钼基催化剂技术发展现状

钼基催化剂广泛用于原油加氢、加氢脱硫,氨氧化丙烷为丙烯腈,气相催化氧化丙烯醛为丙烯酸,1-丁烯氧化脱氢生产1,3-丁二烯,从合成气生产乙醇或混合醇,甲烷干式重整,催化热解含碳气体生产碳纤维或纳米碳管,煤液化或气化和含氮氧化物废气净化等。     

氯化法钛白氧化反应器结构分析与模拟

气相氧化反应器是氯化法钛白工艺中的核心技术，对其设备的组成结构进行分析，并讨论气相氧化反应器的模拟进展，提出建立过程控制模型的思路。     

氯化亚锡的气相氧化水解

研究了气态SnCl2与O2的高温氧化反应及与O2、H2O的高温氧化水解反应。表明，前者的反应产物为SnO2和SnCl4，在900℃和原始气相含O2 5％时，反应进行得极为完全；后者的反应产物为SnO2和HCl，在原始气相含水蒸汽及1％和O2时，只需温度达800℃，SnCl2即可被彻底氧化水解为SnO2。可据此推断，在低锡物料氯化焙烧窑高温区，SnCl2一经氯化形成进入气相，即被窑气中的O2和H2O，氧化水解为SnO2微粒并被窑气携带进入收尘系统。     

多组份钼酸铋催化剂的工作机理

籍用载在CoMoO_4及Co_(11/12)Fe_(1/12)MoOx载体上的钼酸铋薄层来研究多组份钼酸铋氧化催化剂的工作机理。通过添加少量的载在Co_(11/12)Fe(1/12)MoOx载体上的钼酸铋,使丙烯氧化中丙烯醛的选择性和活性得到了明显提高,而添加载在CoMoO_4载体上的钼酸铋则很少使催化行为改变。丙烯氧化主要是在Co_(11/12)Fe_(1/12)MoOx载体上的钼酸铋     

气相氧化法工艺对金刚石与石墨微粉混合物的分离效果的影响研究

采用气相化学分离技术对金刚石与石墨微粉混合物进行了分离,探讨了工艺条件对微粉混合物中石墨的去除率的影响.通过单因素和正交试验对微粉混合物中石墨去除率的影响因素进行了研究,并对所得样品进行了性能测试(强度、纯度).结果表明,金刚石与石墨分离的最佳工艺条件为:氧化分离温度660℃,持续氧化时间7h.性能测试结果表明:气相化...     

用TiCl4制备纳米TiO2的研究状况

综述了以TiCl4为原料制备纳米TiO2的主要方法:氢氧火焰水解法、气相氧化法、气相燃烧法、液相沉淀法、溶胶-凝胶法、微乳液法和水热法,并对其优缺点做了相应的评论,最后指出了今后研究的方向。     

Si-SiC涂层包覆石墨材料的制备及性能表征

为了防止石墨材料在高温下的氧化,以SiC和酚醛树脂为原料,采用气相渗硅法在石墨表面制备了致密的Si-SiC涂层.利用XRD、SEM对涂层的相组成与形貌进行分析,研究了涂层在1 500℃以及1 000℃的热循环氧化行为.结果表明:经过气相渗硅后,涂层结构致密,主要由Si和SiC组成.该涂层具有良好的抗氧化防护能力,在空气条件下1 500℃和1 000℃循环氧化200 h,468 h后,包覆试样的表面质量增加分别为1.676 mg/cm~2,0.36 mg/cm~2.     

稀土氧化物对钼-铋催化剂性能的影响

在异丁烯选择氧化制甲基丙烯醛的钼-铋催化剂中加入La2O3等八种稀土氧化物,并在固定床反应器中考查了反应温度、异丁烯浓度、原料气的流速和稀土氧化物的添加量对异丁烯转化率和生成甲基丙烯醛选择性的影响。实验表明,CeO2、Eu2O3及Tb4O7添加后,可明显提高异丁烯转化率和生成甲基丙烯醛的选择性。     

氧化或氨氧化催化剂

本发明公开了一种用于丙烷或异丁烷的气相催化氧化或气相催化氨氧化的氧化物催化剂，其包含以特定原子比含有钼（Mo）、钒（V）、铌（Nb）和锑（Sb）作为组成元素的氧化物，所述氧化物催化剂的还原率为8％～12％，比表面积为5～30m^2／g。还提供了一种用于高效生产该催化剂的方法。     

