Selectivity engineering in the O‐ versus C‐alkylation of p‐cresol with cyclohexene over sulfated zirconia

Solid acids are more widely used as heterogeneous catalysts, because they are eco‐friendly. This paper reports the results for the Friedel‐Crafts alkylation of p‐cresol with cyclohexene using solid acids sulfated zirconia, 20% w/w dodecatungstophosphoric acid (DTP) supported on K10 clay and ZnCl₂/K10 (Clayzic). This reaction gave substantial amount of 1‐cyclohexyloxy‐4‐methyl benzene (O‐alkylated product) and 4‐cyclo‐hexyl‐4‐methyl phenol (C‐alkylated product). Both products are of commercial importance as perfume and insecticide respectively. Sulfated zirconia catalyst was shown to be better than others studied in terms of activity and selectivity to the O‐alkylated product. The kinetics were studied with sulfated zirconia as catalyst where the rate determining step was the surface reaction between chemisorbed cyclohexene and p‐cresol from the liquid phase within pores according to the Eley‐Rideal mechanism. The production of O‐alkylated p‐cresol is favoured at lower temperatures and C‐alkylated product at higher temperatures. The best operating temperature is 353 K. The activation energies for O‐ and C‐alkylation are 72.68 and 118.28 kj/mol, respectively.     

Oxidation of p‐Cresol to p‐Hydroxybenzaldehyde with Molecular Oxygen in the Presence of CuMn‐Oxide Heterogeneous Catalyst

A high‐yield synthesis of p‐hydroxybenzaldehyde from p‐cresol and molecular oxygen was achieved over a CuMn‐oxide supported carbon catalyst. The reaction parameters such as pressure, stirring speed, reaction temperature, solvent, and the amount of sodium hydroxide in the reaction media were optimized. As a result, a high conversion of p‐cresol (99%) and a high selectivity to p‐hydroxybenzaldehyde (96%) were realized at the same time. Catalyst separation and recycling tests clearly showed that the reaction proceeded on the heterogeneous catalyst but not on dissolved species.     

同步脱氮除硫污泥及其微生物生态学特性

研究了同步脱氮除硫反应器稳态运行时的污泥特性与微生物生态学特性。测得污泥粒径为0.54～3.99mm,沉降速度为56.13～171.43 m·h~(-1),污泥湿密度为1.08 kg·m~(-3)。采用光学显微镜观察发现,污泥形状不规则,由污泥亚单位(菌胶团和絮体污泥)复合而成。采用扫描电镜观察揭示,污泥表面微生物以杆菌为主,内部微生物形态多样。运用PCR-DGGE分析表明,同步脱氮除硫污泥的微生物种类多样性较高,其中以变形菌门的微生物为主。     

pH和碱度对同步厌氧生物脱氮除硫工艺性能的影响

采用UASB反应器研究了pH和碱度对同步厌氧生物脱氮除硫工艺性能的影响。控制进水pH在7.5～8.0之间,反应器的最大容积硫化物和硝酸盐去除速率分别为2.96 kg·(m³·d)^-1和0.47 kg·(m³·d)^-1（分别以硫元素、氮元素计）,反应过程产碱及残留硫化物,均会导致反应液pH值过高（9.11±0.38）,引发高负荷时工艺失稳。控制反应液pH在7.0±0.1范围,容积硫化物和硝酸盐去除速率分别可达4.78 kg·(m³·d)^-1和0.99 kg·(m³·d)^-1,容积效能高于控制进水pH时的相应值。要维持反应所需的中性条件,碱度宜控制在（454.1±40.5）mg ·L^-1（以CaCO₃计）。反应过程中的碱度变化（增量）可以指示反应器内主导反应的类型及其反应进度。单质硫型生物脱氮除硫反应（硫氮比为5∶2）和硫酸盐型生物脱氮除硫反应（硫氮比为5∶8）的硫化物去除量与碱度减少量之比分别为2.27和2.00,混合型生物脱氮除硫反应（硫氮比为5∶5）的硫化物去除量与碱度减少量之比为5.00。     

Biochemical removal of nitrogen from tannery wastewater: performance and stability of a full‐scale plant

