This review summarizes recent applications of nuclear magnetic resonance (NMR) in olefin polymerization catalysis. Due to its capability for quantitative characterization of molecular structures and in situ study, NMR is employed to study the structure of catalysts, and to trace catalyst/cocatalyst interactions, the evolution of active species, monomer insertion, and chain-end formation. This review emphasizes the activation mechanisms of molecular catalysts, ion-pair structures, and the measurement of kinetics. It also discusses the potential applications of in situ multinuclear NMR and isotope labeling technologies in olefin polymerization catalysis studies.

The Haber-Bosch process, which synthesizes ammonia (NH3) from nitrogen (N2) and hydrogen (H2), consumes approximately 2% of the global energy supply. A sustainable alternative is the direct electrochemical conversion of N2 to NH3. The selectivity and activity of the electrocatalysts for this process are assessed by quantifying the NH3 present in the electrolyte. Compared with other analytical methods, 1H NMR offers a straightforward approach for detecting NH3 (by analyzing NH4 +). 1H NMR method can also definitely confirm that the detected ammonia originates from the electroreduction of N2 by comparing results obtained from isotopically labeled 15N2 and regular 14N2 gases. This capability is unique to the 1H NMR method, as no alternative approaches offer this level of specificity. However, this method suffers from low sensitivity when measuring NH4 + of low concentration of such as at μM or lower. To address this issue, we developed a novel approach that improves sensitivity by ∼3-fold through the introduction of 14N decoupling during the 1H NMR data acquisition. Recently [Kolen M.ACS Omega2021, 6, 5698-5704], demonstrated a ∼3.5-fold increase in sensitivity by using a 1 mM concentration of the paramagnetic relaxation agent Gd3+. By combining our 14N decoupling technique with the relaxation agent Gd3+, we achieved a synergistic enhancement in sensitivity, resulting in an overall ∼10.9-fold sensitivity increase for the 1H NMR detection of 14NH4 +. This translates to a reduction in NMR detection time by a factor of ∼119 (10.92). This significant advancement enables the fast detection of ammonia at μM concentration or lower. 1H NMR of 15NH4 + with 15N decoupling was also demonstrated.

Raman mapping was employed to determine the spatial distribution of monomeric units in polypropylene at the micron scale. The instrument was calibrated using a series of ethylene/propylene copolymer samples containing various amounts of comonomer. The calibration model was developed using the Partial Least Squares (PLS) method and validated against NMR results. For the measurement, confocal raman mapping was conducted across the samples to measure the content of ethylene units. The results were demonstrated as heat maps of the ethylene content. It exhibited the different of chemical distribution between a commercial heterophasic copolymer of propylene (HeCoPP) and a commercial random copolymer (RanCoPP). Furthermore, A semi-quantitative evaluation method for compatibility was developed by analyzing the frequency distribution of ethylene content.

Polypropylene (PP) accounts for approximately 28.0% of the global polyolefin market, valued at $243.4 billion in 2022. Known for its lightweight, chemical resistance, cost-effectiveness, high strength and melting point, PP is widely used in various applications. Its properties and applications are closely tied to its tacticity. One-dimensional (1D) conventional 13C NMR has been extensively utilized to analyze PP tacticity, but its low sensitivity and longer relaxation time remain drawbacks. Typically, analyzing a single PP sample requires around 9 h of NMR time. Using of a cryogenically cooled 10 mm NMR probe can significantly reduce this measurement time; however, its high cost makes it inaccessible for most NMR laboratories. While the refocused insensitive nuclei enhanced by polarization transfer (RINEPT) technique is well-known for enhancing NMR sensitivity, there are no published studies using 1D 13C RINEPT to quantify PP tacticity. Relaxation agents like chromium (III) acetylacetonate (Cr(acac)3) have also been used to reduce relaxation times in polyolefin NMR analyses. Here we introduce a straightforward and easily implementable 1D 13C NMR method for rapid PP tacticity quantification. This method combines Cr(acac)3, Bruker's existing RINEPT pulse sequence (ineptrd), and our recently published 1H decoupling sequence (bi_waltz65_256 pl) to eliminate 1H decoupling artifacts. It is worth noting that decoupling artifacts are always present. When the signal-to-noise ratio (SNR) is low, these artifacts are obscured by noise. For example, in some two-dimensional (2D) or three-dimensional (3D) NMR spectra, decoupling artifacts are barely visible because of the low SNR. However, when attempting to observe weak signals in 1D spectra, increasing the sample concentration or the number of scans enhances the SNR, revealing the decoupling artifacts. The decoupling artifacts appeared superimpose with some other weak signals, affecting the measurements of signal intensities. Therefore, improved 1H-decoupling methods are crucial for such data acquisition. This synergy results in a 9.4- to 9.7-fold sensitivity enhancement, equating to an 88- to 94-fold reduction (9.42 ≈ 88, 9.72 ≈ 94) in NMR acquisition time compared to conventional 1D 13C NMR experiment with Cr(acac)3. The time savings are even more substantial compared to experiments without Cr(acac)3. The faster and quantitative approach is accessible to researchers with or without cryoprobes. Beyond PP, this method can be applied to tacticity measurements of other polyolefins, such as polybutene, polyhexene and polyoctene.

