Reactors formaldehyde production

The effluent generated during the production of the resins arises from different operations within the factory. The effluent of the production processes comes mainly from cleaning operations of reactors, storage tanks, filters from the towers of formaldehyde production, and the filters from the reactors. Another source for disposal comprises the spills occurring during the transfer of the resins from the reactors to the storage tanks and from these to the truck used to distribute them to other factories. 

J. Deng and J. Wu, Formaldehyde production by catalytic dehydrogenation of methanol on inorganic membrane reactors, Appl. Catal. A. 709 63 (1994). 

Harold M.P., Cini P, Patenaude B. and Venkataraman K., The catalytically impregnated ceramic tube An alternative multiphase reactor, AIChE Symposium Series 85 (265) 26 (1989). Song J.Y. and Hwang S.-T, Formaldehyde production from methanol using a porous Vycor glass membrane. Proceedings of ICOM 90, Chicago, (30)540 (1990). 

The fractional conversion of methane is 95%, and the fractional yield of formaldehyde is 90%. Calculate the molar composition of the reactor output stream and the selectivity of formaldehyde production relative to carbon dioxide production. 

In contrast to methanol oxidation, oxidative dehydrogenation of methanol [route (b) in Topic 5.3.2] is an endothermic reaction (AH = -F84kJ mol ). Methanol is contacted at normal pressure with a heterogeneous silver at 500-700 °C. Owing to the kinetic instability of the formaldehyde product under the applied reaction conditions, the contact time at the catalyst is very short (t < 0.01 s). This is realized by high flow rates in the reactor and a very effective quenching of the product flow leaving the reactor. The product gas is contacted with water to produce an aqueous... 

Olah and Prakash have reported a method of producing methanol from methane in a three-step system, in which formaldehyde is obtained initially in a quartz-mbe continuous-flow reactor. Formaldehyde is then transformed into formic acid on alkahne-earth oxides and finally methanol/formic acid is transformed into methanol methyl formate employing a WO3/AI2O3 catalyst. However, at the moment, only low yield to oxygenated products has been obtained. 

The fresh feed to the process was 0.5 kmole/h of O2 and an excess methanol. All of the O2 reacts in the reactor. Formaldehyde and water are removed from the product stream first, after which H2 is removed from the recycled methanol. The recycle flow rate of methanol was 1 kmole/h. The ratio of methanol reacting by decomposition to that by oxidation was 3. Draw the flow diagram and then calculate the per pass conversion of methanol in the reactor and the fresh feed rate of methanol. 

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. 

FIGURE 11.7 Flowsheet of formaldehyde production by the gas-phase oxidation of methane in the presence of nitrogen oxides (process of ICP RAS) [174]. (1) Air blower, (2) furnace, (3) receiver, (4) separator, (5,5 ) compressors, (6) contact apparatus for ammonia oxidation, (7) tubular heater, (8) reactor, (9) pipe cooler, (10) absorber, (11, 15) pumps, (12) receptacle for formalin, (13) scrubber, and (14) cooUng coil. 

If the silver catalyst did not catalyze Reaction (7-C), or if we attempted to operate without O2, the conversion of CH3OH would be much lower, and heat would have to be added to the reactor to maintain the necessary high temperature. As we shall see in the next chapter, heating or cooling complicates the mechanical design of a reactor. For these reasons. Reaction (7-C) is desirable, in the context of formaldehyde production. 

Song, J.-Y. and S.-T. Hwang, Formaldehyde production from methanol using a porous Vycor glass membrane reactor. Journal of Membrane Science, 1991. 57(1) 95-113. 

In production, anhydrous formaldehyde is continuously fed to a reactor containing well-agitated inert solvent, especially a hydrocarbon, in which monomer is sparingly soluble. Initiator, especially amine, and chain-transfer agent are also fed to the reactor (5,16,17). The reaction is quite exothermic and polymerisation temperature is maintained below 75°C (typically near 40°C) by evaporation of the solvent. Polymer is not soluble in the solvent and precipitates early in the reaction. 

