降低甲醛回收塔废水中甲醛含量研究

通过稳定甲醛回收塔进料浓度、减少回流比、降低操作压力、降低采出浓度等技术改进和操作优化,使甲醛回收塔塔底废水的甲醛含量降低10倍,增加了甲醛回收量,经济效益突出,减少甲醛排放降低了污水处理成本及对环境的污染。     

脲甲醛缓释肥料

简要回顾了脲甲醛缓释肥料的发展历史;介绍了脲甲醛缓释肥料的生产原理、生产工艺;通过对脲甲醛缓释肥料作用机理和质量评价,以及各国脲甲醛产品标准的规定分析,说明脲甲醛缓释肥料极具发展潜力,有利于缓解能源、环境压力。     

甲醛催化剂与甲醛生产技术展望

通过对甲醛催化剂性能和制作工艺的分析,展望我国甲醛工业工艺技术的发展前景.     

浓甲醛瓶颈

随着甲醛用途和市场的不断增大，国内出售甲醛（低浓度）远远不能满足生产的需要。为此，本文作者从浓甲醛的生产瓶颈、储运瓶颈和使用瓶颈等方面，阐述了生产推广浓甲醛的重要意义，并呼吁专家们尽快制定浓甲醛的国家标准，以适应甲醛下游产品的加工生产。     

我国甲醛需求预测

据全国甲醛行业技术经济月报统计,1993年我国工业甲醛总产量62.61万吨,共有甲醛生产厂家36个,上海溶剂厂是目前国内最大甲醛生产厂,该厂1993年甲醛产量6.94万吨,占全国产量的11.1％。     

便携式甲醛检测仪测定室内甲醛的问题探讨

为了探讨甲醛监测国家标准方法(国标法)与某商品化的便携式甲醛检测仪(快速法)对甲醛检测结果的可比性,本研究采用这两种方法对某研究生公寓室内甲醛和甲醛标准溶液进行平行测定。其测定结果分别为(0.059±0.0041) mg/m~3和(0.093±0.0103) mg/m~3,F检验和异方差t检验表明两种方法的精密度和准确度存在显著性差异;且对0.20 mg/L甲醛标准溶液的t检验表明快速法测定结果有显著性差异,因而采购的该型号甲醛检测仪的测定结果存在非常显著的系统误差。     

机械造粒单元甲醛储罐甲醛稳定性控制探讨

分析尿素装置机械造粒单元甲醛储罐中甲醛的聚合机理,探讨防止甲醛聚合的方法,提出合理的改造方案并用于实际生产。     

缩甲醛类胶粘剂中游离甲醛含量的测定

现行GB18583-2001标准中是采用乙酰丙酮分光光度法来检测胶粘剂中的游离甲醛含量,但是,在高温及强酸性环境中,缩甲醛类胶粘剂会与去甲醛剂发生水解反应,分解出10倍于原产品的游离甲醛。因此,采用GB18583-2001标准已经不能准确测定出缩甲醛类胶粘剂中游离甲醛的真实含量。通过对原有标准进行适当改进,提出了适用于缩甲醛类胶粘剂中游离甲醛含量的检测方法,经实验验证后得知,采用改进的检测方法,所得测试结果比较准确。     

胺类甲醛固定剂清除挥发甲醛的研究

利用氨及氨的衍生物与甲醛发生加成反应,生成一种常温下稳定的化合物,从而固定住游离的挥发性甲醛。选用无机铵盐(硫酸铵)和有机胺(二乙胺、二乙烯三胺、三乙烯四胺)作为固定剂。在室温下,固定剂溶液pH=11,溶液物质的量配比分别为硫酸铵与二乙胺1∶3、硫酸铵与二乙烯三胺1∶2.5和硫酸铵与三乙烯四胺1∶2。将固定剂溶液喷洒在板材表面,形成的液膜阻止了甲醛的释放,且溶液还可以渗入到板材内部,反应掉板材内游离的甲醛,形成稳定的化合物。溶液未干燥的状态下甲醛固定率为95%,溶液干燥后甲醛固定率大于95%。使用甲醛固定剂后,挥发性甲醛释放量不到原来的5%,基本切断了室内空气甲醛污染的来源。     