Polyolefins, which are vital materials in a wide range of industries, demand accurate and rapid microstructural analysis to enhance and optimize their performance characteristics. Triad sequence distributions are widely used to evaluate critical parameters, including comonomer content, monomer number-average sequence length, and the blockiness Koenig B value. While conventional algebraic methods for determining these values often lack accuracy, this study presents a more precise approach based on matrix operations. Traditional quantitative 13C NMR has long served as the primary technique for analyzing polyolefin microstructures. However, its low sensitivity and lengthy acquisition time limit high-throughput analysis and hinder the practical determination of certain microstructural details. To overcome these limitations, we propose a synergistic approach that combines chromium-(III) acetylacetonate (Cr-(acac)3), a relaxation agent, with an artificial intelligence (AI)-optimized quantitative RINEPT (AIOQ-RINEPT) pulse sequence. Using a customized simulated annealing algorithm, a machine learning technique commonly used in AI model training, we optimized the variable delays τ2 in the RINEPT sequence while keeping the delay τ1 fixed. This optimization leads to uniform sensitivity enhancement across CH, CH2, and CH3 signals. The AIOQ-RINEPT technique, incorporating triply compensated 180° pulses (G5), ensures a broad excitation bandwidth. This method achieved a 7.5-fold increase in sensitivity, equivalent to a 56.3-fold reduction in acquisition time compared to conventional inverse-gated 13C NMR. When combined with cryoprobe technology, a 41.3-fold improvement in sensitivity could be realized, resulting in a 1,706-fold decrease in acquisition time, making high-throughput analysis feasible. Experimental validation using a poly-(ethylene-co-1-butene) (EB) copolymer with a sufficiently high weight-average molecular weight (M w = 120,700 kg/mol) demonstrated accurate quantification of triad sequence distributions, comonomer content, and blockiness parameters. Two additional EB samples with lower weight-average molecular weights (M w = 86,000 and 58,000 kg/mol) were also employed to further validate the method. The method also effectively resolved signal overlap issues commonly encountered in samples with a high comonomer content. Moreover, the approach is broadly applicable to a wide range of polyolefins. This advancement enables rapid, automated 13C NMR analysis of virgin and recycled polyolefins, allowing high-throughput characterization and sensitive detection of low-abundance features like long-chain branching (LCB). Additionally, the technique is suitable for analyzing low molecular weight saturated hydrocarbons, including Fischer-Tropsch products, such as waxes, lubricating oils, and jet fuel.

炉底渣的产量约占粉煤灰总产量的20%,年产量过亿吨,但是其综合利用率远低于粉煤灰,综合利用并没有受到重视,缺乏材料特性及差异性研究,未能充分发挥其材料性能.本工作从炉底渣颗粒大小形貌、化学成分及矿物相组成三方面对宁夏地区11 家煤粉炉电厂和 1 家循环流化床电厂的炉底渣进行材料特性研究.结果表明,炉底渣细度模数范围为0.9～2.6,其中11 家样品的砂粒含量都大于50%,属于砂土;煤粉炉和循环流化床炉底渣颗粒形貌均为不规则形貌,都含有少量未燃尽的多孔碳颗粒,但二者的形貌具有显著差异;11 家煤粉炉炉底渣的二氧化硅、三氧化二铝和三氧化二铁总质量分数(%)均大于等于70%,循环流化床炉底渣具有低铁高硫高钙的特点.矿物相方面10 家炉底渣以石英为主,2 家电厂的炉底渣以莫来石为主.炉底渣的材料特性对应其应用的颗粒效应、化学成分效应和矿物相效应,建议根据其颗粒效作为砂土应用于土壤修复和土壤改良,根据其化学效应替代天然砂作为骨料,根据其矿物相效应,应用于莫来石陶瓷,或应用于建材、道路等作为辅助胶凝材料.

对SAPO-34分子筛在700℃、质量分数为100％的水蒸汽下进行水热处理,采用XRD、NH3-TPD及固体MAS-NMR等表征分析了水热处理对分子筛的结构、酸性的影响.结果表明,SAPO-34分子筛在水热处理过程中结晶度提高,Si(4Al)物种逐渐向Si(3Al)物种转变,SAPO-34分子筛酸强度增加.固定床评价结果显示,SAPO-34分子筛经水热处理12 h后与ZnCr2O4制得的双功能催化剂(BS-12)在合成气一步法制烯烃反应中性能最佳,CO转化率约为23％,C2=～C4=的烯烃选择性约为75％.长周期实验显示,催化剂运行120 h无明显失活.

