Reaction pyrolyzer

Homogeneous catalysts. With a homogeneous catalyst, the reaction proceeds entirely in the vapor or liquid phase. The catalyst may modify the reaction mechanism by participation in the reaction but is regenerated in a subsequent step. The catalyst is then free to promote further reaction. An example of such a homogeneous catalytic reaction is the production of acetic anhydride. In the first stage of the process, acetic acid is pyrolyzed to ketene in the gas phase at TOO C ... 

Reaction of myrcene and sulfur dioxide under pressure produces myrcene sulfone. This adduct is stable under ordinary temperatures and provides a way to stabilize the conjugated diene system in order to hydrate it with sulfuric acid. The myrcene sulfone hydrate produced is pyrolyzed in the vapor phase in order to regenerate the diene system to produce myrcenol [543-39-5] (50). 

Pyrolysis of CsjB Hg] at 230°C gives CS2IB2H2] (60%) along with some CS2IB2QH2Q], CS2IB22H22], and CsBH (93). The sensitivity of polyhedral expansion reactions to solvent, temperature, and pressure is further exemplified by the results ia dioxane at 120°C under pressure. To obtain the closo borane, NajB H J is first converted to Cs2[B2 H23], which can be pyrolyzed to give Cs2[B2 H2J (89). 

An interesting reaction occurs when the dihydropyrazine (102 R = CHaPh) is pyrolyzed under vacuum. Toluene is liberated to give the monobenzylpyrazine (103) in high yield, presumably by a radical mechanism. 

Fired reactors contain tubes or coils in which an endothermic reaction within a stream of reac tants occurs. Examples include steam/ hydrocarbon reformers, catalvst-filled tubes in a combustion chamber pyrolyzers, coils in which alkanes (from ethane to gas oil) are cracked to olefins in both types of reac tor the temperature is maintained up to 1172 K (1650°F). 

In this process, the feed (natural gas) is pyrolyzed in preheated furnaces lined with a checker work of hot bricks. The pyrolysis reaction produces carbon, which collects on the bricks. The cooled bricks are then... 

The most common precursor is methane (CH4), which is generally pyrolyzed at 1100°C or above, over a wide range of pressure from about 100 Pa (0.001 atm) to 10 Pa (1 atm). The reaction in a simplified form is as follows ... 

Direct elimination of a carboxylic acid to an alkene has been accomplished by heating in the presence of palladium catalysts.Carboxylic esters in which the alkyl group has a P hydrogen can be pyrolyzed, most often in the gas phase, to give the corresponding acid and an alkene. No solvent is required. Since rearrangement and other side reactions are few, the reaction is synthetically very useful and is often carried out as an indirect method of accomplishing 17-1. The yields are excellent and the work up is easy. Many alkenes have been prepared in this manner. 

The mechanism is Ei (see p. 1322). Lactones can be pyrolyzed to give unsaturated acids, provided that the six-membered transition state required for Ei reactions is available (it is not available for five- and six-membered lactones, but it is for larger rings ). Amides give a similar reaction but require higher temperatures. 

When pyrolyzed, P-hydroxy alkenes cleave to give alkenes and aldehydes or ketones. Alkenes produced this way are quite pure, since there are no side reactions. The mechanism has been shown to be pericyclic, primarily by observations... 

The generation of PPV and corresponding derivatives via the dihalide approach is possible not only in solution reaction, but also - via the gas phase -in a so-called chemical vapor deposition (CVD) process. In this process, the vapor of a dichlorinated para-xylene (a,a or a,a) is pyrolyzed at moderately low pressures (0,1-0,2 torr) to form a chlorinated para-xylylene intermediate, which then condenses and polymerizes on a suitable, cooled substrate. The coating of the chlorinated precursor polymer can be heated to eliminate HCl, to form PPV 60 (or a PPV derivative) [88]... 

To design a pyrolyzer, steam flow required for decomposition of calcium chloride has to be evaluated. The steam flow depends on the equihbrium constant of decomposition reactions... 

DCA reactions are an important means of synthesis of a wide variety of heterocyclic molecules, some of which are useful intermediates in multistage syntheses. Pyrazolines, which are formed from alkenes and diazo compounds, for example, can be pyrolyzed or photolyzed to give cyclopropanes. 

The Marshall group has optimized reaction (14) to obtain a poly-si lazane with Mw A000 Daltons which can be hand drawn to give 10-20 pm preceramic fibers. These fibers are then rendered Infusible by exposure to humid air and pyrolyzed to give fibers with the same ceramic yields, 55+%, as found by Verbeek et al. The ceramic products are mainly amorphous SiC and SijN with some Si02 (a consequence of the humidity treatments). 

