Ionic liquid-assisted preparation of hydroxyapatite and its catalytic performance for decarboxylation of itaconic acid

The synthesis of methacrylic acid from biomass-derived itaconic acid is a green route,for it can get rid of the dependence on fossil resource.In order to solve the problems on this route such as use of a preciousmetal catalyst and a corrosive homogeneous alkali,we prepared a series of hydroxyapatite catalysts by an ionic liquid-assisted hydrothermal method and evaluated their catalytic performance.The results showed that the ionic liquid[Bmim]BF_(4) can affect the crystal growth of hydroxyapatite,provide fluoride ion for fluorination of hydroxyapatite,and adjust the surface acidity and basicity,morphology,textural properties,crystallinity,and composition of hydroxyapatite.The[Bmim]BF4 dosage and hydrothermal temperature can affect the fluoride ion concentration in the hydrothermal system,thus changing the degree of fluoridation of hydroxyapatite.High fluoride-ion concentration can lead to the formation of CaF_(2) and thus significantly decrease the catalytic performance of hydroxyapatite.The hydrothermal time mainly affects the growth of hydroxyapatite crystals on the c axis,leading to different catalytic performance.The suitable conditions for the preparation of this fluoridized hydroxyapatite are as follows:a mass ratio of[Bmim]BF4 to calcium salt=0.2:1,a hydrothermal time of 12 h,and a hydrothermal temperature of 130℃.A maximal methacrylic acid yield of 54.7%was obtained using the fluoridized hydroxyapatite under relatively mild reaction conditions(250℃ and 2 MPa of N_(2))in the absence of a precious-metal catalyst and a corrosive homogeneous alkali.

Electrolyte dependence for the electrochemical decarboxylation of medium-chain fatty acids (n-octanoic acid) into fuel on Pt electrode

The deoxygenation of organic acids, important biomass feedstocks and derivatives, to synthesize hydrocarbon products under mild electrochemical conditions, holds significant importance for the production of carbon-neutral biofuels. There is still limited research on the influential factors of the electrochemical decarboxylation reaction of medium-chain fatty acids. In this study, n-octanoic acid (OA) was chosen as the research subject to investigate the electrochemical decarboxylation behavior of OA on a platinum electrode, focusing on the influence of different alkali metal cations (Li^(+), Na^(+), K^(+)), common anions (SO^(4)^(2−), Cl^(−)), and electrolyte pH. It was found that KOH as an electrolyte exhibited the best performance for OA. Possibly, the larger size of K^(+) increased the alkalinity of the electrode surface, facilitating OA deprotonation. LiOH electrolyte reduced the solubility of OA, thereby inhibiting the decarboxylation reaction. SO^(4)^(2−) exhibited a weak promoting effect on the decarboxylation reaction of OA, while Cl^(−) showed no adverse effect although Cl^(−) may adsorb on the electrode surface. Furthermore, unlike short-chain fatty acids, medium-chain OA can only achieve efficient decarboxylation under alkaline conditions due to its solubility properties. This study provides references and foundations for future efforts to enhance the efficiency of electrochemical decarboxylation synthesis of hydrocarbon biofuels from medium-chain fatty acids.

Influence of Ca/P ratio on the catalytic performance of hydroxyapatite for decarboxylation of itaconic acid to methacrylic acid

Methacrylic acid,an important organic chemical,is commercially manufactured starting from fossil feedstock.The decarboxylation of itaconic acid derived for biomass is a green route to the synthesis of methacrylic acid.In view of the problems existing in the researches on this route such as use of noble metal catalyst,harsh reaction conditions and low desired-product yield,we prepared a series of hydroxyapatite catalysts with different Ca/P molar ratios and evaluated their catalytic performance.The results showed that the hydroxyapatite catalyst with a Ca/P molar ratio of 1.58 had the best catalytic activity.The highest yield of MAA up to 61.2%was achieved with basically complete conversion of itaconic acid under the suitable reaction conditions of 1 equivalent of NaOH,2 MPa of N_(2),250℃,and 2 h.On this basis,a reaction network for the decarboxylation of itaconic acid to methacrylic acid catalyzed by hydroxyapatite was established.With the aid of catalyst characterization using X-ray powder diffraction,NH3/CO2 temperature-programmed desorption,N_(2)physisorption,inductively coupled plasma optical emission spectrometry,and scanning electron microscopy,we found that the distribution of surface acid sites and basic sites,crystal growth orientation,texture properties and morphology of hydroxyapatite varied with the Ca/P molar ratio.Furthermore,the change of the crystal growth orientation and its influence on the surface acidity and alkalinity were clarified.

