稳定硅溶胶的制备方法

硅溶胶用途很广,可作吸附剂、催化剂载体、粘合剂、抗污剂、增稠剂等,特别是作为粘合剂已广泛地用于绝缘材料和催化剂的制造中。目前工业上生产胶体硅溶胶的工业方法,都用硅酸钠作原料,由于硅酸钠能耗的提价,增加了硅溶胶的生产成本。本发明是在一种相当便宜的原料中制备稳定胶体硅溶胶的方法,该法可使制成的硅     

添加硅溶胶对平板式脱硝催化剂性能的影响

采用硅溶胶作为粘结剂制备VMo/Ti平板式脱硝催化剂,考察了硅溶胶的添加对催化剂物化性能和脱硝性能的影响。结果表明,硅溶胶的添加可以提升催化剂的耐磨性能,增加催化剂的比表面积,促进活性组分的分散。然而硅溶胶同时也降低了催化剂的还原性能和酸性性能,对催化剂的脱硝性能有不利影响。相比之下,VMo/Si(5)-Ti是较为合适的工业催化剂配方。     

硅溶胶在分子筛类催化剂制备中的应用研究进展

硅溶胶问世已有超过100 a的历史,其在分子筛的合成及催化剂的制备中具有广泛的应用。简要综述了硅溶胶的市场情况、制备方法和性质。重点介绍了硅溶胶在分子筛类催化剂制备中的应用,包括硅溶胶在硅源、黏结剂以及制备小晶粒分子筛等方面的应用。结合国内外的研究进展,详细论述了催化剂用硅溶胶作为硅源、黏结剂和载体在分子筛的合成和催化剂制备中所起到的作用和优势。结合硅溶胶的应用研究现状,提出硅溶胶在制备分子筛类催化剂过程中存在的一些问题：以硅溶胶为黏结剂制备的硅基催化剂耐磨性差;以硅溶胶为载体制备的催化剂活性组分分散性差;硅溶胶产品的批次质量稳定性差。指出,如何解决以上问题,以更有效地提高硅溶胶在分子筛类催化剂制备中的应用,将是以后研究的重点。最后,对硅溶胶的发展前景进行了展望,指出在硅溶胶可控合成的基础上,分子筛及其催化剂的可控合成和应用开发将会有更广阔的前景。     

纳米TiO_2在泡沫镍上的负载技术研究

采用溶胶-凝胶法制备了锐钛矿型晶体结构的纳米TiO2。以硅溶胶为无机粘结剂,分别采用在含纳米TiO2的乙醇悬浮液中浸涂和直接用悬浮液喷涂的方法,在泡沫镍载体上负载了TiO2催化剂,应用扫描电子显微镜(SEM)对硅溶胶涂层和纳米TiO2催化剂的负载状态进行了分析。研究结果表明,硅溶胶与泡沫镍结合牢固,涂层分布均匀。就TiO2的分散性和负载均匀性而言,喷涂负载优于浸涂负载。采用不同的喷涂次数,可以明显改变纳米TiO2在粘结剂表面的负载量和负载状态。当喷涂次数为1次时,负载的TiO2颗粒呈单分散状态;喷涂次数增加时,会出现纳米颗粒的堆积,但不同于浸涂时的团聚;喷涂5次时,纳米颗粒在泡沫镍表面形成密集层状分布。     

常压浓缩法生产硅溶胶的研究

近年来,涂料、粘接剂、耐火绝热材料、陶瓷、纺织等工业对硅溶胶的需求日益增大,特别是近来无机高分子建筑涂料的兴起,更为硅溶胶的大量应用开辟了广阔的市场。与此同时,对目前硅溶胶产品也提出了高浓度,高稳定性,低价格的要求。制备低浓度硅溶胶的方法很多,归纳起来,大致有三种:1.电渗析硅酸钠法。2.水解有机硅法。3.离子交换硅酸钠法。最常用的是离子交换法。无论使用那种方法生产高浓度硅溶胶,都必须进行浓缩。硅溶胶是不稳定体系,控制何种条件进行浓缩,往往成     