MgO—C砖组织与防氧化剂反应速度的关系

MgO-C（即镁碳）砖是耐蚀性、耐热剥离性优良的材质，一直广泛应用于炼钢领域。然而，其缺点是砖中c瞅）易氧化。C的氧化可分为与O2气的气相氧化、和熔渣中FeO等的液相氧化、以及MgO—C之间的固相氧化，当砖在大气中加热冷却时，则主要是气相氧化。作为防止C氧化的防氧化剂，广泛使用Al、Si、Al—Mg等金属粉。其能有效抑制C的氧化机理，可以从热力学的观点进行解释。     

Acrolein is a product of lipid peroxidation reaction. Formation of free acrolein and its conjugate with lysine residues in oxidized low density lipoproteins

Lipoprotein peroxidation, especially the modification of apolipoprotein B-100, has been implicated to play an important role in the pathogenesis of atherosclerosis. However, there have been few detailed insights into the chemical mechanism of derivatization of apolipoproteins during oxidation. In the present study, we provide evidence that the formation of the toxic pollutant acrolein (CH2=CH-CHO) and its conjugate with lysine residues is involved in the oxidative modification of human low density lipoprotein (LDL). Upon incubation with LDL, acrolein preferentially reacted with lysine residues. To determine the structure of acrolein-lysine adduct in protein, the reaction of acrolein with a lysine derivative was carried out. Employing Nalpha-acetyllysine, we detected a single product, which was identified to be a novel acrolein-lysine adduct, Nalpha-acetyl-Nepsilon-(3-formyl-3,4-dehydropiperidino )lysine. The acid hydrolysis of the adduct led to the derivative that was detectable with amino acid analysis. It was revealed that, upon in vitro incubation of LDL with acrolein, the lysine residues that had disappeared were partially recovered by Nepsilon-(3-formyl-3, 4-dehydropiperidino)lysine. In addition, we found that the same derivative was detected in the oxidatively modified LDL with Cu2+ and that the adduct formation was correlated with LDL peroxidation assessed by the consumption of alpha-tocopherol and cholesteryl ester and the concomitant formation of cholesteryl ester hydroperoxide. Enzyme-linked immunosorbent assay that measures free acrolein revealed that a considerable amount of acrolein was released from the Cu2+-oxidized LDL. Furthermore, metal-catalyzed oxidation of arachidonate was associated with the formation of acrolein, indicating that polyunsaturated fatty acids including arachidonate represent potential sources of acrolein generated during the peroxidation of LDL. These results indicate that acrolein is not just a pollutant but also a lipid peroxidation product that could be ubiquitously generated in biological systems.     

Psychosocial aspects of palliative care

The metabolites of [2,3-14C]acrolein in the urine and feces of Sprague-Dawley rats were identified after either intravenous administration in saline at 2.5 mg/kg or oral administration by gavage as an aqueous solution as either single or multiple doses at 2.5 mg/kg or as a single dose of 15 mg/kg. Selected urine and feces samples were pooled by sex and collection interval and profiled by combinations of reverse-phase, anion-exchange, cation-exchange, and ion-exclusion high-performance liquid chromatography (HPLC). Feces were also profiled by size-exclusion chromatography. Metabolites were identified by comparison with well-characterized standards by HPLC and by mass spectrometry. The urinary metabolites were identified as oxalic acid, malonic acid, N-acetyl-S-2-carboxy-2-hydroxyethylcysteine, N-acetyl-S-3-hydroxypropylcysteine, N-acetyl-S-2-carboxyethylcysteine, and 3-hydroxypropionic acid. The fecal radioactivity from the oral dose groups was partitioned into methanol-soluble, water-soluble, and insoluble radioactivity, some of which could be liberated by dilute acid hydrolysis. HPLC analysis of these extracts revealed no discrete metabolites. Size-exclusion chromatography indicated a molecular weight range of 2,000 to 20,000 Da for the radioactivity, which was unaffected by hydrolysis at reflux with 6 M acid or base. This radio-activity was thought to be a homopolymer of acrolein, which was apparently formed in the gastrointestinal tract. The pathways of acrolein metabolism were epoxidation followed by conjugation with glutathione, Michael addition of water followed by oxidative degradation, and glutathione addition to the double bond either following or preceding oxidation or reduction of the aldehyde. The glutathione adducts were further metabolized to the mercapturic acids.     

