Biodiesel production

Biodiesel is usually produced at 60-70 °C and atmospheric pressure with homogeneous alkaline catalysts and methanol in excess. However, as the reaction is strongly limited by mass transport, a long residence time is required to achieve complete conversion. In order to reduce it from several hours to few seconds, working under supercritical conditions and/or in a MSR has been proposed among different alternatives since it allows reactants to be dissolved in a single phase [63]. 

SRM based on MSRs has acquired an increasing interest due to system compactness with portable apphcations for fuel cells, which could be apphed on auxiliary power imits (APUs). Moreover, catalytic autothermal reforming of methanol has also been considered since it offers some advantages over endothermic steam reforming and exothermic partial oxidation [67]. 

With respect to ethanol reforming, Lee et al. [69] developed an integrated micro-fixed bed reactor loaded with Co/ZnO catalyst combined with a catalytic (commercial Pt/Al203) burner and an evaporator, resulting in a 450 W power fuel cell. Moreover, simulation studies demonstrated that the production of hydrogen at high temperatures and space velocities in MSRs is limited at yields of the order of 70% [70,71], but a thermal output of 65 kW is feasible [72]. 

The steam reforming of hydrocarbons such as diesel has been demonstrated in MSRs whose mechanical stability has been proven at high temperature (750-850 °C). Most of the configurations consist of co-current flow diesel steam reforming combined with combustion of fuel cell anode and/or cathode off-gas surrogate. Full conversion was obtained in all cases. Power equivalent of these systems varied between 2-5 kW thermal energy of the hydrogen produced and 10 kW thermal input of the diesel feed [4,73]. However, the most advanced 

As mentioned earlier, process design as well as the rational development of advanced heterogeneous catalysts is required for significant BDF production [241, 

Polar solvents Electrolytes Surfactants Lubricating oils Membranes Monomer and so on 

Utilization of dialkyl carbonates such as a DMC and diethyl carbonate (DEC) allows operation under much milder conditions, with reduced steps and waste. Taking industrial feasibihty into account, the use of dialkyl carbonates as carbonate sources is reasonable, as the alcohol by-products are easily separated, enabhng simple purification of the desired GC. Urea also has been employed as an easy-to-use source. 

Fundamentally, these reactions are base catalyzed via proton elimination. First, the primary and secondary hydroxyl groups of glycerol gravitate toward the base sites, then the more reactive primary alcohol group electrophilically attacks the carbon of the carbonyl. When Lewis add sites coexist on the catalyst, it is able 

Reaction mechanism of transesterification of glyceroi with diaikyi carbonates 

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Experiments showed that high methyl ester yields can be achieved with solid bases and super acids under moderate reaction conditions. The solid bases were more effective catalysts than the solid super acids. High stability can be achieved by an ordinary inexpensive preparation process, and the catalyst can be separated easily from the reaction products in the heterogeneous catalysis process. The costly catalyst removal process can be avoided compared with the homogeneous process. Therefore, the heterogeneous process using a solid catalyst should be more economical for biodiesel production. 

Gerpen, Van J., Shanks, B., Praszko, R., Clements D. and Knothe, G., Biodiesel Production Technology. NREL/SR-510-36244 (2004). 

The production of biodiesel from low quality oils such as animal fats, greases, and tropical oils is challenging due to the presence of undesirable components especially FFA and water. A pre-treatment step is required when using such high fatty-acid feedstock. Generally, this esterification pre-treatment employs liquid sulfuric acid catalyst which must subsequently be neutralized and either disposed of or recycled. However, requirement of high temperature, high molar ratio of alcohol to FFA, separation of the catalyst, enviromnental and corrosion related problems make its use costly for biodiesel production. 

There is a real opportunity to reduce biodiesel production costs and environmental impact by applying modem catalyst technology, which will allow increased process flexibility to incorporate the use of low-cost high-FFA feedstock, and reduce water and energy requirement. Solid catalysts such as synthetic polymeric catalysts, zeolites and superacids like sulfated zirconia and niobic acid have the strong potential to replace liquid acids, eliminating separation, corrosion and environmental problems. Lotero et al. recently published a review that elaborates the importance of solid acids for biodiesel production. ... 

Apart from a few reports" on solid acid catalyzed esterification of model compounds, to our knowledge utilization of solid catalysts for biodiesel production from low quality real feedstocks have been explored only recently. 12-Tungstophosphoric acid (TPA) impregnated on hydrous zirconia was evaluated as a solid acid catalyst for biodiesel production from canola oil containing up to 20 wt % free fatty acids and was found to give ester yield of 90% at 200°C. Propylsulfonic acid-functionalized mesoporous silica catalyst for esterification of FFA in flotation beef tallow showed a superior initial catalytic activity (90% yield) relative to a... 

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). 

Figure 33.4. Flowsheet of biodiesel production by heat-integrated reactive distillation.

Table 33.2. Mass balance of the biodiesel production based on reactive-distillation.

Sulfur-free fuel, since solid acid catalysts do not leach into the biodiesel product. 

Zhang Y, Dube MA, Mclean DD, Kates M (2003) Biodiesel production from waste cooking oil 1 Process design and technological assessment. Biores Tech 89 1-16... 

Biodiesel production by immobilized lipase on zeolites and related materials... 

In this communication a study of the catalytic behavior of the immobilized Rhizomucor miehei lipase in the transesterification reaction to biodiesel production has been reported. The main drawbacks associated to the current biodiesel production by basic homogeneous catalysis could be overcome by using immobilized lipases. Immobilization by adsorption and entrapment have been used as methods to prepare the heterogeneous biocatalyst. Zeolites and related materials have been used as inorganic lipase supports. To promote the enzyme adsorption, the surface of the supports have been functionalized by synthesis procedures or by post-treatments. While, the enzyme entrapping procedure has been carried out by sol-gel method in order to obtain the biocatalyst protected by a mesoporous matrix and to reduce its leaching after several catalytic uses. 

Liquid biofuels in the form of ethanol and biodiesel products can be imported to a maximum of 30%, corresponding to a default case based on solely domestic biofuel supply. 

As for biodiesel, more than 90% of global production comes from the EU. Germany alone accounts for about half of global biodiesel production (with about 1500 fuelling stations selling biodiesel). Biodiesel in the EU is mainly produced from rapeseed. 

D. Pimentel, T.W. Patzek, Ethanol production using com, switchgrass and wood Biodiesel production using soybean and sunflower, Nat. Resources Res. March 2005. 

Modifications in the production of biodiesel can result in valuable glycerol as a byproduct and in fewer separation steps. The modifications studied or considered include combining etherification of glycerol into the biodiesel production process, etherification in situ within the biodiesel process and a biodiesel process with heterogeneous catalyst. 

Glycerol as a by-product from biodiesel production can be considered as a green chemical feedstock for subsequent catalytic transformation. In contrast to traditional petrochemical feedstocks, the present one is highly functionalized, its transformation requiring selective defunctionalization. 

In conclusion, the economically competitive, non-subsidized production of liquid biofuels requires (a) the use cheaper and more reliable sources of renewable raw material (b) efficient conversion, with minimum waste, of cellulosic, fiber or wood-based, waste biomass into fermentable sugars (c) significantly improved efficiency of the production processes and (d) use by-products (e.g., glycerol in biodiesel production). Several of these aspects are discussed in details in various chapters. 

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