Oxidative Esterification of Methacrolein to Methyl Methacrylate over Supported Palladium Catalyst

Supported palladium catalysts, which were used in the oxidative esterification of methacrolein to methyl methacrylate, have been prepared with different carriers and Pd precursors. Experimental results revealed that Pd catalysts with r-Al2O3 support and Na2PdC14 precursor showed good performance. Pd catalyst modified with Pb and Mg indicated that Pd-Mg bimetallic catalyst exhibited considerably higher activity and Pd-Pb exhibited both higher activity and selectivity. 92.27% methacrolein conversion and 90.57% methyl methacrylate selectivity were obtained on Pd-Pb-Mg catalyst.

The Intermetallic Catalysts for Oxidative Esterification of Methacrolein to Methyl Methacrylate

A series of supported intermetallic Pb-Pb catalysts were prepared with the impregnation method by changing the support(silica,molecular sieve or γ-alumina)and the pore size.The chemical states of the two metals were characterized by XPS analysis,the process for producing methyl methacrylate based on the direct oxidative esterification of methacrolein with methanol in the presence of oxygen was performed in a slurry reactor with the above-mentioned catalysts.The influence of the calcination temperature and the kinds of support as well as the pore size on catalytic activity had been extensively investigated.Under the conditions of temperature at 80℃,catalyst 3.8%(ω)and the reaction time 2 h,the conversion rate of methacrolein reached 85%,the selectivity and the yield of methyl methacrylate were 90% and 76.5%,respectively.

Effect of Bi promoter on the performances of selective oxidation of isobutane to methacrolein over MoVO/AlPO_4 catalysts

The effects of Bi on the catalytic performance of selective oxidation of isobutane to methacrolein over MoVO/AlPO4 catalyst were investigated by XRD, FT-Raman, XPS, UV-vis DRS techniques. The results show that the addition of Bi component into the MoVO/AlPO4 catalyst obviously improves the catalytic performance, and the selectivity to methacrolein can increase from 14.2% to 45.1% with the increase of Bi/V molar ratio from 0 to 1. Combining the characterization results with the reaction evaluation, it is concluded that the catalytic activities of the MoV0.3Bix/AlPO4 catalysts are related to the crystalline phase composition and the dispersion of molybdenum and vanadium oxides species in general, and also to the V5＋/V4＋ molar ratio on the surface in particular.

High dispersion of heteropolyacid nanoparticles on hydrothermally Cs-modified three-dimensionally ordered macroporous SiO2 with excellent selectivity in methacrolein oxidation

Heteropolyacid nanoparticles(NPs)were supported on Cs-modified three-dimensionally ordered macroporous(3DOM)SiO2 and used as the catalyst for the oxidation of methacrolein(MAL)to methacrylic acid(MAA).Hydrothermal treatment and incipient wetness impregnation were employed respectively for the Cs-modification.It was found that hydrothermal Cs-modification of 3DOM SiO2 promoted the dispersion of the supported heteropolyacid,which showed an average particle size of 5.2 nm,much smaller than that(17.6 nm)on the Csmodified 3DOM SiO2 prepared by incipient wetness impregnation.The effects of hydrothermal treatment on the structure and catalytic performance of the catalyst were investigated.Results showed that the ion exchange between Cs+and the surface silanol groups on 3DOM SiO2 was promoted with the increase of the hydrothermal temperature.Meanwhile,Cs-modification helped the heteropolyacid to retain intact Keggin structure,inhibiting the formation of MoO3.Highly dispersed heteropolyacid NPs with enhanced structural stability exhibited excellent selectivity to MAA in the oxidation of MAL.

