基于中国知网数据库(CNKI)和科学引文数据库(WoS),采用知识图谱方法对甲酵制芳烃领域的合作作者、共词网络及关键词聚类进行了分析,归纳了该领域目前主要的研究方向及内容,展望了芳构化反应今后的研究方向.
以煤气化粗渣为原料,分别采用化学法(酸化高温法)和物理法(超声波法)对其进行微观扩孔,并对扩孔后的吸附材料(G1和C1)进行表面改性,制备出改性后的吸附材料G2和C2.利用SEM,BET,XRD和FT-IR对吸附材料的表面形貌、微观结构和官能团组成等进行表征分析,并研究4种吸附材料对水溶液中亚甲基蓝(MB)的吸附特性.结果表明,在同等实验条件下,所制备的4种吸附材料均具有介孔特性,但C1,C2比G1,G2具有更大的比表面积和总孔容,比表面积和总孔容表现为C1＞C2＞G1＞G2.各吸附材料表面均含有以絮状物质形式存在的无定形碳.G1,G2表面粗糙,孔结构丰富,大量的无定形碳阻塞了孔道;而C1,C2表面粗糙且存在明显的断裂层和裂隙孔,孔道结构丰富.MB吸附实验表明,4种吸附材料对MB的吸附效果表现为C1＞C2＞G1＞G2,因材料改性剂影响了样品中Si—O键的含量,阻塞了孔结构,未能明显改善材料的吸附性能.在25 ℃下,4种吸附材料(用量为100 mg)对浓度为60mg/L、体积100 mL的MB溶液进行吸附,其吸附过程均符合伪二阶动力学模型和颗粒内扩散模型.在实验条件下,物理法处理后的气化粗渣在孔结构和吸附能力方面均比用化学法处理后的气化粗渣更具有优势.
以糠醛(FD)和Fe(NO3)3·9H2O为主要原料,采用聚合-热转化两步法探究了Fe2O3/PFD纳米复合材料的制备过程.通过TEM,XRD等技术对Fe2O3/PFD的尺寸、结构等进行了表征;通过室温、自然光环境下亚甲基蓝(MB)溶液的脱色降解实验给出了该材料的光催化特性.结果表明,Fe2O3/PFD在25min内可使MB溶液完全脱色并降解.
甲醇脱水制二甲醚为固体酸催化反应,目前该反应常用的固体酸催化剂有γ-Al2O3和分子筛.γ-Al2O3表面存在弱酸中心或中等强度酸中心,该催化剂有较好的初始催化活性,但其活化所需的反应温度较高,低温活性差,可操作温度窄,耐水稳定性差.分子筛表面有许多强酸位点,导致生成物不易从催化剂表面脱附;当反应温度过高时,副产物会明显增多,积炭严重,从而降低了二甲醚的选择性,容易致使催化剂失活.为改善两类催化剂的催化性能,研究人员进行了各种改性研究,催化剂改性后的活性、选择性和稳定性均在一定程度上有所提高.基于此,综述了近年来关于γ-Al2O3和分子筛催化剂的改性研究,总结并展望了甲醇脱水制二甲醚催化剂的发展方向.
低碳烯烃作为许多高附加值化学品的原料,其主要由石油化工工艺制得.随着石油原料日益枯竭,人们对非石油碳资源越来越重视,由合成气(CO和H2)制备低碳烯烃的路线具有良好的应用前景.合成气经费托合成制备低碳烯烃的反应过程,通常存在副产物CO2选择性高、催化剂失活等问题,因此设计合成出疏水性费托合成催化剂,加速H2O从催化剂体系中脱附,对降低CO2选择性、提高催化剂稳定性具有重要意义.综述了合成气经过费托合成反应生成低碳烯烃的反应机理,深入分析和总结了疏水改性策略对调节产物分布的影响,为设计和构建高效稳定的疏水性费托合成催化剂提供理论参考.
