Reversible crosslinking in cellulose. IV. Reactions of tosylcellulose with potassium thiolacetate

Reactions of tosylated cotton with potassium thiolacetate followed by alkaline hydrolysis yielded products containing both mercaptan and disulfide. The proportion of disulfide in the products depended much on the solvent used for the thiolacetylation. Reactions of tosylcellulose with thiolacetate in various solvents were investigated by polarographic and infrared analyses. Part of the acetylthio groups produced in acetone or in dimethylformamide was found to undergo rearrangement to form mercaptocellulose acetate. On the other hand, acetylthio groups formed in methanol were found to undergo complete methanolysis to form mercaptocellulose, and most of the mercapto groups thus produced were oxidized before hydrolysis treatment to yield the corresponding disulfide. This could account for the high disulfide proportion in the sample obtained through the reaction of tosylcellulose in methanol. Reaction of tosylcellulose with sodium thiosulfate yielded cellulose disulfide without mercaptan formation.     

Reversible crosslinking in cellulose. II. Mono-and bifunctional reactions of bis-β-isocyanatoethyl disulfide with cotton

Bis-β-isocyanatoethyl disulfide (BIED) was synthesized from diethyl dithiodipropionate and its reaction with cotton in dimethylformamide was investigated. The sulfur content of the treated cotton decreased by reduction with tri-n-butylphosphine. The polarographic and infrared analyses revealed that BIED reacted with cotton both monofunctionally and bifunctionally to form branches and crosslinks, respectively. The ratio of the crosslinks to the total amount of BIED combined increased in general as the reaction progressed. X-Ray study indicated that the reaction took place mainly in the original amorphous region.     

Graft copolymerization of vinyl monomers with modified cotton. II. Grafting of acrylonitrile and methyl methacrylate on acetylated cotton

Ce(IV)-induced polymerization of acrylonitrile and methyl methacrylate with acetylated cotton having different acetyl contents was investigated. The extent of interaction between the cotton and monomer is dependent upon the acetyl content of the former as well as on the reaction conditions. Increasing the acetyl content caused a significant decrease in the graft yield. Increasing the acrylonitrile concentration was accompanied by a substantial increase in the graft yields. The same effect was found with the initiator up to a certain concentration, but beyond it there was a reversal. The rate of grafting increased by rising the temperature and follow the order 60° > 40° > 30°C. The Ce(IV) consumption during grafting is greater than that consumed during oxidation. The consumption of Ce(IV) by the cellulosic materials was favorably influenced by the concentrations of monomer and initiator, time, and temperature. Rates of grafting and Ce(IV) consumption during oxidation of acetylated cottons having different acetyl contents strongly support the postulated mechanism of grafting using the Ce(IV)–cellulose redox system. Ce(IV) oxidation had practically no effect on the acetyl groups (expressed as per cent combined acetic acid) of the modified cotton.     

催化氧化正丁硫醇的Co-O/Mg(Al)O催化剂

以NaOH、Na2CO3、Mg(NO3)2、A(lNO3)3和Co(NO3)2为原料,用共沉淀法合成的类水滑石为前体制备固体碱型Co-O/Mg(Al)O催化剂,将其用于常压下催化分子氧氧化正丁硫醇向二硫化物转化。对催化剂进行了XRD测定,讨论了镁铝摩尔比、焙烧温度与催化剂物相组成及其活性关系。考察了溶剂和反应温度对催化剂活性的影响,对氧化产物结构进行了IR、UV和MS表征。     

Reactions of cotton or diethylaminoethyl cotton with 1-chloro-2,3-epithiopropane

Sulfhydryl groups have been introduced into cotton and into diethylaminoethyl (DEAE)-cotton by reaction with neat 1-chloro-2,3-epithiopropane or alcoholic solutions of the thiirane. Reactions at room temperature have been compared with those at higher temperatures, and fabric properties obtained with various S/Cl ratios have been compared. The effects of additional external base catalysis on these reactions have been studied. Fabric properties resulting from cotton–1-chloro-2,3-epithiopropane or DEAE-cotton–1-chloro-2,3-epithiopropane reactions have been compared with properties obtained with the corresponding reactions of cotton or DEAE-cotton with epichlorohydrin. Sulfhydryl groups have also been introduced into cotton and DEAE-cotton by the in situ formation of 1-chloro-2,3-epithiopropane in the fabric as a result of the reaction of the oxygen analog with a thiourea or a thiocyanate. These in situ reactions have been carried out in the absence and presence of solvent and external base catalysts. Attempts to vary the wet and conditioned (dry) recovery angles by oxidation of sulfhydryl groups and by reduction of disulfide groups met with little success. Smaller improvement in wrinkle recovery properties imparted by the thiirane than by epichlorohydrin at a given add-on has been explained on the basis of greater tendency of the thiirane to open abnormally in neutral or slightly acidic conditions and thus the greater tendency of the thiirane to form polymers rather than to crosslink cotton. Tendency of the oxirane to open normally and therefore act difunctionally results in finished fabrics with low chlorine contents, a high degree of crosslinking, and little polymer formation.     