This paper describes the performance of a full‐scale common effluent plant treating tannery wastewater, based on a single‐sludge nitrification/denitrification process, with the objective of investigating the reasons for its instability. The plant was monitored over a 1.5‐year period; operational parameters were evaluated daily and their impact on process rates assessed together with the characteristics of the wastewater sampled at different points in the treatment scheme. The results showed that instability problems and a periodic failure of nitrification/denitrification occurred due to a series of reasons, often persisting simultaneously and having an additive synergetic effect. Factors whose magnitude would be insufficient to affect the performance of a plant treating domestic wastewater, eg; small deviations from the optimal pH in nitrification or denitrification basins, a temperature decrease to 17 °C or an increase of the influent nitrogen content, caused the plant's efficiency to drop from 100% to 40% in some periods. To ensure stable performance, the dilution rate, D, along with the sludge retention time were shown to be key parameters for the control of the process. Maintaining values of D considerably lower than critical theoretical values calculated from the specific growth rate of nitrifiers at a given temperature and sludge recycle ratio may prevent problems in the plant's performance, particularly when high fluctuations of the concentration of inflow solids make calculation of the sludge age uncertain and proper sludge management difficult. Copyright © 2004 Society of Chemical Industry     

Improvement in mechanical properties of poly(p‐phenylene sulfide) fibers by high‐tension multiannealing method

High‐tension multiannealing (HTMA) was applied to improve the tensile properties of poly(p‐phenylene sulfide) fibers, which was furthermore applied to the fibers produced and improved with the zone‐drawing and zone‐annealing treatments. The HTMA treatment was repeatedly applied to the fibers under the conditions of a 250°C temperature and an applied tension of between 201.0 and 188.0 MPa. As a result, at the 13th treatment the degree of crystallinity increased to 40%. On the other hand, the orientation factor of crystallites increased dramatically to 0.982 during the zone‐drawing treatment, but increased only slightly during the subsequent treatments of zone annealing and HTMA. The finally obtained fiber had a tensile modulus of 10.4 GPa and a tensile strength of 0.73 GPa. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 1569–1576, 2000     

Nucleation effect of hydroxyl‐purified multiwalled carbon nanotubes in poly(p‐phenylene sulfide) composites

To investigate the nucleation effect of hydroxyl‐purified multiwalled carbon nanotubes (MWNTs‐OH) in poly(p‐phenylenesulfide) (PPS), a series of composites were prepared by blending PPS with MWNTs‐OH at 1, 2, and 3 wt %, respectively. Under SEM observation MWNTs‐OH were found homogeneously dispersed in the PPS matrix. DSC thermograms revealed that the enthalpy (ΔH_c) of the composites increased with increasing MWNT‐OH content, whereas the crystallization temperature (T_c) decreased progressively. The decrease in T_c was in accordance with the smaller crystallite size determined with WXRD characterization, and the increase in ΔH_c was evidenced by FTIR and XPS analyses. The higher ΔH_c shows that MWNTs‐OH serves as a nucleating agent, providing sufficiently multiplied sites for crystal growth. The lowering of T_c was attributed not only to MWNTs‐OH network hindrance to PPS chain fusing rearrangement, but also to a poorer affinity between MWNTs‐OH and PPS; both effects coordinately govern T_c of PPS/MWNTs‐OH composites. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Modification of an o‐cresol formaldehyde epoxy resin by the thermotropic liquid crystalline polymer

Two novel liquid crystalline polymers, polydiethyleneglycol bis(4‐hydroxybenzoate) terephthaloyl and block copolymer (PDBH), were synthesized by condensation reaction. The blends of the two liquid crystalline polymers and o‐cresol formaldehyde epoxy resin were prepared by linear phenol‐formaldehyde resin as curing reagent. Both mechanical and thermal properties of the blends containing liquid crystalline polymer were improved to a certain extent. By adding 5 wt % PDBH, the impact strength, bending strength, and the glass transition temperature were enhanced by 128%, 23.84%, and 28°C, respectively, compared with the unmodified version. The results of curing kinetics showed that the curing reaction active energy of the modified system by PDBH decreased from 79.70 to 70.26 kJ/mol. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1626–1631, 2005     

Effect of LED optical characteristics on temporal behavior of o‐cresol decomposition by UV/TiO2 process

BACKGROUND: An ultraviolet light‐emitting diode (UV‐LED) was used in this investigation as the light source for the photocatalytic decomposition of o‐cresol in aqueous solution because of its efficiency, design flexibility, and durability. The UV light intensities of the corn‐shaped LED tube designed in this investigation were relatively uniform due to the correct arrangement of LEDs. RESULTS: For experiments conducted with initial o‐cresol concentrations of 9 mg L^?1 and pH 3, more than 80% of o‐cresols were decomposed after 8 h of irradiation. The calculated photonic efficiency (about 1·06%) for experiments conducted with continuous illumination was much lower than those (1·69–6·27%) obtained with periodic illumination. CONCLUSION: The proposed Langmuir–Hinshelwood kinetic model with modification of UV light intensity attenuation could be adequately applied to describe the temporal behavior of the o‐cresol decomposition in aqueous solution by the UV‐LED/TiO₂ process. Copyright © 2007 Society of Chemical Industry     

