Benzene, as feedstock

Most maleic anhydride production in the United States is based on benzene as feedstock, even though substantial Hterature exists on the use of butenes (132—134). However, the rapidly increasing demand and price for benzene (as high as 620 /t in 1986 versus 310 /t for ethylene) have made benzene (qv) less attractive and butenes a better feedstock. Not only are theoretical yields better, 1.75 kg/kg of butenes compared to 1.26 kg/kg of ben2ene, but less oxygen is required and the oxidation produces less heat, which is critical in reactor design. 

Another pertinent example is provided by the manufacture of caprolactam [135]. Current processes are based on toluene or benzene as feedstock, which can be converted to cyclohexanone via cyclohexane or phenol. More recently, Asahi Chemical [136] developed a new process via ruthenium-catalysed selective hydrogenation to cyclohexene, followed by zeolite-catalysed hydration to cyclo-hexanol and dehydrogenation (Fig. 1.49). The cyclohexanone is then converted to caprolactam via ammoximation with NH3/H202 and zeolite-catalysed Beckmann rearrangement as developed by Sumitomo (see earlier). 

Ma.leic Anhydride. The largest chemical use for / -butane is as feedstock for maleic anhydride. A dilute air—butane mixture is passed over a vanadium—phosphoms catalyst 400—500°C to produce maleic anhydride [108-31-6] in good yield. Formerly benzene was used as feedstock, but in the last few years nearly all maleic anhydride in the United States, and an increasing proportion worldwide, is made from butane. 

Process Technology Evolution. Maleic anhydride was first commercially produced in the early 1930s by the vapor-phase oxidation of benzene [71-43-2]. The use of benzene as a feedstock for the production of maleic anhydride was dominant in the world market well into the 1980s. Several processes have been used for the production of maleic anhydride from benzene with the most common one from Scientific Design. Small amounts of maleic acid are produced as a by-product in production of phthaHc anhydride [85-44-9]. This can be converted to either maleic anhydride or fumaric acid. Benzene, although easily oxidized to maleic anhydride with high selectivity, is an inherently inefficient feedstock since two excess carbon atoms are present in the raw material. Various compounds have been evaluated as raw material substitutes for benzene in production of maleic anhydride. Fixed- and fluid-bed processes for production of maleic anhydride from the butenes present in mixed streams have been practiced commercially. None of these... 

The aromatic hydrocarbons are used mainly as solvents and as feedstock chemicals for chemical processes that produce other valuable chemicals. With regard to cyclical hydrocarbons, the aromatic hydrocarbons are the only compounds discussed. These compounds all have the six-carbon benzene ring as a base, but there are also three-, four-, five-, and seven-carbon rings. These materials will be considered as we examine their occurrence as hazardous materials. After the alkanes, the aromatics are the next most common chemicals shipped and used in commerce. The short-chain olefins (alkenes) such as ethylene and propylene may be shipped in larger quantities because of their use as monomers, but for sheer numbers of different compounds, the aromatics will surpass even the alkanes in number, although not in volume. 

The use of pyrolysis for the recycling of mixed plastics is discussed and it is shown that fluidised bed pyrolysis is particularly advantageous. It is demonstrated that 25 to 45% of product gas with a high heating value and 30 to 50% of an oil rich in aromatics can be recovered. The oil is found to be comparable with that of a mixture of light benzene and bituminous coal tar. Up to 60% of ethylene and propylene can be produced by using mixed polyolefins as feedstock. It is suggested that, under appropriate conditions, the pyrolysis process could be successful commercially. 23 refs. 

Typical applications at Polysar included the quantification of residual solvents and monomers in finished rubber products (e.g. styrene in SBR), quality control of feedstocks such as benzene or ethyl benzene as impurities in styrene monomer, and the analysis of samples collected from environmental monitoring programs. 

What are the two good reasons for choosing between butylene, butane, or benzene as the feedstock for MA ... 

The low cost of light alkanes and the fact that they are generally environmentally acceptable because of their low chemical reactivity have provided incentives to use them as feedstock for chemical production. A notable example of the successful use of alkane is the production of maleic anhydride by the selective oxidation of butane instead of benzene (7). However, except for this example, no other successful processes have been reported in recent years. A potential area for alkane utilization is the conversion to unsaturated hydrocarbons. Since the current chemical industry depends heavily on the use of unsaturated hydrocarbons as starting material, if alkanes can be dehydrogenated with high yields, they could become alternate feedstock. 

Petroleum and Petrochemical Processes. I he first large-scale application of extraction was ihe removal of aromatics From kerosene to improve its burning properties. Solvent extraction is also extensively used to meet ihe growing demand for the high purity aromatics such as benzene, toluene, and xylene (BTXl as feedstocks for the petrochemical industry. Additionally, Ihe separation of aromatics from aliphaties is one of the largesi applications of solvent extraclion. 

In the present paper Werther s two-phase model has been applied to the synthesis of maleic anhydride as an example of a complex reaction system. Based on experimental data found in the literature two process routes were investigated. For the synthesis of MA with benzene as a feedstock as well as for the synthesis with C -fractions of naphtha crackers as feedstocks the model is shown to be able to describe the behaviour of the fluid bed reactor. In particular the changes in hydrodynamics in the course of the reactor scale-up are considered in the present model. Thus the model allows to describe the behaviour of the fluidized bed reactor on different scales. The model may therefore be helpful in the development of industrial fluidized bed processes. 

Butane and butenes from refinery crackers and natural gas. Since 1985 butane was introduced to replace benzene as the feedstock. The first commercial production, based on benzene, started in 1930. 

Benzene, toluene, ethylbenzene, and xylenes (known as BTEX) are probably the most widely used aromatics, in abimdant use in automotive fuel, as solvents or as feedstock for more complex compounds. The American Occupational and Safety Administration (OSHA) permissible exposure limit for benzene, for example, is as low as 3.26 mg m (Ippm) due to its carcinogenic nature. This value should be compared with the 10-100 Xgm of BTEX typically foimd in urban outdoor environment (Saarela et al., 2003). The photocatalytic degradation of BTEX might emit a variety of intermediate products and by-products. For example, the photocatalytic degradation... 

Butane oxidation grew rapidly as the preferred process and is now dominant for maleic anhydride production for three reasons i) benzene is a valued petrochemical feedstocks whereas the cost of -butane is effectively that of a fuel a) the recognition of benzene as a carcinogen now requires the adoption of measures against its release in the workplace and in the environment and in) two of its carbon atoms are lost as carbon dioxide. 

As cited in Chapter 1, the first example of commercial process using an alkane as feedstock, in substitution of the older process starting from benzene, was the synthesis of maleic anhydride from n-butane. Figure 2.66 briefly recalls the reaction scheme on the model surface of the catalyst (vanadyl pyrophosphate) to evidence the... 

Synthetic sulphonates, in contrast, are derived from the sulphonation of feedstocks not derived directly from petroleum. The feedstocks commonly used to prepare this class of sulphonates have been polydodecyl benzene bottoms (byproducts of household detergent manufacture) or alkylated benzenes produced specifically as feedstocks for lubricant additive sulphonates. The following generalized reaction sequence. Reaction sequence (7.6), describes the formation of a synthetic alkylate and sulphonation with sulphur trioxide [19], to yield the synthetic sulphonic acid ... 

De Maio, D. A Wffl butane redact benzene as a feedstock for makic anhydride " Chem. Engng, 87 (10) 104-106(1980). 

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