Preparation of Nicotinic Acid from Oxidation of 3-Picoline with Oxygen Under Catalysis of T（o-Cl）PPMn

The oxidation of 3-picoline to nicotinic acid took place efficiently in an ethanol solution with 02 as the oxidant under the catalysis of T（o-Cl）PPMn at 40--150 ℃ and 0.5--3.0 MPa oxygen pressure. The influences of temperature, oxygen pressure, reaction time, concentration of 3-picoline, concentration of sodium hydroxide, and concentration of T（o-Cl）PPMn catalyst, etc. on the production of nicotinic acid were investigated. The results show that T（o-Cl）PPMn presented excellent catalytic activity in the oxidation Of 3-pieoiine to nicotinic acid and the yield of nicotinic acid varied greatly with the reaction temperature, oxygen pressure, T（o-Cl）PPMn concentration, etc.     

A gas-chromatographic study of the retention of reaction components in the catalytic oxidation of β-picoline to nicotinic acid

The gas-chromatographic retention of pyridine, β-picoline, 3-pyridinecarbaldehyde, 3-pyridinenitrile, nicotinic acid, and nicotinamide on polar stationary phases was studied. A scheme was proposed and a procedure was developed for the determination of the reaction components of the catalytic oxidation of β-picoline to nicotinic acid on a column (3 m × 3 mm) packed with Chromosorb WAW + 10 wt % FFAP. The separation time was 28 min. The detection limits were 0.01 and 0.37 ppm for 3-pyridinenitrile and nicotinic acid, respectively.     

Kinetics of the β-picoline oxidation to nicotinic acid over vanadia-titania catalyst. 2. Effect of dioxygen and β-picoline

The effect of the dioxygen and β-picoline concentrations on the oxidation of β-picoline to nicotinic acid was studied at 270°C over a 20% V₂O₅-80% TiO₂ (wt. %) catalyst. The study was performed in a differential reactor at constant concentrations of water and nicotinic acid. A considerable excess of dioxygen was shown to be necessary for the formation of nicotinic acid. It was found that the rates of β-picoline transformation into nicotinic acid, pyridine-3-carbaldehyde, pyridine-3-nitrile, pyridine and carbon oxides as well as selectivities to products and the catalyst state depend strongly on the ratio of dioxygen to β-picoline concentrations. The minimum admissible ratio of these concentrations under industrial conditions was determined.     

N-羟基-1,6-亚甲基桥[10]轮烯-3,4-酰亚胺/乙酸钴液相催化氧化3-甲基吡啶制备烟酸

以1,6-亚甲基桥[10]轮烯-3,4-二甲酸酐为原料,与羟胺基盐酸盐经酰化和脱水反应制得N-羟基-1,6-亚甲基桥[10]轮烯-3,4-酰亚胺(2);构建了2/乙酸钴催化体系,以氧分子为氧源,乙腈为溶剂,在1 MPa氧气压力下于120℃反应20 h,氧化3-甲基吡啶制备烟酸,产率70%,其结构经~1H NMR和IR确证。     

Effect Factors in Synthesis of Nicotinic Acid by Electrooxidation of 3-Picoline

IntroductionNicotinic acid,whose IUPAC name is3-pyridineformic acid,also called Vitamin B3,is an importantraw material of chemical industry,an intermediate inthe synthesis processes of medicine,additives of food,drink and feed.It is also applied to anti-oxidants in ac-tive dyestuff and household chemicals,such as hair dyeand hair tonic agents,plastic stabilizer and photo-sen-sitive materials,etc.[1—3].There are a fewmethods forsynthesizing nicotinic acid at present.The oxidation of3-picoli…     

kinetics of the oxidation of b-picoline to nicotinic acid over vanadia-titania catalyst, 1. The network of the reaction and the effect of water

Over vanadia-titania catalysts, the oxidation of β-picoline into nicotinic acid proceeds under a parallel-consecutive network. Nicotinic acid is formed both directly from picoline and through pyridine-3-carbaldehyde as an intermediate. Products of total oxidation and nitrile are formed on a parallel path from picoline, and on a consecutive path via overoxidation of partial oxidation products. Introduction of water into the reaction mixture raises selectivity and activity due to an acceleration of the formation of carbaldehyde and nicotinic acid and not due to repressing the reactions of total oxidation. This revised version was published online in August 2006 with corrections to the Cover Date.     