Photooxidation of Methacrolein in Fe(III)-Oxalate Aqueous System and Its Atmospheric Implication

Iron and oxalic acids are widely distributed in the atmosphere and easily form ferric oxalate complex(Fe(III)-Ox).The tropospheric aqueous-phase could provide a medium to enable the photo-Fenton reaction with Fe(III)-Ox under solar irradiation.Although the photolysis mechanisms of Fe(III)-Ox have been investigated extensively,information about the oxidation of volatile organic compounds(VOC),specifically the potential for Secondary Organic Aerosol(SOA)formation in the Fe(III)-Ox system,is lacking.In this study,a ubiquitous VOC methacrolein(MACR)is chosen as a model VOC,and the oxidation of MACR with Fe(III)-Ox is investigated under typical atmospheric water conditions.The effects of oxalate concentration,Fe(III)concentration,MACR concentration,and pH on the oxidation of MACR are studied in detail.Results show that the oxidation rate of MACR greatly accelerates in the presence of oxalate when compared with only Fe(III).The oxidation rate of MACR also accelerates with increasing concentration of oxalate.The effect of Fe(III)is found to be more complicated.The oxidation rate of MACR first increases and then decreases with increasing Fe(III)concentration.The oxidation rate of MACR increases monotonically with decreasing pH in the common atmospheric water pH range or with decreasing MACR concentration.The production of ferrous and hydrogen peroxide,pH,and aqueous absorbance are monitored throughout the reaction process.The quenching experiments verify that·OH and O_(2)^(+)are both responsible for the oxidation of MACR.MACR is found to rapidly oxidize into small organic acids with higher boiling points and oligomers with higher molecular weight,which contributes to the yield of SOA.These results suggest that Fe(III)-Ox plays an important role in atmospheric oxidation.

Insights into the Reaction Network and Mechanism of Green Aerobic Oxidative Esterification of Methacrolein over Different Heterogeneous Catalysts

The oxidative esterification of methacrolein(MAL)is an important way to prepare high-valued methyl methacrylate(MMA),but this process is ultra-complex due to the high reactivity of both C=O and C=C bonds in MAL molecule.In order to further improve MMA selectivity,the reaction network and relevant mechanisms have been proposed and profoundly investigated in this paper.Five kinds of fundamental reactions are involved in this process,including(a)the acetal reaction;(b)the aerobic oxidation of hemiacetal;(c)the alkoxylation of C=C double bond;(d)the Diels-Alder reaction;and(e)the hydrogenation reaction of unsaturated double bond.Among them,the Diels-Alder reaction of MAL is non-catalyzed,and the Brönsted acid sites or the Lewis acid sites favor promoting acetal reaction of MAL with methanol,while the alkoxylation of C=C bond with methanol is enhanced under alkaline condition.In particular,by employing the Pd-based catalysts,hydrogenation products are formed in alkaline methanol solution,hence with lower than those obtained by the Au-based catalysts.Notably,it is necessary to match the hemiacetal fromation and aerobic oxidation of hemiacetal,which is relevant with the amount and strength of acid and redox sites.Consequently,this work can provide a good guidance for the further design of both catalysts and processes in future.

Transition metal-doped heteropoly catalysts for the selective oxidation of methacrolein to methacrylic acid

Heteropoly compounds with the general formula Cs1Mo.5X＋H3-o.5xP1.2MOllVO4o （M = Fe, Co, Ni, Cu or Zn） and CslCuyH3_2yP1.2MO11VO40 （y = 0.1, 0.3 or 0.7） were synthesized and then used as catalysts for the selective oxidation of methacrolein to methacrylic acid. The effects of the transition metals on the structure and activity of the catalysts were investigated. FTIR spectra showed that the transition metal-doped catalysts main- tained the Keggin structure of the undoped catalysts. X-ray diffraction results indicated that before calcination, the catalysts doped with Fe and Cu had cubic secondary structures, while the catalysts doped with Co, Ni or Zn had both triclinic and cubic phases and the Co-doped catalyst had the highest content of the triclinic form. Thermal treatment can decrease the content of the triclinic phase. NH3 temperature-programmed desorption and H2 tem- perature-programmed reduction results showed that the transition metals changed the acid and redox properties of the catalysts. The addition of Fe or Cu had positive effects on the activities of the catalyst which is due to the improvement of the electron transfer between the Fe or Cu and the Mo. The effects of the copper content on structure and catalytic activity were also investigated. The CSlCUo.3H2P1.2MO11VO40 catalyst had the best performance for the selective oxidation of methacrolein to methacrylic acid.

