共查询到20条相似文献,搜索用时 171 毫秒
1.
2.
催化剂能大大加快气化反应的进行,而复合催化剂可能比单一催化剂的催化效果更好。在自行搭建的实验台上进行了CO_2恒温气化实验,分别研究了CaO和MgO的催化性能,不同组成比例下复合催化剂的催化效果。所得主要结论如下:CaO在不同气化温度下均有较好的催化效果;MgO在较高的气化温度下有较好的催化效果,但其催化效果要差于CaO;850℃下复合催化剂的催化效果好于MgO,但差于CaO,其它气化温度下复合催化剂有更好的催化效果。 相似文献
3.
4.
5.
6.
7.
催化气化是一种新型煤气化方式,催化气化催化剂主要为碱金属催化剂,但在催化气化过程中碱金属催化剂会与煤中Si、Al矿物质相互反应,直接影响碱金属催化气化催化活性。以Na2CO3为催化剂,分析催化气化过程中碱金属失活行为与Na-Al复合转化行为,采用高岭石和勃姆石为模型化合物对Na-Al复合与转化过程进行研究,并对比Na-Al转化产物的催化作用。研究表明:Na2CO3催化作用良好,催化气化过程中Na2CO3与煤中Si、Al矿物质反应,生成霞石与硅铝酸钠类物质,导致催化剂失活。高岭石与Na2CO3在700℃开始反应,生成硅铝酸钠类物质。勃姆石与Na2CO3在860℃时反应生成偏铝酸钠,偏铝酸钠高温下不稳定,进一步转化为硅铝酸钠类物质。与Na2CO3相比,硅铝酸钠与偏铝酸钠的催化效果较差,导致碱金属催化作用下降,同时,生成的偏铝酸钠催... 相似文献
8.
碱和碱土金属是气化焦气化反应的重要催化剂,其催化效果直接影响气化焦的气化效率。对不同碱或碱土金属与气化焦的混合物,以及不同比例Na_2CO_3的气化焦进行气化反应,研究催化剂种类和用量对气化焦气化反应的催化效果。结果表明,1 000℃和1 050℃下,催化剂的催化活性顺序为:K_2CO3Na_2CO_3Ca CO3;1 100℃下因催化剂高温释放以及Na_2CO_3催化活性显著提高,催化活性顺序变为:Na_2CO_3K_2CO3Ca CO3。气化焦碳转化率由高到低为:5%Na_2CO_31%Na_2CO_32%Na_2CO_30.5%Na_2CO_3无Na_2CO_3,气化焦的催化活性、最大反应速率和反应活性指数排序与气化焦炭转化率一致,表明催化活性并非一直随催化剂添加比例的增加而增加。 相似文献
9.
10.
制备了一种以锐钛矿为主的混晶纳米二氧化钛,并将其均匀负载于纳米凹凸棒土(ATP)上,得到了一类纳米复合催化剂,对二氧化钛及复合催化剂分别进行了X-射线衍射和透射电镜表征。利用催化聚酯反应对二氧化钛及多种复合催化剂的性能进行了评价,结果表明:与常规聚酯催化剂Sb2O3相比较,纳米二氧化钛可达到与Sb2O3相近的催化活性,但催化性能不稳定,聚酯产品b值较高;将二氧化钛负载于纳米凹凸棒土表面后,催化活性中心达到了理想的分散,催化性能更加稳定,同时也改善了聚酯的色相,b值从14.05降为8.17。此外,讨论了复合催化剂对聚酯产品物化性能的影响,通过DSC、TGA等测试手段,发现复合催化剂制备的聚酯结晶温度升高,二甘醇含量和热降解性能与常规聚酯相近。 相似文献
11.
煤催化气化工艺中碱金属催化剂的引入加剧了气化炉的结渣,直接影响了流化床气化炉的正常操作。煤灰的烧结特性是流化床气化炉结渣的主要影响因素之一。通过自制的压差法烧结温度测定实验装置,并结合XRD 等分析表征及Factsage热力学软件模拟计算,考察了不同添加剂对煤灰烧结特性及气化性能的影响,并从矿物学角度探讨了添加剂对煤灰结渣特性及气化工艺的影响。结果表明,添加硅铝系添加剂可提高煤灰的烧结温度;相比硅系添加剂,添加高铝系添加剂对改善煤灰的烧结温度效果更明显;高铝系添加剂可作为一种高效的阻熔剂,但因在气化过程中容易同催化剂反应,导致催化剂催化性能降低,对煤的气化活性及催化剂回收率产生不利影响;添加氧化钙添加剂,煤的灰熔温度及烧结温度均增加,随氧化钙含量增加,灰熔点及烧结温度均升高,且对气化活性及催化剂回收率有良性作用;氧化钙可作为改善煤种结渣性的添加剂用于催化气化工艺中,需根据煤种性质及工艺特点确定适宜的添加量。 相似文献
12.
