半纤维素酶添加对碱处理甘蔗渣结构及酶解的影响

半纤维素作为木质纤维素的重要组分之一,通过氢键与纤维素的微纤丝结合,严重阻碍了纤维素表面与纤维素酶的接触,降低了酶解的效率。该试验以碱处理甘蔗渣作为底物,通过添加不同量的半纤维素酶去除不同比例的半纤维素。通过成分分析、X射线衍射(XRD)和扫描电镜(SEM)等手段分析添加半纤维素酶前后残渣的结构和酶解特性变化,发现随着半纤维素酶添加量的增大,残渣中木质素所占的比例逐渐增大,结晶指数逐渐增大,电镜表面沟壑逐渐加深,纤维束之间结构变得疏松。以半纤维素酶处理过的甘蔗渣作为底物,按照5FPU/g底物加入纤维素酶水解72h,与不添加半纤维素酶对照组相比,添加1600U/g半纤维素酶处理的试验组木聚糖的转化率提高了74.24%,葡聚糖转化率提高了35.30%。通过半纤维素酶添加可以有效促进纤维素酶解过程的进行,节约反应时间提高酶解转化率。     

Optimization of the enzymatic hydrolysis conditions of steam‐exploded wheat straw for maximum glucose and xylose recovery

BACKGROUND: The enzymatic hydrolysis of steam‐exploded wheat straw using commercial enzyme complexes has been studied. A cellulase enzyme complex (Accellerase 1500), along with specific xylanase complements (Accellerase‐XC and Accellerase‐XY) provided by Genencor, have been used to enhance glucose and xylose recovery. A systematic study with response surface methodology (RSM) was used to check the effect of the operating conditions: pH (4–5), temperature (50–60 °C) and enzyme/substrate ratio (0.1–0.5 mL g_cellulose^?1) on the enzymatic hydrolysis with Acellerase 1500 to maximize the sugar yield. Xylanases were used as complements to increase the release of xylose. RESULT: Statistical results from ANOVA analysis demonstrated that the enzymatic hydrolysis was clearly improved by temperature and enzyme/substrate ratio. The optimum conditions for higher glucose and xylose releases were obtained with the higher enzyme dosage ratio (0.5 mL g^?1_cellulose), 50 °C and pH 4. CONCLUSION: Model validation at optimum operating conditions showed good agreement between the experimental results and the predicted responses for a confidence level of 95%. The use of the xylanase complements, Accellerase‐XY (accessory xylanase enzyme complex) and Accellerase‐XC (accessory xylanase/cellulase enzyme complex), increases the conversion of hemicellulose. Accellerase‐XC supplementation was more effective, obtaining an increase in yields of glucose and xylose of 11.8% and 23.6%, respectively, using a dosage of 0.125 mL g^?1_cellulose. © 2012 Society of Chemical Industry     

Synthesis of a new cationic surfactant for the alkaline hydrolysis of solvent‐pretreated polyester fabrics

The synthesis of a cationic surfactant was based on diethanolamine and alkyl halides such as cetyl bromide with epichlorohydrin as a quaternizing agent. It was characterized by the elemental microanalysis of nitrogen and chloride and infrared spectroscopy. Polyester (PET) crepe fabric was pretreated with a series of solvents, including tetrachloroethane and tetrachloroethylene, at 25, 50, and 100°C. Untreated and solvent‐pretreated PET fabric was hydrolyzed with 8 g/L NaOH at 100°C in the absence and presence of a cationic surfactant as a catalyst, and the weight loss was determined. The effects of solvent pretreatment on alkaline hydrolysis and PET dyeing were also examined. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1652–1660, 2002.     

二氧化碳对高温液态水中苯乙腈水解反应的影响研究

为探讨添加了二氧化碳的高温液态水中腈类物质的水解规律,考察了不同的二氧化碳添加量对高温液态水中苯乙腈水解的影响,计算了不同二氧化碳添加量和不同温度对高温液态水反应体系的pH的影响。结果表明：在473.15 K,0、0.2、0.4 MPa二氧化碳压力下的水解反应速率常数分别为6.2 × 10-4、4.1 × 10-4、3.0 × 10-4 min-1,而相对应的pH值分别为5.6、4.1、3.9。对于碱催化机理为主导的苯乙腈水解反应,二氧化碳并不能有效地促进反应进行。     

改善蒸汽驱效果的高温泡沫剂研究

利用自主研发的泡沫剂GFPJ,通过引入不同类型的高温泡沫稳定剂,得到能够满足稠油蒸汽驱要求的高温泡沫剂体系。对不同高温泡沫剂体系的发泡性能、耐高温性能以及高温封堵性能进行了研究。通过对不同高温泡沫剂体系老化前后有效含量的变化测定,表明了高温泡沫稳定剂的主要作用是能够降低泡沫剂的降解速率,从而提高泡沫剂体系的耐高温性能。     