One-pot synthesis of(Z)-4-(2-bromovinyl)benezenesulfonamides by microwave-induced simultaneous debrominative decarboxylation and sulfamation of anti-2,3-dibromo-3-(4-chlorosulfonylphenyl)propanoic acid

One-pot simultaneous debrominative decarboxylation and sulfamation of anti-2,3-dibromo-3-（4-chlorosulfonylphenyl）propa- noic acid in DMF （for alkyl amines） or DMF-pyridine （for aryl amines） using a diverse range of alkyl and aryl amines under microwave irradiation condition stereoselectively afforded （Z）-4-（2-bromovinyl）benzenesulfonamides in good yields.

Synthesis,Structure and Properties of Three-dimensional Gd(Ⅲ),Eu(Ⅲ) Coordination Polymers via in situ Decarboxylation

Two three-dimensional lanthanide（Ⅲ） coordination polymers with the formula [Ln（PYDC）（NA）（H2O）]n [Ln=Gd（1）, Eu（2）, H2PYDC=pyridine-2,5-bicarboxylic acid, HNA=nicotinic acid] have been hydrothermally synthesized and characterized by elemental analysis, IR, and single crystal X-ray diffraction. The NA came from in situ decarboxylation of the part of PYDC. X-ray single crystal structural analyses reveal that complexes 1 and 2 are isomorphous, they possess the 43.63 topology assembled by Gd^3＋/Eu^3＋ and two different multidentate carboxylate ligands Magnetic measurements show that antiferromagnetic coupling exists between adjacent Gd^3＋ ions in complex 1. The complex 2 exhibits the corresponding characteristic luminescence in the visible region under an excitation at 305 nm.

Microwave-Assisted Decarboxylation of Sodium Oleate and Renewable Hydrocarbon Fuel Production

The carboxyl terminal of sodium oleate has a stronger polarity than that of oleic acid;this terminal is more likely to be dipole polarized and ionically conductive in a microwave field.Sodium oleate was used as the model compound to study the decarboxylation of oleic acid leading to hydrocarbon formation via microwave-assisted pyrolysis technology.The pyrolysis gas,liquid,and solid products were precisely analyzed to deduce the mechanism for decarboxylation of sodium oleate.Microwave energy was able to selectively heat the carboxyl terminal of sodium oleate.During decarboxylation,the double bond in the long hydrocarbon chain formed a p-πconjugated system with the carbanion intermediate.The resulting p-πconjugated system was more stable and beneficial to the pyrolysis reaction(decarboxylation,terminal allylation,isomerization,and aromatization).The physical properties of pyrolysis liquid were generally similar to those of diesel fuel,thereby demonstrating the possible use of microwaves for controlling the decarboxylation of sodium oleate in order to manufacture renewable hydrocarbon fuels.

Preparation and Reactions of Pyridinium Ylids via Decarboxylation of Pyridinium Betaines

Pyridinium ylids 4 were generated as reaction intermediates from the decarboxylation of pyridinium betaines 3, which were prepared from the reactions of a-amino acid ester hydrochlorides with 2, 4, 6-triphenylpyrylium tetrafluoroborate. Protonation, addition and substitution reactions of 4 with electrophiles were studied in this paper.

