The alkylation of benzene with olefins is a widely practiced process, especially for the production of alkylbenzenes. Alkylbenzenes having alkyl groups of 8 to 14 carbon atoms per alkyl group, for instance, are commonly sulfonated to make surfactants. The alkylation conditions comprise the presence of homogeneous or heterogeneous alkylation catalyst such as aluminum chloride, hydrogen fluoride, or zeolitic catalysts and elevated temperature.
The catalysts are not selective and other reactions of olefins can occur to produce heavies, i.e., dimers, dialkylaryl compounds and diaryl compounds. Also, skeletal isomerization of the olefin can occur, resulting in a loss of selectivity to the sought alkylbenzene. The formation of dialkylaryl compounds is particularly problematic as the reaction approaches complete conversion of the olefin and the concentration of the alkylbenzene has thus increased thereby increasing the likelihood that an olefin molecule will react with an alkylbenzene molecule rather than benzene. Accordingly, typical processes use a large excess of benzene to reduce the molar ratio of the sought alkylbenzene to the olefin in the reactor. For homogeneous hydrogen fluoride catalyzed processes, the benzene to olefin ratio is generally in the range of 6:1 to 8:1. Solid catalysts are prone to generate more heavies. Hence, for these solid catalysts the mole ratio of benzene to olefin is typically greater than 15:1, often in excess of 20:1 and sometimes as much as 30:1.
The refining system for alkylbenzene production is summarized in Peter R. Pujado, Linear Alkylbenzene (LAB) Manufacture, Handbook of Petroleum Refining Processes, edited by Robert A. Meyers, Second Edition, McGraw-Hill, New York, N.Y., USA, (1996), pp 1.53 to 1.66, especially pages 1.56 to 1.60. Especially for large-scale, commercial alkylation processes such as are used for the production of linear alkylbenzenes, capital and operating costs can be very important, and the reboiler heat required to recover benzene from the alkylbenzene is a significant portion of the energy required in the refining system. Thus, as the ratio of benzene to olefin increases, material additional process costs are also incurred in the recovery and recycling of the unreacted benzene in the alkylation product.
Although the use of hydrogen fluoride as the alkylation catalyst is being used in commercial processes at lower benzene to olefin ratios, the use and handling of hydrogen fluoride does provide operational concerns due to its toxicity, corrosiveness and waste disposal needs. Solid catalytic processes have been developed that obviate the need to use hydrogen fluoride. However, the high benzene to olefin ratios required to minimize heavies make with these solid catalysts have rendered them unattractive to retrofit a production unit using hydrogen fluoride catalyst. Moreover, reducing the benzene to olefin ratio without increasing the amount of heavies produced would render solid acid catalyst processes more attractive for new facilities as compared to the hydrogen fluoride processes. Accordingly, solid catalytic processes are sought to further enhance their attractiveness through reducing energy costs and improving selectivity of conversion while still providing an alkylbenzene of a quality acceptable for downstream use such as sulfonation to make surfactants.
U.S. Pat. No. 3,641,177 discloses the use of steam stabilized hydrogen Y and rare earth-hydrogen Y zeolites containing less than 1% Na for catalyzing the alkylation of benzene with olefins.
U.S. Pat. No. 4,876,408 discloses the use of and ammonium exchanged, steam stabilized zeolite Y for selective monoalkylation of aromatics with olefins, especially ethylene and propylene.
U.S. Pat. No. 4,570,027 discloses the use of low crystallinity, partially collapsed zeolite for producing alkyl aromatic hydrocarbons. The preferred zeolite is zeolite Y. The patentees state that the process has a high degree of selectivity to the monoalkylated product.
U.S. Pat. No. 6,977,319B2 discloses processes for making alkylated aromatics using catalyst compositions comprising zeolite Y and mordenite zeolite having a controlled macropore structure.
US Application Publication 2003/0147805A1 discloses processes for making nanocrystalline inorganic based zeolite such as zeolite Y. The zeolite Y is stated to be useful in a number of hydrocarbon conversion processes including the preparation of linear alkylbenzenes.
US Application Publication 2004/0162454A1 discloses hydrocarbon conversion processes using nanocrystalline zeolite Y.
US Application Publication 2005/0010072A1 discloses an alkylation process using at least two catalysts in at least two distinct reaction zones. A preferred process uses Y zeolite in one reaction zone and mordenite in the other zone.
US Application Publication 2006/0142624A1 discloses zeolite Y catalysts having controlled macropore structures for alkylation.
Gong, et al., in Catalytic Performance of Nanometer MCM-49 Zeolite for Alkylation Reaction of Benzene with 1-Dodecene, Chinese Journal of Catalysis, Vol. 25, No. 10, 809-813, October 2004, relate increased activity with high selectivity for 2- and 3-phenylalkanes using MCM-49 having a diameter of 300 to 500 nanometers and a thickness of 20 to 25 nanometers.