This paper has been written to review journal articles consisting of findings from different case studies. The field of thermodynamic has become an interesting thing because it has been identified as the best approach and method that can be used to evaluate the relationship between vapors and liquids under controlled conditions. Production of hydrogen is achieved when reforming of ethanol and glycerol is carried out (Rade et al, 2012). This is further achieved when catalysts are used.
The LVCM was carried out using the mixing rule that was extended to include the multiple parameter oriented equations. The Scientists did this by combining zero-pressure and infinite pressure mixing models. They coupled the flow by use of patel-Teja equation which is used to analyze the vapor-liquid state equillibria (Xiao-hong et al, 2005). The equations that were used are quite often used to analyze equilibrium of both non polar and polar systems that includes NRTL coefficient model as a method of analyzing excess Gibbs free energy. While using these methodological approaches, they identified that the results they obtained were in agreement with the present or existing experimental information but which can only be interpreted within the wider range of pressures and temperatures. Compared to the normal Vander Waal chemical mixing rule, they were able to determine that the new methods they outlined gave a better correlation between vapor and liquid of both polar and non polar chemical dynamic systems (Xiao-hong et al, 2005).
It is realized that the new methods they employed were better and more precise in evaluating the relationship between the vapor and liquid dynamics (Xiao-hong et al, 2005). They have better analyzed the relationships within the vapor and liquid dynamic frameworks unlike the Vander Waal forces rule which only outlines how weak or stronger the molecules could be (Rade et al, 2012). However, their analysis did lack the aspect of how the gases and liquids behaved when they were exposed to extreme temperature conditions such as the tundra regions where there are variations in chemical binding of molecules (Xiao-hong et al, 2005). Le chartelier principle is also a crucial factor that was not considered in analyzing chemical dynamics that exist between the liquid and vapor. It states that, momentum of electrons within the nucleus of gas and liquid molecules can not be determined at the same time. They failed to consider this factor and therefore the results they obtained may be different from the theoretical available data (Xiao-hong et al, 2005).
Phase relationships between the liquid and vapor is one of the difficult aspects and scientific entity that has been stimulated over time due to the development of improved steam engines (Rade et al, 2012). While several principles have been outlined and formulated to explain thermodynamic aspects of steam conversions, there are still several laws that have developed to define and explain how thermal energy is converted to mechanical energy. The combustion utilizes the abundant available oxygen molecules (Wu, 2004). However, the difficult part of it is that, it is difficult to determine and calculate energy balances that do occur between the vapor and liquid phases (Hakim et al, 2013). Therefore, the research done by Wu outlines that it is also difficult, to determine phase interchanges that occurs between the vapor and chemical phases (Wu, 2004). His study was carried out while considering the fact that precise results could be obtained when nanostructures materials were used in the study in an environmentally controlled environment, and when specific conditions within which protein crystallizations occurred are thermodynamically specified (Wu, 2004).
The researcher also outlined that a combination of statistical and molecular analyzes could generate accurate results (Hakim et al, 2013). The researcher did not consider the effect of the current global warming on thermodynamic properties and behavior of materials. This is because, thermodynamic properties of liquids and gases depend much upon the initial temperature of molecules and atomic energy. However, the past consideration of statistical input was not empirical in analyzing orientations of molecules (Wu, 2004). This means a combination of molecular and statistical approach that the researcher used was to be recommended as a precise method of determining characteristics of vapor-liquid relationships (Wu, 2004).
A group of scholars identified that there is enormous irreversibility that do occur in several biomass gasification processes, and they evaluated and concluded that gasifiers were the least units when efficiency of gas systems is considered. These systems are least efficient especially when they are used to produce biofuels, gas energy, and electricity. They looked at how they gasification occurred within different ranges of temperature when preheated product gas reliable and sensible heat was used (Rade et al, 2012). They carried out these analyzes and inquisitive study using an ash-free biomass oriented feed at the conditions of 10 bar pressure and CH1.4O0.59N0.0017 at 1. They were able to undertake this task by use of a validated model and a typical heat exchanger model. They outlined that the changes that occurred were reflecting the changes that occur during gasification process CH1.4O0.59N0.0017 at 1. The model they used was effective but it lacks the authenticity of research because, there are fluctuations that do occur when gasification process is under taken by use of low quality products. However, their model was empirical because it considered balancing of the gas states.
