甲缩醛合成工艺研究进展

概述了甲缩醛合成工艺的研究进展,根据反应原料和工艺流程复杂程度,对甲醇与甲醛催化缩醛反应制备甲缩醛、甲醇一步氧化法制甲缩醛、二甲醚氧化生成甲缩醛、甲醇与多聚甲醛反应制备甲缩醛等几种工艺进行了比较和评价。     

CuBr2-吡啶离子液体催化甲醇液相一步氧化生成甲缩醛

考察了以CuBr_2与具有不同烷基支链和阴离子类型的吡啶离子液体组成的催化剂体系对甲醇一步液相氧化合成甲缩醛(DMM)的催化性能,发现CuBr_2-N-乙基吡啶溴盐催化性能最好。考察了不同催化剂组成、催化剂浓度、反应温度、氧气压力、反应时间对甲醇一步液相氧化合成甲缩醛反应的影响,得到的最佳反应条件为:n(CuBr_2)/n(N-乙基吡啶溴盐)=1.0、催化剂质量浓度为40 g/L、反应温度130℃、氧气压力3 MPa和反应时间4 h,在该条件下甲醇转化率达到26.1%,DMM选择性达到95.0%。CuBr_2-N-乙基吡啶溴盐重复使用9次后,甲醇转化率为22.2%,DMM选择性为91.2%,催化活性仍然保持稳定。     

甲缩醛的研究进展

概述了甲缩醛的基本合成方法,如甲醛和甲醇反应精馏制备甲缩醛、甲醇与多聚甲醛合成甲缩醛、二甲醚氧化法合成甲缩醛、二溴甲烷合成甲缩醛、甲醇一步氧化法合成甲缩醛,对某些合成方法进行了评述、成本分析和评价,并简单介绍了甲缩醛在各方面的应用以及发展前景。     

甲缩醛的合成、精制及其应用

甲缩醛是天然气和煤化工的重要衍生品,在化工中间体、溶剂以及燃料和燃料添加剂领域有着广泛的应用。工业生产中,甲缩醛主要由甲醇和甲醛反应精馏制得,此外以甲醇和二甲醚为原料选择氧化生产甲缩醛的新工艺也在开发之中。甲缩醛的精制提纯工艺也得到了进一步的研究发展,但是如何开发出一条高效、安全的分离工艺,仍需进一步的研究。     

甲缩醛的研究进展

概述了甲缩醛的基本合成方法,如甲醛和甲醇反应精馏制备甲缩醛、甲醇与多聚甲醛合成甲缩醛、二甲醚氧化法合成甲缩醛、二溴甲烷合成甲缩醛、甲醇一步氧化法合成甲缩醛,对某些合成方法进行了评述、成本分析和评价,并简单介绍了甲缩醛在各方面的应用以及发展前景。     

载体TiO_2晶型对甲醇选择氧化性能的影响

以比表面积相近的锐钛和金红石Ti O2为载体,制备了负载钒氧和硫酸根物种的催化剂,比较了催化甲醇选择氧化的性能。结果表明,与金红石负载的催化剂相比,锐钛负载的钒氧催化剂具有较好的氧化性和酸性,在反应温度为433 K时,甲醇氧化的转化率较为接近,但产物中甲醛和甲酸甲酯的总选择性为63%,高于金红石负载催化剂上的54%。硫酸根的引入增加了甲醇转化率和甲缩醛选择性,在金红石负载型催化剂上尤为明显,甲缩醛选择性提高至88%。     

双效精馏精制甲缩醛的过程模拟

甲缩醛法制甲醛过程中,在精馏浓缩甲缩醛时,容易形成甲醇-甲缩醛共沸体系,不易得到高纯度的甲缩醛。通过研究分析可知甲醇-甲缩醛的共沸组成随压力的变化而变化,因此现有的很多工艺均采用变压精馏分离甲缩醛。其缺点是能耗高、效率低,能量的损失较大。为了进一步提高甲缩醛精馏塔的效率,在变压精馏的基础上运用双效精馏的方法来改进甲缩醛分离提纯工艺。模拟结果,甲缩醛精馏塔为:27块理论板,压力为1 000 kPa,双效精馏过程中塔底再沸器和塔顶冷凝器的节能率分别为54.97%和37.79%。     

高纯度甲缩醛的制备方法研究

采用实验室常用仪器搭建的反应精馏装置,在硫酸催化甲醇与多聚甲醛制备甲缩醛的过程中,考察了原料配比、加热温度、催化剂用量、反应时间等对甲醇转化率、甲缩醛产率及制备甲缩醛纯度的影响,并通过正交实验得出了最优甲缩醛制备条件:n(甲醇)/n(多聚甲醛)=1.9,加热温度为70℃,反应时间2.75 h,催化剂加入量为甲醇体积的3.5%时,甲醇转化率达99.32%,甲缩醛产率99.88%,所制得甲缩醛的质量分数为96.88%,甲醇质量分数为3.11%,水的质量分数小于0.01%。     

