Role of catalyst surface-active sites in the hydrogenation ofα,β-unsaturated aldehyde

As an important technology in fine chemical production,the selective hydrogenation ofα,β-unsaturated aldehydes has attracted much attention in recent years.In the process ofα,β-unsaturated aldehyde hydrogenation,a conjugated system is formed between>C=C<and>C=O,leading to hydrogenation at both ends of the conjugated system,which competes with each other and results in more complex products.Therefore,improving the reaction selectivity is also difficult in industrial fields.Recently,many researchers have reported that surface-active sites on catalysts play a crucial role inα,β-unsaturated aldehyde hydrogenation.This review attempts to summarize recent advances in understanding the effects of surface-active sites(SASs)over metal catalysts for enhancing the process of hydrogenation.The construction strategies and roles of SASs for hydrogenation catalysts are summarized.Particular attention has been given to the adsorption configuration and transformation mechanism ofα,β-unsaturated aldehydes on catalysts,which contributes to understanding the relationship between SASs and hydrogenation activity.In addition,recent advances in metal-supported catalysts for the selective hydrogenation ofα,β-unsaturated aldehydes to understand the role of SASs in hydrogenation are briefly reviewed.Finally,the opportunities and challenges will be highlighted for the future development of the precise construction of SASs.

Chemoselective hydrogenation of α,β-unsaturated aldehydes with modified Pd/C catalyst

Selective hydrogenation of α, β-unsaturated aldehydes with modified Pd/C catalyst was developed.The reduction of C=O bond could be efficiently inhibited by the addition of carbonates,and high selectivity to the corresponding saturated aldehydes was achieved under mild conditions.This protocol provides an alternative for efficient preparation of saturated aldehydes.

Zero-oxidation state precursor assisted fabrication of highly dispersed and stable Pt catalyst for chemoselective hydrogenation ofα,β-unsaturated aldehydes

The chemoselective hydrogenation ofα,β-unsaturated aldehydes is a key strategy for the synthesis of fine chemicals.Herein,we developed an efficient method of depositing Pt particles on FeO_(x)/SBA-15.This strategy is dependent on using a platinumdivinyltetramethyldisiloxane complex(Pt^(0)-DVTMS)as the precursor,which we demonstrate can be removed through a H_(2)-treatment under mild conditions.This,in turn,allowed for the synthesis of catalysts with well dispersed Pt particles.The presence of FeO_(x) species also aided Pt dispersion;when coated onto SBA-15,FeO_(x) strongly interacted with dissociated Pt species,inhibiting both Pt aggregation and metal leaching.Using cinnamaldehyde as a modelα,β-unsaturated aldehyde,it was demonstrated that this catalyst was highly selective towards the unsaturated alcohol and no obvious loss in activity was observed over five recycles.This catalyst was determined to be significantly more effective than an analogous catalyst prepared using chloroplatinic acid as a precursor,evidencing the importance of using the Pt0-DVTMS precursor.We corroborate the excellent catalytic performance to highly dispersed Pt-species,whereby Pt0 and Pt^(2+) play a critical role in activating H_(2) and the C=O bond.This research demonstrates that the Pt precursor can have a significant impact on the physicochemical properties and thus,the performance of the final catalyst.It also evidences how metal support interactions can dramatically influence selectivity in such hydrogenation reactions.This novel catalyst preparation protocol,using a DVTMS ligand for Pt impregnation,offers a facile approach to the design of multi-component heterogeneous catalysts.

Ir nanoclusters confined within hollow MIL-101(Fe)for selective hydrogenation ofα,β-unsaturated aldehyde

Although the selective hydrogenation ofα,β-unsaturated aldehyde to unsaturated alcohol(UOL)is an extremely important transformation,it is still a great challenge to achieve high selectivity to UOL due to thermodynamic favoring of the C=C hydrogenation over the C=O hydrogenation.Herein,we report that iridium nanoclusters(Ir NCs)confined within hollow MIL-101(Fe)expresses satisfied reaction activity(93.9%)and high selectivity(96.2%)for the hydrogenation of cinnamaldehyde(CAL)to cinnamyl alcohol(COL)under 1 bar H;atmosphere and room temperature.The unique hollow structure of MIL-101(Fe)benefits for the fast transport of reactant,ensuring the comparable reaction activity and better recyclability of Ir@MIL-101(Fe)than the counterparts which Ir NCs were on the surface of MIL-101(Fe).Furthermore,The X-ray photoelectron spectroscopy data indicates the electropositive Ir NCs,owing to the electron transfer from Ir to MIL-101(Fe),can interact with oxygen lone pairs,and Fourier transform infrared spectrum shows the Lewis acid sites in MIL-101(Fe)can strongly interact with C=O bond,which contributes to a high selectivity for COL.This work suggests the considerable potential of synergetic effect between hollow MOFs and metal nanoclusters for selective hydrogenation reactions.

