Formation of aldonic acid end groups during NO2/O2 treatment and alkali cooking of wood meal

Summary The increased carbohydrate yield after NaOH cooking of wood resulting from NO₂/O₂ pretreatment is related to the oxidation of reducing sugar end groups to aldonic acid groups during both the pretreatment and the subsequent alkali cook. This leads to a suppressed end-wise degradation during the alkali cook, reflected in a lowered formation of 3-deoxyaldonic and 2-C-methylglyceric acid end groups in competing reactions.     

Alkaline Pre-treatment of Hardwood Chips Prior to Delignification

Abstract

Hardwood (Betula pendula) chips were extracted having alkaline aqueous solutions with varying chemical charges (1, 2, 3, 4, 6, and 8% of NaOH on wood), treatment times (30, 60, 90, and 120 minutes), and temperatures (130°C and 150°C). The total amount of material removed was in the range 2.1–16.5% of the original dry feedstock. This fraction was characterized in terms of carbohydrates and their degradation products (mainly aliphatic carboxylic acids together with some furanoic compounds), lignin, and extractives. Low alkali charges (1–4% of NaOH) were not sufficient to neutralize all the acids formed (mainly acetic acid from the acetyl groups of xylan). In contrast, an increase in alkali charge (6% and 8% of NaOH) more intensively facilitated the alkali-catalyzed degradation reactions of polysaccharides to various hydroxy acids, which were then typically present as one of the main constituents in the dissolved organic matter, along with other aliphatic carboxylic acids (acetic and formic acids), lignin, extractives, and carbohydrates.     

TiO2-Based Heterogeneous Photocatalytic Water Treatment Combined with Ozonation

The degradations of aliphatic carboxylic acids (formic acid, acetic acid, and propionic acid) were investigated by a combination of TiO₂-based photocatalysis and ozonation at pH = 2. The carboxylic acids were analyzed by high-performance liquid chromatography (HPLC), while the mineralization process was characterized by measuring the dissolved organic carbon (DOC) content. The efficiency of heterogeneous photocatalysis combined with ozonation was compared with that of ozonation and that of heterogeneous photocatalysis alone. In all cases, the combined system proved most effective in the oxidation of carboxylic acids. The degradation of carboxylic acids was accompanied by a continuous decrease in the DOC content, and aldehydes and carboxylic acids containing one carbon atom less than the starting material were formed as intermediates.     

Measurement of functionalised carbon nanotube carboxylic acid groups using a simple chemical process

Chemically functionalised single-walled carbon nanotubes were formed using sonication in a mixture of concentrated sulphuric and nitric acids for varying lengths of time which resulted in carboxylic acid group functionalisation, predominantly at the ends. The carboxylic acid groups were used to form an ionic bond with dodecylamine. The weight of this complex was used to monitor the number of carboxylic acid groups present in the cut SWNT.     

Cyclische Konjudien-Carbonsäuren mit einer semicyclischen Doppelbindung aus der Alkali-Cyclisierung langkettiger Triencarbonsäuren

Cyclic Conjugated Dienoic Carboxylic Acids with a Semicyclic Double Bond from Alkali Cyclisation of Long-Chain Trienoic Carboxylic Acids In the alkali cyclisation of 9-cis, 12-cis, 15-cis-octadecatrienoic acid and of 9-cis, 11-trans, 13-trans-octadecatrienoic acid conjugated dienoic carboxylic acids with the structures 9 to 12 are formed in addition to the ω-(2-alkylcyclohexadienyl)carboxylic acids 3 to 8. The formation of these conjugated dienoic carboxylic acids with semicyclic double bond from the corresponding ω-(2-alkylcyclohexa-3,5-dienyl)carboxylic acids (3) is explained by an ionic shift of the conjugated diene system under the action of the base.     

Alkaline Pre-Treatment of Softwood Chips Prior to Delignification

Scots pine (Pinus sylvestris) chips were pre-treated with alkaline solutions (alkali charges of 1, 2, 3, 4, 6, and 8% of NaOH on the oven-dried wood material) at 130°C and 150°C for various treatment times (30, 60, 90, and 120 minutes). Under these conditions, 2.0–13.6% of the wood d.s. was dissolved into the aqueous hydrolysates. The soluble organic fraction was primarily characterized in terms of carbohydrates (monosaccharides and oligo-/polysaccharides) and their alkali-catalyzed degradation products: aliphatic carboxylic acids containing, besides non-volatile hydroxy carboxylic acids, volatile formic and acetic acids. With increasing alkali charge, temperature, and time, the enhanced formation of various hydroxy monocarboxylic acids was detected. Under the most drastic pre-treatment conditions, two-thirds of the total organic fraction dissolved was composed of various aliphatic carboxylic acids, the residual material being mainly degraded lignin and extractives. Only relatively small concentrations of carbohydrates and trace amounts of furans were found.     