铜锰基催化剂浆液特性对其在堇青石载体上的负载量及粘附性的影响

随着大流量工业烟气净化对低气阻技术的迫切需求，负载型催化剂备受关注，然而涂敷浆液特性复杂、对负载的影响因素繁多，使催化剂制备带来挑战。针对铜锰基催化剂在堇青石载体上的真空涂敷制备，探究了固含量，粘结剂种类，pH值和粒径等浆液特性对催化剂负载量和粘附性的影响规律。结果表明：固含量的升高使得催化剂颗粒可以与增稠剂和硅溶胶形成的网状结构更紧密结合，提高了催化剂负载量和粘附性；硅溶胶可有效增加浆液电负性，使浆液内催化剂颗粒分散均匀；pH值的增大使浆液Zeta电位减小，减小浆液黏度并改善稳定性；而球磨会破坏浆液均匀稳定的网状结构，不利于催化剂粘附性。优选硅溶胶质量分数为30%、pH值为7.3、固含量为30%(质量分数)的未球磨浆液，得到负载量为216 kg?m^–3、脱落率为0.6%,CO催化效率大于98%(7 200 h^–1、120℃、8%H₂O)的负载型催化剂。     

硅源对无定形硅铝物化性能的影响

以硅溶胶和九水硅酸钠为硅源,九水硝酸铝为铝源,采用分步沉淀法制备一系列不同硅铝比的无定形硅铝,通过XRD、BET和NH₃-TPD等考察硅源对无定形硅铝物化性能的影响。结果表明,以九水硅酸钠为硅源制备的无定形硅铝比表面积和酸性均明显优于以硅溶胶为硅源制备的无定形硅铝;以九水硅酸钠为硅源,在SiO2质量分数为55%时,该无定形硅铝呈现出最大酸量和高的比表面积,作为性能优异的催化材料将具有良好的应用价值。     

硅源对Cu/SiO_2催化剂催化对羟基苯乙酸乙酯加氢性能的影响

以正硅酸乙酯(TEOS)、硅酸钠(Na_2SiO_3·9H_2O)及硅溶胶(Si-sol)为硅源,采用共沉淀法制备了负载型Cu/SiO_2催化剂,并将其用于对羟基苯乙酸乙酯的加氢。通过XRD、N2物理吸附-脱附、H_2-TPR等手段研究了硅源对催化剂结构及反应性能的影响。结果表明,不同硅源制备的Cu/SiO_2催化剂中Cu物种存在形态及还原行为不同,进而使催化剂表现出不同的催化活性。以硅酸钠为硅源制备的Cu/SiO_2催化剂中CuO分散度高,且易被氢气还原为活性金属Cu,催化剂加氢活性最高,在反应原料25g、催化剂用量1.5g、氢气压力4MPa、反应温度170℃、反应时间15h的条件下,对羟基苯乙酸乙酯转化率达到99.5%,目标产物对羟基苯乙醇收率为99.3%。     

硅溶胶对无机磷酸铝涂料防腐性能的影响

采用化学合成法制备磷酸铝粘结剂,以球形铝粉为骨料,添加不同含量的硅溶胶,制备磷酸铝涂料,再经过热处理制备磷酸铝涂层。通过X射线衍射分析(XRD)表征粘结剂和涂层物相结构,采用扫描电子显微镜(SEM)表征涂层形貌,通过电化学测试和浸泡试验对比研究涂层腐蚀行为。分析结果表明:在磷酸铝涂层中添加适量硅溶胶可以改善涂层表面质量和耐腐蚀性能,从而使涂层腐蚀电位升高,腐蚀电流降低,阻抗值增大。添加10%硅溶胶的涂层质量最佳,耐腐蚀性能最优。     

