老卤-碳铵法制备高纯氧化镁研究

以山东海化集团有限公司老卤（主要组分为氯化镁）和纯碱煅烧冷凝液（富含碳酸铵和碳酸氢铵）为原料制备高纯氧化镁。通过实验确定了老卤净化精制工艺条件：向老卤中加入氯化钙溶液生成硫酸钙沉淀以脱除老卤中的硫酸根,控制钙离子与硫酸根物质的量比为0.9~1.0时硫酸根的脱除效果较好。以净化精制后的老卤和纯碱煅烧冷凝液为原料,在反应温度为65 ℃、搅拌转速为70 r/min、老卤镁离子质量浓度为15 g/L条件下反应,再经热解、陈化合成碱式碳酸镁;碱式碳酸镁经过滤、洗涤、干燥,在900 ℃煅烧2 h,得到合格的高纯氧化镁。研究表明,以山东海化老卤和纯碱煅烧冷凝液为原料可制得高纯氧化镁。     

Degradation of poly(vinyl chloride). I. Kinetics of thermal and radiation-induced dehydrochlorination reactions at low temperatures

The dehydrochlorination reaction arising thermally and from exposure to γ-radiation has been followed, under vacuum, in the temperature range from 80° to 130°C by measuring the pressure of the evolved volatiles. The catalytic action of HCl, which was recently established, has been observed also at these low temperatures. In agreement with previous data, a free-radical mechanism has been accepted to be operating in the radiation-induced reaction, which has been found to be linearly dependent on dose rate and essentially independent of temperature. Assuming the thermal dehydrochlorination to proceed according to the same mechanism, its activation energy, lying within the range of values reported in the literature, represents the activation energy for the thermal process of radical formation by dissociation of normal and anomalous structures in PVC macromolecular chains. Since this value appears to be substantially constant in the temperature range from 90° to 240°C, it can be established whether the dissociation reactions of all the PVC structures are regulated by the same activation energy or, more simply, only one of these structures is concerned.     

碱式氯化镁纳米棒的干燥动力学研究

以六水氯化镁和轻质氧化镁为原料,采用液相法制得长度约为10μm、直径为100～150hm的碱式氯化镁纳米棒。通过干燥动力学实验得到碱式氯化镁纳米棒的干燥曲线和干燥速率曲线。采用薄层干燥模型及热分析动力学对干燥动力学实验数据进行数学处理,获得碱式氯化镁纳米棒的干燥方程、干燥速率方程、指前因子A和表观活化能E。     

氧化镁蒸氨反应的动力学和机理研究

以轻烧粉和氯化铵反应为出发点,研究了氧化镁蒸氨反应过程的动力学和反应机理。结果表明：当反应30 min时,70~90 ℃条件下溶液中镁离子浓度约为0.14 mol/L,100 ℃时浓度为0.5 mol/L。XRD结果表明,蒸氨过程中未反应生成Mg2+的氧化镁以氢氧化镁存在于滤渣中。随着煅烧温度的升高,氧化镁水化反应活化能逐渐增加。当煅烧温度为600 ℃时,反应活化能为64.789 9 kJ/mol;当煅烧温度为800 ℃时,反应活化能为81.350 6 kJ/mol。氢氧化镁和氧化镁按不同物质的量比混合进行蒸氨反应时,蒸氨速率随体系中氢氧化镁含量的增加而升高。氧化镁蒸氨体系可分为2个阶段：第一阶段,氧化镁在铵盐体系中进行水化反应生成氢氧化镁,同时部分氧化镁和氢氧化镁进行蒸氨反应生成镁离子;第二阶段,整个体系完全变成氢氧化镁蒸氨体系。     

A polycarbonate/magnesium oxide nanocomposite with high flame retardancy

A new flame retardant polycarbonate/magnesium oxide (PC/MgO) nanocomposite, with high flame retardancy was developed by melt compounding. The effect of MgO to the flame retardancy, thermal property, and thermal degradation kinetics were investigated. Limited oxygen index (LOI) test revealed that a little amount of MgO (2 wt %) led to significant enhancement (LOI = 36.8) in flame retardancy. Thermogravimetric analysis results demonstrated that the onset temperature of degradation and temperature of maximum degradation rate decreased in both air and N₂ atmosphere. Apparent activation energy was estimated via Flynn–Wall–Ozawa method. Three steps in the thermal degradation kinetics were observed after incorporation of MgO into the matrix and the additive raised activation energies of the composite in the full range except the initial stage. It was interpreted that the flame retardancy of PC was influenced by MgO through the following two aspects: on the one hand, MgO catalyzed the thermal‐oxidative degradation and accelerated a thermal protection/mass loss barrier at burning surface; on the other hand, the filler decreased activation energies in the initial step and improved thermal stability in the final period. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