The D2 dopamine receptor (DRD2) gene has been associated with alcoholism and other drug use disorders. Reduced P300 amplitude has been noted in individuals with psychiatric disorders. Personality variables are also associated with reduced P300 amplitude. The current study was conducted to determine whether variants of the DRD2 would show differential relationships among P300 amplitude and personality traits. The study consisted of 101 adolescent children of alcoholics; 39 carried the A1+ genotype (A1A1, A1A2) and 62 carried the A1− genotype (A2A2). The A1+ genotype group had higher IQ and Self-Directedness scores than the A1− genotype group. As predicted, the negative relationship between Novelty Seeking and Harm Avoidance was present in A1− but not A1+ participants. Additionally, in A1+ but not in A1− participants, there was a negative relationship between Novelty Seeking and Self-Directedness and a positive relationship between P300 amplitude and Cooperativeness. The results suggest that in adolescent children of alcoholics, dopaminergic genetic determinants are critical modifiers of the relationship between neurocognitive and personality endophenotypes proposed as vulnerability markers for substance use disorders.

Biodegradable polyglycolic acid (PGA) has been attracting much attention recently. However, poor melt strength and thermal stability limit the processing of PGA by methods such as film blowing and injection molding. To improve melt strength and thermal stability, two reactive chain extenders, styrene-acrylonitrile-glycidyl methacrylate terpolymer (poly(St-AN-GMA)) and 4, 4 '-methylenebis(phenyl isocyanate) (MDI), were incorporated respectively into PGA using twin-screw extrusion. MDI was found to be more effective in chain extension and enhancing thermal stability than poly(St-AN-GMA). The T-5% (the temperature where the remaining weight percentage is 95%) of PGA modified with 3 wt% MDI increased to 334.5 degrees C from 310.8 degrees C for pure PGA. Melt flow rate for the same materials decreased from 47.2 g/10 min to 13 g/10 min. The activation energy of thermal degradations for MDI-modified PGA was twice that of the unmodified PGA as evaluated by the Flynn-Wall-Ozawa method.

研究了2种国产电缆绝缘专用低密度聚乙烯(LDPE)2220H(分别记作LDPE A,LDPE B)的分子链段结构、动态流变性能、熔融结晶性能、体积电阻率和直流击穿强度.结果表明:LDPE A的相对分子质量和长支链含量高于LDPE B,相对分子质量分布相近;结晶度和熔融温度较高的LDPE A在较高温度条件下的体积电阻率高于LDPE B;LDPE A的特性击穿强度稍高于LDPE B;LDPE的电气性能与其长支链含量和结晶性能密切相关.

选用3种国内商品化的电缆用低密度聚乙烯(LDPE),利用凝胶渗透色谱仪、升温淋洗仪、红外光谱仪、差示扫描量热仪研究了其链结构和交联性能,探讨了相对分子质量及其分布、链支化、双键等因素对树脂结晶行为和交联性能的影响.结果表明:支链含量越少,亚甲基序列越长,结晶能力越强,其结晶度越高;端双键含量越高,其交联反应速率越快;凝胶含量高可能与树脂相对分子质量大、长支链含量高有关.

通过熔融共混方法,采用环氧类扩链剂对聚乙醇酸(PGA)进行反应挤出改性,同时添加亚磷酸酯类抗氧剂来降低熔融加工过程中的热降解.研究了扩链剂与抗氧剂联用对PGA熔体质量流动速率、热稳定性、熔体流变性能以及抗水解性能的影响.结果表明,扩链剂与抗氧剂复配,PGA改性料的熔体质量流动速率由原料的44.2 g/10min下降至11.2 g/10min;起始分解温度T-5％(质量剩余95％的温度点)提高22.1℃;熔体黏度提高6倍以上;在提高了熔体强度的同时,改性料热稳定性明显改善,同时抗水解稳定性也有一定程度提高.

The reaction mechanisms of potassium glycine (KG)-CO2 absorption, thermal desorption and mineralization desorption with CaO were studied based on the contents of carbamate, bicarbonate/carbonate, and KG/protonated KG analyzed by C-13-quantitative nuclear magnetic resonance (C-13 qNMR). KG as the absorbent shows the CO2 absorption efficiency up to 76% which has 57% due to the bicarbonate/carbonate formation and 43% due to the carbamate formation. Mineralization has a higher CO2 desorption efficiency of 59% than that of thermal desorption (47%), and the results also indicate that carbamate is less stable under mineralization than under heat although both processes show the similar profiles as a function of pH value for carbamate and bicarbonate/ carbonate. A new mechanism has been proposed to explain carbamate increasing with significantly decreasing bicarbonate/carbonate at the early stage of mineralization desorption while the other mechanisms reported in literatures have also been confirmed in this study.