Quantitative study of the carboxylic acids in Green River oil shale bitumen

Bitumen fractions were extracted by a benzene/methanol reflux of Green River oil shale (GROS) before and after treatment with HCl, HF, and HCl/HF. Acid leaching released 80% more bitumen than could be extracted without acid treatment. This additional bitumen had greater concentrations of carboxylic acids and their salts than the untreated oil shale bitumen. The carboxylic acids were separated from all bitumen fractions (untreated, post HCI, post HF, and post HF/HCl) and individual acids were identified and quantified by gas chromatography—mass spectrometry and high resolution mass spectrometry. The same types of acids were present in all four bitumen fractions but showed significant differences in their relative abundances. These carboxylic acids and salts were present in the original GROS and were not formed during the treatment. The post-HCl bitumen fraction contained Mg and Fe salts of long-chain aliphatic carboxylic acids with carbon numbers in the range of 21–38. Significantly, even though calcium is the major cation in the carbonate minerals of GROS, no Ca was present in the ash of these carboxylic acid salts. These results indicate that there is a strong interaction between carboxylic acids present in GROS and its mineral matrix (especially carbonate minerals). These carboxylic acids are possible coupling agents that ‘glue’ mineral and organic material together. The treatment of the oil shale also resulted in the formation of highly purified kerogen, low in ash yield (2 wt %) which had undergone only very mild acid treatment.     

Endwise degradation of hydrocellulose in bicarbonate solution

Determinations of individual terminal carboxylic acid endgroups and terminal reducing sugar moieties together with analysis of spent liquor revealed that the same reactions occur during treatment of hydrocellulose with hot sodium bicarbonate as with sodium hydroxide solution. Some fragmentation reactions, of little importance in the presence of sodium hydroxide, are favored in bicarbonate medium while benzilic acid rearrangements are less favored. Hence, the formation of 2-dieoxyerythropentonic acid endgroups is more important. Among the soluble reaction products, 3,4-dideoxypentonic acid formed via 3-deoxypentulose and cyclic compounds formed via the same precursor are much more abundant in bicarbonate medium while 3-deoxy-2-hydroxymethylpentonic (isosaccharinic) acids are less abundant.     

羧酸硒醚、二硒醚及相应硒多糖的合成

用NaBH4还原硒粉得Se2-或-SeSe-,然后在碱性水溶液中与氯乙酸、3-氯丙酸和对-溴甲基苯甲酸在室温下反应,制得相应的羧酸硒醚,收率分别为51.9%、62.6%和58.6%,以及丙酸和对甲基苯甲酸二硒醚,收率67.8%和72.1%。用乙酸硒醚分别与邻氨基苯甲酸和水杨酸反应引入其他基团,收率73.6%和69.8%。最后这些合成的化合物通过形成酰氯与麒麟菜多糖中的羟基醚化得到含硒醚或二硒醚结构的新型硒多糖,收率40%~60%。     

Caustic oxidation as a pretreatment to high pressure bituminous coal gasification

Illinois No. 6 bituminous coal, which had been pretreated with potassium hydroxide, could not be efficiently gasified at the high pressure of 3.5 MPa in a fluidized-bed gasifier. The same feedstock performed well at a much lower operating pressure. However, at the high pressure the pyrolysed coal swelled significantly. The resulting low bed density produced a small carbon inventory in the gasifier. In addition, the coal char was very friable and large quantities of fine particulate material were entrained by the product gas. To prevent the swelling the coal was initially oxidized. A way was discovered to selectively convert the coal bitumen to humic acid, a substance that is rich in carboxylic acid groups. A direct correlation was found between the humic acid's carboxylate content and the swelling characteristics of the pyrolysed coal. The char bulk density was greatest when the humate carboxylic acid group content was maximized. It appears that when the coal was fed to the hot gasifier, these carboxylic acids decarboxylated and produced radical centres. The crosslinks that resulted from these radicals formed relatively stable carbon-carbon bridges, and this was sufficient to prevent the pyrolytic swelling.     

红外光谱法研究降解聚丙烯薄膜的光降解性

本文用红外光谱法评价降解聚丙烯ＰＰ薄膜的光降解性。其研究结果表明，芳香酮类光敏剂与钴或铁络合物光敏剂协同使用，比前者单独使用，具有更好的自氧化或光氧化降解作用。在红外光谱１７１０ｃｍ－１和３４００ｃｍ－１附近出现明显多重缔合羰基和羟基宽峰，表明其氧化降解主要生成羧酸类和过氧化羰基类等含氧产物。     