Studies in chemically modified celluloses. XI. Hypochlorite oxidation of cellulose in the presence of chromium oxide

In the dyeing of mineral Khaki on cotton fabrics, which are mainly used for military uniforms in India, a mixture of Fe₂O₃ and Cr₂O₃ is deposited in the fabric. When these garments are laundered using bleaching powder solution, the chromium oxide is likely to accelerate the oxidation of cotton cellulose. This aspect has been studied by oxidizing cotton yarn with sodium hypochlorite solution in the presence of chromium oxide, varying the chromium content, the pH of the oxidizing medium, and the concentration of the oxidizing agent. The properties of these chemically modified celluloses indicate that chromium oxide does accelerate the hypochlorite oxidation of cellulose and that the maximum extent of acceleration takes place when the oxidation is carried out at pH 7. The oxidized products were further modified separately by treatment with chlorous acid and sodium borohydride, and the effects of these agents on the properties of the oxidized products were studied.     

Removal of sulfur compounds from utility pipelined synthetic natural gas using modified activated carbons

Synthetic natural gas (SNG), which is produced from petroleum and distributed via pipeline in Honolulu by The Gas Company, was analyzed using a gas chromatograph equipped with a sulfur chemiluminescence detector (GC/SCD). Hydrogen sulfide (H₂S), methyl mercaptan (MM), ethyl mercaptan (EM), dimethylsulfide (DMS), dimethyl disulfide (DMDS), tetrahydrothiophene (THT), ethyl disulfide (EDS), and one unidentified compound (UN1) were detected. Among these sulfur compounds, THT is added as an odorant and was present in the highest concentration.A commercial activated carbon (Calgon OLC plus 12X30) was modified by oxidation and impregnation methods and the resulting materials were evaluated for their ability to adsorb sulfur compounds present in SNG. The evaluation results indicate that all of the modification methods can improve the retention of individual sulfur compounds or the total sulfur capacity compared with the untreated virgin carbon. It is also found that activated carbons impregnated with metal impurities have different selectivity for sulfur compounds. Cu and Zn loaded carbons had the highest capacity for H₂S removal, Fe loaded carbon was more efficient for DMS removal (the most difficult S compound to remove), and carbon oxidized by HNO₃ was the best for THT removal.Based on these findings, a composite sorbent consisting of Cu loaded and Fe loaded carbons was designed and tested. The test results indicate that the composite sorbent had improved performance in the removal of individual sulfur compound. A linear programming model was used to design a composite sorbent optimized to minimize the required sorbent mass based on a 1-kW scale fuel cell system service target. Validation tests showed that the optimized sorbent required less of the individual modified carbon components than when they were individually used for the same sulfur removal target.     

Behavior of cyanoethylated cotton towards gamma radiation

Unmodified cotton fabric, cyanoethylated cottons having 0.12, 0.55, 0.77, and 1.24% N as well as cotton treated with NaOH under conditions similar to those of cyanoethylation but in absence of acrylonitrile were exposed to gamma radiation doses (3.199–31.199 Mrads). The six substrates before and after irradiation were assessed for copper number, carboxyl content, degree of polymerization, tensile strength, and elongation at break to determine the extent of degradation of these substrates. The effect of radiation dose on the nitrogen content of cyanoethylated cottons was also examined. It was found that degradation is higher the higher the radiation dose irrespective of the substrate used. Nevertheless, the extent of degradation is determined by nature of the substrate. Introduction of cyanoethyl groups in the molecular structure of cotton cellulose impart certain resistance to radiation degradation of cotton provided that these groups are present in appreciable amounts (0.55% N and above). The cyanoethyl groups seems to impede oxidation of the cellulose hydroxyls and/or glucosidic bonds against radiolysis. On the other hand, when present in smaller amounts, the cyanoethyl groups are not able to outweigh the increased accessibility of cotton cellulose brought about by the alkaline environment of the cyanoethylation reaction. Hence, substrates containing lower cyanoethyl contents are more susceptible to degradation than the modified cotton, and in this respect they are similar to alkali-treated cotton.     