机械力强化作用下轻烧氧化镁碳化过程的传质与反应动力学研究

The carbonization of magnesium oxide particles by CO2 was investigated using a stirring mill reactor. The effects of the system temperature, stirring rotation speed, influx rate of CO2 and initial diameter of the magnesium oxide particles on the carbonization process were determined, The results show that the system temperature and the stirring rotation speed are the most significant influencing factors on the carbonization rate. The determi-nation of critical decomposition temperature (CDT) gives the maximum carbonization rate with other conditions fixed. A theoretical model involving mass transfer and reaction kinetics was presented for the carbonization process. The apparent activation energy was calculated to be 32.8kJ·mol-1. The carbonization process is co-controlled by diffusive mass transfer and chemical reaction. The model fits well with the experimental results.     

液体PVC热稳定剂异辛酸镁/锌制备及应用性能研究

用氢氧化镁、氧化锌、异辛酸为原料制备了异辛酸镁、异辛酸锌,将其作为一种新型液体聚氯乙烯（PVC）热稳定剂用于本试验中。采用热老化烘箱法、刚果红法和电导率法研究了异辛酸镁/锌在PVC制品中的静态热稳定性能,并探究了异辛酸镁和异辛酸锌之间的协同效应。采用热重分析技术分别考察了PVC试片在180℃条件下恒温60min的热损失变化情况及25℃～600℃范围内,以10℃/min等速升温过程中的热损失变化情况。结果表明：当镁与锌的金属含量分别为2%和2.5%时,PVC的热稳定时间可达50min,远远超出市售钙/锌的30min,其静态热稳定效果最优。通过动态双辊塑炼和力学性能试验,表明异辛酸镁/锌对PVC制品具有优良的动态热稳定性能和突出的力学性能。     

氯化镁喷雾热解制备氧化镁的研究

以青海盐湖氯化镁为初级原料,氯化镁经溶解、除杂、精制后采用喷雾热解法在立式热解炉中热解制备氧化镁。着重研究了喷雾热解的温度和进料量对氯化镁分解率的影响,最终确定的最佳工艺条件为：喷雾热解制备氧化镁时氯化镁的最佳热解温度为600 ℃,进料量为12 L/h。最佳工艺条件下氯化镁分解率在99%以上。该方法工艺流程简单、便于操作,是一种很有应用前景的氧化镁生产方法。     

轻烧菱镁矿制备高纯纳米氧化镁

以轻烧菱镁矿为原料,通过酸浸去除杂质得到纯净的含镁溶液,以草酸为沉淀剂,采用直接沉淀法制备纳米氧化镁粉体。考察了草酸和氧化镁的摩尔比、反应温度、前驱体草酸镁热分解温度及时间对纳米氧化镁粒径大小的影响。采用热重-差热分析仪、激光粒度仪、X射线衍射仪、扫描电子显微镜等对前驱体的热分解情况、产品的粒径及晶型结构进行检测。结果表明:合成的氧化镁粉体的粒径分布较窄,分散性良好,平均粒径在80nm左右,纯度达到99.1%。     

Thermogravimetry and decomposition kinetics of British Kimmeridge Clay oil shale

The characteristics of volatile matter evolution and the kinetics of thermal decomposition of British Kimmeridge Clay oil shale have been examined by thermogravimetry. TG has provided an alternative to the Fischer assay for shale grade estimation. The following relation has been derived relating TG % volatiles yield to the shale gravimetric oil yield: oil yield (g kg^?1) = (TG volatiles, % × 5.82) ? 28.1 ± 14.5 g kg^?1. A relationship has also been established for volumetric oil yield estimation: oil yield (cm³ kg^?1) = (TG volatiles, % × 4.97) – 5.43. TG is considered to give a satisfactory estimation of shale oil yield except in certain circumstances. It is found to be less reliable for low yield shales producing <≈40 cm³ kg^?1 of oil (≈10 gal ton^?1) where oil content of the TG volatiles is low: volumetric yield estimation accuracy is affected by variations in shale oil specific gravity. First order rate constants, k = 4.82 × 10^?5s^?1 (346.3 cm³ kg^?1shale) and k = 6.78 × 10^?5s^?1 (44.6cm³ kg^?1shale) have been obtained for the devolatilization of two Kimmeridge oil shales at 280 °C using isothermal TG. Using published pre-exponential frequency factors, an activation energy of ≈57.9 kJ mol^?1 is calculated for the decomposition. Preliminary kinetic studies using temperature programmed TG suggest at least a two stage process in the thermal decomposition, with two maxima in the volatiles evolution rate at ≈450 and 325 °C being obtained for some samples. Use of published pre-exponential frequency factors gives activation energies of ≈212 and 43 kJ mol^?1 for these two stages in the decomposition.     

