Studies on synthesis of methyl glycolate and methyl methoxy acetate from the coupling of formaldehyde and methyl formate

Catalytic performance of various acids in the coupling reaction of formaldehyde and methyl formate to produce methyl glycolate and methyl methoxy acetate has been studied. The influence of reaction conditions, such as catalyst amount, reaction temperature, reaction time, and molar ratio of formaldehyde to methyl formate, has also been investigated. The results showed that the acid strength had great influence on the reaction, namely, stronger acids had higher activities. It was also found that the reaction temperature and time had significant effect on the reaction, and the preferable conditions were quite different as different acids were used.     

酸-酸法合成甲基异丙基酮催化剂的研究

研究了酸-酸法合成甲基异丙基酮催化剂,利用扫描电镜(SEM)、X射线衍射(XRD)和表面酸性分析等手段,进行新鲜催化剂和评价1 300 h的催化剂表征。结果表明,催化剂的活性中心不是氧化稀土晶胞;增加氧化钕和氧化镨(RE1O RE2O)可提高催化剂的低温活性,抗积碳能力弱;加入氧化铈(RE3O)抗积碳能力强;降低酸强度有利于提高催化剂的选择性,延长催化剂的寿命。     

Effect of acetic acid on poly-(3-hydroxybutyrate-CO-3-hydroxyvalerate) synthesis in recombinantEscherichia coli

The synthesis of poly-(3-hydroxybutyrate-co-3-hydroxyvalerate) [P(3HB-co-3HV)] copolymer by recombinantEscherichia coli was studied in the medium containing glucose and valeric acid as carbon sources. A recombinantE. coli strain (fadR atoC) harboring a stable high-copy number plasmid containing theAlcaligenes eutrophus polyhydroxyalkanoate (PHA) biosynthesis genes was constructed for the production of the copolymer P(3HB-co-3HV). Accumulation of acetic acid not only had a detrimental effect on cell growth but also decreased the flux of acetyl-CoA into the P(3HB-co-3HV) biosynthetic pathway. Reducing specific growth rate by increasing the initial acetic acid concentration resulted in enhanced copolymer synthesis due to less accumulation of acetic acid. Initial acetic acid concentration of 50 mM was found to be optimal at 20 g/l glucose and 20 mM valeric acid concentration. The fraction of 3-hydroxyvalerate (3HV) increased with decreasing growth temperature. The ratios of 3HV to 3HB in the copolymer could be controlled by altering the concentrations of valeric acid and glucose in the medium. Catabolite repression was in part responsible for the inefficient copolymer synthesis. Various nutritional components were examined for their ability to relieve catabolite repression. An addition of oleic acid resulted in threefold increase of the 3HV fraction in the copolymer. An addition of a small amount of tryptone and peptone considerably promoted P(3HB-co-3HV) synthesis.     

Decomposition of acetic acid by advanced oxidation processes

Decomposition of acetic acid, known as a non-degradable organic compound, was conducted for several advanced oxidation processes such as TiO₂-UV-H₂O₂, Fe²⁺-H₂O₂-UV, UV-H₂O₂ and TiO₂-UV system. Acetic acid was efficiency decomposed within 120 minutes of UV radiation under the initial concentration of 500 ppm. The initial chemical oxygen demands (COD _cr ) tended to increase as H₂O₂ was added in most reactions. However, the initial COD _cr was not increased as H₂O₂ was consumed for the oxidation of iron salt in the photo-Fenton oxidation process. COD _cr and concentration of acetic acid rapidly decreased as the mole ratio of hydrogen peroxide increased owing to rapid decomposition of the reactant at the beginning of reaction. All reactions show first order pseudo reaction rate. The COD _cr removal rate and the decomposition efficiency of acetic acid were fastest in the UV-H₂O₂ process.     

废水中乙酸回收方法的研究

采用萃取和蒸馏2种方法从水溶液中回收乙酸。用物理萃取、络合萃取和共沸蒸馏使各浓度段的乙酸进行了再循环,并对上述方法做了比较。低质量分数乙酸用n(三辛胺)∶n(乙酸)=1∶1,且有机相中V(三辛胺)∶V(环己烷)∶V(石油醚)=3∶5∶2时萃取率达95%以上,高质量分数乙酸可先用乙酸乙酯萃取或先共沸蒸馏,再用三辛胺络合萃取。     

甲基异丁基酮的合成及其催化剂的研究进展

介绍了生产甲基异丁基酮的几种生产路线及生产过程用到的各种催化剂,重点介绍了丙酮一步法合成甲基异丁基酮的方法,并对其合成过程中用到催化刺的研究进展进行了综述.     