李珊 《化学工业与工程技术》2013,(5):10-15
煤与气化剂(如水蒸气、CO2、H2和O2)之间的气化反应最有效的催化剂主要为碱金属、碱土金属以及过渡金属的盐类,根据其组成,详细论述了煤催化气化催化剂的特性。据研究,在气化反应中碱金属催化剂如Na、K等易与煤中矿物质如Si或Al反应致使催化剂失活,同时过渡金属易被煤中S毒化,这在一定程度上制约了煤催化气化工业化进程。论述了煤催化气化催化剂的研究方向,认为开发新型高效、低廉且易回收催化剂是有必要的。 相似文献
13.
《Fuel Processing Technology》1987,16(1):45-53
A gravimetric study of the catalytic activity of alkali metal hydridotetracarbonylferrates on steam gasification of oil coke at 800°C revealed the following order with respect to the cation: Na > Li > K > Rb > Cs. This order was not consistent with that of the catalytic activity of alkali metal carbonates. The most reactive rubidium and potassium carbonates at a higher loading level exhibited poor binary effect when they were used with iron in the form of alkali metal ferrate. This offered important information for interpreting the mechanism of steam gasification of coal using the Fe-Na binary catalyst. The reactivity of the oil coke was slightly enhanced by preoxidation. The sodium ferrate gave a remarkable difference in the catalytic reactivity of gasification between the original and pre-oxidized cokes. The increase in oxygen content rather than that in surface area may play an important role in the pre-oxidized coke impregnated with the catalyst. 相似文献
14.
15.
在常压热分析仪上,采用纸浆黑液催化剂对福建无烟粉煤的水蒸气气化反应动力学进行了研究,在850~950℃温度范围内测定了催化剂浓度由0增至10%时的碳转化率随气化时间的变化。结果表明,纸浆黑液具有显著提高碳转化率和气化速率的作用,进而确定了实验条件下的纸浆黑液催化剂加载饱和浓度;在此基础上采用缩芯模型关联出无烟粉煤水蒸气催化气化反应动力学参数,分析表明,该催化气化过程存在明显的补偿效应,最后给出纸浆黑液对无烟粉煤水蒸气催化气化包括补偿效应的动力学方程。 相似文献
16.
气化是煤、生物质以及其他含碳燃料高值化利用的有效途径之一。为了考察气化过程中焦油的反应转化特性,选取萘作为焦油模型化合物,以流化催化裂化(fluid catalytic cracking,FCC)催化剂及褐煤热解焦作为接触裂解载体,利用微型流化床考察流化条件下萘催化裂解反应规律,并采用Friedman法和积分法计算萘裂解生成CH4和H2等典型气体组分的动力学参数。结果表明,FCC催化剂与褐煤焦均对萘裂解有明显的催化效果,褐煤焦用于萘裂解的反应活化能整体数值低于FCC催化剂。FCC催化剂裂解萘生成H2符合三维扩散(球形对称)模型,生成CH4符合成核与生长(n=2/3)模型。相应地,褐煤焦裂解萘反应生成H2和CH4分别采用收缩几何形状(圆柱形对称)和三维扩散(圆柱形对称)具有较好的拟合度。 相似文献
17.