氧化铈负载铼催化甲醇制甲酸甲酯稳定性研究

以高铼酸铵和氧化铈为原料,通过浸渍法合成了一种甲醇选择氧化制甲酸甲酯催化剂。对催化材料进行了热重-差热(TG-DTG),X射线衍射(XRD)和扫描电子显微镜(SEM)等技术表征;同时研究了甲醇在该催化剂上选择氧化制甲酸甲酯的反应活性和稳定性。结果表明,氧化铈负载铼催化剂表现出良好的催化甲醇选择氧化制甲酸甲酯的活性和选择性。稳定性实验结果表明24小时没有明显失活。     

清洁柴油组分DM＋M3—8新技术

中国科学院兰州化学物理研究所羰基合成与选择氧化国家重点实验窒开发出以离子液体为催化剂，以甲醇和三聚甲醛为原料合成清洁柴油组分聚甲氧基甲缩醛（简称DMM3-8）的新技术。     

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.     

钒钛催化剂制备方法对甲醇氧化制二甲氧基甲烷反应性能的影响

分别用快速燃烧法(RC)、共沉淀法(CP)、浸渍法(IM)和机械混合法(PM)制备了钒钛催化剂,并将其应用于甲醇氧化一步法合成二甲氧基甲烷的反应中.同时采用X射线衍射(XRD)、N2吸附/脱附(BET)、NH_3程序升温脱附(NH_3-TPD),H_2程序升温还原(H_2-TPR)等多种手段对催化剂进行了表征.结果表明RC催化剂上钒的分散度最高,酸中心数最多,同时氧化还原能力较强.甲醇氧化反应结果表明.RC催化剂上甲醇转化率和DMM选择性最高,这可能与RC上较高的钒分散度,较强的氧化还原能力和较多的酸性中心数有关.     

甲醇直接氧化制备二甲氧基甲烷催化剂研究进展

作为一种新型的高性能柴油添加剂,二甲氧基甲烷的研究与生产受到越来越多的关注。论述了气相法甲醇部分氧化直接制备二甲氧基甲烷的机理,通过对甲醇部分氧化直接制备二甲氧基甲烷反应所用的Re、Ru、Mo、V等不同系列的催化剂的研究进展的综述,比较了各催化体系的特点;介绍了液相法甲醇直接氧化制二甲氧基甲烷的研究进展。最后对甲醇直接氧化制备二甲氧基甲烷提出了建议。     

Selective oxidation of methanol to dimethoxymethane over acid-modified V2O5/TiO2 catalysts

Selective oxidation of methanol to dimethoxymethane (DMM) was conducted in a fixed-bed reactor over an acid-modified V₂O₅/TiO₂ catalyst. The influence of the acid modification on its structure, redox and acidic properties, and catalytic performance for methanol oxidation were investigated. The results indicated that the content of vanadia in the catalyst exhibits a vital influence on the dispersion of vanadium species, while the acid modification can enhance its surface acidity. Proper amounts of the acid (W() = 15%) and V₂O₅ (W(V₂O₅) = 15%) components loaded in the acid-modified V₂O₅/TiO₂ catalyst are able to build a bi-functional circumstance that is favorable for the formation of DMM with high activity and selectivity. As a result, for the selective oxidation of methanol, the H₂SO₄-modified V₂O₅/TiO₂ catalyst gives a much higher DMM yield at 150 °C than the unmodified one.     

Methanol selective oxidation to dimethoxymethane on H<Subscript>3</Subscript>PMo<Subscript>12</Subscript>O<Subscript>40</Subscript>/SBA-15 supported catalysts

A series of SBA-15 supported H₃PMo₁₂O₄₀ catalysts were prepared for the one-step oxidation of methanol to dimethoxymethane (DMM). The evaluation and characterization revealed that higher DMM selectivity obtained on the incipient wetness impregnation (IM) catalyst was related to the instability of H₃PMo₁₂O₄₀ on it. Raman spectra showed that 12-molybdophosphoric acid was more stable on the direct synthesis (DS) catalyst than on the IM catalyst and the existence of SBA-15 support enhanced the stability of H₃PMo₁₂O₄₀. Moreover, higher H₃PMo₁₂O₄₀ loading resulted in more acid sites and low DMM selectivity, furthermore the thermal pretreatment on H₃PMo₁₂O₄₀ influenced its structure and thus affected DMM selectivity. This paper was presented at the 7 ^th Korea-China Workshop on Clean Energy Technology held at Taiyuan, China, June 26–28, 2008.     

