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1.
使用分析纯CaCO3、Al2O3与CaSO4·2H2O配料,在1375℃、保温2 h的条件下合成了纯物相硫铝酸钙3CaO·3Al2O3·CaSO4(C4A3S),对其物相组成和微观形貌进行了表征。并探究了碳碱浓度、苛碱浓度、溶出温度、溶出时间、粒度等因素对C4A3S氧化铝溶出性能的影响。结果表明:C4A3S的氧化铝溶出性能随着碳碱与苛碱浓度的增加先提高,之后趋于稳定。粒度越小,溶出率越高。与七铝酸十二钙12CaO·7Al2O3(C12A7)相比,C4A3S的孔洞状结构使其氧化铝更易溶出,在10 min时氧化铝溶出率即达到98%以上,且溶出所需的碳碱浓度与溶出温度均低于C12A7。在最佳条件:碳碱80 g·L-1、苛碱10 g·L-1、溶出温度80℃、溶出时间10 min下,C4A3S的氧化铝溶出率为98.76%。 相似文献
2.
使用分析纯MgO、CaCO3、SiO2、Al2O3与Na2SO4在1350℃保温1 h合成了掺杂Na2SO4的含MgO铝酸钙熟料,在Na2CO3溶液体系下研究了其氧化铝浸出性能,通过XRD等分析手段对其晶体结构和自粉化性能进行了研究。结果表明,Na2SO4可以显著提升铝酸钙熟料的浸出性能,Na2SO4掺杂量由0%提高到4%,熟料的氧化铝浸出率由61.89%提高到92.01%,继续添加Na2SO4,浸出性能趋于稳定。由XRD结果可知,Na2SO4促使20CaO·13Al2O3·3MgO·3SiO2(Q相)发生分解并使其转变为12CaO·7Al2O3(C12A7)。Na+进入C12A7晶格引起晶格畸变,从而提高C12A7的氧化铝浸出性能。Na2SO4的加入降低了熟料的自粉化性能,Na2SO4掺杂量由0%提高到6%,熟料的自粉率由97.46%下降到85.34%,当Na2SO4掺杂量达到10%后,熟料自粉率仅为36.3%。 相似文献
3.
以分析纯试剂CaCO3、Al2O3和Na2CO3为原料,在1350℃烧结1 h合成了Na2O掺杂铝酸钙熟料,并采用XRD、SEM和EDS等方法研究了Na2O掺杂CaO-Al2O3体系铝酸钙化合物的物相演变规律及熟料浸出性能。结果表明:当CaO和Al2O3的摩尔比为1.0时,CaO-Al2O3体系铝酸钙由CaO·Al2O3和12CaO·7Al2O3组成,而Na2O掺杂铝酸钙熟料由CaO·Al2O3、12CaO·7Al2O3、Na2O·Al2O3和Na4Ca3(AlO2)10组成。除形成含Na2O化合物外,熟料中掺杂的Na2O固溶于12CaO·7Al2O3中,而CaO·Al2O3中几乎不含Na2O。随着熟料中Na2O掺杂量的升高,12CaO·7Al2O3和Na4Ca3(AlO2)10的含量逐渐增加,CaO·Al2O3的含量逐渐降低;12CaO·7Al2O3和Na4Ca3(AlO2)10的结晶度逐渐降低,CaO·Al2O3的结晶度逐渐升高。Na2O的掺杂提高了熟料在碳酸钠溶液中的浸出性能,并且使浸出渣中CaCO3的空间群由R-3CH、P63/MMC两种转变为只含有R-3CH一种。 相似文献
4.
含氧化铝类的废催化剂的危险废物热值低,灰分大,直接焚烧处理成本高,若是将其中的氧化铝转化为三氯化铝进行利用,进行PAC的生产,具有较大的社会和经济效益。研究了不同的废氧化铝催化剂的粒径及不同的Al2O3与HCl的摩尔比的废氧化铝催化剂中氧化铝的溶出效率、溶出的氧化铝能否制造合格的PAC成品及溶出氧化铝后的滤渣中和后能否直接填埋。实验表明:当粒径≤250目时,氧化铝的溶出率为95.85%;当该废催化剂Al2O3与盐酸的摩尔比为1∶1.2时溶出效率为96.25%;溶出的氧化铝可以生产PAC,且生产出的PAC符GB/T 22627—2022《水处理剂聚氯化铝》标准;滤渣经中和后符合GB 18598-2019 《危险废物填埋污染控制标准》,可以直接进行填埋。 相似文献
5.