Sources of methacrolein and methyl vinyl ketone and their contributions to methylglyoxal and formaldehyde at a receptor site in Pearl River Delta

Methacrolein(MACR) and methyl vinyl ketone(MVK) are two major intermediate products from the photochemical oxidation of isoprene, the most important biogenic volatile organic compound. In addition, MACR and MVK have primary emissions. Investigating the sources and evolution of MACR and MVK could provide helpful information for the oxidative capacity of the atmosphere. In this study, hourly measurements of isoprene, MACR, and MVK were conducted at a receptor site in the Pearl River Delta region(PRD), i.e., the Heshan site(HS), from 22 October to 20 November, 2014. The average mixing ratios of isoprene,MACR and MVK were 151 ± 17, 91 ± 6 and 79 ± 6 pptv, respectively. The daily variations and the ratios of MVK/MACR during daytime and nighttime suggested that other sources besides isoprene photooxidation influenced the MACR and MVK abundances at the HS.Positive matrix factorization was utilized to resolve the sources of MACR and MVK. Five sources were identified and quantified, including biogenic emissions, biomass burning,secondary formation, diesel, and gasoline vehicular emissions. Among them, secondary formation made the greatest contribution to observed MACR and MVK with average contributions of ～ 45% and ～ 70%, respectively. Through the yields of secondary products from the oxidation of MACR and MVK by the OH radical and the concentrations of MACR and MVK, it was found that methylglyoxal and formaldehyde were the main oxidation products of MACR and MVK at the HS site. Overall, this study evaluated the roles of primary emissions on ambient levels of MACR and MVK and advanced the understanding of photochemical oxidation of MACR and MVK in the PRD.

The production of formaldehyde and hydroxyacetone in methacrolein photooxidation: New insights into mechanism and effects of water vapor

Methacrolein（MACR） is an abundant multifunctional carbonyl compound with high reactivity in the atmosphere. In this study, we investigated the hydroxyl radical initiated oxidation of MACR at various NO/MACR ratios（0 to 4.04） and relative humidities（＆lt; 3% to80%） using a flow tube. Meanwhile, a box model based on the Master Chemical Mechanism was performed to test our current understanding of the mechanism. In contrast to the reasonable predictions for hydroxyacetone production, the modeled yields of formaldehyde（HCHO） were twice higher than the experimental results. The discrepancy was ascribed to the existence of unconsidered non-HCHO forming channels in the chemistry of CH3-UC（=CH2）OO, which account for approx. 50%. In addition, the production of hydroxyacetone and HCHO were affected by water vapor as well as the initial NO/MACR ratio. The yields of HCHO were higher under humid conditions than that under dry condition. The yields of hydroxyacetone were higher under humid conditions at low-NOx level, while lower at high-NOxlevel. The reasonable explanation for the lower hydroxyacetone yield under humid conditions at high-NOx level is that water vapor promotes the production of Umethacrolein nitrate in the reaction of HOCH2 C（CH3）（OO）CHO with NO due to the peroxy radical-water complex formation, which was evidenced by calculational results. And the minimum equilibrium constant of this water complex formation was estimated to be 1.89 × 10 （-18） cm3/molecule. These results provide new insights into the MACR oxidation mechanism and the effects of water vapor.