Effects of vanadium supported on ZrO2 and sulfolane on the synthesis of phenol by hydroxylation of benzene with oxygen and acetic acid on palladium catalyst

The catalyst system consisting of Pd, transition metal-modified ZrO₂ and acetic acid was found to catalyze the hydroxylation of benzene with molecular oxygen without hydrogen and phenol was formed. Of transition metals employed, only vanadium additive was found to be effective for improving the rate of phenol formation as well as the selectivity, while any other transition metals such as iron, molybdenym, tungsten and yttrium were not promotive. Support effects on vanadium were in the order: V/ZrO₂> V/Al₂O₃> V/SiO₂. The highest rate of phenol formation was obtained at 0.5wt%V/ZrO₂ catalyst. Phenol selectivity was dramatically improved by the addition of sulfolane, while benzene conversion and STY of phenol formation decreased. It is assumed that Pd(II) and Pd(IV) intermediates derived from acetic acid, oxygen and palladium acetate could play an important role in hydroxylation of benzene.     

SO42-/ZrO2/MCM-41催化丙烯和乙酸合成乙酸异丙酯的研究

水热合成了介孔材料MCM-41,并以其为载体负载固体超强酸SO42-/ZrO2,通过XRD和N2吸附/脱附对制备的SO42-/ZrO2/MCM-41催化剂进行了表征。在固定床反应器中,以丙烯和乙酸为原料,研究了该催化剂合成乙酸异丙酯的活性。对反应条件进行了系统考察,得出了最佳的反应条件:反应温度140℃;反应压力1.2 MPa;空速(LHSV)1.0h-1;n(C3H6)∶n(CH3COOH)=3∶1。在此条件下,乙酸异丙酯的产率最高可达68.9%。同时,通过48 h的催化剂寿命实验,结果表明该催化剂具有较好的稳定性。     

钛制醋酸回收塔的腐蚀分析及阻滞措施

分析钛制醋酸回收塔不同部位的腐蚀情况 ,提出了提高耐蚀性和延长设备使用寿命的有效措施     

Effects of acetic acid addition methods on butyl acetate enzymatic synthesis

Abstract

Butyl acetate is a versatile chemical due to its excellent solvency for polymers, resins, and oils. In this work, the butyl acetate synthesis was studied by the esterification of n-butanol with acetic acid using the commercial immobilized lipase Novozym^® 435. The acetic acid and n-butanol concentrations have to be limited in the enzymatic synthesis of this ester due to the deleterious effects caused by these reagents on the enzyme. Three methods of acetic acid addition (single, stepwise and continuous addition) were investigated to minimize the acid concentration. A significant drop on acid conversion was observed in the presence of a higher concentration of the reagents when single or stepwise acid addition was used. However, a solvent-free system using a continuous addition of acetic acid favored butyl acetate synthesis, reaching a conversion of 84% at 60?°C, employing 5?wt% of enzyme and n-butanol/acetic acid final molar ratio equal to 1/1.     

对甲苯磺酸催化微波合成乙酰水杨酸的研究

以水杨酸和乙酸酐为原料,以对甲苯磺酸为催化剂,微波辐射合成了乙酰水杨酸,并考察了影响反应的因素.实验表明:在n(水杨酸):n(乙酸酐)=1:1.7,催化剂用量为水杨酸质量的2.5%,微波输出功率为151W,辐射时间为60s,产率可达91.2%.     

管式环流反应器在乙酸/乙酐羰基合成中的应用

介绍了以乙酸甲酯和甲醇为原料合成年产20 kt乙酐和20 kt乙酸的过程,并且介绍了在以LiI为促进剂的铑-碘均相催化剂作用下、170~199℃的温度范围及5.0 MPa压力条件下,管式环流反应器在乙酸/乙酐合成中的应用。分析了反应器内流体的流动特点和羰基合成的反应过程,建立了数学模型。计算得到了反应器内反应物料转化率、各组分浓度、温度和冷却水温度等各种参数沿物料流动方向的分布,同时对反应器进行了热稳定性分析。计算结果表明,当系统在操作过程中转化率偏离定常态0.000 1,温度偏离定常态0.000 1℃时,转化率和温度能分别在4×10-6s和8×10-6s内回到定常态,整个反应体系是稳定的。     

An expedient synthesis of methyl vinyl sulfide from dimethyl disulfide and acetylene

Dimethyl disulfide reacts with acetylene under atmospheric pressure in basic reductive systems MOH (M=Na, K)–N₂H₄?·?H₂O–N-methylpyrrolidone and Na₂S?·?9H₂O–N₂H₄?·?H₂O–N-methylpyrrolidone to form methyl vinyl sulfide in up to 79% yield.     