Biomimetic Decarboxylation of Carboxylic Acids with PhI(OAc)_2 Catalyzed by Manganese Porphyrin [Mn(TPP)OAc]

Manganese（Ⅲ） meso-tetraphenylporphyrin acetate [Mn（TPP）OAc] served as an effective catalyst for the oxidative decarboxylation of carboxylic acids with （diacetoxyiodo）benzene [PhI（OAc）2] in CH2CI2-H2O（95：5, volume ratio）. The aryl substituted acetic acids are more reactive than the less electron rich linear carboxylic acids in the presence of catalyst Mn（TPP）OAc. In the former case, the formation of carbonyl products was complete within just a few minutes with 〉97% selectivities, and no further oxidation of the produced aldehydes was achieved under these catalytic conditions. This method provides a benign procedure owing to the utilization of low toxic（diacetoxyiodo） benzene, biologically relevant manganese porphyrins, and carboxylic acids.

How Effective Is the Single-point Energy Calculation in Investigating the Reaction Mechanisms?New Decarboxylation Mechanism of Pyrrole-2-carboxylic Acid by Full Optimization with CPCM Solvation Model

The decarboxylation of pyrrole-2-carboxylic acid in acid solutions was elucidated by full optimization with the CPCM solvation model at the B3LYP/6-31 l＋＋G（d,p） level. Compared with the single-point energy calculation, CPCM full optimization is better to model solvent environments to gain reasonable reaction mechanisms. The π interactions play a significant role in the decarboxylation of pyrrole-2-carboxylic acid （R）. Firstly, the a hydrogen is protonated, but all of the carbonyl hydration pathways bear relatively higher energy barriers. The carbonyl group can rove over the pyrrole ring, but it does not lead to the speciation of pyrrole and protonated carbon dioxide for the latter is an energy-rich species. The decarboxylation mechanism proposed here is that, the protonated pyrrole-2-carboxylic acid （RH） decarboxylates via direct C-C bond cleavage with the aid of a water molecule to accommodate the proton on the carbonyl group.

Synthesis,Structure and Photoluminescence of a New Cadmium(Ⅱ) Complex Involving in situ Decarboxylation

A new luminescent dinuclear cluster complex [Cd2（pzc）2（AmTAZ）（HEO）4（NO3）]·NO3 （Hpzc = pyrazine-2-carboxylic acid, AmTAZ = 3-amino-4H-1,2,4-triazole） has been prepared by the assembly of Cdn with pyrazine-2,3-dicarboxylic acid and 3-amino-lH-1,2,4-triazole-5-car- boxylic acid ligands under hydrothermal conditions, in which in situ decarboxylation of H2pzdc and HAmTZC ligands simultaneously occurred, and HEpzdc was transformed into Hpzc while HAmTZC into AmTAZ. The crystal structure is of triclinic, space group P1 with a = 7.096（2）, b = 11.140（4）, c = 14.887（5）А, α= 92.641（4）, β= 91.348（6）, γ= 96.058（6）°, V = 1168.5（7）А^3, C12H18Cd2N10O14, Mr = 751.16, Z = 2, Dc = 2.126 g/cm^3, F（000） = 730,μ=1.910 mm^-1, R = 0.0320 and wR = 0.0998 for 4549 observed reflections （I 〉 2σ（I））. The dinuclear cluster of 1 is extended into a 3D supramolecular architecture through intermolecular hydrogen bonding interactions. Complex I exhibits strong blue photoluminescence at room temperature.

The Oxidative Decarboxylation of Nitrilotriacetic Acid (NTA)——A Study of the Reaction of NTA with Cerium(Ⅳ) in HCIO_4

The reaction between Ce (IV ) and NTA was investigated titrimetrically and spectrophotometrically. Two equivalents of Ce( IV ) are reduced per mole of NTA almost instantaneously at room temperature. With increasing reaction time an ultimate of about 7 equivalents of Ce( IV) is consumed per mole of NTA at room temperature. Carbon dioxide, formaldehyde and dimethylamine are the major and readily detectable products of oxidation of NTA by Ce( IV ). The rates of the reaction in HClO4 were measured spectrophotometricaUy using the stopped flow technique. The effects of both acidity of the medium and added salts support and extend preliminary results.

