Carbon disulfide removal

Carbonyl sulfide is hydrolyzed almost quantitatively to hydrogen sulfide and carbon dioxide and better than 99% removal can be achieved. Carbon disulfide is hydrolyzed in two steps— first to carbonyl sulfide and hydrogen sulfide, followed by hydrolysis of the carbonyl sulfide to hydrogen sulfide and carbon dioxide. The two-step reaction is slower than the simple hydrolysis of carbonyl sulfide with the result that only about 75 to 85% carbon disulfide removal is obtained under normal operating conditions. 

Results from one year of continuous operation of a plant ueating about 500,000 cf/d of coal gas are given in Table 13-13. Removal efficiencies for individual sulfur compounds in the same installation are given in Table 13-14. The data show that the total organic sulfur removal efficiency of the process depended strongly on the type of. sulfur compounds present. The process was quite efficient for carbon disulfide removal much less so for carbonyl sulfide and very poor for thiophene. 

As indicated by the analysis, benzene is by far the most abundant compound in the light oil. For this reason the total liquid recovered is sometimes referred to as benzol. The marketable benzene products of specified purity are also referred to as benzol (e.g.. 1° benzol, industrial benzol, etc.), and the word toluol has the same significance with regard to toluene. Carbon disulfide can also be removed from the gas stream during the light oil recovery operation, and, in some installations, which are specifically designed for this service, carbon disulfide removal is of equal importance to benzol recovery. 

Protein-Based Adhesives. Proteia-based adhesives are aormaHy used as stmctural adhesives they are all polyamino acids that are derived from blood, fish skin, caseia [9000-71 -9] soybeans, or animal hides, bones, and connective tissue (coUagen). Setting or cross-linking methods typically used are iasolubilization by means of hydrated lime and denaturation. Denaturation methods require energy which can come from heat, pressure, or radiation, as well as chemical denaturants such as carbon disulfide [75-15-0] or thiourea [62-56-6]. Complexiag salts such as those based upon cobalt, copper, or chromium have also been used. Formaldehyde and formaldehyde donors such as h exam ethyl en etetra am in e can be used to form cross-links. Removal of water from a proteia will also often denature the material. 

Conversion of carbon in the coal to gas is very high. With low rank coal, such as lignite and subbituminous coal, conversion may border on 100%, and for highly volatile A coals, it is on the order of 90—95%. Unconverted carbon appears mainly in the overhead material. Sulfur removal is faciUtated in the process because typically 90% of it appears in the gas as hydrogen sulfide, H2S, and 10% as carbonyl sulfide, COS carbon disulfide, CS2, and/or methyl thiol, CH SH, are not usually formed. 

Alternative means for removal of carbonyl sulfide for gas streams iavolve hydrogenation. For example, the Beavon process for removal of sulfur compounds remaining ia Claus unit tail gases iavolves hydrolysis and hydrogenation over cobalt molybdate catalyst resulting ia the conversion of carbonyl sulfide, carbon disulfide, and other sulfur compounds to hydrogen sulfide (25). 

Carbonyl sulfide occurs as a by-product ia the manufacture of carbon disulfide and is an impurity ia some natural gases, ia many manufactured fuel gases and refinery gases, and ia combustion products of sulfur-containing fuels (25). It tends to be concentrated ia the propane fraction ia gas fractionation an amine sweetening process is needed to remove it. 

This reaction can also be mn in a continuous fashion. In the initial reactor, agitation is needed until the carbon disulfide Hquid phase reacts fully. The solution can then be vented to a tower where ammonia and hydrogen sulfide are stripped countercurrendy by a flow of steam from boiling ammonium thiocyanate solution. Ammonium sulfide solution is made as a by-product. The stripped ammonium thiocyanate solution is normally boiled to a strength of 55—60 wt %, and much of it is sold at this concentration. The balance is concentrated and cooled to produce crystals, which are removed by centrifiigation. 

Agricultural grades of ammonium thiosulfate are prepared by similar processes and contain some excess sulfur. The sulfur can be removed by washiug with carbon disulfide. A typical sulfur-free product contaius 87% (NH 2S203 3.4% (NH 2SC)3, and 9.6% (NH 2SC)4 (67). 

In another process, 50—150% excess carbon disulfide and a small excess of powdered alkah hydroxide are added, with stirring and cooling to the lower alkyl alcohol. After completion of the reaction, the excess CS2 and resulting water of reaction are removed by applyiag a vacuum to the reactor (80). 

One patent describes a continuous process involving an aqueous alkah metal hydroxide, carbon disulfide, and an alcohol (82). The reported reaction time is 0.5—10 min before the mixture is fed to the dryer. The usual residence time is on the order of hours. A study ia the former USSR reported the use of the water—alcohol azeotrope for water removal from isobutyl or isoamyl alcohol and the appropriate alkah hydroxide to form the alkoxide prior to the addition of carbon disulfide (83). 

Various types of detector tubes have been devised. The NIOSH standard number S-311 employs a tube filled with 420—840 p.m (20/40 mesh) activated charcoal. A known volume of air is passed through the tube by either a handheld or vacuum pump. Carbon disulfide is used as the desorbing solvent and the solution is then analyzed by gc using a flame-ionization detector (88). Other adsorbents such as siUca gel and desorbents such as acetone have been employed. Passive (diffuse samplers) have also been developed. Passive samplers are useful for determining the time-weighted average (TWA) concentration of benzene vapor (89). Passive dosimeters allow permeation or diffusion-controlled mass transport across a membrane or adsorbent bed, ie, activated charcoal. The activated charcoal is removed, extracted with solvent, and analyzed by gc. Passive dosimeters with instant readout capabiUty have also been devised (85). 

The Beaven process is also effective in removing small amounts of sulfur dioxide, carbonyl sulfide, and carbon disulfide that are not affected by the Claus process. These compounds are first converted to hydrogen sulfide at elevated... 

TliCNC reactions are reversible. DEA reacts with carbonyl sulfide (CUS) and carbon disulfide (CS2) to form compounds that can be regenerated in the stripping column. Therefore, COS and CS2 are removed without a loss i)f DEA. Typically, DEA systems include a carbon filter but do not include a reclaimer. 

A mixture of 13,3 grams of anhydrous aluminum chloride and 100 ml of carbon disulfide is added to 19,4 grams of 2-propionyloxybenzoic acid (prepared from the reaction of pro-pionyl chloride and 2-hydroxybenzoic acid). After an initial evolution of hydrogen chloride, the solvent is removed by distillation and the mixture is heated at 150° to 160°C for 4 hours. The cooled reaction mixture is treated with ice and hydrochloric acid and the product, 2-hydroxy-3-carboxypropiophenone, is obtained from the oily residue by distillation in vacuo,... 

Samples are hydrolyzed with hydrochloric acid and stannous chloride solution at elevated temperature, and the evolved carbon disulfide is drawn with an air steam through two gas washing tubes in series containing lead acetate and sodium hydroxide solutions and an absorption tube containing an ethanolic solution of cupric acetate and diethanolamine. Lead acetate and sodium hydroxide remove hydrogen sulfide and other impurities. In the absorption tube, the carbon disulfide forms two cupric complexes of Af,Af-bis(2-hydroxyethyl)dithiocarbamic acid with molecular ratios Cu CS2 of 1 1 and 1 2. These complexes are measured simultaneously by spectrophotometry at 453 nm. 

---