添加Y2O3对CaO-MgO-SiO2体系中CMS的影响

为了提高镁质耐火材料的高温性能,以分析纯化学试剂MgO、CaO、SiO₂、Y₂O₃等为主要原料,研究了添加Y₂O₃对CaO-MgO-SiO₂体系中钙镁橄榄石(CMS)的生成和转化的影响,以及转化生成物Ca₄Y₆O(SiO₄)₆的耐火度。结果表明：1)Y₂O₃的添加不仅能够显著减少CaO-MgO-SiO₂体系中低熔点相CMS的生成量,而且能够从CMS中捕获CaO和SiO₂使CMS转化为高熔点相Ca₄Y₆O(SiO₄)₆、MgO和Y₂Si₂O₇,有利于提高镁质材料的高温性能。2)Ca₄Y₆O(...     

CaO杂质对SiO2凝胶粉与Al2O3粉反应生成莫来石的影响

为拓宽SiO₂溶胶结合浇注料的应用,以微米或纳米级Al₂O₃粉和SiO₂凝胶粉为主要原料,研究在不同温度(1 350、1 400、1 500、1 600℃)、不同气氛(氧化气氛、还原气氛)下CaO杂质对Al₂O₃和SiO₂反应生成莫来石的影响。结果表明：1)氧化气氛下,CaO的引入可以促进莫来石的生成,当温度从1 350℃升高到1 600℃时,莫来石的生成量会逐渐增多。2)还原气氛下,CaO的引入不利于莫来石的生成,温度升高,莫来石生成量反而降低。3)Al₂O₃粒度越小,越易与SiO₂凝胶粉反应生成莫来石。     

TiO2与SiO2掺杂对Al2O3相转变的研究

通过球磨混合法,制备TiO₂、SiO₂和TiO₂+SiO₂掺杂的Al₂O₃粉体,经不同温度煅烧后进行X射线衍射(XRD)测试,比较研究这三种掺杂对Al₂O₃粉体相转变温度的影响。研究结果表明,TiO₂、SiO₂掺杂对γ-Al₂O₃向α-Al₂O₃的相转变均有促进作用。在掺杂质量分数为0.5%的情况下,二者可分别使γ-Al₂O₃完全转变为α-Al₂O₃的温度降低100 ℃和125 ℃。而TiO₂+SiO₂复合掺杂对γ-Al₂O₃向α-Al₂O₃相转变的促进作用优于TiO₂、SiO₂单独掺杂。TiO₂、SiO₂的质量分数均为0.3%时,复合掺杂可使γ-Al₂O₃完全转变为α-Al₂O₃的温度降低150 ℃。此外,还对TiO₂、SiO₂和TiO₂+SiO₂掺杂促进Al₂O₃粉体相转变的机理作了简单分析。     

二氧化硅负载磷钨酸催化合成丁醛乙二醇缩醛

本文以二氧化硅负载磷钨酸(H₃PW₁₂O₄₀/SiO₂)为催化剂,丁醛和乙二醇为原料合成丁醛乙二醇缩醛,探讨了H₃PW₁₂O₄₀/SiO₂/SiO₂对缩醛反应的催化活性,研究了醛醇物质的量比、催化剂用量、反应时间等因素对产物收率的影响。实验结果表明:H₃PW₁₂O₄₀/SiO₂/SiO₂是合成丁醛乙二醇缩醛的良好催化剂。在固定丁醛用量为0.2mol的情况下,n（丁醛）:n（乙二醇）=1:1.4,催化剂的用量占反应物料总质量的1%,环已烷用量为4mL,反应时间为45min的条件下,产品收率可达77.6%。     

CaO-B2O3-SiO2微晶玻璃的制备及介电性能

低介电常数、低介电损耗的微晶玻璃是制造低温共烧陶瓷基板的重要材料。本文采用熔融水淬法制备了CaO-B₂O₃-SiO₂(CBS)微晶玻璃,重点研究了m(CaO)/m(SiO₂)质量比、B₂O₃含量对CBS微晶玻璃介电性能的影响。结果表明：CBS微晶玻璃的主要晶相有Ca₃Si₃O₉、Ca₂B₂O₅、CaB₂O₄、SiO₂和Ca₂SiO₄。随着m(CaO)/m(SiO₂)质量比的增加,介电常数增加,介电损耗先降低后增加;硅灰石相的增多使介电损耗从2.87×10^-3降到1.36×10^-3,介电损耗随着SiO₂、Ca₂B...     

