致密无机微粉膜片、其制备方法及由其得到的制品

技术领域

本发明涉及一种致密无机微粉膜片、其制备方法及由其得到的制品。本发明尤其涉及一种用少量聚四氟乙烯粘合的致密无机微粉膜片、其制备方法及由其得到的制品。这些制品可用作电极材料、介电材料、吸附材料和催化剂材料等。

背景技术

众所周知，由于价格便宜、原料易得、含有炭粉、二氧化硅等无机物的无机填充膜可用于很多领域。并且已知，可以加入粘合剂如聚四氟乙烯(PTFE) 等以使无机物粉末结合在一起。PTFE具有化学稳定性、高温稳定性、物理机械性能、电绝缘性能、高度疏水性、润滑性等优异性能，将其加入无机材料中制得的填充PTFE制品，可以大大提高制品的润滑性、耐磨性、耐蠕变性和冲击强度等。但是，过多的PTFE也会破坏无机材料本身的性能，例如使硬度、孔隙率、加工性能等大大降低。

美国专利4194040公开了一种由1－15体积%的原纤化PTFE基体和85－99体积%的被PTFE包埋或连接的颗粒材料形成的板。该专利采用球磨机干混，干混时间长达30－60分钟，因此，在球磨混合时因磨球的撞击和挤压会使加入的粉体材料结构极大地变形或破坏，从而破坏了粉体材料的性能。另外，该专利公开的方法需要采用较高含量的PTFE才能将颗粒材料包埋或连接。因此，无法避免上文所述的问题。

美国专利5478363公开了一种电极制备方法，该方法采用平均粒径为20－50微米的金属氧化物颗粒和平均粒径小于约20微米的PTFE，不用润滑流体进行干混制成电极材料。由于该专利仅采用干法混合、干法压制，从而很难混合均匀，难以形成均匀、致密的结构。简单的干法混合也很难充分发挥PTFE的粘合作用。因此必须采用较高含量的PTFE才能达到较好的粘结效果，而这样做，必然使材料的电化学响应性能受到影响。此外，按照该专利方法制备的膜中存在很多网、孔，密度过小（参见图2和图3），而且该专利的方法不利于大量连续制备，单位体积的吸附量较小，应用受到限制，不适合用做吸附材料，如吸氢膜、液化石油气吸附膜以及天然气吸附膜等。另外戈尔公司的WO97/20881号专利公开了一种用纳米级无机粉体填充聚四氟乙烯得到的制品，为了保持多孔聚四氟乙烯的基本性质，该制品以聚四氟乙烯为主体，无机粉末至多可达50%，并且通过湿混和拉伸得到，用扫描电镜为分析该专利的聚四氟乙烯制品发现，纳米颗粒并未填充到聚四氟乙烯的孔隙中，从而呈拉丝、网状结构，非常疏松。

因此，有必要提供一种结构致密、颗粒分布均匀、PTFE含量很低的无机微粉填充膜片，从而该无机微粉填充膜片不仅可以更大程度地发挥无机粉体材料本身的物理和化学性能，而且保持了一定的使用强度。