预处理对Ru/Al_2O_3催化马来酸二甲酯加氢影响

采用吸附-沉淀法制备负载Ru质量分数为1.0%的Ru/Al_2O_3催化剂,以马来酸二甲酯催化加氢合成丁二酸二甲酯为探针反应,详细考察预处理条件对Ru/Al_2O_3催化剂加氢性能的影响,并对其进行XRD、TEM和H2-TPR表征。结果表明,焙烧温度越高,催化剂催化活性越低;直接还原活化所得催化剂活性高于空气中焙烧后还原活化所得催化剂。以甲醇为溶剂,在70℃和1.0 MPa条件下,直接还原活化所得Ru/Al_2O_3催化剂上马来酸二甲酯转化率达100%,丁二酸二甲酯选择性约100%。相同时间内,空气焙烧后还原活化所得Ru/Al_2O_3催化剂上马来酸二甲酯转化率接近25%,继续延长反应时间,马来酸二甲酯转化率几乎不变。经高温焙烧还原后,活性组分Ru烧结;直接还原活化后,活性组分Ru高度分散。     

In situ combustion synthesis of structured Cu-Ce-O and Cu-Mn-O catalysts for the production and purification of hydrogen

The combustion method was employed for the in situ synthesis of nanocrystalline Cu-Ce-O and Cu-Mn-O catalyst layers on Al metal foam, without the need of binder or additional calcination steps. Copper-manganese spinel oxides have been proposed as a catalytic system for hydrogen production via methanol steam reforming, while CuO-CeO₂ catalysts have been successfully examined for CO removal from reformed fuels via selective oxidation. In this work, the performance of these catalysts supported on Al metal foam has been investigated in the reactions of methanol reforming and selective CO oxidation. The Cu-Ce-O foam catalyst exhibited similar catalytic performance to the one of the powder catalyst in the selective oxidation of CO. The performance of the Cu-Mn-O foam catalyst in the steam reforming of methanol was inferior to the one of the powder catalyst at intermediate conversion levels, but almost complete conversion of methanol was obtained at the same temperature with both foam and powder catalysts.     

催化精馏法处理甲醛废水

通过催化精馏方法使废水中甲醛与加入的甲醇反应生成甲缩醛(DMM),同时实现废水中甲醛含量达标及其资源化利用。考察了醇醛摩尔比、反应温度、反应时间、催化剂添加量、塔顶回流比和待处理废水中甲醛质量分数6个因素对废水中甲醛去除率及产品甲缩醛质量分数的影响,结果表明,待处理废水中甲醛质量分数越高,加入的甲醇利用率越高,并总结出甲醛质量分数5%的废水最佳反应条件:反应温度80℃,醇醛摩尔比5,反应时间30 m in,催化剂加入量是待处理废水质量的1%,塔顶回流比3。在最佳条件下塔釜甲醛去除率达90%,塔顶甲缩醛质量分数达40%,废水中甲醛资源化利用率达98%以上。     

合成二甲氧基甲烷技术研究进展

二甲氧基甲烷作为用途广泛的化工原料,其合成技术在不断创新与发展。根据反应原料和工艺流程的不同对二甲氧基甲烷合成技术进行了概述与简评,该技术包含甲醇与甲醛催化缩合制备二甲氧基甲烷、甲醇与多聚甲醛反应制备二甲氧基甲烷、甲醇一步法制取二甲氧基甲烷、离子液体电催化氧化甲醇制取二甲氧基甲烷、二甲醚氧化生成二甲氧基甲烷、二溴甲烷合成二甲氧基甲烷、合成气制备二甲氧基甲烷、甲醇与二氧化碳反应制取二甲氧基甲烷等。醇醛缩合制备二甲氧基甲烷仍是当前主流的生产工艺,甲醇一步法制取二甲氧基甲烷工艺因在环境和投资上有优势而被广泛研究,是最具工业化前景的新技术,该技术尚需突破的是兼具氧化还原性与酸性的双功能催化剂。     

Preparation of Mesoporous V–Ce–Ti–O for the Selective Oxidation of Methanol to Dimethoxymethane

Mesoporous V–Ce–Ti–O oxides were synthesized through the combination of sol–gel and hydrothermal methods and were characterized by different techniques. N₂ adsorption showed that the mesoporous oxides with 0–20 wt.% V₂O₅ possessed the surface areas of about 160 m² g^?1 with narrow pore size distribution centered around 4–5 nm. Vanadium species were highly dispersed in the samples, as confirmed by the wide angle XRD and Raman spectroscopy. The surface acidity of the materials was determined by the microcalorimetric adsorption of NH₃. Temperature programmed reduction and O₂ chemisorption were used to probe the redox property of the materials. It was found that the mesoporous V–Ce–Ti–O possessed bifunctional characters of acidic and redox properties that catalyzed the oxidation of methanol to dimethoxymethane (DMM). These bifunctional characters were further enhanced by the addition of V₂O₅ and SO₄ ^2? onto V–Ce–Ti–O simultaneously. Such supported catalysts exhibited excellent performance for the selective oxidation of methanol to DMM. Specifically, 72% conversion of methanol with 85% selectivity to DMM was achieved at 423 K over a SO₄ ^2?–V₂O₅/V–Ce–Ti–O catalyst.