The contribution of homogeneous and non-oxidative side reactions in the performance of vanadyl pyrophosphate,catalyst for the oxidation of n-butane to maleic anhydride,under hydrocarbon-rich conditions

The reactivity of vanadyl pyrophosphate, catalyst for the selective oxidation of n-butane to maleic anhydride, was examined under n-butane-rich conditions, simulating a feed in which oxygen is the limiting reactant, and a process in which the unconverted n-butane is recycled. A lower selectivity to maleic anhydride was found with respect to the hydrocarbon-lean conditions, due to the higher selectivity to carbon oxides and to the formation of C₈ by-products: tetrahydrophthalic and phthalic anhydrides. The latter compounds formed by a consecutive reaction of maleic anhydride with the unsaturated C₄ intermediates. This occurred under conditions of total oxygen conversion, due to the decreased catalyst oxidizing property. A relevant contribution of radicalic, homogeneous reactions was also observed, which mainly led to the formation of carbon oxides and olefins. This contribution decreased in the presence of the catalyst, which acted as a radical scavenger, but nevertheless remained important at temperatures higher than 400 °C. When conditions were used under which the conversion of oxygen was not total, olefins generated in the gas phase reacted at the catalyst surface yielding maleic anhydride. This homogeneously initiated heterogeneous process led to an unusual effect, of a relevant increase of maleic anhydride yield over 400 °C.     

Pressurized hot water extraction of benzoic acid and phthalic anhydride from petrochemical wastes using a modified supercritical fluid extractor and a central composite design for optimization

Using the pressurized hot water extraction technique, benzoic acid and phthalic anhydride were selectively removed from solid petrochemical wastes (called molten phthalic anhydride). A statistical experimental design based on “central composite design” was applied for obtaining optimized conditions for the semi-continuous extraction of phthalic anhydride and benzoic acid from their mixture with benzoic acid, maleic acid, phthalic acid, phthalic anhydride, aldehydes, phthaldehyde, toluic acid, and some minor impurities. Variables such as pressure (60-220 bar), temperature (60-140 °C), dynamic time (5-45 min), and flow rate (0.2-1 mL/min) were used.     

Cationic grafting from carbon black

Summary The cationic ring-opening copolymerization of tetrahydrofuran (THF) with a cyclic acid anhydride such as phthalic anhydride (PAn) and maleic anhydride was initiated by acylium perchlorate groups on carbon black to give alternating copolymer, i.e., polyester. Epichlorohydrin was found to act as effective promoter in the copolymerization. The polyester formed was effectively grafted from carbon black depending upon the propagation of the polymer from the surface: the grafting ratio of polyester from THF and PAn was increased up to about 65% with an increase in conversion. The polyester-grafted carbon black gave a stable colloidal dispersion in chloroform.     

Use of Difunctional Compounds During Rapid Steam Hydrolysis (Rash) Pretreatment

Mixed hardwood chips were treated with difunctional compounds as catalysts to study the reaction of wood with steam. The Rapid Steam Hydrolysis (RASH) pretreatment process was used for steam treatment. The difunctional compounds studied were maleic anhydride, phthalic anhydride, isophthalic acid, and terephthalic acid at 1.5% concentration based on dry wood weight. RASH pretreatment was performed for one minute at 180°C, 200°, 220°C, 230°C, 240°C, and 260°C. These compounds strongly modified the RASH pretreated material, especially the physical structure. Overall recovery of the pretreated catalyzed and uncatalyzed solids decreased with an increase in RASH temperatures. Catalyst addition did not make a difference on the recovery of pretreated solids. Cellulose degradation increased with temperature for catalyzed systems. Hemicellulose solubilization and degradation were extremely sensitive to the type of catalyst and RASH temperatures. Almost all of the hemicellulose was lost at higher temperatures. Lignin losses did not appear to be affected by the addition of catalyst except at 260°C. Enzymatic rates were improved by addition of the catalysts, especially at the lower temperatures. The maleic anhydride gave the highest enzymatic rates at all temperatures, and phthalic anhydride gave the second highest. The water solubles generally followed the same trends as the enzymatic hydrolysis rates and increased with the addition of catalysts, especially maleic anhydride.     