发明内容

本发明的一个目的是提供一种结构致密、颗粒均匀、PTFE含量很低的无机微粉膜片。

本发明的另一个目的是提供一种制备结构致密、颗粒均匀、PTFE含量很低的无机微粉膜片的方法。

本发明的再一个目的是提供一种使用本发明的无机微粉膜片得到的各种制品，例如电极材料、吸附材料、介电材料和催化剂材料等。

此外，本发明的无机微粉膜片根据无机粉体材料的性质还可以作为磁性材料、超导体材料等使用。

本发明提供了一种致密均匀的无机微粉复合膜片，其由占膜片总重量95％－99.9％的无机粉体材料和0.1－5％的聚四氟乙烯组成。

根据本发明的一种优选实施方案，本发明的无机微粉复合膜片由占膜片总重量97％－99.9％的无机粉体材料和0.1－3％的聚四氟乙烯组成。

适用于本发明的无机粉体材料包括但不限于碳质材料、硅质材料、金属、金属氧化物及金属硫化物、钛酸盐等。优选炭、活性炭、二氧化钛、氧化铜、氧化铁、硫化钼、钛酸钡、钛酸锶、高岭土、二氧化硅、云母、碳化硅、蛭石、碳酸钙、酪素、玉米蛋白或其混合物。更优选炭、活性炭、二氧化钛、钛酸钡或其混合物。适用于本发明的粉体材料的粒径没有特别的限制，但优选2纳米－0.2毫米。

适用于本发明的聚四氟乙烯优选聚四氟乙烯分散树脂粉末，本发明对PTFE的粒径没有特别的限制，优选的粒径范围为300－600微米。

本发明还提供了一种制备致密无机微粉复合膜片的方法，该方法包括如下步骤：

a)       干态下混合95－99.9重量份无机粉体材料和0.1－5重量份聚四氟乙烯树脂粉末；

b)       向混合物中加入90－1000重量份的溶剂，搅拌混合成胶泥状；

c)       将胶泥状物在60－120摄氏度混炼；

在本发明方法的优选实施方案中，步骤a)中的所述干法混合是在500－3500转/分的较高转速下进行的，步骤b)中的所述混合是在50－500转/分的较低转速下进行的。

在本发明方法的另一优选实施方案中，步骤c)是在开炼机中进行的，混炼时间优选为2－10分钟，更优选为3－5分钟。

根据本发明的一种特别优选的实施方案，本发明致密无机复合膜片是这样制备的：

a)       粉体材料与聚四氟乙烯在高速混合搅拌机内500－3500转/分的较高转速下一次干粉混合5－30分钟，优选混合10－15分钟；

b)       然后加入本体材料重量1－10倍的已加温到其沸点的水、酒精或其他与粉体材料不反应的几种溶剂中的任一种（优选水、酒精或其他溶剂加入前加热至60－100摄氏度），混入已经混合聚四氟乙烯分散树脂后的粉体，在低速高扭力的搅拌机（如和面机）内，以50－500转/分的转速混合成胶泥状（混合时间优选2－10分钟）。

c)       将胶泥状物放入双辊转速不同的开式双辊炼胶/炼塑机，在60－120摄氏度混炼3－5分钟后，形成带状体；

d)       最后挤压至需要的厚度。

Compact Inorganic Micropowder Sheet, Making Method thereof and

Products Made therefrom

Field of the invention

The present invention relates to a compact inorganic micropowder sheet, a making method thereof and products made from the sheet.  In particular, the present invention relates to a compact inorganic micropowder sheet, wherein the micropowder is bonded by a small amount of polytetrafluoroethylene (PTFE), and a making method thereof as well as products made from the sheet.  The products can be used for making electrode material, dielectric material, adsorption material, catalytic material and the like.

Background of the invention

It is well known that inorganic micropowder sheet comprising charcoal micropowder, silicon dioxide and other inorganic compounds can be used in many fields due to its low prices and easily obtainable raw materials.  It is also known that a bonding agent, such as PTFE, can be added to allow the micropowder of the inorganic compounds to be bonded together.  PTFE has excellent chemical stability, high temperature stability, physical and mechanical properties, electric insulating property, high hydrophobicity, lubricity and so forth.  Addition of PTFE to the inorganic material will enhance lubricity, wear resistance, creep resistance, impact resistance and other properties of the micropowder products.  However, excessive PTFE would also destroy the original property of the inorganic materials, e.g., greatly reduce their hardness, porosity and processability.    