我国甲醛行业现状

<正>截至2012年,我国共有甲醛生产企业560家,总产能3 157万t(占世界甲醛总产能的52.18%),共有728套甲醛装置;2012年全国甲醛产量2 123万t(占世界甲醛总产量的51.15%),平均开工率67.24%;2012年比2011年新增甲醛产能165万t,年增长5.5%。我国甲醛产能仍然明显过剩,但增速也已远小于前几年,新建甲醛装置明显减少,遏制产能盲目过快增长成效明显。     

从甲醛催化剂的改进,展望甲醛工业发展前景

甲醛生产所用催化剂经历了铂催化剂、铜催化剂、浮石银、银网、电解银、铁钼氧化物催化剂的变迁,从不断提高设备生产能力,降低物料消耗,减少环境污染起了积极的推动作用。通过对催化剂性能和制作工艺的比较,简述了我国甲醛工业工艺技术的进展和新技术的前景。     

Supported foam-silver catalysts for alcohol partial oxidation

Structural, mechanical, gas-dynamic and catalytic properties of silver catalysts supported on foam ceramics have been studied. The foam catalysts have high gas permeability, mechanical strength, and low density. Catalytic activity and selectivity of the foam catalysts in the process of oxidation of methanol to formaldehyde exceed the characteristics of the commercial crystalline and granulated catalysts. Different electronic states (ions, charged cluster, crystals) of silver on the catalyst surface have been studied by the method of UV–visible spectroscopy.     

Novel sol–gel‐derived Ag/SiO2–Al2O3 catalysts for highly selective oxidation of methanol to formaldehyde

Novel Ag/SiO₂–Al₂O₃ catalysts with low silver content prepared by the sol–gel method exhibit excellent catalytic properties in the catalytic oxidation of methanol to formaldehyde. The silver content was as low as 2% and the yield of formaldehyde was achieved as 90.3%, which is 16% higher than that of pumice‐supported silver and even 5–6% higher than that of a commercial electrolytic silver catalyst. XRD, XPS and SEM results reveal that all silver was present as Ag⁺ before catalytic reaction and was partially reduced to the metallic state after the reaction. It was also found that silver was aggregated on the surface after its reduction. This revised version was published online in July 2006 with corrections to the Cover Date.     

Characterization of silver catalysts for the oxidation of methanol

The selection of a silver catalyst system for further study was determined on a basis of cost and its ability to oxidize formaldehyde selectively. In addition a silver catalyst can provide a low light off temperature for the conversion of methanol to carbon dioxide and water vapor. Silver catalysts were prepared by the deposition of solutions of silver nitrate or silver chloride on gamma alumina washcoat supported on cordierite monolith. These silver catalysts were characterized by a variety of analytical techniques including TEM, SEM, EMP, STEM, XRF, XRD and FTIR.It is concluded that the best silver catalyst is prepared by deposition of silver from a solution of silver ammnonium chloride onto a cordierite supported high surface area gamma alumina washcoat, drying at 100°C in air, followed by reduction in flowing 3% H₂ in N₂ at 500°C for 4 h. This procedure will produce a silver catalyst with highest activity, largest retention and most uniform distribution of silver. The procedure also retains the concentration of silver and the gamma phase of alumina at temperatures as high as 1000°C in air for as long as 6 h.Due to the inability of normal TEM imaqing modes to obtain silver particle size information in the presence of the small gamma alumina washcoat particles a model system was made to test the ability of a dedicated STEM to furnish that information. The model system consisted of silver particles in the range of 1 to 50 nm which had been evaporated onto a uniform thin film of alumina. High resolution X-ray maps obtained from the model system demonstrate the ability to determine location and size of silver particles > 5 nm.A number of catalysts containing noble and base metals supported on gamma alumina washcoat on a cordierite monolith have also been studied. Laboratory flow reactor studies and chassis dynamometer studies using a Mercury Lynx modified to burn neat methanol have shown the following order of activity for conversion of methanol burned in experimental or engine exhaust gas: Pd > Ag > Pt + Rh > CuO + ZnO + Cr₂O₃ > Ni.     

