Mercury catalysts

From Acetylene. Although acetaldehyde has been produced commercially by the hydration of acetylene since 1916, this procedure has been almost completely replaced by the direct oxidation of ethylene. In the hydration process, high purity acetylene under a pressure of 103.4 kPa (15 psi) is passed into a vertical reactor containing a mercury catalyst dissolved in 18—25% sulfuric acid at 70—90°C (see Acetylene-DERIVED chemicals). 

Anthraquinone-l,5-disulfonic acid [117-14-6] (44), and anthraquinone-1, 8-disulfonic acid [82-48-4] (45) are produced from anthraquinone by disulfonation in oleum a higher concentration of SO than that used for 1-sulfonic acid is employed in the presence of mercury catalyst (64,65). After completion of sulfonation, 1,5-disulfonic acid is precipitated by addition of dilute sulfuric acid and separated. After clarification with charcoal, 1,5-disulfonic acid is precipitated as the sodium salt by addition of sodium chloride. The 1,8-disulfonic acid is isolated as the potassium salt from the sulfuric acid mother hquor by addition of potassium chloride solution. 

Effect of hydrogen flow rate on rate of reaction. Temperature, 25-26 °C pressure, O = 534 mm and = 741 mm of mercury catalyst weight, 0.974 g stirrer speed, 1500 rpm. 

Although, as shown above, a number of metals [Hg(II), Rh(I), Ag(I), Pd(II), Au(III) and Cu(I)[ are active for the cycloisomerization of allenyl ketones, some substrates are still restricted to the use of Hg(II) as Leclerc and Tius demonstrated recently for 113, the cyclopentane-anellated furan 114 was only accessible with the mercury catalyst (Scheme 15.32) [73],... 

Black phosphorus also starts with heating white phosphorus. The difference is that the white phosphorus is heated in the presence of a mercury catalyst and a small amount of already-formed black phosphorus. Its density is 2.4 g/cm. ... 

Anlhraquinone- 1-sulfonic acid is prepared from anthraquinone by sulfonation with 20% oleum in the presence of mercury catalyst, a Hg(ii) salt such as HgSOr or HgO. at 120 C. 

Addition of halogens and hydrogen halides May require mercury catalyst... 

This method was developed to replace the hazardous mercury catalyst required in the original mercuric oxide Kjeldahl method. It has been evaluated through an interlaboratory comparison of catalysts and has been adopted as the official replacement for the mercuric-oxide catalyzed Kjeldahl method. An inter-laboratory evaluation (Berner, 1990) indicated that this method (which uses the copper/titanium catalyst mixture) produces results more closely in agreement with the mercuric oxide catalyst method than methods using a copper sulfate catalyst. As a result of this study, mercuric... 

The performance of the combustion method compares favorably with that of the mercury catalyst Kjeldahl method for determination of crude protein in feeds. Standard deviations by the combustion method covered the full range of possibilities compared to the Kjeldahl method values were either equivalent, better than, or not as good as for the Kjeldahl method. For the 0.5-mm pairs, values ranged from 0.09% to 0.58% protein for the Kjeldahl method and from 0.14% to 0.33% protein for the combustion method, and (SR) values ranged from 0.23% to 0.86% protein (Kjeldahl) and from 0.30% to 0.61% protein (combustion). 

See also Chapter 2. As has been already mentioned, the lanthanide metals react with PrOH only on prolonged reflux and in the presence of the mercury catalysts [1084] (method 1). The normal chain alcohols do not react at all because of the insolubility of La(ORn)3. 

Traditionally, mercury catalysts have been the catalyst of choice, but because they are highly dangerous, they have, to a large degree, been replaced by bismuth-based catalysts. The mercury catalysts are both toxic and caustic. 

Depending on the temperature at which the material is processed, various amounts of a metallic catalyst are added. Tin-based catalysts, such as Air Products T12, catalyze the OH-NCO reactions. The metallic catalyst increases the total reaction speed but also equals out the reaction rates of the high molecular polyols and the low molecular polyols. Bismuth catalysts are now preferred to the previously used mercury catalysts. Polyether polyols are slow in reaction, and both a tin and an amine catalyst may be needed to obtain the best speed and properties. 

MDI-diol-cured polyurethanes generally can receive FDA approval for use, provided no mercury catalysts are used. Polyurethanes made from most amine-cured TDI material will not meet the requirements for FDA approval. Trimetyleneglycol di-p-aminobenzote (Versalink 740M) of the diamine... 

Esters, lactones, and peptides. The reagent serves as a dehydration agent for condensation of RCOOH with alcohols or amines to provide esters, lactones or lactams, or peptides, usually in the presence of a mercury catalyst (HgO). 

In 1954, van der Kerk and Luijten658 found that in the direct synthesis of tetraorganyl-stannanes the tin — sodium alloy can be replaced with a tin-magnesium alloy659-661. A mercury catalyst (Hg or HgCl2) was required for this variant and the process was conducted at 160 °C under pressure. 

These gold catalysts are a significant improvement on the mercury catalysts used previously and the reactions are conducted under mild conditions (293-323 K) in the presence of acid co-catalysts. 2-Propynol reacts with excess methanol at 328 K in the presence of 0.01 mol% CH3Au PPh3 and sulfuric acid to give the following dioxane derivative, f -2,5-dimethyl-2,5-dimethoxy-l,4-dioxane, in 93% yield after 20h at 328 K ... 

REACTIONS OF NITRILES WITH COFj OVER MERCURY CATALYSTS [1524]... 

The role of the mercury catalyst is not shown in this mechanism. As a Lewis acid, it may act like the proton in the first step, helping to form vinyl cations the mercury is replaced when acid is added. 

The importance of chemical structure in determining ease of sulfonation is further illustrated in the pyridine series. These compounds as a group are very, difficult to sulfonate, ordinarily requiring a mercury catalyst at over 250°C using oleum. 2,6-Di-tert-butylpyridine has been found, on the other hand, to sulfonate easily even at — 10°C, using SO3 dissolved in SOj. In this exceptional case, steric hindrance prevents formation of the difficultly sulfonatable addition compound with SO3. 

Now the sulfur atoms work to stabilize an anion (organolithium) formed by deprotonation. Alkylation and hydrolysis with a mercury catalyst gives the product. 

As the water formed is removed axeotropically, the mercury impregnated Nafion-H catalyst can be recovered by filtration without any loss of activity and can be recycled. Comparison of data with nitration in the absence of mercury catalyst shows that formation of less hindered isomeric nitroarenes are favored. It is interesting to note that attempted azeotropic nitration of ethylbenzene with nitric acid/Nafion-H yielded only acetophenone via side-chain oxidation, whereas in the presence of mercury salt under similar reaction conditions, niiroethylbenzenes were obtained in good yield with only 13% of product of side chain oxidation. 

Mercury catalysts were used in the production of acetaldehyde, acetic acid, and vinyl chloride. The major use of mercury in the decade 1959-1969 has been as a cathode in the electrolytic preparation of chlorine and caustic. In 1968, this use accounted for about 33% of the total U.S. demand for mercury. In that same period, electrical apparatus accounted for about 27% of U.S. mercury consumption industrial and control instruments, such as... 

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