Formation of acrolein-derived 2'-deoxyadenosine adduct in an iron-induced carcinogenesis model

Acrolein is a representative carcinogenic aldehyde found ubiquitously in the environment and formed endogenously through oxidation reactions, such as lipid peroxidation and myeloperoxidase-catalyzed amino acid oxidation. It shows facile reactivity toward DNA to form an exocyclic DNA adduct. To verify the formation of acrolein-derived DNA adduct under oxidative stress in vivo, we raised a novel monoclonal antibody (mAb21) against the acrolein-modified DNA and found that the antibody most significantly recognized an acrolein-modified 2' -deoxyadenosine. On the basis of chemical and spectroscopic evidence, the major antigenic product of mAb21 was the 1,N6-propano-2' -deoxyadenosine adduct. The exposure of rat liver epithelial RL34 cells to acrolein resulted in a significant accumulation of the acrolein-2' -deoxyadenosine adduct in the nuclei. Formation of this adduct under oxidative stress in vivo was immunohistochemically examined in rats exposed to ferric nitrilotriacetate, a carcinogenic iron chelate that specifically induces oxidative stress in the kidneys of rodents. It was observed that the acrolein-2' -deoxyadenosine adduct was formed in the nuclei of the proximal tubular cells, the target cells of this carcinogenesis model. The same cells were stained with a monoclonal antibody 5F6 that recognizes an acrolein-lysine adduct, by which cytosolic accumulation of acrolein-modified proteins appeared. Similar results were also obtained from myeloperoxidase knockout mice exposed to the iron complex, suggesting that the myeloperoxidase-catalyzed oxidation system might not be essential for the generation of acrolein in this experimental animal carcinogenesis model. The data obtained in this study suggest that the formation of a carcinogenic aldehyde through lipid peroxidation may be causally involved in the pathophysiological effects associated with oxidative stress.     

Aldose reductase-catalyzed reduction of acrolein: implications in cyclophosphamide toxicity

Acrolein, a highly cytotoxic aldehyde, is a metabolic by-product of the antineoplastic agent cyclophosphamide and is responsible for the development of hemorrhagic cystitis, a serious side effect of cyclophosphamide therapy. Aldose reductase (EC 1.1.1.21), a member of the aldo-keto reductase superfamily, catalyzes the NADPH-dependent reduction of acrolein to allyl alcohol (Km = 80 microM, kcat = 87 min-1). Aldose reductase is expressed at different levels in individuals. This suggests that individual differences in the reductive metabolism of acrolein may be a determinant of acrolein toxicity. In addition to being a substrate, acrolein also produces a time-dependent 7-20-fold increase in the activity of aldose reductase toward a variety of substrates. This involves initial binding of acrolein to a second site (Ks = 58 microM). Acrolein activation of aldose reductase results not only in higher kcat values for all substrates but also in higher Km values and decreased catalytic efficiencies. Acrolein activation of aldose reductase reduces its affinity for aldose reductase inhibitors.     

Relationships between cell density, glutathione and proliferation of A549 human lung adenocarcinoma cells treated with acrolein

Acrolein is a highly electrophilic alpha,beta-unsaturated aldehyde to which humans are exposed in various situations. Acrolein reacts rapidly with and depletes cellular glutathione (GSH), and is toxic to various types of cells. In the current study, the ability of acrolein to alter proliferation of A549 cells was found to be dependent on cell density as well as total cell number. Thus, 'doses' must be expressed per cell rather than as a concentration, and all related studies need to be performed by plating a constant number of cells. A549 cells were plated at various densities and treated with acrolein after 48 h. Acrolein doses up to 47 fmol/cell at the time of treatment did not cause cell lethality. However, growth of A549 cells (as shown by thymidine incorporation, alamarBlue and total protein) was inhibited at acrolein levels > 34 fmol/cell in 6-well plates seeded at 5000 cells/cm2 48 h prior to treatment. Cellular GSH levels were decreased 34% by 2 h at acrolein levels of 6.7 fmol/cell and by 65% at 47 fmol/cell. Recovery of GSH was rapid at 6.7-47 fmol/cell acrolein, returning to control levels or above by 12 h post-treatment. These data show a strong correlation between cellular GSH and proliferation. The apparent conflict with a previous study of Ramu et al., suggesting that sublethal concentrations (up to 10 microM) of acrolein inhibited the proliferation of A549 cells without a decline in total cellular GSH, arose because, while the acrolein concentration was the same in cells used for proliferation and GSH assays, GSH measurements were done in cells plated at a higher density, resulting in a much lower acrolein dose per cell. Interestingly, very low dose levels of acrolein with cells seeded at low densities stimulated cell growth despite an initial decline in GSH content. Preliminary studies with the stress genes hsp70 and gadd153 suggest that acrolein at 35 fmol/cell does not stimulate formation of their mRNA beyond the level stimulated by a 2 h incubation in serum-free medium but may actually delay or decrease the induced expression. The mechanism(s) of the inhibitory and mitogenic effects of acrolein remains to be determined, but could be due to changes in gene expression induced by this electrophile, perhaps mediated by changes in GSH.     

