Solid acid catalyst process

The reaction occurs in the liquid phase at relatively low temperatures (about 50°C) in the presence of a solid acid catalyst. Few side reactions occur such as the hydration of isohutene to tertiary hutyl alcohol, and methanol dehydration and formation of dimethyl ether and water. However, only small amounts of these compounds are produced. Figure 5-8 is a simplified flow diagram of the BP Etherol process. 

During the last decade many industrial processes shifted towards using solid acid catalysts (6). In contrast to liquid acids that possess well-defined acid properties, solid acids contain a variety of acid sites (7). Sohd acids are easily separated from the biodiesel product they need less equipment maintenance and form no polluting by-products. Therefore, to solve the problems associated with liquid catalysts, we propose their replacement with solid acids and develop a sustainable esterification process based on catalytic reactive distillation (8). The alternative of using solid acid catalysts in a reactive distillation process reduces the energy consumption and manufacturing pollution (i.e., less separation steps, no waste/salt streams). 

In summary, the Avada process is an excellent example of process intensification to achieve higher energy efficiency and reduction of waste streams due to the use of a solid acid catalyst. The successful application of supported HP As for the production of ethyl acetate paves the way for future applications of supported HP As in new green processes for the production of other chemicals, fuels and lubricants. Our results also show that application of characterization techniques enables a better understanding of the effects of process parameters on reactivity and the eventual rational design of more active catalysts. 

Traditionally, the production of LABs has been practiced commercially using either Lewis acid catalysts, or liquid hydrofluoric acid (HF).2 The HF catalysis typically gives 2-phenylalkane selectivities of only 17-18%. More recently, UOP/CEPSA have announced the DetalR process for LAB production that is reported to employ a solid acid catalyst.3 Within the same time frame, a number of papers and patents have been published describing LAB synthesis using a range of solid acid (sterically constrained) catalysts, including acidic clays,4 sulfated oxides,5 plus a variety of acidic zeolite structures.6"9 Many of these solid acids provide improved 2-phenylalkane selectivities. 

HETACAT An alkylation process using a solid acid catalyst. Not commercialized as of 1997. 

This contribution is an in-depth review of chemical and technological aspects of the alkylation of isobutane with lightalkenes, focused on the mechanisms operative with both liquid and solid acid catalysts. The differences in importance of the individual mechanistic steps are discussed in terms of the physical-chemical properties of specific catalysts. The impact of important process parameters on alkylation performance is deduced from the mechanism. The established industrial processes based on the application of liquid acids and recent process developments involving solid acid catalysts are described briefly. 2004 Elsevier Inc. 

The technology and chemistry of isoalkane-alkene alkylation have been thoroughly reviewed for both liquid and solid acid catalysts (15) and for solid acid catalysts alone (16). The intention of this review is to provide an up-to-date overview of the alkylation reaction with both liquid and solid acids as catalysts. The focus is on the similarities and differences between the liquid acid catalysts on one hand and solid acid catalysts, especially zeolites, on the other. Thus, the reaction mechanism, the physical properties of the individual catalysts, and their consequences for successful operation are reviewed. The final section is an overview of existing processes and new process developments utilizing solid acids. 

This section is a review of alkylation process technology. The processes in which liquid acids are used are all mature technologies and described briefly here. Information about process developments with solid acid catalysts is also presented. 

Haldor Topspe s fixed-bed alkylation (FBA ) technology is a compromise between liquid and solid acid-based processes. It applies a supported liquid-phase catalyst in which liquid triflic (trifluoromethanesulfonic) acid is supported on a porous material (206,241). The acid in the bed is concentrated in a well-defined catalyst zone, in which all the alkylation chemistry takes place at the upstream... 

Liquid acid-catalyzed processes are mature technologies, which are not expected to undergo dramatic changes in the near future. Solid acid-catalyzed alkylation now has been developed to a point where the technology can compete with the existing processes. Catalyst regeneration by hydrogen treatment is the method of choice in all the process developments. Some of the process developments eliminate most if not all the drawbacks of the liquid acid processes. The verdict about whether solid acid-catalyzed processes will be applied in the near future will be determined primarily by economic issues. 

The modem gasolines are produced by blending products from cmde oil distillation, that is, fluid catalytic cracking, hydrocraking, reforming, coking, polymerization, isomerization, and alkylation.Two clear examples of the possible use of solid-acid catalysts in refining processes are the isomerization of lineal alkanes and the alkylation of isobutene with butanes. In both these cases, and due to the octane... 

In addition to this, solid acid catalysts can also be used in the hydroisomerization cracking of heavy paraffins, or as co-catalysts in Fischer-Tropsch processes. In the first case, it could also be possible to transform inexpensive refinery cuts with a low octane number (heavy paraffins, n-Cg 20) to fuel-grade gasoline (C4-C7) using bifunctional metal/acid catalysts. In the last case, by combining zeolites with platinum-promoted tungstate modified zirconia, hybrid catalysts provide a promising way to obtain clean synthetic liquid fuels from coal or natural gas. 