煤加氢气化制天然气技术具有工艺路径短、热效率高等优点,其应用基础研究备受关注。但煤中存在部分致密的芳香碳结构,加氢反应性较差,即使在苛刻的反应条件下(~1 000℃、~7 MPa H_2),仍难以转化。通过引入催化剂,进行煤催化加氢气化可在温和的反应条件下实现煤的碳转化率和CH_4收率的同步提高。论述了碱金属(K、Na等)、碱土金属(Ca)和过渡金属(Fe、Co、Ni等)催化剂对模型碳加氢气化的催化作用原理。探讨了反应温度、氢气压力、和碳结构对C-H_2催化反应的影响规律,分析了适用于原煤催化加氢气化的最佳催化剂及工艺条件,并从CH_4和轻质液体焦油等产物生成规律、煤中碳结构随着反应进行的衍变过程等角度,讨论了催化剂分别对煤加氢热解和热解半焦加氢气化的催化作用行为。提出了煤催化加氢气化联产CH_4和轻质液体焦油技术从基础走向应用的进一步研究建议。现有研究结果表明,过渡金属与碱土金属组成的二元催化剂(Fe/Co/Ni-Ca)对煤加氢气化的活性较高。过渡金属元素在反应过程中主要提供C-H_2反应所需的活性氢,并削弱C—C键的键能;碱土金属元素Ca主要促进Fe/Co/Ni的分散,防止其发生硫中毒失活,并增强Fe/Co/Ni与碳之间的相互作用。温度升高一方面为化学键断裂过程提供了更高能量,加速C-H_2反应,另一方面促进催化剂在煤结构中扩散,提升催化剂的供氢和断键效率。升高压力促进了活性氢的供应,同时CH_4浓度得到稀释,反应向生成CH_4的方向移动。以5%Co-1%Ca为催化剂,在850℃、3 MPa H_2反应条件下,30 min内可同时达到90.0%的碳转化率和77.3%的CH_4收率。Co-Ca催化剂在煤加氢热解过程中具有催化解聚和催化加氢的作用,提高焦油和CH_4收率,同时催化剂在煤加氢热解过程中对煤结构产生催化活化作用,使得生成的半焦具有较高的气化活性。煤催化加氢气化的机理研究目前仍处于推测阶段,另外,该技术气化剂、煤种的适应性,催化剂循环利用性能有待进一步阐明。 相似文献
18.
A new concept in catalytic coal gasification has been developed. The use of crude vinegars (CVs) derived from different lignocellulosic biomass resources is described for the recovery and reuse of calcium in coal gasification. Calcium introduced by impregnation with a CV solution produced a higher catalytic activity than calcium loaded by impregnation with an aqueous acetic acid solution. Furthermore, CVs were found to be capable of reclaiming calcium from gasification residue and of improving the catalytic activity of the indigenous crystalline calcite in bituminous coal as in situ catalyst. 相似文献
19.
CO2 gasification of Fuijian high-metamorphous anthracite with black liquor (BL) and/or mixture of BL and calcium stuff (BL+Ca) as catalyst was studied by using a thermogravimetry under 750-950℃ at ambient pressure. When the coal was impregnated with an appropriate quantity of Ca and BL mixture, the catalytic activity of CO2 gasification was enhanced obviously. With a loading of 8%Na-BL+2%Ca, the carbon conversion of three coal samples tested reaches up to 92.9%-99.3% at 950℃ within 30min. The continuous formation of alkali surface compounds such as ([-COM], [-CO2M]) and the presence of exchanged Ca, such as calcium phenolate and calcium carboxylates (COO)2Ca, contribute to the increase in catalytic efficiency, and using BL+Ca is more efficient than that adding BL only, The homogeneous model and shrinking-core model were applied to correlate the data of conversion with time and to estimate the reaction rate constants under different temperature. The corresponding reaction activation energy (Ea) and pre-exponential factor of three anthracites were estimated. It is found that Ea is in the range from 73.6 to 121.4kJ·mol^-1 in the case of BL+Ca, and 74.3 to 104.2kJ·mol^-1 when only BL was used as the catalyst, both of which are much less than that from 143.5 to 181.4kJ·mol^-1 if no catalyst used. It is clearly demonstrated that both of BL+Ca mixture and BL could be the source of cheap and effective catalyst for coal gasification. 相似文献
20.
The catalytic gasification of char from co-pyrolysis of coal and wheat straw was studied. Alkali metal salts, especially potassium salts, are considered as effective catalysts for carbon gasification by steam and CO2, while too expensive for industry application. The herbaceous type of biomass, which has a high content of potassium, may be used as an inexpensive source of catalyst by co-processing with coal. The reactivity of chars from co-pyrolysis of coal and straw was experimentally examined. The chars were prepared in a spout-entrained reactor with different ratios of coal to straw. The gasification characteristics of chars were measured by thermogravimetric analysis (TGA). The co-pyrolysis chars revealed higher gasification reactivity than that of char from coal, especially at high level of carbon conversion. The influence of the alkali in the char and the pyrolysis temperature on the reactivity of co-pyrolysis char was investigated. The experimental results show that the co-pyrolysis char prepared at 750 °C have the highest alkali concentration and reactivity. 相似文献