The enthalpy of the copolymerization of trioxane is such that bulk polymerization is feasible. For production, molten trioxane, initiator, and comonomer are fed to the reactor a chain-transfer agent is in eluded if desired. Polymerization proceeds in bulk with precipitation of polymer and the reactor must supply enough shearing to continually break up the polymer bed, reduce particle size, and provide good heat transfer. The mixing requirements for the bulk polymerization of trioxane have been reviewed (22). Raw copolymer is obtained as fine emmb or flake containing imbibed formaldehyde and trioxane which are substantially removed in subsequent treatments which may be combined with removal of unstable end groups. 

A typical flow diagram for pentaerythritol production is shown in Figure 2. The main concern in mixing is to avoid loss of temperature control in this exothermic reaction, which can lead to excessive by-product formation and/or reduced yields of pentaerythritol (55,58,59). The reaction time depends on the reaction temperature and may vary from about 0.5 to 4 h at final temperatures of about 65 and 35°C, respectively. The reactor product, neutralized with acetic or formic acid, is then stripped of excess formaldehyde and water to produce a highly concentrated solution of pentaerythritol reaction products. This is then cooled under carefully controlled crystallization conditions so that the crystals can be readily separated from the Hquors by subsequent filtration. 

Staged reactions, where only part of the initial reactants are added, either to consecutive reactors or with a time lag to the same reactor, maybe used to reduce dipentaerythritol content. This technique increases the effective formaldehyde-to-acetaldehyde mole ratio, maintaining the original stoichiometric one. It also permits easier thermal control of the reaction (66,67). Both batch and continuous reaction systems are used. The former have greater flexibiHty whereas the product of the latter has improved consistency (55,68). 

Some alkylphenol appHcations can tolerate "as is" reactor products, most significantly in the production of alkylphenol—formaldehyde resins. These resins can tolerate some of the reactant and by-product from the alkylphenol reactor because they undergo purification steps. This resin production route has both capital and operating cost advantages over using purer alkylphenol streams as feedstock. For these savings, the resin producer must operate the process in such a way as to tolerate a more widely varying feedstock and assume the burden of waste disposal of some unreactive materials from the alkylphenol process. 

An example of what can happen in a production situation is provided in Fig. 1. This photo shows the devastation resulting from a phenol-formaldehyde reactor explosion that occurred at the Borden Chemical plant in Demopolis, Alabama on June 28, 1974. In this explosion, the stainless steel reactor was blown to bits. The reactor operators control room was obliterated. Two people were killed and several others were injured. All nearby property was demolished and windows were broken in homes for a distance of five miles from the plant. 

The Grignard reagent from 2-thenyl chloride can be obtained by the use of the "cyclic reactor.However, rearrangement occurs in its reaction with carbon dioxide, ethyl chlorocarbonate, acetyl chloride, formaldehyde, and ethylene oxide to 3-substituted 2-methylthio-phenes, Only in the case of carbon dioxide has the normal product also been isolated. 

There is not much to be said about the use of micro reactors for bulk chemicals and commodities. Worz et al. are so far the only ones who have disclosed their work on the potential of micro-structured reactors for the optimization of chemical processes performed on a large scale ofindustrial relevance [110,112,154,288-290]. This included a fast exothermic liquid/liquid two-phase reaction, which was used for the industrial production of a vitamin intermediate product, and a selective oxidation reaction for an intermediate, a substituted formaldehyde derivative. 

GP 4] [R 5] Formaldehyde synthesis has been known at BASF for more than 100 years [1, 49-51,108]. Hence it was expected to be able to handle the synthesis of substituted analogue, an undisclosed methanol derivative, with the same processsing concepts, major problems not being anticipated. This expectation was still supported by first attempts with the tried and tested pan-like reactor concept (5 cm diameter), which were promising. At 50% conversion, a selectivity of 90% was achieved. However, transfer to production scale using a 3 m production reac-... 

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