Physico-chemical Conversion

Pure vegetable oil can be used in some existing engines either for mobile (e.g. in cars) or stationary application (i.e. in CHP-systems), but in most cases it lowers engine lifetime and increases maintenance requirements. Therefore only under very specific frame conditions could the use of crude vegetable oils be a promising option for the transportation sector or to provide power (or decentralized electrification and heat, if required) especially in rural areas. This is true for developing as well as for industrialized countries. 

FAME can be used directly as a substitute for diesel fuel in conventional compression ignition engines (see Chapter 8) or in CHP-systems with installed capacities from some tens of kW up to several MW (Table 7.5). The prerequisite for this is that the produced FAME fulfils the existing standards. Normally this is easily possible with FAME based on rape oil but it might become difficult using other types of vegetable oil (like crude palm oil). 

Besides the use of vegetable oil for the production of FAME also waste cooking oil (waste grease) can be used under certain conditions. Due to limited availability of waste grease this option is not playing a significant role in the market so far. 

Available experiences with FAME based on rape oil (RME) have shown that there are no significant problems when using them in conventional diesel engines although the higher solvency of RME compared to conventional diesel fuel requires biodiesel compatible fuel lines. 

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Biomass Sources Biomass Production and Supply Thermo-Chemical Conversion Physico-Chemical Conversion Blo-Chemical Conversion Outlook... 

Physico-chemical conversion This may be used to produce liquid fuel by physical (e.g., pressing) or chemical (e.g., esterification) means. The only important process with a certain market potential so far is vegetable oil production from oil seed and esterification of this vegetable oil to fatty acid methyl ester as a substitute for diesel fuel. This technology is used to some extent in Europe. 

Transformation of parent contaminants into secondary products may occur during the processes of atmospheric diffusion and transport as a result of physical, chemicjd, and photochemical processes (22). Chemical conversion within the atmosphere may also change the physico-chemical characteristics of contaminants, dramatically altering their atmospheric residence times and fates from those of the parent contaminants. The complex reactions within the atmosphere that are driven by chemical processes such as hydroxyl scavenging... 

Most methods for the resolution of enantiomers contained in a reaction mixture consist in the conversion of the compounds into stable or transient diastereoisomers and separation of the latter on the basis of their different physico-chemical properties. 

Direct conversion of methane to ethane and ethylene (C2 hydrocarbons) has a large implication towards the utilization of natural gas in the gas-based petrochemical and liquid fuels industries [ 1 ]. CO2 OCM process provides an alternative route to produce useful chemicals and materials where the process utilizes CO2 as the feedstock in an environmentally-benefiting chemical process. Carbon dioxide rather than oxygen seems to be an alternative oxidant as methyl radicals are induced in the presence of oxygen. Basicity, reducibility, and ability of catalyst to form oxygen vacancies are some of the physico-chemical criteria that are essential in designing a suitable catalyst for the CO2 OCM process [2]. The synergism between catalyst reducibility and basicity was reported to play an important role in the activation of the carbon dioxide and methane reaction [2]. 

In this work, the MeOH kinetic model of Lee et al. [9] is adopted for the micro-channel fluid dynamics analysis. Pressure and concentration distributions are investigated and represented to provide the physico-chemical insight on the transport phenomena in the microscale flow chamber. The mass, momentum, and species equations were employed with kinetic equations that describe the chemical reaction characteristics to solve flow-field, methanol conversion rate, and species concentration variations along the micro-reformer channel. 

In the laboratory, electroanalysis is used for two main purposes, either for direct measurement of a physico-chemical property that is informative with respect to the identity and/or amount of the analyte, or for detecting the course of conversion of the analyte or indicating the separate appearance of analyte components, which is informative with respect to their identity and amount. In the former instance we are dealing with conductometry, voltammetry and coulometry and in the latter with various titrations and mostly separational flow techniques such as chromatography and flow injection analysis. 

Selectivity parameters can be used to compare the catalytic performance of the different catalysts, and to find relationships between catalysts performance and physico-chemical features. Specifically, the following parameters were chosen (a) the O/C-methylation ratio, that is the ratio between the selectivity to 3-MA and that to 2,3-DMP+2,5-DMP+3,4-DMP (b) the ortho/para-C-alkylation ratio, that is the ratio between the selectivity to 2,3-DMP+2,5-DMP and the selectivity to 3,4-DMP (c) the 2,5-DMP/2,3-DMP selectivity ratio. Table 2 compares these parameters for MgO, Mg/Al/O and Mg/Fe/O catalysts. Data were reported at 30% m-cresol conversion, thus under conditions of negligible consecutive reactions. In this way it is possible to compare the ratio of the sole parallel... 

