With the information from the first stage was elaborated an experiment with three treatments and three repetitions, were used three bioreactors of 2000 liters each them. The treatments were integrated by three values of duration to acid pretreatment (3, 7 and 10 days) and three values of pH to operation of the bioprocess (4,5 — 5,0; 5,1 — 5,5 and 5,6 — 6,0). The materials used were wastes of different fruits and vegetal from Central Wholesaler of Antioquia. The wastes were

triturated and mixed with water in a relation of 1:2,5. In each test were taken samples of wastes and sludge to determinate the organic load, in addition was recorded daily the pH and the gas production. When the pretreatment of acidification ended, agricultural lime was added like at the first stage. The methodology employed to obtain the quantity of gas generated was the same of the first stage, was used a gas flow meter Metrex G2,5 with accurate of 0,040 m3/h and maximum pressure of 40 kPa. Samples of gas were collected in Tedlar bags and then were analyzed in a chromatographic gas (Perkin Elmer) to determinate its composition.

The organics load of wastes was obtained at the beginning and end of bioprocess; this included the total suspended solids (TSS), total solids (TS), volatile fatty acids (VFAs), chemical oxygen demand (COD) and biochemical oxygen demand (BOD). The analytic method employed was the Standard Method by water and residual water like the first stage. Was calculated the production of gas (liters/day), hydrogen percentage (% de H2) and yield of biohydrogen (liters of H2/day).

Laszlo Kotai, Janos Szepvolgyi, Maria Szilagyi, Li Zhibin, Chen Baiquan, Vinita Sharma and Pradeep K. Sharma

Additional information is available at the end of the chapter http://dx. doi. org/10.5772/52379

1. Introduction

Biobutanol (n-C4H9OH, available as fermentation product of various carbohydrate derivatives obtained from different resources of agricultural production such as crops and wastes) is one of the most promising biofuels in the near future. It can be produced by the so-called ABE (acetone-butanol-ethanol) type anaerobic fermentation discovered by Pasteur [1, 2] and industrialized by Weizmann [3]. Main problems associated with industrial production of biobutanol include high energy demand for processing of dilute ferment liquors and high volume of wastewater. A bioreactor with a volume of 100 m3 produces at 90% filling ratio 1053 kg of butanol, 526 kg of acetone and 175 kg of ethanol together with 2900 kg of carbon dioxide, 117 kg of hydrogen and 84150 kg of wastewater. Efforts to increase productivity and decrease production costs resulted in many new methods. This chapter summarizes some selected results on methods of biobutanol production.

2. History of industrial biobutanol production

During investigations aimed at discovering cheaper sources of acetone and butanol for chemical industry, Weizmann [3] isolated an organism which could ferment a fairly concen­trated corn mash with good yields of acetone and butanol. In 1915 the British Admirality took over the research and carried out large-scale tests in an improvised apparatus but without

providing proper conditions for laboratory testing. Thus the experiment failed due to lack of strict sterility throughout the system. Later on, British Acetones Ltd. undertook the initiation to duplicate laboratory bacteriological conditions on a commercial scale using corn meal. Butanol and acetone were produced from April 1916 to November 1919 in a total of 3458 runs of 24,000 gals of mash each. There was no run unfit for distillation [4]. By modifying the raw materials and technological conditions an explosion-like development of acetone-butanol fermentation technologies took place. Beesch [5] collected the available knowledge about industrial acetone-butanol fermentation process details, including usability of raw materials, problems of contaminations, infections, treatment of the by-products and recovering the end — products. During World War II the ABE fermentation became the most voluminous industrial biochemical process. However, the cheap petrochemical-based butanol production withdrawn it almost completely in the USA and Europe later on. In China, however, the ABE fermentation industry started only in the early 1950s in Shanghai and expanded rapidly thereafter. At its peak, there were about 30 plants all over the country and the total annual production of solvents reached 170,000 tons [6]. The success of the ABE industry in China had special features like development of continuous fermentation technologies such as in Russia, where the AB plants were the only full-scale industrial plants which used hydrolyzates of lignocellosic wastes for butanol fermentation and the process was finally run in a continual mode [7]. In China, the main strategic considerations were as follows: maintaining maximal growth and acid production phase, adoption of multiple stages in the solvent phase to allow gradual adaptation to increasing solvent, and incorporation of stillage to offer enough nutrients to delay cell degeneration. A biorefinery concept for the use of all byproducts has been elaborated and was partially put into practice. Due to the tremendous national demand for solvents, China has begun a new round of ABE fermentation research. It is expected that a new era in the ABE industry is on the horizon [6].