BiOCl是一种新型半导体光催化剂,在光催化降解有机污染物、光催化制氢等领域受到广泛关注.采用溶剂热合成法制备BiOCl纳米结构,结合XRD,SEM,UV-Vis DRS等表征以及光催化性能检测,研究了氯源、表面活性剂对BiOCl纳米结构的微观形貌、结构和光催化性能的影响.结果表明,以NH4Cl为氯源时,有利于提高BiOCl中的光电子迁移率及其光催化活性.表面活性剂是影响BiOCl纳米结构形貌和光催化活性的重要因素.以乙二醇-水混合溶液为反应介质、PVPK30为表面活性剂时,合成的BiOCl纳米盘自组装成三维结构的纳米花,纳米花直径约为200nm;以柠檬酸为表面活性剂时,形成厚度为10nm、直径约为100nm的BiOCl纳米盘.在紫外光辐照4min时,BiOCl纳米盘对Rh B的降解率为99.36％;辐照40min时,该纳米盘对Phenol的降解率为96.95％,其光催化活性远高于P25.
共轭微孔聚合物(CMPs)是一种新型微孔材料,具有微孔骨架稳定、比表面积大、孔径大小可调等优点.介绍了 CMPs的分子结构设计、光催化机理,概述了 CMPs在光催化领域的应用,包括光催化水分解、CO2还原、有机合成、污染物降解等内容,并对CMPs的未来发展方向进行了展望.
聚乳酸(PLA)因受自身分子组成影响,热稳定性不佳、易燃且燃烧后几乎不留任何物质.为此,以膨胀型阻燃剂(IFR)和羟基磷灰石纳米线改性的酸性纳米ZSM-5分子筛作为协效剂(HAP/HN)来改善PLA燃烧过程中火焰蔓延以及熔滴滴落现象.结果显示:极限氧指数值(LOI)由18.0％(纯PLA)升至38.2％(含HAP/HN样品);垂直燃烧测试(UL-94)达到V-0级;在锥形量热测试(CCT)中,燃烧速率峰值(pHRR)由553 kW/m2(纯PLA)降至191 kW/m2(含HAP/HN样品),表明HAP/HN对PLA阻燃性能有良好的改善作用.
可充电Li-CO2电池为碳捕获和储能提供了一种非常有前景的新途径.Li-CO2电池通过Li阳极失去电子形成的Li+与CO2、电子结合生成LizCO3和C,从而实现碳捕获和能量释放.阴极催化剂对Li-CO2电池至关重要,而碳基催化剂因其来源广泛、经济性好等原因成为了研究的热点.简要叙述了 Li-CO2电池的充放电机理和发展简史,归纳了 Li-CO2电池碳基阴极材料的研究进展,重点介绍了碳基材料及其改性对Li-CO2电池性能的提升情况,并总结了 Li-CO2电池未来发展面临的挑战与问题.由于Li-CO2电池在放电过程中形成的绝缘Li2CO3在充电过程中难以分解,容易产生积聚,最终导致电池性能快速衰减,探索具有独特结构和高催化活性的高效阴极催化剂以促进CO2与Li反应以及Li-CO2电池的充放电机理将成为未来研究的重点和难点.
[深入学习贯彻党的二十大精神·宁夏大学] 党的二十大报告指出,我们必须坚定历史自信、文化自信,坚持古为今用、推陈出新,把马克思主义思想精髓同中华优秀传统文化精华贯通起来、同人民群众日用而不觉的共同价值观念融通起来,不断赋予科学理论鲜明的中国特色,不断夯实马克思主义中国化时代化的历史基础和群众基础,让马克思主义在中国牢牢扎根.
为了实现甲烷干重整(DRM)自热的同时制取高品质的合成气,提出了由重整反应器(reforming reactor,RR)、裂解反应器(splitting reactor,SR)和空气反应器(air reactor,AR)组成的基于 Ca2Fe2O,载氧体(oxygen carrier,OC)两级氧化的自热化学链甲烷干重整新工艺.首先,利用AspenPlus软件对该工艺进行了模拟分析,研究了温度、压力、OC与CH4的摩尔流量比以及CO2与CH4的摩尔流量比对重整反应和裂解反应的影响.其次,探究了在自热条件下该工艺的最大潜力.最后,对系统的冷煤气效率进行了计算,并与DRM进行比较.结果表明,在最优条件下,重整反应器中CH4转化率能够达到99.58％,合成气中Hz与CO的摩尔流量比为1.98,反应器内均无积碳,且系统实现了自热.该工艺的冷煤气效率比DRM提高了 2.78％.通过载氧体的两级氧化,提高了化学链甲烷干重整过程效率,并实现碳捕集.