Ca2Mg2Al28O46 (C2M2A14)耐火材料具有优异的高温使用性能,为了将这类耐火材料应用在高温窑炉,本工作采用高温固相反应烧结法合成了三元化合物C2M2A14,研究了烧成温度及添加1%(质量分数) Fe2O3对试样相组成演变与组构及其致密化进程的影响。结果表明:C2M2A14在1 650℃由六铝酸钙(CA6)与尖晶石反应生成,在1 750℃大量生成,随着六方板状CA6转化为多面体C2M2A14和低共熔液相的出现,致密化进程加快。加入Fe2O3后,由原来(1,1,15)晶面择优取向的六方板状晶体转变为... 相似文献
6.
本文以Fe2O3、l2O3粉体为原料,在室温进行高能球磨,然后热压烧结制备(Fe,Al)2O3单相固溶体。对单相固溶体在H2气氛下进行热处理,使固溶的Fe选择性还原析出为分散于Al2O基体中的金属颗粒。利用XRD、TEM分析还原产物,研究还原产物的物相,并观察还原后铁在氧化铝基体中的分布情况。 相似文献
7.
新法铝热炼镁工艺以白云石和菱镁石为原料、以铝粉为还原剂,在真空还原获得金属镁的同时得到富含CaO·2Al2O3的还原渣,该还原渣可通过氢氧化钠和碳酸钠的混合碱液溶出得到铝酸钠溶液,并通过碳酸化分解制备氢氧化铝。以该工艺所得还原渣为原料,系统地研究各溶出条件对氧化铝溶出率的影响,并对碳分所得氢氧化铝进行性能检测。结果表明,在氢氧化钠浓度80 g·L-1、碳碱浓度110 g·L-1、溶出时间120 min、溶出温度95℃、液固比为6的条件下,炼镁还原渣中氧化铝的溶出率在85%以上。氢氧化铝产品白度均大于98,平均粒径为26.98 μm,能够达到高白氢氧化铝的要求。 相似文献
8.
与传统金属材料相比,氧化铝纤维增强氧化铝基(Al2O3/Al2O3)复合材料因具有比强度高、密度低、耐高温和抗氧化等特点,已经成为新一代备受国内外学者关注的航空航天热结构复合材料。本文介绍了目前常用的氧化铝纤维及其基本性能,总结了Al2O3/Al2O3复合材料中常用的界面相及其对复合材料性能的影响规律,归纳了Al2O3/Al2O3复合材料的制备工艺及性能,指出了该材料未来的发展趋势,旨在为国内Al2O3/Al2O3复合材料的研究提供借鉴和参考,促进Al2O3/Al2O3复合材料在航空航天领域热端高温部件上的广泛应用。 相似文献
9.
以Al4SiC4为原料、Y2O3为添加剂,采用无压烧结制备Y3Al5O12–Al4Si C4复合耐火材料,研究Y2O3添加量[0~5%(质量分数)]对复合材料物相组成、微观形貌与力学性能的影响,并通过DFT模拟计算Y3+对Al4Si C4不同晶面表面能的影响。结果表明:高温下Y2O3与Al4SiC4表面固有氧化层形成共晶液相,在复合材料晶界处生成Y3Al5O12和少量Y2SiO5。Y2O3的添加促使Al4Si C4... 相似文献
10.
通过固定床反应器,对4种金属氧化物(Al2O3、MgO、CaO、Fe2O3)对油页岩热解所得油、气产率及成分的影响进行了研究。结果显示,碱性CaO对油、水、气、焦产率分布影响较为突出,可提高页岩油与半焦产率,并降低热解气产率;而酸性较强的Al2O3可同时提高页岩油、热解气和热解水的产率,有利于促进挥发分的析出;比较而言,MgO和Fe2O3的作用相对较弱。4种金属氧化物均可提高热解气中H2、CH4和C2的产率;CaO作用下CO2含量降低,而其他金属氧化物对CO2的产生有不同程度的促进作用;Fe2O3可促进H2产生;Al2O3作用下CH4含量有所增加。4种金属氧化物均可促进页岩油中芳香烃的产生,并且CaO和MgO两种碱土金属氧化物作用下,短链(C6~C12)烷烃和烯烃含量均增加,而掺混Al2O3时页岩油中仅短链(C6~C12)烷烃含量增加。对此机理进行推测认为,碱性CaO和MgO首先与以脂肪酸形式存在的有机质进行酸碱反应,得到脱羧活性更高的羧酸盐,后者脱羧所得中间产物具有生成烷烃或烯烃两条可能路径,同时得到碳酸盐;而在具有Lewis酸特征的Al2O3作用下,脱羧产物为CO2,并同时得到饱和烃产物。 相似文献
11.
