Reactions of syngas with different kind of catalysts Essay Example

Synthesis gas

Synthesis gas

Declaration of originality

This is a declaration that the work is entirely mine and other information sourced has been acknowledged. To the best of my knowledge this work has not been submitted in any form to any learning institution for assessment or has been copyrighted by any other person. No part of the material contained herein should be reproduced or transmitted in any means unless for the intended purpose for this paper.

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Acknowledgements

I will like to thank all the people who were involved in making this paper successful. This primarily includes my supervisor———— whose support proved essential in the completion of the paper. His continuous guidance, feedback and encouragement proved to be essential. I will also thank my friends who gave me humble time during the period I was completing the paper

Executive summary

Synthesis gas being a combination of various such as carbon monoxide, carbon dioxide, hydrogen and other gases it poses a challenge to industrial use of usage. The reaction of Synthesis gas with other catalyst is essential. This paper was investigating the reactions of synthesis gas with different kind of catalyst with the intention of making suggestion for the production of various products. The results show that there are many, which react with Syn gas, and they include iron, carbon monoxide, zinc oxide, water, and many others. To produce ethanol, methanol mixed alcohol, gasoline, waxes, ammonia, and many other products. Synthesis gas is made from feedstock and it can be used as natural gas since it has carbon and hydrogen which are ingredients of oil biomass, and coal. Synthesis gas is produced because of gasification of a carbon-containing fuel to a gaseous product that has heating value. If Synthesis gas contains nitrogen, it must be separated, as both nitrogen and carbon monoxide have similar boiling points and it will be difficult to recover pure carbon monoxide through cryogenic processing.

Table of Contents

2Declaration of originality

3Acknowledgements

4Executive summary

6Introduction

6Objectives

6Methodology

7Literature review

8Results

10Reversible reactions and equilibrium

11Types of catalyst that react with Snygas

13Ruthenium-copper catalysts

14Concentration

16Temperature

17Conclusion

19Works Cited

Introduction

The synthesis gas is a gas that contains carbon dioxide, carbon monoxide, and hydrogen; however, hydrogen and carbon monoxide are the main substance in its composition. It is produced using various methods including Fischer-Tropsch. This process involves thermal classification to extract it from waste organic matter, which is in liquid form, coal, biomass and oil. The type of material used in extracting this biomass determines its composition[ CITATION Sup02 p 23 l 1033 ]. The reaction of synthesis gas depends on its composition that is hydrogen, carbon monoxide, and carbon dioxide. These components are environmentally clean thus reducing the Ozone layer.

Objectives

The aim of the research will be to collect information on reactions of synthesis gas with different kinds of catalyst so that one can have a good understanding of the chemical processes of synthesis gas. Catalyst of synthesis gas can be grouped into various groups from monometallic to bimetallic. This will provide information that is critical in the future use of synthesis gas. Changes in chemical composition of various catalysts will be affected by reaction parameters such as pressure and temperature.

The paper will be introducing the methods of determining the rate of reaction as well as the products of reaction by taking into consideration the amount of reactants, the temperature of the reaction while they are mixed together are discussed in details. The results of the experiment are shown and the discussion on how the mixing process goes about is discussed at the end.

Methodology

This research methodology required gathering relevant data from specified documents in order to analyze the materials gathered and try to reach and have more understanding about the reaction and the whole experiment. The findings of the research will lead to an understanding of Synthesis gas and the possible reactions of Synthesis gas with different kind of catalysts. Also, see the affect of changing the reaction parameters such temperatures and pressures. The information and data used in this research has been sourced from documents provided by supervisor, books, journals, and internet websites in order to arrive at the main goal of this research.

Literature review

Elements with atomic number greater than 92 are called the transuranium elements. All of the synthesized transuranium elements have been produced by converting a lighter element into a heavier one. Such a change requires an increase in the number of protons in the nucleus. One of the processes of synthetic transuranium occurs between iron and synthesis gas.

The reaction of the difference chemical compounds brings a change of the compounds composition as they react to each other. Since different chemical compounds will have unique conductivity properties, we will be able to infer the rate of reaction and the amount of end substance produced. There are other several other factors that affect the rate of reaction time but they all follow and complement each other. The amount of reactants, the rate of flow by which they are mixed, the volume of the holding vessel and the temperature at which they are held plays an important role. The reaction;

CH
4+H2OReactions of syngas with different kind of catalysts CO +3H2 or

The overall energy change for this reaction is positive; the reaction does not take place spontaneously. Carbon oxide does not spontaneously decompose at room temperature. It is said to be thermodynamically stable.

When the overall energy change for a reaction is negative, a reaction will proceed spontaneously. However, some spontaneous reactions take place so slowly that hundreds of years may pass before any observable change occurs. The overall energy change for the combustion of Synthesis gas is 2870 KJ.