A revision of the mechanism of o-xylene oxidation to phthalic anhydride with V/Ti/O catalysts, and the role of the promoter Cs

This paper describes the effect of Cs oxide, a promoter of an anatase-supported 7 wt.% V₂O₅ catalyst for the oxidation of o-xylene to phthalic anhydride. The effect of Cs was investigated in relation to the reaction network at 320 °C, i.e., under conditions of incomplete o-xylene conversion. It was found that at this temperature the catalytic performance was affected by a surface-saturation effect. However, Cs had the role of favoring the desorption of intermediates and keeping a cleaner and more oxidizing catalyst surface, so accelerating the conversion of the reactant and the consecutive oxidations occurring upon the reaction intermediates finally leading to phthalic anhydride. This de-saturation derived from the enhancement of the V re-oxidation rate, which is one main effect of Cs in V/Ti/O catalysts. Besides the route of o-xylene oxidation to the main reaction intermediate o-tolualdehyde, a parallel reaction pathway included the direct oxidation of o-xylene to phthalaldehyde; the latter was one intermediate in the formation of phthalide, via intramolecular condensation, and of phthalic acid.     

Influence of backbone rigidity on the curing and the dielectric relaxations of unsaturated polyesters

Unsaturated polyesters with maleic acid and different molar ratio of phthalic anhydride to adipic acid were produced, mixed with styrene, and cured. The degree of double bonds conversion, determined by differential scanning calorimetry (α_DSC), indicating the initial curing, increases significantly with the molar ratio of phthalic anhydride. On the other hand, the degree of double bonds conversion of maleate (α_UP,FTIR) and styrene (α_St,FTIR) units determined by Fourier transform infrared spectroscopy after prolonged curing are considerably higher than α_DSC and increase slightly with the molar ratio of phthalic anhydride. Polyester containing phthalic anhydride without adipic acid (M5P5) has the lowest tetrahydrofuran uptake and diffusion parameter D/α² due to its more rigid segments, in opposite to polyester containing adipic acid (M5A5) having the highest values. According to dielectric spectroscopy measurements, two different relaxations were determined, one beginning above 130°C (with peak above 180°C) attributed to α‐relaxation (dielectric glass transition) and a second one at lower temperatures, attributed to β‐relaxation. The peak of β‐relaxation is at around 130, 75–80, and 30°C for the rigid, intermediate rigidity/flexibility, and flexible polyesters, respectively. The α‐relaxation is determined at low frequencies and the β‐relaxation at intermediate or high frequencies. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Assessment of micro-structured fixed-bed reactors for highly exothermic gas-phase reactions

The application of micro-structured fixed-bed reactors for highly exothermic partial oxidation reactions and their comparison to established multi-tubular fixed-bed reactors was investigated by numerical simulation. As examples, the partial oxidations of butane to maleic anhydride and of o-xylene to phthalic anhydride were chosen. The simulation results revealed that the reactor productivity, i.e. the amount of product per unit of reactor volume, achievable in micro-structured fixed-bed reactors is between 2.5 and 7 times higher than in conventional multi-tubular fixed-bed reactors without the danger of excessive pressure drop. For the partial oxidation of butane to maleic anhydride this can be explained by the increased reactor efficiency caused by lower efficiency losses through heat and mass transfer limitations. In addition, maleic anhydride selectivities and yields are higher in micro-structured fixed-bed reactors. In the case of o-xylene oxidation to phthalic anhydride the main advantage is that egg-shell catalysts in the conventional fixed-bed reactor can be replaced by bulk catalysts in the micro-structured fixed-bed reactor. For this reaction, product selectivities are very similar for all reactor configurations. Thus the catalyst inventory and reactor productivity are strongly increased. This study underlines, that micro-structured fixed-bed reactors exhibit the potential to intensify large scale industrial processes significantly.     

