Cooperative catalysis of Co single atoms and nanoparticles enables selective CAr-OCH_(3) cleavage for sustainable production of lignin-based cyclohexanols

In this work,a dual-size MOF-derived Co catalyst(0.2Co_(1-NPs)@NC)composed of single atoms(Co_(1))and highly dispersed nanoparticles(Co NPs)was prepared by in-situ Zn evaporation for the highperformance conversion of lignin-derived o-methoxyphenols(lignin oil)to cyclohexanols(up to 97%yield)via cascade demethoxylation and dearomatization.Theoretical calculations elaborated that the dual-size Co catalyst exhibited a cooperative effect in the selective demethoxylation process,in which the Co NPs could initially dissociate hydrogen at lower energies while Co1remarkably facilitated the cleavage of the C_(Ar)-OCH_(3)bond.Moreover,the intramolecular hydrogen bonds formed in the omethoxy-containing phenols were found to result in a decrease in the bond energy of the C_(Ar)-OCH_(3)bond,which was more prone to be activated by the dual-size Co sites.Notably,the pre-hydrogenated intermediate(e.g.,2-methoxycyclohexanol from guaiacol)is difficult to undergo demethoxylation,indicating that the selective C_(Ar)-OCH_(3)bond cleavage is a prerequisite for the synthesis of cyclohexanols.The 0.2Co_(1-NPs)@NC catalyst was highly recyclable with a neglect decline in activity during five consecutive cycles.This cooperative catalytic strategy based on the metal size effect opens new avenues for biomass upgrading via enhanced C-O bond cleavage of high selectivity.

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.

Synthesis and Characterization of Iron Oxide Nanoparticles Supported on Ziconia and Its Application in the Gas-Phase Oxidation of Cyclohexanol to Cyclohexanone

Iron oxide nanoparticles supported on zirconia were prepared by precipitation-deposition method and characterized by XRD, SEM, FT-IR, TGA/DTA, surface area and particle size analysis. Catalytic activities of the catalysts were tested in the gas-phase conversion of cyclohexanol in a fixed-bed flow type, Pyrex glass reactor, at 433 - 463 K. Major detected products were cyclohexanone, cyclohexene and benzene, depending on the used catalyst. The rate of reaction was significantly raised by the introduction of molecular oxygen in the feed gas, thereby suggesting the oxidation of cyclohexanol to cyclohexanone. Furthermore, the catalytic activity of iron oxide nanoparticles supported on zirconia treated with hydrogen at 553 K for 2 hours, was more selective and better than the unreduced iron oxide nanoparticles supported on zirconia, in the gas-phase oxidation of cyclohexanol to cyclohexanone. Experimental results showed that there was no leaching of metal, and that the catalyst was thus truly heterogeneous.

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 cyclohexanone 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.

Selective hydrodeoxygenation of guaiacol to cyclohexanol using activated hydrochar-supported Ru catalysts

Lignin,an abundant aromatic polymer in nature,has received significant attention for its potential in the production of bio-oils and chemicals owing to increased resource availability and environmental issues.The hydrodeoxygenation of guaiacol,a lignin-derived monomer,can produce cyclohexanol,a nylon precursor,in a carbon-negative and environmentally friendly manner.This study explored the porous properties and the effects of activation methods on the Ru-based catalyst supported by environmentally friendly and cost-effective hydrochar.Highly selective cleavage of C_(ary)-O bonds was achieved under mild conditions(160°C,0.2 MPa H2,and 4 h),and alkali activation further improved the catalytic activity.Various characterization methods revealedthat hydrothermal treatment and alkali activation relatively contributed to the excellent performance of the catalysts and influenced their porous structure and Ru dispersion.X-ray photoelectron spectroscopy results revealed an increased formation of metallic ruthenium,indicating the effective regulation of interaction between active sites and supports.This synergistic approach used in this study,involving the valorization of cellulose-derived hydrochar and the selective production of nylon precursors from lignin-derived guaiacol,indicated the comprehensive and sustainable utilization of biomass resources.

金属氧化物负载钌催化木质素衍生酚类化合物制备环己醇的研究

本研究采用初湿浸渍法,制备得到一系列钌负载于金属氧化物载体的催化剂(Ru/CeO_(2)、Ru/Nb_(2)O_(5)、Ru/ZrO_(2)、Ru/Al_(2)O_(3)和Ru/CeOx),用于木质素衍生酚类化合物苯酚提质加氢转化为环己醇的研究。通过采用X射线晶体衍射(XRD)、扫描电子显微镜(SEM)、X射线光电子能谱(XPS)等手段对所制备催化剂进行结构和物化特征的表征,发现Ru/CeOx中含有的氧空位可以很好地吸附带有含氧基团的原料,从而有利于苯酚的高效加氢;同时XPS表明,Ru/CeOx中的有效活性中心RuO_(2)和Ru0是催化加氢的活性位点,因此,氧空位和金属活性位点的共同作用使得催化剂有较好的加氢活性。探究了反应温度、压力、时间对加氢效果的影响,发现催化剂能够在140℃下使苯酚完全转化,得到目标产物环己醇得率为90.2%,并对催化剂的循环特性进行考察,发现循环使用四次后催化剂仍表现出优异的加氢活性。同时采用GC-MS检测加氢过程的中间产物,进而推断出苯酚加氢过程的反应路径。

ZnFe2O4 deposited on BiOCl with exposed （001） and （010） facets for photocatalytic reduction of C02 in cyclohexanol