During study by Hakim and other scientists, hydroxyapatite catalysts were used for synthesis and they were tested to analyze their potential to be used in the reformation of glycerol to achieve a viable production of hydrogen. This was achieved when the reformation was done in the presence of steam. These catalytic products were prepared using the precipitation-deposition method using the nickel, copper loadings, and use of cerium. Performance of these catalysts was tested and evaluated at a temperature of 600 oC and the key factor was the amount of hydrogen yield. The whole process was carried out in a fixed-bed micro reactor that had a form of a tube. It was certain and empirical or of scientific significance because the catalysts were modeled and characterized by use of XRD, TPR, BETA surface area, and Tem techniques. It was timed that the reaction was to take place for a period of 240 minutes at an approximate temperature of 600°C. The water to glycerol was fed into the micro-reactor at a molar ratio of 8:1 molarities. After the experiment was over, the researchers found that a combination of 3 % mass of Ni, 7.5 % mass of Ce, and 7.5 % mass of Cu resulted into high percentages of hydrogen if the experiment was supported by hydroxyapatite catalysts (Hakim et al, 2013). This ratio also resulted into glycerol conversion percentage of 97.3% with a hydrogen production of 57.5%. It was empirical established that the combination was the most efficient for production of hydrogen when steam reforming of glycerol was required (Hakim et al, 2013). This study was a good and most effective method of analyzing thermodynamism and conversion of liquids into vapors and essential liquids. However, the bulk density of the glycerol and hydrogen produced has not been outlined accurately in the paper. Compressibility and bulkiness of molecules has a big impact on the production of hydrogen gases (Hakim et al, 2013).
Studies have been done to monitor and evaluate performance of Ni/SiO2 catalysts. The studies have evaluated how reforming of glycerol can be modified to produce the necessary hydrogen amounts. The studies have evaluated hoe operational conditions can be varied to produce enough hydrogen (Sadanandan et al, 2012). A study using a commercial based Engelhard catalyst was used to compare gas production and distribution when water to carbon ration was altered or adjusted. The stability of the catalysts under these variations was also analyzed and compared (Sadanandan et al, 2012). During this study, three catalysts of sizes 2×4, 3×5 and 2×2 were used. In addition, glycerol, and a water mixture of 600o C was used to produce an approximate value of 2 L H2 g−1 cat h−1. After the study, it was realized and established that 3×5 pellet was associated with a constant production of hydrogen while the 2×3 and 2×2 indicated that reforming activity was affected by the formation of carbon. However, when the molar ratio of 1:9 of glycerol to water was used, there was a relative production of 3 mg carbon g−1 cat h−1 and it occurred in 20 significant cycles. When the ration mentioned was adjusted to 1:18, 1.5 mg carbon g−1 cat h−1 was produced through the same number of cycles (Sadanandan et al, 2012). The strength of the research is that, the production of the gas was monitored within the frameworks of thermodynamics and the results generated were compared by varying the inputs and catalytic compositions of the materials that were used (Sadanandan et al, 2012). The weaknesses of these results was that, evaluation from gamma radiation examination, x ray radiation analysis and that of beta radiation were to be compared to see which method was the best to track thermodynamic changes that do occur when different catalysts are mixed and when the reaction is conducted under varying conditions (Sadanandan et al, 2012).
Nickel catalysts supported by Al2O3, ZrO2 and CeO2 were made available and prepared using the wet impregnation method after which they were used to evaluate reforming of glycerol in the presence of steam. Before that, the catalysts were evaluated for structural, crystalline, textural, chemical, and reducibility characteristics (Manfro, Ribeiro, & Souza, 2013). The results indicated that a good amount of Ni was dispersed when Al2O3 was used to support the process. The process was evaluated at a temperature of 500 degrees Celsius when glycerol of 10 % vol was used. All the process was carried out in a continuous flow reactor. It was empirical that all the catalytic conversions indicated that the conversion was effective and the results were almost 100%. The rate and level of gas production was seen to be dependent upon the type of support that was used (Manfro, Ribeiro, & Souza, 2013). Hydrogen production increased when the order of production was supported in the order of ZrO2 > Al2O3 ≈ CeO. However, among all the catalyst, a very low activity was recorded when CeO2 was used. The variation in results of the catalysts used was not compared statistically by use of measures of dispersion. Data should be analyzed and the results compared to see how the production of by products of lower activity catalyst deviates from activity of the highest rated catalyst (Manfro, Ribeiro, & Souza, 2013).