Enantioselective Organocatalytic Aza-Michael Additions of Phthalimide Derivatives to α,β-Unsaturated Aldehydes

Phthalimide derivatives as nitrogen nucleophiles with α,β-unsaturated aldehydes for asymmetric aza-Michael additions have been reported. The reactions proceed smoothly to afford corresponding Michael adducts in good yields （up to 98%） and enantioselectivities （up to 95% ee）.

Organocatalytic enantioselective Michael addition reactions of fluoromalonates with α,β-unsaturated aldehydes

A new organocatalytic enantioselective Michael addition of α-fluoromalonate to enals has been developed.The process is efficiently catalyzed by readily available chiral diphenylpyrolinol TES ether under mild reaction conditions to afford versatile highly enantioenriched fluorinated aldehydes.

Sulfonated carbon catalyzed oxidation of aldehydes to carboxylic acids by hydrogen peroxide

Sulfonated carbon as a strong and stable solid acid catalyst exhibited excellent catalytic performance in various acid-catalyzed reactions. Here, sulfonated carbon, as catalyst for oxidation reaction, was prepared via the carbonization of starch followed by sulfonation with concentrated sulfuric acid. N2 physisorption, X-ray diffraction, Fourier transform infrared spectroscopy, X-ray fluorescence and acid-base titration were used to characterize the obtained materials. The catalytic activity of sulfonated carbon was studied in the oxidation of aldehydes to carboxylic acids using 30 wt% H2O2 as oxidant. This oxidation protocol works well for various aldehydes including aromatic and aliphatic aldehydes. The sulfonated carbon can be recycled for three times without obvious loss of activity.

Efficient benzaldehyde photosynthesis coupling photocatalytic hydrogen evolution

Photosynthesis of organic compounds in coupling with promoted hydrogen evolution under mild conditions of light irradiation is considered as one of the most efficient and promising approach to obtain high purity hydrogen and value-added chemicals concurrently by utilizing green solar energy.Here,we report the synthesis of Ni S nanoparticle-modified Cd S nanorod composites(Ni S/Cd S)as an efficient bifunctional catalyst for the highly selective photocatalytic synthesis of high-value-added product benzaldehyde(BAD)from aqueous solution of benzyl alcohol(BA)under oxygen-free conditions,in accompanying with the efficient hydrogen evolution.The synergetic catalytic effect between Ni S and Cd S is proposed to play an important role in elevating the photo-redox performance.The composition-optimized 30%Ni S/Cd S catalyst affords an extraordinarily high H;generation rate of 207.8μmol h^(-1)and a simultaneous BAD generation rate of 163.8μmol h^(-1)under visible light irradiation,which are respectively 139 and 950 times higher than those of Cd S without Ni S modification.To our knowledge,these are the highest photocatalytic production rates of both H_(2)and aldehyde ever reported on the concurrent photocatalytic of aldehyde synthesis and hydrogen evolution in green aqueous solution.This work provides a highly efficient photosynthesis strategy for the concurrent productions of high-value-added fine chemicals and hydrogen.

Performant Au hydrogenation catalyst cooperated with Cu-doped Al_(2)O_(3) for selective conversion of furfural to furfuryl alcohol at ambient pressure

Catalytic hydrogenation of furfural to furfuryl alcohol is an important upgrading process for valorization of biomass-derived furanyl platform molecules.However,selective hydrogenation of a,b-unsaturated aldehydes like furfural to the corresponding alcohols at ambient pressure remains challenging in sustainable chemistry.Till date heterogeneous Au hydrogenation catalyst has been scarcely reported for this reaction due to the low reactivity of Au for H_(2)dissociation.In this work,we showed that Au nanoparticles(loading:0.2 wt%)with a mean size of about 3 nm supported on Cu-doped Al_(2)O_(3)can efficiently hydrogenate furfural to furfuryl alcohol in liquid phase at ambient pressure.We demonstrated that doping a small amount of Cu(2 mol%)to g-Al_(2)O_(3)may modify the Lewis acidity-basicity of Al_(2)O_(3)and simultaneously induce the presence of sufficient Cu^(+) species on surface,which facilitated the hydrogen transfer from i-PrOH to furfural.Moreover,we observed an enhanced reactivity of Au toward molecular H_(2)via cooperation with the Lewis acidic-basic Cu_(2)O-Al_(2)O_(3)support.Hence,100%yield to furfuryl alcohol with a productivity of 0.98 g_(FA),h^(-1),g^(-1)_(cat.)at 120C and 0.1 MPa H_(2)can be obtained.The prepared Au/Cu-Al_(2)O_(3)catalyst was found reusable and was effective to the concentrated furfural solution,as well as several typical unsaturated aldehydes.