Pickering乳液催化非均相羟醛缩合反应研究

近年来,煤基合成甲基丙烯酸甲酯(MMA)工艺获得广泛关注,但甲醛、丙醛羟醛缩合反应存在反应过程不连续、分离回收过程复杂等瓶颈问题。本文以表面改性的二氧化硅(SiO_(2))纳米球为乳化剂,乳化剂颗粒交联进一步“加固”,在液滴周围形成了致密SiO_(2)壳层,构筑了强化型油包水(W/O)Pickering乳液。该Pickering乳液催化体系不仅实现了催化剂的“固载”和羟醛缩合温和反应过程的非均相转化,也为其他均相催化反应体系提供了机遇。

C_(4)烃氧化制备甲基丙烯醛催化剂的研究进展

甲基丙烯酸甲酯(MMA)是一种重要的有机化工原料,被广泛用于制备表面涂层、合成树脂、油漆涂料和高分子材料等。随着我国石化工业的不断发展,特别是大型乙烯装置的建成,将会副产大量的C_(4)烃(异丁烷和异丁烯等),经C_(4)烃氧化法生产MMA清洁工艺表现出明显的经济和技术优势。其中,C_(4)烃氧化制备甲基丙烯醛(MAL)是C_(4)烃生产MMA的关键步骤。综述了C_(4)烃氧化制备MAL的催化剂(Mo-Bi系,Mo-Sb系,Mo-V-Te系,杂多酸系及V系等催化剂)的研究现状,并提出了未来催化剂的重点研究方向。

3-甲基-8-喹啉磺酰氯的合成

以硝基苯作为起始原料,经还原后,与2-甲基丙烯醛环合,再与氯磺酸反应制备得到阿加曲班的关键中间体3-甲基-8-喹啉磺酰氯,结构经1H NMR、ESI-MS等确证,并对合成工艺进行了优化。优化条件下,总收率达78.4%(以硝基苯计),纯度达98.6%(HPLC)。制备方法操作简单,反应条件比较温和,使用的起始物料和试剂廉价易得,可用于工业化生产。

离子液体对甲基丙烯醛氧化酯化反应的影响

Ionic liquid（IL）,[bmim]PF6,was used in the reaction of one-step oxidative esterification from methacrolein to methyl methacrylate. It was found that ionic liquid not only increased the selectivity of methyl methacrylate but also inhibited its polymerization. The selectivity of methyl methacrylate was increased from 45% to 100% with ionic liquid. The experiment results showed that the content of ionic liquid had no effects on the selectivity of methyl methacrylate in a certain range of IL concentration,which indicated that ionic liquid could be used as a potential inhibitor of polymerization. [WT5HZ]

杂多化合物膜催化异丁烯选择氧化反应

以多孔钛片为支撑体 ,将组成为HxCu1.2 PAs0 .6Mo12 Oy的杂多化合物与具有氧溢流效应的氧化物Sb2 O4 制成催化膜 ,在特制的膜催化反应器中进行异丁烯选择氧化反应 .结果表明 ,杂多化合物 Sb2 O4 催化膜具有较高的催化活性 ;在适宜的条件下 ,甲基丙烯酸收率可达 2 6 3 % ,甲基丙烯醛收率可达 2 2 4% ,液体产物 (即可用产物 ,包括甲基丙烯酸、甲基丙烯醛、乙酸和丙酮 )收率可达 6 7 4%

异丁烯制备甲基丙烯醛催化剂的研究进展

异丁烯选择氧化制备甲基丙烯醛是异丁烯法制备甲基丙烯酸甲酯的关键步骤。本文综述了异丁烯选择氧化生成甲基丙烯醛催化剂,其中包括复合氧化物催化剂和杂多化合物催化剂等的研究现状,讨论了在Mo-Bi催化剂上异丁烯选择氧化生成甲基丙烯醛的反应机理。

甲基丙烯醛一步氧化酯化制备甲基丙烯酸甲酯

制备了用于甲基丙烯醛(MAL)一步氧化酯化为甲基丙烯酸甲酯(MMA)的新型催化剂. 在常压和连续搅拌的条件下,考察了反应条件对MAL转化率和MMA选择性的影响,并对反应动力学进行了初步研究. 实验结果表明:当反应温度50℃、氧气流速6 mL/min、甲醇与甲基丙烯醛的摩尔比75、催化剂在反应物中含量2.4%、反应时间60 min时,MAL的转化率可达99.4%, MMA的选择性为95.7%.