The Synthesis of Phthalic Anhydride via Ozonation of Naphthalene

The oxidation of naphthalene (1) (Scheme 1) in dichloromethane or acetonitrile with excess ozone gives phthalic aldehyde (3), 2-formyl benzoic acid (4) and phthalic anhydride (8). Small amounts of the (E)- and (Z)-isomer of 3-phenyl-(2-formyl)-propenal (10) and (11) are also observed in some cases. The reaction is faster in acetonitrile than in dichloromethane owing to the higher solubility of ozone in the former solvent. The reaction is faster on lowering the temperature because of the increase of the concentration of ozone in solution at lower temperature. With a 1:1 or a 1:2 naphthalene:ozone ratio high conversion and low selectivity for the anhydride (8) is observed.     

不饱和聚酯树脂/蒙脱土纳米复合材料的研制

通过微波交换法将天然钙基蒙脱土转变为钠基蒙脱土，进而转变成镍基蒙脱土。镍基蒙脱土与1，2-丙二醇进行络合，再与顺丁烯二酸酐和邻苯二甲酸酐缩聚为不饱和聚酯，并固化为不饱和聚酯树脂/蒙脱土纳米复合材料，使不饱和聚酯树脂的抗弯性能得以大大改善。     

A first step to the rational design of an organometallic catalyst: RhxHySnz (CH3)n

V/P/O catalysts were prepared using isobutanol as solvent, which contained either cobalt or iron as the dopant (Me/V 0.01). The catalysts were characterized with several techniques, both after thermal treatment and after reaction in n-pentane/air. The catalytic performance was compared for the selective oxidation to maleic and phthalic anhydrides under conditions at which results were stable (i.e., after at least 200 h time-on-stream). It was found that iron had a dramatic effect on the structural evolution of the catalyst both during calcination and during aging; in contrast, the effect of cobalt was much less marked. Doping with 1% cobalt remarkably improved the selectivity to the phthalic anhydride at the expense of the maleic anhydride with respect to the undoped catalyst, while doping with iron led to a catalyst less selective to phthalic anhydride and more selective to carbon oxides. This revised version was published online in July 2006 with corrections to the Cover Date.     

Asymmetric Sequential Michael Addition–N–Heterocyclization Reactions Involving Chiral Imines

The reaction of chiral imines ent- 14, 27 , and 31 with α-chloroacrylonitrile 6 , maleic anhydride 9 , and citraconic anhydride 35 has been investigated. Addition of imine 27 to 6 furnished, after NaBH₃CN-reduction of the crude product, the bicyclic derivative 28 as a single isomer. When the same protocol was applied to imine ent- 14 , a mixture of adducts 29 and 30 was obtained. Addition of imine 31 to 6 gave the annulated pyrrole 32. Condensation of imine 27 with maleic anhydride 9 afforded compound 33 as a single isomer. Addition of imine ent- 14 to citraconic anhydride 35 led, after esterification of the crude product with CH₂N₂, to a mixture of adducts 36 and 37. The mechanism of these aza-annulations was discussed on the basis of the regio- and stereoselectivities observed.     

Oxidation of o-Xylene to Phthalic Anhydride on Sb-V/ZrO2 Catalysts

Zirconia-supported and bulk-mixed vanadiumantimonium oxide catalysts were used for the oxidation of o-xylene to phthalic anhydride. X-ray diffraction, Raman spectroscopy and photoelectron spectroscopy were used for characterization. It was found that vanadium promotes the transition of tetragonal to monoclinic zirconia. The simultaneous presence of Sb and V on zirconia at low coverage led to a preferential interaction of individual V and Sb oxides with the zirconia surface rather than the formation of a binary Sb-V oxide, while at higher Sb-V contents the formation of SbVO₄ took place. Sb-V/ZrO₂ catalysts showed high activity for o-xylene conversion and better selectivity to phthalic anhydride as compared to V/ZrO₂ catalysts. However, their selectivity to phthalic anhydride was poor in comparison to a V/TiO₂ commercial catalyst. The improved selectivity of the Sb-containing catalysts is attributed to the blocking of non-effective surface sites of ZrO₂, the decrease of the total amount of acid sites and the formation of surface V-O-Sb-O-V structures.     