改性SiO2源对合成高纯莫来石材料结构及性能的影响

在天然石英中引入质量分数为8%的γ-Al₂O₃,经1 550 ℃加热处理实现了对SiO₂源的掺杂改性。以不同SiO₂源和γ-Al₂O₃为原料,对比研究了改性SiO₂源对合成高纯莫来石材料结构和性能的影响。结果表明:SiO₂中掺入少量γ-Al₂O₃后,其熔融温度降低;改性SiO₂源在较窄的温度范围(1 570~1 580 ℃)内转化为富SiO₂液相。大量富SiO₂液相的形成促进了莫来石化反应,加速了颗粒重排,提高了材料的致密度,从而改善了高纯莫来石材料的反应烧结性能。在煅烧过程中,富SiO₂液相逐渐被反应消耗转化为高温相的莫来石;同时,改性SiO₂源熔融提供的液相环境,促进了莫来石晶体的各向异性生长。经1 700 ℃保温3 h煅烧后,莫来石晶体发育呈柱状并形成交叉的网络结构,增强了晶体间的结合程度。采用改性SiO₂源合成的高纯莫来石材料,表现出更好的力学性能。     

SiC惰性氧化对Al2O3-SiO2浇注料线变化率的影响

以三级矾土（5～0.088、≤0.088 mm）、特级矾土（1～0.088、≤0.088 mm）、碳化硅（≤0.074 mm）为主要原料,以铝酸钙水泥为结合剂,加入适量的α-Al₂O₃微粉、SiO₂微粉和减水剂制备了Al₂O₃-SiO₂浇注料。对经1 400℃空气气氛保温24 h烧后试样的线变化率、显气孔率、化学组成、物相组成和微观结构进行分析,探讨了SiC加入量（w）分别为3%、6%、8%、10%时SiC的惰性氧化对试样线变化率的影响。结果表明：1)SiC惰性氧化产物SiO₂可以填充气孔,降低显气孔率,但SiO₂生成后并不会立即与Al₂O₃发生反应形成莫来石;2)二次莫来石化是试样线变化率提高的主要因素,过量SiC抑制了自身的惰性氧化,氧化产物SiO₂相对减少,不利于试样的烧结以及二次莫来石化的持续进行;3)全组分试样中SiC加入量（w）为6%时...     

SiO2微粉加入量对β-SiAlON-SiC材料性能的影响

在保证承烧锂电池三元正极材料匣钵用β-SiAlON-SiC材料抗碱性的前提下,以SiC颗粒和细粉、Si粉、Al粉、α-Al₂O₃微粉等为原料,采用高温氮化法制备β-SiAlON-SiC材料,研究了SiO₂微粉加入量(外加质量分数分别为0、1%、2%、3%)对β-SiAlON-SiC材料的显气孔率、体积密度、常温抗折强度、高温抗折强度、物相组成、抗碱性的影响。结果表明：1)在β-SiAlON-SiC材料中添加SiO₂微粉可以降低其显气孔率,显著提高其常温抗折强度和高温抗折强度;2)添加SiO₂微粉不会影响Si粉和Al粉的氮化效果,但会影响Al₂O₃在Si₃N₄中的固溶度和β-SiAlON的生成量;3)SiO₂微粉的最优添加量为1%(w),所得试样的抗碱性明显优于未添加SiO₂微粉试样的。     

用废弃煤矸石制备高比表面积的SiO2-Al2O3二元复合气凝胶

以兖州煤矸石为原料,经过低温焙烧、酸浸除杂、碱熔活化,采用溶胶-凝胶法和真空干燥法制备完整的块状SiO₂-Al₂O₃二元复合气凝胶。通过X射线衍射、扫描电镜、傅里叶变换红外光谱、氮气吸附等检测手段对原料、SiO₂-Al₂O₃气凝胶及其制备过程中得到的中间产物的物理、化学特性进行表征,研究SiO₂-Al₂O₃凝胶的形成机制。实验结果表明,煤矸石经过酸浸除去了大部分的铁、钾、碱土金属等杂质。在经过碱熔活化后,煤矸石主要组分石英和高岭石均转化为非晶态,反应活性提高。制备得到的SiO₂-Al₂O₃气凝胶是以Si-O-Si、Si-O-Al网络结构为骨架的非晶态纳米颗粒聚集体,其堆积密度0.37 g·cm^-3,比表面积483 m²·g^-1,比孔容1.87 cm³·g^-1,平均孔径10.29 nm,最可几孔径9.32 nm,具有较好的介孔特征。     