2CH
4+O2Reactions of syngas with different kind of catalysts 1 2CO +4H2 or

2CH4+O2Reactions of syngas with different kind of catalysts 2 CO2 +2H2 O

At room temperature, the reaction proceeds so slowly that we can never detect a change. Thus, Synthesis gas is said to be kinetically stable. Note that a compound is stable in terms of its tendency to decompose if the overall energy change which is negative and still be stable if the rate of change is imperceptible.

Results

It is clear that chemical reactions of synthesis gas depends catalysts that are used using the process of production. Cobalt and iron have chemical reaction which depends on temperature and partial pressure. The steady reaction with catalyst will also depend on the concentration of synthesis gas. When the concentration is high and catalyst is alkaline, carbon formation is increased thus producing high carbon monoxide rich synthesis gas[ CITATION Par52 p 352 l 1033 ]. However this reaction depends on the number of moles which are contained in the reactants. Therefore the numbers of moles are predetermined before reaction takes place. The increase of carbon dioxide on vapour will change the reaction and increase the production of synthesis gas. This means that H20 gas is a good reactant at partial pressure of synthesis gas. The following graphs show how various reactions take place at various conditions.

Reactions of syngas with different kind of catalysts 3

Adapted From [ CITATION Dav99 p 52 l 1033 ]

The graph above shows the rate of reaction of different reactants to produce synthesis gas. In the graph, it is shown that the rate of reaction of iron and cobalt will increase to the optimum rate of reaction at 550oC and starts coming down. That means that any reaction will depend on the temperature the reactants are exposed to. The result from the graph above confirms that naturally that is at room temperature iron and cobalt will not react with synthesis gas. In any reaction different reactants with different chemical compounds react to produce end products which have different bonding and molecular masses. It also can be noted that temperature and concentration of both synthesis gas and catalysts will influence the reaction thus determining expected result. The concentration has to be high for quick reaction if the result is required immediately. It is also important to note that temperature is critical between a catalyst and synthesis gas. Too much temperature will have a slowed reaction while any temperature below 300oC will have a slowed or no reaction at all. Thus the temperature that is required to influence reaction between synthesis gas and catalyst is critical.

To determine the reaction rate for synthesis gas and catalyst, concentration of synthesis gas will be used to calculate the molar of the final product as well as show conductivity of the reactants. This means moles of end product are determined by understanding initial concentration.

Reversible reactions and equilibrium

A reverse reaction is where a catalyst and synthesis gas react to produce end product by absorption of energy and when temperature is changed to unfavourable to reaction to produce end product, there is a reverse reaction that is the original reactant are produced from the end product. The classic case of such reaction is shown below for the reaction of two elements to produce synthesis gas.

H
2O(l) + CO(g)
Reactions of syngas with different kind of catalysts 4 CO2 (g) + H2 (g) (reversible reaction)

CH4 (g) + CO2 (g)
Reactions of syngas with different kind of catalysts 5 2CO (g) + 2H2 (g) (reversible reaction)

The reverse reactions above show that there is a formation of a product from left to light at the same time fro right to left. This is quite interesting as in the first case, synthesis gas is formed on the right while in the second case it is in right but strong that is containing carbon monoxide. These represents reverse reactions in the production of synthesis gas. Synthesis gas is formed when reverse reactions are at equilibrium. In reverse reaction, the net carbon dioxide formation depends on the catalyst used. If the catalyst is alkali, the rate of carbon monoxide formation is increased since the removal of O from alkali takes place thus increasing conversion.

Iron based catalysts are good in the formation of synthesis gas in reverse reactions because double displacement will take place which will involve a collision of ions without transferring electrons. A reaction between the ions affects the bond arrangement of the substances. In essence in reverse reaction, neutralization reactions and ion displacement takes place at the same time giving reasons why synthesis gas is produced at equilibrium.

In reverse reactions, it is deemed to be slower when the molecules are involved in reactions rather than ion. This is because molecules do not involve bond rearrangement but electron transfer and in order for a faster reaction to be successful, bond rearrangement must occur. This molecular reaction involves elastic collusions rather than energy transfer.

Types of catalyst that react with Snygas

A catalyst is a substance that increases a reaction rate without being permanently changed is called a catalyst. Catalysis is the process of increasing rates of reaction by the presence of a catalyst. The catalyst appears to be chemically unaffected by the reaction[ CITATION Jak11 p 26 l 1033 ]. It changes the reaction mechanism in such a way that the activation energy required is less than in the unanalyzed reaction[ CITATION Bed05 l 1033 ]. Catalysts are important Syngas conversion reactions such as H2O(l) + CO(g)
Reactions of syngas with different kind of catalysts 6 CO2 (g) + H2 (g). This is because catalytic reactions are that reactants absorb onto the surface of catalysts and rearrange or combine into products.

