On the acidity of liquid and solid acid catalysts. Part 2. A thermodynamic and kinetic study for acid-catalysed nitrations

Solid acids prepared by adding sulfuric acid on silica gel have been used as catalysts in the nitration of nitrobenzenes and their properties have been tested by kinetic studies at 25°C. Nitration rates in concentrated aqueous solutions of sulfuric acid were also analysed and the catalytic efficiencies of sulfuric acid in liquid and solid phase were compared by using kinetic data of analogous compounds. The results show that the solid acid samples exhibit nitrating properties very similar to those observed in concentrated aqueous solutions of sulfuric acid (range of 90 wt%). The relationship between nitration rates and effective concentration of electrophilic species [NO ₂ ⁺ ], determined by studying the protonation–dehydration equilibrium of nitric acid in strong acids (HNO₃ + H⁺ ⇌ H₂O + NO ₂ ⁺ ), was tested to better understand the acidity properties of medium. This revised version was published online in November 2006 with corrections to the Cover Date.     

Synthesis and characterization of sulphonated polymer derived from 6FDA-ODA polyimide

Summary 6FDA-ODA polyimide was sulfonated with concentrated sulfuric acid at room temperature in order to convert the polymer into proton-conducting polymer. The sulfonation process was supervised with UV-vis. The results indicated that the reaction carried out quickly and was agreement with the analysis of resulted polymer. The sulfonation degree can be controlled by reaction time. The structure of the resulted polyelectrolytes were analyzed and confirmed by NMR, FT-IR. There are two weight-loss steps at 300 and 500 °C in TG curves, which correspond to the presence of two degradation processes for –SO₃H and polymer backbone. It indicated that the sulfonated polyimide had good thermo stability. The solubility of sulfonated polymer are also discussed.     

富马酸二丁酯的合成研究简

富马酸二丁酯是一种重要的增塑剂,可与多种单体共聚反应制备新的高分子材料,同时也可用作有机溶剂和有机合成中间体.本实验以富马酸和正丁醇为原料,用浓硫酸为催化剂研究合成富马酸二丁酯的最佳反应条件,并同时对比其他催化剂如：对甲苯磺酸、磷钨酸和硫酸氢钠的实验效果.采用正交实验的方法碍到的反应最佳条件是：富马酸、正丁醇、浓硫酸物质的量比为1∶15∶7.5,反应时间为1.5h,产率可达到90.5％,所得产品的主要物理常数和红外光谱数据与文献基本一致.     

Electroinitiated polymerization of methyl methacrylate in aqueous sulfuric acid

The polymerization of methyl methacrylate electroinitiated at the cathode was examined in concentrated solutions of the monomer containing aqueous sulfuric acid. The initiating reaction is not due to the formation of hydrogen atoms, as demonstrated by varying the nature of the cathode and of the acid, but involves the participation of the polymeric peroxide contained in the monomer. The cathodic material greatly affects the molecular weights and the yields, as does the composition of the solutions. Lead cathodes, which proved to be particularly efficient, showed phenomena of adsorption of both monomer and polymer. Kinetic curves are similar to those obtained in conventional radical polymerizations of MMA; a marked gel effect, limiting the termination reaction and leading to very high molecular weights, was observed.     

Solvent extraction reaction of hafnium(IV) from strong sulfuric acid solutions with D2EHPA and PC 88A

Hafnium can be selectively extracted over zirconium from strong sulfuric acid solutions by D2EHPA or PC 88A. Solvent extraction experiments have been performed to identify the reaction of Hf from strong sulfuric acid solutions (1 to 7 M) by these two extractants. Hafnium extraction was gradually decreased and then increased again with the increase of sulfuric acid concentration. By applying a slope method, the extracted Hf species was proposed to be HfA₄·(HA)₂ by D2EHPA and Hf(HSO₄)₂A₂·(HA)₂ by PC 88A, respectively. This difference in the nature of the extracted species was verified by FT-IR spectra.     

High molecular weight poly(p-arylene sulfide ketone): synthesis and membrane-forming properties

High-molecular-weight poly(p-arylene sulfide ketone) (PPSK) was prepared by nucleophilic substitution reaction of 4,4’-diflurobenzophenone (DFBP) and sodium sulfide in the compound solvents of diphenyl sulfone (DPS) and 1,3-dimethyl-2-imidazolidinone (DMI) with catalysts under elevated temperature. The inherent viscosity (η_int) of the PPSK synthesized was 0.703 dl/g. PPSK was characterized by Fourier-transform infrared spectroscopy, elemental analysis, x-ray diffraction, differential scanning calorimetry, and thermogravimetric analysis. It was found that the polymer had excellent thermal properties: glass transition temperature (T_g) was 142.8 °C, melting temperature (T_m) was 362.3 °C. Under nitrogen atmosphere, 5 % (T_5%) and 10 % (T_10%) weight-loss temperatures were about 498.5 °C and 526.2 °C, respectively, while in the air the T_5% and T_10% were about 517 °C and 535.8 °C, respectively. The PPSK was found to be a semi-crystalline polymer, as confirmed by XRD. The polymer was insoluble in any solvent except concentrated sulfuric acid at room temperature. A series of the PPSK separating membranes were prepared by dissolving PPSK to concentrated sulfuric acid. The fluxes and the porosities of the separating membranes were in the range of 230–43 L/(m²?·?h) and 77.7-84.7 %, respectively. At the same time, these separating membranes showed moderate tensile strength of 1.02-1.88 MPa.     