A study of nicotinic acid synthesis on a pilot installation and its simulation

Technological process parameters of the nicotinic acid synthesis by oxidation of β-picoline on a vanadium-titanium catalyst in a unit tube of a pilot installation were determined: conversion of β-picoline, yield and selectivity for products, and parametric sensitivity of the "hot point" temperature to variation of parameters at the reactor inlet. A mathematical simulation of the process was carried using the model of heat-and-mass transfer in a bed of a tubular reactor and the kinetic model of oxidation of β-picoline.     

2-甲基吡啶的槽内式间接电氧化

在质子交换膜为隔膜的电解槽内, 以2-甲基吡啶为原料, 以Cr2O72-/Cr3+为媒质, 采用间接电氧化法研究了合成2-吡啶甲酸的反应条件. 实验结果表明, 硫酸浓度、硫酸铬浓度、 反应温度、2-甲基吡啶浓度和阳极电位对产率、转化率、 选择性和电流效率均有影响. 通过变化规律的研究, 找到了各个影响因素的最佳条件为: 硫酸浓度为6.0 mol/L, 反应温度为60 ℃, 硫酸铬浓度为0.15 mol/L, 2-甲基吡啶浓度为0.1 mol/L, 阳极电位为1.50 V.     

Surface chemistry of nanometer-sized aerosol particles: reactions of molecular oxygen with 30 nm soot particles as a function of oxygen partial pressure

The kinetics of the reaction between soot nanoparticles and molecular oxygen were studied by tandem differential mobility analysis (TDMA). The particles were extracted from the tip of an ethene diffusion flame. Reactions were studied at atmospheric pressure in mixtures of nitrogen and oxygen. The studies involved particles of an initial mobility diameter of 30 nm over broad ranges of temperature (500-1100 degrees C) and oxygen volume fraction (0-1). Measurements as a function of oxygen partial pressure establish that the oxidation kinetics are not first-order in oxygen volume fraction (F(O2)). Rather, the oxidation rate increases rapidly and linearly with F(O2) between 0 and 0.05 and then more slowly but still linearly between 0.05 and 1. Temperature dependent measurements are consistent with a reaction pathway involving two kinetically distinguishable oxidation sites which interconvert thermally and through oxidation. Results and conclusions are compared to those of earlier studies on the oxidation of soot.     

The vapor phase oxidation of 3-picoline on tin and titanium vanadates

The oxidation of 3-picoline with air on fused tin and titanium vanadates gives as the main reaction products nicotinaldehyde and nicotinic acid, the yield of which amounts to 45–50% of theory calculated on the alkylpipidine taken and 75–80% calculated on that which has reacted.Part LXIV of the series Oxidation of organic compounds: for part LXIII, see [1].     

C_6H_2(OH)_3CH_3氧化成羟基苯甲酸反应路径的DFT研究

运用密度泛函(DFT)理论,采用Materials Studio 8.0,用GGA/BP方法研究了C_6H_2(OH)_3CH_3氧化成羟基苯甲酸的反应路径。结果表明,甲基上的氢原子被氧化成羟基以及羟基被氧化为醛基及醛基被氧化成羧基均为放热过程。分子C_6H_2(OH)_3CH_3中甲基氧化成羧基的主路径为三个氢原子氧化反应路径,其路径为C_6H_2(OH)_3CH_3+3O→C6H2(OH)3C(OH)3→C6H2(OH)3COOH+H2O,该路径受限于羟基直接被氧化成羧基过程,需克服130 k J/mol的反应势垒,反应速率常数对数ln(k)为-22.96 s-1;醛基、羟基优先被氧化成羧基的顺序为:-CHO-C(OH)3-HC(OH)2-H2C(OH);提高反应温度、氧气浓度均有利于羟基苯甲酸的生成,适当的催化剂有利于促进整个反应的进行。     

表面活性剂对3-甲基吡啶电氧化制取烟酸的影响

研究了在阳极液中加入不同类型和不同浓度表面活性剂对3-甲基吡啶电氧化的影响. 结果表明, 十六烷基三甲基溴化铵、脂肪醇聚氧乙烯醚硫酸钠、十二烷基苯磺酸钠、十二烷基二甲基甜菜碱和山梨醇酐单硬脂酸酯的胶团对3-甲基吡啶电氧化有明显的促进作用. 实验结果还表明, 在低浓度的硫酸为支持电解质阳极液中加入表面活性剂与不加表面活性剂相比, 3-甲基吡啶电氧化制取烟酸的选择性和电流效率明显提高.     