The difference between Syngas and the catalysts is dissociation of CO molecule onto catalyst surface. If CH4 are brought into contact in the presence of H2O the reaction is rapid. Notice that CH4 is a solid and the reactants are gases[ CITATION PHI82 p 183 l 1033 ]. The CH4 lowers the required activation energy by providing a surface on which the activated complex can form.

CH4 + CO2 çè 2 CO + 2 H2

Synthesis gas can be used to produce different kind of products. This is made possible by reacting a catalysts and Synthesis gas at different range of pressure and temperature. Looking at the figure below, clearly we see some of the possible products formed from Synthesis gas by Fischer-Tropsch method where it reacts with catalysts or even by any other possible way to get the desired product.

Reactions of syngas with different kind of catalysts 7

Synthesis gas is made from various oxides, which are manufactured using the above method. The diagram above shows the commercial use of synthesis gas. From the diagram, CuO/ZnO is good catalysts in forming carbon dioxide which is a component from synthesis gas. The diagram also iron, cobalt, ruthenium are good catalysts with synthesis gas to produce ethanol, methanol, mixed alcohol wax diesel, gasoline and many other products. The diagrams below show the conversion rate of carbon monoxide to carbon monoxide or oxygen.

When iron, copper, manganese, zinc and cobalt oxidesreact with synthesis gas, there is heterogeneous reaction that is a reaction between two elements with different bonding. The main reason behind this is that there is service for reactions on catalysts. When the reaction takes place, a new substance is formed which can be used for other purposes. Absorption takes place for a successful reaction on heterogeneous catalyst[ CITATION Tom05 p 8 l 1033 ]. Absorption involves the catalysts absorbing one substance to form products that is useable weakening the bond for oxygen.

In this case there is a reaction of a catalyst and synthesis gas such as water and they are on the same phase where some elements are interchanged in the equation below. The reaction is quick since the activation energy that is required is less.

O + HReactions of syngas with different kind of catalysts 8C2O CO2 + H2

The reaction is normally very slow. If, however, the solution is made acidic, the presence of the acid causes the reaction to proceed readily. In the reaction, all substances are in aqueous solution. Thus, the reaction is a homogeneous one, and the acid is a homogeneous catalyst.

Ruthenium-copper catalysts

A catalyst will react with synthesis gas since it has ions that are sensitive to changes in temperature, pressure and concentration. It reacts at a certain temperature level which when exceeded the reaction rate is reduced. When the concentration is low the reaction is reduced while when the concentration is high, the reaction rate is increased. Ruthenium- copper catalysts have hydrocarbon contaminations which are difficult to eliminate since they have strong bonds thus affecting their reaction rate with synthesis gas.[ CITATION SYL84 p 358 l 1033 ]. This makes ruthenium-copper catalysts weak bonded and can produce a carbon monoxide that is mixed with ruthenium-copper. Ruthenium ions are involved in hydro-carbonation as well as carbon monoxide disproportionate. This is known as bimetallic formation where the ratio of copper –ruthenium is 0.1 thus having a strong bond[ CITATION Mic96 l 1033 ]. Theses catalysts will be production of synthesis gas from alcohols in a continuous-flow system and it was found out that Synthesis gas was produced from alcohols as shown below

Reactions of syngas with different kind of catalysts 9

[ CITATION Dav99 p 52 l 1033 ]

CO conversion was determined through an internal standard, and the carbon-based selectivity of the carbon-containing products was calculated by an internal normalization method.

Concentration

Another factor affecting reaction rate is concentration to for Synthesis gas. Concentration refers to the quantity of matter that exists in a unit volume. For the reaction to take place, the particles must collide. If the number of particles per unit volume is increased, the chance of their colliding is also increased. If keep the concentration of the synthesis gas molecules the same, we would expect doubling the concentration of products generated to double the number of collisions between catalystand synthesis gas molecules. In turn, the reaction rate of reaction varies directly as the concentration of catalyst[ CITATION Jam02 p 3 l 1033 ]. An equation form; Rate1 =k1 [Cu]

Where the brackets around the Cu ( [ ] )means concentration expressed in mol/dm3 . If the concentration of Cu or other reactant remains constant, and the concentration of synthesis gas is allowed to vary thus it can be can be that the number of collisions and, therefore, the reaction rate, varies directly as the concentration of synthesis gas molecules[ CITATION Jam02 p 3 l 1033 ]. We write:

Rate2 =K2 [2CO (g) + 2H2 (g)]

If we allow the concentration of both reactant and synthesis gas to vary, there will be 4times as many molecules. There will be 4times as many molecules per unit volume and 4times as many collisions. The reaction rate is found to be quadrupled thus the reaction rate varies directly as the product of the concentrations of reactants. One write

Rate = k [synthesis gas][catalyst]

In this case, the constant k depends upon the size, speed, and kind of molecule involved in the reaction. Each reaction has only one value of k for a given temperature; this k is called the specific rate constant of the reaction. It should be pointed out here that the actual mechanism of this reaction involves the breaking of the 2CO (g) + 2H2 (g)] bond before collision.

