Nickel catalysts hydrocarbon conversion

The first demonstration of catalytic conversion of synthesis gas to hydrocarbons was accompHshed ia 1902 usiag a nickel catalyst (42). The fundamental research and process development on the catalytic reduction of carbon monoxide was carried out by Fischer, Tropsch, and Pichler (43). Whereas the chemistry of the Fischer-Tropsch synthesis is complex, generalized stoichiometric relationships are often used to represent the fundamental aspects ... 

Effects of Different Metal Salicylaldimine Chelates. Varying the central metal profoundly affected catalytic and inhibitory properties. There were only small quantitative variations, however, between N-phenyl- and V-butylsalicylaldimines having the same central metal atom. The only other salicylaldimines where catalyst-inhibitor conversion could be demonstrated were those of copper (II). With copper (II) both the catalytic and the inhibitory effects are much less pronounced than for cobalt (II). Surprisingly nickel (II) complexes behaved like conventional catalysts for hydrocarbon autoxidation—i.e., the rate is proportional to... 

At present, the most important industrial method for producing hydrogen is the three-step, steam-hydrocarbon re-forming process. The first step in the process is the conversion of steam and methane to a mixture of carbon monoxide and hydrogen known as synthesis gas (so-called because it can be used as the starting material for the synthesis of liquid fuels). The reaction requires high temperature, moderately high pressure, and a nickel catalyst ... 

Examples of first-order reversible reactions are gas phase cis-trans isomerization, isomerizations in various types of hydrocarbon systems, and the racemization of a and (3 glucoses. An example of a catalytic reaction is the ortho-para hydrogen conversion on a nickel catalyst. 

Steam reforming refers to the endothermic, catalytic conversion of light hydrocarbons (methane to gasoline) in the presence of steam [see Eq. (5.1)]. The reforming reaction takes place across a nickel catalyst that is packed in tubes in an externally-fired, tubular furnace (the Primary Reformer). The lined chamber reactor is called the secondary reformer , and this is where hot process air is added to introduce nitrogen into the process. Typical reaction conditions in the Primary Reformer are 700°C to 830°C and 15 to 40 bar46. 

In the field of hydrocarbon conversions, N. D. Zelinskii and his numerous co-workers have published much important information since 1911. Zelinskii s method for the selective dehydrogenation of cyclohexanes over platinum and palladium was first applied to analytical work (155,351,438,439), but in recent years attempts have been made to use it industrially for the manufacture of aromatics from the cyclohexanes contained in petroleum. In addition, nickel on alumina was used for this purpose by V. I. Komarewsky in 1924 (444) and subsequently by N. I. Shuikin (454,455,456). Hydrogen disproportionation of cyclohexenes over platinum or palladium discovered by N. D. Zelinskii (331,387) is a related field of research. Studies of hydrogen disproportionation are being continued, and their application is being extended to compounds such as alkenyl cyclohexanes. The dehydrocyclization of paraffins was reported by this institute (Kazanskil and Plate) simultaneously with B. L. Moldavskil and co-workers and with Karzhev (1937). The catalysts employed by this school have also been tested for the desulfurization of petroleum and shale oil fractions by hydrogenation under atmospheric pressure. Substantial sulfur removal was achieved by the use of platinum and nickel on alumina (392). 

In general, iron as a reducing catalyst requires a higher temperature than nickel. Reactions requiring temperatures of 200° to 230° C. with nickel catalysts do not occur at comparable rates over iron until a temperature of about 400° C. is reached. At 300° C. isopropyl alcohol tends to decompose into water and saturated hydrocarbons over nickel catalysts. A temperature of 570° C. is required for the same decomposition over iron. This tendency for nickel to decompose the alcohols into saturated hydrocarbons makes its use for the conversion of alcohols into aldehydes and ketones difficult from an industrial standpoint. 

The steam-carbon dioxide-hydrocarbon conversion is conducted over a catalyst such as nickel (oxide) on alumina. This type of catalyst can be purchased in quite similar composition from a number of catalyst vendors. In the case in which the feed stock is processed over a catalyst as in steam-hydrocarbon reforming, it is essential that the gas be purified, at least to some extent, prior to its passage over the reforming catalyst, particularly if the catalyst is of the typical composition of supported and promoted nickel (oxide). In steam hydrocarbon reforming, the methane (natural gas) is usually detoxified using an adsorbent such as carbon on which is impregnated suitable chemical adsorbents such as elemental iron or copper. There are at least two of these metallized carbon desulfurizers in parallel with one on... 

Figure 11.19 shows the process flow sheet for a pilot-scale fluidized bed gasifier, capable of processing some 20 kg/h of biomass feed, coupled with a thermal cracker and reformer reactor. The reformer is loaded with fluidizable nickel-based reforming catalyst and fitted with gas analysis ports at its inlet and outlet. The system has been used to evaluate catalyst activity and the decay of hydrocarbon conversion with time from a slip stream sample of the raw fuel gas. In this way, it is possible to quantify the frequently reported phenomenon of commercial catalyst deactivation, sometimes quite rapid, from high activity of fresh samples to lower residual activity brought about by various factors, including the presence of poisons (sulphur, chlorine) and coke formation. 

While the first commercial installation of a unit employing the t5q)e of technology in use today was started up in Chevron s Richmond, California refinery in 1960, hydrocracking is one of the oldest hydrocarbon conversion processes. Its origin is the work done by Sabatier and Senderens, who in 1897 published the discovery that unsaturated hydrocarbons could be hydrogenated in the vapor phase over a nickel catalyst. In 1904, Ipatieff extended the range of feasible hydrogenation reactions by the introduction of... 

Flame-ionization gas chromatography detection can also be used for the analysis of carbon monoxide. This detector system is selective for hydrocarbons, and conversion of CO to methane in the sample is required. This is accomplished by reaction with hydrogen over a nickel catalyst at 360 °C ... 

Tubular Fixed-Bed Reactors. Bundles of downflow reactor tubes filled with catalyst and surrounded by heat-transfer media are tubular fixed-bed reactors. Such reactors are used most notably in steam reforming and phthaUc anhydride manufacture. Steam reforming is the reaction of light hydrocarbons, preferably natural gas or naphthas, with steam over a nickel-supported catalyst to form synthesis gas, which is primarily and CO with some CO2 and CH. Additional conversion to the primary products can be obtained by iron oxide-catalyzed water gas shift reactions, but these are carried out ia large-diameter, fixed-bed reactors rather than ia small-diameter tubes (65). The physical arrangement of a multitubular steam reformer ia a box-shaped furnace has been described (1). 

---