Kinetics and Activation Energy of Magnesium Oxide Hydration

The kinetics of hydration of magnesium oxide (MgO) powder to form magnesium hydroxide (Mg(OH)₂) were measured using isothermal calorimetry at different temperatures, and the morphology of the powders before and after hydration were examined. The hydration kinetics of light‐burned MgO exhibit a hydration rate peak similar to that of portland cement hydration, whereas the hydration kinetics of hard‐burned MgO are comparatively slower at the same temperature, and exhibit a continuously declining hydration rate after the first several minutes of reaction. The hydration kinetics of both light‐burned and hard‐burned MgO can be fit using a boundary nucleation and growth model that has previously been applied to the hydration of portland cement and tricalcium silicate. Activation energy values for MgO hydration were determined from the fitted rate constants and were also measured directly using small temperature excursions according to a recently proposed method. For light‐burned MgO the resulting values are in good agreement and indicate a value of 77 kJ/mol. For the hard‐burned MgO the activation energy values vary considerably depending on temperature and how the activation energy is measured, but are always lower than the value obtained for the light‐burned MgO.     

Thermal behavior and morphological properties of novel magnesium salt–polyacrylamide composite polymers

Magnesium salt–polyacrylamide composite polymers have been prepared by blending magnesium chloride and magnesium hydroxide, respectively, with polyacrylamide aqueous solution. The thermal behavior of the dried magnesium salt–polyacrylamide composite polymers has been studied. Differential scanning calorimetric (DSC) analysis and thermal gravimetric analysis (TGA) were carried out to investigate the changes of the composite polymers' behavior with temperature. The kinetics of the thermal decomposition of magnesium salt–polyacrylamide composite polymers was investigated over temperature range of 35–800°C with three heating rates of 10, 20, and 40°C/min under nitrogen atmosphere. Flynn and Wall's model was usedto determine the activation energies of thermal decomposition for magnesium salt–polyacrylamide composite polymers. The activation energies needed to decompose 50 wt% of magnesium hydroxide‐polyacrylamide (MHPAM) composite polymer ranged from of 28.993–174.307 kJ/mol which are higher than the values for magnesium chloride–polyacrylamide (MCPAM) composite polymer (21.069–39.412 kJ/mol). Therefore, MHPAM composite polymer has a better thermal stability compared with MCPAM composite polymer. The morphological properties of magnesium salt–polyacrylamide composite polymers were studied using scanning electron microscopy (SEM). Energy‐dispersive X‐ray (EDX) spectroscopy was used to determine the composition of the chemical elements. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

基于高温环境下高绝缘高响应性铠装热电偶的研究

介绍了一种以新型高温混合材料作为铠装热电偶的绝缘材料,通过大量试验验证了封装后的热电偶传感器具有较高的测量精度、长期热电势稳定性、高绝缘性和较短的热响应时间,能够满足高温、高响应性测量要求。在1 000℃的情况下测量,其性能不亚于以氧化镁作为绝缘材料的产品,因此可应用于工业生产和科学研究中。     

Surface properties of magnesium oxide obtained from basic magnesium carbonate: Influence of preparation conditions of magnesium carbonate

Surface area, total basicity and base strength distribution (weak, strong and intermediate strength basic sites) of magnesium oxide obtained from basic magnesium carbonate (by its decomposition at 873 K) prepared by precipitation using different magnesium slats, precipitating agents and precipitating conditions (viz. concentration of magnesium salt. pH, temperature, mode of mixing and ageing period) have been thoroughly investigated. The total basicity and base strength distribution of the different magnesium oxide samples have been determined by step-wise thermal desorption of carbon dioxide from 323 to 1253 K. The chemical composition of basic magnesium carbonate and the surface properties and carbon dioxide content of magnesium oxide are found to be strongly influenced by the aforementioned preparation conditions of basic magnesium carbonate.     

Coal volatile yield and element partition in rapid pyrolysis

The volatile yields from thirteen coals, varying in rank from lignite to anthracite, were measured under conditions of high heating rate (10⁵Ks^?1) and high temperature (1600–2400 K) representative of pulverized coal combustion and were related to coal characteristics as determined in standard laboratory tests. Positive correlations with coal reflectance and elemental composition were obtained. The distribution of coal elements between the volatiles and residual char was also investigated. The results show that hydrogen and oxygen from the coal are preferentially distributed in the volatile phase. Coal nitrogen evolution parallels the total volatiles at high temperature, whereas coal sulphur is preferentially retained in the char and no relationship between S evolution and coal rank is evident. These results are discussed in relation to the prevalent active groups in the various ranks of coal.     