单塔精馏生产优级品乙酸的研究

用理论计算与实验相结合的办法 ,采用单塔精馏生产优级品乙酸 ,以降低能耗 ,减少物料损失 ,提高产品收率 ,缩短生产周期 ,避免了双塔精馏所造成的设备与能源的浪费。在国内首次成功研究了单塔精馏生产优级品乙酸的生产工艺。     

Unusual selectivity of oxygenate synthesis: Formation of acetic acid from syngas over unpromoted Rh in NaY zeolite

Syngas conversion over Rh/zeolite-NaY catalysts at high-pressure lead to high yields of acetic acid. This unusual selectivity toward one oxygenate in the absence of any catalyst promoter is most pronounced at lower temperature; the apparent activation energy for overall CO-hydrogenation is 23.7 kcal/mol, but for the formation of acetic acid it is 11.9 kcal/mol. The selectivity is little affected by the protons formed during the reduction of Rh. In stiu FT-IR measurement reveals that changes in activity and selectivity during the start-up period are caused by thorough catalyst reconstruction, converting the original Rh⁰ clusters to multinuclear Rh₆(CO)₁₆ and CH₃Rh_y(CO)_x and/or mononuclear CH₃Rh(CO)_x carbonyl complexes, and smaller Rh⁰ clusters. Stable acetate groups, but not the surface bound acetyls, are formed and detected by FT-IR. Most of the cooperating Rh species survive when the pressure is lowered from 1.0 to 0.1 MPa, maintaining a high acetic acid selectivity that is vastly superior to that of the fresh catalyst.     

The use of dilute acetic acid for butyl acetate production in a reactive distillation: Simulation and control studies

The recovery of dilute acetic acid, which is widely found as a by-product in many chemical and petrochemical industries, becomes an important issue due to economic and environmental awareness. In general, separation of acetic acid in aqueous solution by conventional distillation columns is difficult, requiring a column with many stages and high energy consumption. As a result, the primary concern of the present study is the application of reactive distillation as a potential alternative method to recover dilute acetic acid. The direct use of dilute acetic acid as reactant for esterification with butanol to produce butyl acetate in the reactive distillation is investigated. Simulation studies are performed in order to investigate effect of the concentration of dilute acetic acid and key process parameters on the performance of the reactive distillation in terms of acetic acid conversion and butyl acetate production. In addition, three alternative control strategies are studied for the closed loop control of the reactive distillation. The control objective is to maintain the butyl acetate in a bottom product stream at the desired purity of 99.5 wt%.     

An effective catalyst,Cu-B2O3/SiO2, for hydrogenolysis of methyl formate and one-step synthesis of methanol in slurry-phase with potassium methoxide

Some chromium-free copper-based catalysts are tested for the gas-phase hydrogenolysis of methyl formate, in which Cu-B₂O₃/SiO₂ catalyst is identified to be the most promising. The behaviors of Cu-B₂O₃/SiO₂ catalysts are also examined in the slurry-phase hydrogenolysis of methyl formate, along with a discussion of the promoting effect of B₂O₃. Also, Cu-B₂O₃/SiO₂ is used with potassium methoxide as a co-catalyst for the carbonylation of methanol to regenerate the potassium methoxide from potassium formate and potassium methyl carbonate. Moreover, the slurry-phase one-step synthesis of methanol is studied using KOCH₃/Cu-B₂O₃/SiO₂ mixed catalyst under relatively mild conditions.     

对甲苯磺酸催化合成对羟基苯甲酸乙酯的研究

以对甲苯磺酸为催化荆，合成了对羟基苯甲酸乙酯，同时对影响产率的诸因素进行了考察，其最佳反应条件为：醇酸物质的量比4：l，催化剂用量7．5％，反应时间3．5h。     

Design and control of acetic acid dehydration system via heterogeneous azeotropic distillation

Acetic acid dehydration is an important operation in the production of aromatic acid, such as terephthalic acid or in the manufacture of cellulose acetate. Although acetic acid and water does not form azeotrope, but using simple distillation to separate these two components is not practical. The reason is because the system has tangent pinch on the pure water end, thus it is more customary in industry to use an entrainer via a heterogeneous azeotropic distillation column system for the separation. In this study, a suitable entrainer is selected from three candidate acetates through rigorous steady-state simulation of this system. Optimum process design and operating condition are determined to keep high-purity bottom acetic acid composition and also keep a small acetic acid loss through top aqueous draw. Furthermore, the overall control strategy of this column system is proposed to hold both bottom and top product specifications in spite of feed rate and feed composition load disturbances. The proposed overall control strategy is very simple requiring only one tray temperature control loop inside the heterogeneous azeotropic column.