The carbon templated tin incorporated mesoporous silicalite catalysts with MFI structure were successfully synthesized using microwave and well characterized using all the physico-chemical techniques. The catalytic activity of these catalysts was studied for liquid phase Baeyer-Villiger oxidation of various cyclic ketones using hydrogen peroxide. All the catalyst showed high conversion ( 100%) for bicyclic ketones with 100% selectivity to the corresponding lactone. 

The temperature reached by a monomer undergoing photopolymerization plays a key role on the reaction kinetics, in particular on the ultimate degree of conversion and therefore on the physico-chemical properties of the UV-cured polymer. It is strongly dependent on the formulation reactivity, the film thickness, as well as on the light intensity. 

The correct physico-chemical parameters to be used in simulations of the stirred cell reactor presents some difficulty since some parameters are susceptible to uncertainty. In particular, the influence of viscosity changes as conversion proceeds has a simultaneous effect upon the diffusion coefficients and the mixing intensity generated by the liquid phase stirrer. The simulations presented in Fig. 4(a) to 4(c) use the relationship... 

A component can undergo considerable physico-chemical speciation alterations in an estuary. With respect to dissolved constituents, the composition and concentration of available ligands changes. Depending upon the initial pH of the riverine water, OH may become markedly more important down the estuary. Similarly, chlorocomplexes for metals such as Cd, Hg and Zn become more prevalent as the salinity increases. Conversely, the competitive influence of seawater derived Ca and Mg for organic material decreases the relative importance of humic complexation for Mn and Zn. 

At this time, data relative to approximately 220 catalytic experiments for the considered reactions are taken into accoimt in the factual knowledge base. Most of them (60%) concern the alkylation of toluene with methanol to produce xylene, the reaction which is most studied according to the literature. Each experiment is characterized by different parameters stored in frame structures. Such a hierarchical representation allows an easy and rapid retrieval of the information stored in the knowledge base. Particularly, for each experiment corresponding to one particular reaction type, one considers an identification number, the catalyst used with its chemical and physico-chemical characterizations, the reaction conditions, and the results of the catalytic testing, i.e., reactant conversions (conversion), isomer selectivities (selectivity), and product and side product selectivities (productivity) (Fig. 2). 

Butanethiol addition decreases catalytic activity but not selectivity in 1,3-butadiene hydrogenation. Both activation energy and pre-exponential factor decrease with increasing S/Pd ratio. Sulfur adsorption not only reduces the number of active sites but also weakened the adsorption strength of the remaining sites. It has been demonstrated that physico-chemical information from AFM XPS combined with kinetic data enables prediction of conversion at other conditions based on the S/Pd ratio. 

The effect on activity of the presence of conq>lexing agent (AcAc) in SZ synthesis is shown in Fig. 4. The catalytic tests of Pt-SZl and Pt-SZ3 were performed at the same operative conditions. A strong increase of n-heptane conversion is observed for Pt-SZ3, obtained with AcAc. The physico-chemical characterisation presently performed on this material is not able to give reason to this improved catafytic performances. Further detailed work is going on, especialfy to study the surface properties of SZ3 (e.g. defectivity and acidity distribution). 

Aromatic hydrocarbons (benzene, toluene and p-xylene) also exert a cocatalytic effect on the conversion of aqueous methanol, which is limited to a narrow temperature range below that at which conversion is complete without the added aromatic. The effect 1s of a mechanistic rather than physico-chemical nature since ethylene with some C-label is obtained from unlabelled methanol in the presence of C-labelled benzene (ref. 17,18). 

Added benzene, toluene or p-xylene accelerates conversion of aqueous methanol at ca.300°. The effect is small, but has a mechanistic origin rather than a physico-chemical one, since, if -labelled benzene or toluene is used,... 

Recipes which resulted in better quality precipitates were tried for further investigation and the samples were subjeeted to various physico chemical tests viz surface area determination, porosity, pore size distribution and CO-Conversion activity following techniques described in earlier communications [12] from this Laboratory. Details of such studies are given in Table-II. In a particular series, obtained by direct precipitation techniques, pore size distribution in the 4-60 A was found to increase with R values. Basing on these studies some 50 kg batches were prepared in Pilot Plant following reverse technique. Quality eis obtained in Laboratory... 

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