白云石制备高纯氧化镁的工艺研究

以白云石为原料,通过煅烧、消化、硫酸酸浸、过滤得硫酸镁溶液,采用氨水沉淀法制备氢氧化镁中间体,经煅烧得高纯氧化镁。研究了加入硫酸后白云石灰乳终点pH、反应温度、硫酸镁浓度和煅烧温度对镁的浸出率、沉淀率以及产品氧化镁纯度的影响,最终确定最佳工艺条件为：灰乳终点pH为6,反应温度为40 ℃,硫酸镁浓度为0.8 mol/L,煅烧温度为900 ℃。在此条件下制备的氧化镁纯度达到99.0%以上,满足高纯氧化镁的要求。     

卤水中氧化镁提取工艺研究

采用卤水－纯碱法,向经过净化的卤水中加入碳酸钠,制取碱式碳酸镁,经过煅烧得到氧化镁。实验结果表明：反应浓度O．13mol／L、反应温度40℃、加科速度5mL／min、陈化时间1h时卤水的净化效果较好。原料配比110％、反应温度60℃、反应时间30min时氧化镁的收率较好。     

Thermal decomposition behavior of carbon nanotube reinforced thermotropic liquid crystalline polymers

Thermotropic liquid crystalline polymers (TLCP), 4‐hydroxybenzoic acid (HBA)/6‐hydroxyl‐2‐naphthoic acid (HNA) copolyester, and HNA/hydroxylbenzoic acid (HAA)/terephthalic acid (TA) copolyester reinforced by carbon nanotube (CNT) were prepared by melt compounding using Hakke internal mixer. The thermal behavior and degradation of CNT reinforced HBA/HNA copolyester and HNA/HAA/TA copolyester have been investigated by dynamic thermogravimetric analysis under nitrogen atmosphere in the temperature range 30 to 800°C to study the effect of CNT on the thermal decomposition behavior of the TLCP/CNT nanocomposites. The thermal decomposition temperature at the maximum rate, residual yield, integral procedural decomposition temperature, and activation energy for thermal decomposition was studied to investigate thermal stability of TLCP/CNT nanocomposites. The thermal stability of CNT reinforced HBA/HNA copolyester was increased by addition of a very small quantity of CNT and the residual weight was 42.4% and increased until 50.8% as increasing CNT contents. However, the thermal stability of CNT reinforced HNA/HAA/TA copolyester was decreased initially when a very small quantity of CNT added. The residual weight was decreased from 50.4% to 45.1%. After addition of CNTs in the TLCP matrix, the thermal stability of CNT reinforced HNA/HAA/TA copolyester increased as increasing content of CNT and the residual weight was increased until 53% as increasing CNT contents. The activation energy was calculated by multiple heating rate equations such as Friedman, Flynn‐Wall‐Ozawa, Kissinger, and Kim‐Park methods to confirm the effect of CNT in two different TLCP matrices. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

A study on the pyrolysis of asphalt

The pyrolysis of asphalt has been studied using thermogravimetric analysis at atmospheric pressure and with nitrogen as the ambient gas. The heating rates ranged from 50 or 80 °C min⁻¹ to a final temperature of 650 °C. A two-stage first-order model is established to describe the pyrolysis of asphalt. In the model, the activation energy, E, is different for each stage, but is independent of the type of asphalt and its heating rate. The frequency factor depends on the heating rate and is independent of the asphalt. The final yield of volatiles depends on the type of asphalt. The modeled results agree with the experimental measurements, so the model is reasonable.     

高硫煤泥燃烧过程中的汞排放特性

通过固定床程序升温汞脱附试验系统对所选高硫煤泥中汞排放特性进行在线监测,并利用热重分析仪对煤泥热解和燃烧特性进行研究,结合试验所得热解和燃烧特性参数,采用分布活化能模型,进行动力学分析。结果表明：煤泥的热解和燃烧过程可分为3个阶段,非等温条件下,随着升温速率增加,热解过程在高温区发生,最大失重率提升,对应峰值温度偏移,产生热滞后,利于挥发分析出;在煤泥热解过程中少量氧气的参与,抑制挥发分的析出,在7% O₂条件下综合热解特性参数值D最大。热解性能随CO₂浓度升高而得到改善;煤泥燃烧性能随升温速率的增加而得到加强,其活化能随转化率变化呈现“U”型趋势分布;煤泥中无机汞化合物主要为HgCl₂、α-HgS、HgSO₄以及硅铝酸盐类结合汞,总汞释放主要范围对应200~600℃;煤泥中汞释放量随O₂浓度增大,CO₂气氛条件下,随着CO₂浓度增加,总汞释放量逐渐增大。