There are problems of agglomeration and low tapped density during ball-milling of producing high tapped-density and large silver flakes. To solve them, the effect of dispersion of raw spherical silver flakes on silver flakes ball-milling was investigated by analyzing the microscopic morphology and physical properties data of silver flakes before and after ball-milling. The results show that the dispersion of the raw flakes has a large influence on the quality of the silver flakes after ball milling, and when the value of the particle size distribution(D 100 -D 10 )/D 50 of the ball-milled raw material is closer to 1.0, the specific surface area is close to 0.22 m~2/g, and the tapped density is greater than 4.5 g/cm~3, the silver flakes obtained after ball-milling has a correspondingly higher tapped density and dispersion, and is used well at the customer application end. It can be used to quickly select the suitable raw material for ball-milling when producing high tapped-density and large particle size silver flakes.
以宁夏贺兰山东麓沿线分布的碎石土竖直边坡为研究对象,运用PFC 2D软件建立二维模型,分析动力荷载作用下的边坡稳定性,并根据颗粒位移及应力演变过程中的监测数据,分析碎石土边坡的滑动与灾变演化特征.结果表明:在 2 种动力荷载作用下,坡面颗粒最大运动距离均超过 5 m;横向地震波作用时,颗粒在临空状态下产生的横向位移较大;纵向地震波作用时,颗粒沿坡面滚落;2 种动力条件下坡体内的应力演变规律较为接近,应力变化与坡面的距离相关,距离越大,应力降低的速度越慢,幅度越小;纵向地震波作用时,其滑动范围小于横向地震波,但应力释放快于横向地震波;由坡体内部应力变化幅度可知,在动力荷载条件下,坡内大部分区域的应力降低至初始应力的 1/10,不利于灾害防治.
Based on conventional meteorological observation data and Himawari satellite remote sensing data, the strong sandstorm in Bayannaoer from May 5 to 6 in 2021 was analyzed. The results show that the sandstorm was caused by the combined actions of the upper-level jet stream, the strong frontal zone, a cold wave at the surface, the Mongolian cyclone, and a strong cold front generated in the transition zone. The stratification condition analysis shows that the “forward rolling flow” formed by uneven wind speed lead to the turning change of the weather from sunny to strong windy and dusty. It can provide reference for the study of air quality in Bayannaoer City by analyzing the changes of AQI, PM 2.5 and PM 10 during the weather process.
The large number of immigrants and the rapid advancement of urbanization have led to problems such as tension between people and land and serious land use conflicts in resettlement areas. Evaluating land bearing capacity and exploring the path of characteristic rural revitalization have become an inevitable requirement for promoting the sustainable development of resettlement areas. Minning Town, a typical ecological resettlement area in Ningxia, was selected as the research area to quantitatively evaluate its land bearing capacity and explore the sustainable development model and path in line with the rural revitalization strategy and ecological civilization construction of Minning Town. The results show that the per capita land bearing capacity of Minning Town in descending order are farmlands, construction lands, grasslands, forest lands, industrial and mining lands and waters, and the total land bearing capacity is proportional to the per capita land bearing capacity. Based on the research result, when determining rural revitalization path, Minning Town should choose the development mode of ecological agriculture and characteristic rural tourism, try to control the development of industry and mining, so as to reduce the bearing pressure of industrial and mining land, give full play to the advantages of land bearing capacity of farmland, construction land and grassland, mainly develop industries such as ecological agriculture and rural characteristic tourism, and strengthen infrastructure construction, so that Minning Town can achieve the goal of rural revitalization under the premise of sustainable development of land, ecology and environment.