Two types of nanocalcium aluminate powders containing 70 and 60 wt.% Al2O3 were prepared by thermal decomposition and investigated in terms of mineralogical composition, hydration, mechanical properties and microstructure. The results revealed that S1 is composed mainly of the CA and CA2 phases, while S2 composed of CA and C12A7 phases after heat-treatment at 1000 °C. The maximum crystallite sizes for S2 and S1 were 44 and 52 nm and the minimum ones 12 and 19, respectively. Both samples still have small crystallite size after heat-treatment at 1000 °C. The present phases, i.e. CA, CA2 and C12A7 affect the properties of hydrated and sintered ceramic bodies. S2 hydrated sample achieved higher strength (58.5 MPa) than S1 (52.4 MPa). The higher strength of S2 is ascribed to the presence of CA and C12A7 as a major component, since it reacts rapidly with water. In S1, the poor hydration of CA2 at the early stage of hydration lowers strength after 7 days hydration as compared with S2. Cold crushing strength (CCS) data of the sintered ceramics bodies exhibit high strength of both samples after firing at 1550 and 1450 °C for S1 and S2, respectively. This is due to the formation of a ceramic bond. 相似文献
12.
The effectiveness of Ag/Al2O3 catalyst depends greatly on the alumina source used for preparation. A series of alumina-supported catalysts derived from AlOOH, Al2O3, and Al(OH)3 was studied by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), ultraviolet–visible (UV–vis) spectroscopy, diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, O2, NO + O2-temperature programmed desorption (TPD), H2-temperature programmed reduction (TPR), thermal gravimetric analysis (TGA) and activity test, with a focus on the correlation between their redox properties and catalytic behavior towards C3H6-selective catalytic reduction (SCR) of NO reaction. The best SCR activity along with a moderated C3H6 conversion was achieved over Ag/Al2O3 (I) employing AlOOH source. The high density of Ag–O–Al species in Ag/Al2O3 (I) is deemed to be crucial for NO selective reduction into N2. By contrast, a high C3H6 conversion simultaneously with a moderate N2 yield was observed over Ag/Al2O3 (II) prepared from a γ-Al2O3 source. The larger particles of AgmO (m > 2) crystallites were believed to facilitate the propene oxidation therefore leading to a scarcity of reductant for SCR of NO. An amorphous Ag/Al2O3 (III) was obtained via employing a Al(OH)3 source and 500 °C calcination exhibiting a poor SCR performance similar to that for Ag-free Al2O3 (I). A subsequent calcination of Ag/Al2O3 (III) at 800 °C led to the generation of Ag/Al2O3 (IV) catalyst yielding a significant enhancement in both N2 yield and C3H6 conversion, which was attributed to the appearance of γ-phase structure and an increase in surface area. Further thermo treatment at 950 °C for the preparation of Ag/Al2O3 (V) accelerated the sintering of Ag clusters resulting in a severe unselective combustion, which competes with SCR of NO reaction. In view of the transient studies, the redox properties of the prepared catalysts were investigated showing an oxidation capability of Ag/Al2O3 (II and V) > Ag/Al2O3 (IV) > Ag/Al2O3 (I) > Ag/Al2O3 (III) and Al2O3 (I). The formation of nitrate species is an important step for the deNOx process, which can be promoted by increasing O2 feed concentration as evidenced by NO + O2-TPD study for Ag/Al2O3 (I), achieving a better catalytic performance. 相似文献
13.
针对建筑工程中混凝土构件表面出现的点状爆裂现象,对出现爆裂的混凝土构件进行采样,通过XRD分析确定了样品的主要组成有CaO、C3A、C12A7、Ca(OH)2等矿物,结合样品的DSC/TGA定量分析数据,确定了导致混凝土点状爆裂的主要原因是CaO水化生成Ca(OH)2体积膨胀导致的;此外,混凝土中的C12A7与找平材料(主要指石膏)中的CaSO4·2H2O会水化生成AFt,也会导致混凝土开裂,因此,在混凝土抹面后点状爆裂现象会集中出现。采用乙二醇-EDTA化学滴定法测定样品游离总钙,结合DSC/TGA定量分析结果,发现爆裂中心底层未粉化骨料中f-CaO含量依然较高,解释了工程中采用当前修补方式修补后混凝土继续爆裂的原因。 相似文献
14.