A methanesulfonic acid/sulfuric acid‐based route for easily‐controllable chloromethylation of poly(ether ether ketone)

A mixed methanesulfonic acid/sulfuric acid solvent based chlromethylation of poly(ether ether ketone) (PEEK) is described. Methanesulfonic acid is the solvent, sulfuric acid is the catalyst, and chloromethyl octyl ether (CMOE) is the chloromethylating reagent. ¹H‐NMR spectra confirmed the successful synthesis of chloromethylated PEEK (CMPEEK). The effects of polymer concentration, catalyst/polymer ratio, and reaction temperature on the rate of PEEK chloromethylation were investigated. In order to minimize crosslinking, the PEEK concentration must be kept very low (< 2%). The reaction rate increases with increased catalyst/polymer ratio and reaction temperature. The activation energy of PEEK chloromethylation is 30.9 kJ mol^?1. The extent of reaction for the new route is more easily controllable as compared with the previous sulfuric acid based route. The reaction rate constant at 25°C for the new route is 1.29 h^?1 which is lower than that for chloromethylation by concentrated sulfuric acid at ?10°C (rate constant 1.88 h^?1). As a result, the degree of chloromethylation of CMPEEK can be easily controlled at room temperature using this mixed solvent. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41404.     

Surface chemical modification of polypropylene fiber waste by H2SO4: Mechanistic investigation and application as cation‐exchange adsorbent

In this work, polypropylene (PP) fiber waste was modified by the reaction with concentrated H₂SO₄. IR, TG, Raman, CHN, acid titration, SEM, and XRD suggested that sulfuric acid at about 105°C reacts with PP to produce mainly surface sulfonic groups. The kinetic experiments showed that these SO₃H groups decompose to form SO₂ gas leading to an aromatization of the polymer to form amorphous and graphitic carbon. Adsorption isotherms of the cationic model molecule methylene blue showed that the modified PP fibers have a great potential as ion‐exchange adsorbent. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

四乙酰基二氯乙酰基六氮杂异伍兹烷的硝解研究

研究了几种硝解剂及硝解条件对四乙酰基二氯乙酰基六氮杂异伍兹烷（TADCIW）硝解产物的纯度和得率的影响。讨论了有关的机理,用发烟硝酸-浓硫酸或碱金属硝酸盐-浓硫酸硝解TADCIW,可得到纯度很高的四硝基二氢乙酰基六氮杂异伍兹烷（TNDCIW）,得率达到94%-98%,硝解时间短,硝硫混酸可以再利用;但用发烟硝酸-五氧化二磷或浓硝酸-浓硫酸硝解TADCIW的得率很低。     

Dynamic rheological properties and microstructures of liquid-crystalline poly(<Emphasis Type="Italic">p</Emphasis>-phenyleneterephthalamide) solutions in the presence of single-walled carbon nanotubes

The rheological properties and microstructures of both poly(p-phenylene terephthalamide)/sulfuric acid(PPTA/H₂SO₄) and poly(p-phenylene terephthalamide)/ single-walled carbon nanotubes/sulfuric acid (PPTA/SWNT/H₂SO₄) dopes were investigated with flat plate rotational rheometer, polarized optical microscope and differential scan calorimeter. The results showed that, the two types of dopes presented typical shear thinning behaviour even at low frequencies, at various temperatures as well as at all polymer concentrations, and that the relationships between complex viscosity and freqency and between zero shear viscosity and weight average molecular weight implied the tight PPTA chain contacts, somewhat the feature of flexible polymer entanglements. The protonation due to concentrated sulfuric acid allowed SWNT to be well dispersed in PPTA/SWNT/H₂SO₄ dopes. At the concentrations of SWNT, approximately over 0.2 wt%, a novel type of single phase nematic liquid crystal was formed. The dopes can be used to fabricate high performance fibers by dry-jet wet spinning process.     

