微晶纤维素的羧甲基化反应

纤维素通过特殊的化学物理手段处理后，得到的微晶纤维素在有机溶剂中能很好地分散开，且所需要的有机溶剂的量较少。对其反应条件的探索表明，用微晶纤维素来进行羧甲基化反应，碱化和醚化时间较短，且一氯醋酸的利用率较高；用异丙醇作溶剂比乙醇作溶剂反应效果好。产物用1H－NMR研究表明，取代基在2位、3位和6位上的分布较均匀。     

Variables affecting the in situ transesterification of microalgae lipids

This paper describes the effect of important reaction variables on the production of biodiesel from non-edible microalgae lipids, using the acid-catalysed in situ transesterification process. The specific gravity of the biodiesel product was used to monitor the conversion progress. The results indicate that increasing the reacting alcohol volume and the temperature lead to improved fatty acid methyl ester (FAME) conversions. With the exception of in situ transesterification carried out at room temperature (23 °C), the equilibrium FAME conversions appear to approach asymptotic limits for reaction times greater than 8 h for all temperatures investigated. Stirring the reaction vessel had a significant positive influence on the rate of biodiesel formation. Increasing the moisture content of the microalgae biomass had a strong negative influence on the equilibrium FAME yield, and in situ transesterification was inhibited when the biomass water content was greater than 115% w/w (based on oil weight).     

Function of sheets of cellulose chains in swelling reactions on cellulose

An x-ray investigation of the products formed by the action of caustic soda on different samples of cellulose and those formed on the decomposition of these products by aqueous reagents and alchols shows that the fundamental reacting unit is a sheet of cellulose chains, and not individual cellulose chains. Although the caustic soda can affect the relative dispositions of the chains within these sheets to some extent, it cannot separate the chains, and the products then depend on the aggregation of the cellulose sheets with or without other molecules between them. Such aggregation leads to variables products whose x-ray diagrams can, however, show distinct reflections and be mistaken for those from more precise crystal structures. It is, therefore, important in swelling reactions to take into account the ability of the swelling agent to modify the cellulose sheets and the mode of decomposition of the complexes formed on swelling. Thus swelling with caustic soda cannot be taken as typical of all aqueous swelling reagents in its reaction towards cellulose, and the possibility with other reagents of finding cellulose I, instead of cellulose II, after a series of swelling reactions must be taken into consideration.     

Variables affecting the yields of fatty esters from transesterified vegetable oils

Transesterification reaction variables that affect yield and purity of the product esters from cottonseed, peanut, soybean and sunflower oils include molar ratio of alcohol to vegetable oil, type of catalyst (alkaline vs acidic), temperature and degree of refinement of the vegetable oil. With alkaline catalysts (either sodium hydroxide or methoxide), temperatures of 60 C or higher, molar ratios of at least 6 to 1 and with fully refined oils, conversion to methyl, ethyl and butyl esters was essentially complete in 1 hr. At moderate temperatures (32 C), vegetable oils were 99% transesterified in ca. 4 hr with an alkaline catalyst. Transesterification by acid catalysis was much slower than by alkali catalysis. Although the crude oils could be transesterified, ester yields were reduced because of gums and extraneous material present in the crude oils. Presented at the American Oil Chemists’ Society annual meeting, Chicago, May 1983.     

Arylstearic acids from oleic acid. Variables affecting the yield and properties

Summary Twenty-six aromatic compounds were compared in the synthesis of arylstearic acids from oleic acid by the Friedel and Crafts reaction. Xylylstearic acid was the arylstearic acid obtained in the highest yield (92.4%) from technical m-xylene and commerical oleic acid. The various side reactions are disussed including the possible conversion of oleic acid into products which on vacuum distillation of the crude arylstearic acid appear as a forerun and as a still residue. Oleic acid of about 98% purity did not improve the yield but resulted in nearly colorless, rather than yellow viscous oils. Crystalline arylstearic acids have for first time been isolated from the reaction products but only in small yields. Presented at the 39th Annual Meeting of the American Oil Chemists' Society, New Orleans, La., May 4–6, 1948. One of the laboratories of the Bureau of Agricultural and Industrial Chemistry, Agricultural Research Administration. U. S. Dept. of Agriculture.     