铬掺杂对V2O5/TiO2催化氧化3-甲基吡啶合成烟酸性能的影响

为进一步提高V2O5/TiO2催化剂对气相一步催化合成烟酸反应的活性和选择性.通过浸渍法制备一系列掺杂过渡金属铬的V2O5/TiO2催化剂,并对催化剂进行了BET、XRD、H2-TPR、NH3-TPD表征.结果表明,掺杂Cr后催化剂产生了新晶相CrVO4,减小了V2O5晶粒尺寸,并提高了催化剂的酸性,可较大地提高催化剂...     

Mechanism of carboxylic acid formation on vanadium-containing oxide catalysts

The surface intermediates in acrolein oxidation into acrylic acid on a V-Mo oxide catalyst, formaldehyde oxidation into formic acid on a V-Ti catalyst, and 3-pyridinecarboxaldehyde and -picoline oxidation into nicotinic acid on a V-Ti catalyst are identified by in situ IR spectroscopy. The acids are found to form by similar mechanisms. The intermediates in acid formation are saltlike surface compounds (formates, acrylates, and nicotinates) stabilized on vanadium ions. The role of vanadium in acid formation is discussed in terms of the mechanisms suggested.__________Translated from Kinetika i Kataliz, Vol. 46, No. 2, 2005, pp. 233–242.Original Russian Text Copyright © 2005 by Popova, Andrushkevich, Zakharov, Chesalov.     

Continuous flow metal-free oxidation of picolines using air

The metal free, direct oxidation of 2-, 3-, and 4-picoline to the corresponding carboxylic acid using either oxygen or air has been developed under continuous flow conditions. Complete conversion for all three substrates was obtained at moderate temperatures and pressures within minutes.     

在Pt/Al2O3催化剂上苯的内扩散对负0.9级动力学的影响

在Pt/Al₂O₃催化剂上用外循环反应器研究了内扩散对苯完全氧化动力学的影响,当用30～40目(即0.45～0.60mm)催化剂时反应在动力学区域进行.若O₂过量时则动力学区域苯的完全氧化可用-0.9级速率方程描述.当催化剂粒径增至φ6×5mm时,反应在内扩散区域进行并变为一0.1级反应.催化剂有效因子η在0.24～0.12之间.在同一温度下,η_实验随苯分压p_苯的增加而增大;而p_苯相近时,η_实验则随温度的升高而减小.动力学区域的反应活化能为55.5kJ/mol,内扩散区域的反应活化能为34.9kJ/mol,其值约为动力学区域的活化能与苯分子扩散活化能的算术平均值.     

Flammability studies of 3-methyl pyridine/water system

In industrial processes, information on the safety property of chemicals is essentially crucial for safe handling during unit operations. Ensuring the safe use of combustible or flammable substances in processes is unlikely without detailed investigations of their flammability characteristics and related hazards. We studied 3-methyl pyridine (3-picoline), e.g., flammability limits (LFL/UFL), maximum explosion pressure (P _max), maximum explosion pressure rise (dP/dt)_max, minimum oxygen concentration (MOC), vapor deflagration index (K _g), and characterized the influence of inert steam (H₂O) on critical parameters for 3-picoline/water mixtures at 270°C, 1 atm, various oxygen concentrations, and vapor mixing ratios (100/0, 30/70, 10/90 and 5/95 vol.%) with a 20-L-Apparatus in simulated conditions, respectively. The results showed that the flammability characteristics of 3-picoline_(aq) all increased with the oxygen concentration. However, as the composition of inert steam increased, the flammability parameters and the degree of fire and explosion hazards were significantly reduced, instead. This study elucidated the flammability properties of 3-picoline mixed with inert steam. The conclusions could be applied to proactively prevent the relevant processes from incurring fire and explosion accidents.     