Polyaniline nanotubes: conditions of formation

The courses of aniline oxidation with ammonium peroxydisulfate in aqueous solutions of strong (sulfuric) and in weak (acetic) acids, followed by temperature and acidity changes, are different. In solutions of sulfuric acid, granular polyaniline (PANI) was produced; in solutions of acetic acid, PANI nanotubes were obtained. The external diameter of the nanotubes was 100–300 nm, the internal cavity 20–100 nm, and the length extended to several micrometres. The morphology of PANI, granular or tubular, depends on the acidity conditions during the reaction rather than on the chemical nature of the acid. PANI nanotubes were also produced when aniline was oxidized in the absence of any acid. The bulk conductivity of PANI prepared in solutions of acetic acid was 0.08–0.27 S cm^?1, depending on the acid concentration. Protonated PANI prepared in sulfuric and acetic acids were deprotonated with ammonium hydroxide to obtain PANI bases and the ammonium salt of the protonating acid. FTIR spectroscopy showed the differences in the molecular structure of the PANI bases. Irrespective of whether the polymerization was performed in solutions of sulfuric or acetic acid, PANI had hydrogen sulfate counter‐ions only. The PANI morphology is thus not controlled by the nature of counter‐ions. The acidity of the reaction medium determines the protonation of monomer, oligomer and polymer species. The chemistry of aniline oxidation is likely to be affected especially by the protonation of an intermediate in the pernigraniline form. It is proposed that, in the course of aniline oxidation, pH‐dependent self‐assembly of aniline oligomers predetermines the final PANI morphology. Copyright © 2005 Society of Chemical Industry     

4-溴-4~’碘联苯的合成研究

对两种不同体系下合成4-溴-4’碘联苯进行了研究。通过对比发现,浓硫酸做催化剂,I2/KIO4为碘化试剂的反应体系具有可行性。对该体系的反应温度和浓硫酸的用量进行了优化。原料4溴联苯,在浓硫酸催化下,与碘/碘酸钾在冰醋酸水溶液中,于100℃下反应2h,紫色褪尽,过滤得到白色固体粗品34g,纯度98%(HPLC),收率为95%。该方法降低了原料成本,简化操作,缩短反应时间,是较为理想4-溴-4’碘联苯的工业合成方法。     

Preparation and characterization of chloromethylated/quaternized poly(phthalazinone ether sulfone ketone) for positively charged nanofiltration membranes

Chloromethylated poly(phthalazinone ether sulfone ketone) (CMPPESK) as a novel membrane material was successfully prepared from poly(phthalazinone ether sulfone ketone), with concentrated sulfuric acid as the solvent and catalyst, and chloromethyl octyl ether with lower toxicity as the chloromethylated regent. The effects of the reaction conditions on the preparation of CMPPESKs with different degrees of chloromethylation were examined. The quantity of chloromethyl groups per repeated unit (DCM) of CMPPESK was determined by the method of analysis of the chlorine element, and structures were characterized by ¹H‐NMR spectroscopy. The introduction of chloromethyl groups into the polymer chains led to a decrease in the decomposition temperature. With increasing DCM, the initial degradation temperature declined. CMPPESK had good solubility and was soluble in N‐methyl‐2‐pyrrolidone (NMP), N,N‐dimethylacetamide (DMAc), and chloroform. However, quaternized poly(phthalazinone ether sulfone ketone) (QAPPESK) had excellent solvent resistance, was only partly soluble in sulfuric acid (98%), and was swollen in N,N‐dimethylformamide. QAPPESK nanofiltration (NF) membranes had about 90% rejection for MgCl₂, and the performance of the NF membrane prepared with DMAc as the solvent was superior to that of the NF membrane prepared with NMP as the solvent. In addition, the rejection to the different salt solutions followed the following sequence: MgCl₂ > MgSO₄ > NaCl > Na₂SO₄. Furthermore, the thermotolerance of the QAPPESK NF membrane was examined, and the results show that when the solution temperature rose from 11 to 90°C, the water flux increased more than threefold with stable salt rejection. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

溴代仲丁烷的合成新法

以工业上生产紫外线吸收剂的副产品溴化钾为原料,与仲丁醇在浓硫酸存在条件下,以水为溶剂,进行反应合成溴代仲丁烷,考察了两种生产工艺及不同反应因素对产率的影响。实验结果表明,在反应物用量相同情况下(溴化钾0.1mol,仲丁醇0.08moL,浓硫酸8mL,水4.5mL),追加浓硫酸法比传统的一次性加入合成方法产率提高了10%。采用追加浓硫酸生产工艺,实验结果的重复性和稳定性较好。对粗产品纯度进行了色谱分析,对纯产品进行了红外表征及折光率的测定。     

染料厂废酸制富过磷酸钙工艺研究

采用染料厂废酸和磷酸的混合酸分解磷矿石制备富过磷酸钙，研究了废酸制备富有磷酸钙生产过程中反应温度、酸用量、磷酸替代量和熟化时间等工艺参数对生产工艺过程的影响，并确定了适宜操作参数。     