Factors affecting vapor phase photografting of vinyl monomers on cellulose

Effects of water contained in the sample, the type of sensitizer, and the nature of vinyl monomer on vapor phase photografting on cellulose were investigated at 60°C. The grafting was enhanced by the water contained in the cellulose sample, resulting in an increased percent grafting with increasing the quantity of water. The use of sensitizers such as ferric chloride, ferrous sulfate, ceric ammonium nitrate, hydrogen peroxide, benzophenone, and sodium anthraquinone-2,7-disulfonate led to accelerated graftings. However, the maximum grafting was observed at an optimum quantity of sensitizer for each sensitized system, and the formation of grafted polymer was restricted by the use of sensitizer beyond the quantity. Ferric chloride and hydrogen peroxide exhibited higher activities among the sensitizers. With respect to the nature of monomer, methyl methacrylate, acrylic acid, methacrylic acid, and acrylonitrile were observed to be introduced into cellulose substrate by the vapor phase photografting, though no initiation was recorded for styrene and N-vinylpyrrolidone. However, the latter monomers were introduced by using monomer mixtures with acrylonitrile, affording a maximum percent grafting at a certain monomer composition.     

ESR study of post-irradiation reactions of cellulose and acrylonitrile

An ESR study of the free-radical mechanisms of the post-irradiation reactions of cotton cellulose with acrylonitrile is reported. The effects of atmosphere, moisture content, and solutions of acrylonitrile on the yield and stability of free-radical sites in irradiated cellulose were determined. On interaction of γ-radiation from a ⁶⁰Co source with cotton cellulose, long-lived free-radical sites were found within the molecular lattice. Short-lived free-radical sites were apparently also formed on chain cleavage, gave strong singlet spectra, and were readily accessible to interaction with water. Other free-radical sites were formed within regions of the cellulosic fiber which were inaccessible to moisture or aqueous solutions even after contact times as long as three days. It was suggested that long-lived free-radical sites in cellulose I (containing regain moisture) resulted from dehydrogenation at C₅, and in cellulose II (containing regain moisture) resulted from dehydrogenation at C₅ and dehydrogenation of the OH group or dehydroxylation at C₆. When irradiated cellulose was contacted with a solution of acrylonitrile (15%) in 75% aqueous zinc chloride, the initial rate of decrease in spin concentration was higher than the rate of decrease as the time of contact increased. The ESR spectrum of the reacted cellulose, observed at ?100°C., as compared with the spectrum for the irradiated cellulose, had decreased in signal strength with increase in time of contact and changed from a three-line spectrum to an ill-defined spectrum. The free radical being observed was probably due to unreacted sites in the cellulose. The extent of the graft copolymerization reaction was directly related to the initial spin concentration in the irradiated cellulose.     

Electron-microscopic investigation of cerium–cotton cellulose reactions

Cotton fibers were treated with an aqueous solution of ceric ammonium nitrate and examined with the electron microscope. The greatest deposition of cerium occurred in the primary wall due largely to the reaction with noncellulosic constituents in this area of the fiber. The use of ceric ions for an electron-microscopic stain was found ineffective for producing the desired contrast in the cotton fiber.     

Kinetics and mechanism of olefin methylation reactions on zeolites

Ethylene and propylene methylation rates increased linearly with olefin pressure but did not depend on dimethyl ether (DME) pressures on proton-form FER, MFI, MOR, and BEA zeolites at low conversions (<0.2%) and high DME/olefin ratios (30:1) in accordance with a mechanism that involves the zeolite surface being predominantly covered by DME-derived species reacting with olefins. Higher first-order reaction rate constants for both ethylene and propylene methylation were observed over H-BEA and H-MFI compared with H-FER and H-MOR, indicating that olefin methylation reaction cycles involved in the conversion of methanol-to-gasoline over zeolitic acids are propagated to varying extents by different framework materials. Systematically lower activation barriers and higher rate constants were observed for propylene methylation in comparison with ethylene methylation over all frameworks studied, reflecting the increased stability of reaction intermediates and activated complexes with increasing olefin substitution. A binomial distribution of d₀/d₃/d₆ in unreacted DME upon introduction of equimolar protium- and deuterium-form DME under steady-state reaction conditions of ethylene methylation over H-MFI suggests the presence and facile formation of reactive surface-bound methoxide species and the absence of C–H bond cleavage.     

ESR study of reactions of cellulose initiated by the ceric ion method

The ESR spectra of microcrystalline cellulose and purified cotton cellulose reacted with ceric ammonium nitrate in nitric acid were determined. The effects of the concentration of ceric ion, atmosphere, temperature, and graft copolymerization with acrylonitrile on the rates of formation and decay of radicals in the cellulose molecule were determined under both static and dynamic conditions. Under static conditions, after the desired conditions of reaction, the samples were frozen at –100 or –160°C., and then the concentration of free radicals was determined. Under dynamic conditions ceric ion solution was continuously flowed through the celluloses while these determinations were being made at 25°C. In the presence of oxygen the rate of decay of free radicals was decreased. On initiation of copolymerization reactions with acrylonitrile, there was an increase in radical concentration, then a decrease. Apparently, during graft copolymerization the radical site initially on the cellulose molecule was retained on the end of the growing polymer chain. Then additional ceric ion coordinated with the hydroxyl groups of the cellulose, leading to the formation of additional radical sites. An Arrhenius interpretation of the effect of temperature on the formation of these additional radical sites gave apparent activation energies for radical formation on cotton cellulose as 34 kcal./mole and on microcrystalline cellulose as 29 kcal./mole.     

