Liquid petroleum feedstock, removal

Spent caustic solutions from petroleum refining. Petrochemical refineries use caustics to remove acidic compounds such as mercaptans from liquid petroleum streams to reduce produced odor and corrosivity as well as to meet product sulfur specifications. Spent liquid treating caustics from petroleum refineries are excluded from the definition of solid waste if they are used as a feedstock in the manufacture of napthenic and cresylic acid products. U.S. EPA believes that spent caustic, when used in this manner, is a valuable commercial feedstock in the production of these particular products, and is therefore eligible for exclusion. 

Catalytic hydrodenitrogenation (HDN) and hydrodeoxygenation (HDO) are the processes of removing nitrogen and oxygen, respectively, from petroleum feedstocks to provide more processable and environmentally compatible liquid fuels. A review of heterogeneous HDN process and homogeneous models summarized the research till ca. 1997. ... 

The batch process consists of heating high-boiling petroleum feedstocks under pressure to approximately 430°C, usually for several days.I l This promotes the growth of mesophase-liquid polycylic crystals. The material is then calcined up to 1200°C, to remove almost all the residual hydrogen, and finally ground and sized. 

Higher molecular weight hydrocarbons present in natural gases are important fuels as well as chemical feedstocks and are normally recovered as natural gas liquids. For example, ethane may be separated for use as a feedstock for steam cracking for the production of ethylene. Propane and butane are recovered from natural gas and sold as liquefied petroleum gas (LPG). Before natural gas is used it must be processed or treated to remove the impurities and to recover the heavier hydrocarbons (heavier than methane). The 1998 U.S. gas consumption was approximately 22.5 trillion ft. ... 

With all of the scenarios in place, there is no doubt that petroleum and its relatives residua, heavy oil, and extra heavy oil (bitumen) will be required to produce a considerable proportion of liquid fuels into the foreseeable future. Desulfurization processes will be necessary to remove sulfur in an environmentally acceptable manner to produce environmentally acceptable products. Refining strategies will focus on upgrading the heavy oils and residua and will emphasize the differences between the properties of the heavy crude feedstocks. This will dictate the choice of methods or combinations thereof for conversion of these materials to products (Schuetze and Hofmann, 1984). 

The changing pattern of the availability of conventional petroleum has focused the attention of refiners on heavy feedstocks and their economic use is a necessity (Dickenson et al., 1997). The move to process these less desirable feedstocks has led to legislation to control the amount of sulfur in the various grades of liquid fuels. This, in turn, has meant that processing facilities must be adjusted accordingly to effectively remove the sulfur from the feedstocks (or products) as an integral part of the processing sequence. Furthermore, the lack of use of residua can also create environmental problems due to disposal issues or result in the production of low-quality asphalt that has limited life span in service. 

The objective of this work was to study the activity of the Monolith catalyst for removing sulfur and nitrogen from a Synthoil process liquid (heavy stock) and Raw Anthracene Oil (light feedstock), and to make a preliminary assessment of the advantages and/or disadvantages of the Monolith catalyst over a commercial catalyst used in the petroleum industry. 

The liquid hydrocarbon by-product has a high cyclic content and so is useful as a petroleum refinery feedstock or as a source of aromatic organic chemicals. This material has a relatively high nitrogen content compared with the corresponding petroleum fraction. Its use as a refinery feedstock would require additional nitrogen removal processing by the refinery. 

Liquid membrane technology has been applied to a great extent for separation of mixtures of saturated and aromatic hydrocarbons. Investigations reveal that the LSM process offers potential for dearomatization of petroleum streams like naphtha and kerosene to meet product specifications for naphtha cracker feedstock and aviation kerosene, respectively [25, 63, 85, 144-146]. The separation is based on a simple permeation technique and occurs due to the difference in solubility and diffusivity of permeating species through the membrane. Kato and Kawasaki [70] conducted studies on the enhancement of hydrocarbon permeation by the use of a polar additive like sulfolane or triethyl glycol. Sharma et al. [147] enhanced the selectivity of the membrane by several orders with the addition of a carrier. Chakraborty et al. [85] used cyclodextrins to enhance the separation factor and removal efficiency of aromatic compound. 

Coal-conversion processes under development are directed towards producing either gaseous or liquid feedstocks which approximate in composition to petroleum-derived feedstocks. They can then be utilized directly in existing petrochemical plant and processes. To achieve this, however, two problems must be overcome, which are a consequence of the differing natures of coal and oil. Firstly, the H C ratios are different for coal and for petroleum-derived liquid feedstocks. Secondly, significant amounts of heteroatoms are present in coal, particularly sulphur which may reach levels as high as 3%. The sulphur has to be removed for two reasons (i) on combustion it will form the atmospheric pollutant SO2, and (ii) it is a potent catalyst poison, and most of the downstream petrochemical processes are catalytic. However, its removal from coal is difficult and it is therefore removed from the conversion products instead. 

On the industrial scene, the most prominent applications both in scale and number are seen in the petroleum industry. Liquid extraction is used here to separate petroleum fractions selectively and to purify or otherwise refine them. In the Edeleanu process, which is close to a century old, liquid sulfur dioxide is used to extract aromatics from various feedstocks. The removal of the ever-present sulfur compounds is accomplished by extraction with sodium hydroxide solutions. In addition, a wide range of organic solvents is used in the purification and refining of various lubricants. 

---