Effect of glycol and filler types on some polymeric composite properties

Two unsaturated polyesters based on maleic anhydride, phthalic anhydride, and sebasic acid with each of linear 1,6‐hexanediol (PE_L) and cyclic 1,4‐cyclohexanediol (PE_C) were prepared. Their structures were characterized by IR and ¹H NMR spectra. Their composites were prepared by mixing different ratios (60, 70, and 80%) with talc and kaolin with polyester/styrene mixture. The effect of linear and cyclic glycols and the effect of filler type and concentration of these composites were studied in terms of their electrical properties and the hardness before and after aging. The thermal behavior of styrenated polyesters and their composites was studied using thermogravimetric analysis. It has been found that both fillers increase the thermal stability and decrease the weight loss. The permittivity ε′ and the dielectric loss ε″ were measured in the frequency range 100 Hz up to 100 kHz at room temperature 25°C ± 1. The polyester composite samples containing 70% filler lead to good electrical properties in addition to its resistance to thermal aging. The hardness value was increased by increasing the filler content before and after aging. The polyester composites based on cyclic glycol and loaded with 80% kaolin gave the highest hardness values. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Thermal degradation of polyester thermosets prepared using dibromoneopentyl glycol

Polyester thermosets have been prepared from maleic anhydride, phthalic anhydride, dibromoneopentyl glycol, and styrene, and their thermal degradation has been studied. Thermogravimetry has shown that degradation in air occurs in three main stages. For the 10% bromine polyester, the weight losses corresponded to 16.3%, 69.7%, and 13.9% of the original polymer weight—the temperatures of the DTG peak maxima being 217°C, 345°C, and 530°C, respectively. Infrared analysis of the residues showed that above 250°C there was a gradual reduction in the absorbance of all peaks with increasing temperature, indicating the degradation of all parts of the 3-dimensional polymer structure was occurring in a simultaneous manner. Degradation of the dibromoneopentyl glycol polyesters at 530°C in air proved to be a very complex process since a mixture of organic products was produced which gave rise to well over 100 peaks in the capillary column chromatograms. Under the conditions used, the low temperature degradation products proved to be rich in phthalic anhydride with no benzaldehyde being detected. The yields of benzene, toluene, styrene, and naphthalene increased with increase in temperature.     

SYNTHESIS OF UNSATURATED POLYESTER RESIN—EFFECT OF CHOICE OF REACTANTS AND THEIR RELATIVE PROPORTIONS

Unsaturated polyesters are synthesized in the laboratory by the condensation of saturated and unsaturated anhydrides with glycols. The condensate obtained is mixed with styrene monomer to get an unsaturated polyester resin formulation. The properties of the polyester resin synthesized are affected by the synthesis parameters. In this study, the parameters investigated are the effect of choice of reactants and their relative proportions. Properties such as tensile strength, tensile modulus, elongation-at-break, toughness, impact strength, surface hardness, abrasion resistance, and water absorption were tested after curing the resin. Various combinations of (a) maleic anhydride and phthalic anhydride, (b) propylene glycol and ethylene glycol, and (c) propylene glycol and diethylene glycol were used to investigate the effect on the properties of the synthesized resin. The combinations of the anhydrides and glycols that give optimum properties are identified. The results show that most of the properties are maximum at 60% maleic anhydride composition in a mixture of maleic anhydride and phthalic anhydride. Similarly, a better balance of properties is obtained when propylene glycol is mixed with 30% ethylene glycol or 20% diethylene glycol.     