氧-氮等离子体表面改性石墨烯用于肉桂醛水相加氢反应

使用等离子体表面改性技术对石墨烯(GR)进行处理,通过优化气源、放电功率、放电时间和工作气压,制备了具有两亲表面的氮掺杂GR(NDGR),以其为载体制备了Pt纳米催化剂(Pt/NDGR)。采用FTIR、Raman、元素分析仪、TEM和光学接触角测量仪对催化剂进行了表征,并评价了其对肉桂醛(CAL)水相加氢反应的催化性能。结果表明,采用等离子体两步接枝工艺,即先以O_(2)为等离子体气源活化GR表面,再以NH_(3)为等离子体气源在GR表面接枝含氮基团得到的氮掺杂GR[NDGR(O_(2)-NH_(3))]具有最佳的表面性质。与GR负载Pt催化剂(Pt/GR)相比,在放电功率140 W、工作气压200 Pa、放电时间6 min的最佳条件下制备的NDGR(O_(2)-NH_(3))负载Pt催化剂[Pt/NDGR(O_(2)-NH_(3))]在CAL水相加氢反应中显示出优良的催化性能。在80℃、3MPa、Pt/NDGR(O_(2)-NH_(3))为催化剂、4 h的反应条件下,CAL的转化率达98%,肉桂醇的选择性约为84%,反应速率常数为(1.072±0.051)h^(–1),远高于Pt/GR为催化剂的(0.624±0.023)h^(–1);其反应活化能约为14 kJ/mol,仅为Pt/GR为催化剂的(约29k J/mol)的48.3%。Pt/NPGR(O_(2)-NH_(3))的高催化性能得益于GR表面接枝少量含氮基团后Pt纳米粒子锚定位点的增加、对底物的高吸附性能以及金属-载体间协同作用。

α,β-不饱和醛高选择性加氢研究进展

α,β-不饱和醛选择性加氢制备不饱和醇是一类具有挑战性的反应,是生产药品,香水和香料等有价值中间体的有效方法之一。对单金属非均相催化剂来讲,不饱和醇的形成在热力学上比饱和醛的形成更不利。因此,常需要高效的催化剂来达到高选择性。与单金属催化剂相比,双金属合金催化剂对不饱和醇的选择性显著提高。本文主要介绍了近年来关于α,β-不饱和醛在双金属合金催化剂上选择性加氢的研究进展。并主要综述了在不同金属表面的作用以及促进不饱和醛通过其C=O键吸附的因素,其中最明显的影响因素是通过表面的电子修饰作用和亲电性位点的形成。

Silica supported sodium hydrogen sulfate(NaHSO_4/SiO_2):A mild and efficient reusable catalyst for the synthesis of aryl-14-H-dibenzo[a,j]xanthenes under solvent-free conditions

A simple and efficient procedure for the preparation of aryl- 14-H-dibenzo [aj]xanthenes by a one-pot condensation reaction of 2-naphthol and aryl aldehydes, in the presence of silica supported sodium hydrogen sulfate （NaHSO4/SiO2） as a catalyst and in the absence of solvent has been developed. The present method offers several advantages such as excellent yields, short reaction time （10-30min）, mild condition, simple work-up, and the use of a cheap and environmentally friendly catalyst with remarkable reusability.

Converting Co^(2+)-impregnated g-C_(3)N_(4) into N-doped CNTs-confined Co nanoparticles for efficient hydrogenation rearrangement reactions of furanic aldehydes

The cyclopentanone and derivatives are a class of crucial fine chemicals for various industries and currently produced by conventional petrochemical synthetic routes.Here,we demonstrated a new synthetic approach to directly fabricate N-doped carbon nanotube(N-CNTs)networks with confined Co nanoparticles from Co^(2+)-impregnated bulk g-C_(3)N_(4) as high performance hydrogenation rearrangement(HR)catalyst to efficiently convert a wide spectrum of biomass-derived furanic aldehydes to the corresponding cyclopentanones in water under a record-low H2 pressure of 0.5 MPa and mild temperature.We unveiled a Co-catalysed bulk g-C_(3)N_(4) decomposition/carbonisation CNTs formation mechanism.A new HR pathway was also unveiled.