Torsades de pointes: a case with multiple variables

PURPOSE: The human medulloblastoma cell line D283 Med (4-HCR), a line resistant to 4-hydroperoxycyclophosphamide (4-HC), displays enhanced repair of DNA interstrand crosslinks induced by phosphoramide mustard. D283 Med (4-HCR) cells are cross-resistant to 1,3-bis(2-chloroethyl)- -nitrosourea, but partial sensitivity is restored after elevated levels of O6-alkylguanine-DNA alkyltransferase (AGT) are depleted by O6-benzylguanine (O6-BG). Studies were conducted to define the activity of 4-HC and 4-hydroperoxydidechlorocyclophosphamide against D283 Med (4-HCR) after AGT is depleted by O6-BG. METHODS: Limiting dilution and xenograft studies were conducted to define the activity of 4-HC and 4-hydroperoxydidechlorocyclophosphamide with or without O6-BG. RESULTS: The activity of 4-HC and 4-hydroperoxydidechlorocyclophosphamide against D283 Med (4-HCR) was increased after AGT depletion by O6-BG preincubation. Similar studies with Chinese hamster ovary cells, with or without stable transfection with a plasmid expressing the human AGT protein, revealed that the AGT-expressing cells were significantly less sensitive to 4-HC and 4-hydroperoxydidechlorocyclophosphamide. Reaction of DNA with 4-HC, phosphoramide mustard, or acrolein revealed that only 4-HC and acrolein caused a decrease in AGT levels. CONCLUSIONS: We propose that a small but potentially significant part of the cellular toxicity of cyclophosphamide in these cells is due to acrolein, and that this toxicity is abrogated by removal of the acrolein adduct from DNA by AGT.     

The role of malonyl-coa in the coordination of fatty acid synthesis and oxidation in isolated rat hepatocytes

Fatty acid synthesis and fatty acid oxidation were examined in rat hepatocytes under a variety of experimental conditions. In cells from fed animals, glucagon acutely switched the direction of fatty acid metabolism from synthesis to oxidation. Addition of lactate plus pyruvate had the opposite effect. The inhibitory action of glucagon on fatty acid synthesis and its stimulatory effect on fatty acid oxidation were largely, but not completely, offset by the simultaneous addition of lactate plus pyruvate. Changes in cellular citrate and malonyl-CoA levels indicated that glucagon exerted its inhibitory effect on fatty acid synthesis at two levels: (i) blockade of glycolysis; and (ii) partial inhibition of a more distal step, probably acetyl-CoA carboxylase. Under all conditions, fatty acid oxidation was related in a linear and reciprocal fashion to the rate of fatty acid synthesis and the tissue malonyl-CoA content. The latter fluctuated through a range of 1 to 6 nmol per g wet weight of cells. Since malonyl-CoA inhibits carnitine acyltransferase I of liver mitochondria with a Ki in the region of 1 to 2 micron, the present studies support the concept that this compound plays a pivotal role in the coordination of hepatic fatty acid synthesis and oxidation. The ketogenic effect of glucagon on liver appears to be manifested in large part through the ability of the hormone to reduce the tissue malonyl-CoA concentration.     

含砷金精矿催化压力氧化—氰化提金试验研究

针对某含砷金精矿,进行了催化压力氧化—氰化提金工艺研究,考察了亚硝酸钠用量、氧化温度、硫酸用量、氧分压等对催化压力氧化效果的影响。结果表明:在亚硝酸钠用量50 kg/t,硫酸用量135 kg/t,氧化温度200℃,氧分压0.6 MPa,氧化时间2.0 h的最佳条件下,金浸出率为97.65%;催化压力氧化过程中金溶解率为24.25%;酸性氧化液采用活性炭吸附,金吸附率达到99.51%。该工艺可有效处理含砷金精矿,指标较好。     

Autoxidation in milk rich in linoleic acid. II. Modification of the initiation system and control of oxidation

Factors contributing to the initiation of lipid oxidation in cow's and mare's milk containing high levels of polyunsaturated fatty acids were studied. Addition of H2O2 just after milking, in slight excess of the stoichiometric amounts required to destroy ascorbic acid, delayed the development of oxidized flavours in cow's milk high in linoleic acid. Hydrogen peroxide treatment followed by the addition of alpha-or gamma-tocopherols prevented lipid oxidation in cow's milk even when 0.1 mg Cu/l milk was added. When used separately in the presence of Cu these treatments were ineffective as was butylated hydroxyanisole treatment. The lipid and ascorbic acid in mare's milk were remarkably stable to oxidation. Addition of 0.05 or 0.1 mg Cu/l, ethylenediamine tetraacetic acid, neocuproine, or H2O2 had very little effect on the loss of ascorbic acid and lipid oxidation in mare's milk.