异丁烯两段法制甲基丙烯酸甲酯

将异丁烯三步法制甲基丙烯酸甲酯简化为两段法,异丁烯首先被氧化到甲基丙烯醛(MAL),再将甲基丙烯醛氧化到甲基丙烯酸和酯化为甲基丙烯酸甲酯(MMA)的反应合并为一步进行,缩短了工艺流程,提高了产率。第一段用共沉淀法制备含有镧系元素La的MoBiFeCoSbLaCsO催化剂,氧化反应在固定床反应器中进行。反应温度365℃,原料气n〔i(C4H8)〕∶n(O2)∶n(N2)=6∶19∶75,空速1800h-1。异丁烯转化率为93 8%;生成MAL的选择性为88 9%。第二段反应的催化剂为Pd5Pb2FeLa,反应温度为70℃,空气流速为100mL min。MAL转化率为89 2%;生成MMA的选择性为92 3%。

CsCuHPVAs MoO杂多化合物对异丁烯选择性氧化反应的催化性能

用组合法合成了CsCuHPVAsMoO系列杂多化合物催化剂 ,并采用FT IR ,H2 TPR ,NH3 TPD和TG DTA等方法对催化剂进行了表征 .在自制固定床反应器中对异丁烯进行选择性氧化 ,考察了Cs,Cu和As含量、催化剂焙烧温度及反应条件对催化剂催化性能的影响 .结果表明 ,Cs的引入有利于提高催化剂的选择性 ;Cu和As的引入在提高催化剂活性的同时 ,也提高了催化剂的选择性 ;当焙烧温度为 340℃时 ,催化剂的活性和选择性最高 .组成为Cs0 1 Cu0 2 HxPVAs0 2 Mo1 0 Oy 的催化剂对异丁烯具有很强的选择性氧化能力 ,在最佳反应条件下 ,甲基丙烯酸、甲基丙烯醛和乙酸的收率分别可达 5 2 84 % ,1 2 0 5 %和1 8 2 1 % .

Cs-Fe-Co-Bi-Mn-Mo复合氧化物选择性催化氧化异丁烯

Mixed oxide catalyst Cs 0 1 Fe 2Co 6BiMnMo 12 O x was prepared by the interprecipitation method,then the catalyst was calcined at different temperature.Selective oxidation of isobutene was carried out in a fixed bed reactor.The results showed that the catalyst has high catalytic activity.Under the optimum reaction conditions (n( C = 4)∶n(O 2)=1∶2 1∶4,space velocity=180h 1 ,T=360℃),the yield of methacrolein and methacrylic reached 80%,8%,respectively.The total yields of liquid products(methacrolein,methacrylic acid and acetic acid)reached about 90%.

制备条件对异丁烯选择性氧化催化剂性能的影响

通过正交实验设计,改变钼酸铵溶液的质量分数、pH值和催化剂焙烧温度,利用共沉淀法制备了一系列Mo Bi Co Fe Ce Cs K复合氧化物催化剂。借助于BET、TG DSC、XRD等分析方法对催化剂的物理化学性质进行了表征。在常压连续流动固定床反应器中,系统地考察了上述三种制备条件对复合氧化物催化剂催化异丁烯选择性氧化生成甲基丙烯醛反应性能的影响。结果表明,大比表面积的催化剂具有较高的活性,而平均孔径小的催化剂选择性较差。催化剂的最佳制备条件为:钼酸铵溶液的质量分数10%、pH值2～3、焙烧温度500℃。在异丁烯∶空气=6∶94(体积比)、GHSV=3600h-1和360℃条件下,异丁烯转化率87.2%,甲基丙烯醛选择性72.0%,甲基丙烯醛收率62.7%。