Chuanhua He Martin Paulus Wei Chu Josef Find Julius A. Nickl Klaus Khler 《Catalysis Today》2008,131(1-4):305-313
A series of CoOx/Al2O3 catalysts was prepared, characterized, and applied for the selective catalytic reduction (SCR) of NO by C3H8. The results of XRD, UV–vis, IR, Far-IR and ESR characterizations of the catalysts suggest that the predominant oxidation state of cobalt species is +2 for the catalysts with low cobalt loading (≤2 mol%) and for the catalysts with 4 mol% cobalt loading prepared by sol–gel and co-precipitation. Co3O4 crystallites or agglomerates are the predominant species in the catalysts with high cobalt loading prepared by incipient wetness impregnation and solid dispersion. An optimized CoOx/Al2O3 catalyst shows high activity in SCR of NO by C3H8 (100% conversion of NO at 723 K, GHSV: 10,000 h−1). The activity of the selective catalytic reduction of NO by C3H8 increases with the increase of cobalt–alumina interactions in the catalysts. The influences of cobalt loading and catalyst preparation method on the catalytic performance suggest that tiny CoAl2O4 crystallites highly dispersed on alumina are responsible for the efficient catalytic reduction of NO, whereas Co3O4 crystallites catalyze the combustion of C3H8 only. 相似文献
15.
采用纯γ-氧化铝和改性氧化铝(2.5%La2.5%Ba/Al2O3)为担体,经550 ℃,950 ℃不同温度煅烧后分别负载钯、铑,制备成系列催化活性材料,通过贵金属分散度分析、TPR氧化还原特性分析,研究了氧化铝制备条件对催化活性的影响。结果表明,改性氧化铝上的贵金属分散性优于纯γ-氧化铝,Rh3+与2.5%La2.5%Ba/Al2O3间的相互作用强于Pd2+,从而具有更高的分散度;钯在高温处理后的2.5%La2.5%Ba/Al2O3上的分散性更优,铑则相反。通过TPR还原特性分析认为,贵金属在950 ℃煅烧后的2.5%La2.5%Ba/Al2O3上的低温还原活性更佳,钯与2.5%La2.5%Ba/Al2O3结合的低温还原活性优于铑。 相似文献
16.
The selective catalytic reduction (SCR) of NO by C3H6 in excess oxygen was evaluated and compared over Ag/Al2O3 and Cu/Al2O3 catalysts. Ag/Al2O3 showed a high activity for NO reduction. However, Cu/Al2O3 showed a high activity for C3H6 oxidation. The partial oxidation of C3H6 gave surface enolic species and acetate species on the Ag/Al2O3, but only an acetate species was clearly observed on the Cu/Al2O3. The enolic species is a more active intermediate towards NO + O2 to yield—NCO species than the acetate species on the Ag/Al2O3 catalyst. The Ag and Cu metal loadings and phase changes on Al2O3 support can affect the activity and selectivity of Ag/Al2O3 and Cu/Al2O3 catalysts, but the formation of enolic species is the main reason why the activity of the Ag/Al2O3 catalyst for NO reduction is higher than that of the Cu/Al2O3 catalyst. 相似文献
17.
Effect of additives, In2O3, SnO2, CoO, CuO and Ag, on the catalytic performance of Ga2O3–Al2O3 prepared by sol–gel method for the selective reduction of NO with propene in the presence of oxygen was studied. As for the reaction in the absence of H2O, CoO, CuO and Ag showed good additive effect. When H2O was added to the reaction gas, the activity of CoO-, CuO- and Ag-doped Ga2O3–Al2O3 was depressed considerably, while an intensifying effect of H2O was observed for In2O3- and SnO2-doped Ga2O3–Al2O3. Of several metal oxide additives, In2O3-doped Ga2O3–Al2O3 showed the highest activity for NO reduction by propene in the presence of H2O. Kinetic studies on NO reduction over In2O3–Ga2O3–Al2O3 revealed that the rate-determining step in the absence of H2O is the reaction of NO2 formed on Ga2O3–Al2O3 with C3H6-derived species, whereas that in the presence of H2O is the formation of C3H6-derived species. We presumed the reason for the promotional effect of H2O as follows: the rate for the formation of C3H6-derived species in the presence of H2O is sufficiently fast compared with that for the reaction of NO2 with C3H6-derived species in the absence of H2O. Although the retarding effect of SO2 on the activity was observed for all of the catalysts, SnO2–Ga2O3–Al2O3 showed still relatively high activity in the lower temperature region. 相似文献