Extraction residue (ER) is, in this study, considered as an insoluble portion derived from a novel extraction process with direct coal liquefaction residue, which is the byproduct from 1000 kton/y direct coal liquefaction and oil production process in Ordos, China. ER mostly consists of unreacted coal and minerals, spent catalyst, and solvent. It is considered as a hazardous waste in China. Gasification is a promising way to employ ER, as the carbon resource contained in it could be adequately utilized, so strongly reducing the environmental impact of this material. In this paper, a kinetic study is carried out concerning CO2 gasification (in thermobalance) of ER char, coal char, and their blends. The results show that, at temperatures ranging from 1123 to 1323 K, the reactivity of ER char is much larger than that of coal char, and the reactivity of ER/coal char blends increases when the ER fraction increases, consistently resulting in between the reactivities shown by ER char and coal char alone. The partial pressure of CO2 promotes the reactivity of all samples. BET surface area resulted three times larger for ER char vs coal char, while pore surface area and pore volume were four times larger. Moreover, the relevant parameters of the random pore model for CO2 gasification of ER char, coal char, and their blend #2 (with 20% ER) were obtained; the activation energy resulted 210.6, 240.5, and 232.8 kJ/mol, and the reaction order 0.30, 0.45, and 0.40, respectively.

采用脉冲序列t1irpg测定甘氨酸钾-二氧化碳吸收体系13 C的纵向弛豫时间(1.4～24.6 s),确定了循环延迟时间为50 s.采用反转门控去耦技术(脉冲序列Zgig30),建立了测定甘氨酸钾-二氧化碳吸收体系的二氧化碳负载量的定量核磁共振碳谱(13 C-qNMR)方法.方法用于多个样品的分析,并与传统滴定方法进行对比,方法具有准确度高、环境友好、可以根据化学位移识别物种的变化等优点.

以某进口料滚塑交联聚乙烯油桶制品缺陷为研究对象,采用扫描电子显微镜、体视显微镜、计算机断层扫描技术等对缺陷制品的横纵切面、内外表面泡孔形貌及泡孔分布进行分析,并对横切面层的凝胶含量进行测试.结果表明,制品内有丰富的泡孔,除与模具接触的外表面几乎无孔,其余部分都有不同程度的泡孔,次外层孔分布最多,且发现层间贯穿孔,其深度超过1.9 mm,整体制品的孔隙率为2.4％;切片层每层的凝胶含量均超过60％;综合分析认为缺陷制品内部丰富的气泡是由于在滚塑过程中过早发生了交联而使体系黏度变大,气泡未能排出从而留在了制品中,最终造成了多孔缺陷,并给出了预防多孔缺陷的建议.

采用分步沉淀法制备出一系列不同铝含量的催化剂样品,通过X射线衍射(XRD)、热重-质谱(TG-MS)、荧光光谱仪(XRF)、N2物理吸附、氢气程序升温还原(H2-TPR)对样品进行表征,考察了不同铝添加量对铜基甲醇催化剂性能的影响.结果表明,铝元素的添加对前驱物中碱式碳酸盐组分产生作用,促进了焙烧后样品中高温碳酸盐的形成,进而影响到催化剂的性能.随着铝元素的添加,焙烧后催化剂的比表面积、催化剂活性和热稳定性均有增加.当Al3+/(Cu2++Zn2++Al3+)物质的量比增加至30％时,催化剂在230℃、4 MPa和合成气(13％CO、1.2％CO2、80％H2、5.8％Ar)的评价条件下,热处理前后的CO转化率分别为76％和67％,仍保持着较高的活性和热稳定性.

为准确测定粉煤灰中的碳含量,采用热重质谱联用(TG-MS)模拟、追踪了传统烧失量方法(GB/T 176-2008)及在热重双气氛下(先惰性气氛再氧化性气氛)粉煤灰烧失过程.结果 表明,传统马弗炉法测得的粉煤灰烧失量主要由水挥发、无机化合物分解及未燃尽碳的燃烧组成,该方法表征的碳含量值会高于实际值;双气氛热重法可区分失重的来源.在惰性气氛下的失重来自于水的挥发及无机盐的分解,在氧化气氛下的失重源自未燃尽碳的真实含量.双气氛热重法可通过一次试验得到水和无机盐含量、碳含量及烧失量,测试方法更便捷,测量值更准确.