Thermal decomposition kinetics of thermotropic copolyesters made from trans‐p‐hydroxycinnamic acid and p‐hydroxybenzoic acid

A series of thermotropic copolyesters were synthesized by direct thermal melt polycondensation of p‐acetoxybenzoic acid (PHB) with trans‐p‐acetoxycinnamic acid (PHC). The dynamic thermogravimetric kinetics of the copolyesters in nitrogen were analyzed by four single heating‐rate techniques and three multiple heating‐rate techniques. The effects of the heating rate, copolyester composition, degradation stage, and the calculating techniques on the thermostability and degradation kinetic parameters of the copolyesters are systematically discussed. The four single heating‐rate techniques used in this work include Friedman, Freeman–Carroll, Chang, and the second Kissinger techniques, whereas the three multiple heating‐rate techniques are the first Kissinger, Kim–Park, and Flynn–Wall techniques. The decomposition temperature of the copolyesters increases monotonically with increasing PHB content from 40 to 60 mol %, whereas their activation energy exhibits a maximal value at the PHB content of 50 mol %. The decomposition temperature, activation energy, the order, and the frequency factor of the degradation reaction for the thermotropic copolyester with PHB/PHC feed ratio of 50/50 mol % were determined to be 374°C, 408 kJ/mol, 7.2, and 1.25 × 10²⁹ min^?1, respectively. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 445–454, 2004     

同步反硝化短程除硫功能菌群的变化及鉴定

依据反硝化除硫理论,利用全混流反应器富集反硝化除硫菌,采用平板计数法和PCR-DGGE法对功能菌群进行跟踪和鉴定,并对分离纯化得到的单菌株SNB1进行鉴定。结果表明,反应器中细菌总量、除硫菌和反硝化菌分别增加了1.92×10、6.49×105和1.66×103倍。稳定运行时反应器内存在3种优势菌群。a菌群与Thauera sp.的同源性高达99%,为反硝化菌;其包含的SNB1生理生化指标显示为一株兼性自养反硝化除硫菌,且与Thauera selenatis(同源性高达99.0%)最相似;反硝化除硫菌的比例为49.3%,数量约为3.70×109cfu.ml-1。b菌群与Desulfovibrio sp.的同源性高于98%,为硫酸盐还原菌。c菌群和Rhodococcus sp.的同源性高于94%,为反硝化菌。当S/N在0.007～0.386间变化时,除S2-始终被100%转化为S0外,还有大于46.47%的SO42--S被转化为S0;而NO3-和COD的去除率分别为72.3%～95.8%和9.8%～43.5%。     

Crystallization and melting behavior of poly(p‐phenylene sulfide) in blends with poly(ether sulfone)

Crystallization and melting behaviors of poly(p‐phenylene sulfide) (PPS) in blends with poly(ether sulfone) (PES) prepared by melt‐mixing were investigated by differential scanning calorimetry (DSC). The blends showed two glass transition temperatures corresponding to PPS‐ and PES‐rich phases, which increased with increasing PES content, indicating that PPS and PES have some compatibility. The cold crystallization temperature of the blended PPS was a little higher than that of pure PPS. Also, the heats of crystallization and melting of the blended PPS decreased with increasing PES content, indicating that the degree of crystallinity decreased with an increase of PES content. The isothermal crystallization studies revealed that the crystallization of PPS is accelerated by blending PPS with 10 wt % PES and further addition results in the retardation. The Avrami exponent n was about 4 independent on blend composition. The activation energy of crystallization increased by blending with PES. The equilibrium melting point decreased linearly with increasing PES content. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1686–1692, 1999     

Synthesis and light‐emitting properties of a novel π‐conjugated poly[di(p‐phenyleneethynylene)‐alt‐ (p‐phenylenecyanovinylene)] containing n‐octyloxy side branches

A novel π‐conjugated poly[di(p‐phenyleneethynylene)‐alt‐(p‐phenylenecyanovinylene)] having n‐octyloxy side chains (PPE‐C₈PPE‐PPV) was prepared by polymerization of the monomer DEDB with BCN. Chemical structure of the polymer obtained was confirmed by ¹H NMR, FTIR, and EA. PPE‐C₈PPE‐PPV had a molecular weight enough to fabricate the electroluminescent (EL) device, and showed a good organosolubility, excellent thermal stability, and film‐forming property. In UV absorption and PL spectra in film it showed a maximum at 430 and 543 nm, respectively, which appeared 5 and 41 nm longer wavelengths than that of the solution, respectively. HOMO, LUMO energy levels and band gap were determined to be ?5.70, ?3.29, and 2.41 eV, respectively. Two EL devices with low‐work function cathodes were fabricated with the structures of ITO/PEDOT/PPE‐C₈PPE‐PPV/cathodes (LiF/Al and Mg:Ag/Ag). The both devices exhibited a bright green light emission at 545 nm and the maximum luminescence of 197 cd/cm² (LiF/Al) and 158 cd/cm² (Mg:Ag/Ag). © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Hydrogenation of p‐Nitrophenol to p‐Aminophenol as a Test Reaction for the Catalytic Activity of Supported Pt Catalysts