Reactions of methyl radicals with propene at temperatures between 750 and 1000 K

The pyrolysis of propene, initiated by methyl radicals, has been studied in the temperature range 750-1000 K and at a pressure of 0.13 bar in a quasi-wall-free reactor using laser heating by fast vibrational-translational (V-T) energy transfer. This is a convenient method to study homogeneous high-temperature kinetics since the reactor walls remain cold. The radial temperature distribution in the reactor has been investigated by four different methods: a stationary heat balance, optical absorption, pressure rise, and the temperature dependence of the rate of an isomerization reaction. Methyl radicals were produced via the fast thermal dissociation of di-tert-butyl-peroxide and the products were analysed using GC-MS. The main products of the overall reaction of the model system propene and methyl (C3H6 + CH3) were isopentane (iso-C5H12) and but-1-ene (1-C4H8), whereas allene (C3H4), trans-but-2-ene (trans-2-C4H8) and cis-but-2-ene (cis-2-C4H8) were minor components, all showing a strong dependence on temperature. The product distribution and the temperature dependence were analysed by a kinetic model of 61 species and 166 reactions developed for the high-temperature oxidation of butane and the low-temperature oxidation of n-pentane and isopentane. It was necessary to include a few missing reactions and to adjust some rate constants to make the modeling agree with the experimental investigations. This extended mechanism has to be evaluated further in forthcoming experiments.     

Enhanced low-temperature CO oxidation on a stepped platinum surface for oxygen pressures above 10(-5) Torr

The rate of CO oxidation has been characterized on the stepped Pt(411) surface for oxygen pressures up to 0.002 Torr, over the 100-1000 K temperature range. CO oxidation was characterized using both temperature-programmed reaction spectroscopy (TPRS) and in situ soft X-ray fluorescence yield near-edge spectroscopy (FYNES). New understanding of the important role surface defects play in accelerating CO oxidation for oxygen pressure above 10(-5) Torr is presented in this paper for the first time. For saturated monolayers of CO, the oxidation rate increases and the activation energy decreases significantly for oxygen pressures above 10(-5) Torr. This enhanced CO oxidation rate is caused by a change in the rate-limiting step to a surface reaction limited process above 10(-5) Torr oxygen from a CO desorption limited process at lower oxygen pressure. For example, in oxygen pressures above 0.002 Torr, CO(2) formation begins at 275 K even for the CO saturated monolayer, which is well below the 350 K onset temperature for CO desorption. Isothermal kinetic measurements in flowing oxygen for this stepped surface indicate that activation energies and preexponential factors depend strongly on oxygen pressure, a factor that has not previously been considered critical for CO oxidation on platinum. As oxygen pressure is increased from 10(-6) to 0.002 Torr, the oxidation activation energies for the saturated CO monolayer decrease from 24.1 to 13.5 kcal/mol for reaction over the 0.95-0.90 ML CO coverage range. This dramatic decrease in activation energy is associated with a simple increase in oxygen pressure from 10(-5) to 10(-3) Torr. Activation energies as low as 7.8 kcal/mol were observed for oxidation of an initially saturated CO layer reacting over the 0.4-0.25 ML coverage range in oxygen pressure of 0.002 Torr. These dramatic changes in reaction mechanism with oxygen pressure for stepped surfaces are consistent with mechanistic models involving transient low activation energy dissociation sites for oxygen associated with step sites. Taken together these experimental results clearly indicate that surface defects play a key role in increasing the sensitivity of CO oxidation to oxygen pressure.     

Vapor-phase oxidation of β-picoline to nicotinic acid on V2O5 and modified vanadium oxide catalysts

Modification of V₂O₅ with Ti, Sn, Zr, Nb, and Al oxides improves the activity and selectivity of the vanadium oxide catalyst in vapor-phase oxidation of β-picoline to give nicotinic acid. It is shown that the conversion of β-picoline and the yield of nicotinic acid on two-component V₂O₅-TiO₂, V₂O₅-SnO₂, V₂O₅-ZtrO₂, V₂O₅-Nb₂O₅, and V₂O₅-Al₂O₃ catalysts may be several times those on the V₂O₅ catalyst. It was found that, on passing from V₂O₅ to double-component vanadium-containing catalysts, the proton affinity of active oxygen bonded to vanadium, calculated by the quantum-chemical method, grows simultaneously with the increase in the activity of the catalysts in the oxidation reaction.