U.S. Patent 4,194,040 disclosed a sheet consisting of about 85-99 %, by volume, of a particulate material interconnected and entrapped in a matrix of about 1-15 %, by volume, of fibrillated PTFE resin.  In the patent, a ball mill is used for dry-milling an admixture of particulate materials for up to 30-60 minutes.  Therefore, the structure of the particulate materials is greatly deformed or destroyed during ball milling due to collision and squeeze caused by milling balls, and the original properties of the particulate material are destroyed.  In addition, the method disclosed in the patent requires relatively high content of PTFE for entrapping or interconnecting the particulate material.  Therefore, it is impossible to avoid the above described problems.

U.S. Patent 5,478,363 disclosed a method of making an electrode, by which the electrode material is made with particles of metal oxides having an average particle size of 20-50 microns and PTFE particles having an average particle size of less than 20 microns, by dry-mixing without using a lubricating fluid.  Since only dry-mixing and dry calendering is used in the patent, it is very difficult to mix the admixture uniformly and to form a uniform and compact structure.  Meanwhile, it is also difficult for the simple dry-mixing to bring the bonding effect of PTFE into full play.  Therefore, relatively higher content of PTFE must be used to obtain better bonding results.  However, in doing so, it would be inevitable that the electrochemically active characteristics of the material would be affected.  In addition, the density of the sheet made in accordance with the patent is too low due to a lot of networks and holes existing inside the sheet (see Fig. 2 and Fig. 3).  The method of the patent is disadvantageous for continuous large-volume production, and its applications are restricted, not suitable for making adsorption material, such as adsorption membrane of hydrogen, liquefied petroleum gases and natural gas, due to its low adsorption rate per unit volume.  Moreover, Gore Company disclosed in patent WO 97/20881 a PTFE product filled with inorganic micropowder having particle size in nanometers.  In order to preserve basic properties of porous PTFE, the product is composed of PTFE as matrix and up to 50 % inorganic micropowder.  The product is made by wet-milling and stretching.  By using a scanning electron microscope for analyzing the PTFE product of the patent, it is found that the micropowder in nanometers have not filled up the gaps among the PTFE matrix.  Therefore, the product presents a very loose structure consisting of many threads and networks.

Therefore, it is necessary to provide an inorganic micropowder sheet with a compact structure, uniform particle size and low PTFE content, so that the inorganic micropowder sheet will not only take full advantage of the physical and chemical properties of the inorganic micropowder material, but also maintain a certain degree of working strength.   

Description of the invention

An objective of the present invention is to provide an inorganic micropowder sheet with a compact structure, uniform particle size and low PTFE content.

Another objective of the present invention is to provide a method of making inorganic micropowder sheet with a compact structure, uniform particle size and low PTFE content.

A further objective of the present invention is to provide various products made from the inorganic micropowder sheet, such as electrode material, dielectric material, adsorption material, catalytic material and the like.

Furthermore, the inorganic micropowder sheet made in accordance with the present invention can be used as magnetic material, superconductive material and the like in accordance with the properties of the inorganic micropowder material.

The present invention provides a compact and uniform inorganic micropowder composite sheet comprising 95-99.9 % of the inorganic micropowder material and 0.1-5 % PTFE relative to the total weight of the sheet.

In accordance with a preferred embodiment of the present invention, the inorganic micropowder composite sheet of the present invention is consisting of 97-99.9 % of the inorganic micropowder material and 0.1-3 % PTFE relative to the total weight of the sheet.

The inorganic micropowder material suitable for the present invention includes, but not limited to, carbon material, silicon material, metals, metal oxides and metal sulfides, titanates, etc.; preferably, charcoal, active carbon, titanium dioxide, copper dioxide, ferric oxide, molybdenum sulfide, barium titanate, strontium titanate, kaolin, silicon dioxide, mica, silicon carborundum, vermiculite, calcium carbonate, casein, zein, or their mixture; more preferably, charcoal, active carbon, titanium dioxide, barium titanate, or their mixture.  There is no specific limitation to the particle size of the micropowder material suitable for the present invention.  Preferably, it is from 2 nm to 0.2 mm. 