SPME-GC-MS分析榴莲果肉中的挥发性成分

为了研究榴莲果肉中的挥发性香气成分,采用两种固相微萃取纤维提取了榴莲果肉中的挥发性成分,并利用气相色谱-质谱联用技术对所得挥发性成分进行了分离与鉴定。采用保留指数和质谱进行定性,共鉴定出60种挥发性成分,其中酯类26种,含硫化合物12种,醇类7种,烃类7种,醛类3种,酸类2种、含氮化合物2种和酚类1种;采用面积归一化法确定了它们相对含量,相对含量较高的是2-甲基丁酸乙酯、丙酸乙酯、1-十四醇、乙酸乙酯、丁酸乙酯、反-2-丁烯酸乙酯、二乙基二硫醚、2-甲基丁酸丙酯、十四醛、乙硫醇。从鉴定出的挥发性成分的香气特征可知,榴莲的香气主要是由酯类化合物和含硫化合物赋予的,其中大多数酯类化合物是脂肪酸乙酯,含硫化合物中硫醇和硫醚的含量相对较高。     

含硫恶臭气体处理方法的研究进展

含硫恶臭气体因其嗅觉阈值低、涉及的行业广泛、毒性大而备受关注。主要的代表物为硫化氢、二硫化碳、硫醇、硫醚等。介绍了含硫恶臭气体的常规处理方法,如物理法,燃烧法、吸收法、吸附法等化学方法,还有近年来发展较快的光催化氧化技术、等离子体技术、生物脱臭技术、无极紫外辐射技术等新兴处理技术。对各种处理方法和技术的未来发展趋势进行了展望。     

Studies on disulfide-crosslinked nylon. II. Stress relaxation of disulfide-crosslinked polycaprolactam fibers in water

The stress relaxation at 100% elongation in water was investigated for disulfide-crosslinked polycaprolactam (DSPC) fibers prepared from N-mercaptomethyl polycaprolactam. The stress decreased faster with increasing temperature and with increasing mercaptan content of the fiber. Little stress decay took place when the fiber was treated with a mercaptan-blocking reagent. It was concluded that the controlling mechanism of the stress relaxation was the mercaptan/disulfied (SH/SS) interchange reaction. The remanent stress observed for the stress relaxation was fairly high and increased with decreasing mercaptan content of the fiber. The stress decay curve was not Maxwellian. It has been suggested that the concentration of mercaptan that could not participate in the interchange with stressed disulfide bonds increased with increasing cycles of the interchange reaction. A kinetic equation is presented and the activation energy of the SH/SS interchange reaction was evaluated as 22.3–23.9 kcal/mole. The stress relaxation of DSPC fibers in dilute β-mercaptoethanol was also studied. The stress decreased more rapidly to almost zero and the decay curve was Maxwellian. The activation energy of the reaction was 17.1 kcal/mole. These results were compared with the stress relaxation of wool fibers.     

Differential inhibitory effects of garlic-derived organosulfur compounds on cholesterol biosynthesis in primary rat hepatocyte cultures