Selective Recovery of Rhenium from Gas-Scrubbing Solutions of Molybdenite Roasting Using Direct Precipitation and Separation on Resins

Abstract

Rhenium, a by-product of molybdenum's extractive metallurgy, can be recovered from acidic gas-scrubbing solutions by using the techniques of direct precipitation and separation on resin. Direct precipitation is achieved by using tetraphenylphosphonium bromide (φ₄P). This technique yields an organometallic precipitate containing more than 25% Re and less than 1% Mo and Se. The reaction is fast and selective, with a stoichiometry φ₄P/Re = 1/1. Separation on resins is achieved with a weak base anionic resin of the tertiary amine type. By using the reflux method, the weakly coadsorbed molybdenum and selenium are removed by a concentrated sulfuric acid solution containing rhenium. Rhenium is then selectively eluted by an ammoniacal solution from which pure ammonium perrhenate is crystallized.     

Heterogeneous Reactions of Chlorine Nitrate and Dinitrogen Pentoxide on Sulfuric Acid Surfaces Representative of Global Stratospheric Aerosol Particles

Increasing evidence from field measurements, modeling studies, and laboratory experiments suggests that heterogeneous reactions on stratospheric sulfate aerosol particles can change the partitioning in the nitrogen and chlorine families and thereby affect global ozone levels. In this study, a Knudsen cell flow reactor was used to measure the uptake of ClONO₂ and N₂O₅ by sulfuric acid solutions representative of background and volcanic stratospheric aerosol particles. The uptake coefficient (γ) of chlorine nitrate on 50–75 wt% H₂SO₄ at 223 K was found to be markedly dependent on the acid concentration, with γ ranging from about 1 × 10⁻² to 1 × 10⁻⁴. These results are in good agreement with literature reports and the data fit the expression log γ= 1.87 – 0.074 × (wt% H₂SO₄). This reaction will thus have its largest impact when stratospheric temperatures are low and sulfuric acid aerosols are most dilute. Uptake of N₂O₅ was studied on solutions with compositions in the range 58–96 wt% H₂SO₄ at temperatures from 193 to 303 K. N₂O₅ reacted readily on sulfuric acid surfaces with uptake coefficients of about 0.06. The uptake coefficient was found to be independent of the sulfuric acid concentration and the solution temperature over the ranges studied. These results suggest that the reaction of N₂O₅ with H₂O will occur readily on sulfuric acid aerosol particles for most stratospheric conditions.     

Synthesis of isoamyl salicylate using a novel mesoporous titania superacid as a catalyst

Mesoporous titania was prepared by hydrothermal method and mesoporous titania solid superacid catalyst was prepared by wet impregnation method. The structure and property of the as-prepared catalysts were characterized by means of XRD, FT-IR and N₂ physical adsorption. Isoamyl salicylate was synthesized by using concentrated sulfuric acid and solid superacid as catalyst, respectively. The effects of the molar ratio of raw material, the amount of catalyst, reaction time and reaction temperature on the yield of the product were systematically investigated. The results show that mesoporous titania solid superacid is a good catalyst for synthesizing isoamyl salicylate. The optimum conditions of isoamyl salicylate synthesized by using mesoporous titania solid superacid are the following: the molar ratio of salicylic acid to isoamyl alcohol is 1: 4, the quantity of catalyst is 1.6 g, the reaction time is 5 h, the reaction temperature is 130 °C and the yield can reach 94.6%.     

Thermochemistry of the dissolving of poly-p-phenyleneterephthalamide in concentrated sulfuric acid

Conclusions A thermochemical method has been used to estimate the compositions of additive compounds between PPTA polymer and sulfuric acid.The presence of an energetic interaction of poly-p-phenyleneterephthalamide with the solvent has been established; this explains the effective dissolving action of concentrated sulfuric acid.Translated from Khimicheskie Volokna, No. 5, pp. 45–46, September–October, 1966.     

Sulfonation of polysulfones: Suitability of the sulfonated materials for asymmetric membrane preparation

The effect of the starting polymer on the reaction of sulfonation of polysulfones was investigated. When concentrated sulfuric acid is used as the sulfonation reagent in an organic solvent‐free reaction, a polymer degradation equally occurs, leading to a decrease in the yield of product recovery. Poly(ether sulfone) Cardo appears to be the most resistant to chain scission in the medium and a control of the sulfonation degree can be performed via the reaction condition control. The reaction can be monitored by UV–Visible spectrophotometry. Phase inversion by immersion of a N‐methyl‐2‐pyrrolidone–polymer dope in water led to asymmetric membranes with an average pore size in the range of that of ultrafiltration and that of nanofiltration membranes. The latter membranes can only be obtained at high polymer concentrations and at moderate sulfonation degrees. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2461– 2473, 2002