By-products hydrogen

In the early 1990s, processes were developed for the production of 1,4-butanediol and y-butyrolactone by gas-phase catalytic hydrogenation of maleic anhydride (131—134). Succinic anhydride is obtained as a partial hydrogenation by-product in these processes. It can be recycled to complete the hydrogenation to the desired products, or be separated and purified. This process could in the future become a significant commercial route for succinic anhydride. 

Despite the limited solubility of 1-octene in the ionic catalyst phase, a remarkable activity of the platinum catalyst was achieved [turnover frequency (TOP) = 126 h ]. However, the system has to be carefully optimized to avoid significant formation of hydrogenated by-product. Detailed studies to identify the best reaction conditions revealed that, in the chlorostannate ionic liquid [BMIM]Cl/SnCl2 [X(SnCl2) = 0.55],... 

LBST (Ludwig-Bolkow-Systemtechnik GmbH) (1998). Identification of Hydrogen By-product Sources in the European Union, ed. Zittel, W. and Niebauer, P. (LBST), study funded by the European Commission under Contract No. 5076-92 11 EO ISP D Amendment No. 1. 

A critical factor here is the reactivity of the hydrogen by-product that is not only able to gasify the initial surface termination of the carbon fiber but also to etch away the newly formed pyrolytic carbon. This effect is desirable for optimization of the growing structure but additionally slows down the reaction. 

A feature common to both ir complex mechanisms is the nature of the second reagent in the exchange reaction [Eqs. (11), (12a), (12b)], namely heavy water or deuterium gas. Water is generally preferred in exchange reactions as it does not produce hydrogenated by-products. The important aspect concerning water and deuterium gas is the rapid exchange between these compounds on transition metal catalysts, which has been explained by dissociative chemisorption. 

This table estimates the carbon dioxide emissions from propane dehydrogenation at about 0.9 t/t of propylene. This should be compared to the value for naphtha which is less than 0.4 t/t. This results from the lower thermodynamic efficiency of the process. However, again emission costs could be lowered by distributing some of the emissions to the hydrogen by-product. 

There are few reports on the use of rhodium for methanol homologation, although this metal is best suited for the related methanol carbonylation. The extreme selectivity of rhodium for carbonylation is noteworthy and even when a 1 1 H]/CO mixture Ls applied, selective formation of acetic acid occurs and virtually no hydrogenated by products, such as ethanol or acetaldehyde, arc detected [68],... 

The formation of hydrogenation by-products such as alcohols and hydrocarbons is favored at low p(CO). Extensive hydrogenation was often the aim of special cobalt process variants, in order to produce alcohols in one step - for instance, butanols. Especially for short-chain olefins, this technique has been replaced by two-step processes rhodium 0x0 synthesis along with a separate hydrogenation step. 

The observations that these reactions are inhibited by nitrobenzene (a free radical inhibitor), no hydrogenated by-products are formed and that CF BrCl gives only a-CFjCl carbonyl compounds, led the authors to propose a radical chain mechanism for these reactions (Scheme 1). The chain initiation step is the formation of XFiC radical and enamine radical cation by electron transfer from the enamine to BrCFjX. The addition of this perhaloalkyl radical to the enamine generates a RjNC R R" type radical which is known to have an unusually low oxidation potential with 1/2 in the range of — 1 V (sce). An electron transfer from this radical to another molecule of perhaloalkane then takes place to form the iminium salt and another perhaloalkyl radical which continues the chain. A similar mechanism operates in the case of Rp. ... 

Electrolysis of salt also provides the major method of producing sodium hydroxide. The hydrogen by-product may be reacted with the chlorine to make... 

Hydrogen by-product from the chlorine-caustic industry... 

The main reaction is the transformation of toluene to benzene in the presence of hydrogen. By-products are diphenyl, naphtalene and other heavy hydrocarbons. 

While the basic electrolytic reaction in all three processes is the same, the methods for collecting chlorine generated at the anode are different. Each process represents a variation on keeping the chlorine produced at the anode separated from the caustic soda and hydrogen by-products. In all three processes, nearly saturated purified brine is introduced into the electrolytic cell at the beginning. 

Sewage sludge Hydrogenation ) By-product chemicals Oxygenated liquids... 

Compact high-pressure water electrolyscrs have been utilized to produce oxygen on board nuclear-powered submarines as part of the life-support system the hydrogen by-product, while flammable, is non-toxic and easily handled. Moreover, water and electrical power are the only utilities required. Since 1966, over I million running hours have been accumulated in service by such high-pressure electrolysers (Fig. 5.6(a)). 

The relatively pure hydrogen by-product is used either as a chemical feedstock or as fuel gas in the furnace. The generation rate of hydrogen is in the range of 0.19 to 0.231b H2/lb HCN. 

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