Zn2+掺加的包覆型Fe2O3/SiO2颜料的制备及其呈色性能

包覆型Fe₂O₃/SiO₂颜料由于包覆完整性并不理想,该颜料高于800 ℃时呈色会产生变黑、变暗的问题。采用溶胶-凝胶法制备包覆型Fe₂O₃/SiO₂颜料,研究催化剂浓度、反应温度、硅/铁质量比等因素对包覆型Fe₂O₃/SiO₂颜料呈色性能的影响。在此基础上,通过掺加Zn²⁺,进行了Zn²⁺掺加的包覆型Fe₂O₃/SiO₂颜料的呈色性能研究。研究表明,当催化剂(氨水)浓度为0.75 mol/L,反应温度为40 ℃,硅/铁质量比m(SiO₂)/m(Fe₂O₃)为0.20,铁/锌摩尔比n(Fe)/n(Zn)为4时,制备得到的Zn²⁺掺加的包覆型Fe₂O₃/SiO₂颜料的呈色耐热性能获得明显提升,样品在850 ℃煅烧后仍然呈现出明亮的红橙色色调。     

磁性Fe3O4@SiO2@介孔SiO2空心微球的制备及漆酶固定化

磁性介孔二氧化硅复合材料作为酶固定化载体具有优异的酶固定化性能和良好的磁分离性能,受到国内外学术界广泛关注。本文在自制的β-FeOOH空心微球表面上包覆致密的SiO₂保护层,在酸性条件下以P123为模板剂,十六烷基三甲基溴化铵（CTAB）为辅助导向剂成功制备出了磁性β-FeOOH@SiO₂@介孔SiO₂空心复合微球,最后在还原气氛下煅烧得到Fe₃O₄@SiO₂@介孔SiO₂空心微球。结果表明,所制备的Fe₃O₄@SiO₂@介孔SiO₂微球空心结构未坍塌,具有规整的球形结构,介孔SiO₂壳层（平均厚度约为11nm）均匀地包覆在β-FeOOH@SiO₂中空微球表面。伴随着CTAB量的增加,微球的最可几孔径由4.30nm减小到3.19nm,比表面积从376m²/g升高到640m²/g,孔容从0.36cm³/g升高到0.56cm³/g。复合微球的饱和磁化强度为11.3emu/g,矫顽力为111.5Oe,外加磁场作用下可以实现样品的快速分离,且样品的再分散性良好。当介孔孔径为4.30nm时,Fe₃O₄@SiO₂@介孔SiO₂空心复合微球漆酶固定量高达234mg/g。固定化漆酶在不同pH、温度下的活性显著优于游离酶。     

Effect of SiO2/Al2O3 ratio on the conversion of methanol to olefins over molecular sieve catalysts

A series of SAPO-34 molecular sieves with different SiO₂/Al₂O₃ ratios have been synthesized for the methanol-to-olefin (MTO) reaction. Their physico-chemical properties are characterized by various techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FT-IR) and N₂ adsorption-desorption. The results are compared with those of the commercial HZSM-5, which show that the crystallinity and particle diameter of SAPO-34 as well as HZSM-5 increase with SiO₂/Al₂O₃ ratio. The variation of BET surface area of SAPO-34 is different from that of HZSM-5 and the sample with SiO₂/Al₂O₃ ratio of 0.4 exhibits the highest BET surface area. FT-IR spectra indicate that HZSM-5 has both Br?nsted and Lewis acid sites and Br?nsted acid sites are stronger, whereas SAPO-34 samples are dominated only by Lewis acid sites. When the SiO₂/Al₂O₃ ratio increases, propylene and butylenes become the predominant product of the MTO reaction over HZSM-5. In contrast, the main products of this reaction catalyzed by SAPO-34 are ethylene and propylene. According to the product distribution, the reaction mechanism over HZSM-5 catalysts is proposed.     

CO oxidation over promoted Pt catalysts

A study of CO oxidation by O₂ over Pt catalysts, promoted by MnO_x and CoO_x, is described. The activities of Pt/SiO₂, Pt/MnO_x/SiO₂ and Pt/CoO_x/SiO₂ are compared with commercial Pt/Al₂O₃, Pt/Rh/Al₂O₃ and Pt/CeO_x/Al₂O₃ catalysts. Since these catalysts differ in dispersion and weight loading of platinum, the turnover frequencies are also compared. The following order in activity in CO oxidation after a reductive pretreatment is found: Pt/CoO_x/SiO₂ > Pt/MnO_x/SiO₂, Pt/CeO_x/Al₂O₃ > Pt/Al₂O₃, Pt/Rh/Al₂O₃, Pt/SiO₂. Over Pt/CoO_x/SiO₂ CO is already oxidised at room temperature. Possible models to account for the high activity of Pt/CoO_x/SiO₂ in the CO/O₂ reaction are presented and discussed. Partially reduced metal oxides are necessary to increase the activity of the Pt/CoO_x/SiO₂, Pt/MnO_x/SiO₂ or Pt/CeO_x/Al₂O₃ catalysts. It was shown that mild ageing treatments did not affect the activity of the Pt/CoO_x/SiO₂ catalyst in CO oxidation.     