高温液态水中腺苷无催化水解反应动力学

腺嘌呤作为一种重要的化工原料，已广泛应用于医药、有机合成等领域，目前腺嘌呤采用丙二酸二乙酯与甲酰胺缩合反应合成，环境污染较大。为实现腺嘌呤生产的绿色化，同时探索腺苷中C-N断裂的机理，开展了在高温液态水中无催化腺苷水解反应的研究，考察了高温液态水中初始浓度、搅拌速率、温度对腺苷水解的影响，研究了150～190 ℃下腺苷的水解反应动力学，在假设反应为零级反应的情况下拟合得到了各温度的反应速率常数，并得出活化能为174.1 kJ•mol-1。实验结果表明，高温水解中腺苷无催化水解制备腺嘌呤是可行的，而且产率较高。     

高温季节碱浓缩高效运行的对策

介绍了碱浓缩装置高温季节运行的现状，分析了影响高效运行的原因，并提出了在设备和工艺方面采取的措施。     

Preparation of high molecular weight poly(N‐vinylcarbazole) in high yield by low‐temperature precipitation polymerization of N‐vinylcarbazole

To produce high molecular weight poly(N‐vinylcarbazole) (PVCZ) with high conversion, N‐vinylcarbazole (VCZ) was heterogeneously polymerized in methanol at 30, 40 and 50 °C using a low temperature initiator, 2,2′‐azobis(2,4‐dimethylvaleronitrile) (ADMVN), and the effects of polymerization temperature and concentration of initiator and solvent on the polymerization behaviour and molecular parameters of PVCZ investigated. Globally, experimental results correspond to predicted ones. Low polymerization temperature using ADMVN and a heterogeneous system using methanol proved to be successful in obtaining poly(N‐vinylcarbazole) (PVCZ) of high molecular weight and high conversion with small temperature rise during polymerization, although free radical polymerization by azoinitiator was used. The polymerization rate of VCZ in methanol at 30 °C is proportional to the 0.88th power of ADMVN concentration. The molecular weight is higher and the molecular weight distribution is narrower with PVCZ polymerized at lower temperatures. For PVCZ produced in methanol at 30 °C using an ADMVN concentration of 0.0001 mol/mol of VCZ, a weight average molecular weight of 1 750 000 g mol⁻¹ is obtained, with a polydispersity index of 1.82 © 2000 Society of Chemical Industry     

Transient analysis of the steam‐water direct contact condensation in the packed column

The transient heat transfer behaviour of direct contact condensation of steam in spray cooling water in a packed column was investigated experimentally and theoretically in this work for the first time. A new analysis method of the state equation was applied to analyze the molar quantity variation of steam in the course of the experiment. The results showed that increasing the cooling water flow rate properly could significantly accelerate the steam condensation rate and this was more obvious at the beginning of the operation. The higher the flow rate of the cooling water was, the shorter a time it took for the steam to be completely condensed. When the cooling water flow rate was 840 L/h, the steam was mainly condensed within 13 s, which indicated that it would rapidly handle steam by regulating cooling water flow rate. However, the effect of changing cooling water temperature on steam condensation rate is slight with the cooling water temperature inceasing from 23 °C to 42 °C. The volumetric heat transfer coefficient in this experiment is in the range of 1.47 kW · m^?3 · K^?1 to 10.93 kW · m^?3 · K^?1 with the cooling water flow rate inceasing from 120 L/h to 840 L/h, and the maximum uncertainty in the results is 2.2 %.

     

Effect of temperature on the shear strength of aluminium single lap bonded joints for high temperature applications

An experimental and numerical investigation into the shear strength behaviour of adhesive single lap joints (SLJs) was carried out in order to understand the effect of temperature on the joint strength. The adherend material used for the experimental tests was an aluminium alloy in the form of thin sheets, and the adhesive used was a high-strength high temperature epoxy. Tensile tests as a function of temperature were performed and numerical predictions based on the use of a bilinear cohesive damage model were obtained. It is shown that at temperatures below T_g, the lap shear strength of SLJs increased, while at temperatures above T_g, a drastic drop in the lap shear strength was observed. Comparison between the experimental and numerical maximum loads representing the strength of the joints shows a reasonably good agreement.     

Preparation of carbon/carbon‐ultra high temperature ceramics composites with ultra high temperature ceramics coating

In order to increase the oxidation resistance of carbon/carbon (C/C) composites at long‐term high temperature, C/C‐Ultra High Temperature Ceramics composites (UHTCs) with a dual‐layer UHTCs oxidation coating was successfully designed and fabricated. The microstructure and ablation resistance were investigated and discussed. After ablation in arc‐heated wind tunnel with temperature being 2200°C for 1000s, the mass ablation rate and linear ablation rate were ?1.9 × 10^?2 mg/cm²s and 2.9 × 10^?5 mm/s, respectively. The formation of thermodynamically compatible oxide scale including ZrO₂ skeleton and SiO₂ or Zr–Si–O glass on the surface were mainly contributed to the excellent ablation resistance of the composite.     