Using primary rat hepatocyte cultures, the potency of several garlic-derived organosulfur compounds to inhibit cholesterol biosynthesisin toto as well as at early and late steps of this metabolic pathway was compared. Concerning early steps, allicin significantly inhibited incorporation of [¹⁴C]acetate into nonsaponifiable neutral lipids already at concentrations as low as 10 μM, while diallyl disulfide and allyl mercaptan were effective above 100 μM only. Likewise, inhibition in response to the two vinyl-dithiins started at 500 μM. If [¹⁴C]acetate was replaced by [¹⁴C]mevalonate, inhibition due to allicin, diallyl disulfide, and allyl mercaptan disappeared suggesting that HMGCoA-reductase was the target of inhibition. In contrast, for the vinyl-dithiins a stimulation of mevalonate incorporation was found. Concerning the late step, the potency to exert accumulation of lanosterol presumably by inhibiting lanosterol 14α-demethylase decreased in the order allicin>diallyl disulfide>allyl mercaptan=1,3-vinyl-dithiin≫1,2-vinyldithiin, the effect of the latter compound being close to zero. With respect to the total inhibition of [¹⁴C]acetate labeling of cholesterol, the half-maximal effective concentration-value of allicin was determined to be 17±2 μM compared to 64±7 μM for diallyl disulfide and to 450±20 μM for allyl mercaptan. Cytotoxicity as determined by the lactate dehydrogenase leakage assay was slightly higher for the two vinyl-dithiins than for diallyl disulfide and allyl mercaptan, but was apparent only at concentrations higher than 10 mM and, consequently, was irrelevant for the effects described. These results demonstrate that different garlic-derived organosulfur compounds interfere differently with cholesterol biosynthesis and, thus, may provoke multiple inhibition of this metabolic pathway in response to garlic consumption. The fact that allicin was the most effective inhibitor argues against the possibility that its degradation products, namely diallyl disulfide or allyl mercapatan, might mediate its effects, a possibility that might be true, however, in the case of the vinyl-dithiins.     

硫醇转化催化剂及硫醇氧化反应机理研究进展

综述了国内外硫醇转化催化剂及硫醇氧化反应机理的研究概况。介绍了酞菁钴类硫醇转化催化剂、固体碱硫醇转化催化剂以及硫醇的碱催化氧化反应机理和氧化还原催化氧化反应机理。指出以新型硫醇转化催化剂取代目前工业上的酞菁钴类催化剂势在必行。     

Graft copolymerization of vinyl monomers on modified cottons. III. Grafting of acrylonitrile and methyl methacrylate on cyanoethylated cotton by the ceric ion method

The interaction of acrylonitrile and methyl methacrylate with cyanoethylated cotton in the presence of ceric ion has been studied under a variety of conditions. Increasing the reaction time, the monomer concentration, and the temperature favorably influences the degree of grafting. The same holds true for initiator concentration up to a certain limit, after which a decrease in the graft yield was obtained. On the other hand, ceric consumption during grafting and oxidation increases by increasing the magnitudes of all these factors. However, the consumption during grafting is always higher than that during oxidation. The graft yields obtained with cyanoethylated cotton are greater than those of the control, being increased by increasing the degree of substitution (D.S.) of the cyanoethylated cotton, suggesting that the cyanoethyl groups afford additional sites of grafting. On the other hand, the ceric consumption during oxidation of cyano-ethylated cotton was much lower than that of the control, being increased also by increasing the D.S., indicating perhaps that ceric ion attacks the cyanoethylated cotton exclusively at the cyanoethyl groups. Based on these findings, a scheme for the mechanism of reaction of a vinyl monomer with cyanoethylated cotton was proposed.     

Catalytic adsorptive desulfurization of mercaptan,sulfide and disulfide using bifunctional Ti-based adsorbent for ultra-clean oil

Ultra-deep desulfurization of transformer oil is of great demand among power industry. In this work, the effective and deep removal of various types of organosulfurs, including mercaptan, sulfide and disulfide via catalytic adsorptive desulfurization (CADS) using bifunctional Ti-based adsorbent is reported. Compared to adsorptive desulfurization (ADS), dramatically improvement of the organosulfur uptakes were achieved under CADS process. The equilibrium adsorption capacity at 5 μg·g^-1 S reached up to 15.7, 33.4, 11.6 and 11.9 mg·g^-1 for propyl mercaptan(n-PM), dimethyl sulfide(DMS), di-t-butyl disulfide (DTBDS) and dibenzyl disulfide (DBDS), which was 262, 477, 97 and 128 times to that of ADS process, respectively, and was the highest among the reported desulfurization adsorbents. Moreover, it achieved superior breakthrough capacity of 2050, 530 and 210 ml F·(g A)^-1 at the breakthrough S concentration of 1 μg·g^-1 of the commercial transformer oil S containing 10, 50 and 150 μg·g^-1, respectively. The effectiveness of CADS is associated to the transformation of sulfur species to higher polar sulfonic species with the assistance of mild oxidant, which can be readily captured by silanol groups on SiO₂ through H-bonding interaction. The excellent recyclability of the adsorbent can be realized through solvent washing or oxidative air treatment. This work provides an effective and economic approach for the elimination of trace amount of mercaptan, sulfide and disulfide from transformer oil.     