Syntheses of regular copolyamides using triphenyl phosphite and pyridine

In this article, a method of preparing of regular copolyamide (co‐PA) in a reactor using triphenyl phosphite/pyridine as the activating agent was investigated. In two‐step reactions of copolymers prepared from two kinds of dicarboxylic acids and one kind of diamine, oligomer PAs containing amine end groups were first synthesized; then, the second dicarboxylic acid was added to the same reactor to polymerize high molecular weight and regular co‐PAs. However, when oligomers having carboxylic acid end groups were first prepared and another kind of diamine was added, the degree of polymerization was low. The reason proposed was that if the oligomer has an amine end group, it would coexist with the activating agent without deactivating; if the end group was the carboxylic acid end group, deactivation would occur. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 116–122, 2000     

New thermosetting coatings using blocked carboxyl groups

Characteristics of blocked carboxylic acid compounds obtained by blocking carboxyl groups with alkyl vinyl ethers were studied, and new thermosetting coatings using blocked carboxyl groups and epoxide were also studied. Polybasic carboxylic acids were esterified with alkyl vinyl ethers to obtain blocked carboxylic acids having the hemiacetal ester moieties. Most of blocked carboxylic acids obtained were liquids and showed an excellent solubility in organic solvents and a good compatibility with epoxy resins. Although the blocked carboxylic acids were stable under ambient conditions, they could regenerate the corresponding carboxylic acids accompanied by the elimination of alkyl vinyl ethers by the thermal dissociation. They could be used as noble thermal latent hardeners. Curing of the blocked carboxyl groups and epoxide in the presence of relatively weak Lewis acid proceeded through a sequence of three-step reactions consisting of deblocking of alkyl vinyl ethers, esterification of epoxide, and the addition of alkyl vinyl ether to 2-hydroxyalkyl ester. The main product of the curing system was 2-acetalalkyl ester, but not 2-hydroxylalkyl ester. The new one-package thermosetting coatings using blocked carboxyl groups have been evaluated for use in the practical automotive and coil coatings line production. VOCs reduction, low-toxicity, and cost saving are satisfactory for the application of the systems. And the cured films of the coatings offered advantages in the high durability, the acid resistance and the soil resistance.     

EFFECTS OF STRUCTURAL VARIATION WITHIN PROTON-IONIZABLE CROWN ETHERS UPON THE SELECTIVITY AND EFFICIENCY OF SOLVENT EXTRACTION OF ALKALI METAL AND ALKALINE EARTH CATIONS

Lipophilic crown ethers with pendant proton-ionizable groups are novel complexing agents for use in solvent extraction of alkali metal and alkaline earth cations. A variety of crown carboxylic acids, crown phosphonic acid monoesters, and crown phosphonic acids have been synthesized to probe the effect of structural variation within the complexing agent upon selectivity and efficiency in solvent extraction. Synthetic routes to these novel extractants and results from competitive solvent extractions of alkali metal cations and of alkaline earth cations from aqueous solutions into chloroform are summarized     

Methacrylate-based block ionomers I: Synthesis of block ionomers derived from t-butyl methacrylate and alkyl methacrylates

Diblock and triblock copolymers of t-butyl methacrylate (tBMA) with 2-ethylhexyl methacrylate (EHMA) and n-hexyl methacrylate were prepared via alkyl lithium initiation and sequential addition techniques in THF at ?78°C. The tBMA blocks were quantiatively and selectively hydrolyzed to afford poly(methacrylic acid) (PMAA) blocks which were then neutralized with alkali metal bases to form block ionomers. The unhydrolyzed copolymers had a phase mixed morphology as evidenced by thermal analysis while the hydrolyzed and neutralized polymers were multiphase materials. The carboxylic acid and ioncontaning triblock copolymers formed gels in nonpolar solvents which could be disrupted by the addition of polar additives. Certain carboxylic acid and ioncontaining EHMA/tBMA diblock copolymers also showed this behavior. The triblock ionomers did not show thermoplastic flow prior to degradation, except at the lowest ionic content studied (2%).     

The effects of carboxylic acids on the aqueous dispersion and electrophoretic deposition of ZrO2

The agglomeration, electrokinetic properties and electrophoretic deposition behaviour of aqueous suspensions of ZrO₂ with carboxylic acid additives were studied in comparison with conventional pH adjustment. It was found that citric acid imparted negative zeta-potential values and electrosteric stabilisation to particles in suspensions at all pH levels. The examination of additions of carboxylic acids to ZrO₂ suspensions revealed that these reagents cause a sharp drop in zeta-potential at distinct addition levels, which correspond to surface saturation of the particles with negatively charged carboxylate groups. Adsorption cross sections of citric acid, EDTA and oxalic acid were evaluated from these results, showing that both citric acid and EDTA coordinate to ZrO₂ surfaces by two carboxylate groups while oxalic acid is coordinated by one group. The use of carboxylic acids was shown to facilitate superior electrophoretic deposition in comparison with zeta-potential modification by conventional pH adjustment through improved suspension stability.     