Variables affecting parison diameter swell and their correlation with rheological parameters

An important factor in the selection of blow molding resins for producing handled bottles is the effective diameter swell of the parison. Ideally, the diameter swell is directly related to the weight swell and would require no separate consideration. In actual practice, the existence of gravity, the finite parison drop time and the anisotropic aspects of the blow molding operation prevent reliable prediction of the parison diameter swell directly from the weight swell. The parison diameter swell is a complex function of the weight swell, the rate of swell and the melt strength. Elements of this function are presented which show the effect of extrusion rate, parison drop time and parison weight. A technique is presented which allows the estimation of local weight and diameter swell ratios. Their direct relationship is confirmed by data obtained on several blow molding resins. The relationship between weight swell and diameter swell is definitely anisotropic. A mathematical model for swell is proposed which incorporates experimentally determined rate constants and swell coefficients. Correlations are given which suggest fundamental relationships between these derived coefficients and basic variables such as resin properties or process conditions. The model's predictive capability is demonstrated by using it to back calculate parison dimensions.     

Nucleophilic displacement reactions on tosyl cellulose by chiral amines

Summary New 6-deoxy-6-amino cellulose derivatives with a degree of substitution (DS) in the range from 0.4 to 0.6 were synthesized by nucleophilic displacement (S_N) reactions of cellulose tosylates (DS_Tos 0.74 and 1.29) with R(+)-, S(−)- and racemic 1-phenylethylamine under homogeneous conditions in N,N-dimethylformamide and water. The structure of the polymers was characterized by elemental analysis, FTIR and ¹³C NMR spectroscopy. The DS values obtained as well as the optical rotation and circular dichroism measurements in dimethyl sulfoxide reveal that the initial chirality of the cellulose backbone does not have any significant influence on its reactivity with either of the two enantiomeric amines. Received: 21 September 2000/Accepted: 5 January 2001     

Further studies on cellulose III polymorphs. Transformations to cellulose IV lattices and subsequent reactions

Production of cellulose IV polymorphs, their characterization using X-ray diffraction and infrared spectroscopy, as well as the effect of chemical treatments on these polymorphs have been investigated. Cellulose III_I and III_II polymorphs, produced from celluloses I and II using EDA—MeOH treatments, were of particular interest as starting materials in the study. Celluloses IV_I and IV_II gave identical equatorial X-ray patterns in the absence of other crystal lattices in the samples. Crystallinity as well as conformation were indicated to influence production and further reactions of the samples. The latter included boiling in water, acid hydrolysis, and treatments with EDA—water, EDA—MeOH, and NaOH solutions. Cellulose IV_I → I, IV_I → I → II, and cellulose IV_II → II lattice conversions were demonstrated to occur with EDA—water treatments, thereby providing a new technique for observing these transformations. Conformational differences were apparent among celluloses I, II, III_I, and III_II, each produced using different experimental procedures.     

Chemical reactions affecting halloysite dispersion in epoxy nanocomposites

Halloysite nanotubes (HNTs) have attracted a technologic and scientific attention as reinforcements of epoxy-based nanocomposites. However, their reported interaction with epoxy matrices is varied and the controlled dispersion of HNTs is still a challenge. In this work, we study the effect of chemical reactions taking place in the dispersion process of halloysite and their possible influence in the composite's properties. HNTs' surface was modified through an alkaline treatment and by grafting two aminosilanes with different chain lengths and functionality numbers. Evidence of homopolymerization and degradation reactions was found, depending on the surface treatment. The rheological study indicated that an interconnected network can be achieved in epoxy/HNTs blends depending on the surface chemical characteristics of the nanofillers and the blending method. The better dispersion was accomplished when ultrasonicating with the aid of a solvent. Nevertheless, the mechanical properties of the nanocomposites are not warranted by selecting a dispersion method. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47979.     

