Catalytic cracking process for biofeeds (Exxonmobil)

CATEGORY: BIOMASS 
Catalytic cracking process for biofeeds (Exxonmobil)

Type	Patent
Inventor	John Scott Buchanan
Inventor	Halou Oumar-Mahamat
Inventor	Wayne Richard Kliewer
URL	Free Full Text: http://www.google.com/patents/US20140163285
Assignee	Exxonmobil Research And Engineering Company
Patent Number	US20140163285 A1
Issue Date	Jun 12, 2014
Abstract	A process of catalytically cracking a feedstock based on a biocomponent contacts the feedstock with a catalytic cracking catalyst comprising a basic metal oxide on a porous oxide support at an elevated cracking temperature to eliminate oxygen from the biocomponent to form cracked hydrocarbon residues. The basic metal oxide of the cracking catalyst is preferably a metal oxide of Group 2 of the Periodic Table (IUPAC) such as calcium or magnesium on a support comprised of a non-acidic form of alumina such as gibbsite or boehmite. Preferred feedstocks are those based on triglycerides, especially vegetable oils, animal fats and algae oils. BACKGROUND Petroleum derived fuels supply the majority of the world's energy and petroleum based products are used in a wide range of industrial applications; petrochemicals serve as raw materials for the chemical industry in the manufacture of numerous products. The enormous growth in consumption of crude petroleum during the middle and late twentieth century can be attributed to the ease with which petroleum can be discovered, produced, transported, processed, and utilized. The oil crisis in the 1970s, the depletion of reserves resulting from the growth in consumption, national security issues, price uncertainty, and growing environmental concern over the combustion of fossil fuels highlight major issues associated with the current levels of petroleum use. As a result, there has been renewed interest in the discovery of non-petroleum or “green” fuels, chemicals and sources of energy including wind power, solar power, hydrogen production, fuel cells, and biomass. Government regulations are expected to drive the use of increasing amounts of bio-derived liquid fuels. A significant proportion of renewable energy research is devoted to harnessing energy from biomass. Biomass is the only renewable energy source that yields solid, gaseous and liquid fuels and has been described as the renewable energy source with the highest potential to contribute to the energy needs of modern society. Biomass also has the significant environmental advantage of maintaining some level of carbon balance: even though biomass combustion releases carbon dioxide into the atmosphere, plants consume carbon dioxide in the process of photosynthesis thus tending to an improved carbon balance. Ethanol is one option as a gasoline component. Ethanol can be made efficiently from sugar cane in tropical climates but much less efficiently from corn and other crops in temperate zones. Vegetable oils (mainly triglycerides) can be produced effectively in warm climates (e.g. palm oil) or temperate zones (rapeseed, soy) but triglycerides must be converted by some means for use in vehicles. Transesterification is one option for making diesel fuel suitable for use in road vehicles, commonly referred to as biodiesel. Biodiesel (100%, referred to as B100) is a renewable fuel, defined officially by the National Biodiesel Board (USA) according to ASTM D 6751 as a fuel comprised of mono-alkyl esters of long chain fatty acids derived from vegetable oils or animal fats. It is typically produced by a reaction of a vegetable oil or animal fat with an alcohol such as methanol or ethanol in the presence of a catalyst to yield mono-alkyl esters and glycerin, which is removed as a by-product. Biodiesel can be blended with petroleum based diesel fuels for use in existing diesel engines usually with little or no modification to the engine or fuel systems and is thus distinct from the vegetable and waste oils used in diesel engines which have been suitably modified. Another potential biomass conversion process is hydrocracking; the process is proven technology but incurs considerable cost for operation, especially in extra hydrogen consumption. Yet another technique used to convert biomass into valuable liquid derivatives is pyrolysis. Pyrolysis is a severe form of thermal cracking with subsequent rearrangement of fragments. The resulting bio-oil can then be used as fuel or for the production of chemicals. Although triglyceride based vegetable oils or animal fats have the potential to be a suitable source of fuel or hydrocarbons under the right processing conditions, pyrolysis of triglyceride materials is not as well established as with other lignocellulosic biomass sources such as switchgrass, bagasse, etc. and it has been shown that these two types of bio-oils are entirely different in nature. Triglycerides such as those found in canola and other vegetable oils and animal fats are, however, promising feeds for catalytic cracking as they are essentially aliphatic hydrocarbons, apart from the three ester groups. The loss of the six oxygens from the ester groups as water will however leave the remaining hydrocarbon fragments deficient in hydrogen and thus prone to coking and other sorts of aromatization. Catalytic cracking of bio-derived liquids has previously been reported. U.S. Pat. No. 8,231,777 (Silva) describes a method of converting oils of vegetable origin to products in the diesel boiling range using conventional fresh or equilibrium FCC catalysts such as zeolites, e.g. ZSM-5, faujasite or mordenite, or with silica-aluminum phosphate (SAPO) or aluminum phosphate (ALPO) in a twin reactor unit with one reactor dedicated to use with the vegetable oil feed. The catalytic cracking of rapeseed oil using commercial FCC equilibrium catalyst (Ecat) and Ecat catalysts with deposited metal (nickel and platinum) is also described by Rao et al in Chem Sus Chem 2010, 3, 807-8101 with the conclusion that with such catalysts, a judicious choice of metal is vital for performance. The increase in aromatization is confirmed by Dupain et al in Applied Catalysis B: Environmental, vol. 72, Issues 1-2, 8 Mar. 2007, 44-612 which reported a high aromatization rate of rapeseed oil fatty acids causing the formation of large amounts of aromatics of up to 30-40 wt. % in the gasoline fraction with relatively high amounts of coke when cracking with a commercial equilibrium catalyst under FCC conditions. 1©2010 Wiley-VCH Verlag GmbH& Co. KGaA, Weinheim, available online at http://onlinelibrary.wiley.com/doi/10.1002/cssc.201000128/pdf2©Elsevier 2006, available online at http://www.sciencedirect.com/science/article/pii/S092633730600419X Idem et al., Fuel Processing Technology 51 (1997) 101-1253 described the catalytic conversion of canola oil over a suite of catalysts, including ZSM-5, silica, silica-alumina, gamma-alumina, calcium oxide and magnesium oxide. 3©Elsevier 1997, available online at http://www.sciencedirect.com/science/article/pii/S0378382096010855 Thus, while vegetable oils are amenable to catalytic cracking, the yields and product distributions are less than desired when using conventional catalysts such as the commercial FCC catalysts used in this earlier work. For this reason, catalytic cracking of biofeeds is not known to be practiced commercially anywhere.