Glycerol was defined as a by product of biodiesel processing and production and is the chief source of hydrogen, which is regarded as a renewable source of energy (Vaidya, & Rodrigues 2009). Conversion of glycerol into hydrogen can be achieved by use of a reforming process where by catalysts are used at different temperatures both to initiate and drive the whole process of reforming. However there are other methods that can be used to achieve the same results and they include steam, auto thermal, and aqueous reforming. Thermodynamic analyzes and considerations are always considered to be the core process that drives and sustains all the changes (Zana, 2002). For example, the het required, steam, and the atmospheric conditions should all be reframed and directed towards achieving a large conversion of hydrogen. Not all catalysts produce leads to the production of oxygen but there are specific catalysts that are used to facilitate the conversion (Zana, 2002). What drives these conversions and changes depends upon quality of catalysts and the available environment in which they are used. There are variations that can not be overlooked such that if one catalyst is used to perform a reforming process, it does not mean that the rate of production will remain the same when the same catalyst is used to reform glycerol at different temperatures. Apart from glycerol, these catalysts are viable and effective when ethanol is used as a reforming agent (Vaidya, & Rodrigues 2009). Ethanol and glycerol have been identified as renewable sources of energy and still, there are more researchers that are being conducted to evaluate and determine if methanol is also a good source of enough and efficient hydrogen gas. Most of the researches have been done to identify how the Gibbsian energy equation can be sued to calculate the exact amount of hydrogen that can be produced at any given time (Zana, 2002). The best way to go has been to identify exact catalysts that suit a specific raw material to produce hydrogen gas. So far, Ni, Ru, and Pt catalysts have been empirical and theoretically been identified to be among the best catalysts that aid or initiates production of hydrogen from reformation of glycerol and ethanol (Zana, 2002).
The amount of hydrogen produced depends upon the sizes of catalysts and the chemical composition. This is because; any presence of impurities in the catalysts may reduce activity of reforming process or may alter slightly the process. Poor temperature conditioning and presence of impurities in some catalysts poses danger to the overall production process and therefore, any alteration must be prevented in good time and without affecting the thermodynamic behavior of the liquid and vapor phase orientations (Hedwig & Hinz 2003). Before, using the catalysts, structural analysis should be done to determine if they are viable and if they will give rise to good results. The results obtained should be compared with other results to determine and detect any variations so that a table that shows choice of specific catalysts for specific reforming processes is drafted to guide scientists and thermodynamic specialists (Hedwig & Hinz 2003). Specialization is a nice selection when it is considered that thermodynamic is a broad engineering and technological subject that requires a well directed procedure to evaluate variations in production of liquid-vapor products such as hydrogen. Ethanol and glycerol have different densities and thermodynamic properties and which determines the amount of heat required to obtain good results (Zana, 2002). Ethanol is an effective because it does not pose any challenge and health hazard to people or scholars investigating the reforming process. It is also cheap and it is a good liquid that can generate a good amount of hydrogen (Hedwig & Hinz 2003).
Behavior at the interface is critically analyzed while putting into consideration the strict variations that occur when conditions are altered and modified to suit the procedures and objectives of any research findings (Hedwig & Hinz 2003). Goals and objectives of any research is required to conform to the outlined scientific applications and variations that occur when diametric and oligomeric surfants and reactants are used study behavior and characteristics of fluids and phase changes (Ebshish et al, 2012). Phase changes are used to outline that different reactions occur when there is an optimum temperature and when there is no critical variations that affect transition of a liquid to a gas or to a vapor state (Ebshish et al, 2012). Different state of phase transition are affected by the nature of catalysts and the results obtained should be evaluated to know the amount of hydrogen produced when different catalysts (Hedwig & Hinz 2003).
Glycerol is also produced during the biodiesel production and in fact, it is a biofuels product that is produced when transesterification process is done on vegetables (Zana, 2002). Vegetables are available in almost all areas of the world and its supply is abundant in the international market (Vaidya, & Rodrigues, 2009). Because hydrogen is an effective and clean energy source, conversion has become the most effective way to produce hydrogen by steam reforming processes (Hedwig & Hinz 2003). Experiments on production of hydrogen from reforming of glycerol have been carried out in a fixed bed oriented reactor by different scholars and the results have marched to some extend. Some experiments have been carried out using 10wt% by supporting it using alumina xerogel catalysts (Ebshish et al, 2012). This was carried out by supporting the catalysts using Ni which was highly impregnated by alumina xerogel and before it was used, it had been preheated at 800°C, 900°C, 700°C, and 1000°C. The rate of active reaction reduces doubly when the molar ratio is increased by two and production increases in the same ratio (Hedwig & Hinz 2003).
X-ray diffractions are used to ensure that structure of catalysts is not impaired or does not affect production of hydrogen gases. In addition, SEM analysis is used to assess whether the production of hydrogen will be increased if a different source apart from ethanol or glycerol is used (Hedwig & Hinz 2003).
Thermodynamics is a branch of engineering that analyzes how liquids and vapor interrelate when temperatures and pressures are changed or adjusted. This is because, all variations of temperatures and pressures have effect on phase relationships between liquids and vapors. Catalytic studies have currently evaluated that specific catalysts have a more capability of aiding production of hydrogen that others even though not all produces the same amount of hydrogen. Hydrogen production is accelerated when an optimum temperature is obtained and used. However, modification or variations can be done to ensure that the production of hydrogen is extended beyond what a single or theoretical cycle allows.
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