Preferably, the PTFE suitable for the present invention is PTFE dispersion resin powder.  There is no specific limitation to the particle size of the PTFE powder suitable for the present invention.  Preferably, it is from 300-600 microns. 

The present invention also provides a method for making compact inorganic micropowder composite sheet, consisting of the following steps:

a)         Dry-mixing 95-99.9 %, by weight, of inorganic micropowder material with 0.1-5 %, by weight, of PTFE resin powder;

b)         Adding 90-1,000 parts, by weight, of solvent to the admixture and mixing them under agitation to form a putty-like mass; and

c)         Milling the putty-like mass at a temperature of 60-120 ˚C.

In a preferred embodiment of the present invention, the dry-milling as described in step (a) is carried out at a high rotating speed of 500-3,500 RPM, and the mixing as described in step (b) is carried out at a lower rotating speed of 50-500 RPM.

In another preferred embodiment of the present invention, the step (c) is carried out in a mill mixer, preferably, for 2-10 minutes, and more preferably, for 3-5 minutes.

In a particularly preferred embodiment of the present invention, the compact inorganic composite sheet of the present invention is made as per the following steps:

a)         The micropowder material and PTFE is dry-mixed at a high rotating speed of 500-3,500 RPM in an agitated mixer without interruption for 5-30 minutes, preferably, for 10-15 minutes.

b)         Relative to the total weight of the main body of the micropowder material, 1-10 times of water and alcohol or any one of other solvents, which are non-reactive with the micropowder material, are heated to the boiling point of water, alcohol or other solvent (preferably, to 60-100 ˚C), before being added to the micropowder material, which has already been mixed with PTFE dispersion resin powder, and then mixed together in a agitator of low speed and high torque (similar to a flour dough mixer) at 50-500 RPM (preferably, for 2-10 minutes) to form a putty-like mass.

c)         The putty-like mass is fed into an open-type double-roller rubber/plastics mill with the two rollers rotating at different speeds, and is milled at a temperature 60-120 ˚C for 3-5 minutes to form a belt.

d)         Finally, the belt is calendered into a desired thickness.

CERAMIC TECHNOLOGY IMPROVES

HYDROTREATER PERFORMANCE

Oil refiners are under increasing pressure to improve the performance of their processing units, especially with regard to operating costs and reduced downtime.  The use of ceramic technologies results in important improvements in this area.  Pressure drop increases may be reduced such that skimming operations may be eliminated. In addition, dual function media can also allow for the initial removal of nickel and vanadium.  New ceramic shapes can lower the initial pressure drop.

The hydrotreating operation is now one of the most important parts of the oil refining chain and it is crucial to the overall performance of the refinery that this group of reactors works at maximum efficiency with minimum downtime.  The increasingly integrated nature of a modern oil refinery increases the impact of a hydrotreater shutdown on the performance of the whole refinery.  The shutdown of the primary desulfurizer in such a modern refinery can cost large amounts of money when loss of production from other units is factored in.  Factors that increase the importance of the hydrotreating operations include the need for lower product sulfur levels to meet clean fuel initiatives and the increase in the cost of crude oil.

Aggressive clean fuel specifications are being implemented in the short term in the USA, the European Union and in Japan.  Such initiatives are also increasingly being implemented in the so-called developing countries, especially India, China and Brazil. Globally, on average, in 2005, gasoline fuels will be required to have 50% of the sulfur removed and diesel fuels, 40%. By 2015, these numbers increase to 82% and 87% respectively. Specifically, new EPA regulations in the USA mandate a maximum level of sulfur in diesel fuel of 15wppm by mid-2006.  European refiners are currently required to produce some diesel fuel with a sulfur content <10wppm.  The shift towards diesel engines for private automobiles is especially strong in Europe, where over half of new car sales are of diesel-powered models.  This trend will eventually result in a worldwide movement towards small diesel engines, with the resultant impact on refineries to produce greater proportions of diesel fuel compared to gasoline.