In 1972 Wynberg and Heldersl> reported a facile reaction between tetramethyl-thiophene (80) and dicyanoacetylene at room temperature in the presence of aluminum chloride. On the basis of spectroscopic data of the reaction product as well as its sulfone, 3,4-dicyano-2,5,6,7-tetramethylthiepin structure (81) was assigned. The product was pyrolyzed at 140 and 300 °C to 83 and 84, respectively. Un-... 

On the other hand, numerous examples are already known in which monomeric metaphosphoric esters are generated by thermolysis reactions. Most worthy of mention in this context is the gas phase pyrolysis of the cyclic phosphonate 150 which leads via a retro-Diels-Alder reaction to butadiene and monomeric methyl metaphosphate (151) 108,109, no). While most of the phosphorus appears as pyrophosphate and trimeric and polymeric metaphosphate, a low percentage (<5%) of products 152 and 153 is also found on condensation of the pyrolyzate in a cold trap containing diethylaniline or N,N,N, N,-tetraethyl-m-phenylene-diamine. The... 

The electrocatalysts for oxygen reduction were prepared as follows. These complex compounds were inoculated onto the carbon (AG-3, BET area near 800 m2/g) by means of adsorption from dimethylformamide solutions. The portion of complex compound weighed so as to achieve 3% of Co content was mixed with the carbon, then 5 ml of dimethylformamide per 1 g of the carbon were added and the mixture was cured at room temperature for 24 hours. Series of samples obtained were thermally treated (pyrolyzed), and the resulting grafted carbons were tested as electrode materials in the reaction of molecular oxygen reduction. 

Modification of carbon materials by tri-nuclear complexes of 3d-metals with ethanolamine ligands increases the catalytic activity with regard to the electrochemical reaction of oxygen reduction. The Co-Ni complex is most active in this reaction if pyrolyzed at 600°C. 

Borazine originally was obtained by the reaction of ammonia with diborane.1 Mixtures of lithium or sodium tetrahydro-borate with ammonium chloride also have been pyrolyzed to yield this product.2 More recently, the reduction of B,B, B"-trichloroborazine with alkali metal hydroborates has proved to be a convenient laboratory-scale method for the preparation of this compound.3-7 The procedure described herein is a variation of the last method as reported by Dahl and Schaeffer.7 This method is effective for the synthesis of iV-substituted alkyl- and arylborazines, i.e., compounds of the formula (HBNR)3 where R is CH3, C2H6, C6H , C6H5, p-C6H4CH3, or p-C6H4OCH3.5... 

When pure DBDPO was pyrolyzed at 390° C and the volatile products analyzed by CGC, 98% was recovered. The only reaction of note appeared to be the degradation of the nonabromodiphenyl oxide which had been detected as an impurity present in the starting sample. 

Previous thermal analysis studies had indicated that while Sb203 did not react directly with DBDPO, there was some evidence that the reaction of a polymer substrate with the Sb203 generated a species which was very reactive (23), and that this product was antimony metal (Sb°). Therefore, simple mixtures of DBDPO with powdered antimony, bismuth and zinc metals (mole ratio of bromine to metal of 3 1) were pyrolyzed and the extent of reaction determined by CGC. 

Several series of ternary mixtures containing DBDPO with PP and a variety of metals, metal oxides and other third components have been pyrolyzed in the TGA at 390° C and their volatiles analyzed by CGC. The CGC data from these experiments were found to fall into three distinct categories with respect to the observed extent of reaction. In the first class. Class I, the extent of reaction was found to be not significantly greater than that measured for the PP/DBDPO mixture alone. 

Reaction of K3Co(CN) with PMMA. A 1.0 g sample of PMMA and 1.0g of the cobalt compound were combined in a standard vessel and pyrolyzed for 2 hrs at 375°C. The tube was removed from the oven and the contents of the tube were observed to be solid (PMMA is liquid at this temperature). The tube was reattached to the vacuum line via the break-seal and opened. Gases were determined by pressure-volume-temperature measurements on the vacuum line and identified by infrared spectroscopy. Recovered were 0.22g of methyl methacrylate and 0.11 g of CO and C02. The tube was then removed from the vacuum line and acetone was added. Filtration gave two fractions, 1.27g of acetone insoluble material and 0.30g of acetone soluble (some soluble material is always lost in the recovery process). The acetone insoluble fraction was then slurried with water, 0.11 g of material was insoluble in water. Infrared analysis of this insoluble material show both C-H and C-0 vibrations and are classified as char based upon infrared spectroscopy. Reactions were also performed at lower temperature, even at 260°C some char is evident in the insoluble fraction. 

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