Lab Report Essay Research Paper Table of

Lab Report Essay, Research Paper

Table of Contents

Introduction ..........................

Background and Theory ......................

Experimental Procedure ......................

Results and Discussion ......................

Conclusions and Recommendations .................

Nomenclature ...........................

References ...........................

Appendixes

A. Data ...........................

B. Equipment Diagram ......................

Introduction

The hydrogenolysis of ethane on a nickel on kieselguhr catalyst has only been conducted using a cylindrical pellet shaped catalyst of unknown surface area. We used a powdered version of this catalyst and compared its performance with that of the pellet catalyst. This comparison was conducted using one gram of catalyst in each reactor. Holding all other variables constant, ethane conversion was tracked while varying total flowrate. We then varied the temperature while holding the flowrate, input composition, and all other variables constant.

The reaction that converts ethane to methane occurs on the surface of the catalyst. A determination of the surface area is an important factor in comparison of the performance of the pellet and powdered catalyst. We conducted the surface area determination using a nitrogen adsorption apparatus and analyzed the data in accordance with BET theory using the single point method.

Background and Theory

This experiment involves the kinetics of ethane cracking. Ethane cracking is where a molecule of ethane is hydrogenated and produces two molecules of methane, as seen in Equation 1. The catalyst is nickel on kieselguhr, a porous medium.

(1)

This reaction was conducted in a single tubular packed bed reactor (PBR). The catalyst was supported by glass wool and placed in the center section of the PBR. The composition of the product stream was measured using a gas chromatograph (GC). The GC detector signal was fed to an integrator. The integrated area under the signal peaks can be related to the conversion of ethane (XE) by the following equation:

(2)

where M and Eare the integrated areas under the corresponding peaks for methane, and ethane and CF is a correction factor based on a standard of known composition.

In addition, we investigated methods for the determination of both catalysts. surface area using a Quantasorb nitrogen adsorption apparatus. The adsorption apparatus consisted of a sample cell through which nitrogen and helium flowed. The effluent passed through a thermal conductivity detector that detected nitrogen. The detector signal was sent to an integrator where the area of the peak was displayed. The first step in the process involved affecting adsorption by immersion of the sample cell into liquid nitrogen. Once nitrogen adsorption was complete the sample cell was withdrawn from the liquid nitrogen bath. As the sample warmed to room temperature desorption of the nitrogen began and the integrated signal was recorded. A known volume of nitrogen calibration gas was then injected into the detector. The data was then analyzed in accordance with Brunauer, Teller and Emmet theory using the single point method. The following equation was used to determine the total surface area of the sample based upon volume of desorbed nitrogen:

where A/Ac is the ratio of the integrated areas of the desorbate to the calibration gas, Vc is the volume of calibration gas, Pa is the ambient pressure, N is Avogadro.s number, R is the gas constant, T is temperature, P/Po is the ratio of the partial pressure of the adsorbate to the saturated vapor pressure of the adsorbate and Acs is the cross-sectional area of the adsorbate molecule.

Experimental Procedure

In this experiment we only used Reactor 1 from the diagram in Appendix B. We first collected data with 1 g of the pellet catalyst. The first set of trials involved varying the total flow rate while keeping the composition and temperature constant. We used a composition of ethane (53.3 vol. %), helium (26.7 vol. %), and hydrogen (20 vol. %), and maintained the reactor temperature at 240.C. The flow rates that we used were between 100 cc/min to 400 cc/min. Once this was accomplished we chose the flow rate of 200 cc/min and then varied the temperature for the second set of trials. The range of temperatures across which the experiment was conducted was 190.C . 265.C. We then conducted the same series of varied flow rates and temperature trials upon 1 g of the powdered catalyst. In both cases we took several standard readings of the GC at the beginning of each lab period.

Matt, using glass wool as a support for the catalyst, packed the powdered reactor. The catalyst was distributed over a certain length as evenly as possible. A test was conducted to see if the high-pressure gasses would blow the catalyst out of the reactor, and the results indicated that the catalyst would stay in the glass wool inside the reactor.

A possible safety concern could have arisen if the powdered catalyst dramatically increased conversion. This reaction is exothermic, and by going to completion, it could have produced more heat that this experiment was designed for. We didn.t know the heat limitations, but we assumed that the powdered catalyst would o

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