Solvent- and Catalyst-Free Microwave-Assisted Decarboxylation of Malonic Acid Derivatives

It has been found that microwave assisted decarboxylation of malonic acid derivatives can be achieved under solvent-free and catalyst free conditions. This new method produces the corresponding carboxylic acid in a pure manner and with a high yield in a very short reaction time: 3 - 10 min. In general terms, the condition under which this reaction is carried out accelerates the decarboxylation significantly of a series of disubstituted malonic acid derivatives, and makes this new process efficient, easy and environmentally friendly.

Organocatalyzed Decarboxylation of Naturally Occurring Cinnamic Acids: Potential Role in Flavoring Chemicals Production

The mechanism and the final outcome of the Knoevenagel-Doebner reaction are discussed. The condensation reaction between different hydroxy-substituted aromatic aldehydes and malonic acid is performed using piperidine as organocatalyst. The key role of the catalyst is clearly pointed out during the decarboxylation of ferulic acid, without the use of a strong decarboxylating agent, leading to a 4-vinylphenol derivative. Based on the results obtained, the studied pathway may be important in the understanding of vinylphenol production during malting and brewing of wheat and barley grains. Finally, changing the solvent of the reaction from pyridine to water in the Knoevenagel-Doebner reaction of 4-hydroxybenzaldehydes, dimerization of resulting styrene derivatives is observed. These results can be of interest also in the field of food chemistry, since cinnamic acids are frequently found in fruits and vegetables used for human consumption.

Molecular Simulation of Naphthenic Acid Removal on Acidic Catalyst(I) Mechanism of Catalytic Decarboxylation

In this paper, the charge distribution, the chemical bond order and the reactive performance of carboxylic acid model compounds on acidic catalyst were investigated by using molecular simulation technology. The simulation results showed that the bond order of C—O was higher than that of C—C, and C—C bond connected to the carbon atom in the carboxyl radical had the lowest bond order. The charge distributions of model naphthenic acids were similar in characteristics that the negative charges were concentrated on carboxyls. According to the simulation results, the mechanisms of catalytic decar- boxylation over acidic solid catalyst were proposed, and a new route was put forward regarding removal of the naphthenic acid from crude oil through catalytic decarboxylation.

One-pot synthesis of bimetallic CeCu-SAPO-34 for high-efficiency selective catalytic reduction of nitrogen oxides with NH_(3) at low temperature

NH_(3) selective catalytic reduction(SCR) has been widely recognized as a promising technique for reducing nitrogen oxides from diesel vehicle exhausts. High-efficiency SCR catalysts that could perform at low temperatures are essential to denitration. In this work, a series of bimetallic CeCu-SAPO-34 molecular sieves were synthesized by one-step hydrothermal method. The Ce Cu-SAPO-34 maintained good crystallinity and a regular hexahedron appearance of Cu-SAPO-34 after introducing Ce species, while exhibiting a higher specific surface area and pore volume. The as-prepared CeCu-SAPO-34 with 0.02%(mass) Ce constituent exhibited the best catalytic activity below 300℃ and a maximum NO_(x) conversion of 99% was attained;the NO_(x) removal rates of more than 68% and 94% were achieved at 150℃ and 200℃, respectively. And the introduction of cerium species in Cu-SAPO-34 improves the low-temperature hydrothermal stability of the catalyst towards NH_(3)-SCR reaction. Additionally, the introduced Ce species could enhance the formation of abundant weak Br?nsted acid centers and promote the synergistic effect between CuO grains and isolated Cu^(2+) to enhance the redox cycle, which benefit the NH_(3)-SCR reaction.This work provides a facile synthesis method of high-efficiency SCR denitration catalysts towards diesel vehicles exhaust treatment under low temperature.

Molecular Simulation of Naphthenic Acid Removal on Acidic Catalyst II. Experimental results of catalytic decarboxylation over acidic catalysts

The energy barriers of thermal decarboxylation reactions of petroleum acids and catalytic decarboxylation reactions of Bronsted acid and Lewis acid were analyzed using molecular simulation technology. Compared with thermal decarboxylation reactions of petroleum acids, the decarboxylation reactions by acid catalysts were easier to occur. The decarboxylaton effect by Lewis acid was better than Bronsted acid. The mechanisms of catalytic decarboxylation over acid catalyst were also verified by experiments on a fixed bed and a fluidized bed, the experimental results showed that the rate of acid removal could reach up to 97% over the acidic catalyst at a temperature above 400℃.

