A gas decomposition fluidized bed reactor for the decomposition of a gas into a mixture of solid and gaseous by-products, the gas decomposition reactor comprising: a reactor vessel having an inlet for receiving an inlet gas and an exhaust outlet for releasing an exhaust gas, wherein the inlet gas is a mixture of a reaction gas and a fluidizing gas; a Raman spectrometer connected with the exhaust outlet for determining a chemical composition of the exhaust gas and generating a corresponding exhaust signal, and connected with the inlet for determining a chemical composition of the inlet gas and generating a corresponding inlet signal, wherein the Raman spectrometer is connected with the exhaust outlet and the inlet through one or more Raman probes; a processor connected with the Raman spectrometer to receive the inlet signal and the exhaust signal from the Raman spectrometer, the processor being configured to compare the chemical composition of the inlet gas and the chemical composition of the outlet gas and determine a conversion efficiency of a reaction in the reactor vessel based on the inlet signal and the exhaust signal, the processor being configured to calculate a flow rate ratio of reaction gas to fluidizing gas that would yield optimum conversion, the processor communicating with a pressure-flow control system to optimize the flow rate of the reaction gas and fluidizing gas by manipulation of the reaction control valve and/or the fluidizing control valve based on the determined conversion efficiency; and a pressure-flow control system connected with the processor and the inlet gas for adjusting a flow of the inlet gas through the inlet, wherein the Raman spectrometer is configured to determine the composition of the exhaust gas and the chemical composition of the inlet gas, and the processor is configured to ratiometrically determine the conversion efficiency of the reaction. a reactor vessel having an inlet for receiving an inlet gas and an exhaust outlet for releasing an exhaust gas, wherein the inlet gas is a mixture of a reaction gas and a fluidizing gas; a Raman spectrometer connected with the exhaust outlet for determining a chemical composition of the exhaust gas and generating a corresponding exhaust signal, and connected with the inlet for determining a chemical composition of the inlet gas and generating a corresponding inlet signal, wherein the Raman spectrometer is connected with the exhaust outlet and the inlet through one or more Raman probes; a processor connected with the Raman spectrometer to receive the inlet signal and the exhaust signal from the Raman spectrometer, the processor being configured to compare the chemical composition of the inlet gas and the chemical composition of the outlet gas and determine a conversion efficiency of a reaction in the reactor vessel based on the inlet signal and the exhaust signal, the processor being configured to calculate a flow rate ratio of reaction gas to fluidizing gas that would yield optimum conversion, the processor communicating with a pressure-flow control system to optimize the flow rate of the reaction gas and fluidizing gas by manipulation of the reaction control valve and/or the fluidizing control valve based on the determined conversion efficiency; and a pressure-flow control system connected with the processor and the inlet gas for adjusting a flow of the inlet gas through the inlet, wherein the Raman spectrometer is configured to determine the composition of the exhaust gas and the chemical composition of the inlet gas, and the processor is configured to ratiometrically determine the conversion efficiency of the reaction.