Varied Thermal Chemistry of Hydrocarbons on Nickel Single-Crystal Surfaces

Temperature programmed desorption (TPD) results are reported for the conversion of styrene, bromocyclopentane, 1-pentene, 1,5-pentadiene, and 1,5-diiodopentane on Ni(100), and of iodoethane and 1- and 2-iodopropane on Ni(110) single-crystal surfaces. The purpose of these experiments was to illustrate the versatility of nickel in promoting a variety of surface steps for the conversion of adsorbed hydrocarbons. Our examples include the selective hydrogenolysis of styrene to toluene, the migration of carbon?Ccarbon double bonds in cyclopentene and 1-pentene, the ring closure of C₅ metallacyclic surface intermediates, the coupling of alkyl groups, and the growth of hydrocarbon chains starting from ethyl and propyl surface intermediates. Additional information is reported on the relative rates of the hydrogenation and dehydrogenation surface steps responsible for multiple H?CD exchange steps.     

New aspects of unsaturated polyester resin synthesis. Part 2. Reactant sequence distribution and its effect on cure kinetics

The distribution of unsaturations in the prepolymer of a typical unsaturated polyester (UP) resin (maleic anhydride, phthalic anhydride and 1,2‐propylene glycol) has been shown to influence the kinetics of the cure process with styrene monomer. Segments containing double bonds in close proximity appear to lower the reactivity of the resin due to steric hindrance, as indicated by the fact that the rate of cure and the final degree of cure, measured by differential scanning calorimetry (DSC), increase as the average sequence length (SL) of maleic units decreases. This implies that the reactivity of UP resins may be improved by synthesis of prepolymers with certain reactant sequence‐length distributions. The copolymer formed by the melt condensation process of maleic anhydride, phthalic anhydride and 1,2‐propylene glycol in the absence of a transesterification catalyst has a non‐random structure with a tendency towards blockiness. This was established using ¹H NMR analysis in tandem with deterministic and Monte Carlo modelling techniques. Copyright © 2003 Society of Chemical Industry     

聚丙烯纤维水相异相接枝马来酸酐

本文研究了用水相异相法在聚丙烯纤维上接枝马来酸酐，用称重法测定接枝率，结果认为，随着反应中使用的马来酸酐和过硫酸铵浓度的提高，所得产物的接枝率显著提高，而反应温度和反应时间的影响则是开始随温度升高和时间延长接枝率上升，达到最大值后下降，在本实验中，各种反应条件下，都可以得到超过1．8％的接枝率。     

Microwave radiation copolymerization in solid state of maleic anhydride and allylthiourea

Microwave radiation copolymerization of maleic anhydride and allylthiourea was studied in solid state. Composition of the monomer feed and the power and time of microwave radiation on conversion and intrinsic viscosity were discussed. Reactivity ratios for maleic anhydride and allylthiourea were also determined. Values of r₁ and r₂ were 0.875 and 0.650 for maleic anhydride and allylthiourea, respectively. The copolymer can be used as soluble macromolecular complexing agents for metal ions. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1563–1566, 1998     

Characteristic properties of cutting fluid additives derived from the reaction products of hydroxyl fatty acids with some acid anhydrides

Several adducts were prepared from the thermal reaction of hydroxyl fatty acids (ricinoleic acid oligomers, 12-hydroxystearic acid oligomers, oleyl alcohol, dehydrated castor oil fatty acids, and dimer acid) with maleic anhydride and screened as water-soluble cutting fluids. For example, aqueous solutions of triethanolamine salts with the products of ricinoleic acid oligomers, 12-hydroxystearic acid dimer, and 12-hydroxysteric acid hexamer showed good antirust properties for waterbased cutting fluids. Various half esters of hydroxyl fatty compounds with acid anhydrides were prepared. Aqueous solutions of triethanolamine salts of half esters of maleic anhydride and succinic anhydride and phthalic anhydride with hydroxyl fatty acids gave good antirust and antiwear properties for waterbased cutting fluids.