Moreover, the catalyst deactivation must also be considered in order to use these solid materials in industrial processes. Figure 13.8 shows the variation of catal54ic activity (2-butene conversion) with the time on stream obtained under the same reaction conditions on different solid-acid catalysts. It can be seen how all the solid-acids catalysts studied generally suffer a relatively rapid catalyst deactivation, although both beta zeolite and nafion-sihca presented the lower catalyst decays. Since the regeneration of beta zeolite is more easy than of nafion, beta zeolite was considered to be an interesting alternative. ... 

Zeolite catalysts play a vital role in modern industrial catalysis. The varied acidity and microporosity properties of this class of inorganic oxides allow them to be applied to a wide variety of commercially important industrial processes. The acid sites of zeolites and other acidic molecular sieves are easier to manipulate than those of other solid acid catalysts by controlling material properties, such as the framework Si/Al ratio or level of cation exchange. The uniform pore size of the crystalline framework provides a consistent environment that improves the selectivity of the acid-catalyzed transformations that form C-C bonds. The zeoHte structure can also inhibit the formation of heavy coke molecules (such as medium-pore MFl in the Cyclar process or MTG process) or the desorption of undesired large by-products (such as small-pore SAPO-34 in MTO). While faujasite, morden-ite, beta and MFl remain the most widely used zeolite structures for industrial applications, the past decade has seen new structures, such as SAPO-34 and MWW, provide improved performance in specific applications. It is clear that the continued search for more active, selective and stable catalysts for industrially important chemical reactions will include the synthesis and application of new zeolite materials. 

Measurement of the thermokinetic parameter can be used to provide a more detailed characterization of the acid properties of solid acid catalysts, for example, differentiate reversible and irreversible adsorption processes. For example, Auroux et al. [162] used volumetric, calorimetric, and thermokinetic data of ammonia adsorption to obtain a better definition of the acidity of decationated and boron-modified ZSM5 zeolites (Figure 13.7). 

The benefits of using biodiesel as renewable fuel and the difficulties associated with its manufacturing are outlined. The synthesis via fatty acid esterification using solid acid catalysts is investigated. The major challenge is finding a suitable catalyst that is active, selective, water-tolerant and stable under the process conditions. The most promising candidates are sulfated metal oxides that can be used to develop a sustainable esterification process based on continuous catalytic reactive distillation. 

Technologically, the Alkylene process is a break-through. Several significant inventions were required to make it technically feasible. The development of a unique solid-acid catalyst and transport reactor by UOP allows for the potential elimination of hazardous liquid acid processes. About 1 MM gallons of hydrofluoric acid inventory could be eliminated, transport of 33 MM lbs (4 MM gallons) of hydrofluoric acid per year would be stopped, and ca. 20 MM lbs per year of other fluoride containing solids would not have to be land filled. 

In the long run solid catalysts are expected to be used, which would reduce the safety problems of liquid-phase alkylations. However, much further work is needed to develop such processes,7 and their introduction will be costly. The startup of a pilot plant to demonstrate a solid acid catalyst alkylation technology jointly developed by Catalytica, Conoco, and Neste Oy has been announced.307... 

A more recent development in ethylbenzene technology is the Mobil-Badger process,161,314-316 which employs a solid acid catalyst in the heterogeneous vapor-phase reaction (400-45O C, 15-30 atm). A modified H-ZSM-5 catalyst that is regenerable greatly eliminates the common problems associated with... 

Concentrated sulfuric acid and hydrogen fluoride are still mainly used in commercial isoalkane-alkene alkylation processes.353 Because of the difficulties associated with these liquid acid catalysts (see Section 5.1.1), considerable research efforts are still devoted to find suitable solid acid catalysts for replacement.354-356 Various large-pore zeolites, mainly X and Y, and more recently zeolite Beta were studied in this reaction. Considering the reaction scheme [(Eqs (5.3)—(5.5) and Scheme 5.1)] it is obvious that the large-pore zeolitic structure is a prerequisite, since many of the reaction steps involve bimolecular bulky intermediates. In addition, the fast and easy desorption of highly branched bulky products, such as trimethylpentanes, also requires sufficient and adequate pore size. Experiments showed that even with large-pore zeolite Y, alkylation is severely diffusion limited under liquid-phase conditions.357... 

Solid Acid Catalysts. There have been commercial alkylation processes in operation that apply solid acids (viz., zeolites) in the manufacture of ethylbenzene... 

A solid acid catalyst introduced in 1985 is used in UOP s Hexall process to selectively dimerize propylene at high conversion.24 The Colefin content of the product can reach higher than 90% with an octane number of 95-96. 

A porous clay heterostructure was prepared by an intragallery templating process using synthetic saponite as the layered host. The SAP-PCH exhibits a basal spacing of 32.9 A, a surface area of 850m2/g, and a pore volume of 0.46 cm3/g. The material was successfully employed as solid acid catalyst in the Friedel-Crafts alkylation of bulky 2, 4-di-tert-butylphenol (DBP) (molecular size (A) 9.5x6.1x4.4) with cinnamyl alcohol to produce 6,8-di-tert-butyl-2, 3-dihydro[4H] benzopyran (flavan) (molecular size (A) 13.5x7.9x 4.9). A much higher yield of flavan (15.3%) was obtained over PCH as compared with H+-Saponite (1.2%). It is also confirmed by this reaction that mesoporosity was formed in the PCH. 

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