Dyeing transition temperature of wools treated with low temperature plasma,liquid ammonia,and high‐pressure steam in dyeing with acid and disperse dyes

Wool fibers treated with oxygen low‐temperature plasma, liquid ammonia (NH₃), and high‐pressure (HP) steam were dyed with two acid and three disperse dyes. Rate of dyeing, saturation dye uptake, and dyeing transition temperature were measured. Rate of dyeing of the O₂ plasma, NH₃, and HP steam‐treated wools increased with acid dyes, whereas it did not increase with disperse dyes. Although dyeing transition temperature for acid dyes was decreased by the plasma, NH₃, and HP steam treatments, the temperature for disperse dyes was not changed by the treatments. Therefore, it seems that acid dyes penetrate by the intercellular diffusion through the interscale Cell Membrane Complex (CMC) of wool, whereas disperse dyes penetrate by the intracellular diffusion through the intrascale cuticle surface independently with CMC relaxation by the treatments. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1058–1062, 2001     

高颗粒通量循环流化床的构型作用

In order to achieve high solids circulation rate (G_s),an idea of coupling a moving bed to the bottom section of the riser of a circulating fluidized bed (CFB) was proposed and tested.The results from the preliminary study demonstrated that the solids circulation rate in the new-structure bed approached 370 kg·m^-2·s^-1 at superficial gas velocities around 10.5 m·s^-1 for sand particles with an average Sauter mean size of 378 μm.This study was devoted to further justifying the effects of the coupled moving bed by performing comparative studies in two CFBs with conventional configurations.It was shown that the pressure at the riser bottom and the realized solid circulation rate were only about 15 kPa and 230 kg·m^-2·s^-1 in the two conventionally configured CFBs,obviously lower than 25 kPa and 370 kg·m^-2·s^-1 in the moving bed coupled CFB.These verified that the coupled moving bed increased the force driving particles form the particle recycling side into the riser.The study further tested the effect of a few specially designed riser exit configurations,revealing that a smooth riser exit could facilitate solids circulation to increase the solids circulation rate.     

Anomalous heat capacity of high‐density polyethylene melts at high temperature

The first measurements of heat capacity of high‐density polyethylene have been obtained for melts in the high‐temperature region of 180–260°C. A heat‐flow twin calorimeter was used. Abrupt transitions are noticed at 212 and 228°C, analogous to transitions seen earlier with rheological and surface tension measurements. Possible explanations for these phenomena are offered. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Effect of ball milling on the hydrolysis of microcrystalline cellulose in hot‐compressed water

Ball milling leads to a considerable reduction in cellulose particle size and crystallinity, as well as a significant increase in the specific reactivity of cellulose during hydrolysis in hot‐compressed water (HCW). Cryogenic ball milling for 2 min also results in a significant size reduction but only little change in cellulose crystallinity and specific reactivity during hydrolysis. Therefore, crystallinity is the dominant factor in determining the hydrolysis reactivity of cellulose in HCW while particle size only plays a minor role. Ball milling also significantly influences the distribution of glucose oligomers in the primary liquid products of cellulose hydrolysis. It increases the selectivities of glucose oligomers at low conversions. At high conversions, the reduction in chain length plays an important role in glucose oligomer formation as cellulose samples become more crystalline. An extensive ball milling completely converts the crystalline cellulose into amorphous cellulose, substantially enhancing the formation of glucose oligomers with high degrees of polymerization. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

高温热处理对聚酰亚胺薄膜性能的影响

研究了高温热处理对聚酰亚胺(PI)薄膜拉伸性能和热性能的影响。在薄膜完全环化后,随着热处理温度的升高,薄膜的拉伸强度、弹性模量先增大后基本保持不变,断裂伸长率先保持不变后明显降低,热膨胀系数也显著降低,而薄膜的玻璃化转变温度略有增大。高温热处理工艺可制备高强度和低热膨胀系数的高性能PI薄膜。     

低温下UASB反应器处理高浓度有机废水的运行特性研究

采用配制的高浓度有机废水对7～25℃的低温条件下UASB反应器的运行进行了小试研究,考察了其运行状况和影响运行的特性参数.研究结果表明,只要维持温度在15.5～25℃且不发生突降、反应器pH值在6.8～7.2、进水碱度大于800 mg/L,即能保证UASB的稳定高效运行.其中反应器处理的最高容积负荷为9.5 kg[COD]/(m3·d)、甲烷菌产气率最高达每去除千克COD产气1.11 m3、COD的去除率稳定在60%以上、VFA小于400 mg/L.