Simultaneous HDS and HDN over supported PtSn catalysts in comparison to commercial NiMo/Al2O3

The performance of platinum-tin catalysts, supported on Al₂O₃ and SiO₂ and subjected to reduction prior to use, has been studied. The catalysts were characterized in reduced forms by X-ray diffraction (XRD) and XPS. The surface properties were determined by N₂ BET specific surface area and CO chemisorption. The model compounds were 4,6-dimethyldibenzothiophene (4,6DMDBT) and carbazole. The PtSn catalysts supported on either Al₂O₃ or SiO₂ were characterised by high activity, but the catalyst PtSn/SiO₂ was found the most effective, even more effective than the commercial KF848 catalyst. Both PtSn catalysts studied were more effective in the reaction of 4,6DMDBT hydrogenation, the dominant product obtained with the use of PtSn/Al₂O₃ was methyl-cyclohexyltoluene (MCHT) and with PtSn/SiO₂ the dominant product was dimethylbicyclohexyl (DMBCH). The amount of dimethylbiphenyl (DMBPh) obtained was small and practically independent of the contact time. In the HDN reaction of carbazole the most active was PtSn/SiO₂. It was also more active in the consecutive reaction of isomerisation of the main product of the HDN reaction, bicyclohexyl (BCH) to methylcyclopentylcyclohexane (MCPCH). The large differences shown in the hydrotreating activity specially in the HDN reaction between PtSn catalysts supported on Al₂O₃ and SiO₂ result from the physicochemical properties of both samples. The significantly higher CO chemisorption for PtSn/SiO₂ indicates the presence of larger amount of metallic species and better hydrogenation properties so important for deep hydrotreating process.     

A new route to prepare supported nickel phosphide/silica–alumina hydrotreating catalysts from amorphous alloys

Supported nickel phosphides were prepared by treating an amorphous Ni–B alloy on silica–alumina support with phosphine (15 vol.% PH₃/H₂) at relatively low temperature. The amorphous Ni–B/SiO₂–Al₂O₃ precursors were synthesized by silver-induced electroless plating. The amorphous precursors and catalysts were characterized by X-ray diffraction, high-resolution transmission electron microscopy, selected area electron diffraction, BET surface area and inductively coupled plasma measurements. The transmission electron micrographs of the Ni₂P/SiO₂–Al₂O₃ particles with their size ranging from 60 to 80 nm showed that they were homogeneously dispersed over the SiO₂–Al₂O₃ support. The as-prepared catalysts exhibited an excellent catalytic activity in the hydrodesulfurization (HDS) of dibenzothiophene.     

CoCr_2O_4/SiO_2催化剂上二氯甲烷催化氧化

采用浸渍法制备了不同CoCr_2O_4负载量x CoCr_2O_4/SiO_2催化剂(x=5%、10%、20%和30%),考察其对二氯甲烷催化燃烧性能的影响。结果表明,催化剂的整体活性顺序为:30CoCr_2O_4/SiO_220CoCr_2O_4/SiO_210CoCr_2O_4/SiO_25CoCr_2O_4/SiO_2,但按照活性组分CoCr_2O_4质量归一化后本征活性顺序为:10CoCr_2O_4/SiO_2≈5CoCr_2O_4/SiO_220CoCr_2O_4/SiO_230CoCr_2O_4/SiO_2。表征结果发现催化剂本征活性与可还原性能和表面酸性存在密切关系。10CoCr_2O_4/SiO_2和5CoCr_2O_4/SiO_2具有较高的表面酸性和耗氢量,因此具有较高的本征活性。     

晶化条件对HZSM-5分子筛合成收率和性能的影响

考察了SiO2-Al2O3-TPABr-NH3·H20—H2O体系晶化时间、晶化温度和原料用量等对合成HZSM-5性能的影响。当n（SiO2）：n（Al2O3）=100、n（TPABr）：n（SiO2）=0．1、n（NH3）：n（SiO2）=1．5、n（H2O）：n（SiO2）=22和晶种添加质量分数为4％时,180℃静态晶化72h,合成收率与相对结晶度分别为10．1％和99．8％,对应理论收率为11．4％,合成收率与理论收率比为0．89。当投料n（SiO2）：n（A1203）从50增加到400,合成收率与结晶度分别超过8．9％和82．8％,合成收率与理论收率比为0．76—0．89;样品酸量随着n（SiO：）：n（Al2O3）的增加逐渐减小,比表面积为405m2·g-1,合成样品HZSM-5对甲醇制烯烃反应具有良好的酸催化活性。设定反应条件,采用投料n（SiO2）：n（AlO3）=250的样品,甲醇转化率、丙烯选择性和C=2～C=4选择性分别为100％、39．27％和62．01％。