Catalytic dehydrogenation of methanol to water-free formaldehyde

Catalytic dehydrogenation of methanol is a promising process of producing water-free formaldehyde. The present paper reviews research in this field. As effective catalysts mainly transition metal compounds as well as oxides and salts containing sodium have been reported. Several catalysts exhibit high activity and high selectivity, for formaldehyde at low conversions while further efforts have to be made to improve catalyst stability and selectivity at high conversions. Catalytic dehydrogenation of methanol to formaldehyde is compared with methanol oxidation.     

银系复合导电膏的研制

通过工艺条件的初探和优化选择，研制了根系－环氧树脂复合导电膏。讨论了生成银粒子的甲醛用量和加料速度及银在复合组成中的含量对复合导电膏导电性能的影响。     

甲醛生产中甲醇的消耗及其影响因素分析

分析了甲醛生产中银催化剂的制备、处理以及生产过程的控制，阐述了甲醛生产中甲醇消耗的影响因素，以催化剂的制造、使用及保护为重点 ，并相应提出了解决措施。     

甲醇脱氢制无水甲醛的研究进展

甲醇直接脱氢制无水甲醛是具有工业化前景的新工艺。介绍了该领域催化剂及相关工艺的研究现状。利用金属、金属氧化物、金属难熔盐和分子筛催化剂以及相关工艺技术制得定量的无水甲醛,该技术目前处于研发阶段,离工业化尚有一定距离,在催化剂的选择性、稳定性及使用寿命等方面有待于改进。     

The oxidative dehydrogenation of methanol over a novel low‐loading Ag/SiO2–TiO2 catalyst

Catalytic oxidation of methanol to formaldehyde was carried out over Ag/TiO₂-SiO₂ catalysts prepared by chemical reduction. The catalytic activity was measured at the temperature interval 820-920 K, O₂/CH₃OH molar ratio between 0.35 and 0.50 and at the space velocity of 1.2 × 10⁵ h^-1. The optimal content of silver determined by chemical analysis was about 1.7 wt%. The yield of formaldehyde over this catalyst was ~13% higher than that of the industrial pumice-supported silver catalyst and even ~3.5% higher than that of electrolytic silver. The XRD patterns for silver particles supported on TiO₂-SiO₂ are corresponding to Ag(111), (200) and (220), respectively. SEM was used to determine its morphology and particle size. Isolated silver particles were observed on the surface of the catalyst. O₂ chemisorption by using the pulse technique was carried out to determine the free silver surface areas. The average silver particle size from the calculation of selective oxygen chemisorption was found to be in good agreement with that observed from SEM. This revised version was published online in July 2006 with corrections to the Cover Date.     

A review on direct synthesis of dimethoxymethane

Polyoxymethylene dimethyl ethers are recognized as the prospective diesel additive to decrease the pollutant emission from the light-duty vehicles, which can be polymerize form the monomer of dimethoxymethane (DMM). The industrial synthesis of DMM is mainly involved two-step process: methanol is oxidized to form the formaldehyde in fixed bed reactor and then reacted with the generated formaldehyde through acetalization in continuous stirred-tank reactor. Due to huge energy consumption, this typical synthesis route of DMM needs to be upgraded and more green routes should be determined. In this review, four state-of-the-art one-step direct synthetic routes, including two upgrading routes (methanol direct oxidation and direct dehydrogenation) and two green routes (methanol diethyl ether direct oxidation and carbon oxides direct hydrogenation), have been summarized and compared. Combination with the reaction mechanism and catalytic performance on the different catalysts, the challenges and opportunities for every synthetic route are proposed. The relationships between catalyst structure and property in different synthesis strategy are also investigated and then the suggestions of the design of catalyst are given about future research directions that efforts should be made in. Hopefully, this review can bridge the gap between newly developed catalysts and synthesis technology to realize their commercial applications in the near future.