Stella Bezergianni

Additional information is available at the end of the chapter http://dx. doi. org/10.5772/52649

1. Introduction

The depletion of world petroleum reserves and the increased concern on climate change has stimulated the recent interest in biofuels. The most common biofuels are based on energy crops and their products, i. e. vegetable oil for Fatty Acid Methyl Esters (FAME) biodiesel [1] and sugars/starch for bioethanol. However these first generation biofuels and associated production technologies face several considerations related to their economic and social im­plications regarding energy crops cultivation, by-products disposal, necessity for large in­vestments to ensure competitiveness and the "food versus fuel" debate.

As a result, second generation biofuel technologies have been developed to overcome the limitations of first generation biofuels production [2]. The goal of second generation biofuel processes is to extend biofuel production capacity by incorporating residual biomass while increasing sustainability. This residual biomass consists of the non-food parts of food crops (such as stems, leaves and husks) as well as other non-food crops (such as switch grass, ja- tropha, miscanthus and cereals that bear little grain). Furthermore the residual biomass po­tential is further augmented by industrial and municipal organic waste such as skins and pulp from fruit pressing, waste cooking oil etc. One such technology is catalytic hydropro­cessing, which is an alternative conversion technology of liquid biomass to biofuels that is lately raising a lot of interest in both the academic and industrial world and is the proposed subject of this chapter.

Catalytic hydroprocessingis a key process in petrochemical industry for over a century ena­bling heteroatom (sulfur, nitrogen, oxygen, metals) removal, saturation of olefins and aro­matics, as well as isomerization and cracking [3]. Due to the numerous applications of catalytic hydroprocessing, there are several catalytic hydroprocessing units in a typical re­finery including distillate hydrotreaters and hydrocrackers (see Figure 1). As a result several

refinery streams are treated with hydrogen in order to improve final product quality includ­ing straight-run naphtha, diesel, gas-oils etc. The catalytic hydroprocessing technology is evolving through the new catalytic materials that are being developed. Even though hydro­processing catalysts development is well established [4], the growing demand of petroleum products and their specifications, which are continuously becoming stricter, have created new horizons in the catalyst development in order to convert heavier and lower quality feedstocks [5]. Furthermore the expansion of the technology to bio-based feedstocks has also broadened the R&D spam of catalytic hydrotreatment.

Catalytic hydroprocessing of liquid biomass is a technology that offers great flexibility to the continuously increasing demands of the biofuels market, as it can convert a wide variety of liquid biomass including raw vegetable oils, waste cooking oils, animal fats as well as al­gal oils into biofuels with high conversion yields. In general this catalytic process technolo­gy allows the conversion of triglycerides and lipids into paraffins and iso-paraffins within the naphtha, kerosene and diesel ranges. The products of this technology have improved characteristics as compared to both their fossil counterparts and the conventional biofuels including high heating value and cetane number, increased oxidation stability, negligible acidity and increased saturation level. Besides the application of this catalytic technology for the production of high quality paraffinic fuels, catalytic hydroprocessing is also an effective

technology for upgrading intermediate products of solid biomass conversion technologies such as pyrolysis oils and Fischer-Tropsch wax (Figure 2). The growing interest and invest­ments of the petrochemical, automotive and aviation industries to the biomass catalytic hy­droprocessing technology shows that this technology will play an important role in the biofuels field in the immediate future.

In the sections that follow, the basic technical characteristics of catalytic hydrotreatment are presented including a description of the process, reactions, operating parameters and feed­stock characteristics. Furthermore key applications of catalytic hydroprocessing of liquid bi­omass are outlined based on different feedstocks including raw vegetable oils, waste cooking oils, pyrolysis oils, Fischer-Tropsch wax and algal oil, and some successful demon­stration activities are also presented.

Catalytic transfer hydrogenation (CTH) is a process in which hydrogen is transferred from a hydrogen donor molecule to an acceptor [80]. CTH reactions can be of industrial importance as the renewable production, transportation and storage of hydrogen donors can be cheaper than those for molecular hydrogen. For CTH, it has been reported that adjacent sites may be necessary for donor and acceptor molecules [73]. Therefore, the first criterion to be fulfilled by the selected hydrogen donor molecules is to be soluble in the compound to be hydro­treated. Moreover, in order to improve the yield of desired products, reactions other than dehydrogenation of the donor should be minimized under the operating conditions. The best hydrogen donors for heterogeneous CTH include simple molecules like cyclohexene, hydrazine, formic acid and formates [81]. Alcohols like 2-propanol (2-PO) or methanol can also be used as hydrogen donors; primary alcohols are generally less active than the corre­sponding secondary alcohols due to the smaller electron-releasing inductive effect of one al­kyl group as against two [82]. The most active catalysts for heterogeneous transfer reduction are based on palladium metal. Other noble metals such as Pt and Rh are also widely utiliz­ed. Sometimes, other transition metals such as Ni and Cu have also been reported but for operation at higher temperature [73].