大麻二酚酸脱羧反应动力学分析

以工业大麻花叶为原料,利用高效液相色谱(HPLC)和热重分析仪(TGA)对大麻二酚酸(CBDA)的脱羧反应过程进行表征,分析CBDA及其脱羧产物大麻二酚(CBD)在不同温度(50~145℃)和反应时间(4~180 min)的含量变化,并开展脱羧反应动力学分析。结果表明,CBDA脱羧反应遵循一级动力学,初步推测最佳脱羧温度区间为95~125℃,加热时间50~70 min。

FAU分子筛催化γ-戊内酯脱羧制丁烯研究

生物质基γ-戊内酯脱羧制备丁烯反应为碳四烯烃的可持续生产提供了一条新的途径。针对现有无定形SiO_(2)-Al_(2)O_(3)催化剂只能在低空速下运转的现状,开发了一种高效的NaY分子筛催化剂。因其丰富的Lewis酸与适宜的碱性,可在高空速下实现原料γ-戊内酯的100%转化,同时丁烯选择性高达99.6%。NaY分子筛催化剂显示出良好的反应稳定性和反应-再生循环性能,在连续运转1320 min后,丁烯收率保持在99.4%;经历5次反应-再生循环后,丁烯收率保持在99.2%。在此基础上,通过离子交换法制备LiY,KY,CaY分子筛,对比研究分子筛中金属阳离子种类对分子筛催化脱羧性能的影响。结果表明:NaY分子筛因其适宜的酸碱匹配度,脱羧性能最好;LiY分子筛和KY分子筛次之;CaY分子筛因存在强Br nsted酸位,催化性能最低。

离子液体中PMBA脱羧反应及界面水影响的电化学SERS研究

基于气-液界面自组装法和转移技术制备了负载Au纳米粒子单层膜的玻碳电极(Au MLF@GC),并将其用于离子液体-电化学体系界面过程现场的研究.以对巯基苯甲酸(PMBA)的表面等离激元共振(SPR)催化脱羧生成苯硫酚(TP)反应为探针,采用电化学-表面增强拉曼光谱(SERS)技术,通过电位阶跃法研究了其在离子液体体系中的反应动力学行为.结果表明,亲水性离子液体[BMIm]BF_(4)/Au MLF@GC的零电荷电位(pzc)为−0.95 V,PMBA脱羧反应仅在pzc以正区间发生;通过SERS谱峰强度变化以二级反应拟合获得该反应的速率常数,发现其反应速率常数的对数与阶跃后电位呈线性关系;随着体系外加水的含量(摩尔分数)由0增至0.001和0.003,阶跃后发生脱羧反应的起始电位负移,且同一阶跃电位下反应速率常数随着外加水量的增加而增大.

脂肪酸光脱羧酶及其在有机合成中应用的研究进展

生物基脂肪酸是极具应用潜力的可再生资源.以绿色、低碳的方式对生物基脂肪酸进行转化合成高价值的化学品和燃料可满足现代社会可持续发展的迫切需要,也符合绿色生物制造的需求.生物催化因反应条件温和、选择性高等特点受到众多学者的广泛关注,其中,近年来新发现的由可见光驱动的脂肪酸光脱羧酶(fatty acid photodecarboxyase, CvFAP)可催化不同链长的脂肪酸进行脱羧反应用来合成燃料和化学品,反应过程具有极高原子经济性,在绿色催化工艺及能源领域具有广阔的应用前景.我们旨在对脂肪酸光脱羧酶(CvFAP)的最新研究进展进行总结分析,并对脂肪酸光脱羧酶的发展趋势进行展望,以期为脂肪酸光脱羧酶(CvFAP)在绿色合成领域的进一步开发利用提供参考.