Higher hydrocarbons, removal

The impurities usually found in raw hydrogen are CO2, CO, N2, H2O, CH, and higher hydrocarbons. Removal of these impurities by shift catalysis, H2S and CO2 removal, and the pressure-swing adsorption (PSA) process have been described (vide supra). Traces of oxygen in electrolytic hydrogen are usually removed on a palladium or platinum catalyst at room temperature. 

Fiiikelshtein Sh, Ushakov NV, Yampolsldi YuP (2003) The method of higher hydrocarbons removal from natural and petroleum gases. Patent Russian Federation 2218979 Bull of Inventions 15... 

For cathode modification obtained results have shown that cell resistance is lower when electrodes are in contact with soil sample, and this allowed for higher hydrocarbon mobility, so residual concentration profile exhibits an increasing trend from anode to cathode. Otherwise, physical barrier inclusion increased soil resistance and so far, hydrocarbon mobility is lowered, this fact resulted in a decreasing concentration trend from anode to cathode. From oil and grease extractions it was determined that CF provides higher hydrocarbon removal, although this option is not the best because transported hydrocarbons get adsorbed in the electrode, being difficult its recovery. 

Aliphatic hydrocarbons can be prepared by the reduction of the readily accessible ketones with amalgamated zinc and concentrated hydrochloric acid (Clemmensen method of reduction). This procedure is particularly valuable for the prep>aration of hydrocarbons wdth an odd number of carbon atoms where the Wurtz reaction cannot be applied with the higher hydrocarbons some secondary alcohol is produced, which must be removed by repeated distillation from sodium. 

Higher Hydrocarbons. The VPO of higher hydrocarbons is similar to that of the lower members of the series with two significant additional comphcations (/) the back-bitiag reactions of alkylperoxy radicals (eq. 32), particularly at positions 2 or 3 carbons removed from the peroxy position, and (2) above the NTC region, radical fragmentation (eq. 28). 

Activated alumina and phosphoric acid on a suitable support have become the choices for an iadustrial process. Ziac oxide with alumina has also been claimed to be a good catalyst. The actual mechanism of dehydration is not known. In iadustrial production, the ethylene yield is 94 to 99% of the theoretical value depending on the processiag scheme. Traces of aldehyde, acids, higher hydrocarbons, and carbon oxides, as well as water, have to be removed. Fixed-bed processes developed at the beginning of this century have been commercialized in many countries, and small-scale industries are still in operation in Brazil and India. New fluid-bed processes have been developed to reduce the plant investment and operating costs (102,103). Commercially available processes include the Lummus processes (fixed and fluidized-bed processes), Halcon/Scientific Design process, NIKK/JGC process, and the Petrobras process. In all these processes, typical ethylene yield is between 94 and 99%. 

Natural gas consists mainly of methane together with some higher hydrocarbons (Tab. 8.1). Sulfur, if present, must be removed to a level of about 0.2 ppm prior to the steam reforming process as it poisons the catalyst. This is typically done by cata-lytically converting the sulfur present as thiols, thiophenes or COS into H2S, which is then adsorbed stochiometrically by ZnO, at 400 °C, upstream of the reactor. 

In some cases, the initial LNG composition may lie in a region where RPTs are improbable (e.g., LNG with a high methane concentration), but boiling removes methane preferentially and the residual liquid composition would be enriched in ethane and higher hydrocarbons. In this case the LNG may reach the RPT region. These events would be referred to as delayed RPTs, and they are possible unless surface ice has formed. Spills on open water do not lead to extensive ice formation and just such a delayed RPT was noted in one of the ESSO tests sponsored by the American Petroleum Institute (Feldbauer et al., 1972). Seven cubic meters of LNG (with a methane content of about 85%) were spilled in Matagorda Bay, Texas, in about 25 sec. A strong RPT occurred about 17 sec after the termination of the spill. In the next 15 sec, other, smaller RPTs resulted. 

Uses Solvent for elastomers, natural rubber, synthetic rubber heat-transfer liquid transformer and hydraulic fluid wash liquor for removing C4 and higher hydrocarbons sniff gas recovery agent in chlorine plants chemical intermediate for fluorinated lubricants and rubber compounds fluid for gyroscopes fumigant for grapes. Not produced commercially in the U.S. 

Any condensation of methane to ethane and subsequently to higher hydrocarbons must overcome the unfavorable thermodynamics. This can be achieved in condensation processes of oxidative nature, where hydrogen is removed by the oxidant. SbF5- or FS03H-eontaining superacid systems also act as oxidants. The oxidative condensation of methane was subsequently found to take place with more economical cooxidants such as halogens, oxygen, sulfur, or selenium 91... 

Carbon tetrachloride is prepd by the interaction of CS2 Cl in the presence of a catalyst(iron) or by the chlorination of methane or higher hydrocarbons at 250-400° (Ref 21). See also Refs 1,4,5,9,15,18 19- The crude product is purified by treating with caustic soln to remove sulfur chloride, followed by rectification... 

Methane. Research Grade (about 99.65 mole % pure) and CP (about 99.0 mole % pure) methane are available in cylinders. The removal of C02, Q, N2, and higher hydrocarbons from methane by adsorption on charcoal has been described in the literature.65... 

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