Studies in chemically modified celluloses. IV. Lactones in chemically modified celluloses

Cellulose has been modified by hydrolysis followed by oxidation with chlorous acid to produce gluconic carboxyl groups, which can form only δ-lactones. A method has been described for reducing these gluconic acid groups by sodium borohydride into alcoholic groups. Iodometric and alkalimetric methods were used for estimating the carboxyl value of various chemically modified samples.     

Fabrication of a Bio-Based Superhydrophobic and Flame-Retardant Cotton Fabric for Oil–Water Separation

It is an urgent task to develop environmentally friendly and flame retardant durable oil–water separation materials. A green TA/B@PDA coating derived from bio-based materials such as tannic acid (TA), borax (B), and polydopamine (PDA) is deposited on cotton fabric through facile dip-coating method and step-by-step assembly method. A series of methods are used to characterize the as-prepared cotton fabric. PDA provides a reactive interface, while n-dodecyl mercaptan enhances the hydrophobicity of the surface with a water contact angle (WCA) and shedding angle (SA) of 153.3° ± 1.2° and 9° ± 0.8°, respectively. The as-prepared fabric exhibits outstanding oil/water separation efficiency (>98.5%) for various types of oil, and wear resistivity, washability, and reusability. Meanwhile, combustion test and limit oxygen index (LOI) test show that the modified fabric has excellent flame retardant performance. The cone calorimeter test (CCT) indicates that compared with the pristine cotton fabric, the peak heat release rate (PHRR) and total heat release (THR) of the TA/B@PDA cotton is decreased by 50% and 32%, respectively. Through the analysis of char residues, the flame retardant mechanism is studied. This method provides a general green way for the construction of superhydrophobic surfaces, and can be further applied to the broad fields of durable oil–water separation.     

Synthesis and applications of reactive carbohydrates. IV. Reactive finishes based on CMC and oxidized CMC copolymers

Carboxymethyl cellulose (CMC) and persulfate-oxidized CMC samples were assessed for acidic and reducing properties before and after graft copolymerization with acrylamide using K₂S₂O₈ as initiator. The acidic properties were expressed as milliequivalents of carboxyl groups/100 g CMC while the copper number was taken as a measure for the reducing properties. Results obtained signify that increasing the duration of persulfate oxidation from 15 to 60 min causes a significant enhancement in the carboxyl content of CMC particularly during the first 50 min of oxidation. The same holds true for the copper number, but no further significant enhancement could be observed after 30 min. The copolymerization reaction decreases substantially the acidic and reducing groups of the CMC substrates examined. The results showed also that oxidation of CMC increases its susceptibility toward grafting: The higher the extent of oxidation, the higher the extent of grafting. Methylolation of the polyacrylamide–CMC graft copolymers results in reactive finishes. The latter were applied either alone or together with etherified methylolated melamine to cotton fabric samples according to the conventional pad–dry–cure method. The treated samples withstand severe washing, suggesting the occurrence of chemical bonding between the methylolated CMC products and cotton.     

Formation of peroxides in fatty esters. II. Methyl linoleate: application of the polarographic and direct oxygen methods

Summary This study of the prolonged autoxidation of methyllinoleate at 80°C. has included polarographic identification and determination of hydroperoxides, the direct determination of oxygen contents, and catalytic micro-hydrogenation for the determination of unsaturation. The polarographic method has further substantiated the observations of other workers that the principal peroxidic substance formed during the autoxidation of methyl linoleate at 80°C. is a hydroperoxide. The direct oxygen measurements have shown that most of the oxygen absorbed in the initial stages of autoxidation can be accounted for as hydroperoxide. During the latter stages there was a continuous increase of oxygen uptake, half of which can be accounted for as free acid and half as forms other than hydroperoxide, ester, or free acid. By means of the catalytic micro-hydrogenation method it has further been shown that as the autoxidation progresses there is a continuous decrease in unsaturation.     

Ageing of low-temperature coal tar pitch. 2. Influence of additives

Several additives were tested with respect to their ability to slow down the weathering process of pitch. Four metals (Mn, Co, Cu, Pb) were found to speed up the formation of carbonyl groups, but otherwise, had little or no influence. A mercaptan and a hindered phenol antioxidant, both inhibitors for olefin polymerization, caused only small changes in the rate of formation of oxidation products. Sulphur, however, slowed down the formation of carbonyls considerably.