硅溶胶用作FCC催化剂粘结剂的研究现状

介绍了硅溶胶的性质,总结了单质溶解法、离子交换法、电解渗析法、胶溶法、分散法等制备方法,论述了pH值、溶胶粒子粒径、助剂及其他影响因素对硅溶胶稳定性的影响,并对粘结剂用硅溶胶的发展前景做了展望。     

活性氧化铝在FCC催化剂中的应用研究

采用N^₂吸附法、IR和XRD等手段研究了活性氧化铝用于催化裂化(FCC )催化剂中的性能。结果表明,在FCC催化剂制备及应用条件下,活性氧化铝保持比较稳定的比表面积、孔容和酸性等性能。磷易与活性氧化铝作用,分子筛与磷的作用存在一个逐步平衡的过程;氧化铝有利于改善基质的孔结构;对以铝溶胶为粘结剂制备的催化剂进行磷改性处理,催化剂基质与活性组分分子筛上的磷含量基本相当。     

Application of Novel Zeolite Y Nanoparticles in Catalytic Cracking Reactions

The cracking activity of a fluid catalytic cracking (FCC) catalyst containing novel zeolite Y nanoparticles fabricated using mesoporous silica (average particle size of 150 nm) was examined and compared with the performance of other catalysts. The activity experiments were carried out in a fluidized bench-scale batch riser simulator reactor. The bulky probing compound of 1,3,5-triisopropylbenzene (TIPB) was cracked to lighter compounds over a catalyst containing 25% of the developed zeolite. The synthesized sodium-type zeolite nanoparticles were subjected to two cycles of ion-exchange treatment using ammonium sulfate and lanthanum chloride and then to calcination. To investigate the effects of particle size on the activity, three additional catalysts were prepared with the mean particle size of the supported zeolites ranging from 450 to 1800 nm. The preparation of the FCC catalysts was conducted by mixing the highly aqueous dispersed zeolite Y nanoparticles with colloidal silica–alumina as a matrix and silica sol as a binder. The results of the catalytic cracking of TIPB demonstrated the significant effect of the size reduction of the synthesized zeolite Y nanoparticles on the catalytic performance of the catalyst. The FCC catalyst that contained zeolite Y nanoparticles (150 nm) showed superior conversion and selectivity percentages for the main products. The results of this study have a direct implication on the preparation of colloidal catalysts containing zeolite Y nanoparticles, which form stable emulsion with petroleum products. These emulsions can be utilized for slurry and ebullated bed reactors in heavy oil upgrading applications.     

高纯硅溶胶制备及在加氢精制催化剂中的应用

以市售硅溶胶为晶种,水玻璃为原料,采用离子交换及络合除杂等方法,制备了粒径为20~24 nm、质量分数为40%的高纯硅溶胶。分析了硅溶胶制备过程中的主要影响因素,即晶种浓度、反应过程pH、除杂过程络合剂选型。通过透射电镜（TEM）、纳米激光粒度仪、比表面积测试（BET）等方法对制备的高纯硅溶胶进行了分析。实验结果证明了该制备工艺的可行性。测试了制备的高纯硅溶胶在加氢精制催化剂中的应用效果。     

红外遮光剂对硅酸盐隔热保温涂料性能的影响

分别选取六钛酸钾晶须(PTW),金红石型二氧化钛(TiO2)和钛溶胶作为红外遮光剂,以九水合硅酸钠为粘结剂,添加SiO2气凝胶等隔热填料,用机械搅拌的方法制备出硅酸盐隔热保温涂料.研究了红外遮光剂对涂料红外透过率,消光系数和导热系数的影响.结果表明:三种红外遮光剂中,钛溶胶分散性最好,掺杂钛溶胶的涂料红外透过率最低,消光系数最大,导热系数最低,可降低至0.032 W·m-1·K-1.     