Even though two 2CO (g) + 2H2 (g)] molecules appear in the equation, only one appears in the rate expression. An increase in the pressure on a gas at constant temperature results in a decrease in the volume occupied by the molecules. Since there more molecules per unit volume, there have been an increase in concentration. Increasing the pressure on a gas, then, will also increase reaction rate[ CITATION Mic96 p 164 l 1033 ].

Reactions such as the preceding in which the reactants are in the same phase are called homogeneous reactions. Chemical reactions that take place at the interface between two phases are called heterogeneous reactions. The reaction takes place on the surface of the zinc that is the interface between the two phases. Exposing more surfaces, in effect, increases concentration. Increasing surface area, then, increases the rate of reaction[ CITATION SYL84 p 338 l 1033 ].

Temperature

Reaction rate is determined by the frequency of collision between molecules and increases as the frequency of collision increase. According to the kinetic theory, the speed and, therefore, the kinetic energy of molecules increase as the temperature increases. Increased speed mean that more collisions will occur and the reaction rate depends less on the increase in the number of molecules that have the activation energy. Molecules must collide with a kinetic energy sufficient to form the activated complex. Otherwise, a collision will not lead to reaction[ CITATION The07 p 6 l 1033 ].

Reactions of syngas with different kind of catalysts 10

[ CITATION Dav99 p 52 l 1033 ]

Temperature helps in thermo-chemical process in which carbon-rich feedstock like petro-coke, biomass or coal are converted into a gaseous compound consisting of carbon monoxide and hydrogen under high-heat, high pressure, oxygen depleted conditions. These results would naturally be different for different chemical compounds seeing as they will have different end products and molecular masses. The underlying principles of the reaction remain the same however. The temperature will and the concentration of two or more substances reacting to each other will determine the end results[ CITATION Wan11 p 15 l 1033 ]. The temperature can be set higher if the operator wants to hasten reaction and lower the temperature if he wants to slow down the reaction time[ CITATION HID84 p 25 l 1033 ].

The differences in the temperature did not provide a lot of difference although it can be noted that the temperature with the lower range showed a slightly lower reaction time as it can be expected from the lower kinetic energy of the lower temperature range.

Conclusion

The oxygen removal from carbon dioxide in the synthesis gas is usually determined with the temperature and catalyst present, the formed oxygen is absorbed leaving carbon monoxide. Temperature is critical in this process as well as the time the reaction takes. When optimum rate reaches any additional time will lead to reduced reaction rate. Carbon dioxide reaction rate is critical during reverse reactions which mean that it is critical in minimizing the formation of synthesis gas because of reverse reactions ability as shown in the reverse equations below..[ CITATION Jam04 p 280 l 1033 ] Cobalt catalyst reactions with synthesis gas will increase when the temperature is around 483 – 623K to produce methane. The reaction of iron catalysts with synthesis gas to produce methane occurs at temperatures of 623K.[ CITATION Hon09 p 8 l 1033 ]C under a certain pressure. The reactions between Cobalt and iron catalyst are critical in influencing the production of synthesis gas when Ammonia is involvedoC. The reactions between catalysts and synthesis gas can be partial oxidation, reforming, carbon dioxide reforming and steam reforming. These various methods of reactions usually occur at temperatures between 200 and 600oThere are many catalysts which have chemical reactions with the synthesis gas to produce various products. One of the product is methanol which is produced through various chemical reactions between a catalyst and synthesis gas at temperatures of 300-500

(g)2 2CO (g) + 2HReactions of syngas with different kind of catalysts 11
(g) 2 (g) + CO4CH

Synthesis gas reaction with alkali leads to increased rate of reaction because it has weak bonds. In this case there is a swift in reaction because alkali reaction weakens the catalyst bonds leading to restructuring of the bonds of the reactants..[ CITATION Chr90 p 21 l 1033 ]The production of methane increases when the concentration of synthesis gas and water partial pressure is increased. This is because the reaction of cobalt and iron with synthesis gas depends on the temperature and concentration. The increase of water partial pressure will affect the reaction of synthesis gas with cobalt and iron leading to lower methane selectivity and increasing the production of synthesis gas

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Tomohisa Miyazawa, Takeo Kimura, Jin Nishikawa, Kimio Kunimori, Keiichi Tomishige. «Catalytic properties of Rh/CeO2/SiO2 for synthesis gas production from biomass by catalytic partial oxidation of tar.» 30 6 2005. Science and Technology of Advanced Materials. 6 June 2013 <http://iopscience.iop.org/1468-6996/6/6/A08/pdf/STAM_6_6_A08.pdf>.

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