LT: In-Situ Generation of Hazardous Reactants for Chemical Synthesis

化学工业经常通过采用替代技术来处理危险化学品，从而避免使用这些原材料。这是一个很有吸引力的策略，但它并不普遍适用。替代过程可能是对环境有害的废物的主要产生者，并且可能涉及的材料只是稍微不那么危险。因此，需要其他选项。本提案探讨了一种新的方法来解决使用反应性和危险化学品的问题：就地发电。这一概念的成功发展将在无害环境的化学合成领域创造重要的新选择。甲醛是一种危险而昂贵的化学品，传统上在化学合成中是避免使用的。它是一种疑似或可能的人类致癌物，它的反应性很强，不能以纯形式储存或运输。然而，与目前的商业生产工艺相比，通过甲醛生产一些重要化学品的污染要少得多，安全性也更高。例如，仅在美国，以甲醛为基础的工艺取代目前用于生产甲基丙烯酸甲酯和苯乙烯的技术，每年可减少约80亿磅苯和约2.5亿磅氰化氢的使用，每年可减少约10亿磅亚硫酸铵废物和约1亿磅三氯化铝废物。近年来，本实验室高温泥浆反应器的发展，以及多步反应催化和反应工程的稳步进展，为危险化学品的利用提供了新的途径。实质上，危险化学品将在一个反应堆中就地产生和消耗。例如，已知甲醛可以在300至400℃的温度范围内与丙酸甲酯在各种异相催化剂上反应生成甲基丙烯酸甲酯。应该有可能在同一反应器中，使用不同的催化剂同时将甲醇脱氢成甲醛。这两个反应的偶联将导致甲醇和丙酸甲酯合成甲基丙烯酸甲酯。同样，苯乙烯也可以由甲醇和甲苯合成。关键是使用一个浆料反应器，其中包含甲醇脱氢催化剂和甲醛消耗反应催化剂的物理混合物，并使两个反应的速率适当平衡。本研究将重点研究原位甲醛生成，即在高温泥浆反应器中甲醇脱氢制甲醛。重点将放在理解催化剂组成和结构的影响，以及反应器设计和操作变量，对反应的动力学和选择性。这一知识将为原位甲醛生成与各种甲醛消耗反应的耦合提供良好的基础。拟议的研究计划有可能在无害环境的化学合成方面取得重大进展，因为原位生成的新概念应该具有广泛的适用性，可以作为工艺替代的使能技术。所提出的研究也将提供重要的科学进展，即为浆体反应器中多步反应催化剂体系的先验设计提供更基本的依据。＊＊＊

9727137 McConica The chemical industry frequently deals with hazardous chemicals by adopting alternative technologies that avoid the use of such raw materials. This is an attractive strategy, but it is not universally applicable. The alternative processes can be major generators of environmentally-harmful waste, and can involve materials that are only marginally less hazardous. Thus, other options are needed. This proposal examines a novel approach to the problem of using reactive and hazardous chemicals: in- situ generation. Successful development of this concept will create important new options in the area of environ- mentally-benign chemical synthesis. Formaldehyde is an example of a hazardous and costly chemical that has traditionally been avoided in chemical synthesis. It is a suspected or probable' man carcinogen, and it is so reactive that it cannot be stored or shipped in pure form. However, a number of important chemicals could be produced with much less pollution and with greater safety via formaldehyde than by their current commercial processes. For example, substitution of formaldehyde-based processes for the technologies currently used to produce methyl methacrylate and styrene could eliminate the use of about 8 billion pounds of benzene and about 250 million pounds of hydrogen cyanide annually, and could eliminate about 1 billion pounds of ammonium bisulfate waste and about 100 million pounds of aluminum trichloride waste annually, in the United States alone. The recent development of high-temperature slurry reactors in our laboratory, coupled with steady progress in the catalysis and reaction engineering of polystep reactions, permits a new approach to utilization of hazardous chemicals. In essence, the hazardous chemical will be generated and consumed in situ in a single reactor. For example, it is known that formaldehyde can react with methyl propionate over various heterogeneous catalysts in the temperature range of 300 to 400' C to form methyl methacrylate. It should be possible to simultaneously dehydrogenate methanol to formaldehyde in the same reactor, using a different catalyst. The coupling of these two reactions would result in the synthesis of methyl methacrylate from methanol and methyl propionate. Similarly, styrene could be synthesized from methanol and toluene. The key is to employ a slurry reactor containing a physical mixture of a methanol dehydrogenation catalyst and a catalyst for the formaldehyde-consuming reaction, with the rates of the two reactions properly balanced. This research will focus on in-situ formaldehyde generation, i.e., the dehydrogenation of methanol to formaldehyde, in a high-temperature slurry reactor. Emphasis will be placed on understanding the effect of catalyst composition and structure, and the reactor design and operating variables, on the kinetics and selectivity of the reaction. This knowledge will provide a sound fundamental basis for coupling in-situ formaldehyde generation with various formaldehyde-consuming reactions. The proposed research program has the potential to produce a major advance in environmentally-benign chemical synthesis, since the novel concept of in-situ generation should have broad applicability as an enabling technology for process substitution. The proposed research will also provide an important scientific advance, i.e., a more fundamental basis for the a priori design of catalyst systems for polystep reactions in slurry reactors. ***