Chloride-free biodegradable organic acid hydrolyzed zinc silicate coating

Partially hydrolyzed ethyl silicate has widely been used as a binder to formulate inorganic zinc silicate paint for anticorrosive coating applications. Hydrochloric acid is used most popularly to catalyze the hydrolysis of ethyl silicate. Although different acids have been tried as catalysts for ethyl silicate hydrolysis, no attempt has been made to make stable paints out of those hydrolyzed silicate binders. In this study, environment benign biodegradable organic acids such as oxalic acid, citric acid, lactic acid and acetic acid were used for the hydrolysis of ethyl silicate and compared with the hydrolysis using conventional hydrochloric acid. The hydrolyzed silicate sols were pigmented further with silica powder and evaluated for their stability. Of the various organic acids catalyst used, only oxalic acid catalyzed sol acted as a stable binder system. The pigmented binder was then mixed with metallic zinc to formulate anticorrosive inorganic zinc silicate paint. The resultant coatings were characterized for various physical, surface, mechanical and chemical resistance properties such as drying, hardness, adhesion (cross hatch) and solvent resistance. Corrosion resistance properties were analyzed by means of salt spray, open circuit potential (OCP) and electrochemical impedance spectroscopy (EIS). The results revealed that the physical, mechanical, chemical and anticorrosive properties of the coating hydrolyzed with hydrochloric acid and oxalic acid are comparable. Thus, a chloride free biodegradable organic acid hydrolyzed inorganic zinc silicate primer is reported and due to its long term stability same also can be scaled up commercially.     

Fabrication of homogeneous mullite-based fiber porous ceramics with high strength and porosity

Silica sol is widely used in the preparation of mullite-based fiber porous ceramics (MFPCs), but it aggregates at the top surface of MFPCs during the drying process. This leads to the decrease in mechanical strength and porosity. To overcome the problem and fabricate homogeneous MFPCs, the sodium silicate solution and glass fibers were applied in the fabrication process of MFPCs. The effects of concentrations of sodium silicate solution and silica sol, amounts of glass fibers and sintering temperatures on the properties of prepared MFPCs were studied. The sodium silicate solution consolidated the silica sol and mullite fibers, forming a homogeneous structure and ensuring the even distribution of silica sol. Compared with other reported MFPCs, this process required low sintering temperature while maintaining high compressive strength (2.14 MPa) and porosity (75.93%). This study provides an effective method for preparing MFPCs with high strength, uniformity and porosity.     

The effect of silica availability on the mechanism of geopolymerisation

The effect of silica availability on geopolymer binder formation is investigated in the geothermal silica–sodium aluminate–water system, using sodium silicate solution as an additional, highly available silica source. Time-resolved and spatially-resolved FTIR data are combined to provide a mechanistic understanding of the role of silica availability in controlling geopolymer nucleation and gel growth behaviour. A higher degree of alumina contribution to geopolymer gels and newly formed crystal phases is observed in systems with higher silica availability. Gel nucleation is observed to take place in the region immediately surrounding the solid silica source particles when no dissolved silica is initially supplied. Conversely, mixes which initially contain dissolved silica show nucleation in bulk regions, and involving more of the Al which is rapidly released from the sodium aluminate precursor. These differences in nucleation lead to a more chemically heterogeneous binder in the case where silica is released more gradually.     

The effect of SiO_2 particle size on iron based F–T synthesis catalysts

The effect of particle size of silica, as catalyst binder, on the chemical and mechanical properties of iron based FT catalyst was studied in this work. The samples were characterized using XRD, BET, TEM, FT-IR, and H2-TPR, respectively. The attrition resistance and the FT activity were tested. Si-8–Si-15 catalysts prepared with 8–15 nm silica sol show good attrition resistance(attrition loss b 4%), especially Si-13 with an attrition loss of 1.89%. Hematite appeared in XRD patterns when silica sol above 15 nm is used. TEM micrographs show that no obvious Si O_2 particles appear when silica sol particle with size less than 8 nm was used, but Si O_2 particles coated with small ferrihydrite particles appear when silica sol above 8 nm was used. Si–O–Si vibration peak in FT-IR spectra increases with increasing silica sol size. Samples prepared with silica sol show good stability of FT reactions, and the average molecular weight of FT products increases with the increase of Si O_2 particle.