Preparations to meet these new specifications are being made in almost all oil refineries worldwide.  Maximum efficiency in meeting the new specifications can be achieved by the design and construction of optimally designed new units, but in most cases, this is not possible, as the existing equipment has not reached the end of its life.  It thus becomes very important to insure that existing equipment, which may not be optimally designed for the new specifications, is operated in a manner that maximizes efficiency, minimizes running costs and eliminates unnecessary downtime.  While the following decisions refer specifically to hydrotreater operation, but the principles have also been applied to other catalytic and absorption units throughout the refinery, as well as in other petrochemical and chemical operations in integrated chemical plants.

Sub-optimal Operation

Important factors that affect the efficiency, and therefore the operating costs of hydrotreaters include increase in pressure drop, high initial pressure drop and added hydrometallisation requirements.

Appropriate choice of catalyst and careful operation can reduce greatly the increase in pressure drop caused by coke formation in the catalyst bed. Traditionally, graded beds of spherical ceramic bed support media, such as proprietary XYZ^® media or other materials, have been installed over the catalyst.  Increase in pressure drop that does occur is often due to partial blockage of these graded beds or of the catalyst bed itself, due to the deposition of particulate matter (often referred to as “tramp iron”) and of polymeric gums (such as iron sulfide gums, FeS_x).  In many instances, the pressure drop rises to such an extent that the unit has to be shut down and “skimmed” to allow operation of the unit.  The skimming process can take several days with much of an integrated refinery being affected by the shut down of the hydrotreating unit.  Bed topping materials that act as guard beds can reduce or even eliminate the extra running costs caused by this pressure drop increase.

The cost of electric power to run a unit increases with the pressure drop experienced over that unit.  The use of lower pressure drop catalysts often conflicts with the requirement for the maximum overall catalyst activity in the unit.  Using low-pressure drop bed toppings may lower the initial pressure drop.

The introduction of very high efficiency desulfurization catalysts has allowed even the most intractable sulfur containing molecules to be desulfurized.  However, these high-performance catalysts are often even more susceptible to poisoning by other metallic components in the feed.  This results in the need for extra guard reactors or layers of demetallization catalysts to remove such metals as vanadium and nickel.  The use of a dual function guard bed material that can remove some of these metals, in addition to preventing pressure drop increase, can further lower the operating costs of the unit.

Pressure drop increase

Ceramic technology has been developed to provide a highly macroporous ceramic material that can trap particles with diameters between 5 and 25 microns in the guard bed layer with insignificant increase in pressure drop.  Particles of this type, usually iron oxide particles, can flow through the graded beds that are often installed causing blocking of the catalyst bed with resulting pressure drop increase. The catalyst bed, comprising catalyst particles of various shapes but usually 0.8 - 2mm in diameter, can act as an efficient “sand filter” for particles in this size range. It is believed that particles smaller than about 5 micron will flow through the catalyst bed without becoming trapped and will thus not contribute to any pressure drop increase problems.

应用陶瓷技术改善加氢处理装置性能

炼油厂受到与日俱增的压力，迫使其改善加工装置性能，尤其是降低操作成本和缩短停工时间。陶瓷技术的应用导致了这方面重大的进步。压降增加的现象可减轻至可免除撇顶操作过程的程度。此外，具有双重功能的填料介质还可初步脱除镍和钒等金属。新颖的陶瓷形状还能降低初始压降。

现在，氢化处理操作过程是石油炼制环节中一个最重要的组成部分。这一组反应器能否以最高效率和最短停工时间进行操作，对于炼油厂的整体运转状况甚为关键。现代化炼油厂日臻完善的一体化本质提高了加氢处理装置的停工对整个炼油厂运转状况的影响。若将其它装置的生产损失也计算在内，这种现代化炼油厂内主脱硫装置的停工将造成巨额的金钱损失。导致氢化处理操作重要性增加的因素包括因实施清净燃料法案而对硫含量更低的产品的需求，以及原油成本的上升。