ZnFe2O4-BiOC1 composites were prepared by both hydrothermal and direct precipitation processes and the structures and properties of the samples were characterized by various instrumental techniques. The samples were then used as catalysts for the photocatalytic reduction of CQ in cyclohexanol under ultraviolet irradiation to give cyclohexanone （CH） and cyclohexyl formate （CF）. The photocatalytic CO2 reduction activities over the hydrothermally prepared ZnFeaO4-BiOCl composites were higher than those over the directly-precipitated composites. This is because compared to the direct-precipitation sample, the ZnFe2O4 nanoparticles in the hydrothermal sample were smaller and more uniformly distributed on the surface of BiOCl and so more heterojunctions were formed. Higher CF and CH yields were obtained for the pure BiOCl and BiOCl composite samples with more exposed （001） facets than for the samples with more exposed （010） facets. This is due to the higher density of oxygen atoms in the exposed （001） facets, which creates more oxygen vacancies, and thereby improves the separation efficiency of the electron-hole pairs. More importantly, irradiation of the （001） facets with ultraviolet light produces photo-generated electrons which is helpful for the reduction of CO2 to -CO2^-. The mechanism for the photocatalytic reduction of CO2 in cyclohexanol over ZnFe204-BiOCl composites with exposed （001） facets involves electron transfer and carbon radical formation.

Chemoselective hydrogenation of phenol to cyclohexanol using heterogenized cobalt oxide catalysts

Cyclohexanol is an important intermediate in the synthesis of Nylon-6 and plasticizers. In this work,cobalt oxide nanoparticles（NPs） supported on porous carbon（Co Ox@CN） were fabricated by one-pot method and the hybrids could efficiently and selectively hydrogenate phenol to cyclohexanol with a high yield of 98%. The high catalytic performance of Co Ox@CN was associate with the high surface area（340 m2/g） and uniformly dispersed NPs. Furthurmore, by detailed analysing the relationship between catalytic activity and catalysts composition, it clearly indicated that the Co3O4 in Co Ox@CN played an important role for the adsorption and activation of phenol and the in situ gernerated Co was responsible for hydrogen adsorption and dissociation. These findings provide a fundamental insight into the real active sites in hydrogenation of phenol using Co-based catalysts.

Organic solvent-and phase transfer catalyst-free oxidation of cyclohexanol to cyclohexanone with dilute H_2O_2

The oxidation of cyclohexanol to cyclohexanone with 30% aqueous hydrogen peroxide by using peroxotung-state complexes formed in situ from sodium tungstate di-hydrate and various bidentate organic ligands as the catalysts, without organic solvents, halide and phase transfer catalyst has been carried out. The influence of 13 ligands on the oxidation is investigated. The maximum yield of cyclohexanone is obtained when using 1,10-phenanthroline (96%) and oxalic acid (95%) as the ligand. Very high yields (around 90%) have also been obtained for the instances of using salicylic acid, 3,5-dibromosalicylic acid, and 8-hydro- xylquino-line as ligands. A research to improve the reaction condition using cheap oxalic acid as the ligand indicates that the optimum condition is that the reaction mixture with a molar ratio of cycohexanol:tungstate dihydrate:oxalic acid: 30% H2O2=100:2:2:120 was stirred at 85-90℃ for 12 h.

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%。

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。

环己醇工业生产概述和展望

通过对环己醇工业生产发展情况进行总结,并重点追踪环己烯水合法生产工艺优化,分别就加氢工序、水合工序、精馏工序进行了总结,并针对生产工艺劣势提出了发展方向。

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。

多级孔HZSM-5催化环己烯水合制环己醇

环己醇是生产尼龙6和尼龙66的关键中间体,其主要生产工艺为环己烯水合法,面临环己烯单程转化率较低(小于10%)的困扰。通过催化剂改性来提高环己烯单程转化率是一种经济有效的方法。本文通过碱溶液脱硅的后处理方法构筑了多级孔HZSM-5分子筛,详细考察了碱种类、碱浓度、处理温度和处理时间等对HZSM-5分子筛催化剂物化性质和环己烯水合反应性能的影响。实验结果表明:0.4 mol/L NaOH在323 K下处理3 h所得HZSM-5分子筛催化剂催化效果最优,环己烯单程转化率可达12.98%;表征结果表明HZSM-5分子筛催化性能的提高是传质过程强化和催化剂表面适宜酸性质两方面因素的综合结果。

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。

环己烷中痕量组分的测定

采用GC-2030气相色谱仪、介质阻挡放电离子化(BID)检测器、InertCap 1非极性气相色谱柱,建立了环己烷中痕量环己酮、环己醇组分的定量检测方法。结果表明:该方法合适色谱分析条件为采用程序升温,载气流速为1 mL/min,进样量为1.0μL,分流比为201;该方法测定环己烷中痕量环己酮、环己醇时,环己醇的加标回收率为96.7%~104.8%、相对标准偏差(RSD)为0.25%~1.00%、检出限为0.06 mg/kg,环己酮的加标回收率为97.1%~104.1%、RSD为0.03%~1.04%、检出限为0.09 mg/kg;该方法精密度、准确度高,重现性好,分析时间短,有助于聚合溶剂用环己烷生产工艺的精准调控。

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。

环己醇生产装置节水技改优化方法

为了解决环己醇生产装置冷却水用量大的问题,采取在萃取精馏工段中的精馏塔塔顶与进精馏塔顶冷凝器之间串联一个闭式循环冷却器,同时采用换热效率高的精馏塔冷却器,并优化工艺流程,大大降低了冷却水的使用量,也减少了废水的产生量,极大地降低了环己醇生产过程中的成本,因此,节水改造的实施具有良好的经济效益和社会效益,对企业的可持续发展起到积极的作用。