Hydrogenation of p‐nitrophenol (PNP) to p‐aminophenol (PAP) using NaBH₄ as a reducing agent was studied as a test reaction for determining the catalytic activity of supported Pt catalysts. The initial reaction rate, which is accessible within less than 10 min via online UV‐vis spectroscopy at room temperature, ambient pressure, and in water as solvent, was applied as measure for catalytic activity. For three Pt catalysts supported on porous SiO₂, porous glass, and Al₂O₃, respectively, significant differences in the catalytic activity by almost one order of magnitude were observed. However, especially in the case of very active catalysts, limitations of the reaction by internal or external mass transfer have to be considered.     

The inhibitive effect of poly(p‐toluidine) on corrosion of iron in 1M HCL solutions

In recent years, polymer amines have been recognized as an excellent corrosion inhibitors for iron in acid solutions. In this work, the inhibitive effect of p‐toluidine and poly(p‐toluidine) on corrosion of iron in 1M HCl has been studied by the electrochemical methods such as impedance, linear polarization, Tafel polarization techniques. The effectiveness of poly(p‐toluidine) was found to be high in comparison with that of monomer. The results showed that p‐toluidine and poly(p‐toluidine) suppressed both cathodic and anodic processes of iron dissolution in 1M HCl. The inhibition efficiency of both p‐toluidine and poly(p‐toluidine) were found to increase with the inhibitor concentrations. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Structure and high‐resolution thermogravimetry of liquid‐crystalline copoly(p‐oxybenzoate‐ethylene terephthalate‐p‐benzamide)

Thermotropic liquid‐crystalline copoly(ester‐amide)s consisting of three units of p‐oxybenzoate (B), ethylene terephthalate (E) and p‐benzamide (A) were studied by proton nuclear magnetic resonance at 200 and 400 MHz, wide‐angle X‐ray diffraction, and high‐resolution thermogravimetry to ascertain their molecular and supermolecular structures, thermostability and kinetics parameters of thermal decomposition in both nitrogen and air. The assignments of all resonance peaks of [¹H]NMR spectra for the copoly(ester‐amide)s are given and the characteristics of X‐ray equatorial and meridional scans are discussed. Overall activation energy data of the first major decomposition have been evaluated through three calculating techniques. The thermal degradation occurs in three steps in nitrogen and air. The degradation temperatures are higher than 447 °C in nitrogen and 440 °C in air and increase with increasing B‐unit content at a fixed A‐unit content of 5 mol%. The temperatures at the first maximum weight‐loss rate are higher than 455 °C in nitrogen and 445 °C in air and also increase with an increase in B‐unit content. The first maximum weight‐loss rates range between 11.1 and 14.5%min⁻¹ in nitrogen and between 11.9 and 13.5%min⁻¹ in air. The char yields at 500 °C in both nitrogen and air range from 45.8 to 54.3 wt% and increase with increasing B‐unit content. But the char yields at 800 °C in nitrogen and air are quite irregular with the variation of copolymer composition and testing atmosphere. The activation energy and Ln (pre‐exponential factor) for the first major decomposition are usually higher in nitrogen than in air and increase slightly with an increase in B‐unit content at a given A‐unit content of 5 mol%. The activation energy, decomposition order, and Ln (pre‐exponential factor) of the thermal degradation for the copoly(ester‐amide)s in two testing atmospheres, are situated in the ranges of 210–292 kJmol⁻¹, 2.0–2.8, 33–46 min⁻¹, respectively. The three kinetic parameters of the thermal degradation for the aromatic copoly(ester‐amide)s obtained by high‐resolution thermogravimetry at a variable heating rate are almost the same as those by traditional thermogravimetry at constant heating rate, suggesting good applicability of kinetic methods developed for constant heating rate to the variable heating‐rate method. These results indicate that the copoly(ester‐amide)s exhibit high thermostability. The isothermal decomposition kinetics of the copoly(ester‐amide)s at 450 and 420 °C are also discussed and compared with the results obtained based on non‐isothermal high‐resolution thermogravimetry. © 1999 Society of Chemical Industry