In this area, the most studied process has been the conversion of glycerol into 1,2-PDO. Mu- solino et al. [83] studied glycerol hydrogenolysis by transfer hydrogenation under 5 bar in­ert atmosphere, using ethanol and 2-PO as solvents and hydrogen donor molecules over 10PdFe2O3 catalyst at 453 K. They observed that complete glycerol conversion and high se — lectivities to 1,2-PDO could be obtained when the hydrogen came from the dehydrogenation of the solvent. Formic acid has also been used as a hydrogen donor molecule in the glycerol hydrogenolysis process using Ni-Cu/Al2O3 catalysts [84]. Under the operating conditions used, formic acid was readily converted into CO2 and H2, therefore, a semi-continuous set­up was used to continuously pump formic acid to the glycerol water solution, in order to ensure a constant supply of hydrogen at an appropriate rate [85]. For a constant metal con­tent of 35 wt-% (Ni+Cu), increasing Ni proportion caused an increase in glycerol conversion but also an increase in C-C bond cleavage reactions. Cu is known to be active in the C-O bond cleavage but not in the C-C bond cleavage. The presence of Cu and the creation of a

Ni-Cu alloy notably reduced formation of products <C3. This was related to the fact that C-C bond cleavage reactions are ensemble size sensitive and that the formation of a Cu-Ni alloy causes a decrease in the Ni ensemble size. Therefore, the presence of both metals is required for obtaining high 1,2-PDO yields: Ni to provide high hydrogenolysis activity and Cu to shift the selectivity towards C-O bond cleavage. It was also observed that above a certain metal content, further increments led to a decrease in glycerol conversion. This was correlat­ed to the total acidity of the catalyst that also decreased with increasing metal content. A di­rect glycerol hydrogenolysis mechanism was also proposed (Figure 15).

4. Conclusions

Bio-oils coming from the pyrolysis of biomass feedstocks and biomass based platform chem­icals present a common limiting feature: their high oxygen content. This oxygen can be re­moved by catalytic hydrotreating in the form of H2O. Intensive research is required in this field in order to develop catalytic systems active and stable under the hard operating condi­tions used: high temperatures and pressures, and high concentrations of sub-critical water. The required bifunctional catalysts must have Bronsted acidity to catalyze dehydration reac­tions or/and Lewis acid sites to attract the oxygen ion pair of the target molecule; but also metal sites that show the ability to activate hydrogen molecules. In this sense, the combina­tion of oxophilic metals (Re, Mo or W) with Ni or noble metals has shown to be a promising approach. In the case of bio-oil upgrading, the developed catalysts should promote hydro­deoxygenation reactions against hydrogenation reactions that lead to higher hydrogen con­sumption and reduction in the octane number of the oil. In order to avoid coke formation under the hard operating conditions used, neutral supports appear as an interesting option. In the case of catalysts for platform chemical valorization, C-C bond cleavage reactions should be avoided. Therefore, for some applications, like glycerol hydrogenolysis to 1,2- PDO, Cu based catalysts have to be considered due to the high selectivity of Cu for C-O bond cleavage reactions.

Hydrogenolysis processes for oxygen removal require the use of large amounts of hydro­gen, which is commonly supply by operating under high molecular hydrogen pressures. Nonetheless, this might be a problem because nowadays, most technologies to obtain hydro­gen are energy intensive and non-renewable. An interesting alternative might be to in-situ generate the required hydrogen. Among all the alternatives, the use of hydrogen donor mol­ecules that can be obtained from biomass in a renewable way, such as formic acid, appears as a promising approach.

Author details

Inaki Gandarias* and Pedro Luis Arias

*Address all correspondence to: inaki_gandarias@ehu. es

Department of Chemical and Environmental Engineering, University of the Basque Country (UPV/EHU) Alameda Urquijo s/n, Bilbao, Spain

The diesel engine, created by Rudolph Diesel in 1893 as an alternative to steam engines, has seen a marked rise in use over the past decades as newer engines coming to market have become such cleaner combustors. Since the engines are so efficient, they are ideal for use in heavy transport such as rail and ship, but as technology and advances in fuel make the en­gine emissions cleaner, more and more small engine vehicles are coming to market in light trucks and passenger cars in the US and Europe as well as the rest of the world.