Taking a simply-supported hollow-slab girder bridge of an interchange lane on the Baocheng Railway as the engineering background, the Midas FEA was used to establish a finite element model for the whole process of reinforcement construction.Considering the material nonlinearity of concrete, the structural forces of the simply-supported hollow-slab girder bridge before and after reinforcement and the key construction stages in the reinforcement process were calculated. The structural deformation, stress and crack width of the simply-supported hollow-slab girder bridge before and after reinforcement were compared and analyzed, and the effect of jacking on the reinforcement effect was also discussed. The results show that the structural deflection, stress, crack width and reinforcement stress are reduced to a certain extent after the reinforcement of simply-supported hollow-slab girder bridge with steel plates, but the reduction is small. It is suggested to lift the simply-supported hollow-slab girder bridge before the reinforcement of steel plates to increase the degree of synergistic stress of steel plates and improve the reinforcement effect.
为研究大面积超重堆场的地基处理方式,以某钢铁厂封闭环保型原料场项目为例,介绍了场地地质特点和地基处理方案,并通过静荷载试验进行了评价.原料场地层条件复杂,岩层分布不均,起伏及厚度差异大,因此需根据地质特点,实行分区处理:场地内大部分区域采用CFG桩网复合地基,桩径为 600 mm,桩顶设置桩帽,桩帽上覆级配砂石褥垫层,垫层内铺设土工格栅;局部安山岩埋深较浅区域不作处理.由静荷载试验可知,单桩承载力和复合地基承载力特征值均满足设计要求,表明该地基处理方案可行,可为类似地质情况和大面积超重堆场、原料场地基处理提供参考.
To study the influence of freeze-thaw cycles on the mechanical properties of concrete, compression strength experiments of concrete mixed with desert sand and fly ash（DSC） after freezing and thawing cycles at different low temperatures（-20 ℃,-30 ℃ and-40 ℃） were carried out. The influence of desert sand replacement rate（DSRR）, temperature and number of freezethaw cycles on DSC compressive strength and ultrasonic velocity was analyzed. The regression models between DSC compressive strength, ultrasonic velocity and temperature, DSRR and number of freeze-thaw cycles were established. The results show that as the number of freeze-thaw cycles increases, the DSC compressive strength and ultrasonic velocity decrease. When the temperature decreases, the DSC compressive strength and ultrasonic velocity decrease. With the increase in DSRR, DSC compressive strength firstly increase and then decrease. When the DSRR is 40%, its compressive strength reaches the maximum.
In order to understand the corrosivity of reinforced concrete（RC） structures in service in Ningxia, some RC structures in five cities of Ningxia were selected for investigation. Through water quality analysis of surface water and XRD analysis of damaged concrete, the corrosivity of RC structures adjacent to water in Ningxia were revealed. The results show it is the worst in Wuzhong City with the highest mass concentration of sulfate ion in water. The deterioration of RC structures adjacent to water is mainly caused by the physical erosion of sulfate crystals, accompanied by a small amount of chemical erosion, and freeze-thaw cycles. According to the investigation results, the corrosivity of concrete in Ningxia are divided into four grades frommoderate to severe: salt crystallization on surface, pitting corrosion, protective layer falling off and core concrete collapsing. The present anti-corrosion measures are with great deficiencies, which need to be studied from the anti-corrosion materials under the combined action of sulfate crystallization, dry-wet cycle and freeze-thaw cycle and the bonding performance with the old base.
In order to grasp the variation law of precipitation in Pengyang County of Ningxia under the background of climate change and to improve the utilization efficiency of water resources and the level of agricultural development in this area, the climate tendency rate, M-K mutation test method, Sen’s slope method, R/S method, sliding t test method, wavelet analysis method and other methods were used to analyze the daily precipitation data of Pengyang County from 1975 to 2019. The results show that the average annual precipitation in Pengyang County in the past 45 years is 459.87 mm, and the precipitation change is relatively stable.Except for summer, the precipitation in each period of the year show an insignificant increasing trend, and the annual precipitation and summer precipitation in the next 5 years will decrease. The precipitation of multiple research periods changes abruptly in the 1990s, and the mutation in 2009 is significant. The annual precipitation process shows periodic changes in multi-time scale, with 12 a as the first main cycle and 9 a as the second main cycle. The research results are with reference significance for the optimal allocation of water resources and sustainable development of agriculture in Pengyang County.
