Zn/Al Catalyst Pore Volume Retention
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Solution Overview
Problem
Existing water gas shift catalysts face challenges during startup under steam condensing conditions, leading to leaching of alkali metal compounds and loss of catalytic activity, and require dedicated guard materials to mitigate halogen poisoning, limiting their mechanical strength and number of start-ups.
Innovation Solution
A Zn/Al-based catalyst with a mixture of zinc aluminum spinel and alkali metals like potassium, having a specific pore volume and density, allowing retention of alkali metal compounds within the catalyst pores and maintaining mechanical strength, thus preventing significant loss of activity during steam condensation and halogen exposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If steam is used to heat the HTS reactor during startup, then heating efficiency is improved and dedicated nitrogen loops are eliminated, but alkali metal compounds are leached from the catalyst causing loss of catalytic activity
Solution Approach 1:
The catalyst employs a porous support structure with controlled pore size distribution that physically confines alkali metal compounds within the pores. The pore dimensions are specifically designed to retain the alkali metals during steam condensation while still allowing reactant and product molecules to diffuse freely, thus preventing leaching during steam heating startup
Solution Approach 2:
The catalyst uses a composite structure combining metal oxide active phases with a porous support material. This composite design provides both the catalytic functionality and the structural framework that retains alkali metal promoters during steam exposure, resolving the contradiction between steam heating efficiency and alkali metal retention
2Reliability
If guard materials are added to mitigate halogen poisoning, then catalyst protection is improved, but device complexity and pressure drop increase
Solution Approach 1:
The invention extracts and eliminates the need for separate guard materials by incorporating halogen resistance directly into the main catalyst formulation. The catalyst composition includes components specifically designed to withstand halogen exposure, thereby removing the requirement for additional protective beds or guard materials
Solution Approach 2:
The catalyst is designed with multi-functionality, simultaneously providing water-gas shift activity, halogen resistance, and alkali metal retention. This universal design consolidates multiple functions into a single catalyst material, eliminating the need for separate guard materials and reducing reactor complexity
3Productivity
If the number of start-ups is increased, then catalyst utilization is improved, but mechanical strength degradation and activity loss occur
Solution Approach 1:
The catalyst undergoes preliminary stabilization treatment during manufacturing that strengthens its mechanical structure before service. This pre-treatment creates a more robust catalyst formulation that can withstand repeated thermal cycling and mechanical stress from multiple start-ups without significant strength degradation or activity loss
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The catalyst maintains high mechanical strength and catalytic activity through the alkali-buffer effect, enabling over 100 start-ups without substantial activity loss, eliminating the need for dedicated nitrogen loops and reducing halogen poisoning, while being environmentally friendly by avoiding chromium and iron.
Implementation Method 1
allowing retention of alkali metal compounds within the catalyst pores
Implementation Method 2
heating up the reactor and the HTS catalyst inside it... While the reactor temperature is below the dew point of water, condensation will take place inside the reactor
Implementation Method 3
heats up the reactor and the HTS catalyst inside it
Implementation Method 4
Water gas shift is a well-known method for increasing the hydrogen content of a synthesis gas... Water gas shift enables increasing the hydrogen yield and decreasing the carbon monoxide content of the synthesis gas according to the equilibrium reaction: CO+H2O═CO2+H2
Data Source
AI summary
The present disclosure relates to an improved water gas shift catalyst, in particular an improved high temperature shift catalyst and process using the catalyst. The water gas shift catalyst includes Zn, Al, optionally Cu, and an alkali metal or alkali metal compound, wherein the content of alkali metal, preferably K, is in the range 1-6 wt %, such as 1-5 wt % or 2.5-5 wt % based on the weight of oxidized catalyst, and wherein the water gas shift catalyst has a pore volume, as determined by mercury intrusion, of 240 ml/kg or higher, such as 250 ml/kg or higher. A process for enriching a synthesis gas in hydrogen by contacting the synthesis gas in a water gas shift reactor with the water gas shift catalyst.