Hydrogen attack prevention

Bonner, W. A., et al Prevention of Hydrogen Attack on Steel in Refinery Equipment," paper presented at API Div. of Refining 18th Mid-year Meeting, May 1953. 

For hot wall vessels, the increased strength may be such that the use of chromium and molybdenum alloy steels will be cheaper. Also, these steels may be required to prevent hydrogen attack and to reduce oxidation and sulfidation. 

For refinery units such as hydrocrackers in which the hydrogen partial pressure is much higher, e.g., above l,350psi and the operating temperatures are above 800°F, the 2V4 Cr-1 Mo steel is commonly used. The higher alloy content is necessary to prevent hydrogen attack in these applications. The 2V4 Cr-1 Mo steel also has better creep... 

In accordance with these definitions, stress-corrosion cracking has been a familiar problem in the petroleum and chemical industries for decades. Consequently, measures seem to be rather well established and generally known for preventing stress-corrosion cracking or for keeping it in check. Where conditions are such that this type of hydrogen attack can be expected, appropriate supplemental requirements should be included in the specification. A vessel built only to code requirements could be rendered unserviceable in a matter of hours by stress-corrosion cracking. 

Protective liners such as concrete, neoprene-type rubber, or plastics also may be used to prevent hydrogen attack. Other procedures which are helpful are removal of cyanides, removal of sulfur compounds from feedstocks, and the injection of polysuffides which form a film over the interior of the vessel. ... 

Corrosion and Materials Selection 2.2.2 Prevention of Hydrogen Attack... 

The only practical way to prevent hydrogen attack is to use only steels that, based on plant experience, have been found to be resistant to this type of deterioration. The following general rules are applicable to hydrogen attack ... 

For most refinery and petrochemical plant applications, low-alloy chromium- and molybdenum-containing steels are used to prevent hydrogen attack. However, questions have recently been raised regarding the effect of long-term hydrogen exposure on C-0.5 Mo steel. As a result, low-alloy steels are preferred over C-0.5 Mo steel for new construction. 

The formation of silicon carbide, SiC (carborundum), is prevented by the addition of a little iron as much of the silicon is added to steel to increase its resistance to attack by acids, the presence of a trace of iron does not matter. (Addition of silicon to bronze is found to increase both the strength and the hardness of the bronze.) Silicon is also manufactured by the reaction between silicon tetrachloride and zinc at 1300 K and by the reduction of trichlorosilane with hydrogen. 

Hydrogen at elevated temperatures can also attack the carbon in steel, forming methane bubbles that can link to form cracks. Alloying materials such as molybdenum and chromium combine with the carbon in steel to prevent decarburization by hydrogen (132). 

If tin and sulfur are heated, a vigorous reaction takes place with the formation of tin sulfides. At 100—400°C, hydrogen sulfide reacts with tin, forming stannous sulfide however, at ordinary temperatures no reaction occurs. Stannous sulfide also forms from the reaction of tin with an aqueous solution of sulfur dioxide. Molten tin reacts with phosphoms, forming a phosphide. Aqueous solutions of the hydroxides and carbonates of sodium and potassium, especially when warm, attack tin. Stannates are produced by the action of strong sodium hydroxide and potassium hydroxide solutions on tin. Oxidizing agents, eg, sodium or potassium nitrate or nitrite, are used to prevent the formation of stannites and to promote the reactions. 

An unusual solvent system was chosen for the intramolecular reductive alkylation of the masked amino ketone (15). The purpose of the strongly acid system was to prevent cyclization of the deblocked amino ketone to 16, further hydrogenation of which gives the unwanted isomer 17 by attack at the convex face. The desired opposite isomer can be obtained by reduction of 16 with UAIH4 (52). 

A common technique for minimizing secondary amine formation is to carry out the hydrogenation in the presence of ammonia (21,23,42). Ammonia is thought to complete with the primary amine in attack on the intermediate imine. Anhydrous ammonia is preferred to prevent hydrolysis reactions,... 

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