超重力法制备气相醛加氢催化剂中试放大研究

在超重力共沉淀中试装置上进行了铜基气相醛加氢催化剂制备放大试验。研究发现,在超重力机转速1 200 r/min、中和温度80℃、pH 7.5、老化温度80℃、老化时间30 min及焙烧温度380℃条件下,制得催化剂的比表面积高、CuO晶粒度低,活性组分分散度较好。以某石化公司丁辛醇装置丁醛和辛烯醛为原料,通过催化剂加氢评价考察催化剂活性结果显示,中试放大催化剂原料转化率及产品选择性均高于99%,且在空速高出约14%情况下,产品性质与参比剂相当,且产品杂质含量略低,表明放大剂活性略好于参比剂。

铜基催化剂结构对烯醛脂肪醇溶液吸附扩散性能的影响

烯醛加氢制备2-丙基庚醇工艺过程中非铬催化剂的开发是实现该工艺绿色化的关键。采用吸附扩散法,考察了原料2-丙基庚烯醛与2-丙基庚醇混合溶液在铜硅、铜铬和铜锌铝等3种不同催化剂表面的吸附及孔道扩散特性;并结合3种不同铜基复合氧化物的结构特征,与其2-丙基庚烯醛液相加氢催化性能进行关联。结果表明:铜硅复合氧化物在考察浓度范围均优先吸附2-丙基庚烯醛,而铜锌铝、铜铬复合氧化物在混合溶液中2-丙基庚烯醛质量分数分别高于4.6%和4.1%时,才优先吸附2-丙基庚烯醛;铜铬复合氧化物具有最大2-丙基庚烯醛吸附选择性、扩散系数和最优催化2-丙基庚烯醛液相加氢性能。

Decatungstate as a direct hydrogen atom transfer photocatalyst for synthesis of trifluromethylthioesters from aldehydes

We have developed a versatile,mild protocol for trifluoromethylthiolation reactions of aldehydes with catalysis by a decatungstate hydrogen atom transfer photocatalyst under redox-neutral conditions.The protocol is highly selective,operationally simple,and compatible with a wide array of sensitive functional groups.It can be used for late-stage functionalization of bioactive molecules,which makes it convenient for drug discovery.

Ni-Co-B非晶态合金催化肉桂醛常压加氢制3-苯丙醛的研究

采用化学还原法制备了一系列Ni-Co-B非晶态合金催化剂,通过调变金属盐混和液中Ni2+/Co2+的比例,可制得不同Co含量的Ni-Co-B非晶态合金.用ICP,BET,XRD,TEM,SAED,DSC,XPS和H2-TPD对其组成、结构、粒子大小、表面形貌和表面电子态进行了系列表征,并以肉桂醛常压加氢制苯丙醛作为探针反应,考察了所制备的Ni-Co-B非晶态合金的催化性能.结果表明,Ni-Co-B非晶态合金中Ni为活性中心,Co的引入可显著增加其催化活性.由于催化测试中金属总量固定为1.0g,因此增加Ni-Co-B中Co的含量具有正负两方面的效应.一方面,由于Ni活性位数目的减少加氢活性降低;另一方面,Co对Ni活性中心具有协同作用,有利于增加合金的无序度、金属-类金属间相互作用、表面Ni含量和电子相互作用,从而提高催化活性.最佳Co与(Ni+Co)摩尔比含量的范围为0.2～0.5.

SiO_2负载壳聚糖席夫碱钯催化剂催化芳香醛酮还原为芳香烃

制备了SiO2负载的壳聚糖席夫碱钯催化剂,利用X射线衍射、红外光谱和热重等方法对催化剂进行了表征,并考察了该催化剂催化羰基加氢为亚甲基的反应性能,以二苯甲酮为底物,系统地研究了反应时间、反应温度和催化剂用量等因素对反应性能的影响.结果表明,该催化剂具有较高的催化芳香羰基加氢为亚甲基的活性和选择性,且反应可在较低的温度和常压的温和条件下进行.

乙酰丙酮氧钒催化氧化α-蒎烯一步转化成龙脑烯醛

以乙酰丙酮氧钒为催化剂,过氧化氢为氧化剂,研究了由α-蒎烯直接合成龙脑烯醛的反应。考察了溶剂、温度、催化剂用量、反应时间等因素对催化性能的影响。结果表明,乙酰丙酮氧钒与H2O2反应得到的高价态V5+是优良的氧化还原-Lewis酸双功能催化剂,易使α-蒎烯经氧化、2,3-环氧蒎烷异构得到龙脑烯醛。在n(H2O2):n(α-蒎烯):n(乙酰丙酮氧钒)=2.5:1:0.01、反应温度为20℃、丙酮为溶剂、反应2h条件下,α-蒎烯转化率为50.2%,龙脑烯醛的选择性达58.7%,反应6h后α-蒎烯转化率可达73.0%,主要产物龙脑烯醛和马鞭草烯酮的选择性分别为47.2%和13.2%。