在美国、欧盟和日本，正以很短的期限实施严格的清净燃料规格。在所谓发展中国家，尤其是印度、中国和巴西，也正在逐渐实施类似的法案。在2005年，全球平均而言，要求汽油燃料脱除50%的硫含量，柴油燃料则脱除40%。到2015 年，这些数字将分别增加为82%和87%。具体而言，美国环保署（EPA）的新规定指定，到2006年中期，柴油燃料的最高硫含量必须低于15 wppm。目前，欧洲正要求各炼油厂生产某些硫含量低于10 wppm的柴油燃料。在欧洲，私人汽车向柴油发动机转换的趋势尤为强烈，在那里销售的新车中有一半以上是柴油发动机型。这种趋势最终将导致一股向小型柴油发动机转换的世界性潮流，其对炼油厂的影响将是柴油燃料生产的比例高于汽油。

全世界几乎所有的炼油厂都在为达到这些新规格作准备。通过设计和建造优化设计的新装置固然能最有效地达到这些新规格，但在大多数情况下，这是不现实的，因为现有设备尚未达到其寿命终点。因此，对于那些也许并非按照新规格而优化设计的现有设备，保证它们以效率最高、操作成本最低的方式运行并消除不必要的停工时间，就显得极为重要。虽然以下措施是专门针对加氢处理装置的操作，但这些原则也已经用于炼油厂的所有其它催化和吸收装置，以及化工联合企业中其它石化和化工操作过程。

近乎最佳状态的操作

影响效率从而影响加氢处理装置操作成本的重要因素包括压降增加、初始压降高以及附加的氢化脱金属要求。

适当的催化剂选择和谨慎的操作可大大地减軽因催化剂床积碳而导致的压降增加。传统上，将球状陶瓷负载介质如专有的XYZ^®介质或其它材料构成的多级床安装在催化剂床顶上。那种确实会发生的压降增加现象往往是由于微粒状杂质（经常被称为“铁杂质”）和高分子胶质（例如硫化铁胶质，FeS_x）的沉积而造成了上述多级床或催化剂床本身的部分堵塞。在许多情况下，压降增加到一定的程度将迫使该装置必须停车并进行“撇顶”操作后才能再投入运行。该撇顶操作过程可能需要几天的时间，炼油联合装置的很大一部分也将受到氢化处理装置停车的影响。某些起保护床作用的床顶层材料能够减少甚至消除因这种压降增加而造成的额外操作费用。

操作一套装置所耗的电力费用随着该装置的压降增加而增加。采用低压降催化剂的做法往往与希望该装置具有最高的整体催化剂活性的要求发生冲突。使用低压降的床顶层介质可以降低初始压降。

效率极高的脱硫催化剂的问世使得即使最难以处理的含硫分子的脱硫也成为可能。但是，这类高效催化剂往往更容易因原料中的其它金属组分而中毒。这就需要设置额外的保护反应器或脱金属催化剂层，以脱除钒和镍之类的金属。采用能脱除其中一部分金属的具有双重功能的保护床材料，除了防止压降增加之外，还能进一步降低装置的操作成本。

压降增加

陶瓷技术的发展导致了一种多孔型陶瓷材料的诞生。该材料能在保护床层内捕获直径为5至25微米的微粒，却无显著的压降增加。这种微粒往往是氧化铁微粒，能够穿过通常采用的多级床而造成催化剂床堵塞及压降增加。由形状各异但直径通常为0.8 – 2毫米的催化剂微粒构成的催化剂床，对于此粒度范围内的微粒可起一种高效“沙滤器”的作用。据信，直径约小于5微米的微粒将穿过催化剂床而不被捕获，故不会造成任何压降增加的问题。

