Formaldehyde Processes

The oxidation of an undisclosed methanol derivative to the corresponding formaldehyde compound is a large-scale BASF process which was established in recent years, whereas the similar methanol-to-formaldehyde process, performed on a much larger scale, has been practised at BASF for more than 100 years [1,49-51, 108]. The exact nature of the substituent(s) was not disclosed by BASF for reasons of confidentiality, although many publications on that topic appeared. The nature of the substituent makes the derivative, as the results of the investigations show, more labile to temperature. 

The formaldehyde process is an air oxidation of methanol, CH3OH, which has water as a by-product. Formaldehyde is a gas at room temperature, but is usually handled either as a water solution called formalin or as polymers called paraformaldehyde and trioxane. Both are readily converted back ro formaldehyde. Some uses of formaldehyde are the manufacture of polymer resins and as a germicide. 

Diacetoxy-2-butene. Mitsubishi commercialized a new proces, the acetoxy-lation of 1,3-butadiene, as an alternative to the Reppe (acetylene-formaldehyde) process for the production of l,4-diacetoxy-2-butene. l,4-Diacetoxy-2-butene is tranformed to 1,4-butanediol used in polymer manufacture (polyesters, polyurethanes). Additionally, 1,4-butanediol is converted to tetrahydrofuran, which is an important solvent and also used in polymer synthesis. 

Properties of formaldehyde, properties of byproducts, disposal of waste products -this can be rather (fifficult )n the case of the formaldehyde process. 

Acheson ED, Barnes HR, Gardner MJ, et al. 1984a. Formaldehyde process workers and lung cancer. Lancet 1 1066-1067. 

Figure 3.22 shows a schematic of the Haldor-Topsoe A/S Formaldehyde Process. The process starting material is methanol and the catalyst used is Haldor Topsoe A/S FK-series iron/molybdenum-oxide catalysts [9]. The process is carried out in a recirculation loop at near atmospheric pressure (I—... 

Figure 3.22 A schematic of the Haldor-Topsoe A/S Formaldehyde Process. (I) pump, (2) heat exchanger, (3) reactor, (4) low pressure steam boiler, (5) absorber, (6,7) cooling cycles, (8) tail gas scrubber, (9) reactor heater, (10) methanol evaporator, (11) boiler feed-water preheater.

Claims have been made that by the maintenance of a substantially neutral reaction mixture throughout the formaldehyde process, the formation of by-products is greatly decreased. For this purpose a basic material such as ammonia is added to the reaction mixture prior to the conversion. " Rapid cooling is used to prevent the formation of paraformaldehyde. 

Homer, C W, A formaldehyde process to accommodate rising energy costs Cbem. Eagng, 84 (14) 108-110 (1977). 

The same principal products were detected in the photolysis of an alcohol and its corresponding ether. For example, ethanol and ethyl ether gave ethylene (process a), acetaldehyde (process b), and formaldehyde (process b). In an attempt to find out whether the formaldehyde and... 

Depending on the purpose of the experiment to be performed, embryos operated and cultured as described can be subjected to histochemistry, immunological procedures (as whole mounts), or whole-mount in-sim hybridization. In many cases, it is possible to combine two or more of these methods. For example, it is possible to fix the embryos in formaldehyde, process them as whole mounts for in-situ hybridization, postfix in formaldehyde, then perform whole-mount immunoperoxidase histochemistry with QCPN antibody to detect the quail cells. After this, they can be embedded in wax and sectioned. Methods for this have been published elsewhere in some detail (18). 

Patience, G.S. and Cenni, R. (2007). Formaldehyde process intensification through gas heat capacity. Chemical Engineering Science, Vol. 62, pp. 5609-5612. 

Hi) The isobutylene-formaldehyde process These two intermediates react to form 4,4-dimethyl-m-dioxane which is catalytically converted to isoprene. 

In a subsequent simulation study, two important industrial selective oxidation processes were addressed in detail, namely the partial oxidation of methanol to formaldehyde and the epoxidation of ethylene to ethylene oxide. In both cases secondary undesired reactions play a significant role, i.e. the combustion of the primary product in the formaldehyde process and the combustion of the ethylene reactant in the ethylene oxide process, so that the study also provided information on how the adoption of high conductivity monolith catalysts would alfect the selectivity of industrial partial oxidation processes for both a consecutive and a parallel reaction scheme. For both processes intrinsic kinetics applicable to industrial catalysts as well as design and operational parameters for commercial reactors were derived from simulation studies and experimental investigations collected in the literature. 

This last section provides the reader with examples dealing with not only reactor design and predictive calculations but also with several ancillary equipment that often are part of the reactor process . A total of ten illustrative examples follow. The last illustrative example examines a formaldehyde process from a conversion, yield, material balance, etc., point of view. 

FIGURE 11.5 Flow diagram of the oxidation of methane to formaldehyde (process of the Gutehoffnungshutte Company) [93] (1) reactor for the synthesis of nitrogen dioxide, (2) reactor for formaldehyde production, (3) heat exchanger, (4) air blower, (5) refrigerator, (6) wash column, (7) receptacle for the crude product, (8) converter, (9) distillation column, (10) receptacle for finished product. (I) ammonia (II) air (III) methane (IV) discharge gas and (V) water. 

The second commercial formaldehyde process is based on an iron molybdate catalyst. This process operates at about 450 °C, atmospheric pressure, and with a large stoichiometric excess of oxygen. Reaction (7-A) is the principal source of CH2O. The reaction temperature is so low that Reaction (7-B) is unimportant. 

As an aside, we might ask why both of the commercial formaldehyde processes operate with feeds where the ratio of air to methanol is far removed from the stoichiometric ratio. The answer is safety, specifically the need to avoid the possibility of an explosion. In both processes, the feed compositions are outside the flammability limits of methanol/air mixtures, so that an explosion is not possible, even if an ignition source is present. In the silver catalyst process, the methanol/air ratio is above the upper flammability limit. In the iron molybdate process, the methanol/air ratio is below the lower flammability limit. 

Several reviews of the coimnercial formaldehyde processes then available had been pubUshed by 1953 and gave sununaries of the operating conditions used. Simplified flow sheets for both processes are shown in Figures 4.7 and 4.8, and a photograph of a metal-oxide catalyzed plant is shown in Figure 4.9. Typical catalyst properties are given in Table 4.4. 

Figure 4.7. Simplified flow sheet of a typieal silver-catalysed formaldehyde process. Reprinted from Catalyst Handbook, ed., by kind permission of M. Twigg.

Additives such as chromium or cobalt oxides can stabihze the catalyst. In Table 4.5, catalyst compositions and operating conditions in modem formaldehyde processes are shown. 

Table 1.. Analysis of Formaldehyde Process Exit Gases.

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