行表征。结果表明:与添加Cu、Fe、Na组分相比,添加组分Ce后Ni/N-rGO催化剂的比表面积和孔径均显著增大,可有效促进金属Ni在载体表面均匀分散,提高催化剂的活性;组分Ce的添加减弱了石墨烯表面含氧官能团的酸性质,有利于提高环己酮的选择性;在反应温度150℃、反应压力0.4 MPa、反应时间2.0 h、催化剂用量0.2 g的条件下,Ce/Ni摩尔比0.2时制备的Ni-Ce/N-rGO催化剂作用下,苯酚转化率为95.2%,环己酮选择性为72.6%。

对叔丁基苯酚选择加氢催化剂的制备与性能评价

以氢氧化铝为前体制备了Al_(2)O_(3)载体,以MgO为结构助剂、Ni为活性组分制备了催化剂;采用XRD、N_(2)吸附-脱附、H_(2)-TPR、压汞法对催化剂进行了表征;以对叔丁基苯酚为原料、异丙醇为溶剂,在微型固定床反应器上对催化剂进行评价,考察了Ni负载量、反应温度、压力、液时空速对对叔丁基苯酚选择加氢反应的影响,并考察了催化剂的稳定性。实验结果表明,Ni负载量为30%(w)时,催化剂的选择加氢性能最佳;最佳反应条件为:反应温度160℃、液时空速2.5 h^(-1)、反应压力2 MPa,在此条件下,对叔丁基苯酚转化率可达到96.39%、对叔丁基环己醇的选择性可达到95.68%。在连续反应300 h的过程中,催化剂的稳定性较好。

Cu/SiO_(2)复合材料体系的构建及其高效催化醇类脱氢性能研究

铜基催化剂对环己醇的非氧化脱氢具有较高的选择性,但转化率仍然不足,且铜基催化剂的稳定性因铜烧结而需要提高。通过湿化学法制备了Cu/SiO_(2)纳米颗粒,并对催化剂进行了XRD、SEM、TEM、FT-IR、BET、XPS和UV-Vis表征。结果表明,在280℃和WHSV为11.62 h^(-1)的条件下,该催化剂对环己醇脱氢制环己酮的选择性接近100%,摩尔转化率为81%。此外,该催化剂对苯甲醇脱氢制苯甲醛也有良好的性能,在260℃、WHSV为12.48 h^(-1)时,苯甲醇的摩尔转化率为75%,苯甲醛的收率为61%;该条件下,催化剂的活性在48 h内保持稳定。

环己酮的制备实验改进

氧化反应是有机化学课程中需掌握的重要知识点,然而,有机化学实验教材中环己醇氧化为环己酮,所用的重铬酸钠和浓硫酸组合,毒性大,腐蚀性强,有些学校取消了这个氧化实验,从而导致理论与实验之间的脱节。为了弥补这个环节,开发了一种新的氧化方法,使用4-乙酰氨基-2,2,6,6-四甲基-1-氧杂哌啶四氟硼酸盐(巴比特盐)将环己醇清洁地氧化成环己酮。可作为一种安全、方便和绿色的反应用于本科教学实验,并且可以在标准的3~4 h内完成实验。

我国环己酮合成工艺技术研究进展

环己酮是一种具有重要用途的有机化工原料中间体,主要用于生产己内酰胺和己二酸等产品。随着我国己内酰胺和己二酸生产能力的不断发展,对环己酮的需求量越来越大,环己酮具有较好的发展前景。本文综述了我国以环己醇、环己烷、苯酚以及环己烯等为原料合成环己酮的工艺技术及研究进展,提出了今后的发展建议。

金属基催化剂在环己烷氧化中的应用研究进展

综述了金属基多相催化剂催化氧化环己烷合成各类化学品的研究进展,包括环己烷催化氧化制环己醇/环己酮、环己烷一步氧化制己二酸、环己烷氧化脱氢制环己烯等。重点介绍了金属基催化剂中活性位点类型、组成等对环己烷氧化过程转化率及选择性的影响。开发高分散、高活性、高选择性的金属多相催化剂是今后环己烷催化氧化制环己酮/环己醇、环己烷一步氧化制己二酸、环己烷选择性氧化定向生成环己烯的主要研究方向,特别是具有多金属复合纳米结构及特殊活性位点的催化剂体系。