Diesel engines have the ability to run on various sources of fuel. Originally the engine was tested using pure peanut oil and vegetable oil, though today, the engine is commonly run on fossil fuel based diesel fuel, a type of kerosene. To reduce the amount of petroleum based diesel being used in today’s market several alternative types of fuel have been introduced that are compatible with these engines. Among the alternatives, generally seen are the lipid based straight vegetable oils and the modified biodiesels. Straight vegetable oil will burn

without problem in diesel engines; however, preheating of the fuel is required in order to reduce viscosity to pumpable levels. Biodiesel fuels, which are generally from the same source of lipids as straight vegetable oils or algal oils, are a much better suited fuel because they match several of the same characteristics as modern diesel fuel, and thus, require little to no engine modifications or fuel pretreatment modifications.

1.4. Gas composition

The gas composition and its impurities can have an impact on the productivity of the gas fer­mentation process. Greater molar ratio of H2:CO allows greater efficiency in the conversion of the carbon from CO into products such as ethanol, because reducing equivalents are generat­ed from oxidation of H2 (rather than CO). However, CO is also a known inhibitor of hydroge — nase which can affect utilization of H2 during fermentation. In B. methylotrophicum, H2 utilization was inhibited until CO was exhausted [108]. When CO is consumed, acetogens are able to grow using CO2 and H2. Common impurities from biomass gasification or other waste gases are tar, ash, char, ethane, ethylene, acetylene, H2S, NH3 and NO [17, 22, 24, 188].These have been shown to cause cell dormancy, inhibition of hydrogen uptake, low cell growth and shift between acidogenesis and solventogenesis in acetogens [13, 188]. For instance, NH3 from the feed gas readily convert into NH4+ in the culture media and these ions were recently shown to inhibit hydrogenase and cell growth of acetogen "C. ragsdalei” [189]. A number of strategies to mitigate the impact of such impurities have been proposed, for example installing 0.025 mm filters, or the use of gas scrubbers or cyclones, and improvement in gasification efficiency and scavenging for contaminants in the gas stream using agents such as potassium permanganate, sodium hydroxide or sodium hypochlorite [24, 190—192]. H2S does not have a negative effect on acetogens such as C. Ijungdahliiup to 5.2% (v/v) [193].

The simplest recovering method is removal of ABE solvent during fermentation by using vacuum, because the relative volatility of ethanol, acetone or butanol is much higher than the volatility of water. The I. G.Farbenindustrie] [116] used this method periodically, and removed the butanol in vacuum before completion of the fermentation, fresh wort was added and the fermentation was continued. Dreyfus [117] removed the ABE solvents during fermentation by vaporization with the aid of cyclohexane forming an azeotropic mixture therewith and, passing an oxygen-free gas through the liquor. The cyclohexane may be added continuously or intermittently and may be carried as vapor by the gas stream. Removal of ABE solvents in vacuum-assisted in-situ pervaporation techniques at the temperature of fermentation is discussed in chapter 6.6.

The effectiveness of catalytic hydroprocessing was also explored for co-processing of lipid feedstocks with petroleum fractions as catalytic hydroprocessing units are available in al­most all refineries. The first co-processing study involved experiments of catalytic hydro­treating of sunflower oil mixtures with heavy petroleum fractions aiming to produce high quality diesel [55]. The experiments were conducted in a continuous fixed-bed reactor over a wide range of temperatures 300-450°C employing a typical NiMo/Al2O3 hydrotreating cata­lyst. The study was focused on the hydrogenation of double C-C bonds and the subsequent paraffin formation via the three different reactions routes: decarbonylation, decarboxylation and deoxygenation. Furthermore the large carbon-chain paraffins can also undergo isomeri­zation and cracking leading to the formation of smaller paraffins. This study concluded that the selectivity of products on decarboxylation and decarbonylation is increasing as the tem­perature and vegetable oil content in the feedstock increase [55].

In a similar study catalytic hydrocracking over sunflower oil and heavy vacuum gas oil mix­tures was investigated [56]. The experiments were conducted in a continuous-flow hydro­processing pilot-plant over a range of temperatures (350-390°) and pressures (70-140bar). Three different hydrocracking catalysts were compared under the same conditions and four different feedstocks were employed, incorporating for 10% and 30%v/v of lipid bio-based feedstock and considering non-pretreated and pretreated sunflower oil as a bio-based feed­stock. The results indicated that a prior mild hydrogenation step of sunflower oil is necessa­ry before hydrocracking. Furthermore, conversion was increased with increasing sunflower oil ratio in the feedstock and increasing temperature, while the later decreased diesel selec­tivity.