稠油水热裂解采油技术的影响因素分析

本文对水热裂解开采稠油技术的影响因素进行详细的综述。水热裂解降粘开采稠油技术,是在注入蒸汽的条件下,借助于稠油与蒸汽之间发生的化学反应,降低稠油的粘度,从而达到井下降粘开采稠油的目的。水热裂解开采稠油技术具有很高的潜在价值,是未来经济高效开采稠油的新途径。     

Structural features of the polymer matrix affecting the efficiency of acyl transfer reactions

Polystyrene and polyacrolein were prepared using divinylbenzene (DVB) and tetraethylene glycol diacrylate (TEGDA) as crosslinking agents with varying extents of crosslinking. These polymeric supports were used to prepare acyl transfer reagents like oximino esters and oximino dithiocarbonic anhydrides. The reactivity of the acylating function was determined as a function of the varying macromolecular characters. Investigations revealed a significant influence of the nature of macromolecular support, nature and extent of crosslinking, and the chemical environment of the reagent functions in deciding the extent of the acyl transfer reaction. In the case of DVB crosslinked reagents, the reactivity decreased with increase in the extent of crosslinking, whereas in the case of TEGDA crosslinked reagents, the reactivity increased up to 4% crosslinking and then decreased as the degree of crosslinking was increased. © 1996 John Wiley & Sons, Inc.     

Variables affecting the yields of methyl esters derived from in situ esterification of rice bran oil

The influence of specific factors on in situ methanolic esterification of rice bran oil (RBO) using sulfuric acid catalyst was investigated. using high-FFA rice bran was found to be the most effective means to increase methyl ester yields. The ester content of the extract increased about 67% when the FFA content of oil was increased from 16.6 to 84.5%. Increasing the reaction time beyond 30 min did not affect yields. Increasing the temperature from 20 to 65°C elevated the FAME yield by about 30%, but increasing the amount of acid catalyst above 5 mL did not enhance yield, and increasing the methanol dose from 200 to 250 mL had a negligible effect.     

Variables affecting the yield of normal oleic acid produced by the catalytic hydrogenation of cottonseed and peanut oils

Summary 1. The effects of the following factors have been investigated in the hydrogenation of cottonseed and peanut oils: temperature, concentration of catalyst, pressure of the hydrogen, degree of agitation, and nature of the nickel catalyst. 2. The formation of stearic acid was found to be repressed and the formation of “iso-oleic” acid simultaneously favored by increasing the temperature, increasing the catalyst concentration, decreasing the pressure, and decreasing the agitation. 3. The nature of the nickel catalyst, as influenced by its method of preparation, may have a large effect on the composition of the hydrogenated product. One of the nickel catalysts investigated formed excessive amounts of iso-oleic acid without being correspondingly selective. 4. In the hydrogenation of cottonseed oil, within a comparatively wide range of conditions, the production of total solid acids with a given catalyst is relatively constant, since the conditions leading to the formation of stearic and iso-oleic acid are mutually exclusive. Extremes in either direction, however, lead to the production of excessive amounts of total solid acids. 5. Peanut oil is a more suitable raw material than cottonseed oil for the production of normal oleic acid, because of its initially greater content of this constituent and its lesser content of linoleic acid. 6. On the assumption that a quantitative separation could be made of the liquid acids from the solid acid fraction (saturated and iso-oleic) of the hydrogenated products, leaving minor amounts of unhydrogenated linoleic acid as an impurity in the separated normal oleic acid, the following maximum yields of “impure normal oleic acid” could be obtained: from cottonseed oil, 56 per cent of oleic acid of 85 per cent purity, 53 per cent of oleic acid of 90 per cent purity, and 48 per cent of oleic acid of 95 per cent purity; and from peanut oil, 70 per cent of oleic acid of 85 per cent purity, 68 per cent of oleic acid of 90 per cent purity, and 66 per cent of oleic acid of 95 per cent purity. Presented before the American Oil Chemists’ Society, Houston, Texas, April 30 to May 1, 1942.     

Kinetic analysis of radiation-initiated copolymerization reactions of water-soluble vinyl monomers with cellulose

A kinetic analysis of the radiation-initiated copolymerization reactions of 2-hydroxyethyl methacrylate (HEMA), hydroxypropyl methacrylate (HPMA), and methacrylic acid (MAA) from water, methanol (MeOH), N,N-dimethylformamide (DMF), dimethysulfoxide (DMSO), and combinations of these solvents with irradiated fibrous cellulose I and II was made. The maximum extent of copolymerization of HEMA and HPMA with irradiated cellulose occurred from water solutions. When organic solvents were added to the water solution, while the concentration of monomer was kept constant, the extent of copolymerization decreased. The maximum extent of copolymerization of MAA with irradiated cellulose occurred from mixtures of MeOH (15–30 vol-%) and water (85–70 vol-%) solutions rather than from water. After initiation of the copolymerization reactions, they were apparently diffusion controlled and exhibited second-order kinetics. The relative concentrations of grafted polymer and homopolymer formed with irradiated cellulose from aqueous solutions depended primarily on the concentration of water in the solutions. From MeOH (60 vol-% or less)–water (40 vol-% or more) solutions, about 60% of poly(MAA) formed was apparently grafted polymer; from solutions containing less water, the fraction of grafted polymer decreased to about 40%.