A convenient preparative method of 3-hydroxy acids,and the reaction of 3-hydroxy acids with acidic materials

3-Hydroxy acids were synthesised in good yield from ketones and carboxylic acids using lithium naphthalenide in the presence of diethylamine. From cyclohexanone and propionic acid, 2-(1′-hydroxycyclohexan-1′-yl) propionic acid ( I ) was obtained in 98.3% yield. 3-Hydroxy acids were treated with various acidic materials to give 3,4-unsaturated carboxylic acids and γ-butyrolactones. From the reaction of ( I ) with p-toluenesulphonic acid or potassium bisulphate, 2-(cyclohexen-1′-yl) propionic acid ( II ) (a 3,4-unsaturated acid) was obtained (yield 98%), and with 97% sulphuric acid 2-(1′-hydroxycyclohexan-1′-yl) propionic acid lactone ( III ) was formed (93% yield). Several new γ-butyrolactones were obtained in good yield by this method.     

Thermal degradation of EVA and EBA—A comparison. II. Changes in unsaturation and side group structure

This is the second in a series of papers in which the thermal degradation of ethylene-vinyl acetate (EVA) and ethylene-butyl acrylate (EBA) copolymers are compared. The EBA samples contain 0.8, 1.6, and 5.4 mol % butyl acrylate (BA), respectively, and the EVA samples 1.2 and 6.7 mol % vinyl acetate (VA). The samples were heated in nitrogen in a tubular oven at 285, 333, 350, 370 and 390°C for 6–120 min. The samples were analyzed with IR, NMR, gravimetry, and titration of carboxylic groups. The EVA samples were rapidly degraded by deacetylation, which was complete after about 30 min at 333°C. A linear relation between the loss of acetate groups and the formation of trans double bonds was found. A small amount of keto groups and traces of lactones were also observed. The data confirm the previously proposed mechanisms for deacetylation and the formation of acetaldehyde. A mechanism for lactone formation is suggested. The deacetylation rate is increasing with the VA content, presumably because of an increased amount of block sequences and an enhanced acid catalytic effect. The acrylate sidegroups are much more stable than the acetate groups, and are similar in stability to the main hydrocarbon chain. The BA decomposition results in carboxylic and anhydride groups. Decarboxylation also occur and increases with the thermal treatment. In LDPE and EBA the increase in unsaturation is small and mainly due to vinyl end groups formed via β-cleavage or disproportionation. In EVA the formation of vinyl end groups is suppressed.     

Production and Emulsifying Effect of Polyglycerol and Fatty Acid Esters with Varying Degrees of Esterification

Esters with acyl groups can be formed by the esterification of polyglycerol. The purpose of the present study was to produce fatty acid esters [hexanoic (caproic), octanoic (caprylic), decanoic (capric), dodecanoic (lauric), tetradecanoic (myristic), hexadecanoic (palmitic), octadecanoic (stearic)] and polyglycerol (average number‐of degrees of polymerization of 5) with varying degrees of esterification and to examine their emulsifying properties. A number of fundamental catalysts of polyglycerol acylation reactions by methyl esters of carboxylic acid were studied, and sodium methoxide was found to be the best choice. The temperature rate of transesterification increased from 180 to 220 °C with the fatty acid chain alkyl residue. Synthesized mono‐, di‐, tri‐, tetra‐, and heptaesters of various fatty acids and polyglycerol provided the highest hydroxyl values from 15 to 815 mg KOH g^?1 and saponification values from 82 to 321 mg KOH g^?1. The emulsifying properties were assessed for all polyglycerol and fatty acid esters, with results showing maximum emulsifying effect for tri‐ and tetraesters of capric, lauric, and caprylic acids. Regardless of the hydrophilic–lipophilic balance value (HLB) of polyglycerol esters and carboxylic acid, a 4:1 ratio of sunflower oil to water formed a water‐in‐oil type emulsion. When mixing oil and water in a 1:1 ratio, mono‐ and diesters of polyglycerol formed an oil‐in‐water type emulsion, heptaesters formed a water‐in‐oil type emulsion, and tri‐ and tetraesters formed both of types of emulsions, depending on the length of the acid hydrocarbon radicals.     

Effect of Carboxylic Acid Adsorption on the Hydrolysis and Sintered Properties of Aluminum Nitride Powder

To suppress the reactivity of ALN powder with water, chemical surface modification with carboxylic acids has been investigated. It was found that the chemical stability of ALN powder increased as the number of carbon atoms in carboxylic acids used for the surface treatment increased. Among the carboxylic acids tested, stearic acid was the most promising from the viewpoint of the chemical stability of the treated powder and the thermal conductivity of the sintered ceramics prepared by cold isostatic pressing and pres-sureless sintering.