The effect of the process parameters and the vegetable oil content of the feedstocks on the yield, physical properties, chemical properties and application properties during co-hydro­treating of sunflower oil and gas-oil mixtures utilizing a typical NiMo/Al2O3hydrotreating catalyst was also studied [57]. The experimental results of this study indicated that catalytic co-hydrogenation of gas oil containing sunflower oil in different percentages allowed both vegetable oil conversion reactions (saturation, deoxygenation) and the gas oil quality im­provement reactions (hetero atom removal, aromatic reduction). The optimal operating con­ditions (360-380°C, P=80 bar, LHSV=1.0h-1, H2/oil=600 Nm3/m3and 15% sunflower oil content of feed) resulted in a final diesel product with favorable properties (e. g. less than 10 wppm sulfur, ~20% aromatics) but poor cold flow properties (CFPP=3°C). The study also indicated that for sunflower content in the feedstock higher than 15% reduced the desulfurization effi­ciency. Furthermore, the authors also concluded that the presence of sunflower oil in the feedstock has augmented the normal and iso-paraffins content of the final product and as a result has increased the cetane number but degraded the cold flow properties, indicating that an isomerization step is required as an additional step.

The issue of catalyst development suitable for co-hydrotreating and co-hydrocracking of gas-oil and vegetable oil mixtures was recently addressed [10], as there are no commercial hydroprocessing catalysts available for lipid feedstocks. New sulfided Ni-W/SiO2-Al2O3 and sulfided Ni-Mo/Al2O3 catalysts were tested for hydrocracking and hydrotreating of gas­
oil and vegetable oil mixtures respectively. The results indicated that the hydrocracking cat­alyst was more selective for the kerosene hydrocarbons (140-250°C), while the less acidic hydrotreating catalyst was more selective for the diesel hydrocarbons (250-380°C). The study additionally showed that the deoxygenation reactions are more favored over the hy­drotreating catalyst, while the decarboxylation and decarbonylation reactions are favored over the hydrocracking catalyst.

Most alcohols, especially the ones used as raw materials for the synthesis of ether oxygen­ates, have very high microwave absorptivity. Table 2 shows attained temperatures if 50 ml of typical alcohols at room temperature is heated for 1 min at microwave power of 560 W and frequency of 2.45 GHz [15]. The data indicate the benefits of using microwave irradia­tion, such as effective and efficient use of energy, to the synthesis of ether oxygenates. Reac­
tion relying on microwave can also be easily terminated by turning the supply of microwave irradiation off, thus further reaction or decomposition of the target compounds can be avoided resulting into higher selectivity. Also, reaction could reach completion in shorter time due to rapid heating, thus development of a compact process for a more efficient ener­gy utilization could be possible.

Using solid catalysts, instead of homogeneous ones, rapid heating on the surface of the cata­lysts likely occur upon microwave irradiation. Due this localized heating, the actual temper­ature at which reaction takes place may be higher than the measured bulk temperature as depicted in Figure 4, thus significantly increasing reaction rates compared to those with the conventional heating.

Tt E

bulk temperature, TB

catalyst surface

(where reaction takes place) surface temperature, Ts

Solid Catalysts

Figure 4. Phenomenon for microwave-assisted solid catalyzed reaction

Here are 4 biofuel sources, with some of their application in developmental stages, some ac­tually implemented:

1.1. Algae

Algae come from stagnant ponds in the natural world, and more recently in algae farms, which produce the plant for the specific purpose of creating biofuel. Advantage of algae focude on the followings: No CO2 back into the air, self-generating biomass, Algae can produce up to 300 times more oil per acre than conventional crops. Among other uses, algae have been used experimentally as a new form of green jet fuel designed for commercial travel. At the moment, the upfront costs of producing biofuel from algae on a mass scale are in process, but are not yet commercially viable (Figure 2)

1.2. Carbohydrate (sugars) rich biomaterial

It comes from the fermentation of starches derived from agricultural products like corn, sugar cane, wheat, beets, and other existing food crops, or from inedible cellulose from the same. Produced from existing crops, can be used in an existing gasoline engine, making it a logical transition from petroleum. It used in Auto industry, heating buildings ("flueless fireplaces") At present, the transportation costs required to transport grains from harvesting to process­ing, and then out to vendors results in a very small net gain in the sustainability stakes.