一种均相羰基化反应催化剂及其制法和应用

本发明涉及一种均相羰基化反应催化剂及其制法，本发明还涉及其在催化甲醇羰基化为乙酸和乙酸甲酯以及在催化乙酸甲酯为乙酐反应中的应用。

在催化剂的作用下，甲醇羰基化制备醋酸是目前醋酸工业的重要技术路线。在可溶性的小分子铑配合物催化的均相甲醇羰基化反应中，其活性物种通常为铑单齿配合物，如：[Brodrk D. Ledere. C; Benise. B; Pannetier Gi Bull. Soc. Chim., Fr. 1976.61]，或二羰基二碘铑结构形式如：美国孟山都公司应用低压法均相溶液法制备的小分子铑配合物二羰基二碘铑[Rh(CO)₂I₂]¯N¯R₄ [Roth, JF et al. Chem Technol. 1971, 600]。由于单齿铑配合物不稳定，在反应温度超过180 ˚C时，就开始分解失活，二羰基二碘铑(I)在反应过程中很容易转化为二羰基四碘铑(III)阴离子配合物，而失去催化活性，在有利于反应进行的高温下尤其如此，因此在生产过程中除保持一氧化碳的分压外，还需加入过量的碘化氢以保持催化剂以铑(I)状态存在，这样就极大地增加了对生产设备的腐蚀作用。

为解决以上问题，本发明的目的在于提供一种具有高的催化活性和稳定性的均相羰基化反应催化剂。

本发明的另一目的在于提供一种均相羰基化反应催化剂的制法。

本发明的目的还在于提供一种均相羰基化反应催化剂在催化甲醇羰基化为乙酸和乙酸甲酯以及在催化乙酸甲酯为乙酐反应中的应用，反应体系无需添加氢碘酸，可减少对生产设备的腐蚀作用。

本发明的一种均相羰基化反应催化剂，以有机金属锂为配体与羰基铑形成正方平面的螯合型顺二羰基铑(I)配合物，其结构式如下：

(结构式略)

式中X¯ 为BPh₄¯、BF₄¯、CH₃COO¯或OH¯；n=0, 1, 2, 3, 4。

所述有机金属锂配体是指含有两个羧基的二羧酸的锂盐，其结构式如下：

(结构式略)

式中n=0, 1, 2, 3, 4。例如，乙二酸锂、丙二酸锂、丁二酸锂、戊二酸锂等。

本发明的催化剂具有下列特征：

1、由于配体中含有两个配位氧原子，在配合物形成过程中与金属铑形成两个配位键，这两个配位氧原子以一定挠性的碳链相连，形成了双齿配位的螯合型正方平面的双金属配合物。

2、该配合物具有相对良好的稳定性，可在无需惰性气体保护下制备获得。经电子能谱(XPS)研究测定证明有两个O->Rh配键存在，红外光谱表明，在2000 - 2100 cm^-1之间有配合物铑的末端羰基特性吸收峰，说明该类配合物含有顺二羰基结构。

3、由于配合物中形成的螯合物结构及两个较弱的O->Rh配键的存在，使催化剂体系在反应中利于完成助催化剂碘甲烷的加成。

4、由于该催化剂中含有两种金属，即金属铑和与羧酸以离子键结合的金属锂，两种金属之间的协同效应，使金属铑的末端羰基得到了活化，从而提高了催化剂的活性。

5、由于该催化剂高的催化活性和稳定性，使甲醇羰基化反应的反应条件极其温和，反应体系无需添加极性溶剂如氢碘酸，仅添加乙酸甲酯、乙酸、乙酐、水等作为溶剂。

A Catalyst for Homogeneous Carbonylation, Preparation Method and

Applications thereof

The present invention relates to a catalyst for homogeneous carbonylation and its preparation method.  The present invention also relates to applications of the catalyst in carbonylation of methanol to obtain acetic acid and methyl acetate, as well as in carbonylation of methyl acetate to obtain acetic anhydride.

