Cyanamides conversion

The calcium cyanamide feed is weU mixed with the recycled slurry and filtrate ia a feed vessel. The calcium cyanamide is added at a rate to maintain a pH of 6.0—6.5 ia the cooling tank. The carbonation step can be conducted ia a turbiae absorber with a residence time of 1—2 min. After the carbonation step, the slurry is held at 30—40°C to complete the formation of calcium carbonate, after which the slurry is cooled and filtered. AH equipment for the process is preferably of stainless steel. The resulting solution is used directiy for conversion to dicyandiamide. 

Conversion of Tertiary Amines to Cyanamides The von Braun Reaction... 

Selected examples of the conversion of IVA-disubstituted ureas into cyanamides... 

Ferrihydrite Conversion cyanamide to urea or dicyanamide Amberg and Vilsmeier, 1978... 

Conversion of Alkyl Halides to Secondary Amines with Cyanamide Imino-de-dihalo-aggre-substitution (overall transformation)... 

Conversion of [l,3,4]oxadiazolo[3,2-a]pyridinium salts (51) to [1,2,4]-triazolo[l,5-a]pyridines can take two pathways using aniline 1-phenyltria-zolopyridinium salts (52) are obtained,67 whereas using cyanamide and triethylamine, the 2-aminotriazolopyridine 53 is formed.68... 

The cyanamides are active anticorrosive pigments which have a passivating action under alkaline conditions. The action of lead in anticorrosive pigments is discussed in Section 5.2.10.1. Heavy metal oxides, especially of iron and manganese, catalyze the conversion of cyanamide to urea even below 20 °C [5.126] ... 

An interesting variation on the above conversion of pyrylium into pyridinum salts is the reaction of the former with cyanamide in which a 3-acyl-2-aminopyridine (61) is formed in 75% yield, probably by the mechanism shown (71JCS(C)3873). 

One of the chief disadvantages involved in this process is the large quantity of energy that must be employed in the production of calcium carbide and in its conversion to calcium cyanamide. 

In connection with biosynthetic studies, compound (41) or (42) has been prepared, starting with OO-diacetyl-lycorine (37) (Scheme 6).13 Treatment of (37) with cyanogen bromide gave the cyanamide (38) in 80% yield this was not isolated but was directly oxidized to the aldehyde (39). Acetalization followed by reduction with lithium aluminium hydride gave the unstable amine (40), which upon hydrolysis gave a compound which, on the basis of its conversion into lycorine (37 OH in place of OAc) may be formulated as (41). This assignment is in doubt, since spectral evidence favours structure (42). 

TVA Process (Refs 85, 93 102). In 1933 the Tennessee Valley Authority inherited a World War I plant designed to produce ammonia by a roundabout and obsolete method in the following steps first the manuf of lime and subsequently Ca carbide, then Ca cyanamide, ammonia, nitric acid and finally AN. In 1940 a modern high-pressure ammonia plant was constructed, in which there were used an improved ammonia synthesis catalyst and a water-gas conversion catalyst. During WW II, the TVA produced 29000 tons of anhydrous ammonia, 10000 t of AN liquor, 64000 t of AN crysts and over... 

It is worth noting that HCN is also an important by-product of propylene ammonoxidation to acrylonitrile (the yield may be as large as 20% in relation to acrylonitrile). Other methods have been used in the past, for example, the conversion of nitrogen to cyanamide (NHj C=N) followed by a subsequent further hydrogenation to hydrogen cyanide, or the thermolysis of trimeihyl-amine obtained from niolasses. 

This program concentrated on the requirements and problems that are expected during typical refinery processing. The main concerted efforts, therefore, were to detect and differentiate levels of performance of the synthetic liquids compared with the performances of an appropriate petroleum counterpart stream. Temperature was used as the primary process variable. If catalyst on-stream life and conversion are to be optimized, then an accurate temperature profile performance must be the initial step. Hydro-treating performances were evaluated under simulated refinery conditions while varying the most practical primary process variable, temperature. All experimental work utilized American Cyanamid HDS-3A catalyst. 

Problem 20.26 Give equations for the individual steps probably involved in the conversion of calcium cyanamide into ammonia in the presence of water. What other product or products will be formed in this process Label each step with the name of the fundamental reaction type to which it l longs. 

---