In current acetic acid industry, preparation of acetic acid via carbonylation of methanol in the presence of a catalyst is an important technological route.  In homogeneous carbonylation of methanol in the presence of a soluble small-molecule rhodium coordination complex as the catalyst, the active species is usually a unidentate rhodium coordination complex, as described, for example, by Brodrk D. Ledere C, Benise B, Pannetier Gi; Bull. Soc. Chim., Fr. 1976. 61; or it is in a structure of dicarbonyl rhodium diiodide, such as a small-molecule rhodium coordination complex, i.e., dicarbonyl rhodium diiodide [Rh(CO)₂I₂] ¯N¯R₄, prepared by Monsanto USA using homogeneous carbonylation in solution under low pressure [Roth, JF, et al.  Chem. Technol. 1971, 600].  As unidentate rhodium coordination complex is unstable and would be decomposed and deactivated as soon as reaction temperature exceeds 180 degrees Celsius, dicarbonyl rhodium (I) diiodide would be easily converted into an anionic coordination complex of dicarbonyl rhodium (III) tetraiodide, resulting in loss of its activity, especially at high temperatures that are favorable to the reaction.  Therefore, in addition to maintaining partial pressure of carbon monoxide, it is necessary to add an excessive amount of hydrogen iodide for maintaining the catalyst in the form of rhodium (I).  However, this measure causes a tremendous worsening of corrosion to production equipment. 

To solve the above problems, an objective of the present invention is to provide a catalyst for homogeneous carbonylation with high catalytic activity and stability. 

Another objective of the present invention is to provide a method for preparation of the catalyst for homogeneous carbonylation.

A further objective of the present invention is to provide a catalyst for homogeneous carbonylation, which will be used in carbonylation of methanol to obtain acetic acid and methyl acetate, and in carbonylation of methyl acetate to obtain acetic anhydride.  The reaction system does not need addition of hydroiodic acid, therefore, will alleviate the corrosion to production equipment.

A catalyst for homogeneous carbonylation of the present invention is a chelated cis-dicarbonyl rhodium (I) coordination complex in a square planar geometry formed by carbonyl rhodium with an organic lithium ligand as shown by the following structure:

(structure I)

wherein X¯ is BPh₄¯, BF₄¯, CH₃COO¯ or OH¯; n=0, 1, 2, 3 or 4.

The above-mentioned organic lithium ligand refers to lithium dicarboxylate containing two carboxyl groups as shown by the following structure:

(structure II)

wherein n=0, 1, 2, 3 or 4; for example, lithium oxalate, lithium malonate, lithium succinate, lithium glutarate and so on.

The catalyst of the present invention has the following characteristics:

1.        As the ligand contains two coordinate oxygen atoms that will form two coordination bonds with rhodium during formation of the coordination complex, the two coordinate oxygen atoms are connected by a somewhat flexible carbon chain to form a dual metal bidentate chelated complex in a square planar geometry.

2.        The complex has a relatively high stability and can be prepared without protection of inert gas.  In a study using X-ray photoelectron spectroscopy (XPS) measurement, it is proved that there exist two O->Rh coordination bonds.  Infrared spectra show that there is a characteristic absorption peak between 2000 and 2100 cm^-1, corresponding to the terminal carboxyl of the rhodium complex, indicating that these complexes have a cis-dicarbonyl structure.

3.        Due to the existence of the chelated structure and the two relatively weak O->Rh coordinate bonds in the complex, the catalytic system will facilitate addition of methyl iodide as a promoter in the reaction.

4.        As the catalyst contains two types of metals, i.e., rhodium and lithium that is linked with carboxylic group through an ionic bond, the synergistic effect between the two types of metals activates the terminal carboxylic groups that are connected with the rhodium atom and thus increases activity of the catalyst.

5.        Because of the high catalytic activity and stability of the catalyst, reaction conditions of methanol carbonylation become extremely moderate, and the reaction system does not need addition of a polar solvent, such as hydroiodic acid, but will only need addition of methyl acetate, acetic acid, acetic anhydride and water as a solvent.